Lead bit and drilling machine equipped therewith

Abstract

Improve the durability of the lead bit. [Solution] The bit has a shank portion S2 having an upper surface F1 facing the drilling face and inclined surfaces F2 and F3 that intersect at both ends and are inclined in the direction of the drilling diameter facing the drilling face, tip portions C2a installed at both ends of the shank portion S2, tip portion C2b installed between the tip portions C2a via the shank portion S2, and cylindrical tip portions C2c provided on the shank portion S2 between adjacent tip portions C2a and C2b, and between adjacent tip portions C2b, with the central axis oriented perpendicular to the upper surface F1 and one end face in the axial direction exposed along surfaces F1, F2, F3, and with the diameter of tip portion C2c as A, the distance L1 between tip portion C2c and the end of the bit body in the direction perpendicular to the direction of movement during the drilling process is set to A / 4 ≤ L1, and the distance L2 between tip portion C2c and the adjacent tip portion C2a or tip portion C2b is set to A / 2 ≤ L2 ≤ A.

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 to be 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 part for breaking up the ground and making 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 in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Recently, the shield method using such a shield machine has been increasingly applied not only to sewers and subways but also to road tunnels, agricultural waterways, etc. The cross-section of construction has become larger and the distance has become longer, and a technology for efficiently excavating ground composed of various geologies is required.

[0007] Among these challenges, improving the performance of the cutter bit used in excavators, which significantly impacts excavation performance, is one of the key issues. It has been found that wear and tear on the cutter bit is particularly pronounced in gravelly ground.

[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 to protect the tooth bit (the main cutter bit that takes the excavated soil into the chamber). However, the tip installed on the cutter machine at the end of the lead bit is subjected to large forces during the excavation process, making it prone to chipping.

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

[0010] To solve the above problems, the lead bit of the present invention described in claim 1 has 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, and facing the face; two first tip portions installed at the corners at both ends of the direction of movement of the bit body during the excavation process on the face side of the bit body; a second tip portion installed adjacent to the two first tip portions on the face side of the bit body via a part of the bit body; and between the adjacent first tip portion and the second tip portion and the second The bit has a cylindrical third tip portion provided on the bit body between adjacent tip portions and the second tip portion, the third tip portion having a central axis oriented perpendicular to the first surface and one axial end surface exposed along at least one of the first surface, the second surface and the third surface, wherein when the diameter of the third tip portion is A, the distance L1 between the third tip portion and the end of the bit body in a direction perpendicular to the direction of movement during the drilling process when viewed from the front with the first surface is set to A / 4 ≤ L1, and the distance L2 between the third tip portion and the first tip portion or second tip portion adjacent to the third tip portion is set to A / 2 ≤ L2 ≤ A.

[0011] The leading bit of the present invention as described in claim 2 is characterized in that, in the invention described in claim 1, the interval L1 is set to A / 2 ≤ L1.

[0012] The lead bit of the present invention as described in claim 3 is characterized in that, in the invention described in claim 1, a plurality of third tip portions are provided between adjacent first tip portions and second tip portions, and between adjacent second tip portions, along the drilling diameter direction during the drilling process of the bit body, and the spacing L3 between the third tip portions provided in the same adjacent space is set to A ≤ L3.

[0013] The prototype bit of the present invention described in claim 4 is characterized in that, in the invention described in claim 1, the face-side ends of the first tip portion, the second tip portion, and the third tip portion protrude from the first surface, the second surface, and the third surface of the bit body portion.

[0014] The excavator of the present invention as described in claim 5 is characterized in that a leading bit described in any one of claims 1 to 4 is installed on the cutter machine.

[0015] The excavator of the present invention as described in claim 6 is characterized in that, in the invention described in claim 5, the leading bit is installed such that the inclination direction of the second surface faces the rotation center of the cutter disc.

[0016] The excavator according to claim 7 is characterized in that, in the invention according to claim 5 described above, the leading bit is installed at a location from the outer circumference of the cutter plate to an intermediate radial position.

[0017] The excavator according to claim 8 is characterized in that, in the invention according to claim 5 described above, the leading bit is mounted on the cutter plate in a state that it protrudes toward the face side more than the tip of the scraper tooth mounted on the cutter plate. [Effects of the Invention]

[0018] According to the present invention, by setting the interval L1 to A / 4 ≤ L1 and the interval L2 to A / 2 ≤ L2 ≤ A, wear of the bit body between adjacent first and second tip portions and between adjacent second tip portions is suppressed, thereby improving the durability of the lead bit. [Brief explanation of the drawing]

[0019] [Figure 1] This is a diagram showing the main components of an excavator according to one embodiment of the present invention, viewed from the side. [Figure 2]It is a front view of the cutter head that constitutes 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 bits and the scraper tools of the cutter head of FIG. 2. [Figure 5] It is a front view of the 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] It is an explanatory view showing the chip portion installed at the corner of the leading bit as a comparative example. [Figure 11] It is an explanatory view showing the chip portion installed at the corner of the leading bit of the present embodiment.

Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment as an example of the present invention will be described in detail based on the drawings. In the drawings for explaining the embodiment, the same reference numerals are generally given to the same components, and the repeated description thereof will be omitted.

[0021] First, an example of the excavator of the present embodiment will be described with reference to FIG. 1. FIG. 1 is a main part configuration diagram of the inside of the excavator of the present embodiment seen through from the side.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] Next, the configuration of the lead bit Bs described above will be explained using Figures 5 to 10. 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, Figure 9 is a cross-sectional view of the lead bit along line II in Figure 5, and Figure 10 is an explanatory diagram showing the positional relationship of the chip portion installed in the lead bit in Figure 5 in a plan view. 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.

[0043] 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. In this embodiment, the leading bit Bs 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. In this embodiment, the width of the leading bit Bs is 250 mm, the height (projection length) is 180 mm, the thickness (length perpendicular to the width) is 44 mm, the length of the upper surface F1 in the short direction is 14 mm, and the inclination angle of the inclined surfaces F2 and F3 relative to the upper surface F1 is, for example, 30 degrees.

[0044] 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.

[0045] 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.

[0046] 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. In this embodiment, the width of the tip portion C2a (length in the direction along the direction of movement R) is 40 mm, the height (length in the direction along the protruding length) is 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 46 mm (protrusion length of 1 mm in the thickness direction from the shank portion S2).

[0047] 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 part 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, fitted into each of these grooves. In this embodiment, the width (length in the direction along the movement direction R) of each tip portion C2b is 25 mm, the height (length in the direction along the protrusion length) is 70 mm (protrusion length from the shank portion S2 toward the face side is 2 mm), and the thickness (length perpendicular to the width) is 46 mm (protrusion length in the thickness direction from the shank portion S2 is 1 mm).

[0048] 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.

[0049] 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.

[0050] 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, 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 encompassing the upper surface F1 and inclined surfaces F2, F3 of the leading bit Bs. As shown in Figure 6, in this embodiment, two tip portions C2c are arranged in each shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b.

[0051] 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.

[0052] As shown in the figure, the tip portion C2c positioned across the upper surface F1 and inclined surface F2 of the leading bit Bs has its central axis oriented perpendicular to the upper surface F1, and its axial upper end surface is exposed while straddling and following the upper surface F1 and inclined surface F2. Similarly, the tip portion C2c positioned across the upper surface F1 and inclined surface F3 of the leading bit Bs has its central axis oriented perpendicular to the upper surface F1, and its axial upper end surface is exposed while straddling and following the upper surface F1 and inclined surface F3. However, the tip portion C2c may be positioned so that it is not positioned across the upper surface F1 and inclined surface F2 of the leading bit Bs with its upper end surface exposed along these surfaces F1 and F2, nor so that it is positioned across the upper surface F1 and inclined surface F3 of the leading bit Bs with its upper end surface exposed along these surfaces F1 and F3, but rather it may be positioned on the upper surface F1 of the leading bit Bs with its upper end surface exposed along the upper surface F1, positioned on the inclined surface F2 of the leading bit Bs with its upper end surface exposed along the inclined surface F2, or positioned on the inclined surface F3 of the leading bit Bs with its upper end surface exposed along the inclined surface F3.

[0053] 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 can be columnar in shape, but 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.

[0054] 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.).

[0055] In Figure 10, in this embodiment, the diameter A of each tip portion C2c is 10 mm, the height (length in the direction along the protruding length) is 60 mm (the protruding length of the shank portion S2 toward the face is 2 mm), the distance L1 between the tip portion and the end of the shank portion S2 in the direction perpendicular to the direction of movement R when the upper surface F1 of the leading bit Bs is viewed from the front is 6 mm, satisfying the relationship A / 2 ≤ L1, the distance L2 between the tip portion C2a or tip portion C2b is 6 mm, satisfying the relationship A / 2 ≤ L2 ≤ A, and the distance L3 between the tip portion C2c exposed spanning the upper surface F1 and the inclined surface F2 and the tip portion C2c exposed spanning the upper surface F1 and the inclined surface F3 is 12 mm, satisfying the relationship A ≤ L3.

[0056] The reason for setting the interval L1 to A / 2 ≤ L1 here is that if the interval L1 is too narrow (i.e., if the position of the tip portion C2c becomes too close to the end (the end in the direction perpendicular to the movement direction R of the shank portion S2)), there will be insufficient margin against wear of the shank portion S2, causing the tip portion C2c to be exposed from the end of the shank portion S2, and as a result the wear suppression effect of the leading bit Bs will decrease. Note that the degree of wear of the shank portion S2 differs depending on the ground being excavated, so the interval L1 of the leading bit Bs may be set to A / 4 ≤ L1, but in order to ensure a sufficient margin against wear, it is preferable to set it to A / 2 ≤ L1 as in this embodiment.

[0057] Furthermore, the reason for setting the interval L2 to A / 2 ≤ L2 ≤ A is that if the interval L2 becomes smaller than A / 2, the function of distributing the stress applied to the tip portion C2c by the shank portion S2 will weaken. On the other hand, if the interval L2 becomes larger than A, the wear of the shank portion S2 will increase, and there is a risk that the tip portion C2c will be exposed.

[0058] The reason the interval L3 was set to A ≤ L3 is that, since the interval L3 is perpendicular to the direction of movement R, even if the interval L3 is made smaller than A (i.e., even if the distance between tip portions C2c and tip portions C2c is made too close to be smaller than the diameter of tip portion C2c), the effect of suppressing wear of tip portion C2c will not increase. Therefore, as shown in Figure 11, depending on the relationship between the thickness of the preceding bit Bs and the diameter of tip portion C2c, there may be one tip portion C2c or three or more tip portions C2a, C2b and the shank portion S2 between adjacent tip portions C2b, C2b.

[0059] The specific dimensions of each part mentioned above are merely examples; any dimensions can be set within the range where interval L1 satisfies the relationship A / 2 ≤ L1, interval L2 satisfies the relationship A / 2 ≤ L2 ≤ A, and interval L3 satisfies the relationship A ≤ L3.

[0060] 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 at the aforementioned intervals (intervals L1, L2, L3) 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. By preventing wear of the shank portion S2, breakage or cracking of the tip portion C2a can also be suppressed or prevented. Therefore, the overall durability (lifespan) of the lead bit Bs can be improved in the shield drilling process, which can suppress or prevent a decrease in the cutting ability of the lead bit Bs and suppress 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.

[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, in the above embodiment, two tip portions C2c are installed in the shank portion S2 between adjacent tip portions C2a, C2b and C2b, C2b, but there may be one (see Figure 11), or three or more. It goes without saying that when only one tip portion C2c is installed, as shown in Figure 11, the aforementioned gap L3 between tip portions C2c does not exist.

[0064] Furthermore, 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 combining a ribbon type and a shaft type may be used.

[0065] 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.

[0066] 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]

[0067] 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]

[0068] 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 V1 Mounting surface (first mounting surface) V2 Mounting surface (second mounting surface)

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 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 cylindrical 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 its central axis oriented perpendicular to the first surface and one end face in the axial direction exposed along at least one of the first surface, second surface, and third surface, It has, When the diameter of the third tip portion is A, The distance L1 between the third tip portion and the end portion of the bit body in a direction perpendicular to the direction of movement during the drilling process, when the first surface is viewed from the front, is set to A / 4 ≤ L1, and the distance L2 between the third tip portion and the first tip portion or the second tip portion adjacent to the third tip portion is set to A / 2 ≤ L2 ≤ A. A leading bit characterized by the following features.

2. The interval L1 is set to A / 2 ≤ L1. The preceding bit according to claim 1, characterized in that it is as follows.

3. Multiple third tip portions are provided between adjacent first tip portions and second tip portions, and between adjacent second tip portions, along the drilling diameter direction of the bit body during the drilling process. The distance L3 between the third chip portions provided in the same adjacent space is set to A ≤ L3. The preceding bit according to claim 1, characterized in that it is as follows.

4. The face-side ends of the first tip portion, the second tip portion, and the third 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.

5. A leading bit according to any one of claims 1 to 4 is installed on a cutter machine. An excavator characterized by the following features.

6. 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 5, characterized in that it is as described above.

7. 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 5, characterized in that it is as described above.

8. 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 5, characterized in that it is as described above.

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