JP2001090464A - Excavator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further strongly attach a pilot bit portion and an enlarged diameter bit to a main body of an excavator in which the pilot bit portion is attached to the front end of the main body and the enlarged diameter bit is attached to the rear end of the same. SOLUTION: An excavator main body 11 having an almost multi-stepped columnar shape which stepwise enlarges in diameter toward the front end thereof, has a cutting blade attached to the front end thereof, to form a pilot bit portion 14, and an installing portion 13 formed on one side of the pilot bit portion 14 closer to the rear end, and a ring-shaped installing member 24 is fitted on the periphery of the installing portion 13 from the rear end, whereby the installing member 24 is installed on the main body 11 in one body. Then, enlarged diameter bits 28 each having a cutting blade attached to the front end of a bit main body 28A are installed at respective locations between the front end of the installing member 24 and a rear end surface 14B of the pilot bit portion 14, in a manner being supported by the pilot bit portion 14 and the installing member 24 and being rotatable on center axes X which are decentered from an axial line O of the main body 11 toward the periphery of the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool in which a pilot bit portion is provided at a front end portion of a tool main body and an enlarged bit is attached to a rear end side of the pilot bit portion.

[0002]

2. Description of the Related Art The inventors of the present invention have proposed such a drilling tool as shown in FIGS. 9 and 10 in Japanese Patent Application No. 9-235246. In the excavating tool shown in these figures, the axis of the tool body 1 is located at the center of the tip of a substantially multi-stage cylindrical tool body (device) 1 whose diameter gradually increases toward the tip side (the left side in FIG. 9). A mounting hole 2 is formed along O, and a number of chips 4 made of a hard material such as cemented carbide are implanted in the mounting hole 2 at the tip of a disc-shaped bit body 3A, and a cutting edge is provided. The pilot bit 3 is mounted by screwing a mounting shaft 3B protruding from the rear end surface of the bit main body 3A. A plurality of recesses 5 are formed on the outer periphery of the distal end portion of the tool body 1, and a support hole having a center axis X eccentric to the outer circumference with respect to the axis O is formed on the bottom surface of these recesses 5. 5A are respectively formed, and in this support hole 5A,
A tip 7 is also implanted at the tip of the bit body 6A, and an enlarged bit 6 provided with a cutting edge is provided.
A shaft portion 6B protruding from the rear end surface of A is fitted and rotatably mounted around the central axis X.

[0003] The excavating tool thus constructed is provided with a hammer (not shown) attached to a shank portion 1A on the rear end side of the tool body 1 to be rotated about an axis O in a tool rotation direction T and to have a tip end in the axis O direction. Receiving the impact force on the side, the enlarged diameter bit 6 is rotated to the rear side in the tool rotation direction T around the central axis X, and is positioned in a state in which the outer diameter from the axis O is enlarged, and the diameter is increased. The cutting edge 7 of the bit 6
A hole is formed in the ground or the like by the cutting blade 4 of the pilot bit 3 and the casing pipe 8 is built into the hole. After the end of the excavation, by rotating the tool body 1 in the opposite direction to the tool rotation direction T, the diameter-enlarging bit 6 rotates in the opposite direction, and the bit body 6A is housed in the recess 5 and the axis line is removed. Since the positioning is performed in a state in which the outer diameter from O is reduced, the drilling tool can be pulled out by leaving the tool body 1 as it is, leaving only the casing pipe 8 in the hole.

[0004]

However, in the drilling tool configured as described above, the pilot bit 3
Is attached to the attachment hole 2 formed at the tip of the tool body 1 by screwing the attachment shaft 3B.
Considering that the concave portion 5 for accommodating the enlarged diameter bit 6 must be formed on the outer periphery of the tip end portion of the tool body 1, the inner diameter of these mounting holes 2 and the outer diameter of the mounting shaft portion 3B are made too large. Therefore, there is a problem that it is difficult to sufficiently secure the mounting rigidity of the pilot bit 3. Further, since the pilot bit 3 is attached by screws as described above, the leading end of the enlarged bit 6 cannot be supported by the rear end face of the bit body 3A of the pilot bit 3, that is, the enlarged bit 6 Is supported only by the shaft portion 6B at the rear end thereof, so that there is a problem that it is difficult to secure sufficient mounting rigidity also for the enlarged diameter bit 6.

The present invention has been made in view of such circumstances, and thus a pilot bit portion is provided at the front end portion of the tool body, and an enlarged diameter bit is attached to the rear end side of the pilot bit portion. It is an object of the present invention to provide an excavating tool in which the pilot bit portion and the enlarged bit can be more firmly provided on the tool body.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention provides a tool body having a substantially multi-stage cylindrical outer shape whose diameter increases stepwise toward the distal end. A pilot bit is provided by providing a cutting blade at the distal end, and a mounting portion is provided at the rear end side of the pilot bit portion, and a ring-shaped mounting member is fitted around the outer periphery of the mounting portion from the rear end side. The enlarged bit having a cutting edge provided at the tip of the bit body is provided between the tip of the attachment member and the rear end face of the pilot bit. And mounted so as to be rotatable around a central axis eccentric to the outer peripheral side from the axis of the tool main body. Therefore, in the excavating tool having such a configuration, the pilot bit portion is provided integrally with the tip portion of the tool main body, so that it is possible to provide the pilot bit portion with high rigidity. Even if the pilot bit portion is integrated with the front end portion of the tool body, it is possible to attach an enlarged-diameter bit to the rear end side of the pilot bit portion by a mounting member inserted from the rear end side of the tool body. Since the enlarged bit can be rotatably supported from the front and rear end sides by the pilot bit portion and the mounting member, it is possible to secure high mounting rigidity also to the enlarged bit.

Here, in order to attach the attachment member to the tool body in this way, one of the above is to form a concave groove and a ridge which are fitted into the outer periphery of the attachment portion and the inner periphery of the attachment member. Formed along the axial direction, an annular groove is formed around the axis on the outer periphery of the tool body on the rear end side of the mounting portion, and an outer diameter larger than the inner diameter of the mounting member is formed in the annular groove. The mounting member is fixed in the circumferential direction of the tool body by fitting the concave groove and the ridge, and is fitted in the annular groove by fitting and attaching the ring-shaped retainer divided in the circumferential direction. The fixed retainer can also be fixed in the axial direction. Further, as another one, a concave groove and a ridge to be fitted with each other are formed along the axial direction on the outer circumference of the mounting portion and the inner circumference of the mounting member, and one groove perpendicular to the axial line is formed. The mounting member is fixed in the axial direction via the stopper by forming the mounting groove extending along the plane of each of the mounting holes and interposing a stopper in the mounting hole defined by the mounting groove. The mounting member can be securely mounted on the mounting portion.

[0008]

1 to 4 show a first embodiment of the present invention.
1 shows an embodiment of the present invention. In the present embodiment, the tool main body 11 is formed in a substantially multi-stage cylindrical shape with an outer diameter centered on an axis O whose outer diameter increases in three stages toward the distal end side (the left side in FIG. 1), and the last stage has a small diameter. Shaft is shank 1
2, the spline grooves 12A are formed on the outer periphery, the middle portion is a mounting portion 13, and the tip portion is formed in a disk shape to be a pilot bit portion 14. The tool body 11 is rotated around the axis O in the tool rotation direction indicated by the symbol T in the figure during excavation by attaching a hammer (not shown) to the shank portion 12 via the spline grooves 12A. At the same time, it receives a striking force toward the tip side in the direction of the axis O and is subjected to excavation. In the tool body 11, a supply hole 15 for compressed air or the like is formed along the axis O from the rear end toward the front end side, and the supply hole 15 is formed in the pilot bit portion 14 on the front end side. The bifurcated portion is divided into two, and an axis O
Are opened on opposite sides of each other.

The distal end surface 14A of the pilot bit portion 14 is formed in a mortar shape with a concave central portion, and a pair of ejection grooves for compressed air or the like extends from the central portion to the outer periphery of the concave distal end surface 14A. The supply holes 15 are formed so as to extend in the diameter direction with respect to the axis O, and the supply holes 15 branched into two are opened in the bottom surfaces of these ejection grooves 16, 16, respectively. Further, on the outer periphery of the pilot bit portion 14, there are formed six strips of excavated dust discharge grooves 17 extending in parallel with the axis O at equal intervals in the circumferential direction. The distal ends of the pair of discharge grooves 17, 17 are located at the ejection grooves 16, 1.
6 is communicated with the outer peripheral end. A large number of chips 18 made of a hard material such as cemented carbide are implanted on the distal end surface 14A of the pilot bit portion 14 and on the distal end side of the outer peripheral surface so as to avoid the ejection groove 16 and the discharge groove 17. The cutting edges of the pilot bit portion 14 are formed by the tips 18. In the rear end face 14B of the pilot bit portion 14, there are provided three support holes 19 having a circular cross section centered on a central axis X eccentric to the outer peripheral side with respect to the axis O in the present embodiment. Is formed.

On the other hand, on the outer peripheral surface of the mounting portion 13, three concave grooves 20 extending in parallel with the axis O over the entire length of the mounting portion 13 are formed. It is formed at equal intervals according to the position. These concave grooves 20 ...
In the present embodiment, as shown in FIG. 3, an arc-shaped bottom surface 20 </ b> A that is recessed one step from the outer peripheral surface to the inner peripheral side and protrudes toward the outer peripheral side from the outer peripheral surface of the mounting portion 13, and extends parallel to the outer peripheral side from the bottom surface 20 </ b> A. It is defined by a pair of wall surfaces 20B, 20B, and is formed to be symmetrical with respect to a plane including the axis O and the central axis X, respectively. Further, on the immediately rear end side of the mounting portion 13, an axis O is provided between the spline groove 13A of the shank portion 12 in the direction of the axis O.
An annular groove 21, which is open in a U-shape on the outer peripheral side in a cross section including, a male screw portion 22, and an opening in a U-shape cross section on the outer peripheral side with a smaller width and depth than the annular groove 21 And the outer diameter of the male screw portion 22 is smaller than the diameter formed by the bottom surface 20A of the concave groove 20 of the mounting portion 13 around the axis O. At the same time, the diameter of the valley is made larger than the outer diameter of the shank portion 12, and the groove depth of the annular groove 21 and the annular groove 23 is made larger than the depth of the valley of the male screw portion 22.

A ring-shaped mounting member 24 is mounted on the outer periphery of the mounting portion 13 by fitting its inner peripheral portion from the rear end side of the tool body 11. This mounting member 24 is
The length in the direction of the axis O is slightly longer than the length of the mounting portion 13, and the outer diameter thereof is also slightly larger than the outer diameter of the pilot bit portion 14. On the inner peripheral portion to be fitted are formed three protruding ridges 25 which can be respectively fitted into the concave grooves 20. That is, in the present embodiment, as shown in FIG. 3, each protruding ridge 25 has a concave-arc-shaped top surface 25A that can be in close contact with the bottom surface 20A of the concave groove 20, and extends from the top surface 25A to the outer peripheral side and With the side surfaces 25B, 25B parallel to each other capable of closely adhering to the wall surfaces 20B, 20B, the ridge 25 and the concave groove 20 are fitted to each other so that the mounting member 24 is mounted on the mounting portion 13, and the axis is O and the central axis X
Are formed symmetrically with respect to a plane including

Further, on the outer peripheral side of the distal end portion of the mounting member 24, a concave portion 26 opening on the distal end surface and the outer peripheral surface of the mounting member 24 has a tool rotation direction T around the central axis X in the above-described mounting state. Is formed to extend to the side,
A support hole 27 having a circular cross section with a larger inner diameter than the support hole 19 is formed around the center axis X, that is, coaxially with the support hole 19, on a bottom surface 26 </ b> A facing the distal end side of each recess 26. I have. Then, in the above mounting state, the rear end face 14B of the pilot bit portion 14 and the mounting member 2
In the concave portion 26 located between the front end portion and the front end portion, the support shafts 28B and 28C each having a circular cross section are coaxially protruded from the front and rear end surfaces on one side of the block-shaped bit main body 28A. 28, the support shaft 28B on the front end side is inserted into the support hole 19 and the support shaft 28C on the rear end side is inserted into the support hole 27 so as to be rotatable around the central axis X. I have. Also, the bottom surface 26 of the concave portion 26
From A to the distal end side, a concave arc-shaped wall surface 26B smoothly connected from the inner periphery of the support hole 27 to the distal end side and facing the tool rotation direction T side and the outer peripheral side, and an outer peripheral side of the wall surface 26B. Wall surface 2 that extends in smooth contact and faces tool rotation direction T
6C and a convex arc-shaped wall surface 26D centered on an axis O extending in the tool rotation direction T side in smooth contact with the inner peripheral side of the wall surface 26B are formed.

The enlarged diameter bit 28 is formed so that the bit main body 28A is supported by the support shaft 28 when viewed in the central axis X direction.
The bit body 28A has a blade shape that gradually widens from the one side where the B and 28C are formed to the other side opposite to the one side, and the one side of the bit main body 28A is supported. A tip 29 made of a hard material such as a cemented carbide is implanted on the tip surface on the other side while being formed in a convex arcuate shape smoothly connected to the outer peripheral surface of the shaft 28C. The cutting edge of the diameter-enlarging bit 28 is formed. The enlarged bit 28 is rotated in the tool rotation direction T at the time of excavation to rotate around the central axis X rearward in the tool rotation direction T, so that the bit body 28A
2 is in close contact with the wall surface 26C of the concave portion 26, and is positioned in a state where the outer diameter from the axis O is enlarged as shown in FIG.
By rotating in the tool rotation direction T side by being rotated in the opposite direction, the bit main body 28A is housed in the concave portion 26 in close contact with the wall surface 26D,
The outer diameter from the axis O is set smaller than the outer diameter of the mounting member 24. In addition,
On the outer peripheral surface of the mounting member 24, three excavated swarf discharge grooves 30 communicating with the recesses 26 in the tool rotation direction T and extending in parallel with the axis O are also formed at equal intervals in the circumferential direction. .

As shown in FIG. 1, the mounting member 24 externally fitted to the mounting portion 13 has its front end abutting against the rear end surface 14B of the pilot bit portion 14, and its rear end surface 24A is attached to the mounting portion 13 as shown in FIG. Is slightly projected from the rear end face into the annular groove 21. Retainers 31, 31 are attached to the annular groove 21, and the rear end face 24A is formed.
By being interposed between the annular groove 21 and the wall surface 21A facing the distal end side, it is also fixed to the mounting portion 13 in the direction of the axis O and integrated with the tool body 11. Here, as shown in FIG. 4, the retainers 31, 31 each include a ring having a rectangular cross section having an inner diameter whose inner peripheral portion can be fitted into the annular groove 21.
In the present embodiment, the shape is divided into two in the circumferential direction by a plane extending in the diametrical direction, and the outer diameter is larger than the inner diameter of the mounting member 24, and is fitted into the annular groove 21 from the outer peripheral side. Attached. Further, the retainers 31, 3 attached to the annular groove 21 in this manner.
1 is a screw ring 32 formed with a cylindrical wall portion 32A fitted to the outer periphery of the retainers 31, 31;
A snap ring 33 is attached to the annular groove 23 on the rear side of the male screw portion 22 to prevent the screw ring 32 from coming off.

In the drilling tool configured as described above, the pilot bit 14 is provided at the tip of the tool body 11 in the same manner as the above-mentioned conventional drilling tool.
Although the enlarged diameter bits 28 are rotatably attached to the rear end side of this, the enlarged diameter bits 28 are attached to the attachment portion 13 from the rear end side of the tool body 11 by the attachment member 2.
4, the pilot bit portion 14 can be formed integrally with the tool body 11,
Therefore, it is possible to give high rigidity to the pilot bit portion 14. For this reason, the striking force and the rotational force given to the tool main body 11 from the hammer can be reliably transmitted to the pilot portion 14, and the cutting edge can be used to excavate the ground or the like, and the excavation efficiency can be improved. Moreover, in the excavating tool having the above-described configuration, the support shaft 28C on the rear end side is inserted into the support hole 27 of the mounting member 24, and the support shaft 28B on the front end side is also connected to the pilot bit portion 14 with respect to the enlarged bits 28. Is inserted into the support hole 19 of
That is, since the bit main body 28A is supported and attached from both front and rear ends, high support rigidity can be secured, and the excavation efficiency can be further improved.

In the present embodiment, the diameter-enlarging bit 2
8 is held, and the mounting member 24 that is fitted and mounted in the mounting portion 13 is attached to the concave groove 2 on the outer periphery of the mounting portion 13.
And the retainer 31 which is fixed around the axis O by fitting the ridges 25... On the inner periphery of the mounting member 24 and which is fitted into the annular groove 21 formed on the rear end side of the mounting portion 13. , 31 fixed in the direction of the axis O,
Therefore, the load acting on the diameter-enlargement bits 28 as a reaction force of the rotational force during excavation to the rear side in the tool rotation direction T moves from the ridge 25 of the mounting member 24 to the tool rotation direction T side of the concave groove 20. The load acting on the enlarged diameter bit 28 toward the rear end in the axial direction O by the facing wall surface 20B and as a reaction force of the striking force is applied to the annular groove 21 from the mounting member 24 via the retainers 31, 31. Each of the loads is received by the wall surface 21A facing the distal end side, that is, these loads are eventually received by the tool body 11. For this reason, according to this embodiment, it becomes possible to hold the enlarged bits 28... Without changing from the conventional excavating tool in which the enlarged bits are directly held by the tool body. In addition to the fact that the enlarged diameter bit 28 is also supported on the tip end side, the supporting rigidity can be ensured more reliably.

Further, in the present embodiment, concave grooves 20 are formed on the outer periphery of the mounting portion 13 and ridges 25 are formed on the inner periphery of the mounting member 24 so that they are fitted to each other.
The concave grooves 20 and the ridges 25 form a central axis X and an axial line which are the rotation centers of the enlarged bits 28 in the circumferential direction of the tool body 11 with the mounting member 24 mounted on the mounting portion 13. O is formed symmetrically with respect to a plane including O. Therefore, according to the present embodiment, the mounting member 2
4 and the inner circumference of the mounting member 24, a relatively large thickness can be ensured by the ridge 25, so that the support holes 27 are provided as in the present embodiment.
And, the diameter of the support shaft 28C inserted into the support hole 27 is increased to further secure the mounting rigidity of the enlarged diameter bit 28, or the outer diameter of the mounting portion 13 while securing the mounting rigidity of the enlarged diameter bit 28 in this way. And the rigidity of the pilot bit portion 14 at the tip thereof can be further improved.

In this embodiment, as shown in FIG. 3, the circumferential width of the concave groove 20 and the ridge 25 is larger than the circumferential width between the adjacent concave grooves 20 and the ridge 25. Is also small, so that the concave groove 2
0 indicates that a ridge 25 is formed on the inner periphery of the mounting member 24. From a different point of view, a portion between the concave grooves 20 is a ridge, and a portion between the ridges 25 is Since the groove may be a groove, the groove and the ridge may be located on either side of the outer periphery of the mounting portion or the inner periphery of the mounting member as long as they can be fitted to each other. In the present embodiment, the retainer 3
Although 1 has a half-split ring shape, it may have a ring shape divided into three or more in the circumferential direction.

Next, FIG. 5 to FIG. 8 show a second embodiment of the present invention, and the first embodiment shown in FIG. 1 to FIG.
The same reference numerals are assigned to the same parts as those of the embodiment, and the description is omitted. In the second embodiment, the tool main body 41 has substantially the same cross-sectional shape from the rear end shank portion 42 to the middle mounting portion 43, and only the front end side pilot bit portion 44 has a one-step diameter increase. It is a two-stage multi-stage cylindrical shape having a disc shape and a plurality of (eight in this embodiment) spline grooves 42A of the shank portion 42.
Extend in parallel to the axis O to reach the rear end surface 44A of the pilot bit portion 44 to form a concave groove 45 on the outer periphery of the mounting portion 43. Here, in the present embodiment, the spline grooves 42A and the concave grooves 45 each have a substantially trapezoidal shape in which the cross section orthogonal to the axis O becomes narrower toward the inner peripheral side, and are circumferentially adjacent grooves. They are formed at equal intervals in the circumferential direction so that the wall surfaces are parallel to each other. In addition, the portion of the concave grooves 45 connected to the rear end face 44A is formed so as to be cut off to the outer peripheral side as shown in FIG. Further, on the outer periphery of the mounting portion 43 on the shank portion 42 side, a mounting groove 46 having a groove depth deeper than the concave groove 45 having a “U” shape whose cross section including the axis O is open on the outer peripheral side. Are formed in a ring shape so as to orbit around the axis O along one plane P orthogonal to the axis O.

On the other hand, the inner periphery of the attachment member 47 attached to the attachment portion 43 is inserted into the attachment portion 43 from the rear end side of the tool body 41 through the spline grooves 42A of the shank portion 42. The spline grooves 42A and the concave grooves 45 are fitted in the concave grooves 45 in the circumferential direction.
... (ie, eight in this embodiment) as many ridges 48
... are formed. Therefore, these ridges 48 ...
The cross section has a substantially square shape having side surfaces that can be in close contact with mutually parallel wall surfaces of the concave grooves 45 adjacent in the circumferential direction. The protruding ridges 48 are also formed so as to be cut on the outer peripheral side at the tip side in accordance with the cut-out of the concave grooves 45. Further, the mounting member 47 is attached to the position of the plane P in which the mounting groove 46 is formed in a state where the mounting member 47 is mounted on the mounting portion 43, and a cross section along the plane P is shown in FIG. Extending from the outer periphery of the mounting member 47 to the inner peripheral side to open to the inner peripheral portion of the mounting member 47, and extending around the semi-periphery substantially along this inner peripheral portion, then extending to the outer peripheral side and opening to the discharge groove 28.
A letter-shaped hole 49 is formed.

The U-shaped hole 49 has a circular cross-section from the outer periphery to the inner periphery of the mounting member 47 as shown in FIG. The part that makes a half-turn around the mounting portion 43 has a groove width that is the same as the mounting groove 46 of the mounting portion 43 and a groove depth that is greater than the protruding height of the protruding ridge 48. Groove 5
Since the mounting grooves 46 and 50 are overlapped in the mounting state described above, a mounting hole 51 having a rectangular cross section is provided between the mounting portion 43 and the mounting member 47 so as to include a fitting portion between them. In the cross section along the plane P, the mounting member 51 is defined so as to make a substantially half circumference. The square formed by the cross section of the mounting hole 51 extends from the outer circumference of the mounting member 47 of the U-shaped hole 49 to the inner circumference. The cross-section of the leading part is inscribed in a circle formed by the part or has a smaller shape and size. In the mounting state, a plurality of columnar stoppers 52 each having a rectangular shape whose cross section including the center line can be fitted into the U-shaped hole 49 including the mounting hole 51 into the rectangular shape formed by the mounting hole 51. Are sequentially inserted so that this center line is parallel to the axis O, and further, snap rings 53 are attached to both openings on the outer peripheral side of the attachment member 47 of the U-shaped hole 49 to prevent the U-shaped holes 49 from coming off. The mounting member 47 is engaged with the mounting portion 43 in the direction of the axis O and fixed by the stopper 52 inserted into the mounting hole 51 and interposed between the mounting grooves 46 and 50.

Therefore, in the excavating tool according to the second embodiment having the above-described configuration, the mounting member 47 to which the enlarged diameter bits 28 are mounted is inserted into the mounting portion 43 from the rear end side of the tool body 41. As a result, the pilot bit portion 44 at the tip can be formed integrally with the tool main body 41 to improve its rigidity, and the diameter-enlarged bit 28 is also supported from both front and rear ends to be high. Since the mounting rigidity can be ensured, it is possible to reliably transmit the rotary impact force given from the hammer and to promote efficient excavation. Also in the present embodiment, the tool body 41
Mounting groove 46 formed on the outer periphery of mounting portion 43 and mounting member 4
The stoppers 52 are interposed in the mounting holes 51 defined by the mounting grooves 50 formed on the inner periphery of
The mounting member 47 is fixed in the direction of the axis O, and the load acting on the mounting member 47 from the diameter-enlarging bits 28 during excavation is eventually received by the tool body 41 via the stoppers 52. It is possible to reliably support the excavating bits 28... Without changing the bits from the conventional excavating tools directly attached to the tool body.

In the second embodiment, as described above, the mounting hole 51 is formed to have a rectangular cross section, and the columnar stoppers 52 are mounted and interposed in the mounting hole 51, thereby mounting the mounting member. The fixing groove 47 is fixed in the direction of the axis O. For example, the mounting grooves 46 and 50 are formed in an arc shape in cross section, and the mounting hole 51 is defined to have a circular cross section having the same diameter as the U-shaped hole 49. So that the U-shaped hole 4
9 to load a spherical stopper,
Alternatively, a flexible linear member such as a wire rope or a metal wire wound in a coil shape is inserted in a U-shape following the U-shaped hole 49 to serve as a stopper, and the mounting portion 43 and the mounting member 47 may be interposed. Also,
Depending on the case, the fixing by the stopper and the fixing by the retainer as in the first embodiment may be used together.

[0024]

As described above, according to the present invention,
By forming the pilot bit portion integrally with the tip of the tool body, the rigidity of the pilot bit portion can be improved, and the mounting member is inserted into the mounting portion on the rear end side from the rear end side of the tool body. Thus, by supporting and attaching the enlarged diameter bit between the pilot bit portion and the mounting member at the front and rear ends, it is possible to secure high support rigidity also to the enlarged diameter bit.
Efficient excavation can be achieved by reliably transmitting the rotational impact force and the like applied to the tool body.

[Brief description of the drawings]

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

FIG. 2 is a front view of the first embodiment shown in FIG. 1 as viewed from a distal end side.

FIG. 3 is a sectional view taken along line YY in FIG.

FIG. 4 is a sectional view taken along the line ZZ in FIG. 1;

FIG. 5 is a side sectional view showing a second embodiment of the present invention.

FIG. 6 is a front view of the second embodiment shown in FIG. 5, as viewed from the distal end side.

FIG. 7 is a sectional view taken along the line YY in FIG.

8 is a sectional view taken along the line ZZ in FIG.

FIG. 9 is a side sectional view showing a conventional excavation tool.

FIG. 10 is a front view of the excavating tool shown in FIG. 9 as viewed from a tip end side.

[Explanation of symbols]

 11, 41 Tool body 13, 43 Attachment part 14, 44 Pilot bit part 18, 29 Tip 19, 27 Support hole 20, 45 Concave groove 21 Annular groove 24, 47 Attachment member 25, 48 Protrusion 28 Large diameter bit 28B, 28C Support shaft 31 Retainer 32 Screw ring 33, 53 Snap ring 46, 50 Mounting groove 49 U-shaped hole 51 Mounting hole 52 Stopper O Axis of tool body 11, 41 T Tool rotation direction during excavation X Center axis of enlarged diameter bit 28

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Fujimori 1528 Nakashinda, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture F-term in Mitsubishi Materials Corporation Gifu Works (reference) 2D029 EB04 PA02

Claims (3)

[Claims] 1. A cutting tool is provided at a front end of a substantially multi-stage cylindrical tool body whose diameter gradually increases toward a front end side to form a pilot bit portion, and a rear end of the pilot bit portion is provided. A mounting portion is provided on the side, and a ring-shaped mounting member is fitted and mounted on the outer periphery of the mounting portion from the rear end side, and the front end portion of the mounting member and the rear end surface of the pilot bit portion are connected to each other. A large diameter bit having a cutting edge provided at the tip of the bit body is supported by the pilot bit and the mounting member, and is rotatable about a central axis eccentric to the outer peripheral side from the axis of the tool body. A drilling tool attached to a drilling tool. 2. An outer periphery of the mounting portion and an inner periphery of the mounting member are formed along the axial direction with a concave groove and a ridge to be fitted to each other, and are located on a rear end side of the mounting portion. An annular groove orbiting around the axis is formed on the outer periphery of the tool body, and a ring-shaped retainer divided in a circumferential direction having an outer diameter larger than the inner diameter of the mounting member is fitted into the annular groove and attached. 2. The method according to claim 1, wherein
A drilling tool according to. 3. An outer periphery of the attachment portion and an inner periphery of the attachment member are formed with a groove and a ridge to be fitted to each other along the axial direction, and one of the grooves is perpendicular to the axis. The excavating tool according to claim 1, wherein mounting grooves extending along a plane are formed, and a stopper is interposed in the mounting hole defined by the mounting grooves.