JP2003097176A - Excavating tool and excavating construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excavating tool provided with a cut-type bit capable of improving the bitability to the ground and reducing the resistance during excavation. SOLUTION: An excavating bit 4 is mounted on a tip part of an tool body 1 which is approximately cylindrical on an axis O in a state of being expandable and contractible to an outer peripheral side of the tool body 1, and a pilot part 5 provided with the cutting-type bit 13 having a cutting blade 13A on its tip, is mounted on a tip side of the cutting bit 4 in a state that its outer diameter around the axis O is smaller than an outer diameter of the excavating bit 4 in an expanded state. Only the torque around the axis O is applied to the excavating tool by a rotation driving means through a drill rod by using the excavating tool, and the excavating tool digs into the ground by the own weights of the excavating tool, the drill rod and the rotation driving means to form a borehole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting type excavating tool in which a cutting type bit is attached to the tip of a tool body, and an excavating method using the excavating tool.

[0002]

2. Description of the Related Art As an excavating tool to which a cutting bit of this kind is attached, for example, in Japanese Patent Laid-Open No. 10-140959, a plurality of cutting bits having an expanding / reducing diameter function with a variable cutting radius are attached to the tip of a tool body. In this publication, the ground is excavated by entraining a cylindrical casing in the state where these cutting bits are expanded, and after the excavation, the cutting bits are reduced in diameter to be excavated from inside the casing. An excavation method has been proposed in which only the tool is pulled out and the casing remains in the ground. Therefore, according to the excavating tool equipped with such a cutting bit, since excavation is performed by rotating the tool body, it is possible to prevent generation of large vibration and noise such as hammering. Even when the casings are carried as described above, since the vibration is small, there is no loosening even if the casings are coupled by screwing, and the coupling work can be facilitated.

[0003]

However, in the excavating tool provided with such a conventional cutting bit, the cutting edge of each cutting bit is located on one plane at the tip of the tool body, which is orthogonal to the axis thereof. Therefore, even when these cutting edges bite into the ground and excavate, all cutting edges bite into the ground at the same time, and the biting property is poor. It was difficult to efficiently excavate by a cutting bit that forms a hole while cutting the ground by cutting the cutting edge. This is the same not only when biting into the ground, but also when the tool body excavates in the ground, that is, because the ground excavation is performed on the plane of the above 1, the resistance is large, and as a result, There is a risk that efficient excavation by the cutting bit will be hindered.

The present invention has been made under such a background, and in the excavating tool provided with the cutting bit as described above, the biting property to the ground is improved and the resistance during excavation is also reduced. It is an object of the present invention to provide a drilling tool capable of doing the above and to provide a drilling method using the drilling tool.

[0005]

In order to solve the above-mentioned problems and to achieve such an object, a drilling tool of the present invention comprises:
A drilling tool attached to the tip of a drill rod rotated around an axis, wherein a drilling bit capable of expanding / contracting on the outer peripheral side of the tool body is provided at the tip of the tool body having a substantially columnar shape centering on the axis. At the same time as mounting, on the tip side of this excavating bit, a pilot section provided with a cutting bit with a cutting edge protruding from the tip is provided, and the outer diameter of the excavating bit around the axis is expanded. Further, the excavation method of the present invention uses such an excavating tool, and rotational force about the axis line is applied to the excavating tool via the drill rod by the rotation driving means. It is characterized in that the excavation tool, the drill rod, and the rotation driving means are self-weighted, and the excavation tool is dug down while biting into the ground to form a hole. Therefore, according to such an excavating tool and the excavating method using the excavating tool, when the excavating tool bites into the ground, first, the cutting bit of the pilot portion having a small outer diameter located at the tip of the tool body is used. Since it will bite, it is possible to increase the pressure at the time of biting and improve biting property, while during excavation, a large diameter drill bit that follows the small diameter drill hole formed by this pilot part. As a result, the excavation form is expanded so that the outer peripheral portion of the small-diameter hole to be excavated by the excavation bit is likely to collapse, so that excavation resistance can be reduced.

In the excavating tool of the present invention, when the excavating bit can be expanded / contracted, the tip end and the rear end of the excavating bit are rotatable about a central axis eccentric from the axis of the tool body. Further, by supporting the pilot portion and the tool body respectively, it is possible to secure a high mounting rigidity for the drill bit. Further, even when forming a drilling hole having a different inner diameter by detachably attaching the pilot portion and the drilling bit to the tool body, the drilling bit and the pilot portion are replaced with those having different outer diameters in accordance with this. It is possible to deal with this. On the other hand, by further providing a pilot bit having an outer diameter smaller than that of the pilot portion projecting to the tip side of the cutting bit of the cutting bit of the pilot portion on the axial line on the tip side of the pilot portion, Since the pilot bit bites into the ground ahead of the cutting bit of the pilot part, and during drilling, a drilling hole with a smaller diameter is formed and the pilot part becomes an excavation form that digs and expands this,
It is possible to further improve the biting property and reduce the excavation resistance. Further, particularly in this case, the pilot bit is formed into a gate shape in which the center of the rear end portion continuing from the pilot portion is opened, and the blow portion formed in the tool main body is formed in the opened portion. If the holes are opened, even if the tip of the tool body is blocked by the provision of these pilot bits and pilot parts, compressed air etc. will be ejected from this blow hole through the open part. Therefore, it is possible to promote smooth discharge of the starch powder generated during excavation.

[0007]

1 to 5 show an embodiment of the present invention. In the present embodiment, the tool main body 1 has a shank 2 in order from the rear end side (right side in FIG. 1) of the axis O toward the front end side (left side in FIG. 1).
The device 3, the three excavating bits 4, ..., And the pilot member 5 that constitutes the pilot portion are formed in combination, and form a substantially multistage cylindrical shape with the axis O as the center. Of these, the shank 2 has a large diameter in the central portion in the direction of the axis O and both end portions having male screw portions 2A and 2B having a smaller diameter than that of the shank 2. This device 3 is screwed into the female screw portion 3B on the inner periphery of the mounting hole 3A opened at the rear end.
It is detachably attached to the rear end. On the other hand, the male screw portion 2B on the rear end side of the shank 2 is formed as a taper screw so that it can be screwed to the tip portion of a drill rod (not shown), and the drill rod is rotated by a rotation driving means (not shown). , The tool body 1,
At the time of excavation, it can be rotated about the axis O in the rotational direction indicated by T in the figure, and after the completion of excavation, it can be rotated in the direction opposite to the rotational direction T.

The device 3 has a rear end portion having a small-diameter portion having the same diameter as the central portion of the shank 2, and a portion closer to the tip end than this has a contour that is gradually reduced in diameter toward the tip end. Since it has a multi-stage cylindrical shape, the step portion on the rearmost end side of the tip end side portion is the large diameter portion 3C having the largest outer diameter in the device 3, and the tip end side of this large diameter portion 3C is formed. The facing annular surface has a tapered surface shape that inclines toward the tip side toward the inner peripheral side. From the rear end of the device 3 to the center of the shank 2, a pair of flat surfaces 6 and 6 which are flush with each other when the shank 2 is attached to the attachment hole 3A of the device 3 are parallel to the axis O. Further, they are formed so as to be parallel to each other and located on the opposite side with the axis O interposed therebetween. Further, by screwing the male screw portion 2A into the female screw portion 3B, the shank 2 is attached to the device 3
The tip surface of the shank 2 is pressed against the bottom of the mounting hole 3A and the annular surface of the shank 2 facing the front end of the central portion is pressed against the rear end surface of the device 3 while being attached to the mounting hole 3A. It is supposed to be in close contact.

Further, on the outer periphery of the device 3, a plurality of (three in this embodiment) discharge grooves 7 for the powdered chips are provided at equal intervals in the circumferential direction from the tip to the large diameter portion 3C. It is formed so as to be twisted rearward in the rotation direction T as it goes to the rear end side at the same twist angle. Here, each discharge groove 7 is formed in a generally U-shape that is flat so that a cross section orthogonal to the axis O extends in the circumferential direction and opens to the outer peripheral side, and the distance from the groove bottom to the axis O is It is constant over the direction of the axis O. Therefore, these discharge grooves 7
As a result, the annular surface of the large diameter portion 3C of the device 3 is divided into three arc-shaped surfaces in the circumferential direction. Also,
On the rear side in the rotation direction T on the tip side of each discharge groove 7, a recess 8 is formed so as to further recess from the groove bottom of the discharge groove 7 to the inner circumference of the device 3, and a bottom surface of a part of the recess 8 is formed. 8A is a flat surface parallel to the axis O and is formed so as to extend toward the inner peripheral side of the device 3 toward the rear side in the rotation direction T. In addition, a concave portion 9 is formed on the tip side of the concave portion 8 and further rearward in the rotation direction T.
Is a wall surface 9A extending flush with the bottom surface 8A and extending rearward in the rotation direction T, and a wall surface 9B having a concave cylindrical surface smoothly connecting to the wall surface 9A and recessed rearward in the rotation direction T.
By the flat wall surface 9C which is also smoothly connected to the outer peripheral side of the wall surface 9B and extends toward the rotation direction T side toward the outer peripheral side, and the bottom surface 9D which is orthogonal to these wall surfaces 9A to 9C and faces the tip side. Well defined. In addition, this bottom surface 9
A hole 9E having a circular cross section centered on the central axis X of the concave cylindrical surface formed by the wall surface 9B is formed in D in parallel with the axis O.

Furthermore, at the tip portion of the device 3, three projecting wall portions 10 of the same shape and the same size that project toward the tip side are equally spaced in the circumferential direction so as to extend from the outer circumference of the device 3 to the inner circumference side. And a recess 11 to which the pilot member 5 is attached is formed between the projecting wall portions 10 ... The recess 11 has a wall surface 11A that faces the rotation direction T side of the protruding wall portion 10 and a planar shape that faces the tip end side that extends in a direction orthogonal to the wall surfaces 11A. And a bottom surface 11B of the device 3, and the wall surface 11A is further flush with the wall surface 9C of each recess 9 and extends from the outer circumference of the device 3 to the inner circumference side.
A and a wall surface 10B that intersects the wall surface 10A at an obtuse angle and that extends further toward the inner peripheral side and is parallel to the axis O, and there is a space between the protruding wall portions 10, 10 that are adjacent in the circumferential direction. In addition, the wall surfaces 9A and 9B of the concave portion 9 are formed on the bottom surface 1 of the concave portion 11 at the portion where the space is provided.
A screw hole (not shown) is formed in parallel with the axis O on the bottom surface 11B which is orthogonal to 1B and inside the intersecting portion of the wall surfaces 9A and 9B. Further, the wall surface 10C facing the rear side in the rotation direction T of the projecting wall portion 10 is inclined so as to extend toward the rear end side toward the rear side in the rotation direction T, and the tips of the discharge groove 7 and the recess 8 are formed. It is designed to be connected to the side.

The pilot member 5 attached to the recess 11 is thicker than the protruding height from the bottom surface 11B of the projecting wall portion 10 and has a substantially equilateral triangle shape when viewed from the tip end side in the axis O direction. A shape in which three arm portions 5B ... E project at equal intervals in the circumferential direction and at equal lengths on the outer periphery of the center portion 5A so as to extend in the rotational direction T side from each corner of the equilateral triangle toward the outer peripheral side. And each arm 5B
Is fitted in the space between the adjacent projecting wall portions 10 of the recess 11, and the rear end surface 5C of the pilot member 5, which is a flat surface perpendicular to the axis O, has the bottom surface 11B of the recess 11. Then, the clamp bolts 12 inserted into the root portions of the respective arm portions 5B are screwed into the screw holes of the bottom surface 11B, so that the clamp bolts 12 are detachably attached to the recesses 11. The portion of the arm portion 5B facing the rear side in the rotation direction T is inclined so that its tip end side extends toward the rear side in the rotation direction T, similarly to the wall surface 10C of the projecting wall portion 10, as described above. And a portion on the rear end side thereof is formed by two flat surfaces extending in parallel to the axis O and bent at an obtuse angle toward the inner peripheral side, and these flat surfaces of the projecting wall portion 10 are formed. The pilot member 5 is attached to the recess 11 while being in close contact with the wall surfaces 10A and 10B.

The outer peripheral surface of the tip of the arm portion 5B has an arcuate surface centered on the axis O having a diameter substantially the same as the outer diameter of the device 3 on the tip side of the large diameter portion 3C when viewed from the tip in the direction of the axis O. Therefore, the arm portion 5B is arranged so as to cover the tip side of the recess 9 of the device 3 and project rearward in the rotational direction T on the tip side of the discharge groove 7 and the recess 8. Become. Then, on the outer peripheral side of the protruding arm 5B in this way, at the intersection ridge line portion of the surface facing the tip side and the surface facing the rotation direction T side, this intersection ridge line portion is L-shaped in cross section when viewed from the outer peripheral side. The recess 5C is formed so as to be notched like a groove so as to open to the outer peripheral surface, and the cutting bit 13 made of a hard material such as cemented carbide is joined to the recess 5C by brazing or the like. It has been installed. The cutting bit 13 has a convex V-shaped surface facing the tip side and a surface facing the rotational direction T side, and the cutting edge 13A also has a convex V-shape at the intersection ridge portion of these surfaces. And the surface facing the front end side is directed toward the rear end side toward the rear side in the rotation direction T, and the surface facing the rotation direction T side is directed toward the rear end side in the rotation direction. Each is slightly tilted toward the rear side of T. The convex V-shaped apex formed by these surfaces is chamfered with a short width.

In this embodiment, such a cutting bit 13 has two cutting edges 13A for each recess 5C.
Are arranged so as to be aligned in the radial direction with respect to the axis O when viewed from the front. However, among the two cutting blades 13A, 13A, the cutting blade 13A located on the outer peripheral side has the cutting bit 13 provided on the three arm portions 5B ... The radial positions from the axis O are substantially equal to each other. On the other hand, the cutting blade 13A located inside has a convex V formed by the cutting blade 13A of at least one of the three arm portions 5B.
The radial position of the top of the letter is the cutting edge 13A of the other arm 5B.
The cutting blades 13A are arranged so as to be displaced in the radial direction so as to be different from the position of the top of the
... are designed to overlap. The cutting edge 13A on the outer peripheral side of these cutting bits 13 is so arranged that its outer peripheral end is located on an extension of the above-mentioned circular arc surface formed by the outer peripheral surface of the projecting end of the arm portion 5B. In the present embodiment, the outer diameter of the cutting-type bit 13 ... Provided in 5 is substantially the same as the outer diameter of the device 3 on the tip side of the large diameter portion 3C. Further, as described above, the rear end surface 5C of the arm portion 5B extending to cover the tip side of the recess 9 is coaxial with the central axis X of the hole 9E formed in the bottom surface 9D of the recess 9. Thus, the hole 5D having a circular cross section is formed.

On the other hand, the excavation bit 4 is formed in a block shape having a substantially vane shape when viewed from the front end in the direction of the axis O, and at the root portion thereof, the wall surface 9 of the recess 9 becomes closer to the root side.
A pair of flat side surfaces 4A, 4B approaching each other at an angle smaller than the included angle formed by A, 9C, and these side surfaces 4A,
4B and a side surface 4C having a convex cylindrical surface shape which is in smooth contact with the side surfaces 4A and 4B.
Can be slidably contacted with the concave cylindrical wall surface 9B of the concave portion 9 with its central axis aligned with the central axis X. Then, the front end portion and the rear end portion of the root portion of the excavating bit 4 can be fitted into the hole 5D of the pilot member 5 and the hole 9E of the recess 9 while the side surface 4C is in sliding contact with the wall surface 9B. The cylindrical shaft portions 4D and 4E are provided so as to be coaxial with the central axis X, and the drill bit 4 has a rear end portion in which the shaft portion 4E is fitted into the hole 9E and the root portion thereof is a recess. 9, the pilot member 5 is attached to the recess 11 of the device 3 while inserting the hole 5D into the shaft portion 4D on the distal end side, so that the side surfaces 4A and 4B are the wall surfaces 9A of the recess 9.
The device 3 is attached to the device 3 so as to be rotatable about the central axis X within the range of abutting on the device 9C and detachably as the pilot member 5 is attached and detached.

In this embodiment, a blade edge portion opposite to the root portion of the excavating bit 4 thus mounted is provided with a ridge line intersecting the tip-facing surface and the extended surface of the side surface 4A. A recess 4F is formed so as to be cut out in an L-shaped cross section when viewed from the front side, and in this recess 4F, a convex V-shape is formed on the intersecting ridge line portion of the two surfaces inclined like the cutting bit 13 described above. A cutting bit 14 made of a hard material such as cemented carbide and having two cutting edges 14A, 14A forming a shape is joined and attached by brazing or the like. Here, the cutting type bit 14 of the excavating bit 4 is such that the side surface 4B is brought into contact with the wall surface 9C of the recess 9 to expand the diameter of the excavating bit 4 and, as shown in FIG. In view, the cutting edge 14A is arranged so as to be continuously aligned with the cutting edge 13A of the cutting bit 13 of the pilot member 5 in the radial direction with respect to the axis O, and has an outer diameter around the axis O. It is designed to be larger than the large diameter portion 3C of the device 3. In addition, these cutting edges 14A, 14
Contrary to the cutting edges 13A of the cutting bit 13 ..., A is a cutting edge 14 located on the inner peripheral side in this expanded state.
The positions of the convex V-shaped tops of A ... are made to coincide with each other in the rotational locus around the axis O, while the tops of the cutting edges 14A located on the outer peripheral side of the cutting bit 14 of at least one drilling bit 4 are other drilling bits. Cutting edge 14 on the outer peripheral side of the cutting type bit 14 of 4
The cutting edges 13A ... Are overlapped with each other in a rotation locus around the axis O by being radially displaced to a position different from A. In the state where the side surface 4A is brought into contact with the wall surface 9A of the recess 9 to reduce the diameter of the excavation bit 4, the outer diameter of the excavation bit 4 is larger than that of the large diameter portion 3C of the device 3 as shown in FIG. The outer diameter of the side portion is made substantially equal.

Furthermore, a pilot bit 15 is projectingly provided on the central portion 5A of the pilot member 5. In this embodiment, the pilot bit 15 has a flat plate-shaped member whose outer shape is a deviated pentagon and is arranged along one virtual plane including the axis O with its one corner 15A located on the axis O. Then, one peripheral surface portion facing the corner portion 15A is joined to the central portion 5A by welding or the like, so that it is integrally provided on the pilot member 5. However, in the central portion of the peripheral surface portion 1 joined to the central portion 5A, an opening portion 15B opening in a "U" shape toward the rear end side is provided with the pilot bit 15 in the thickness direction ( It is formed so as to penetrate in the direction orthogonal to the imaginary plane), whereby the pilot bit 15 is erected at the central portion 5A of the pilot member 5 with its rear end center being opened strictly. It will have a gate shape. Further, a cutting blade member 15C formed of a hard material such as cemented carbide is embedded in the center portion in the thickness direction of a pair of peripheral surfaces that intersect the corner portion 15A of the pilot bit 15 and face the front end side. In addition, the pair of peripheral surfaces, including the portion of the cutting blade member 15C, are formed in a convex V-shaped cross section that protrudes toward the tip side toward the center side in the thickness direction.
The top of the convex V-shape serves as the cutting edge 15D of the pilot bit 15 formed on the cutting edge member 15C. The outer diameter of the cutting edge 15D around the axis O is substantially equal to the diameter of the circle formed around the axis O by the inner peripheral edge of the cutting edge 13A of the cutting bit 13 disposed on the innermost side. Therefore, it is made smaller than the outer diameter of the cutting bit 13.

Further, in the tool body 1 thus constructed, a blow hole 16 is formed so as to penetrate the shank 2, the device 3 and the pilot member 5 along the axis O, and the blow hole 16 is The central portion 15A of the pilot member 5 on the distal end side is opened to the open portion 15B of the pilot bit 15, and is branched into three directions toward the outer peripheral side in the device 3 toward the distal end side. Recess 8
The bottom surface 8A is also opened.

In the case of forming a hole in the ground by using the thus constructed drilling tool, particularly when the casing is carried along with the drilled hole as in the conventional case, the casing is first constructed as shown in FIGS. The tool body 1 is inserted downward into the casing C in a state where the side face 4A of the excavating bit 4 is in contact with the wall surface 9A of the recess 9 to reduce the diameter as shown in FIG. The annular surface of the large-diameter portion 3C of the device 3 is brought into contact with the inner peripheral rear end surface of the casing top P that is fitted in the peripheral portion and joined by welding or the like, and is closer to the tip side than the recess 8 of the device 3. The portion of is projected from the lower end of the casing top P. Then, as described above, while rotating the tool body 1 in the rotation direction T by the rotation driving means via the drill rod having the tip end screwed to the male screw portion 2B at the rear end of the shank 2, the tool body 1 and the drill rod are rotated. And the weight of the rotation driving means causes the tool body 1 to bite into the ground from its tip, so that the pilot bit 15 at the front end of the tool body 1
The cutting edge 15D of the pilot member 5 bites into the ground from its corner 15A, and then the cutting edge 13 of the cutting bit 13 of the pilot member 5 ...
After biting A ..., cutting bit 1 of excavating bit 4 ...
Cutting edge 14A of 4 ... bites into the ground.

Then, each excavation bit 4 is rotated by the excavation resistance toward the rear side in the rotation direction T about the central axis X, and positioned when the side surface 4B abuts the wall surface 9C of the recess 9. Since the outer diameter around the axis O is made larger than the outer diameter of the casing C or the casing top P as shown in FIGS. 1 to 3, the weight of the self-weight is increased while rotating the tool body 1 as it is. A hole is formed by digging into the ground by the casing top P, and the casing top P engages with the large diameter portion 3C of the device 3 while slidingly contacting the casing top P, and the casing C moves forward together with the tool main body 1 without rotating. (Descent) and it is carried in the drilling hole. During the excavation, the blow hole 1 of the tool body 1 is inserted through the drill rod.
Compressed air, water, or a mist that is a mixture of these is supplied to 6 to be ejected, and the pressure caused by the compressed dust is discharged through the discharge groove 7 and the recess 8 to the ground through the casing C. The dust collected in this manner is collected by a dust collector or the like. Then, after the drilling is formed to a predetermined depth and the casing C is built in, by rotating the tool body 1 in the direction opposite to the rotation direction T, the diameter of the excavation bit 4 is reduced and the tool body 1 is rotated. Since the outer diameter of the portion closer to the tip side than the large diameter portion 3C is smaller than the inner diameter of the casing top P, the casing is left in the drilled hole by retracting (raising) the tool body 1 together with the drill rod. The tool body 1 can be pulled out from the casing C.

Therefore, in such a drilling tool and a drilling method using the drilling tool, first, the tool body 1 is
Since the cutting bits 13 ..., 14 ... and the cutting edges 13A ..., 14A ..., 15D of the pilot bit 15 bite into the ground only by the rotational force given from the rotary driving means via the drill rod, excavation is performed. For example, in comparison with the case where the tool body is moved forward by the impact force of the hammer in addition to the rotational force, the occurrence of noise and vibration is extremely small, and compressed air and water as described above as the soil discharge fluid for discharging the dust powder, Since mist can be used and bentonite etc. are not required, efficient and economical construction is possible. By the way, the excavation method is based on sandy soil, gravel layer,
Applicable soil range from cohesive soil to soft rock, excavation diameter 150
It is possible to excavate up to ~ 700 mm and a digging depth of about 30 m, and as the rotational driving means, a leader radial method, a pile driver method, a hanging drill method, or a rotary table method can be used. It should be noted that a weight may be attached to the tool body 1 or the like in order to more reliably bite due to its own weight, and when excavating a self-supporting stratum or a hard rock layer, excavation by a down-the-hole hammer can be easily switched. Furthermore, when a means for inserting the casing C into the drilled hole is provided, the casing top P may not be provided at the tip of the casing C.

Further, in the excavating tool and the excavating method constructed as described above, the pilot portion is formed at the tip of the tool body 1 by the pilot member 5, and the outer diameter of the cutting edge 13A of the cutting bit 13 of the pilot member 5 is set. Is smaller than the excavation diameter of the excavating tool, that is, the outer diameter of the cutting edge 14A of the cutting bit 14 of the excavating bit 4 in the expanded state. When it bites into the ground,
The weight of the tool body 1, the drill rod, and the rotation driving means is concentrated on the cutting bit 13 of the pilot member 5 having a small outer diameter, and the pressure at the time of biting can be increased. Therefore, the cutting edges 13A of the cutting bits 13 of the pilot member 5 can surely bite into the ground to start excavation, and the biting property can be improved. It becomes possible to form the hole smoothly and stably at the position.

On the other hand, while the tool main body 1 as a whole bites into the ground and the excavation is in progress, the cutting bit 13 of the pilot member 5 having such a small diameter has a relatively large diameter. Since the excavating bit 4 in the state is arranged closer to the tip side than the cutting bit 14 described above, in the excavating tool and the excavation method, the cutting bit 13 having a small diameter on the tip side is used.
The drilling form is such that the drilled hole is drilled by the cutting bit 14 of the subsequent large-diameter drilling bit 4. Therefore, since the large-diameter drilling bit 4 excavates the outer peripheral portion of the drilled hole, which is easily collapsed by forming the small-sized drilled hole, a drilled hole having a predetermined diameter is formed. Since the resistance at the time of excavation by the excavation bit 4 can be reduced, more efficient drilling can be performed, and the load acting on the excavation bit 4 can be reduced, so that the diameter can be expanded / contracted. Therefore, it is possible to prevent the excavation bit 4 from being damaged by an excessive load, which tends to be difficult to secure the mounting rigidity especially when the diameter is expanded, and to prolong the tool life. Is possible.

Moreover, in the excavating tool of the present embodiment, the excavating bit 4 has the shaft portions 4D, which are provided at the front and rear ends thereof in a protruding manner.
4E is a hole 5D formed in the rear end surface 5C of the arm 5B of the pilot member 5 and a hole 9 formed in the recess 9 of the device 3.
By being inserted into and fitted to E, it is attached so as to be rotatable about its central axis X, that is, the front and rear ends of this rotating portion are supported by the tool body 1, so that the rear end side The mounting rigidity is higher than that of the conventional excavating tool provided with the above-mentioned conventional cutting bit, and it is possible to more reliably prevent damage to the excavating bit 4. In the present embodiment, the shaft portions 4D and 4E are thus provided on the side of the excavation bit 4 and fitted into the holes of the device 3 and the pilot bit 5 to make the excavation bit 4 rotatable. On the contrary, a hole is formed in the drill bit 4 and a shaft portion projecting from the device 3 or the pilot member is inserted, or a shaft portion is provided at one of the front and rear ends of the drill bit 4 and a hole is formed in the other end. Then, the device 3 and the pilot member 5 are formed with a hole into which the shaft portion of the drill bit 4 can be fitted and a shaft portion into which the hole of the drill bit 4 can be fitted, or a through hole in the drill bit 4. By forming a hole in the device 3 and the pilot member 5 and inserting a pin into them, the drill bit 4 may be rotatable with both ends supported.

Further, in this embodiment, the pilot member 5 constituting the pilot portion is fitted into the recess 11 formed in the tip portion of the device 3, and then the clamp bolt 1 is inserted.
It is detachably attached to the tool body 1 by 2.
Along with this, the drill bit 4 in which the tip side shaft portion 4D is fitted into the hole 5D of the pilot member 5 is also attached to the pilot member 5
And remove the rear end side shaft portion 4E from the hole 9 of the device 3
By pulling it out from E, it can be detached from the tool body 1 as well. Therefore, it becomes possible to replace the drill bit 4 and the pilot member 5 without changing the shank 2 and the device 3, depending on the drilling conditions such as the diameter of the drilled hole to be formed and the soil quality of the ground. The excavating bit 4 can be exchanged with one having a different outer diameter when the diameter is expanded, and the pilot member 5 also has a different outer diameter from the cutting bit 13 in relation to the outer diameter of the excavating bit 4. It is also possible to more reliably achieve the effect of excavating the small-diameter drilled hole formed by the pilot member 5 by the excavation bit 4 to perform efficient excavation by exchanging the excavated portion with the excavated member.

In this embodiment, the pilot member 5 is fitted in the recess 11 and the clamp bolts 12 ... Inserted from the tip side are screwed into the device 3 so that the tool body 1 can be attached to and detached from the tip portion. Attached to the pilot member 5 fitted in the recess 11,
The pilot member 5 may be detachably attached by driving a pin through the projecting wall portion 10 or screwing a clamp bolt or a clamp screw in a direction along a plane orthogonal to the axis O or the like. .
Further, in the present embodiment, the excavating bit 4 that is also detachable is provided with the cutting bit 14 similarly to the pilot member 5, but the excavating bit 4 is not provided.
Will excavate the outer peripheral portion where the small-diameter hole formed by the pilot member 5 is likely to collapse as described above, so that, for example, a so-called button type in which a hemispherical bit is projected on the surface is used. A bit may be provided, or these cutting type bit and button type bit may be used together. Furthermore, in the present embodiment, the shank 2 also has the male screw portion 2A of the shank 2 which is the attachment hole 3A of the device 3.
By being screwed into the female screw portion 3B on the inner circumference, the tool body 1
Since the shank 2 is detachably attached to the shank 2, the shank 2 having a screw diameter different from that of the male screw portion 2B on the rear end side thereof or a taper screw is used according to the size and shape of the tip portion of the drill rod to which the shank 2 is attached. Alternatively, the rear end side can be replaced with one having only an engaging portion having a hexagonal cross section or a square shape instead of a male screw portion, and the device 3, the drill bit 4, and the pilot member 5 can be replaced as they are.
The tool body 1 can be attached to the tip of various drill bits.

On the other hand, in the present embodiment, a pilot bit 15 having an outer diameter smaller than the outer diameter of the cutting bit 13 of the pilot member 5 is further provided at the tip of the pilot member 5 constituting the pilot portion. Cutting edge 15
It is provided so that D is projected to the tip side from the cutting edge 13A of the cutting bit 13 and is positioned on the axis O of the tool body 1. Therefore, when the tool body 1 bites into the ground, the corner portion 1 at the tip of the pilot bit 15 is first
Since 5A concentrates its own weight at one point and bites it, the biting property is extremely high. Moreover, even during excavation, a small-diameter hole is formed by the pilot bit 15 in the pilot member 5 and it collapses. Whereas it becomes easier to perform, the following cutting bit 13 adopts an excavation form in which the outer peripheral portion thereof is excavated and expanded, and therefore, efficient excavation is performed as in the case of excavation by the pilot member 5 and the excavation bit 4. The pilot bit 15 makes it possible to secure the straightness of the tool body 1 during excavation.

By the way, when the pilot bit 15 is arranged on the axis O at the tip of the pilot member 5 in this way, simply by joining a flat plate member to be the pilot bit 15 on the axis O, the axis bit is formed. Since the blow hole 16 formed along the O along the tool body 1 is closed by the flat plate-shaped member, the blow hole 16 is not opened on the axis O at the tip of the tool body 1, and the pilot bit 15 and the pilot member 5 are cut. There is a risk that the starch powder produced by the bit 13 cannot be discharged reliably and efficiently. On the other hand, in the present embodiment, however, the pilot bit 15 is formed in a gate shape in which the center of the rear end is opened by the opening 15B, and the blow hole 16 is opened in this opening 15B. Therefore, even if the pilot bit 15 is projected on the axis O in this way, the blow hole 16 can be prevented from being blocked, and compressed air, water, mist, etc. ejected from the blow hole 16 It is possible to evenly and uniformly discharge the dusted powder through the discharge groove 7 and the recess 8 to the rear end side. Moreover, in this embodiment, the blow hole 16 is branched in the middle, and when the diameter is reduced, the drill bit 4
Since the opening 8 is also opened in the bottom surface 8A of the recess 8 for accommodating the drill bit, the boring powder remains in the recess 8 and the recess 9 connected to the drill bit 4 when the diameter of the drill bit 4 is reduced. It is also possible to prevent a situation in which the diameter reduction is hindered by being sandwiched.

[0028]

As described above, in the excavating tool of the present invention, the excavating bit capable of expanding and contracting the diameter is provided at the tip of the tool body which receives the rotational force via the drill rod, and further more than this excavating bit. On the tip side, a pilot portion having an outer diameter smaller than the outer diameter of the drill bit at the time of diameter expansion is provided by projecting the cutting bit, and therefore, in the drilling method of the present invention using such a drilling tool. , When biting into the ground, the weight of the tool body, etc. is concentrated on the small-diameter pilot part, so the biting property is high, and during drilling, the small-diameter holes formed in the pilot part are easily collapsed. The following excavation bit has a form in which the excavation bit expands so that the excavation resistance can be reduced,
It is possible to reduce the load on the excavating bit to prevent the damage and improve the excavation efficiency.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view showing a state in which a diameter of a drill bit 4 ... Shows an embodiment of the present invention.

FIG. 2 is a front view of the embodiment shown in FIG. 1 viewed from the front end side in the direction of the axis O.

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

FIG. 4 is a front view showing a state in which the diameter of the excavating bit 4 of the embodiment shown in FIG. 1 is reduced, as viewed from the front end side in the direction of the axis O.

5 is a perspective view showing a state in which the drill bits 4 of the embodiment shown in FIG. 1 have a reduced diameter. FIG.

[Explanation of symbols]

1 Tool body 2 shank 3 devices 4 drill bits 5 Pilot member (pilot section) 7 discharge groove 9 recess 13,14 Cutting Bit 13A, 14A Cutting bits 13, 14 cutting edge 15 pilot bits Cutting edge of 15D pilot bit 15 16 Blowhole O Tool body 1 axis T Direction of rotation of tool body 1 during excavation C casing P casing top

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hitoya Hisada             1528, Nakashinden, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture             Address Ryotech Co., Ltd. Construction Tool Factory             Within F-term (reference) 2D029 EB04

Claims (6)

[Claims] 1. A drilling tool to be attached to the tip of a drill rod rotated about an axis, wherein the tip of a tool body having a substantially cylindrical shape centered on the axis is enlarged and reduced on the outer peripheral side of the tool body. The excavation bit is attached as much as possible, and at the tip side of this excavation bit, there is a pilot part provided with a cutting bit with a cutting edge protruding from the tip. A drilling tool, which is provided so as to be smaller than the outer diameter of the drilling bit. 2. The drill bit can be expanded / contracted by having its front end and rear end rotatably supported by the pilot portion and the tool body around a central axis eccentric from the axis. The excavating tool according to claim 1, wherein: 3. The excavating tool according to claim 1, wherein the pilot portion and the excavating bit are detachably attached to the tool body. 4. The tip end side of the pilot portion is further provided with:
4. A pilot bit having an outer diameter smaller than that of the pilot portion protruding toward the tip side of the cutting edge of the cutting bit of the pilot portion is provided on the axis. The drilling tool according to any one of 1. 5. The pilot bit has a gate shape whose rear end center is opened, and a blow hole formed in the tool body is opened in this opened portion. The excavating tool according to claim 4. 6. The excavating tool according to any one of claims 1 to 5, wherein only the rotational force about the axis is applied to the excavating tool via the drill rod by the rotation driving means. An excavation method is characterized in that the excavation tool is dug down while biting the excavation tool into the ground by the self-weight of the drill rod and the rotation driving means to form a hole.