JP3750441B2 - Drilling tools - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an excavation tool in which a pilot bit portion is provided at a tip end portion of a tool body, and a diameter expanding bit is attached to a rear end side of the pilot bit portion.
[0002]
[Prior art]
As such excavation tools, the inventors of the present invention have proposed the one shown in FIGS. 9 and 10 in Japanese Patent Application No. 9-235246. In the excavating tool shown in these drawings, the axis of the tool body 1 is arranged at the center of the tip of the tool body (device) 1 having a substantially multi-stage cylindrical shape whose diameter gradually increases toward the tip side (left side in FIG. 9). A mounting hole 2 is formed along O, and a large number of chips 4 made of a hard material such as cemented carbide are implanted in the mounting hole 2 at the tip of the disc-shaped bit body 3A to provide a cutting blade. The pilot bit 3 is attached by screwing a mounting shaft portion 3B protruding from the rear end surface of the bit body 3A. A plurality of recesses 5 are formed on the outer periphery of the tip of the tool body 1, and a support hole having a central axis X that is eccentric to the outer periphery side with respect to the axis O on the bottom surface of the recesses 5. 5A is formed, and in this support hole 5A, the diameter-expanding bit 6 in which the tip 7 is also implanted at the tip of the bit body 6A and provided with a cutting blade protrudes from the rear end surface of the bit body 6A. The shaft 6B is fitted and inserted so as to be rotatable around the central axis X.
[0003]
The excavation tool configured in this way is attached to a shank portion 1A on the rear end side of the tool body 1 and is rotated in the tool rotation direction T around the axis O and hits the front end side in the axis O direction. By receiving the force, the diameter-enlarged bit 6 is rotated around the central axis X to the rear side in the tool rotation direction T, and positioned in a state where the outer diameter from the axis O is expanded. The cutting edge 7 and the cutting edge 4 of the pilot bit 3 form a hole in the ground or the like, and the casing pipe 8 is built into the hole. Further, after the excavation is completed, the tool main body 1 is rotated in the direction opposite to the tool rotation direction T, whereby the diameter-expanding bit 6 rotates in the opposite direction, and the bit main body 6A is accommodated in the concave portion 5 and the axis line Since the positioning is performed in a state where the outer diameter from O is reduced, the tool body 1 can be retracted as it is, so that the excavation tool can be pulled out leaving only the casing pipe 8 in the hole.
[0004]
[Problems to be solved by the invention]
However, in the excavation tool configured in this way, 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 portion 3B. Considering that the concave portion 5 for accommodating the above-described diameter-enlarged bit 6 must be formed on the outer periphery of the distal end portion of the main body 1, it is difficult to make the inner diameter of the mounting hole 2 and the outer diameter of the mounting shaft portion 3B too large Therefore, there is a problem that it is difficult to secure sufficient mounting rigidity of the pilot bit 3. Further, since the pilot bit 3 is attached by screwing in this way, the tip end portion of the diameter expanding bit 6 cannot be supported by the rear end surface of the bit body 3A of the pilot bit 3, that is, the diameter expanding bit 6 Is in a state of being supported only by the shaft portion 6B at the rear end, there is also a problem that it is difficult to secure sufficient mounting rigidity for the diameter-expanded bit 6.
[0005]
The present invention has been made in view of such circumstances, and in such an excavation tool in which a pilot bit portion is provided at the front end portion of the tool body and a diameter-expanding bit is attached to the rear end side of the pilot bit portion. An object of the present invention is to provide an excavation tool capable of providing the pilot bit portion and the diameter expansion bit more firmly on the tool body.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve such an object, the present invention provides a cutting edge at the distal end of a substantially multi-stage cylindrical tool body whose diameter gradually increases toward the distal end. Pilot bit section Is formed integrally with the tip of the tool body. In addition, a mounting portion is provided on the rear end side of the pilot bit portion, and a ring-shaped mounting member is fitted on the outer periphery of the mounting portion from the rear end side, and is attached to the tool body integrally. A support hole centered on a central axis that is eccentric from the axis of the tool body to the outer peripheral side is provided at the tip of the mounting member, and a support hole that is coaxial with the central axis is provided at the rear end surface of the pilot bit part. Is provided, A cutting blade is provided at the tip of the bit body between the tip of the mounting member and the rear end surface of the pilot bit. Support shafts are coaxially provided on the front and rear end surfaces of the bit body. Expanded bit The support shaft on the front end side is inserted into the support hole of the pilot bit portion and the support shaft on the rear end side is inserted into the support hole of the mounting member, Supported by these pilot bits and mounting members Let The tool body is attached so as to be rotatable about a central axis that is eccentric from the axis of the tool body to the outer peripheral side. Therefore, in the excavation tool having such a configuration, the pilot bit portion is integrally provided at the tip portion of the tool main body, so that it is possible to give the pilot bit portion high rigidity and in this way. Even if the pilot bit is integrated with the tip of the tool body, it is possible to attach an enlarged bit to the rear end of the pilot bit by means of a mounting member that is inserted from the rear end of the tool body. Since the diameter-expanding 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 ensure high mounting rigidity for the diameter-expanding bit.
[0007]
Here, in order to attach the mounting member to the tool body in this way, firstly, in the axial direction, a concave groove and a protrusion that are fitted to each other on the outer periphery of the mounting portion and the inner periphery of the mounting member are provided. And an annular groove that circulates around the axis is formed on the outer periphery of the tool body on the rear end side of the attachment portion, and the annular groove has an outer diameter larger than the inner diameter of the attachment member. By fitting and attaching the ring-shaped retainer divided into two, the attachment member is fixed in the circumferential direction of the tool body by fitting the concave groove and the protrusion, and is fitted into the annular groove. The retainer can also be fixed in the axial direction. Further, as another one, a concave groove and a protrusion to be fitted to each other are formed along the axial direction on the outer periphery of the mounting portion and the inner periphery of the mounting member, and one orthogonal to the axial line. By forming mounting grooves that extend along the plane of each of these, and mounting a stopper in a mounting hole defined by these mounting grooves, the mounting member is fixed in the axial direction via this stopper. The attachment member can be securely attached to the attachment portion.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
1 to 4 show a first embodiment of the present invention. In the present embodiment, the tool main body 11 is formed in a substantially multi-stage cylindrical shape centering on an axis O whose outer diameter expands in three steps toward the tip side (left side in FIG. 1), and has a small diameter at the last step. The shaft portion is a shank portion 12, spline grooves 12 </ b> A are formed on the outer periphery thereof, the middle step portion is a mounting portion 13, and the tip portion is formed in a disc shape to be a pilot bit portion 14. Yes. And this tool main body 11 is rotated in the tool rotation direction shown by the code | symbol T in the figure around the said axis O at the time of excavation by attaching the hammer which is not illustrated to the shank part 12 via the said spline groove | channel 12A .... At the same time, it receives an impact force toward the front end side in the direction of the axis O and is used for excavation. Further, a supply hole 15 for compressed air or the like is formed in the tool body 11 along the axis O from the rear end toward the front end side. The supply hole 15 is formed in the pilot bit portion 14 on the front end side. It is branched into two and is opened on the opposite side to the front end surface 14A of the pilot bit portion 14 with the axis O therebetween.
[0009]
Further, the tip surface 14A of the pilot bit portion 14 is formed in a mortar shape having a recessed central portion, and a pair of jet grooves 16, 16 such as compressed air is formed from the central portion to the outer periphery of the recessed tip surface 14A. 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 at the bottom surfaces of the ejection grooves 16 and 16, respectively. Further, on the outer periphery of the pilot bit portion 14, six drilling waste discharge grooves 17 extending in parallel to the axis O are formed at equal intervals in the circumferential direction. The front ends of the pair of discharge grooves 17 and 17 that are positioned are in communication with the outer peripheral ends of the ejection grooves 16 and 16. A large number of tips 18 made of a hard material such as cemented carbide are implanted on the tip end surface 14A of the pilot bit portion 14 and the tip end side of the outer peripheral surface so as to avoid the ejection grooves 16 and the discharge grooves 17. The cutting edges of the pilot bit portion 14 are formed by these chips 18. Further, in the rear end surface 14B of the pilot bit portion 14, support holes 19 having a circular cross section centering on the central axis X that is eccentric to the outer peripheral side with respect to the axis O are equally spaced in the circumferential direction in this embodiment. Is formed.
[0010]
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 along the entire length of the mounting portion 13 are aligned with the positions of the support holes 19 in the circumferential direction. Are formed at regular intervals. As shown in FIG. 3, in the present embodiment, these concave grooves 20 are formed in a circular arc-shaped bottom surface 20A that is recessed one step from the outer peripheral surface of the mounting portion 13 to the inner peripheral side and is convex toward the outer peripheral side, and the bottom surface 20A. Are defined by a pair of wall surfaces 20B, 20B extending in parallel to each other on the outer peripheral side, and are symmetrical with respect to a plane including the axis O and the central axis X. Further, an annular groove opening in a “U” shape on the outer peripheral side in the cross section including the axis O is formed between the spline groove 13A of the shank portion 12 in the direction of the axis O and the spline groove 13A in the axis O direction. 21, a male screw portion 22, and an annular groove 23 having a smaller width and depth than the annular groove 21 and opening in a cross-sectional “U” shape on the outer peripheral side are formed in order toward the rear end side. Of these, the outer diameter of the male screw portion 22 is made smaller than the diameter formed by the bottom surface 20A of the recessed groove 20 of the mounting portion 13 around the axis O, and the diameter of the valley is smaller than the outer diameter of the shank portion 12. The groove depth of the annular groove 21 and the annular groove 23 is made deeper than the depth of the valley of the male screw portion 22.
[0011]
A ring-shaped attachment member 24 is attached to the outer periphery of the attachment portion 13 by fitting the inner periphery thereof from the rear end side of the tool body 11. The mounting member 24 has a length in the axis O direction slightly longer than the length of the mounting portion 13 and an outer diameter slightly larger than the outer diameter of the pilot bit portion 14. In addition, three ridges 25... That can be respectively fitted in the concave grooves 20 are formed on the inner peripheral portion that is inserted into the mounting portion 13. That is, in the present embodiment, as shown in FIG. 3, each protrusion 25 has a concave arcuate surface 25A that can be in close contact with the bottom surface 20A of the groove 20, and extends from the top surface 25A to the outer peripheral side. The side surfaces 25B and 25B which are parallel to each other and can be brought into close contact with the wall surfaces 20B and 20B. In this manner, the protrusion 25 and the concave groove 20 are fitted to each other, and the attachment member 24 is attached to the attachment portion 13 in the axis line. It is formed symmetrically with respect to a plane including O and the central axis X.
[0012]
Further, on the outer peripheral side of the distal end portion of the mounting member 24, a concave portion 26 opened to the distal end surface and the outer peripheral surface of the mounting member 24 extends from the periphery of the central axis X to the tool rotation direction T side in the mounting state described above. The bottom surface 26A facing the distal end side of each recess 26 has a circular cross section with a larger inner diameter than the support hole 19 around the central axis X, that is, coaxially with the support hole 19. Each hole 27 is formed. Then, in the mounting state, the recess 26 positioned between the rear end surface 14B of the pilot bit portion 14 and the front end portion of the mounting member 24 has a cross-section on the front and rear end surfaces on one side of the block-shaped bit body 28A. A diameter expansion bit 28 having circular support shafts 28B and 28C projecting coaxially inserts the support shaft 28B on the front end side into the support hole 19 and fits the support shaft 28C on the rear end side into the support hole 27. It is inserted and attached so as to be rotatable around the central axis X. Further, from the bottom surface 26A of the concave portion 26 toward the front end side, a concave arcuate wall surface 26B smoothly connected from the inner periphery to the front end side of the support hole 27 and facing the tool rotation direction T side and the outer peripheral side; A wall surface 26C facing the tool rotation direction T extending smoothly in contact with the outer peripheral side of the wall surface 26B, and a convex arcuate surface centering on an axis O extending smoothly in the tool rotation direction T side in contact with the inner peripheral side of the wall surface 26B. Wall surface 26D.
[0013]
The diameter-expanding bit 28 has the bit body 28A from the one side where the support shafts 28B and 28C are formed as viewed from the central axis X direction to the other side opposite to the side. The one side portion of the bit body 28A is formed in a convex arc surface shape that smoothly continues to the outer peripheral surface of the support shaft 28C, and the tip on the other side portion side. On the surface, chips 29 made of a hard material such as cemented carbide are implanted to form a cutting edge of the expanded bit 28. And this diameter expansion bit 28 rotates to the back side of the tool rotation direction T around the said central axis X by the rotation to the tool rotation direction T at the time of excavation, and thereby the bit main body 28A is placed on the wall surface 26C of the recess 26. As shown in FIG. 2, the tool body 11 is positioned in a state where the outer diameter from the axis O is enlarged, and the tool body 11 is rotated in the direction opposite to the tool rotation direction T after the end of excavation. By rotating in the tool rotation direction T side, the bit body 28A is accommodated in the recess 26 so as to be in close contact with the wall surface 26D, and the outer diameter from the axis O is smaller than the outer diameter of the mounting member 24 It is made to be positioned by. In addition, on the outer peripheral surface of the mounting member 24, three slicing waste discharging grooves 30 extending in parallel with the axis O in communication with the recesses 26 on the tool rotation direction T side are also formed at equal intervals in the circumferential direction. ing.
[0014]
As shown in FIG. 1, the mounting member 24 externally fitted to the mounting portion 13 in this manner has a rear end surface 24 </ b> A whose rear end surface is abutted against the rear end surface 14 </ b> B of the pilot bit portion 14 and a rear end surface of the mounting portion 13. The retainer 31, 31 is attached to the annular groove 21 and is interposed between the rear end surface 24A and the wall surface 21A facing the front end side of the annular groove 21. By this, it is fixed to the attachment part 13 also in the direction of the axis O and integrated with the tool body 11. Here, as shown in FIG. 4, the retainers 31, 31 are formed by surrounding a ring having a square cross section with an inner diameter that can be fitted into the annular groove 21 in the present embodiment by a plane extending in the diameter direction. It has a shape divided into two in the direction, and its 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. Further, the retainers 31, 31 attached to the annular groove 21 in this way are fixed by screwing a screw ring 32 formed with a cylindrical wall portion 32 </ b> A fitted to the outer periphery of the retainers 31, 31 to the male screw portion 22. In addition, a snap ring 33 for preventing the screw ring 32 from coming off is attached to the annular groove 23 on the rear side of the male screw portion 22.
[0015]
In the excavation tool configured as described above, the pilot bit portion 14 is provided at the tip end portion of the tool main body 11 in the same manner as the conventional excavation tool, and the diameter expansion bit 28. The pilot bit portion 14 is attached to the tool main body 11 because the diameter-expanding bit 28 is attached by the attachment member 24 inserted into the attachment portion 13 from the rear end side of the tool main body 11 in spite of being rotatably attached. Therefore, the pilot bit portion 14 can be given high rigidity. For this reason, the striking force and rotational force applied to the tool main body 11 from the hammer can be reliably transmitted to the pilot unit 14 and the ground or the like can be excavated by the cutting blade, and the excavation efficiency can be improved. Moreover, in the excavation tool having the above-described configuration, the support shaft 28C on the rear end side of the diameter-expanding bits 28 is inserted into the support hole 27 of the mounting member 24, and the support shaft 28B on the front end side is also in the pilot bit portion 14. Since the bit main body 28A is supported and attached from both ends, the high support rigidity can be secured and the excavation efficiency can be further improved.
[0016]
Further, in the present embodiment, the mounting member 24 that is fitted and attached to the mounting portion 13 while holding the diameter-enlarged bits 28 is attached to the concave groove 20 on the outer periphery of the mounting portion 13 and the inner periphery of the mounting member 24. Are fixed around the axis O by fitting with the above-mentioned protrusions 25... And are retained in the direction of the axis O by retainers 31, 31 fitted in an annular groove 21 formed on the rear end side of the mounting portion 13. The load on the rear side in the tool rotation direction T acting on the diameter-expanding bits 28 as a reaction force of the rotational force during excavation is fixed to the tool in the groove 20 from the protrusion 25 of the mounting member 24. The load toward the rear end side in the shaft tip O direction acting on the diameter expanding bit 28 as a reaction force of the striking force by the wall surface 20B facing the rotation direction T side is applied from the mounting member 24 via the retainers 31 and 31. It faces the tip side of this annular groove 21 By the surface 21A, it will be are received respectively, i.e. these loads so that the received on the tool body 11 consequently. For this reason, according to the present embodiment, it is possible to hold the diameter-expanding bits 28 ... without changing from the conventional excavation tool in which the diameter-expanding bits are directly held by the tool body. In addition, the diameter expansion bit 28 is supported on the distal end side, so that the support rigidity can be ensured more reliably.
[0017]
Further, in the present embodiment, the recessed grooves 20 are formed on the outer periphery of the mounting portion 13 and the ridges 25 are formed on the inner periphery of the mounting member 24 and are fitted to each other. The ridges 25 are planar surfaces including the central axis X and the axis O that are the rotation centers of the diameter-enlarged bits 28 in a state where the attachment member 24 is attached to the attachment portion 13 in the circumferential direction of the tool body 11. It is symmetrically formed on the plane according to the position. Therefore, according to the present embodiment, a relatively large thickness can be secured by the protrusion 25 between the support holes 27 formed in the mounting member 24 and the inner periphery of the mounting member 24. As in the embodiment, the diameter of the support hole 27 and the support shaft 28C inserted into the support hole 27 is increased to further secure the mounting rigidity of the diameter-expanding bit 28, or to secure the mounting rigidity of the diameter-expanding bit 28 in this way. It is possible to further increase the rigidity of the pilot bit portion 14 at the tip of the mounting portion 13 by increasing the outer diameter of the mounting portion 13 as it is.
[0018]
In the present embodiment, as shown in FIG. 3, the circumferential widths of the concave grooves 20 and the ridges 25 are made smaller than the circumferential widths between the adjacent concave grooves 20 and the ridges 25. Therefore, it is assumed that the groove 20 is formed on the outer periphery of the mounting portion 13 and the ridge 25 is formed on the inner periphery of the mounting member 24. In addition, since the portion between the ridges 25 can also be a concave groove, the concave groove and the ridge can be fitted to each other on either side of the outer periphery of the mounting portion and the inner periphery of the mounting member. May be. Moreover, in this embodiment, although the retainer 31 is made into the half ring shape, it is good also as a ring shape divided into 3 or more in the circumferential direction.
[0019]
Next, FIGS. 5 to 8 show a second embodiment of the present invention, and the same reference numerals are assigned to the same parts as those in the first embodiment shown in FIGS. Is omitted. In the second embodiment, the tool body 41 has substantially the same cross-sectional shape from the shank portion 42 on the rear end side to the middle mounting portion 43, and only the pilot bit portion 44 on the front end side is enlarged by one step. The disc shape is a two-stage multi-stage cylindrical shape, and a plurality of (in this embodiment, eight) spline grooves 42A of the shank portion 42 are directly behind the pilot bit portion 44 in parallel to the axis O. Grooves 45 are formed on the outer periphery of the mounting portion 43 so as to reach the end surface 44A. In this embodiment, the spline grooves 42A and the concave grooves 45 form a substantially trapezoidal shape in which the cross section perpendicular to the axis O is narrowed toward the inner peripheral side, and adjacent grooves in the circumferential direction. It is formed at equal intervals in the circumferential direction so that the wall surfaces are parallel to each other. In addition, as shown in FIG. 5, the part connected to the said rear end surface 44A of this ditch | groove 45 ... is formed so that it may cut off to the outer peripheral side. Further, on the outer periphery of the mounting portion 43 on the shank portion 42 side, there is a mounting groove 46 having a deeper groove depth than the concave groove 45 having a “U” shape whose cross section including the axis O opens to the outer peripheral side. , It is formed in an annular shape so as to circulate around the axis O along one plane P orthogonal to the axis O.
[0020]
On the other hand, on the inner periphery of the attachment member 47 attached to the attachment portion 43, the concave groove is inserted into the attachment portion 43 from the rear end side of the tool body 41 through the spline groove 42 </ b> A of the shank portion 42. 45 are formed in the same number as the spline grooves 42A and the concave grooves 45 (that is, eight in this embodiment). Therefore, these protrusions 48... Exhibit a substantially rectangular shape whose cross section has side faces that can be in close contact with the mutually parallel wall surfaces of the concave grooves 45 adjacent in the circumferential direction. These ridges 48 are also cut off on the outer peripheral side in accordance with the above-mentioned cut-out of the concave grooves 45 on the tip side. Further, the mounting member 47 is shown in FIG. 8 in a cross-section along the plane P in accordance with the position of the plane P where the mounting groove 46 is formed in a state where the mounting member 47 is mounted on the mounting portion 43. Thus, the U extends from the outer periphery of the mounting member 47 to the inner peripheral side, opens to the inner peripheral portion of the mounting member 47, and then extends to the outer peripheral side after approximately a half turn around the inner peripheral portion and opens to the discharge groove 28. A character-shaped hole 49 is formed.
[0021]
The U-shaped hole 49 has a circular section from the outer periphery to the inner periphery of the mounting member 47 as shown in FIG. The portion to be mounted is a mounting groove 50 formed in a cross-sectional “U” shape that opens to the inner peripheral side with the same groove width as the mounting groove 46 of the mounting portion 43 and a groove depth larger than the protruding height of the protrusion 48. When the mounting grooves 46 and 50 are overlapped in the above-described mounting state, the mounting hole 51 having a square cross section is formed between the mounting portion 43 and the mounting member 47 so as to include a fitting portion of both. In the cross section along P, it is defined so as to go around substantially a half circumference. The square formed by the cross section of the mounting hole 51 extends from the outer periphery of the mounting member 47 of the U-shaped hole 49 to the inner peripheral portion. Or inscribed in the circle formed by the cross section There is also a small shape and size. A plurality of cylindrical stoppers 52 having a square shape in which the cross section including the center line can be fitted into the square shape formed by the mounting hole 51 in the U-shaped hole 49 including the mounting hole 51 in the mounting state. Are inserted and filled so that the center line is parallel to the axis O, and snap rings 53 are attached to both openings on the outer peripheral side of the mounting member 47 of the U-shaped hole 49 to prevent it from coming off. The mounting member 47 is engaged with the mounting portion 43 in the direction of the axis O and fixed by a stopper 52 inserted between the mounting grooves 46 and 50 by being inserted into the mounting hole 51.
[0022]
Therefore, also in the excavation tool according to the second embodiment configured as described above, the attachment member 47 to which the diameter expansion bits 28 are attached is fitted into the attachment portion 43 from the rear end side of the tool body 41 and attached. Therefore, the pilot bit portion 44 at the tip can be formed integrally with the tool body 41 to improve its rigidity, and the diameter-expanding bit 28 is also supported from both ends of the front and rear and has a high mounting rigidity. Since it can be ensured, it is possible to reliably transmit the rotary striking force applied from the hammer and promote efficient excavation. Also in this embodiment, stoppers 52 are interposed in the mounting holes 51 defined by the mounting grooves 46 formed on the outer periphery of the mounting portion 43 of the tool body 41 and the mounting grooves 50 formed on the inner periphery of the mounting member 47. As a result, the mounting member 47 is fixed in the direction of the shaft tip O, and the load acting on the mounting member 47 from the diameter expanding bit 28 during excavation is received by the tool body 41 as a result via the stopper 52. Therefore, the drill bits 28 can be reliably supported without changing from the conventional drill tools in which the diameter expansion bit is directly attached to the tool body.
[0023]
In the second embodiment, as described above, the mounting hole 51 is defined to have a square cross-section, and the mounting member 47 is pivoted by loading and inserting a cylindrical stopper 52. For example, the mounting grooves 46 and 50 are formed in a circular arc shape so that the mounting hole 51 is defined as a circular cross section having the same diameter as the U-shaped hole 49. A spherical stopper is loaded into the mounting hole 51 through the U-shaped hole 49, or a flexible linear member such as a wire rope or a coiled metal wire is U-shaped. It may be inserted between the mounting portion 43 and the mounting member 47 by inserting it into a U shape following the hole 49 to form a stopper. Further, in some cases, fixing by such a stopper and fixing by a retainer as in the first embodiment may be used in combination.
[0024]
【The invention's effect】
As described above, according to the present invention, since the pilot bit portion is integrally formed at the tip of the tool body, the rigidity of the pilot bit portion can be improved and the mounting portion on the rear end side can be achieved. A mounting member is inserted into the tool body from the rear end side, and a large-diameter bit is supported and attached between the pilot bit part and the mounting member at both the front and rear ends to ensure high support rigidity for this large-diameter bit. As a result, it is possible to reliably transmit the rotary striking force and the like applied to the tool body, thereby achieving efficient excavation.
[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 the distal end side.
3 is a YY cross-sectional view in FIG. 1. FIG.
4 is a ZZ cross-sectional view in FIG. 1. FIG.
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 front end side.
7 is a YY cross-sectional view in FIG. 5. FIG.
FIG. 8 is a ZZ cross-sectional view in FIG.
FIG. 9 is a side sectional view showing a conventional excavation tool.
10 is a front view of the excavation tool shown in FIG. 9 as viewed from the front end side.
[Explanation of symbols]
11, 41 Tool body
13, 43 Mounting part
14,44 Pilot bit part
18,29 chips
19, 27 Support hole
20, 45 groove
21 annular groove
24, 47 Mounting member
25, 48 ridges
28 Expanding 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 expanded bit 28

Claims (3)

A cutting edge is provided at the tip of the tool body having a substantially multi-stage cylindrical shape whose diameter gradually increases toward the tip side, and a pilot bit is formed integrally with the tip of the tool body. A mounting portion is provided on the rear end side of the portion, and a ring-shaped mounting member is fitted and attached to the outer periphery of the mounting portion from the rear end side. A support hole centered on the central axis that is eccentric from the axis of the tool main body to the outer peripheral side is provided, and a support hole that is coaxial with the support hole is provided on the outer peripheral side of the distal end portion of the mounting member about the central axis. A cutting blade is provided at the front end portion of the bit body between the front end portion of the mounting member and the rear end surface of the pilot bit portion, and a support shaft is coaxially provided at the front and rear end surfaces of the bit body. diameter bit, the tip Of the support shaft and the support shaft of the rear end was inserted into the support hole of the mounting member causes inserted into the supporting hole of the pilot bit part is supported on and a mounting member thereof pilot bits section above An excavation tool characterized in that it is mounted so as to be rotatable around a central axis that is eccentric from the axis of the tool body toward the outer periphery.   The outer periphery of the mounting portion and the inner periphery of the mounting member are formed with recessed grooves and ridges that fit with each other along the axial direction, and on the outer periphery of the tool body on the rear end side of the mounting portion. An annular groove that circulates around the axis is formed, and a ring-shaped retainer that is divided in the circumferential direction and has an outer diameter larger than the inner diameter of the mounting member is fitted and attached to the annular groove. The excavation tool according to claim 1, wherein   The outer periphery of the mounting portion and the inner periphery of the mounting member are formed with recessed grooves and protrusions that are fitted to each other along the axial direction, and extend along a plane that is orthogonal to the axial line. The excavation tool according to claim 1, wherein attachment grooves are respectively formed, and stoppers are interposed in the attachment holes defined by the attachment grooves.

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