TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a spiral-shaped roller cutter for cutting a reinforcement
embedded in an existing pipe and a tunnel excavator cutter head provided with the
same.
BACKGROUND ART
[0002] A conventional cutter head for excavating and crushing an existing pipe is disclosed,
for example, in Japanese Unexamined Utility Model Publication No. 4-122798. In accordance
with the publication, in Figs. 7A to 8C, a plurality of roller bits 74 to 76 supported
in such a manner as to freely rotate around support axes O2 to O4 arranged in a periphery
of an axis O1 of rotation of a cutter head 71 at a predetermined angle in a radial
direction respectively are arranged on a front surface of the cutter head 71 of a
shield excavator 61. That is, they are respectively constituted by a roller bit 74
of a vertical blade type on which blade portions 74b are respectively formed along
a plurality of surfaces including the support axis O2, a roller bit 75 of a spiral
blade type on which blade portions 75b are spirally formed around the support axis
O3 and a roller bit 76 of a horizontal blade type on which circular blade portions
76b are formed at a predetermined interval in a direction of the support axis within
a surface perpendicular to the support axis O4. Then, axial portions 74a to 76a of
the plurality of roller bits 74 to 76 are rotatably supported to the cutter head 71
through bearings 77 and 77, respectively. An existing pipe 72 in Fig. 9 is constituted
by a concrete pipe wall 72a, a vertical reinforcement 72b and a horizontal reinforcement
72c.
[0003] Here, an operation of the roller bit 76 of the horizontal blade type will be described
below. In Figs. 10A to 10C, four paths 76c on the surface of the existing pipe 72
to be crushed by the roller bit 76 of the horizontal blade type is coaxial with respect
to the center O1 of rotation of the cutter head 71. Accordingly, there is little possibility
that the roller bit 76 of the horizontal blade type cuts the vertical reinforcement
72b bent in a direction the same as a rotating direction S1 of the cutter head 71,
and this is provided simply in order to crush the concrete pipe wall 72a.
[0004] Next, an operation of the roller bit 74 of the vertical blade type will be described
below. In Figs. 11A to 11C, a plurality of paths 74c on the surface to be crushed
of the existing pipe 72 by the roller bit 74 of the vertical blade type is substantially
perpendicular to the vertical reinforcement 72b bent in the same direction as the
rotating direction S1 of the cutter head 71. Accordingly, the roller bit 74 of the
vertical blade type can cut the vertical reinforcement 72b at the pitch interval of
the blade portion 74b thereof.
[0005] Next, an operation of the roller bit 75 of the spiral blade type will be described
below with reference to Figs. 12A to 12B.
Since the roller bit 75 of the spiral blade type is structured such that a blade portion
75b is a spiral having a thread, paths 75c thereof (a two dot chain line) displaces
an angle θ1 from paths (a single dot chain line) along the rotating direction S1 of
the cutter head 71, respectively. Accordingly, a vertical reinforcement 72b bent to
the same direction as the rotating direction S1 of the cutter head 71 is changed a
direction to a position shown by a broken line at a slight angle θ2, however, is not
cut away. In this case, the disc cutter of the spiral blade type is also disclosed
in Japanese Unexamined Utility Model Publication No. 1-138995 as another embodiment.
In accordance with the publication, in Figs. 13A to 13B, in a small diameter pipe
excavator in which a cutter head 53 having each of disc cutters 54 and 55 in a distal
end portion of a leading apparatus 51 in a freely rotatable manner, spiral blades
54b and 55b each having a thread are projected from an outer peripheral surface of
each of cutter main bodies 54a and 55a. These spiral blades 54b and 55b also serve
the same function as that of the blade portion 75b of the roller bit 75 of the spiral
blade type.
[0006] In this case,
(1) The conventional roller bit 76 of the horizontal blade type is provided in order
to crush the concrete pipe wall 72a, and hardly cuts the vertical reinforcement 72b.
(2) Since the path 74c on the cutting surface of the conventional roller bit 74 of
the vertical blade type is perpendicular to the vertical reinforcement 72b, it can
cut the vertical reinforcement 72b to chips at an interval of the pitch of the roller
bit 74 of the vertical blade type.
However, as shown in Fig. 11B, the vertical reinforcement 72b sinks into the concrete
pipe 72a due to a pressing force F1 for pressing the blade tip 74b of the roller bit
74 of the vertical blade type, so that a sufficient reaction force can not be secured.
Accordingly, there has been a problem that the vertical reinforcement 72b can not
certainly cut by the roller bit 74 of the vertical blade type.
(3) The conventional roller bit 75 of the spiral blade type can displace the vertical
reinforcement 72b bent to the same direction as the rotating direction S1 of the cutter
head 71 at a slight angle θ2, however, as shown in Fig. 12B, it is almost impossible
to cut the vertical reinforcement 72b.
[0007] In this case, when the angle θ1 is made large, the angle θ2 is increased, so that
it is easy to cut the vertical reinforcement 72b. However, since the pitch of the
blade is increased when the pitch angle θ1 is set to be large in the spiral blade
having a single thread, there has been a problem that the vertical reinforcement 72b
can not be cut to a suitable length.
DISCLOSURE OF THE INVENTION
[0008] The present invention is made in order to solve the problems in the above prior arts,
and an object of the present invention is to provide a spiral-shaped roller cutter
and a tunnel excavator cutter head provided with the same, which can efficiently and
surely cut a reinforcement embedded in an existing pipe.
[0009] In accordance with a first invention of a spiral-shaped roller cutter in accordance
with the present invention, there is provided a spiral-shaped roller cutter having
a spiral-shaped blade portion on an outer peripheral surface, wherein the spiral-shaped
blade portion is constituted by a plurality of threads.
[0010] Since the spiral-shaped blade portion is constituted by a plurality of threads, the
spiral-shaped roller cutter having a great pitch angle and a narrow interval between
the blades can be formed. Since the pitch of the blade is widened when increasing
the pitch angle by the conventional spiral-shaped blade having a single thread, the
interval between the blades is increased. Then, when setting to a plurality of threads,
the interval between the blades can be set to be narrower than that of the single
thread and in an optional manner even when the pitch angle is increased since it is
produced by placing the other thread between one thread.
[0011] In accordance with a second invention of a spiral-shaped roller cutter, there is
provided a spiral-shaped roller cutter as recited in the first invention, wherein
the spiral-shaped blade portion is formed in a taper shape in a facewidth direction
of a tooth.
[0012] In accordance with the structure, a tooth groove gradually becomes wide toward a
large diameter side from a small diameter side. Accordingly, the crushed concrete
can be easily discharged without stopping the blade groove.
[0013] In accordance with a third invention of a spiral-shaped roller cutter, there is provided
a spiral-shaped roller cutter as recited in the first or second invention, wherein
a pitch angle of the spiral-shaped blade portion having a plurality of threads is
set to be 20 degrees to 80 degrees.
[0014] When the pitch angle is made great, the operation that the spiral-shaped roller cutter
rolls on the cut surface of the reinforcement is reduced. On the contrary, when the
pitch angle is made small, the path along which the spiral-shaped roller cutter rolls
on the crush surface gets near a tangential direction of the rotation of the cutter
head so as to make it hard to catch the reinforcement. Accordingly, when the pitch
angle of the spiral-shaped blade portion is set to be 20 degrees to 80 degrees, the
spiral-shaped roller cutter can easily catch the distal end portion of the reinforcement
bent in the rotating direction of the cutter head, and the reinforcement caught by
the spiral-shaped roller cutter can be easily cut due to the rolling operation of
the spiral-shaped roller cutter. In this case, the pitch angle can be determined to
an optimum value in accordance with the object to be cut by changing the number of
a plurality of threads.
[0015] In accordance with a first invention of a tunnel excavator cutter head, there is
provided a tunnel excavator cutter head comprising a rotatable roller cutter mounted
around an axis of rotation extending substantially to a radial direction of the cutter
head, wherein the roller cutter is a spiral-shaped roller cutter provided with a spiral-shaped
blade portion having a plurality of threads on an outer peripheral surface thereof.
[0016] In accordance with the structure mentioned above, since an angle (a pitch angle)
formed between the axial direction of the reinforcement bent in the rotating direction
of the cutter head and the spiral-shaped blade portion becomes great in an operation
of crushing the concrete embedding the reinforcement by providing the spiral-shaped
roller cutter having the spiral-shaped blade portion having a plurality of threads
in the tunnel excavator cutter head, the reinforcement can be efficiently cut by a
small pressing force due to a rolling operation of the spiral-shaped roller cutter.
Further, since the interval between the blades is narrow, the reinforcement and the
like can be finely crushed.
[0017] Further, the spiral-shaped roller cutter can easily catch the distal end portion
of the reinforcement bent in the rotating direction of the cutter head by changing
a number of the threads so as to select a magnitude of the pitch angle to an appropriate
value in correspondence to the material to be cut, the reinforcement caught thereby
can be easily cut due to a rolling operation of the spiral-shaped roller cutter, and
the reinforcement can be shortened so that the length of the cut reinforcement becomes
near the pitch length of the spiral-shaped blade portion.
[0018] Accordingly, there are significant effects mentioned below.
(1) The pressing force of the spiral-shaped roller cutter can be reduced by cutting
the distal end portion of the reinforcement due to the rolling operation of the spiral-shaped
roller cutter. The reinforcement can be surely cut without sinking in the concrete
in the same manner as the roller bit of the vertical blade type in the second prior
art.
(2) The distal end portion of the reinforcement exposed from the concrete is bent
substantially in the rotating direction of the cutter head, however, the path along
which the spiral-shaped blade portion of the spiral-shaped roller cutter rolls on
the distal end portion of the reinforcement becomes short and the cut area of the
reinforcement is reduced, so that the crushing force becomes small. Further, since
the angle formed between the cut surface of the reinforcement and the axial direction
of the reinforcement becomes near a right angle and the cut piece of the reinforcement
is shortened. Accordingly, the cut piece can be easily conveyed in the same manner
as normal excavated earth and sand without being caught in the cutter head or a screw
conveyor.
[0019] In accordance with a second invention of a tunnel excavator cutter head, there is
provided a tunnel excavator cutter head as recited in the first invention, wherein
the spiral-shaped roller cutter is constituted by two kinds of spiral-shaped roller
cutters in which pitch angles of the spiral-shaped blade portion having a plurality
of threads are mutually directed to inverted directions.
[0020] In accordance with the structure mentioned above, since the two kinds of spiral-shaped
roller cutters in which the pitch angles are mutually directed to the inverted directions
are mounted to the cutter head, the paths of the respective blade portions of the
two kinds of spiral-shaped roller cutters on the crushed surface of the concrete pipe
cross to each other, so that even when the reinforcement exposing from the crushed
surface of the concrete pipe is bent to a direction of the blade groove of one of
the spiral-shaped roller cutters, it can be cut by the other of the spiral-shaped
roller cutters.
[0021] In accordance with a third invention of a tunnel excavator cutter head, there is
provided a tunnel excavator cutter head as recited in the first invention, wherein
the spiral-shaped roller cutter is provided with the spiral-shaped roller cutter provided
with the spiral-shaped blade portion having a plurality of threads, and any one of
a disc-shaped roller cutter having a disc-shaped blade portion perpendicular to the
axis of rotation and a spiral-shaped roller cutter having a thread of spiral-shaped
blade portion.
[0022] In accordance with the structure mentioned above, the reinforcement bent in the rotating
direction of the cutter head by the spiral-shaped roller cutter having a plurality
of threads can be efficiently cut by a small pressing force due to the rolling operation
of the spiral-shaped roller cutter. At this time, even when there is a reinforcement
bent in the direction of the blade groove of the spiral-shaped blade portion, the
reinforcement can be efficiently cut by a small pressing force in the same manner
as that of the spiral-shaped roller cutter having a plurality of threads due to the
rolling operation of the disc-shaped roller cutter and the spiral-shaped roller cutter
having a single thread.
[0023] In accordance with a fourth invention of a tunnel excavator cutter head, there is
provided a tunnel excavator cutter head as recited in the third invention, wherein
a cutting surface of the spiral-shaped roller cutter provided with the spiral-shaped
blade portion having a plurality of threads and a cutting surface of any one of the
disc-shaped roller cutter and the spiral-shaped roller cutter having a thread of spiral-shaped
blade portion are disposed so as to be shifted at a predetermined amount in a direction
of excavating a tunnel.
[0024] In accordance with the structure mentioned above, the concrete portion can be crushed
by the roller cutter suitable for each of the steps and subsequently the reinforcement
is cut by the cutting surface of the other kind of roller cutter provided a predetermined
amount at the back thereof. As mentioned above, since the roller cutters respectively
suitable for crushing the concrete and cutting the reinforcement can be determined,
a durability of each of the roller cutters can be improved.
[0025] In accordance with an fifth invention of a tunnel excavator cutter head, there is
provided a tunnel excavator cutter head as recited in any one of the first, second,
third and fourth inventions, wherein the cutter head is structured such as to rotate
in a direction that an angle formed between a crush surface of a existing pipe and
a hoop reinforcement within a non-crushed portion rotates from an acute angle to an
obtuse angle when crushing the existing pipe in which the hoop reinforcement is embedded.
[0026] In accordance with the structure mentioned above, since the hoop reinforcement can
be surely cut without being caught in the cutter head, a cutting efficiency of the
hoop reinforcement can be improved. Further, since the hoop reinforcement is cut to
a short piece, it can be efficiently conveyed in the same manner as normal excavated
earth and sand without being caught in the cutter head or the screw conveyor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027]
Fig. 1A is a front elevational view of a tunnel excavator cutter head in accordance
with a first embodiment of the present invention and Fig. 1B is a schematic view which
explains a crushing operation on a crushed surface of an existing pipe by the cutter
head in Fig. 1A;
Fig. 2A is an enlarged front elevational view of a spiral-shaped roller cutter in
Fig. 1A, Fig. 2B is a side elevational view of Fig. 2A and Fig. 2C is a perspective
view of Fig. 2A;
Fig. 3A is a schematic view which explains a rolling and cutting operation by the
spiral-shaped roller cutter in Fig. 1A and Fig. 3B is a schematic view which explains
a crushing operation of a cutter head in which each of distal end position of outer
peripheral portions of two kinds of roller cutters is different from each other;
Fig. 4A is a front elevational view of a tunnel excavator cutter head in accordance
with a second embodiment of the present invention and Fig. 4B is a schematic view
which explains an operation on a crushed surface of an existing pipe by the cutter
head in Fig. 4A;
Fig. 5A is a front elevational view of a tunnel excavator cutter head in accordance
with a third embodiment of the present invention and Fig. 5B is a schematic view which
explains a crushing operation on a crushed surface of an existing pipe by the cutter
head in Fig. 5A;
Fig. 6A is a perspective view of a concrete existing pipe embedding a hoop reinforcement
therein which is crushed by the cutter head in accordance with the first, second or
third embodiment and Fig. 6B is an enlarged view of a P portion in Fig. 6A as seen
from an arrow V;
Fig. 7A is a vertical cross sectional view of a shield excavator in accordance with
a prior art and Fig. 7B is a front elevational view of a cutter head in Fig. 7A;
Fig. 8A is a mounting view of a roller bit of a spiral blade type mounted to the cutter
head in Fig. 7A, Fig. 8B is a mounting view of a roller bit of a horizontal blade
type and Fig. 8C is a mounting view of a roller bit of a vertical blade type;
Fig. 9 is a perspective view of a concrete existing pipe embedding a reinforcement
in vertical and horizontal directions;
Fig. 10A is a schematic view which explains an operation of the roller bit of the
horizontal blade type on the crush surface of the existing pipe, Fig. 10B is a cross
sectional view along a line B-B in Fig. 10A and Fig. 10C is a cross sectional view
along a line C-C in Fig. 10A;
Fig. 11A is a schematic view which explains an operation of the roller bit of the
vertical blade type on the crush surface of the existing pipe, Fig. 11B is a cross
sectional view along a line B-B in Fig. 11A and Fig. 11C is a cross sectional view
along a line C-C in Fig. 11A;
Fig. 12A is a schematic view which explains an operation of the roller bit of the
spiral blade type on the crush surface of the existing pipe, Fig. 12B is a cross sectional
view along a line B-B in Fig. 12A; and
Fig. 13A is a vertical cross sectional view a shield excavator in accordance with
another prior art and Fig. 13B is a front elevational view of the cutter head in Fig.
13A.
BEST MODE FOR CARRYING OUT THE INVENTION
[0028] A tunnel excavator cutter head in accordance with a first embodiment of the present
invention will be in detail described below with reference to Figs. 1A to 3B.
[0029] A tunnel excavator cutter head 1 has axes 2 and 2 respectively in a diametrical direction
of the cutter head 1 and near an outer peripheral surface as shown in Fig. 1A, and
spiral-shaped roller cutters 3 and 3 having a spiral-shaped blade portion 3a having
a plurality of threads formed thereon are respectively mounted to the respective axes
2 and 2 of rotation so as to be freely rotated. Each of cutter bits 4 and 4 is fixed
to an edge portion of a mounting hole of each of the spiral-shaped roller cutters
3 and 3 toward a rotational direction S1 of the cutter head 1. In detail, the spiral-shaped
roller cutter 3 is provided with the spiral-shaped blade portion 3a having a plurality
of threads, as shown in Figs. 2A to 2C. The spiral-shaped blade portion 3a having
a plurality of threads is formed in a taper shape and a pitch angle θ thereof is,
for example, 45 degrees.
[0030] Each of normal disc cutters 5 and 5 are rotatably mounted in a diametrical direction
perpendicular to the axes 2 and 2 of rotation of each of the spiral-shaped roller
cutters 3 and 3.
[0031] Next, a crushing operation of an existing pipe 6 in accordance with this embodiment
will be described below.
[0032] When the cutter head 1 rotates in a direction of an arrow S1 in Fig. 1A, each of
the spiral-shaped roller cutters 3 and 3 is pressed to a crushed surface of the existing
pipe 6 and is rotated in a direction of an arrow S2.
[0033] Fig. 1B shows a part of the crushed surface of the existing pipe 6 as seen toward
an excavating direction of the tunnel excavator, in which a lateral direction is inverted
to the case of Fig. 1A. A front end portion of a reinforcement 7 embedded in the existing
pipe 6 projects from the crushed surface of a concrete portion 8 in the existing pipe
6, however, is bent in the S1 direction corresponding to a rotating direction of the
cutter head 1 by the cutter head 1.
[0034] Then, since a path 10 of a spiral-shaped blade portion 3a of each of the spiral-shaped
roller cutter 3 rotated by a rotation of the cutter head 1 on the crushed surface
moves in a direction of an arrow S3 while moving to an inner peripheral direction
of the existing pipe 6, as shown by a two dot chain line in Fig. 1B, a distal end
of the reinforcement 7 is cut to a length of ΔL by the path 10. In this case, when
a pitch of the path 10 along an axial direction of the reinforcement is set to be
p, an angle (corresponding to a pitch angle) formed between a rotational tangent of
the cutter head 1 and the path 10 of the spiral-shaped blade portion 3 is set to be
θ and a diameter of the reinforcement is set to be d, a length ΔL of the cut reinforcement
7 is expressed by the following formula.

[0035] Accordingly, the length ΔL of the reinforcement 7 becomes (d/tan θ) longer than the
pitch p of the path 10 of the spiral-shaped blade portion 3a.
[0036] In this case, when the pitch angle θ of the path 10 is set to be 90 degrees,

is established, which is shortest, and this corresponds to the roller bit 74 of the
vertical blade type in accordance with the prior art, so that the effect due to the
rolling cut by the spiral-shaped roller cutter 3 can not be obtained.
[0037] That is, when a pitch angle θ of the path 10 (which is equal to the pitch angle of
the spiral-shaped blade portion 3a if no slip is present between the spiral-shaped
blade portion 3a and the crushed surface of the existing pipe 6) is set to be great,
it gets near the roller bit 74 of the vertical blade type in accordance with the prior
art and an operation of rolling on the cut surface of the reinforcement 7 is reduced.
On the contrary, when the pitch angle θ of the path 10 is set to be small, it gets
near the roller bit 76 of the horizontal blade type in accordance with the prior art,
and the path 10 gets near the tangential direction S1 of the rotation of the cutter
head 1, so that it is hard to catch the reinforcement 7. Even if the reinforcement
7 can be caught, the cut reinforcement 7 is long since the angle formed between the
axis of the reinforcement 7 and the cut surface is small, so that the reinforcement
7 is easily caught in the cutter head 1, the screw conveyor or the like.
[0038] Then, an appropriate pitch angle θ is selected in accordance with the object to be
cut among a range of 20 degrees to 80 degrees, however, an angle of 45 degrees (

) corresponding to a middle value is a standard for selection.
[0039] Next, a case of cutting the distal end portion of the reinforcement 7 bent in the
rotating direction S1 of the cutter head 1 by a disc cutter 9 corresponding to a pitch
of a plurality of spiral-shaped blade portion 3a shown in Figs. 2A to 2C will be described
below with reference to Fig 3A.
[0040] The distal end portion of the reinforcement 7 bent in the same direction as the rotating
direction S1 of the cutter head 1 is pressed to the crushed surface of the concrete
portion 8 due to a pressing force F by a blade portion 9a of the disc cutter 9 rotating
in the S2 direction so as to be cut. As mentioned above, since the disc cutter 9 is
pressed to the distal end portion of the reinforcement 7 while rotating, the reinforcement
7 is significantly easily cut in comparison with the case that the disc cutter 9 is
simply pressed to the distal end portion of the reinforcement 7. Accordingly, the
distal end portion of the reinforcement 7 can be surely cut without entering into
the concrete portion 8 by making the pressing force F small.
[0041] Further, a case that a front end position of an outer peripheral portion of the spiral-shaped
roller cutter 3 provided with the spiral-shaped blade portion 3a having a plurality
of threads corresponding to a specific roller cutter crushes the existing pipe 72
shown in Fig. 9 by a cutter head which is placed a predetermined distance L1 rearward
from a front end position of an outer peripheral portion of a disc-shaped roller cutter
12 having the disc-shaped blade portion corresponding to the other kind of roller
cutter will be described below with reference to Fig. 3B.
[0042] When crushing the existing pipe 72, the concrete portion 72a is first crushed by
the disc-shaped roller cutter 12 since the disc-shaped roller cutter 12 is placed
L1 forward from the spiral-shaped roller cutter 3, so that a plurality of vertical
reinforcements 72b are exposed from the crushed surface thereof. The vertical reinforcements
72b are cut by the spiral-shaped roller cutter 3 after being bent in the rotational
direction thereof by the cutter head 1. As mentioned above, since the concrete portion
72a can be crushed by the disc-shaped roller cutter 12 and a plurality of vertical
reinforcements 72b can be cut by the spiral-shaped roller cutter 3, respectively in
an exclusive manner, each of the roller cutters 3 and 12 can be efficiently used.
[0043] Next, a second embodiment in accordance with the present invention will be described
below with reference to Figs. 4A and 4B.
[0044] The cutter head 1a in accordance with this embodiment is rotatably mounted by replacing
one of two spiral-shaped roller cutters 3 and 3 shown in Fig. 1A by a spiral-shaped
roller cutter 23 having an inverse pitch angle. Since the structure is the same as
that of the first embodiment except this, the detailed description will be omitted.
[0045] An operation of this embodiment will be described below only in view of the operation
different from that of the first embodiment.
[0046] When a cutter head 1a rotates in a direction of an arrow S1, the spiral-shaped roller
cutter 23 is rotated in a direction of an arrow S2a since it is pressed to a crushed
surface. Accordingly, as shown by a rightward ascending two dot chain line in Fig.
4B, the concrete portion 8 is crushed by a path 10a of a blade portion of the spiral-shaped
roller cutter 23 rotated by a rotation of the cutter head 1a on the crushed surface.
The distal end portion of the reinforcement 7 projecting from the crushed surface
of the crushed concrete portion 8 is cut by the spiral-shaped roller cutter 23 after
being bent in the rotational direction S1 of the cutter head 1a.
[0047] Further, since the other spiral-shaped roller cutter 3 is also pressed to the crushed
surface, it is rotated in the S2 direction. Accordingly, since the path 10 becomes
the same as the path 10 of the blade portion shown by the two dot chain line in Fig.
1B, the distal end portion of the reinforcement 7 projecting from the crushed surface
of the crushed concrete portion 8 is finely cut by the spiral-shaped roller cutter
3 and the spiral-shaped roller cutter 23 after being bent in the rotational direction
S2 of the cutter head 1a.
[0048] Next, a third embodiment in accordance with the present invention will be described
below with reference to Figs. 5A and 5B.
[0049] The cutter head 1b in accordance with this embodiment is rotatably mounted to the
cutter head 1b by replacing one of two spiral-shaped roller cutters 3 and 3 shown
in Fig. 1A by a known disc-shaped roller cutter 12. Since the structure is the same
as that of the first embodiment except this, the detailed description will be omitted.
[0050] An operation of this embodiment will be also described below only in view of the
operation different from that of the first embodiment.
[0051] When the cutter head 1b rotates in a direction of an arrow S1, the disc-shaped roller
cutter 12 is rotated in a direction of an arrow S4 since it is pressed to a crushed
surface. Accordingly, as shown by a two dot chain line in Fig. 5B, the concrete portion
8 is crushed by paths 11 of four blade portions of the disc-shaped roller cutter 12
rotated by a rotation of the cutter head 1b on the crushed surface. The distal end
portion of the reinforcement 7 projecting from the crushed surface of the crushed
concrete portion 8 is bent in the rotational direction S1 of the cutter head 1b. As
mentioned above, when the concrete portion 8 is crushed by the disc-shaped roller
cutter 12, the other spiral-shaped roller cutter 3 is reduced in a load for crushing
the concrete portion 8, so that a cutting performance of the reinforcement 7 and a
durability of the spiral-shaped roller cutter 3 are widely improved.
[0052] Further, when the crushing surface of the disc-shaped roller cutter 12 is placed
so as to be a predetermined amount forward from the cutting surface of the spiral-shaped
roller cutter, the concrete portion 8 can be surely crushed by the disc-shaped roller
cutter 12, so that a load of the spiral-shaped roller cutter 3 is further reduced,
whereby the performances mentioned above are further improved.
[0053] Next, as shown in Fig. 6A, a crushing and cutting operation of an existing pipe 6a
in which a plurality of vertical reinforcements 13 and a spiral-shaped hoop reinforcement
7 corresponding to the horizontal reinforcement are embedded in a concrete portion
8a will be described below.
[0054] When the existing pipe 6a is excavated by the cutter head 1, 1a or 1b mentioned above,
a distal end portion of the hoop reinforcement 7a is projected from a crushed surface
8b in a state of being inclined to a surface 8b to be crushed of the concrete portion
8a since the horizontal reinforcement is the hoop reinforcement 7a. In this case,
when rotating the cutter head 1, 1a or 1b in a direction that an angle formed between
the crush surface 8b of the existing pipe 6a and the hoop reinforcement 7b within
the concrete portion 8a corresponding to a non-crushed portion changes to an acute
angle α from an obtuse angle β as shown in Fig. 6B, that is, a direction of an arrow
X, it rotates toward a root portion from the distal end of the hoop reinforcement
7a, so that the hoop reinforcement 7a is caught in the cutter head 1. Accordingly,
the concrete portion 8a in the root portion of the hoop reinforcement 7a on the crushed
surface 8b is broken and a sufficient reacting force against the pressing force by
each of the roller cutters 3, 23 and 12 mounted in the cutter head 1 can not be secured.
As a result of this, the pressing force of each of the roller cutters 3, 23 and 12
is reduced, so that the hoop reinforcement 7a can not be surely cut.
[0055] In this case, when rotating the cutter head 1, 1a or 1b from an inverted direction
of an arrow Y, the cutter head rotates toward the distal end from the root portion
of the hoop reinforcement 7a, so that the hoop reinforcement 7a is not caught in the
cutter head 1, 1a or 1b. Accordingly, the concrete portion 8a in the root portion
of the hoop reinforcement 7a on the crushed surface 8b is not broken, and the pressing
force of each of the roller cutters 3, 23 and 12 is increased. As a result of this,
the hoop reinforcement can be surely cut. In this case, since a cutting of a plurality
of vertical reinforcement 13 is performed by the same manner as that of the prior
art, the description thereof will be omitted.
INDUSTRIAL APPLICABILITY
[0056] The present invention is useful for a spiral-shaped roller cutter and a tunnel excavator
cutter head provided with the same, which can efficiently and surely cut a reinforcement
embedded in an existing pipe.