JP4891661B2 - Bit switching device - Google Patents

Description

The present invention relates to bit switch equipment for performing exchange of bits provided in the cutter head to be rotated relative to the working face (the switching).

  In the shield machine, a tunnel is constructed by excavating a natural ground with a cutter provided in front of the shield body and sequentially assembling segments behind the cutter. A plurality of bits are arranged at the front end of the cutter, and the ground is excavated by the bits by rotating the cutter.

  In such a shield machine, as the tunnel excavation work becomes longer, it is necessary to replace a worn bit during the tunnel excavation work.

  As a method for exchanging a worn bit, conventionally, there is a method in which an operator goes out to a chamber formed between the back surface of the cutter and the bulkhead (partition) of the shield body and manually replaces the bit. ing.

  However, when a worker goes out into the chamber and manually replaces the bit, it is necessary for the worker to go out to the chamber and work after improving the ground, but there is a risk of ground collapse and ground improvement. There are various problems such as an increase in construction costs.

  Therefore, in order to solve such a problem, it is desired to develop a device that can easily exchange bits. As such devices, there are known devices capable of exchanging preceding bits (for example, refer to Patent Document 1) and devices capable of exchanging shell bits (for example, refer to Patent Document 2).

  For example, in Patent Document 1 described above, in a shield machine having a cutter pork, a rotary shaft (shaft) extending in the radial direction is rotatably provided on the cutter pork, and a cylindrical shape ( By attaching a ring-shaped preceding bit and rotating the above rotating shaft with a motor provided in the shield body, the worn portion of the preceding bit is replaced with the worn portion of the preceding bit instead of the worn portion of the preceding bit. It is made to protrude from.

  Further, in Patent Document 2 described above, in a shield machine having a cutter face plate, a rotary shaft extending in the radial direction is rotatably provided on the cutter face plate, and a cylindrical shell bit is provided on the outer periphery of the rotary shaft. When mounting or not replacing, the rotation of the shell bit is restrained by the stopper pin, and at the time of replacement, the shell bit is rotated with the contact resistance with the face by rotating the cutter face plate in a state where the rotation restraint of the shell bit is released, Instead of the worn portion of the shell bit, the non-weared portion of the shell bit is projected from the surface of the cutter face plate.

JP 2003-301893 A Japanese Patent Laid-Open No. 9-60482

  By the way, in the above-mentioned patent documents 1 and 2, the portion where the bit is not worn is accommodated in the cutter pork or the cutter face plate, and the portion where the bit is not worn is provided on the surface of the cutter pork or the cutter face plate. It is made to protrude from the surface of a cutter pork or a cutter face plate. For this reason, there is a problem that if the earth or sand is clogged between the opening and the bit, the bit or the like is fixed and it is difficult to exchange (switch) the bit.

  In Patent Documents 1 and 2, since the rotation direction of the rotation shaft to which the bit is attached is the same as the rotation direction of the cutter, the force to rotate the rotation shaft in the rotation direction rotates with the rotation of the cutter. There is a problem that a large load is applied to the rotating shaft (or means for restricting the rotation of the rotating shaft) acting on the shaft.

Accordingly, an object of the present invention is to provide a bit switching device capable of easily exchanging (switching) bits without causing the bits or the like to adhere to the earth and sand and reducing the load on the rotating shaft to which the bits are attached. Is to provide a place.

In order to achieve the above object, the invention according to claim 1 is a cutter head having a head member arranged to rotate with respect to a face and to extend in a radial direction, and the cutter head is provided in the head member. A rotary shaft that is rotatable about an axis extending in the direction of rotation of the head member and that has at least one end projecting from the side of the head member to the outside of the head member, and projecting out of the head member at the rotational shaft. A plurality of bits provided at predetermined intervals in the rotation direction, rotation restriction means for restricting rotation of the rotation shaft, and rotation restriction of the rotation shaft by the rotation restriction means. and a rotation means for rotating the rotary shaft in released condition, the plurality of bits, and greater than the height of the bit the height of the bits to be initially used then use bit A switching device.

According to a second aspect of the present invention, the rotation restraining means is provided in the head member, and a lock rod that is movable in the radial direction of the cutter head, a recess provided in the lock rod, and the rotation shaft. An engagement portion that is provided and engaged with the recess of the lock rod; a position where the recess of the lock rod engages with the engagement portion of the rotary shaft; and the engagement is released. The bit switching device according to claim 1 , further comprising a lock jack for moving to a position.

According to a third aspect of the present invention, there is provided a cutter head having a head member that is rotated with respect to the face and arranged to extend in the radial direction, and an axis that is provided in the head member and extends along the rotational direction of the cutter head. The rotary shaft is rotatable around and at least one end of the rotary shaft protrudes from the side of the head member to the outside of the head member, and the end of the rotary shaft that protrudes to the outside of the head member is rotated. A plurality of bits provided at predetermined intervals in the direction, a rotation restricting means for restricting the rotation of the rotation shaft, and the rotation shaft in a state where the rotation restriction of the rotation shaft by the rotation restriction means is released. and a rotation means for rotating said rotary restraining means and the rotating means is a bit switch device characterized by having a rack and pinion mechanism.
According to a fourth aspect of the present invention, in the bit switching device according to the third aspect, the height of the bit used initially is larger than the height of the bit used next.

  According to a fifth aspect of the present invention, a plurality of the rotating shafts are provided at predetermined intervals in the radial direction of the cutter head, and the rotating means does not rotate the adjacent rotating shafts simultaneously. 4. The bit switching device according to any one of 4.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the outermost peripheral bit is arranged so as to be displaced outwardly in the radial direction of the cutter head with respect to the rotary shaft at a position where the outermost peripheral bit contacts the face. It is a bit switching device.

  According to the present invention, the bit can be easily replaced (switched) without the bit being fixed by the earth and sand, and the excellent effect that the load on the rotating shaft to which the bit is attached can be reduced. Play.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a side sectional view of a shield machine to which a bit switching device according to an embodiment of the present invention is applied. FIG. 2 is an enlarged front view of a main part of the shield machine according to the embodiment of FIG. FIG. 3 is an enlarged side view of a main part of the shield machine according to the embodiment of FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 5A is a cross-sectional view taken along the line Va-Va in FIG. 2, and FIG. 5B is a cross-sectional view taken along the line Vb-Vb in FIG.

  This embodiment is applied to a mud pressure shield excavator, but can also be applied to a mud shield shield excavator.

  As shown in FIG. 1, the shield machine 1 according to this embodiment includes a shield body 3 having a cutter 2 in front of the digging direction. A plurality of erectors (not shown) for assembling a segment in a hole excavated by the cutter 2 to construct a tunnel and a plurality of gaps are provided on the inner periphery of the shield body 3 at a rear portion of the shield body 3, A shield jack (not shown) for propelling the shield body 3 by taking a reaction force on the segment is provided.

  The cutter 2 has a cutter head 4 that extends radially outward from its center of rotation and is rotated relative to the face. On the front surface of the cutter head 4, a center bit 5 is disposed at the center in the radial direction, and a plurality of cutter bits 6 and 7 are disposed on the outer peripheral side of the center bit 5.

  Between the cutter head 4 and a bulkhead (partition wall) 8 provided in the vicinity of the front end of the shield body 3, a chamber 9 for taking in the earth and sand (excavated earth and sand) excavated by the cutter 2 is formed. A screw conveyor 10 that passes through the bulkhead 8 and opens to the chamber 9 is provided under the bulkhead 8. On the rear surface of the cutter head 4, an agitating blade 11 is provided that extends rearward in the excavation direction and agitates the excavated earth and sand in the chamber 9.

  The cutter head 4 of the present embodiment includes a center member 12 and a plurality of cutter spokes 13 that are radially attached to the center member 12. That is, in this embodiment, the cutter head 4 is formed in a spoke shape. Note that the cutter head 4 may be formed in a face plate shape.

  A cutter bit (fixed bit) 7 is attached to the front end of the cutter spoke 13.

  A ring-shaped member 17 having a gear 16 is rotatably supported on the bulkhead 8. The ring-shaped member 17 is connected to the cutter head 4 by a cylindrical body 18 extending rearward from the cutter head 4 (center member 12). A plurality of drive motors 19 (hydraulic motors in the present embodiment) for rotating the ring-shaped member 17 are provided in the shield body 3. A pinion 20 is attached to the drive motor 19, and the pinion 20 meshes with a gear 16 provided on the ring-shaped member 17.

  The bulkhead 8 is provided with a support mechanism 21 that rotatably supports the ring-shaped member 17. The support mechanism 21 is housed in the casing 22, and bearings 23 and 24 for supporting the ring-shaped member 17, and a seal mechanism 25 for preventing earth and sand from entering the shield body 3. have.

  As shown in FIGS. 2 to 5, the bit switching device 30 according to the present embodiment includes a cutter pork 13 as a head member provided in the cutter head 4 and arranged to extend in the radial direction of the cutter head 4. Provided on the spoke 13 and rotatable about an axis extending along the direction of rotation of the cutter head 4, and both end portions from the side portion (side surface portion) in the width direction (left and right direction in FIG. 2) of the cutter spoke 13. A rotating shaft 31 projecting out of the cutter pork 13, and a plurality of (two in the illustrated example) bits 6 provided at both ends of the rotating shaft 31 at predetermined intervals in the rotational direction of the rotating shaft 31; The rotation restricting means for restricting the rotation of the rotary shaft 31 at the position where at least one of the plurality of bits 6 abuts against the face and the rotation restricting means for switching the bit 6 abutting against the face. And a rotation means for rotating the rotary shaft 31 at a release state the rotation restraint of the rotation shaft 31 with.

  In the present embodiment, the rotary shaft 31 is supported by bearings 33 on pedestals 32 provided on both side portions of the cutter spoke 13 at the inner side in the longitudinal direction (left-right direction in FIG. 2) than both ends thereof. Has been.

  In the present embodiment, the plurality of bits 6 are provided on the outer periphery of the rotating shaft 31 via the bit holding member 34.

  A plurality of the rotating shaft 31, the plurality of bits 6, the bit holding member 34, and the like are arranged in the longitudinal direction (vertical direction in FIG. 2) (the radial direction of the cutter head 4) of the cutter pork 13. Here, in the present embodiment, the rotation shaft 31 adjacent to the longitudinal direction of the cutter pork 13 has a plurality of rotation trajectories 35 of the plurality of bits 6 provided on the one rotation shaft 31. It arrange | positions so that it may pass along on the rotation locus | trajectory 35 of the bit 6 (refer FIG. 3).

  The rotation restraining means of the present embodiment is provided in the cutter pork 13 and is movable in the longitudinal direction of the cutter pork 13 (the radial direction of the cutter head 4), and a recess 37 provided in the lock rod 36. The engagement portion 38 provided on the rotation shaft 31 and engaged with the recess 37 of the lock rod 36, the lock rod 36, and the recess 37 of the lock rod 36 and the engagement portion 38 of the rotation shaft 31 are engaged. And a lock jack 14 (in this embodiment, a hydraulic jack) for moving to a position where the engagement is released and a position where the engagement is released.

  In the present embodiment, the lock rod 36 is moved along the slider 39 in the longitudinal direction of the cutter spoke 13.

  In the present embodiment, the engaging portion 38 of the rotating shaft 31 is provided in the middle portion in the longitudinal direction of the rotating shaft 31. This engaging part 38 is formed by making the cross section of the longitudinal direction intermediate part of the rotating shaft 31 non-circular (in this embodiment, hexagonal).

  When restraining the rotation of the rotary shaft 31, the lock jack 14 is extended, and the lock rod 36 is moved to a position where the concave portion 37 of the lock rod 36 is engaged with the engaging portion 38 of the rotary shaft 31 (extrusion). ) (See FIG. 6D), the lock rod 36 is fixed with a stroke of the lock jack 14 so that the lock rod 36 does not move in the longitudinal direction, or a stopper (not shown) such as a bolt or a pin is used. Is fixed to the cutter pork 13.

  On the other hand, when releasing the rotation restraint of the rotating shaft 31, the lock jack 14 is retracted to the position where the engagement between the recess 37 of the lock rod 36 and the engaging portion 38 of the rotating shaft 31 is released. 36 is moved (pulled) (see FIG. 6A).

  As shown in FIG. 2, the chain spoke 13 as a head member is provided with a chain drive mechanism 41 as a rotating means. When the chain drive mechanism 41 is used as the rotating means, a sprocket 42 is attached to the rotating shaft 31 and a motor or the like (not shown) is provided in the center member 12 or the cutter spoke 13, and between these sprockets 42 and the motor. The endless chain 43 is bridged and the rotating shaft 31 is rotated by driving the chain 43 with a motor or the like.

  In the present embodiment, in order to simultaneously rotate the plurality of rotating shafts 31 by one motor, the sprockets 42 are respectively attached to the plurality of rotating shafts 31 provided at predetermined intervals in the longitudinal direction of the cutter spoke 13. A chain 43 is laid over the sprocket 42.

  Further, the sprocket 42 is arranged in the longitudinal direction of the cutter pork 13 so as not to rotate the other rotary shaft 31 while rotating one of the rotary shafts 31 adjacent to the longitudinal direction of the cutter spoke 13. It is arranged so as to be alternately arranged with respect to a plurality of rotating shafts 31 provided at predetermined intervals (see FIG. 2), and the rotating shafts 31 adjacent to each other in the longitudinal direction of the cutter pork 13 are rotated by different motors or the like. I have to. That is, in the present embodiment, the rotation shafts 31 adjacent to each other in the longitudinal direction of the cutter pork 13 are not rotated simultaneously. By doing so, the distance between the plurality of adjacent bits 6 can be reduced. In addition, the sprocket 42 does not need to be arranged every other rotation shaft 31.

  Next, the operation of this embodiment will be described.

  When excavating the face, rotation of the rotating shaft 31 is restricted by the rotation restricting means at a position where one of the plurality of bits 6 attached to the rotating shaft 31 contacts the face. Then, by rotating the cutter head 4 in this state, the face is excavated by the bit 6 that contacts the face.

  On the other hand, when switching the bit 6 in contact with the face, the rotation of the cutter head 4 is stopped, and then the rotation restriction of the rotation shaft 31 by the rotation restriction means is released as shown in FIG. In this state, as shown in FIGS. 6B and 6C, the rotating shaft 31 is sequentially rotated by a predetermined angle by the rotating means, and the bit 6 that contacts the face is switched. As shown in FIG. 6D, after the switching of the bit 6 contacting the face is completed, the rotation of the rotary shaft 31 is restrained again by the rotation restraining means.

  The plurality of bits 6 has a height h1 (see FIGS. 3 and 5A) of the bit 6 that is initially used than a height h2 (see FIGS. 3 and 5A) of the bit 6 that is used next. It is set so as to increase (h1> h2). When the initially used bit 6 is worn down to a predetermined height hc (see FIG. 3 and FIG. 5A, hc> h2) which is larger than the height h2 of the next used bit 6, it hits the face. By switching the bit 6 that is in contact with each other, it is possible to prevent the next bit 6 to be used as a face at the time of rotation (no interference), and a plurality of bits 6 can be easily rotated.

  Here, in the present embodiment, the cutter pork 13 as the head member can be rotated around an axis extending in the rotation direction of the cutter head 4, and both end portions are outside the cutter pork 13 from the side surface portion of the cutter pork 13. The rotary shaft 31 is provided so as to protrude to the end, and the plurality of bits 6 are provided at both ends of the rotary shaft 31 at a predetermined interval in the rotational direction of the rotary shaft 31, thereby clogging earth and sand. Such a part is not formed. Therefore, it is possible to easily replace (switch) the bit 6 without the bit 6, the rotating shaft 31 and the like being fixed by the earth and sand.

  In the present embodiment, the rotary shaft 31 is provided so as to be rotatable around an axis extending along the rotation direction of the cutter head 4, so that the rotary shaft 31 is rotated in the rotation direction as the cutter head 4 rotates. The force that acts on the rotating shaft 31 hardly acts on the rotating shaft 31 and the lock rod 36, and the load on the rotating shaft 31 and the lock rod 36 can be reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

  For example, the shapes of the engaging portion and the recessed portion of the rotation restraining means are not limited to the above-described embodiment. For example, as shown in FIG. 7, the engaging portion 44 may be formed in a trapezoidal cross section. In this case, the recesses 45 are provided on both sides of the lock rod 36 in the longitudinal direction.

  When restraining the rotation of the rotary shaft 31, if the small bottom side 46 of the engaging portion 44 faces the radially inner side of the cutter head 4, the lock jack 14 is extended so that the concave portion 45 of the lock rod 36 is The lock rod 36 is moved (extruded) to a position where it is engaged with the engaging portion 44 of the rotary shaft 31 (see FIG. 7), and the stroke of the lock jack 14 is fixed so that the lock rod 36 does not move in the longitudinal direction. Alternatively, the lock rod 36 is fixed to the cutter pork 13 using a stopper (not shown) such as a bolt or a pin.

  Further, when the rotation of the rotary shaft 31 is restricted, if the small bottom side portion 46 of the engaging portion 44 faces the radially outer side of the cutter head 4, the lock jack 14 is retracted and the concave portion of the lock rod 36 is The lock rod 36 is moved (retracted) to a position where 45 is engaged with the engaging portion 44 of the rotating shaft 31 (see FIG. 8D), and the lock jack 36 is prevented from moving in the longitudinal direction. 14 is fixed, or a lock rod 36 is fixed to the cutter pork 13 using a stopper (not shown) such as a bolt or a pin.

  On the other hand, when releasing the rotation restraint of the rotary shaft 31, the lock jack 14 is extended or retracted until the engagement between the recess 45 of the lock rod 36 and the engaging portion 44 of the rotary shaft 31 is released. The lock rod 36 is moved (see FIG. 8A).

  The procedure for switching bit 6 is substantially the same as that shown in FIG.

  Further, as in the embodiment shown in FIGS. 9 to 12, the rotary shaft 47 is provided on the cutter pork 13 so that only one end protrudes from the side surface portion of the cutter pork 13 to the outside of the cutter pork 13. A plurality of (in the illustrated example, three) bits 6 may be provided at one end of the rotary shaft 47 at a predetermined interval in the rotational direction of the rotary shaft 47.

  In this embodiment, the rotation shaft 47 adjacent to the longitudinal direction of the cutter pork 13 is set to have different end portions that project out of the cutter pork 13.

  In addition, the rotation shaft 47 adjacent to the longitudinal direction of the cutter spoke 13 has a rotation locus 35 of a plurality of bits 6 provided on one rotation shaft 47 and a rotation locus of a plurality of bits 6 provided on the other rotation shaft 47. 35 so that it does not pass over 35 (see FIG. 10).

  In this embodiment, a rack and pinion mechanism 48 is used as the rotating means. When the rack and pinion mechanism 48 is used as the rotating means, a pinion 49 is attached to the rotating shaft 47, the lock rod 51 having the rack portion 50 is engaged with the pinion 49, and the lock rod 52 is connected to the lock rod 51 by the lock jack 52. The rotary shaft 47 is rotated by moving 51 in the longitudinal direction. In this embodiment, the lock rod 51 is moved in the longitudinal direction of the cutter pork 13 along the slider 53.

  In this embodiment, the rack and pinion mechanism 48 is used as the rotation restraining means. When the rack-and-pinion mechanism 48 is used as the rotation restraining means, the lock jack 52 prevents the lock rod 51 from moving in the longitudinal direction when the pinion 49 attached to the rotation shaft 47 and the lock rod 51 are engaged with each other. The lock rod 51 is fixed to the cutter pork 13 using a stopper (not shown) such as a bolt or a pin.

  Further, as in the embodiment shown in FIGS. 13 to 17, the outermost peripheral bit 6 a may be arranged so as to be shifted in the longitudinal direction of the cutter pork 13 (the radial direction of the cutter head 4) with respect to the rotating shaft 31. good. In the present embodiment, the outermost peripheral bit 6a is arranged so as to be displaced outward in the radial direction of the cutter head 4 with respect to the rotary shaft 31 at a position where it contacts the face (see FIG. 14). By doing in this way, the problem that there exists an iron plate in the edge part of the cutter pork 13, and the rotating shaft 31 cannot be provided can be solved. A space on the outer side in the radial direction of the cutter head 4 for the rotation of the outermost peripheral bit 6a is ensured by an extra excavation device (not shown) such as a copy cutter provided in another cutter pork.

  The plurality of bits 6 has a height h1 (see FIGS. 14 and 16 (a)) of the initially used bit 6 higher than a height h2 (see FIGS. 14 and 16 (a)) of the next used bit 6. It is set so as to increase (h1> h2). When the initially used bit 6 is worn down to a predetermined height hc (see FIG. 14 and FIG. 16A, hc> h2) which is larger than the height h2 of the next used bit 6, it hits the face. By switching the bit 6 that is in contact with each other, it is possible to prevent the next bit 6 to be used as a face at the time of rotation (no interference), and a plurality of bits 6 can be easily rotated.

  In this embodiment, the rotation restraining means has a wedge part 54 provided on the lock rod 36 and an engagement part 55 provided on the rotary shaft 31 and engaged with the wedge part 54 of the lock rod 36. is doing.

  When restraining the rotation of the rotary shaft 31, the lock jack 14 is extended, and the lock rod 36 is moved to a position where the wedge portion 54 of the lock rod 36 is engaged with the engaging portion 55 of the rotary shaft 31 ( (Extruded) (see FIG. 17 (d)), the lock rod 14 is fixed in a stroke so that the lock rod 36 does not move in the longitudinal direction, and a lock rod is used by using a stopper (not shown) such as a bolt or a pin. 36 is fixed to the cutter pork 13.

  On the other hand, when releasing the rotation restraint of the rotating shaft 31, the lock jack 14 is retracted and locked to a position where the engagement between the wedge portion 54 of the lock rod 36 and the engaging portion 55 of the rotating shaft 31 is released. The rod 36 is moved (pulled) (see FIG. 17A).

  The procedure for switching bit 6 is substantially the same as that shown in FIG.

It is a sectional side view of the shield machine which applied the bit switching device concerning one embodiment of the present invention. It is a principal part enlarged front view of the shield machine which concerns on embodiment of FIG. It is a principal part expanded side view of the shield machine which concerns on embodiment of FIG. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2. (A) is Va-Va arrow sectional drawing of FIG. 2, (b) is Vb-Vb arrow sectional drawing of FIG. (A)-(d) is the schematic which shows the 1st-4th process of bit switching, respectively. It is a principal part expanded side sectional view of the shield machine which shows the modification of a rotation restraint means. (A)-(d) is the schematic which shows the 1st-4th process of bit switching, respectively. It is a principal part enlarged front view of the shield machine which concerns on other embodiment. It is a principal part enlarged side view of the shield machine which concerns on embodiment of FIG. FIG. 10 is a cross-sectional view taken along line XI-XI in FIG. 9. (A) is XIIa-XIIa arrow directional cross-sectional view of FIG. 9, (b) is XIIb-XIIb arrow directional cross-sectional view of FIG. It is a principal part enlarged front view of the shield machine which concerns on other embodiment. It is a principal part enlarged side view of the shield machine which concerns on other embodiment. It is XV-XV arrow directional cross-sectional view of FIG. (A) is a sectional view taken along line XVIa-XVIa in FIG. 13, and (b) is a sectional view taken along line XVIb-XVIb in FIG. (A)-(d) is the schematic which shows the 1st-4th process of bit switching, respectively.

Explanation of symbols

1 Shield machine 4 Cutter head 6 Cutter bit (bit)
6a Outermost peripheral bit 13 Cutter pork (head member)
14 Lock jack (rotation restraint)
30 Bit switching device 31 Rotating shaft 36 Lock rod (Rotation restraint means)
37 Concavity (rotation restraint means)
38 Engagement part (rotation restraint means)
41 Chain drive mechanism (rotating means)
42 Sprocket (Rotating means)
43 Chain (Rotating means)
44 Engagement part (rotation restraint means)
45 Recess (Rotation restraint means)
47 Rotating shaft 48 Rack and pinion mechanism (rotation restraining means, rotating means)
49 Pinion (rotation restraint means, rotation means)
51 Lock rod (rotation restraint means, rotation means)
52 Lock jack (rotation restraint means, rotation means)
54 Wedge (rotation restraint)
55 Engagement part (rotation restraint means)

Claims (6)

A cutter head having a head member that rotates relative to the face and is arranged to extend in the radial direction; provided on the head member; and rotatable about an axis extending in a rotation direction of the cutter head; and At least one end of the rotating shaft that protrudes from the side of the head member to the outside of the head member and an end of the rotating shaft that protrudes to the outside of the head member are provided at predetermined intervals in the rotational direction. A plurality of bits, a rotation restraining means for restraining the rotation of the rotation shaft, and a rotation means for rotating the rotation shaft in a state where the rotation restriction of the rotation shaft by the rotation restraining means is released. And a bit switching device characterized in that the plurality of bits have a height of an initially used bit larger than a next used bit . The rotation restraining means is provided in the head member and is movable in the radial direction of the cutter head, a recess provided in the lock rod, a recess provided in the rotation shaft, and a recess in the lock rod. And a lock for moving the lock rod to a position where the concave portion of the lock rod and the engagement portion of the rotating shaft are engaged and a position where the engagement is released. The bit switching device according to claim 1 , further comprising a jack. A cutter head having a head member that rotates relative to the face and is arranged to extend in the radial direction; provided on the head member; and rotatable about an axis extending in a rotation direction of the cutter head; and At least one end of the rotating shaft that protrudes from the side of the head member to the outside of the head member and an end of the rotating shaft that protrudes to the outside of the head member are provided at predetermined intervals in the rotational direction. A plurality of bits, a rotation restraining means for restraining the rotation of the rotation shaft, and a rotation means for rotating the rotation shaft in a state where the rotation restriction of the rotation shaft by the rotation restraining means is released. A bit switching device, wherein the rotation restraining means and the rotating means have a rack and pinion mechanism. The bit switching device according to claim 3, wherein a height of a bit used initially among the plurality of bits is larger than a height of a bit used next. A plurality of the rotation shafts are provided at predetermined intervals in the radial direction of the cutter head,
The bit switching device according to any one of claims 1 to 4, wherein the rotating means does not simultaneously rotate the adjacent rotating shafts.   The bit switching device according to any one of claims 1 to 5, wherein the outermost peripheral bit is arranged so as to be displaced radially outward of the cutter head at a position where the outermost peripheral bit comes into contact with the face.

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