bit

Abstract

To provide a bit having excellent soil discharge properties. [Solution] A cylindrical bit 100 that excavates ground G by rotating around a central axis Ax, having an attachment portion 12, a drilling portion 13 formed with a larger diameter than the attachment portion 12 and provided at the tip side of the attachment portion 12, and a groove-shaped flow path 21 extending axially from the tip surface 14 of the drilling portion 13 toward the rear end, and the flow path 21 has a length Lb that is 50% or more of the total axial length La of the drilling portion 13.

Description

[Technical Field]

[0001] The present invention relates to a bit. [Background technology]

[0002] A known drilling tool for excavating the ground is a bit that has a cylindrical body with multiple tips at the tip and excavates the ground using rotational and impact forces from a rotary percussion machine transmitted through a casing pipe (see, for example, Patent Document 1).

[0003] In some cases, an inner bit is incorporated inside an outer bit, and the inner bit excavates the central portion, while the outer bit excavates the radially outer region (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-164864 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-97263 Summary of the Invention [Problem to be solved by the invention]

[0005] When excavating the ground with a bit, water is poured into the excavation site to drain the soil while excavating. However, particularly when the soil is sandy or mudstone, a large amount of soil is generated during excavation. If stones or pieces of wood are mixed in, the flow path can be blocked, reducing the efficiency of soil discharge and increasing excavation resistance. For this reason, it is desirable to improve the soil discharge performance of bits used to excavate the ground.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a bit having excellent soil and sand discharge properties. [Means for solving the problem]

[0007] A bit according to one embodiment of the present invention is a cylindrical bit that excavates the ground by rotating it around a central axis, and has an attachment portion, a drilling portion that is formed with a larger diameter than the attachment portion and is provided at the tip side of the attachment portion, and a groove-shaped flow path that extends axially from the tip surface of the drilling portion toward the rear end side, and the flow path has a length that is 50% or more of the total axial length of the drilling portion.

[0008] With a bit having the above structure, the soil generated during excavation can be discharged from the inner periphery to the outer periphery of the excavation section through a flow path extending axially from the front end face of the excavation section to the rear end. In particular, since the flow path has a length of 50% or more of the total axial length of the excavation section, a sufficient cross-sectional area of ​​the flow path can be ensured, improving the discharge of soil and sand.

[0009] The length of the flow path may be 60% or more and 95% or less of the total axial length of the excavation part.

[0010] The flow path may have, on the rear end side of the excavation portion, an inclined surface that inclines radially outwardly of the excavation portion toward the rear end side of the excavation portion.

[0011] The flow passage may be inclined radially outwardly of the excavation portion and rearward in the direction of rotation during excavation.

[0012] The excavation portion may be provided with a reinforcing member at a position adjacent to the flow channel at least on the rear side in the direction of rotation during excavation, so as to straddle the boundary between the inner side surface and the bottom surface of the flow channel.

[0013] A plurality of the flow channels may be arranged at intervals in the circumferential direction of the excavated portion.

[0014] The drilling portion may have a plurality of tips on its tip surface.

[0015] An inner diameter bit may be provided inside the bit to be rotated together with the bit and excavate the ground. [Effects of the Invention]

[0016] According to the present invention, a bit having excellent soil discharge properties is provided. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a side view of a bit according to this embodiment. [Figure 2] FIG. 2 is a view of the bit according to this embodiment as viewed from the tip side along the central axis. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view of an excavation location illustrating the excavation of the ground by the bit. [Figure 5] FIG. 5 is a side view of a bit according to another embodiment. [Figure 6] FIG. 6 is a view of a bit according to another embodiment, viewed from the tip side along the central axis. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIGS. 1 to 4 , the bit 100 according to this embodiment includes a cylindrical body 11. The body 11 has an attachment portion 12 and a drilling portion 13, and is made of, for example, steel or molybdenum. The drilling portion 13 is provided on the tip side of the attachment portion 12. The drilling portion 13 has a diameter larger than that of the attachment portion 12. The drilling portion 13 has an annular tip surface 14, on which a plurality of tips 15 are provided. These tips 15 are formed in a conical shape that narrows toward the tip, and are each embedded and fixed in the tip surface 14 of the drilling portion 13. In this example, twelve tips 15 are fixed to the drilling portion 13. The tips 15 may have various shapes, such as a generally conical shape with an outward bulging circumferential surface or a multi-stage conical shape with a diameter reduced at at least one point along the axial direction.

[0019] A pipe (also called a rod) 16 is connected to the attachment portion 12 of the bit 100, and a rotational force is transmitted from an excavation machine (not shown) via the pipe 16 (see FIG. 4). As a result, the bit 100 is rotated in one rotational direction R about the central axis Ax, and excavates the ground G with the tip 15 fixed to the tip surface 14 of the excavation portion 13 while applying a rotational force to the ground G. Note that the ground G may also be excavated by applying an impact force to the bit 100 along with the rotational force.

[0020] The bit 100 has a plurality of flow paths 21 in the drilling portion 13. In this example, four flow paths 21 are formed in the drilling portion 13.

[0021] In this example, three tips 15 are arranged between each flow path 21. Of these three tips 15, the central one is an inner peripheral tip 15a, and both sides of this inner peripheral tip 15a are outer peripheral tips 15b. The outer peripheral tips 15b are arranged tilted radially outward of the excavation part 13 toward the tip of the excavation part 13 with respect to the central axis Ax, and the inner peripheral tips 15a are arranged toward the inner peripheral side of the outer peripheral tips 15b.

[0022] The flow paths 21 formed in the excavation part 13 are formed as grooves extending axially from the tip surface 14 of the excavation part 13 toward the rear end side, penetrating the inner and outer peripheries of the excavation part 13. These flow paths 21 are arranged at equally spaced positions in the circumferential direction in the excavation part 13. The flow paths 21 have a pair of inner side surface portions 22 along the central axis Ax of the excavation part 13, and a bottom surface portion 23 that is recessed in a curved shape on the rear end side of the excavation part 13. It is preferable that the flow paths 21 are formed at equally spaced positions in the circumferential direction in the excavation part 13, but they do not necessarily have to be formed at equally spaced positions.

[0023] The drilling section 13 of the bit 100 has an effective length of the total length La from the front end to the rear end, including the tip 15, and each flow path 21 has a length Lb from the front end to the rear end of the drilling section 13 that is 50% or more of the total length La of the drilling section 13 (see FIG. 1). Here, the rear end of the flow path 21 is the boundary 24 between the inner side surface 22 and the bottom surface 23 of the flow path 21, and the length Lb of the flow path 21 is the length from the front end, including the tip 15, of the drilling section 13 to the boundary 24 on the rear end side. It is preferable that the length Lb of the flow path 21 be 60% or more and 95% or less of the total length La of the drilling section 13.

[0024] The flow path 21 has an inclined surface 25 on the rear end side of the excavation portion 13. This inclined surface 25 is inclined radially outward of the excavation portion 13 toward the rear end side of the excavation portion 13. The inclination angle α of this inclined surface 25 with respect to the central axis Ax of the bit 100 is preferably 5° to 60° (see FIG. 3).

[0025] Furthermore, the flow passage 21 is inclined radially outward of the excavation section 13 toward the rear side in the rotation direction R during excavation. The inclination angle β of the flow passage 21 with respect to the line D passing through the central axis Ax is preferably set to 5° to 45° (see FIG. 2). At the tip surface 14 of the excavation section 13, in the outer peripheral portion, the dimension Wa between the flow passage 21 and the tip 15 on the front side in the rotation direction R is larger than the dimension Wb between the flow passage 21 and the tip 15 on the rear side in the rotation direction R (see FIG. 2).

[0026] A reinforcing member 31 is provided in the excavation portion 13. This reinforcing member 31 is formed, for example, from a cemented carbide alloy that is harder than the body 11. The reinforcing member 31 is disposed adjacent to the flow path 21 on the rear side in the rotation direction R during excavation. The reinforcing member 31 is formed in the shape of a long, thin plate, and is embedded in the excavation portion 13 along the flow path 21 so as to straddle the boundary 24 between the inner side surface portion 22 and the bottom surface portion 23 of the flow path 21. The reinforcing member 31 is provided at a position 2 mm to 5 mm away from the flow path 21 on the rear side in the rotation direction R during excavation. The reinforcing member 31 is embedded in the excavation portion 31 so as to be recessed approximately 0.5 mm to 1.0 mm from the outer peripheral surface of the excavation portion 31. The reinforcing member 31 preferably has a thickness of 5 mm to 7 mm and a width of 3 mm to 10 mm. Furthermore, the length of the reinforcing member 31 is preferably 50% or more and 100% or less of the total length La of the excavation portion 13, and is preferably 10 mm or more on both the front and rear end sides of the excavation portion 13, with the boundary 24 between the inner surface portion 22 and the bottom surface portion 23 of the flow path 21 as the boundary.

[0027] The bit 100 described above is rotated in one rotation direction R around the central axis Ax, thereby applying a rotational force to the ground G and performing excavation using the tip 15 fixed to the tip surface 14 of the excavation part 13. At this time, water is poured into the inside of the bit 100. As a result, the soil and sand generated during excavation are sent out to the outer periphery of the excavation part 13 together with the water through the flow path 21 and are then discharged outside the hole through the gap between the outer periphery of the bit 100 and the inner periphery of the excavated hole.

[0028] When excavating soft ground G, such as sand or mudstone, a large amount of soil is excavated. For this reason, when using a drill bit, it is necessary to efficiently take in and remove the soil using the power of injected water. However, if stones or wood chips are mixed in the excavated area, the efficiency of removing the soil decreases and the excavation resistance increases. In such cases, in order to remove the stones or wood chips and reduce the excavation resistance, the rotation is stopped temporarily and the bit is moved up and down in the excavation direction (flushing). However, if flushing is performed frequently, the excavation time increases and the excavation efficiency decreases.

[0029] In contrast, with the bit 100 according to this embodiment, the soil produced when excavating the ground G can be discharged from the inner periphery to the outer periphery of the excavation section 13 through a plurality of flow paths 21 that extend axially from the tip end surface 14 of the excavation section 13 toward the rear end. In particular, since the flow paths 21 have a length Lb that is 50% or more of the total axial length La of the excavation section 13, a sufficient cross-sectional area of ​​the flow paths 21 can be ensured, and the soil dischargeability can be improved. Note that if the length Lb of the flow paths 21 is set to be 60% or more and 95% or less of the total axial length La of the excavation section 13, a larger cross-sectional area of ​​the flow paths 21 can be ensured, and the soil dischargeability can be further improved.

[0030] Furthermore, the flow path 21 has an inclined surface 25 at the rear end side of the excavation part 13 that inclines radially outward from the excavation part 13 toward the rear end side of the excavation part 13. This allows the flow of sediment from the inner periphery side to the outer periphery side of the excavation part 13 to be smoother while maintaining the strength of the excavation part 13, thereby further improving the dischargeability of sediment.

[0031] Furthermore, the flow path 21 is inclined radially outward from the excavation section 13 toward the rear side in the rotation direction R during excavation. Therefore, the flow of soil and sand in the flow path 21 during excavation of the ground G can be made smoother, and the discharge of soil and sand from the inner periphery side to the outer periphery side of the excavation section 13 can be further improved.

[0032] Furthermore, the drilling section 13 of the bit 100 is provided with a reinforcing member 31 at an adjacent position on the rear side of the flow path 21 in the rotation direction R during drilling, so as to straddle the boundary 24 between the inner side surface 22 and bottom surface 23 of the flow path 21. Although the provision of the flow path 21 in the bit 100 reduces the strength (tool rigidity) of the drilling section 13, providing the reinforcing member 31 reinforces the vicinity of the flow path 21 in the drilling section 13, thereby preventing a reduction in the strength of the drilling section 13 due to the provision of the flow path 21. The reinforcing member 31 may be provided at an adjacent position on the rear side of the flow path 21 in the rotation direction R and an adjacent position on the front side of the rotation direction R.

[0033] In the above embodiment, the ground G is excavated using the bit 100, but the ground G may be excavated using a double-tube bit in which an inner diameter bit (not shown) is inserted into the bit 100 to form an integrated structure. In this case, too, earth and sand can be smoothly discharged from the inner periphery to the outer periphery of the excavation part 13 through the multiple flow paths 21 formed in the excavation part 13 of the bit 100.

[0034] Next, a bit 200 according to another embodiment will be described. Note that the same components as those in the bit 100 according to the above embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0035] 5 and 6, this bit 200 is provided with mountain-shaped tips 41 on the tip surface 14 of the drilling portion 13. The tips 41 are formed in a mountain-shaped cross section toward the tip, and are embedded and fixed in the drilling portion 13 so that their ridge lines 42 extend along the radial direction of the drilling portion 13. In this example, nine tips 41 are fixed to the drilling portion 13.

[0036] In the bit 200, three flow paths 21 are formed at equally spaced positions in the circumferential direction of the excavation portion 13, and three tips 41 are arranged between each of the flow paths 21.

[0037] In the case of this bit 200 as well, earth and sand can be smoothly discharged from the inner periphery of the excavation part 13 to the outer periphery through the multiple flow paths 21 formed in the excavation part 13 of the bit 200 .

[0038] Furthermore, on the tip surface 14 of the drilling portion 13 of the bit 200, arc-shaped recessed portions 45 are formed between the tips 41 other than where the flow path 21 is formed, and on the outer circumferential surface of the drilling portion 13, groove portions 46 connected to each recessed portion 45 extend along the central axis Ax to the vicinity of the rear end of the drilling portion 13. This makes it possible to suppress clogging between the tips 41 during drilling, while sending earth and sand discharged to the outer circumferential side out of the hole along the groove portions 46.

[0039] The present disclosure is not limited to the above specific examples, and designs that are appropriately modified by a person skilled in the art from these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of the above specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above specific examples can be combined as appropriate as long as no technical contradictions arise. [Explanation of symbols]

[0040] 12 Mounting part 13 Excavation Section 14 Tip surface 15, 15a, 15b, 41 chips 21 Flow path 22 Inner side 23 Bottom part 24 Boundary 25 Slope 31 Reinforcement member 100,200 bits Ax center axis G Ground La Total length Lb length R Rotation direction

Claims

1. A cylindrical bit that excavates the ground by rotating around a central axis, A mounting portion; a drilling portion formed to have a larger diameter than the mounting portion and provided on a tip side of the mounting portion; a flow path formed in a groove shape extending along the axial direction from the tip end surface of the excavation portion toward the rear end side and penetrating the inner periphery and the outer periphery of the excavation portion; and the excavation portion has a plurality of tips on the tip surface, The flow path has an inner side surface portion and a bottom surface portion in this order from the tip surface side of the excavation part, and the length from the tip of the excavation part including the tip to the boundary between the inner side surface portion and the bottom surface portion of the flow path is 50% or more of the total axial length from the tip of the excavation part including the tip to the rear end. bit.

2. The length of the flow path is 60% or more and 95% or less of the total axial length of the excavation section. The bit of claim 1 .

3. The flow path has an inclined surface on the rear end side of the excavation portion that inclines toward the rear end side of the excavation portion radially outward of the excavation portion. The bit of claim 1 .

4. The flow path is inclined radially outwardly of the excavation portion toward the rear side in the rotation direction during excavation. The bit of claim 1 .

5. The excavation portion is provided with a reinforcing member at a position adjacent to the flow path at least on the rear side in the rotation direction during excavation, so as to straddle a boundary portion between an inner side surface portion and a bottom surface portion of the flow path. The bit of claim 1 .

6. The flow paths are arranged in a plurality at intervals in the circumferential direction of the excavation portion. The bit of claim 1 .

7. The bit according to any one of claims 1 to 6 includes an inner diameter bit that is rotated together with the bit to excavate the ground. bit.

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