Description
Title of Invention: PIPE JOINT
Technical Field
[0001]
The present invention relates to a pipe joint,
particularly to a pipe joint in which a spigot formed at
an end of one pipe is inserted into a socket formed at an
end of another pipe, the pipes being joined to each other
and made of, for example, ductile cast iron.
Background Art
[0002]
A so-called slip-on detachment preventive pipe joint
known as this kind of pipe joint is described in, for
example, Japanese Patent Laid-Open No. 5-231570 (1993).
In the pipe joint, a lock ring is attached to the inner
circumference of a socket, and an annular sealing
material made of rubber is disposed to seal the pipe
joint over the periphery between the inner
circumferential surface of the socket and the outer
peripheral surface of a spigot. The sealing material
includes a heel part held by the socket and a bulb part
compressed between the inner circumferential surface of
the socket and the outer peripheral surface of the spigot
to generate a sealing surface pressure. The inner
diameter of the bulb part is reduced towards the socket
inner side, and the bulb part has a substantially
elliptical cross-section formed so as to project
obliquely towards the pipe center. A projection formed on
the outer periphery of the distal end of the spigot is
engaged with the lock ring to exhibit a detachment
prevention function between the socket and the spigot.
[0003]

In the pipe joint configured thus, when joining the
pipes to each other by inserting the spigot into the
socket, the inner circumferential portion of the bulb
part is bent and deformed (diameter expansion) outward in
the pipe diameter direction, while the projection of the
spigot passes by the inner circumference of the sealing
material towards the inner side of the socket.
[0004]
After the projection of the spigot passes by the
inner circumference of the sealing material, the bulb
part is compressed between the outer peripheral surface
of the spigot and the inner circumferential surface of
the socket, so that a sealing surface pressure is
obtained.
Summary of Invention
Technical Problem
[0005]
In the above-described known configuration, however,
a large force is required to deform the bulb part so as
to bend (diameter expansion) outward in the pipe diameter
direction when the spigot is inserted into the socket.
Thus, a large insertion force (joining force) has to be
applied when the spigot is inserted into the socket.
[0006]
An object of the present invention is to provide a
pipe joint in which a spigot is inserted into a socket
with a small insertion force (joining force).
[0007]
Another object of the present invention is to
efficiently attach a sealing material in a satisfactory
pressed state in a so-called mechanical-type pipe joint.
[0008]
Another object of the present invention is to
eliminate the need for the control of a tightening torque

for a bolt and a nut pressing a push ring, bring a
sealing material into surface contact with a socket and a
spigot uniformly over a wide area to exhibit sealing
properties, and maintain desired sealing properties even
if a part of the sealing material contributing to the
sealing properties moves in the pipe axial direction, in
a so-called mechanical-type pipe joint.
[0009]
Another object of the present invention is to join
pipes even with bent pipe axes while satisfactorily
maintaining a detachment prevention function, and
satisfactorily perform centering of a lock ring without
controlling the orientation of a lock ring centering
member.
[0010]
Another object of the present invention is to reduce
the weight and cost of a pipe joint by making a liner
disposed between the inner end of a socket and the distal
end of a spigot arrangeable onto the axes of the socket
and the spigot.
[0011]
Another object of the present invention is to
effectively prevent the occurrence of corrosion of a
press claw and pipes in a detachment preventive pipe
joint using the press claw.
[0012]
Another object of the present invention is to prevent
the diameter expansion maintaining portion of a spacer
from being misaligned with a lock ring, when the diameter
expansion maintaining portion of the spacer is inserted
into a space between two ends of a constituent member at
the divided part of the lock ring, in a pipe joint in
which the spacer is fitted in the divided part in the
circumferential direction of the lock ring provided in a

socket to keep the lock ring in a diameter-expanded state
while a spigot is inserted into the socket.
Solution to Problem
[0013]
A pipe joint according to a first aspect of the
present invention in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the one pipe and the other pipe being
joined to each other,
the pipe joint comprising:
a fitting groove formed on the inner circumferential
surface of the socket; and
an annular sealing material for sealing a gap between
the socket and the spigot over the periphery,
the sealing material including a heel part fitted
into the fitting groove, and a bulb part interposed
between the inner circumferential surface of the socket
and the outer peripheral surface of the spigot, closer to
the inner side of the socket than the heel part,
the bulb part including a first bulb continuous with
the heel part, a second bulb positioned closer to the
inner side of the socket than the first bulb, and a
narrow part present on the boundary between the first
bulb and the second bulb,
the first bulb having a first sealing portion formed
on the outer peripheral portion of the first bulb, the
first sealing portion being pressed against the inner
circumferential surface of the socket,
the second bulb having a second sealing portion
formed on the inner circumferential portion of the second
bulb, the second sealing portion being pressed against
the outer peripheral surface of the spigot,
wherein the second bulb is inclined from the first
bulb towards a pipe center in a natural state before the

second bulb is provided between the socket and the spigot,
the inner diameter of the second bulb is smaller than the
outer diameter of the spigot in the natural state, and
the second bulb is expansible and contractible in the
pipe diameter direction due to elastic deformation of the
narrow part.
[0014]
A pipe joint according to a second aspect of the
present invention in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the pipes being joined to each other,
the pipe joint comprising:
an annular sealing material interposed and compressed
between the inner circumferential surface of the socket
and the outer peripheral surface of the spigot to exhibit
desired sealing properties; and
a push ring fastened to the socket to keep the
sealing material in a compressed state in which the
sealing material is interposed between the inner
circumferential surface of the socket and the outer
peripheral surface of the spigot.
[0015]
A pipe joint according to a third aspect of the
present invention,
the pipe joint comprising a sealing material
compressed between the outer peripheral surface of a
spigot and the inner circumferential surface of a socket
formed parallel to the outer peripheral surface of the
spigot to exhibit desired sealing properties, wherein
the sealing material includes a cylindrical portion
having an outer peripheral surface formed parallel to the
inner circumferential surface of the socket and an inner
circumferential surface formed parallel to the outer
peripheral surface of the spigot, and

the cylindrical portion is brought into surface
contact with the outer peripheral surface of the spigot
and the inner circumferential surface of the socket when
the sealing material is compressed between the socket and
the spigot.
[0016]
A pipe joint according to a fourth aspect of the
present invention,
the pipe joint comprising:
a lock ring accommodating groove formed on the inner
circumference of a socket;
a lock ring accommodated in the accommodating groove
and singularly divided in a circumferential direction;
an annular centering member disposed between the
inner circumferential surface of the accommodating groove
and the outer peripheral surface of the lock ring, for
holding the lock ring centered with respect to the socket
when a spigot is not inserted into the socket; and
a protrusion which is formed on the outer periphery
of the distal end of the spigot, is capable of
elastically pushing out the lock ring accommodated in the
accommodating groove with the spigot inserted into the
socket in the pipe diameter direction to pass through the
inner circumference side of the lock ring, and is capable
of being engaged with the lock ring from the inner side
of the socket when a detachment force is applied in the
pipe axial direction between the socket and the spigot
joined to each other to prevent the spigot from being
detached from the socket,
the centering member including a plurality of divided
parts in the pipe circumferential direction, and a
connecting part connecting the adjacent divided parts in
the pipe circumferential direction,
the divided part including a holder holding the lock
ring from the outer peripheral side, and a hold width

protruding inward in the diameter direction from the
socket inner side portion of the holder so as to be
engaged with the lock ring in the pipe axial direction,
wherein
the connecting part is disposed closer to the outer
peripheral side than the divided parts and is elastically
deformable in the pipe diameter direction in response to
the elastically pushed-out lock ring.
[0017]
A pipe joint according to a fifth aspect of the
present invention,
the pipe joint comprising:
a liner pushed into the inner side of a socket by a
spigot and disposed between the distal end surface of the
spigot and the inner end surface of the socket when the
spigot is inserted into the socket; and
a guiding surface formed on the inner surface of the
socket for guiding the liner in the pipe diameter
direction such that the axis of the liner is positioned
at the axis of the socket and the spigot when the liner
is pushed into the inner side of the socket by the spigot.
[0018]
A pipe joint according to a sixth aspect of the
present invention,
the pipe joint comprising:
a press claw disposed on the inner circumferential
portion of a socket, or disposed on the inner
circumferential portion of an annular member fitted onto
a portion of a spigot on the outer side of the socket and
connected to the socket; and
a press bolt for pushing the press claw to fix the
press claw pressed against the outer surface of the
spigot to the spigot, wherein

the press claw is made of an iron material and has an
anticorrosive coating formed on a surface of a portion in
contact with the spigot, and
the anticorrosive coating contains any one of a Zn-Sn
alloy sprayed coating, a Zn-Sn-Mg alloy sprayed coating,
and a Zn-Al alloy sprayed coating.
[0019]
A spacer according to the present invention for a
pipe joint in which a spigot formed at an end of one pipe
is inserted into a socket formed at an end of another
pipe, the pipes being joined to each other,
an annular lock ring is accommodated in a lock ring
accommodating groove formed on the inner circumference of
the socket, the lock ring including divided parts in the
circumferential direction and being elastically
expansible in diameter,
a protrusion is formed on the outer periphery of the
spigot, and
the protrusion of the spigot is allowed to pass
through the lock ring having an expanded diameter, and
the diameter-expanded state of the lock ring is released
after the passage of the protrusion,
the spacer being capable of being inserted into and
removed out from the divided part of the lock ring and
maintaining the diameter-expanded lock ring when the
spacer is inserted into the divided part,
the spacer comprising:
a diameter-expanded maintaining portion being capable
of being inserted into and removed out from a gap between
two ends of the lock ring along the circumferential
direction at the divided part, and being interposed
between the two ends when the maintaining portion is
inserted; and
a handle reaching from the diameter-expanded
maintaining portion outside the socket beyond a socket

opening portion when the diameter-expanded maintaining
portion is interposed between the two ends of the lock
ring, wherein
the spacer is capable of being removed out from the
gap between the two ends of the lock ring at the divided
part after the spigot is inserted into the socket,
passing through a space between the socket and the spigot
and being collected outside the socket beyond the socket
opening portion,
the spacer further comprises insertion grooves on two
side portions of the diameter-expanded maintaining
portion,
■ the two ends of the lock ring can be fitted into the
insertion grooves when the diameter-expanded maintaining
portion is inserted into the gap between the two ends of
the lock ring at the divided part, and
the diameter-expanded maintaining portion is capable
of being detached in a removal direction from the two
ends of the lock ring when the diameter-expanded
maintaining portion moves to be removed out from the gap
between the two ends of the lock ring at the divided part.
Advantageous Effects of Invention
[0020]
According to the present invention, the sealing
material including the first bulb, the second bulb, and
the narrow part is provided, so that high sealing
properties can be exhibited between the socket and the
spigot as well as reducing an insertion force (joining
force) required when the spigot is inserted into the
socket.
[0021]
According to the present invention, provided are the
annular sealing material interposed and compressed
between the inner circumferential surface of the socket

and the outer peripheral surface of the spigot to exhibit
desired sealing properties, and a push ring fastened to
the socket to keep the sealing material in a compressed
state in which the sealing material is interposed between
the inner circumferential surface of the socket and the
outer peripheral surface of the spigot. Thus, the push
ring can be efficiently attached without minutely-
controlling the interval between the push ring and a
flange. Accordingly, the operation efficiency can be
improved and the sealing material can be easily kept in a
favorable compressed state. As a result, the reliability
of the pipe joint can be improved.
[0022]
According to the present invention, the sealing
material has a cylindrical portion having an outer
peripheral surface formed parallel to the inner
circumferential surface of the socket, and an inner
circumferential surface formed parallel to the outer
peripheral surface of the spigot. The cylindrical portion
is brought into surface contact with the outer peripheral
surface of the spigot and the inner circumferential
surface of the socket when the sealing material is
compressed between the socket and the spigot. Thus,
sealing properties can be maintained by bringing the
sealing material into surface contact with the spigot and
the socket uniformly over a wide area. Further, desired
sealing properties can be obtained even when the sealing
material receives a pressure in pipe to move a portion of
the sealing material exhibiting the sealing properties.
[0023]
According to the present invention, the centering
member includes a plurality of divided parts in the pipe
circumferential direction and a connecting part
connecting the adjacent divided parts in the pipe
circumferential direction. The divided part has a holder

holding the lock ring from the outer peripheral side, and
a hold width which projects inward in the diameter
direction from the socket inner side portion of the
holder and is engageable with the lock ring in the pipe
axial direction. The connecting part is disposed closer
to the outer peripheral side of the lock ring than the
divided part and is elastically deformable in the pipe
diameter direction in response to the elastically pushed-
out lock ring. Thus, the lock ring can be reliably
prevented from being detached from the accommodating
groove, and the detachment preventive function can be
satisfactorily maintained, to improve the reliability of
the pipe joint. Further, the lock ring can be elastically
pressed inward in the diameter direction of the socket by
a reaction force of the elastically deformed connecting
part. Thus, the lock ring can be satisfactorily centered
by the centering member.
[0024]
According to the present invention, when the spigot
is inserted into the socket, provided are the liner
pushed into the inner side of the socket by the spigot
and disposed between the distal end surface of the spigot
and the inner end surface of the socket, and the guiding
surface for guiding the liner in the pipe diameter
direction such that the axis of the liner is located at
the axis of the socket and the spigot when the liner is
pushed into the inner side of the socket by the spigot.
The liner can be self-aligned, so that the outer diameter
and thickness of the liner can be reduced according to
the outer diameter and thickness of the spigot. Thus, the
liner can be reduced in weight and cost.
[0025]
According to the present invention, the press claw
pressed against the outer surface of the spigot by being
pushed by the press bolt in the annular member and fixed

to the spigot is made of an iron material, and contains
any one of a Zn-Sn alloy sprayed coating, a Zn-Sn-Mg
alloy sprayed coating, and a Zn-Al alloy sprayed coating
on the surface of a portion in contact with the spigot,
thereby exerting an excellent anticorrosive effect.
Further, an anticorrosive effect due to a sprayed coating
can be expected even when the distal end portion of the
press claw cuts into the spigot of the pipe. Thus, the
occurrence of corrosion can be effectively prevented in
the press claw and the pipe.
[0026]
According to the present invention, the spacer used
for the divided part of the lock ring has insertion
grooves on two side portions of the diameter-expanded
maintaining portion. Two ends of the lock ring at the
divided part can be fitted into the insertion grooves
when the diameter-expanded maintaining portion is
inserted into a gap between the two ends of the lock ring.
Further, the diameter-expanded maintaining portion can be
detached in a removal direction from the gap between the
two ends of the lock ring when the diameter-expanded
maintaining portion moves to be removed out from the gap
between the two ends of the lock ring at the divided part.
Thus, the diameter-expanded maintaining portion of the
spacer can be prevented from being displaced in the
diameter direction and the insertion direction from the
lock ring when the diameter-expanded maintaining portion
of the spacer is inserted into the divided part of the
lock ring to keep the lock ring in a diameter-expanded
state. Consequently, the diameter-expanded maintaining
portion can be set at a normal position of the divided
part of the lock ring without being displaced.
Brief Description of Drawings
[0027]

[FIG. 1] FIG. 1 is a cross-sectional view showing the
essential part of a pipe joint according to an embodiment
of the present invention.
[FIG. 2] FIG. 2 is a cross-sectional view showing a
sealing material of FIG. 1.
[FIG. 3] FIG. 3 is an explanatory diagram showing the
dimension of the sealing material.
[FIG. 4] FIG. 4 shows the joining operation of the pipe
joint of FIG. 1.
[FIG. 5] FIG. 5 shows the operating stage following the
joining operation of FIG. 4.
[FIG. 6] FIG. 6 shows the operating stage following the
stage of FIG. 5.
[FIG. 7] FIG. 7 shows the operating stage following the
stage of FIG. 6.
[FIG. 8] FIG. 8 is a vertical cross-sectional view
showing the essential part of a pipe joint according to
another embodiment of the present invention.
[FIG. 9] FIG. 9 is an enlarged view showing the essential
part of the part shown in FIG. 8.
[FIG. 10] FIG. 10 is a transverse cross-sectional view
showing the essential part of the part shown in FIG. 9.
[FIG. 11] FIG. 11 shows the joining operation of the pipe
joint of FIG. 8.
[FIG. 12] FIG. 12 shows the operating stage following the
joining operation of FIG. 11.
[FIG. 13] FIG. 13 shows the operating stage following the
stage of FIG. 12.
[FIG. 14] FIG. 14 shows the operating stage following the
stage of FIG. 13.
[FIG. 15] FIG. 15 shows a pipe joint according to another
embodiment of the present invention.
[FIG. 16] FIG. 16 shows a pipe joint according to another
embodiment of the present invention.

[FIG. 17] FIG. 17 shows the joining operation of the pipe
joint of FIG. 16.
[FIG. 18] FIG. 18 shows the end surface of a socket
flange in the pipe joint of FIG. 16.
[FIG. 19] FIG. 19 is a front view showing a push ring in
the pipe joint of FIG. 16.
[FIG. 20] FIG. 20 shows a pipe joint according to another
embodiment of the present invention.
[FIG.. 21] FIG. 21 shows a pipe joint according to another
embodiment of the present invention.
[FIG. 22] FIG. 22 shows a push ring and a sealing
material in the pipe joint of FIG. 21.
[FIG. 23] FIG. 23 shows the joining operation of the pipe
joint of FIG. 21.
[FIG. 24] FIG. 24 shows the operating stage following the
joining operation of FIG. 23.
[FIG. 25] FIG. 2 5 shows a modification example of the
pipe joint of FIG. 21.
[FIG. 26] FIG. 26 shows the joining operation in another
modification example of the pipe joint of FIG. 21.
[FIG. 27] FIG. 27 shows the operating stage following the
joining operation of FIG. 26.
[FIG. 28] FIG. 28 shows the operating stage following the
stage of FIG. 27.
[FIG. 29] FIG. 29 shows another modification example of
the pipe joint of FIG. 21.
[FIG. 30] FIG. 30 shows a pipe joint according to another
embodiment of the present invention.
[FIG. 31] FIG. 31 shows a push ring in the pipe joint of
FIG. 30.
[FIG. 32] FIG. 32 shows the joining operation of the pipe
joint of FIG. 30.
[FIG. 33] FIG. 33 shows a method for inspecting the pipe
joint of FIG. 30.

[FIG. 34] FIG. 34 shows a modification example of the
push ring which can be used in the pipe joint of FIG. 30.
[FIG. 35] FIG. 3 5 shows another modification example of
the push ring which can be used in the pipe joint of FIG.
30.
[FIG. 36] FIG. 36 is a cross-sectional view showing the
push ring of FIG. 35.
[FIG. 37] FIG. 37 shows a modification example of the
pipe joint of FIG. 30.
[FIG. 38] FIG. 38 is a side view showing the essential
part of the pipe joint of FIG. 37.
[FIG. 39] FIG. 39 shows another modification example of
the push ring which can be used in the pipe joint of FIG.
30.
[FIG. 40] FIG. 40 shows a pipe joint according to another
embodiment of the present invention.
[FIG. 41] FIG. 41 is a cross-sectional view showing a
sealing material shown in FIG. 40.
[FIG. 42] FIG. 42 shows the joining operation of the pipe
joint of FIG. 40.
[FIG. 43] FIG. 43 is an enlarged view showing a push ring
in FIG. 42.
[FIG. 44] FIG. 44 is an enlarged view showing the sealing
material in FIG. 42.
[FIG. 45] FIG. 45 shows a pipe joint according to another
embodiment of the present invention.
[FIG. 46] FIG. 46 is an enlarged view showing the
essential part of FIG. 45.
[FIG. 47] FIG. 47 is an overall side view showing a
centering member of FIG. 45.
[FIG. 48] FIG. 48 is a three-dimensional view showing the
centering member.
[FIG. 49] FIG. 49 shows the positional relationship
between the centering member and a lock ring.

[FIG. 50] FIG. 50 shows the joining operation of the
joint of a pipe joint according to another embodiment of
the present invention.
[FIG. 51] FIG. 51 shows the operating stage following the
joining operation of FIG. 50.
[FIG. 52] FIG. 52 shows the operating stage following the
stage of FIG. 51.
[FIG. 53] FIG. 53 shows a modification example of the
pipe joint of FIGS. 50 to 52.
[FIG. 54] FIG. 54 shows a socket of the pipe joint of
FIGS. 50 to 52 in another modification example.
[FIG. 55] FIG. 55 shows the joining operation of the
joint of the pipe joint of FIGS. 50 to 52 in still
another modification example.
[FIG. 56] FIG. 56 shows the operating stage following the
. joining operation of FIG. 55.
[FIG. 57] FIG. 57 is a three-dimensional view showing a
liner centering member in the pipe joint of FIG. 55.
[FIG. 58] FIG. 58 shows a modification example of the
liner centering member of FIG. 57.
[FIG. 59] FIG. 59 shows the joining operation of the
joint of the pipe joint of FIGS. 50 to 52 in still
another modification example.
[FIG. 60] FIG. 60 shows the operating stage following the
joining operation of FIG. 59.
[FIG. 61] FIG. 61 is a cross-sectional view showing a
pipe joint according to another embodiment of the present
invention.
[FIG. 62] FIG. 62 shows an example of a state of an
anticorrosive coating formed on a press claw in the pipe
joint of FIG. 61.
[FIG. 63] FIG. 63 shows another example of the state of
the anticorrosive coating formed on the press claw.

[FIG. 64] FIG. 64 shows still another example of the
state of the anticorrosive coating formed on the press
claw.
[FIG. 65] FIG. 65 shows a modification example of the
pipe joint of FIG. 61.
[FIG. 66] FIG. 66 is a cross-sectional view showing a
pipe joint according to another embodiment of the present
invention.
[FIG. 67] FIG. 67 is a side view enlargedly showing the
essential part of the pipe joint of FIG. 66.
[FIG. 68] FIG. 68 is a three-dimensional view showing a
spacer which can be used in the pipe joint of FIG. 66.
[FIG. 69] FIG. 69 is a plane view showing the spacer of
FIG. 68.
[FIG. 70] FIG. 70 is a right side view showing the spacer
of FIG. 69.
[FIG. 71] FIG. 71 is an enlarged view showing the
essential part of the spacer of FIG. 70.
[FIG. 72] FIG. 72 is a front view showing the spacer of
FIG. 69.
[FIG. 73] FIG. 73 shows the essential part of the spacer
of FIG. 72.
[FIG. 74] FIG. 74 is another drawing showing the
essential part of the spacer of FIG. 72.
[FIG. 75] FIG. 75 shows the joining operation of the pipe
joint of FIG. 66.
[FIG. 76] FIG. 76 is a cross-sectional view showing the
essential part of the pipe joint of FIG. 75.
[FIG. 77] FIG. 77 is a bottom view showing the spacer and
the vicinity of the spacer in the pipe joint of FIG. 75.
[FIG. 78] FIG. 78 is a bottom view showing that the
spacer is separated from a lock ring accommodating groove
in the pipe joint of FIG. 75.
[FIG. 79] FIG. 79 shows the diameter-expanded state of a
lock ring before the spacer of FIGS. 68 to 78 is used.

Description of Embodiments
[0028]
In a push-on detachment preventive pipe joint 11 of
FIG. 1, a spigot 15 formed at an end of one ductile cast-
iron pipe 14 is inserted into a socket 13 formed at an
end of another ductile cast-iron pipe 12, the pipes 12
and 14 being joined to each other.
[0029]
On the inner circumferential surface of the socket 13,
a fit-in groove 17, a recess 18 located closer to the
socket inner side than the fit-in groove 17, and a lock
ring accommodating groove 19 located closer to the socket
inner side than the recess 18 are formed across the
periphery. A projection 20 is formed between the fit-in
groove 17 and the recess 18. An inner end surface '21 is
formed in the pipe diameter direction on the socket inner
side in the interior of the socket 13, away from the lock
ring accommodating groove 19.
[0030]
The lock ring accommodating groove 19 accommodates a
lock ring 22 which is made of metal and singularly
divided in the circumferential direction. The lock ring
22 has such an elastic diameter reducing force that the
lock ring 22 is elastically pressed against the outer
peripheral surface of the spigot 15. A centering rubber
23 is disposed between the outer peripheral surface of
the lock ring 22 and the bottom surface of the lock ring
accommodating groove 19. The centering rubber 23
facilitates the insertion of the spigot 15 into the lock
ring 22, so that the lock ring 22 can be held to be
centered with respect to the socket 13 when the spigot 15
is not inserted into the socket 13. A projection 24 is
formed on the outer periphery of the distal end portion
of the spigot 15, the projection 24 being engageable with

the lock ring 22 from the socket inner side. The
projection 24 is formed in the pipe axial direction at a
predetermined distance from the distal end surface of the
spigot 15. The projection 24 is engaged with the lock
ring 22 from the socket inner side, thereby preventing
the spigot 15 from being detached from the socket 13.
[0031]
An annular sealing material 25 made of rubber seals
the pipe joint over the periphery between the socket 13
and the spigot 15. The sealing material 25 is configured
as follows.
[0032]
As shown in FIGS. 1 to 3, the sealing material 25
integrally includes a hard heel part 26 fitted in the
fit-in groove 17 and a bulb part 27, which is softer than
the heel part 26, interposed between the inner
circumferential surface of the socket 13 and the outer
peripheral surface of the spigot 15. The heel part 26 is
an annular member with a rectangular traverse section.
[0033]
The bulb part 27 is annularly formed and includes a
first bulb 28 and a second bulb 29 joined to each other.
The traverse section of the first bulb 28 is elliptically
elongated in the pipe axial direction with two ends along
the pipe axial direction each having a semicircular
portion with radius r1. The traverse section of the
second bulb 29 is circular-shaped with radius r2. Radius
rl is smaller than radius r2, and thickness t1 of the
first bulb 28 along the pipe diameter direction is
smaller than thickness t2 of the second bulb 29. The
diameter (= 2 x r2) of the traverse section of the second
bulb 2 9 is larger than space S in the pipe diameter
direction between the inner circumferential surface of
the projection 2 0 and the outer peripheral surface of the
spigot 15.

[0034]
The first bulb 28 is joined to the heel part 26, and
an annular recess 31 is formed on the outer peripheral
portion of the joint between the first bulb 28 and the
heel part 26. Inner diameter K of the first bulb 28 is
slightly smaller than the outer diameter of the spigot 15,
and the outer diameter of the first bulb 2 8 is slightly
larger than the inner diameter of the projection 20.
[0035]
The first bulb 28 is located closer to the inner side
of the socket 13 than the heel part 26. A narrow part
32 is formed at the joint of the first bulb 28 and the
second bulb 29, and the narrow part 32 is smaller in
thickness than the first bulb 28 and the second bulb 29.
On the inner circumferential surface and the outer
peripheral surface of the narrow part 32, annular
recesses 33 and 34 with arc-like cross-sections are
formed, respectively.
[0036]
The second bulb 29 is located closer to the inner
side of the socket 13 than the first bulb 28, and is
inclined from the first bulb 28 towards the pipe center.
As shown in FIG. 3, a line containing center P1 of the
semicircular portion of the end of the first bulb 28
closer to the second bulb 29 and center P2 of the second
bulb 29 is denoted as L1, a line containing the center P1
and extending along the diameter direction of the sealing
material 25 is denoted as L2, and inclination angle N of
the line L1 with respect to the line L2 is set to be 15°
to 35°. The second bulb 29 has an inner diameter (d)
smaller than outer diameter D1 of the spigot 15, and is
expansible and contractible in the pipe diameter
direction due to the elastic deformation of the narrow
part 32. Inner diameter J of the heel part 26 is larger
than the inner diameter K of the first bulb 28.

[0037]
A first sealing portion 35 is formed in the pipe
axial direction over the outer periphery of the first
bulb 28 so as to be pressed against the inner
circumferential surface of the projection 20 of the
socket 13. A second sealing portion 36 is formed over the
inner circumference of the second bulb 29 so as to be
pressed against the outer peripheral surface of the
spigot 15. The first sealing portion 35 is not aligned
with the second sealing portion 36 in the pipe axial
direction. As shown in FIG. 1, a gap 3 7 is present in the
pipe diameter direction across the periphery between the
outer periphery of the second bulb 2 9 and the bottom
surface of the recess 18 of the socket 13. The length of
the projection 20 of the socket 13 in the pipe axial
direction is set such that the second bulb 29 is not
compressed.
[0038]
In the above configuration, when the other pipe 12
and the one pipe 14 are joined to each other, first, the
centering rubber 23 and the lock ring 22 are accommodated
in the lock ring accommodating groove 19. As shown in FIG.
4, the heel part 26 of the sealing material 25 is fitted
in the fit-in groove 17, so that the sealing material 25
is attached into the socket 13.
[0039]
Next, the spigot 15 is inserted into the socket 13.
At this point in time, as shown in FIG. 5, the distal end
of the spigot 15 is inserted into the inner circumference
of the first bulb 28, is brought into contact with the
second bulb 29 and pushes the second bulb 29 in the
insertion direction. Thus, the second bulb 29 is
elastically expanded (diameter expansion) in the pipe
diameter direction.
[0040]

After that, when the spigot 15 is inserted further
into the socket 13, as shown in FIG. 6, the projection 24
of the spigot 15 passes by the inner circumference of the
heel part 2 6 and is brought into contact with the inner
circumference of the first bulb 28. The first bulb 28 is
then interposed between the outer peripheral surface of
the projection 24 and the inner circumferential surface
of the projection 20 of the socket 13, and is compressed
in the pipe diameter direction. At this point, a gap 38
is kept across the periphery between the outer periphery
of the second bulb 29 elastically diameter-expanded in
the pipe diameter direction and the bottom surface of the
recess 18.
[0041]
When the spigot 15 is inserted further into the
socket 13, as shown in FIG. 7, the projection 24 of the
spigot 15 passes by the inner circumference of the first
bulb 28, and is brought into contact with the inner
circumference of the second bulb 29. At this point, since
the gap 38 is formed as shown in FIG. 6, the second bulb
29 can be displaced outward in the pipe diameter
direction to escape from the projection 24.
[0042]
Thereafter, when the spigot 15 is inserted further
into the socket 13, as shown in FIG. 1, after passing by
the inner circumference of the second bulb 29, the
projection 24 of the spigot 15 passes by the lock ring 22
from the socket outer side towards the socket inner side
while elastically expanding the lock ring 22 in diameter.
Thus, the other pipe 12 and the one pipe 14 are joined to
each other. At this point, the second bulb 29 is
elastically expanded in the pipe diameter direction, so
that the second bulb 29 sticks to the outer peripheral
surface of the spigot 15. The diameter expansion of the
second bulb 29 pushes the first bulb 28 outward in the

pipe diameter direction. Thus, the first sealing portion
35 of the first bulb 28 is pressed against the inner
circumferential surface of the projection 20 of the
socket 13, and the second sealing portion 3 6 of the
second bulb 29 is pressed against the outer peripheral
surface of the spigot 15, so that high sealing properties
can be obtained between the socket 13 and the spigot 15.
[0043]
When the spigot 15 is inserted into the socket 13,
the narrow part 32 smaller in thickness than the first
and second bulbs 28 and 29 is elastically deformed, so
that the second bulb 2 9 can be easily expanded in the
pipe diameter direction. Thus, only a small force is
sufficient to expand the second bulb 29 in the pipe
diameter direction. As a result, the spigot 15 can be
inserted into the socket 13 with a small insertion force
(joining force).
[0044]
As shown in FIG. 5, first, the distal end of the
spigot 15 expands the second bulb 29 in the pipe diameter
direction. After that, as shown in FIG. 6, the projection
24 compresses the first bulb 28. Thus, the expansion of
the second bulb 29 in the pipe diameter direction does
not coincide with the compression of the first bulb 28,
so that the spigot 15 can be inserted into the socket 13
with a small insertion force (joining force). Further,
since the inner diameter J of the heel part 26 is larger
than the inner diameter K of the first bulb 2 8 as shown
in FIG. 3, when the first bulb 28 is compressed, a part
of the first bulb 28 can escape into a gap between the
heel part 26 and the spigot 15. Also with this
configuration, the spigot 15 can be inserted into the
socket 13 with a small insertion force.
[0045]

As shown in FIG. 6, when the first bulb 28 is
interposed and compressed between the outer peripheral
surface of the projection 24 and the inner
circumferential surface of the projection 20, the
recesses 31, 33, and 34 specifically shown in FIG. 2
serve as a relief margin, so that the amount of the
compressed second bulb 2 9 is reduced. Thus, the
projection 24 of the spigot 15 can smoothly pass by the
inner circumference of the first bulb 28, so that the
spigot 15 can be inserted into the socket 13 with a small
insertion force (joining force). As shown in FIG. 3,
since the thickness t1 of the first bulb 28 is smaller
than the thickness t2 of the second bulb 29, the amount
of the compressed first bulb 28 in the pipe diameter
direction can be reduced, and the projection 24 of the
spigot 15 can smoothly pass by the inner circumference of
the first bulb 28, thereby enabling the spigot 15 to be
inserted into the socket 13 with a small insertion force
(joining force).
[0046]
As shown in FIG. 7, when the projection 24 of the
spigot 15 passes inside the annular second bulb 29, the
gap 38 of FIG. 6 serves as a relief margin, and the
second bulb 29 is elastically displaced (diameter
expansion) outward in the pipe diameter direction to
escape from the projection 24. Thus, the spigot 15 can be
inserted into the socket 13 with an even smaller
insertion force (joining force).
[0047]
If hydraulic pressure is applied in the pipes 12 and
14 joined to each other, as shown in FIG. 1, push-out
force F1 is applied by the hydraulic pressure to push out
the bulb part 2 7 from the inner side towards the opening
side of the socket 13. On the other hand, the first
sealing portion 35 is not aligned with the second sealing

portion 36 in the pipe axial direction, so that the bulb
part 27 can be prevented from being pushed out from the
inner side to the opening side of the socket 13 by the
push-out force F1. In particular, as the amount of
misalignment (A) between the first sealing portion 35 and
the second sealing portion 36 in the pipe axial direction
in FIG. 1 increases, the bulb part 27 can be prevented
from being pushed out by larger push-out force Fl. Thus,
the sealing properties between the socket 13 and the
spigot 15 are improved.
[0048]
Since the diameter of traverse section of the second
bulb 29 (= 2 x r2) is larger than the space S in the pipe
diameter direction between the inner circumferential
surface of the projection 20 of the socket 13 and the
outer peripheral surface of the spigot 15, even if the
bulb part 27 is pushed out by the push-out force Fl, the
second bulb 2 9 hardly passes through the space S. Thus,
the bulb part 27 can be prevented from being pushed out
from the inner side to the opening side of the socket 13.
[0049]
Moreover, hydraulic pressure is applied also to the
gap 37, push-out force F2 is applied towards the pipe
center onto the second bulb 29. Thus, the second sealing
portion 36 of the second bulb 29 is pressed hard against
the outer peripheral surface of the spigot 15, so that
the sealing properties are further improved between the
socket 13 and the spigot 15.
[0050]
In the configuration of FIG. 1, when the other pipe
12 and the one pipe 14 are joined to each other with the
spigot 15 inserted into the socket 13, the inner
circumferential surface of the first bulb 28 contacts the
outer peripheral surface of the spigot 15. Instead of
this configuration, a gap may be formed between the inner

circumferential surface of the first bulb 28 and the
outer peripheral surface of the spigot 15. In this case,
when the bulb part 2 7 is pushed out by the push-out force
F1, the second bulb 2 9 is pushed so as to enter the gap
between the inner circumferential surface of the first
bulb 28 and the outer peripheral surface of the spigot 15,
so that an improvement in sealing properties between the
socket 13 and the spigot 15 can be expected.
[0051]
In a known technique, a straight pipe having a
prescribed length is cut based on an actually measured
pipe dimension at a construction site to adjust the pipe
length, so that the cut pipe may be connected to another
pipe. Referring to FIGS. 8 to 15, the following will
describe an example in which the pipe joint shown in FIGS.
1 to 7 is applied when the cut pipe is connected to the
other pipe.
[0052]
In FIG. 8, reference numeral 41 denotes a pipe joint
in which a cut pipe 42 is connected to another pipe 43
via a connecting pipe 44. The cut pipe 42 is obtained by
cutting a pipe at a conduit construction site to have a
prescribed length. The cut end of the pipe 42 constitutes
a spigot 46. The other pipe 43 is a standard straight
pipe having a spigot (not shown) at one end and a socket
13 at the other end.
[0053]
The connecting pipe 44 is made of ductile cast iron,
and has a socket 4 7 at one end and a spigot 4 8 at the
other end. The spigot 46 of the cut pipe 42 is inserted
into the socket 47 of the connecting pipe 44, and a
spigot 48 of the connecting pipe 44 is inserted into the
socket 13 of the other pipe 43. Onto the cut end of the
spigot 46 of the cut pipe 42, an annular anticorrosive

material 4 9 which is made of, for example, rubber with
water-tightness is attached.
[0054]
The socket 47 of the connecting pipe 44 includes a
detachment preventive mechanism 5 0 for preventing the
socket 47 and the spigot 46 of the cut pipe 42 from being
detached from each other and a sealing material 25. The
socket 13 of the other pipe 43 includes a similar sealing
material 25 and a lock ring 22.
[0055]
As shown in FIGS. 9 and 10, the detachment preventive
mechanism 50 has a plurality of retaining members 51
disposed in the circumferential direction of the socket
47 and a wedging mechanism 53. The retaining members 51
can cut into the outer peripheral surface of the spigot
4 6 of the cut pipe 42 and move in the pipe diameter
direction, and the wedging mechanism 53 causes the
retaining members 51 to cut in and move towards an inward
52 side in the pipe diameter direction when the spigot 46
and the socket 4 7 are relatively moving in a detachment
direction.
[0056]
A plurality of retaining recesses 54 are formed at
intervals in the circumferential direction on the inner
circumferential surface of the socket 47 of the
connecting pipe 44. The retaining recesses 54 open
towards the inward 52 in the pipe diameter direction. The
retaining members 51 are fitted in the retaining recesses
54 so as to cut in and move towards the inward 52 in the
pipe diameter direction. Edge cutting-in projections 55
are formed on the inner surfaces of the retaining members
51.
[0057]
The wedging mechanism 53 has a receiving surface 57
formed on the outer surface of the retaining member 51

and a press bolt 58 for pressing the retaining member 51
towards the inward 52 in the pipe diameter direction via
the receiving surface 57. The receiving surface 57 is
inclined outward in the pipe diameter direction as the
receiving surface 57 is closer to the inner side of the
socket 47. The press bolt 58 is screwed with a screw hole
59 penetrating the inner and outer sides of the socket 47,
and is inclined in an orthogonal direction to the
receiving surface 57 with a distal end in contact with
the receiving surface 57.
[0058]
The configuration of the socket 47 of the connecting
pipe 44 for attaching the sealing material 25 is the same
as that in the pipe joint of FIGS. 1 to 7.
[0059]
The joint structure of the cut pipe 42 and the other
pipe 43 including the configuration of the sealing
material 25 is the same as that in the pipe joint of FIGS.
1 to 7.
[0060]
In order to connect the cut pipe 42 to the other pipe
43 via the connecting pipe 44, as shown in FIG. 11, the
sealing material 25 is attached inside the socket 47 of
the connection pipe 44.
[0061]
After that, the spigot 46 of the cut pipe 42 is
inserted into the socket 47. At this point, as shown in
FIG. 12, the distal end of the spigot 46 is inserted to
the inward side of a first bulb 2 8 and is brought into
contact with a second bulb 29 to push the second bulb 29
in the insertion direction. Thus, as shown in FIG. 13,
the second bulb 29 is elastically expanded (diameter
expansion) in the pipe diameter direction, so that a gap
is formed across the periphery between the outer
periphery of the expanded second bulb 2 9 and the bottom

surface of a recess 18. Then, as shown in FIG. 14, the
spigot 46 is further inserted into the socket 47, so that
the cut pipe 42 and the connecting pipe 44 are connected
to each other.
[0062]
Subsequently, as shown in FIG. 9, the press bolts 58
are tightened up and the retaining members 51 are pressed
towards the inward 52 in the pipe diameter direction, so
that the cutting-in projections 55 of the retaining
members 51 cut into the outer peripheral surface of the
spigot 46.
[0063]
The process of joining the spigot 48 of the
connecting pipe 44 to the socket 13 of the other pipe 43
is the same as that in the pipe joint of FIGS. 1 to 7.
[0064]
A conduit including a pipe joint having such a
configuration is buried in the ground in many cases. When
earthquake deformation causes a detachment force (removal
force) to be applied to the pipe joint 41, and the
connecting pipe 44 and the other pipe 43 are being
detached and moved relatively from each other, a
projection 24 of the spigot 48 is engaged with the lock
ring 22 from the socket inner side, so that the spigot 48
and the socket 13 are largely prevented from being
detached and moved from each other.
[0065]
Further, when the detachment force is applied to
relatively detach and move the cut pipe 42 and the
connecting pipe 44 from each other, the wedging mechanism
53 moves the retaining members 51 towards the inward 52
side in the pipe diameter direction. Thus, the cutting-in
projections 55 cut into the outer peripheral surface of
the spigot 46 of the cut pipe 42, so that the connection

between the spigot 46 and the socket 47 is forcibly
maintained.
[0066]
The cut end surface of the spigot 46 of the cut pipe
42 is not coated but the anticorrosive material 49 is
attached to the cut pipe 42. Thus, the cut end surface
can be prevented from being corroded.
[0067]
The detachment preventive structure of the other pipe
43 and the connecting pipe 44 and the detachment
preventive structure of the connecting pipe 44 and the
cut pipe 42 may be any structure in addition to the
above-described structure.
[0068]
FIG. 15 is a modification example of the pipe joint
shown in FIGS. 8 to 14.
[0069]
In FIG. 15, a detachment preventive mechanism 60 is
provided on an annular detachment preventive ring 61
which is externally fitted across a spigot 46 of a cut
pipe 42 and a portion beyond a socket 47 of a connecting
pipe 44. Similarly to the pipe joint of FIGS. 8 to 14,
the detachment preventive mechanism 60 has a plurality of
retaining members 51 and wedging mechanisms 53. A
plurality of retaining recesses 54 are formed in the
inner circumference of one end of the detachment
preventive ring 61 in the pipe axial direction.
[0070]
On the other end of the detachment preventive ring 61
in the pipe axial direction, a fixing mechanism 62 for
fixing the detachment preventive ring 61 on the outer
periphery of the socket 47 of the connecting pipe 44 is
provided. The fixing mechanism 62 has a groove 63 formed
over the inner circumference of the detachment preventive
ring 61, a fixed ring 64 fitted into the groove 63, and a

plurality of fixing bolts 65 for pressing the fixed ring
64 towards inward 52 in the pipe diameter direction.
[0071]
The fixed ring 64 is a metal ring singularly divided
in the circumferential direction, and is fitted onto the
socket 47 of the connecting pipe 44. The fixing bolts 65
are provided at intervals in the circumferential
direction of the fixed ring 64.
[0072]
In such a configuration, during piping construction,
the detachment preventive ring 61 is fitted onto the
connecting pipe 44 from the opening side of the socket 47
with the fixed ring 64 fitted into the groove 63, and the
fixing bolts 65 are tightened up to press the fixed ring
64 towards the inward 52 in the pipe diameter direction.
Thus, the fixed ring 64 is pressed against the outer
peripheral surface of the neck of the socket 47 while
being engaged with the neck of the socket 47 of the
connecting pipe 44, so that the detachment preventive
ring 61 is fixed on the outer periphery of the connecting
pipe 44.
[0073]
Next, the retaining members 51 are fitted into the
retaining recesses 54. In this state, the spigot 46 of
the cut pipe 42 is inserted into the socket 47 of the
connecting pipe 44, and then a press bolt 58 is tightened
up to press the retaining member 51 towards the inward 52
in the pipe diameter direction. Thus, cutting-in
projections 55 cut into the outer peripheral surface of
the spigot 4 6 of the cut pipe 42.
[0074]
With this configuration, when earthquake deformation
causes a detachment force to be applied to the pipe joint,
and the cut pipe 42 and the connecting pipe 44 are
relatively detached and moved from each other, the

wedging mechanisms 53 cause the retaining members 51 to
cut in and move towards the inward 52 side in the pipe
diameter direction, and the cutting-in projections 55 cut
into the outer peripheral surface of the spigot 46. Thus,
the connected state of the spigot 46 of the cut pipe 42
and the socket 47 of the connecting pipe 44 is forcibly
maintained.
[0075]
FIGS. 16 and 17 show the cross-sectional structure of
a pipe joint of a mechanical type according to the
present invention.
[0076]
In the pipe joint, a socket 72 is formed on an end of
one pipe 71 made of ductile cast iron, and a spigot 74
inserted into the socket 72 is formed on an end of
another pipe 73 made of ductile cast iron, the pipes 71
and 73 being joined to each other. On the inner
circumference of the socket 72, a sealing material
accommodating portion 75 is formed at the opening end of
the socket 72 and a lock ring accommodating groove 76 is
formed closer to the socket inner side than the sealing
material accommodating portion 75. The sealing material
accommodating portion 75 has a tapered surface 75a
reduced in diameter from the opening end towards the
inner side of the socket 72, and a cylindrical surface
75b extended with a constant diameter from the inner end
of the tapered surface 75a towards the inner side of the
socket 72 .
[0077]
In a space where the sealing material accommodating
part 75 is provided, that is, a space between the inner
circumferential surface of the socket 72 and the outer
peripheral surface of the spigot 74 where the sealing
material accommodating part 75 is formed, an annular
sealing material 77 made of rubber is accommodated. The

sealing material 77 is pushed into the inner side of the
socket 72 by an annular-plate-like push ring 78 made of
metal. The push ring 78 is disposed on the outer
periphery of a portion of the spigot 74 not inserted into
the socket 72. Thus, the sealing material 77 is
compressed between the inner circumferential surface of
the socket 72 and the outer peripheral surface of the
spigot 74 to seal the space between the inner
circumferential surface of the socket 72 and the outer
peripheral surface of the spigot 74.
[0078]
The sealing material 77 integrally includes a
circular distal end portion 77a formed at a point serving
as the distal end of the sealing material 77 pushed into
the socket 72, and a base portion 77b having a
trapezoidal cross section. The circular distal end
portion 77a has a circular cross section, and the
trapezoidal cross section of the base portion 77b is thin
at a point connected to the circular distal end portion
77a and is thicker as it is closer to the push ring 78.
[0079]
In the push ring 78, a stepped concave 79 is formed,
into which a part of the base portion 77b of the sealing
material 77 is fitted, for preventing the part of the
base portion 77b from moving in a diameter expansion
direction (outward in the pipe diameter direction).
Specifically, a portion inward in the pipe diameter
direction on a surface of the plate-like push ring 78
facing the socket 72 is more recessed than a portion
outward in the pipe diameter direction on the surface, so
as to be thinner in the pipe axial direction. The stepped
concave 79 has a concave bottom surface 79a and a stepped
portion 79b formed at the boundary between the bottom
surface 79a and the portion outward in the pipe diameter
direction. The push ring 78 is attached such that the end

of the base portion 77b of the sealing material 77 is
fitted into the stepped concave 79 of the push ring 78.
[0080]
As shown in FIG. 16, in a state in which the sealing
material 77 is attached, a surface of the push ring 78
facing a flange 80 is closely attached to the end surface
of the flange 8 0 formed on the outer periphery of the
socket 72.
[0081]
Specifically, as shown in FIG. 18, through holes 8 0a
extending in the pipe axial direction are formed in the
flange 80. As shown in FIG. 19, through holes 78a
extending in the pipe axial direction are formed also in
the push ring 78. As shown in FIGS. 16 and 17, bolts 81
for fastening the push ring 78 to the flange 80 pass
through the through holes 80a and 78a.
[0082]
As many through holes 78a of the push ring 78 as the
bolts 81 are equally spaced along the circumferential
direction. Meanwhile, the through holes 80a of the flange
80 equally spaced along the circumferential direction are,
for example, multiple times as many as the bolts 81.
[0083]
In the illustration, two fastening bolts 81 are used.
Correspondingly, in the push ring 78, two through holes
78a are formed at 180° intervals along the
circumferential direction. In the flange 80, four through
holes 80a are formed at 90° intervals along the
circumferential direction.
[0084]
In the lock ring accommodating groove 76, an annular
lock ring 82 singularly divided in the circumferential
direction is accommodated. When the lock ring 82 is
accommodated, the lock ring 82 is elastically pressed
against the outer periphery of the spigot 74. A

projection 83 is formed on the outer periphery of the
distal end portion of the spigot 74 so as to be engaged
with the lock ring 82.
[0085]
In the above configuration, when the pipes 71 and 73
are joined to each other, the lock ring 82 has been
accommodated in the accommodating groove 76 of the socket
72, and the push ring 78 and the sealing material 77 have
been fitted onto the spigot 74. The spigot 74 in this
state is inserted into the socket 72. Thus the projection
83 of the spigot 74 elastically pushes out the lock ring
82 and passes through the lock ring 82 to the inner side
of the socket 72. After the projection 83 passes through
the lock ring 82, the lock ring 82 is pressed against the
outer peripheral surface of the spigot 74 by the elastic
force.
[0086]
Thereafter, the sealing material 77 and the push ring
78 having been fitted onto the spigot 74 are disposed at
positions shown in FIG. 17. Specifically, the distal end
portion of the sealing material 77 comes into contact
with the tapered surface 75a of the accommodating portion
75, and the sealing material 77 and the push ring 78 are
disposed at such a position that the push ring 78 is in
contact with the base portion 77b of the sealing material
77. Further, the bolts 81 are made to pass through the
through holes 78a of the push ring 78 and the through
holes 80a of the flange 80 to screw the bolts 81 into
nuts 84.
[0087]
At this point, since the stepped concave 79 is formed
in the push ring 78, the base portion 77b of the sealing
material 77 is fitted into the stepped concave 79 of the
push ring 78 only by bringing the sealing material 77
into contact with the push ring 78. The centers of the

sealing material 77 and push ring 78 are aligned with
each other. Thus the centering of the sealing material 77
can be easily performed.
[0088]
After that, the bolts 81 are tightly screwed into the
nuts 84, thereby moving the push ring 78 towards the
flange 80 to compress and insert the sealing material 77
into the accommodating portion 75. Specifically, first,
as shown in FIG. 17, the circular distal end portion 77a
of the sealing material 77 comes into contact with the
tapered surface 75a of the sealing material accommodating
portion 75, and the sealing material 77 is entirely
accommodated in the accommodating portion 75 while being
guided by the tapered surface 75a.
[0089]
At this point, in response to the force of the push
ring 78 pushing the sealing material 77, a reaction force
is generated to push back the sealing material 77 to the
push ring 78 side, from the tapered surface 75a of the
sealing material accommodating portion 75 in contact with
the circular distal end portion 77a of the sealing
material 77 and the outer peripheral surface of the
spigot 74. The reaction force moves the base portion 7b
of the sealing material 77 along the pressing surface of
the pressing ring 78 in the diameter expansion direction,
with a contact portion of the outer peripheral surface of
the spigot 74 and the inner circumferential surface of
the socket 72 at the circular distal end portion 77a of
the sealing material 77 as the fulcrum of moment.
[0090]
However, since the stepped concave 79 is formed in
the push ring 78 to prevent the base portion 77b of the
sealing material 77 from moving in the diameter expansion
direction, that is, outward in the pipe diameter
direction, the sealing material 77 is prevented from

being moved in the diameter expansion direction. As a
result, the base portion 77b of the sealing material 77
does not move in the diameter expansion direction. Thus
the sealing material 77 is satisfactorily accommodated in
the accommodating portion 75 and is placed in a favorable
compressed state. After that, until the push ring 78 is
sufficiently brought into contact with the flange 80,
that is, the push ring 78 and the flange 80 are in a
metal touch state, the nuts 84 are tightened up.
[0091]
In this configuration, since the sealing material 77
is pressed with the push ring 78 sufficiently brought
into contact with the flange 80 formed on the outer
periphery of the socket 72, the sealing material 77 is
satisfactorily compressed between the socket 72 and the
spigot 74 only by closely attaching the push ring 78 to
the flange 80. This eliminates the need for carefully
controlling intervals between the push ring and the
flange, unlike in a known mechanical pipe joint. Thus,
the push ring 78 can be efficiently attached to the
flange 80 and the sealing material 77 can be easily held
in a favorable compressed state.
[0092]
Further, the push ring 78 is provided only to push
the sealing material 77 into the accommodating portion 75
and hold the pushed sealing material 77 in the
accommodating portion 75 against a fluid pressure in the
socket 72. Compared to the known mechanical pipe joint in
which a bolt causes a compression force to act on a
sealing material to exhibit desired sealing properties,
the present embodiment can reduce the tightening force
and the number of bolts 81.
[0093]
Moreover, the push ring 78 has the stepped concave 79,
so that the sealing material 77 can be satisfactorily

held in the accommodating portion 75 without moving in
the diameter expansion direction when the push ring 78
presses the sealing material 77. Thus, even if the
circular distal end portion 77a of the sealing material
77 has a larger cross section than that in the known pipe
joint, the sealing material 77 can be inserted into the
accommodating portion 75 without any difficulties. With
this configuration, after the sealing material 77 is once
accommodated in the accommodating portion 75, the
circular distal end portion 77a of the compressed sealing
material 77 receives a relatively large force to adhere
tightly to the cylindrical surface 75b of the sealing
material accommodating portion 75 and the outer
peripheral surface of the spigot 74. In other words,
after the push ring 78 is moved until the push ring 78
comes into close contact with the flange 80, it is not
necessary to constantly apply a high specific pressure to
the sealing material 77 by the push ring 78. Thus, even
in the case where the nuts 84 are loosened, the sealing
properties of the sealing material 77 can be favorably
maintained.
[0094]
In the illustration, in the flange 80 formed on the
outer periphery of the socket 72, the through holes 80a
twice as many as the bolts 81 actually used are formed.
Thus, even in the case where the pipe 71 having the
socket 72 is a deformed pipe buried in a predetermined
orientation in the ground, the bolts 81 may be inserted
into the through holes 80a of the socket 72 not
positioned at the bottom of the pipe 71.
[0095]
Specifically, when only two through holes 80a of the
flange 80 of the socket 72 as many as the bolts 81 are
formed, the through holes 80a may be forced to be
arranged at the upper portion (pipe top) and the lower

portion (pipe bottom) of the flange 80. In such a case,
the bolts 81 have to pass through the through holes 8 0a
and 78a at the pipe bottom serving as the ground contact
area, and the nuts 84 have to be tightened up, thereby
disadvantageously involving much time and effort. On the
other hand, in the illustration, even in similar
conditions, the through hole 8 0a in the side portion of
the flange 80 may be selected to have the bolt 81 placed
into the through hole 80a. Specifically, the bolts 81 can
be placed away from the bottom of the pipe 71 and the
bolts 81 can be efficiently tightened up.
[0096]
The number of bolts 81 is not limited to two as in
the illustration, but the same configuration may be
adopted even when the number of bolts 81 is at least
three. In such a case, the number of through holes 78a
formed in the push ring 78 corresponds to the number of
bolts 81, and through holes 80a twice (or an integer at
least three times is possible) as many as the through
holes 78a may be formed in the flange 80.
[0097]
Since the push ring 78 can freely rotate about the
axis, the through holes 78a as many as the bolts 81 have
only to be formed.
[0098]
In contrast, the through holes 8 0a as many as the
bolts 81 (the through holes 78a of the push ring 78) may
be formed in the flange 80. In addition, a sealing
material having a circular distal end portion 77a which
is not as large as that in the illustration may be used
as in the known pipe joint. Thus, in the pipe joint
having the known structure, only a push ring 78 is
changed to the plate-like push ring having the stepped
concave 79 as in the illustration, so that existing

products may be used for parts other than the push ring
78.
[0099]
As shown in FIGS. 16 and 17, the stepped concave 79
is formed only on the surface of the push ring 78 facing
the socket 72. However, in addition to this, as shown in
FIG. 20, a stepped concave 79 may be formed also on a
surface opposed to the surface of the push ring 78 facing
the socket 72. Specifically, stepped concaves 79 may be
provided on two surfaces of the plate-like push ring 78.
[0100]
In the configuration in which the stepped concaves 79
are provided on the two surfaces of the plate-like push
ring 78, when the push ring 78 is fitted onto a spigot 74
beforehand, a sealing material 77 is reliably fitted into
the stepped concave 79 in joining the pipes, no matter
which one of the two surfaces of the push ring 78 the
socket 72 faces. Regardless of the orientation of the
surface of the push ring 78, nuts 84 can be tightened up
until the push ring 78 is reliably brought into close
contact with a flange 80.
[0101]
Therefore, since the stepped concaves 79 are formed
on the two surfaces of the push ring 78, when the push
ring 78 is fitted onto the spigot 74, an operator does
not have to worry about misorienting the surfaces of the
push ring. Thus, operation errors can be avoided and the
confirmation of orientation of the surfaces can be
omitted, so that the operation efficiency can be improved.
[0102]
FIGS. 21 to 24 show a modification example of the
pipe joint according to the present invention.
[0103]
As shown in FIGS. 21 and 22, a push ring 78 has a
center hole portion 86 formed so as to penetrate the push

ring, a plurality of through holes 78a formed in the
circumferential direction for allowing bolts 81 to pass
through the through holes 78a, and joint surfaces 87 in
contact with the opening end surface of a socket 72. The
inner diameter of the center hole portion 86 of the push
ring 78 is set larger by a predetermined dimension than
the outer diameter of a spigot 74.
[0104]
On two surfaces of the push ring 78 along the pipe
axial direction, annular stepped concaves 79 are formed.
The end of a base portion 77b of a sealing material 77 is
fitted into the stepped concave 79. The concave 79 has a
bottom surface 79a and a constraint surface 79c formed in
the vicinity of the bottom surface 79a.
[0105]
Reference numeral 88 denotes a centering mechanism.
The centering mechanism 88 has the constraint surface 79c
of the stepped concave 79 of the push ring 78 and a
tapered surface 77c formed over the outer peripheral edge
of the base portion 77b of the sealing material 77.
[0106]
The constraint surface 79c of the concave 79 is
tapered such that the diameter of the constraint surface
is gradually expanded towards the socket 72. The tapered
surface 77c of the sealing material 77 is formed along
the tapered portion of the constraint surface 79c.
Specifically, the tapered surface 77c of the sealing
material 77 is formed such that the diameter of the
tapered surface 77c is gradually expanded towards a
circular distal end portion.
[0107]
Inclination angle α of the constraint surface 79c and
inclination angle β of the tapered surface 77c with
respect to the pipe diameter direction are the same and,
for example, 60°. The concave bottom surface 79a of the

push ring 78 and the end surface of the base portion 77b
of the sealing material 77 are formed in the pipe
diameter direction.
[0108]
In such a configuration, when one pipe 71 and another
pipe 73 are joined to each other, as shown in FIG. 23,
first, a lock ring 82 is fitted into a lock ring
accommodating groove 76 in the socket 72. Further, as in
the illustration, the sealing material 77 and the push
ring 78 are fitted onto the spigot 74, and the distal end
portion of the base portion 77b of the sealing material
77 is fitted into the concave 79 of the push ring 78. In
this state, the spigot 74 is inserted into the socket 72.
[0109]
When a projection 83 of the spigot 74 passes through
the inner circumference of the lock ring 82 towards the
inner side of the socket 72, the bolts 81 are inserted
through the through holes 80a and the through holes 78a.
As shown in FIG. 24, nuts 84 are tightened up to move the
push ring 78 closer to the socket 72. Thus, as shown in
FIG. 21, the sealing material 77 is pushed by the push
ring 78 into a gap between the outer peripheral surface
of the spigot 74 and the inner circumferential surface of
the socket 72, and is accommodated in a sealing material
accommodating portion 75. The nuts 84 are tightened up to
bring the joint surface 87 of the plate-like push ring 78
into contact with the end surface of the socket 72.
[0110]
At this point, the end of the base portion 77b of the
sealing material 77 is constrained in the pipe diameter
direction by the constraint surface 79c of the concave 79.
Thus, the end of the base portion 77b of the sealing
material 77 is prevented from moving (deforming) along
the bottom surface 79a of the concave 79 in the pipe
diameter direction, so that the base portion 77b of the

sealing material 77 is not interposed between the joint
surface 87 of the push ring 78 and the opening end
surface of the socket 72 (effect of preventing the
sealing material 77 from being interposed). In addition,
the joint surface 87 of the push ring 78 is brought into
surface contact with the opening end surface of the
socket 72, so that the sealing material 77 can be
satisfactorily inserted into the accommodating portion 75.
[0111]
In the above-described joining step, as shown in FIG.
23, when the sealing material 77 and the push ring 78 are
fitted onto the spigot 74, the center of the push ring 78
is placed below the pipe axis by the action of gravity.
Thus, a gap 8 9 between the inner circumference of the
center hole portion 8 6 of the push ring 7 8 and the outer
periphery of the spigot 74 is the smallest (= 0) at the
pipe top and the largest at the pipe bottom.
[0112]
In this sate, when the nuts 84 are tightened up to
move the push ring 78 in the pipe axial direction, as
shown in FIG. 24, the constraint surface 79c of the push
ring 78 is guided in contact with the tapered surface 77c
of the sealing material 77 along the pipe diameter
direction. Thus, the push ring 78 gradually rises against
the spigot 74, so that the center of the push ring 78 is
aligned with the pipe axis. That is, the push ring 78 is
automatically centered (effect of automatically centering
the push ring 78). While the centered state is maintained,
as shown in FIG. 21, the one pipe 71 and the other pipe
73 are joined to each other. This saves an operator the
effort of lifting up and moving the push ring 78 in the
pipe diameter direction and centering the push ring 78.
[0113]
As in the illustration, since the stepped concaves 79
are formed on the two surfaces of the push ring 78, when

the pipes 71 and 73 are joined to each other, the push
ring 78 may be fitted onto the spigot 74 in any direction.
[0114]
FIG. 25 shows a modification example of the pipe
joint shown in FIGS. 21 to 24. In the pipe joint shown in
FIGS. 21 to 24, as specifically shown in FIG. 22, the
centering mechanism 88 has the tapered constraint surface
79c formed in the stepped concave 79 of the push ring 78
and the tapered surface 77c formed at the end of the base
portion 77b of the sealing material 77. Instead, in the
modification example of FIG. 25, a sealing material 77
does not have a tapered surface, and a centering
mechanism 88 has only a tapered constraint surface 79c.
[0115]
In this configuration, the nuts 84 are tightened up
to move the push ring 78 in a push direction, so that the
constraint surface 79c of the push ring 78 is brought
into contact with the outer peripheral edge of a base
portion 77b of the sealing material 77 and guided in the
pipe diameter direction.
[0116]
FIGS. 26 to 28 show another modification example of
the pipe joint shown in FIGS. 21 to 24. In the
modification example, a constraint surface 79c has a
straight portion 91 formed in a direction orthogonal to a
bottom surface 79a, and a tapered portion 92 diameter-
expanded towards the socket 72. The straight portion 91
is positioned on the bottom side of a concave 79, and the
tapered portion 92 is positioned on the opening side of
the concave 79. As shown in FIG. 28, the straight portion
91 is fitted into the end of the base portion 77b of the
sealing material 77 having no tapered surface at the
outer peripheral edge of the end of the base portion 77b.
[0117]

In such a configuration, as shown in FIG. 26, when
the nuts 84 are tightened up to move a push ring 78
closer to the socket 72, the tapered portion 92 of the
constraint surface 79c of the push ring 78 is brought
into contact with the peripheral edge of the end of the
base portion 77b of the sealing material 77 and is guided
in the pipe diameter direction. Thus, as shown in FIG. 27,
the push ring 78 gradually rises against the spigot 74,
the center of the push ring 78 is aligned with the pipe
axis, and the push ring 78 is automatically centered.
Further, as shown in FIG. 28, the end of the base portion
77b of the sealing material 77 is fitted into the
straight portion 91 of the constraint surface 79c, and in
this state, the one pipe 71 and the other pipe 73 are
joined to each other.
[0118]
As shown in FIG. 28, the end of the base portion 77b
of the sealing material 77 is fitted into the straight
portion 91 of the constraint surface 79c, so that the
base portion 77b of the sealing material 77 is reliably
constrained by the straight portion 91 of the constraint
surface 79c in the diameter expansion direction. Thus,
the base portion 77b of the sealing material 77 can be
prevented from moving (deforming) along the bottom
surface 79a of the concave 79 in the pipe diameter
direction.
[0119]
FIG. 29 shows still another modification example of
the pipe joint shown in FIGS. 21 to 24. In this
modification example, constraint surfaces 79c of a push
ring 78 are not tapered but straight in the pipe axial
direction. Thus, a centering mechanism 88 includes only a
tapered surface 77c of a sealing material 77.
[0120]

In this configuration, the nuts 84 are tightened up
to move the push ring 78 closer to the socket 72, so that
the corner portion of the constraint surface 79c and a
joint surface 87 of the push ring 78 is brought into
contact with the tapered surface 77c of the sealing
material 77. Thus, the push ring 78 is guided in the pipe
diameter direction.
[0121]
The following will describe the inclination angle a
of the constraint surface 79c and the inclination angle (3
of the tapered surface 77c of the sealing material 77
which are shown in FIG. 22. It is preferable that the
inclination angles a and (3 are set to be 60° as described
above, but the inclination angles may be set in a range
of 50° to 80°.
[0122]
Table 1 shows experimental results obtained by
determining whether the above-described "effect of
preventing the sealing material 77 from being interposed"
is produced and whether the above-described "effect of
automatically centering the push ring 78" is produced
when the inclinations angles α and (3 are changed. As
described above, "the effect of preventing the sealing
material 77 from being interposed" is an effect of
preventing the end of the base portion 77b of the sealing
material 77 from being interposed between the joint
surface 87 of the push ring 78 and the opening end
surface of the socket 72. Further, "the effect of
automatically centering the push ring 78" is an effect of
automatically centering the push ring 78 with respect to
the spigot 74.
[0123]
As shown in Table 1, the inclination angles α and β
are set in a range of 50° to 80°, so that both the effect
of preventing the sealing material 77 from being

interposed and the effect of automatically centering the
push ring 78 are surely exerted.
[0124]
In contrast, in the case where the inclination angles
a and (3 are set less than 50°, the constraint function of
the constraint surface 79c is insufficient for the base
portion 77b of the sealing material 77, so that the base
portion 77b of the sealing material 77 easily slides
along the constraint surface 79c and moves (deforms) in
the diameter expansion direction. Conversely, in the case
where the inclination angles α and β exceed 80°, the push
ring 78 insufficiently rises against the spigot 74, the
center of the push ring 78 is not aligned with the pipe
axis.
[0125]
The inclination angle a of the constraint surface 79c
of the push ring 78 and the inclination angle β of the
tapered surface 77c of the sealing material 77 may be the
same or different from each other within a range of 50°
to 80°.
[0126] [Table 1]


[0127]
In the embodiment of FIGS. 21 to 29, the stepped
concaves 79 are formed on the two surfaces of the plate-
like push ring 78. However, the concave 79 may be formed
on only one of the two surfaces of the plate-like push
ring 78.
[0128]
FIGS. 3 0 to 33 show another embodiment of the present
invention.
[0129]
In the illustration, a stepped concave 79 and a
sealing material 77 do not have a tapered surface.
However, the stepped concave 79 and the sealing material
77 may have a tapered surface.

[0130]
A plurality of spacers 95 are interposed between a
side surface 93 of a push ring 78 and an end surface 94
of a socket 72. As shown in FIGS. 3 0 and 31, the spacers
95 are integrally formed on two surfaces of the plate-
like push ring 78 made of ductile cast-iron. In the
illustration, two spacers 95 are disposed at 180°
intervals along the circumferential direction of the push
ring 78. Two through holes 78a of the push ring 78 are
disposed at 180° intervals along the circumferential
direction of the push ring 78. The spacers 95 and the
through holes 78a are formed in the same positions along
the circumferential direction of the push ring 78. The
spacers 95 are formed closer to the outer side along the
diameter direction of the push ring 78 than the through
holes 78a. The spacers 95 are formed in a truncated
conical shape so as to project from the push ring 78 in
the pipe axial direction as in the illustration. Height M
from the side surface 93 of the push ring 78 to the
distal end portion of the spacer 95 is set constant.
[0131]
In this configuration, when one pipe 71 and another
pipe 73 are joined to each other, as shown in FIG. 32,
after a spigot 74 is inserted into the socket 72, bolts
81 are made to pass through the through holes 78a of the
push ring 78, and nuts 84 are tightened up to move the
push ring 78 closer to the socket 72. Thus, the sealing
material 7 7 is pushed into a gap between the outer
peripheral surface of the spigot 74 and the inner
circumferential surface of the socket 72 by the push ring
78 and is accommodated in an accommodating portion 75.
[0132]
The push ring 78 is moved closer to the socket 72 in
this way, so that the distal ends of the spacers 95 hit
against the end surface 94 of the socket 72. Thus, a gap

96 between the side surface 93 of the push ring 78 and
the end surface 94 of the socket 72 can be accurately and
easily kept at a value equal to the height M of the
spacer 95. As a result, the sealing material 77 can be
prevented from being insufficient in sealing properties
and pushed by an excessive force.
[0133]
Further, the state of the attached sealing material
77 can be visually confirmed through the gap 96. As shown
in FIG. 33, a special thin-plate-like gauge 97 is
inserted into the gap 96, and the distal end of the gauge
97 is brought into contact with the outer peripheral
surface of a base portion 77b of the sealing material 77,
so that a distance in the diameter direction from the
outer peripheral surface of a flange 8 0 of the socket 72
or the outer peripheral surface of the push ring 78 to
the outer peripheral surface of the base portion 77b of
the sealing material 77 can be measured. Thus, the state
of the attached sealing material 77 can be confirmed more
accurately.
[0134]
As in the illustration, since the spacers 95 are
arranged along with the through holes 7 8a in the same
diameter direction and the spacers 95 are positioned near
the through holes 78a, as shown in FIG. 30, when the push
ring 78 is fastened to the flange 80 of the socket 72 by
the bolts 81 and the nuts 84, the tightening force of the
bolts 81 acts in the vicinity of the spacers 95. Thus,
the bending deflection of the push ring 78 in the
thickness direction can be reduced.
[0135]
As shown in FIG. 34, the spacers 95 may be formed
closer to the inner side in the diameter direction of the
push ring 78 than the through holes 78a.
[0136]

As shown in FIGS. 3 5 and 36, the spacers 9 5 may be
displaced from the through holes 78a by a predetermined
angle in the direction of the push ring 78. In the
illustration, the predetermined angle is 90°.
[0137]
In the above-described embodiment, the through holes
78a and the spacers 95 are respectively formed at two
points in the circumferential direction of the push ring
78, but the number of through holes 78a and spacers 95 is
not limited to two. The through holes '78a and the
spacers 95 may be formed at more than two points. The
spacers 95 may be formed on only one of the two surfaces
of the plate-like push ring 78. The number of through
holes 78a and the number of spacers 95 provided on one of
the side surfaces 93 of the push ring 78 may be the same
or different from each other as described above.
[0138]
The spacers 95 may be integrally formed not in the
push ring 78 as described above but in the socket 72 of
the pipe 71 made of ductile cast-iron. Alternatively, the
spacers 95 may be formed on both the side surface 93 of
the push ring 78 and the end surface 94 of the socket 72.
[0139]
As shown in FIGS. 3 7 and 38, the spacers 95 may be
formed in a member separated from the push ring 7 8 and
the socket 72. In the illustration, the spacers 95 are
provided in an annular thin plate member 98. The spacers
95 and the thin plate member 98 may be integrally resin-
molded. In this configuration, the sum of the height of
the spacer 95 and the thickness of the thin plate member
98 is a predetermined dimension M.
[0140]
In this configuration, the thin plate member 98 and
the spacers 95 integrally formed are interposed and held
between the side surface 93 of the push ring 78 and the

end surface 94 of the socket 72. Thus, the gap 96 between
the side surface 93 of the push ring 78 and the end
surface 94 of the socket 72 can be accurately and easily
kept at the predetermined dimension M.
[0141]
In the above-described embodiments, the spacers 95
are formed in a truncated conical shape but may be formed
in any shape. For example, as shown in FIG. 39, the
spacers 95 may be elliptical in the circumferential
direction of the push ring 78 or the socket 72.
[0142]
Even in the embodiment in which the spacers 95 are
used, the stepped concaves 79 of the push ring 78 may be
provided on the two surfaces or one of the two surfaces
of the plate-like push ring 78.
[0143]
FIGS. 4 0 to 44 show still another embodiment of the
present invention. This embodiment is different from the
above-described embodiments in the configuration of a
sealing material 77. FIG. 41 is a cross-sectional view
showing an uncompressed sealing material 77. A base
portion 77b of the sealing material 77 has the same
configuration as that in FIG. 22. In contrast, a circular
distal end portion 77a of the sealing material 77 is
different from that in FIG. 22.
[0144]
An arc portion 101 is formed at the distal end of the
circular distal end portion 77a, and in continuity with
the arc portion 101, a cylindrical portion 104 is formed
which has an outer peripheral surface 102 and an inner
circumferential surface 103 both formed in the pipe axial
direction. In continuity with the cylindrical portion 104,
an arc portion 105 connected to the base portion 77b is
formed. On the outer periphery of the base portion 77b, a
tapered surface 106 is formed, the diameter of which is

gradually reduced towards the circular distal end portion
77a. Reference numeral 107 denotes the end surface of the
base portion 77b.
[0145]
FIG. 42 is a cross-sectional view showing the process
of accommodating the sealing material 77 in an
accommodating portion 75. As shown in FIG. 42, a push
ring 78 is in contact with the end surface 107 of the
base portion 77b and the end of the base portion 77b is
fitted into a stepped concave 79, in a state in which the
circular distal end portion 77a of the sealing material
77 is in contact with a tapered surface 75a of a socket
72. As shown in FIG. 43, the stepped concave 79 has a
tapered portion 92 at inclination angle a. In the example
of FIGS. 40 to 42, the sealing material 77 does not have
a tapered surface, but as shown in FIG. 44, the sealing
material may have a tapered surface 77c at inclination
angle (3.
[0146]
When the sealing material 77 is pushed into the
accommodating portion 75 further than the state of FIG.
42, the sealing material 77 is completely accommodated in
the accommodating portion 75 as shown in FIG. 40. Thus,
the tapered surface 106 of the sealing material 77 is
brought into contact with the tapered surface 75a of the
accommodating portion 75. When the tapered surfaces 106
and 75a contact each other, a spacer 95 of the push ring
78 is metal-touch-joined to an end surface 94 of the
socket 72. Thus, after the tapered surface 106 of the
sealing material 77 is brought into contact with the
tapered surface 75a of the accommodating portion 75, the
tapered surface 106 of the sealing material 77 is further
pressed against the tapered surface 75a of the
accommodating portion 75 to prevent the sealing material
77 from being deformed.

[0147]
A cylindrical surface 75b of the accommodating
portion 75 of the socket 72 and the outer peripheral
surface of a spigot 74 form a space 108. The cylindrical
surface 75b and the outer peripheral surface of the
spigot 74 are arranged in a concentric manner. In the
space 108, the circular distal end portion 77a of the
sealing material 77 is accommodated, and the cylindrical
portion 104 is brought into contact with the cylindrical
surface 75b and the outer peripheral surface of the
spigot 74. The outer peripheral surface 102 and the inner
circumferential surface 103 forming the cylindrical
portion 104 are uniformly compressed while keeping the
concentric state even after the circular distal end
portion 77a is accommodated in the space 108.
[0148]
The outer peripheral surface 102 and the inner
circumferential surface 103 are in surface-contact with
the cylindrical surface 75b and the outer peripheral
surface of the spigot 74 over the periphery and are
uniformly compressed, so that desired sealing properties
are exhibited. The circular distal end portion 77a does
not exhibit sealing properties by receiving a reaction
force against the force of the push ring 78 pressing the
sealing material 77.
[0149]
The following will describe the case where the
sealing material 77 receives a fluid pressure in the pipe.
The circular distal end portion 77a tends to expand in
the pipe diameter direction by the fluid pressure, but
the expansion is limited by the cylindrical surface 75b
of the socket 72 and the outer peripheral surface of the
spigot 74. Thus, the circular distal end portion 77a is
additionally provided with a compression force by the
fluid pressure. The outer peripheral surface 102 and the

inner circumferential surface 103 are in surface-contact
with the cylindrical surface 75b of the socket 72 and the
outer peripheral surface of the spigot 74 over the
periphery while keeping the concentric state even after
the circular distal end portion 77a receives the fluid
pressure in the pipe, and are uniformly compressed with
the compression force added by the fluid pressure in the
pipe. Thus, the sealing properties are sufficiently
exhibited.
[0150]
The following will describe the case where the
circular distal end portion 77a is compressed by the
fluid pressure in the pipe to move towards the opening
side of the socket 72. If the circular distal end portion
77a moves within the length of the cylindrical portion
104 in the pipe axial direction, even after the circular
distal end portion 77a moves, the surface-contact of the
outer peripheral surface 102 and the inner
circumferential surface 103 of the sealing material 77,
the cylindrical surface 75b of the socket 72, and the
outer peripheral surface of the spigot 74 over the
periphery is kept within a certain area along the pipe
axial direction. Thus, the desired sealing properties are
maintained.
[0151]
As described above, the sealing material 77 has the
cylindrical portion 104 in which the outer peripheral
surface 102 is formed concentrically with the cylindrical
surface 75b of the socket 72, and the inner
circumferential surface 103 is formed concentrically with
the outer peripheral surface of the spigot 74. Thus, when
the sealing material 77 is compressed between the socket
72 and the spigot 74, the cylindrical portion 104 is in
surface-contact with the outer peripheral surface of the
spigot 74 and the inner circumferential surface of the

socket 72 over the periphery. As a result, the sealing
material 77 can be uniformly brought into surface-contact
with the socket 72 and the spigot over a wide area to
maintain the sealing properties. Further, even when a
portion of the sealing material 77 exhibiting sealing
properties under a fluid pressure in the pipe moves, the
desired sealing properties are maintained.
[0152]
FIGS. 45 to 49 show a slip-on detachment preventive
pipe joint according to another embodiment.
[0153]
In the pipe joint, between the outer peripheral
surface of a lock ring 22 and the inner circumferential
surface of an accommodating groove 19, a centering member
111 made of rein is disposed for holding and centering
the lock ring 22 before a spigot 15 is inserted into a
socket 13. A tapered surface 112 is formed at the distal
end of a projection 24 of the spigot 15 so as to be
tapered towards the distal end side of the spigot 15. A
tapered surface 113 is formed on the inner
circumferential part of the lock ring 22 on the socket
opening side, so as to expand towards the socket opening
side. When the spigot 15 is inserted into the socket 13,
the tapered surface 112 at the distal end of the
projection 24 of the spigot 15 and the tapered surface
113 of the lock ring 22 are in slidable contact with each
other, thereby elastically expanding the diameter of the
lock ring 22 .
[0154]
As in the illustration, on the inner circumferential
surface of the socket 13, three inner circumferential
projections 114, 115, and 116 are formed in this order
from the opening side towards the inner side of the
socket 13. The three inner circumferential projections
114, 115, and 116 form an accommodating groove for

accommodating a sealing material 25 and the lock ring
accommodating groove 19. The three inner circumferential
projections 114, 115, and 116 are formed to have a larger
inner diameter than the outer diameter of the projection
24 such that the projection 24 of the spigot 15 can be
inserted into the socket 13. More specifically, the inner
circumferential projections 114 and 116 at the opening
part and inner part of the socket are larger in inner
diameter than the inner circumferential projection 115 at
the middle part. In other words, the inner diameter of
the inner circumferential projection 115 at the middle
part is the smallest.
[0155]
With this configuration, the spigot 15 can be swung
about the inner circumferential projection 115 at the
middle part such that the axis of the spigot 15 is bent
and misaligned with the axis of the socket 13. As a
result, the flexibility of connected state of the socket
13 and the spigot 15 is increased. Further, when the
spigot 15 is inserted into the socket 13, the socket 13
and the spigot 15 can be satisfactorily connected to each
other even in a state where the axes of the socket 13 and
the spigot 15 are not accurately aligned with each other,
for example, the axes are bent.
[0156]
However, when the inner circumferential projection
116 on the socket inner side is larger in inner diameter
than the inner circumferential projection 115 at the
middle part, the lock ring 22 may not be prevented from
projecting towards the socket inner side by being pushed
by the projection 24 when the spigot 15 is inserted.
[0157]
In order to address the problem, as shown in FIGS. 45
to 48, a holder 117 and a hold width 118 are integrally
formed in the centering member 111 so that the traverse

section of the holder and the hold width is L-shaped. The
holder 117 is disposed between the inner circumferential
surface of the accommodating groove 19 and the outer
peripheral surface of the lock ring 22 to hold the lock
ring 22 from the outer peripheral side thereof. The hold
width 118 protrudes inward in the pipe diameter direction
from the socket inner side part of the holder 117 and
enters between the inner side surface of the
accommodating groove 19 and the inner side surface of the
lock ring 22, so that the hold width 118 is caught by the
inner side surface of the lock ring 22 when the spigot 15
is inserted into the socket 13. Thus, the lock ring 22 is
prevented from projecting from the accommodating groove
19 towards the inner side of the socket 13.
[0158]
The hold width 118 and the holder 117 are plurally
divided along the circumferential direction, and curved-
plate-like connecting parts 120 are integrally formed on
the outer peripheral surfaces of divided parts 119. The
connecting parts 120 are disposed in arc shape on the
divided parts 119 in an elastically deformable state and
are brought into contact with the inner circumferential
surface of the accommodating groove 19. Further, the
divided parts 119 are connected to each other so as to
move in the pipe diameter direction while elastically
pushing each other inward in the pipe diameter direction.
[0159]
The centering member 111 made of resin is formed of
polypropylene or nylon 6. The overall centering member
111, that is, the holder 117, the hold width 118, and the
connecting parts 120.are integrally formed.
[0160]
In FIGS. 45 to 48, the connecting parts 120 and the
holder 117 are formed with the same width but the present

invention is not limited to this. The connecting parts
120 may be different from the holder 117 in width.
[0161]
As shown in FIG. 4 6 in an enlarged manner, the hold
width 118 of the centering member 111 is formed in such a
dimension that an end 121 of the hold width 118 on the
inner side in the diameter direction protrudes more
inward in the pipe diameter direction than the inner
circumferential part of the inner circumferential
protrusion 116 at the socket inner side while the
centering member 111 is centered in the lock ring
accommodating groove 19.
[0162]
Since the connecting part 120 is smaller in thickness
than the holder 117, the largest outer diameter of the
centering member 111 is almost equal to the inner
diameter of the accommodating groove 19. Specifically,
when the centering member 111 is formed of polypropylene
and nylon 6, it is preferable that the holder 117 is 2 mm
to 5 mm and the connecting part 120 is 0.5 mm to 1.5 mm
in thickness. However, the thicknesses of the holder 117
and the connecting part 12 0 are not limited and may be
any values as long as the lock ring 22 may be
satisfactorily centered by the elasticity of the
connecting part 12 0 and the connecting part 12 0 may be
appropriately bent when the pipes are connected to each
other.
[0163]
In this configuration, the inner circumferential
protrusion 116 on the socket inner side is larger in
inner diameter than the inner circumferential protrusion
115 at the middle part. Thus, the socket 13 and the
spigot 15 can be favorably joined to each other and the
efficiency of joining the socket and the spigot can be
improved even in a state where the pipe axes of the

socket 13 and the spigot 15 are bent. Further, since the
hold width 118 is formed in the centering member 111, the
hold width 118 is caught by the lock ring 22 when the
spigot 15 is inserted, so that the lock ring 22 is
prevented from projecting from the accommodating groove
19 towards the inner side of the socket 13. As a result,
the detachment preventive function can be favorably-
maintained and the reliability can be improved. Since the
end 121 of the hold width 118 on the inner side in the
pipe diameter direction protrudes more inward in the pipe
diameter direction than the inner circumferential
protrusion 116 on the socket inner side while the
centering member 111 is centered, the lock ring 22 can be
prevented more reliably from projecting towards the
socket inner side when the spigot 15 is inserted.
[0164]
The centering member 111 is plurally divided along
the circumferential direction, and the divided parts 119
are elastically pressed by the connecting parts 120
inward in the pipe diameter direction at least when the
diameter of the lock ring 22 is expanded. Thus, the lock
ring 22 can be favorably centered. Since the connecting
parts 12 0 are provided in an elastically deformable
orientation from the outer peripheral surfaces of the
divided parts 119 towards the outside, the connecting
parts 120 do not fit into a divided gap 122 of the
singularly divided lock ring 22 shown in FIG. 49. Thus,
the orientation of the centering member 111 in the
circumferential direction does not need to be controlled
with respect to the lock ring 22, so that the operation
efficiency can be enhanced.
[0165]
Since the connecting parts 120 are formed so as to
extend in arc shape from the outer peripheral surfaces of
the divided parts 119 and have a relatively simple

configuration, the divided parts 119 can be
satisfactorily elastically pressed inward in the pipe
diameter direction, and the lock ring 22 can be favorably
centered.
[0166]
In FIGS. 47 to 49, the number of the holders 117 and
hold widths 118 of the centering member 111 is eight
along the circumferential direction, but the present
invention is not limited to this. The centering member
111 is integrally made of resin, so that the
manufacturing cost can be reduced as compared to a known
centering member made of rubber, but the present
invention is not limited to this.
[0167]
As in the illustration, a portion of the socket 13
closer to the socket inner side than the inner
circumferential protrusion 116 is larger in inner
diameter than the inner circumferential protrusion 116 on
the inner side of the socket 13. In this case, the
projection 24 of the spigot 15 can be preferably swung in
the pipe diameter direction. However, the present
invention is not limited to this configuration, and the
portion of the socket 13 closer to the socket inner side
may be constant up to the inner end of the socket 13 in
the same inner diameter as the inner circumferential
projection 116.
[0168]
The following will describe still another embodiment
of the present invention. A force is not uniformly
applied by a water pressure in a deformed pipe such as a
bent pipe and a T-shaped pipe of a water pipeline. In
order to prevent a water pipeline from being displaced
from a normal position by such a non-uniform force, as
shown in FIG. 52, a cylindrical liner 125 made of metal
is attached between the inner end of a socket 13 and the

distal end portion of a spigot 15, for the purpose of
constraining the expansion and contraction and the
bending of a pipe joint and obtaining predetermined
bending rigidity. The outer diameter and thickness of the
liner 125 are equal to those of the spigot 15.
[0169]
Specifically, an inner circumferential surface 126 is
formed in the pipe axial direction closer to the inner
side of the socket 13 than a lock ring accommodating
groove, on the inner circumference of the socket 13
horizontally provided. A tapered surface 127 is formed
closer to the inner side of the socket than the inner
circumferential surface 126. The tapered surface 127
serves as a guiding surface whose diameter is reduced
towards the inner part of the socket. At a portion
connecting the inner circumferential surface 126 and the
tapered surface 127, a connecting part 128 having an arc-
shaped cross section is formed. The inner circumferential
surface 126 and the tapered surface 127 are smoothly
connected to each other by the connecting part 128. An
inner end surface 129 is formed in the pipe diameter
direction closer to the inner side of the socket than the
tapered surface 127.
[0170]
In this configuration, when the socket 13 and the
spigot 15 are joined to each other, as shown in FIG. 50,
the liner 125 is inserted into the socket 13. Thus, the
liner 125 is placed at the bottom of the inner
circumferential surface 126 with the central axis
parallel to the pipe axial direction.
[0171]
Next, as shown in FIG. 51, when the spigot 15 is
inserted into the socket 13, an end surface 130 of the
spigot 150 is brought into contact with an end surface
131 of the liner 125 on the socket opening side in a non-

concentric state. The liner 125 moves on the inner
circumferential surface 126 towards the inner side of the
socket 13 by being pushed by the spigot 15. Since the
inner circumferential surface 126 is connected to the
tapered surface 127 via the connecting part 128, the
distal end portion of the liner 125 can move smoothly
from the inner circumferential surface 126 to the tapered
surface 127 without falling at the corner portion
connecting the inner circumferential surface 126 and the
tapered surface 127. The liner 125 having the distal end
portion moved to the tapered surface 127 rises against
the tapered surface 127, with a lower portion 132 at the
end of the liner 125 on the socket inner side in contact
with the tapered surface 127.
[0172]
Further, as shown in FIG. 52, the liner 125 is
positioned on the axes of the socket 13 and the spigot 15
while being pushed by the spigot 15 with an end face 133
on the socket inner side in contact with the inner end
surface 129 of the socket 13. The tapered surface 127 is
formed so that the liner 125 can be self-aligned and
positioned on the axes of the socket 13 and the spigot 15
when the end surface 133 of the liner 125 on the socket
inner side is in brought into contact with the inner end
surface 129 of the socket 13.
[0173]
The liner 125 is center-aligned with the axes of the
socket 13 and the spigot 15 with the lower portion 132 at
the end on the socket inner side guided by the tapered
surface 127. Thus, the liner 125 does not need to be
larger in outer diameter and thickness than the spigot 15
for center-alignment, but the outer diameter and
thickness of the liner 125 can be the same as those of
the spigot 15 as described above.
[0174]

FIG. 53 shows a modification example of the pipe
joint shown in FIGS. 50 to 52. In FIG. 53, instead of the
tapered surface 127 of in FIGS. 50 to 52, a guiding
surface 134 having an arc-shaped cross-section is formed
in the socket 13. The guiding surface 134 is formed so as
to be in smooth continuity with the inner circumferential
surface 126 of the socket 13 and have an inner diameter
reduced towards the inner side of the socket 13.
[0175]
Similarly to the pipe joint of FIGS. 50 to 52, the
liner 125 pushed by the spigot 15 can move on the inner
circumferential surface 126 towards the inner side of the
socket 13 and be smoothly transferred from the inner
circumferential 126 onto the guiding surface 134.
[0176]
The lower portion 132 of the liner 125 transferred to
the guiding surface 134 rises against the guiding surface
134. Similarly to the pipe joint of in FIGS. 51 and 52,
the liner 125 is center-aligned with the axes of the
socket 13 and the spigot 15 while being pushed by the
spigot 15 with the end surface 133 in contact with the
inner end surface 12 9 of the socket 13.
[0177]
FIG. 54 shows another modification example of the
pipe joint shown in FIGS. 50 to 52. In FIG. 54, the inner
circumferential surface 126 and the tapered surface 127
are smoothly connected to each other at a connecting
surface 135 having an arc-shaped cross-section, and the
tapered surface 127 and the inner end surface 129 of the
socket are smoothly connected to each other at a
connecting surface 136 having an arc-shaped cross-section.
The tapered surface 127 and the connecting surfaces 135
and 13 6 each have a diameter reduced towards the inner
side of the socket 13. Radius R1 of arc of the connecting

surface 135 is larger than radius R2 of arc of the
connecting surface 136.
[0178]
With this configuration, the liner provided on the
inner circumferential surface 12 6 can smoothly move by-
being pushed by the spigot (not shown). Thus, the liner
can be easily center-aligned with the axes of the socket
13 and the spigot 15.
[0179]
FIGS. 55 to 57 show still another modification
example of the pipe joint of FIGS. 50 to 52. In the
modification example, a liner centering member 13 8 is
provided between the inner circumferential surface 12 6
and the liner 125. The liner centering member 138 leads
the liner 125 to the center portion of the socket 13
along the pipe diameter direction. The liner centering
member 13 8 is formed in a cylindrical shape by using
resin such as nylon 6, and an outer peripheral surface
139 of the liner centering member 138 is provided in
contact with the inner circumferential surface 126 of the
socket 13. As shown in FIG. 57, the liner centering
member 138 includes a plurality of projections 141
integrally formed along the circumferential direction on
the inner circumference of a thin tubular member 140.
Thus, the liner centering member 13 8 is lighter in weight
than in a case where the overall periphery of the liner
centering member 138 is uniform in thickness.
[0180]
The outer peripheral surface 13 9 may be attached to
the inner circumferential surface 126 to fix the liner
centering member 13 8 on the inner circumferential surface
126. The cylindrical liner 125 has an outer peripheral
surface 142 supported by the liner centering member 138.
[0181]

The liner 125 supported by the liner centering member
13 8 is pushed by the spigot 15 to move to the inner side
of the socket 13, so that the lower portion 132 is
brought into contact with the tapered surface 12 7. The
liner 125 rises against the tapered surface 127 with the
lower portion 132 in contact with the tapered surface 127,
and is self-aligned as shown in FIG. 56. Thereafter, the
end surface 133 of the liner 125 hits against the inner
end surface 129 of the socket 13.
[0182]
With this configuration, since the liner 125 is
supported by the centering member 13 8, the moving
distance of the liner 125 in the pipe diameter direction
is shortened during aligning, so that the aligning is
facilitated. The liner 125 moved by being pushed by the
spigot 15 is restricted and prevented from falling by the
centering member 138.
[0183]
The liner 125 can be inserted into the socket 13
after the liner centering member 138 is attached to the
inner circumferential surface 126 of the socket 13, but
the present invention is not limited to this. For example,
after the liner 125 is inserted into the socket 13, the
centering member 138 can be attached by being inserted
into a gap between the liner 125 and the inner
circumferential surface 126.
[0184]
FIG. 58 shows a modification example of the liner
centering member 138. A liner centering member 138 of FIG.
58 is singularly divided such that the liner centering
member 13 8 includes a tubular member 14 0 along the
circumferential direction which is partly cut out.
Reference numeral 148 denotes a singularly divided part.
The liner centering member 13 8 singularly divided in this
way is elastically reduced in diameter and easily

inserted to the inner circumferential surface 12 6 of the
socket 13. When the outer diameter of the liner centering
member 138 is set in such a natural state that the liner
centering member 138 elastically sticks to the inner
circumferential surface 126 of the socket 13, the liner
centering member 13 8 does not need to adhere to the inner
circumferential surface 126 of the socket 13.
[0185]
The liner centering member 138 is not limited to the
above-described configuration. Specifically, the liner
centering member 138 may have, for example, a half-arc-
shaped or less-than-half-arc-shaped cross-section, as
long as the liner centering member 13 8 supports the lower
portion of the liner 125.
[0186]
FIGS. 59 and 60 show still another modification
example of the pipe joint shown in FIGS. 50 to 52. In the
modification example, a thin annular guiding member 145
is provided at the peripheral edge portion of a part of
the liner 125 in contact with the spigot 15.
[0187]
The guiding member 145 integrally has a cylindrical
portion 146 fitted and fixed onto the end of the liner
125 and a tapered portion 147 provided so as to project
from the liner 125. The guiding member 145 may be
composed of, for example, a resin molded article.
[0188]
In this configuration, first, the liner 125 is
provided horizontally on the inner circumferential
surface 126 of the socket 13, as shown in FIG. 59. In
this state, when the spigot 15 is inserted into the
socket 13, the liner 125 is pushed by the spigot 15 to
move to the inner side of the socket 13. The lower
portion 132 on the socket inner side rises against the
tapered surface 127 of the socket 13 and is center-

aligned with the socket 13, and in this state the end
surface 133 of the liner 125 is brought into contact with
the inner end surface 129 of the socket 13.
[0189]
At this point, the distal end portion of the spigot
15 is guided by the tapered surface 147 of the guiding
member 145 to enter the guiding member 145. In other
words, the guiding member 14 5 covers the distal end
portion of the spigot 15. Conversely, due to the entering
of the spigot 15, the end of the liner 125 on the socket
opening side with the guiding member 145 attached thereto
rises against the spigot 15. Thus, the end of the liner
125 on the socket opening side is center-aligned with the
spigot 15, and the end surface 130 of the spigot 15 is
brought into contact with the end surface 131 of the
liner 125.
[0190]
With the above-described configuration, the liner 125
is center-aligned with the socket 13 and the spigot 15.
[0191]
FIGS. 61 to 65 show a mechanical-type detachment
preventive pipe joint according to another embodiment.
[0192]
As shown in FIG. 61, a flange 8 0 is integrally formed
on the outer periphery of the opening part of a socket 72
formed at the end of one pipe 71 made of ductile cast
iron, and a tapered sealing material pressing surface 150
is formed on the inner circumference of the opening part
of the socket 72. The tapered sealing material pressing
surface 15 0 has a diameter expanded gradually towards the
opening end of the opening part of the socket. An annular
sealing material 77 made of rubber is fitted onto a
spigot 74 formed at the end of another pipe 73 made of
ductile cast iron, and the sealing material 77 is

disposed between an outer peripheral surface 151 of the
spigot 74 and the sealing material pressing surface 150.
[0193]
A push ring 152 as an annular member is fitted onto a
part of the spigot 74 outside the socket 72. The push
ring 152 may be made of ductile cast iron as in the pipes
71 and 73 and formed in a continuous annular shape in the
circumferential direction. Alternatively, the push ring
152 may be divided in an appropriate number along the
circumferential direction, and the divided parts may be
joined to each other by a bolt or the like.
[0194]
A flange 153 is formed over multiple points of the
push ring 152 along the circumferential direction. Across
the flange 153 of the push ring 152 and the flange 80 of
the socket 72, a fastening element 154 including a T-head
type bolt 81 and a nut 84 is disposed in the pipe axial
direction. The fastening element 154 provided across
multiple points of the push ring 152 along the
circumferential direction is operated, so that the
sealing material 77 can be pressed against the pressing
surface 150 by a pressing part 155 of the push ring 152.
Thus, the sealing material 77 can be compressed between
the pressing surface 150 and the outer peripheral surface
151 of the spigot 74 to exhibit desired sealing
properties.
[0195]
In addition to the above-described flange 153, a
press claw accommodating portion 156 is formed over other
multiple points of the push ring 152 along the
circumferential direction. An accommodating recess 157 is
formed on the inner circumferential part of the push ring
152 in the press claw accommodating portion 156. In the
accommodating recess 157, a press claw 158 is

accommodated which is formed of ductile cast iron with a
constant length along the circumferential direction.
[0196]
The press claw 158 includes double ridge type claw
portions 159a and 159b formed in the inner
circumferential portion of the press claw 158. The claw
portions 159a and 159b are formed away from each other in
the pipe axial direction. As a result, an inner
circumferential surface 160 is formed between the claw
portions 159a and 159b in a direction parallel to the
pipe axis. A tapered surface 161 is formed in the outer
peripheral portion of the press claw 158. The diameter of
the tapered surface 161 is gradually reduced with
distance from the socket 72. Reference numerals 162 and
163 denote the end surfaces of the press claw 158 along
the pipe axial direction.
[0197]
Reference numeral 164 denotes a press bolt which may
be also made of ductile cast iron. The press bolt 164 is
screwed into the push ring 152 along a direction
orthogonal to the tapered surface 161 of the push claw
158, so that the tapered surface 161 can be pressed
inward along the pipe diameter direction by the distal
end of the press bolt 164.
[0198]
On the outer peripheries of the pipes 71 and 73
including the socket 72 and the spigot 74, an
anticorrosive coating is formed using a Zn-Sn alloy
sprayed coating or Zn-Sn-Mg alloy sprayed coating.
Further, a synthetic resin coating layer is formed on the
outer periphery of the alloy sprayed coating.
[0199]
As shown in FIGS. 61 and 62, an anticorrosive coating
165 is formed using a sprayed coating also in the inner
circumferential portion of the push claw 158, that is,

the claw portions 159a and 159b, the inner
circumferential surface 160, and the inner
circumferential portion of the end surfaces 162 and 163.
As the anticorrosive coating 165, a Zn-Sn alloy sprayed
coating or a Zn-Sn-Mg alloy sprayed coating may be used
similarly to the pipes 71 and 73. Alternatively, as the
anticorrosive coating 165 of the press claw 158, a Zn-Al
alloy sprayed coating may be used. Further, on the
anticorrosive coating 165, a synthetic resin coating is
applied over the outer surface of the press claw 158. In
FIG. 62, reference numeral 166 denotes a synthetic resin
coating layer formed by the application of the synthetic
resin coating. Alternatively, instead of the synthetic
resin coating layer 166, a coating layer 167 may be
formed using heavy coating. The heavy coating includes
powder coating, liquid epoxy coating, and tar epoxy
coating.
[0200]
Alternatively, as shown in FIG. 63, the anticorrosive
coating 165 is formed in the inner circumferential
portion of the press claw 158 using a sprayed coating,
the synthetic resin coating film 166 may be formed on the
anticorrosive coating 165, and the coating layer 167 may
be formed on the outer periphery of the press claw 158
using heavy coating.
[0201]
Further, as shown in FIG. 64, the anticorrosive
coating 165 may be formed over the outer surface of the
press claw 158 using a sprayed coating, and the synthetic
resin coating layer 166 or the coating layer 167 using
heavy coating may be formed over the outer surface of the
anticorrosive coating 165.
[0202]
It is necessary to select such a coating used for
forming the coating layer 167 using heavy coating that

the dried coating layer does not become harder than
necessary. If the coating layer becomes excessively hard,
the coating layer becomes brittle accordingly, so that
peeling off of the coating layer may occur when a large
removal force is applied on the pipe joint, thereby
remarkably decreasing the corrosion resistance.
[0203]
The sprayed coatings formed on the press claw 158 and
the pipes 71 and 73 will be specifically described.
[0204]
First, the Zn-Sn alloy sprayed coating will be
described. It is preferable that the Zn-Sn alloy sprayed
coating contains Sn of over 1 mass-% but less than 50
mass-% and Zn of the balance.
[0205]
Since the alloy sprayed coating is obtained by adding
Sn to Zn which is the essential component, the
anticorrosive performance can be improved compared to a
sprayed coating using only Zn. The anticorrosive
performance may be about the same as Zn-15Al (Zn: 85
mass-%, Al: 15 mass-%). In a case where the content of Sn
is not more than 1 mass-% or at least 50 mass-%, the
anticorrosive performance cannot be actually improved by
the addition of Sn.
[0206]
The Zn-Sn alloy containing soft Sn has an advantage
in that a Zn-Sn alloy wire can be easily made as a
material for spraying. Further, the alloy sprayed coating
containing only Zn and Sn does not cause hygienic
problems even when water supply conduits are constructed
by the pipes 71 and 73.
[0207]
Next, the Zn-Sn-Mg alloy sprayed coating will be
described. It is preferable that the sprayed coating
contains Sn of over 1 mass-% but less than 50 mass-%, Mg

of over 0.01 mass-% but less than 5 mass-%, and Zn of the
balance.
[0208]
Also in this case, the anticorrosive performance can
be improved compared to the sprayed coating using only Zn.
The anticorrosive performance can be the same as or
greater than Zn-15A1 (Zn: 85 mass-%, Al: 15 mass-%).
[0209]
In a case where the content of Sn is not more than 1
mass-% and/or the content of Mg is not more than 0.01
mass-%, the anticorrosive performance cannot be actually
improved by the addition of Sn and Mg. Also in a case
where the content of Sn is equal to or more than 50 mass-
% and/or the content of Mg is equal to or more than 5
mass-%, the anticorrosive performance cannot be actually
improved by the addition of Sn and Mg.
[0210]
The Zn-Sn-Mg alloy also has an advantage in that a
wire can be easily made and hygienic problems are not
caused, as in the Zn-Sn alloy sprayed coating.
[0211]
Next, the Zn-Al alloy sprayed coating will be
described. As shown in FIG. 61, the press claw 158
provided closer to the outer side of the socket 72 than
the sealing material 77 does not contact water in the
pipe. Thus, the press claw 158 does not cause any
hygienic problems even when the Zn-Al alloy sprayed
coating is formed.
[0212]
It is preferable that the Zn-Al alloy sprayed coating
contains Al of over 1 mass-% but less than 3 0 mass-% and
Zn of the balance. Especially, the above-described Zn-15
Al (Zn: 85 mass-%, Al: 15 mass-%) can be preferably used.
In a case where the content of Al is equal to or less
than 1 mass-% or equal to or more than 30 mass-%, the

anticorrosive performance cannot be actually improved by
the addition of Al.
[0213]
The above-described alloy sprayed coatings may
contain at least any one of Ti, Co, Ni, and P. That is,
the alloy sprayed coatings may contain any one or two to
four of Ti, Co, Ni, and P. It is preferable that the
contents of the elements are each at least 0.001 mass-%
but not more than 3 mass-%. If these elements are
contained in addition to Sn, Sn-Mg, and Al, the amount of
Zn is reduced accordingly.
[0214]
By containing these elements in the alloy sprayed
coatings, the anticorrosive performance can be improved.
However, in a case where the contents of the elements are
less than 0.001 mass-%, the anticorrosive performance
cannot be actually improved by the addition of the
elements. Also in a case where the contents of the
elements exceed 3 mass-%, the anticorrosive performance
cannot be actually improved by the addition of the
elements.
[0215]
Similarly, since the contents of the elements are low,
an alloy wire can be made without any difficulties and
hygienic problems are not caused.
[0216]
The alloy sprayed coatings may be porous but the
anticorrosive performance can be further improved by
sealing the pores.
[0217]
Next, a method of forming an alloy sprayed coating
will be described. As a method for forming an alloy
sprayed coating on the surfaces of the pipes 71 and 73
and a method for forming an alloy sprayed coating on the
press claw 158, known spraying methods can be adopted.

Specifically, the known spraying methods include a method
of performing arc spraying using a Zn-Sn wire, a Zn-Sn-Mg
wire, a Zn-Al wire (only when an alloy spraying coating
is formed on the press claw 158), or a wire obtained by
adding at least any one of Ti, Co, Ni, and P to the alloy,
and a method of performing spraying using alloy powder
instead of a wire.
[0218]
Instead, the Zn-Sn alloy sprayed coating can be
obtained by performing arc spraying using a Zn-Sn wire or
a wire obtained by adding at least any one of Ti, Co, Ni,
and P to Zn-Sn alloy as a first wire, and a Zn wire as a
second wire. Similarly, the Zn-Sn-Mg alloy sprayed
coating can be obtained by performing arc spraying using
a Zn-Sn-Mg wire or a wire obtained by adding at least any
one of Ti, Co, Ni, and P to the Zn-Sn-Mg alloy as a first
wire, and a Zn wire as a second wire. The same applies to
the Zn-Al alloy sprayed coating.
[0219]
For example, in order to obtain an alloy sprayed
coating containing Zn-25Sn-0.5Mg (Sn: 25 mass-%, Mg: 0.5
mass-%, Zn: balance, hereinafter, may be expressed the
same), arc spraying can be performed using a Zn-50Sn-
1.0Mg wire and a Zn wire in equal amounts, instead of
using two Zn-25Sn-0.5Mg wires.
[0220]
Thus, the anticorrosive performance can be further
improved. Moreover, the amount of a Zn-Sn-Mg wire used
can be reduced to half, so that a cost required for
mixing can be reduced.
[0221]
It is not clear why the anticorrosive performance can
be further improved by adopting such spraying methods,
but the improvement can be thought to be due to (i) , (ii) ,
and (iii) described below or a synergy effect of them.

[0222]
(i) For example, in a case where arc spraying is
performed using a Zn-Sn-Mg alloy wire and a Zn wire, the
Zn-Sn-Mg alloy and Zn are distributed in the formed
sprayed coating. At this point, since the Zn-Sn-Mg alloy
has a lower potential than the Zn, the Zn-Sn-Mg alloy is
preferentially dissolved out when the Zn-Sn-Mg alloy and
the Zn serve as a sacrificial anode. The dissolved Zn-Sn-
Mg alloy forms, on the surface of the coating, another
coating which is relatively stable. The improvement of
the anticorrosive performance can be thought to be
because the other coating suppresses the consumption and
dissolution of the Zn-Sn-Mg alloy and the Zn.
[0223]
(ii) The improvement of the anticorrosive performance
can be thought to be because the Zn in the coating
physically prevents the dissolution of the Zn-Sn-Mg alloy,
and when the Zn-Sn-Mg alloy is dissolved, the corrosion
product suppresses the dissolution of the Zn.
[0224]
(iii) The present inventors observed that the
porosity of the Zn-25Sn-0.5Mg sprayed coating obtained by
using two Zn-25Sn-0.5Mg wires was about 15%. Meanwhile,
the porosity of the Zn-25Sn-0.5Mg sprayed coating
obtained by using a Zn-50Sn-1.0Mg wire and a Zn wire in
equal amounts was about 12%. That is, since the latter
porosity is lower, the anticorrosive performance can be
considered to be improved. The lower porosity may be
because different wires in hardness were used such that
the Zn-50Sn-1.0Mg wire was softer than the Zn wire.
[0225]
According to the present invention, it is preferable
that a Zn-Sn alloy sprayed coating or a Zn-Sn-Mg alloy
sprayed coating is formed and heated at at least the
eutectic temperature of alloy (198°C) but less than the

melting point. Such heating is performed, so that the
anticorrosive performance can be further improved. This
is presumed to be because heating is performed at a
temperature in excess of the eutectic temperature of the
Zn-Sn alloy or the Zn-Sn-Mg alloy to dissolve only Sn,
thereby filling minute pores generated in the sprayed
coating to prevent electrolytes from entering the coating
when the cast iron pipes are buried in the ground.
[0226]
Therefore, the Sn does not actually dissolve by
heating at a temperature less than the eutectic
temperature, and the above-described effect cannot be
achieved. Conversely, if the heating temperature is not
less than the melting point of the alloy sprayed coating,
the alloy is further oxidized to lose the original
anticorrosive performance.
[0227]
The heating time is not particularly limited but is
preferably 1 second to 60 minutes. When the heating time
is shorter than this range, necessary heating is not
sufficiently performed.
[0228]
As described above, the coating layers 166 and 167
are formed after the alloy sprayed coating is formed.
[0229]
As shown in FIGS. 62 to 64, the coating layer 16 6 or
167 forms a coating layer having high electrical
insulation performance on a part of the press claw 158 on
the outer peripheral portion, that is, the tapered
surface 161. Thus, the press bolt 164 and the press claw
158 are insulated from each other, so that the press bolt
164 and the press claw 158 can be prevented from being
electrically connected to each other to avoid corrosion
due to electrical connection. As described above, when
the coating layer 167 is formed by heavy coating on the

outer periphery of the press claw 158, electrical
insulation can be particularly favorably achieved.
[0230]
In order that the coating layers 166 and 167 may not
be damaged to inhibit the electrical insulation when the
press claw 158 is pressed by the press bolt 164, a sheet
material may be disposed between the press bolt 164 and
the press claw 158. A sheet material made of metal can
reliably prevent the coating layers 166 and 167 from
being damaged. Alternatively, a sheet material made of
resin can achieve insulation between the press bolt 164
and the press claw 158.
[0231]
When the pipes 71 and 73 are joined to each other,
the spigot 74 is inserted into the socket 72 with the
push ring 152 accommodating the press claw 158 and the
sealing material 77 externally fitted. Next, the push
ring 152 is fastened to the socket 72 by the fastening
element 154, so that the pressing part 155 compresses the
sealing material 77 to exhibit desired sealing properties.
After that, when the press bolt 164 is tightened up, the
claw portions 159a and 159b of the press claw 158 cut
into the outer peripheral surface of the spigot 74. Thus,
the spigot 74 is integrated with the socket 72 by the
press claw 158, the press bolt 164, the push ring 152,
and the fastening element 154, to exert a desired
detachment preventive function.
[0232]
When a large removal force is applied between the
socket 72 and the spigot 74 in the event of an earthquake,
the tapered surface 161 causes the claw portions 159a and
159b of the press claw 158 to forcefully cut into the
outer peripheral surface of the spigot 74, thereby
resisting the removal force.
[0233]

In such a case, the distal ends of the claw portions
159a and 159b of the press claw 158 and the inner
circumferential surface 160 may be damaged, but an
anticorrosion effect can be reliably obtained by the
anticorrosive coatings of sprayed coatings formed on the
pipes 71 and 73 and the anticorrosive coating 165 of a
sprayed coating formed on the press claw 158. For example,
when the distal ends of the claw portions 159a and 159b
cut into the outer surface of the spigot 74 with a large
removal force applied, the coating layer on portions into
which the distal ends cut peels off, and then the
portions generally corrode to cause water leakage due to
the perforation corrosion of the pipe wall and inhibit
the desired detachment preventive function. However,
according to the present invention, since anticorrosive
coatings of sprayed coatings are formed on the pipes 71
and 73 and the press claw 158, even when the coating
layer peels off, the anticorrosive coatings impede the
progress of corrosion.
[0234]
In the above description, the anticorrosive coatings
of sprayed coatings are formed on both the pipes 71 and
73 and the press claw 158. According to the present
invention, the anticorrosive coating 165 has only to be
formed on at least the press claw 158. The pipes 71 and
73 may have, for example, the above-described coating
layer formed by heavy coating rather than a sprayed
coating, as long as the coating layer exhibits a desired
anticorrosive performance.
[0235]
On the push ring 152, a highly anticorrosive coating
layer can be formed by powder coating or epoxy resin
coating to prevent the corrosion of the push ring 152. As
a result, it is possible to reduce the amounts of the
anticorrosive coating 165 of a sprayed coating on the

press claw 158 and the anticorrosive coatings of sprayed
coatings on the pipes 71 and 73, serving as a sacrificial
anode for anticorrosion.
[0236]
FIG. 65 shows a modification example of the press
claw. On a press claw 168 of FIG. 65, as on the above-
described press claw 158, an outer peripheral surface 169
is formed which has a semicircular transverse section,
instead of the tapered surface 161. A claw portion 159
has a single ridge.
[0237]
In this case, when a large removal force 170 is
applied between the socket 72 and the spigot 74, the
removal force acts such that the press claw 168 rises up
from the state of FIG. 65. Thus, the claw portion 159
significantly cuts into the spigot 74 to exert a desired
detachment preventive function.
[0238]
Also in this case, on the inner circumferential part
of the press claw 168, that is, on and around the claw
portion 159, an anticorrosive coating 165 of a sprayed
coating is formed to exert the same anticorrosive
function.
[0239]
In the above description, the press claw
accommodating portion 156 and the accommodating recess
157 are formed on the push ring 152 as a separate annular
member from the socket 72. However, instead of this
configuration, the press claw accommodating portion 156
and the accommodating recess 157 may be formed on the
inner circumference closer to the opening side of the
socket 72 than the accommodating portion of the sealing
material 77 on the socket 72, the press claws 158 and 168
may be accommodated in the press claw accommodating
portion 156 and the accommodating recess 157, and the

press bolt 164 may be screwed in from the outer surface
side of the socket 72.
[0240]
As described in Japanese Patent Application Laid-Open
No. 2009-138737 of the present applicant, when a pipe for
a detachment preventive pipe joint having an annular
projection on the outer periphery of the distal end of a
spigot is cut to have a desired length, the socket of
another pipe having a socket-spigot structure is joined
to the end of the cut pipe. An annular projection for
detachment prevention is formed on the outer periphery of
the spigot of the other pipe. When the total length of
the cut pipe and the other pipe is the above-described
desired length, a pipe can be configured which is shorter
than a standard length with the same detachment
preventive function as a pipe having the standard length.
In this case, according to the present invention, the end
of the cut pipe and the socket of the other pipe can be
joined to each other with the detachment preventive
structure having the above-described press claw of the
present invention.
[0241]
Results of a corrosion test actually conducted will
be described.
[0242]
(Experimental Examples 1, 2)
The detachment preventive pipe joint of FIG. 61 was
used which includes the pipes 71 and 73, the push ring
152, the press claw 158, and the press bolt 164 all made
of ductile cast iron. The pipes 71 and 73 had a nominal
diameter D of 75 mm. A Zn-Sn-Mg alloy sprayed coating was
formed with a thickness of about 5 0 µm on the outer
peripheries of the pipes 71 and 73. After filling the
pores of the coating, a synthetic resin coating layer was

formed with a thickness of about 100 µm on the outer
surface of the coating.
[0243]
As shown in FIG. 62, the Zn-Sn-Mg alloy sprayed
coating 165 was formed with a thickness of about 50 µm on
the inner circumferential part of the press claw 158, the
filling of the pores was performed on the coating 165,
and the synthetic resin coating layer 166 was formed with
a thickness of about 100 µm so as to cover the entire
outer surface of the press claw 158 including the alloy
sprayed coating 165 (Experimental Example 1).
[0244]
Further, instead of the synthetic resin coating layer
166 of Experimental Example 1, an epoxy resin powder
coating layer which was the coating layer 167 obtained by
heavy coating was formed with a thickness of about 300 µm,
so as to cover the entire outer surface of the press claw
158 including the sprayed coating 165 (Experimental
Example 2).
[0245]
Electrical insulation was provided between the press
bolt 164 and the press claw 158 by the coating layers 166
and 167 or by interposing an insulating sheet between the
press bolt 164 and the press claw 158 as necessary.
[0246]
In the detachment preventive pipe joints of
Experimental Examples 1 and 2 thus obtained, as described
above, when the pipes 71 and 73 had the diameter D [mm]
and a removal force of 3D [kN] was applied to the joint
portion, the coating layer 166 or 167 obtained by coating
and the sprayed coating 165 peeled off on the claw
portions 159a and 159b of the press claw 158, but
peeling-off was not found on other portions.
[0247]

After the removal force of 3D [kN] was applied in
this way, a cyclic corrosion test (by means of Society of
Automotive Engineers of Japan, Inc. (antifreezing agent
to be tested), JASO M609, 610) was conducted on the pipe
joints of Experimental Examples 1 and 2. Specifically, a
cycle of the following conditions was repeated.
(1) salt spray (two hours, 35 ± 1°C, 5% NaCl
solution)
(2) dry condition (four hours, 60 ± 1°C, 20 to 30 +
5% RH)
(3) wet condition (two hours, 50 + 1°C, > 95% RH)
[0248]
After the test had been continued for four months,
red rust was not observed with the naked eye on the press
claw 158 and the claw portions 159a and 159b, and on the
pipe 71 near the press claw 158 in both of the detachment
preventive pipe joints of Experimental Examples 1 and 2.
[0249] (Experimental Example 3)
Compared to Experimental Example 1, the Zn-Sn-Mg
alloy sprayed coating 165 was formed with a thickness of
about 50 µm on the inner circumferential part of the
press claw 158 as shown in FIG. 63, sealing was performed
on the coating 165, and the synthetic resin coating layer
166 was formed with a thickness of about 100 µm on the
outer surface of the coating 165. Further, on a portion
of the press claw 158 where the coating 165 and the
synthetic resin coating layer 166 were not formed, that
is, the outer peripheral part of the press claw 158, an
epoxy resin powder coating layer was formed as the
coating layer 167 obtained by heavy coating with a
thickness of about 3 00 µm. Other configurations were the
same as those in Experimental Example 1.
[0250]
Under such conditions, similarly to Experimental
Example 1, when a removal force of 3D [kN] was applied to

the joint portion, the coating layer 166 obtained by
coating and the sprayed coating 165 peeled off on the
claw portions 159a and 159b of the press claw 158 but did
not peel off on the other portions. Further, the above-
described cyclic corrosion test was conducted on the pipe
joint with a removal force applied thereto and had been
continued for four months. After that, red rust was not
observed with the naked eye on the press claw 158 and the
claw portions 159a and 159b, and on the pipe 71 near the
press claw 158.
[0251] (Experimental Examples 4 and 5)
Compared to Experimental Example 1, as shown in FIG.
64, the Zn-Sn-Mg alloy sprayed coating 165 was formed
with a thickness of about 50 urn so as to cover the entire
outer surface of the press claw 158, and the filling of
the pores was performed on the coating 165. Other
configurations were the same as those in Experimental
Example 1 (Experimental Example 4).
[0252]
Compared to Experimental Example 2, as shown in FIG.
64, the Zn-Sn-Mg alloy sprayed coating 165 was formed
with a thickness of about 50 urn so as to cover the entire
outer surface of the press claw 158, and sealing was
performed on the coating 165. Other configurations were
the same as those in Experimental Example 2 (Experimental
Example 5).
[0253]
Under such conditions, when a removal force of 3D
[kN] was applied to the joint portion, the coating layer
166 or 167 obtained by coating and the sprayed coating
165 peeled off on the claw portions 159a and 159b of the
press claw 158 but did not peel off in the other portions.
Further, after the above-described corrosion test had
been conducted on the pipe joint with a removal force
applied thereto and continued for four months, red rust

was not observed with the naked eye on the press claw 158
and the claw portions 159a and 159b and on the pipe 71
near the press claw 158.
[0254] (Comparative Examples 1 and 2)
Compared to Experimental Example 1, the press claw 158
did not have an alloy sprayed coating formed thereon but
had only the synthetic resin coating layer 166 formed
with a thickness of about 100 µm thereon. Other
configurations were the same as those in Experimental
Example 1 (Comparative Example 1).
[0255]
Compared to Experimental Example 2, the press claw 158
did not have an alloy sprayed coating formed thereon but
had only an epoxy resin powder coating layer which is the
coating layer 16 7 obtained by heavy coating with a
thickness of about 3 00 urn. Other configurations were the
same as those in Experimental Example 2 (Comparative
Example 2).
[0256]
Under such conditions, in both of Comparative Examples
1 and 2, when a removal force of 3D [kN] was applied to
the joint portion, the coating layer 166 or 167 by
coating peeled off on the claw portions 159a and 159b of
the press claw 158 but did not peel off on the other
portions.
[0257]
However, when the above-described cyclic corrosion
test had been conducted on the pipe joint with a removal
force applied thereto, in Comparative Example 1, red rust
was found on the entire press claw 158 in two weeks after
the beginning of the test, while in Comparative Example 2,
red rust was found on the claw portions 159a and 159b of
the press claw 158 in two weeks after the beginning of
the test.
[0258] (Comparative Example 3)

Compared to Experimental Example 1, a Zn sprayed
coating was formed with a thickness of about 2 0 µm on the
outer peripheries of the pipes 71 and 73, and a synthetic
resin coating layer was formed with a thickness of about
100 urn on the outer surface of the sprayed coating. The
press claw 158 did not have an alloy sprayed coating
formed thereon but had only the synthetic resin coating
layer 166 formed with a thickness of about 100 urn. Other
configurations were the same as those in Experimental
Example 1.
[0259]
Under such conditions, similarly to Experimental
Example 1, when a removal force of 3D [kN] was applied to
the joint portion, the coating layer 166 peeled off on
the claw portions 159a and 159b of the press claw 158 but
did not peel off on the other portions.
[0260]
However, when the above-described cyclic corrosion
test had been conducted on the pipe joint with a removal
force applied thereto, red rust was found on the entire
press claw 158 in a week after the beginning of the test.
[0261]
FIGS. 66 to 79 show still another embodiment of the
present invention.
[0262]
FIG. 66 shows a mechanical-type pipe joint according
to the embodiment. The pipe joint has the same
configuration as that of the pipe joint having a
detachment preventive function or earthquake-proof
function shown in FIGS. 3 0 and 40. The present embodiment
is applicable to the slip-on type pipe joint shown in FIG.
1.
[0263]
In the pipe joint of FIG. 66, an inner circumferential
protrusion 175 is formed between a sealing material

accommodating portion 75 and a lock ring accommodating
groove 76. The inner circumferential protrusion 175
protrudes inward along the pipe diameter direction and is
formed over the periphery of a socket 72 to form the lock
ring accommodating groove 76. As shown in FIGS. 66 and 67,
in a proper position along the circumferential direction
of the inner circumferential protrusion 175, an arc-like
cut-out portion 176 is formed to have the lock ring
accommodating groove 7 6 communicating with the opening
side of the socket 72. The end of a sealing material 77
on the socket inner side is placed between the inner
circumferential protrusion 175 and the opening side of
the socket 72 without contacting the inner
circumferential protrusion 175.
[0264]
As shown in FIG. 67, a lock ring 82 is an annular
member having a divided part 177 at one point in the
circumferential direction. On the inner circumference of
the end of the lock ring 82 on the opening side of the
socket 72, a tapered surface 178 is formed which expands
towards the opening side of the socket 72.
[0265]
A protrusion 83 on the outer periphery of the distal
end portion of a spigot 74 is formed at a predetermined
distance from the distal end surface of the spigot 74. In
other words, a straight pipe portion is formed between
the protrusion 83 and the distal end surface of the
spigot 74. A tapered surface 179 is formed on the outer
periphery of the protrusion 83 on the spigot distal end
side.
[0266]
When a compression force is applied in the pipe axial
direction to the pipe joint due to an earthquake, the
protrusion 83 of the spigot 74 can move from the position
of a lock ring 82 towards an inner end surface 21 of the

socket 72. Further, when a tensile force is applied to
the pipe joint, the protrusion 83 is engaged with the
lock ring 82 from the inner side of the socket 72, so
that the spigot 74 can be reliably prevented from being
detached from the socket 72. Thus, the pipe joint as in
the illustration is provided with an earthquake-proof
function.
[0267]
When the socket 72 of one pipe 71 and the spigot 74 of
another pipe 73 are joined to each other, the lock ring
82 is maintained to elastically have an expanded diameter
such that the protrusion 83 of the spigot 74 can easily
pass through the lock ring 82. Thus, a spacer 180 is used
to maintain the lock ring 82 to elastically have an
expanded diameter. The following will describe the spacer
180.
[0268]
As shown in FIGS. 68 to 74, the spacer 180 is made of
a synthetic resin such as polycarbonate, and integrally
includes a handle 181 and a maintaining portion 182 for
maintaining the diameter of the lock ring 82 in an
expanded state. The maintaining portion 182 can be freely
inserted into or removed from the socket 72 through the
opening of the socket 72, and can be interposed between
two end surfaces 183, 183 in the circumferential
direction of a lock ring constituting member at the
divided part 177, shown in FIGS. 67 and 70, of the
diameter-expanded lock ring 82 accommodated in the lock
ring accommodating groove 76 of FIG. 66. The lock ring 82
is maintained to elastically have an expanded diameter
with the maintaining portion 182 interposed thus. The
spacer 180 can be passed through a gap between the socket
72 and the spigot 74 and be removed out of the socket 72
when the spigot 74 is inserted into the socket 72.
[0269]

The maintaining portion 182 is formed in an arc shape
corresponding to the cut-out portion 176. As shown in
FIGS. 68 to 74, on two side portions of the maintaining
portion 182 along the width direction, that is, the pipe
circumferential direction at the distal end of the
maintaining portion 182, insertion grooves 184 are formed
in the pipe axial direction. The insertion grooves 184
are opened at the distal end portions of the maintaining
portion 182 and the lateral side portions in the width
direction thereof. Thus, the maintaining portion 182
includes a pair of guiding surfaces 185a and 185b facing
each other in the thickness direction, that is, the pipe
diameter direction, regulating surfaces 186 constituted
by the end walls of the insertion grooves 184, and groove
bottom surfaces 187.
[0270]
When the maintaining portion 182 of the spacer 180 is
inserted into the divided part 177 of the lock ring 82,
the two end portions of the constituting member of the
lock ring 82 at the divided part 177 of the lock ring 82
are fitted into the insertion grooves 184, as shown in
FIGS. 69 and 74. When the two end portions of the
constituting member of the lock ring 82 are fitted into
the insertion grooves 184, the regulating surfaces 186
hit against an end surface 188 on the socket opening side
of the lock ring 82 to regulate the further movement of
the spacer 180 as shown in FIG. 74. As shown in FIGS. 70
and 71, when the two end portions of the member at the
divided part 177 of the lock ring 82 are fitted into the
insertion grooves 184, 184 of the spacer 180, the groove
bottom surfaces 187 of the insertion grooves 184 are
brought into surface contact with the end surfaces 183 of
the lock ring 82.
[0271]

The groove bottom surfaces 187, 187 of the insertion
grooves 184, 184 are parallel to each other. Face-to-face
dimension E of the groove bottom surfaces 187, 187 shown
in FIG. 6 9 is set in such a range that the diameter of
the lock ring 82 can be expanded to allow the protrusion
83 of the spigot 74 to smoothly pass through the lock
ring 82, and the lock ring 82 can be elastically reduced
in diameter and be restored to the original state when
the spacer 180 is removed.
[0272]
Thickness T of the maintaining portion 182 of the
spacer 180 is set such that the maintaining portion 182
has a sufficient strength to withstand a tightening force
as a reaction force from the lock ring 82 whose diameter
is elastically expanded by the spacer 180.
[0273]
The handle 181 has an annular grip 190 exposed outside
from the opening of the socket 72, and a connecting
portion 191 connecting the grip 190 and the maintaining
portion 182. As shown in FIG. 75, a distal end portion
192 of the grip 190 in the pipe diameter direction is
located more inward in the pipe diameter direction than
the outer peripheral surface of a flange 80 of the socket
72. The grip 190 is formed like a plate having a hole,
and as shown in FIG. 75, can be placed parallel to the
end surface of the flange 80. Width W1 of the connecting
portion 191 is smaller than width W of the maintaining
portion 182. Thickness T1 of the connecting portion 191
is smaller than the thickness T of the maintaining
portion 182.
[0274]
Reference numeral 193 denotes the linking portion of
the connecting portion 191 and the maintaining portion
182, and the width dimension of the linking portion

gradually increases from the connecting portion 191
towards the diameter-expanded maintaining portion 182.
[0275]
As shown in FIGS. 76 to 78, the maintaining portion
182 of the spacer 180 can pass by the cut-out portion 176
of the inner circumferential protrusion 175 of the socket
72 in the pipe axial direction and enter the lock ring
accommodating groove 76. The spacer 180 integrally has a
displacement preventive portion 194 formed in accordance
with the dimension of the cut-out portion 176 to prevent
the spacer 180 from being displaced in the
circumferential direction of the pipe when the diameter-
expanded maintaining portion 182 enters the lock ring
accommodating groove 76. The displacement preventive
portion 194 protrudes outward in the pipe diameter
direction from the linking portion 193 in the vicinity of
the maintaining portion 182.
[0276]
The operation of joining the socket 72 and the spigot
74 using the spacer 180 having such a configuration will
be described.
[0277]
Before the pipes 71 and 73 separated from each other
are shipped to a piping construction site, as shown in
FIG. 67, the lock ring 82 has been accommodated in the
accommodating groove 76 of the socket 72, and the divided
part 177 of the lock ring 82 along the pipe
circumferential direction has been aligned with the cut-
out portion 176 of the socket 72. As shown in FIG. 79,
the distal end portion of a scissors-like lock ring
diameter expansion member 195 is inserted into the
divided part 177 of the lock ring 82, and the lock ring
diameter expansion member 195 is opened, so that the
inner diameter of the lock ring 82 is expanded to be

larger than the outer diameter of the protrusion 83 of
the spigot 74.
[0278]
In this state, as shown in FIGS. 76 and 77, the
maintaining portion 182 of the spacer 180 is caused to
pass by the cut-out portion 176 of the protrusion 175
from the opening end of the socket 72 and is inserted
into the divided part 177 of the lock ring 82. Thereafter,
the lock ring diameter expansion member 195 of FIG. 79 is
taken off from the lock ring 82. Thus, as shown in FIGS.
70 and 75, the lock ring 82 is maintained to have an
expanded diameter by the spacer 18 0.
[0279]
At this point, as in the illustration, the two end
portions of the lock ring constituting member at the
divided part 177 of the lock ring 82 are inserted into
the insertion grooves 184 of the spacer 180. Thus,
misalignment of the spacer 180 and the lock ring 82 is
prevented in the pipe axial direction and the pipe
diameter direction, so that the diameter-expanded
maintaining portion 182 of the spacer 180 can be set at a
normal position of the divided part 177 of the lock ring
82 without misalignment.
[0280]
Further, since the displacement preventive portion 194
of the spacer 180 is fitted into the cut-out portion 176
of the protrusion 175, the spacer 180 is prevented from
being displaced in the circumferential direction with
respect to the cut-out portion 176.
[0281]
With the spacer 180 set thus to maintain the lock ring
82 in the diameter-expanded state, the pipes 71 and 73
separated from each other are shipped from a
manufacturing facility. While the shipped pipes 71 and 73
are transported to a destination where a pipeline is to

be constructed, since the distal end portion 192 of the
grip 190 of the spacer 180 recedes more inward in the
pipe diameter direction than the outer peripheral surface
of the flange 80 of the socket 72, the spacer 180 can be
prevented from hitting against a foreign matter and being
damaged or falling off.
[0282]
Thereafter, the pipes 71 and 73 are joined to each
other at the piping construction site. At this point, as
shown in FIG. 75, the protrusion 83 of the spigot 74
inserted into the socket 72 passes inside the diameter-
expanded lock ring 82. At this point, the tapered surface
179 of the protrusion 83 and the tapered surface 178 of
the lock ring 82 interact with each other to allow smooth
passage of the protrusion 83.
[0283]
When the protrusion 83 passes inside the lock ring 82
and reaches the inner side of the socket 72 beyond the
lock ring 82, an operator holds the grip 190 of the
spacer 180, pulls the grip 190 out from the opening end
of the socket 72, and pulls the spacer 180 out from the
socket 72 through the gap between the socket 72 and the
spigot 74. At this point, since the insertion grooves 184
have the ends on the inner side of the socket 72 opened
as in the illustration, the spacer 180 can move in the
pull-out direction without any troubles. As a result, as
indicated by the virtual line of FIG. 75 and FIG. 78, the
maintaining portion 182 is removed out from the divided
part 177 of the lock ring 82. Consequently, the diameter-
expanded state of the lock ring 82 is released, and as
shown in FIG. 66, the lock ring 82 is elastically reduced
in diameter and is pressed against the outer periphery of
the spigot 74.
[0284]

After the spacer 18 0 is removed out thus, as shown in
FIG. 66, the sealing material 77 and a push ring 78 are
moved along the outer surface of the spigot 74 to a
predetermined position, and a bolt 81 and a nut 84 are
tightened up. Thus, the push ring 78 presses the sealing
material 77, the sealing material 77 accommodated in the
accommodating portion 75 seals the joint portion, and the
pipes 71 and 73 are joined to each other. The operation
of joining the pipes at the piping construction site is
completed.
[0285]
The cut-out portion 176 can be formed at at least one
position along the circumferential direction of the inner
circumferential protrusion 175 of the socket 72.
[0286]
In the illustration, only the lock ring 82 is
accommodated in the lock ring accommodating groove 76 but
in addition to the lock ring 82, a centering rubber
member 23 of FIG. 1 or a centering member 111 of FIGS. 45
to 49 may be accommodated in the lock ring accommodating
groove 76.

we claim:
[Claim 1]
A pipe joint in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the one pipe and the other pipe being
joined to each other,
the pipe joint comprising:
a fitting groove formed on an inner circumferential
surface of the socket; and
an annular sealing material for sealing a gap between
the socket and the spigot over a periphery,
the sealing material including a heel part fitted
into the fitting groove, and a bulb part interposed
between the inner circumferential surface of the socket
and an outer peripheral surface of the spigot, closer to
an inner side of the socket than the heel part,
the bulb part including a first bulb continuous with
the heel part, a second bulb positioned closer to the
inner side of the socket than the first bulb, and a
narrow part present on a boundary between the first bulb
and the second bulb,
the first bulb having a first sealing portion formed
on an outer peripheral portion of the first bulb, the
first sealing portion being pressed against the inner
circumferential surface of the socket,
the second bulb having a second sealing portion
formed on an inner circumferential portion of the second
bulb, the second sealing portion being pressed against
the outer peripheral surface of the spigot, wherein
the second bulb is inclined from the first bulb
towards a pipe center in a natural state before the
second bulb is provided between the socket and the spigot,
an inner diameter of the second bulb is smaller than
an outer diameter of the spigot in the natural state, and

the second bulb is expansible and contractible in a
pipe diameter direction due to elastic deformation of the
narrow part.
[Claim 2]
The pipe joint according to claim 1, wherein the
first sealing portion is pressed against an inner
circumferential surface of a projection formed closer to
the inner side of the socket than the fitting groove.
[Claim 3]
The pipe joint according to claim 1, wherein the
first bulb is smaller in thickness than the second bulb
in the pipe diameter direction, and a gap is formed
between an outer peripheral surface of the second bulb
and the inner circumferential surface of the socket in
the pipe diameter direction.
[Claim 4]
An annular sealing material used in the pipe joint
according to claim 1,
the sealing material comprising:
a heel part fitted into the fitting groove formed in
the socket; and
a bulb part interposed between the inner
circumferential surface of the socket and the outer
peripheral surface of the spigot, closer to the inner
side of the socket than the heel part,
the bulb part including a first bulb continuous with
the heel part, a second bulb positioned closer to the
inner side of the socket than the first bulb, and a
narrow part present on a boundary between the first bulb
and the second bulb,
the first bulb having a first sealing portion formed
on an outer peripheral portion of the first bulb, the
first sealing portion being pressed against the inner
circumferential surface of the socket,

the second bulb having a second sealing portion
formed on an inner circumferential portion of the second
bulb, the second sealing portion being pressed against
the outer peripheral surface of the spigot, wherein the
second bulb is inclined from the first bulb towards the
pipe center in a natural state before the second bulb is
provided between the socket and the spigot,
an inner diameter of the second bulb is smaller than
the outer diameter of the spigot in the natural state,
and
the second bulb is expansible and contractible in the
pipe diameter direction due to elastic deformation of the
narrow part.
[Claim 5]
The sealing material according to claim 4, wherein an
inner circumferential surface and an outer peripheral
surface of the narrow part form recesses, respectively,
in a circumferential direction.
[Claim 6]
The sealing material according to claim 4, wherein an
annular recess is formed on an outer periphery of a
boundary portion between the heel part and the first bulb.
[Claim 7]
A pipe joining mechanism in which a cut pipe obtained
by cutting a pipe to have a predetermined dimension at a
pipeline construction site and another pipe are connected
to each other via a connecting pipe, wherein at least one
of a first pipe joint for joining the cut pipe and the
connecting pipe and a second pipe joint for joining the
connecting pipe and the other pipe is constituted by the
pipe joint according to claim 1.
[Claim 8]
The pipe joining mechanism according to claim 7,
wherein the first pipe joint and the second pipe joint

each have a structure for preventing pipes from being
detached from each other.
[Claim 9]
A pipe joint in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the pipes being joined to each other,
the pipe joint comprising:
an annular sealing material interposed and compressed
between an inner circumferential surface of the socket
and an outer peripheral surface of the spigot to exhibit
desired sealing properties; and
a push ring fastened to the socket to keep the
sealing material in a compressed state in which the
sealing material is interposed between the inner
circumferential surface of the socket and the outer
peripheral surface of the spigot.
[Claim 10]
The pipe joint according to claim 9, wherein the push
ring fastened to the socket is capable of pushing the
sealing material into a gap between the inner
circumferential surface of the socket and the outer
peripheral surface of the spigot, and an end of the
sealing material is fitted into the push ring to form a
stepped concave for preventing the end of the sealing
material from moving in a diameter expansion direction.
[Claim 11]
The pipe joint according to claim 10, wherein the
push ring is constituted by a plate-like member, and the
stepped concave is formed on one or two surfaces of the
plate-like member.
[Claim 12]
The pipe joint according to claim 9, wherein the push
ring is fastened to the socket in contact with an end
surface of the socket.
[Claim 13]

The pipe joint according to claim 9, wherein a flange
is formed on an outer periphery of an end of the socket,
through holes are formed in the flange and the push ring,
the through holes allowing bolts for fastening the push
ring to the socket to pass through, and the through holes
of the flange of the socket multiple times the bolts are
formed along a circumferential direction of the flange.
[Claim 14]
The pipe joint according to claim 9, wherein the push
ring fastened to the socket is capable of pushing the
sealing material into a gap between the inner
circumferential surface of the socket and the outer
peripheral surface of the spigot, and the pipe joint
further comprises a centering mechanism for guiding the
push ring in a pipe diameter direction such that a center
of the push ring is aligned with a pipe axis when the
push ring pushes the sealing material into the socket.
[Claim 15]
The pipe joint according to claim 14, wherein the
centering mechanism comprises at least one of a first
tapered surface and a second tapered surface, the first
tapered surface being formed on the push ring in contact
with an outer periphery of an end of the sealing material,
the second tapered surface being formed on the outer
periphery of the end of the sealing material in contact
with the push ring.
[Claim 16]
The pipe joint according to claim 15, wherein a
stepped concave is formed on the push ring for preventing
the end of the sealing material fitted into the stepped
concave from moving in a diameter expansion direction,
and the first tapered surface of the centering mechanism
is formed on a peripheral edge of the stepped concave.
[Claim 17]

The pipe joint according to claim 15, wherein the
first tapered surface and the second tapered surface are
inclined with respect to the pipe diameter direction at
50° to 80°.
[Claim 18]
The pipe joint according to claim 15, wherein the
push ring is constituted by a plate-like member, and the
first tapered surface is formed on one or two surfaces of
the plate-like member.
[Claim 19]
The pipe joint according to claim 9, wherein a spacer
for forming a space between the socket and the push ring
is provided between the socket and the push ring fastened
to the socket.
[Claim 20]
The pipe joint according to claim 19, wherein the
spacer is formed on at least one of the socket and the
push ring so as to protrude in a pipe axial direction.
[Claim 21]
The pipe joint according to claim 19, wherein the
spacer is a separate member from the socket and the push
ring and is interposed between the socket and the push
ring fastened to the socket.
[Claim 22]
A pipe joint in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the pipes being joined to each other,
the pipe joint comprising a sealing material
compressed between an outer peripheral surface of the
spigot and an inner circumferential surface of the socket
formed parallel to the outer peripheral surface of the
spigot to exhibit desired sealing properties, wherein
the sealing material includes a cylindrical portion
having an outer peripheral surface formed parallel to the
inner circumferential surface of the socket and an inner

circumferential surface formed parallel to the outer
peripheral surface of the spigot, and
the cylindrical portion is brought into surface
contact with the outer peripheral surface of the spigot
and the inner circumferential surface of the socket when
the sealing material is compressed between the socket and
the spigot.
[Claim 23]
A pipe joint in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the pipes being joined to each other,
the pipe joint comprising:
a lock ring accommodating groove formed on an inner
circumference of the socket;
a lock ring accommodated in the accommodating groove
and singularly divided in a circumferential direction;
an annular centering member disposed between an inner
circumferential surface of the accommodating groove and
an outer peripheral surface of the lock ring, for holding
the lock ring centered with respect to the socket when
the spigot is not inserted into the socket; and
a protrusion which is formed on an outer periphery of
a distal end of the spigot, is capable of elastically
pushing out the lock ring accommodated in the
accommodating groove with the spigot inserted into the
socket in a pipe diameter direction to pass through an
inner circumference side of the lock ring, and is capable
of being engaged with the lock ring from an inner side of
the socket when a detachment force is applied in a pipe
axial direction between the socket and the spigot joined
to each other to prevent the spigot from being detached
from the socket,
the centering member including a plurality of divided
parts in a pipe circumferential direction, and a

connecting part connecting the adjacent divided parts in
the pipe circumferential direction,
the divided part including a holder holding the lock
ring from an outer peripheral side, and a hold width
protruding inward in the diameter direction from a socket
inner side portion of the holder so as to be engaged with
the lock ring in the pipe axial direction, wherein
the connecting part is disposed closer to an outer
peripheral side than the divided parts and is elastically
deformable in the pipe diameter direction in response to
the elastically pushed-out lock ring.
[Claim 24]
The pipe joint according to claim 23, wherein the
connecting part is arc-shaped, and one end and another
end of the arc are connected respectively to the pair of
adjacent divided parts in the pipe circumferential
direction.
[Claim 25]
The pipe joint according to claim 23, wherein an
inner circumferential protrusion for forming the lock
ring accommodating groove is formed closer to the inner
side of the socket than the lock ring accommodating
groove, and in the divided part, the hold width protrudes
more inward in the pipe diameter direction than the inner
circumferential protrusion when the holder holds the lock
ring from the outer peripheral side before the spigot is
inserted into the socket.
[Claim 26]
An annular centering member in a pipe joint in which
a spigot formed at an end of one pipe is inserted into a
socket formed at an end of another pipe, the pipes being
joined to each other, the centering member being disposed
between an inner circumferential surface of a lock ring
accommodating groove formed on an inner circumference of
the socket and an outer peripheral surface of a lock ring

accommodated in the accommodating groove and singularly
divided in a circumferential direction, for holding the
lock ring centered with respect to the socket when the
spigot is not inserted into the socket,
the spigot including a protrusion on an outer
periphery of the spigot, wherein
the protrusion is capable of elastically pushing out
the lock ring accommodated in the accommodating groove
with the spigot inserted into the socket to pass through
an inner circumferential side of the lock ring, and is
capable of being engaged with the lock ring from an inner
side of the socket when a detachment force is applied in
a pipe axial direction between the socket and the spigot
joined to each other to prevent the spigot from being
detached from the socket,
the centering member includes a plurality of divided
parts in a pipe circumferential direction and a
connecting part connecting the adjacent divided parts in
the pipe circumferential direction,
the divided part includes a holder holding the lock
ring from an outer peripheral side, and a hold width
protruding inward in the diameter direction from a socket
inner side portion of the holder so as to be engaged with
the lock ring in the pipe axial direction, and
the connecting part is disposed closer to an outer
peripheral side than the divided parts and is elastically
deformable in the pipe diameter direction in response to
the elastically pushed-out lock ring
[Claim 27]
A pipe joint in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the pipes being joined to each other,
the pipe joint comprising:
a liner pushed into an inner side of the socket by
the spigot and disposed between a distal end surface of

the spigot and an inner end surface of the socket when
the spigot is inserted into the socket; and
a guiding surface formed on an inner surface of the
socket for guiding the liner in a pipe diameter direction
such that an axis of the liner is positioned at an axis
of the socket and the spigot when the liner is pushed
into the inner side of the socket by the spigot.
[Claim 28]
The pipe joint according to claim 27, wherein the
guiding surface is a tapered surface whose diameter is
reduced towards an inner portion of the socket.
[Claim 29]
The pipe joint according to claim 27, wherein the
guiding surface has an arc-like cross-section formed such
that an inner diameter of the socket is reduced towards
an inner portion of the socket.
[Claim 30]
The pipe joint according to claim 27, wherein the
guiding surface includes a tapered surface whose diameter
is reduced towards an inner portion of the socket, and a
surface having an arc-like cross-section formed such that
an inner diameter of the socket is reduced towards an
inner portion of the socket.
[Claim 31]
The pipe joint according to claim 27, further
comprising a liner centering member for supporting the
liner at a center portion of the socket along the pipe
diameter direction.
[Claim 32]
The pipe joint according to claim 27, wherein a
guiding member is provided on the liner, for covering a
distal end portion of the spigot to position the liner
center-aligned with the spigot when the liner is pushed
into the inner side of the socket by the spigot.
[Claim 33]

A pipe joint in which a spigot formed at an end of
one pipe is inserted into a socket formed at an end of
another pipe, the pipes being joined to each other,
the pipe joint comprising:
a press claw disposed on an inner circumferential
portion of the socket, or disposed on an inner
circumferential portion of an annular member fitted onto
a portion of the spigot on an outer side of the socket
and connected to the socket; and
a press bolt for pushing the press claw to fix the
press claw pressed against an outer surface of the spigot
to the spigot, wherein
the press claw is made of an iron material and has an
anticorrosive coating formed on a surface of a portion in
contact with the spigot, and
the anticorrosive coating contains any one of a Zn-Sn
alloy sprayed coating, a Zn-Sn-Mg alloy sprayed coating,
and a Zn-Al alloy sprayed coating.
[Claim 34]
A press claw for a pipe joint in which a spigot
formed at an end of one pipe is inserted into a socket
formed at an end of another pipe, the pipes being joined
to each other,
the press claw is disposed on an inner
circumferential portion of the socket or an inner
circumferential portion of an annular member fitted onto
a portion of the socket on an outer side of the socket
and connected to the socket, and
the press claw is pushed by a distal end portion of a
press bolt to fix the press claw pressed against an outer
surface of the spigot to the spigot, wherein
the press claw is made of an iron material and has an
anticorrosive coating formed on a surface of a portion in
contact with the spigot, and

the anticorrosive coating contains any one of a Zn-Sn
alloy sprayed coating, a Zn-Sn-Mg alloy sprayed coating,
and a Zn-Al alloy sprayed coating.
[Claim 35]
A spacer for a pipe joint in which a spigot formed at
an end of one pipe is inserted into a socket formed at an
end of another pipe, the pipes being joined to each other,
an annular lock ring is accommodated in a lock ring
accommodating groove formed on an inner circumference of
the socket, the lock ring including a divided part in a
circumferential direction and being elastically
expansible in diameter,
a protrusion is formed on an outer periphery of the
spigot, and
the protrusion of the spigot is allowed to pass
through the lock ring having an expanded diameter, and
the diameter-expanded state of the lock ring is released
after the passage of the protrusion,
the spacer being capable of being inserted into and
removed out from the divided part of the lock ring and
maintaining the lock ring in a diameter-expanded state
when the spacer is inserted into the divided part,
the spacer comprising:
a maintaining portion for maintaining the diameter of
the lock ring in an expanded state being capable of being
inserted into and removed out from a gap between two ends
of the lock ring along the circumferential direction at
the divided part, and being interposed between the two
ends when the maintaining portion is inserted; and
a handle reaching from the maintaining portion
outside the socket beyond a socket opening portion when
the maintaining portion is interposed between the two
ends of the lock ring, wherein
the spacer is capable of being removed out from the
gap between the two ends of the lock ring at the divided

part after the spigot is inserted into the socket,
passing through a space between the socket and the spigot
and being collected outside the socket beyond the socket
opening portion,
the spacer further comprises insertion grooves on two
side portions of the maintaining portion,
the two ends of the lock ring can be fitted into the
insertion grooves when the maintaining portion is
inserted into the gap between the two ends of the lock
ring at the divided part, and
the maintaining portion is capable of being detached
in a removal direction from the two ends of the lock ring
when the maintaining portion moves to be removed out from
the gap between the two ends of the lock ring at the
divided part.
[Claim 36]
The spacer for the pipe joint according to claim 35,
wherein the insertion grooves have a regulating surface
capable of regulating movement of the spacer in an
insertion direction by being brought into contact with an
end of the lock ring on a socket opening side.
[Claim 37]
The spacer for the pipe joint according to claim 35,
wherein the insertion grooves are opened at distal end
portions and lateral side portions of the maintaining
portion.
[Claim 38]
The spacer for the pipe joint according to claim 35,
wherein
an inner circumferential protrusion for forming the
lock ring accommodating groove is formed closer to an
opening side of the socket than the lock ring
accommodating groove,
a cut-out portion is formed on the inner
circumferential protrusion,

the cut-out portion allows the lock ring
accommodating groove to communicate with a portion closer
to the opening side of the socket than the lock ring
accommodating groove, and allows the maintaining portion
of the spacer to pass by, and
the spacer includes a displacement preventive portion
capable of preventing the spacer from being displaced in
a circumferential direction of the pipe by being fitted
into the cut-out portion.
[Claim 39]
A pipe comprising a socket formed at an end thereof
for a pipe joint in which a spigot formed at an end of
another pipe is inserted into the socket, wherein
an annular lock ring is accommodated in a lock ring
accommodating groove formed on an inner circumference of
the socket, the lock ring including a divided part in a
circumferential direction and being elastically
expansible in diameter,
the spacer for the pipe joint according to claim 35
is attached to the socket,
the maintaining portion of the spacer is interposed
between two ends of the lock ring at the divided part in
the circumferential direction, and
the handle of the spacer is exposed outside an
opening portion of the socket.

An annular sealing material seals a pipe joint
between a socket and a spigot. The sealing material
includes a bulb part which is composed of a first bulb, a
second bulb located closer to the inner side of the
socket than the first bulb, and a narrow part present
between the first and second bulbs. The first bulb is
pressed against the inner circumferential surface of the
socket. The second bulb is pressed against the outer
peripheral surface of the spigot. The second bulb is
inclined towards the pipe center from the first bulb in a
natural state before it is provided between the socket
and the spigot. The inner diameter of the second bulb is
smaller than the outer diameter of the spigot in the
natural state. The second bulb is extensible in the pipe
diameter direction due to elastic deformation of the
narrow part.