JP3067267B2 - Drilling method - Google Patents

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 the ground or earth and sand in various types of anchor work, various well drilling works, and various types of foundation pile hole works. It relates to a material that can be reduced in diameter.

[0002]

2. Description of the Related Art Conventionally, as one of excavating tools for excavating ground, earth and sand, the one described in Japanese Patent Application Laid-Open No. 63-11789 is known. As shown in FIGS. 18 to 20, the excavating tool is provided on the bottom surface of the device 2 which receives the impact force of the hammer (not shown) and the rotational force of the hammer cylinder 1 in a point-symmetric manner with respect to the center of the device 2. 2 shaft holes 2
a and 2b are formed, and the block shafts 3a and 3b are fitted around the shaft holes 2a and 2b such that the block shafts 3a and 3b are rotatable around the axes and are prevented from coming off.
A block 5a, which has a substantially semi-circular shape having substantially the same diameter as the device 2 and has a large number of bits 4.
5b is provided with the straight end faces 6a, 6b facing each other, and the position of the block shafts 3a, 3b is adjusted by the end of each of the two blocks 5a, 5b when the device 2 rotates in the excavation direction. Are both eccentric from the center of the device 2 so as to protrude from the outer peripheral surface of the device 2 by a predetermined excavation amount, and at this time, the straight end surfaces 6a and 6b of both blocks come into contact with each other.

In the excavating tool, when the device 2 is rotated by the hammer cylinder 1 in the excavating direction X as shown in FIG. 20, the blocks 5a and 5b receive the excavation resistance and are driven around the block shafts 3a and 3b. One end of the straight end faces 6a, 6b of the blocks 5a, 5b protrudes from the outer peripheral surface of the device 2 by a predetermined amount, and a part of the straight end faces 6a, 6b abuts on each other to block 5a, 5b.
5b stops rotating, and in this state, the blocks 5a, 5b
Receives the rotational force of the device 2 and excavates underground with the bits 4... And further advances underground by the impact force of the hammer.

At this time, the excavated earth and sand is blown out from air holes 8a and 8b provided on the bottom surface of the device 2 by compressed air that is expelled when the hammer piston falls in the hammer cylinder 1. It is separated from the tip and then moves into the excavation pipe 9 via the discharge groove 9a provided in the device 2, from which it is discharged further upward.

[0005]

By the way, in the above-mentioned excavating tool, after excavation is completed, the device 2 is rotated by rotating the hammer cylinder 1 in the opposite direction to the above, and at this time, the blocks 5a and 5b are excavated. The hammer cylinder 1
Can be pulled out of the borehole by pulling it upward. However, in the above-mentioned excavation tool, the bit 21 planted on the bottom surface of the blocks 5a and 5b bites into the bottom surface of the excavation hole immediately after the end of excavation. In this state, the blocks 5a and 5b are hard to rotate. Therefore, there is a problem to be solved that diameter reduction is difficult. The present invention has been made in view of the above circumstances, and has as its object to provide an excavation method capable of reliably reducing the diameter of a block.

[0006]

In order to achieve the above object, the present invention provides an excavating method , wherein the excavating method is provided on a casing pipe so as to be rotatable around an axis and movable in an axial direction so that the impact force of the hammer and the hammer can be reduced. Each of the block shafts is rotatably fitted around the axis of the block in a point-symmetric manner with respect to the center of the device on the bottom surface of the device receiving the rotational force of the cylinder. Providing a block having a substantially semi-circular shape of the same diameter and having a bit planted on the tip end surface with the respective straight end faces facing each other, and when the device rotates in the excavation direction, the position of the block shaft is One end of each of the blocks protrudes from the outer peripheral surface of the device by a predetermined excavation amount, and the device is designed such that the straight end surfaces of both blocks come into contact with each other when the block is expanded in diameter. In drilling method using the drilling tool comprising eccentrically from the center of the scan, after drilling completion, the Bro
Pull out the bit from the bottom of the drill hole
And raising the block while raising the block.
The inclined surface formed on the outer peripheral portion of the end face is
Pressing the tip of the
You .

[0007]

According to the excavation method of the present invention, before the rotation of the block in the diameter reduction operation after the excavation is completed, the block is raised and the bit is extracted to some extent from the bottom surface of the drill hole, or the bit is removed from the bottom surface of the drill hole. Since the blocks can be separated from each other, the blocks can be easily rotated, so that the diameter of the blocks can be reliably reduced. In addition,
When the lock is pulled up, the slope is
Abuts the end, and the slope faces the device axis.
Due to the force acting, the block is placed on the axial side of the device.
A force that moves, that is, a force that reduces the diameter
Then, the diameter of the block is reduced more reliably.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 17 show an embodiment of the present invention. The excavating tool shown in the figures is basically similar to the excavating tools shown in FIGS. Each of the block shafts 20 is rotatably fitted on the bottom surface of the device 10 that receives the rotational force in a point-symmetric manner with respect to the center of the device 10 around the axis of the block shaft 20. A block 22 having a substantially semi-circular shape having substantially the same diameter as the diameter and having a bit 21 planted on the tip end face is provided with the straight end faces 22a facing each other, and the position of the block shaft 20 is adjusted by the device 10. When rotated in the direction of excavation, the two blocks 2
The two end portions of the device 10 project from the outer peripheral surface of the device 10 by a predetermined excavation amount, and the straight end surfaces 22a of the two blocks 22 come into contact with each other when the block 22 is expanded. It has a basic configuration decentered from the center.

However, in the present invention, as shown in FIGS. 1 and 2, the outer peripheral portion of the base end surface of the block 22 is gradually separated from the axis of the device 10 toward the distal end side of the block 22. The greatest feature is that an inclined surface 22k is formed. The inclined surface 22k is formed in a portion of the outer peripheral portion of the base end surface of the block 22 that protrudes outward from the distal end surface of the device 10 when the block 22 is in the expanded state, and is formed between the base end surface of the block 22 and the inclined surface 22k. The ridge portion is configured to be located radially inward of the excavation pipe 30 from the end face of the excavation pipe ( part of the casing pipe) 30.

As shown in FIGS. 1 to 3, the excavating pipe 30 is formed in a cylindrical shape having a size enough to insert the device 10, and a retaining pipe is provided at the inner end of the excavating pipe.
(Part of the casing pipe ) 31 is integrally fixed. A flange portion 31a is provided on the outer periphery of the retaining pipe 31 to be in contact with the tip of the excavation pipe 30.
The flange portion 31a is welded to the tip of the excavation pipe 30 by a welded portion S over the entire circumference. The retaining pipe 31 has a notch 31 extending in the axial direction thereof and communicating with the inside and outside of the retaining pipe 31.
b is formed, and the retaining pipe 31 and the excavation pipe 30 are integrally welded by the welded portion S via the cutout hole 31b.

The reason for setting the range of L ₁ as described above is that if L ₁ is less than 3L ₂ , most of the bit 21 will bite into the bottom surface of the excavation hole even if the block 22 is raised. This is because it is difficult to reduce the diameter, while if L ₁ exceeds 12L ₂ , the device 10 becomes longer and the weight increases more than necessary.

Further, in the excavating tool of the above-described embodiment, an inclined surface 22k is provided on the outer peripheral portion of the base end surface of the block 22 so as to be gradually separated from the axis of the device 10 toward the distal end surface of the block 22. It is characterized by being formed. The inclined surface 22k is formed in a portion of the outer peripheral portion of the base end surface of the block 22 that protrudes outward from the distal end surface of the device 10 when the block 22 is in the expanded state, and is formed between the base end surface of the block 22 and the inclined surface 22k. The ridge portion is configured to be located radially inward of the excavation pipe 30 from the end surface of the retaining pipe 31 of the pipe.

When the device 10 is pulled up by the hammer cylinder 1 on the inclined surface 22k formed on the outer peripheral portion of the base end surface of the block 22, the distal end surface of the retaining pipe 31 of the excavation pipe 30 comes into contact. 10 is pulled up, the retaining pipe 3
A pressing force upward from 1 acts. Since the inclined surface 22k is gradually inclined away from the axis of the device 10 toward the distal end surface of the block 22, a component force directed toward the axis of the device 10 acts on the inclined surface 22k. Thus, a force acts on the block 22 so as to move toward the axis of the device 10, that is, to reduce the diameter.

When the device 10 is lifted, the device 10 is rotated by the hammer cylinder 1 in the direction opposite to the direction of excavation, and the rotational force causes the block 22 to be reduced in diameter. Since the force via the surface 22k acts to reduce the diameter of the block 22, the block 22 is reliably reduced in diameter by the synergistic effect of the forces in the direction of reducing the diameter of the block 22. Even if excavation debris is caught between the straight end faces 22a of the block 22 at the time of this diameter reduction, the block 22 is applied to the inclined surface 2 in addition to the rotational force.
Since the force via 2k acts, the drilling debris
It is crushed between 2a and removed from between the straight end faces 22a.
Therefore, when the diameter is reduced, the straight end face 22
Since the sliding between a is not hindered, the diameter can be reliably reduced. In the above embodiment, the inclined surface 22k is a flat surface. However, the inclined surface 22k may be formed by a curved surface that is convex or concave in the radial direction of the block 22.

Next, other main members of the excavating tool of this embodiment will be described. As shown in FIG.
When the inner diameter (d) of the insertion hole 11 of the block shaft 20 provided on the bottom surface of the block 22 and the diameter of the block 22 are expanded (when one end of the straight end face 22a of the block 22 projects a predetermined amount from the outer peripheral surface of the device 10) The ratio (d / l) to the distance (l) between the block ends is set within the range of 0.22 to 0.34, and on the other hand, the rotation angle α of the block 22 is The angle is set in a range of 10 ° to 35 ° with respect to a center line WZ of a line XY connecting the axis G of the shaft 20.

As shown in FIG. 7, in order to dispose the block shaft 20 in the above-mentioned range, the axis of the insertion hole of the block shaft 20 provided on the bottom surface of the device is shifted from the center of the bottom surface of the device to the tip of the device. The distance is set within a range of diameter (B) × (0.2 to 0.3).

Here, the ratio (d / l) of the inner diameter (d) of the insertion hole 11 of the block shaft 20 to the distance (l) between the block ends when the block is expanded is 0.22 or more. ,
The ratio (d / d) of the inner diameter (d) of the insertion hole 11 of the block shaft 20 to the distance (l) between the block ends when the block is expanded.
If l) is 0.22 or less, the diameter of the block shaft 20 decreases, the strength of the block shaft 20 decreases, and the block shaft 20 is easily damaged. Ratio (d / l) between the inner diameter (d) of No. 11 and the distance (l) between the block ends when the block is expanded.
Is greater than 0.34, the strength of the block shaft 20 can be increased, but the inner diameter d of the insertion hole 11 is increased, so that the thickness of the device 10 becomes thinner, and the durability of the device is lost. This is because the life is shortened.

The rotation angle α of the block 22 is shown in FIG.
As shown in FIG. 6, the reason why the rotation angle α is set in the range of 10 ° to 35 ° with respect to the center line WZ of the line XY connecting the axis G of the block shaft 20 is that the rotation angle α is If the angle is smaller than 10 ° with respect to the center line WZ of the line segment XY connecting the axis G of 20, the block 22 is likely to contract due to impact vibration during use. If the rotation angle α is larger than 35 ° with respect to the center line WZ of the line XY connecting the axis G of the block shaft 20, the distance m between the straight end face of the block 22 and the contact surface m Is shortened, and the overhang of the bit 21 becomes large, causing a neck break.

Further, in the present invention, the axis of the insertion hole of the block shaft provided on the bottom surface of the device is defined as the diameter (B) of the tip of the device (0.2 to 0.2.
The reason for setting the position apart in the range of 3) is that the distance of the axis from the device center is the diameter of the device tip (B).
If it is not more than × 0.2, the distance between the two block shafts 20 is too short, the diameter of the block shaft 20 becomes small, and the block shaft 20 is easily broken. If the distance from the device is within a range of the diameter (B) of the tip of the device (B) × 0.3 or more, the distance between the outer periphery of the device and the insertion hole 11 becomes short, and cracks easily occur in the device itself.

As shown in FIGS. 1 and 2, the device 10 has a small-diameter portion 10A having a spline groove 12 on the outer peripheral surface and a large-diameter portion 10B having an insertion hole 11 into which the block shaft 20 is inserted. The outer peripheral surface of the large-diameter portion 10B has a flange portion 1 that fits with the retaining pipe 31 provided on the inner periphery of the tip of the excavation pipe 30.
3 are provided integrally, and a discharge groove 14 for discharging the excavation chips upward is formed.

An exhaust hole 15a extending in the axial direction is formed at the center of the device 10. This exhaust
The hole 15a is open at the upper end of the small diameter portion of the device 10,
From this opening, compressed air discharged when the hammer piston falls is introduced.

The device 10 is formed with a communication hole 15b communicating with the distal end of the exhaust hole 15a and extending outward in the radial direction. The communication hole 15b extends from both ends of the communication hole 15b toward the distal end of the device 10. An air hole 15c is formed extending to the bottom surface of the device shaft 10 and opening. A notch 15d is provided between the bottom of the device and the outer peripheral surface of the air hole 15c and communicates with the discharge groove 14 and the air hole 15c.

Further, the flange portion 13 of the device 10
A peripheral groove 16a is formed on the outer peripheral surface of the device 10 located in the vicinity of the device 10, and the peripheral groove 16a and the exhaust hole 15a communicate with each other inside the device 10. A communication hole 16b is provided (see FIG. 1).

Further, a blow hole 16c is formed in the communication hole 15b communicating with the exhaust hole 15a to reach the upper surface of the large-diameter portion 10B of the device 10, and is opened.
Care is taken so that when c is clogged, the compressed air escapes and the hammer H does not stop. The blow hole 16c
As shown in FIG. 2, the opening is located outside the hammer H so that the blow hole 16 c is not closed by the hammer H when the hammer H is lowered.

The insertion hole 11 is formed so as to be shifted from the center of the device 10 and to be point-symmetric with respect to the center of the device 10, and more specifically, shown in FIG. 4 and FIG. As described above, the axis G is from the center position C of the device bottom surface to the diameter of the device tip (B) × (0.2-0.2
It is set and provided at a position separated in the range of 3).

The insertion hole 11 has a block shaft 2.
0 is inserted into the block shaft 20 so as to be freely rotatable and prevented from falling out. For example, when the block shaft 20 is fitted into the insertion hole 11, the locking pin 17 is inserted through the pin hole 18 of the device 10. Is inserted, and the locking pin 17 is inserted.
Is engaged with a notch 20a formed in the outer peripheral portion of the block shaft 20.

Next, the structure of the block shaft 20 and the block 22 will be described. The block shaft 20 and the block 22 are provided to be orthogonal to each other, and even if the block shaft 20 and the block 22 are formed integrally. Alternatively, they may be formed separately and connected by bolts or the like.
More specifically, as shown in FIG. 9, the length L of the block shaft 20 is 1.5 times the outer diameter D of the block shaft 20.
And a notch 20a into which the locking pin 17 is inserted is formed on the outer periphery of the block shaft 20 as shown in FIGS. Have been.

The notch 20a has a configuration in which the outer periphery of the block shaft 20 is cut out only at a position corresponding to the angle at which the block 22 rotates, and the block shaft 20 has a diameter larger than the diameter a of the locking pin 17. 22 has a basic structure that is notched long in the axial direction. In practice, the notch 20a is set to be about 1/3 of the outer diameter of the locking pin 17, and more specifically, is formed to have a size of about 4 to 8 mm. is there.

On the other hand, each block 22 has the same shape formed in a substantially fan shape (semicircular shape in the embodiment) when viewed from the bottom, and the radius of the fan shape is set to substantially the same value as the radius of the device 10. . The blocks 22 are arranged such that the straight end faces 22a face each other and the arc portions 22b of the blocks form a substantially circular shape as a whole. Block 22
A first inclined surface 22c is formed on the outer peripheral portion of the distal end surface (bottom surface) of the first inclined surface 22c.
A second inclined surface 22d that is inclined toward the base end side in the axial direction of the device 10 at an inclination angle different from that of the first inclined surface 22c is formed on the outer peripheral portion of 2c.

When the device 10 is rotated in the excavation direction, the end of the straight end surface 22a of the block 22 protruding from the outer peripheral surface of the device 10 is provided in the axial direction of the device 10 gradually toward the front in the rotation direction. A third inclined surface 22e inclined toward the base end side is formed.
reference). A plurality of bits 21 made of a carbide tip are implanted on the tip surface of the block 22 and the first to third inclined surfaces 22c, 22d, 22e perpendicularly to the surfaces.

In the embodiment, these bits 21
Are located near the straight end face 22a of the block 22 and are implanted along the straight end face 22a.
Of the bits 22a in the vicinity of the straight end face, one end of each of the two blocks 22 is located outside a circular arc portion 22b of one of the blocks 22 at a position where both ends protrude from the outer peripheral surface of the device by a predetermined excavation amount. (In the embodiment, the bit on the third inclined surface 22e), the vertex R is located outside the extension line AB extending along the curvature of the outer surface of the block as shown in FIG. Have been allowed.

In the embodiment, one end of each of the two blocks 22 has a predetermined excavation amount from the outer peripheral surface of the device 10 between the bottom surface (tip surface) of the two blocks 22 and the straight end surface 22a. When protruding by an amount corresponding to each other, concave portions 22 f which are arranged to face each other and form a concentric concave portion 25 with the device 10 are formed at the center of the block 22.

In the embodiment, the recessed portion 22f is formed of a circular bottom and a tapered surface inclined upward from the bottom, but the shape is not limited to the embodiment. For example, the shape shown in FIGS. 14 and 15 may be used. Incidentally, FIG. 14 shows a configuration in which only the tapered surface is formed, and FIG. 15 shows a configuration in which the tapered surface is eliminated and a wall portion extending substantially perpendicularly from the bottom surface is formed. Next, the operation of the excavating tool having the above configuration will be described.

As shown in FIG. 2 and the like, in order to mount the block 22 on the bottom surface of the device 10, first, the block shaft 2
The block shaft 20 is inserted into the insertion hole 11 on the bottom surface of the device 10 such that the straight end faces 22a of the block 22 face each other.

Next, from the pin hole 18 of the device 10,
When the engaging pin 17 is inserted and fixed, the block shaft 20 is engaged with the engaging pin 17, and the block and the device are assembled as shown in FIG. This assembling is a simple operation of inserting the block shaft 20 into the insertion hole 11 of the device 10 and engaging the engaging pin 17, and locking the two block shafts 20 with one engaging pin 17. Therefore, there is an effect that the workability can be improved.

In the above-mentioned excavating tool, when the hammer cylinder receives a driving force and is rotated in the arrow X direction, the device 1
0, the block shaft 20 and the block 22 also rotate in the same direction integrally therewith. Further, when the hammer piston disposed in the hammer cylinder is driven to apply a downward impact force to the device 10, the block 22 pushes into the ground and the bit 21 excavates the debris by the rotational force.

When the block 22 rotates together with the hammer cylinder and the device 10 in the direction of excavation, the block 2
Numeral 2 rotates around the block shaft 20 due to the excavation resistance, and one end of the upper right end surface of the block 22 protrudes from the outer peripheral surface of the device 10, and this portion functions as an outer peripheral blade A. Also,
When the blocks 22 rotate, the upper end faces 22a of the blocks abut against each other, which function as stoppers to restrict further rotation of the blocks.
In this state, the block 22 receives the rotational force of the device 10 and excavates underground by the outer peripheral blade A or the like.

At this time, when the hammer piston falls, the compressed air flows in from the exhaust hole 15a and is blown out from the air hole 15c to remove the excavated swarf. Since a notch 15d communicating with the discharge groove 14 is formed at the tip of the air hole 15c, a part of the compressed air flows directly as shown by the arrow in FIG. Excavated debris can be efficiently removed.

In the embodiment, as shown in FIGS. 16 and 17, when the hammer piston falls, a part of the compressed air flows into the circumferential groove 16a through the communication hole 16b and is exhausted to the outside. Therefore, the flange portion 13 of the device 10
There is an advantage that it is possible to prevent excavation debris from entering the lower surface (contact surface) and protect the device contact surface. Also, at the time of excavation, a concave portion 22f is formed in each block 22 and a concave portion 25 is formed at the center position of the block 22 when the diameter of the block 22 is expanded, so that the block 22 becomes difficult to insert into the rock when drilling. As a result, rattling is less likely to occur during excavation, good excavation can be performed, and a component force Fa of propulsion generated in the concave portion 25 acts on a force Fb acting on the outer peripheral blade A by acting in the radial direction as shown in FIG. Because it works to oppose, while being able to prevent neck break effectively,
Tool life can be extended.

In the embodiment, a part of the plurality of bits 21 implanted on the distal end face of the block 22 is positioned near the straight end face of the block 22 and implanted along the straight end face. In addition, the bit 21 near these straight end faces
Of the two blocks 22, the vertices of the bit 21 located outside the outer surface of the one block 22 at the position where one end of each of the blocks 22 protrudes from the outer peripheral surface of the device by a predetermined excavation amount, As shown in FIG. 11, since the block 22 is located outside the extension line AB extending along the curvature of the outer surface of the block, when an impact force is applied to the block 22 during excavation, the radial direction of the device 10 There is an advantage that a force can be applied in the outward direction and a force acting on the outer peripheral blade A can be borne.

Further, since the bit 21 on the extension line AB can be made to act outward, the wear of the bit can be reduced and the tool life can be extended. is there. Further, when the piston in the hammer cylinder falls, the compressed air pushed out by the hammer piston flows into the exhaust hole 15a and is blown out from the blow hole 16c through the communication hole 15b, so that the air hole 15c at the tip of the device becomes soft mud. Even if a problem such as clogging due to a layer or other factors occurs, the compressed air is blown through the blow hole 16c.
Since the air is blown out, the operation of the piston does not stop, the drilling operation is not impaired, and the operation efficiency can be improved.

In addition, the excavation as described above reduces the bottom surface of the device due to the impact thereof, or the length dimension of the device becomes smaller than the original one due to rework due to damage to the impact surface. Since the notch 22a into which the locking pin 17 is inserted is formed longer in the axial direction of the block shaft 20 than the diameter of the locking pin 17, even when the length of the device 10 is reduced, Locking pin 1
Without increasing the shearing force acting on 7,
There is an advantage that the shaft of the locking pin 17 can be prevented from being broken.

Further, in the embodiment, since the notch portion 22a has a notch structure in which only the rotation range of the block shaft 20 is cut, the sectional loss of the block shaft 20 can be reduced, and There is also an advantage that strength can be improved. In the embodiment, a flange portion 30a is provided on the outer periphery of the retaining pipe 31 so as to be in contact with the tip of the excavation pipe 30, and the flange portion 30a and the tip of the excavation pipe 30 are welded over the entire circumference. A notch 31b extending in the axial direction of the stopper pipe 31 and communicating with the inside and outside of the stopper pipe is formed, and the stopper pipe 31 and the excavation pipe 30 are welded through the notch 31b. Therefore, the retaining pipe 31 and the excavating pipe 30 can be firmly and integrally fixed. In particular, the retaining pipe 31 is welded at the position of the notch 31b communicating with the inside and outside of the retaining pipe 31. Since the fastening effect by welding occurs in this portion, the retaining pipe 31 and the excavating pipe 3
There is an advantage that 0 can be more firmly fixed.

After the excavation is completed, first, the hammer cylinder is raised and the device 10 is pulled up, so that the block 22 is pulled up and the bit 21 is pulled out from the bottom surface of the drilling hole. As a result, the block 22 becomes rotatable. Thereafter, the hammer cylinder is raised while rotating in the direction opposite to the excavation direction. Then, each block 22 is rotated in the opposite direction to the direction of excavation, and the straight end faces 22a of each block slide to reduce the diameter.
The distal end surface of the retaining pipe 31 of the excavation pipe 30 abuts against the inclined surface 22k formed on the outer peripheral portion of the base end surface, and an upward pressing force acts. The block 22 is surely reduced in diameter by the component force of the pressing force facing the axis of the device 10 and the rotational force of the device 10, and
Is located on the bottom surface of the device 10 or on the inner side thereof. When the diameter of the block 22 is reduced as described above, the air hole 15c on the bottom surface of the device is temporarily closed by the block 22 while the diameter of the block 22 is reduced. Since the cutout 15d is formed on the side surface of the device, the compressed air can be exhausted to the outside through the cutout 15d, and by blowing the compressed air to the contact surface between the device and the block, Excavation debris on the contact surface can be effectively removed, and the resistance at the time of block shrinkage can be removed.

[0045]

As explained above, the excavation method of the present invention
According to the law, before the rotation of the block in the drilling after the end of the reduced-diameter work by pulling the block, to some degree or extracted bits from the bottom of the borehole, or it is possible to separate from the bottom surface of the borehole, The block becomes easily rotatable. Therefore, the diameter of the block can be reliably reduced. In addition, pull up the block
When the slope comes into contact with the end of the casing pipe,
Force that moves the device toward the axis of the device,
Since a force that acts on the diameter acts, the block diameter can be reduced more.
Be certain.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing an entire excavation tool.

FIG. 2 is a sectional view showing the entire excavation tool.

FIG. 3 is a cross-sectional view showing an enlarged state of the device.

FIG. 4 is a plan view schematically showing a state where the diameter of the block is expanded.

FIG. 5 is a diagram showing a state where a block is arranged at an intermediate position;
It is a top view similar to.

FIG. 6 is a plan view similar to FIG. 4, showing a state where the diameter of the block is reduced.

FIG. 7 is a plan view showing a bottom surface of the device.

FIG. 8 is a perspective view of a device and a block.

FIG. 9 is a front view of the block.

FIG. 10 is a sectional view showing an engagement state between a block shaft and a locking pin.

FIG. 11 is a plan view showing a state where the diameter of the block is expanded.

FIG. 12 is a plan view showing a state where the diameter of the block is reduced.

FIG. 13 is a sectional view of a block.

FIG. 14 is a cross-sectional view shown for explaining another shape of the concave portion on the block bottom surface.

FIG. 15 is a cross-sectional view shown for explaining another shape of the concave portion on the bottom surface of the block.

FIG. 16 is a side view for explaining the operation of the contact surface between the device and the drilling pipe.

FIG. 17 is a side view for explaining the operation of the contact surface between the device and the drilling pipe.

FIG. 18 is a sectional view of a conventional excavation tool.

FIG. 19 is a plan view showing a bottom surface of the block.

FIG. 20 is a plan view showing a bottom surface of the block.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Device 20 Block axis 21 bit 22 block 22k Inclined surface 30 Drilling pipe (casing pipe) 31 Retaining pipe

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuaki Tsujimoto 1528 Nakashinta, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture Mitsubishi Materials Corporation Gifu Works (56) References A) Fully open 1987-85592 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) E21B 3/00-4/20 E21B 10/00-10/66

Claims (1)

(57) [Claims] 1. A bottom surface of a device which is provided on a casing pipe so as to be rotatable around an axis and movable in an axial direction and receives an impact force of a hammer and a rotation force of a hammer cylinder. Each of the block shafts was symmetrically fitted so as to be rotatable around the axis, and a bit was implanted at the distal end of each block shaft in a substantially semicircular shape having substantially the same diameter as the device and at the distal end surface. The blocks are provided with their straight ends facing each other, and the position of the block shaft is adjusted such that when the device is rotated in the excavation direction, one end of each of the blocks is excavated by a predetermined amount from the outer peripheral surface of the device. amount amount project and the drilling method using the drilling tool comprising eccentrically from the center of the device to straight end faces of the blocks during the time of enlarged diameter of the block in contact with each other, drilling After completion, the bit is pulled up to the block
Withdrawing from the bottom of the borehole and pulling the block
Inclined surface formed on the outer periphery of the base end face of the block while raising
Pressing the tip of the casing pipe against the end of the casing pipe.
An excavation method characterized by: