JPH04169687A - Drilling tool - Google Patents

Abstract

PURPOSE:To firmly fix a fall-preventing pipe to a drilling pipe by welding a flange part provided on the outer circumference of the fall-preventing pipe to the top end of the drilling pipe over the whole circumference, and welding the fall-preventing pipe and the drilling pipe through a notch hole formed on the fall-preventing pipe. CONSTITUTION:A flange part 30a in contact with the top end of a drilling pipe 30 is provided on the outer circumference of a fall-preventing pipe 31, and the flange part 30a is welded to the top end of the drilling pipe 30 over the whole circumference. Then, a notch hole 31b extending in the axial direction of the fall-preventing pipe 31 and communicating with the inside and outside of the fall-preventing pipe 31 is formed on the fall-preventing pipe 31, and the fall-preventing pipe 31 and the drilling pipe 30 are welded together through the notch part 31b.

Description

[Detailed Description of the Invention] "Field of Industrial Application" The present invention relates to an excavation tool used to excavate the ground or earth in various anchor construction works, various drilling works, various foundation pile hole constructions, etc. In particular, the present invention relates to an excavation tool that can firmly fix an excavation pipe and a retaining pipe at its tip.

"Conventional technology" Conventionally, as one of the excavation tools for excavating the ground, earth, etc.
The one described in JP-A-63-11789 is known.

As shown in FIGS. 15 to 17, this excavation tool is characterized by the impact force of the hammer (not shown) and the
Two shaft holes 2a and 2b are formed point-symmetrically with respect to the center of the device 2 on the bottom surface of the device 2 which receives the rotational force of the device 2,
Each shaft hole 2a.

2b, the block shafts 3a, 3b are fitted into the block shafts 3a, 3b so as to be rotatable around the shafts and prevented from coming off.
Blocks 5a and 5b, each having a substantially semicircular shape with approximately the same diameter as the diameter of the device 2 and having a large number of bits 4 implanted in the tip surface, are attached to each other's straight end surfaces 6a and 6b. are provided facing each other, and the positions of the block shafts 3a and 3b are changed when the device 2 rotates in the excavation direction.

The device 2 is arranged such that one end of each of the blocks 5b protrudes from the outer peripheral surface of the device 2 by a predetermined amount of excavation, and at this time, the straight end surfaces 6a and 6b of both blocks abut each other.
It is eccentric from the center.

In the excavation tool, when the device 2 is rotated in the excavation direction X by the hammer cylinder 1, the blocks 5a,
Block 5b rotates around the prong shafts 3a and 3b while receiving excavation resistance, and the block 5a.

One end of the straight end surfaces 6a, 6b of the device 2 protrudes from the outer peripheral surface of the device 2 by a predetermined amount, and the straight end surfaces 6a, 6
Parts of the blocks 5a and 5b come into contact with each other and the rotation of the blocks 5a and 5b is stopped, and in this state, the blocks 5a and 5b receive the rotational force of the device 2 and excavate underground with the bit 4... , Furthermore, it advances underground due to the impact force of the hammer.

At this time, the excavated earth and sand are removed through an air hole 8a provided at the bottom of the device 2, through which compressed air is discharged when the hammer piston falls inside the hammer cylinder 1.

By being blown out from 8b, it is separated from the tip of the excavation tool, and then moves into the excavation pipe 9 via a discharge groove 9a provided in the device 2, and is discharged further upward from there.

"Problem to be Solved by the Invention" By the way, in the above-mentioned excavation tool, a retaining pipe is inserted into the inner circumference of the tip of the excavation pipe 9 to form a step 9b that engages with the device 2 on the inner circumference of the tip of the excavation pipe 9. However, since the impact force of a hammer is applied to the step 9b during drilling, it is necessary to firmly fix the retaining pipe to the excavation pipe 9.

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide an excavation tool that can firmly fix a retaining pipe to the tip of the excavation pipe.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a device that is attached to the tip of a hammer cylinder and receives the rotational force of the hammer cylinder and the impact force of the hammer, and an excavation pipe into which the device is inserted. , a retaining pipe that is inserted and fixed to the inner periphery of the tip of the excavation pipe to prevent the device from coming off; and blocks are provided on the bottom of the device in point symmetry with respect to the center of the device. A block is inserted into the shaft so as to be freely rotatable around the shaft, and a block having a substantially semicircular shape having the same diameter as the device and having a bit implanted in the end surface is placed at the tip of each block shaft. The straight end surfaces of the blocks are arranged to face each other, and the position of the block axis is such that when the device rotates in the excavation direction, one end of each of the blocks is a predetermined amount of excavation from the outer peripheral surface of the device. In the excavation tool, the block is eccentric from the center of the device so that the straight end surfaces of both blocks abut each other when the diameter of the block is expanded, and the tip of the excavation pipe abuts the outer periphery of the retaining pipe. A flange portion is provided, the flange portion and the tip of the excavation pipe are welded over the entire circumference, and a notch hole is formed in the retaining pipe that extends in the axial direction and communicates with the inside and outside of the retaining pipe. In addition, the locking pipe and the excavation pipe are welded together through this notch hole.

"Function" In the present invention, a flange portion that contacts the tip of the excavation pipe is provided on the outer periphery of the retaining pipe, and the flange portion and the tip of the excavation pipe are welded over the entire circumference, and the retaining pipe further includes: A notch hole is formed that extends in the axial direction and communicates with the inside and outside of the retaining pipe, and the retaining pipe and excavation pipe are welded through this notch hole. In particular, since the retaining pipe is welded at the position of the notch hole that communicates with the inside and outside of the retaining pipe, welding is effective in this area. The retaining pipe and the excavation pipe can be fixed even more firmly.

"Example" Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 to 14 show an embodiment of the present invention, and the excavation tool shown in the figures includes a device 10 that is attached to the tip of a hammer cylinder and receives the rotational force of the hammer cylinder and the impact force of the hammer; - It is equipped with a drilling pipe 30 into which the device 10 is inserted, and a retaining pipe 31 that is inserted and fixed to the inner periphery of the tip of the drilling pipe 30 and prevents the device 10 from coming off; A block shaft 20 is fitted into the bottom surface of the device 10 which receives the force and the rotational force of the hammer cylinder so as to be rotatable around the axis, respectively, point symmetrical with respect to the center of the device 10,
The device 1 is attached to the tip of each block shaft 20.
Blocks 22 are provided with straight end surfaces 22a facing each other, and each block 22 has a substantially semicircular shape with the same diameter as the diameter of 0, and a bit 21 is implanted on the tip surface, and the position of the block shaft 20 is adjusted as described above. When the device 10 rotates in the excavation direction, one end of each of the blocks 22 is connected to the device 10.
The straight end surfaces 22 of both blocks 22 protrude from the outer peripheral surface by a predetermined amount of excavation, and when the diameter of the block 22 is expanded.
The basic configuration is such that the points a are eccentric from the center of the device 10 so that they abut each other.

In the present invention, in particular, the retaining pipe 31
The biggest feature is the way it is fixed to the excavation pipe 30.
Specifically, a flange portion 30a that contacts the tip of the excavation pipe 30 is provided on the outer periphery of the retaining pipe 31, and the flange portion 30a and the tip of the excavation pipe 30 are welded over the entire circumference via the welding portion S. Furthermore, a notch hole 31a is formed in the retaining pipe 31, extending in the axial direction thereof and communicating with the inside and outside of the retaining pipe 31, and the retaining pipe is connected to the welded portion S through the notch hole 31a. 31 and the excavation pipe 30 are welded together.

Below is a detailed explanation of the main components of the excavation tool.
First, as shown in FIGS. 1 and 2, the device 10 includes a small diameter portion 10A having a spline groove 12 on the outer peripheral surface;
Large diameter portion 1 provided with insertion hole 11 into which block shaft 20 is inserted
0B, and a flange portion 13 is integrally provided on the outer circumferential surface of the large diameter portion 10B to fit a retaining pipe 31 provided on the inner periphery of the tip of the excavation pipe 30. A discharge groove 14 is formed for discharging debris upward.

An exhaust hole 15a extending in the axial direction is formed in the center of the device 10. The exhaust hole 15a opens at the upper end of the small diameter portion of the device 10, and compressed air discharged when the hammer piston falls flows into the opening. Also, device 10
A communication hole 15b that communicates with the tip of the exhaust hole 15a and extends radially outward is formed in the communication hole 15.
An air hole 15c extends from both ends of b toward the distal end of the device 10 and further reaches the bottom surface of the device shaft 10 and opens.
is formed. The exhaust groove 1 is located at the tip of the air hole 15c between the bottom surface and the outer peripheral surface of the device.
4 and the air hole 15c are provided with cutout portions 15d that communicate with each other.

Further, a circumferential groove 16a that goes around the device 10 in the circumferential direction is formed on the outer circumferential surface of the device 10 located near the flange portion 13 of the device 10, and the circumferential groove 16a is formed inside the device 10. A communication hole 16b is provided that communicates the exhaust hole 15a with the exhaust hole 15a (see FIG. 2).

Furthermore, a blow hole 16c is formed in the communication hole 15b that communicates with the exhaust hole 15a, and the blow hole 16c reaches the upper surface of the large diameter portion 10B of the device 10 and opens, so that when the air hole 15c is clogged, compressed air escapes and the hammer H care has been taken to ensure that the system does not stop. Note that, as shown in FIG. 2, this blow hole 16c is located outside the hammer H and opens, and when the hammer H is lowered, the blow hole 16c is opened by the hammer H.
Care has been taken to ensure that c is not blocked.

Now, the insertion hole 11 is formed to be offset from the center of the device 10 and point symmetrical with respect to the center of the device 10, and more specifically, as shown in FIG. The center G is set and provided so that it is located at a position of a length T which is shifted from the center position C of the bottom surface of the device by about 174 times the distance l between the block ends.

A block shaft 20 is fitted into the insertion hole 11 so as to be rotatable and not come off, and the block shaft 20 is prevented from coming off when the block shaft 20 is inserted into the insertion hole 11, for example. This is done by inserting the locking pin 17 through the No. 10 pin hole 18 and engaging the locking pin 17 with a notch 20a formed on the outer circumference of the block shaft 20.

Next, the structure of the block shaft 20 and the block 22 will be explained. The block shaft 20 and the block 22 are provided perpendicularly to each other, and the block shaft 20 and the block 22 may be formed integrally. It is also possible to construct them separately and connect them with bolts or the like.

More specifically, as shown in FIG. 6, the length of the block shaft 20 is 1.5 of the outer diameter of the block shaft 20.
The outer periphery of the block shaft 20 has a notch 20a into which the locking pin 17 is inserted, as shown in FIGS. 6 and 7. is formed. This notch 20a is configured such that the outer periphery of the block shaft 20 is cut out only at a position corresponding to the rotation angle of the block 22, and the axis of the block shaft 22 is smaller than the diameter a of the locking pin 17. It has a basic structure with a long cutout in the direction. In reality, the notch 20a is set to be about 1/3 of the outer diameter of the locking bottle 17, and more specifically, it is formed to have a size of about 4 to 8 mm. be.

On the other hand, each of the blocks 22 has the same shape that is substantially fan-shaped (semi-circular in the embodiment) when viewed from the bottom, and the radius of the fan-shape is set to approximately the same value as the radius of the device 10. The blocks 22 are arranged so that their straight end faces 22a face each other and the arcuate portions 22b of the blocks form a substantially circle as a whole.

A first inclined surface 22c is formed on the outer periphery of the distal end surface (bottom surface) of the block 22, and the first inclined surface 22c is gradually inclined toward the proximal end side in the axial direction of the device 10 as it goes outward. This first inclined surface 2 is provided on the outer periphery of 22c.
A second inclined surface 22d is formed which is inclined toward the base end side in the axial direction of the device 10 at an inclination angle different from that of the second inclined surface 22c.

Further, when the device 10 rotates in the excavation direction, the end of the straight end surface 22a of the block 22 protruding from the outer circumferential surface of the device 10 is gradually attached to the base end in the axial direction of the device 10 as it goes forward in the rotation direction. The third slope slopes towards
An inclined surface 22e is formed (see FIG. 8).

Then, the tip surface of the block 22 and the first to third
A plurality of bits 21 made of carbide tips are installed perpendicularly to the inclined surfaces 22c, 22d, and 22e, respectively.

Incidentally, in the embodiment, the negative portions of these bits 21... are located near the straight end surface 22a of the block 22 and are planted along the straight end surface 22a, and the bits 22a near these straight end surfaces Of these, both blocks 22
Bits located outside the arcuate portion 22b of one block 22 at a position where one end of each of the two protrudes from the outer peripheral surface of the device by a predetermined amount of excavation (in the embodiment, the bit is located on the third inclined surface 22e). As shown in FIG. 8, the vertex R of the bit (bit) is positioned outward from the extension line A-B extending along the curvature of the outer surface of the block.

Further, in the embodiment, the bottom surface (tip surface) of both blocks 22 is
and the straight end surface 22a, when one end of both blocks 22 protrudes from the outer circumferential surface of the device 10 by a predetermined amount of excavation, the device is disposed opposite to each other at the center of the block 22. 10 and a concentric recess 25
A recessed portion 22f is formed, respectively. In the embodiment, the concave portion 22f is composed of a circular bottom portion and a tapered surface that slopes upward from the bottom portion, but this shape is not limited to the embodiment. The shape shown in the figure and FIG. 12 may be used.

Incidentally, FIG. 11 shows a configuration in which only a tapered surface is formed, and FIG. 12 shows a configuration in which the tapered surface is eliminated and a wall portion extending approximately perpendicularly from the bottom surface is formed.

In addition, on the upper surface of the block 22, a contact portion 22g that contacts the bottom surface of the device 10 is provided at the center of the block 22, and on the outside of this contact portion 22g, there is a portion lower than the contact portion 22g. A relief portion 22h is provided, and the contact portion 22g and the relief portion 22h are provided.
An inclined surface 22j is formed between the two and the starting end thereof is at the same height as the abutting section 22g, and the terminal end thereof is at the same height as the relief section 22h.

Next, the operation of the excavation tool having the above configuration will be explained.

As shown in FIG. 1, etc., in order to attach the block 22 to the bottom surface of the device 10, first, the block shaft 20 and the block 22 are integrated, and the straight end surface of the block 22 is inserted into the insertion hole 11 on the bottom surface of the device 10. 22a are arranged so as to face each other, and the block shaft 20 is inserted.

Next, the engagement bottle 17 is inserted through the bottle hole 18 of the device 10.
When the block shaft 2 is inserted and fixed, the block shaft 2 is inserted into the engagement pin 17.
0 are engaged, and the block and device are assembled, as shown in FIG.

This assembly involves inserting the block shaft 2 into the insertion hole 11 of the device 10.
0 and engage the locking pin 17, and since the two block shafts 20 can be locked with one locking pin 17, the workability can be improved. There is.

In the excavation tool as described above, when the hammer cylinder receives a driving force and is rotated in the direction of arrow X, the device 10, block shaft 20, and block 22 also rotate integrally in the same direction.

Furthermore 1. When the hammer piston placed in the hammer cylinder is driven to apply a downward impact force to the device 10,
The block 22 thrusts into the ground, causing a pop due to the rotational force)
21 excavates the earth and stones.

Block 2 with hammer cylinder and device 10
2 rotates in the excavation direction, the block 22 rotates around the block axis 20 due to excavation resistance, and one end of the right upper end surface of the block 22 protrudes from the outer peripheral surface of the device 10, and this portion functions as the outer peripheral blade A.

Further, when the blocks 22 rotate, the end surfaces 22a directly above each block abut each other, and these act as stoppers to restrict further rotation of each block. In this state, the block 22 receives the rotational force of the device 10 and excavates underground using the peripheral blade A and the like.

At this time, as the hammer piston falls, compressed air flows in from the exhaust hole 15a and is blown out from the air hole 15c, removing the excavated debris. Air hole 1
Since a notch 15d communicating with the discharge groove 14 is formed at the tip of the groove 5c, a portion of the compressed air flows directly as shown by the arrow in Fig. 5, assisting in the discharge of excavated debris. Debris can be removed efficiently.

In addition, in the embodiment, as shown in FIGS. 13 and 14,
When the hammer piston falls, a part of the compressed air passes through the communication hole 16b, flows into the circumferential groove 16a, and is exhausted to the outside, so that it is not applied to the lower surface (contact surface) of the flange portion 13 of the device IO. This has the advantage of preventing the intrusion of excavated debris and protecting the device contact surface.

In addition, when excavating, each block 22 is formed with a concave part 22f, and when the diameter of the block 22 is expanded, a four part 25 is formed at the center position of the block 22, so that the block 22 sinks into the rock when drilling, Good excavation is possible with less rattling during excavation, and the force Fb of the propulsive force generated in the recess 25 acts in the radial direction on the outer peripheral blade A, as shown in FIG. Since it works to counteract this, neck breakage can be effectively prevented and tool life can be extended.

In addition, in the embodiment, some of the plurality of bits 21 planted on the tip surface of the block 22 are located near the straight end surface of the block 22 and planted along the straight end surface, and Among the bits 21 near these straight end faces, one end of each of the blocks 22 is located outside the outer surface of one of the blocks 22 at a position where both blocks 22 protrude by a predetermined amount of excavation from the outer peripheral surface of the device. As shown in Fig. 8, the apex of the bit 21 is positioned outward from the extension line A-B extending along the curvature of the outer surface of the block, so that no impact force is applied to the block 22 during excavation. In this case, there is an advantage that force can be applied in the radially outward direction of the device 10, and the force acting on the peripheral blade A can be applied. Moreover, since the bit 21 located on the extension line A-B can be operated in an outward direction, wear of the bit can be reduced and the tool life can be extended.

Furthermore, when the piston in the hammer cylinder falls, the compressed air pushed out by the hammer piston is discharged through the exhaust hole 15.
a, passes through the communication hole 15b, and is blown out from the blow hole 16c. Therefore, even if the air hole 15c at the tip of the device becomes clogged due to a layer of soft mud or other factors, the compressed air will still be blown out from the blow hole 16c. Therefore, the operation of the piston does not stop, and the drilling work is not impaired, so that the work efficiency can be improved.

In addition, due to the above-mentioned excavation, the bottom surface of the device is reduced by the impact, or the length of the device becomes smaller than the original one due to rework due to damage to the impact surface. The notch 22a into which the locking pin 17 is inserted is larger than the diameter of the locking pin 17 on the block shaft 20.
Since the locking pins 17 are formed to be long in the axial direction, even if the length dimension of the device 1o is short and there are only three, the shearing force acting on the locking pins 17 does not increase, and the locking pins 17
It has the advantage of being able to prevent shaft breakage.

Moreover, in the embodiment, the cutout portion 22a is
Since it has a notch structure in which only the zero rotation range is cut, there is an advantage that the cross-sectional defect of the block shaft 2o can be reduced, and the strength of the block shaft 20 can be improved.

In addition, in the embodiment, a flange portion 3a that contacts the tip of the excavation pipe 30 is provided on the outer periphery of the retaining pipe 31, and the flange portion 30a and the tip of the excavation pipe 30 are welded over the entire circumference, and further, The plate forms a cutout hole 31b in the stopper pipe 31 that extends in the axial direction and communicates with the inside and outside of the stopper pipe, and welds the stopper pipe 31 and the excavation pipe 30 through the cutout hole 31b. Therefore, the retaining pipe 31 and the excavation pipe 30 can be firmly fixed together, and in particular, the retaining pipe 31 is welded at the position of the notch hole 31b that communicates with the inside and outside of the retaining pipe 31. By doing so, the tightening by welding is effective in this portion, so there is an advantage that the retaining pipe 31 and the excavation pipe 30 can be fixed even more firmly.

After the excavation is completed, the hammer cylinder is rotated in the opposite direction to the excavation direction, but at this time, each block 22
The block 22 rotates in the direction opposite to that during excavation, and as shown in FIG. 6, the arcuate portion 22b located at the outermost periphery of the block 22 is located at the same level as the bottom surface of the device 10 or inside it.

In this way, the excavation tool can be slid within the excavation pipe 30, so that the excavation tool can be pulled out by pulling the hammer cylinder upward.

Note that during the diameter reduction operation of the block 22 as described above, the air hole 15c on the bottom of the device is temporarily blocked by the block 22 during the diameter reduction of the block 22. Since a notch 15d that opens on the side surface of the block is formed, compressed air can be exhausted to the outside through the notch 15d, and by blowing compressed air onto the contact surface between the device and the block, It is possible to effectively remove excavated debris on the abutting surface, and there are effects such as being able to eliminate resistance when the block is contracted.

In addition, in the embodiment, the device 1 is provided on the top surface of the block 22.
A contact portion 22g that contacts the bottom surface of the block 22 is provided at the center of the block 22, and a relief portion 2 is formed on the outside of the contact portion 22g to be one step lower than the contact portion 22g.
2h is provided between the abutting portion 22g and the relief portion 22h, and a slope whose starting end is at the same height as the abutting portion 22g and whose terminal end is at the same height as the relief portion 22h is provided. Side 2
2j is formed, even when the block 22 is contracted and pulled up into the excavation pipe 30, the block 22 can be easily pulled up along the inclined surface 22j. Even if curling occurs, the relief portion 22h is formed one step lower than the abutting portion 22g, so it will not hinder the lifting of the block 22, and work efficiency on site can be improved. effective.

It goes without saying that the present invention is not limited to the embodiments described above, and that various changes can be made without departing from the gist of the invention.

"Effects of the Invention" As explained above, according to the present invention, a flange portion that comes into contact with the tip of the excavation pipe is provided on the outer periphery of the retaining pipe, and the flange portion and the tip of the excavation pipe are welded over the entire circumference. Further, the wave forms a cutout hole in the stopper pipe that extends in the axial direction and communicates with the inside and outside of the stopper pipe, and welds the stopper pipe and the excavation pipe through the cutout hole. Therefore, the retaining pipe and the excavation pipe can be firmly fixed together. In particular, by welding the retaining pipe at the position of the notch that communicates with the inside and outside of the retaining pipe, it is possible to firmly fix the retaining pipe and the excavation pipe in this part. Tightening by welding is effective, so it has an excellent effect of being able to more firmly fix the retaining pipe and the excavation pipe. As a result, it is possible to provide an excavation tool that can firmly fix the retaining pipe to the tip of the excavation pipe.

[Brief explanation of drawings]

1 to 14 show an embodiment of the present invention, in which FIG. 1 is a sectional view showing the entire excavation tool, FIG. 2 is a half sectional view showing the entire excavation tool, and FIG. 3 is a sectional view showing the entire excavation tool. FIG. 4 is a cross-sectional view showing the device in an enlarged state, FIG. 4 is a plan view showing the bottom of the device, FIG. 5 is a perspective view of the device and block, FIG. 6 is a front view of the block, and FIG. 7 is a block shaft and relationship. 8 is a plan view showing the block with its diameter expanded; FIG. 9 is a plan view showing the block with its diameter reduced; FIG. 10 is a sectional view of the block; FIGS. 11 and 12 are cross-sectional views shown to explain other shapes of the four parts, respectively, and FIGS. 13 and 14 are side views shown to explain the action of the contact surfaces of the device and the drilling pipe. Figure, 1st
5 to 17 show an example of a conventional excavation tool, FIG. 15 is a sectional view of the excavation tool, and FIGS. 16 and 17 are plan views showing the bottom of the block, respectively. G: Axial center, C: Center of device,
10...device, 11...insertion hole,
13... Flange portion, 14... Exhaust groove, 15a... Exhaust hole, 15b... Communication hole, 15c... Air hole, 15d...Notch, 16a...Peripheral groove, 16b...Communication hole, 16c...Blow hole, 17...
Locking bottle, 18... Bottle hole, 20...
Block shaft, 20a...notch, 21...
...Bit, 22...Block, 22a...
... straight end surface, 22 c122 d, 22 e-slanted surface, 22 f ... recessed part, 25 ... recessed part, 30 ... excavation pipe, 31 ... ...Preventing pipe.

Claims (1)

[Scope of Claims] A device attached to the tip of a hammer cylinder and receiving the rotational force of the hammer cylinder and the impact force of the hammer, a drilling pipe into which the device is inserted, and a state inserted into the inner periphery of the tip of the drilling pipe. and a retaining pipe that is fixed to the device and prevents the device from coming off, and is fitted into the bottom surface of the device so as to be rotatable around a block axis in point symmetry with respect to the center of the device, respectively. A block having a substantially semicircular shape with a diameter approximately the same as the diameter of the device and having a bit implanted in the tip surface is provided at the tip of the block shaft, with the straight end surfaces of the blocks facing each other. such that when the device rotates in the excavation direction, one end of each of the blocks protrudes from the outer peripheral surface of the device by a predetermined amount of excavation, and when the block is expanded in diameter, both ends In an excavation tool in which the straight end surfaces of the blocks are eccentric from the center of the device so that they abut each other, a flange portion that abuts the tip of the excavation pipe is provided on the outer periphery of the retaining pipe, and the flange portion and the tip of the excavation pipe are provided. Furthermore, a notch hole is formed in the retaining pipe that extends in the axial direction and communicates with the inside and outside of the retaining pipe, and the retaining pipe and the excavated An excavation tool characterized by being welded to a pipe.