JP3275852B2 - Drilling tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool used for excavating earth and sand, rocks and the like in civil engineering works such as anchor works, various drilling works, foundation pile works and the like.

[0002]

2. Description of the Related Art In a drilling tool of this type, a tool body is composed of a substantially cylindrical device having a shank portion on a rear end side, and a drilling bit attached to a tip end of the device. There is known a so-called rotary impact type excavating tool which rotates a device around an axis and applies an impacting force in the axial direction to excavate by the excavating bit. Then, the inventors of the present invention provide a pilot bit attached to the center of the front end of the device via a shaft as the above-mentioned drill bit, and a rotatable outer periphery of the front end of the device on the rear end side of the pilot bit. And Japanese Patent Application No. 9-235246 and Japanese Patent Application No. 10-6112 propose an excavating tool having a diameter-enlarging bit which is attached to a device and which expands and contracts with the rotation of the device.

However, according to such a drilling tool,
At the time of excavation, the expansion bit is formed by expanding the dirt and rocks, etc., which are likely to be crushed by the preceding pilot bit, so that the excavation efficiency is improved and the burden on the expansion bit is reduced. Can be. Also, for example, when a casing pipe is erected in an excavated hole, excavation is performed together with the casing pipe during excavation, and after excavation is completed, the device is rotated in the opposite direction to the excavation time so that the above-described diameter expansion bit is removed. By reducing the diameter, the tool body can be pulled out while leaving only this casing pipe in the hole.

[0004]

However, in the excavating tool proposed in the above-mentioned application, the diameter-enlarging bit has a cylindrical shaft formed at the rear end thereof attached to an outer peripheral portion at the tip end of the device. It is simply attached by inserting it into the hole, or it is only attached by engaging the pin inserted facing the attachment hole with the annular groove formed in this shaft part That is, since the configuration is such that the enlarged diameter bit is only supported and attached to the device, there is naturally a limit in securing the mounting rigidity of the enlarged diameter bit. In particular, the diameter-expanding bit is designed to excavate earth and sand, rocks, and the like by extruding from the outer periphery of the device to the outer peripheral side of the tool by rotating as described above during excavation. Since a stress acting to bend the shaft part inserted into the hole will act, if the mounting rigidity is not sufficiently ensured in such an enlarged bit, if an excessive excavation load is applied, For example, there is a possibility that the shaft portion may be broken or even hinder the excavation work.

The present invention has been made in view of such circumstances, and a purpose thereof is to provide a pilot bit and a rotatable diameter-enlarging bit at the tip of the device as described above. It is an object of the present invention to provide an excavating tool capable of securing sufficient mounting rigidity to the enlarged bit.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention provides a device which is eccentric from the center axis on an outer periphery of a distal end portion of a device rotated around the center axis. At the center of the tip of the device, a disc-shaped pilot bit is attached so as to protrude more toward the tool tip than the above-mentioned diameter-enlarging bit. The diameter bit is supported such that an engaging portion provided on the tool tip side is engaged with an engaged portion provided on the pilot bit side facing the tool rear end side. . Therefore, in the excavating tool configured as described above, the enlarged-diameter bit engages the engaging portion with the engaged portion on the pilot bit side protruding toward the tool tip side, thereby allowing the excavating tool to communicate with the device. Since it is supported so as to be sandwiched in the direction of the rotation axis, it is possible to improve the mounting rigidity of the enlarged diameter bit.

Here, for example, when excavation is performed by applying a rotary impact force to the device, the rotary impact force is reliably transmitted to the pilot bit, or excavated chips generated during excavation are engaged with the engaging portion and the engaging bit. In order to prevent penetration of the pilot bit, it is desirable to interpose a disc-shaped spacer between the surface of the pilot bit facing the tool rear end and the front end surface of the device. In this case, the engaged portion may be provided on the spacer. Also, when the spacer is attached in this manner, in a state where the diameter-expanding bit is rotated and expanded during excavation, there is a space at a position where the diameter-expanded bit is housed in a state where the diameter-expanded bit is reduced. However, if drilling debris generated during excavation enters and accumulates here, there is a possibility that the enlarged bit may not be able to be accommodated in the space even if the enlarged bit is reduced in diameter after the end of excavation. . Therefore, in such a case, it is desirable to form a cutout portion that is cutout so as to be depressed inward on the outer periphery of the spacer so as to avoid the engaged portion. Excavation waste can be discharged from the tank to prevent its accumulation.

[0008]

FIG. 1 to FIG. 4 show an embodiment of a drilling tool according to the present invention. The excavation tool according to the present embodiment has a tool body 1 having a substantially multi-stage cylindrical device 2.
, And three enlarged bits 3 attached to the outer periphery of the distal end of the device 2, and a pilot bit 4 attached to the center of the distal end of the device 2. A hammer (not shown) is attached to a shank (not shown) to be formed and inserted into a cylindrical casing pipe 5. A casing top 6 attached to a tip end of the casing pipe 5 is provided.
Project from the pilot bit 4 and the enlarged bits 3.
2. The tool rotation direction T during excavation shown in FIG.
While receiving a striking force toward the tool tip side (left side in FIG. 1) in the direction of the axis O by the hammer,
Excavation is performed with the casing pipe 5.

Here, the casing top 6 is formed in a multi-stage cylindrical shape in which the outer diameter at the rear end side of the tool (right side in FIG. 1) is reduced by one step, and a large diameter portion 6A at the tool tip side. Is smaller than the outer diameter of the casing pipe 5, and the outer diameter of the small diameter portion 6B on the tool rear end side is a size that can be inserted into the inner peripheral portion of the casing pipe 5. Large diameter section 6A after fitting from the tool tip side
Is welded integrally to the tip of the casing pipe 5. Further, the outer peripheral surface 7 of the device 2
A step 8 is formed at the rear end side of the tool to increase the diameter by one step.
, The tool body 1 is relatively rotatable around the axis O with respect to the casing pipe 5 and the casing top 6, and is integrally formed by the above-mentioned impact force toward the tool tip in the direction of the axis O. It is possible to move forward.

On the other hand, on the outer periphery of the distal end of the device 2, three recesses of the same shape to which the diameter-enlarging bits 3 are respectively mounted are formed so as to open to the distal end surface 9 of the device 2 and the outer peripheral surface 7. Are formed at equal intervals in the circumferential direction. A through-hole 11 is formed in the center of the device 2 along the axis O. The portion of the through-hole 11 on the tool tip side is formed so as to increase in diameter in multiple steps. A female screw portion 12 </ b> A is formed in the periphery to form an attachment hole 12 to which the pilot bit 4 is attached. The tip surface 9 of the device 2 has an inner peripheral portion 9A.
Are formed so as to form a substantially circular shape more than the outer peripheral portion 9B and project one step toward the tool tip side, and a step 9C is formed between the inner and outer peripheral portions 9A and 9B. As shown in FIG. 2, it is formed so as to extend beyond the step 9C to the inner peripheral portion 9A of the tip end surface 9. Further, button-shaped chips 13 made of a hard material such as a cemented carbide are implanted in the outer peripheral portion 9B of the front end surface 9. Also, in the inner peripheral portion 9A of the distal end surface 9, three pin holes 9D are formed around the opening of the mounting hole 12 at equal intervals in the circumferential direction.

The recess 10 is recessed from the front end surface 9 of the device 2 to the rear end side of the tool by one step and arranged perpendicular to the axis O, and from the outer peripheral surface 7 of the device 2 to the inner side of the tool. And successively in the tool rotation direction T, and the bottom surface 10A
Wall 10B-1 that rises vertically from above and intersects the tip surface 9
0G. Here, when viewed from the tool tip side, these wall surfaces 10B to 10G are a wall surface 10B facing the tool rotation direction T side and a wall surface 10D-10 facing the tool outer peripheral side.
F has a wall surface 10D located on the rear side in the tool rotation direction T and is disposed in a direction intersecting each other at an acute angle via a concave arc-shaped wall surface 10C smoothly connected to both wall surfaces 10B and 10D. The wall surface 10D is formed in a convex circular arc shape and smoothly continues to the tool rotation direction T side of the wall surface 10D, and the wall surface 10F is disposed so as to intersect the wall surface 10E and the wall surface 10G facing the rear side in the tool rotation direction T at an obtuse angle. Have been. On the tool rotation direction T side of the bottom surface 10A,
A concave portion 14 that gradually becomes deeper toward the tool outer peripheral side is formed, and a central axis X of a concave arc formed by the wall surface 10C as viewed from the front end side is formed on a bottom surface 10A on the rear side of the concave portion 14 in the tool rotation direction T. A mounting hole 15 having a circular cross section is formed so as to be coaxial.

In the device 2, the through hole 11
Are formed at equal intervals in the circumferential direction. The three exhaust holes 16 are formed at equal intervals in the circumferential direction.
.., And from the middle of the exhaust hole 16 toward the outer periphery of the tool along an imaginary plane P including the center line C of the exhaust hole 16 and the axis O. An exhaust hole 17 having substantially the same diameter as the exhaust hole 16 extending toward the end, and a pair of small-diameter exhaust holes 18 extending toward the tool tip side so as to form a V-shape symmetrical with respect to the virtual plane P. The exhaust holes 18 are opened at the bottom surface 10A of the recess 10 toward the outer periphery of the tool on the wall surface 10E. In the vicinity of the openings of the exhaust holes 16 and 17, cap members 16A and 17A having one or a plurality of small holes penetrating a cylindrical main body are attached. In addition, three exhaust holes 19 branching from the through hole 11 perpendicularly to the through hole 11 and reaching the outer peripheral surface 7 in the radial direction with respect to the axis O avoid the exhaust holes 16 to 18. Are formed at equal intervals in the circumferential direction, and at the middle of the exhaust holes 19, there are formed exhaust holes 20 which branch vertically and extend toward the tip end of the tool.
5 is opened to the bottom surface 15A.

Furthermore, on the outer peripheral surface 7 of the device 2,
Three excavation dust discharge grooves 21 extending parallel to the axis O from the tip end surface 9 and reaching the rear end of the step portion 8 are formed at equal intervals in the circumferential direction. Open at the tool tip side in the tool rotation direction T of the recesses 10... And communicate with the tool outer peripheral side of the recesses 10 and the recesses 14 formed on the bottom surface 10A thereof. The bottom surface 21A of the discharge groove 21 facing the outer peripheral side of the tool is formed by a pair of flat surfaces bent at an obtuse angle in the circumferential direction as shown in FIG. 2, and extends toward the outer peripheral side of the rear end of the tool. The above-described exhaust hole 17 is opened to the bottom surface 21A. The wall surface 21B of the discharge groove 21 facing the rear side in the tool rotation direction T is formed so as to be flush with the wall surface 10G of the recess 10 on the tool tip side. Further, the device 2 is provided with a blind hole 22 extending from the outer peripheral surface 7 toward a tool inner circumferential side along a plane perpendicular to the axis O, and the blind hole 22 is provided with a female screw of the mounting hole 12. At the rear end side of the tool relative to the portion 12A, an opening is provided to intersect the tangential direction of the inner periphery of the mounting hole 12.

Further, the diameter-enlarging bit 3 mounted in the recess 10 has a cylindrical shaft portion 24 perpendicular to the rear end face 23A of the block-shaped main body 23 which can be accommodated in the recess 10. The shaft portion 24 is formed as follows.
By fitting into the mounting hole 15 formed in the bottom surface 10A of the recess 10, the shaft portion 24 and the mounting hole 15 are inserted.
Is rotatable around the central axis X. here,
The main body 23 has a blade shape having a protruding end portion 23B that is one step wider on the side opposite to the shaft portion 24 when viewed from the tool tip side, and a side surface 23C of the main body 23 on the wider side and the main body 23 The side surface 2 is located at the intersection ridge line portion with the tip end surface 23D.
A two-step inclined surface 23E, 23E that retreats in a stepwise manner on the rear end surface 23A side toward the 3C side is formed, and an inclined surface 23F is also formed on the distal end surface 23D side of the protruding end 23B. A large number of button-shaped or columnar chips 25 made of a hard material such as cemented carbide are planted on the inclined surfaces 23E and 23F, the tip surface 23D of the side surface 23C, and the side surface 23C of the tip surface 23D. ing.

The enlarged bit 3 is turned around the central axis X toward the outer periphery of the tool (clockwise in FIG. 2). The side surface 23G opposite to the side 23B is positioned in a state where the diameter is increased by contacting the wall surface 10B facing the tool rotation direction T side of the recess 10 and the side surface 23C is positioned from the outer periphery of the casing pipe 5 in this expanded state. Are also projected to the outer peripheral side of the tool. In addition, this side surface 23C
Are formed so as to form a convex arc surface centered on the axis O in this expanded state. On the other hand, by rotating the tool around the center axis X toward the tool inner circumference side (counterclockwise direction centering on the center axis X in FIG. 2),
The enlarged-diameter bit 3 has a wall surface 10 having a side surface 23H connected to the protruding end portion 23B of the main body 23 facing a tool outer peripheral side of the recess 10.
The main body 23 is positioned on the inner periphery of the casing top 6 in the state of reduced diameter by abutting on the shaft D.
In order not to interfere in the direction, the outer peripheral surface 7 of the device 2 is set within a circle formed by viewing from the tool tip side.
The side surface 23I of the main body 23 opposite to the side surface 23C is formed in a convex arc surface centered on a center axis X which can slide on the concave wall surface 10C of the recess 10. Have been.

Further, in the present embodiment, the length of the shaft portion 24 of the enlarged diameter bit 3 is formed to be slightly longer than the depth of the mounting hole 15 of the concave portion 10, and as a result, as shown in FIG. As described above, in a state where the shaft portion 24 is inserted into the mounting hole 15 and the enlarged diameter bit 3 is mounted, the rear end surface 24A of the shaft portion 24 contacts the bottom surface 15A of the mounting hole 15 while the enlarged diameter bit 3 is mounted.
A slight gap is formed between the rear end face 23A of the main body 23 and the bottom face 10A of the recess 10. Further, the side surface 2 of the distal end surface 23D of the main body 23 of the diameter-enlarged bit 3
The portion on the 3I side is a flat surface 23J on which the chip 25 orthogonal to the central axis X is not implanted.
3J is formed so as to protrude slightly toward the distal end side from the tip 25 implanted in the other portion via the step portion 23K between itself and the other portion of the distal end surface 23D. Furthermore, as described above, the rear end face 24A of the shaft portion 24 is
The flat surface 23J is slightly smaller than the protruding inner peripheral portion 9A of the distal end surface 9 of the device 2 in a state in which the enlarged diameter bit 3 is attached to the concave portion 10 of the device 2 by being brought into contact with the bottom surface 15A of the device 2. It is located at the position where it recedes.

On the flat surface 23J of the distal end surface 23D of the main body 23 of the diameter expanding bit 3, a shaft portion 26 as an engaging portion in the present embodiment is formed so as to protrude toward the tool distal end. . The shaft portion 26 is formed in a disk shape with the center axis X as the center, and is integrally formed on the main body 23 of the enlarged diameter bit 3 coaxially with the shaft portion 15. In the state where the diameter-enlarged bit 3 is attached to the recess 10 as described above, the bit 2 is made to protrude more toward the tool tip than the inner peripheral portion 9A of the tip surface 9 of the device 2 as described above. ing. The stepped portion 23K formed on the distal end surface 23D of the enlarged diameter bit 3 is
When viewed from the tool tip side, in a state where the diameter-increased bit 3 is enlarged, the enlarged diameter bit 3 forms an arc shape centered on the axis O connected to the step 9C formed on the end surface 9 of the device 2. In the state where the diameter-increased bit 3 is reduced in diameter, as shown in FIG. 2, it faces the tool rotation direction T side, and moves rearward in the tool rotation direction T from the tool inner circumference to the tool outer circumference. It is arranged to extend to the side.

On the other hand, in the present embodiment, the pilot bit 4 attached to the attachment hole 12 of the device 2 has a button-like shape made of a hard material such as a cemented carbide on the distal end surface 27A and the outer peripheral surface 27B of the disk-shaped main body 27. A large number of columnar chips 28 are implanted, and a shaft portion 29 to be attached to the attachment hole 12 is formed at the center of the rear end surface 27C of the main body 27. However,
On the outer periphery of the shaft portion 29, the tool tip side, that is, the main body 2
A male screw portion 29A screwed into the female screw portion 12A of the mounting hole 12 is formed on the side of the mounting hole 12, and the male screw portion 29A is formed.
A annular groove 29B is formed at the rear end side of the tool A. The blind hole 29B is formed by screwing the male screw portion 29A into the female screw portion 12A and opening the position of the annular groove 29B in the direction of the axis O to the inner periphery of the mounting hole 12. After being adjusted to the position of 22, the cylindrical portion 30 is inserted into the blind hole 22 and engaged with the annular groove 29 </ b> B, whereby the shaft portion 29 is attached to the attachment hole 12 while being prevented from falling off. The pilot bit 4 is integrally fixed to the device 2 with the rear end surface 27C of the main body 27 being spaced from the front end surface 9 of the device 2.

The body 27 of the pilot bit 4
The tip surface 27A is formed so that the central portion is recessed one step through a concave conical surface. From this central portion, a pair of concave grooves 31, 31 is formed across the axis O toward the tool outer peripheral side. They are formed to extend to opposite sides. On the outer peripheral surface 27B of the main body 27, six grooves 32 extending in the direction of the axis O are formed at equal intervals in the circumferential direction. The grooves 32, 32 are formed so as to communicate with the respective grooves 31 at the outer peripheral ends of the grooves 31, 31, respectively.
Further, an exhaust hole 33 is formed in the pilot bit 4 so as to extend toward the tool tip along the axis O from the shaft portion 29 toward the main body 27. The tool rear end side of the exhaust hole 33 is The through hole 11 is opened at the rear end of the shaft portion 29.
At the tip end side of the tool, and is formed so as to branch into two and open to the inner circumferential side of the tool in the concave grooves 31, 31. Further, similarly to the exhaust holes 16 and 17, a cap member 33A having a large number of small holes penetrating therethrough is also mounted near the opening of the exhaust hole 33 on the tool tip side.

Further, in this embodiment, a spacer 34 is interposed between the rear end surface 27C of the main body 27 of the pilot bit 4 and the front end surface 9 of the device 2. In the present embodiment, the spacer 34 is the device 2 of the tool body 1.
3 and 4 are formed of a metal material having a hardness slightly smaller than that of the metal material forming the pilot bit 4. As shown in FIGS. The outer diameter of the surface 34A is substantially the same as the rear end surface 27C of the main body 27 of the pilot bit 4, while the outer diameter of the rear end surface 34B is attached to the recess 10 of the device 2 from the axis O of the tool main body 1. Shaft portion 26 of enlarged bit 3
Is slightly larger than the outer diameter up to the edge on the outer peripheral side of the tool, and the main body 23 is
Is formed so as to have substantially the same diameter as the arc formed by the stepped portion 23K formed on the distal end surface 23D. In the rear end surface 34B of the spacer 34, three concave holes 35 are formed at regular intervals in the circumferential direction as engaged portions in the present embodiment.

Each of these recesses 35 is formed in such a size that the above-mentioned shaft portion 26, which is an engaging portion of the diameter-enlarging bit 3, can be inserted thereinto. The spacer 34 is formed so as to have a distance equal to the distance to the center axis of the spacer 34. The depth of the recess 35 from the rear end surface 34B of the spacer 34 is determined by bringing the rear end surface 24A of the shaft portion 24 on the tool rear end side of the enlarged diameter bit 3 into contact with the bottom surface 15A of the mounting hole 15 of the device 2. In the state
As shown in FIG. 1, an extremely small gap is defined between the distal end surface of the shaft portion 26 on the tool distal end side of the diameter expanding bit 3 and the bottom surface of the concave hole 35.

At the center of the spacer 34, an insertion hole 36 through which the shaft 29 of the pilot bit 4 is inserted is formed so as to penetrate the spacer 34 along the central axis, and Around the opening of the insertion hole 36 in the end face 34B, three mounting holes 34C for mounting the spring pins 37 are formed, and the spring pins 37 mounted in these mounting holes 34C are formed.
To the inner peripheral portion 9A of the distal end surface 9 of the device 2 as shown in FIG.
Is inserted into the pin holes 9D.
The spacer 34 is positioned in the circumferential direction on the distal end surface 9 of the device 2, and in this positioning state, the shaft portions 26 of the diameter-enlarging bits 3 can be fitted into the concave holes 35.

Further, the spacer 34 has three notches 38 which are cut out so that the outer peripheral portion is depressed toward the inner peripheral side. The notches 38 are formed so as to avoid the concave holes 35.
Are formed at equal intervals in the circumferential direction with an interval between them. These notches 38 are formed so as to cut out the spacers 34 substantially in accordance with the positions and shapes of the recesses 14 formed in the recesses 10 of the device 2 when viewed from the tool tip side in the positioning state. Particularly, in this embodiment, in this positioning state, the wall surface 38A of each notch 38 facing the outer peripheral side of the tool is in contact with the corresponding recess 1.
4 is formed so as to be perpendicular to the virtual plane P including the center line C of the exhaust hole 16 and facing the tool rotation direction T side so as to be parallel to the virtual plane P. The rear wall surface 38C is formed so as to be gradually separated from the virtual plane P toward the tool outer peripheral side, and the recess from the outer periphery of the spacer 34 is reduced from the wall surface 38B toward the wall surface 38C. Is formed.

However, the spacer 34 configured as described above is positioned as described above at the tip of the device 2 in which the diameter-enlarging bit 3 is attached to the recess 10, and
6 is inserted into the concave hole 35, and then the shaft portion 29 of the pilot bit 4 is inserted into the insertion hole 36 and attached to the mounting hole 12 as described above, whereby the rear end face 27C of the main body 27 of the pilot bit 4 is inserted. The front and rear end surfaces 34A and 34B are pressed and sandwiched between the inner peripheral portion 9A of the front end surface 9 of the device 2 and thereby, the tool body 1 of the excavating tool of the present embodiment is assembled. Furthermore, the drilling tool thus configured receives a striking force on the tool tip side while the tool body 1 is rotated in the tool rotation direction T during drilling, so that the drill bit is easily drilled by the pilot bit 4 and crushed. The casing pipe 5 can be built into the drilled hole while being further cut and expanded by the enlarged diameter expanding bits 3... After the excavation is completed, the tool rotation direction when the tool body 1 is excavated is excavated. By rotating in the opposite direction to T to reduce the diameter of the diameter-enlarging bit 3, the tool main body 1 can be pulled out while the casing pipe 5 and the casing top 6 are left in the hole.

Thus, in the excavating tool having the above structure, the rear end face 27C of the main body 27 of the pilot bit 4 is provided.
The spacer 34 provided on the front end of the hole is formed as an engaged portion with a recessed hole 35 protruding from the tool tip side of the enlarged diameter bit 3 and into which the shaft portion 26 as an engaging portion can be inserted. The enlarged diameter bit 3 fits the shaft portion 26 and the concave hole 35, and the shaft portion 24 on the tool rear end side and the concave portion 1 of the device 2.
By being fitted to the mounting hole 15 formed at 0, both ends in the direction of the center axis X are supported, and the tool body 1 is attached to the tool body 1 so as to be rotatable around the center axis X. For this reason, according to the present embodiment, the mounting rigidity of the enlarged diameter bit 3 can be improved, and a sufficient mounting rigidity can be ensured even for a load acting on the main body 23 of the enlarged diameter bit 3 during excavation. Thus, it is possible to prevent the diameter-enlargement bit 3 from rattling or even break the shaft portion 24, and to promote smooth and efficient excavation.

In this embodiment, as described above, the rear end surface 27C of the main body 27 of the pilot bit 4 is
Between the inner peripheral portion 9A of the front end surface 9 of the
The impact force in the direction of the axis O applied to the device 2 during excavation is applied to the main body 27 of the pilot bit 4 from the distal end surface 9 of the device 2 via the spacer 34.
To the rear end face 27C. For this reason, a sufficient impact area from the device 2 to the pilot bit 4 can be ensured, the impact force can be reliably transmitted, the excavation efficiency can be improved, and the pilot bit can be counteracted by the impact force. The reaction acting on the device 2 from 4 can also be stably received by the spacer 34.

Further, with the spacer 34 interposed in this way, the shaft portion 29 of the pilot bit 4 screwed to the mounting hole 12 of the device 2 is tightly tightened in the mounting hole 12 by rotation during excavation. Even if
By removing the spacer 34 by breaking or the like, the shaft portion 29 can be easily loosened, and the advantage that the pilot bit 4 can be easily replaced can be obtained. Moreover, in this embodiment, the spacer 3
4 is formed of a softer material having a lower hardness than the device 2, the enlarged bit 3, and the pilot bit 4, even if an excessive load acts on the tool body 1 during excavation, the spacer 34 having the smallest hardness. Is simply damaged, and by exchanging it, the original state of the tool body 1 can be easily restored.

In this embodiment, the spacer 3
4 is formed with a concave hole 35 as an engaged portion that engages with the shaft portion 26 as an engaging portion on the tool tip side of the diameter-enlargement bit 3. It is possible to avoid a large gap between the flat surface 23J of the main body 23 of the bit 3 and the rear end face 34B of the spacer 34 in which the recess 35 is formed. Can be prevented from entering the space and hindering the smooth rotation and stable support of the diameter-enlarging bit 3. Moreover, by interposing the spacer 34 in this manner, in the present embodiment, even when the pilot bit 4 is screwed and attached to the device 2 as described above, the concave hole 35 is formed. By positioning the spacer 34 in the circumferential direction on the distal end surface 9 of the device 2, the shaft portion 26 of the diameter-enlarged bit 3 can be reliably supported.

However, in this embodiment, the recesses 35 as the engaged portions are formed in the spacers 34 as described above.
For example, by attaching the shaft portion 29 of the pilot bit 4 to the mounting hole 12 of the device 2 by a spline connection or the like and then retaining the shaft portion 29 with the pin 30 or the like, the pilot bit 4 is attached to the device 2 without rotating. Is possible, such a spacer 3
The recess 35 as an engaged portion may be formed directly on the rear end surface 27C of the main body 27 of the pilot bit 4 without the interposition of the pilot bit 4. Further, in the present embodiment, the shaft portion 26 as the engaging portion is formed on the tool tip side of the diameter-enlarging bit 3 and the concave hole 35 as the engaged portion is formed on the rear end surface 34B of the spacer 34. Conversely, a concave hole is formed as an engaging portion on the tool tip side of the enlarged diameter bit 3, and a shaft that can be inserted into the concave hole is formed on the rear end face of the spacer 34 or the main body 27 of the pilot bit 4. It is also possible to form and support the enlarged diameter bit 3.

Further, in this embodiment, notches 38 are formed in the spacer 34 so that the outer peripheral portion of the spacer 34 is recessed toward the inner peripheral side. 34 is positioned in the device 2 and is interposed between the pilot bit 4 and the position and shape of the concave portion 14 formed in the concave portion 10 of the device 2, that is, the enlarged diameter bit 3
Of the device 2 in which the main body 23 of the device 2 is accommodated when the diameter is reduced.
Is formed so as to open toward the tool tip side. Therefore, according to the present embodiment, particularly in the case where a hole is formed in the ground with the tip of the tool body 1 facing downward, the recess 10 of the device 2 after the diameter-enlargement bit 3 is enlarged during excavation. It is possible to prevent excavation dust from accumulating in the space to be cut, and when reducing the diameter of the diameter expansion bit 3 after the excavation is completed, such accumulation of excavation waste causes the main body 23 to accumulate.
To prevent a situation where the accommodation of the
Reducing the diameter of the expanding bit 3 reliably and promptly, and
Can be pulled out from the casing pipe 5.

In this embodiment, a pair of exhaust holes 18 are formed in the bottom surface 10A of the recess 10.
At the time of excavation, a medium for excavating debris such as compressed air supplied to the through hole 11 of the device 2 is ejected from the exhaust holes 18 into the recess 10 through the exhaust hole 16. In this way, the accumulation of excavation debris at the location can be more reliably prevented. By the way, the drilling waste generated during drilling is
These exhaust holes 18, 18 and other exhaust holes 16, 17, 33
The medium is discharged from the groove 21 into the casing pipe 5 by the discharge medium ejected from the casing, and is discharged toward the rear end of the tool. In the present embodiment, the exhaust holes 16, 17, 3
The cap members 16A, 17A, 33A having one or a plurality of small holes penetrating therethrough are mounted in the vicinity of the opening of the exhaust hole 3, so that large drilling debris enters these exhaust holes 16, 17, 33, and the exhaust holes 16 , 17, 33 can be prevented from being blocked.

Further, in the present embodiment, a projection as viewed from the tool tip side is provided between the tip end face 23D on which the tip 25 of the main body 23 of the diameter-enlarged bit 3 is implanted and the flat face 23J on which the shaft portion 26 is provided. An arc-shaped step portion 23K is formed, and this step portion 23K faces the tool rotation direction T side as shown in FIG. 9 is arranged so as to protrude to the outer peripheral portion 9B, which is lowered by one step, so that the diameter of the enlarged bit 3 is reduced toward the rear side in the tool rotation direction T by the rotation of the tool body 1 at the time of excavation. When a resistance acts on the step portion 23K, the diameter expansion bit 3 is rotated in the direction of expanding the diameter around the central axis X due to the resistance, so that the diameter expansion bit 3 can be expanded more quickly. Becomes possible. On the other hand, the stepped portion 23K is arranged in an arc shape centered on the axis O of the tool body 1 in a state where the diameter-expanding bit 3 is expanded. It is possible to avoid an unnecessary load acting on the vehicle.

[0033]

As described above, according to the present invention,
The engaging part provided on the tool tip side of the diameter expanding bit attached to the outer periphery of the tip end of the device is engaged with the engaged part on the pilot bit side attached so as to protrude at the center of the tip of the device to increase the diameter. By supporting the bit, it is possible to secure the mounting rigidity of the enlarged bit and prevent rattling or damage to the enlarged bit due to the load during excavation, etc., and smooth and efficient excavation work Can be encouraged.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a partially cutaway front view of the embodiment shown in FIG. 1 as viewed from a tool tip side (a casing pipe 5 and a casing top 6 are not shown).

FIG. 3 is a front view of a spacer 34 attached to the embodiment shown in FIG.

FIG. 4 is a side sectional view of a spacer 34 shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tool main body 2 Device 3 Diameter expansion bit 4 Pilot bit 5 Casing pipe 6 Casing top 10 Depression 12 Pilot bit 4 mounting hole 13, 25, 28 Chip 14 Depression 15 Mounting hole of diameter expansion bit 3 16, 17, 18, 19, 20, 33 Exhaust hole 23 Body of enlarged diameter bit 3 24 Shaft of enlarged diameter bit 3 26 Shaft (engagement part) of enlarged diameter bit 3 27 Body of pilot bit 4 29 Shaft of pilot bit 4 34 Spacer 35 Depressed hole of spacer 34 (engaged part) 38 Notch O Central axis of device 2 T Rotation direction of device 2 during excavation X Central axis of enlarged diameter bit 3 (rotation axis)

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jinya Hisada 1528 Nakashinta, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Mitsubishi Materials Corporation Gifu Works (56) References JP-A-11-315688 (JP, A) JP-A-3-262891 (JP, A) JP-A-6-10582 (JP, A) JP-A-9-217578 (JP, A) JP-A-11-200753 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) E21B 10/32 E21B 10/36

Claims (3)

(57) [Claims] A diameter-enlarging bit is attached to an outer periphery of a distal end portion of a device which is rotated around a central axis so as to be rotatable around a rotational axis eccentric from the central axis. A disk-shaped pilot bit is attached so as to protrude more toward the tool tip side than the diameter-enlargement bit. A drilling tool, which is engaged with and supported by an engaged portion provided at a rear end side of the tool. 2. A spacer is interposed between a surface of the pilot bit facing the tool rear end and a distal end surface of the device, and the engaged portion is provided on the spacer. The drilling tool according to claim 1, characterized in that: 3. The spacer according to claim 2, wherein a cutout portion is formed on an outer periphery of the spacer so as to be recessed inwardly to avoid the engaged portion. Drilling tools.