JP3382555B2 - Drilling tools - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool attached to the tip of a rod that is inserted into a casing pipe for drilling, and in particular, it is possible to pull out the tool body together with the rod through the casing pipe after the drilling is completed. Related to excavation tools.

[0002]

2. Description of the Related Art As an excavating tool of this type, those proposed in Japanese Patent Application Nos. 48-128892 and 48-188893 are known. That is, these excavation tools are provided with a tip cutting edge portion at the tip of a tool body that is attached to the tip of a rod that is inserted into a cylindrical casing pipe and that is rotated around its axis. The outer periphery is provided with a protruding cutting edge portion protruding toward the outer peripheral side of the tool, and the outer diameter of the tool main body including this protruding cutting edge portion is set to a size that can be inserted into the casing pipe, The diameter of rotation of the protruding cutting edge portion is larger than the outer diameter of the casing pipe.

However, in such an excavating tool, at the time of excavation, the rod is rotated by aligning the axis with the central axis of the casing pipe to first form a pilot hole in the ground by the leading tip cutting edge portion. While being guided by the pilot hole, the tool body advances to form a hole having a larger diameter by the protruding cutting edge portion, and the casing pipe is built in the hole thus formed. In addition,
Excavation chips generated by the cutting edges of the tip cutting edge portion and the protruding cutting edge portion at the time of this excavation are sent to the tool rear end side and discharged through the outer circumference of the rod in the casing pipe. On the other hand, after the end of excavation, by bending the rod in the casing pipe to eccentric the axis of the tool body to the side opposite to the protruding cutting edge portion with respect to the central axis of the casing pipe,
It is possible to pull the rod and tool body through the casing pipe, leaving only the casing pipe in the drilled hole.

[0004]

However, in the case of the excavating tool for pulling out the rod and the tool body from the casing pipe after completion of the excavation in this way, since the tool body is located at the bottom of the excavated hole at the end of excavation, the extraction is not possible. In this case, it is difficult to bend the rod so that the axis of the tool body is surely eccentric to the side opposite to the protruding cutting edge with respect to the central axis of the casing pipe. Here, in the above-mentioned conventional excavating tool, the rear end surface of the protruding cutting edge portion that faces the tool rear end side is inclined toward the tool rear end side toward the tool inner peripheral side, and this rear end surface is the casing. It is also possible to bend the rod by guiding the tool main body while sliding it to the tip edge of the pipe so as to guide it to the inclination, but even in such a case, in the above-mentioned excavating tool, the protruding cutting edge portion is Since there is only one, the rear end face and the tip edge of the casing pipe are in sliding contact with each other only at one point, and there is a risk that the tool body will swing around this point during retraction, and again the tool body It became difficult to surely make the axis line eccentric to the side opposite to the protruding cutting edge portion, resulting in hindering smooth and rapid extraction of the tool body.

The present invention has been made under such a background, and is provided with a projecting cutting edge portion on the outer periphery of the tool body attached to the tip of the rod inserted into the cylindrical casing pipe as described above. During excavation, the axis is aligned with the central axis of the casing pipe to form a hole, and after the excavation is finished, the axis is eccentric to the side opposite to the protruding cutting edge portion with respect to the central axis, and the casing pipe is formed. It is an object of the present invention to provide an excavation tool that can be pulled out from the excavation tool that can surely decenter the axis of the tool body on the side opposite to the protruding cutting edge portion when the excavation tool is pulled out.

[0006]

In order to solve the above problems and to achieve such an object, the present invention is directed to a tip cutting edge centered on the axis line at the tip of a tool body rotated about the axis line. A part is provided, and on the outer periphery of the tool body on the rear end side of the tip cutting edge part, a pair of projecting cutting edge parts projecting to the tool outer peripheral side are provided adjacent to each other in the circumferential direction. The rear end faces of the parts facing the tool rear end side are both inclined toward the tool inner peripheral side toward the tool rear end side. However, in the excavating tool configured in this way, when the tool body is pulled in while sliding the rear end surface of the protruding cutting edge portion onto the tip edge of the casing pipe after the end of excavation, both of these pair of protruding cutting edge portions are formed. The slanted rear end surface of the will slide into contact with the front edge of the casing pipe,
That is, since the casing pipe tip edge and the tool body are in sliding contact with each other at two points, the swinging of the tool body around one point can be restricted by the sliding contact with the casing pipe tip edge at the other point. As a result, the tool body can be reliably guided to the side opposite to the protruding cutting edge portion and eccentric.

Here, in order to guide the tool main body to the side opposite to the projecting cutting edge portion and to withdraw it smoothly and more quickly from the casing pipe, the rear end face of the projecting cutting edge portion should be the same as that of the tool main body. The angle of inclination with respect to the axis is 15 ° to 4
It is desirable to set in the range of 0 °. That is, if this inclination angle is larger than 40 ° and the inclination of the rear end surface of the protruding cutting edge portion is steep, when the rear end surface is slidably contacted with the front end edge of the casing pipe and the tool body is retracted. ,
This rear end face may be caught on the tip edge of the casing pipe and hinder smooth extraction. On the contrary, if the inclination angle is smaller than 15 °, the axial distance of the rear end face becomes long, and the tool main body becomes longer. This results in more time being taken out.

On the other hand, in the tip cutting edge portion provided at the tip of the tool body, the protruding length from the tip of the protruding cutting edge portion to the tool tip side is the outside of the cutting edge of the tip cutting edge portion. It is desirable to set it in the range of 1.4 to 2.6 × D ₁ with respect to the diameter D ₁ . This is because when the protrusion length is short enough to fall below 1.4 × D ₁ with respect to the outer diameter D ₁ , the pilot hole formed by the tip cutting edge portion has an outer diameter D of the cutting edge.
_{Since the} depth becomes shallower than ₁ and the tool body cannot be guided straight, and the straightness of the drilling hole may be impaired, the protruding length is 2. with respect to the outer diameter D _{1 of the} cutting edge. If it is larger than 6 × D ₁ , the cutting edge of the tip cutting edge portion at the time of excavation may impair the dischargeability of the cutting waste generated by excavating the ground, which may lead to a decrease in excavation efficiency. is there.

Further, the excavating tool having the above construction is attached to the tip of the rod inserted into the cylindrical casing pipe as described above, is rotatable about the axis, and is used for excavation. However, at this time, the outer diameter of the rod is preferably set in the range of 0.3 to 0.6 × D ₂ with respect to the inner diameter D _{2 of the} casing pipe. That is, if the outer diameter of the rod is so thin as to be less than 0.3 × D ₂ with respect to the inner diameter D _{2 of the} casing pipe, the rod acts on the tool body to form a drilling hole having an inner diameter capable of incorporating the casing pipe. The rigidity of the rod becomes insufficient with respect to the excavating load, and particularly in the excavating tool as described above provided with the protruding cutting edge portion projecting to the outer peripheral side of the tool, during excavation, the tool body rotates while decentering from its axis. Therefore, the straightness and roundness of the hole may be impaired. On the other hand, if the outer diameter of the rod is so large that it exceeds 0.6 × D ₂ with respect to the inner diameter D _{2 of the} casing pipe, the rigidity of the rod becomes too high, and after the completion of excavation, the projecting cutting The deflection of the rod when the tool body is eccentric by sliding the rear end surface of the blade section against the tip edge of the casing pipe becomes small, and in some cases it becomes difficult to pull out the rod and tool body. There is a risk that the space inside the casing pipe for discharging the cutting waste sent to will be reduced and the dischargeability will be impaired.

[0010]

1 to 5 show an embodiment of the present invention. In the present embodiment, the tool main body 1 has a substantially multi-stepped columnar shape whose center is an axis O whose diameter is reduced by one step toward the tool tip side except for a pair of protruding cutting edge portions 2 and 2 which will be described later. The tip portion that is reduced in diameter by one step is the tip cutting edge portion 3. In addition, in this tool body 1,
A mounting hole 4 centering on the axis O is formed from the end face toward the tool tip side, and an inner thread of the mounting hole 4 is internally threaded with a male thread portion 5A formed on the outer circumference of the tip of the rod 5. The portion 4A is formed, and from the bottom surface of the mounting hole 4 toward the tool tip side, a hole 6 having a small diameter is bored along the axis O to the middle of the tip cutting edge portion 3 in the axis O direction. Has been done.

On the outer periphery of the tip cutting edge portion 3, there are three discharge grooves 7 for excavating debris, which have a substantially arcuate cross section and extend in the circumferential direction from the tip end thereof in parallel with the axis O toward the rear end side of the tool. These discharge grooves 7 are formed at intervals and are rounded up toward the outer peripheral side in the middle of the tip cutting edge portion 3 in the axis O direction.
Further, a cylindrical core piece 8 is embedded in the center of the tip of the tip cutting edge portion 3, and from the core piece 8 toward the tool outer peripheral side, the discharge grooves 7, which are adjacent in the circumferential direction,
A flat plate-shaped tip 9 made of a hard material such as cemented carbide is made to abut on the core piece 8 at the center of the 7 so that it extends in the radial direction of the tip cutting edge portion 3 when viewed from the tool tip side. The cutting blades 10 are formed along the plane including the axis O on the tip surfaces of the tips 9 ...

Here, the cutting edge 10 is formed in a mountain shape that extends from the inner peripheral edge toward the outer peripheral edge once toward the tool tip side, then bends at an obtuse angle and extends toward the tool rear edge side. The tip surface of the tip cutting edge portion 3, including the tip surface of the tip 9, is a plane between the discharge grooves 7, 7 perpendicular to a plane including the axis O in which the cutting edge 10 is formed. It is inclined toward the rear end side of the tool as it is separated from, that is, it is formed in a mountain-shaped inclined surface shape with the cutting edge 10 as a ridge line. In the present embodiment, the diameter of the circle formed by the outer peripheral ends of these cutting edges 10 ...
In the present embodiment, the outer diameter D ₁ is substantially equal to the outer diameter of the one-step expanded portion on the rear end side of the tool body 1, and the cutting blades 10 ... Of the cutting edge 10, that is, the protruding length L in the direction of the axis O to the apex of the chevron formed by the cutting edge 10 is 1.4 to 2.6 × D ₁ with respect to the outer diameter D _{1 of the} cutting edge 10. It is considered to be a range. Furthermore, the tip end side is formed in the valley between the mountain-shaped inclined surfaces formed by the tip end face of the tip cutting edge portion 3, that is, the portion on the side opposite to the chips 9 with the core piece 8 sandwiched therebetween when viewed from the tool tip side. Are formed so as to communicate with the discharge groove 7 on the opposite side along a plane including the axis O where the cutting edge 10 is formed. There is.

On the other hand, the pair of protruding cutting edge portions 2 and 2 are located at a portion where the outer diameter of the tool main body 1 on the tool rear end side of the tip cutting edge portion 3 is increased by one step, and the tool of the enlarged diameter portion is used. It is formed on the tip side and is provided adjacent to each other in the circumferential direction. Here, in each of the projecting cutting edge portions 2 of the present embodiment, a projecting portion 12 projecting toward the tool outer peripheral side is integrally formed on the tool body 1 at the tool tip side of the expanded diameter portion of the tool body 1,
A tip 13 made of a hard material such as cemented carbide is implanted in a tip surface 12A of the protrusion 12 facing the tool tip side, and a cutting edge 14 is formed in the tip 13, which is particularly preferable in the present embodiment. Then, the projecting cutting edge parts 2 and 2 are the tip cutting edge parts 3
Of the three cutting edges 10 ... Are formed symmetrically with respect to a plane P including the axis O on which one cutting edge 10 is formed.

Here, the projecting portion 12 projects toward the outer peripheral side of the tool in the radial direction with respect to the axis O of the tool body 1 as viewed from the tip end side of the tool, and its width in the circumferential direction becomes smaller toward the outer peripheral side of the tool. The front end surface 12A facing the tool tip side is formed so as to extend to the tool outer peripheral side substantially perpendicular to the axis O. On the other hand, the rear end face 12 of the protruding portion 12 facing the tool rear end side
B is formed so as to incline toward the tool rear end side toward the inner peripheral side of the tool.
The inclination angle α formed by B with respect to the axis O is 1 in this embodiment.
It is set in the range of 5 ° to 40 °. It should be noted that this rear end face 12B has an axis O in a cross section orthogonal to the axis O.
Is formed so as to form an arc shape around the center, and the portion where this rear end surface 12B intersects the outer peripheral surface of the tool main body 1 on the tool rear end side is concavely curved in a cross section including the axis O. It is formed so as to smoothly connect to the surface.

Further, the outer peripheral surface 12C of the protruding portion 12 facing the tool outer peripheral side has an inclination angle extremely smaller than the inclination angle of the rear end surface 12B, and is also directed toward the tool inner peripheral side toward the tool rear end side. And a cross section orthogonal to the axis O is formed in an arc shape centering on the axis O. Furthermore, among the side surfaces of the protruding portion 12 facing the circumferential direction, the side surface 12D facing the side opposite to the side where the pair of protruding cutting edge portions 2 and 2 are adjacent to each other, that is, the side opposite to the plane P side, It is formed so as to contact the outer peripheral surface of the tool body 1 substantially smoothly.

Further, the tip 13 is formed in a substantially rectangular flat plate shape, and extends in the radial direction with respect to the axis O at the approximate center of the tip end surface 12A of the projecting portion 12 in the circumferential direction of the tool body 1. It has been planted. Here, the tip end surface 12A of the protruding portion 12 is formed in a triangular mountain shape protruding toward the tool tip end side as shown in FIG. 3 when viewed from the tool outer peripheral side including the tip end surface of the tip 13, The cutting edge 14 is formed along a mountain-shaped ridge line formed by the tip surface 12A, and the cutting edge 14 is formed in a direction orthogonal to the axis O of the tool body 1. The protruding length L of the tip cutting edge portion 3 is the length in the direction of the axis O from the cutting edge 14 to the tip of the cutting edge 10. In addition, in the present embodiment, the cutting blades 14 of the pair of protruding cutting blade portions 2 and 2,
14 is an included angle 3 centered on the axis O when viewed from the tool tip side.
In the excavating tool of the present embodiment, which is formed so as to be arranged within an arc of 8 ° to 78 °, that is, the cutting edges 14 and 14 are formed in a direction orthogonal to the axis O, when viewed from the tool tip side. The included angle θ between the cutting edges 14 and 14 with the axis O as the center
Is set in the range of 38 ° to 78 °, and more preferably in the range of 45 ° to 55 °.

In the present embodiment, between the pair of protruding cutting edge portions 2 and 2 thus formed, the front end surfaces 12A, 12A to the rear end surface 12B of the protruding portions 12, 12 are oriented in the direction of the axis O. , 12B, which is a drainage channel for excavated dust
5 are formed along the plane P. Therefore, the position of the discharge groove 15 in the circumferential direction of the tool body 1 is made to coincide with one of the discharge grooves 7 for excavating chips formed on the outer periphery of the tip cutting edge portion 3, and the tool of the discharge groove 7 is aligned. It will be formed on the rear end side. Here, the discharge groove 15 is formed so that a cross section orthogonal to the axis O has a substantially V shape having an included angle slightly larger than the included angle θ, and the groove bottom has a concave curved surface shape. While being formed, the depth to the groove bottom is approximately half the height of the protrusion 12 from the outer peripheral surface of the tool body 1. Further, on the peripheral edge of the open groove portion of the discharge groove 15 in the tip surfaces 12A, 12A of the protruding portions 12, 12, a concave curved surface-like inclined surface that inclines toward the tool rear end side toward the open groove portion peripheral edge. 15A is formed.

Further, three branch holes 6A, 6 extending toward the rear end side of the tool from the approximate center of the hole 6 formed in the tool body 1 in the direction of the axis O toward the outer peripheral side of the tool.
B and 6B are formed at substantially equal intervals in the circumferential direction of the tool main body 1, and one of the branch holes 6A extends along the plane P and is opened at the groove bottom of the discharge groove 15, and The two branch holes 6B, 6B are opened in the outer peripheral surface of the tool body 1. From the tip of the hole 6,
A branch hole 6C extending toward the tool tip side is formed toward the tool outer peripheral side, and the branch hole 6C is one of the three discharge grooves 7 formed on the outer periphery of the tip cutting edge portion 3 ... The discharge groove 15 is opened to one of the two discharge grooves 7, 7 other than the discharge groove 7 whose circumferential position matches.

In the thus constructed drilling tool, the male screw portion 5A at the tip of the rod 5 inserted into the cylindrical casing pipe 16 has the female screw portion 4 of the mounting hole 4 as described above.
It is attached to the tip of this rod 5 by being screwed into A. Here, as for the size of this excavating tool, as shown in FIG. 4, the outer diameter around the axis O of the cutting edge 14 of the protruding cutting edge portions 2 and 2 becomes slightly larger than the outer diameter of the casing pipe 16. At the same time, as shown in FIG. 5, the maximum diameter of the circle circumscribing the tool body 1 of the excavating tool in the cross section orthogonal to the axis O is set to be slightly smaller than the inner diameter D ₂ of the casing pipe 16. The outer diameter D ₃ of the rod 5 is the inner diameter D _{2 of the} casing pipe 16.
Is set in the range of 0.3 to 0.6 × D ₂ . However, the outer diameter D ₃ of this rod 5 is
If the cross-section of the outer peripheral surface of the rod is circular, it is defined by its diameter. If the cross-section of the outer peripheral surface of the rod 5 is polygonal such as regular hexagon, it is defined by the diameter of the circle circumscribing this polygon. It

However, at the time of excavation with such an excavating tool, the projecting cutting edge portion 2, which extends from the tip of the casing pipe 16,
2 is projected, the above-mentioned axis O is attached to the casing pipe 1
The tool body 1 is rotated around the axis O along with the rotation of the rod 5 while being aligned with the central axis C of the rod 6, and is struck in the direction of the axis O toward the tip of the tool. Cutting blades 10 ... form a small-diameter pilot hole in the ground in advance, and then the tool body 1 moves straight in the direction of the axis O while being guided by the pilot hole, and the projecting cutting edge portion 2 ,. A large-diameter hole is formed by the two cutting edges 14, 14, and the casing pipe 16 is built in the hole formed in this way. At the time of this excavation, a high-pressure fluid such as compressed air is supplied from the inner peripheral portion of the rod 5 to the hole 6 of the tool body 1 and ejected from the branch holes 6A to 6C, and the cutting blades 10 ... 14,14
The cutting waste generated by this is extruded to the rear end side of the tool by this, and is discharged through the space between the rod 5 and the casing pipe 16.

After the hole is formed and the casing pipe 16 is built up to a predetermined depth and the excavation is completed, the tool body 1 together with the rod 5 is pulled into the casing pipe 16 and retracted. ,
First, the protruding cutting edge portion 2, which protrudes toward the outer peripheral side of the tool body 1,
The rear end surfaces 12B, 12B of the projecting portions 12, 12 of 2 hit the front edge of the casing pipe 16, and the rear end surfaces 12B, 12B are guided by the inclination while slidingly contacting the front edge of the casing pipe 16, and the tool main body. The rod 5 is bent so that the axis O of the tool 1 is eccentric to the center axis C of the casing pipe 16 in the direction opposite to the direction in which the projecting cutting edge portions 2 and 2 project, and the tool body 1 projects. The parts 2 and 2 are accommodated in the casing pipe 16. Therefore, by pulling out the rod 5 and the tool body 1 as they are,
The rod 5 and the tool body 1 can be pulled out with the casing pipe 16 left in the drilled hole.

However, in the excavating tool having the above-mentioned structure, the tool body 1 is formed with the pair of projecting cutting edge portions 2, 2 on the outer periphery thereof, and the projecting portions 12, 2 of these projecting cutting edge portions 2, 2 are formed.
The rear end surfaces 12B and 12B of the tool 12 facing the tool rear end side are both inclined toward the tool rear end side toward the tool inner peripheral side.
Is guided to be eccentric with respect to the central axis C, the tool body 1 is guided by sliding contact between the rear end surfaces 12B and 12B and the leading edge of the casing pipe 16 at two sliding contact points. Therefore, the tool body 1 is attached to the casing pipe 16
Even when a force that causes the tool main body 1 to swing about one of the above-mentioned two sliding contacts is generated when it is pulled into the inside, this swinging causes the trailing end surface 12B to move to the casing pipe at the other sliding contact. The protruding cutting edge portions 2 are projected along the direction in which the tool body 1 equally divides the sliding contact points of these two points, that is, along the plane P in the present embodiment. Since the eccentricity is surely eccentric to the side opposite to the side where the tool body 1 and the rod 5, the tool body 1 and the rod 5 can be smoothly and quickly pulled out from the casing pipe 16 and taken out.

Further, in this embodiment, the inclination angle α formed by the rear end surfaces 12A, 12A of the protruding portions 12, 12 of the protruding cutting edge portions 2, 2 with respect to the axis O of the tool body 1 is 15 as described above. It is set in the range of ° to 40 °, which allows the tool body 1 to be more smoothly and quickly guided to the side opposite to the protruding cutting edge portions 2 and 2 and pulled out from the casing pipe 16. That is, when the inclination angle α is larger than 40 ° and the rear end surfaces 12A, 12A become steep, the tool body 1 is pulled in while sliding the rear end surfaces 12A, 12A to the front edge of the casing pipe 16. At this time, the rear end faces 12A, 12A are
There is a risk that it will be caught at the tip edge of the and the smooth extraction will be hindered. On the other hand, conversely, if the inclination angle α is small enough to fall below 15 °, the tool body 1
Since the distance of the rear end face 12A in the direction of the axis O becomes long, it takes a longer time to slide the rear end face 12A into the tip edge and draw the tool body 1 into the casing pipe 16. The main body 1 and the rod 5 may not be able to be pulled out quickly.

On the other hand, the tip cutting edge portion 3 provided at the tip of the tool body 1 is used during excavation as in the present embodiment.
In this type of excavating tool, which does not have a mechanism for supporting the axis O of the above-mentioned axis coaxially with the central axis C of the casing pipe 16, and moreover the run-out is likely to occur during excavation due to the protruding cutting edge portion 2 provided on the outer periphery of the tool body 1. , Is an important element for guiding the tool body 1 straight along its axis O. Therefore, in the excavating tool of the present embodiment, the protruding length L of the tip cutting edge portion 3 from the tip of the protruding cutting edge portion 2 toward the tool tip side is the cutting edge 10 of the tip cutting edge portion 3. It is set in the range of 1.4 to 2.6 × D ₁ with respect to the outer diameter D ₁ of the tool body 1. By this, the tool body 1 is guided straight along the axis O while preventing the reduction of the excavation efficiency. It becomes possible.

That is, the protrusion length L is 1.4 ×
If the length is shorter than D ₁ , the pilot hole formed by the tip cutting edge portion 3 becomes shallow, the tool body 1 cannot be guided straight, and center runout occurs, and the straightness of the drilled hole is impaired. If the protrusion length L is large enough to exceed 2.6 × D ₁ , conversely, the dischargeability of the cutting waste generated by the cutting blades 10 of the tip cutting blade portion 3 is impaired and the excavation efficiency is improved. There is a risk of lowering. In addition, in the excavating tool having the above-described configuration, the tool body 1 is provided with the pair of protruding cutting edge portions 2 and 2 as described above. It is possible to reduce the load that acts on the protruding cutting edge portion 2, and thereby obtain the effect that the excavation efficiency can be improved.

By the way, in this type of excavating tool, center excursion is likely to occur in the tool body 1 during excavation due to the above-mentioned factors. Therefore, it is desirable that the rod 5 for rotating the tool body 1 is as rigid as possible. On the other hand, the casing pipe 1 is provided with the inclined rear end surfaces 12A and 12A of the protruding cutting edge portions 2 and 2 as in the excavating tool having the above configuration.
6 is slidably brought into contact with the leading edge of the rod 6 to guide the rod 5.
When the tool main body 1 is eccentrically pulled out while being bent, if the rigidity of the rod 5 is too high, the bending becomes small, and when the tool main body 1 is pulled out through the casing pipe 16, the protruding cutting edge portions 2, 2 Is strongly pressed against the inner circumference of the casing pipe 16, which may make it difficult to pull out the tool body 1 and the rod 5. However, in this embodiment, the outer diameter D of the rod 5 is
₃ is 0.3 to the inner diameter D _{2 of the} casing pipe.
It is set in the range of 0.6 × D ₂ , which prevents the core runout more effectively in combination with setting the protruding length L of the tip cutting edge portion 3 in the above range. The tool body 1 and the rod 5 can be reliably pulled out.

That is, the casing pipe 1 having the inner diameter D ₂
In order to build up 6, the drilling hole having an inner diameter at least larger than this inner diameter D ₂ must be formed no matter how thin the wall thickness of the casing pipe 16 is, that is, the protruding cutting edge portion 2 of the tool main body 1 The outer diameter of the cutting edge 14 around the axis O is the inner diameter D
_Since it has to be set larger than _2, the outer diameter D ₃ of the rod 5 which rotates with the tool body 1 attached to the tip thereof is so thin that it is smaller than 0.3 × D ₂ with respect to the inner diameter D ₂ . Then, the rigidity of the rod 5 against the load acting on the tool body 1 during excavation may be insufficient. And in the above-mentioned excavating tool which is provided with the protruding cutting blade portions 2 and 2 which particularly project to the outer periphery of the tool, the tool main body 1 is in the radial direction with respect to the axis O during excavation due to the excavating load acting on the protruding cutting blade portions 2 and 2. Therefore, when the rod 5 becomes insufficient in rigidity in this way, the tool body 1 rotates while being eccentric from the axis O, and the straightness and roundness of the drilling hole are impaired, and the casing pipe 16 is built. There is a risk that it will be difficult to get crowded.

On the other hand, if the outer diameter D ₃ of the rod 5 is thicker than the inner diameter D ₂ of the casing pipe 16 by more than 0.6 × D ₂ , the rigidity of the rod 5 becomes too high. As described above, by pulling the rod 5 and the tool main body 1 after the end of excavation, the rear end surfaces 12B and 12B of the protruding cutting edge portions 2 and 2 are slidably brought into contact with the tip edge of the casing pipe 16 to bend the rod 5. Meanwhile, when the axis O of the tool body 1 is eccentric with respect to the central axis C of the casing pipe 16, the deflection of the rod 5 becomes small, and the rear end faces 12B and 12B are strongly pressed against the tip edge of the casing pipe 16. In some cases, it may be difficult to store or pull out the rod 5 and the tool body 1 in the casing pipe 16. Further, if the outer diameter D ₃ of the rod 5 is large in this way, the space for discharging the cutting waste defined between the rod 5 and the inner circumference of the casing pipe 16 becomes small, and the cutting waste is clogged. There is a risk that the dischargeability will be impaired and smooth excavation will be hindered.

In this embodiment, as described above, the projecting cutting edge portions 2 and 2 are symmetrical with respect to the plane P including the axis O, and the cutting edges 14 and 14 are arranged in the direction orthogonal to the axis O. However, it is not always necessary to adopt such a configuration. For example, the projecting cutting edge portions 2 and 2 are asymmetrical, or one or both of the cutting edges 14 and 14 are displaced from the axis O when viewed from the tool tip side. It may be formed so as to extend in the direction, or may be formed obliquely to the axis O in a side view of the tool body 1. Further, in the above-described embodiment, the cutting blades 14, 14 of the projecting cutting blade portions 2, 2 are formed on the ridge line portion of which the tip surfaces 12A, 12A of the projecting portion 12 are formed in a mountain-shaped inclined surface shape. Although it is formed in a straight line, for example, this is formed into a tip surface 12A of the protrusion 12.
Alternatively, a large number of button-shaped chips made of a hard material such as cemented carbide may be implanted to form the cutting blade.

Further, in the above embodiment, the rear end faces 12B, 12B of the protruding portions 12, 12 of the protruding cutting edge portions 2, 2 are
The cross section orthogonal to the axis O has an arc shape with the axis O as the center, and the cross section including the axis O is formed so as to be inclined at a constant inclination angle α. The cross section orthogonal to the axis O may be formed in a straight line shape, or may be formed in a triangular or trapezoidal mountain shape or in a curved shape other than an arc, and also in a cross section including the axis O, Even if it is formed so as to form a polygonal line that connects straight lines with different inclination angles, it may be formed in a curved shape that is concave or convex, or it may be formed in a cross section that combines straight lines and curves. Good. Furthermore, in the above embodiment, the outer peripheral surface 12C of the protruding portion 12 of the protruding cutting edge portion 2 facing the tool outer peripheral side is also formed in an inclined surface shape toward the tool inner peripheral side toward the tool rear end side. By this, the tool body 1 is more reliably accommodated in the casing pipe 16. However, with respect to the outer peripheral surface 12C, the cross section including the axis O of the tool body 1 is made parallel to the axis O. Alternatively, the inclined rear end face 12B may be formed so as to directly intersect the front end face 12A of the protrusion 12 without forming the outer peripheral face 12C.

[0031]

As described above, according to the present invention,
Since a pair of projecting cutting edges that are inclined toward the tool rear end side as the rear end surface moves toward the tool inner peripheral side are provided adjacent to the outer periphery of the tool main body in the circumferential direction, the tool main body after the excavation is completed. When pulling out the rod and the rod from the casing pipe, the rear end surface of these protruding cutting blades is slidably guided to the tip edge of the casing pipe to prevent the tool body from swinging and to project. The part can be reliably eccentrically arranged on the side opposite to the side where the part projects, and can be housed in the casing pipe, and can be smoothly and promptly pulled out from the casing pipe.

[Brief description of drawings]

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

FIG. 2 is a front view of the embodiment shown in FIG. 1 viewed from the tool tip side.

FIG. 3 is a view as seen in the direction of the arrow X in FIG.

FIG. 4 is a view in YOY section (chain line is a ZOZ section) in FIG. 2;

5 is a front view showing a state in which the excavating tool of the embodiment shown in FIG. 1 is housed in a casing pipe 16. FIG.

[Explanation of symbols]

1 Tool Main Body 2 Protruding Cutting Edge Part 3 Tip Cutting Edge Part 5 Rod 6 Holes 6A, 6B, 6C Branch Hole 7 Excavation Waste Discharge Groove of Tip Cutting Edge Part 9, 13 Chip 10, 14 Cutting Edge 12 Projecting Part 12B Projection Rear end face 15 of the portion 12 Discharge groove 16 of the cutting waste of the protruding cutting edge portion 2 Casing pipe O Axis P of the tool body 1 Plane C including the axis O where the cutting edge 10 is formed Central axis D ₁ of the casing pipe 16 rear end face 12B is the axis of the outer diameter D ₂ the inner diameter D ₃ rods 5 of the outer diameter L distal cutting edge 3 of the protruding length α protruding cutting edge portion 2 of the protruding portion 12 of the casing pipe 16 of the cutting edge 10 of the blade 3 O
Inclined angle θ with respect to the angle of the cutting edge 14 about the axis O as viewed from the tool tip side

Front page continuation (72) Inventor Kazuyoshi Yoshida, Gifu Prefecture, Anpachi-gun, Kobe-cho, Yokoi, Nakaida 1528, Mitsubishi Materials Corporation Gifu Manufacturing Co., Ltd. 1528 Nakashinden Mitsubishi Materials Corporation Gifu Works (72) Inventor Hiroyuki Fukuda 1-3-15 Awaza, Nishi-ku, Osaka City, Osaka Prefecture Kashima Construction Co., Ltd. Kansai Branch (72) Inventor Jun Muta Sendai City, Miyagi Prefecture 1-27 Fukkamachi, Aoba-ku Kashima Construction Co., Ltd. Tohoku Branch (72) Inventor Takeo Sonoda 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 8 −4465 (JP, A) Actual development 50-71503 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) E21B 10/26-10/34 E21B 10/64

Claims (4)

(57) [Claims] 1. A tip cutting edge portion centering on the axis is provided at a tip of a tool body rotated about an axis, and an outer periphery of the tool body on a rear end side of the tip cutting edge portion is provided. A pair of protruding cutting blades projecting to the outer peripheral side of the tool are provided adjacent to each other in the circumferential direction, and the rear end faces of these protruding cutting blades facing the tool rear end side are both directed toward the inner peripheral side of the tool. An excavation tool characterized by being inclined toward the rear end side. 2. The tilt angle formed by the rear end surface of the protruding cutting edge portion with respect to the axis of the tool body is set in a range of 15 ° to 40 °. Drilling tool. 3. The length of protrusion of the tip cutting edge from the tip of the protruding cutting edge to the tool tip side is 1.4 to the outer diameter D ₁ of the cutting edge of the tip cutting edge. The range of 2.6 × D ₁ is set, and the range is 1 or 2.
Drilling tool described in. 4. The tool body is attached to the tip of a rod inserted into a cylindrical casing pipe and is rotatable around the axis, and the outer diameter of the rod is the inner diameter D of the casing pipe. ₂ with respect to the 0.3 to 0.
The excavating tool according to any one of claims 1 to 3, wherein the excavating tool is set in a range of 6 x D ₂ .