JP4844279B2 - Drilling tools - Google Patents

Description

  The present invention relates to an excavation tool used to insert a casing pipe into a drilling hole while excavating the ground to form a drilling hole in civil engineering work such as anchor work, various drilling works, and foundation pile work.

  As an excavation tool that inserts a casing pipe while excavating the ground in this way and builds it into a drilling hole, for example, Patent Document 1 discloses that the outer periphery of the tip of the device rotated around the central axis is spaced from the central axis. A diameter-enlarged bit is attached so as to be rotatable around an eccentric rotation axis, and a disk-like pilot bit is attached to the center of the tip of the device so as to protrude further toward the tip of the tool than the enlarged-diameter bit. The diameter expansion bit is supported by an engagement portion provided on the tool front end side engaging with an engaged portion provided on the pilot bit side facing the tool rear end side. Drilling tools that have been proposed.

  Patent Document 2 discloses an excavation tool attached to the tip of a drill rod that rotates about an axis, and the outer peripheral side of the tool main body has a substantially cylindrical shape centering on the axis. A drilling bit is attached to the drill bit so that the diameter of the drill bit can be expanded and reduced, and a pilot portion provided with a cutting bit with a cutting edge protruding from the tip is provided on the tip side of the drill bit so that the outer diameter around the axis is increased. There has been proposed a drill bit provided so as to be smaller than the outer diameter of the drill bit.

  Such a conventional drilling tool is called a so-called double pipe method, and the device and the tool body are attached to the tip of a drill rod (inner rod) and inserted into a casing pipe. The diameter expansion bit and the excavation bit are expanded by being rotated in the forward rotation direction during excavation in a state of protruding from the tip of the casing pipe, and the rotational force around the axis and the axial direction are expanded via the inner rod. Drilling holes are formed by applying thrust or striking force to the tip side.

Here, the device and the tool main body are engaged with the casing pipe so as to be rotatable and toward the distal end side in the axial direction, and are built into the drilling hole by the thrust and striking force. In addition, after the drilling hole is formed to a predetermined depth and the casing pipe is built, the diameter is increased by rotating the device or the tool body in the reverse rotation direction opposite to the normal rotation direction via the inner rod. Since the diameter of the bit or excavation bit is reduced, the inner rod can be recovered by being pulled out from the casing pipe, and only the casing pipe can be left on the ground and used as a foundation pile.
JP 2000-145343 A JP 2003-97176 A

  However, such a conventional drilling tool requires an inner rod as well as a casing pipe regardless of the diameter of the drilling hole, and the wall thickness can reliably transmit rotational force, thrust, and striking force to the device and tool body. Therefore, not only the material cost (material cost) is required, but also the transportation cost and the management cost for transporting the inner rod together with the casing pipe to the excavation work site are required.

  In addition, if the drilling hole is deeper than the length of a single casing pipe or inner rod, drilling will be performed while adding the casing pipe or inner rod, so that the labor and time required for this extension will be doubled. In addition, when the drilling tool is pulled out from the casing pipe after excavation is completed, it is necessary to pull it out while removing the added inner rod. I was supposed to press.

  The present invention has been made under such a background. Even if an inner rod is not required, the casing pipe is inserted while forming a drilling hole, and after the excavation is completed, the casing pipe can be left and recovered. An object of the present invention is to provide an excavation tool that can reduce the cost required for excavation work.

In order to solve the above-described problems and achieve such an object, the present invention provides a bit support body on the inner periphery of the tip of a cylindrical casing pipe that is rotated about the axis and advanced toward the tip in the axial direction. The excavation bit is supported at the tip of the bit support body so as to be rotatable around a center line eccentric from the axis to the outer peripheral side, and the casing pipe has a diameter at the tip of the casing pipe. A notch that penetrates in the direction is formed, and when the casing pipe is rotated in the forward rotation direction during excavation, the excavation bit rotates about the center line in the direction in which the outer diameter from the axis increases. In this state, the wall surface of the cutout portion facing the positive rotation direction and the bottom surface facing the tip side are brought into contact with the excavation bit to perform excavation, and the casing pipe is When rotated in the reverse rotation direction opposite to the normal rotation direction, the excavation bit has an outer diameter from the axis that is greater than the inner diameter of the tip of the casing pipe by the wall surface of the notch portion facing the reverse rotation direction. Is also rotated around the center line so as to reduce the diameter.

  Therefore, in the excavation tool having such a configuration, the rotational force, thrust, and striking force conventionally applied from the device or the tool body to the diameter expanding bit, the excavating bit, or the pilot bit via the inner rod rotate around the axis. At the same time, it is given directly to the excavation bit from the wall surface facing the forward rotation direction and the wall surface facing the front end side of the cutout portion of the casing pipe that is advanced to the front end side in the axial direction. For this reason, drilling is possible without inserting the inner rod into the casing pipe and attaching the bit support to the tip, and after the casing pipe is built after the drilling hole is formed to a predetermined depth Because the excavation bit is reduced in diameter by rotating the casing pipe in the reverse rotation direction, for example, by providing a hook or the like at the rear end of the bit support and hooking it on the rope passing through the casing pipe The bit support can be pulled out through the casing pipe and recovered together with the drilled bit having a reduced diameter.

  Here, a casing top whose inner diameter is reduced by one step is attached to the tip of the casing pipe, the notch is formed in the casing top, and the inner diameter of the casing top is formed on the outer periphery of the rear end of the bit support. By forming a step portion with a larger outer diameter, the step portion can be engaged with the casing top to prevent the bit support body from falling off to the tip end side of the casing pipe, and the casing top As a thick wall, it is possible to reliably transmit the rotational force, thrust, and striking force from the notch to the excavation bit.

  Further, the notch is formed by forming, on the inner peripheral surface of the tip portion of the casing pipe, a recess extending from the wall surface facing the reverse rotation direction of the cutout portion toward the positive rotation direction and cutting toward the inner peripheral side. It is possible to smoothly perform the diameter-reducing operation of the excavation bit that is rotated around the center line eccentric from the axis to the outer peripheral side by the wall surface facing the reverse rotation direction.

  Further, a recess for accommodating the excavation bit is formed at the tip of the bit support, and the recess is rotated in a direction in which the outer diameter from the axis is increased. By forming a wall portion facing the excavation bit and facing the reverse rotation direction, the excavation bit expanded in diameter by the wall portion and the wall surface facing the positive rotation direction of the notch portion is supported in the circumferential direction. For example, even when a pilot bit is provided at the tip of the bit support, excavation is performed by reliably transmitting rotational force from the wall to the pilot bit via the bit support. It becomes possible.

  As described above, according to the present invention, the casing pipe can be inserted and built while forming the hole without requiring the inner rod, and the material cost, transportation cost, management cost of the inner rod, and the inner rod can be added. Since the operation | work which removes etc. becomes unnecessary, it becomes possible to reduce significantly the cost which excavation work requires.

  1 to 5 show an embodiment of the present invention. In this embodiment, the casing pipe 1 is attached to the tip of a cylindrical pipe body 2 centered on the axis O by joining a substantially cylindrical casing top 3 centered on the axis O by welding or the like. The pipe body 2 having the same diameter is sequentially added to the rear end of the pipe body 2 at the front end as necessary, and a drilling device (not shown) is connected to the pipe body 2 at the rear end to connect the axis O to the entire casing pipe 1. By applying the rotational force around and the thrust and striking force toward the front end side in the direction of the axis O, during excavation, it is moved forward while being rotated in the normal rotation direction indicated by T in the figure.

  Here, the casing top 3 has an outer diameter at the front end equal to that of the pipe body 2 and an outer diameter at the rear end so that it can be inserted into the pipe main body 2. The pipe body 2 has a constant diameter smaller than the inner diameter of the pipe body 2, and is attached by inserting the rear end portion into the most advanced pipe body 2 as shown in FIG. 1. Therefore, a stepped portion having a smaller inner diameter is formed by the casing top 3 on the inner periphery of the front end portion of the casing pipe 1. A surface of the stepped portion facing the rear end side in the axis O direction, that is, the casing top 3. The rear end surface 3A is a tapered surface that inclines toward the front end side toward the inner peripheral side.

  On the other hand, two notches 4 penetrating the casing top 3 in the radial direction are formed at the tip of the casing top 3 in a rotationally symmetrical manner around the axis O in this embodiment. The bottom surface 4A facing the front end side of the notch 4 is a flat surface perpendicular to the axis O, and is substantially in the direction of the axis O of the front end of the casing top 3 at the front end side of the joint between the casing top 3 and the pipe body 2. Located in the center. In addition, the front end surface of the casing top 3 left between the notches 4 is also a flat surface perpendicular to the axis O in this embodiment.

  The wall surfaces 4B and 4C of the notch 4 extending from the tip surface to the bottom surface 4A are formed so as to extend perpendicular to the tip surface and the bottom surface 4A, that is, parallel to the axis O. Among these, the wall surface 4B facing the positive rotation direction T side of the casing pipe 1 at the time of excavation is formed as a flat surface parallel to the axis O over the entire thickness direction of the tip portion of the casing top 3. In this embodiment, as it goes to the outer peripheral side in the radial direction, it is formed so as to go to the reverse rotation direction R side opposite to the normal rotation direction T at a slight angle with respect to the radial direction orthogonal to the axis O. .

  On the other hand, the wall surface 4C facing the reverse rotation direction R opposite to the wall surface 4B is formed on the outer peripheral side excluding a slight portion on the inner peripheral side of the casing top 3, and in the present embodiment, as it goes toward the outer peripheral side. In addition, it is formed on a flat surface parallel to the axis O and directed toward the reverse rotation direction R with respect to the radial direction at an angle larger than the angle formed by the wall surface 4B.

  Further, a concave portion 5 is formed in the inner peripheral portion of the casing top 3 from the inner peripheral end of the wall surface 4C toward the positive rotation direction T, and the concave portion 5 is directed from the wall surface 4C toward the positive rotation direction T. After extending so as to be recessed with a certain width on the outer peripheral side in the radial direction, a concave curved surface is drawn at a position spaced from the wall surface 4B, and it is cut off to the inner peripheral side to reach the inner periphery of the casing top 3 Has been. Here, the inner wall surface of the recess 5 is also formed as a plane parallel to the axis O, and the bottom surface facing the tip side of the recess 5 is flush with the bottom surface 4A of the notch 4.

  In the casing pipe 1 configured as described above, the bit support 6 is inserted from the rear end side thereof, and the front end portion thereof is projected from the front end of the casing top 3. The bit support 6 has a substantially multi-stage cylindrical shape in which a step portion 6A having a step-up diameter is formed on the outer periphery of the rear end portion, and the outer diameter of the step portion 6A is larger than the inner diameter of the casing top 3. In addition, the inner surface of the pipe body 2 is slightly smaller than the inner diameter, and the surface facing the front end side of the stepped portion 6A is inclined toward the front end side toward the inner peripheral side at an angle substantially equal to the rear end surface 3A of the casing top 3. Further, the outer diameter of the bit support 6 on the tip side of the stepped portion 6A is slightly smaller than the inner diameter of the casing top 3, and is sized to be fitted into the inner periphery of the casing top 3. ing.

  Furthermore, two recesses 7 are formed in the tip end portion of the bit support body 6 in the present embodiment in a 180-degree rotational symmetry around the axis O as in the case of the notch portions 4, and excavation is made in these recesses 7. Bit 8 is accommodated. Further, in this embodiment, a pilot bit 9 is attached to the tip of the bit support 6, and the excavation bit 8 is supported between the pilot bit 9 and the bit support 6, and the outer periphery from the axis O respectively. 2, the outer diameter from the axis O is larger than the outer diameter of the casing pipe 1 as shown in FIG. 2 when rotating in the positive rotation direction T. Is positioned in a reduced diameter state in which the outer diameter from the axis O is smaller than the inner diameter of the casing top 3 when it is rotated in the reverse rotation direction R. .

  Here, the excavation bit 8 has a cylindrical shaft portion centered on the center line X at the base portion of the block-shaped bit body 10 which is projected and retracted on the outer peripheral side of the casing pipe 1 by the rotation around the center line X. 11A and 11B are integrally formed so as to protrude to the front end side and the rear end side in the center line X direction. Between these shaft portions 11A and 11B, a through hole 8A extends in the bit body 10. It is formed along the center line X. The shaft portions 11A and 11B have a shaft portion 11B on the rear end side having a larger outer diameter than the shaft portion 11A on the tip end side, and the protruding amount from the bit body 10 is also the shaft portion 11A from the tip surface 10A of the bit body 10. The protruding amount of the shaft portion 11B from the rear end surface 10B is made larger than the protruding amount.

  Further, on the base side of the bit body 10, a side surface 10C having a convex arc surface centering on a center line X having a radius larger than that of the shaft portion 11B, and a center line X smoothly touching both sides in the circumferential direction of the side surface 10C. A pair of flat surface-like side surfaces 10D and 10E parallel to each other is formed. These side surfaces 10D and 10E extend in a direction that intersects at an acute angle when viewed from the center line X direction, and in the expanded diameter state, the side surface 10D that faces the reverse rotation direction R side is more than the side surface 10E that faces the normal rotation direction T side. The side surface 10 </ b> E is disposed so as to extend in the radial direction so as to reach a position substantially equal to the outer diameter of the casing pipe 1, and to be positioned substantially equal to the inner diameter of the casing top 3.

  Further, on the side opposite to the side surface 10C of the side surface 10E, a side surface 10F that intersects the side surface 10E at an obtuse angle and extends substantially parallel to the side surface 10D is formed. Here, in the cross section perpendicular to the axis O as shown in FIG. 5A, the inner radius of the recess 5 of the casing top 3, that is, the distance from the axis O to the portion excluding the rounded-up portion of the recess 5 (for example, A distance A to the intersection point Q between the concave portion 5 and the wall surface 4C) is larger than the sum B + C of the distance B between the intersection point P of the side surfaces 10E and 10F and the center line X and the distance C between the center line X and the axis O. It is supposed to be.

  Furthermore, the side surface 10G of the bit body 10 directed to the outer peripheral side in the above-described diameter-expanded state is a bent surface along a cylindrical surface that is generally centered on the axis O, intersects the side surface 10F at an obtuse angle, and The side surface 10D is connected to both side surfaces 10D and 10G via a side surface 10H intersecting at an obtuse angle. Further, the width between the front and rear end surfaces 10A and 10B of the bit body 10 is larger than the width between the side surfaces 10D and 10F, shorter than the length between the side surfaces 10C and 10G, and the depth of the notch portion 4 of the casing top 3. It is bigger than that.

  And tip 12 which excavates the ground is planted in the portion located in the tip end side of casing top 3 in the above-mentioned diameter expansion state among the above-mentioned tip end face 10A of bit body 10. In the present embodiment, the tip 12 is made of a hard material such as a cemented carbide, and is a cutting die in which a cutting edge 12B is formed on a side ridge portion of a rake face 12A facing the normal rotation direction T in the above-mentioned expanded diameter state. A rake angle is given to the rake face 12A so as to go in the reverse rotation direction R toward the rear end side, and the face facing the tip side in the reverse rotation direction R from the cutting edge 12B. The clearance angle is given so that it goes to the rear-end side as it goes, and therefore the cutting edge angle of the cutting blade 12B is an acute angle.

  Further, the rake face 12A has a right triangle shape with chamfered vertices. In this embodiment, a plurality (three) of such chips 12 are provided on the outer peripheral side of the tip face 10A of the bit body 10 in the expanded diameter state. In addition, the right triangle formed by the rake face 12A has the same orientation and the protruding height of the tip face 10A is equal to each other so that the ridge face 12A is substantially aligned in the radial direction with respect to the axis O. In addition, on the outer peripheral side of the tip surface 10A in the diameter-expanded state, the forward rotation direction T side and the reverse rotation direction R side portions of the tip 12 thus planted are the forward rotation direction T side and the reverse rotation direction R side, respectively. The tip surface 10A of the other part is a flat surface perpendicular to the center line X. Further, the rear end surface 10B of the bit body 10 is also a flat surface perpendicular to the center line X from the portion located on the front end side of the casing top 3 in the expanded diameter state. As shown in FIG. 4, the head is inclined so as to go to the tip side as it goes to the outer peripheral side.

  The recess 7 of the bit support 6 in which the excavation bit 8 is accommodated is a one that passes through the axis O when the tip of the bit support 6 fitted in the casing top 3 is viewed in the direction of the axis O. After notching both sides of the diameter line L in parallel with the one diameter line L from the reverse rotation direction R toward the positive rotation direction T side, on the outer peripheral side at this forward rotation direction T side portion A bottom surface 7A perpendicular to the axis O and the center line X, a long wall portion 7B extending in parallel to the diameter line L in the front end view, and shorter than the wall portion 7B, A wall portion 7C extending in a direction intersecting the obtuse angle with the wall portion 7B and facing the reverse rotation direction R side formed in a portion that is rounded up to the outer peripheral side on the forward rotation direction T side, and these wall portions 7B and 7C A concave arcuate surface-like wall portion 7D for smooth connection, and these walls 7B~7D is formed on the bottom surface 7A vertically, i.e. so as to extend parallel to the axis O and the center line X. However, a stepped portion 7E is formed at the tip of the wall 7B on the reverse rotation direction R side so as to be recessed by one step from the wall 7B.

  Further, the bottom surface 7A is positioned on the positive rotation direction T side, more specifically, on the positive rotation direction T side with respect to the other diameter line M orthogonal to the one diameter line L in the front end view. A support hole 7F having a circular cross section is formed. The center line of the support hole 7F is the center line X, and the center of the concave arcuate wall portion 7D is also aligned with the center line X. Yes. Here, the inner diameter of the support hole 7F is such that the shaft portion 11B on the rear end side of the excavation bit 8 can be inserted and rotated, and the radius of the wall portion 7D is thus fitted to the support hole 7F. The side surface 10C of the bit body 10 is slidable in the inserted state.

  In this way, the excavation bit 8 in which the shaft portion 11B is inserted into the support hole 7F abuts so that the side surface 10E of the bit body 10 is in close contact with the wall portion 7C substantially in the expanded diameter state. The side surface 10D is positioned on the positive rotation direction T side with respect to the other diameter line M in the front end view, and the wall surface 4B of the casing top 3 is in a radial direction perpendicular to the axis O. It extends so that it may go to the said reverse rotation direction R side as it goes to the outer peripheral side at an angle equal to the angle formed, and it is arranged so as to extend in parallel with said other diameter line M. Further, in the reduced diameter state, the side surface 10D is brought into contact with the wall portion 7B so that the bit body 10 is outside the inner periphery of the casing top 3 as shown in FIG. It is accommodated in the recess 7 so as not to protrude.

  In addition, the circumferential width of the outer peripheral side opening of the recess 7 is smaller than the circumferential width of the notch 4 of the casing top 3. The depth of the support hole 7F from the bottom surface 7A of the recess 7 is slightly larger than the protruding amount of the shaft portion 11B from the rear end surface 10B of the bit body 10. Further, the distance in the axis O direction from the bottom surface 7A to the stepped portion 6A on the rear end side of the bit support 6 is from the bottom surface 4A of the cutout portion 4 of the casing top 3 to the rear end surface 3A of the casing top 3. As shown in FIG. 1, a slight gap is formed between the rear end surface 3A and the stepped portion 6A in a state where the distance is longer than the distance in the axis O direction and the bottom surfaces 4A and 7A are aligned with the axis O direction. Is defined.

  On the other hand, in the present embodiment, such a recess 7 is formed to be 180 ° rotationally symmetric with respect to the two axes O, so that the tip of the bit support 6 has the above-described recess 7 between the recesses 7. A convex wall portion 6B extending from the axis O along the one diameter line L with a constant width in the front end view and wide at both ends on the outer peripheral side is formed, and the pilot bit 9 is formed on the convex wall portion 6B. Is attached. The pilot bit 9 has the stepped portion 7E formed in the wall portion 7B of the one recess 7 on both ends of the bit body 13 extending along the one diameter line L and on the positive rotation direction T side. The support part 13B extending in a fan shape in the front end view is provided in the support hole of the other recess 7 so that the plate-like part 13A that can be fitted to the rear part extends toward the rear end side. 7F is formed integrally with the bit body 13 so as to cover the tip end side, and is attached to the convex wall portion 6B by bolting the plate-like portion 13A fitted to the stepped portion 7F.

  In this attached state, the surface of the plate-like portion 13A facing the positive rotation direction T is flush with the wall portion 7B, and the rear end surface of the support portion 13B is perpendicular to the axis O and the center line X. Thus, the bit body 10 of the excavation bit 8 is fitted and sandwiched between the bottom surface 7A of the opposing recess 7 and a support hole 13C having a circular cross section centering on the center line X is formed on the rear end surface. The shaft portion 11A on the distal end side of the excavation bit 8 is rotatably inserted into the support hole 13C. Further, the portion of the bit body 13 along the one diameter line L is formed into a stepped portion whose inner peripheral side protrudes one step from the outer peripheral side except for the periphery of the axis O, and the stepped portion includes a drill bit. A plurality of cutting chips 12 similar to those in FIG. 8 (five in this embodiment) are planted so as to be aligned in the radial direction with their protruding heights aligned for each stepped portion.

  As shown in FIG. 1, the bit support 6 is provided with a blow hole 6C from the rear end thereof toward the front end side along the axis O, and the blow hole 6C is reduced in diameter in the middle to form a convex wall. It extends through the portion 6B, and further communicates with and branches into the bit body 13 of the pilot bit 9, and is opened near the axis O at the tip of the bit body 13. In addition, the blow hole 6C is obliquely branched toward the outer peripheral side of the tip, before being reduced in diameter, and is opened at a portion on the reverse rotation direction R side of the bottom surface 7A of the recess 7, while the center line X and A branch is also made in the diameter direction of the orthogonal axis O to be opened on the outer peripheral surface on the tip side from the stepped portion 6A of the bit support body 6, and further branched along the center line X from the branched hole. From the bottom surface of 7F to the support hole 13C of the pilot bit 9 through the through-hole 8A of the excavation bit 8, the inside of the support portion 13B extends from the bottom surface of the support hole 13C to the front end side, and then bends to the outer peripheral side to expand. The excavation bit 8 in the diameter state is opened toward the positive rotation direction T side of the tip 12.

  In the excavation tool configured as described above, the bit support 6 is inserted from the rear end side of the casing pipe 1 with the diameter of the excavation bit 8 reduced, and the recess 7 faces the notch 4 in the circumferential direction. The top end of the casing top 3 protrudes from the top of the casing top 3 so that the bottom surfaces 4A and 7A of the casing 4 are flush with each other. It is made to project from the notch portion 4 to the outer peripheral side, and is positioned when the side surface 10E of the bit body 10 contacts the wall portion 7C of the recess 7. Next, the casing pipe 1 is rotated in the normal rotation direction T so that the wall surface 4B of the notch 4 is brought into contact with the side surface 10D facing the reverse rotation direction R side of the bit body 10 of the excavation bit 8 as shown in FIG. Thus, the excavation bit 8 is supported in an expanded state so that the bit body 10 is sandwiched with the side surfaces 10D and 10E contacting the wall surface 4B and the wall portion 7C of the recess 7.

  Therefore, excavation is performed by moving the casing pipe 1 forward by rotating the casing pipe 1 in the forward rotation direction T in this expanded diameter state and applying thrust and a striking force as necessary to the tip side in the axis O direction. As a result, the excavation bit 8 is rotated integrally with the casing pipe 1 together with the bit support 6 and the pilot bit 9 with the diameter expanded, and the bottom surface 4A of the notch 4 and the rear end surface 10B of the bit body 10 of the excavation bit 8 And the thrust and striking force are transmitted to the excavation bit 8, and the thrust and striking force are further caused by the front end surface 10 </ b> A of the bit body 10 abutting against the rear end surface of the support portion 13 </ b> B in the bit body 13 of the pilot bit 9. It is also transmitted to the pilot bit 9, and the tip 12 embedded in the drill bit 8 and the pilot bit 9 Large boring is formed than the outer diameter of the casing pipe 1 I.

  At the time of excavation, air is sent to the front end side through the casing pipe 1, and this air branches from the blow hole 6 </ b> C formed in the bit support 6 and is ejected from the pilot bit 9 and the bottom surface 7 </ b> A of the recess 7. To remove the chips generated during excavation. Further, the scraped powder thus removed is discharged from the gap between the outer periphery of the casing pipe 1 and the inner periphery of the drilling hole. Even if an excessive impact force or the like is applied from the casing pipe 1 to the excavation bit 8, the pilot bit 9, and the bit support 6, the stepped portion 6 </ b> A of the bit support 6 contacts the rear end surface 3 </ b> A of the casing top 3. The forward movement of the bit support 6, the excavation bit 8, and the pilot bit 9 is restrained so that the bit support 6, the excavation bit 8, and the pilot bit 9 are not detached from the casing top 3 to the tip side.

  When the drilling holes are formed to a predetermined depth and the casing pipe 1 is inserted, the casing pipe 1 is rotated in the reverse rotation direction R, and the reverse rotation direction R side of the notch 4 is moved as shown in FIG. The facing wall 4C is brought into contact with the side surface 10F of the bit body 10 of the excavation bit 8, and the casing pipe 1 is rotated in the reverse rotation direction R, so that the excavation bit 8 is reduced in diameter as shown in FIG. It is stored in the recess 7 of the support 6. Here, the case where the diameter of the excavation bit 8 is reduced will be described in further detail with reference to FIG. 5. By rotating the casing pipe 1 in the reverse rotation direction R from the state shown in FIG. 3, the distance A is greater than the distance B + C. 5A, the intersection Q between the wall surface 4C and the recess 5 abuts on the side surface 10F of the bit body 10 so that the bit body 10 rotates in the reverse rotation direction R about the center line X. Rotated.

  Further, when the casing pipe 1 is rotated as it is, as shown in FIG. 5 (b), the bit body 10 continues to rotate in the reverse rotation direction R while the intersection P is accommodated in the recess 5, and FIG. 5 (c). When the intersection point P is located on the inner peripheral side of the outer diameter of the tip end portion of the bit support 6, the intersection S portion between the recess 5 and the inner peripheral surface of the casing top 3 contacts the side surface 10 </ b> F of the bit body 10. Since the casing body 1 is further rotated in the reverse rotation direction R, the bit body 10 is pushed into the inner peripheral side by the intersection S, and the bit body 10 supports the bit as shown in FIG. The reduced diameter is accommodated on the inner peripheral side without protruding from the outer diameter of the tip of the body 6.

  Therefore, in this reduced diameter state, the excavation bit 8 and the pilot bit 9 together with the bit support 6 are retracted and pulled out from the casing pipe 1, so that only the casing pipe 1 remains in the drilling hole and is built. it can. In order to pull out the bit support 6, the excavation bit 8, and the pilot bit 9 in this way, for example, a hooked portion such as a hook or an I bolt (not shown) is provided at the rear end of the bit support 6, and after excavation is completed. A rope or the like provided with a hooking means capable of hooking the hooked portion is inserted into the casing pipe 1 to be hooked on the hooked portion, or the bit support 6 is directly attached by suction or the like. What is necessary is just to insert the rope etc. which provided latching means, such as a magnet which can be latched, in the front-end | tip in the casing pipe 1, and to pull back the excavation bit 8 of a reduced diameter state to the rear-end side. .

  Therefore, according to the excavation tool having the above-described configuration, the rotational force is applied to the bit bodies 10 and 13 of the excavation bit 8 and the pilot bit 9 from the bottom surface 4A and the wall surface 4B of the notch 4 formed in the casing top 3 at the tip of the casing pipe 1. Since drilling can be performed with thrust and striking force, it is possible to form a drill hole and insert the casing pipe 1 into the drill hole without requiring an inner rod as in the prior art. After the excavation is completed, the excavation bit 8 can be reduced in diameter by the reverse rotation of the casing pipe 1, and the bit support 6 can be pulled out and collected. For this reason, material costs required for the inner rod itself, its management costs, transportation costs for transporting the inner rod to the excavation site, etc. can be reduced. There is no need to remove the added inner rod and collect the bit, and the cost, labor, and time required for excavation work can be greatly reduced.

  Further, in this embodiment, a step 6A is formed at the rear end of the bit support 6 and the inner diameter of the most advanced pipe body 2 of the casing pipe 1 is reduced by one step without using an inner rod. Since the casing top 3 is attached and the stepped portion 6A abuts against the rear end surface 3A of the casing top 3, it is possible to prevent the bit support body 6, the excavation bit 8, and the pilot bit 9 from falling off. Can be urged. Moreover, the casing top 3 is made thicker than the pipe body 2 by reducing the inner diameter by one step in this way, and the notch 4 is formed in the casing top 3 thus made thick, so that the excavation bit 8 has rotational force and thrust. Since the bottom surface 4A and the wall surface 4B for transmitting the striking force are formed, it is possible to reliably transmit these rotational force, thrust and striking force to the excavation bit 8 and the pilot bit 9 for efficient excavation. .

  Further, in the present embodiment, a concave portion 5 is formed on the inner peripheral surface of the casing top 3 so as to extend from the wall surface 4C facing the reverse rotation direction R side of the cutout portion 4 in the forward rotation direction T and to cut toward the inner peripheral side. Therefore, when the diameter of the excavation bit 8 is reduced, it is possible to perform a smooth diameter reduction operation by the recess 5 as shown in FIG. That is, since the bit body 10 of the excavation bit 8 is rotated about the center line X eccentric from the axis O as described above, the diameter P is reduced at the root portion of the bit body 10. In doing so, it once protrudes outside the outer diameter of the tip of the bit support 6 and then pushed into the inner periphery.

  Therefore, if such a recess 5 is not formed and the wall surface 4C reaches the inner periphery of the casing top 3 with a flat surface, for example, when the casing pipe 1 is rotated in the reverse rotation direction R, the wall surface 4C There is a possibility that 4C will come into contact with the side surface 10E of the bit body 10 and get caught and cannot be rotated further in the reverse direction. Thus, the recess 5 is formed, and the inner radius, that is, the distance A in particular is set to the center line. By making the distance B greater than the sum B + C of the distance B between X and the intersection point P and the distance C between the axis O and the center line X, the wall surface 4C including the intersection point Q is prevented from coming into contact with the side surface 10E. It is possible to reliably reduce the diameter of the excavation bit 8 while accommodating the inside of the recess 5.

  However, for example, when the diameter P is increased, the intersection point P is located on the inner peripheral side with respect to the inner diameter of the casing top 3, and this point P remains even if the bit body 10 is rotated in the reverse rotation direction R side when the diameter is reduced. In the case where it does not protrude beyond the inner diameter of the casing top 3, the wall surface 4 </ b> C facing the reverse rotation direction R side of the notch 4 without providing such a recess 5 is directly in the inner diameter of the casing top 3. It may be made to reach up to. Further, in the present embodiment, the wall surface 4C is formed in a flat surface shape in the reverse rotation direction R as it goes to the outer peripheral side, but it is the intersection point Q that pushes the excavation bit 8 when the diameter is reduced. If the required strength is ensured at the intersection Q, the wall surface 4C may be a surface facing the forward rotation direction T side as it goes toward the outer periphery. This also applies to the wall surface 4B. If the casing pipe 1 is rotated in the normal rotation direction T during excavation, the wall surface 4B can also be transferred to, for example, the axis O if the rotational force can be reliably transmitted to the excavation bit 8. It may be a surface extending in the reverse rotation direction R side toward the outer peripheral side.

  Further, in the present embodiment, a recess 7 is formed in the distal end portion of the bit support 6 so that the excavation bit 8 is accommodated, and the side surface 10E of the bit body 10 of the excavation bit 8 is the recess 7 in the expanded diameter state. Is positioned in contact with the wall portion 7C facing in the reverse rotation direction R side, in the forward rotation direction T given to the excavation bit 8 from the casing pipe 1 through the wall surface 4B of the notch portion 4 during excavation. Since the rotational force can be reliably received by the wall portion 7C to support the excavation bit 8, more stable excavation can be performed. In this regard, for example, the shaft portion 11A and the shaft portion 11B of the excavation bit 8 are provided with a convex portion, and the convex portion can be accommodated in the support hole 13C and the support hole 7F in a predetermined range in the circumferential direction. It is possible to form a recess having a wall surface against which the excavator abuts and to position the excavation bit 8 by the abutment of the convex portion. In this case, however, the convex portion or the shaft portion 11A is used. , 11B may increase and cause damage, but in the present embodiment, the wall portion 7C can secure a relatively large contact area and receive the rotational force.

  However, also in this case, for example, without providing the recess 7 or the pilot bit 9 at the tip of the bit support 6, the plurality of excavation bits 8 can be rotated in one direction around the center line X eccentric from the axis O. The side surfaces of the excavation bit 8 are brought into contact with each other and positioned so that the outer diameter of the excavation bit 8 is larger than that of the casing pipe 1 and the excavation bit 8 is rotated in the opposite direction. It is good also as a structure by which the outer diameter is made into the state diameter-reduced rather than the internal diameter of the casing pipe 1 front-end | tip part (casing top 3), when the side surfaces of a drill bit remove | deviate from a diameter-expanded state and contact | abut.

It is a longitudinal cross-sectional view which shows one Embodiment of this invention. It is the front view seen from the axis line O direction front end side in the diameter expansion state of embodiment shown in FIG. It is the front view seen from the axis line O direction front end in the state where wall surface 4C contacted side surface 10F at the time of diameter reduction of the embodiment shown in FIG. It is the front view seen from the axis line O direction front end side in the diameter expansion state of embodiment shown in FIG. FIG. 5 is an explanatory view corresponding to the Z cross section (above the axis O) of FIG. 1 from the state shown in FIG. 3 to the reduced diameter state shown in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing pipe 3 Casing top 4 Notch part 4A Bottom surface of the notch part 4B, 4C Wall surface of the notch part 5 Recessed part 6 Bit support body 6A Step part 7 Recess 7A Bottom face of the recessed part 7B-7D Wall part of the recessed part 7 8 Drilling bit 9 Pilot bit 10, 13 Bit body 12 Tip

Claims (4)

A bit support is inserted into the inner periphery of the tip of a cylindrical casing pipe that is rotated about the axis and advanced toward the tip in the axial direction, and a drill bit is inserted into the tip of the bit support from the axis. The casing pipe is supported so as to be rotatable about an eccentric center line, and a cutout portion is formed at the tip of the casing pipe in a radial direction so that the casing pipe rotates forward during excavation. A wall surface facing the positive rotation direction of the notch portion in a state in which the excavation bit is rotated around the center line in a direction in which the outer diameter from the axis expands when rotated in a direction. When the excavation is performed with the bottom surface facing the tip side being brought into contact with the excavation bit and the casing pipe is rotated in the reverse rotation direction opposite to the normal rotation direction, Wherein said drill bit by a wall facing the opposite direction of rotation of the missing portion, the outer diameter from the axis is rotated to the center line around to reduced diameter than the inner diameter of the tip portion of the casing pipe And drilling tools.   A casing top whose inner diameter is reduced by one step is attached to the tip of the casing pipe. The notch is formed in the casing top, and the outer periphery of the casing top is formed on the outer periphery of the rear end of the bit support. The excavation tool according to claim 1, wherein a step portion having an outer diameter larger than the inner diameter is formed.   The inner peripheral surface of the front end portion of the casing pipe is formed with a concave portion extending from the wall surface facing the reverse rotation direction of the notch portion toward the positive rotation direction and cutting toward the inner peripheral side. The excavation tool according to claim 1 or 2. A recess for accommodating the excavation bit is formed at the tip of the bit support, and the recess is rotated in a direction in which the outer diameter from the axis increases. The excavation tool according to any one of claims 1 to 3, wherein a wall portion facing the reverse excavation bit and facing the reverse rotation direction is formed.

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