Shield tunneling machine

Abstract: A shield tunnelling machine comprises a cylindrical shield body (10), a rotary cutter head (12) disposed on a front end of the shield body and provided with a face plate (20) having one or a plurality of slits (28) extending in the radial direction, an intermediate support member (22) for supporting a plurality of cutter bits (38) respectively having forward bit portions (39a) and backward bit portions (39b) in each ofthe slits, means (24) for supporting the intermediate support member swingably around an axis extending in the radial direction, and a member (26) for movably guiding the support means in the axial direction of the shield body, and means (48) for moving the support means in the axial direction of the shield body to move the cutter bits toward and away from the front face of the face plate, the face plate and the guide member sharing the excavation reaction of the cutter bits.

Description: BACKGROUND OF THE INVENTION Field of the Invention: This invention relates to a shield tunnelling machine, comprising: a cylindrical shield body; a rotary cutter head disposed on a front end of said shield body, and provided with a face plate having one or a plurality of slits extending in the radial direction, an intermediate support member for supporting a plurality of cutter bits respectively having forward bit portions and backward bit portions in each of said slits and means for supporting said intermediate support member swingably around an axis extending in the radial direction. Description of the Prior Art: In a tunnelling machine having a rotary cutter head disposed on a front end of a cylindrical shield body, the rotary cutter head is provided with a face plate having one or a plurality of slits extending in the radial direction, and a plurality of cutter bits are disposed in the respective slits under the condition that respective portions of the cutter bits are projected from the slit. When the rotary cutter head is rotated while the shield body is advanced, the natural ground is excavated by the cutter bits. The length of each cutter bit projecting from the front face of the face plate varies depending on the natural ground to be excavated. When the natural ground is soft, it is preferable to make the projecting length of each cutter bit long to improve the operability. On the other hand, when the natural ground is hard, it should be made short to ensure the excavation by a predetermined power. In this connection, there has been proposed a tunnelling machine, in which the cutter bits are formed to be movable toward and away from the front face of the face plate (See Japanese Patent Publication (KOKOKU) No. 62-24597). Otherwise, in consideration of the cutter bits respectively provided with forward bit portions and backward bit portions wherein the backward bit portions are severely worn away in the forward rotation and also the forward bit portions are worn away in the backward rotation, there has been proposed a rotary cutter head, in which the cutter bits are mounted on the face plate swingably around an axis extending in the radial direction (See Japanese Patent Publication (KOKOKU) No. 62-317). In case the natural ground is composed of a very hard viscous soil layer or a mud stone layer, such natural ground is not excavated by the cutter head movable forward and backward, since the bit portions of the cutter bits serving to excavate the natural ground should intrude into the natural ground, and at the same time the bit portions not serving to excavate the natural ground should also intrude into the natural ground, while the cutter head is rotated in simple contact with the natural ground without intruding not only the bit portions serving for excavation but also the bit portions not serving for excavation into the natural ground, even if the cutter bits are pressed against the hard self-supporting natural ground as noted above and a turning force is given to the cutter head. If the bit portions are forced to intrude into the natural ground, an extremely large thrust is needed, and the strength of each cutter bit should be increased. When the rotary cutter head having the swingable cutter bits is used, only the bit portions serving for excavation are enabled to intrude into the natural ground, so that the hard natural ground as noted above may be excavated. However, since each cutter bit as described in the above-mentioned Japanese Patent Publication (KOKOKU) No. 62-317 is fixed to a bit seat swinging around a pivot pin supported to the face plate, the cutter bits are unable to move toward and away from the front face of the face plate. Thus, the length of each cutter bit projecting from the front face of the face plate is constant, so that it is necessary to cope with the excavation of either hard or soft natural ground by the use of the cutter bits respectively having the constant length. If the projecting length of each cutter bit is determined with reference to the hard natural ground, while attaching importance to the safety, the efficiency of operation for excavating the soft natural ground is restrained. On the other hand, if the projecting length of each cutter bit is determined with reference to the soft natural ground, while attaching importance to the efficiency of operation, the hard natural ground is not excavated. Further, in the cutter bits of swingable type as noted above, the excavation reaction exerted to the cutter bits is received by the pivot pin, the bit seat and the contact surface of the bit seat with the face plate. Thus, when the particularly hard natural ground is excavated, the large bending moment is exerted to the pivot pin, so that it is liable to result in the defective swing of the cutter bits due to the bending of the pivot pin, and hence to create the shear of the pivot pin. SUMMARY OF THE INVENTION An object of the present invention is to provide a shield tunnelling machine provided with swingable cutter bits which are able to intrude into the hard natural ground and to excavate the same, and performs not only the excavation of the hard natural ground in correspondence to a drive force, but also the excavation of the soft natural ground with high efficiency of operation. Another object of the present invention is to provide a shield tunnelling machine capable of reducing the excavation reaction exerted to a pivot for swingably supporting the cutter bits. At least one of these objects will be achieved with a shield tunnelling machine comprising the features of the generic part of claim 1, in that said intermediate support member is movable in the axial direction of said shield body; means are provided for moving said support means in the axial direction of said shield body to move said cutter bits toward and away from the front face of said face plate said moving means being connected to said intermediate support member via said support means; and that the face plate is provided with a member in each of said slits for movably guiding said support means in the axial direction of said shield body. The support means is moved by the means for moving the support means according to the hardness or softness of the natural ground to be excavated, and the length of each cutter bit projecting from the front face of the face plate is adjusted. When the rotary cutter head is rotated while the shield body is moved, the cutter bits are swung through the intermediate support member, and the bit portions serving for the excavation intrude into the natural ground. The excavation reaction then exerted to the cutter bits is shared by the face plate and the member for movably guiding the support means to continue the excavating operation. Since the intermediate support member supporting a plurality of cutter bits is swingable, the cutter bits are swung and the bit portions serving for the excavation intrude into the natural ground as long as the cutter bits are pressed against the natural ground while rotating the cutter head. Thus, even the hard natural ground is excavated. When the support means for supporting the intermediate support member is moved by the moving means, the cutter bits are moved toward and away from the front face of the face plate. Accordingly, if the natural ground to be excavated is of hard one, such hard natural ground is excavated in correspondence to the power by shortening the length of each cutter bit projecting from the front face of the face plate. Also, if the natural ground to be excavated is of soft one, such soft natural ground is excavated with the improved efficiency of operation by elongating the projecting length of each cutter bit. Namely, the efficient excavation is performed without useless effect. Since the face plate and the guide member share the excavation reaction generated on the cutter bits, the excavation reaction exerted to a pivot shaft for swingably supporting the intermediate support member is sufficiently reduced. Thus, the occurrence of the defective swing due to the bending of the pivot shaft is prevented. When the excavation reaction of the cutter bits is shared, the intermediate support member is preferably constituted to abut against the face plate. By so doing, it is possible not only to prevent the bending or deformation of the cutter bits resulting from abutting the cutter bits directly against the face plate, but also to give a certain cutting angle to each cutter bit irrespective of the width of the slit and the dimension of the cutter bit or the like by changing the shape or the dimension of the intermediate support member. Then, as long as the face plate has a plurality of tips provided on both side edges of the slit at intervals in the radial direction so as to abut against the intermediate support member, a certain cutter angle of the cutter bit is ensured even by the tips, and anti-wear measure is provided by the tips. In case a plurality of tips are provided on both side edges of the slit, the slit is preferably constituted to be substantially closed by the intermediate support member and the tips, when the cutter bits are moved rearward to the limit of the movement. Thus, the tunnelling machine in its inoperative condition permits to resist the earth pressure of the natural ground or the underground water pressure to prevent the natural ground from its collapse. As long as the intermediate support member and each tip are constituted to have respectively slant surfaces fitting to each other and provided in portions where the intermediate support member and each tip confront each other, a rake angle of each cutter bit is made constant to obtain a fixed excavation effect, even if the cutting height of each cutter bit, i.e., the length of each cutter bit projecting from the face plate is varied. Also, since each tip receives the excavation reaction with a plane, the stress concentrated to the tip is obviated, so that the tip may be made of a material having low strength. In case the intermediate support member and each tip respectively have the slant surface fitting to each other, the support means is provided with a pivot shaft for swingably supporting the intermediate support member. When the pivot shaft is located in front of a portion of the support means guided by the guide member, the intermediate support member is swung around the pivot shaft, and the slant surface of the intermediate support member surely comes into contact with the slant surface of each tip, when the support means is moved. In case the intermediate support member and each tip respectively have the slant surfaces and the support member is provided with the pivot shaft, the tips provided on both side edges of the slit are preferably as being symmetrical about an imaginary plane including an axis of the shield body and an axis of the pivot shaft, and the intermediate support member is preferably formed as being symmetrical about the imaginary plane, when the intermediate support member is not swung. By so doing, the same effect is obtained both in the forward rotation and the backward rotation. When the cutter bits reach the rearward limit of the movement, the cutter bits are preferably constituted to be located as being spaced rearward from the front face of the face plate. Since the cutter bits do not project from the face plate, the cutter head may be rotated with small resistance. Thereby, the adjustment of various apparatuses prior to the use of the tunnelling machine is facilitated. As long as the support means is provided with a planar portion to be guided and the guide member is composed of two plates disposed at an interval corresponding to the thickness of the portion to be guided, the structure is simplified. Besides, the guide member is made to have an area enough to come into contact with portion to be guided of the support means, so that the guide member is liable to receive the excavation reaction. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and features of the invention will become apparent from the following description of a preferred embodiment of the invention with reference to the accompanying drawings, in which: Fig. 1 is a sectional view showing a shield tunnelling machine according to the present invention; Fig 2 is a front view showing a rotary cutter head; Fig 3 is an enlarged-scale sectional view taken along a line 3-3 in Fig. 2 and showing a cutter bit, which is projected forward; and Fig 4 is an enlarged-scale sectional view taken along a line 4-4 in Fig. 2 and showing the cutter bit, which is in the backward limit of its movement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A shield tunnelling machine comprises a cylindrical shield body 10 and a rotary cutter head 12, as shown in Fig. 1. In the illustrated embodiment, the shield body 10 is composed of a front tube 14 and a rear tube 16, and a plurality of direction correcting jacks 18 (one of them is shown in the drawing) are disposed between a flange of the front tube 14 and a flange of the rear tube 16. When the direction correcting jacks 18 are expanded or contracted, the front tube 14 oscillates relative to the rear tube 16 to thereby correct the advance direction of the shield body. The rotary cutter head 12 is disposed on a front end of the shield body 10 and provided with a face plate 20, an intermediate support member 22, support means 24 and a guide member 26, as shown in Figs. 2 and 3 in detail. The face plate 20 with a circular planar shape has one or a plurality of slits 28 (two slits in the illustrated embodiment) extending in the radial direction. Both slits 28 respectively with rectangular planar shapes as shown in the drawing extend along the diameter of the face plate 20. A rotary shaft 30 rotatably supported by the shield body 10 and extending in the axial direction of the shield body 10 extends through a central portion of the face plate 20 to project forward from the face plate 20. A projecting end of the rotary shaft 30 is covered with a cap 32. The cap 32 has a center bit 34. A plurality of preceding bits 36 are provided on a peripheral edge of the face plate 20 at intervals in the circumferential direction. The intermediate support member 22 supports a plurality of cutter bits 38, so that the cutter bits 38 are respectively disposed in respective slits 28. In the illustrated embodiment, the intermediate support member 22 is provided with two slant side faces 23a, 23b and a flat front face 23c and has the length substantially equal to the radial length of the slit 28. Five cutter bits 38 and a plurality of bosses 23d are respectively mounted on the front face 23c and to the rear face of the intermediate support member 22 at uniform intervals in the length direction, i.e., in the radial direction of the face plate 20. Each cutter bit 38 consists of a forward bit portion 39a and a backward bit portion 39b. The excavation reaction of the cutter bits 38 is shared by the face plate 20 and the guide member 26, as will be later described, while it is preferable that the intermediate support member 22 abuts against the face plate 20 directly or through tips 40. In the illustrated embodiment, a plurality of tips 40 are respectively disposed on both side edges of the slit 28 at uniform intervals in the radial direction. The tips 40 are mounted by means of welding or press fit on an edge of the face plate 20 defining the slit 28 in such manner that the tips 40 alternate with the cutter bits 38. Each tip 40 has a slant face 41 on a portion confronting the intermediate support member 22. In Fig. 3, the slant face 41 of each tip 40 located at the left side and the slant face 41 of each tip 40 located at the right side are respectively capable of abutting against the slant face 23a and the slant face 23b of the intermediate support member 22. The support means 24 support the intermediate support member 22 swingably around an axis extending in the radial direction of the face plate 20. In the illustrated embodiment, the support means 24 has a planar member 42 to be guided and a pivot 43. The member 42 to be guided is provided with a plurality of bosses 42a provided to alternate with the bosses 23d of the intermediate support member 22 (See Fig. 1). The bosses 23d of the intermediate support member 22 and the bosses 42a of the member 42 to be guided are arranged on a straight line. The pivot 43 extends through these bosses and is prevented from dropping out by a locking pin 44, so that the intermediate support member 22 is swingably supported. In the illustrated embodiment, the tips 40 on both side edges of the slit 28 are arranged as being symmetrical about an imaginary plane P (See Fig. 3) including the axis of the shield body 10 and the axis of the pivot 43. The intermediate support member 22 is formed as being symmetrical about the imaginary plane P when it is in its inoperative condition as shown in Fig. 4. Namely, the slant face 41 of each tip 40 disposed at the left side in the slit 28 is arranged in planar symmetrical relationship with the slant face 41 of each tip 40 disposed at the right side, and two slant faces 23a, 23b of the intermediate support member 22 are also in planar symmetrical relationship with each other. The guide member 26 movably guides the support means 24 in the axial direction of the shield body 10. In the illustrated embodiment, the guide member 26 consists of two plates 27a, 27b. Two plates 27a, 27b are arranged at an interval corresponding to the thickness of the planar member 42 to be guided of the support means 24 and welded to the face plate 20. The guide member 26 is provided in each of the slits 28 and located in the rear of the pivot 43. The excavation reaction exerted to each cutter bit 38 is shared by the face plate 20 and the guide member 26. Therefore, in case the guide member 26 is made of plate material as shown in the drawing, the guide member 26 will not do unless a plurality of guide members 26 are provided in the respective slits 28. Nevertheless, the reason that the guide member 26 is provided in each of the slits 28 is because the member 42 to be guided of the support means 24 provided in correspondence to each slit is welded to a cylindrical slide member 50, which will be later described. There is provided means 48 for moving the support means 24 in the axial direction of the shield body 10 to move the cutter bits 38 toward and away from the front face 21 of the face plate 20. The moving means 48 consists of a slide member 50 mounted to the rotary shaft 30 to be movable in the axial direction, a connecting member 52 and a cylinder device 54, as shown in Fig. 1. Two members 42 to be guided are welded to the slide member 50, and the slide member 50 is connected to the connecting member 52 through a connecting rod 56. The connecting member 52 is connected to an operating rod 58 extending rearward through the rotary shaft 30. The operating rod 58 is axially movable relative to the rotary shaft 30, and a rear end of the operating rod 58 is connected to a piston 60 of the cylinder device 54. A bulkhead 70 is provided in the shield body 10 as being spaced rearward from the rotary cutter head 12, and a bearing 72 is mounted to the center of the bulkhead 70. A reduction gear 74 is disposed in the rear of the bearing 72, and two motors 76 are connected to the reduction gear 74. The rotary shaft 30 extends through the bearing 72 to the reduction gear 74. Two motors 76 are disposed on both sides of the reduction gear 74, and the cylinder device 54 is mounted on the center of the reduction gear 74. Thus, the operating rod 58 extending from the cylinder device 54 is inserted into the rotary shaft 30 in the reduction gear 74. A hydraulic pump (not shown) is connected to the cylinder device 54. Two pipes 78 for guiding muddy water (one of the pipes is shown in the drawing) are disposed laterally at an interval. These muddy water pipes are inserted into openings provided in the bulkhead 70 to be welded to the bulkhead 70. In use of the tunnelling machine, muddy water is supplied from one muddy water pipe into a liquid chamber 80 defined in front of the bulkhead 70, and muddy water mixed with excavated earth and sand is discharged from the other muddy water pipe. In use of the tunnelling machine, pressurized oil is supplied to a push-side oil chamber of the cylinder device 54 of the means 48 for moving the support means 24 to move the support means 24 according to the hardness or softness of the natural ground to be excavated, and to adjust the length of cutter bits 38 projecting from the front face 21 of the face plate 20. When the rotary cutter head 12 is rotated while the shield body 10 is moved, each cutter bit 38 is swung through the intermediate support member 22, and each bit portion 39a, for example, intrudes into natural ground. In excavation, one excavation reaction of the cutter bits 38 is shared by the tips 40 provided on the face plate 20, and the other excavation reaction is shared by the member 26 for movably guiding the support means 24 to continue the excavating operation. While the excavation reaction acts also on the pivot 43, the excavation reaction exerted on the pivot 43 is small, since the support means 24 engages the guide member 26 according to the present invention. After the completion of excavation, when pressurized oil is supplied to a return-side oil chamber of the cylinder device 54 of the moving means 48 to move the cutter bits 38 rearward to the limit of the movement, the slit 28 is substantially closed by the cutter bits 38, the intermediate support member 22 and the tips 40, as shown in Fig. 4. Each cutter bit 38 is preferably sized such that it is located as being spaced rearward from the front face of the face plate 20.

Claims: A shield tunnelling machine, comprising: a cylindrical shield body (10); a rotary cutter head (12) disposed on a front end of said shield body (10), and provided with a face plate (20) having one or a plurality of slits (28) extending in the radial direction, an intermediate support member (22) for supporting a plurality of cutter bits (38) respectively having forward bit portions (39a) and backward bit portions (39b) in each of said slits (28) and means (24) for supporting said intermediate support member (22) swingably around an axis extending in the radial direction, characterised in that said intermediate support member (22) is movable in the axial direction of said shield body (10); means (48) are provided for moving said support means (24) in the axial direction of said shield body (10) to move said cutter bits (38) toward and away from the front face of said face plate (20), said moving means (48) being connected to said intermediate support member (22) via said support means (24); and that the face plate (20) is provided with a member (26) in each of said slits (28) for movably guiding said support means (24) in the axial direction of said shield body (10). A shield tunnelling machine according to claim 1, wherein said face plate (20) and said guide member (26) are arranged to share the excavation reaction of said cutter bits (38). A shield tunnelling machine according to claim 1, wherein said intermediate support member (22) abuts against said face plate (20) when the excavation reaction of said cutter bits (38) is shared. A shield tunnelling machine according to claim 1, wherein said face plate (20) is provided with a plurality of tips (40), against which said intermediate support member (22) is abutted, on both side edges of said slit (28) at intervals in the radial direction. A shield tunnelling machine according to claim 4, wherein when said cutter bits (38) are moved rearward to the limit of the movement, said slit (28) is substantially closed by said cutter bits (38), said intermediate support member (22) and said tips (40). A shield tunnelling machine according to claim 4, wherein said intermediate support member (22) and each of said tips (40) have respectively slant faces (41) fitting to each other on portions thereof confronting each other. A shield tunnelling machine according to claim 6, wherein said support means (24) has a pivot (43) for swingably supporting said intermediate support member (22), said pivot (43) being located in front of a portion of said support means (24) guided by said guide member (26). A shield tunnelling machine according to claim 7, wherein said tips (40) provided on both side edges of said slit (28) are disposed as being symmetrical about an imaginary plane including an axis of said shield body (10) and an axis of said pivot (43), and said intermediate support member (22) is formed as being symmetrical about said imaginary plate, when said intermediate support member (22) is not swung. A shield tunnelling machine according to claim 1, wherein when said cutter bits (38) are moved rearward to the limit of the movement, said cutter bits (38) are positioned as being spaced rearward from the front face of said face plate (20). A shield tunnelling machine according to claim 1, wherein said support means (24) is provided with a planar portion to be guided, and said guide member (26) consists of two plates disposed at an interval corresponding to the thickness of said portion to be guided, said two plates guiding said portion to be guided.

Inventors: AKESAKA TOSHIO, KAJIYAMA MAKOTO, AKESAKA, TOSHIO, KAJIYAMA, MAKOTO
Applicants: ISEKI KAIHATSU KOKI, KABUSHIKI KAISHA ISEKI KAIHATSU KOKI
Application year: 1990
Main classification: E21D9
IPC codes: E21D9