Lead bit and drilling machine equipped therewith

Abstract

To improve the crushing performance of the lead bit. [Solution] The shank portion S2 has an upper surface F1 facing the working face and inclined surfaces F2 and F3 on the working face side that intersect at both ends of the upper surface F1 and are inclined in the direction of the excavation diameter facing the working face; two tip portions C2a installed at the corners at both ends of the shank portion S2; a tip portion C2b installed between the two tip portions C2a via a part of the shank portion S2; and cylindrical tip portions C2c provided on the upper surface F1 and inclined surfaces F2 and F3 of the shank portion S2 between adjacent tip portions C2a and C2b, and between adjacent tip portions C2b, with the ends on the working face side projecting spherically from the upper surface F1 and inclined surfaces F2 and F3, respectively.

Description

Technical Field

[0001] The present invention relates to a pilot bit and an excavator equipped with the same, and more particularly to a pilot bit mounted on a cutter head of an excavator such as a shield machine used in the shield method, for example.

Background Art

[0002] In the shield method, a cutter head rotatably installed in front of a shield machine is pressed against the face and rotated to form an excavation pit in the ground while ensuring the stability of the face. At the same time, a tunnel is constructed by assembling a plurality of steel or concrete segments on the inner wall surface of the excavation pit. A plurality of cutter bits for excavators are regularly arranged on the front surface and the like of the cutter head of this shield machine.

[0003] This cutter bit for an excavator is an excavation component that breaks up the ground and makes a notch in the excavation process. For example, it includes a steel shank part constituting the bit body part and a carbide tip part constituting the blade body part.

[0004] Note that the configuration of the cutter bit for an excavator is described, for example, in Patent Document 1.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Nowadays, in recent years, the shield method using such a shield machine is not only applied to sewers and subways but also shows an increasing trend in applications to road tunnels, agricultural waterways, etc., and the cross-section and length of construction are increasing, and there is a demand for technology to efficiently excavate ground composed of various geologies.

[0007] Among these challenges, improving the performance of the cutter bit used in excavators, which significantly impacts excavation performance, is a key issue. In particular, when excavating gravelly ground, there is a need to improve the crushing performance of the cutter bit used in excavators.

[0008] In shield tunneling, a lead bit is used for pre-excavation of the ground, launching, cutting of temporary walls at the arrival point, cutting of ground improvement sections, and protecting the teeth bit (the main cutter bit that takes the excavated soil into the chamber). Among the cutter bits for the excavator, the crushing performance of the lead bit has a significant impact.

[0009] This invention was made in light of the above-mentioned technical background, and aims to provide a technology that can improve the crushing performance of the lead bit. [Means for solving the problem]

[0010] To solve the above problems, the lead bit of the present invention as described in claim 1 is characterized by having a bit body having a rectangular first surface facing the face and a second surface and a third surface facing the face that intersect at both ends of the first surface and are inclined in the direction of the excavation diameter during the excavation process; two first tip portions installed at the corners at both ends of the bit body in the direction of movement during the excavation process on the face side of the bit body; a second tip portion installed on the face side of the bit body adjacent to the two first tip portions via a part of the bit body; and a columnar third tip portion provided on the bit body between adjacent first tip portions and second tip portions and between adjacent second tip portions, with the face-side end projecting spherically from the first surface.

[0011] Furthermore, if the third tip portion is arranged across the first surface and the second surface, or across the first surface and the third surface, the third tip portion that is arranged across the surface becomes the third tip portion in which the end on the face side protrudes spherically from the first surface.

[0012] The preceding bit of the present invention as described in claim 2 is characterized in that, in the invention as described in claim 1, the bit body is provided on the face side of the bit body between adjacent first tip portions and second tip portions and between adjacent second tip portions, and further has a columnar third tip portion whose face-side end is exposed from the second surface and the third surface, respectively.

[0013] The lead bit of the present invention as described in claim 3 is characterized in that, in the invention described in claim 2, the third tip portion whose face-side end is exposed from the second and third surfaces has its face-side end protruding spherically from the second and third surfaces.

[0014] The leading bit of the present invention described in claim 4 is characterized in that, in the invention described in claim 3, the third tip portion is formed in a cylindrical shape.

[0015] The preceding bit of the present invention as described in claim 5 is characterized in that, in the invention described in claim 1, the face-side ends of the first tip portion and the second tip portion protrude from the first surface, the second surface, and the third surface of the bit body portion.

[0016] The excavator of the present invention as described in claim 6 is characterized in that a leading bit described in any one of claims 1 to 5 is installed on the cutter machine.

[0017] The excavator of the present invention as described in claim 7 is characterized in that, in the invention described in claim 6, the leading bit is installed such that the inclination direction of the second surface faces the rotation center of the cutter disc.

[0018] The excavator of the invention according to claim 8 is characterized in that, in the invention according to claim 6 described above, the leading bit is installed at a position in the radial middle from the outer peripheral side of the cutter head to the middle position in the radial direction.

[0019] The excavator of the invention according to claim 9 is characterized in that, in the invention according to claim 6 described above, the leading bit is mounted on the cutter head in a state of protruding toward the cutting face side from the tip of the scraper tool mounted on the cutter head.

Effect of the Invention

[0020] According to the present invention, since the end portion on the cutting face side of the third chip portion protrudes in a spherical shape, in addition to the first chip portion and the second chip portion, the third chip portion also breaks the ground. As a result, it becomes possible to improve the crushing performance of the leading bit.

Brief Description of the Drawings

[0021] [Figure 1] It is a main part configuration diagram showing the inside of an excavator according to an embodiment of the present invention seen through from the side. [Figure 2] It is a front view of a cutter head constituting the excavator of FIG. 1. [Figure 3] It is a cross-sectional view taken along line I-I of the cutter head of FIG. 2. [Figure 4] It is a side view showing a comparison of the protruding lengths of the cutter bit and the scraper tool of the cutter head of FIG. 2. [Figure 5] It is a front view of a leading bit attached to the cutter head of FIG. 2. [Figure 6] It is a plan view of the leading bit of FIG. 5. [Figure 7] It is a side view of the leading bit of FIG. 5. [Figure 8] It is a cross-sectional view taken along line I of the leading bit of FIG. 5. [Figure 9] It is a cross-sectional view taken along line II of the leading bit of FIG. 5. [Figure 10]This is a plan view showing a prior bit as a modified example of the present invention. [Figure 11] Figure 10 is a cross-sectional view of the leading bit on line II. [Modes for carrying out the invention]

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings used to illustrate the embodiments, the same reference numerals are generally used for identical components, and repeated descriptions of such components will be omitted.

[0023] First, an example of the excavator of this embodiment will be described with reference to Figure 1. Figure 1 is a diagram showing the main components of the excavator of this embodiment as seen from the side.

[0024] The excavator 1 of this embodiment is, for example, a mud pressure type shield machine. By injecting additives into the soil excavated by the cutter head 2 and mixing it, the excavator fills the chamber 4 between the cutter head 2 and the machine body 3 with mud that has plastic fluidity (the property of being able to be freely deformed and moved), and excavates while generating mud pressure that counteracts the earth pressure at the face, thereby ensuring the stability of the tunnel face. The overall operation of the excavator 1 is controlled by a control unit located in the driver's cab of a trailing carriage (not shown) behind it. Furthermore, although not particularly limited, the excavator 1 of this embodiment is, for example, equipment used in long-distance excavation work of 3304 km, and most of the excavation section contains hard sedimentary layers in which sand layers, mudstone layers and interlayers thereof are distributed.

[0025] The cutter head 2 is a cutter disc for excavating the ground and is installed on the front of the excavator 1 so as to be rotatable in both forward and reverse directions along the circumferential direction of the main body 3 of the machine. The front surface of the cutter head 2 (the surface facing the excavation face) is equipped with a center bit CB, a lead bit B, and a scraper tooth (not shown in Figure 1). A copy cutter CC is also installed on the outer circumference of the cutter head 2. The copy cutter CC is responsible for over-excavation during sharp curve construction and for controlling the attitude of the excavator 1. A stirring blade (not shown) is installed on the back surface of the cutter head 2. The stirring blade is formed, for example, with cylindrical protruding members and is responsible for stirring and mixing the soil and additives in the chamber 4 when the cutter head 2 rotates. The cutter head 2 will be described in detail later.

[0026] The main body of the equipment 3 comprises a front body plate (front section) 3a, a rear body plate (rear section) 3b behind it, and a tail seal 3c on the rear inner surface of the rear body plate 3b. The front body plate 3a and the rear body plate 3b are formed, for example, from cylindrical steel plates and form the outer shape of the main body of the equipment 3, as well as forming a hollow space inside the main body of the equipment 3. The front body plate 3a and the rear body plate 3b are engaged by the spherical bearing portion at the tip of the rear body plate 3b fitting into contact with the inner surface of the front body plate 3a at the rear end of the front body plate 3a. The tail seal 3c is a sealing member that prevents groundwater and the like from entering the main body of the equipment 3 from the rear during excavation work, and is installed at the rear end of the rear body plate 3b in an annular frame shape along the inner circumference of the rear body plate 3b.

[0027] On the front side of the front shell plate 3a, a bulkhead 7 is installed at a position recessed inward from its front surface into the main body 3, dividing the hollow space within the main body 3 into a face side and a machine side. The chamber 4 is provided on the face side of this bulkhead 7, that is, between the cutter head 2 and the bulkhead 7. Excavated soil and other materials are taken into the cutter head 2 through a through-hole (not shown in Figure 1) on the front surface of the cutter head 2.

[0028] Meanwhile, the inside of the main body 3 of the excavator 1 is equipped with a cutter drive unit 8, a folding 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, among other things.

[0029] The cutter drive unit 8 is a motor (drive source) that rotates the cutter head 2 in forward and reverse directions, and multiple units are arranged in a line along the circumferential direction of the cutter head 2, near the outer circumference on the front surface of the cutter head 2. In this example, an outer circumference support drive system is used as the cutter drive system.

[0030] The folding jacks 9a are devices used to correct the propulsion direction and attitude of the excavator 1. Multiple folding jacks 9a are installed in a row along the circumferential direction of the equipment body 3, straddling the boundary between the front plate 3a and the rear plate 3b, so as to connect the front plate 3a and the rear plate 3b within the equipment body 3. By supplying pressurized oil to these folding jacks 9a and propelling the excavator 1 while the front plate 3a and the rear plate 3b are bent in a predetermined direction and angle, it is possible to control the propulsion direction and attitude of the excavator 1.

[0031] The shield jacks 9b are devices that generate thrust to advance the excavator 1 by taking a reaction force from the segment SG installed at the rear of the main body 3, and multiple shield jacks are installed in a row along the circumferential direction of the main body 3.

[0032] The screw conveyor 10 is a device for discharging soil and sand taken into the chamber 4. It is installed in a manner that it extends continuously diagonally upward from the soil and sand intake end 10a, which penetrates the partition wall 7 at the bottom of the device body 3 and is located inside the chamber 4, to the discharge end 10b, which is located at the rear of the device body 3 at a position slightly higher than the center of the device body 3 in the height direction. In this example, a ribbon screw conveyor is shown.

[0033] The erector 11 is an assembly device that grips the segment SG, rotates it in the circumferential direction of the borehole, and transports it to the assembly position in the circumferential direction of the borehole. It is installed in the hollow of the rear shell plate 3b in a state that allows it to rotate along the circumferential direction of the borehole by a hydraulic motor (not shown) or the like for driving the erector.

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

[0035] The additive injection section 13a is the part that injects the above-mentioned additive (soil preparation material) into the face or outer circumference of the excavator 1, and is installed in multiple locations within the plane of the partition wall 7 or along the circumferential direction of the front body plate 3a.

[0036] Next, an example of the cutter head 2 described above will be explained with reference to Figures 2 to 4. Figure 2 is a front view of the cutter head that constitutes the excavator in Figure 1, Figure 3 is a cross-sectional view of the cutter head in Figure 2 along line II, and Figure 4 is a side view showing a comparison of the protruding lengths of the cutter bit and scraper tooth of the cutter head in 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 sections 2sa and 2sb arranged in a cross shape, cover sections 2c installed on both ends of the spoke section 2sa, an outer peripheral ring section 2r connecting the tips of the spoke sections 2sa and 2sb, and a through hole 2h formed between these members.

[0038] Within the front surface of the cutter head 2, the center bit CB described above is installed in the center of the spoke portion 2sa, extending along the longitudinal direction of the spoke portion 2sa. On the face side of this center bit CB, as shown in Figure 3, a part of the shank portion S1 and the tip portion C1 are installed alternately along the longitudinal direction of the center bit CB. The shank portion S1 of the center bit CB is the main body of the bit that forms 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 blade portion that strikes and breaks up the ground, and is made of, for example, a superhard alloy in which metal carbide particles such as tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) are bonded together with a binder metal such as cobalt (Co), nickel (Ni), or iron (Fe). In addition to the center bit CB, other cutter members for excavators, such as a cone-head type roller bit, may be installed.

[0039] Furthermore, as shown in Figure 2, multiple lead bits B (Bs, Bn) and multiple scraper teeth ST are installed inside the front surface of the cutter head 2. One type of lead bit Bs is a cutter bit that is mainly used for preliminary cutting of the ground and protection of the scraper teeth ST, and is arranged in a row along the longitudinal direction of the spoke sections 2sa and 2sb, and is installed near the outer circumference of the cutter head 2 in the cover section 2c. The other type of lead bit Bn is a cutter bit that functions as an outer circumference bit, having the same function as the lead bits Bs, and is installed at both longitudinal ends of the spoke sections 2sa and 2sb.

[0040] As shown in Figures 3 and 4, such a lead bit B(Bs,Bn) has a rectangular upper surface (first surface) F1 facing the face, and inclined surfaces (second surface) F2 and (third surface) F that intersect at both ends of the upper surface F1 and face the face, and are inclined in the radial direction of excavation during the excavation process (the radial direction of the ground excavated in a circular shape by the rotation of the cutter head 2). The lead bit B(Bs,Bn) is installed with the inclination direction of one of the inclined surfaces F2 (or F3) facing the rotation center of the cutter head 2. This allows the excavated soil and other materials excavated by the lead 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, so that the excavated soil and other materials can be easily contained in the chamber 4. In addition to the lead bit B(Bs,Bn), other cutter members for excavators such as roller bits may also be installed on the cutter head 2. The configuration of the lead bit Bs will be described in detail later.

[0041] Furthermore, as shown in Figure 2, the scraper tooth ST is a cutting component primarily used for cutting soil and sand, and is installed on both sides of the spoke sections 2sa and 2sb in the width direction, aligned along the longitudinal direction of the spoke sections 2sa and 2sb. As shown in Figure 4, the leading bit B(Bs, Bn) is installed so as to protrude toward the face side beyond the tip of the scraper tooth ST. In this way, the scraper tooth ST is protected by the leading bit 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. Alternatively, leading bits Bs or Bn with different protrusion lengths may be used. However, since the function of the leading bits B(Bs,Bn) is to perform preliminary cutting of the ground and protect the scraper tooth ST, they are set to be longer than the protrusion length of the scraper tooth ST.

[0043] As shown in Figure 2, additive injection sections 13b and 13c are installed near the center and near the outer periphery of the cutter head 2, respectively, on both halves in the longitudinal direction of the spoke section 2sb within the front surface of the cutter head 2. These additive injection sections 13b and 13c are components for injecting a soil preparation material, such as a bentonite-based additive, toward the cutting face at the front of the cutter head 2. In addition, a foaming agent may be used instead of a bentonite-based additive, or both a bentonite-based additive and a foaming agent may be used.

[0044] Next, the configuration of the lead bit Bs described above will be explained using Figures 5 to 9. Figure 5 is a front view of the lead bit attached to the cutter head in Figure 2, Figure 6 is a top view of the lead bit in Figure 5, Figure 7 is a side view of the lead bit in Figure 5, Figure 8 is a cross-sectional view of the lead bit along line I in Figure 5, and Figure 9 is a cross-sectional view of the lead bit along line II in Figure 5. In Figures 5 and 6, the symbol R indicates the direction in which the lead bit B (Bs, Bn) moves due to the rotational movement of the cutter head 2, and the soil collides with the lead bit B in the opposite direction.

[0045] The leading bit Bs is formed, for example, in a flat plate shape, 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, and are inclined in the direction of the excavation diameter during the excavation process. The leading bit Bs in this embodiment is shaped with the upper surface F1 and inclined surfaces F2 and F3 on the face side in order to reduce the scoop angle and escape angle when targeting boulder layers and mitigate damage from boulders. Although not particularly limited, the width of the leading bit Bs is, for example, 250 mm, the height (projection length) is, for example, 180 mm, the thickness (length perpendicular to the width) is, for example, 60 mm, the length of the upper surface F1 in the short direction 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 lead bit Bs comprises a shank portion S2 and tip portions C2a, C2b, and C2c. The shank portion S2 of the lead bit Bs is the main body of the lead bit Bs, which serves as its base. The material of this shank portion S2 is more prone to wear than the tip portions C2a, C2b, and C2c, but is made of a material that 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 be used.

[0047] The tip portions C2a and C2b of the leading bit Bs are blade sections that primarily function to strike, break down, and disturb the ground.

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

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

[0050] The constituent materials of these tip sections C2a and C2b are made of JIS E3 type alloys (JIS standard E3 type alloys), which are harder than the constituent material of the shank section S2. For example, they are made of ultra-hard alloys in which metal carbide particles such as tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) are bonded together with binder metals such as cobalt (Co), nickel (Ni), or iron (Fe). Here, for example, SG30 manufactured by Starloy Co., Ltd. is used as the constituent material for the tip sections C2a and C2b.

[0051] In this embodiment, the durability of the lead bit Bs as a whole is improved by alternately arranging the tip portions C2a and C2b and a portion of the shank portion S2, which is softer than the tip portions C2a and C2b, on the face side of the lead bit Bs along the direction of movement R of the lead bit Bs (the direction in which force is applied from the ground side). For example, during shield drilling, the impact applied to the tip portions C2a and C2b can be absorbed by the relatively softer shank portion S2. Therefore, the durability (lifespan) of the lead bit Bs is improved.

[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, and multiple pieces (two pieces in this embodiment) are installed in the shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b, along the drilling diameter direction during the drilling process. That is, on the face side of the leading bit Bs, holes are formed in the shank portion S2 between adjacent tip portions C2a, C2a and C2b, C2b, and the tip portion C2c is fixed in a fitted state within these holes. Here, one tip portion C2c is installed on the upper surface F1 of the leading bit Bs, one on the inclined surface F2, and one on the inclined surface F3, in each shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b. Therefore, as shown in Figure 6, in this embodiment, three tip portions C2c are arranged in each shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b.

[0053] As shown in the figure, the face-side end of the tip portion C2c positioned on the upper surface F1 of the leading bit Bs, the face-side end of the tip portion C2c positioned on the inclined surface F2, and the face-side end of the tip portion C2c positioned on the inclined surface F3 protrude in a spherical shape. In this way, because the face-side end of the tip portion C2c protrudes in a spherical shape, not only the tip portions C2a and C2b but also the tip portion C2c will crush the ground, so in addition to the function of the tip portion C2c described above (function as a reinforcing member that suppresses or prevents wear of the face-side shank portion S2), the crushing performance when excavating the ground is improved.

[0054] Furthermore, 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. As a result, the tip portion C2c is less likely to break or crack. Note that the tip portion C2c does not need to be cylindrical, and can be any shape. However, as mentioned above, a cylindrical shape is preferable because it allows the applied stress to be distributed almost evenly.

[0055] As mentioned above, the tip portion C2c is primarily a reinforcing member that suppresses or prevents wear of the shank portion S2 on the face side. Therefore, the more tip portions C2c there are, the better the wear resistance of the shank portion S2 on the face side. For this reason, it is desirable to have multiple tip portions C2c along the drilling diameter direction during the drilling process of the leading bit Bs. However, it is sufficient to have at least one tip portion C2c on the upper surface F1 of the leading bit Bs, on the shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b. It is not necessary to have multiple tip portions C2c along the drilling diameter direction during the drilling process of the leading bit Bs.

[0056] Furthermore, if multiple tip sections C2c are provided along the excavation diameter direction during the excavation process of the preceding bit Bs, it is sufficient that the face-side end of the tip section C2c located on the upper surface F1 protrudes in a spherical shape, while the face-side ends of the tip sections C2c located on the inclined surfaces F2 and F3 do not need to protrude in a spherical shape, but simply need to be exposed. However, when excavating ground with a higher gravel content, it is desirable that the face-side ends of the tip sections C2c located on the inclined surfaces F2 and F3 also protrude in a spherical shape.

[0057] In the illustration, the tip portion C2c is installed on the upper surface F1, inclined surface F2, and inclined surface F3 of the leading bit Bs at each shank portion S2 between adjacent tip portions C2a, C2b, and tip portions C2b, C2b, respectively. However, as shown in Figure 10, a plan view of the leading bit as an example of modification, and Figure 11, a cross-sectional view of the leading bit along line III, the tip portion C2c may be arranged to straddle the upper surface F1 and inclined surface F2 of the leading bit Bs, or to straddle the upper surface F1 and inclined surface F3. In this case, the tip portion C2c arranged to straddle the upper surface F1 and inclined surface F2, or the tip portion C2c arranged to straddle the upper surface F1 and inclined surface F3, will have an end on the face side that protrudes spherically from the upper surface F1.

[0058] The tip portion C2c is made of a JIS E5 alloy (a JIS standard E5 alloy) that is harder than, for example, the shank portion S2 but harder than the tip portions C2a and C2b. Here, for example, SG50 manufactured by Starloy Co., Ltd. is used as the constituent material for the tip portion C2c. This makes it possible to improve the strength of the tip portion C2c compared to the tip portions C2a and C2b. As a result, the tip portion C2c can be made less likely to break or crack. In addition, in this case the cost of the tip portion C2c can be reduced, and therefore the cost of the leading bit Bs can be reduced. However, the tip portion C2c may also be made of the same JIS E3 material as the tip portions C2a and C2b described above (for example, SG30 manufactured by Starloy Co., Ltd.). While not particularly limited, the diameter of each tip portion C2c is, for example, 15 mm, the height (length in the direction along the protruding length) is, for example, 60 mm (protruding length 2 mm from the shank portion S2 toward the face), and the distance between the tip portion C2c located on the upper surface F1 and the tip portion C2c located on the inclined surface F2, and the distance between the tip portion C2c located on the upper surface F1 and the tip portion C2c located on the inclined surface F3 is, for example, 3 mm.

[0059] The shank portion S2 that constitutes the lead bit Bs is softer than the ultra-hard alloy tip portions C2a and C2b, and therefore tends to wear out before the tip portions C2a and C2b during shield drilling. For this reason, strengthening the shank portion S2 is important for improving the durability (lifespan) of the lead bit Bs. In the lead bit Bs of this embodiment, by installing cylindrical tip portions C2c on the shank portion S2 between adjacent tip portions C2a, C2a and tip portions C2b, C2b, wear of the shank portion S2 during shield drilling can be suppressed or prevented. This prevention of wear of the shank portion S2 also suppresses or prevents the tip portions C2a from breaking or cracking. Therefore, the overall durability (lifespan) of the lead bit Bs can be improved in the shield drilling process, which suppresses or prevents a decrease in the cutting ability of the lead bit Bs and suppresses a decrease in the drilling speed of the drilling machine 1. In addition, the number of times the lead bit Bs needs to be replaced can be reduced.

[0060] Furthermore, in this embodiment, the end of the tip portion C2c on the face side has a spherical protruding shape, which causes it to crush the ground. Therefore, in addition to the tip portions C2a and C2b, the tip portion C2c also crushes the ground, improving the crushing performance when the leading bit Bs excavates the ground.

[0061] Furthermore, the installation locations of the lead bits Bs may be limited to the radially intermediate position from the outer circumference of the cutter head 2. For example, the installation locations of the lead bits Bs may be limited to the 5th stage from the outer circumference to the inner circumference of the cutter head 2, where the sliding distance to reach the final drilling position exceeds approximately 1.5 million m. This reduces the number of lead bits Bs installed without significantly reducing the drilling capacity of the drilling machine 1, compared to the case where multiple lead bits Bs are installed across the entire surface of the cutter head 2. Therefore, the cost of the drilling machine 1 can be reduced.

[0062] The present inventors have described the invention in detail based on embodiments, but the embodiments disclosed herein are illustrative in all respects and are not limited to the disclosed technology. That is, the technical scope of the present invention should not be interpreted restrictively based on the description of the embodiments above, but rather in accordance with the claims, and includes the equivalent technology of the claimed technology and all modifications that do not depart from the gist of the claims.

[0063] For example, although the above embodiment described the case in which a ribbon screw conveyor is used, it is not limited to this and can be modified in various ways. For example, a screw conveyor that combines a ribbon type and a shaft type may be used.

[0064] Furthermore, although the above embodiment described the case in which an outer perimeter support drive type earth pressure balance shield machine was used, it is not limited to this, and other earth pressure balance shield machines such as a center shaft drive type or an intermediate support drive type may also be used.

[0065] Furthermore, in the above embodiment, the case 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 via a part of the shank portion S2 has been described. However, the invention is not limited to this, and 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 via a part of the shank portion S2. [Industrial applicability]

[0066] The above description has focused on the application of the present invention to a shield tunneling method using a slurry shield machine. However, the invention is not limited to this. For example, it may also be applied to a shield tunneling method using a slurry shield machine, in which slurry is pumped under pressure into a slurry chamber between the cutter head and the machine body, and the ground is excavated by pressing the cutter head against the tunnel face and rotating it while adjusting the pressure of the slurry in the slurry chamber to match the earth pressure and groundwater pressure at the tunnel face to stabilize the tunnel face. [Explanation of symbols]

[0067] 1. Excavator 2 cutter heads 3. Main unit of the device 4 chambers 7 Bulkhead 8. Cutter drive unit 9a Folding jack 9b Shield Jack 10 Screw conveyor 11 Erecta B, Bn, Bs leading bits C1 Chip section C2a Chip section (first chip section) C2b Chip section (second chip section) C2c chip section (third chip section) CB Center Bit CC Copy Cutter F1 Top surface (first surface) F2 Inclined surface (second surface) F3 Inclined surface (third surface) R Direction of movement S1, S2 Shank section ST Scraper Tooth

Claims

1. A bit body having a rectangular first surface facing the face, and a second and third surface that intersect at both ends of the first surface and face the face, and are inclined in the direction of the excavation diameter during the excavation process, On the face side of the bit body, two first tip portions are provided at the corners at both ends in the direction of movement during the drilling process of the bit body, On the cutting face side of the bit body, a second tip portion is installed adjacent to the two first tip portions via a part of the bit body, On the face side of the bit body, a columnar third tip portion is provided on the bit body between adjacent first tip portions and second tip portions, and between adjacent second tip portions, with the face-side end projecting spherically from the first surface, A leading bit characterized by having the following features.

2. The bit body has a columnar third tip portion provided on the bit body between adjacent first tip portions and second tip portions, and between adjacent second tip portions, with the end on the face side exposed from the second surface and the third surface, respectively. The preceding bit according to claim 1, characterized in that it is as follows.

3. The third tip portion, whose face-side end is exposed from the second and third surfaces, has its face-side end projecting spherically from the second and third surfaces. The preceding bit according to claim 2, characterized in that way.

4. The third tip portion is formed in a cylindrical shape. The preceding bit according to claim 3, as described above.

5. The face-side ends of the first tip portion and the second tip portion protrude from the first surface, the second surface, and the third surface of the bit body portion. The preceding bit according to claim 1, characterized in that it is as follows.

6. A leading bit according to any one of claims 1 to 5 is installed on a cutter machine. An excavator characterized by the following features.

7. The preceding bit is installed such that the inclination direction of the second surface faces the rotation center of the cutter disc. The excavator according to claim 6.

8. The aforementioned lead bit is installed at a location from the outer circumference of the cutter disc to an intermediate radial position. The excavator according to claim 6.

9. The aforementioned lead bit is mounted on the cutter disc in such a state that it protrudes toward the cutting face side beyond the tip of the scraper tooth mounted on the cutter disc. The excavator according to claim 6.

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