Leading bit and excavator including the same

Abstract

To provide a leading bit capable of improving durability.SOLUTION: The leading bit includes: a shank S2 that has an upper surface F1 facing the cutting face and inclined surfaces F2 and F3 on the cutting face side that intersect at both ends of the upper surface F1 and are inclined in the excavation radial direction facing the cutting face; two tips C2a that are installed at the corners of both ends of the shank S2; a tip C2b that is installed between two tips C2a via a part of the shank S2; and a columnar tip C2c that is provided on the upper surface F1 and the inclined surfaces F2 and F3 of the shank S2 between the adjacent tips C2a and C2b and between the adjacent tips C2b and C2b, in which one end surface in the axial direction is exposed along the upper surface F1 and the inclined surfaces F2 and F3. First two mounting surfaces V1 on the tip C2c side of the two tips C2a are inclined so that the cutting face side and the opposite side are inclined away from each other, and a second mounting surface V2 on the opposite side to the cutting face side of tip C2a is inclined from the end opposite to the cutting face side of the first mounting surface V1 toward the cutting face.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a leading bit and an excavator equipped with the same, and more particularly to a leading bit attached to the cutter board of an excavator such as a shield machine used in shield tunneling. [Background technology]

[0002] The shield tunneling method involves forming a tunnel in the ground while stabilizing the tunnel face by rotating a cutter plate installed in front of the shield machine and pressing it against the tunnel face, while also assembling multiple steel or concrete segments onto the inner wall of the tunnel to construct a tunnel. Multiple excavator cutter bits are installed in a regular array on the front of the shield machine's cutter plate.

[0003] This cutter bit for an excavator is an excavation part that breaks up the ground and creates notches during the excavation process, and is equipped with, for example, a steel shank portion that forms the bit body, and a tip portion made of cemented carbide that forms the cutting edge.

[0004] The configuration of a cutter bit for an excavator is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-061483 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the shield tunneling method using such shield machines has been increasingly applied not only to sewers and subways but also to road tunnels and agricultural waterways, and as construction work becomes larger in cross section and over longer distances, there is a demand for technology that can efficiently excavate ground made up of a variety of geology.

[0007] One of the challenges is to improve the performance of excavator cutter bits, which determine excavation performance. It is known that wear of excavator cutter bits is particularly noticeable in gravelly ground.

[0008] In the shield tunneling method, a leading bit is used for preliminary excavation of the ground, cutting temporary walls at the starting and arrival areas, cutting ground improvement areas, and to protect the teeth bit (the main cutter bit that takes the cut soil into the chamber).The tips attached to the corners at both ends of the leading bit in the direction of movement of the cutter disk during the excavation process are subject to large forces and are therefore prone to breakage.

[0009] The present invention has been made in view of the above technical background, and has an object to provide a technique that can improve the durability of the leading bit. [Means for solving the problem]

[0010] In order to solve the above problems, the preceding bit of the present invention as set forth in claim 1 comprises a bit body portion having a rectangular first surface facing the working face, and second and third surfaces on the working face side which intersect at both ends of the first surface and face the working face and are inclined in the excavation radial direction during the excavation process; two first tip portions respectively installed at corners on both ends of the bit body portion on the working face side in the movement direction of the bit body portion during the excavation process; a second tip portion installed adjacent to the two first tip portions via a part of the bit body portion on the working face side of the bit body portion; and a columnar third tip portion provided on the blade side on the bit body portion between adjacent first tip portion and second tip portion and between adjacent second tip portion and second tip portion, with one axial end face exposed along the first face, the second face and the third face, wherein the two first mounting faces on the third tip portion side of the two first tip portions are formed with the sides opposite the cutting face inclined away from each other, and the second mounting face on the side opposite the cutting face of the first tip portion is formed with the end of the first mounting face opposite the cutting face inclined toward the cutting face.

[0011] The leading bit of the present invention described in claim 2 is characterized in that, in the invention described in claim 1, the face of the first tip portion on the face side is formed parallel to the movement direction of the bit body portion during the drilling process and is approximately flush with the face-side faces of the bit body portion between adjacent first tip portion and second tip portion and between adjacent second tip portion and second tip portion, and the faces of the first tip portion located at both ends of the leading bit are formed flush with both end faces of the leading bit in the bit body portion.

[0012] The precursor bit of the present invention as set forth in claim 3 is characterized in that, in the invention as set forth in claim 1, the third tip portion is formed in a cylindrical shape.

[0013] The preceding bit of the present invention described in claim 4 is characterized in that, in the invention described in claim 1, the third tip portion is composed of the third tip portion arranged across the first surface and the second surface and having an exposed upper end surface straddling the first surface and the second surface, and the third tip portion arranged across the first surface and the third surface and having an exposed upper end surface straddling the first surface and the third surface.

[0014] The preceding bit of the present invention described in claim 5 is characterized in that, in the invention described in claim 1, the third tip portion is composed of the third tip portion arranged on the first surface and having an exposed upper end surface aligned with the first surface, the third tip portion arranged on the second surface and having an exposed upper end surface aligned with the second surface, and the third tip portion arranged on the third surface and having an exposed upper end surface aligned with the third surface.

[0015] The pioneer bit of the present invention described in claim 6 is characterized in that, in the invention described in claim 1, the third tip portion is provided in multiple locations along the drilling diameter direction of the bit body portion during the drilling process.

[0016] The excavator of the present invention as set forth in claim 7 is characterized in that the leading bit as set forth in any one of claims 1 to 6 is installed on a cutter board.

[0017] The excavator of the present invention described in claim 8 is characterized in that, in the invention described in claim 7, the leading bit is installed with the inclination direction of the second surface facing the center of rotation of the cutter board.

[0018] The excavator of the invention described in claim 9 is characterized in that, in the invention described in claim 7, the leading bit is installed at a position from the outer periphery of the cutter board to a radial midpoint.

[0019] The excavator of the invention described in claim 10 is characterized in that, in the invention described in claim 7, the leading bit is attached to the cutter plate in a state where it protrudes toward the face further than the tip of the scraper tooth attached to the cutter plate. [Effects of the Invention]

[0020] According to the present invention, the first tip portion located at the corner of the leading bit is less likely to break even when a large force is applied during shield drilling, thereby making it possible to improve the durability of the leading bit during the shield drilling process. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a perspective side view of the interior of an excavator according to an embodiment of the present invention; [Figure 2] FIG. 2 is a front view of a cutter head constituting the excavator of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view of the cutter head taken along line II in FIG. 2. [Figure 4] 3 is a side view showing a comparison of the protruding lengths of the cutter bits and scraper teeth of the cutter head of FIG. 2. FIG. [Figure 5] FIG. 3 is a front view of a leading bit attached to the cutter head of FIG. 2. [Figure 6] FIG. 6 is a plan view of the leading bit of FIG. 5. [Figure 7] FIG. 6 is a side view of the leading bit of FIG. 5. [Figure 8] FIG. 6 is a cross-sectional view of the preceding bit taken along line I in FIG. 5. [Figure 9] FIG. 6 is a cross-sectional view of the preceding bit taken along line II in FIG. 5. [Figure 10] FIG. 10 is an explanatory diagram showing a tip portion installed at a corner of a leading bit as a comparative example. [Figure 11] 10 is an explanatory diagram showing a tip portion installed at a corner of the leading bit of the present embodiment. FIG. [Figure 12] FIG. 2 is a front view of a cutter head as a modification of the excavator of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings for explaining the embodiment, the same components are generally designated by the same reference numerals, and repeated description thereof will be omitted.

[0023] First, an example of an excavator according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a perspective side view of the inside of the excavator according to this embodiment, showing the main components.

[0024] The excavator 1 of this embodiment is, for example, a mud pressure shield machine. The excavator excavates in a chamber 4 between the cutter head 2 and the main body 3, filled with mud having plastic fluidity (the ability to deform and move freely) created by injecting and mixing additives into the soil excavated by the cutter head 2. This creates mud pressure that counteracts the earth pressure at the excavation face, ensuring the stability of the excavation face. The overall operation of the excavator 1 is controlled by a control unit installed in the cab of a trailing bogie (not shown) behind the excavator. The excavator 1 of this embodiment is, for example, a machine used in a long-distance excavation project of 3,304 km, and most of the excavation section is filled with hard sedimentary layers consisting of sand layers, mudstone layers, and alternating layers of these.

[0025] The cutter head 2 is a cutting board used to excavate the ground and is installed on the front of the excavator 1 so that it can rotate forward and backward along the circumferential direction of the equipment body 3. The front of the cutter head 2 (the surface facing the working face) is equipped with a center bit CB, a leading bit B, and scraper teeth (not shown in FIG. 1). A copy cutter CC is installed on the outer periphery of the cutter head 2. The copy cutter CC performs functions such as over-excavating when constructing sharp curves and controlling the posture of the excavator 1. A stirring blade (not shown) is installed on the back of the cutter head 2. The stirring blade is formed, for example, of a cylindrical protruding member and serves to stir and mix the soil and additives in the chamber 4 as the cutter head 2 rotates. The cutter head 2 will be described in detail later.

[0026] The equipment main body 3 comprises a forward body plate (forward section) 3a, an aft body plate (aft section) 3b behind it, and a tail seal 3c on the inner peripheral surface of the aft section of the aft body plate 3b. The forward body plate 3a and the aft body plate 3b are formed, for example, from cylindrical steel plates, and are components that form the outer shape of the equipment main body 3 and also form a hollow space inside the equipment main body 3. The forward body plate 3a and the aft body plate 3b are engaged by inserting a spherical bearing portion at the tip of the aft body plate 3b into the aft end side of the forward body plate 3a while contacting the inner peripheral surface of the forward body plate 3a. The tail seal 3c is a sealing member that prevents groundwater and the like from entering the equipment main body 3 from the aft section during excavation work, and is installed in the shape of an annular frame at the aft end of the aft body plate 3b along the inner periphery of the aft body plate 3b.

[0027] On the front side of the front body plate 3a, at a position set back from the front side toward the inside of the equipment body 3, a bulkhead 7 is installed which divides the hollow space inside the equipment body 3 into a face side and an inboard side. The chamber 4 is provided on the face side of the bulkhead 7, i.e., between the cutter head 2 and the bulkhead 7. Earth and sand excavated by the cutter head 2 is taken into the cutter head 2 through a through-hole (not shown in FIG. 1) on the front side of the cutter head 2.

[0028] On the other hand, inside the main body 3 of the excavator 1, a cutter drive body 8, a center bending jack 9a, a shield jack 9b, a screw conveyor 10, an erector 11, an earth pressure detection unit 12, and an additive injection unit 13a are installed.

[0029] The cutter drivers 8 are motors (drive sources) that rotate the cutter head 2 in forward and reverse directions, and a plurality of them are arranged side by side in the circumferential direction of the cutter head 2 at positions near the outer periphery within the front surface of the cutter head 2. Note that a periphery support drive system is exemplified here as the cutter drive system.

[0030] The articulating jacks 9a are devices that correct the propulsion direction and attitude of the excavator 1, and a plurality of them are installed side by side along the circumferential direction of the equipment body 3, straddling the boundary between the front and rear plates 3a, 3b so as to connect the front and rear plates 3a, 3b within the equipment body 3. By supplying pressure oil to these articulating jacks 9a and propelling the excavator 1 with the front and rear plates 3a, 3b bent in a predetermined direction and angle, it is possible to control the propulsion direction and attitude of the excavator 1.

[0031] The shield jack 9b is a device that generates a propulsive force to move the excavator 1 forward by receiving a reaction force from the segment SG installed at the rear of the equipment main body 3, and multiple shield jacks 9b are installed in a row along the circumferential direction of the equipment main body 3 within the equipment main body 3.

[0032] The screw conveyor 10 is a device for discharging the soil and sand taken into the chamber 4, and is installed at the bottom of the main body 3, penetrating the partition wall 7, extending continuously diagonally upward from a soil and sand intake end 10a located inside the chamber 4 to a discharge end 10b located at the rear of the main body 3, slightly higher than the center of the height of the main body 3. Note that a ribbon screw conveyor is shown as an example here.

[0033] The erector 11 is an assembly device that grasps the segment SG, rotates it in the inner circumferential direction of the excavation hole, and transports it to an assembly position in the inner circumferential direction of the excavation hole, and is installed in the hollow of the rear body plate 3b in a state that allows it to rotate in the circumferential direction of the excavation hole by a hydraulic motor (not shown) for driving the erector, etc.

[0034] The earth pressure detection unit 12 is a sensor that detects the mud pressure inside the chamber 4. By managing the mud pressure inside the chamber 4 detected by the earth pressure detection unit 12, the excavator 1 is able to excavate while ensuring the stability of the face.

[0035] The additive injection section 13a is a section for injecting the additive (mud making material) into the face or outer periphery of the excavator 1, and is installed at multiple locations within the surface of the bulkhead 7 or along the circumferential direction of the front body plate 3a.

[0036] Next, an example of the cutter head 2 will be described with reference to Figures 2 to 4. Figure 2 is a front view of the cutter head constituting the excavator of Figure 1, Figure 3 is a cross-sectional view of the cutter head of Figure 2 taken along line II, and Figure 4 is a side view showing a comparison of the protruding lengths of the cutter bit and scraper teeth of the cutter head of Figure 2.

[0037] As shown in Figure 2, the cutter head 2 is composed of, for example, a disc-shaped spoke-type cutter head, and includes two spoke portions 2sa, 2sb arranged in a cross shape, cover portions 2c installed on both ends of the spoke portion 2sa, an outer ring portion 2r connecting the tips of the spoke portions 2sa, 2sb, and a through hole 2h formed between these components.

[0038] The center bit CB is installed at the center of the spoke portion 2sa within the front surface of the cutter head 2, extending along the longitudinal direction of the spoke portion 2sa. As shown in FIG. 3, a portion of the shank portion S1 and a tip portion C1 are installed on the face side of the center bit CB, arranged alternately along the longitudinal direction of the center bit CB. The shank portion S1 of the center bit CB is the bit body portion that serves as the base of the center bit CB and is made of, for example, steel. On the other hand, the tip portion C1 of the center bit CB is the cutting edge portion that strikes and breaks down the natural ground. It is made of, for example, a cemented carbide alloy in which metal carbide particles such as tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) are bound with a binder metal such as cobalt (Co), nickel (Ni), or iron (Fe). Note that the center bit CB may be replaced with another excavator cutter component, such as a cone-head roller bit.

[0039] 2, multiple leading bits B (Bs, Bn) and multiple scraper teeth ST are installed within the front surface of the cutter head 2. One of the leading bits Bs is a cutter bit that mainly performs preliminary cutting of the natural ground and protects the scraper teeth ST, and is arranged in a row along the longitudinal direction of each of the spoke portions 2sa, 2sb, and is installed near the outer periphery of the cutter head 2 in the cover portion 2c. The other leading bits Bn are cutter bits that function similarly to the leading bits Bs and are installed at both longitudinal ends of each of the spoke portions 2sa, 2sb.

[0040] As shown in Figures 3 and 4, the leading bit B (Bs, Bn) has a rectangular upper surface (first surface) F1 facing the excavation face, and inclined surfaces (second surface) F2 and (third surface) F that intersect at both ends of the upper surface F1 and face the excavation face, respectively, and are inclined in the radial direction of the excavation process (the radial direction of the ground excavated in a circular shape by the rotation of the cutter head 2). The leading bit B (Bs, Bn) is installed with the inclination direction of one of the inclined surfaces F2 (or F3) facing the center of rotation of the cutter head 2. This allows the excavated soil and sand excavated by the leading bit B (Bs, Bn) to be guided to the inside of the front of the cutter head 2 and into the chamber 4 through the through-hole 2h, making it easy to store the excavated soil in the chamber 4. In addition to the leading bit B (Bs, Bn), other excavator cutter components, such as roller bits, may be installed on the cutter head 2. The configuration of the leading bit Bs will be described in detail later.

[0041] As shown in Fig. 2, the scraper teeth ST are cutting parts that mainly cut earth and sand, and are installed side by side along the longitudinal direction of the spokes 2sa and 2sb on both sides of the width of the spokes 2sa and 2sb. As shown in Fig. 4, the leading bits B (Bs, Bn) are installed so that they protrude further toward the face than the tips of the scraper teeth ST. This allows the scraper teeth ST to be protected by the leading bits B (Bs, Bn).

[0042] In this embodiment, the leading bits Bs and Bn have the same protrusion length, but the leading bits Bs and Bn may have different protrusion lengths. Also, leading bits Bs with different protrusion lengths or leading bits Bn with different protrusion lengths may be used. However, since the function of the leading bits B (Bs, Bn) is to pre-cut the natural ground and protect the scraper teeth ST, the protrusion length is set longer than that of the scraper teeth ST.

[0043] As shown in Fig. 2, additive injection sections 13b, 13c are provided near the center and periphery of the cutter head 2 on both longitudinal halves of the spoke section 2sb within the front of the cutter head 2. These additive injection sections 13b, 13c are components that inject a soil-making material, such as a bentonite-based additive, toward the cutting face on the front of the cutter head 2. Note that, as the additive, an aerated material may be used instead of the bentonite-based additive, or both the bentonite-based additive and the aerated material may be used.

[0044] Next, the configuration of the preceding bit Bs will be described with reference to Figures 5 to 9. Figure 5 is a front view of the preceding bit attached to the cutter head of Figure 2, Figure 6 is a plan view of the preceding bit of Figure 5, Figure 7 is a side view of the preceding bit of Figure 5, Figure 8 is a cross-sectional view of the preceding bit of Figure 5 taken along line I, and Figure 9 is a cross-sectional view of the preceding bit of Figure 5 taken along line II. In Figures 5 and 6, the symbol R indicates the direction in which the preceding bits B (Bs, Bn) move due to the rotation of the cutter head 2, and earth and sand collide with the preceding bits B in the opposite direction.

[0045] The leading bit Bs is formed, for example, in the shape of a flat plate, and on its face side, as described above, it has a rectangular upper surface F1 facing the face, and inclined surfaces F2 and F3 that intersect at both ends of the upper surface F1 and face the face, respectively, and are inclined in the excavation radial direction during the excavation process. The leading bit Bs of this embodiment has a shape formed on the face side by the upper surface F1 and inclined surfaces F2 and F3 in this way in order to reduce the rake angle and clearance angle when targeting boulder layers and to mitigate damage from boulders. Note that, although not particularly limited, the width of the leading bit Bs is, for example, 250 mm, the height (protrusion length) is, for example, 180 mm, the thickness (length perpendicular to the width) is, for example, 60 mm, the length in the short direction of the upper surface F1 is, for example, 15 mm, and the inclination angle of the inclined surfaces F2 and F3 relative to the upper surface F1 is, for example, 30 degrees.

[0046] The leading bit Bs includes a shank portion S2 and tip portions C2a, C2b, and C2c. The shank portion S2 of the leading bit Bs is the bit body portion that serves as the base of the leading bit Bs. The shank portion S2 is made of a material that is more susceptible to wear than the tip portions C2a, C2b, and C2c, but has sufficient rigidity and strength, such as hollow steel SKC24 (JIS G4410). However, the material of the shank portion S2 is not limited to the above and can be changed in various ways; for example, SS material or S45C material may also be used.

[0047] The tip portions C2a and C2b of the leading bit Bs are blade portions having functions such as striking the ground to break it down and disturb it.

[0048] Here, the tip portion (first tip portion) C2a is installed at both corners of the shank portion S2 on the face side of the leading bit Bs in the direction of movement R during the drilling process (the direction in which the leading bit Bs attached to the cutter head 2 moves as the cutter head 2 rotates). That is, notches are formed in the corners of both ends of the shank portion S2 on the face side of the leading bit Bs in the direction of movement R, and the tip portion C2a is fixed to the notches. Although not particularly limited, the width (length along the direction of movement R) of the tip portion C2a is, for example, 40 mm, the height (length along the protruding length) is, for example, 70 mm (protruding length from the shank portion S2 toward the face side is 2 mm), and the thickness (length perpendicular to the width) is, for example, 62 mm (protruding length in the thickness direction from the shank portion S2 is 1 mm).

[0049] Next, the tip portion (second tip portion) C2b is installed adjacent to the two tip portions C2a, C2a located at both corners on the cutting face side of the leading bit Bs, with part of the shank portion S2 interposed between them. That is, two grooves are formed in the shank portion S2 between the tip portions C2a, C2a located at both corners on the cutting face side of the leading bit Bs, and the tip portions C2b, C2b are fitted and fixed into each groove. Although not particularly limited, the width (length along the direction of movement R) of each tip portion C2b is, for example, 25 mm, the height (length along the protruding length) is, for example, 65 mm (protruding length from the shank portion S2 toward the cutting face side is 2 mm), and the thickness (length perpendicular to the width) is, for example, 62 mm (protruding length in the thickness direction from the shank portion S2 is 1 mm).

[0050] The tip portions C2a and C2b are made of a JIS E3 alloy (JIS E3 alloy) that is harder than the material of the shank portion S2, and are made of a cemented carbide alloy in which metal carbide particles such as tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) are bound with a binder metal such as cobalt (Co), nickel (Ni), or iron (Fe). Here, the tip portions C2a and C2b are made of, for example, SG30 manufactured by Starloy Corporation.

[0051] In this embodiment, the tip portions C2a and C2b and portions of the shank portion S2, which are softer than the tip portions C2a and C2b, are alternately arranged on the face side of the leading bit Bs along the direction R of movement of the leading bit Bs (the direction in which force is applied from the natural ground), thereby improving the durability of the leading bit Bs as a whole. For example, during shield excavation, the relatively soft shank portion S2 can absorb impacts applied to the tip portions C2a and C2b. This improves the durability (lifespan) of the leading bit Bs.

[0052] Next, the tip portion (third tip portion) C2c is a reinforcing member that mainly suppresses or prevents wear of the shank portion S2 on the face side. It is installed on the shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b. That is, on the face side of the leading bit Bs, a hole is formed in the shank portion S2 between adjacent tip portions C2a, C2a and C2b, C2b, and the tip portion C2c is fitted and fixed in the hole. Here, at least one tip portion C2c is installed in the shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b, in the area including the upper surface F1 and the inclined surfaces F2, F3 of the leading bit Bs. As shown in FIG. 6, in this embodiment, two tip portions C2c are installed on each shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b.

[0053] As mentioned above, the tip portion C2c is a reinforcing member that mainly suppresses or prevents wear of the shank portion S2 on the face side, and therefore the greater the number of tip portions C2c arranged, the better the wear resistance of the shank portion S2 on the face side.

[0054] As shown in the figure, the axial upper end surface of the tip portion C2c, which is arranged across the upper surface F1 and inclined surface F2 of the preceding bit Bs, is exposed along the upper surface F1 and inclined surface F2, and the axial upper end surface of the tip portion C2c, which is arranged across the upper surface F1 and inclined surface F3 of the preceding bit Bs, is exposed along the upper surface F1 and inclined surface F3. However, the tip portion C2c may be positioned on the top surface F1 of the preceding bit Bs so that its top surface is exposed along the top surface F1, rather than being positioned across the top surface F1 and inclined surface F2 of the preceding bit Bs so that its top end surface is exposed along these surfaces F1 and F2, or on the top surface F1 and inclined surface F3 of the preceding bit Bs so that its top end surface is exposed along these surfaces F1 and F3.

[0055] The tip portion C2c is formed, for example, in a cylindrical shape. This allows the stress applied to the tip portion C2c during shield excavation to be distributed almost evenly, thereby improving the durability of the tip portion C2c. This makes it possible to make the tip portion C2c less susceptible to breaking or cracking. Note that the tip portion C2c may be in any shape as long as it is columnar, and is not limited to a cylindrical shape. However, as mentioned above, a cylindrical shape is preferable because it allows the applied stress to be distributed almost evenly.

[0056] The tip portion C2c is made of, for example, a JIS E5-class alloy (JIS E5-class alloy) that is harder than the shank portion S2 but less hard than the tip portions C2a and C2b. Here, the tip portion C2c is made of, for example, SG50 manufactured by Starloy Corporation. This allows the strength of the tip portion C2c to be improved compared to the tip portions C2a and C2b. This makes the tip portion C2c less likely to break or crack. Furthermore, this reduces the cost of the tip portion C2c, thereby reducing the cost of the preceding bit Bs. However, the tip portion C2c may also be made of the same JIS E3-class material (for example, SG30 manufactured by Starloy Corporation) as the tip portions C2a and C2b. Although not particularly limited, the diameter of each tip portion C2c is, for example, 15 mm, the height (length in the direction along the protrusion length) is, for example, 60 mm (protrusion length from the shank portion S2 toward the face side: 2 mm), and the distance between the tip portion C2c exposed across the upper surface F1 and the inclined surface F2 and the tip portion C2c exposed across the upper surface F1 and the inclined surface F3 is, for example, 15 mm.

[0057] The shank portion S2 constituting the leading bit Bs is softer than the tip portions C2a, C2b made of cemented carbide, and therefore tends to wear out before the tip portions C2a, C2b during shield drilling. For this reason, strengthening the shank portion S2 is important for improving the durability (lifespan) of the leading bit Bs. Furthermore, in the leading bit Bs of this embodiment, cylindrical tip portions C2c are provided on the shank portion S2 between the adjacent tip portions C2a, C2a and the adjacent tip portions C2b, C2b, thereby suppressing or preventing wear of the shank portion S2 during shield drilling. This prevention of wear of the shank portion S2 also suppresses or prevents the tip portion C2a from breaking or cracking. This improves the overall durability (lifespan) of the leading bit Bs during the shield drilling process, thereby suppressing or preventing a decrease in the cutting ability of the leading bit Bs and a decrease in the excavation speed of the excavator 1. Furthermore, the number of times the leading bit Bs needs to be replaced can be reduced.

[0058] Furthermore, the installation location of the leading bits Bs may be from the outer periphery of the cutter head 2 to a radially intermediate position. For example, the installation location of the leading bits Bs may be limited to the fifth row from the outer periphery of the cutter head 2 to the inner periphery, where the sliding distance to reach the final excavation position exceeds approximately 1.5 million meters. This allows the number of leading bits Bs to be installed to be reduced without significantly reducing the excavation capacity of the excavator 1, compared to when multiple leading bits Bs are installed across the entire surface of the cutter head 2. Therefore, the cost of the excavator 1 can be reduced.

[0059] As shown in Figure 5, the two mounting surfaces (first mounting surfaces) V1, V1 on the tip portion C2c side of the two tip portions C2a described above are formed so that the face and opposite sides are inclined away from each other. If the mounting surfaces V1, V1 were formed so that the face sides were inclined toward each other, the width of the shank portion S2 between adjacent tip portions C2a, C2b would be narrow. However, in this embodiment, the mounting surfaces V1, V1 are formed so that the face and opposite sides are inclined away from each other, so that the width does not become narrow. This ensures space for arranging the tip portion C2c.

[0060] Furthermore, the attachment surface (second attachment surface) V2 on the opposite side of the cutting face of the tip portion C2a is formed to be inclined from the end of the attachment surface V1 on the opposite side of the cutting face toward the cutting face. Although not particularly limited, the inclination angle of the attachment surface V2 (inclination angle with respect to the moving direction R) is, for example, 10 degrees.

[0061] Here, when the tip portion C2a, which is formed in an approximately rectangular shape when viewed from the direction shown in Figure 5, is fitted into the inclined mounting surfaces V1 and V2, the face side of the tip portion C2a is inclined upward, and the surfaces located at both ends of the preceding bit Bs in the tip portion C2a protrude outward beyond the surfaces located at both ends of the preceding bit Bs in the shank portion S2.

[0062] In contrast, in the preceding bit Bs of this embodiment, as shown in Figure 5, the face-side surface of the tip portion C2a is formed parallel to the movement direction R of the preceding bit Bs and is formed approximately flush with the face-side surfaces of the tip portions C2a, C2b and each shank portion S2 between adjacent tip portions C2b, C2b. This reduces the force that peels the downstream tip portion C2a from the shank portion S2 when the preceding bit Bs moves in the rotational direction, making the tip portion C2a less likely to be damaged. In addition, the surfaces of the tip portion C2a located at both ends of the preceding bit Bs are formed flush with the end faces of the shank portion S2 of the preceding bit Bs, so as to fit within the original width of the preceding bit Bs.

[0063] The mounting surface V1 and the mounting surface V2 of the tip portion C2a of the preceding bit Bs will be described below with reference to Figures 10 and 11. Figure 10 is an explanatory diagram showing a tip portion installed at a corner of a preceding bit as a comparative example, and Figure 11 is an explanatory diagram showing a tip portion installed at a corner of a preceding bit of this embodiment.

[0064] As shown in Figure 10, when the two mounting surfaces V1, V1 on the tip portion C2c side of the tip portion C2a installed at the corner are formed perpendicular to the face and parallel to each other, and the mounting surface V2 on the opposite side of the tip portion C2a from the face side is formed parallel to the excavation surface, when the leading bit Bs moves in the direction of symbol R due to the rotation of the cutter head 2, a force is applied to the tip portion C2a excavating the ground in a direction along the moving direction R indicated by symbol D1.

[0065] In Figure 10, force D1 in the direction opposite to the movement direction R is a force that pulls the tip portion C2a located at the corner of the preceding bit Bs away from the shank portion S2. As mentioned above, the tip portion C2a located at the corner of the preceding bit Bs is subjected to a large force during shield drilling, and is therefore prone to breakage due to the action of force D1. As a result, the durability of the preceding bit Bs decreases during the shield drilling process.

[0066] In contrast, in the leading bit Bs of this embodiment, the two mounting surfaces V1, V1 on the tip portion C2c side of the tip portion C2a installed at the corner are formed so that the sides opposite the face side of the two mounting surfaces V1 are inclined away from each other, and the mounting surface V2 on the side opposite the face side of the tip portion C2a is formed so that it is inclined toward the face from the end of the mounting surface V1 opposite the face side. When the leading bit Bs configured in this way moves in the direction of symbol R due to the rotation of the cutter head 2, as shown in Figure 11, a force in the direction opposite to the moving direction R indicated by symbol D1 is applied to the tip portion C2a on the downstream side of the moving direction on the face side, and a force in the moving direction R along the mounting surface V2 indicated by symbol D2 is applied to the side opposite the face side.

[0067] The force D1 in the direction opposite to the movement direction R is a force that pulls the tip portion C2a located at the corner of the preceding bit Bs off from the shank portion S2, but the force D2 in the movement direction R along the mounting surface V2 is a force that absorbs the force D1 in the pulling direction on the inclined mounting surface V2, and as a result, the tip portion C2a is less likely to break off.

[0068] In this way, the tip portion C2a located at the corner of the leading bit Bs is less likely to break even when a large force is applied during shield excavation, improving the durability of the leading bit Bs during the shield excavation process. Furthermore, since the durability of the leading bit Bs is improved and a decrease in cutting ability can be suppressed or prevented, a decrease in the excavation speed of the excavator 1 can be suppressed. In addition, the number of times the leading bit Bs needs to be replaced can be reduced.

[0069] 5, in the leading bit Bs of this embodiment, the surface of the tip portion C2a facing the working face is formed parallel to the direction R of movement of the shank portion S2 during the drilling process. This surface may be formed so as to be inclined upward and outward with respect to the direction R of movement of the shank portion S2 during the drilling process, as shown in FIG. 12. However, forming the surface of the tip portion C2a facing the working face parallel to the direction R of movement of the shank portion S2 during the drilling process as shown in FIG. 5 is preferable because, compared to when the surface is formed so as to be inclined upward and outward as shown in FIG. 12, the force D1 acting in the direction to peel the tip portion C2a from the shank portion S2 is smaller, making the tip portion C2a less likely to break.

[0070] The invention made by the inventor has been specifically described above based on the embodiments, but the embodiments disclosed in this specification are illustrative in all respects and are not limited to the disclosed technology. In other words, the technical scope of the present invention should not be interpreted restrictively based on the description of the above embodiments, but should be interpreted solely in accordance with the claims, and includes technologies equivalent to the technologies described in the claims and all modifications that do not deviate from the gist of the claims.

[0071] For example, in the above embodiment, a ribbon screw conveyor is used, but this is not limited to this and various modifications are possible. For example, a screw conveyor that combines a ribbon type and a shaft type may be used.

[0072] Furthermore, in the above embodiment, a case has been described in which a peripheral support drive type mud shield machine is used, but this is not limited to this, and other mud shield machines may also be used, such as a center shaft drive type or an intermediate support drive type mud shield machine.

[0073] Furthermore, in the above embodiment, a case has been described in which two tip portions C2b, C2b are installed adjacent to each other between the tip portions C2a, C2a at both corners on the face side of the leading bit Bs, with part of the shank portion S2 sandwiched between them, but this is not limited to this; for example, three or more tip portions C2b may be installed adjacent to each other between the tip portions C2a, C2a at both corners on the face side of the leading bit Bs, with part of the shank portion S2 sandwiched between them. [Industrial Applicability]

[0074] The above explanation has been given of the application of the present invention to a shield construction method using a mud pressure shield machine, but the present invention is not limited to this. For example, the present invention may be applied to a shield construction method using a mud shield machine in which mud is pumped into a mud chamber between the cutter head and the main body of the equipment, and the pressure of the mud in the mud chamber is adjusted to a pressure that corresponds to the earth pressure and groundwater pressure at the face, thereby stabilizing the face and rotating the cutter head against the face to excavate the ground. [Explanation of symbols]

[0075] 1. Excavator 2 cutter heads 3. Device body 4 chambers 7 Bulkhead 8 Cutter driver 9a Folding jack 9b Shield Jack 10 Screw conveyor 11 Erector B,Bn,Bs leading bits C1 Tip part C2a Tip part (first tip part) C2b Tip section (second tip section) C2c Tip section (third tip section) CB Center Bit CC copy cutter F1 Top surface (first surface) F2 Inclined surface (second surface) F3 Inclined surface (third surface) R Movement direction S1, S2 shank part ST Scraper Tooth V1 Mounting surface (first mounting surface) V2 Mounting surface (second mounting surface)

Claims

1. a bit body portion having a rectangular first surface facing the drilling face, and second and third surfaces on the drilling face side, the second and third surfaces intersecting each other at both ends of the first surface and inclined in the drilling radial direction during the drilling process so as to face the drilling face; two first tip portions respectively installed at corners at both ends of the bit body portion in the movement direction during the excavation process on the face side of the bit body portion; a second tip portion disposed adjacent to the two first tip portions on the face side of the bit body portion, with a part of the bit body portion interposed therebetween; a columnar third tip portion provided on the bit body portion between adjacent first and second tip portions and between adjacent second tip portions on the face side of the bit body portion, the third tip portion having one axial end surface exposed along the first surface, the second surface, and the third surface; and The two first mounting surfaces of the two first tip portions on the third tip portion side are formed so as to be inclined in directions away from each other on the side opposite to the face, and the second mounting surfaces of the first tip portions on the side opposite to the face are formed so as to be inclined from the end portions of the first mounting surfaces on the side opposite to the face toward the face. A leading bit characterized by:

2. a face-side surface of the first tip portion is formed parallel to the movement direction of the bit body portion during the drilling process and is approximately flush with a face-side surface of the bit body portion between adjacent first tip portion and second tip portion and between adjacent second tip portion and second tip portion; The surfaces of the first tip portion located at both ends of the preceding bit are formed flush with the both end surfaces of the preceding bit of the bit body portion.

2. The preceding bit of claim 1.

3. The third tip portion is formed in a cylindrical shape.

2. The preceding bit of claim 1.

4. The third tip portion is composed of the third tip portion arranged across the first surface and the second surface and having an upper end surface exposed in a state of straddling the first surface and the second surface, and the third tip portion arranged across the first surface and the third surface and having an upper end surface exposed in a state of straddling the first surface and the third surface.

2. The preceding bit of claim 1.

5. The third tip portion is composed of the third tip portion disposed on the first surface and having an upper end surface exposed along the first surface, the third tip portion disposed on the second surface and having an upper end surface exposed along the second surface, and the third tip portion disposed on the third surface and having an upper end surface exposed along the third surface.

2. The preceding bit of claim 1.

6. The third tip portion is provided in plurality along the drilling radial direction of the bit body portion during the drilling process.

2. The preceding bit of claim 1.

7. The leading bit according to any one of claims 1 to 6 is installed on a cutter board. An excavator characterized by:

8. The leading bit is installed with the inclination direction of the second surface facing the rotation center of the cutter board.

8. An excavator according to claim 7.

9. The preceding bit is installed at a position from the outer periphery of the cutter board to a radial midpoint.

8. An excavator according to claim 7.

10. The leading bit is attached to the cutter board in a state where it protrudes toward the face side more than the tip of the scraper tooth attached to the cutter board.

8. An excavator according to claim 7.

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