JPH1171981A - Excavating tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the concentration of excess excavation load to the shaft section, etc., of a diameter-expanding bit in an excavating tool with the diameter-expanding bit. SOLUTION: A plurality of diameter-expanding bits 4 capable of being rotated around shaft sections 18 at intervals among the shaft sections 18 and the axis O of a device 3 are installed in the circumferential direction at the front end sections 7 of the device 3 being turned around the axis O while receiving striking force in the direction of the axis O, and the diameter-expanding bits 4 are revolved in the direction that outside diameters from the axis O are expanded with rotation to the T side in the direction of the excavation rotation of the device 3, and positioned by abutting the diameter-expanding bits 4 against the wall sections 8B of recessed sections 8 formed to the device 3. Pilot bits 5 are mounted on the axes O of the front end sections 7 of the device 3 so as to be projected to the front end sides from the diameter-expanding bits 4, and it is desirable that the outside diameters of the pilot bits 5 are set at values larger than intervals in the radial direction among the inner circumferential ends of the diameter-expanding bits 4 and the axes O.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As this kind of excavating tool, for example, the one described in Japanese Patent Application Laid-Open No. 63-11789 is known. The excavating tool described in this publication is provided with a tip of a device that is inserted into a drilling pipe and receives a rotary impact force by a hammer, is symmetric with respect to the rotation axis of the device by the hammer, and is spaced apart from this axis. A pair of shaft portions are provided, and a diameter expanding bit having a substantially semicircular shape is rotatably provided on each of these shaft portions,
These diameter-enlarging bits rotate around the shaft in a direction in which the outer diameter from the axis expands with the rotation of the hammer in the excavation direction, and are positioned when the side surfaces abut each other. In this state, the side surfaces are arranged in a direction including the axis.

[0003] The excavating tool whose diameter of the diameter-expanding bit has been increased is crushed and excavated by a large number of chips provided on the end face of the diameter-expanding bit by the rotary impact force. Drilling pipes are being buried underground. After the drilling pipe is embedded to a predetermined depth in this way, by rotating the device in the direction opposite to the above-mentioned drilling direction, the outer diameter from the axis is reduced in reverse to the above case. Is rotated around the shaft portion in the direction in which the side surfaces of the drill bits are again brought into contact with each other, and in this state, the outer diameter of the diameter-enlarging bit is smaller than the inner diameter of the drilling pipe. By pulling out the device whose diameter has been reduced by the diameter-enlarging bit from the inside of the drilling pipe, it becomes possible to leave only the drilling pipe in the ground and bury it.

[0004]

However, in such a drilling tool, as described above, the diameter-enlarging bit provided at the tip of the device is positioned with its side surfaces in contact with each other to expand the diameter. In order to excavate by receiving the rotary impact force from the hammer, especially the rotational force from the hammer and the force acting on the expanding bit during drilling, especially It becomes concentrated on the shaft part to be supported, and there is a possibility that the support rigidity of the enlarged diameter bit is impaired and stable excavation is impaired.For example, when an excessive load is applied to the enlarged diameter bit during excavation, There was even a possibility that the shaft portion might be damaged. In addition, if the shaft is damaged during excavation and breaks in this way, the enlarged diameter bit will fall out of the device and be left behind in the excavation hole. Is required.

Further, in the above-mentioned excavating tool, in a state where the diameter-enlarging bit is expanded and the above-mentioned side surfaces are positioned by contact with each other, these side surfaces are arranged in a direction including the axis of the device. That is, since the center of rotation of the tool tip is located on the mating surface between the enlarged bits, it is difficult to provide a tip near the center of rotation. However, on the other hand, in the vicinity of the rotation center of such a tool tip, the rotation speed is reduced and becomes zero at the rotation center, so that the excavation is performed only by the impact force from the hammer. Become. Therefore, if a tip is not provided near such a tool rotation center, excavation will be performed while the tip end face of the diameter-enlargement bit crushes earth and sand or rock at this portion, thereby deteriorating excavation efficiency and enlarging. There is a problem that damage such as wear of the diameter bit is promoted.

The present invention has been made under such a background, and in a drilling tool provided with an enlarged bit which is enlarged by rotation of a device, excessive load is concentrated on a shaft portion of the enlarged bit. The first object is to prevent the excavation, and especially the second purpose is to improve the excavation performance near the center of rotation of the tool. It is a third object to provide a drilling tool capable of preventing the occurrence of a drilling tool.

[0007]

In order to solve the above-mentioned problems and achieve the first object, the present invention provides a device which is rotated about an axis and receives a striking force in the axial direction. At the tip of the device, a plurality of diameter-enlarging bits that are rotatable around an axis portion spaced from the axis are provided in the circumferential direction, and these diameter-enlarging bits are rotated in the excavation direction side of the device. Accordingly, the device rotates in a direction in which the outer diameter from the axis increases, and is positioned by contacting a wall formed on the device.
Therefore, by positioning the enlarged diameter bit in contact with the wall portion formed on the device in this way, it is possible to secure the support rigidity of the enlarged diameter bit at the time of enlarging, and to promote stable excavation. It is possible to prevent a situation where the part is damaged beforehand.

In order to achieve the second object, it is desirable to provide a pilot bit on the axis of the distal end of the device so as to protrude further toward the distal end than the enlarged diameter bit. That is, by providing such a pilot bit, it is possible to reliably provide a tip for excavation also in the vicinity of the tool rotation center at the tip of the device, and at the time of excavation, the pilot bit is crushed by leading. Since the expanded bit excavates the soil, rocks, etc., which have become easier, the excavation efficiency can be improved and the load on the expanded bit can be further reduced. Further, by setting the outer diameter of the pilot bit to be larger than the radial distance between the inner peripheral end of the enlarged bit and the axis, the shaft portion of the enlarged bit may be damaged. Also, it is possible to prevent the diameter expanding bit from falling off.

[0009]

1 to 3 show an embodiment of the present invention. A drilling tool according to this embodiment is a device disposed at a tip of a drilling pipe 1 via a casing top 2. 3 and four pilot bits 4... And one pilot bit 5 arranged at the distal end of the device 3. The device 3 is formed in a substantially multi-stage cylindrical shape, and a rear end portion having a smaller diameter is formed as a shank portion 6, and a hammer (not shown) is attached to the shank portion 6, and the device 3 is rotated around a central axis O thereof. While being rotated in the excavation rotation direction T, it receives a striking force on the tip side in the direction of the axis O. The casing top 2 is welded to the tip of the excavation pipe 1, and the inner diameter is formed to be one step smaller than the inner diameter of the excavation pipe 1,
The distal end portion 7 of the device 3 can be fitted into the inner peripheral portion of the casing top 2, and the distal end portion 7 has the rear end side of the outer peripheral surface facing the casing top 2 and the distal end side in the axis O direction. The device 3 is rotatable relative to the excavation pipe 1 and the casing top 2 around the axis O, and can be advanced integrally with the tip side in the axis O direction. It has been.

Further, on the outer periphery of the distal end portion 7 of the device 3, there are provided four concave portions 8 opened on the distal end surface and the outer peripheral surface.
Are formed at equal intervals in the circumferential direction.
.. Are mounted with the above-described enlarged bits 4 respectively.
A through-hole 9 is formed in the center of the device 3 along the axis O. The tip of the through-hole 9 is formed so as to increase in diameter in a multi-step manner. A hole 10 is provided. Here, the recess 8 has a bottom surface 8 </ b> A that retreats one step from the front end surface of the device 3.
And a wall surface 8B rising from the bottom surface 8A and connected to the tip end surface and facing the excavation rotation direction T side, a wall surface 8C facing the outer peripheral side, and a wall surface 8D facing the rear side in the excavation rotation direction T.
And the walls 8B and 8D.
Are formed so as to extend in directions crossing each other at an acute angle toward the rear side in the excavation rotation direction T toward the inner peripheral side as viewed from the distal end surface side of the device 3.

The recess 8 has a wall surface 8B and a wall surface 8B.
At the corner where C intersects, there is formed a concave arc surface 8E that is concave toward the inner peripheral side when viewed from the tip surface side of the device 3, and the concave bottom surface 8A of the concave portion 8 has the concave arc surface 8E. The mounting hole 11 is formed so as to be coaxial with the center of the arc. The device 3 is formed with four small-diameter air holes 12 extending vertically from the through hole 9 to the outer peripheral side, and these air holes 12 extend in the radial direction to form the distal end portion 7 of the device 3. The outer peripheral surface is formed so as to be opened slightly to the front end side from the convex portion 7A, and to be branched vertically in the middle in the direction of the axis O in the middle to open also to the bottom surface of the mounting hole 11. Further, four blind holes 13 are formed from the outer peripheral surface of the distal end portion 7 of the device 3 toward the radially inner peripheral side with respect to the axis O, and these blind holes 13 are respectively provided with the mounting holes. .. Are opened so as to intersect with each other in the tangential direction.

On the other hand, in the device 3, the air holes 12 are provided.
In addition, four large-diameter air holes 14 are formed so as to extend obliquely from the through hole 9 toward the outer peripheral side of the tip, and these air holes 14 are respectively formed on the bottom surfaces 8A of the recesses 8. In the above, the wall 8C and the wall 8D are opened near the corner where the wall 8C and the wall 8D are closer to the excavation rotation direction T side than the mounting hole 11. Further, on the outer peripheral surface of the distal end portion 7 of the device 3, four concave grooves 15 are formed so as to extend in parallel with the axis O. The distal side of these concave grooves 15 is Each of the recesses 8 is communicated with each other so as to open to a portion on the outer peripheral side of the bottom surface 8A on the excavation rotation direction T side.

The enlarged diameter bit 4 mounted in the recess 8 formed as described above has a large number of hard materials made of a hard material such as a cemented carbide on the distal end surface 16A of the block-shaped main body 16 housed in the recess 8. Chips 17 are implanted, and a shaft 18 to be fitted into the mounting hole 11 is formed on the rear end side. Here, an annular groove 19 having a substantially semicircular cross section is formed in the shaft portion 18.
Is formed so as to coincide with the position of the blind hole 13 in the mounting hole 11 in a state where the shaft portion 18 is inserted into the mounting hole 11 and the main body 16 is in contact with the bottom surface 8A of the concave portion 8. After the shaft portion 18 is fitted into the mounting hole 11 in this manner, the pin 20 and the spacer 2 are inserted into the blind hole 13.
1 is fixed by the snap ring 22 so that the pin 20 is engaged with the annular groove 19 to prevent the enlarged diameter bit 4 from coming off, and the main body 16 is rotated around the shaft 18 in the recess 8. Is supported rotatably.

Further, the main body 16 of the enlarged diameter bit 4
The tip end surface 16A has a substantially polygonal shape, and the outer periphery of the main body 16 has a convex circle having a large radius of curvature facing the outer peripheral side in a state where the enlarged diameter bit 4 is enlarged as shown in FIG. An arc-shaped side surface 16B, a side surface 16C abutting on the wall surface 8B of the concave portion 8, and the wall surfaces 8C, 8D of the concave portion 8 with the diameter-enlarging bit 4 reduced in diameter as shown in FIG.
Are formed, and side surfaces 16D and 16E are respectively formed to abut against them. Here, the side surface 16B and the side surface 16E are formed so as to be substantially orthogonal to each other, and the opposite ridge line between the side surface 16C and the side surface 16D is provided with the shaft 1
A convex arc surface 16F that is coaxial with the center axis of the concave portion 8 and that can slide on the concave arc surface 8E of the concave portion 8 is formed. The edges of the front end surface 16A on the side surfaces 16B and 16E are formed so as to be inclined so as to recede toward the side surfaces 16B and 16E. In addition, this side 16
A small chip (not shown) is embedded in B.

On the other hand, the pilot bit 5 attached to the attachment hole 10 is provided with a distal end surface 23A of a disk-shaped main body 23.
A large number of chips 17 made of a hard material such as a cemented carbide are implanted on the outer peripheral surface 23B in the same manner as the enlarged diameter bit 4 and a shaft portion inserted into the mounting hole 10 is provided on the rear end side. 24 are formed. Here, a male screw portion 24A is formed on the outer periphery of the shaft portion 24, and a female screw portion 10A screwed to the male screw portion 24A is formed on the inner periphery of the mounting hole 10, and the female screw portion is formed. 10
A, the pilot bit 5 is attached to the mounting hole 10 by screwing the male screw portion 24A into
Is fixed on the axis O of the distal end portion 7. And the main body 23 of the pilot bit 5 thus attached is
As shown in FIG. 1, the device is located on the tip side in the direction of the axis O with respect to the enlarged bits 4 attached to the concave portions 8 of the device 3, and the outer diameter of the device is from the inner peripheral end of each enlarged bit 4. 3, so that the main body 23 of the pilot bit 5 covers the inner peripheral portion of the enlarged diameter bit 4 as shown in FIG. Will be arranged as follows.

The main body 23 of the pilot bit 5
Of the concave portion 8 of the device 3 are orthogonal to the wall surface 8C of the concave portion 8 of the device 3 when viewed from the distal end side in the direction of the axis O on the distal end surface 23A of the device 3 at equal intervals in the circumferential direction and from the center toward the outer peripheral side. It is formed to extend in the direction. On the outer peripheral surface 23B of the main body 23, a large number of concave grooves 26 are formed so as to extend in the direction of the axis O, and four of the concave grooves 26 are formed on the outer periphery of the concave grooves 25, respectively. The end is formed so as to communicate with each of the grooves 25. Further, an air hole 27 is formed in the pilot bit 5 so as to extend from the shaft portion 24 toward the main body 23 along the axis O toward the distal end. It is formed so as to be branched and open at the inner peripheral side end of the pair of concave grooves 25, 25 located on the opposite sides of the concave grooves 25.

In the excavating tool thus configured, when the device 3 is rotated in the excavation rotation direction T by the rotary impact force from the hammer during excavation, each of the enlarged bits 4. As shown in the drawing, the diameter is increased by rotating clockwise around the shaft portion 18 as viewed from the distal end side, and the side surface 16C is positioned by abutting against the wall surface 8B of the concave portion 8, and in this expanded state, each diameter is increased. The side surfaces 16B of the bits 4 are arranged so as to be located on one cylindrical surface centered on the axis O, and the outer diameter of this cylindrical surface is larger than the outer diameters of the excavation pipe 1 and the casing top 2. Is done. And, by the above-mentioned rotary impact force from the hammer, an enlarged-diameter bit 4 which is enlarged at the tip of the excavation pipe 1;
While the pilot bit 5 disposed at the center of rotation of the tip of the device 3 crushes earth and sand, rocks and the like, the device 3 moves forward with the excavation pipe 1 through the casing top 2 to perform excavation.

The opening of the air hole 14 on the bottom surface 8A of the recess 8 is closed by the diameter-expanding bit 4 when the diameter-expanding bit 4 is reduced in diameter. Thereby, as shown in FIG. 2, it is exposed between the side surface 16D and the wall surface 8D of the concave portion 8. At the time of excavation, the compressed air supplied from the through hole 9 is jetted through the air holes 14 and 27, and the ground powder crushed at the time of excavation is passed through the grooves 25, 26 and the groove 15. And discharge to the rear end side of the drilling pipe 1. on the other hand,
When the digging tool is pulled out from the digging pipe 1 after the digging is completed, the device 3 is rotated backward in the digging rotation direction T so that each of the enlarged bits 4. The diameter is reduced by rotating in the clockwise direction, and the side surfaces 16D, 16E abut against the wall surfaces 8C, 8D and are positioned. Then, in this reduced diameter state, the outer diameter of each of the enlarged bits 4... From the axis O is smaller than the outer diameter of the tip 7 of the device 3, that is, smaller than the inner diameters of the excavation pipe 1 and the casing top 2. Thus, if the device 3 is pulled out as it is, it becomes possible to leave only the excavation pipe 1 and the casing top 2 in the ground and bury it.

However, in the excavating tool having the above-described configuration, when the diameter-enlarging bits 4 are expanded as described above, the side surface 16B of the main body 16 is attached to the wall surface 8B of the recess 8 formed in the device 3.
, And most of the excavation load acting on the enlarged diameter bit 4 during excavation is received by the wall surface 8B of the device 3. Therefore, according to the excavating tool of the present embodiment, it is possible to improve the support rigidity of the enlarged diameter bit 4 as compared with the conventional excavating tool in which the enlarged diameter bit is supported only by the shaft portion, and to perform stable excavation. In addition to this, the excavation load is not concentrated only on the shaft portion 18 of the diameter-enlargement bit 4, so that even if an excessive load is applied, the shaft portion 18 is damaged and 4 can be prevented from falling off.

Moreover, in the present embodiment, the above-described enlarged bit 4
A convex arc surface 16F is formed on the body 16 of the device 3 and a concave arc surface 8E is formed on the concave portion 8 of the device 3. These concave and convex arc surfaces 8E and 16F are coaxial with the shaft portion 18 and the mounting hole 11. Therefore, the contact state is maintained irrespective of the diameter of the diameter expanding bit 4. Therefore, according to the present embodiment, the concavo-convex arc surface 8 is made rotatable around the shaft portion 18 in order to expand and contract the diameter of the diameter-enlarging bit 4.
Since the enlarged diameter bit 4 can be supported by the device 3 even by contact with E and 16F, the support rigidity of the enlarged diameter bit 4 can be more effectively improved together with the support by the wall surface 8B. In addition, it is possible to more reliably prevent the diameter expanding bit 4 from being damaged by the excavation load.

On the other hand, in the present embodiment, a pilot bit 5 is provided on the axis O in addition to the diameter-enlarging bits 4 at the tip of the device 3. Since the drill bits are projected more toward the tip side than the diameter bits 4,... In excavation, the pilot bit 5 first drills a small diameter drilling hole, and then the succeeding diameter expansion bits 4. The excavation mode is such that excavation is performed so as to widen the hole. Therefore, according to the present embodiment, it is possible to avoid a situation in which a tip cannot be provided near the center of rotation because the mating surface of the diameter-enlarging bit is located on the rotation axis as in the related art. Of course, it is possible to prevent the tool from being worn at the rotation center where the tool acts, and as described above, the rotary impact excavation by the preceding pilot bit 5 causes earth and sand or rock around the small diameter excavation hole to be excavated first. Is likely to collapse, and the subsequent enlarged bits 4 ... will excavate the portion that has become easily collapsed,
Excavation efficiency can be improved.

In this embodiment, the outer diameter of the main body 23 of the pilot bit 5 projecting toward the distal end is larger than the radial distance from the inner peripheral end of the enlarged diameter bits 4 to the axis O of the device 3. Since the main body 23 of the pilot bit 5 is disposed so as to cover the inner peripheral side of the distal end of the main body 16 of the enlarged diameter bit 4, an excessive load acts on the enlarged diameter bit 4. Even if the shaft portion 18 is damaged, it is possible to prevent the enlarged diameter bit 4 from dropping to the tip side as it is, and it takes a lot of time and labor to collect the dropped enlarged diameter bit 4. Such a situation can be prevented beforehand. In addition, in the present embodiment, the main body 16 of the diameter-enlarging bit 4 is also constrained in the circumferential direction of the device 3 by the wall surfaces 8B to 8D of the concave portion 8 formed in the device 3. 4 can be more reliably prevented from falling off. In addition, since the pilot bit 5 covers the inner peripheral side of the enlarged diameter bit 4 in this way, it is possible to suppress the excavation load from acting on the inner peripheral side portion of the main body 16 of the enlarged diameter bit 4. Another advantage is that damage to the diameter bit 4 can be more effectively prevented.

The main body 23 of the pilot bit 5
The amount of overhang that covers the outer periphery of the distal end of the main body 16 of the enlarged bit 4 is, as shown in FIG. 1 in the direction of the axis O, from the distal end face 16A of the main body 16 of the enlarged bit 4 23 The distance to the rear end face is
The distance from the rear end surface of the main body 16 of the enlarged diameter bit 4 to the annular groove 19 of the shaft portion 18 is set to be smaller, and in the radial direction, as shown in FIGS. It is desirable that the surface 23 </ b> B is set to be larger than the radial distance from the axis O of the device 3 to the outer peripheral surface of the shaft portion 18 of the enlarged diameter bit 4. This is because, when an excessive load acts on the diameter-enlarging bit 4 and the shaft portion 18 is damaged, the portion of the annular groove 19 in the shaft portion 18 has low strength, so that breakage or the like usually occurs at this portion. Therefore, if it is set as described above, the shaft portion 1 should be
This is because, even if 8 breaks, the main body 16 of the enlarged diameter bit 4 comes into contact with the rear end face of the main body 23 of the pilot bit 5, so that it can be reliably prevented from falling off.

[0024]

As described above, according to the present invention,
Since the expanding bit provided at the tip of the device is positioned by abutting against a wall formed on the device at the time of expanding the diameter, a load during excavation can be received by the wall, and the expanding bit can be received. It is possible to perform stable excavation by improving the support rigidity of the above, and it is possible to prevent the excavation load from being concentrated on the shaft portion of the enlarged diameter bit and causing damage. Further, by providing a pilot bit on the rotation axis of the device distal end so as to protrude more distally than the diameter-enlarging bit, it is possible to improve the excavation efficiency particularly near the rotation center of the tool distal end, and By setting the outer diameter of the pilot bit to be larger than the radial distance between the inner peripheral end of the enlarged bit and the axis, it is possible to reliably prevent the enlarged bit from falling off in case of an emergency. Can be.

[Brief description of the drawings]

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

FIG. 2 is a front view of the embodiment shown in FIG.

FIG. 3 is a front view of the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drilling pipe 2 Casing top 3 Device 4 Diameter expansion bit 5 Pilot bit 7 Tip of device 3 8 Depression 8A Bottom of depression 8 8B-8D Wall of depression 8 8E Concave arc surface 10,11 Mounting hole 12,14,27 Air Hole 15, 25, 26 Groove 16 Body of enlarged diameter bit 4 17 Tip 18 Shaft of enlarged diameter bit 4 23 Body of pilot bit 5 O Rotation axis of device 3 T Excavation rotation direction

Continued on the front page (72) Inventor Kazuyoshi Yoshida 1528 Nakashinden, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Gifu Works, Mitsubishi Materials Corporation

Claims (3)

[Claims] 1. A plurality of diameter-enlarging bits rotatable about an axis spaced apart from the axis are provided at a distal end of the device which is rotated about the axis and receives an impact force in the axis direction. Provided in the circumferential direction, these diameter-enlarging bits rotate in a direction in which the outer diameter from the axis expands with the rotation of the device in the excavation direction side, and are attached to a wall formed on the device. An excavating tool characterized by being positioned by abutting. 2. The excavating tool according to claim 1, wherein a pilot bit is provided on the axis of the distal end of the device so as to project more distally than the enlarged diameter bit. . 3. The pilot bit according to claim 2, wherein an outer diameter of the pilot bit is set to be larger than a radial interval between an inner peripheral end of the enlarged bit and the axis. Drilling tools.