JP2001140578A - Drilling tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lock and fit a ring bit to the tip of a casing pipe on the tip side in the axial direction rotatably and very easily without complicating a structure in a drilling tool of the double tube type bit. SOLUTION: The ring bit 9 is fitted to the tip of the casing pipe 1 rotatably around the axis O, and an inner bit 10 is fitted to the tip of an inner rod 6 inserted into the casing pipe 1 couplably around the axis O with the ring bit 9. The casing pipe 1 and the ring bit 9 are coupled wit their inner and outer peripheries faced to each other, and annular grooves 11, 13 extending around the axis O are formed on the opposite inner and outer peripheries respectively. A locking member 15 elastically deformable in the radial direction relative to the axis O is inserted in an annular hole 14 formed by coinciding with the annular grooves 11, 13 each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a so-called double-pipe type bit in which a ring bit is attached to the tip of a casing pipe and an inner bit is attached to the tip of an inner rod inserted into the casing pipe. It relates to a drilling tool.

[0002]

2. Description of the Related Art A drill bit of this type is disclosed, for example, in Japanese Utility Model Publication No. 7-43264, in which a ring bit is rotatably attached to a tip of a casing pipe, and an inner bit is attached to a tip of an inner rod. And an inner rod, which is provided with a linkage that is slidable in the axial direction of the casing pipe and transmits rotation of the inner rod to a ring bit. Here, in the above-mentioned linking portion of the excavating tool described in this publication, a locking pin is fixed to the inner wall of the ring bit and is engaged with an outer peripheral groove formed on the outer periphery of the inner bit. The inner rod and the ring bit are integrally rotated about an axis, and the inner rod and the inner bit can move relatively to the casing pipe and the ring bit in the axial direction.

However, in such a drilling tool, the inner bit is provided with a rotational force around the axis from the inner rod and a hitting force toward the axial end, while the ring bit is provided with only a hitting force from the casing pipe. In addition to the rotation of the inner bit and the rotation of the inner bit, the ground is excavated by the rotational impact of the inner bit and the ring bit, and a casing pipe is built into the drilled hole. After the excavation,
By retracting the inner rod to the rear end side in the axial direction, the locking pin is disengaged from the outer peripheral groove of the inner bit, and the inner rod can be pulled out together with the inner bit while the ring bit and the casing pipe remain in the drilled hole. .

[0004]

In the case of such a drilling tool, when a trouble such as jamming occurs during the excavation, the inner rod is retracted once together with the inner bit to eliminate the trouble, and then these troubles are re-established. Excavation may be continued by advancing the inner rod and the inner bit. However, if the locking pin of the ring bit comes off from the outer peripheral groove of the inner bit during the retreat, the next time the inner bit is advanced again to continue excavation, the locking pin is inserted into the outer peripheral groove. It is difficult to advance the inner bit after adjusting the rotational position of the inner bit so that the inner bit is securely fitted.When the inner rod and the inner bit are advanced, the tip of the inner bit is It may hit the rear end.

However, in the above-mentioned conventional excavating tool, the ring bit is only rotatably attached to the tip of the casing pipe, and is attached so as to engage with the casing pipe toward the tip in the axial direction. Therefore, when the inner bit is advanced together with the inner rod with the tip of the inner bit being in contact with the rear end of the locking pin on the inner periphery of the ring bit, the ring bit is pushed out by the inner bit so that the ring bit is pushed out. There is a possibility that it will be detached from the tip of the casing pipe, and it will not be possible to continue the excavation thereafter. On the other hand, in order to solve such a problem, there has been considered an excavation tool in which the ring bit is rotatable at the tip of the casing pipe and can be attached in a state of being locked at the tip in the axial direction, Even with such an excavating tool, there is a possibility that a new problem may occur such that the structure becomes complicated or the operation of attaching the ring bit to the tip of the casing pipe becomes complicated.

The present invention has been made under such a background, and in the above-described double-pipe type bit drilling tool, the ring bit is rotatably attached to the tip of the casing pipe and is attached to the tip in the axial direction. An object of the present invention is to provide an excavating tool which can be mounted very easily without complicating the structure when stopping and mounting.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve such an object, the present invention provides a cylindrical casing pipe having a ring bit rotatable around the axis of the casing pipe. Attached to
At the tip of the inner rod that is inserted into the casing pipe and rotated around the axis, an inner bit is inserted into the inner periphery of the ring bit and is attached to be able to engage with the ring bit around the axis. In the excavation tool, the casing pipe and the ring bit are
The inner and outer peripheral surfaces of the casing pipe and the ring bit opposing each other are fitted with the inner and outer peripheral surfaces facing each other, and annular grooves extending around the axis are formed on the inner and outer peripheral surfaces of the facing casing pipe and the ring bit. The ring bit is locked to the casing pipe in the axial direction by interposing a locking member elastically deformable in the radial direction with respect to the axis in the defined annular hole.

Accordingly, in the excavating tool having such a configuration,
The ring bit is attached to the end of the casing pipe in a state where the ring bit is locked to the tip end side in the axial direction while being rotatable at the tip end of the casing pipe by the locking member interposed in the annular hole. And
Since the locking member is elastically deformable in the radial direction with respect to the axis, when the casing pipe and the ring bit are inserted and attached, they are formed on one outer peripheral surface of the casing pipe and the ring bit. Attach the locking member to the annular groove formed on the other inner peripheral surface while attaching the locking member to the annular groove and elastically deforming it into a reduced diameter state, or vice versa. When the other is fitted and inserted while elastically deforming the expanded state, the locking member returns to its original state due to its elasticity when the annular grooves coincide with each other to define an annular hole. It is interposed in the annular hole. Therefore, according to the excavating tool having the above configuration, it is possible to attach the ring bit to the end of the casing pipe very easily with a relatively simple structure.

Here, in order to further facilitate the attachment of the ring bit to the tip of the casing pipe, the annular groove on one of the inner and outer peripheral surfaces of the casing pipe and the ring bit opposed to each other is provided in the annular groove. When the locking member is mounted, it is desirable to form a chamfered inclined surface on the other peripheral surface at the end on the side where the casing pipe and the ring bit are inserted. By simply inserting the ring bit and the casing pipe, the locking member mounted on the annular groove on one peripheral surface is elastically expanded and contracted so as to be guided by the inclined surface formed on the other peripheral surface. be able to. When the inner bit is made to be able to abut on the ring bit toward the axial end, the axial force applied to the inner rod during the excavation is transmitted from the inner bit to the ring bit. And more efficient excavation can be promoted.

[0010]

FIG. 1 to FIG. 3 show an embodiment of the present invention. In the present embodiment, the casing pipe 1 has a cylindrical casing top 3 at the end of a tubular pipe body 2.
Are mounted coaxially by welding, and an inner rod 6 having a stabilizer 5 attached to the tip of a relay rod 4 is coaxially mounted on the inner periphery of the casing pipe 1 with the central axis O of the casing pipe 1. The inner rod 6 is also inserted into the rear end of the intermediate rod 4 if necessary through a sleeve 7 to be connected to the intermediate rod 4. The rod 6 is connected to a shank rod 8 of a drifter that applies a rotational force about the axis O and a striking force toward the tip side in the axis O direction. A ring bit 9 is attached to the tip of the casing top 3 at the tip of the casing pipe 1, and an inner bit 10 is attached to the tip of the stabilizer 5 at the tip of the inner rod 6.
It is inserted in the inner circumference of.

Here, the casing top 3 is formed such that its rear end is reduced in diameter by one step in both the inner and outer diameters with respect to the front end, and its rear end is gradually increased in diameter toward the rear end. A tapered portion 3A is formed, the rear end of which is inserted into the inner periphery of the pipe body 2 at the foremost end, and the rear end of the front end portion is welded to the front end of the pipe body 2 by welding. Installed. The tip of the casing top 3 has an inner and outer diameter that is substantially equal to the inner and outer diameters of the pipe body 2, and the tip of the inner peripheral surface of the tip is gradually increased in diameter toward the tip. An inclined surface 3B chamfered into a tapered surface shape is formed. Further, on the inner peripheral surface of the distal end portion of the casing top 3, the inner peripheral surface is wrapped around the axis O substantially at the center of the distal end portion on the rear end side of the inclined surface 3 </ b> B in the direction of the axis O. Thus, the annular groove 11 is formed. In the annular groove 11, the position of the groove bottom is made substantially equal to the position of the tip of the inclined surface 3B which is the largest diameter in the radial direction with respect to the axis O, and the width in the axis O direction is sufficiently larger than the groove depth. In a cross section including the axis O, as shown in FIG. 2, the cross section has a “U” shape which is flattened in the radial direction and opens on the inner peripheral side.

The outer peripheral surface of the rear end of the ring bit 9 attached to the distal end of the casing top 3 has an outer diameter that can be inserted into the inner periphery of the distal end of the casing top 3. The tip is raised to the outer peripheral side, and its outer diameter is made larger than the outer diameter of the casing top 3 and the pipe body 2. A large number of tips 12 made of a hard material such as cemented carbide are planted on the tip of the ring bit 9. Has been established. In this embodiment, the ring bit 9
Has a flat annular surface orthogonal to the axis O and two tapered surfaces connected to the inner and outer circumferences of the annular surface and inclined toward the rear end toward the inner and outer circumferences. Six chips 12 are implanted on the tapered surface so as to be inclined toward the outer periphery toward the distal end side, and half of the three chips 12 are parallel to the axis O on the annular surface. Three chips 12 are also provided on the peripheral taper surface.
Are arranged in such a manner as to be inclined inward toward the distal end, and these chips 12 are arranged at equal intervals in the circumferential direction for each surface, and also between all the chips 12. They are arranged at equal intervals in the circumferential direction.

On the other hand, the inner peripheral surface of the ring bit 9 is formed to have an inner diameter one step smaller than the rear end of the casing top 3 over substantially the entire length, and the rear end of the ring bit 9 is directed toward the rear end. A tapered portion 9A whose diameter gradually increases is formed. On the inner peripheral surface of the ring bit 9, six grooves 9B extending parallel to the axis O are arranged at equal intervals in the circumferential direction.
The tip of the ring bit 9 is formed from the tapered surface of the tip to the rear end of the tapered portion 9A so as not to interfere with the chips 12 implanted on the tapered surface on the inner peripheral side of the tip of the ring bit 9. I have. As shown in FIG. 3, the groove 9B has a cross section in which a groove wall surface 9a on the rear side (clockwise side in FIG. 3) in the rotation direction T of the inner bit 10 by the shank rod 8 during excavation is orthogonal to the axis O. About 1 in
The groove wall surface 9b on the rotation direction T side is also formed as a concave curved surface having a larger radius of curvature than the groove wall surface 9a. The groove bottom surface 9c located between 9a and 9b and facing the inner peripheral side is formed in a planar shape whose cross section smoothly continues to the wall surfaces 9a and 9b and extends in the tangential direction of a circle centered on the axis O. .

The outer peripheral surface of the rear end of the ring bit 9 is slightly rearward from the center of the rear end in the direction of the axis O. An annular groove 13 is formed so as to extend around the ring bit 9.
An annular hole 14 defined by fitting the annular groove 13 and the annular groove 11 on the inner peripheral surface of the casing top 3 by being inserted into the inner periphery of the distal end portion of the casing top 3 is elastically deformed in the radial direction with respect to the axis O. A possible locking member 15 is interposed. here,
The annular groove 13 has a U-shape that is open to the outer peripheral side in a cross section including the axis O, and the groove depth is equal to the annular groove 11.
And the groove width in the direction of the axis O is annular groove 1
1 so that the annular hole 14 defined by the annular grooves 11 and 13 is positioned in a substantially central portion of the annular groove 11 in the axis O direction. The cross section including O is formed so as to form a T-shape flattened in the radial direction.

In the present embodiment, the locking member 15 has a shape in which a ring formed of a material having appropriate elasticity and sufficient strength such as spring steel is partially cut out in the circumferential direction. This is a so-called C-shaped retaining ring, and its cross section is formed in a rectangular shape having a width in the direction of the axis O that can be fitted into the annular groove 13 and a thickness in the radial direction equal to the groove depth of the annular groove 13. In a natural state where no load is applied to the locking member 15, the outer diameter of the locking member 15 is larger than the outer diameter of the rear end of the ring bit 9 and the inner diameter of the front end of the casing top 3. Large, annular groove 11 about axis O
The inner diameter of the locking member 15 in this natural state is set to be substantially equal to the inner diameter of the groove bottom surface.
It is set so as to be larger than the outer diameter of the groove bottom of the annular groove 13 about the axis O and smaller than the outer diameter of the rear end of the ring bit 9. Therefore, the locking member 15 interposed in the annular hole 14 is substantially in the above-described natural state, and the inner peripheral portion is fitted in the annular groove 13 in the direction of the axis O over the entire circumference, and the outer peripheral portion is annular. It is in a state of protruding into the groove 11 and slidingly contacting the groove bottom surface.

Further, the inner bit 10 is
The outer diameter of the outermost portion of the first stage is the inner diameter of the ring bit 9, and the outer diameter of the outermost stage is reduced to one stage after increasing the diameter in two stages from the front end to the rear end. The outer diameter of the second stage part is 3 mm on the inner peripheral part at the rear end of the casing top 3.
The outer diameter of the largest part of the step is a size that can be loosely inserted into the inner peripheral part of the pipe body 2. Also, the outer peripheral edge of the distal end surface of the first stage portion of the inner bit 10, that is, the outer peripheral edge of the distal end surface of the inner bit 10, the step portion between the first and second stages, and 2 The step portion from the third stage to the third stage is a tapered portion that expands conically toward the rear end side toward the outer peripheral side. Of these, the tapered portion 10A of the first to second stages is used. The taper angle of the taper portion 10B of the second to third stages is equal to the taper portion 9A of the ring bit 9 and the taper portion 3A of the casing top 3, and as shown in FIG. 10A and 10B are tapered portions 9
A, 3A, the annular grooves 11, 13 of the casing top 3 and the ring bit 9 are aligned with each other so that the cross section T
A ring-shaped hole 14 is defined, and the tip of the inner bit 10 is set to protrude beyond the tip of the ring bit 9.

Further, inside the inner bit 10, a female screw portion to be screwed to the male screw portion at the tip of the stabilizer 5 is formed on the inner periphery from the rear end toward the tip along the axis O. While the mounting hole 16 is drilled,
At the rear end side of the diameter-reduced portion at the last stage of the inner bit 10, there are formed pin holes 18, 18 into which a pin 17 for locking a tip end of the stabilizer 5 screwed into the mounting hole 16 is inserted. On a plane perpendicular to O, the section extends parallel to a tangent direction of a circle formed by the mounting hole 16 in a cross section of the plane, and is formed so as to open to the mounting hole 16. Further, from the bottom of the mounting hole 16, a supply hole 19 for supplying compressed air or the like sent through the relay rods 4 of the inner rod 6 or the stabilizer 5 also has a tip side along the axis O. Towards
The diameter of the supply hole 19 is reduced by one step. From the middle of the supply hole 19, three ejection holes 19A which extend toward the distal end toward the outer peripheral side. The three ejection holes 19B extending to the rear end side toward the side are alternately branched at equal intervals in the circumferential direction, and from the leading end of the supply hole 16 toward the outer periphery toward the front end side. The ejection hole 19C is formed so as to open at a position slightly eccentric from the axis O of the tip surface of the inner bit 10.

On the other hand, the outer periphery of the first stage portion of the inner bit 10 extends perpendicularly to the axis O from a position slightly retracted from the tip end surface of the inner bit 10 in the direction of the axis O to the front portion of the tapered portion 10A. Are formed at regular intervals in the circumferential direction, and the injection holes extend obliquely from the supply holes 19 to the distal end side. 19A ...
Are opened on the outer peripheral surface of the first stage portion on the tip side of the ridges 20. When the first-stage portion of the inner bit 10 is inserted into the inner periphery of the ring bit 9, these ridges 20 are formed on the inner periphery of the ring bit 9 as shown in FIG. Of the concave grooves 9B, three concave grooves 9B which are located every other in the circumferential direction are sized so that they can be loosely inserted along the direction of the axis O, and thus the protrusions 20 are formed in the concave grooves 9B. By being loosely inserted, the inner bit 10 and the ring bit 9 are
It is made to engage around and can be rotated integrally.

On the outer periphery of the inner bit 10, there are formed three strips of excavated waste grooves 21 extending from the front end to the rear end of the inner bit 10 in parallel with the axis O. Are formed so as to be alternately and equidistantly arranged with the ridges 20. The discharge grooves 21 are concave portions whose cross sections perpendicular to the axis O form a substantially ４ arc shape in the first stage portion. The groove surface is defined by curved groove wall surfaces 21a and 21b and a planar groove bottom surface 21c smoothly connected to the groove wall surfaces 21a and 21b and extending tangentially to a circle centered on the axis O. In the third stage, the groove wall surfaces 21a and 21b are formed so as to extend to the outer peripheral side perpendicular to the groove bottom surface 21c. Groove 21
Are opened in the groove bottom surface 21c. Further, the width of the discharge groove 21 in the circumferential direction is substantially equal to the width of the concave groove 9B on the inner periphery of the ring bit 9, and as described above, the three concave grooves 9B located every other in the circumferential direction. When the inner bit 10 is inserted into the inner periphery of the ring bit 9 by loosely inserting the protruding ridges 20 into the ring bit 9, the remaining three concave grooves 9 </ b> B and these discharge grooves 21. A discharge hole is formed that opens at the tip of the excavating tool and communicates with the space between the inner rod 6 and the casing pipe 1.

Further, the opening of the discharge grooves 21 and the ejection holes 1 are also provided on the tip end surface of the inner bit 10.
A large number of chips 22 made of a hard material such as a cemented carbide are implanted so as to avoid 9C. In the present embodiment, six chips 22 are implanted in the tapered portion on the outer peripheral edge of the tip surface of the inner bit 10 and the center of the axis O is on the inner peripheral side of the tapered portion. Three chips 22... Are implanted in the circular flat portion, and the three chips 22.
And the discharge grooves 2 in the circumferential direction.
The two chips 22, 22 are arranged at regular intervals in accordance with the position of 1 .... and in the radial direction such that the two chips 22, 22 are located on the outer peripheral side of the circular flat portion and the other one is located on the inner peripheral side,
The ejection hole 19C is opened at a position substantially symmetrical with respect to the axis O with the tip 22 on the inner peripheral side. On the other hand, the tips 22... Of the tapered portion on the outer peripheral edge of the distal end surface are implanted so as to be inclined toward the outer peripheral side toward the distal end side. The configuration is such that three pairs of symmetrically arranged chips 22, 22 are arranged. Note that these inner bits 10
The tips 22 inclined to the outer periphery of the tip and the tips 12 inclined to the inner periphery of the tip of the ring bit 9 do not interfere with the insertion and removal of the inner bit 10 from the inner periphery of the ring bit 9. ing.

In such an excavating tool, the rear end of the ring bit 9 having the locking member 15 mounted on the annular groove 13 as described above is mounted on the casing top 3 welded to the tip of the pipe body 2 of the casing pipe 1. The engaging member 15 is inserted into the casing top 3 from the front end side.
The ring groove 9 is elastically reduced so as to be guided on the inclined surface 3B on the inner peripheral front end side of the casing top 3 and the annular bit 13 is inserted into the rear end side as it is to form the annular groove 13 on the inner periphery of the casing top 3. When the locking member 15 is aligned with the groove 11, the locking member 15 expands its diameter by its elasticity and returns to the original natural state, so that the outer peripheral portion is fitted into the annular groove 11 side, and the annular groove 11, 13 defines The locking member 15 is interposed in the formed annular hole 14. Therefore, in this state, the ring bit 9 is rotatable around the axis O with respect to the casing pipe 1, and the locking member 15 abuts on the leading edge of the annular groove 11 toward the leading end side in the axis O direction. Then, the movement is restricted and locked.

Further, the inner bit 10 attached to the tip of the inner rod 6 is inserted into the casing pipe 1 from the rear end side, and the tapered portion 10B
Abuts on the tapered portion 3A of the casing top 3 and loosely inserts the ridges 20 into the concave grooves 9B of the ring bit 9 so that the ring bit 9 has an inner bit 10 and an inner In addition to being rotatable integrally with the rod 6, the movement of the inner bit 10 is restrained when the tapered portion 9A contacts the tapered portion 10A of the inner bit 10 toward the rear end side in the axis O direction. Accordingly, from this state, the ring bit 9 and the inner bit 10 are integrally formed by giving the inner rod 6 a rotational force about the axis O in the rotation direction T and a striking force toward the tip end in the axis O direction. While being rotated, the tapered portion 9A,
The tip 12A is hit by the contact with the tip 10A, and excavation of the ground or the like is performed by the chips 12,. Further, since the tapered portions 3A and 10B are in contact with each other, only the impact force toward the distal end side is transmitted to the casing top 3 from the inner bit 10, whereby the casing pipe 1 does not rotate, and It is built into the hole drilled by the ring bit 9 and the inner bit 10.

As described above, in the excavating tool having the above-described configuration, the above-described engagement is formed in the annular hole 14 defined by the annular groove 11 on the inner periphery of the casing top 3 at the tip of the casing pipe 1 and the annular groove 13 on the outer periphery of the ring bit 9. With the member 15 interposed, the ring bit 9 is rotatable with respect to the casing pipe 1, but is locked on the tip side in the axis O direction. Therefore, for example, when jamming or the like occurs during excavation and the inner bit 10 is once retracted together with the inner rod 6, when the jamming or the like is eliminated and the inner rod 6 and the inner bit 10 are advanced again, the inner bit 10 Even when the ridges 20 are not loosely inserted into the concave grooves 9B of the ring bit 9 and come into contact with the tapered portion 9A on the rear end side, the locking member 15 is positioned at the leading edge of the annular groove 11. Since the movement of the ring bit 9 is restrained at the contact, the ring bit 9 does not come off the tip of the casing pipe 1 as it is, and the movement of the ring bit 9 is restrained and the inner rod 6 moves forward. When it becomes impossible to rotate the inner bit 10 little by little, the ridges 20 are aligned with the concave grooves 9B in the circumferential direction. It is possible to re-advance the inner bit 10 ridges 20 ... were loosely inserted into the groove 9B ... and to continue the excavation.

According to the excavating tool having the above-described configuration, the locking member 15 is elastically deformable in the radial direction with respect to the axis O like the C-shaped retaining ring. By simply inserting the rear end of the ring bit 9 into the inner periphery of the casing top 3 while elastically reducing the diameter of the locking member 15 attached to the The member 15 is expanded in diameter, and the ring bit 9 is rotatable with respect to the casing pipe 1 and is locked in the direction of the axis O. Therefore, the ring bit 9 can be attached to the casing pipe 1 very easily while the ring bit 9 is prevented from coming off by the locking member 15 in this manner, and the assembling work of the excavating tool can be simplified. It is possible to plan. On the other hand, in the above-mentioned excavating tool, it is only necessary to form the annular grooves 11 and 13 in the casing top 3 and the ring bit 9 of the casing pipe 1 and mount the locking member 15, and the processing to be performed on the parts is minimal. In addition to the above, it is economical because it is limited, and there is an advantage that there is no possibility that the structure is complicated.

Further, in the excavating tool of the present embodiment, after the locking member 15 is attached to the annular groove 13 of the ring bit 9, the ring bit 9 is inserted into the inner periphery of the casing top 3 at the tip of the casing pipe 1. At this time, a chamfered shape whose diameter gradually increases toward the fitting direction side is provided at an end portion on the tip end side of the inner periphery of the casing top 3, that is, an end portion on the direction side in which the ring bit 9 is fitted into the casing top 3. An inclined surface 3B is formed, and when the ring bit 9 is inserted into the inner periphery of the casing top 3, the inclined surface 3B is formed.
By B, the locking member 15 is guided to reduce the diameter and is elastically deformed. For this reason, according to the present embodiment, when the locking member 15 is elastically deformed, the locking member 15 made of, for example, a C-shaped retaining ring is elastically deformed by caulking, and the state is maintained. There is no need to insert the ring bit 9 into the inner periphery of the casing top 3, but only by pushing the ring bit 9 into the casing top 3 and inserting it, after the locking member 15 is elastically deformed and reduced in diameter. The ring bit 9 can be attached to the casing pipe 1 more easily because the ring bit 9 can be interposed in the annular hole 14 defined by the fitting.

On the other hand, in the present embodiment, the tapered portion 10A formed on the inner bit 10 is
Can be brought into contact with the tapered portion 9A formed at the rear end portion toward the tip side in the direction of the axis O, whereby the impact force from the inner rod 6 to the tip end applied to the inner bit 10 is reduced. Since it is possible to transmit directly and simultaneously to the ring bit 9 via these tapered portions 10A and 9A, the impact force transmitted to the ring bit 9 and the inner bit 10 causes the tip 12 of the tip to be transmitted.
, 22... Can be reliably eroded into the ground or the like, and more efficient excavation can be promoted. Moreover, in addition to this, in the present embodiment, the inner bit 10 is configured such that the tapered portion 10B formed on the rear end side of the tapered portion 10A abuts on the tapered portion 3A formed on the casing top 3. The casing pipe 1 can also be brought into contact with the casing pipe 1 toward the distal end side, and only the striking force of the rotary striking force applied to the inner bit 10 is transmitted, so that the casing pipe 1 can be built into the drilled hole. Therefore, it is not necessary to separately apply a rotary impact force and an impact force to the inner rod and the casing pipe as in the conventional excavating tool described in the above-mentioned publication, so that more efficient excavation can be achieved.

In this embodiment, as described above, annular grooves 11 and 13 are formed in the inner circumference of the casing top 3 at the tip of the casing pipe 1 and the outer circumference of the rear end of the ring bit 9, and the ring bit 9 By attaching the locking member 15 to the annular groove 13 on the outer periphery and inserting the ring bit 9 into the casing top 3, the locking member 15 is elastically deformed so as to reduce the diameter of the locking member 15 by the inclined surface 3B. The annular grooves 11 and 13 are aligned with each other to define an annular hole 14, and a locking member 15 that has been returned to its original state by expanding its diameter by its elastic force is interposed in the annular hole 14. However, for example, by reversing the configuration of the annular grooves 11 and 13, an annular groove 11 which is wide in the direction of the axis O and has a small depth is formed on the outer periphery of the ring bit 9, and a width is formed on the inner periphery of the casing top 3. Narrow and groove depth An annular groove 13 is formed, and a retaining member 15 is attached to the annular groove 13 on the inner periphery of the casing top 3, and the retaining member 15 is expanded by fitting the rear end of the ring bit 9. An annular hole 14 is defined by matching the annular grooves 11 and 13 while being elastically deformed so as to have a diameter, and a locking member which has been reduced in diameter by elasticity and returned to the original state is interposed in the annular hole 14. You may make it. In this case, a chamfered inclined surface whose diameter gradually increases toward the front end may be formed on the outer periphery of the rear end of the ring bit 9.

Also, contrary to the above embodiment, the tip of the casing pipe 1 can be fitted into the inner periphery of the rear end of the ring bit 9, and this fitting can be fitted to the outer periphery of the ring bit 9 and the inner periphery of the casing pipe 1. The annular grooves 11 and 13 are formed so as to coincide with each other by insertion to define an annular hole 14, and the casing pipe 1 and the ring are formed while elastically expanding or reducing the diameter of the locking member 15 mounted in the annular groove 13. When the bit 9 is inserted and the above-described annular hole 14 is defined, the locking member 15 which is restored by the elastic force may be interposed in the annular hole 14. In this case, the inclined surface may be formed in a chamfered shape on the outer periphery of the front end portion of the casing pipe 1 toward the rear end side, or may be formed on the inner periphery of the rear end portion of the ring bit 9 with the diameter reduced toward the front end side. It may be formed in a chamfered shape. Furthermore, in the above embodiment,
The annular grooves 11 and 13 are formed so as to go around the inner and outer peripheries of the casing top 3 and the ring bit 9, and as the locking member 15, a C-shaped retaining ring in which a part of the ring is cut off in the circumferential direction as described above is used. Although used, for example, the annular groove 11 or the annular groove 13 and the locking member 15 may be provided by being divided into a plurality in the circumferential direction.

Further, in order to improve the locking strength of the locking member 15, a plurality of annular grooves 11 and 13 are formed parallel to each other in the direction of the axis O to define a plurality of annular holes 14. The locking member 15 may be interposed in each of the annular holes 14. At this time, for example, a case where the ring bit 9 is fitted and attached to the inner periphery of the casing top 3 at the tip of the casing pipe 1 as in the above-described embodiment, and the distance between the inner periphery of the casing top 3 and the outer periphery of the ring bit 9 is two. Annular hole 1
When the lines 4 and 14 are defined so as to be aligned in the direction of the axis O,
The annular hole 14 on the distal end side is defined by the annular groove 11 of a wide and shallow groove on the inner periphery of the casing top 3 and the annular groove 13 of a narrow and deep groove on the outer periphery of the ring bit 9 as in the above-described embodiment. The locking member 15 is mounted in the annular groove 13 on the side of the ring bit 9, while the annular groove 14 on the rear end side is formed on the outer periphery of the ring bit 9 as in the case where the configuration of the annular grooves 11 and 13 is reversed. An annular groove 11 having a wide and shallow groove is formed at the same time, and an annular groove 13 having a narrow and deep groove is formed at the inner periphery of the casing top 3 so as to be defined by these annular grooves 11 and 13. May be mounted in the annular groove 13 on the casing top 3 side.

[0030]

As described above, according to the present invention,
The annular groove formed on the inner and outer circumferences of the casing pipe and the ring bit is aligned with an annular hole, and a locking member that can be elastically deformed in the radial direction is interposed, thereby complicating the structure. Without inviting the ring bit to the casing pipe and making it extremely easy to attach the ring bit to the casing pipe, the ring bit can be securely locked to the tip end in the axial direction without jamming. Even when the inner bit and inner rod are retracted and then moved forward again when troubles such as occur, the situation where the ring bit comes off from the end of the casing pipe is prevented, and smooth excavation work is performed. Can be planned.

[Brief description of the drawings]

FIG. 1 is a partially broken side view showing one embodiment of the present invention.

FIG. 2 is an enlarged side sectional view of a distal end portion of the embodiment shown in FIG.

FIG. 3 is an enlarged front view of the embodiment shown in FIG. 1 as viewed from the distal end side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing pipe 3 Casing top 6 Inner rod 9 Ring bit 9B Concave groove 10 Inner bit 11,13 Annular groove 12,22 Tip 14 Annular hole 15 Locking member 20 Protrusion 21 Discharge groove O Center axis line of casing pipe 1 Excavation Rotation direction of inner bit 10

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuyoshi Yoshida 1528 Nakashinda, Yokoi, Kobe-cho, Anpachi-gun, Gifu F-term in Mitsubishi Materials Corporation Gifu Works (reference) 2D029 DC01 PA07 PC02

Claims (3)

[Claims] 1. A ring bit is attached to a tip of a cylindrical casing pipe so as to be rotatable around the axis of the casing pipe, and a ring bit is inserted into the casing pipe and is attached to a tip of an inner rod rotated around the axis. In an excavation tool in which an inner bit is inserted into the inner periphery of the ring bit and is attached so as to be able to engage with the ring bit around the axis, the casing pipe and the ring bit are arranged such that the inner and outer peripheral surfaces of each other are An annular groove extending around the axis is formed on each of the inner and outer peripheral surfaces of the casing pipe and the ring bit facing each other. The annular grooves are defined by matching these annular grooves. The annular hole is provided with a locking member elastically deformable in the radial direction with respect to the axis, whereby An excavating tool characterized in that a drill bit is locked to a casing pipe in the axial direction. 2. An inner peripheral surface of the casing pipe and the ring bit facing each other, the locking member is mounted on the annular groove on one peripheral surface, and the casing member is mounted on the other peripheral surface. The excavation tool according to claim 1, wherein a chamfered inclined surface is formed at an end on the side where the pipe and the ring bit are inserted. 3. The excavating tool according to claim 1, wherein the inner bit is capable of contacting the ring bit toward the distal end in the axial direction.