JP3402211B2 - Drilling tools - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excavating tool used for excavating earth and sand, rocks and the like in civil works such as anchor work, various well works and foundation pile work.

[0002]

2. Description of the Related Art In an excavating tool of this type, a tool body (device) of a substantially columnar shape having a shank portion on the rear end side thereof.
And a drill bit attached to the tip of the tool body, the tool body is rotated around its axis and a striking force is applied in the axial direction to perform excavation by the drill bit, a so-called rotary striking. Type drilling tools are known. Then, the inventors of the present invention have, as the excavating bit, a pilot bit fixed by inserting a shaft portion into a mounting hole formed in the tool body, and a rear end side outer periphery of the tool body with respect to the pilot bit. Japanese Patent Application No. 9-235246 proposes a drilling tool provided with a diameter-expanding bit rotatably attached to a section. However, with such an excavating tool, the expanding bit will excavate the earth and sand, rocks, etc. that were easily crushed by the preceding pilot bit. It is possible to reduce the burden of.

[0003]

By the way, when the drill bit is fixed to the tool body by inserting the shaft portion into the mounting hole formed in the tool body, as in the pilot bit, the drill bit of this type is used. Also in the tool, a female screw portion is formed on the inner circumference of the mounting hole and a male screw portion is formed on the outer circumference of the shaft portion so that the female screw portion and the male screw portion are screw-fitted to each other. However, in such an excavating tool, a rope screw having a smooth R-shaped thread or a high lead screw having a reverse buttress type screw shape is used as the type of the screw instead of a general triangular screw. In a screw with such a shape, the angle of inclination of the bevel surface of the thread with respect to the central axis of the thread in the cross section including the central axis of the thread part is relatively small, that is, the bevel of the thread is gently inclined. If the heights of the crests are the same, the contact area of the male and female threaded parts for each crest is large, and the lead angle of the threaded part is set to be relatively small, which makes the screws difficult to loosen.

However, in the excavating tool for excavating by the rotary impact force applied to the tool body as described above, due to the resistance at the time of excavation, the pilot bit is rotated in a direction in which the pilot bit is screwed deeper into the mounting hole of the tool body. Has a problem that the shaft portion of the pilot bit is excessively tightened in the mounting hole. Moreover, if the screw part for attaching the pilot bit to the tool body is a type of screw that is hard to loosen as described above, the shaft of the pilot bit will be tightened in the tighter mounting hole, making it excessively strong. Since the pilot bit is fixed to the tool body, it may be difficult to remove the pilot bit from the tool body even when the pilot bit used for excavation to some extent is to be replaced.

Further, in this type of drilling tool, after the drilling is completed, the drilling bit is removed from the tool body (casing pipe, rod, etc.) and left in the drilled hole, and only the tool body is pulled out from the drilled hole. , Those that use so-called lost bits as drilling bits are, for example,
6-121786 and the like. However, in such a drilling tool, if the drilling bit and the tool body are tightly tightened as described above, the drilling bit cannot be removed. Therefore, the drilling bit is attached to the tool body by screw fitting. That was previously impossible.

The present invention has been made in view of the above circumstances, and in an excavating tool in which the excavating bit is attached to the tool body by screw fitting, the excavating bit is excessively tightened even when a rotational force is applied. It is an object of the present invention to provide a drilling tool that prevents the occurrence of damage and can easily remove the drilling bit at the time of replacement.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve such an object, the present invention provides a drill bit at the tip of a tool body on one of the tool body and the drill bit. The male threaded portion on the outer periphery of the shaft portion provided on the other side is screw-fitted to the female threaded portion on the inner periphery of the mounting hole, and the lead angle of these threaded portions is set in the range of 5 ° to 16 ° The inclination angle of the slope of the screw thread with respect to the central axis in the cross section including the central axis of the part is 40 °.
Set within the range of ~ 70 °, and set the internal thread part to the tool body
And a cylindrical pick mounted on one of the drill bits
Formed on the inner circumference of the sleeve to divide this sleeve in the circumferential direction
The feature is that it is possible . However, in the excavating tool in which the excavating bit is attached to the tool body by such a screw portion, the lead angle of the screw portion is 5 ° or more, which is larger than that of the conventional one, and the inclination angle of the slope of the screw thread is 40 °. Since the contact angle between the male and female screw portions is steep with a steep slope of more than °, even if the male screw portion is screwed into the female screw portion, the shaft portion is not overtightened. However, if the lead angle is larger than 16 ° or the inclination angle is larger than 70 °, the excavation bit may be too loose and rattling may occur during excavation.

In the excavating tool having the above structure, the screw thread of the screw portion is formed to have a trapezoidal cross section, so that the contact area of the male and female screw portions is further reduced and the excavation bit is more easily removed. Can be On the other hand, in such an excavating tool, in order to securely attach the excavating bit on which a large excavating load is applied, it is necessary to secure a certain outer diameter to the shaft portion, and accordingly, the inner diameter of the mounting hole is naturally increased. growing. However, it is not easy to directly form the above-mentioned female screw portion in such a mounting hole having a large inner diameter, and this results in an increase in the number of steps for manufacturing the drilling tool. Therefore, in the present invention
Is the female screw portion, so as to form the inner peripheral portion of the cylindrical sleeve attached to one of the tool body and the drill bit, to allow dividing the sleeve in the circumferential direction
As a result , the formation of the female screw portion can be facilitated and the number of steps can be suppressed, and play is caused by the clearance defined between the divided sleeve and one of the tool body and the drill bit, It becomes possible to make the drill bit easier to remove.

[0009]

1 to 6 show a first embodiment of the present invention.
FIG. The excavating tool of the present embodiment is inserted into an annular casing top 2 joined to the tip of a cylindrical casing 1 and is rotated around its axis O, and at the same time a striking force is applied toward the tip side in the direction of the axis O. A tool body (device) 3 for receiving the force, a pilot bit 4 as a drill bit of the present embodiment fixedly attached to the center of the tip of the tool body 3, and a pilot bit 4 at the tip of the tool body 3 from the pilot bit 4. Is also arranged on the outer peripheral side of the rear end at equal intervals in the circumferential direction, and is roughly composed of three diameter-increasing bits 5 ... Which are mounted rotatably around a central axis X parallel to the axis O. Here, the casing top 2 is attached to the front end of the casing 1 by inserting the rear end portion thereof into the casing 1 and welding the casing top 2, whereby the inner peripheral portion on the front end side of the casing 1 has the above-mentioned structure. A step portion is formed by the rear end surface 2A of the casing top 2.

The tool body 3 is formed in a generally multi-stage cylindrical shape, and a shank portion 6 is formed at the rear end portion thereof, and a hammer (not shown) attached to the shank portion 6 causes the tool body 3 to have the above-described structure. A rotary impact force is applied. In addition, a flange portion 7 which can be inserted into the casing 1 and has an outer diameter larger than the inner diameter of the casing top 2 is formed on the outer peripheral portion of the tool body 3, and the outer peripheral portion on the tip side of the flange portion 7 is formed. The outer diameter of is the size that can be inserted into the casing top 2. Further, on the outer peripheral portion of the tool main body 3, there are provided three discharge grooves 8 for cutting powder having a U-shaped cross section which penetrates from the tip of the tool main body 3 to the flange portion 7 in parallel with the axis O. Are formed at equal intervals in the direction, and three recesses 9 ... In which the enlarged diameter bits 5 ... Are accommodated are formed on the tip end surface of the tool main body 3.
It is formed so as to communicate with each of the openings.

The recess 9 has a bottom surface 9A that recedes one step from the tip surface of the tool body 3, a wall surface 9B that stands upright from the bottom surface 9A and faces the outer peripheral side of the tool, and a tool rotation direction T side during excavation. The wall surface 9C is substantially defined by the wall surface 9C, and the wall surface 9B has a stepped shape when viewed from the tool tip side, and the outer peripheral side intersects the portion of the discharge groove 8 on the tool rotation direction T side, while the wall surface 9C is It is formed so as to intersect with the wall surface 9B via a wall surface having a concave arc surface, and the outer peripheral side thereof is connected to the outer peripheral surface of the tool body 3 at a portion rearward of the discharge groove 8 in the tool rotation direction T. . Further, on the bottom surface 9A of the recess 9, a recess 10 is formed at an intersection with the discharge groove 8 so as to be gradually deepened toward the outer peripheral side of the tool, and the wall surfaces 9B and 9C are formed. A mounting hole 11 having a circular cross section is formed in the vicinity of the intersecting portion so as to be coaxial with the central axis of the wall surface having the concave arc shape when viewed from the tool tip side. Is the central axis X of the rotation of. In addition, the tip surface of the tool body 3 is formed so that the inner peripheral portion thereof protrudes one step further toward the tool tip side than the outer peripheral portion through a substantially circular step portion 12, and the recess 9
Is formed so as to extend beyond the step portion 12 and reach the inner peripheral portion of the tip surface.

The expanded bit 5 housed in the recess 9 thus formed is fitted into the mounting hole 11 on the rear end surface of the block-shaped main body 5A which is blade-shaped when viewed from the tip side of the tool. A possible columnar shaft portion 5B is integrally formed, and a large number of chips 13 made of a hard material such as cemented carbide are implanted on the front end surface and the outer peripheral side end surface of the main body 5A. Further, when viewed from the tool tip side, a side surface of the main body 5A opposite to the outer peripheral end surface is formed in a convex arc surface shape having a radius of curvature substantially equal to the concave arc wall surface of the recess 9, and The shaft portion 5B is arranged coaxially with the central axis of the convex arc surface, and when the shaft portion 5B is fitted into the mounting hole 11 as described above, the convex arc-shaped side surface of the main body 5A is concave. It can be slidably contacted with the concave arc-shaped wall surface of the place 9. Then, the shaft portion 5B is fitted into the mounting hole 11 and the recess 9 is formed.
When the tool body 3 is rotated in the tool rotation direction T, the diameter expansion bit 5 accommodated in is expanded by the excavation resistance and is positioned by contacting the wall surface 9C as shown in FIG. On the contrary, when the tool main body 3 rotates in the direction opposite to the tool rotation direction T, the diameter is reduced as shown in FIG.

The body 5A of the expanding bit 5 has its axis O when the expanding bit 5 is contracted.
While the outer diameter from the axis O of the portion farthest from the outer diameter is made smaller than the inner diameter of the casing top 2, the outer peripheral side end surface is larger than the outer peripheral surface of the casing 1 in a state where the diameter expanding bit 5 is expanded. Also protrudes to the outer peripheral side and has an axis O
It is formed so as to form an arc surface centering on. Further, in the present embodiment, the shaft portion 5B of the expanded diameter bit 5 is
Is formed to be slightly longer than the depth of the mounting hole 11, and the rear end surface of the shaft portion 5B abuts the bottom surface of the mounting hole 11, while the rear end surface of the main body 5A and the bottom surface 9A of the recess 9 are formed. A small gap is defined between the and. Furthermore, the main body 5A
Of the tip end surface of the main body 5A on the side of the convex arc surface side is a flat surface that protrudes one step toward the tool tip end side via the step portion 14, and this flat surface extends the shaft portion 5B. While being in contact with the bottom surface of the mounting hole, the tool body 3 is arranged so as to recede slightly from the inner peripheral portion of the tip surface of the tool body 3 that protrudes one step, while the step portion 14 is viewed from the tool tip side. When the diameter-enlarging bit 5 is expanded, it is formed in an arc shape that is continuous with the step portion 12 on the tip end surface of the tool body 3, and when the diameter-enlarging bit 5 is reduced in diameter, it crosses the step portion 12. It is arranged so as to extend and face the tool rotation direction T side during excavation.

On the other hand, a through hole 15 is formed in the tool main body 3 along the axis O, and the tool tip side of the through hole 15 is formed so as to have a diameter increased by one step. 4 is used as the mounting hole 16 in this embodiment. A recess 17 is formed at the center of the inner periphery of the mounting hole 16 in the direction of the axis O toward the tool rear end side. Is attached with a sleeve 18 having a substantially cylindrical shape centered on the axis O, and a single threaded portion 19 is formed on the inner circumference of the sleeve 18.
The lead angle of the internal thread portion 19 is set in the range of 5 ° to 16 °, and the thread 19A has a trapezoidal shape as shown in FIG. 6 in a cross section including the axis O. The inclination angle θ formed by the inclined surface 19B of the screw thread 19A with respect to the axis O is set in the range of 40 ° to 70 °. The twisting direction of the female screw portion 19 is
Pilot bit 4 by rotation of tool body 3 during excavation
So as not to loosen, it is twisted in a direction opposite to the direction of the tool rotation direction T as it goes toward the tool rear end side.

Here, in the present embodiment, this sleeve 1
Reference numeral 8 denotes three sleeve members 18A, 18B, 18 having an outer shape of an arc plate having a substantially 1/3 circumference as shown in FIGS.
It is separable in the circumferential direction by C, and these sleeve members 18A to 18C are housed in the recess 17 so as to form a cylindrical shape, and the sleeve 18 is configured. A convex portion 20 is formed on the outer peripheral surface of each of the sleeve members 18A to 18C, the diameter of which is increased by one step toward the outer peripheral side. The sleeve members 18 </ b> A to 18 </ b> C are constrained in the direction of the axis O by being fitted and housed in the recess 17. Further, a concave groove 21 having an arcuate cross section is formed in the convex portion 20 so as to extend in the direction of the axis O, while the tip end surface of the tool body 3 communicates with the second expanded portion of the concave portion 17. Are formed in parallel with the axis O and at equal intervals in the circumferential direction so that the pin 23 and the spacer 24 are formed in the pin hole 22 from the tool tip side.
Is inserted and is prevented from coming off by a snap ring 25, and each of the sleeve members 18A to 18C has a pin hole 22.
By engaging the concave groove 21 with the pin 23 exposed in the concave portion 17 from above, it is also restrained in the circumferential direction with respect to the axis O.

Further, in the present embodiment, a slight gap is provided between the sleeve members 18A to 18C which are adjacent to each other in the circumferential direction, and the pins 26 are respectively interposed therebetween. Further, as shown in FIG. 4, the side surfaces of the sleeve members 18A to 18C adjacent to each other in the circumferential direction facing each other are inclined so as to be separated from each other toward the outer peripheral side, and the sleeve members 18A and 18B face each other. The included angle β formed by the opposing side surfaces of the sleeve members 18A and 18B and the sleeve member 18C is larger than the included angle α formed by the side surfaces.
Furthermore, from the outer peripheral surface of the tool body 3, the mounting hole 1
A blind hole 27 is formed so as to be in contact with the inner circumference of the mounting hole 16 in a cross section orthogonal to the axis O of the tool body 3 toward a portion of the tool body 6 on the rear end side of the recess 17. Furthermore, three air holes 28 ...
Are formed so as to be branched and extend toward the outer peripheral side of the tool tip, and these air holes 28 ...
Each recess 10 is opened.

On the other hand, the pilot bit 4 mounted in the mounting hole 16 thus constructed has a large number of hard materials such as cemented carbide on the tip end surface and outer peripheral surface of the disk-shaped main body 4A in this embodiment. The chips 29 are planted, and the mounting hole 1 is provided at the center of the rear end surface of the main body 4A.
The shaft portion 4B to be inserted into the shaft 6 is integrally formed. On the outer circumference of the shaft portion 4B, a male screw portion 30 that is screwed into the female screw portion 19 on the inner circumference of the sleeve 18 is formed. . Therefore, the lead angle of the male screw portion 30 and the inclination angle of the slope of the screw thread with respect to the axis O are set to be the same as those of the female screw portion 19, that is, the lead angle is 5 °.
In the range of up to 16 °, and the slope 30B of its thread 30A
The inclination angle θ is set in the range of 40 ° to 70 °. Further, an annular groove 31 is formed on the rear end side of the male screw portion 30 of the shaft portion 4B, and the annular groove 31 is
With the male screw portion 30 screwed into the female screw portion 19 and the pilot bit 4 is attached to the tool body 3, the mounting hole 1
6 are arranged so that the blind holes 27 on the inner circumference coincide with the positions in the direction of the axis O and communicate with each other. The pins 32 and the spacers 33 are inserted into the blind holes 27 from the outer peripheral side of the tool, and the snap rings 34 are provided. By fixing
The pin 32 is engaged with the annular groove 31 of the shaft portion 4B to prevent the pilot bit 4 from coming off.

Further, the main body 4A of the pilot bit 4 thus mounted in the mounting hole 16 has its rear end face located on the front end side with a space from the front end face of the tool main body 3, and outside thereof. The diameter ranges from the axis O to each expanded bit 5 ...
It is set to be larger than the distance to the inner peripheral edge of. Further, in the present embodiment, this pilot bit 4
Between the rear end surface of the main body 4A and the front end surface of the tool main body 3,
A spacer 35 having an annular flat plate shape is interposed. The spacer 35 is made of a metal material having a hardness slightly lower than that of the metal material forming the tool body 3, the pilot bit 4, and the expanded diameter bit 5 ... By screwing the shaft portion 4B of the bit 4 into the mounting hole 16, the front and rear end surfaces of the spacer 35 are the main body 4A of the pilot bit 4.
The rear end face and the front end face of the tool body 3 are in close contact with each other.

As described above, since the flat surface at the tip of the diameter-increasing bit 5 is slightly retracted with respect to the tip surface of the tool body 3, the spacer 35 and the diameter-increasing bit 5 are formed.
A very small gap will be defined between and. Further, on the tip surface of the main body 4A of the pilot bit 4, two recessed grooves 36, 36 extending from the center to the outer peripheral side in the diameter direction with respect to the axis O are formed.
6 recessed grooves 37 extending in the direction of the axis O are formed at equal intervals in the peripheral direction on the outer peripheral surface of, and 2 of them are formed so as to communicate with the outer peripheral ends of the recessed grooves 36, 36. Has been done. Further, the pilot bit 4 has an air hole 3 extending from the shaft portion 4B along the axis O toward the tip side.
8 is formed, and the air hole 38 is formed so as to be branched into two on the tip end side and open to the inner peripheral side end portions of the concave grooves 36, 36.

In the excavating tool thus constructed, however, a turning force is applied to the tool body 3 in the tool rotating direction T and a striking force is applied toward the tip end side in the axis O direction during excavation. The diameter-enlarging bits 5 ... Rotate to expand around the axis X, and the rock and the like are crushed together with the pilot bit 4 for excavation. At this time, in the above-mentioned excavation tool, the rock bed that is easily crushed by the pilot bit 4 protruding toward the tool tip side and preceding to the tip side in the direction of the axis O is the pilot bit 4
Since the tool rear end side is excavated by the diameter-enlarging bit 5 ... whose diameter is expanded to the outer peripheral side of the tool, efficient excavation can be performed. Further, after the excavation is completed, the tool body 3 is rotated in the direction opposite to the tool rotation direction T, so that the diameter-enlarging bits 5 ... Rotate in the direction in which the diameter-enlarging bits 5 ... Since the outer diameter from the axis O is smaller than the inner diameter of the casing top 2, it is possible to extract the excavating tool while leaving the casing 1 and the casing top 2 in the hole.

In the excavating tool, the pilot bit 4 fixedly attached to the tool body 3 among the pilot bit 4 and the diameter-expanding bit 5, ... Is the male screw portion 30 formed on the shaft portion 4B of the tool. The female screw portion 19 provided on the inner circumference of the mounting hole 16 of the main body 3 is screwed into the female screw portion 19 to be attached.
Has a lead angle in the range of 5 ° to 16 ° and the central axis of the male and female threaded portions 19, 30, that is, the axis O of the slopes 19B, 30B of the threads 19A, 30A in a cross section including the axis O. The inclination angle θ with respect to 40 ° to 7
It is set in the range of 0 ° and is made larger than the conventional drilling tools. Therefore, such a male and female screw part 1
In the excavating tool in which the pilot bit 4 is screw-fitted by the screws 9 and 30, since the lead angle is large, the male screw portion 30 is easily loosened from the female screw portion 19, and since the inclination angle θ is large, the female and male screw portions 19 and 30 are The contact area becomes smaller and the resistance between the two becomes smaller.

Therefore, according to the excavating tool having the above structure,
Due to the excavation resistance due to the rotational force of the tool body 3 during excavation, even if a rotational force such that the shaft portion 4B of the pilot bit 4 is strongly screwed into the mounting hole 16 of the tool body 3, the male screw portion 30 of the shaft portion 4B is The female screw portion 19 provided in the mounting hole 16 is not too tightly tightened,
Therefore, for example, when exchanging the pilot bit 4 worn by excavation, the pilot bit 4 can be easily removed. In the above excavating tool, as described above, the lead angles of the female and male threaded portions 19 and 30 are 5 ° to 1 °.
Slope 1 of the thread 19A, 30A in the range of 6 °
The inclination angles θ of 9B and 30B are set in the range of 40 ° to 70 °, but if the lead angle is less than 5 ° or the inclination angle θ is less than 40 °, the above effect is obtained. On the other hand, if the lead angle is larger than 16 ° or the inclination angle θ is larger than 70 °, the male screw portion 30 becomes too easy to loosen from the female screw portion 19 and the excavation during excavation becomes insufficient. This is because the pilot bit 4 may rattle due to an impact or the like.

Further, particularly in the excavating tool of this embodiment, the threads 19A, 30A of the female and male threaded portions 19, 30 have a trapezoidal cross section, for example, as compared with a thread having a triangular cross section. If the screw pitch is the same, the thread 19
The slopes 19B and 30B of A and 30A can be shortened, whereby the contact area between the male and female screw portions 19 and 30 can be further reduced, and the pilot bit 4 can be removed more easily. Moreover, the screw thread 19A,
Since the cross section of 30A is trapezoidal, the height of the threads 19A, 30A can be kept low even if the inclination angle θ of the threads 19A, 30A is set large as described above. As a result, the thickness in the radial direction with respect to the axis O required to form the female and male threaded portions 19 and 30 can be reduced, so that the inner circumference of the mounting hole 16 can be shaved larger than necessary to provide the female threaded portion 19, for example. Alternatively, it is possible to avoid a situation in which the effective diameter of the shaft portion 4B is limited to be small because the male screw portion 30 is formed.

Further, in this embodiment, when the female screw portion 19 is provided on the inner periphery of the mounting hole 16, the mounting hole 16 is
Is formed with a concave portion 17 on the inner periphery thereof, and a sleeve 18 having an internal thread portion 19 formed on the inner periphery thereof is attached to the concave portion 17. The sleeve 18 is circumferentially formed by three sleeve members 18A to 18C. It is supposed to be divisible. Therefore, according to the present embodiment, in order to secure the outer diameter of the shaft portion 4B of the pilot bit 4 that receives the excavating load, the inner diameter of the mounting hole 16 must be increased to some extent. As compared with the case where the female screw portion 19 is directly formed in the mounting hole 16 having a large inner diameter, after forming the female screw portion 19 individually on each of the sleeve members 18A to 18C, these are combined to form a continuous female screw portion 19. And the internal thread portion 19
It is possible to suppress the number of man-hours when manufacturing the excavating tool provided with.

Further, by making the cylindrical sleeve 18 circumferentially separable by the plurality of sleeve members 18A to 18C, the sleeve members 18A can be divided.
18C and the recess 17 of the mounting hole 16 of the tool body 3 and the shaft portion 4B of the pilot bit 4 define a slight clearance in the radial direction.
This clearance is used when removing the female thread 1
Since play occurs between the male screw portion 9 and the male screw portion 30, the pilot bit 4 can be removed more easily.
Moreover, in the present embodiment, each sleeve member 18A-18
Since Cs are arranged at intervals in the circumferential direction and clearances are also generated in the circumferential direction between the sleeve members 18A to 18C adjacent to each other, the pilot bit 4 can be further easily removed. Further, in addition to the sleeve members 18A to 18C being circumferentially spaced apart in this manner, in the present embodiment, the side surfaces of the adjacent sleeve members 18A to 18C facing each other are inclined, and the side surfaces facing each other are inclined. Since the included angles α and β formed by the two are different from each other, the sleeve member 18A
There is also an advantage that it is possible to easily attach / detach to / from 18C of the concave portion 17.

By the way, as in the present embodiment, the tool body 3
In an excavating tool that excavates rock or the like by the rotational impact force applied to the tool body, in order to efficiently transmit the impact force applied to the tool tip 3 to the tool tip side to the pilot bit 4 as an excavation bit at the tip thereof. It is desirable that the tool body 3 and the pilot bit 4 are in surface contact with each other with a larger contact area and are in close contact with each other. Therefore, in this embodiment,
The spacer 35 is interposed between the tip surface of the tool body 3 and the rear end surface of the body 4A of the pilot bit 4, and thus the tool body 3 and the pilot bit 4 are
When the pilot bit 4 is indirectly contacted with the spacer 35 through the spacer 35 as in the present embodiment, the pilot bit 4 is generated by the rotational force.
Is strongly screwed into the mounting hole 16, the tool body 3 and the body 4A of the pilot bit 4 and the spacer 35 are excessively tightly adhered, and the pilot bit 4 is further removed from the tool body 3 by the frictional force between them. The problem of becoming difficult arises. This is the same even when the tool body 3 and the pilot bit 4 are directly brought into close contact with each other.

However, in the excavating tool having the above-described structure, the female and male screw portions 19 and 30 are easily loosened as described above, and thus the tool main body 3 and the main body 4A of the pilot bit 4 as the excavating bit are formed. Even if they are indirectly attached through the spacer 35, or the tool body 3
Even when the main body 4A of the pilot bit 4 and the pilot bit 4 are brought into close contact with each other, the shaft portion 4B can be reliably pulled out from the mounting hole 16 and the pilot bit 4 can be removed from the tool main body 3. Moreover, in this embodiment, the spacer 35 is interposed between the tip end surface of the tool main body 3 and the rear end surface of the main body 4B of the pilot bit 4, as described above.
Is formed of a material having a hardness lower than that of the material forming the tool body 3 and the pilot bit 4, so that even if the pilot bit 4 strongly adheres to the tool body 3, the spacer 35 is destroyed. By removing the pilot bit 4 by, for example, the frictional force acting between the two, it is possible to easily remove the pilot bit 4. Further, since the spacer 35 is formed of a material having a low hardness as described above, even if a shocking excavating load acts on the pilot bit 4, the shock can be absorbed by the spacer 35, and the tool body can be absorbed. It is also possible to obtain the effect of preventing a situation in which 3 or the pilot bit 4 is damaged.

In this embodiment, in the excavating tool in which the tool body 3 inserted into the casing 1 is formed with the mounting hole 16 and the pilot bit 4 as the excavating bit is formed with the shaft portion 4B, Male and female screw portions 19 provided on the inner circumference of the mounting hole 16 and the outer circumference of the shaft portion 4B,
Although the lead angle of 30 and the inclination angle θ of the slopes 19B and 30B of the screw threads 19A and 30A are set as described above, for example, the casing pipe itself is rotated as a tool body to attach the inner circumference of the casing pipe. It is also possible to employ the above configuration in a drilling tool in which a female screw portion is provided as a hole and a rear end portion of a drill bit is a shaft portion and a male screw portion is provided on the outer peripheral surface thereof. In contrast to these, a mounting hole is formed at the rear end of the drill bit and an internal thread is provided on the inner periphery of the drill bit. It is also possible to provide male screw portions on the outer circumference of the portion and adopt the above-described configuration for these female and male screw portions.

7 to 10 show an excavating tool according to a second embodiment of the present invention, which adopts the latter structure among them. In these figures, reference numeral 41 designates a cylindrical casing pipe, the rod 4 of which is provided on the inner peripheral portion thereof.
2 is inserted from the rear end side, and a shank 43 as a tool body in the present embodiment is attached to the tip of this rod 42.
However, the tip of the shank 43 is attached so as to project from the casing pipe 41, and the lost bit 44 as an excavation bit in the present embodiment is attached to the protruding tip of the shank 43. Here, the rod 42
Is formed in a substantially cylindrical shape having an outer diameter slightly smaller than the inner diameter of the casing pipe 41, and a male screw portion 42A is formed on the outer periphery of the tip end portion thereof. However, as the shape of the screw formed by the male screw portion 42A, a general rope screw or the like is used.

The shank 43 has an outer diameter that can be fitted into the inner circumference of the casing pipe 41, and has a multi-stage cylindrical shape in which the tip end portion is formed so that its diameter is reduced by one step. A female screw portion 43A into which the male screw portion 42A at the tip of the rod 42 can be screwed is formed on the inner circumference of the rear end portion. Therefore, a general rope screw or the like is also used for the screw shape of the female screw portion 43A. Further, the male screw portion 4 is attached to the female screw portion 43A.
With the 2A screwed in, spring pins 45, 45 are fitted between the inner peripheral portion of the rear end of the shank 43 and the outer peripheral portion of the distal end of the rod 42 in the tangential direction of a circle centered on the axis O. .

Incidentally, on the outer circumference of the large diameter portion of the shank 43 fitted into the casing pipe 41, as shown in FIG. 9, a cross section orthogonal to the axis O has a "U" shape opening toward the outer circumference. The plurality of recessed grooves 43B are formed so as to open at the front and rear ends of the large diameter portion, extend parallel to the axis O over the entire length of the large diameter portion, and are located at equal intervals in the circumferential direction. Is formed. Further, air holes 43C, which are branched so as to extend toward the tool rear end side from the inner peripheral portion of the shank 43 toward the outer peripheral side, are respectively formed on the bottom surfaces of the concave grooves 43B. It has been opened. The shank 43 has a one-step-diameter-reduced tip portion which is a shaft portion 43D on the tool body side in the present embodiment, and a male screw portion 46 is formed on the outer periphery of the shaft portion 43D.

On the other hand, the lost bit 44 attached to the tip of the shank 43 has a substantially cylindrical outer shape, and the inner peripheral portion of the cylindrical portion is the same as the attachment hole 44A on the tool body side in this embodiment. At the same time, a female screw portion 47 into which the male screw portion 46 of the shank 43 is screwed is formed on the inner circumference of the mounting hole 44A, and the bottom portion of the bottomed cylinder is used as the tip portion toward the tool tip side. It is attached to the tip of the shank 43. Here, the outer diameter of the cylindrical portion of the lost bit 44 is made larger than the outer diameter of the casing pipe 41, and the outer periphery of the rear end portion is formed in a tapered surface shape that gradually decreases in diameter toward the tool rear end side. On the other hand, the inner circumference of the tip portion of the casing pipe 41 is also formed in a tapered surface shape with a taper equal to the taper of the outer circumference of the rear end portion of the lost bit 44 and gradually decreasing in diameter toward the tool rear end side. .

The tip of the lost bit 44 is
The outer diameter is formed to be one step larger than that of the cylindrical portion, and the tip surface of the tip portion facing the tool tip side is uneven on the tool tip rear end side along the circumferential direction around the axis O. The tip 48 made of a hard material such as cemented carbide is radially formed around the axis O at the ridge line portion of the mountain portion having a triangular cross section which is convex toward the tool tip side. Grooves 44B having an arc-shaped cross section are formed parallel to the axis O on the outer peripheral side of the valley portion which is recessed toward the rear end side of the tool while being planted. Furthermore, this lost bit 44
An air hole 44C communicating with the inner peripheral portion of the shank 43 is bored from the bottom surface of the inner peripheral portion of the cylindrical portion toward the tool tip side along the axis O, and the air hole 44C is formed in the tip portion. In the above, it is branched into two and opened at the above-mentioned troughs located on opposite sides of the axis O.

Further, in the second embodiment, the male screw portion 4 formed on the outer periphery of the shaft portion 43D of the shank 43.
6 and the lost bit 4 into which the male screw portion 46 is screwed
10 and the lead angle of the female screw portion 47 of the mounting hole 44A of No. 4 is set in the range of 5 ° to 16 °.
As shown in FIG. 4, in the cross section including the axis O, the screw threads 46A and 47A of the male screw portion 46 and the female screw portion 47 have a trapezoidal shape, and further, these screw threads 46A and 47A.
The inclination angle θ formed by the slopes 46B and 47B of A with respect to the axis O is set in the range of 40 ° to 70 °. In addition,
The twisting directions of the male and female screw portions 46 and 47 are such that the rod 42 and the shank 43 move toward the tool rear end side so that the lost bit 44 does not loosen due to the rotation of the rod 42 and the shank 43 during excavation. It is designed to twist in the direction opposite to the direction of rotation.

In the excavating tool constructed as described above, the rod 42 is rotated about the axis O in the rotation direction, and a striking force is applied to the rod 42 toward the tool tip side. Is transmitted to the lost bit 44 via the shank 43 and is rotationally hit integrally, whereby excavation is performed and the casing pipe 41 is built in the drilled hole. After the excavation is performed to a predetermined depth and the casing pipe 41 is built, the rod 42 is rotated in the direction opposite to the rotation direction at the time of excavation to loosen the male and female screw portions 46 and 47. The lost bit 44 having an outer diameter larger than the inner diameter of the casing pipe 41 is removed, and then the lost bit 44 is left in the drilled hole to remove the rod 42.
And the shank 43 is pulled out from the casing pipe 41.

However, also in the excavating tool of the second embodiment, the lead angles of the female and male threaded portions 46 and 47 for attaching the lost bit 44 as the excavating bit to the shank 43 as the tool main body are 5 ° to 16 °. The inclination angle θ formed by the slopes 46A, 47A of the threads 46A, 47A with respect to the axis O is 40 °.
Since it is set within a range of up to 70 °, even if the male screw portion 46 is screwed into the female screw portion 47 due to the rotation at the time of excavation, the female and male screw portions 46, 47 are too tightly tightened. Therefore, when removing the lost bit 44 from the shank 43 as described above, it is possible to remove the lost bit 44 only by surely loosening the male and female screw portions 46 and 47 by rotating the rod 42 in the reverse direction. . In addition, the rod 42 and the shank 4
Since a general rope screw or the like is used for the female and male screw portions 42A and 43A connecting the male and female screws 3, the male and female screw portions 42A and 43A will not be loosened even if the rod 42 is rotated in the reverse direction.

[0037]

As described above, according to the present invention,
In a drilling tool in which the tool body and the drill bit are attached by screw fitting, it is possible to prevent the drill bit from being over-tightened by the tool body due to the rotational force applied to the tool body during drilling, and drilling due to wear etc. The excavation bit can be easily removed from the tool body when exchanging the bit or when the excavation bit is left in the drilling hole and only the tool body is pulled out after completion of the excavation.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the embodiment shown in FIG.
FIG. 4 is a front view from the tool tip side showing a state in which the diameter is expanded.
(However, illustration of the casing 1 and the casing top 2 is omitted.)

FIG. 3 is a diagram showing the embodiment shown in FIG.
It is a front view from the tool tip side which shows the state where diameter was reduced.
(However, illustration of the casing 1 and the casing top 2 is omitted.)

FIG. 4 is a ZZ sectional view in FIG.

5 is a side sectional view showing the sleeve 18 shown in FIG.

FIG. 6 is a diagram showing the female and male screw portions 19 and 30 of the embodiment shown in FIG.
It is an expanded sectional view containing the axis line of (axis O of a tool main body).

FIG. 7 is a side sectional view showing a second embodiment of the present invention.

FIG. 8 is a front view of the embodiment shown in FIG. 7 viewed from the tool tip side.

9 is a ZZ sectional view in FIG. 7.

FIG. 10 is a diagram showing the female and male screw portions 46 and 4 of the embodiment shown in FIG.
It is an expanded sectional view containing the axis line of 7 (axis line O of a tool body).

[Explanation of symbols]

1 Casing 2 Casing Top 3 Tool Body 4 Pilot Bit (Excavation Bit) 4B, 43D Shaft 5 Expanding Bit 13, 29, 48 Tip 16, 44A Mounting Hole 17 Recess 18 Sleeve 18A, 18B, 18C Sleeve Member 19, 47 Female Thread Parts 19A, 30A, 46A, 47A Male and female screw parts 19, 3
0, 46, 47 threads 19B, 30B, 46B, 47B threads 19A, 30
A, 46A, 47A inclined surface 30, 46 Male screw part 35 Spacer 41 Casing pipe 42 Rod 43 Shank (tool body) 44 Lost bit (drilling bit) O Tool body 3, shank 43 axis T Tool rotation direction θ screw during drilling Slope 19 of mountains 19A, 30A, 46A, 47A
Inclination angle of B, 30B, 46B, 47B

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoya Hisada 1528 Nakanishi, Yokoi, Kobe, Anpachi-gun, Gifu Prefecture Mitsubishi Materials Corporation Gifu Manufacturing Co., Ltd. (56) Reference JP-A-7-243295 (JP, A) Shuichi Okano et al., Enlarged Dictionary of Mechanical Terminology, Japan, Jikkyo Publishing Co., Ltd., February 10, 1993, p. 455 (58) Fields investigated (Int.Cl. ⁷ , DB name) E21B 17 / 04

Claims (2)

(57) [Claims] 1. A drill bit 4 is provided at the tip of the tool body 3 .
A female screw portion 19 on the inner periphery of a mounting hole 16 provided on one of the tool body 3 and the drill bit 4 is attached to a male screw portion 30 on the outer periphery of a shaft portion 4B provided on the other by screw fitting. The lead angle of the threads 19 and 30 is 5 °
Is set in the range of up to 16 °, and the screw portion 19,
Threads 19A, 3 in a cross section including the central axis O of 30
The inclination angle θ of the inclined surfaces 19B and 30B of 0A with respect to the central axis O is set in the range of 40 ° to 70 °, and the internal thread portion is
19 is mounted on one of the tool body 3 and the drill bit 4
It is formed on the inner circumference of the attached cylindrical sleeve 18.
The sleeve 18 is separable in the circumferential direction.
Drilling tool, characterized in that that. 2. Threads 19A of said threaded portions 19 , 30 ;
The excavating tool according to claim 1, wherein 30A has a trapezoidal cross section.