Description
SEAL MEMBER WITH SEPARATION PREVENTIVE FUNCTION AND
SEPARATION PREVENTIVE PIPE JOINT
Field of the Invention
[0001]
The present invention relates to a separation
preventive pipe joint for preventing pipes connected to
each other from being separated, and a seal member with a
separation preventive function used in the separation
preventive pipe joint.
Background of the Invention
[0002]
It has been already widely known that a plurality of
pipes such as ductile cast-iron pipes are connected to
constitute a pipeline as a water pipeline laid
underground. When a deformed pipe such as a bent pipe or
a T-shaped pipe is used for such a pipeline, a force
(uneven force) to move the pipe by a water pressure acts
on the bent portion or the branch portion (that is, an
area where a water flow direction is changed) of the
deformed pipe. Thus, a separation preventing function is
added to the connecting portion of the deformed pipe or
the like to prevent the pipes from being separated even
when such an uneven force acts.
[0003]
As a conventional pipe separation preventing
structure, the structure (referred to as a concrete block
structure) of FIG. 23 is used in which a deformed pipe
(bent pipe in FIG. 23) 51 and joining portions (joint
portions) 54 of the deformed pipe 51 and pipes 52 and 53
connected to the deformed pipe 51 are covered with a
concrete block 55. Specifically, the pipes 52 and 53 and

the deformed pipe 51 are integrated by the concrete block
55 to prevent the pipes 52 and 53 and the deformed pipe
51 from being separated. Another pipe separation
preventing structure is shown in FIGS. 24 and 25.
Specifically, lock ring housing grooves 66 and 67 having
a lock ring 65 are formed in the inner peripheral surface
of a socket 63 and the outer peripheral surface of a
spigot 64 of pipes 61 and 62, and the lock ring 65 having
one slit in its circumference is provided across the
grooves 66 and 67. Further, after the pipes 61 and 62 are
joined, the lock ring 65 is pressed inward in a pipe
diameter direction by a set bolt 68 passing through the
socket 63 in the pipe diameter direction to prevent an
increase in the diameter of the lock ring 65. Thus the
pipes 61 and 62 are prevented from being separated from
each other via the lock ring 65.
[0004]
However, when the concrete block structure of FIG. 23
is used, since the concrete block 55 has to be completely
cured and then provided underground, it takes a long time
until concrete is cured. Thus, when a road has to be
restored quickly, the concrete block structure of FIG. 23
is not used but the structure of FIG. 25 using the lock
ring 65 is used.
[0005]
However, in the use of the lock ring structure as
shown in FIG. 25, when the lock ring 65 is reduced in
diameter and fitted into the groove 66 of the socket 63,
a jig or equipment for diameter reduction is required, so
that equipment cost and the like are increased, or it
takes a long time to fit the lock ring 65 into the groove
66.
[0006]
As a separation preventive pipe joint that can
alleviate such a disadvantage, it is proposed that a seal

member (hereinafter referred to as a seal member with a
separation preventive function or simply as a seal
member) 70 having a separation preventing function, as
shown in FIGS. 26 to 30, are provided in a separation
preventive pipe joint. Specifically, an elastic seal
member body 78 is provided in a seal member housing
groove 72 formed in the inner peripheral surface of a
socket 71, and further a lock body 73 having pawl
portions 73a and 73b formed in the inner peripheral
portion thereof is embedded in the seal member body 78.
Then, when pipes are about to move in separating
directions by an uneven force or the like as shown in FIG.
30 (in other words, when a spigot 75 is about to be
separated from the socket 71 to move in a direction c
relative to the socket 71), the lock body 73 rotates in a
direction a while abutting against a socket inner surface
protrusion 76 formed in the seal member housing groove 72
of the socket 71, and the pawl portions 73a and 73b of
the lock body 73 engage into the outer peripheral surface
of the spigot 75, so that the pipes are prevented from
being separated from each other (in other words, the
spigot 75 is prevented from being separated from the
socket 71).
[0007]
In the outer peripheral portion of the lock body 73,
a curved groove portion 73c abutting against the socket
inner surface protrusion 76 formed in the seal member
housing groove 72 of the socket 71 is formed in a
recessed shape. During insertion of the spigot (joining
of the pipes), as shown in FIGS. 28 and 29, the spigot 75
is pressed in a state where the curved groove portion 73c
formed in the lock body 73 is brought into sliding
contact with the socket inner surface protrusion 76
formed in the seal member housing groove 72 of the socket
71, and the pawl portion 73b of the lock body 73 firmly

abuts against the outer peripheral surface of the spigot
75. Then, the lock body 73 is entirely rotated in a
direction d while the seal member body 78 is deformed
such that the pawl portion 73a of the lock body 73 is
pushed outward of the outer peripheral surface of the
spigot 75 by the insertion force of the spigot 75,
thereby allowing the spigot 75 to be inserted into the
lock body 73.
[0008]
With the separation preventive pipe joint structure,
it is only necessary to previously prepare the seal
member 70 with a separation preventing function having
the lock body 73 embedded therein and provide the seal
member 70 in the socket 71, as an operation required for
preventing separation. This eliminates the need for a jig
or equipment for diameter reduction and the need for the
diameter reduction of the lock ring, thereby saving labor
and time for the diameter reduction.
[0009]
A separation preventive pipe joint having a structure
similar to that of the separation preventive pipe joint
shown in FIGS. 26 to 30 is disclosed in Patent Document 1.
Citation list
Patent Documents
[0010]
Patent Document 1: Japanese Patent Laid-Open No. 6-
221478
Disclosure of the Invention
Problems to be Solved by the Invention
[0011]
However, in the separation preventive pipe joint
shown in FIGS. 26 to 30 or the separation preventive pipe
joint disclosed in Patent Document 1, when the spigot 75

is inserted into the socket 71 to join the pipes, a large
force is applied from the spigot 75 to the lock body 73
to rotate the lock body 73 in a state where the pawl
portion 73b of the lock body 73 applies a relatively
large pressing force to and is in direct contact with the
outer peripheral surface of the spigot 75. Thus, the
outer peripheral surface of the spigot 75 is scratched at
a contact portion thereof with the pawl portion 73b, and
corrosion may occur from the scratched portion during the
passing of water or the like.
[0012]
The present invention solves the above-described
problems, and an object of the present invention is to
provide a separation preventive pipe joint and a seal
member with a separation preventive function which allow
pipes to be easily joined in a short time, and in which
the pawl portion of a lock body does not scratch the
outer peripheral surface of a spigot when the spigot is
inserted into a socket to join the pipes to each other.
Means for Solving the Problems
[0013]
To achieve the above-described object, the present
invention provides a seal member with a separation
preventive function that is used in a separation
preventive pipe joint in which, into a socket formed at
the end of one of pipes being to be joined to each other,
a spigot formed at the end of the other pipe is inserted,
is provided in a seal member housing groove formed in the
inner periphery of the socket and is compressed between
the socket and the spigot to seal a gap between the
spigot and the socket, wherein a lock body for preventing
separation is embedded in an annular seal member body
that is elastic and compressible, the lock body has a
pawl portion formed therein, the pawl portion engaging

into the outer peripheral surface of the spigot when the
spigot is about to be removed from the socket, and the
seal member is provided with a rotating elastic body that
abuts against the outer peripheral surface of the spigot
during the insertion of the spigot to rotate the lock
body in a direction in which the pawl portion is
separated from the outer peripheral surface of the spigot.
It is preferable that in the lock body, a plurality of
the pawl portions are formed in a pipe axis direction,
and the rotating elastic body is provided near the pawl
portion closer to a socket opening end.
[0014]
With the above-described configuration, when into the
socket formed at the end of the one pipe, the spigot
formed at the end of the other pipe is inserted to join
the pipes to each other, the rotating elastic body
provided in the seal member abuts against the outer
peripheral surface of the spigot, and the lock body is
rotated in the direction in which the pawl portion of the
lock body is separated from the outer peripheral surface
of the spigot. Therefore, when the spigot is inserted
into the socket to join the pipes to each other, the pawl
portion of the lock body is separated from the outer
peripheral surface of the spigot, thereby preventing the
pawl portion from scratching the outer peripheral surface
of the spigot.
[0015]
In the seal member with a separation preventive
function of the present invention, the rotating elastic
body is provided to protrude inward in a pipe diameter
direction in an area where at least a part of the pawl
portion is removed in the lock body.
[0016]
With such a configuration, at least a part of the
pawl portion is removed in the area where the rotating

elastic body is provided, and thus the rotating elastic
body is not provided with the pawl portion being provided
(left), and the lock body can be rotated during the
insertion of the spigot to separate the pawl portion from
the outer peripheral surface of the spigot. Specifically,
when the rotating elastic body is provided so as to cover
and surround the pawl portion with the pawl portion being
provided, the pawl portion cuts the rotating elastic body
during the insertion of the spigot and the pawl portion
is brought into contact with and scratches the outer
peripheral surface of the spigot, the rotating elastic
body is released from between the pawl portion and the
outer peripheral surface of the spigot to prevent the
lock body from being satisfactorily rotated, and the pawl
portion is brought into contact with and scratches the
outer peripheral surface of the spigot, or a force during
the insertion of the spigot is extremely increased to
reduce workability. However, the present invention does
not cause such problems.
[0017]
The rotating elastic body may include an inclined
surface portion having a sectional shape in which the
amount of inward protrusion in the pipe diameter
direction increases by increments from the inner
peripheral surface portion of the seal member body toward
a back side in the pipe axis direction, and a thick plane
portion continuous with the back end side in the pipe
axis direction of the inclined surface portion in a thick
plane shape. Preferably, the rotating elastic body
includes a curved inclined surface portion having a
sectional shape that increases so that the increment of
inward protrusion in the pipe diameter direction
increases toward the back side in the pipe axis direction
and is inclined into a curved shape, and a thick plane
portion smoothly continuous with a thick portion at the

back end in the pipe axis direction of the curved
inclined surface portion, and the rotating elastic body
is provided so that the tip of the spigot first abuts
against the thin protruding portion of the curved
inclined surface portion during the insertion of the
spigot.
[0018]
Such a separation preventive pipe joint has the
structure in which the seal member is deformed during the
insertion of the spigot to rotate the lock body to allow
for the insertion of the spigot, and thus a relatively
large force is required during the insertion of the
spigot. The rotating elastic body is provided to prevent
the pawl portion from scratching the outer peripheral
surface of the spigot during the insertion of the spigot,
but the rotating elastic body abuts against the outer
peripheral surface of the spigot during the insertion of
the spigot, which requires a larger force. However, as
described above, the rotating elastic body includes the
curved inclined surface portion having the sectional
shape that increases so that the increment of inward
protrusion in the pipe diameter direction increases
toward the back side in the pipe axis direction from the
inner peripheral surface portion of the seal member body,
and the rotating elastic body is provided so that the tip
of the spigot first abuts against the thin protruding
portion of the curved inclined surface portion during the
insertion of the spigot, thereby minimizing an increase
in the insertion force of the spigot at this time.
Further, the curved inclined surface portion of the
rotating elastic body has the curved sectional shape.
Thus, when the spigot is continuously inserted during the
insertion of the spigot, the seal member is smoothly
deformed depending on the amount of protrusion of the
rotating elastic body to satisfactorily rotate the lock

body. Finally, the spigot is brought into contact with
the thick plane portion of the rotating elastic body, and
the pawl portion of the lock body is separated from the
outer peripheral surface, thereby more reliably
preventing the pawl portion from scratching the outer
peripheral surface of the spigot.
[0019]
In the seal member with a separation preventive
function of the present invention, a protective member
for preventing the pawl portion of the lock body rotated
by the rotating elastic body from abutting against the
outer peripheral surface of the spigot or reducing an
abutment force during the insertion of the spigot is
provided on a surface on a socket end side continuous
with the tip of the pawl portion.
[0020]
In the above-described configuration, if the rotating
elastic body is simply provided in the lock body, the
pawl portion may be brought into contact with and scratch
the outer peripheral surface of the spigot during the
insertion of the spigot because of an extremely small
space between the outer peripheral surface of the spigot
and the socket, or the like, in spite of the fact that
the lock body is rotated by the rotating elastic body in
the direction in which the pawl portion is separated from
the outer peripheral surface of the spigot during the
insertion of the spigot. However, as described above, the
protective member is provided in the lock body to prevent
the pawl portion of the lock body from abutting against
the outer peripheral surface of the spigot or reduce the
abutment force. This can more reliably prevent the pawl
portion from scratching the outer peripheral surface of
the spigot or minimize scratches during the insertion of
the spigot.
[0021]

The protective member may be formed into a thin shape
having a substantially constant thickness on the inner
side surface in the pipe diameter direction of the
corresponding pawl portion. As required, a thick portion
may be provided on the inner side surface in the pipe
diameter direction near the tip of the pawl portion where
the protective member is provided, and the thick portion
of the protective member may be formed in a narrower and
smaller region than the pawl portion. The protective
member may be formed to have a gap between the protective
member and the corresponding pawl portion.
[0022]
For example, in a case where the pawl portion
provided with the protective member is pointed so that
the pawl portion is reliably locked to the spigot when
the spigot is about to be separated, merely forming the
protective member into the thin shape having a
substantially constant thickness on the inner side
surface of the corresponding pawl portion may provide an
insufficient protective function of the protective member,
and the pawl portion may scratch the outer peripheral
surface of the spigot. In response, forming the
protective member into a thick shape having a
substantially constant thickness can prevent the pawl
portion from scratching the outer peripheral surface of
the spigot, but the protective member more firmly abuts
against the outer peripheral surface of the spigot during
the insertion of the spigot, which requires a much larger
force. In contrast, as described above, the thick portion
of the protective member is formed only in the narrower
and smaller region than the pawl portion. This can
prevent the pawl portion from scratching the outer
peripheral surface of the spigot, and allows the thick
portion to be easily deformed by a relatively small force,
thereby minimizing an increase in the required insertion

force of the spigot during the insertion of the spigot.
When the protective member is formed on and around the
tip of the corresponding pawl portion, in some cases, the
protective member enters between the pawl portion and the
outer peripheral surface of the spigot during the
insertion of the spigot to cut the protective member.
This requires a large force for the insertion of the
spigot. In contrast, the protective member is formed to
have the gap between the pawl portion and the protective
member, thereby preventing the protective member from
entering between the pawl portion and the outer
peripheral surface of the spigot during the insertion of
the spigot, and reducing a required force for the
insertion of the spigot.
[0023]
As an arrangement of the rotating elastic body and
the protective member, the rotating elastic bodies may be
provided at opposite ends in the width direction of the
lock body along the circumferential direction of the pipe
of the lock body, and the pawl portion provided with the
protective member may be formed between the rotating
elastic bodies, or the rotating elastic body may be
provided at the middle in the width direction of the lock
body along the circumferential direction of the pipe of
the lock body and the pawl portions provided with the
protective members may be provided at opposite ends in
the width direction of the lock body.
[0024]
The rotating elastic body is formed of the same
material as that of the seal member body or a material
having the same hardness as that of the seal member body,
thereby allowing the seal member body and the rotating
elastic body to be integrally formed.
[0025]

The rotating elastic body may be formed of a
different material from that of the seal member body or a
material having different hardness from that of the seal
member body.
Advantageous Effects of the Invention
[0026]
As described above, according to the present
invention, the rotating elastic body is provided that
abuts against the outer peripheral surface of the spigot
during the insertion of the spigot to rotate the lock
body in the direction in which the pawl portion is
separated from the outer peripheral surface of the spigot.
Thus, the rotating elastic body rotates the lock body in
the direction in which the pawl portion of the lock body
is separated from the outer peripheral surface of the
spigot during the insertion of the spigot, thereby
preventing the pawl portion from scratching the outer
peripheral surface of the spigot. This allows pipes to be
easily joined in a short time and prevents the outer
peripheral surface of the spigot from being scratched.
Even when the pipe joint having the seal member is used
as a water pipeline, the possibility of corrosion during
the passing of water or the like can be minimized to
maintain high reliability.
[0027]
According to the present invention, the rotating
elastic body is provided in the area where at least a
part of the pawl portion of the lock body is removed,
thereby more reliably preventing the pawl portion from
scratching the outer peripheral surface of the spigot.
[0028]
The rotating elastic body includes the curved
inclined surface portion increasing so that the increment
of inward protrusion in the pipe diameter direction

increases toward the back side in the pipe axis direction,
and the tip of the spigot first abuts against the thin
protruding portion of the curved inclined surface portion
during the insertion of the spigot, thereby preventing
the pawl portion from scratching the outer peripheral
surface of the spigot, and minimizing an increase in the
insertion force of the spigot during the insertion of the
spigot. Thus, when the insertion force of the spigot is
extremely increased during the insertion of the spigot, a
special joining jig is sometimes required, but with the
above-described configuration, there is no need to use a
special joining jig, thereby increasing the workability
of joining and reducing equipment cost.
[0029]
According to the present invention, the protective
member for preventing the pawl portion of the lock body
from abutting against the outer peripheral surface of the
spigot or reducing the abutment force during the
insertion of the spigot is provided on the surface on the
socket end side continuous with the tip of the pawl
portion. This can more reliably prevent the pawl portion
from scratching the outer peripheral surface of the
spigot during the insertion of the spigot, or minimize
scratches, thereby further improving reliability.
[0030]
The thick portion is provided on the inner side
surface in the pipe diameter direction near the tip of
the pawl portion provided with the protective member, and
the thick portion of the protective member is formed in
the narrower and smaller region than the pawl portion.
This can more reliably prevent the pawl portion from
scratching the outer peripheral surface of the spigot,
and minimize an increase in the required insertion force
of the spigot during the insertion of the spigot. The
protective member is formed to have the gap between the

pawl portion and the protective member, thereby
preventing the protective member from entering between
the pawl portion and the outer peripheral surface of the
spigot during the insertion of the spigot, and reducing a
force required for the insertion of the spigot to improve
working efficiency.
Brief Description of the Drawings
[0031]
FIG. 1 is a sectional view of a separation preventive
pipe joint including a seal member with a separation
preventive function according to an embodiment of the
present invention;
FIG. 2 is a sectional view of the seal member with a
separation preventive function of the separation
preventive pipe joint and shows an area where a lock body
is not provided;
FIG. 3A is a perspective view of the lock body, a
rotating elastic body and a protective member of the seal
member with a separation preventive function, viewed from
obliquely below;
FIG. 3B is a bottom view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, viewed
from below;
FIG. 4A is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
along arrows IVA-IVA in FIG. 3B;
FIG. 4B is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
along arrows IVB-IVB in FIG. 3B;
FIG. 5A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint

and shows a state immediately before the insertion of a
spigot;
FIG. 5B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state immediately before the insertion of
the spigot;
FIG. 6A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted.
FIG. 6B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state where the tip of the spigot is being
inserted;
FIG. 7A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where the spigot has been inserted;
FIG. 7B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where the spigot has been inserted;
FIG. 8 is an enlarged sectional view of the essential
parts of the separation preventive pipe joint and shows a
state where the spigot is about to be separated from a
socket;
FIG. 9 is a front view of the seal member with a
separation preventive function of the separation
preventive pipe joint;
FIG. 10A is an enlarged sectional view of the
essential parts of a lock body and a rotating elastic
body of a seal member with a separation preventive
function of a separation preventive pipe joint as a
comparative example;
FIG. 10B is an enlarged sectional view of the
essential parts of the lock body and the rotating elastic
body of the seal member with a separation preventive

function of the separation preventive pipe joint as a
comparative example;
FIG. IOC is an enlarged sectional view of the
essential parts of the lock body and the rotating elastic
body of the seal member with a separation preventive
function of the separation preventive pipe joint as a
comparative example;
FIG. 11A is a sectional view of a separation
preventive pipe joint according to an embodiment of the
present invention and shows a case where a gap between a
socket and a spigot is wide (large);
FIG. 11B is a sectional view of the separation
preventive pipe joint according to the embodiment of the
present invention and shows the case where a gap between
the socket and the spigot is wide (large);
FIG. 12A is a perspective view of a lock body, a
rotating elastic body and a protective member of a seal
member with a separation preventive function according to
another embodiment of the present invention, viewed from
obliquely below;
FIG. 12B is a bottom view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function
according to the embodiment of the present invention,
viewed from below;
FIG. 13A is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
along arrows XIIIA-XIIIA in FIG. 12B;
FIG. 13B is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
along arrows XIIIB-XIIIB in FIG. 12B;
FIG. 13C is a sectional view of the lock body, the
rotating elastic body, and the protective member of the

seal member with a separation preventive function, taken
along arrows XIIIC-XIIIC in FIG. 12B;
FIG. 14A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state immediately before the insertion of a
spigot;
FIG. 14B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state immediately before the insertion of
the spigot;
FIG. 14C is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state immediately before the insertion of
the spigot;
FIG. 15A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted;
FIG. 15B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted;
FIG. 15C is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted;
FIG. 16A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where the spigot has been inserted;
FIG. 16B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state where the spigot has been inserted;
FIG. 16C is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state where the spigot has been inserted;

FIG. 17A is a perspective view of a lock body, a
rotating elastic body and a protective member of a seal
member with a separation preventive function according to
still another embodiment of the present invention, viewed
from obliquely below;
FIG. 17B is a bottom view of the lock body, the
rotating elastic body, and the protective member of the
seal member with a separation preventive function
according to the embodiment of the present invention,
viewed from below;
FIG. 18A is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
along arrows XVIIIA-XVIIIA in FIG. 17B;
FIG. 18B is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
long arrows XVIIIB-XVIIIB in FIG. 17B;
FIG. 18C is a sectional view of the lock body, the
rotating elastic body and the protective member of the
seal member with a separation preventive function, taken
along arrows XVIIIC-XVIIIC in FIG. 17B;
FIG. 19A is an enlarged sectional view of the
essential parts of a separation preventive pipe joint and
shows a state immediately before the insertion of a
spigot;
FIG. 19B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state immediately before the insertion of
the spigot;
FIG. 19C is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state immediately before the insertion of
the spigot;

FIG. 20A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted;
FIG. 20B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted;
FIG. 20C is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where a tip of the spigot is being
inserted;
FIG. 21A is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows a state where the spigot has been inserted;
FIG. 21B is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state where the spigot has been inserted;
FIG. 21C is an enlarged sectional view of the
essential parts of the separation preventive pipe joint
and shows the state where the spigot has been inserted;
FIG. 22 is an enlarged sectional view of the
essential parts showing a state where the protective
member enters in the separation preventive pipe joint
shown in FIGS. 12 to 16;
FIG. 23 schematically shows a conventional pipe
separation preventing structure;
FIG. 24 shows an appearance of a separation
preventive pipe joint as another conventional separation
preventing structure;
FIG. 25 is a sectional view of the conventional
separation preventive pipe joint;
FIG. 26 is a sectional view of still another
conventional separation preventive pipe joint;

FIG. 27 is an enlarged sectional view of the
essential parts of the conventional separation preventive
pipe joint and shows a state immediately before the
insertion of a spigot;
FIG. 28 is an enlarged sectional view of the
essential parts of the conventional separation preventive
pipe joint and shows a state where the spigot is being
inserted;
FIG. 29 is an enlarged sectional view of the
essential parts of the conventional separation preventive
pipe joint and shows a state where the spigot has been
inserted; and
FIG. 30 is an enlarged sectional view of the
essential parts of the conventional separation preventive
pipe joint and shows a state where the spigot is about to
be separated from a socket.
Description of the Embodiments
[0032]
Now, a separation preventive pipe joint including a
seal member with a separation preventive function
according to embodiments of the present invention will be
described with reference to the drawings. FIGS. 1 and 5A
to 8 are sectional views of a separation preventive pipe
joint including a seal member with a separation
preventive function according to an embodiment of the
present invention, FIGS. 5A and 5B show a state
immediately before the insertion of a spigot, FIGS. 6A
and 6B show a state where a tip of the spigot is being
inserted, FIGS. 7A and 7B show a state where the spigot
has been inserted, and FIG. 8 shows a state where the
spigot is about to be separated from a socket. FIGS. 3A
and 3B are a perspective view and a bottom view of a lock
body, a rotating elastic body and a protective member of
the seal member with a separation preventive function,

viewed from obliquely below and from below, respectively,
and FIGS. 4A and 4B are sectional views of the lock body,
the rotating elastic body and the protective member of
the seal member with a,separation preventive function,
taken along arrows IVA-IVA and IVB-IVB, respectively.
[0033]
As shown in FIG. 1, in a separation preventive pipe
joint 1 according to the embodiment of the present
invention, into a socket 3 formed at the end of a pipe 2,
a spigot 5 formed at the end of a pipe 4 is inserted, the
pipes2 and 4 being to be joined to each other. An annular
seal member 7 is provided in a seal member housing groove
6 formed in the inner periphery of the socket 3
(specifically, the inner periphery on the back side of a
pipe end surface 3a of the socket 3), and the seal member
7 is compressed between the socket 3 and the spigot 5 to
seal a gap between the spigot and the socket. Reference
numeral 5a in FIG. 1 refers to the inclined surface of
the spigot 5 that is formed in the outer periphery of the
tip of the spigot 5 and tapered.
[0034]
The seal member 7 provided in the separation
preventive pipe joint 1 according to the embodiment of
the present invention has a separation preventing
function of preventing the pipes 2 and 4 connected from
being separated from each other as described later. The
pipes 2 and 4 are made of, for example, ductile cast-iron,
but not limited to this.
[0035]
The structures or the like of the seal member (seal
member with a separation preventive function) 7 and the
seal member housing groove 6 of the socket 3 in which the
seal member 7 is provided will be described in detail
below. As shown in FIG. 2 and the like, the seal member 7
includes a heel portion 7a for holding the seal member 7

in a predetermined position in the seal member housing
groove 6 and a valve portion 7b for sealing a gap between
the spigot and the socket, the heel portion 7a and the
valve portion 7b being integrated with each other. The
valve portion 7b has a substantially circular section (or
a substantially oval section) without receiving an
external force. In response, the seal member housing
groove 6 has a fitting groove 6a into which the heel
portion 7a of the seal member 7 is fitted to lock the
seal member 7 and a valve portion housing groove 6b in
which the valve portion 7b of the seal member 7 is housed.
[0036]
A socket inner surface protrusion 8 protruding inward
(inward in a pipe diameter direction) is formed between
the fitting groove 6a and the valve portion housing
groove 6b of the seal member housing groove 6 in the
socket 3, and a curved groove portion 7c in sliding
contact with the socket inner surface protrusion 8 is
formed also in the seal member 7. In the embodiment, the
end of the socket inner surface protrusion 8 has a
substantially semi-circular sectional shape, but not
limited to this.
[0037]
As shown in FIGS. 1 to 4B and the like, the seal
member 7 includes an annular seal member body 9 that is
made of elastic and compressible rubber or the like, and
a plurality of lock bodies 10 for preventing separation
that are made of a material having high rigidity such as
a metal piece and are circumferentially at intervals in
the seal member body 9 as shown in FIG. 9. In this
embodiment, a case where eight lock bodies 10 are
provided circumferentially at regular intervals is shown,
but the number of the lock bodies 10 may be increased or
decreased, or the intervals may be changed depending on
the number.

[0038]
In the lock body 10, as shown in FIG. 8, pawl
portions 10a and 10b are formed which engage into the
outer peripheral surface of the spigot 5 when the spigot
5 is about to be removed from the socket 3, that is, when
the pipes 2 and 4 are about to be moved in directions in
which the pipes are separated from each other, and a
curved groove portion 10c is formed which can be brought
into sliding contact with the socket inner surface
protrusion 8 in the seal member housing groove 6 of the
socket 3 when the spigot 5 is inserted into the socket 3
to join the pipes 2 and 4 to each other as shown in FIGS.
1 and 5A to FIG. 7B.
[0039]
As shown in FIGS. 3A to 7B, the pawl portions 10a and
10b are formed to protrude obliquely from the lock body
10 inward of the seal member 7, specifically, toward the
back side of the socket 3 and inward in the pipe diameter
direction. In this embodiment, a case is shown where each
lock body 10 has the two pawl portions 10a and 10b formed
in parallel in a pipe axis direction. Three or more pawl
portions 10a and 10b may be formed in parallel in the
pipe axis direction, although not shown.
[0040]
As shown in FIGS. 3A, 3B, 4A, 4B and the like, the
pawl portion (also referred to a back side pawl portion)
10a on the back side of the opening end of the socket 3
is formed over the entire width of the lock body 10 (the
width direction of the lock body 10 is along the
circumferential direction of the pipe having the socket 3
or the like formed therein). However, the pawl portion
(also referred to as an opening side pawl portion) 10b
closer to the opening end of the socket 3 is formed so as
to remain only at the middle in the width direction of
the lock body 10. The opening side pawl portion 10b is

removed by cutting or the like at an area closer to each
of opposite ends in the width direction of the lock body
10, and in the cut portion, for example, a rotating
elastic body 11 that is made of a similar material to
that of the seal member body 9 made of rubber or the like
and has similar elasticity to that of the seal member
body 9 is integrally formed with the seal member body 9.
The rotating elastic body 11 may be formed by any methods,
and may be formed separately from the seal member body 9
and stuck to the cut area of the opening side pawl
portion 10b.
[0041]
As shown in FIGS. 5A to 7B, the rotating elastic body
11 has a function of abutting against the outer
peripheral surface of the spigot 5 during the insertion
of the spigot 5 to rotate the lock body 10 in a direction
in which the pawl portions 10a and 10b are separated from
the outer peripheral surface of the spigot 5. As shown in
FIGS. 3A, 4A and the like, the rotating elastic body 11
is provided to protrude inward in the pipe diameter
direction beyond the opening side pawl portion 10b. The
rotating elastic body 11 is formed to have a trapezoidal
sectional shape including, as shown in FIG. 3A, an
inclined surface portion 11a that is linearly inclined
and has a sectional shape in which the amount of inward
protrusion in the pipe diameter direction increases by
increments from an inner peripheral surface portion 9a of
the seal member body 9 toward a back side in the pipe
axis direction, and a thick plane portion lib that is
continuous with the back side in the pipe axis direction
of the inclined surface portion 11a in a thick plane
shape, in a state where an external force is not applied.
In this embodiment, the rotating elastic body 11 is
integrally formed with the seal member body 9 as
described above, but the total thickness of the rotating

elastic body 11 and the seal member body 9 is
substantially constant from the lock body 10 toward an
inside in the pipe diameter direction as shown in FIG. 4A
and the like.
[0042]
Further, as shown in FIGS. 3A, 3B, and 4B, on a
surface (surface facing the inside in the pipe diameter
direction) of a socket end side continuous with a tip of
an area where the opening side pawl portion 10b of the
lock body 10 is formed, a protective member 12 formed of
a thin rubber plate having a constant thickness (for
example, a thickness of 1 mm) is formed integrally with
the seal member body 9, and the protective member 12
prevents the opening side pawl portion 10b of the lock
body 10 rotated by the rotating elastic body 11 from
abutting against the outer peripheral surface of the
spigot 5 or reduces an abutment force during the
insertion of the spigot 5. The protective member 12 may
be formed by any method, and may be formed separately
from the seal member body 9 and stuck to the opening side
pawl portion 10b.
[0043]
In the above-described configuration, in a state
where the pipes 2 and 4 have not yet been joined to each
other, that is, the spigot 5 has not yet been inserted
into the socket 3, the seal member 7 is merely fitted in
the seal member housing groove 6 of the socket 3, and
thus as shown in FIGS. 2, 5A and 5B, the valve portion 7b
of the seal member 7 is greatly expanded inward in the
pipe diameter direction. Accordingly, the lock body 10 is
brought closer to the inside (lower side of the sheet
surface of FIG. 2 or the like) in the pipe diameter
direction as compared with during the insertion of the
spigot 5 described later, and the pawl portions 10a and

10b greatly protrude inward in the pipe diameter
direction.
[0044]
From this state, the spigot 5 is inserted into the
socket 3 to join the pipes 2 and 4 to each other, so that,
as shown in FIGS. 6A and 6B, the inside (inside portion
in the pipe diameter direction) of the seal member 7 is
first brought into contact with the inclined surface 5a
of the spigot 5. Further, as shown in FIGS. 7A and 7B,
the inside of the seal member 7 is brought into contact
with the outer peripheral surface of the spigot 5. Inside
the seal member 7, the pawl portions 10a and 10b of the
lock body 10 protrude. Further, on the pawl portion
(opening side pawl portion) 10b of the lock body 10, the
rotating elastic body 11 protruding beyond the pawl
portion 10b is provided. Thus, the rotating elastic body
11 is brought into contact with the inclined surface 5a
or the outer peripheral surface of the spigot 5, and the
rotating elastic body 11 receives a force in the
insertion direction of the spigot 5 in association with
further insertion of the spigot 5. Thus, the lock body 10
of the seal member 7 is rotated in a direction e, that is,
a direction in which the pawl portions 10a and 10b are
separated from the outer peripheral surface of the spigot
5, with the curved groove portion 10c in sliding contact
with the socket inner surface protrusion 8. This can
prevent the pawl portions 10a and 10b from being brought
into contact with the outer peripheral surface of the
spigot 5 during the insertion of the spigot 5, and
prevent the pawl portions 10a and 10b from scratching the
outer peripheral surface of the spigot 5. During the
insertion of the spigot 5, the seal member body 9 needs
to be compressed and deformed when the lock body 10 is
rotated, which requires a certain insertion force during
the insertion of the spigot 5.

[0045]
When the rotating elastic body 11 is merely provided
in the lock body 10 in the above-described configuration,
the pawl portion 10b may be brought into contact with the
outer peripheral surface of the spigot 5 during the
insertion of the spigot 5 because of an extremely small
gap between the outer peripheral surface of the spigot 5
and the socket 3, in spite of the fact that the rotating
elastic body 11 rotates the lock body 10 in the direction
in which the pawl portions 10a and 10b are separated from
the outer peripheral surface of the spigot 5 during the
insertion of the spigot 5. However, as described above,
the rotating elastic body 11 is provided in the lock body
10, and further, the thin plate-shaped protective member
12 is provided on the surface of the socket end side
continuous with the tip of the pawl portion 10b. Thus,
even in the above-described case, the protective member
12 is brought into contact with the outer peripheral
surface of the spigot 5, thereby preventing the pawl
portions 10a and 10b of the lock body 10 from abutting
against the outer peripheral surface of the spigot 5, or
reducing an abutment force. This can more reliably
prevent the pawl portions 10a and 10b from scratching the
outer peripheral surface of the spigot 5 or minimize
scratches during the insertion of the spigot 5.
[0046]
In the above-described configuration, the pawl
portion (opening side pawl portion) 10b is removed in the
area provided with the rotating elastic body 11. Thus,
the rotating elastic body 11 is not provided with the
pawl portion 10b being provided (left), and the lock body
10 can be satisfactorily rotated during the insertion of
the spigot 5 to separate the pawl portions 10a and 10b
from the outer peripheral surface of the spigot 5.
[0047]

Specifically, as shown in FIG. 10A, if the rotating
elastic body 11 is provided so as to cover the tip of the
pawl portion 10b (opening side pawl portion) with the
pawl portion 10b provided, the pawl portion 10b cuts the
rotating elastic body 11 to expose the pawl portion 10b
during the insertion of the spigot 5, and the pawl
portion 10b is brought into contact with and scratches
the outer peripheral surface of the spigot 5. If the
rotating elastic body 11 is formed of an elastic body
such as thick rubber or a hard elastic body so as not to
be cut by the pawl portion 10b, the pawl portion 10b does
not engage with the outer peripheral surface of the
spigot 5 when the spigot 5 is separated from the socket 3,
thereby providing a poor separation preventing function.
[0048]
As shown in FIG. 10B, if the rotating elastic body 11
is provided so as to cover the surface (surface facing
the inside in the pipe diameter direction) on the socket
end side continuous with the tip of the area where the
pawl portion 10b (opening side pawl portion) is formed
with the pawl portion 10b provided, the rotating elastic
body 11 moves (escapes) in a direction f (outward in the
pipe diameter direction) along the surface on the socket
end side of the pawl portion 10b during the insertion of
the spigot 5, and the lock body 10 is not rotated. Thus,
the pawl portion 10b is brought into contact with and
scratches the outer peripheral surface of the spigot 5.
[0049]
Further, as shown in FIG. 10C, if the rotating
elastic body 11 is provided so as to protrude from the
surface (surface facing the inside in the pipe diameter
direction) on the socket end side continuous with the tip
of the area where the pawl portion 10b is formed toward
the tip of the pawl portion (opening side pawl portion)
10b with the pawl portion 10b provided, the rotating

elastic body 11 wedges in between the pawl portion 10b
and the outer peripheral surface of the spigot 5 during
the insertion of the spigot 5, and the spigot 5 cannot be
inserted without an extremely large force during the
insertion of the spigot 5, which requires a special jig
and high equipment cost separately or increases working
hours and reduces workability.
[0050]
In this way, the above-described problems occur if
the rotating elastic body 11 is provided with the pawl
portion 10b (opening side pawl portion) provided. However,
in the embodiment of the present invention, the pawl
portion 10b is removed in the area provided with the
rotating elastic body 11, thereby preventing the above-
described problems, and allowing the lock body 10 to be
satisfactorily rotated during the insertion of the spigot
5 to separate the pawl portions 10a and 10b from the
outer peripheral surface of the spigot 5.
[0051]
In the embodiment, as shown in FIGS. 3A, 3B, 4A and
4B, the rotating elastic bodies 11 are provided at
opposite ends in the width direction of the lock body 10
along the circumferential direction of the pipes 2 and 4
in an area corresponding to the pawl portion (opening
side pawl portion) 10b of the lock body 10, and the pawl
portion 10b provided with the protective member 12 is
formed between the rotating elastic bodies 11. Thus,
during the insertion of the spigot 5, the rotating
elastic bodies 11 are satisfactorily brought into contact
with the outer peripheral surface of the spigot 5 on
opposite sides of the pawl portion 10b to rotate the lock
body 10, thereby satisfactorily preventing the pawl
portion 10b from being brought into contact with and
scratching the outer peripheral surface of the spigot 5.
When the pipes 2 and 4 are about to move in the

separating directions and the spigot 5 is about to be
separated from the socket 3, as shown in FIG. 8, the
rotating elastic body 11 moves toward the socket opening
end side together with the spigot 5, and thus the lock
body 10 is rotated in a direction g, and the pawl portion
10b of the lock body 10 engages into the outer peripheral
surface of the spigot 5, thereby preventing the pipes
from being separated from each other, and preventing the
spigot 5 from being separated from the socket 3.
[0052]
In the case where the gap between the socket 3 and
the spigot 5 is wide (large), as shown in FIG. 11A, when
the pipes are about to move in the separating directions,
the spigot 5 is about to be separated from the socket 3,
and the rotating elastic body 11 moves toward the socket
opening end side together with the spigot 5 to rotate the
lock body 10 in a direction h, the back side pawl portion
10a rather than the opening side pawl portion 10b of the
lock body 10 engages into the outer peripheral surface of
the spigot 5 to prevent the pipes 2 and 4 from being
separated from each other. In the lock body 10, the
rotating elastic body 11 and the protective member 12 are
not provided in an area corresponding to the back side
pawl portion 10a. Thus, in the case where the gap between
the socket 3 and the spigot 5 is wide (large), when the
spigot 5 is inserted into the socket 3 to join the pipes
2 and 4 to each other, as shown in FIG. 11B, the back
side pawl portion 10a of the lock body 10 is brought into
contact with the outer peripheral surface of the spigot 5.
However, in this case, a small rotation angle (rotation
amount) in a direction i of the lock body 10 and a small
compression amount of the seal member 7 (seal member body
9) prevent scratches on the outer peripheral surface of
the spigot 5. For the prevention of scratches on the
outer peripheral surface of the spigot 5, only the

opening side pawl portion 10b that may be brought into
contact with the outer peripheral surface of the spigot 5
when the gap between the socket 3 and the spigot 5 is
narrow, has to be considered (the same applies to the
case with three or more pawl portions).
[0053]
In the above-described embodiment, the rotating
elastic body 11 includes the inclined surface portion 11a
having the section in which the amount of inward
protrusion in the pipe diameter direction increases by
increments from the inner peripheral surface portion 9a
of the seal member body 9 toward the back side in the
pipe axis direction (that is, linearly increases), but
not limited to this. FIGS. 12A, 12B, and 13A to 13C show
a rotating elastic body 11 according to another
embodiment. In this embodiment, as shown in FIG. 12A, the
rotating elastic body 11 is formed to have a
substantially trapezoidal sectional shape with a curved
inclined surface portion lie and a thick plane portion
lib. The curved inclined surface portion lie has a
section increasing so that the increment of inward
protrusion in a pipe diameter direction increases from
the inner peripheral portion of a seal member body 9
toward a back side in a pipe axis direction (that is, an
amount of protrusion and an increment of protrusion are
small on an opening side in the pipe axis direction and
increase toward the back side in the pipe axis direction) ,
and is thus inclined into a curved shape (specifically, a
curved shape in which a middle is recessed to be close to
a lock body 10). The thick plane portion 11b is smoothly
continuous with a thick portion at the end on the back
side in the pipe axis direction of the curved inclined
surface portion 11e. Then, as shown in FIGS. 14A, 15A and
16A, the tip of the spigot 5 first abuts against the thin
protruding portion of the curved inclined surface portion

11e (a portion closer to the outside of the curved
inclined surface portion 11e) during the insertion of the
spigot. The rotating elastic body 11 is integrally formed
with the seal member body 9, but as shown in FIG. 13A,
the total thickness of the rotating elastic body 11 and
the seal member body 9 is the thinnest at the middle of
the curved inclined surface portion 11e and thick at the
thick plane portion 11b from the lock body 10 toward the
inside in the pipe diameter direction.
[0054]
In the separation preventive pipe joint 1, the seal
member 7 is deformed to rotate the lock body 10 to allow
for the insertion of the spigot 5, and thus a relatively
large force is required during the insertion of the
spigot 5. The rotating elastic body 11 is provided to
prevent pawl portions 10a and 10b from scratching the
outer peripheral surface of the spigot 5 during the
insertion of the spigot, but the rotating elastic body 11
abuts against the outer peripheral surface of the spigot
5 during the insertion of the spigot, which requires a
larger force. Specifically, as shown in FIG. 4A and the
like, in the case where the rotating elastic body 11
includes the inclined surface portion 11a having the
section in which the amount of protrusion increases by
increments from the inner peripheral surface portion of
the seal member body 9 toward the back side in the pipe
axis direction, the increment of protrusion of the
rotating elastic body 11 is relatively large when the tip
of the spigot 5 abuts against the inclined surface
portion 11a of the rotating elastic body 11. This
requires a large, insertion force of the spigot 5 during
the insertion of the spigot, thereby reducing working
efficiency or requiring a special joining jig in some
cases.
[0055]

In contrast, as described above, the curved inclined
surface portion 11e that has the sectional shape
increasing so that the increment of inward protrusion in
the pipe diameter direction increases toward the back
side in the pipe axis direction and is inclined into the
curved shape, is formed on a surface inside the pawl
portion (opening side pawl portion) 10b (inside in the
pipe diameter direction) of the rotating elastic body 11.
Thus, as shown in FIG. 15A, the tip of the spigot 5 first
abuts against the thin protruding portion (portion closer
to the outside of the curved inclined surface portion
11e) of the curved inclined surface portion 11e of the
rotating elastic body 11 during the insertion of the
spigot, and the amount of protrusion in this area is
small and then smoothly increases, thereby minimizing an
increase in the insertion force of the spigot 5 at this
time. Thus, workability during the insertion of the
spigot 5 can be improved, and a special joining jig is
not required but a general joining jig can be used,
thereby reducing equipment cost.
[0056]
The area provided with the curved inclined surface
portion 11e in the rotating elastic body 11 has the
curved sectional shape, and the curved inclined surface
portion 11e is formed to be smoothly continuous with the
thick plane portion 11b. Thus, if the spigot 5 is
continuously inserted during the insertion of the spigot,
the spigot 5 can be smoothly inserted, and the thick
plane portion 11b is finally brought into contact with
the spigot to more reliably prevent the pawl portions 10a
and 10b from scratching the outer peripheral surface of
the spigot 5.
[0057]
In the embodiment shown in FIGS. 3A to 7B, the
protective member 12 is formed into a thin shape having a

substantially constant thickness on the surface inside
the corresponding pawl portion (opening side pawl
portion) 10b (inside in the pipe diameter direction), but
not limited to this. FIGS. 12A to 16C show another
embodiment. In this embodiment, a protective member 12 is
provided with a thick portion 12a on an inside surface
(inside in a pipe diameter direction) near the tip of a
pawl portion (opening side pawl portion) 10b where the
protective member 12 is provided, and the thick portion
12a of the protective member 12 is formed only in a
narrower and smaller (shorter) region than the pawl
portion 10b. In this embodiment, the thick portion 12a
and a thin portion 12b of the protective member 12 are
smoothly continuous with each other, but not limited to
this.
[0058]
When the protective member 12 merely formed into the
thin shape having a constant thickness is used, the
protective function of the protective member 12 sometimes
becomes insufficient depending on the shape of the pawl
portion 10b, and the pawl portion 10b may scratch the
outer peripheral surface of the spigot 5 during the
insertion of the spigot. To address this, if the entire
protective member 12 is formed to be thick, the pawl
portion 10b can be prevented from scratching the outer
peripheral surface of the spigot 5, but the protective
member 12 more firmly abuts against the outer peripheral
surface of the spigot during the insertion of the spigot,
which requires an extremely large force. In contrast, in
this embodiment, the thick portion 12a of the protective
member 12 is formed to be narrower and smaller than the
pawl portion 10b to prevent the pawl portion 10b from
scratching the outer peripheral surface of the spigot 5.
Further, a region having the thick portion 12a formed
therein is small, and thus the thick portion 12a can be

easily deformed by a relatively small force, thereby
minimizing an increase in the required insertion force of
the spigot 5 during the insertion of the spigot.
[0059]
Thus, with this configuration, working efficiency
during the insertion of the spigot 5 can be improved, and
a special joining jig is not required but a general
joining jig can be used, thereby reducing equipment cost.
[0060]
In the embodiment shown in FIGS. 1 to 9 and 11A to
16C, the protective member 12 is provided substantially
close to the tip of the pawl portion (opening side pawl
portion) 10b, but not limited to this. FIGS. 17A to 21C
show still another embodiment, and in this embodiment, a
protective member 12 is not provided near the tip of a
pawl portion (opening side pawl portion) 10b, but the
protective member 12 is formed to have a gap S between
the pawl portion 10b and the protective member 12 as
shown in FIG. 18C.
[0061]
In FIGS. 17A to 21C, a case is shown where the
protective member 12 is not provided in an area
corresponding to a thick portion 12a of the protective
member 12, but not limited to this. In the entire region
provided with the pawl portion 10b (that is, areas
corresponding to the thick portion 12a of the protective
member 12 and thin portions 12b on opposite sides of the
thick portion 12a), a gap may be formed between the pawl
portion 10b and the protective member 12 without
providing the protective member 12 near the tip of the
pawl portion 10b.
[0062]
As in the embodiment shown in FIGS. 11A to 16C, when
the protective member 12 (the thick portion 12a of the
protective member 12 in FIG. 11A to FIG. 16C) is provided

up to the tip of the pawl portion (opening side pawl
portion) 10b, as shown in FIG. 22, a tip near portion 12'
of the protective member 12 near the tip of the pawl
portion 10b may enter between the pawl portion 10b and
the outer peripheral surface of the spigot 5 during the
insertion of the spigot 5 to cut the tip near portion 12'
of the protective member 12 in some cases. At this time,
the protective member 12 can prevent the pawl portion 10b
from scratching the outer peripheral surface of the
spigot 5. However, when the tip near portion 12' of the
protective member 12 enters between the pawl portion 10b
and the outer peripheral surface of the spigot 5 during
the insertion of the spigot 5, a force to cut the tip
near portion 12' of the protective member 12 is required,
and the tip near portion 12' to be cut, that is a contact
portion of the protective member 12 with the outer
peripheral surface of the spigot, firmly abuts against
the spigot 5 and is drawn, and thus the insertion of the
spigot 5 requires a large force in some cases.
[0063]
In contrast, the protective member 12 is formed so as
to have the gap S between the pawl portion 10b and the
protective member 12. This can prevent the protective
member 12 from entering between the pawl portion 10b and
the outer peripheral surface of the spigot 5, and reduce
a force required for the insertion of the spigot 5 to
improve working efficiency during the insertion of the
spigot 5.
[0064]
In the above-described embodiment, the case is
described where the rotating elastic bodies 11 are
provided at opposite ends in the width direction of the
lock body 10, and the pawl portion (opening side pawl
portion) 10b provided with the protective member 12 is
formed between the rotating elastic bodies 11, but not

limited to this. The rotating elastic body 11 may be
provided at the middle in the width direction of the lock
body 10, and the pawl portions (opening side pawl
portions) 10b provided with the protective members 12 may
be provided at the opposite ends in the width direction
of the lock body 10.
[0065]
The rotating elastic body 11 and the protective
member 12 are made of the same material as that of the
seal member body 9 or a material having the same hardness
as that of the seal member body 9, so that the seal
member 7 can be integrally formed and easily produced.
However, not limited to this, the rotating elastic body
11 and the protective member 12 may be made of a material
having different hardness from that of the seal member
body 9 or a different material from that of the seal
member body 9, for example, resin. Thus, when the
rotating elastic body 11 and the protective member 12 are
made of a material having different hardness from that of
the seal member body 9 or a different material from that
of the seal member body 9, the shapes of the rotating
elastic body 11 and the protective member 12 can be more
freely determined, allowing for optimum design, or in
some cases, more inexpensive production than a case where
the rotating elastic body 11 and the protective member 12
are made of the same material.

WE CLAIM
1. A seal member with a separation preventive function
that is used in a separation preventive pipe joint in
which, into a socket formed at an end of one pipe being
to be joined to each other, a spigot formed at an end of
the other pipe is inserted, is provided in a seal member
housing groove formed in an inner periphery of the socket,
and is compressed between the socket and the spigot to
seal a gap between the spigot and the socket,
wherein a lock body for preventing separation is
embedded in an annular seal member body that is elastic
and compressible,
the lock body has a pawl portion formed therein, the
pawl portion engaging into an outer peripheral surface of
the spigot when the spigot is about to be removed from
the socket, and
the seal member is provided with a rotating elastic
body that abuts against the outer peripheral surface of
the spigot during insertion of the spigot to rotate the
lock body in a direction in which the pawl portion is
separated from the outer peripheral surface of the spigot.
2. The seal member with a separation preventive function
according to claim 1, wherein in the lock body, a
plurality of the pawl portions are formed in a pipe axis
direction, and the rotating elastic body is provided near
the pawl portion closer to a socket opening end.
3. The seal member with a separation preventive function
according to claim 1 or 2, wherein the rotating, elastic
body is provided to protrude inward in a pipe diameter
direction in an area where at least a part of the pawl
portion is removed in the lock body.

4. The seal member with a separation preventive function
according to claim 3, wherein the rotating elastic body
includes an inclined surface portion having a sectional
shape in which an amount of inward protrusion in the pipe
diameter direction increases by increments from an inner
peripheral surface portion of the seal member body toward
a back side in the pipe axis direction, and a thick plane
portion continuous with a back end side in the pipe axis
direction of the inclined surface portion in a thick
plane shape.
5. The seal member with a separation preventive function
according to claim 3, wherein the rotating elastic body
includes a curved inclined surface portion having a
sectional shape that increases so that an increment of
inward protrusion in the pipe diameter direction
increases toward a back side in the pipe axis direction
and inclined into a curved shape, and a thick plane
portion smoothly continuous with a thick portion at a
back end in the pipe axis direction of the curved
inclined surface portion, and the rotating elastic body
is provided so that a tip of the spigot first abuts
against a thin protruding portion of the curved inclined
surface portion during the insertion of the spigot.
6. The seal member with a separation preventive function
according to any one of claims 1 to 5, wherein a
protective member for preventing the pawl portion of the
lock body rotated by the rotating elastic body from
abutting against the outer peripheral surface of the
spigot or reducing an abutment force during the insertion
of the spigot is provided on a surface on a socket end
side continuous with a tip of the pawl portion.

7. The seal member with a separation preventive function
according to claim 6, wherein the protective member is
formed into a thin shape having a substantially constant
thickness on the surface on the socket end side of the
corresponding pawl portion.
8. The seal member with a separation preventive function
according to claim 6, wherein a thick portion is provided
on an inner side surface in the pipe diameter direction
near the tip of the pawl portion where the protective
member is provided, and the thick portion of the
protective member is formed in a narrower and smaller
region than the pawl portion.
9. The seal member with a separation preventive function
according to claim 6, wherein the protective member is
formed to have a gap between the protective member and
the corresponding pawl portion.
10. The seal member with a separation preventive function
according to any one of claims 6 to 9, wherein a
plurality of the lock bodies are provided at intervals in
a circumferential direction of the pipe in the annular
seal member body, rotating elastic bodies are provided in
areas corresponding to opposite ends in a width direction
of each lock body along the circumferential direction of
the pipe in the seal member, and the pawl portion
provided with the protective member is formed between the
rotating elastic bodies.
11. The seal member with a separation preventive function
according to any one of claims 6 to 9, wherein a
plurality of the lock bodies are provided at intervals in
a circumferential direction of the pipe in the annular
seal member body, the rotating elastic body is provided

in an area corresponding to a middle in a width direction
of each lock body along the circumferential direction of
the pipe in the seal member, and the pawl portions
provided with the protective members are provided at
opposite ends in the width direction of the lock body.
12. The seal member with a separation preventive function
according to any one of claims 1 to 11, wherein the
rotating elastic body is formed of a same material as
that of the seal member body or a material having same
hardness as that of the seal member body.
13. The seal member with a separation preventive function
according to any one of claims 1 to 11, wherein the
rotating elastic body is formed of a different material
from that of the seal member body or a material having
different hardness from that of the seal member body.
14. A separation preventive pipe joint comprising the
seal member with a separation preventive function
according to any one of claims 1 to 13.

There is provided a seal member with a separation
preventive function in which the pawl portion of a lock
body does not scratch the outer peripheral surface of an
spigot when the spigot is inserted into a socket to join
pipes to each other. A lock body 10 for preventing
separation is embedded in a seal member body 9 of a seal
member 7. In the lock body 10, pawl portions 10a and 10b
are formed that engage into the outer peripheral surface
of the spigot 5 when the spigot 5 is about to be removed
from a socket 3, and the seal member is provided with a
rotating elastic body 11 that abuts against the outer
peripheral surface of the spigot 5 during the insertion
of the spigot 5 to rotate the lock body 10.