Double drill bit

Abstract

A double drill bit is composed of a main drill bit body and an auxiliary drill bit body, and the width of the two cutter points and the angle of the digging position can be set by adjusting the cutter point position of the main drill bit body and the cutter point position of the auxiliary drill bit body. The double drill bit (1) comprises a main drill bit (2) and an auxiliary drill bit (3), the main drill bit and the auxiliary drill bit are provided with mountain-shaped superhard drill tips (7, 9, 14, 15) protruding in the digging direction at least at the upper and lower parts of the front ends of the base parts (4, 13), and the mountain-shaped top of the superhard drill tip of the auxiliary drill bit is larger than the mountain-shaped top of the superhard drill tip of the main drill bit. The device is located behind the digging direction. The top of the mountain-shaped main drill bit 2 is close to the hole wall direction, close to the pile core direction or located in the center, and the hole wall direction is perpendicular to the excavation direction. The top of the mountain-shaped auxiliary drill bit 3 is close to the hole wall direction or the pile core direction or located in the center, and the hole wall direction is perpendicular to the excavation direction.

Description

Technical Field

[0001] The invention relates to an excavating tool installed at the front end of a casing, in particular to a double drill bit integrating a main drill bit and an auxiliary drill bit. Background Art

[0002] At present, as a pile construction method for pouring concrete underground and forming a pile, a so-called full casing construction method is generally known, in which a casing is pressed into the ground, and while protecting the hole wall, excavation and silt are discharged with a grab bucket, and concrete is poured into the hole formed by excavation. In this full casing construction method, a cutting blade drill bit for an inner blade, a middle blade, and an outer blade is mounted on the front end of the casing through a drill bit mounting holder, and excavation of the cutting blade drill bit is performed by rotating the casing.

[0003] Here, as such a cutting blade drill bit, there is a cutting blade drill bit for excavation installed at the front end portion of the casing pipe along the circumferential direction of the casing pipe, and the cutting blade drill bit includes a head portion of a blade body having a superhard drill tip fixed to the front end portion, and a leg portion provided with a fixing unit for a retainer fixed to the casing pipe (for example, refer to Patent Document 1).

[0004] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2016-223196 Summary of the invention

[0005] Problems to be solved by the invention However, Patent Document 1 only discloses a cutting blade drill bit for excavation, and does not disclose that the main drill bit and the auxiliary drill bit are integrated, and the width of the two blades and the angle of the excavation position are varied by adjusting the blade position of the main drill bit and the blade position of the auxiliary drill bit.

[0006] The present invention is completed in view of the above problems, and its purpose is to provide a twin bit, in which the main drill bit and the auxiliary drill bit are integrated, and the widths of the two blades and the angles of the excavation positions are varied by adjusting the blade positions of the main drill bit and the auxiliary drill bit.

[0007] Technical solutions to solve problems In order to solve the above-mentioned problem, a double drill bit according to one aspect of the present invention includes a main drill bit and an auxiliary drill bit, wherein the main drill bit and the auxiliary drill bit are both provided with a mountain-shaped superhard drill tip protruding in the excavation direction at least at the upper and lower parts of the front end of the base, and the mountain-shaped top of the superhard drill tip of the auxiliary drill bit is located behind the mountain-shaped top of the superhard drill tip of the main drill bit in the excavation direction.

[0008] Effects of the Invention According to the present invention, a double drill bit can be provided, in which the main drill bit and the auxiliary drill bit are integrated, and the width of the two blades and the angle of the excavation position can be varied by adjusting the blade position of the main drill bit and the blade position of the auxiliary drill bit. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 (a) to Figure 1 (d) is a layout diagram of the double drill head according to the first embodiment of the present invention.

[0010] Figure 2 (a) to Figure 2 (d) is a layout diagram of a double drill according to a second embodiment of the present invention.

[0011] Figure 3 (a) to Figure 3 (d) is a layout diagram of a double drill according to a third embodiment of the present invention.

[0012] Figure 4 (a) to Figure 4 (d) is a layout diagram of a double drill according to a fourth embodiment of the present invention.

[0013] Figure 5 (a) to Figure 5 (d) is a layout diagram of a double drill according to a fifth embodiment of the present invention.

[0014] Figure 6 (a) to Figure 6 (d) is a layout diagram of a double drill according to a sixth embodiment of the present invention.

[0015] Figure 7 (a) to Figure 7 (d) is a layout diagram of a double drill according to a seventh embodiment of the present invention.

[0016] Figure 8 (a) to Figure 8 (d) is a layout diagram of a double drill according to an eighth embodiment of the present invention.

[0017] Fig. 9 (a) and Fig. 9 (b) is a diagram showing a state where the double drill bit is mounted on the casing.

[0018] Fig.10 (a) and Fig.10 (b) is a diagram showing a state where the double drill bit is mounted on the casing.

[0019] Fig.11 (a) and Fig.11 (b) is a diagram showing a state where the double drill bit is mounted on the casing.

[0020] Fig.12 (a) and Fig.12 (b) is a diagram showing a state where the double drill bit is mounted on the casing.

[0021] Fig.13 (a) and Fig.13 (b) is a diagram showing a state where the double drill bit is mounted on the casing.

[0022] Fig.14 (a) and Fig.14 (b) is a diagram showing a state where the double drill bit is mounted on the casing.

[0023] Fig.15 (a) to Fig.15 (d) is a layout diagram of a modified example of the double drill according to the first embodiment of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described below in conjunction with the accompanying drawings.

[0025] The double drill bit according to the embodiment of the present invention has the following features.

[0026] (1) A main drill bit and an auxiliary drill bit are arranged in parallel in a direction perpendicular to the excavation direction, and the blade of the auxiliary drill bit is located behind the blade of the main drill bit in the excavation direction, forming a so-called step structure. Therefore, the load applied to the inner plate (or outer plate) of the casing can be reduced and the excavation efficiency can be improved, while preventing the retention of excavated soil (or cuttings) generated when excavating with a single blade, thereby improving the excavation efficiency.

[0027] (2) The base material shape of the main drill bit blade can be selected from a straight shape or an inclined shape that forms an angle with the base material. In addition, by adjusting the blade position of the main drill bit and the blade position of the auxiliary drill bit, the width of the two blades and the angle of the excavation position can be set. Therefore, not only can the excavation position of the blade be expanded, the load applied to the inner plate (or outer plate) of the casing be further reduced, and the retention of excavated soil (or cuttings) be further reduced, but the upward flow of excavated soil (or cuttings) can also be controlled.

[0028] (3) An auxiliary super-hard drill tip is provided on the base material of the blade. Therefore, the wear resistance can be improved. The hardness of the super-hard drill tip can be freely selected according to the excavation object.

[0029] (4) The double drill bit of this embodiment is used for bidirectional rotation. Therefore, excavation in both the forward excavation and the reverse excavation directions can be performed.

[0030] <First Embodiment> Figure 1 (a) to Figure 1 (d) shows and describes the configuration of the double drill head of the first embodiment of the present invention. More specifically, Figure 1(a) shows a top view of the double drill bit, Figure 1 (b) is a stereoscopic view showing the double drill head, Figure 1 (c) shows a side view of the double drill bit, Figure 1 (d) shows the front view of the double drill. In the double drill, the main drill is a straight outer blade, and the auxiliary drill is a middle blade attached to the inside. By using the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object easier to dig out. It should be noted that in order to clearly show the structure of each part, only Figure 1 The hard thickened portion is shown in (a).

[0031] As shown in these figures, the double drill bit 1 is provided so that the front end cutting edges of the main drill bit 2 and the auxiliary drill bit 3 are stepped backward in the excavation direction.

[0032] The main drill bit 2 is composed of a base 4 and two legs 5 and 6 extending from the base 4. Hereinafter, the base 4 side is also referred to as the front end of the dual drill bit 1, and the legs 5 and 6 side is also referred to as the installation side facing the casing or the rear end of the dual drill bit 1. The direction facing the front end is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the dual drill bit 1). The direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is called the width direction of the dual drill bit 1.

[0033] The pile core direction refers to the "pile center" in all pile projects such as precast piles, cast-in-place piles, and steel pipe piles used in foundation construction, and means the center of the casing and excavation wings used in various pile extraction works, obstacle removal works, etc. On the other hand, the hole wall direction refers to the outer peripheral side of the pile in all pile projects such as precast piles, cast-in-place piles, and steel pipe piles used in foundation construction, and the outer peripheral side of the casing and excavation wings used in various pile extraction works and obstacle removal works, that is, the hole wall of the underground hole constructed by digging the ground or obstacles.

[0034] The base 4 has a so-called mountain shape with the tops of the upper and lower parts protruding toward the excavation direction, that is, the front end side of the double drill bit 1. In addition, superhard drill tips 7 and 8 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 4.

[0035] More specifically, the superhard drill tip 7 includes, at the upper portion of the front end of the base 4, an inclined portion 7a that rises at a predetermined angle from the first plane portion 9 of the base 4 toward the top of the excavation direction; and an inclined portion 7b that rises at a predetermined angle from the second plane portion 10 of the base 4 toward the top of the excavation direction. Since the length of the inclined portion 7a is smaller than the length of the inclined portion 7b, the top is located close to the first plane portion 9. On the other hand, the superhard drill tip 8 includes, at the lower portion of the front end of the base 4, an inclined portion 8a that rises at a predetermined angle from the first plane portion 9 of the base 4 toward the top of the excavation direction, and an inclined portion 8b that rises at a predetermined angle from the second plane portion 10 of the base 4 toward the top of the excavation direction. Since the length of the inclined portion 8a is smaller than the length of the inclined portion 8b, the top is located close to the first plane portion 9.

[0036] like Figure 1 As shown in (c), the top where the inclined portions 7a and 7b of the superhard drill tip 7 are connected and the top where the inclined portions 8a and 8b of the superhard drill tip 8 are connected form edges for excavation at the top and bottom of the base 4, respectively. In addition, at the front end of the base 4, a recess 11 is formed between the superhard drill tips 7 and 8, which not only further reduces the retention of excavated soil (or chips), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or chips).

[0037] The legs 5 and 6 extend in parallel from the base 4 to the rear end at a predetermined interval, so as to be in a U-shape when viewed from a plane. The legs 5 and 6 are provided with holes 12 for mounting the double drill 1 on the casing by bolts or the like.

[0038] On the other hand, the auxiliary drill bit 3 includes a base 13. The rear end portion of the base 13 is an inclined portion 13a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 1, and a superhard drill tip 13b is arranged on the inclined surface of the inclined portion 13a. The inclined portion 13a is provided with a hole portion that communicates with the hole portion 12 of the leg portions 5 and 6.

[0039] The base 13 has a so-called mountain shape with the tops of the upper and lower parts protruding toward the excavation direction, that is, the front end side of the double drill head 1. Superhard drill tips 14 and 15 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 13.

[0040] More specifically, the superhard drill tip 14 includes, at the upper portion of the front end of the base 13, an inclined portion 14a that rises at a predetermined angle from the third plane portion 17 of the base 13 toward the excavation direction and the top, and an inclined portion 14b that rises at a predetermined angle from the second plane portion 10 toward the excavation direction and the top. Since the length of the inclined portion 14a is the same as the length of the inclined portion 14b, the top is located in the middle of the excavation direction of the auxiliary drill bit 3 or the hole wall direction. In other words, the top is located in the center of the thickness direction of the auxiliary drill bit 3. On the other hand, the superhard drill tip 15 includes, at the lower portion of the front end of the base 13, an inclined portion 15a that rises at a predetermined angle from the third plane portion 17 of the base 13 toward the excavation direction and the top, and an inclined portion 15b that rises at a predetermined angle from the second plane portion 10 of the base 13 toward the excavation direction and the top. Since the length of the inclined portion 14a is the same as the length of the inclined portion 14b, the top is located in the middle of the excavation direction of the auxiliary drill bit 3 or the hole wall direction. In other words, the top portion is located at the center of the auxiliary drill bit 3 in the thickness direction.

[0041] like Figure 1 As shown in (c), the top where the inclined parts 14a and 14b of the super-hard drill tip 14 are connected and the top where the inclined parts 15a and 15b of the super-hard drill tip 15 are connected form edges for excavation at the top and bottom of the base 14, respectively. In addition, at the front end of the base 13, a recess 16 is formed between the super-hard drill tips 14 and 15, which not only further reduces the retention of excavated soil (or chips), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or chips).

[0042] Among them, regarding the materials of each part, the base material of the base 4, the legs 5, 6 can be SCM440 (chrome steel) or the like. Moreover, the superhard drill tips 7, 8, 14, 15 can be JIS classification symbols E3 (material name MG30), E4 (material name MG40), E5 (material name MG50), E6 (material name MG60), etc., and CIS standard G4 (CIS material type symbol VC-40), G5 (CIS material type symbol VC-50), etc. However, it is not limited to the above materials. In addition, the base 4, 13 is provided with a hard thickening portion 18.

[0043] <Second Embodiment> Figure 2 (a) to Figure 2 (d) shows and describes the configuration of the double drill head of the second embodiment of the present invention. More specifically, Figure 2 (a) shows a top view of the double drill bit, Figure 2 (b) is a stereoscopic view showing the double drill head, Figure 2 (c) shows a side view of the double drill bit, Figure 2(d) shows the front view of the double drill. In the double drill, the main drill is a straight outer blade, and the auxiliary drill is a middle blade attached to the outside. By using the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object easier to dig out. It should be noted that in order to clearly show the structure of each part, only Figure 2 (a) Figure 2 The hard thickened portion is shown in (c).

[0044] As shown in these figures, the double drill bit 21 is provided so that the front end cutting edges of the main drill bit 22 and the auxiliary drill bit 23 are stepped backward in the excavation direction.

[0045] The main drill bit 22 is composed of a base 24 and two legs 25, 26 extending from the base 24. Hereinafter, the base 24 side is also referred to as the front end of the double drill bit 21, and the legs 25, 26 side is also referred to as the installation side toward the casing or the rear end of the double drill bit 21. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the double drill bit 21). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the double drill bit 21. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0046] The base 24 has a so-called mountain shape with the tops of the upper and lower parts protruding toward the excavation direction, that is, the front end side of the double drill bit 21. Superhard drill tips 27 and 28 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 24.

[0047] More specifically, the superhard drill tip 27 includes, at the upper portion of the front end of the base 24, an inclined portion 27a that rises at a predetermined angle from the first plane portion 29 of the base 24 toward the excavation direction and the top, and an inclined portion 27b that rises at a predetermined angle from the second plane portion 30 of the base 24 toward the excavation direction and the top. Since the length of the inclined portion 27a is smaller than the length of the inclined portion 27b, the top is located near the first plane portion 29. On the other hand, the superhard drill tip 28 includes, at the lower portion of the front end of the base 24, an inclined portion 28a that rises at a predetermined angle from the first plane portion 29 of the base 24 toward the excavation direction and the top, and an inclined portion 28b that rises at a predetermined angle from the second plane portion 30 of the base 24 toward the excavation direction and the top. Since the length of the inclined portion 28a is smaller than the length of the inclined portion 28b, the top is located near the first plane portion 29.

[0048] like Figure 2As shown in (c), the top where the inclined portions 27a and 27b of the super-hard drill tip 27 are connected and the top where the inclined portions 28a and 28b of the super-hard drill tip 28 are connected form edges for excavation at the top and bottom of the base 24, respectively. In addition, a recess 31 is formed between the super-hard drill tips 27 and 28 at the front end of the base 24, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0049] The legs 25 and 26 extend in parallel from the base 24 to the rear end at a predetermined interval, so as to be in a U-shape when viewed from a plane. The legs 25 and 26 are provided with holes 32 for mounting the double drill bit 21 on the sleeve by bolts or the like.

[0050] On the other hand, the auxiliary drill bit 23 includes a base 33. The rear end portion of the base 33 is an inclined portion 33a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 21, and a superhard drill tip 33b is arranged on the inclined surface of the inclined portion 33a. The inclined portion 33a is provided with a hole portion that communicates with the hole portion 32 of the leg portions 25 and 26.

[0051] The base 33 has a so-called mountain shape with the tops of the upper and lower parts protruding toward the excavation direction, that is, the front end side of the double drill bit 21. Superhard drill tips 34 and 35 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 33.

[0052] More specifically, the superhard drill tip 34 includes, at the upper portion of the front end of the base 33, an inclined portion 34a that rises at a predetermined angle from the third plane portion 37 of the base 33 toward the excavation direction and the top, and an inclined portion 34b that rises at a predetermined angle from the first plane portion 29 toward the excavation direction and the top. Since the length of the inclined portion 34a is the same as the length of the inclined portion 34b, the top is located in the middle of the excavation direction of the auxiliary drill bit 23 or the hole wall direction. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 23. On the other hand, the superhard drill tip 35 includes, at the lower portion of the front end of the base 33, an inclined portion 35a that rises at a predetermined angle from the third plane portion 37 of the base 33 toward the excavation direction and the top, and an inclined portion 35b that rises at a predetermined angle from the first plane portion 29 of the base 33 toward the excavation direction and the top. Since the length of the inclined portion 34a is the same as the length of the inclined portion 34b, the top is located in the center of the excavation direction of the auxiliary drill bit 23 or the hole wall direction. In other words, the top is located in the middle of the auxiliary drill bit 23 in the thickness direction.

[0053] like Figure 2As shown in FIG. 5( c ), the top where the inclined portions 34a and 34b of the super-hard drill tip 34 are connected and the top where the inclined portions 35a and 35b of the super-hard drill tip 35 are connected form edges for excavation at the top and bottom of the base 33, respectively. In addition, a recess 36 is formed between the super-hard drill tips 34 and 35 at the front end of the base 33, which not only further reduces the retention of excavated soil (or cuttings), but also helps improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0054] The material of each part is the same as that described in the first embodiment. The base parts 24 and 33 are provided with a hard thickened part 38 .

[0055] <Third Embodiment> Figure 3 (a) to Figure 3 (d) shows and describes the configuration of the double drill bit of the third embodiment of the present invention. More specifically, Figure 3 (a) shows a top view of the double drill bit, Figure 3 (b) is a stereoscopic view showing the double drill head, Figure 3 (c) shows a side view of the double drill bit, Figure 3 (d) shows the front view of the double drill. In the double drill, the main drill is a straight inner blade, and the auxiliary drill is a middle blade attached to the inner side. By using the auxiliary drill as the middle blade, the digging can be performed at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object more smoothly dug out. It should be noted that in order to clearly show the structure of each part, only Figure 3 (a) Figure 3 The hard thickened portion is shown in (c).

[0056] As shown in these figures, the double drill bit 41 is provided so that the front end cutting edges of the main drill bit 42 and the auxiliary drill bit 43 are stepped backward in the excavation direction.

[0057] The main drill bit 42 is composed of a base 44 and two legs 45, 46 extending from the base 44. Hereinafter, the base 44 side is also referred to as the front end of the double drill bit 41, and the legs 45, 46 side is also referred to as the installation side toward the casing or the rear end of the double drill bit 41. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the double drill bit 41). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the double drill bit 41. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0058] The base 44 has a so-called mountain shape in which the tops of the upper and lower parts protrude in the digging direction, that is, the front end side of the double drill bit 41. Superhard drill tips 47 and 48 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 44.

[0059] More specifically, the superhard drill tip 47 includes, at the upper portion of the front end of the base 44, an inclined portion 47a that rises at a predetermined angle from the first plane portion 49 of the base 44 toward the excavation direction and the top, and an inclined portion 47b that rises at a predetermined angle from the second plane portion 50 of the base 44 toward the excavation direction and the top. Since the length of the inclined portion 47a is longer than the length of the inclined portion 7b, the top is located close to the second plane portion 50. On the other hand, the superhard drill tip 48 includes, at the lower portion of the front end of the base 44, an inclined portion 48a that rises at a predetermined angle from the first plane portion 49 of the base 44 toward the excavation direction and the top, and an inclined portion 48b that rises at a predetermined angle from the second plane portion 50 of the base 44 toward the excavation direction and the top. Since the length of the inclined portion 48a is longer than the length of the inclined portion 48b, the top is located close to the second plane portion 50.

[0060] like Figure 3 As shown in FIG. 5( c ), the top where the inclined portions 47a and 47b of the super-hard drill tip 47 are connected and the top where the inclined portions 48a and 48b of the super-hard drill tip 48 are connected form edges for excavation at the top and bottom of the base 44, respectively. In addition, a recess 51 is formed between the super-hard drill tips 47 and 48 at the front end of the base 44, which not only further reduces the retention of excavated soil (or cuttings), but also helps improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0061] The legs 45 and 46 extend in parallel from the base 44 to the rear end at a predetermined interval, so as to be in a U-shape when viewed from a plane. The legs 45 and 46 are provided with holes 52 for mounting the double drill bit 41 on the sleeve by bolts or the like.

[0062] On the other hand, the auxiliary drill bit 43 includes a base 53. The rear end portion of the base 53 is an inclined portion 53a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 41, and a superhard drill tip 53b is arranged on the inclined surface of the inclined portion 53a. The inclined portion 53a is provided with a hole portion that communicates with the hole portion 52 of the leg portions 45 and 46.

[0063] The base 53 has a so-called mountain shape with the tops of the upper and lower parts protruding in the excavation direction, that is, the front end side of the double drill bit 41. Superhard drill tips 54 and 55 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 53.

[0064] More specifically, the superhard drill tip 54 includes, at the upper portion of the front end of the base 53, an inclined portion 54a that rises at a predetermined angle from the third plane portion 57 of the base 53 toward the excavation direction and the top, and an inclined portion 54b that rises at a predetermined angle from the second plane portion 50 toward the excavation direction and the top. Since the length of the inclined portion 54a is the same as the length of the inclined portion 54b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 431. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 431. On the other hand, the superhard drill tip 55 includes, at the lower portion of the front end of the base 53, an inclined portion 55a that rises at a predetermined angle from the third plane portion 57 of the base 53 toward the excavation direction and the top, and an inclined portion 55b that rises at a predetermined angle from the second plane portion 50 of the base 53 toward the excavation direction and the top. Since the length of the inclined portion 54a is the same as the length of the inclined portion 54b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 43. In other words, the top portion is located in the middle of the auxiliary drill bit 43 in the thickness direction.

[0065] like Figure 3 As shown in (c), the top where the inclined parts 54a and 54b of the super-hard drill tip 54 are connected and the top where the inclined parts 55a and 55b of the super-hard drill tip 55 are connected form edges for excavation at the top and bottom of the base 53. In addition, at the front end of the base 53, a recess 56 is formed between the super-hard drill tips 54 and 55, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0066] The material of each part is the same as that described in the first embodiment. The base parts 44 and 53 are provided with a hard thickened part 58 .

[0067] <Fourth Embodiment> Figure 4 (a) to Figure 4 (d) shows and describes the configuration of the dual drill bit of the fourth embodiment of the present invention. More specifically, Figure 4 (a) shows a top view of the double drill bit, Figure 4 (b) is a stereoscopic view showing the double drill head, Figure 4 (c) shows a side view of the double drill bit, Figure 4 (d) shows the front view of the double drill. In the double drill, the main drill is a straight inner blade, and the auxiliary drill is a middle blade attached to the outside. By using the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object easier to dig out. It should be noted that in order to clearly show the structure of each part, only Figure 4 The hard thickened portion is shown in (a).

[0068] As shown in these figures, the double drill bit 61 is provided so that the front end cutting edges of the main drill bit 62 and the auxiliary drill bit 63 are stepped backward in the excavation direction.

[0069] The main drill bit 62 is composed of a base 64 and two legs 65, 66 extending from the base 64. Hereinafter, the base 64 side is also referred to as the front end of the double drill bit 61, and the legs 65, 66 side is also referred to as the installation side toward the casing or the rear end of the double drill bit 61. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the double drill bit 61). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the double drill bit 61. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0070] The base 64 has a so-called mountain shape with the tops of the upper and lower parts protruding in the excavation direction, that is, the front end side of the double drill bit 61. Superhard drill tips 67 and 68 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 64.

[0071] More specifically, the superhard drill tip 67 includes, at the upper portion of the front end of the base 64, an inclined portion 67a that rises at a predetermined angle from the first plane portion 69 of the base 64 toward the excavation direction and the top, and an inclined portion 67b that rises at a predetermined angle from the second plane portion 70 of the base 64 toward the excavation direction and the top. Since the length of the inclined portion 67a is longer than the length of the inclined portion 67b, the top is located near the second plane portion 70. On the other hand, the superhard drill tip 68 includes, at the lower portion of the front end of the base 64, an inclined portion 68a that rises at a predetermined angle from the first plane portion 69 of the base 64 toward the excavation direction and the top, and an inclined portion 68b that rises at a predetermined angle from the second plane portion 70 of the base 64 toward the excavation direction and the top. Since the length of the inclined portion 68a is longer than the length of the inclined portion 68b, the top is located near the second plane portion 70.

[0072] like Figure 4 As shown in FIG. 5( c ), the top where the inclined portions 67a and 67b of the super-hard drill tip 67 are connected and the top where the inclined portions 68a and 68b of the super-hard drill tip 68 are connected form edges for excavation at the top and bottom of the base 64, respectively. In addition, a recess 71 is formed between the super-hard drill tips 67 and 68 at the front end of the base 64, which not only further reduces the retention of excavated soil (or cuttings), but also helps improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0073] The legs 65 and 66 extend in parallel from the base 64 to the rear end at a predetermined interval, so as to be in a U-shape when viewed from a plane. The legs 65 and 66 are provided with holes 72 for mounting the double drill bit 61 on the sleeve by bolts or the like.

[0074] On the other hand, the auxiliary drill bit 63 includes a base 73. The rear end portion of the base 73 is an inclined portion 73a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 61, and a superhard drill tip 73b is arranged on the inclined surface of the inclined portion 73a. The inclined portion 73a is provided with a hole portion that communicates with the hole portion 72 of the leg portions 65 and 66.

[0075] The base 73 has a so-called mountain shape with the tops of the upper and lower parts protruding toward the excavation direction, that is, the front end side of the double drill bit 61. Superhard drill tips 74 and 75 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 73.

[0076] More specifically, the superhard drill tip 74 includes, at the upper portion of the front end of the base 73, an inclined portion 74a that rises at a predetermined angle from the third plane portion 77 of the base 73 toward the excavation direction and the top, and an inclined portion 74b that rises at a predetermined angle from the first plane portion 69 toward the excavation direction and the top. Since the length of the inclined portion 74a is the same as the length of the inclined portion 74b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 63. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 63. On the other hand, the superhard drill tip 75 includes, at the lower portion of the front end of the base 73, an inclined portion 75a that rises at a predetermined angle from the third plane portion 77 of the base 73 toward the excavation direction and the top, and an inclined portion 75b that rises at a predetermined angle from the first plane portion 69 of the base 73 toward the excavation direction and the top. Since the length of the inclined portion 74a is the same as the length of the inclined portion 74b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 63. In other words, the top portion is located in the middle of the auxiliary drill bit 63 in the thickness direction.

[0077] like Figure 4 As shown in FIG. 5( c ), the top where the inclined portions 74a and 74b of the super-hard drill tip 74 are connected and the top where the inclined portions 75a and 75b of the super-hard drill tip 75 are connected form edges for excavation at the top and bottom of the base 73, respectively. In addition, a recess 76 is formed between the super-hard drill tips 74 and 75 at the front end of the base 73, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0078] The material of each part is the same as that described in the first embodiment. The base parts 64 and 73 are provided with a hard thickened part 78 .

[0079] <Fifth Embodiment> Figure 5 (a) to Figure 5 (d) shows and describes the configuration of the double drill head of the fifth embodiment of the present invention. More specifically, Figure 5 (a) shows a top view of the double drill bit, Figure 5 (b) is a stereoscopic view showing the double drill head, Figure 5 (c) shows a side view of the double drill bit, Figure 5 (d) shows the front view of the double drill. In the double drill, the main drill is a straight middle blade, and the auxiliary drill is a middle blade attached to the inside. By using the main drill and the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object more smoothly dug out. It should be noted that in order to clearly show the structure of each part, only Figure 5 (a) Figure 5 The hard thickened portion is shown in (c).

[0080] As shown in these figures, the double drill bit 81 is provided so that the front end cutting edges of the main drill bit 82 and the auxiliary drill bit 83 are stepped backward in the excavation direction.

[0081] The main drill bit 82 is composed of a base 84 and two legs 85, 86 extending from the base 84. Hereinafter, the base 84 side is also referred to as the front end of the double drill bit 81, and the legs 85, 86 side is also referred to as the installation side toward the casing or the rear end of the double drill bit 81. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the double drill bit 81). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the double drill bit 81. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0082] The base 84 has a so-called mountain shape in which the tops of the upper and lower parts protrude in the digging direction, that is, the front end side of the double drill bit 81. Superhard drill tips 87 and 88 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 84.

[0083] More specifically, the superhard drill tip 87 includes, at the upper portion of the front end of the base 84, an inclined portion 87a that rises at a predetermined angle from the first plane portion 89 of the base 84 toward the excavation direction and the top thereof; and an inclined portion 87b that rises at a predetermined angle from the second plane portion 90 of the base 84 toward the excavation direction and the top thereof. The length of the inclined portion 87a is the same as the length of the inclined portion 87b, and the top thereof is located at the center of the first plane portion 89 and the second plane portion 90. In other words, the top thereof is located in the middle of the thickness direction of the double drill bit 81. On the other hand, the superhard drill tip 88 includes, at the lower portion of the front end of the base 84, an inclined portion 88a that rises at a predetermined angle from the first plane portion 89 of the base 84 toward the excavation direction and the top thereof, and an inclined portion 88b that rises at a predetermined angle from the second plane portion 90 of the base 84 toward the excavation direction and the top thereof. The length of the inclined portion 88a is the same as the length of the inclined portion 88b, and the top thereof is located at the center of the first plane portion 89 and the second plane portion 90. In other words, the top thereof is located in the middle of the thickness direction of the double drill bit 81.

[0084] like Figure 5As shown in (c), the top where the inclined portions 87a and 87b of the super-hard drill tip 87 are connected and the top where the inclined portions 88a and 88b of the super-hard drill tip 88 are connected form edges for excavation at the top and bottom of the base 84. In addition, a recess 91 is formed between the super-hard drill tips 87 and 88 at the front end of the base 84, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0085] The legs 85 and 86 extend in parallel from the base 84 to the rear end at a predetermined interval, so as to be in a U-shape when viewed from a plane. The legs 85 and 86 are provided with holes 92 for mounting the double drill bit 81 on the sleeve by bolts or the like.

[0086] On the other hand, the auxiliary drill bit 83 includes a base 93. The rear end portion of the base 93 is an inclined portion 93a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 81, and a superhard drill tip 93b is arranged on the inclined surface of the inclined portion 93a. The inclined portion 93a is provided with a hole portion that communicates with the hole portion 92 of the leg portions 85 and 86.

[0087] The base 93 has a so-called mountain shape in which the tops of the upper and lower parts protrude in the excavation direction, that is, the front end side of the double drill bit 81. Superhard drill tips 94 and 95 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 93.

[0088] More specifically, the superhard drill tip 94 includes, at the upper portion of the front end of the base 93, an inclined portion 94a that rises at a predetermined angle from the third plane portion 97 of the base 93 toward the excavation direction and the top, and an inclined portion 94b that rises at a predetermined angle from the second plane portion 90 toward the excavation direction and the top. Since the length of the inclined portion 94a is the same as the length of the inclined portion 94b, the top is located in the center of the excavation direction of the auxiliary drill bit 83 or the hole wall direction. In other words, the top is located in the middle of the thickness direction of the double drill bit 81. On the other hand, the superhard drill tip 95 includes, at the lower portion of the front end of the base 93, an inclined portion 95a that rises at a predetermined angle from the third plane portion 97 of the base 93 toward the excavation direction and the top, and an inclined portion 95b that rises at a predetermined angle from the second plane portion 90 of the base 93 toward the excavation direction and the top. Since the length of the inclined portion 95a is the same as the length of the inclined portion 95b, the top is located in the center of the excavation direction of the auxiliary drill bit 83 or the hole wall direction. In other words, the top is located in the middle of the double drill bit 81 in the thickness direction.

[0089] like Figure 5As shown in (c), the top where the inclined parts 94a and 94b of the super-hard drill tip 94 are connected and the top where the inclined parts 95a and 95b of the super-hard drill tip 95 are connected form edges for excavation at the top and bottom of the base 93. In addition, at the front end of the base 93, a recess 96 is formed between the super-hard drill tips 94 and 95, which not only further reduces the retention of excavated soil (or chips), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or chips).

[0090] The material of each part is the same as that described in the first embodiment. The base parts 84 and 93 are provided with a hard thickened part 98 .

[0091] <Sixth Implementation Method> Figure 6 (a) to Figure 6 (d) shows and describes the configuration of the double drill bit of the sixth embodiment of the present invention. More specifically, Figure 6 (a) shows a top view of the double drill bit, Figure 6 (b) is a stereoscopic view showing the double drill head, Figure 6 (c) shows a side view of the double drill bit, Figure 6 (d) shows the front view of the double drill. In the double drill, the main drill is a straight middle blade, and the auxiliary drill is a middle blade attached to the outside. By using the main drill and the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object more smoothly dug out. It should be noted that in order to clearly show the structure of each part, only Figure 6 (a) Figure 6 The hard thickened portion is shown in (c).

[0092] As shown in these figures, the double drill bit 101 is provided so that the front end cutting edges of the main drill bit 102 and the auxiliary drill bit 103 are stepped backward in the excavation direction.

[0093] The main drill bit 102 is composed of a base 104 and two legs 105 and 106 extending from the base 104. Hereinafter, the base 104 side is also referred to as the front end of the dual drill bit 101, and the legs 105 and 106 side is also referred to as the installation side toward the casing or the rear end of the dual drill bit 101. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the dual drill bit 101). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the dual drill bit 101. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0094] The base 104 has a so-called mountain shape with the tops of the upper and lower parts protruding toward the excavation direction, that is, the front end side of the double drill bit 101. Superhard drill tips 107 and 108 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 104.

[0095] More specifically, the superhard drill tip 107 includes, at the upper portion of the front end of the base 104, an inclined portion 107a that rises at a predetermined angle from the first plane portion 109 of the base 104 toward the excavation direction and the top thereof; and an inclined portion 107b that rises at a predetermined angle from the second plane portion 110 of the base 102 toward the excavation direction and the top thereof. The length of the inclined portion 107a is the same as that of the inclined portion 107b, and the top thereof is located at the center of the first plane portion 109 and the second plane portion 110. In other words, the top thereof is located in the middle of the thickness direction of the main drill bit 102. On the other hand, the superhard drill tip 108 includes, at the lower portion of the front end of the base 104, an inclined portion 108a that rises at a predetermined angle from the first plane portion 109 of the base 104 toward the excavation direction and the top thereof, and an inclined portion 108b that rises at a predetermined angle from the second plane portion 110 of the base 104 toward the excavation direction and the top thereof. The length of the inclined portion 108a is the same as that of the inclined portion 108b, and the top portion is located at the center of the first flat portion 109 and the second flat portion 110. In other words, the top portion is located in the middle of the main drill 102 in the thickness direction.

[0096] like Figure 6 As shown in (c), the top where the inclined parts 107a and 107b of the super-hard drill tip 107 are connected and the top where the inclined parts 108a and 108b of the super-hard drill tip 108 are connected form edges for excavation at the top and bottom of the base 104. In addition, at the front end of the base 104, a recess 111 is formed between the super-hard drill tips 107 and 108, which not only further reduces the retention of excavated soil (or chips), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or chips).

[0097] The legs 105 and 106 extend in parallel from the base 104 to the rear end at a predetermined interval, so as to be in a U-shape when viewed from a plane. The legs 105 and 106 are provided with holes 112 for mounting the double drill 101 on the sleeve by bolts or the like.

[0098] On the other hand, the auxiliary drill bit 103 includes a base 113. The rear end portion of the base 113 is an inclined portion 113a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 101, and a superhard drill tip 113b is arranged on the inclined surface of the inclined portion 113a. The inclined portion 113a is provided with a hole portion that communicates with the hole portion 112 of the leg portions 105 and 106.

[0099] The base 113 has a so-called mountain shape in which the tops of the upper and lower parts protrude toward the excavation direction, that is, the front end side of the double drill bit 101. Superhard drill tips 114 and 115 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 113.

[0100] More specifically, the superhard drill tip 114 includes, at the upper portion of the front end of the base 113, an inclined portion 114a that rises at a predetermined angle from the third plane portion 117 of the base 113 toward the excavation direction and the top, and an inclined portion 114b that rises at a predetermined angle from the first plane portion 109 toward the excavation direction and the top. Since the length of the inclined portion 114a is the same as the length of the inclined portion 114b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 103. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 103. On the other hand, the superhard drill tip 115 includes, at the lower portion of the front end of the base 113, an inclined portion 115a that rises at a predetermined angle from the third plane portion 117 of the base 113 toward the excavation direction and the top, and an inclined portion 115b that rises at a predetermined angle from the first plane portion 109 of the base 113 toward the excavation direction and the top. Since the length of the inclined portion 114a is the same as that of the inclined portion 114b, the top portion is located at the center of the excavation direction or the hole wall direction of the auxiliary drill bit 103. In other words, the top portion is located at the middle of the auxiliary drill bit 103 in the thickness direction.

[0101] like Figure 6 As shown in (c), the top where the inclined parts 114a and 114b of the super-hard drill tip 114 are connected and the top where the inclined parts 115a and 115b of the super-hard drill tip 115 are connected form edges for excavation at the top and bottom of the base 113. In addition, at the front end of the base 113, a recess 116 is formed between the super-hard drill tips 114 and 115, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0102] The material of each part is the same as that described in the first embodiment. The base parts 104 and 113 are provided with a hard thickened part 118 .

[0103] <Seventh Embodiment> Figure 7 (a) to Figure 7 (d) shows and describes the configuration of the double drill bit of the seventh embodiment of the present invention. More specifically, Figure 7 (a) shows a top view of the double drill bit, Figure 7 (b) is a stereoscopic view showing the double drill head, Figure 7 (c) shows a side view of the double drill bit, Figure 7(d) shows the front view of the double drill. In the double drill, the main drill is an outer blade with an angle shape, and the auxiliary drill is a middle blade attached to the inside. By using the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object easier to dig out. In order to clearly show the structure of each part, only Figure 7 The hard thickened portion is shown in (a).

[0104] As shown in these figures, the double drill bit 121 is provided so that the front end cutting edges of the main drill bit 122 and the auxiliary drill bit 123 are stepped backward in the excavation direction.

[0105] The main drill bit 122 is composed of a base 124 and two legs 125 and 126 extending from the base 124. Hereinafter, the base 124 side is also referred to as the front end of the double drill bit 121, and the legs 125 and 126 side is also referred to as the installation side toward the casing or the rear end of the double drill bit 121. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the double drill bit 121). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the double drill bit 121. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0106] The base 124 has a so-called mountain shape in which the tops of the upper and lower parts protrude toward the excavation direction, that is, the front end side of the double drill bit 121. Superhard drill tips 127 and 128 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 124.

[0107] More specifically, the superhard drill tip 127 includes, at the upper portion of the front end of the base 124, an inclined portion 127a that rises at a predetermined angle from the first plane portion 129 of the base 124 toward the top of the excavation direction; and an inclined portion 127b that rises at a predetermined angle from the second plane portion 130 of the base 124 toward the top of the excavation direction. Since the length of the inclined portion 127a is smaller than the length of the inclined portion 127b, the top is located near the first plane portion 129. On the other hand, the superhard drill tip 128 includes, at the lower portion of the front end of the base 124, an inclined portion 128a that rises at a predetermined angle from the first plane portion 129 of the base 124 toward the top of the excavation direction; and an inclined portion 128b that rises at a predetermined angle from the second plane portion 130 of the base 124 toward the top of the excavation direction. Since the length of the inclined portion 128a is smaller than the length of the inclined portion 128b, the top is located near the first plane portion 129.

[0108] like Figure 7As shown in (c), the top where the inclined parts 127a and 127b of the super-hard drill tip 127 are connected and the top where the inclined parts 128a and 128b of the super-hard drill tip 128 are connected form edges for excavation at the top and bottom of the base 124. In addition, at the front end of the base 124, a recess 131 is formed between the super-hard drill tips 127 and 128, which not only further reduces the retention of excavated soil (or chips), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or chips).

[0109] The legs 125 and 126 extend from the base 124 to the rear end at a predetermined interval, with the inner planes being parallel and having a substantially U-shaped shape when viewed from a plane. The difference from the first embodiment is that the outer surface of the legs 126 has a predetermined slope. The legs 125 and 126 are provided with holes 132 for mounting the double drill bit 121 on the sleeve by bolts or the like.

[0110] On the other hand, the auxiliary drill bit 123 includes a base 133. The rear end portion of the base 133 is an inclined portion 133a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 121, and a superhard drill tip 133b is arranged on the inclined surface of the inclined portion 133a. The inclined portion 133a is provided with a hole portion that communicates with the hole portion 132 of the leg portions 125 and 126.

[0111] The base 133 has a so-called mountain shape in which the tops of the upper and lower parts protrude toward the excavation direction, that is, the front end side of the double drill bit 121. Superhard drill tips 134 and 135 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 133.

[0112] More specifically, the superhard drill tip 134 includes, at the upper portion of the front end of the base 133, an inclined portion 134a that rises at a predetermined angle from the third plane portion 137 of the base 133 toward the excavation direction and the top, and an inclined portion 134b that rises at a predetermined angle from the second plane portion 130 toward the excavation direction and the top. Since the length of the inclined portion 134a is the same as the length of the inclined portion 134b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 123. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 123. On the other hand, the superhard drill tip 135 includes, at the lower portion of the front end of the base 133, an inclined portion 135a that rises at a predetermined angle from the third plane portion 137 of the base 133 toward the excavation direction and the top, and an inclined portion 135b that rises at a predetermined angle from the second plane portion 130 of the base 133 toward the excavation direction and the top. Since the length of the inclined portion 135a is the same as that of the inclined portion 135b, the top portion is located at the center of the digging direction or the hole wall direction of the auxiliary drill bit 123. In other words, the top portion is located at the middle of the auxiliary drill bit 123 in the thickness direction.

[0113] like Figure 7As shown in (c), the top where the inclined parts 134a and 134b of the super-hard drill tip 134 are connected and the top where the inclined parts 135a and 135b of the super-hard drill tip 135 are connected form edges for excavation at the top and bottom of the base 133. In addition, at the front end of the base 133, a recess 136 is formed between the super-hard drill tips 134 and 135, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0114] The material of each part is the same as that described in the first embodiment. The base parts 124 and 133 are provided with a hard thickened part 138 .

[0115] <Eighth Implementation Method> Figure 8 (a) to Figure 8 (d) shows and describes the configuration of the double drill bit of the eighth embodiment of the present invention. More specifically, Figure 8 (a) shows a top view of the double drill bit, Figure 8 (b) is a stereoscopic view showing the double drill head, Figure 8 (c) shows a side view of the double drill bit, Figure 8 (d) shows the front view of the double drill. In the double drill, the main drill is an inner blade with an angle shape, and the auxiliary drill is a middle blade attached to the outside. By using the auxiliary drill as the middle blade, it is possible to dig at the middle position between the outer blade and the inner blade, which not only improves the digging efficiency but also makes the digging object easier to dig out. In order to clearly show the structure of each part, only Figure 8 The hard thickened portion is shown in (a).

[0116] As shown in these figures, the double drill bit 141 is integrally formed so that the front end cutting edges of the main drill bit 142 and the auxiliary drill bit 143 are stepped backward in the excavation direction.

[0117] The main drill bit 142 is composed of a base 144 and two legs 145 and 146 extending from the base 144. Hereinafter, the base 144 side is also referred to as the front end of the double drill bit 141, and the legs 145 and 146 side is also referred to as the installation side toward the casing or the rear end of the double drill bit 141. The direction in which the front end faces is the excavation direction, and the direction perpendicular to the excavation direction is the hole wall direction or the pile core direction (also referred to as the thickness direction of the double drill bit 141). Moreover, the direction perpendicular to the excavation direction and the hole wall direction or the pile core direction is referred to as the width direction of the double drill bit 141. The definitions of the pile core direction and the hole wall direction are the same as those described in the first embodiment.

[0118] The base 144 has a so-called mountain shape in which the tops of the upper and lower parts protrude in the digging direction, that is, the front end side of the double drill bit 141. Superhard drill tips 147 and 148 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 144.

[0119] More specifically, the superhard drill tip 147 includes, at the upper portion of the front end of the base 144, an inclined portion 147a that rises at a predetermined angle from the first plane portion 149 of the base 1442 toward the excavation direction and the top, and an inclined portion 147b that rises at a predetermined angle from the second plane portion 150 of the base 144 toward the excavation direction and the top. Since the length of the inclined portion 147a is longer than the length of the inclined portion 147b, the top is located near the second plane portion 150. On the other hand, the superhard drill tip 148 includes, at the lower portion of the front end of the base 144, an inclined portion 148a that rises at a predetermined angle from the first plane portion 149 of the base 144 toward the excavation direction and the top, and an inclined portion 148b that rises at a predetermined angle from the second plane portion 150 of the base 144 toward the excavation direction and the top. Since the length of the inclined portion 148a is longer than the length of the inclined portion 148b, the top is located near the second plane portion 150.

[0120] like Figure 8 As shown in (c), the top where the inclined parts 147a and 147b of the super-hard drill tip 147 are connected and the top where the inclined parts 148a and 148b of the super-hard drill tip 148 are connected form edges for excavation at the top and bottom of the base 144. In addition, at the front end of the base 144, a recess 151 is formed between the super-hard drill tips 147 and 148, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0121] The legs 145 and 146 extend from the base 64 to the rear end at a predetermined interval, with the inner planes being parallel and having a substantially U-shaped shape when viewed from a plane. The difference from the fourth embodiment is that the outer surface of the leg 145 has a predetermined slope. The legs 145 and 146 are provided with a hole 152 for mounting the double drill bit 141 on the sleeve by bolts or the like.

[0122] On the other hand, the auxiliary drill bit 143 includes a base 153. The rear end portion of the base 153 is an inclined portion 153a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 141, and a superhard drill tip 153b is arranged on the inclined surface of the inclined portion 153a. The inclined portion 153a is provided with a hole portion that communicates with the hole portion 152 of the leg portions 145 and 146.

[0123] The base 153 has a so-called mountain shape in which the tops of the upper and lower parts protrude in the excavation direction, that is, the front end side of the double drill bit 141. Superhard drill tips 154 and 155 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 153.

[0124] More specifically, the superhard drill tip 154 ​​includes, at the upper portion of the front end of the base 153, an inclined portion 154a that rises at a predetermined angle from the third plane portion 157 of the base 153 toward the excavation direction and the top, and an inclined portion 144b that rises at a predetermined angle from the first plane portion 149 toward the excavation direction and the top. Since the length of the inclined portion 154a is the same as the length of the inclined portion 154b, the top is located in the center of the excavation direction or the hole wall direction of the auxiliary drill bit 143. In other words, the top is located in the middle of the thickness direction of the auxiliary drill bit 143. On the other hand, the superhard drill tip 155 includes, at the lower portion of the front end of the base 153, an inclined portion 155a that rises at a predetermined angle from the third plane portion 157 of the base 153 toward the excavation direction and the top, and an inclined portion 155b that rises at a predetermined angle from the first plane portion 149 of the base 153 toward the excavation direction and the top. Since the length of the inclined portion 155a is the same as that of the inclined portion 155b, the top is located in the center of the digging direction or the hole wall direction of the auxiliary drill bit 143. In other words, the top is located in the middle of the auxiliary drill bit 143 in the thickness direction.

[0125] like Figure 8 As shown in (c), the top where the inclined parts 154a and 154b of the super-hard drill tip 154 ​​are connected and the top where the inclined parts 155a and 155b of the super-hard drill tip 155 are connected form edges for excavation at the top and bottom of the base 153. In addition, at the front end of the base 153, a recess 156 is formed between the super-hard drill tips 154 and 155, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0126] The material of each part is the same as that described in the first embodiment. The base 144, 153 is provided with a hard thickened portion 158.

[0127] The first to eighth embodiments described above show examples in which both the upper and lower superhard drill tips of the auxiliary drill are middle cutting edges, but they may also be outer cutting edges or inner cutting edges.

[0128] That is, taking the first embodiment as an example, in the first embodiment, the top of the superhard drill tip 14 of the auxiliary drill bit 3 is located in the middle of the excavation direction or the hole wall direction of the auxiliary drill bit 3. In other words, the top is located in the center (middle blade) of the thickness direction of the double drill bit 1. Similarly, the top of the superhard drill tip 15 is located in the middle of the excavation direction or the hole wall direction of the auxiliary drill bit 3. In other words, the top is located in the center (middle blade) of the thickness direction of the double drill bit 1. It can be used as an outer blade and an inner blade by approaching it to either the excavation direction or the hole wall direction.

[0129] Combine the following Fig.15 (a) to Fig.15(d) The auxiliary drill bits of the double drill bit according to the first embodiment of the present invention are respectively used as the inner blade and the outer blade as an example for explanation.

[0130] first, Fig.15 (a) and Fig.15 (b) shows an example of a configuration when the auxiliary drill bit is used as an inner blade. Here, in order to simplify the description, the same configuration as the first embodiment is shown. Figure 1 (a) to Figure 1 (d) The same reference numerals are used to denote the same components, and description thereof will be omitted.

[0131] like Fig.15 (a) and Fig.15 As shown in (b), the auxiliary drill bit 303 includes a base 313. The rear end portion of the base 313 is formed into an inclined portion 313a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 301, and a superhard drill tip 313b is arranged on the inclined surface of the inclined portion 313a. The inclined portion 313a is provided with a hole portion that communicates with the hole portion 12 of the leg portions 5 and 6.

[0132] The base 313 has a so-called mountain shape in which the tops of the upper and lower parts protrude toward the excavation direction, that is, the front end side of the double drill bit 301. Superhard drill tips 314 and 315 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 313.

[0133] More specifically, the superhard drill tip 314 includes, at the upper portion of the front end of the base 313, an inclined portion 314a that rises at a predetermined angle from the third plane portion 317 of the base 313 toward the excavation direction and the top, and an inclined portion 314b that rises at a predetermined angle from the second plane portion 10 toward the excavation direction and the top. Since the length of the inclined portion 314a is longer than the length of the inclined portion 314b, the top is close to the second plane portion 10 of the auxiliary drill bit 303. In other words, the top is close to the main drill bit 302 in the thickness direction of the auxiliary drill bit 303. On the other hand, the superhard drill tip 315 includes, at the lower portion of the front end of the base 313, an inclined portion 315a that rises at a predetermined angle from the third plane portion 317 of the base 313 toward the excavation direction and the top, and an inclined portion 315b that rises at a predetermined angle from the second plane portion 10 of the base 313 toward the excavation direction and the top. Since the inclined portion 315a is longer than the inclined portion 315b, the top is close to the second plane 10 in the digging direction or hole wall direction of the auxiliary drill bit 303. In other words, the top is close to the main drill bit 302 in the thickness direction of the auxiliary drill bit 303.

[0134] The top where the inclined parts 314a and 314b of the super-hard drill tip 314 are connected and the top where the inclined parts 315a and 315b of the super-hard drill tip 315 are connected form edges for excavation at the top and bottom of the base 314. In addition, a recess 316 is formed between the super-hard drill tips 314 and 315 at the front end of the base 313, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0135] then, Fig.15 (c) and Fig.15 (d) shows an example of a configuration when the auxiliary drill bit is used as an outer blade. Here, in order to simplify the description, the same configuration as the first embodiment is shown by Figure 1 (a) to Figure 1 (d) The same reference numerals are used to denote the same components, and description thereof will be omitted.

[0136] like Fig.15 (c) and Fig.15 As shown in (d), the auxiliary drill bit 403 includes a base 413. The rear end portion of the base 413 is formed into an inclined portion 413a that is inclined toward the rear of the excavation direction, that is, toward the rear end of the double drill bit 401, and a superhard drill tip 413b is arranged on the inclined surface of the inclined portion 413a. The inclined portion 413a is provided with a hole portion that communicates with the hole portion 12 of the leg portions 5 and 6.

[0137] The base 413 has a so-called mountain shape in which the tops of the upper and lower parts protrude toward the excavation direction, that is, the front end side of the double drill bit 401. Superhard drill tips 414 and 415 are respectively arranged at the front end and the upper and lower mountain-shaped parts of the base 413.

[0138] More specifically, the superhard drill tip 414 includes, at the upper portion of the front end of the base 413, an inclined portion 414a that rises at a predetermined angle from the third plane portion 417 of the base 413 toward the excavation direction and the top, and an inclined portion 414b that rises at a predetermined angle from the second plane portion 10 toward the excavation direction and the top. Since the length of the inclined portion 414a is smaller than the length of the inclined portion 414b, the top is close to the third plane 417 of the auxiliary drill bit 403. In other words, the top is a position close to the side of the auxiliary drill bit 403 opposite to the main drill bit 402 side in the thickness direction. On the other hand, the superhard drill tip 415 includes, at the lower portion of the front end of the base 413, an inclined portion 415a that rises at a predetermined angle from the third plane portion 417 of the base 413 toward the excavation direction and the top, and an inclined portion 415b that rises at a predetermined angle from the second plane portion 10 of the base 413 toward the excavation direction and the top. Since the length of the inclined portion 414a is shorter than that of the inclined portion 414b, the top is close to the third plane 417 in the digging direction or hole wall direction of the auxiliary drill bit 403. In other words, the top is close to the side of the auxiliary drill bit 403 opposite to the main drill bit 402 side in the thickness direction.

[0139] The top where the inclined parts 414a and 414b of the super-hard drill tip 414 are connected and the top where the inclined parts 415a and 415b of the super-hard drill tip 415 are connected form edges for excavation at the top and bottom of the base 414. In addition, a recess 416 is formed between the super-hard drill tips 414 and 415 at the front end of the base 413, which not only further reduces the retention of excavated soil (or cuttings), but also helps to improve the excavation efficiency by controlling the upward flow of excavated soil (or cuttings).

[0140] here, Fig. 9 (a) Fig. 9 (b) to Fig.13 (a) Fig.13 (b) shows and explains an example of installing a dual drill bit to a casing according to an embodiment of the present invention.

[0141] Fig. 9 (a) Fig. 9 (b) shows an example of installation in which the main drill bit is straight and angled, and the auxiliary drill bit is attached to the inside. In this figure, a double drill bit 201 in which the main drill bit is an inner blade and the auxiliary drill bit is an outer blade, a double drill bit 202 in which the main drill bit is a middle blade and the auxiliary drill bit is also a middle blade, a double drill bit 203 in which the main drill bit is an angled outer blade and the auxiliary drill bit is an inner blade, and a double drill bit 204 in which the main drill bit is an outer blade and the auxiliary drill bit is an inner blade are respectively installed on the casing 200.

[0142] Fig.10 (a) Fig.10(b) shows an example of installation in which the main drill bit is straight and angled, and the auxiliary drill bit is attached to the outside. In this figure, a double drill bit 205 in which the main drill bit is an angled outer blade and the auxiliary drill bit is an inner blade, a double drill bit 206 in which the main drill bit is an outer blade and the auxiliary drill bit is an inner blade, a double drill bit 207 in which the main drill bit is a middle blade and the auxiliary drill bit is also a middle blade, and a double drill bit 208 in which the main drill bit is an inner blade and the auxiliary drill bit is an outer blade are respectively installed on the casing 200.

[0143] Fig.11 (a) Fig.11 (b) shows an example of installation in which the main drill bit is straight and the auxiliary drill bit is attached to the outside. In this figure, a double drill bit 209 in which the main drill bit is an outer blade and the auxiliary drill bit is an outer blade, a double drill bit 210 in which the main drill bit is an outer blade and the auxiliary drill bit is a middle blade, and a double drill bit 211 in which the main drill bit is a straight inner blade and the auxiliary drill bit is an inner blade are respectively installed on the casing 200.

[0144] Fig.12 (a) Fig.12 (b) shows an example of installation in which the main drill bit is straight and the auxiliary drill bit is attached to the inside. In this figure, a double drill bit 212 in which the main drill bit is an inner blade and the auxiliary drill bit is an outer blade, a double drill bit 213 in which the main drill bit is an outer blade and the auxiliary drill bit is a middle blade, and a double drill bit 214 in which the main drill bit is a straight outer blade and the auxiliary drill bit is an auxiliary drill bit inner blade are respectively installed on the casing 200.

[0145] Fig.13 (a) Fig.13 (b) shows an example of installation in which the main drill bit is straight or angled and the auxiliary drill bit is attached to the outside. In this figure, a double drill bit 215 in which the main drill bit is an inner blade and the auxiliary drill bit is an outer blade, a double drill bit 216 in which the main drill bit is an angled middle blade and the auxiliary drill bit is a middle blade, and a double drill bit 217 in which the main drill bit is an outer blade and the auxiliary drill bit is an inner blade are installed on the casing 200.

[0146] Fig.14 (a) Fig.14 (b) shows an example of installation in which the main drill bit is straight or angled and the auxiliary drill bit is attached to the inside. In this figure, a double drill bit 218 in which the main drill bit is an outer blade and the auxiliary drill bit is an inner blade, a double drill bit 219 in which the main drill bit is an angled middle blade and the auxiliary drill bit is also a middle blade, and a double drill bit 220 in which the main drill bit is an inner blade and the auxiliary drill bit is an outer blade are respectively installed on the casing 200.

[0147] Finally, in the double drill bits of the first to eighth embodiments described above, the following designs may be made.

[0148] (a) About the cutting edge position of the main drill bit and the auxiliary drill bit In all shapes, a step structure can be adopted so that the blade of the auxiliary drill bit is located 25 mm below the blade of the main drill bit. The reason why the blade of the auxiliary drill bit is located 25 mm below the blade of the main drill bit is that the distance between the blade of the main drill bit and the front end of the casing is 50 mm, and the blade of the auxiliary drill bit is just located in the middle (25 mm below), so that the auxiliary drill bit can dig a position that the main drill bit cannot dig.

[0149] (b) Width setting of main drill bit and auxiliary drill bit The blade width of the main drill bit is 80mm so that the jaws of the blade part are engaged 10mm each front and back on the retainer, and the total width of the auxiliary drill bit is 60mm, which can be just accommodated in the internal dimensions of the retainer. Since the primary impact during excavation is borne by the main drill bit, it is assumed that the impact on the auxiliary drill bit is reduced by about 30%, so the width ratio of the main drill bit and the auxiliary drill bit can be set to 4:3. However, this width ratio can be changed according to the excavation object.

[0150] (c) Thickness setting of main drill bit and auxiliary drill bit Since the thickness of the main drill bit is 40 mm, which is the most common drill bit thickness, it is set to 40 mm in consideration of versatility, and the thickness of the auxiliary drill bit is 30 mm, which can be set to a ratio of 4:3 for the same reason as the width setting. However, the thickness ratio can be changed according to the excavation object.

[0151] In order to dig 10mm outside or inside the straight blade position, the thickness of the main drill bit with an angle shape is 50mm and the thickness ratio of the auxiliary drill bit is 5:3. By combining the angle shape with the straight shape, the effect is maximized, and the impact during digging is not simply increased by 25%. The thickness of the main drill bit with an angle shape can be changed according to the digging object.

[0152] (d) Cone of the auxiliary drill bit Since the auxiliary drill bit is installed inside or outside the main drill bit, it will come into direct contact with the excavation object. Therefore, a super-hard drill tip for impact resistance and wear resistance is installed in the cone part of the auxiliary drill bit. It should be noted that the angle of the cone part can of course vary according to the thickness of the auxiliary drill bit.

[0153] (e) Regarding the hardness of the superhard drill tip Of course, the hardness of the superhard drill tip of the main drill bit and the auxiliary drill bit can be changed according to the excavation object. As mentioned above, the hardness of the superhard drill tip can be set to E7 to E2 of the common E type (JIS standard, coarse grain) and G5 to G2 of the G type (JIS standard, medium grain), and the hardness of the superhard drill tip of the main drill bit and the auxiliary drill bit can also be different.

[0154] For example: Excavation object: super-hard rock, main drill bit E2 + auxiliary drill bit E3 For example: Clearing of reinforced concrete such as beams, columns, and floor slabs, main drill bit E6 + auxiliary drill bit E5 As described above, according to the embodiments of the present invention, the following effects can be achieved.

[0155] That is, according to an embodiment of the present invention, a double drill bit can be provided, including a main drill bit and an auxiliary drill bit, wherein the main drill bit and the auxiliary drill bit are both provided with a superhard drill tip in a mountain shape protruding in the excavation direction at least at the upper and lower parts of the front end of the base, and the mountain-shaped top of the superhard drill tip of the auxiliary drill bit is located behind the excavation direction compared with the mountain-shaped top of the superhard drill tip of the main drill bit. The mountain-shaped top of the main drill bit can be close to the direction perpendicular to the excavation direction, i.e., the hole wall direction, close to the pile core direction, or located in the center. The mountain-shaped top of the auxiliary drill bit can be close to the direction perpendicular to the excavation direction, i.e., the hole wall direction, close to the pile core direction, or located in the center. The main drill bit also includes two legs continuous with the base, and the outer surface of the leg on the side where the auxiliary drill bit is not arranged in parallel can have a specified slope.

[0156] Therefore, firstly, by arranging the main drill bit and the auxiliary drill bit side by side in a direction perpendicular to the excavation direction, and forming a so-called step difference structure in which the blade of the auxiliary drill bit is located behind the blade of the main drill bit in the excavation direction, the load applied to the inner plate (or outer plate) of the casing can be reduced, and the retention of excavated soil (or chips) generated during excavation by a single blade can be prevented, thereby improving the excavation efficiency.

[0157] Secondly, the base material shape of the blade of the main drill bit can be selected from a straight shape or an inclined shape at an angle to the base material, and the blade position of the main drill bit and the blade position of the auxiliary drill bit can be adjusted, so that the width of the two blades and the angle of the excavation position can be set. Therefore, not only the excavation position of the blade is expanded, the load applied to the inner plate (or outer plate) of the casing is further reduced, and the retention of excavated soil (or chips) is further reduced, but also the upward flow of the excavated soil (or chips) can be controlled.

[0158] Third, by providing a superhard drill tip at the base (base material portion) of the blade, wear resistance can be improved.

[0159] Fourth, since the double drill bits are used for bidirectional rotation, bidirectional excavation of forward excavation and reverse excavation can be performed.

[0160] Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various improvements and changes can of course be made without departing from the gist of the present invention.

[0161] Explanation of symbols 1…double drill bit; 2…main drill bit; 3…auxiliary drill bit; 4…base; 5, 6…legs; 7, 8…superhard drill bit; 9…first plane portion; 10…second plane portion; 11…recessed portion; 12…hole portion; 13…base; 14, 15…superhard drill bit; 16…recessed portion; 17, 18…hard thickened portion.

Claims

1. A double drill bit, including a main drill bit and an auxiliary drill bit, The main drill bit and the auxiliary drill bit are provided with a super-hard drill tip in a mountain shape protruding in the digging direction at least at the upper and lower parts of the front end of the base. The top of the mountain-shaped shape of the super-hard drill tip of the auxiliary drill bit is located rearward in the excavation direction compared with the top of the mountain-shaped shape of the super-hard drill tip of the main drill bit.

2. The double drill bit according to claim 1, wherein: The top of the mountain shape of the main drill bit is close to the direction perpendicular to the excavation direction, that is, the hole wall direction, close to the pile core direction, or located in the center.

3. The double drill bit according to claim 1 or 2, wherein: The top of the mountain shape of the auxiliary drill bit is close to the direction perpendicular to the excavation direction, that is, the hole wall direction, close to the pile core direction, or located in the center.

4. The double drill bit according to claim 3, wherein: The main drill bit also includes two legs continuous with the base, The outer surface of the leg portion on the side where the auxiliary drill bits are not arranged in parallel has a predetermined slope.

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