JP2001082063A - Drilling tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drilling tool inserted with a fitting shaft section into a fitting hole, fitted with a drilling bit to a tool body, sufficiently securing the fitting rigidity of the drilling bit even when the tool body 1 is rotated for an excavation, and allowing the drilling bit to be easily removed from the tool body at the time of replacement. SOLUTION: The fitting shaft section 9 of a drilling bit 5 provided with a cutting edge on the tip side and formed with the fitting shaft section 9 on the rear end side is inserted into a fitting hole 4 opened at the tip section center of the tool body 1 and extending along the axis O at the tip section of the tool body 1 rotated around the axis O in this drilling tool. Recessed grooves 26 extending in parallel with the axis O are formed on the inner periphery of the fitting hole 4, and protruded stripes 15 each having both side faces 15A closely stuck to both inner walls 26A of each recessed groove 26 are formed on the outer periphery of the fitting shaft section 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool having a drill bit attached to the tip of a tool body.

[0002]

2. Description of the Related Art As this type of excavating tool, a concave portion formed on the outer periphery of a tip end portion of a tool body so as to be recessed inward is formed around a center line eccentric parallel to the center axis of the tool body. A rotatable bit is attached rotatably,
A drill bit (pilot bit) in which a mounting hole is formed in the center of the tip of the tool body along the axis, and a mounting shaft is formed on the rear end side of the disk-shaped bit body.
However, it has been proposed that the mounting shaft is inserted into the mounting hole and mounted. However, in such a drilling tool, a cutting edge is provided on the tip end surface of the bit body of the drilling bit and the tip end surface of the diameter-enlarging bit by implanting a carbide tip or the like. By rotating around the axis and applying a striking force to the tip side in the axial direction, while excavating with the cutting blade in a state where the diameter-expanding bit is rotated so that the outer diameter from this axis is increased, At the end of excavation, the tool body can be pulled out from the hole by rotating the tool body in a direction opposite to the direction of rotation during excavation, with the diameter-expanding bit reduced in diameter.

[0003]

In such a conventional excavating tool, when the excavating bit is mounted on the tool body by inserting the mounting shaft into the mounting hole, a female is generally provided on the inner periphery of the mounting hole. A method is employed in which a screw portion is formed and a male screw portion is formed on the outer periphery of the mounting shaft portion, and these female and male screw portions are screwed together. The direction of the twist of the male and female threads is directed toward the rear side in the direction of rotation during excavation so that the mounting shaft is not loosened and the excavation bit does not come off due to the rotation of the tool body during excavation. It is formed so as to face the rear end side.

However, in a drilling tool in which the mounting shaft of the drill bit is screwed into the mounting hole of the tool body in such a twisting direction, the mounting shaft is attached to the mounting hole by a load acting on the drill bit during the drilling. As a result, the drill bit needs to be removed and replaced in the event of wear or the like, which requires a great deal of labor and time. On the other hand, in order to prevent such tightening from occurring, for example, when a cylindrical mounting shaft is inserted into a mounting hole having a circular cross section and then fixed with a set screw or a pin, the tool body is There is a possibility that the mounting rigidity of the drill bit with respect to the rotation of the drill bit cannot be ensured, and it becomes impossible to perform drilling with the cutting blade at the tip of the drill bit.

The present invention has been made in view of such circumstances, and in such a drilling tool in which the mounting shaft portion is inserted into the mounting hole and the drill bit is mounted on the tool body, the tool body is rotated. It is an object of the present invention to provide a drilling tool capable of easily removing a drill bit from a tool body at the time of replacement or the like, while ensuring sufficient mounting rigidity of the drill bit even when drilling.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention provides a cutting tool provided at a tip end of a tool body rotated around an axis on the tip end side. An excavating bit having a mounting shaft portion formed on a rear end side thereof, the drill bit being mounted by inserting the mounting shaft portion into a mounting hole that opens at the center of the front end portion of the tool body and extends along the axis. First, a concave groove extending parallel to the axis is formed on the inner periphery of the mounting hole, and both side surfaces of the outer peripheral surface of the mounting shaft portion are in close contact with both inner walls of the concave groove. Secondly, a ridge is formed, and secondly, a fitting portion having a polygonal cross section perpendicular to the axis is formed in the mounting hole, and a side surface of the mounting shaft portion is formed. Forming a fitting part with a polygonal cross section that is in close contact with the inner wall of the fitting part It is characterized in. Therefore, in the excavating tool configured as described above, in any case, the mounting shaft portion is fitted into the mounting hole in a state where the side surface of the mounting shaft portion is in close contact with the inner wall of the mounting hole in the circumferential direction. Even when the female and male screw portions are not screwed together, it is possible to sufficiently secure the mounting rigidity of the drill bit with respect to the rotation of the tool body.

Here, in addition to the above-mentioned excavation bit, when the diameter-expanding bit is attached to the outer periphery of the tip of the tool body as described above, that is, a recess is formed on the outer periphery of the tip of the tool body to be recessed inward. In the case where the large diameter bit provided with the cutting edge on the distal end side is rotatably accommodated in the accommodation concave portion around a center line eccentric in parallel with the axis, the concave groove is formed in the accommodation concave portion. The recess is formed so as to avoid the part which is most concave on the inner peripheral side, or the inner wall of the fitting portion is formed at the part where the concave is most concave on the inner peripheral side, and a cross section orthogonal to the axis is formed on the wall surface of the concave part. If it is formed so as to be parallel, a large thickness can be secured between the concave portion and the mounting hole, and the mounting rigidity of the drill bit can be further improved. Between the recess and the mounting hole It is possible to prevent that or cause.

In this case, the excavating bit is provided with a disk-shaped bit body having the cutting edge provided on a front end face thereof, and the drill bit is provided on the rear end face of the bit main body with the enlarged diameter bit. If a supporting portion for rotatably supporting the distal end portion is provided, it is possible to sufficiently secure the mounting rigidity of the enlarged diameter bit. Further, a pin mounting hole is formed in the tool main body so as to open to the mounting hole, and an engaging pin is protruded into the mounting hole in the pin mounting hole to engage with the mounting shaft. When the mounting shaft is attached to the mounting hole from the front end side of the tool main body, the drill bit can be securely prevented from coming off, and the tool main body is subjected to an impact force in the axial direction. However, it is possible to prevent the drill bit from coming off due to the impact.

[0009]

1 to 3 show a first embodiment of the present invention.
1 shows an embodiment of the present invention. In the present embodiment, the tool main body 1 is formed in a substantially multi-stage cylindrical shape whose outer shape gradually increases in diameter toward the front end side (left side in FIG. 1), and the reduced rear end portion is the shank portion 2. When a hammer or the like (not shown) is attached to the shank portion 2, the tool body 1 receives a striking force toward the front end in the direction of the central axis O during excavation, and the tool main body 1 rotates around the axis O as shown in FIG. Are rotated in the tool rotation direction indicated by the symbol T in FIG. Further, from the rear end face of the shank portion 2 toward the front end side, a through hole 3 through which compressed air or the like is supplied at the time of excavation is formed along the axis O, and the through hole 3 branches in three directions along the way. At the same time, the distal end portion is enlarged in diameter and opened at the center of the distal end surface 1A of the tool main body 1, thereby forming the mounting hole 4 in the present embodiment. A pilot bit 5 is attached. Also, three recesses 6 are formed on the outer periphery of the tip of the tool body 1 so as to be recessed inward.
Are formed at equal intervals in the circumferential direction, and in these recesses 6 are mounted, respectively, rotatable bits 7 rotatable about a central axis X eccentric in parallel with the axis O.

The pilot bit 5 has a disk-shaped bit body 8 having an outer diameter slightly smaller than the outer diameter of the tool body 1.
At the rear end face, a mounting shaft 9 is provided along the center line of the bit body 8.
Are integrally formed to protrude.
Is inserted into the mounting hole 4 so that the pilot bit 5 is mounted on the tip end of the tool main body 1 with the center line being coaxial with the axis O of the tool main body 1. An exhaust hole 10 is formed in the mounting shaft 9 along the axis O. The exhaust hole 10 branches off at the bit body 8 on the tip end side, and the tip of the bit body 8 is formed in a mortar shape. On the outer peripheral surface of the bit body 8, a plurality of excavation chip discharge grooves 12 extending in the direction of the axis O are formed in the outer peripheral surface of the bit body 8 at intervals in the circumferential direction. The exhaust grooves 11 are communicated with some of the exhaust grooves 12. Further, a large number of chips 13 made of a hard material such as a cemented carbide are implanted on the distal end surface of the bit body 6 and the distal end side of the outer peripheral surface so as to avoid the exhaust grooves 11 and the exhaust grooves 12. And
A cutting edge provided on the tip side of the pilot bit 5 is constituted by these tips 13.

On the other hand, the mounting shaft portion 9 of the pilot bit 5 is formed in a substantially multi-stage cylindrical shape whose outer diameter is reduced to three steps as it goes toward the rear end side. An annular groove 14 having a substantially semi-circular cross-section
Are formed on the middle-diameter portion 9B side of the middle tier, and a plurality of ridges 15 extending in the circumferential direction are provided on the outer peripheral surface of the middle-diameter portion 9B at intervals in the circumferential direction. Then 6
Article) Same shape and same size. In the present embodiment, each of the ridges 15... Extends from a position slightly spaced from the foremost large-diameter portion 9C of the mounting shaft portion 9 to the entire length of the middle-diameter middle diameter portion 9B. It is formed so as to extend, and a cross section by a plane including the axis O has a shape of an isosceles trapezoid flat in the radial direction with respect to the axis O as shown in FIG. In the cross section orthogonal to the axis O, the protruding ridge 15 is formed such that a semicircular protruding end protruding from the outer peripheral surface of the middle diameter portion 9B is cut out by a flat surface or a convex curved surface as shown in FIG. That is, a pair of side surfaces 1 facing the circumferential direction of the ridge 15
5A and 15A are arcuate surfaces that are close to each other while protruding toward the outer peripheral surface 15B side of the ridge formed by cutting out the flat surface or the convex curved surface. It is formed so as to form.

Further, as shown in FIG. 4, the six ridges 15 in the present embodiment are formed by a pair of ridges 15, 15 which are close to each other in the circumferential direction of the mounting shaft 9. Three pairs are arranged at regular intervals with an interval larger than the interval between the ridges 15, 15, and one side of each pair of the ridges 15, 15 in the circumferential direction (in the present embodiment, The outer peripheral surface 1 of the ridge 15 (the rear side in the tool rotation direction T).
5B is formed with a concave hole 16 that is concave in the radial direction with respect to the axis O. The intermediate diameter portion 9B on which the ridges 15 are formed has a length in the direction of the axis O longer than the small diameter portion 9A and the large diameter portion 9C.
The length of 5 is also longer than these. The outer diameter of the large diameter portion 9C is substantially the same as the outer diameter formed by the outer peripheral surface 15B of the ridge 15, and is provided on the rear end surface 8A of the bit body 8 of the pilot bit 5 in a cross section including the axis O. It is formed so as to be smoothly connected via a concave curved surface. further,
On the outer peripheral side of the rear end face 8A of the bit main body 8, three support holes 17 having a circular cross-section recessed toward the front end side are formed at equal intervals in the circumferential direction. 5 is arranged coaxially with the central axis X when the tool 5 is attached to the tool body 1, and serves as a support portion in the present embodiment.

On the other hand, the concave portion 6 of the tool body 1 has a bottom surface 18 which is retracted from the tip surface 1A of the tool body 1 and faces the tip side.
And a wall surface 19 extending from the periphery of the bottom surface 18 to the distal end side in parallel to the axis O and reaching the distal end surface 1A. The bottom surface 18 is further located on the rear side of the bottom surface 18 in the tool rotation direction T. A flat bottom surface portion 18A perpendicular to the axis O extending toward the tool rotation direction T and extending inward toward the tool rotation direction T;
The bottom surface portion 18A has a bottom surface portion 18B which is located on the tool rotation direction T side and is inclined toward the rear end side toward the outer peripheral side, and the bottom surface portion 18A has a circular cross section centered on the central axis X. Is formed, and
Branch holes 3A branched from the through hole 3 in three directions are opened in the inclined surface portion 18B. Further, a small-diameter hole 3
B is branched and extends toward the distal end side in parallel with the axis O. The small-diameter hole 3 </ b> B
A, 18B is opened at the intersection ridge. Further, on the outer periphery of the tool body 1, two discharge grooves 21 for excavated swarf extending in parallel to the axis O are formed for each recess 6, and these discharge grooves 21 and 21 are formed on the outer periphery of the bottom portion 18B. The opening is formed on the tool rotation direction T side and the rear side.

On the other hand, the wall surface 19 rises rearward in the tool rotation direction T of the bottom portion 18A so as to intersect the outer peripheral surface of the tool body 1 at an acute angle when viewed from the distal end side as shown in FIG. And a wall portion 19A facing the tool rotation direction T side,
A concave arc-shaped wall portion 19B centered on the central axis X, which smoothly contacts the wall portion 19A;
A wall surface portion 19C extending straight in the tool rotation direction T so as to make an acute angle with the wall surface portion 18A in contact with the wall surface portion 18A, and most concavely on the inner peripheral side of the tool body 1 and close to the mounting hole 4; A step-like wall portion 19D connected to the wall portion 19C and the wall portion 19C via the wall portion 19D.
In the tool rotation direction T side by one step, and
Extending straight in parallel to 9C to the outer periphery of the tool body 1,
And a wall surface portion 19E facing rearward in the tool rotation direction T.

The enlarged-diameter bit 7 attached to the recess 6 configured as described above has a stepped side surface that allows the bit main body 22 to be substantially in close contact with the wall surfaces 19C to 19E as viewed from the distal end side. 22A to 22C and a side surface 22D extending parallel to the side surfaces 22A and 22C.
And a convex semi-circular side surface 22E smoothly contacting the side surfaces 22A and 22D, and a convex curved side surface 22F formed between the side surfaces 22C and 22D. The radius of the side surface 22E is a size that can be in close contact with the wall surface portion 19B having a concave arc shape. At the front and rear end surfaces of the bit main body 22, mounting shafts 23 and 24 having a circular cross section extending coaxially with the central axis of the convex arc formed by the side surface 22E are formed integrally with the bit main body 22, and the mounting on the front end side is performed. The shaft 23 can be fitted into the support hole 17 of the pilot bit 5, and the mounting shaft 24 on the rear end side can be fitted into the support hole 20 of the recess 6, and thus the mounting shafts 23, 24 can be fitted into the support holes 17, 20. By being inserted and supported, the enlarged diameter bit 7 is rotatable about the center axis X as described above while the side surface 22E is in sliding contact with the wall surface portion 19B.

The bit body 22 of the enlarged bit 7 is shown at the lower left side of FIG. 1 when the enlarged bit 7 is rotated in the tool rotation direction T around the central axis X as viewed from the distal end side. The above-mentioned side surfaces 22A to 22
C is housed in the concave portion 6 in close contact with the wall portions 19C to 19E, and its outer diameter from the axis O is reduced, while rotating around the central axis X in the tool rotation direction T rearward. As shown in FIG.
2D abuts against the wall surface portion 19A, and the side surface 22F of the bit main body 22 projects to the outer peripheral side from the outer peripheral surface of the tool main body 1,
The outer diameter from the axis O is increased.
Further, the side surface 22F forms a convex arc surface centered on the axis O in the state where the diameter-expanding bit 7 is expanded in this way, and the front end side of the side surface 22F and the front end side of the side surface 22C, Also, a large number of chips 25 made of a hard material such as a cemented carbide are implanted in the tip end portion of the bit main body 22 projecting outward from the pilot bit 5 in the expanded state. 2
5 constitutes a cutting blade provided on the distal end side of the enlarged diameter bit 7.

Further, the mounting hole 4 into which the mounting shaft 9 of the pilot bit 5 is inserted has an inner diameter corresponding to the shape of the mounting shaft 9 from the tip surface 1A side of the tool body 1 to the through hole. The small diameter portion 4A connected to the rearmost through hole 3 is the small diameter portion 9A of the mounting shaft 9 and the middle diameter portion 4B of the middle stage is the mounting shaft. The medium-diameter portion 9B of the portion 9 and the large-diameter portion 4C on the distal end surface 1A side are formed to have a diameter and depth that the large-diameter portion 9C of the mounting shaft portion 9 can be inserted. From the middle diameter portion 4B to the large diameter portion 4C, the same number (ie, six) of the grooves 26 as the above-mentioned ridges 15 extending parallel to the axis O are formed on the inner periphery thereof.
Are formed in the circumferential direction at equal intervals and arrangement with the ridges 15. Each of the concave grooves 26 has a semi-circular shape whose inner wall 26A has a semi-circular shape with which both side surfaces 15A, 15A of the ridge 15 can be in close contact with each other in a cross section orthogonal to the axis O. It is formed so as to be depressed from the peripheral surface, and the depth from the axis O to the groove bottom is made larger than the radius of the large diameter portion 4C. As shown in FIG. 2 and FIG. 3, the groove extends parallel to the axis O with the groove bottom side left, and the distal end surface 1A
Is reached and opened.

The grooves 26, which are arranged in the same manner as the ridges 15, have three pairs of grooves 26, 26 which are adjacent to each other in the circumferential direction.
26 are arranged at equal intervals in the circumferential direction at an interval larger than the interval between 26. Here, in the present embodiment, these 3
FIG. 2 shows a portion where the interval between the pair of concave grooves 26 is large.
As shown in FIG. 5, the concave groove 26 is formed so as to be located on the wall surface portion 19C most concave on the inner peripheral side among the wall surfaces 19 of the concave portion 6, that is, avoiding the wall surface portion 19C concaved on the inner peripheral side most. Has been made. More specifically, a virtual straight line passing through the axis O and the portion where the concave portion 6 is most recessed on the inner peripheral side as shown in FIG. 1 when viewed from the distal end side (in this embodiment, orthogonal to the wall surface portion 19C through the axis O) It is desirable that the concave groove 26 is not formed on the (straight line) L.

Furthermore, in this embodiment, the tool body 1
The pair of recessed grooves 26, 26 of the mounting hole 4 are formed from the stepped wall portion 19 </ b> D of the wall surface 19 of each of the recesses 6.
A pin mounting hole 27 is formed so as to penetrate the tool body 1 in the radial direction with respect to the axis O toward the concave groove 26 on the rear side in the tool rotation direction T, and is opened in the mounting groove 4. The pin mounting hole 27 projects in the direction of the axis O in a state where the rear end face of the bit body 8 of the pilot bit 5 is brought into close contact with the front end face 1A of the tool body 1 and the mounting shaft 9 is inserted into the mounting hole 4. It is arranged at the same position as the concave hole 16 formed on the outer peripheral surface 15B of the strip 15. On the other hand, the tool main body 1 further extends from the outer peripheral surface of the tool main body 1 in a tangential direction to the inner circumference of the small diameter portion 4A of the mounting hole 4 in a plane perpendicular to the axis O, and comes into contact with the mounting hole 4 to have a half-section. A pin mounting hole 28 is formed so as to open in a circular shape. The pin mounting hole 28 is formed in the middle diameter portion 4A of the small diameter portion 4A in the direction of the axis O.
When the mounting shaft 9 is inserted into the mounting hole 4 and passes through the portion on the side B, the small-diameter portion 9A of the mounting shaft 9 coincides with the annular groove 14 having a semicircular cross section to form a substantially circular cross section. It is formed as follows. The pin mounting holes 27 and 28 have engaging pins 29 and 3 according to the size and depth.
0 is inserted from the outer peripheral side and fixed by a spacer or a snap ring, and its tip is engaged with the concave hole 16 and the annular groove 14 of the pilot bit 5.

In the excavating tool of this embodiment, first, the mounting shaft 24 is inserted into the support hole 20 to accommodate the enlarged bits 7 in the recesses 6. 26, and the mounting shaft 9 is inserted into the mounting hole 4 and the mounting shaft 23 of the diameter-enlarging bit 7 is
7, the pilot bit 5 is mounted on the tip of the tool body 1, and the engaging pins 29, 30 are inserted into the pin mounting holes 27, 28 to be engaged with the concave hole 16 and the annular groove 14. Is assembled. At the time of excavation, the hammer applies a striking force to the tool body 1 and the tool body 1 is moved in the tool rotation direction T via the hammer.
, The diameter-expanding bits 7 are enlarged in diameter, and a drilling is formed in the ground or the like by the cutting edge on the distal end side and the cutting edge on the distal end side of the pilot bit 5. Then, a casing pipe P having an inner diameter through which the tool body 1 can be inserted and an outer diameter slightly smaller than the outer diameter of the enlarged bit 7 when the diameter is enlarged is inserted. After the excavation is completed, the tool body 1 is rotated in the direction opposite to the tool rotation direction T during the excavation, so that the diameter-expanding bits 7 are reduced in diameter.
By pulling out the tool body 1 together with the diameter-enlarging bits 7, only the casing pipe P can be left in the hole.

Thus, in the drilling tool having the above-described configuration, the pilot bit 5 attached as a drill bit to the tip of the tool main body 1 has the mounting shaft 9 attached to the mounting hole 4 of the tool main body 1 as described above. At the time of insertion, the ridges 15 formed on the middle diameter portion 9B of the mounting shaft 9 are fitted into the concave grooves 26 formed on the middle diameter portion 4B of the mounting hole 4. Since both side surfaces 15A, 15A are brought into close contact with the inner wall 26A of the concave groove 26, the tool body 1 at the time of excavation is formed.
, The load acting on the pilot bit 5 can be reliably received by the inner wall 26A closely contacting the side surfaces 15A, 15A, and the mounting rigidity of the pilot bit 5 can be sufficiently ensured. Moreover,
Both side surfaces 15A, 15A of the ridge 15 are the inner walls 26 of the concave groove 26.
Since it is in close contact with A, there is little occurrence of rattling in the circumferential direction between the mounting hole 4 and the mounting shaft 9.

On the other hand, since the ridges 15 and the concave grooves 26 are formed in parallel with the axis O of the tool main body 1, the tool main body 1 is screwed like a conventional male and female screw portion. The rotation of the mounting shaft 9 does not cause the mounting hole 4 to be tightly tightened. When replacing the pilot bit 5, the pilot bit 5 can be easily removed by removing the engaging pins 29 and 30. Is possible. In the present embodiment, the concave groove 26 is used.
Are formed in a semicircular cross section and the side surface 15 of the ridge 15 is formed.
A and 15A are formed in the shape of a circular arc which can be in close contact with the inner wall 26A of the concave groove 26, but the ridge 15 is formed over the entire circumference without notching the outer peripheral surface 15B with a flat or convex curved surface. It may be formed in a semicircular cross section that can be in close contact with the inner wall surface 26A of the concave groove 26, and even if it is not such a semicircular cross section, for example, the cross sections of these ridges and concave grooves are The inner wall may be formed in a square or trapezoidal shape that can be in close contact with each other, or the both side surfaces and the cross section of the inner wall may be formed so as to form an involute curve.

Further, in the excavating tool of the present embodiment, the enlarged diameter bit 7 is accommodated in the concave portion 6 formed on the outer periphery of the tip portion of the tool main body 1 so as to be rotatable around the central axis X. By increasing the diameter of the diameter bit 7, it is possible to form a drilled hole having a diameter larger than that of the tool body 1, and after excavation, by reducing the diameter of the enlarged diameter bit 7, the casing pipe inserted into the drilled hole is formed. Although the tool body 1 can be pulled out through the inside of the P, when forming the concave portion 6 for accommodating such an enlarged bit 7, the concave portion 6 is formed.
Wall portion 19C closest to the mounting hole 4 of the wall surface 19
In the above, the concave groove 26 is not formed on the inner periphery of the mounting hole 4, that is, the concave groove 26 is formed so as to avoid a portion where the concave portion 6 is most concave on the inner peripheral side of the tool body 1. I have. For this reason, in the present embodiment, it is possible to secure a sufficient thickness between the concave portion 6 and the mounting hole 4, which also ensures the mounting rigidity of the pilot bit 5 as a drill bit. Therefore, stable excavation can be promoted even under excavation conditions in which a high load acts on the pilot bit 5.

Further, in the present embodiment, when the diameter-enlarged bit 7 is rotatably mounted on the outer periphery of the distal end portion of the tool body 1 as described above, a support hole as a support portion is provided on the rear end face of the bit body 8 of the pilot bit 5. 17 are formed, and the enlarged diameter bits 7 are attached by fitting the attachment shafts 23 at the tips into the support holes 17 respectively.
That is, since the enlarged bits 7 are attached to the tool body 1 while both ends thereof are supported, according to the present embodiment, it is possible to secure high mounting rigidity also for these enlarged bits 7 and to achieve more stable excavation. Work can be encouraged. In this embodiment, the support hole 17 is formed in the rear end face of the bit body 8 of the pilot bit 5 and the mounting shaft 17 of the enlarged diameter bit 7 is inserted in this manner. Alternatively, a support shaft may be formed as a support portion, and a mounting hole into which the support shaft can be inserted may be formed at the end of the enlarged diameter bit 7 to support the enlarged diameter bit 7.

Furthermore, in the present embodiment, the outer peripheral surface 15B of half of the three ridges 15 that are located at equal intervals in the circumferential direction among the six ridges 15 of the mounting shaft 9. Holes 16 are formed in the mounting shaft 9
An annular groove 14 is formed in the small-diameter portion 9 </ b> A, and engaging pins 29, 30 inserted in pin mounting holes 27, 28 formed in the tool body 1 engage with these concave holes 16 and the annular groove 14. By doing so, the mounting shaft 9 is supported by the mounting hole 4 on the tip side in the axis O direction. Therefore, according to the present embodiment, for example, the mounting shaft 9 does not come off from the mounting hole 4 due to the impact of the impact force given by the hammer during excavation, and the pilot bit 5 does not come off.
The pilot bit 5 and the enlarged bits 7... Can be securely held to perform a smooth excavation operation. The axis O acting on the pilot bit 5 during this excavation
The load in the direction is the bit body 8 of the pilot bit 5.
Since the rear end face is closely contacted with the front end face 1A of the tool body 1 and received by the front end face 1A, there is no possibility that the load applied to the engaging pins 29...

FIGS. 5 to 7 show a second embodiment of the present invention. FIGS. 8 and 9 show a third embodiment of the present invention. Portions common to those of the first embodiment shown in FIG. 1 to FIG. Among them, the second embodiment shown in FIGS. 5 to 7 has three recesses 6 formed on the outer periphery of the distal end of the tool body 1 as in the first embodiment.
In each of the above, a fitting part 31 having a regular hexagonal cross section is formed instead of the concave groove 26 being formed in the mounting hole 4,
The fitting shaft portion 9 of the pilot bit 5 as a drill bit is formed with a fitting portion 32 having a regular hexagonal cross section which can be fitted to the fitting portion 31 instead of the ridge 15. It is characterized by. Further, in the second embodiment, as shown in FIG. 6, in the cross section orthogonal to the axis O, every other six sides of the regular hexagon formed by the inner walls 31A of the fitting portion 31 in the circumferential direction. Are located on the concave portion 6
The concave portion 6 is formed so as to be parallel to the wall surface portion 19C located at a position where the concave portion 6 is most concave on the inner peripheral side.

Further, in the second embodiment, a pair of the pin mounting holes 28, 28 are provided on one plane orthogonal to the axis O on the rear end side of the engaging hole 27 as shown in FIG. Are formed in the tool main body 1 in parallel with each other so as to sandwich the mounting hole 4. These pin mounting holes 28, 28 have a cross section along the one plane, and the inner wall 31 </ b> A of the fitting portion 31.
Are formed so as to extend along two opposing sides of the six sides of a regular hexagon formed by each of the inner walls 31A so as to open in a groove shape having a semicircular cross section. On the other hand, the fitting portion 32 of the mounting shaft 9 is located at the position of the one plane when the pilot bit 5 is mounted, and the fitting portion 32 in a cross section along the one plane. Are formed so as to extend in parallel along two opposing sides out of the six sides of the regular hexagon formed by the side surfaces 32A of the side surfaces 32A. By inserting into
These grooves 32B, 32B and the semicircular grooves of the pin mounting holes 28, 28 opened in the inner walls 31A, 31A coincide with each other to define circular holes communicating with the pin mounting holes 28, 28, respectively. In these holes, pin mounting holes 28 and 2 are inserted.
The engaging pins 30, 30 are respectively fitted and mounted through the mounting shaft 8, and are engaged with the mounting shaft 9.

On the other hand, in the third embodiment shown in FIG. 8 and FIG.
Are formed at equal intervals in the circumferential direction, that is, at intervals of 90 °. Therefore, the wall portions 19A to 19E of the recesses 6 are also arranged at intervals of 90 ° in the circumferential direction. Each of the large-diameter bits 7 is accommodated therein. On the other hand, a fitting portion 33 having a regular octagonal cross section is formed in the mounting hole 4, and the mounting shaft 9 of the pilot bit 5 is A fitted portion 34 also having a regular octagonal cross section that can be fitted to the fitting portion 33 is formed. Further, in the third embodiment, the inner wall 3 of the fitting portion 33 is formed.
Of the eight sides of the regular octagon formed by 3A..., The four sides that are located every other in the circumferential direction are the wall surfaces that are located at the portion of the wall surface 19 of the recess 6 where the recess 6 is most inwardly recessed. Part 19C
Are formed in parallel with each other.

Also, in the third embodiment, as shown in FIG. 9, a pair of the pin mounting holes is formed on one plane perpendicular to the axis O on the rear end side of the engagement hole 27 of the tool body 1. 28,
28 are formed so as to extend along two opposing sides of the eight sides of the regular octagon formed by the inner walls 33A of the fitting portion 33 and to open in the inner walls 33A, 33A in a semicircular cross section. In addition, the fitting portion 34 of the mounting shaft portion 9 has openings of the pin mounting holes 28 along the two opposing sides of the eight sides of the regular octagon formed by the cross section of the side surface 34A. Grooves 34B, 34B having a semicircular arc section are formed to coincide with the portions and define a hole having a circular cross section. Then, the pin mounting holes 28 and 2 are inserted into the holes having the circular cross section thus formed.
The engagement pins 30, 30 are respectively fitted and fixed through the through holes 8, so that the engagement pins 30, 30 are engaged with the mounting shaft 9 in the axis O direction.

In the second and third embodiments, the fitting portions 32 of the mounting shaft 9 are also provided on the inner walls 31A, 33A of the fitting portions 31, 33 of the mounting hole 4. , 3
4 are brought into close contact with each other,
Since the rotation of the mounting shaft 9 in the circumferential direction around the axis O is restricted, the mounting shaft 9 can be mounted to the mounting hole 4 with high rigidity to hold the pilot bit 5 at the tip of the tool body 1. Further, the mounting shaft 9 is not tightly fastened to the mounting hole 4 by a load acting during excavation as in the case of screwing by the male and female screw portions. Moreover, in the second embodiment, the wall portions 19C of the three concave portions 6 are arranged at regular intervals in the circumferential direction, that is, are arranged at intervals of 120 °, whereas the regular hexagonal cross section is used. Are arranged at intervals of 60 °, and every other inner wall 31A is arranged parallel to the wall surface portion 19C,
In the third embodiment, each wall 19 of the four recesses 6...
Are arranged at 90 ° intervals, whereas every other (90 °) inner walls 33A of the fitting portions 33 having a regular octagonal cross section are arranged in parallel with each wall portion 19C. Accordingly, the rigidity around the mounting hole 4 can be secured by keeping the distance between the wall surface portion 19C and the inner walls 31A, 33A constant.

In addition, in the second and third embodiments, a pair of pin mounting holes 28, 28 are formed on the rear end side of the pin mounting hole 27, and these pin mounting holes 2 are formed.
Reference numerals 8, 28 denote the mounting surfaces along the two opposing sides of the polygon formed by the cross sections of the inner walls 31A, 33A of the fitting portions 31, 33 of the mounting hole 4 in the one plane perpendicular to the axis O. The mounting shaft 9 is formed so as to sandwich the hole 4.
, 34A of the mating parts 32, 34
The grooves 32B, 32B and the grooves 34B, 34B are formed along two opposing sides of the polygon formed by the cross section of..., And the engaging pins 30 fitted and mounted in the pin mounting holes 28, 28, respectively. , 30 are engaged with these grooves 32B, 32B and grooves 34B, 34B. Therefore, the first
As compared with the case where the engaging pin 30 is attached to and engaged with one pin attaching hole 28 formed along the tangential direction of the attaching hole 4 having a circular cross section and the attaching shaft portion 9 as in the embodiment of FIG. According to the second and third embodiments, the pilot bit 5 can be extended because the length of the engagement between the engagement pin 30 and the mounting shaft 9 can be extended as well as the number of the engagement bits 30 increases.
Can be more reliably prevented.

In the second and third embodiments,
The fitting portions 31, 33 of the mounting hole 4 and the fitted portion 3 of the mounting shaft portion 9
2 and 34 are formed in a regular hexagonal section and an octagonal section that can be fitted to each other.
In the case of an octagonal shape, for example, the fitted portions 32, 34
, Which have side surfaces 32A... 34A that can be in close contact with the inner walls 31A.
Side faces 32A, which can be formed in a hexagonal shape, a decentered 12-hexagonal shape, or can be in close contact with every other inner wall 31A, 33A,.
34A... Conversely, when the fitting portions 32 and 34 have a regular hexagonal and octagonal cross section, for example, the fitting portions 31 and 33 are formed by alternately forming the side surfaces 32A. , 8A having inner walls 31A, 33A that can be in close contact with 34A.
It may be formed in a square shape, a regular triangular shape in cross section, or a square shape. In the latter case, in particular, corners where adjacent inner walls 31A...
It may be formed in a concave curved surface as long as it does not interfere with 2A..., 34A. Furthermore, other than the regular hexagonal and octagonal shapes, other polygonal cross-sections can be adopted as long as the fitting portion of the mounting shaft can be fitted into the fitting portion of the mounting hole. .

[0033]

As described above, according to the present invention,
First, a concave groove extending parallel to the central axis of the tool body is formed on the inner periphery of the mounting hole, and both sides of the mounting shaft of the drill bit are in close contact with both inner walls of the concave groove. Secondly, by forming the ridge, secondly, a fitting portion having a polygonal cross section orthogonal to the axis is formed in the mounting hole, and a side surface of the mounting shaft portion is formed on the inner wall of the fitting portion. By forming the fitting portion having a polygonal cross section, the mounting rigidity of the drill bit to the tool body can be secured and stable drilling work can be achieved. As described above, the mounting shaft portion of the drill bit is not tightly tightened to the mounting hole of the tool body due to the load at the time of drilling, so that the replacement of the drill bit can be performed extremely easily and in a short time.

[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 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 sectional view taken along line YY in FIG. 5;

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

FIG. 8 is a view showing a third embodiment of the present invention and corresponding to a YY cross section in FIG. 5;

FIG. 9 is a view showing a third embodiment of the present invention and corresponding to a ZZ cross section in FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tool main body 4 Mounting hole 5 Pilot bit (digging bit) 6 Concave part 7 Diameter enlarged bit 8 Bit main body of pilot bit 5 9 Mounting shaft part 13, 25 Tip (cutting blade) 14 Annular groove 15 Protrusion 15A Side face of projection 15 16 Concave hole 17, 20 Support hole 19C Wall surface portion of wall surface 19 of concave portion 6 (portion where concave portion is most concave to the inner peripheral side) 23, 24 Mounting shaft of enlarged diameter bit 7 26 Groove groove 26A Inner wall of concave groove 26 27, 28 Pin mounting holes 29, 30 Engagement pins 31, 33 Fitting parts 31A, 33A Inner walls 32, 34 Fitted parts 32A, 34A Side faces 32B, 34B of fitted parts 32, 34 Groove O Center axis of the tool body 1 X Center axis of the enlarged diameter bit 7 T Tool rotation direction during excavation

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

Claims (6)

[Claims] An excavation bit having a cutting edge provided at a distal end side and a mounting shaft portion formed at a rear end side is provided at a front end portion of the tool main body which is rotated around an axis. In a drilling tool mounted by inserting the mounting shaft into the mounting hole that is open and extends along the axis, a concave groove extending parallel to the axis is formed on the inner periphery of the mounting hole, A digging tool characterized in that a ridge is formed on the outer periphery of the mounting shaft portion so that both side surfaces thereof are in close contact with both inner walls of the concave groove. 2. A concave portion is formed on the outer periphery of the distal end portion of the tool main body, the concave portion being recessed toward the inner peripheral side. The excavating tool according to claim 1, wherein the recess is formed so as to be rotatable around the center line, and the concave groove is formed so as to avoid a portion where the concave portion is most concave on the inner peripheral side. 3. A cutting bit provided with a cutting edge at a tip end and a mounting shaft at a rear end side is provided at a tip end of the tool main body which is rotated about an axis. In a drilling tool mounted by inserting the mounting shaft portion into a mounting hole that is open and extends along the axis, the mounting hole is formed with a fitting portion having a polygonal cross section orthogonal to the axis. And a fitting part having a polygonal cross section whose side surface is in close contact with the inner wall of the fitting part is formed on the mounting shaft part. 4. A concave portion is formed on the outer periphery of the distal end portion of the tool main body, the concave portion being recessed toward the inner peripheral side. The inner wall of the fitting portion is rotatably accommodated around the center line, and the section perpendicular to the axis is parallel to the wall surface of the concave portion at a portion where the concave portion is most concave on the inner peripheral side. The excavating tool according to claim 3, wherein the excavating tool is formed. 5. The excavating bit includes a disk-shaped bit main body having the cutting edge provided on a tip end surface thereof,
The excavating tool according to claim 2 or 4, wherein a supporting portion for rotatably supporting a tip portion of the enlarged diameter bit is provided on a rear end surface of the bit main body. 6. A tool mounting hole is formed in the tool main body so as to open into the mounting hole, and an engaging pin projects into the mounting hole in the pin mounting hole so that the mounting shaft portion is formed. The excavation tool according to any one of claims 1 to 5, wherein the excavation tool is attached so as to engage with the excavation tool.