JP3331992B2 - 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 An excavating tool of this type is provided at a tip of a device inserted into a cylindrical casing pipe and rotated about a central axis so as to be rotatable about a pivot axis eccentric from the central axis. With a diameter bit attached,
For example, it is proposed in JP-A-63-11789. However, in such an excavating tool, when the device is rotated in the tool rotating direction at the time of excavating, the diameter-enlarging bit is rotated and positioned so that the outer diameter from the central axis increases. Excavation is performed by the rotary impact force applied to the device in this state, and the casing pipe is built into the drilled hole. Also, after the casing pipe is erected with a hole formed to a predetermined depth, the device is rotated in the direction opposite to the tool rotation direction to reduce the diameter of the diameter expansion bit, so that only the casing pipe is removed. The device can be pulled out of the casing pipe while leaving the hole.

[0003]

In the drilling tool constructed as described above, the casing pipe is erected in the drilled hole because the ground on which the hole is to be formed is soft. In this case, it is to prevent the excavated hole from collapsing. However, even with such a drilling tool, in the case of digging a more fragile ground, it becomes difficult to make the drilling hole itself into which the casing pipe is to be built up,
For example, there is a possibility that it is impossible to reliably support the built-in casing pipe unless mortar or cement milk is injected.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a drilling tool that can perform drilling on such a fragile ground while making a hole independent. And

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve such an object, the present invention relates to a device which is rotated around a central axis, and which is provided around a rotation axis eccentric from the central axis. At the time of excavation of the device, an expanding bit whose outer diameter increases from the center axis is attached, and a side facing the tool outer peripheral side at the time of expanding the expanding bit has a circumferential direction. Are formed in a plurality of rows in the rotation axis direction. However, according to such an excavating tool, after the hole is formed by the enlarged diameter bit, the ridge portion formed on the side surface of the enlarged diameter bit facing the tool outer peripheral side is formed by the drilling tool. By sliding against the inner wall, the inner wall of the hole is pressed and crushed with a high surface pressure, so that the hole can be made independent even on a fragile ground.

Here, if the ridge is formed in a spiral shape that is inclined toward the tool tip as it goes toward the rotation direction of the device during excavation, the direction in which the ridge extends and the device The direction in which the diameter-enlarging bit advances while rotating by the rotation hit coincides with each other, and the ridge portion comes into sliding contact with the inner wall of the drilled hole along the extending direction, so that the inner wall is more securely tamped. Can be. Also, if the body part, which expands the diameter-expanding bit at least by the rotation of the device at the time of excavation, is formed so as to form a columnar shape extending in the rotation axis direction, more ridges are formed on the side surface. A portion can be formed, and the inner wall of the drilled hole can be more reliably pressed to achieve its independence.

[0007]

1 to 6 show one 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 of the tool rear end side (right side in FIG. 1) is reduced by one step, and a large diameter portion 6A on 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 portion of the device 2, three recesses of the same shape to which the above-mentioned 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.
A step 9C is formed between the recesses 9B.
Are formed so as to extend beyond the step 9C to the inner peripheral portion 9A of the distal end surface 9 as shown in FIG. further,
Button-shaped chips 13 made of a hard material such as a cemented carbide are implanted on the outer peripheral portion 9B of the distal 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
0E. Here, as shown in FIG. 2, when viewed from the tool tip side, these wall surfaces 10B to 10E
A wall surface 10B facing the tool rotation direction T side and a wall surface 10D facing the tool outer peripheral side are arranged in a direction intersecting each other at an obtuse angle via a concave arc-shaped wall surface 10C smoothly connected to both wall surfaces 10B and 10D. The wall surface 10D facing the tool outer peripheral side and the wall surface 10E facing the rear side in the tool rotation direction T are also arranged so as to intersect at an obtuse angle. On the tool rotation direction T side of the bottom surface 10A, a concave portion 14 is formed which gradually becomes deeper toward the tool outer peripheral side, and the bottom surface 10A on the rear side in the tool rotation direction T with respect to the concave portion 14 is formed.
A mounting hole 15 having a circular cross section is formed so as to be coaxial with the central axis X (the rotation axis of the diameter-enlargement bit 3) of the concave arc formed by the wall surface 10C when viewed from the tool tip side.

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.
0.. further,
In addition, from the through hole 11, three exhaust holes 17 branching perpendicularly to the through hole 11 and reaching the outer peripheral surface 7 in the radial direction with respect to the axis O in the circumferential direction so as to avoid the exhaust hole 16. Exhaust holes 18 are formed at regular intervals, and are further vertically branched from the middle of the exhaust holes 17 and extend to the tool tip side.
The mounting hole 15 is opened at the bottom surface 15A so as to be coaxial.

Further, on the outer peripheral surface 7 of the device 2,
Three excavation dust discharge grooves 19 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 19A of the discharge groove 19 facing the tool outer peripheral side is formed by a plurality of flat surfaces bent at an obtuse angle in the circumferential direction as shown in FIG. The wall surface 19B facing the rear side is formed so as to be located closer to the tool rotation direction T than the wall surface 10E of the recess 10. Further, the device 2 has three blind holes 20 extending from the outer peripheral surface 7 thereof along a plane perpendicular to the axis O toward the inner peripheral side of the tool to avoid the exhaust holes 16 to 18 at equal intervals in the circumferential direction. These blind holes 20 are opened on the tool rear end side of the female screw portion 12A of the mounting hole 12 so as to intersect the tangential direction of the inner circumference of the mounting hole 12. I have.

Further, in the present embodiment, the diameter-enlarging bit 3 mounted in the recess 10 is provided with a main body 21 which can be accommodated in the recess 10 and a vertically projecting rear end face 21A of the main body 21. A large-diameter long-axis cylindrical shaft portion 22 and a small-diameter short-axis disk-shaped shaft portion 23 protruding from the distal end surface 21B of the main body 21 coaxially with the shaft portion 22 are integrally formed. The shaft 23 on the rear end side of the tool is
A is attached to the device 2 so as to be rotatable around the central axis X by being fitted into the attachment hole 15 formed in A. Here, the main body 21 is connected to the distal end surface 21B.
Has a substantially sector shape in which the side opposite to the shaft portion 23 is wider when viewed from the tool tip side, and has a column shape in which the length in the central axis X direction is larger than the maximum dimension of the sector shape formed by the tip surface 21B. A two-stage stepped retreating stepwise toward the rear end face 21A toward the side face 21C is formed at the intersection ridge portion of the formed front end face 21B and the side face 21C of the main body 21 on the wider side. The inclined surfaces 21D, 21D are formed, and these inclined surfaces 21D, 21D, the portion of the tip surface 21B on the inclined surface 21D side, and the tool tip side and the tool rotation direction T side of the side surface 21C are formed of cemented carbide. A large number of button-shaped or column-shaped chips 24 made of a hard material such as are implanted.

However, the diameter-enlarging bit 3 has a central axis X
When the tool 21 is rotated around the outer periphery of the tool (clockwise around the center axis X in FIG. 2), the main body 21 is rotated.
The other side surface 21 </ b> E is positioned in a state where the diameter is increased by contacting the wall surface 10 </ b> B facing the tool rotation direction T side of the concave portion 10. Side, and is formed so as to form a convex arc surface centered on the axis O when viewed from the tool tip side. Conversely, by turning the tool toward the tool inner circumference side (counterclockwise direction centered on the center axis X in FIG. 2) about the center axis X, the diameter-enlarging bit 3
The side face 21F opposite to the side face 21E has a recess 10
The main body 21 is positioned in a state in which the diameter is reduced by contacting the wall surface 10D facing the outer peripheral side of the tool so that the main body 21 does not interfere with the inner periphery of the casing top 6 in the direction of the axis O in this reduced diameter state.
When viewed from the tool tip side, the outer peripheral surface 7 of the device 2 fits within a circle. The side surface 21G of the main body 21 opposite to the side surface 21C 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.

In the present embodiment, the diameter-enlarging bit 3
The length of the shaft portion 22 is slightly longer than the depth of the mounting hole 15 of the recess 10, whereby the shaft portion 22 is inserted into the mounting hole 15 as shown in FIG. With the enlarged diameter bit 3 mounted, the rear end face 22A of the shaft portion 22 abuts against the bottom surface 15A of the mounting hole 15, while the rear end face 21A of the main body 21 of the enlarged diameter bit 3 and the bottom face 10A of the recess 10 are provided. , A slight gap is formed. Further, a portion of the tip end surface 21B of the main body 21 of the diameter-enlarged bit 3 on the side surface 21G side is a tip 24 orthogonal to the central axis X.
Is formed as a flat surface 21H where no step is implanted, and the flat surface 21H is a stepped portion 21I between the flat surface 21H and other portions of the distal end surface 21B.
Is formed so as to protrude slightly to the distal end side from the tip 24 implanted in the other portion through the other portion, and the shaft portion 23 is formed on the flat surface 21H.

Further, as described above, with the rear end surface 22A of the shaft portion 22 abutting against the bottom surface 15A of the mounting hole 15 and the enlarged diameter bit 3 mounted in the recess 10 of the device 2, the flat surface 21H Is disposed at a position slightly retreated from the protruding inner peripheral portion 9A of the distal end surface 9 of the device 2, while the shaft portion 23 protrudes more toward the tool distal end than the inner peripheral portion 9A of the distal end surface 9. It is formed so that. The stepped portion 21 formed on the distal end surface 21B of the diameter-enlarged bit 3
I, when viewed from the tool tip side as shown in FIG. 2, indicates that the device 2
Is formed so as to form an arc centered on the axis O which is substantially continuous with the step 9C formed on the distal end surface 9 of the tool, and when the diameter-enlargement bit 3 is reduced in diameter, the tool rotation direction T side is The tool is arranged so as to extend rearward in the tool rotation direction T from the tool inner circumferential side toward the tool outer circumferential side.

As shown in FIGS. 1 and 3, a projecting ridge 25 extending in the circumferential direction of the tool main body 1 is provided on the side surface 21C of the main body 21 of the enlarged diameter bit 3 in the direction of the central axis X. Are formed so as to be parallel to each other and arranged at equal intervals. In the present embodiment, a plurality of grooves 26 recessed from the side surface 21C are formed on the side surface 21C in the present embodiment, so that a side surface 21C portion is left between the recess grooves 26. As shown in FIG. 4, the cross section has a rectangular shape, and the width between the adjacent ridges 25, 25 in the center axis X direction, that is, the width of the groove 26 is defined. The width is made equal to the width of the ridge 25, and the height of the protrusion, that is, the depth of the groove 26 is smaller than the width of the ridge 25. Further, in the present embodiment, in the state where the diameter-expanding bit 3 is expanded as shown in FIG. 3, these protruding ridges 25 move toward the tool tip side (upward in FIG. 3) toward the tool rotation direction T. It is formed so as to form a helical shape that is tilted toward and twisted about the axis O of the device 2.

In this embodiment, the ridges 25 ...
The above-mentioned side surface 21C of the main body 21 of the enlarged diameter bit 3 in which
As shown in FIG. 3, a concave portion 21J is formed by notching the side surface 21C so as to be recessed by one step in a portion on the tool rotation direction T side. The concave portion 21J has a concave amount from the side surface 21C larger than the depth of the groove 26, and a width of the tool body 1 in a circumferential direction (a left-right direction in FIG. 3) is set at a tool rear end side (a lower side in FIG. 3). ), And consequently, the ridges 25 are formed such that the circumferential width of the ridges 25 becomes smaller toward the tool rear end side. At the same time, the grooves 26 are formed such that the side in the tool rotation direction T is opened in the recess 21J.

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 fitting to the position of 20 and inserting a cylindrical pin 30 into each blind hole 20 to engage with the annular groove 29B, the shaft portion 29 is attached to the mounting hole 12 with being prevented from falling off. The pilot bit 4 has the rear end face 27C of the main body 27 connected to the device 2
With the device 2 spaced apart from the distal end surface 9 of the device 2
It is fixed to the one.

The main body 27 of the pilot bit 4
The tip surface 27A is formed so that its central portion is recessed one step through a concave conical surface, and from this central portion, a plurality of concave grooves 31 are formed so as to radially extend toward the outer peripheral side of the tool. Have been. Also, the outer peripheral surface 2 of the main body 27 is used.
7B also includes a plurality of grooves 32 extending in the direction of the axis O.
Are formed at equal intervals in the circumferential direction, and some of them are formed so as to communicate with the concave groove 31 at the outer peripheral end of the concave groove 31. 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 Opened at the rear end of the shaft portion 29 and communicated with the through hole 11,
At the tool tip side, it is branched into two and formed so as to open to a pair of concave grooves 31, 31 located on the opposite side with respect to the axis O among the concave grooves 31 communicating with the concave groove 32. I have.

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.
5 and 6 are formed of a metal material having a slightly lower hardness than the metal material forming the pilot bit 4 and have a substantially disk-shaped outer shape as shown in FIGS. The outer diameter of the surface 34A is substantially the same as the outer diameter of the main body 27 of the pilot bit 4, while the rear end surface 34A
The outer diameter of B is slightly larger than the outer diameter from the axis O of the tool body 1 to the edge of the shaft portion 23 of the enlarged bit 3 on the outer peripheral side of the tool, and in the state where the enlarged bit 3 is enlarged. It is formed so as to have substantially the same diameter as the arc formed by the stepped portion 21I formed on the distal end surface 21B of the main body 21.

Further, the rear end face 3 of the spacer 34
4B, a recess 35 in which the shaft portion 23 protruding toward the tool tip side of the diameter-enlarging bit 3 can be inserted is provided with a distance equal to the distance from the axis O to the center axis X. And the same number as the shaft portions 23 are formed at equal intervals in the circumferential direction. The depth of the recess 35 from the rear end surface 34B of the spacer 34 is determined by the rear end surface 22A of the shaft portion 22 on the tool rear end side of the diameter-enlargement bit 3.
In a state where the shaft portion 2 is in contact with the bottom surface 15A of the mounting hole 15 as shown in FIG.
An extremely small gap is defined between the front end surface of the third hole 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 portion 29 of the pilot bit 4 is inserted is formed. At the rear end surface 34B, mounting holes 34C are formed. 34
C into the pin hole 9D formed in the inner peripheral portion 9A of the distal end surface 9 of the device 2 by a spring pin (not shown).
Are positioned in the circumferential direction on the distal end surface 9 of the device 2. In this positioning state, the recesses 35... 3 can be fitted and inserted.

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 position and shape 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 the present embodiment, the wall surface 38A of each notch 38 facing the tool outer peripheral side.
The wall surface 38B facing the tool rotation direction T side is formed so as to form an L-shape which is orthogonal to each other.

However, such a spacer 34 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 so that the shaft portion 23 has the recess 3.
The pilot bit 4 is inserted into the insertion hole 36, and the shaft portion 29 of the pilot bit 4 is inserted into the insertion hole 36 as described above.
7 and the inner peripheral portion 9A of the front end surface 9 of the device 2.
Then, the front and rear end surfaces 34A and 34B are pressed and clamped, whereby the tool body 1 of the excavating tool of the present embodiment is assembled. Further, in the excavating tool thus configured, the tool body 1 receives a striking force on the tool tip side while being rotated in the tool rotation direction T during excavation, so that the drill bit is excavated by the pilot bit 4 and is easily crushed. The casing pipe 5 can be built into the hole while the hole is further excavated by the enlarged diameter bits 3... After the excavation is completed, the tool rotation when the tool body 1 is excavated is completed. By rotating in the opposite direction to the direction T to reduce the diameter of the diameter-enlargement bit 3, the tool body 1 can be pulled out while the casing pipe 5 and the casing top 6 are left in the drilled holes.

Thus, in the excavating tool having the above-described configuration, the ridge 25 extending in the circumferential direction as described above is provided on the side surface 21C of the diameter-enlarging bit 3 that is enlarged during excavation and facing the tool outer peripheral side.
Are formed in a plurality of rows in the center axis X direction,
As the tool body 1 rotates and advances, these ridges 25 slide in contact with the inner wall of the drilled hole excavated by the tool, so that the inner wall is higher than the ridges 25. It is pressed by the surface pressure and compacted. For this reason, according to the above-mentioned drilling tool, even if the ground on which a drilling is to be formed is fragile, it is possible to reliably drill an independent drilling, and the casing pipe 5 built in the drilling is formed. Can be stably supported.

In the present embodiment, the ridges 25 are used.
Are formed in a spiral shape that is inclined toward the tool tip side as it goes toward the tool rotation direction T of the device 2 at the time of excavation. Therefore, the ridges 25. As the expanding bit 3 digs a hole while drawing a spiral around the axis O,
The inner wall of the hole is slid in contact with the inner wall of the hole so as to extend along the direction in which the ridge 25 extends. That is, according to the present embodiment, the direction in which the ridge 25 extends and the diameter-enlargement bit 3
Can be made to coincide with the direction in which the hole is advanced while rotating, so that the inner wall of the drilled hole can be more securely tamped, and the inner wall thus tamped with the ridge 25
Can be prevented from being scraped off by the edge of the hole, and a self-standing hole can be formed more stably.

Further, in this embodiment, the ridges 25.
Is formed on the side surface 21C.
It has a columnar shape in which the length in the central axis X direction is larger than the maximum external dimension of the fan shape formed by the tip end surface 21B, and it is possible to secure a large dimension in the central axis X direction of the side surface 21C. Therefore, according to the present embodiment, more ridges 25 can be formed on the side surface 21C, and the inner wall of the hole can be more reliably pressed against the inner wall of the hole, thereby further improving the hole. And the casing pipe 5 can be supported more stably. Furthermore, if mortar or cement milk is injected between the casing pipe 5 built in the drilling and the inner wall of the drilling, the casing pipe 5 can be supported more stably. it can.

In this embodiment, the ridge 25 is
Although the cross section is formed so as to form a square shape as shown in FIG. 4, for example, as shown in a modification shown in FIG.
The cross section may be formed to have a trapezoidal shape whose width gradually becomes narrower toward the outer peripheral side of the tool. However, in this modification, the width between the adjacent ridges 25, 25 is equal to the width of the groove 26 defined between the ridges 25, 25 at the top on the tool outer peripheral side. On the groove bottom side of the groove 26, the width of the groove 26 gradually decreases and the ridge 25
Is smaller than the width. In addition, the height of the protrusion 25 from the groove bottom of the groove 26, that is, the depth of the groove 26 is
The width at the top of the ridge 25 is smaller than the above width.

On the other hand, in the excavating tool of this embodiment,
A recessed hole 35 is formed in a spacer 34 provided on the rear end surface 27C of the main body 27 of the pilot bit 4 so that the shaft 26 protruding from the tool tip side of the enlarged diameter bit 3 can be inserted therein. Therefore, the enlarged diameter bit 3 is used for these shaft portions 2.
6 and the concave hole 35, and the fitting between the shaft portion 24 on the tool rear end side and the mounting hole 15 formed in the concave portion 10 of the device 2, both ends of the central axis X direction are supported. Then, it is attached to the tool body 1 so as to be rotatable around the central 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 a situation in which the diameter-enlarged bit 3 rattles or even break the shaft portion 24, and it is possible to obtain an effect that a smooth and efficient excavation can be promoted. .

Further, in the present embodiment, as described above, the rear end face 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 into 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 or the like can be obtained. Moreover, in the present embodiment, since the spacer 34 is formed of a softer material having a hardness lower than that of the device 2, the diameter expansion bit 3, and the pilot bit 4, an excessive load acts on the tool body 1 during excavation. However, only the spacer 34 having the smallest hardness is damaged, and by replacing the spacer 34, the original state of the tool body 1 can be easily restored.

Further, in this embodiment, since the spacer 34 is formed with the concave hole 35 which engages with the shaft 23 on the tool tip side of the diameter-enlarged bit 3, the shaft 23 is formed. It is possible to avoid a large gap between the flat surface 21H of the main body 21 of the diameter-enlarged bit 3 and the rear end face 34B of the spacer 34 in which the concave hole 35 is formed. It is possible to prevent a situation in which debris or the like enters and hinders 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. There is also obtained an advantage that the spacer 34 can be positioned in the circumferential direction on the distal end surface 9 of the device 2 to reliably support the shaft portion 23 of the enlarged diameter bit 3.

However, in this embodiment, the recess 35 is formed in the spacer 34 in this manner. For example, after the shaft 29 of the pilot bit 4 is attached to the attachment hole 12 of the device 2 by spline coupling or the like, When the pilot bit 4 can be attached to the device 2 without rotating the pilot bit 4 by preventing the pilot bit 4 from rotating by the pin 30 or the like, the recess 35 is inserted into the pilot bit 35 without interposing such a spacer 34. 4 27 body rear end surface 27C
Or may be formed directly. Further, in this embodiment, the shaft portion 23 is formed on the tool tip side of the diameter-enlarging bit 3 and the concave hole 35 is formed on the rear end surface 34B of the spacer 34. 3 can be formed on the front end side of the tool, and a shaft portion that can be inserted into the concave hole can be formed on the rear end surface of the spacer 34 or the main body 27 of the pilot bit 4 to 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 21 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 is formed after the diameter-enlarging bit 3 expands during excavation. It is possible to prevent excavation dust from accumulating in the space to be cut, and when the diameter-expanding bit 3 is reduced in diameter after the end of excavation, such accumulation of excavation waste causes the main body 21 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.

Further, in the present embodiment, a projection as viewed from the tool tip side is provided between the tip end face 21B of the main body 21 of the enlarged diameter bit 3 on which the tip 24 is implanted and the flat face 21H on which the shaft portion 23 is provided. An arc-shaped stepped portion 21I is formed, and the stepped portion 21I faces the tool rotation direction T when the diameter-expanding bit 3 is reduced in diameter, and is lowered by one step in the distal end surface 9 of the device 2. Since it is arranged so as to protrude to the outer peripheral portion 9B, the resistance of the stepped portion 21I toward the rear side in the tool rotation direction T due to the rotation of the tool body 1 during excavation from the state in which the diameter-enlarging bit 3 is reduced in diameter is reduced. When acted, the resistance expanding bit 3 is rotated in the direction of expanding the diameter around the central axis X by receiving this resistance, so that the diameter expansion of the diameter expanding bit 3 can be achieved more quickly. On the other hand, since the stepped portion 21I is arranged in an arc shape centered on the axis O of the tool main body 1 in a state where the diameter-expanding bit 3 is expanded.
Excessive load on the diameter expansion bit 3 due to resistance during excavation can be avoided.

[0036]

As described above, according to the present invention,
By forming a plurality of rows of circumferentially extending ridges in the direction of the rotation axis of the diameter-enlarging bit on the side surface of the diameter-enlarging bit that expands by rotation during excavation of the device and facing the tool outer peripheral side, The ridge slides against the inner wall of the drilled hole excavated by the bit, so that the inner wall can be pressed to squeeze the inner wall. Can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a front view of a state in which two of the three enlarged bits 3 are attached to the device 2 of the embodiment shown in FIG. 1 as viewed from the tool tip side.

FIG. 3 shows a main body 2 of the enlarged diameter bit 3 of the embodiment shown in FIG.
FIG. 1 is a side view of FIG. 1 (shaft portions 22 and 23 are omitted).

FIG. 4 is a cross-sectional view of the ridge portion 25.

FIG. 5 is a front view of a spacer attached to the embodiment shown in FIG. 1;

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

FIG. 7 is a sectional view showing a modified example of the ridge portion 25.

[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, 24, 28 Tip 14 Depression 15 Mounting hole of diameter expansion bit 3 16, 17, 18 Exhaust Hole 21 Body of enlarged diameter bit 3 21C Side surface facing the tool outer peripheral side when body 21 of enlarged diameter bit 3 is enlarged 22, 23 Shaft portion of enlarged diameter bit 3 25 Protrusions 26 Adjacent protrusions 25, 25 Groove defined between 27 27 Body of pilot bit 4 29 Shaft of pilot bit 4 34 Spacer 35 Concave hole of spacer 34 Notch O Center axis of device T Rotation direction of device 2 during excavation X Enlarged bit 3 center axis (rotation axis)

────────────────────────────────────────────────── ─── Continuation of the front page Examiner Takayoshi Fukada (56) References JP-A-5-18177 (JP, A) JP-A 5-125885 (JP, A) JP-A 5-141170 (JP, A) JP-A-5-141171 (JP, A) JP-A-10-231677 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E21B 10/26-10/36

Claims (3)

(57) [Claims] 1. A device that is rotated about a central axis,
An expanding bit that is rotatable about a rotation axis eccentric from the central axis and whose outer diameter increases from the central axis by rotation during excavation of the device is attached, and the expanding bit of the expanding bit is mounted. An excavating tool characterized in that a plurality of rows of circumferentially extending ridges are formed in a side surface facing the tool outer peripheral side in the rotation axis direction. 2. The device according to claim 1, wherein the ridge portion is formed in a spiral shape which is inclined so as to be directed toward a tool tip as the device is rotated in the direction of excavation of the device. Drilling tools. 3. The device according to claim 1, wherein at least a body portion of the diameter-expanding bit whose diameter is enlarged by rotation of the device during excavation is formed in a column shape extending in the rotation axis direction. The drilling tool according to claim 2.