Description
Title of Invention: BIT REPLACING DEVICE FOR EXCAVATING
MACHINE
Technical Field
[0001]
The present invention relates to a bit replacing
device provided on the cutter head of an excavating
machine, by which a worn bit during excavation can be
replaced with a new bit.
Background Art
[0002]
In Patent Literature 1, a rotary support member is
arranged in the rear part of the front surface plate of a
cutter head so as to rotate about an axial center
vertical to the front surface plate. Further, a mounting
hole is formed in a position of the rotary support member
facing an opening formed on the front surface plate. A
replacement bit is slidably contained in the mounting
hole. During the replacement of bits, after the
replacement bit is retracted from the opening of the
front surface plate and is contained in the mounting hole
of the rotary support member, the rotary support member
is turned 90 degrees, so that the opening is closed by
the closing surface portion of the front surface of the
rotary support member.
Citation List
Patent Literature
[0003]
Patent Literature 1: Japanese Patent No. 3692267
However, according to Patent Literature 1, in a state
in which the replacement bit is retracted and held in the

mounting hole, the rotary support member is turned. Thus,
a large rotary drive force is required, so that a large
rotation device is disadvantageously required for the
rotary support member.
Summary of Invention
Technical Problem
[0004]
The present invention has been devised to solve the
problem. An object of the present invention is to provide
a bit replacing device for an excavating machine, by
which the need for a large drive force for closing an
opening can be eliminated, a replacement bit can be
replaced by being retracted only in a linear direction,
and the workability is not impaired.
Solution to Problem
[0005]
In order to solve the above-described problem, the
invention according to a first aspect is a bit replacing
device for an excavating machine, the bit replacing
device being provided on a cutter head which is placed in
the front part of an excavating machine body to excavate
the ground, and the bit replacing device includes: a rear
surface frame provided on the rear surface side of the
front surface plate of the cutter head to form a
workspace for an operator to enter and exit; an opening
into and from which at least one replacement bit can be
inserted and removed, the opening being formed on the
front surface plate; a bit guide body provided on the
rear surface side of the opening, the bit guide body
having a bit guide hole through which the replacement bit
can be inserted and fixed; a gate plate placed between
the front surface plate and the bit guide body so as to
turn about an opening/closing axial center vertical to

the front surface plate, the gate plate having a valve
port through which the replacement bit can be inserted
and removed; and a gate opening/closing device capable of
turning the gate plate between a communication position
for communicating the opening with the bit guide hole and
a close position where the opening is closed.
[0006]
The invention according to a second aspect is the bit
replacing device for an excavating machine having the
configuration of the first aspect, wherein the at least
one replacement bit comprises a plurality of replacement
bits provided at equal angles on the same circle centered
about the opening/closing axial center of the gate plate.
[0007]
The invention according to a third aspect is the bit
replacing device for an excavating machine having the
configuration of the second aspect, wherein the two
replacement bits are provided on a radial axis line
passing through the rotation axis of the cutter head, and
the cross section of the workspace vertical to the radial
axis line has a smaller width in the circumferential
direction on the rear surface side than that in the
circumferential direction on the front surface side.
[0008]
The invention according to a fourth aspect is the bit
replacing device for an excavating machine having the
configuration of any one of the first to third aspects,
wherein gate sealing materials are provided between the
gate plate and the front surface plate and between the
gate plate and the bit guide body, respectively, for cut
off at the outer periphery of the gate plate and the
peripheral edge of the valve port, and a bit sealing
material for cut off is provided in a gap between the
replacement bit and the bit guide hole.
[0009]

The invention according to a fifth aspect is the bit
replacing device for an excavating machine having the
configuration of any one of the first to fourth aspects,
wherein the gate opening/closing device includes a gear
rotating mechanism having an external gear formed on the
outer periphery of the gate plate in the circumferential
direction centered about the opening/closing axial center
and a pinion engaged with the external gear.
Advantageous Effects of Invention
[0010]
According to the invention of the first aspect, after
the replacement bit protruding from the opening is
retracted and contained in the bit guide hole, the gate
opening/closing device turns the gate plate from the
communication position to the close position, and the
valve port provided on the gate plate is displaced from
the opening, so that the opening can be closed by the
gate plate. Thus, the opening can be closed with a
smaller drive device than in the prior art in which the
rotary support member is turned together with the
replacement bit. With this configuration, the bit guide
body has only to be placed via the gate plate on the rear
surface of the front surface plate, so that the weight
and size of the bit replacing device can be reduced and
the workspace can be widely obtained. Further, during the
replacement of bits, since soil pressure or water
pressure acts, a jig is required for pulling out the
replacement bit. However, since the replacement bit is
simply retracted in the linear direction and is pulled
out without being positioned in other postures by a
rotation or side shift, it is possible to easily install
a jig. Moreover, the gate plate turned to open or close
the opening is placed between the front surface plate and
the bit guide body and is not exposed, resulting in high

safety. Since the replacement bit is pulled out only
backward, it is also possible to easily design the rear
surface frame such that the workspace behind the
replacement bit can be widely obtained beforehand.
[0011]
According to the invention of the second aspect,
since the multiple replacement bits can be provided on
the same circle centered about the opening/closing axial
center of the gate plate, the invention is advantageous
in manufacturing cost. Further, since the multiple
replacement bits can be closely provided, effective
excavation can be achieved.
[0012]
According to the invention of the third aspect, the
cross section of the workspace is formed such that a
width in the circumferential direction on the rear
surface side (excavating machine body side) is smaller
than that in the circumferential direction on the front
surface side (cutter head side). Thus, it is possible to
reduce frictional resistance due to the intake or
agitation of excavated soil. Further, the depth of the
workspace is smaller on two sides of the workspace in the
circumferential direction. In response, the replacement
bit can be arranged on the radial axis line, so that the
workspace behind the replacement bit can be widely
obtained, and the workability can be enhanced.
[0013]
According to the invention of the fourth aspect, the
gate sealing material can effectively prevent high-
pressure mud water from entering the gap between the gate
plate and the front surface plate and the gap between the
gate plate and the bit guide body. Further, the bit
sealing material can effectively prevent high-pressure
mud water from entering through the gap between the
replacement bit and the bit guide hole.

[0014]
According to the invention of the fifth aspect, the
gate opening/closing device includes the gear rotating
mechanism having the external gear and the pinion, so
that the gate plate can be easily turned by a manually-
operated tool or automatic tool.
Brief Description of Drawings
[0015]
[FIG. 1A] FIG. 1A is a cross-sectional view showing a
main spoke member in an excavation use state of a bit in
a first embodiment of a bit replacing device of a shield
machine according to the present invention.
[FIG. 1B] FIG. 1B is a cross-sectional view showing the
main spoke member in a replacement retreat state of the
bit.
[FIG. 2] FIG. 2 is a front view showing the overall
shield machine.
[FIG. 3] FIG. 3 is a vertical cross-sectional view
showing the overall shield machine.
[FIG. 4] FIG. 4 is a partially enlarged front view
showing a main cutter spoke.
[FIG. 5] FIG. 5 is a partially enlarged cross-sectional
view showing the main cutter spoke as viewed from the
rear.
[FIG. 6] FIG. 6 is a vertical cross-sectional view
showing a bit replacing unit.
[FIG. 7A] FIG. 7A is a partial cross-sectional view
showing a replacement bit as viewed from the bottom.
[FIG. 7B] FIG. 7B is a partial cross-sectional view
showing the replacement bit as viewed from the side.
[FIG. 7C] FIG. 7C is a rear view showing the replacement
bit.
[FIG. 8] FIG. 8 is a cross-sectional view taken along the
line A-A of FIG. 6.

[FIG. 9] FIG. 9 is a cross-sectional view taken along the
line B-B of FIG. 6.
[FIG. 10A] FIG. 10A is a front view showing an outer
peripheral bit replacing unit.
[FIG. 10B] FIG. 10B is a vertical center cross-sectional
view showing the outer peripheral bit replacing unit.
[FIG. 11A] FIG. 11A is a front view of a bit replacing
unit showing a second embodiment of the bit replacing
device of the shield machine according to the present
invention.
[FIG. 11B] FIG. 11B is a cross-sectional view taken along
the line C-C of FIG. 11A.
Description of Embodiments
[0016]
Referring to the accompanying drawings, the following
will describe embodiments of a bit replacing device for a
shield machine which is an excavating machine according
to the present invention.
First Embodiment
[0017]
A first embodiment will be described with reference
to FIGS. 1A, 1B to 10A, and 10B.
[0018]
As shown in FIG. 3, a pressure bulkhead 12 keeping a
face colluvium pressure is provided in the front part of
a cylindrically-shaped shield body (excavating machine
body) 11, and a rotary ring body 14 is supported by the
pressure bulkhead 12 via a rotary bearing 13 so as to
rotate about shield axial center O (excavating machine
axial center). A circular cutter head 16 is supported at
the front ends of a plurality of support legs 15
projecting forward from the rotary ring body 14. A cutter
drive device 17 for rotationally driving the cutter head

16 is provided behind the pressure bulkhead 12. The
cutter drive device 17 includes a ring gear 17a provided
on the backside of the rotary ring body 14, a plurality
of drive pinions 17b engaged with the ring gear 17a, and
a plurality of rotation drive devices (hydraulic or
electric motors) 17c for rotationally driving the drive
pinions 17b. Further, a screw conveyor for soil removal
18 is provided on the pressure bulkhead 12 to discharge
soil excavated by the cutter head 16 backward in the
space kept at an atmospheric pressure while keeping a
face colluvum pressure.
[0019]
As shown in FIG. 2, the cutter head 16 includes a
plurality of main spoke members 21 extended along a
radial axis RL from a center member 20 on the shield
axial center O, a plurality of auxiliary spoke members 22
extended between the main spoke members 21 in a radial
direction, and an intermediate ring member 23 and an
outer peripheral ring member 24 which are placed in an
arc direction centered about the shield axial center 0 to
connect the main spoke members 21 and the auxiliary spoke
members 22. Soil inlets 25 are formed between the members
21 to 24.
[0020]
A plurality of bit replacing units (bit replacing
devices) 3 0 of the present invention are arranged on the
front part of the main spoke member 21, and two
replacement bits 31 are provided for each bit replacing
unit 30. Outer peripheral bit replacing units 60 are
provided on two sides of the outer peripheral end of the
main spoke member 21 in a circumferential direction.
Further, a plurality of fixed bits 26 are provided on the
respective front and side surfaces of the center member
2 0 and auxiliary spoke members 22 and the respective side
surfaces of the main spoke members 21.

[0021]
As shown in FIG. 3, on the rear surface side of the
center member 20, a manhole 2 7 is provided through which
an operator can enter and exit. The manhole 27 passes
through the pressure bulkhead 12 and communicates with
the backward space such that the operator can enter and
exit from the backward space kept at the atmospheric
pressure. Further, a rear surface frame 29 is provided on
the rear surface side of the main spoke member 21 to form
a workspace 2 8 which the operator can enter and exit
through the manhole 27. In the cross section of the rear
surface frame 29 of FIGS. 1A and 1B, a width on the rear
surface side in the circumferential direction (direction
of rotation) is smaller than that on the front surface
side in the circumferential direction (direction of
rotation). In other words, the rear surface frame 29
includes right and left side surface plates 29a suspended
backward from the right and left side edges of a spoke
front surface plate (front surface plate) 21a, inclined
surface plates 29b which are inclined inward from the
back edges of the right and left side surface plates 29a
to the rear surface side, and a rear surface plate 29c
linking the back edges of the right and left inclined
surface plates. The rear surface frame 29 is
substantially trapezoidal in cross section such that the
width of the rear surface plate 29c is small. With this
configuration, the frictional resistance due to the
intake and agitation of excavated soil is reduced, the
strength is ensured, and the workspace 28 has a depth
which is tapered backward on two sides of a radial axis
line RL (FIGS. 2 and 4) in the circumferential direction.
[0022]
As shown in FIGS. 2, 4, and 5, the bit replacing
units 3 0 are arranged on the main spoke member 21 at a
predetermined pitch along the radial direction. Two

replacement bits 31 are placed for each bit replacing
unit 3 0 on the radial axis line RL serving as the center
of the main spoke member 21, and the widths of the
workspace 28 in the depth direction and the
circumferential direction behind the replacement bits 31
are sufficiently obtained, so that the workability is
improved.
[0023]
(Replacement bit)
The replacement bit 31 has, as shown in FIGS. 7A to
7C, a cylindrical base cylinder 31b, an excavating blade
portion 31a composed of a base 31h attached to the front
surface of the base cylinder 31b and an excavating blade
3li protruded forward from the base 31h, and a flange 31c
which projects from the back end of the base cylinder 31b
toward the outer peripheral side and has fixing bolt
holes. The excavating blade portion 31a is smaller in
outer diameter than the base cylinder 31b and is
retractable through a bit guide hole 38 which will be
described later. As shown in FIGS. 1A, 1B, and 6, the
base cylinder 31b has a hollow portion 31d into which a
push pull jack (jig) 55 is inserted, the push pull jack
being capable of pushing and pulling the replacement bit
31. The hollow portion 31d communicates with and opens to
the workspace 28 via a center hole 31j of the flange 31c.
Use position recesses 31e for positioning in an
excavation use state are formed in the symmetric
positions of the flange 31c. Further, retreat position
recesses 31f for positioning in a replacement retreat
position where the replacement bit 31 is retracted are
formed in the front part of the base cylinder 31b.
Moreover, a detent edge 31g is provided on the flange 31c
to notch a face of the flange orthogonally crossing the
use position recess 3le in a parallel fashion.
[0024]

(Bit replacing unit)
As shown in FIG. 4, the bit replacing unit 3 0 has
continuous mounting holes 21b formed on the radial axis
line RL on the spoke front surface plate 21a of the main
spoke member 21, the mounting holes 21b having circles
parts of which overlap each other. Unit front surface
plates 32 are fitted to the circular portions of the
mounting holes 21b via pairs of right and left mounting
ring pieces 4 0 and are fixed by fixing bolts.
Opening/closing axial centers OC are provided in parallel
to the shield axial center O at the center positions of
the unit front surface plates 32. Openings 33 are formed
for each unit front surface plate 32 at two intersection
points of arcs centered about the opening/closing axial
center OC and the radial axis line RL. Further, as shown
in FIGS. 1A, 1B, and 6, a gate plate 34 is arranged on
the rear surface side of the unit front surface plate 32
via the mounting ring pieces 4 0 so as to rotate about the
opening/closing axial center OC. The gate plate 34 has
two valve ports 3 5 capable of communicating with and
closing the two openings 33. A gate opening/closing
device 3 6 is provided which can reciprocatingly turn the
gate plate 34 90 degrees between a communication position
where the opening 3 3 coincides with the valve port 3 5 and
a close position where the valve port 35 is displaced
from the opening 33 to close the opening. A bit guide
body 3 7 is attached on the rear surface side of the gate
plate 34 and has two guide holes 3 8 communicating with
the openings 3 3 via the valve ports 35.
[0025]
(Gate opening/closing device)
The gate opening/closing device 3 6 includes a gear
rotating mechanism having an external gear 36a, a pinion
36b, and a drive shaft 36c. The external gear 3 6a is
formed in the range of about 9 0 degrees in a

circumferential direction centered about the
opening/closing axial center OC on the outer periphery of
the circular gate plate 34. The pinion 36b is
rotationally supported between the bit guide body 37 and
the mounting ring piece 4 0 to engage with the external
gear 36a. The drive shaft 36c having the pinion 36b fixed
thereto protrudes to the side of the workspace 28. A
manually-operated tool such as a ratchet wrench or an
automatic tool such as an electric or hydraulic torque
wrench is mounted on the drive shaft 36c to rotate the
drive shaft 36c, drive the gate opening/closing device 36,
turn the gate plate 34, and open and close the opening 33.
[0026]
Further, a rotation regulating tool 3 9 for regulating
a turn of the gate plate 34 is provided on the rear
surface (or front surface) of the gate plate 34. The
rotation regulating tool 3 9 includes an arc groove 3 9a
and a guide pin 3 9b. The arc groove 3 9a is formed over
the range of 90 degrees centered about the
opening/closing axial center OC on the rear surface of
the gate plate 34. The guide pin 39b projects to the
inner surface of a face plate portion 41 of the bit guide
body 3 7 and is movably fitted to the arc groove 3 9a. Thus,
the turning limit of the gate plate 34 can be formed.
[0027]
The gate opening/closing device 3 6 drives the outer
periphery of the gate plate 34 to turn, reducing spatial
interference with the workspace 28. Further, small torque
can turn the gate plate 34, so that opening/closing can
be easily performed by simple work equipment such as a
manually-operated tool or automatic tool. Moreover, since
the gate plate 34 is circularly-formed and the outer
periphery is rotationally supported via the mounting ring
piece 40, an axis member serving as the turning center of
the gate plate 34 becomes unnecessary. Accordingly, the

outer diameter of the gate plate 34 can be reduced,
resulting in a size reduction in the bit replacing unit
30.
[0028]
(Bit guide body)
The bit guide body 3 7 includes the face plate portion
41, two holding cylinder portions 42, and a linking block
43 . The outer periphery of the face plate portion 41 is
fixed to the unit front surface plate 32 via the mounting
ring piece 40 by fixing bolts to cover the rear surface
of the gate plate 34. The holding cylinder portions 42
project backward from the face plate portion 41 and have
the bit guide holes 38. The linking block 43 links the
holding cylinder portions 42. A fix block 44 engaged with
the detent edge 31g of the replacement bit 31 is attached
to the rear end surface of the linking block 43. Further,
a bolt hole, through which the flange 31c of the
replacement bit 31 is fixed via fixing bolts, is formed
on the rear end surface of the holding cylinder portion
42. Moreover, locking claws 45 for positioning, which can
be engaged with and disengaged from the use position
recesses 31e and retreat position recesses 31f, are
placed in the symmetric positions via
engaging/disengaging bolts 46. The locking claws 45 can
be engaged with or disengaged from the use position
recess 31e and retreat position recess 31f and be fixed,
since the engaging/disengaging bolts 46 are inserted
through the long holes of the locking claws 45.
[0029]
(Cut-off sealing material)
In the bit replacing unit 30, in order to prevent
high-pressure mud water from entering from the face side,
first and second bit sealing materials 51 and 52 are
mounted on the outer peripheries of the base 31h and the
rear ends of the base cylinder 31b of the replacement bit

31 via mounting grooves. In the use position, the first
bit sealing material 51 seals a gap between the
replacement bit 31 and the opening 33, and the second bit
sealing material 52 seals a gap between the base cylinder
31b and the bit guide hole 38. In the replacement retreat
position, the first bit sealing material 51 seals a gap
between the base 31h of the replacement bit 31 and the
bit guide hole 38. The first and second bit sealing
materials 51 and 52 can be replaced during the
replacement of the replacement bit 31, and sufficient
sealing properties can be obtained with high reliability.
[0030]
As a matter of course, the first and second bit
sealing materials 51 and 52 can be mounted on the
slidable contact surface of the spoke front surface plate
32 and the face plate portion 41 via the mounting grooves.
[0031]
First gate sealing materials 53 are mounted on the
peripheral edge of the valve port 3 5 via mounting grooves
on the front and rear surfaces of the gate plate 34.
Further, second gate sealing materials 54 are mounted on
the outer periphery of the gate plate 34 via mounting
grooves. The first and second gate sealing materials 53
and 54 on the front surface prevent mud water from
entering a gap between the gate plate 34 and the spoke
front surface plate 32, and the first and second gate
sealing materials 53 and 54 on the rear surface prevent
mud water from entering a gap between the gate plate 34
and the face plate portion 41.
[0032]
The first gate sealing material 53 for sealing the
periphery of the valve port 3 5 passes through the opening
33 and the bit guide hole 38 during a turn of the gate
plate 34. However, the first gate sealing material 53
completely adheres to a sliding surface with a low risk

of damage during excavation and replacement, so that
sufficient sealing properties can be ensured. Further,
the second gate sealing material 54 for sealing the outer
periphery of the gate plate 34 closely adheres to the
sliding surface at all times without a change in the
capacity of sealing space and with a low risk of damage,
so that sufficient sealing properties can be ensured.
[0033]
As a matter of course, the first and second gate
sealing materials 53 and 54 can be mounted on the side of
the spoke front surface plate 32 or the face plate
portion 41 via mounting grooves.
[0034]
(Push pull jack)
The push pull jack 55 of FIGS. 1A, 1B, and 6 is a jig
for pulling and pushing the replacement bit 31, and a fix
guide member 56 having a dovetail groove-shaped cross-
section is attached to the inner surface of the rear
surface plate 2 9c of the rear surface frame 2 9 along the
radial axis RL. Meanwhile, a jack body 55a of the push
pull jack 55 is inserted into the hollow portion 31d of
the replacement bit 31, and a connecting ring 57 fixed to
the outer periphery of the jack body 55a is connected to
the flange portion 31c via connecting bolts. A piston rod
55b of the push pull jack 55 is connected to an
engagement block 58 which is adjustably fitted to the fix
guide member 56.
[0035]
Thus, the jack body 55a is inserted into the hollow
portion 31d, and the connecting ring 57 is attached to
the replacement bit 31. The piston rod 55b is connected
to the engagement block 58 fitted to the fix guide member
56. Further, the push pull jack 55 is shrunk, and the
replacement bit 31 is pulled out from the opening 33, the
valve port 35, and the bit guide hole 38.

[0036]
With the above-described configuration, bit
replacement can be performed similarly to the following
bit replacing unit 30.
[0037]
(Bit replacement of the bit replacing unit 30)
In a tunnel excavation state, the replacement bit 31
is fixed in an excavation use position. When the
excavation proceeds and the replacement bits 31 are worn,
the cutter drive device 17 stops at a position where the
main spoke member 21 having the targeted replacement bits
31 is positioned, for example, in a horizontal posture.
Further, the operator enters the workspace 28 through the
manhole 27 to replace the bits.
[0038]
1) In the workspace 28 of the targeted bit replacing
unit 30, the operator inserts the jack bodies 55a of the
push pull jacks 55 into the hollow portions 31d via the
center holes 31j of the replacement bits 31 from the rear
surfaces of the holding cylinder portions 42, so that the
jack bodies 55a are attached to the flange portions 31c
of the replacement bits 31 via the connecting rings 57.
Further, the engagement blocks 5 8 are engaged with the
fix guide member 56 attached to the rear surface plate
29c of the rear surface frame 29, and the piston rods 55b
of the push pull jacks 55 are extended, so that the push
pull jacks 55 are connected to the engagement blocks 58.
[0039]
2) The fixing bolts of the flange 31c are removed, so
that the replacement bit 31 and the bit guide bodies 3 7
are separated from each other. Further, the
engaging/disengaging bolts 46 are loosened, so that the
locking claws 45 are retracted from the use position
recesses 31e.
[0040]

3) When the push pull jacks 55 are shrunk, the
replacement bits 31 are retracted, and the leading ends
of the excavation blade portions 31a pass through the
valve ports 35 of the gate plates 34 and are contained in
the bit guide holes 38, the locking claws 45 protrude to
be engaged with the retreat position recesses 31f, the
engaging/disengaging bolts 46 are tightened, and the
replacement bits 31 are fixed in the replacement retreat
positions.
[0041]
4) When the two replacement bits 31 are fixed in the
replacement retreat positions, a manually-operated tool
or automatic tool is used to rotationally drive the drive
shaft 36c of the gate opening/closing device 36. When the
gate plate 34 is turned 90 degrees by means of an
opening/closing gear mechanism, the gate plate 34 closes
the two openings 33.
[0042]
5) The piston rods 55b of the push pull jacks 55 and
the fix guide member 56 are separated from each other,
the connecting rings 57 of the jack bodies 55a are
removed out from the flanges 31c of the replacement bits
31, the push pull jacks 55 are separated from the
replacement bits 31, and then the push pull jacks 55 are
removed out.
[0043]
6) After the engaging/disengaging bolts 4 6 are
loosened and the locking claws 4 5 are retracted from the
retreat position recesses 31f, the worn replacement bits
31 are removed out from the bit guide holes 3 8 and are
transported.
[0044]
7) New replacement bits 31 transported into the
workspace 28 are loaded into the bit guide holes 38. The
locking claws 45 are engaged with the retreat position

recesses 31f, the engaging/disengaging bolts 46 are
tightened, and the replacement bits 31 are fixed in the
replacement retreat positions.
[0045]
8) The jack bodies 55a of the push pull jacks 55 are
inserted into the hollow portions 31d through the center
holes 3lj of the replacement bits 31, and the jack bodies
55a are fixed to the flanges 31c of the replacement bits
31 via the connecting rings 57. Further, the engagement
block 58 engaged with the fix guide member 56 and the
piston rod 55b of the push pull jack 55 are connected to
each other.
[0046]
9) The gate opening/closing device 36 is driven by
the manually-operated tool or automatic tool to turn the
gate plate 34 90 degrees in the opposite direction, the
valve ports 35 coincide with the two openings 33, and the
openings 3 3 are opened.
[0047]
10) After the engaging/disengaging bolts 46 are
loosened and the locking claws 45 are retracted from the
retreat position recesses 31f, the push pull jacks 55 are
extended to push the replacement bits 31 into the bit
guide holes 38. The excavation blade portions 31a
protrude forward from the valve ports 3 5 via the openings
33. Further, the locking claws 45 are engaged with the
use position recesses 31e to be positioned, and the
flanges 31c and the holding cylinder portions 42 are
connected to each other by the fixing bolts, and new
replacement bits 31 are fixed to the bit guide bodies 37
in the excavation use position.
[0048]
11) The connecting rings 5 7 provided on the jack
bodies 55a of the push pull jacks 55 are detached from
the flanges 31c of the replacement bits 31, and the

piston rods 55b and the fix guide member 56 are separated
from each other, and the push pull jacks 55 are removed
out from the replacement bits 31.
[0049]
(Outer peripheral bit replacing unit)
As shown in FIGS. 10A and 10B, an outer periphery
excavation bit (replacement bit) 61 for outer periphery-
excavation is provided in the outer peripheral bit
replacing unit 60. The outer periphery excavation bit 61
is tilted forward at 9° to the opening/closing axial
center OC in an outer peripheral direction. A circular
outer peripheral unit front surface plate 63 is attached
to an outer peripheral front plate connected to the main
spoke member 21 of the cutter head 16 via a mounting ring
62, and an opening 64 is formed close to the outer
periphery of the outer peripheral unit front surface
plate 63. A gate plate 65 is placed on the rear surface
of the outer peripheral unit front surface plate 63 via
the mounting ring 62 so as to turn about the
opening/closing axial center OC in the range of 90
degrees. A valve port 66 is formed on the gate plate 65
so as to coincide and communicate with the opening 64. A
bit guide body 67 is also attached to the rear surface of
the outer peripheral unit front surface plate 63 via the
mounting ring 62. The bit guide body 67 has a bit guide
hole 68 communicating with the valve port 66 and the
opening 64, and is tilted at the same angle 9°. Other
constituent elements are configured similarly to those in
the gate opening/closing device 3 6 and the bit
replacement unit 3 0 and are indicated by the same
reference numerals, and an explanation thereof is omitted.
[0050]
(Effects of the first embodiment)
In the first embodiment, after the replacement bit 31
is retracted and contained in the bit guide hole 38 of

the bit guide body 37, the gate plate 34 is turned by the
gate opening/closing device 36, the valve port 35 is
displaced from the opening 33, and the opening 33 is
closed by the gate plate 34.
[0051]
Thus, compared to the prior art in which a
replacement bit is rotated concurrently with a bit
support member, the opening 33 can be closed with a small
drive force since the gate plate 34 having the valve port
3 5 is turned. Further, the bit guide body 3 7 has only to
be placed on the rear surface of the spoke front surface
plate 2la via the gate plate 34, so that the weight and
size of the bit replacement unit 30 can be reduced and
the workspace 28 can be widely obtained.
[0052]
Further, since soil pressure or water pressure acts
during the replacement of bits, the push pull jack 55 is
required to pull or push the replacement bit 31. However,
the replacement bit 31 is simply retracted in a linear
direction but is not positioned in other postures by a
turn or side shift, so that the push pull jack 55 can be
easily placed.
[0053]
The gate plate 34 is mounted between the spoke front
surface plate 21a and the face plate portion 41 of the
bit guide body 37, the outer periphery of the gate plate
34 is surrounded by the mounting ring piece 40, and the
driven portion is not exposed into the workspace 28. Thus
high safety is provided.
[0054]
Moreover, the cross section of the workspace 28
formed by the rear surface frame 2 9 is formed such that
the width in the circumferential direction on the rear
surface side (excavating machine body side) is narrower
than that on the front surface side (cutter head side).

Thus frictional resistance due to the intake or agitation
of excavated soil can be reduced while ensuring strength.
Furthermore, since the replacement bit 31 is placed on
the radial axis line RL and is retracted only backward
along the linear direction during replacement, the
workspace 28 can be sufficiently ensured in a direction
of pulling out the replacement bit 31 during replacement,
resulting in an improvement in workability.
[0055]
Since the first and second gate sealing materials 53
and 54 are provided, it is possible to effectively
prevent high-pressure mud water from entering through the
gap between the gate plate 34 and the unit front surface
plate 32 and a gap between the gate plate 34 and the bit
guide body 37. Further, since the first and second bit
sealing materials 51 and 52 are provided, it is possible
to effectively prevent high-pressure mud water from
entering the gap between the replacement bit 31 and the
bit guide hole 38.
[0056]
Moreover, since the gate opening/closing device 36
includes the gear rotating mechanism having the external
gear 36a and the pinion 36b, the gate plate 34 can be
turned by a manually-operated tool or automatic tool to
easily open or close the opening 33.
Second Embodiment
[0057]
(Bit replacing unit)
In the bit replacing unit 3 0 of the first embodiment,
the two replacement bits 31 (openings 33) are placed on
the radial axis line RL. However, as shown in FIGS. 11A
and 11B, in a bit replacing unit 70, three replacement
bits 31 are provided at regular intervals (equal angles)
centered about an opening/closing axial center OC. In

other words, in the bit replacing unit 70, openings 33,
valve ports 35, and bit guide holes 38 are formed 120°
apart on the same arc centered about the opening/closing
axial center OC, and the three replacement bits 31 are
provided. The replacement bits 31 are tilted α° toward
the front outer peripheral side, and a gate
opening/closing device 36 reciprocatingly turns a gate
plate 34 in the range of 120°. Other configurations are
the same as those in the first embodiment, the same
components are indicated by the same reference numerals,
and an explanation thereof is omitted.
[0058]
In the bit replacing unit 70, the three replacement
bits 31 can be provided, advantageously reducing cost,
and the three replacement bits 31 can be closely provided,
thereby enabling effective excavation. Further, the
replacement bits 31 are tilted, so that the workspace 28
can be effectively used.

We Claim:
[Claim 1]
A bit replacing device for an excavating machine, the
bit replacing device being provided on a cutter head
which is placed in a front part of an excavating machine
body to excavate ground, the bit replacing device
comprising:
a rear surface frame provided on a rear surface side
of a front surface plate of the cutter head to form a
workspace for an operator to enter and exit;
an opening into and from which at least one
replacement bit can be inserted and removed, the opening
being formed on the front surface plate;
a bit guide body provided on a rear surface side of
the opening, the bit guide body having a bit guide hole
through which the replacement bit can be inserted and
fixed;
a gate plate placed between the front surface plate
and the bit guide body so as to turn about an
opening/closing axial center vertical to the front
surface plate, the gate plate having a valve port through
which the replacement bit can be inserted and removed;
and
a gate opening/closing device capable of turning the
gate plate between a communication position for
communicating the opening with the bit guide hole and a
close position where the opening is closed.
[Claim 2]
The bit replacing device for an excavating machine
according to claim 1, wherein the at least one
replacement bit comprises a plurality of replacement bits
provided at equal angles on a same circle centered about
the opening/closing axial center of the gate plate.
[Claim 3]

The bit replacing device for an excavating machine
according to claim 2, wherein the two replacement bits
are provided on a radial axis line passing through a
rotation axis of the cutter head, and
a cross section of the workspace vertical to the
radial axis line has a smaller width in a circumferential
direction on a rear surface side than that in the
circumferential direction on a front surface side.
[Claim 4]
The bit replacing device for an excavating machine
according to any one of claims 1 to 3, wherein gate
sealing materials are provided between the gate plate and
the front surface plate and between the gate plate and
the bit guide body, respectively, for cut off at an outer
periphery of the gate plate and a peripheral edge of the
valve port, and
a bit sealing material for cut off is provided in a
gap between the replacement bit and the bit guide hole.
[Claim 5]
The bit replacing device for an excavating machine
according to any one of claims 1 to 4, wherein the gate
opening/closing device comprises a gear rotating
mechanism having an external gear formed on the outer
periphery of the gate plate in a circumferential
direction centered about the opening/closing axial center
and a pinion engaged with the external gear.

ABSTRACT

An opening for a replacement bit can be closed
without a large drive force, the replacement bit can be
replaced without being moved, and the workability of
replacement is not impaired. A rear surface frame (2 9)
forms a workspace (28) on the rear surface side of a
spoke front surface plate (21), and openings (33) are
formed on the spoke front surface plate (21) such that a
replacement bit (31) can be inserted into and removed
from the opening (33). A bit guide body (37) having a bit
guide hole (38) is provided on the rear surface side of
the opening (33). A gate plate (34) is provided which has
valve ports (35) capable of communicating and closing the
openings (33) and the bit guide holes (38). A gate
opening/closing device (36) is provided which can turn
the gate plate (34) to open or close the openings (33).