WO2014142011A1 - 掘削工具 - Google Patents
掘削工具 Download PDFInfo
- Publication number
- WO2014142011A1 WO2014142011A1 PCT/JP2014/055854 JP2014055854W WO2014142011A1 WO 2014142011 A1 WO2014142011 A1 WO 2014142011A1 JP 2014055854 W JP2014055854 W JP 2014055854W WO 2014142011 A1 WO2014142011 A1 WO 2014142011A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- tip
- outer peripheral
- inner bit
- bit
- groove
- Prior art date
Links
- 230000002093 peripheral effect Effects 0.000 claims abstract description 118
- 238000009412 basement excavation Methods 0.000 claims description 119
- 238000005553 drilling Methods 0.000 claims description 30
- 239000012530 fluid Substances 0.000 description 63
- 239000002699 waste material Substances 0.000 description 41
- 230000000694 effects Effects 0.000 description 14
- 230000005540 biological transmission Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/60—Drill bits characterised by conduits or nozzles for drilling fluids
- E21B10/602—Drill bits characterised by conduits or nozzles for drilling fluids the bit being a rotary drag type bit with blades
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/20—Driving or forcing casings or pipes into boreholes, e.g. sinking; Simultaneously drilling and casing boreholes
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/08—Roller bits
- E21B10/18—Roller bits characterised by conduits or nozzles for drilling fluids
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/42—Rotary drag type drill bits with teeth, blades or like cutting elements, e.g. fork-type bits, fish tail bits
- E21B10/43—Rotary drag type drill bits with teeth, blades or like cutting elements, e.g. fork-type bits, fish tail bits characterised by the arrangement of teeth or other cutting elements
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
- E21B10/56—Button-type inserts
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/64—Drill bits characterised by the whole or part thereof being insertable into or removable from the borehole without withdrawing the drilling pipe
Definitions
- the tip of the inner bit inserted into the casing pipe is projected from the tip of the casing pipe, and the inner bit is engaged with a ring bit that is rotatably disposed at the tip of the casing pipe.
- the present invention relates to an excavation tool that is integrally rotatable and excavates the ground with these inner and ring bits to form an excavation hole and simultaneously inserts a casing pipe into the excavation hole.
- a cylindrical casing pipe, and the casing pipe is inserted through the casing pipe along the axial direction thereof, and a tip portion along the axial direction is protruded from the tip of the casing pipe.
- the inner bit has an annular shape, and is disposed at the tip of the casing pipe so as to be rotatable about the axis with respect to the casing pipe, and surrounds the tip of the inner bit, Is known that includes a ring bit that can be engaged around the axis and from the front end side in the axial direction (see, for example, Patent Documents 1 and 2 below).
- FIG. 6 and 7 show a conventional excavation tool 100.
- the tip of the inner bit 102 inserted into the casing pipe 101 is projected from the tip of the casing pipe 101, and the inner bit 102 is rotatably disposed at the tip of the casing pipe 101.
- the ring bit 103 is engaged and can rotate integrally.
- the ring bit 103 can be engaged with the inner bit 102 from the front end side in the axis O direction.
- the inner bit 102 and the inner bit 102 are engaged with the inner bit 102 by being given thrust and striking force toward the front end side (the lower side in FIG. 6) in the direction of the axis O and a rotational force around the axis O.
- the ground is excavated by the ring bit 103 to form an excavation hole, and at the same time, the casing pipe 101 is inserted (drawn) into the excavation hole.
- the inner bit 102 includes a supply hole 104 that passes through the inner bit 102 and opens at a tip portion of the inner bit 102, and a discharge groove 105 that is formed on the outer peripheral surface of the inner bit 102 and extends in the axis O direction.
- the supply hole 104 includes a tip blow hole 106 that opens to the tip surface of the inner bit 102 and an outer periphery blow hole 107 that opens to the outer periphery of the inner bit 102.
- the tip blow hole 106 is formed in the tip groove 108 formed on the tip surface of the inner bit 102 and communicated with the discharge groove 105, and the outer peripheral blow hole 107 is opened toward the tip surface of the ring bit 103. Yes.
- fluid ejecting medium
- fluid ejecting medium
- Scrap slime
- the conventional excavation tool 100 described above has the following problems. That is, excavation debris generated by excavating the ground with the excavating tool 100 is discharged by a fluid supplied from an unillustrated excavator, but in soft geological ground, the fluid enters the ground around the excavation hole. Therefore, the excavation waste may not be discharged, and the excavation waste may accumulate in the excavation hole. In some cases, fluid that has entered the ground around the excavation hole loosens the ground and may affect the foundations of nearby structures.
- the present invention has been made in view of such circumstances, and the fluid ejected from the supply hole of the inner bit and the excavation waste generated by the excavation can be efficiently recovered in the discharge groove of the inner bit.
- the excavation work can be stably discharged toward the base end of the tool through the discharge groove, so that excavation work can be carried out with high efficiency and stability, and the influence on the ground around the excavation hole can be suppressed.
- the purpose is to provide tools.
- one aspect of the excavation tool of the present invention is an excavation tool for excavating the ground to form an excavation hole, and is inserted into the casing pipe along the axial direction thereof, and a cylindrical casing pipe. And an inner bit projecting from the tip of the casing pipe with a tip portion along the axial direction and an annular shape, and arranged at the tip of the casing pipe so as to be rotatable about the axis with respect to the casing pipe.
- a ring bit that surrounds the distal end portion of the inner bit and that can be engaged with the inner bit from the distal end side around the axis and in the axial direction.
- An exhaust groove, and the supply hole includes a tip blow hole that opens to the tip surface of the tip portion of the inner bit, and an outer peripheral blow hole that opens to the outer periphery surface of the tip portion of the inner bit,
- An outer peripheral groove that communicates the outer peripheral blow hole and the discharge groove is formed on an outer peripheral surface of the inner bit, and the outer peripheral groove is covered from the radially outer side by the ring bit, and the outer peripheral blow hole Toward the discharge groove, gradually extending toward the proximal end in the axial direction as it goes around the axis.
- the ground is excavated by the inner bit and the ring bit engaged with the inner bit by being given thrust and striking force toward the distal end in the axial direction with respect to the inner bit and rotational force around the axis.
- a casing pipe is inserted (drawn) into the excavation hole at the same time.
- fluid such as air (ejection medium) is ejected to the tip of the inner bit through the supply hole, while fluid and excavation debris (slime) generated by excavation are ejected through the discharge groove toward the tool base end. Is done.
- the outer peripheral blow hole of the supply hole is communicated with the discharge groove through the outer peripheral groove formed on the outer peripheral surface of the inner bit, and the outer peripheral groove is radially formed by the ring bit. Since it is covered from the outer side and gradually extends toward the base end side in the axial direction from the outer peripheral blow hole toward the discharge groove as it goes around the axis, the following effects can be obtained.
- the fluid in the outer circumferential groove flows into the discharge groove while forming a flow toward the proximal end in the axial direction from the outer peripheral blow hole toward the discharge groove.
- the waste easily flows toward the tool proximal side.
- the outer peripheral groove is covered with the ring bit from the outside in the radial direction, the fluid ejected from the outer peripheral blow hole into the outer peripheral groove is prevented from entering the ground and into the discharge groove. The recovery efficiency of the fluid and the drilling waste flowing in the discharge groove is improved.
- the outer peripheral groove is covered with the ring bit in this way, the intrusion of the drilling waste into the outer peripheral groove is suppressed, and the situation where the outer peripheral groove is clogged with the drilling waste is prevented,
- the flow path in the outer circumferential groove is stably secured, and the flow velocity of the fluid flowing in the outer circumferential groove is stably maintained.
- the pressure in the discharge groove is more than the pressure around the tip surface of the inner bit due to the venturi effect. Therefore, the fluid and drilling waste around the front end surface are easily drawn into the discharge groove having a lower pressure, and are easily sent to the tool base end side through the discharge groove.
- fluid ejected from the supply hole of the inner bit and excavation waste generated by excavation can be efficiently collected in the discharge groove of the inner bit, and through the discharge groove. It is possible to discharge stably toward the base end side of the tool, whereby the excavation work can be advanced efficiently and stably, and the influence on the ground around the excavation hole can be suppressed.
- the tip blow hole is opened in a tip groove formed on a tip surface of the inner bit and communicating with the discharge groove, and the outer blow hole is formed in the outer groove. It is good also as opening in.
- the fluid ejected from the tip blow hole is efficiently guided into the discharge groove through the tip groove together with the drilling waste around the tip surface of the inner bit, and the efficiency of collecting the fluid and the drilling waste is increased. . Further, since the outer peripheral blow hole is directly opened in the outer peripheral groove, the above-described operation and effect become more remarkable.
- a plurality of the tip blow holes are opened in the tip surface of the inner bit, and at least one of the tip blow holes is parallel to the axis. It is desirable to extend so that it may approach to the said axis line as it goes to the front end side.
- the fluid ejected from the tip blow hole can be prevented from escaping from the tip surface of the inner bit toward the outer peripheral side, thereby effectively preventing the ground around the excavation hole from being loosened.
- the fluid ejected from the tip blow hole can easily reach the entire tip surface of the inner bit, and the excavation efficiency is further improved.
- the position along the axial direction of the tip surface of the ring bit is the same as or protrudes toward the tip side with respect to the tip surface of the inner bit. It is good.
- the inner bit does not protrude toward the tip side with respect to the ring bit, the intrusion of fluid around the drilling hole is more effectively prevented. That is, since the ring bit surrounds the entire tip of the inner bit, it is possible to prevent fluid and drilling waste from leaking radially outward of the ring bit, and the fluid and drilling waste are It is efficiently recovered into the discharge groove located on the inner side in the radial direction.
- a plurality of tips projecting from the tip surface are disposed on the tip surface of the inner bit, and an outer peripheral edge portion of the tip surface of the inner bit is formed by the excavation tool. It is a gauge surface that gradually extends toward the proximal end side in the axial direction as it goes radially outward in a longitudinal sectional view of the tool, and the radially inner side of the gauge surface at the distal end surface of the inner bit is a face surface.
- the amount of protrusion of the chip disposed on the face surface from the face surface is larger than the amount of protrusion of the chip disposed on the gauge surface out of the plurality of chips. It may be enlarged.
- the tip groove may be gradually extended toward the side opposite to the tool rotation direction as it goes radially outward from the tip blow hole.
- the tip groove gradually extends from the tip blow hole toward the outer side in the radial direction toward the opposite side of the tool rotation direction.
- channel may extend toward the base end side of the said axial direction gradually as it goes to the rotation direction of the said inner bit.
- the fluid in the outer peripheral groove flows into the discharge groove while forming a flow from the outer peripheral blow hole toward the discharge groove toward the proximal end side in the axial direction as the inner bit rotates. Accordingly, the fluid and the excavation waste in the discharge groove are more likely to flow toward the tool base end side.
- the face surface is retreated to the base end side in the axial direction, and the face recedes to the base end side in the axial direction from the first receding surface.
- the amount of protrusion from the second receding surface may be the same. In this case, since it is easy to secure a gap between the chips on the first receding surface and the second receding surface, the retention of fluid and drilling waste on the face surface is effectively suppressed. The discharge is performed stably.
- the face surface is retreated to the base end side in the axial direction, and the face recedes to the base end side in the axial direction from the first receding surface.
- the position in the axial direction may be the same. In this case, the excavation efficiency of the chip on the second retreat surface having a large retreat amount is not reduced.
- fluid ejected from the supply hole of the inner bit and excavation waste generated by excavation can be efficiently collected in the discharge groove of the inner bit, and the tool is passed through the discharge groove. It is possible to discharge stably toward the base end side. Thereby, excavation work can be advanced efficiently and stably, and the influence on the ground around the excavation hole can be suppressed.
- the excavation tool 1 of the present embodiment has a double-pipe bit, and is connected to an excavator (not shown) to excavate the ground to form an excavation hole, and at the same time, a casing pipe is formed in the excavation hole. 2 is inserted.
- the excavation tool 1 includes a casing pipe 2, an inner bit 3, and a ring bit 4.
- the casing pipe 2 has a cylindrical shape.
- the inner bit 3 is inserted through the casing pipe 2 along the direction of the axis O, and the tip of the inner bit 3 along the axis O direction protrudes from the tip of the casing pipe 2.
- the ring bit 4 has an annular shape and is disposed at the tip end portion of the casing pipe 2 so as to be rotatable around the axis O with respect to the casing pipe 2, and surrounds the tip end portion of the inner bit 3. Can be engaged around the axis O and from the front end side in the direction of the axis O.
- the casing pipe 2, the inner bit 3, and the ring bit 4 are arranged coaxially with the axis O as a common axis.
- the ring bit 4 side (lower side in FIG. 1) along the axis O direction is referred to as a distal end side
- the opposite side (upper side in FIG. 1) from the ring bit 4 along the axis O direction is referred to as a proximal end side.
- a direction orthogonal to the axis O is referred to as a radial direction
- a direction around the axis O is referred to as a circumferential direction.
- the direction in which the inner bit 3 is rotated with respect to the casing pipe 2 during excavation is referred to as the tool rotation direction T (or the front of the tool rotation direction T), and is opposite to the tool rotation direction T.
- the direction toward is referred to as the rear of the tool rotation direction T.
- the casing pipe 2 is welded with a short cylindrical (annular) casing top 6 welded to the tip of a long cylindrical (annular) pipe body 5 that is sequentially added according to the excavation length of the excavation hole. It is configured to be mounted coaxially. Further, on the radially inner side of the casing pipe 2, a transmission member for transmitting a striking force, thrust, and rotational force such as an inner rod (not shown) is inserted coaxially with the axis O of the casing pipe 2. It is designed to be added sequentially according to the excavation length.
- the rearmost end (base end side end) of the transmission member is connected to a drilling device that applies a rotational force around the axis O and a thrust toward the front end side in the axis O direction to the transmission member during excavation.
- a short cylindrical ring bit 4 is attached to the tip of the casing top 6 at the tip of the casing pipe 2, and a striking force toward the tip of the axis O direction is given to the tip of the transmission member.
- the inner bit 3 is attached via a hammer (not shown) and is inserted inside the ring bit 4 in the radial direction.
- the casing top 6 has a proximal end portion that is smaller in diameter and outer diameter than the distal end portion, and the end surface of the casing top 6 that is located closest to the proximal end and faces the proximal end is:
- the taper surface 6a is gradually inclined toward the proximal end side toward the radially outer side.
- the casing top 6 is welded so that the proximal end of the distal end portion is abutted against the distal end of the pipe body 5 in a state where the proximal end portion thereof is fitted and inserted in the radially inner side of the most distal portion of the pipe body 5.
- the pipe body 5 is attached.
- the outer diameter of the tip side portion of the casing top 6 is substantially equal to the outer diameter of the pipe body 5, and the inner diameter is slightly larger than the inner diameter of the pipe body 5.
- the step surface 6c facing the front end side in the direction of the axis O in the portion is an annular flat surface perpendicular to the axis O.
- a protruding line 6 d that protrudes radially inward and extends along the circumferential direction is formed.
- a concave groove 6e that is recessed radially outward and extends in the circumferential direction is formed between the protruding line 6d and the stepped surface 6c on the inner peripheral surface of the casing top 6.
- the ring bit 4 attached to the distal end side of the casing top 6 has a small outer diameter whose outer peripheral surface of the base end portion can be substantially fitted or loosely inserted into the inner peripheral surface of the distal end side portion of the casing top 6,
- the tip portion is expanded radially outward, and the outer diameter thereof is larger than the outer diameter of the casing top 6 and the pipe body 5.
- a protrusion 4 a that protrudes radially outward and extends in the circumferential direction is formed, and the protrusion 4 a is a groove 6 e of the casing top 6.
- the ring bit 4 can be rotated in the circumferential direction while being prevented from coming off toward the tip side with respect to the casing top 6.
- the inner peripheral surface of the ring bit 4 is formed to have an inner diameter that is one step smaller than the inner peripheral surface of the base end side portion of the casing top 6.
- an end surface (base end surface 4 b) facing the base end side is formed with a tapered surface 4 c that is gradually inclined toward the front end side as it goes radially inward. Therefore, in the present embodiment, the outer peripheral surface (projection 4a) of the base end portion of the ring bit 4 faces the inner peripheral surface (concave groove 6e) of the distal end side portion of the casing top 6 at the distal end of the casing pipe 2 in the radial direction.
- the base end surface 4b and the stepped surface 6c of the casing top 6 are attached to face each other in the direction of the axis O.
- the distal end surface of the ring bit 4 is connected to the flat annular surface perpendicular to the axis O and the radially inner side and the outer side of the annular surface, and is inclined toward the proximal end side toward the radially inner side and the outer side.
- a plurality of tips 7 made of a hard material such as cemented carbide is disposed on each of the annular surfaces and the radially inner and outer tapered surfaces.
- a plurality of concave grooves 4 e extending in parallel with the axis O are planted on the tapered surface on the radially inner side at intervals in the circumferential direction and at the tip of the ring bit 4. It is formed so as not to interfere with the chip 7.
- the front portion in the tool rotation direction T is formed with a wall portion 4f such as a concave groove 4e shown on the left side of FIG. 1 at its base end side so as not to open in the tapered surface 4c. ing.
- the inner bit 3 has a multi-stage columnar shape in which the diameter is increased in two steps from the distal end toward the proximal end and then gradually reduced, and the outer diameter of the first step portion on the distal end side is the ring bit 4.
- the outer diameter of the second stage portion is radially inward of the base end portion of the casing top 6, and the outermost diameter of the third step largest portion is radially inward of the pipe body 5.
- Each size is designed to be loosely inserted.
- the step portion between the third step and the third step is a tapered surface that expands in a conical shape toward the base end side toward the outer side in the radial direction.
- the taper surface 3a between the first and second stages and the taper surface 3b between the second and third stages have a taper angle of the taper surface 4c of the ring bit 4 and the taper of the casing top 6.
- the ring bit 4 is set to be equal to the taper angle of the surface 6a, with the tapered surfaces 3a, 3b being in contact with the tapered surfaces 4c, 6a as shown in FIG.
- the outer peripheral edge of the face surface 10 to be described later (the first part) among the distal end surfaces of the inner bit 3 (the most distal portion) (note that In FIG. 1, the annular surface which is the foremost portion of the tip surface of the ring bit 4 with respect to the annular surface located between the first receding surface 11 of the face surface 10 and the gauge surface 9.
- the positions along the direction of the axis O are the same.
- a protrusion 3 c that protrudes radially outward from the outer diameter of the ring bit 4, which can be loosely inserted radially inward as described above. While extending along the O direction, a plurality are formed at intervals in the circumferential direction.
- the number of the ridges 3c is the same as the number of the concave grooves 4e, and the ridges 3c extend from the outer peripheral edge of the front end surface of the inner bit 3 along the axis O direction (front end of the tapered surface 3a (front end). It extends over a part slightly spaced apart on the side.
- these ridges 3c can be loosely inserted from the base end side into the penetrating portion of the concave groove 4e to the tapered surface 4c, and are thus loosely inserted into the concave groove 4e.
- the inner bit 3 inserted in the radial direction of the ring bit 4 while accommodating the ridge 3c in the concave groove 4e has an axis O with respect to the ring bit 4 by bringing the tapered surface 3a into contact with the tapered surface 4c.
- the convex strip 3c is on any side wall facing the circumferential direction of the concave groove 4e. By abutting, it is possible to engage also around the axis O and rotate integrally with the ring bit 4.
- a plurality of chips 8 projecting from the tip surface are disposed (planted) on the tip surface of the inner bit 3.
- the outer peripheral edge portion on the distal end surface of the inner bit 3 is a gauge surface 9 that gradually extends toward the proximal end side as it goes radially outward in the longitudinal sectional view of the excavation tool 1 shown in FIG.
- the radially inner portion (the portion other than the gauge surface 9 in the distal end surface) of the gauge surface 9 on the distal end surface of the inner bit 3 is a face surface 10.
- the face surface 10 is retracted stepwise from the gauge surface 9 inward in the radial direction.
- a portion of the face surface 10 of the inner bit 3 which is adjacent to the radially inner side of the gauge surface 9 and is retreated one step toward the proximal end is a first retreat surface 11, and the first retreat surface 11.
- a portion located on the radially inner side of the surface 11 and retracted one step further toward the base end side than the first retracted surface 11 and a portion including the axis O (radially central portion) is defined as a second retracted surface 12.
- the first receding surface 11 is more retracted than the receding amount by which the first receding surface 11 recedes to the base end side with respect to the outermost peripheral edge of the face surface 10.
- the retraction amount by which the retreat surface 12 retreats to the base end side is set large.
- the chip 8 is a round button chip formed such that the tip thereof is hemispherical and the portion other than the tip is formed in a columnar shape.
- the chip 8 ⁇ / b> A disposed on the gauge surface 9 and the chip 8 ⁇ / b> B disposed on the face surface 10 have the same shape.
- the tip 8A disposed on the gauge surface 9 is disposed on the face surface 10 with respect to the protruding amount H1 from the gauge surface 9.
- the protruding amount H2 of the chip 8B from the face surface 10 is increased. In the example shown in FIG.
- the position of the tip 8B in the direction of the axis O is arranged on the tip side of the position of the tip 8A in the direction of the axis O.
- the face surface 10 is provided with a plurality of annular chip support portions so as to support the outer peripheral surface of the chip 8B, and these chip support portions extend along the outer peripheral surface of each chip 8B. As shown in FIG.
- the tip 8 ⁇ / b> B of the first receding surface 11 projects from the first receding surface 11 toward the tip side.
- the protrusion amount H2 and the protrusion amount H2 that the tip 8B of the second receding surface 12 projects from the second receding surface 12 toward the tip side are the same. Therefore, the position in the axis O direction at the tip of the tip 8B disposed on the first receding surface 11 of the face surface 10 is greater than the position in the axis O direction at the tip of the chip 8B disposed on the second receding surface 12. Is also arranged on the tip side.
- the plurality of chips 8B arranged on the first receding surface 11 are arranged in a substantially arc shape along the circumferential direction, and a plurality of such rows are spaced apart in the radial direction. Is formed. Specifically, the chips 8B forming a row along the circumferential direction are arranged in the circumferential direction with slightly different positions along the radial direction, and will be described later in the rear of the row in the tool rotation direction T. A tip groove 18 is arranged.
- the inner bit 3 includes a supply hole 13 that passes through the inner bit 3 and opens at the tip of the inner bit 3, and a discharge groove 14 that is formed on the outer peripheral surface of the inner bit 3 and extends in the direction of the axis O. It is equipped with. Further, the supply hole 13 includes a front end blow hole 15 that opens to a front end surface at the front end portion of the inner bit 3, an outer peripheral blow hole 16 that opens to an outer peripheral surface at the front end portion of the inner bit 3, and the front end blow hole 15 and the outer peripheral blow hole. A communication hole 17 communicating with the base end side of the hole 16 and allowing fluid to flow toward the holes 15 and 16 is provided.
- the diameter-reduced portion of the inner bit 3 on the base end side from the third stage is used as a mounting portion for the hammer, and the inner bit 3 extends along the axis O from the base end.
- a communication hole 17 for receiving fluid such as compressed air (air) sent from the hammer is formed toward the distal end side.
- the communication hole 17 is branched at a distal end portion of the inner bit 3 into a plurality of outer peripheral blow holes 16 extending toward the distal end side toward the radially outer side, and is positioned between both end portions of the outer peripheral blow hole 16. From the intermediate portion, the tip blow hole 15 branches toward the tip surface of the inner bit 3.
- the supply hole 13 has an inner diameter that decreases in the order of the communication hole 17, the outer peripheral blow hole 16, and the tip blow hole 15.
- the plurality of outer peripheral blow holes 16 are branched from the communication hole 17 so as to have a radial shape about the axis O.
- a plurality of tip blow holes 15 are opened in the tip surface of the inner bit 3, and at least one of the tip blow holes 15 extends so as to be parallel to the axis O.
- the tip blow hole 15A is provided.
- the tip blow holes 15 among the plurality of tip blow holes 15 formed at the tip portion of the inner bit 3, the tip blow hole 15 ⁇ / b> A is more than half, specifically, among the four tip blow holes 15.
- Two are the tip blow holes 15A.
- the tip blow holes 15 include tip blow holes 15B that gradually extend rearward in the tool rotation direction T toward the tip side, other than the tip blow holes 15A.
- the tip blow hole 15B extends so as to be gradually separated from the axis O toward the tip side.
- a plurality of digging waste discharge grooves 14 extending in parallel to the axis O are formed from the tip of the inner bit 3 to the third stage having the maximum outer diameter, and These discharge grooves 14 are arranged so as not to interfere with the ridges 3c in the circumferential direction.
- the discharge groove 14 is covered with the casing pipe 2 and the ring bit 4 from the outside in the radial direction, and the end portion on the front end side of the discharge groove 14 is open to the front end surface of the inner bit 3.
- a discharge path 20 is formed on the base end side of the discharge groove 14 to allow fluid and excavation waste to flow toward the base end side between the transmission member and the casing pipe 2.
- an outer peripheral groove 19 that connects the outer peripheral blow hole 16 and the discharge groove 14 is formed on the outer peripheral surface of the inner bit 3.
- the tip blow hole 15 is formed in the tip groove 18 formed in the tip surface of the inner bit 3 and communicated with the discharge groove 14, and the outer blow hole 16 is formed in the outer periphery surface of the inner bit 3.
- 14 is opened in an outer peripheral groove 19 communicating with the outer peripheral groove 14.
- the tip blow hole 15 is opened in the second receding surface 12 of the face surface 10, and the tip groove 18 extends from the second receding surface 12 to the discharge groove 14.
- the tip groove 18 extends gradually rearward in the tool rotation direction T as it goes radially outward from the tip blow hole 15.
- a tip blow hole 15 is opened at the radially inner end of the tip groove 18, and the radially outer end is continuous with the discharge groove 14.
- the groove width of the tip groove 18 is larger than the inner diameter of the tip blow hole 15.
- the cross-sectional shape along the groove width direction of the tip groove 18 is a substantially semicircular arc shape.
- the tip groove 18 gradually increases in depth along the axis O direction from the tip blow hole 15 toward the discharge groove 14, and discharge at the groove bottom of the tip groove 18.
- a connecting portion with the groove 14 is cut out in a chamfered shape.
- the groove width of the front end groove 18 is substantially constant from the front end blow hole 15 to the connection portion, and as the connection portion moves toward the discharge groove 14 on the radially outer side. It is gradually increased.
- the outer peripheral groove 19 is covered by the ring bit 4 from the outside in the radial direction. As shown in FIG. 3, the outer peripheral groove 19 gradually extends toward the proximal end side in the circumferential direction from the outer peripheral blow hole 16 toward the discharge groove 14. In the present embodiment, the outer circumferential groove 19 gradually extends toward the base end side in the tool rotation direction T. An outer peripheral blow hole 16 is opened at the rear end of the outer circumferential groove 19 in the tool rotation direction T, and the front end of the tool rotation direction T is continuous with the discharge groove 14. In the illustrated example, the groove width of the outer peripheral groove 19 is made smaller than the inner diameter of the outer peripheral blow hole 16.
- the cross-sectional shape along the groove width direction of the outer peripheral groove 19 is a substantially semicircular arc shape.
- the inner bit 3 and the inner bit 3 and the inner bit 3 are provided with the thrust and striking force toward the distal end in the direction of the axis O and the rotational force around the axis O.
- the casing pipe 2 is inserted (drawn) into the excavation hole at the same time.
- fluid (ejecting medium) such as air is ejected to the distal end surface of the inner bit 3 through the supply hole 13, while fluid and excavation waste (slime) generated by excavation pass through the discharge groove 14 to the tool base end side. It is discharged towards.
- the outer peripheral blow hole 16 of the supply hole 13 is communicated with the discharge groove 14 through the outer peripheral groove 19 formed on the outer peripheral surface of the inner bit 3. Since it is covered from the radially outer side by the ring bit 4 and gradually extends toward the proximal end side in the axis O direction from the outer peripheral blow hole 16 toward the discharge groove 14 around the axis O, the following Has an effect.
- the fluid in the outer peripheral groove 19 flows into the discharge groove 14 while forming a flow from the outer peripheral blow hole 16 toward the discharge groove 14 toward the base end side in the axis O direction. Accordingly, the fluid and excavation waste in 14 are easily flowed toward the tool proximal end side. Further, since the outer circumferential groove 19 is covered with the ring bit 4 from the outside in the radial direction, the fluid ejected from the outer circumferential blow hole 16 into the outer circumferential groove 19 is prevented from entering the ground. The recovery efficiency of the fluid flowing in the discharge groove 14 and the excavation waste is improved by being efficiently sent toward the discharge groove 14.
- the outer peripheral groove 19 is covered with the ring bit 4 in this way, the intrusion of the drilling waste into the outer peripheral groove 19 is suppressed, and the situation where the outer peripheral groove 19 is clogged with the drilling waste is prevented.
- the flow path in the outer circumferential groove 19 is stably secured, and the flow velocity of the fluid flowing in the outer circumferential groove 19 is stably maintained.
- the discharge groove 14 into which the fluid flows from the outer peripheral groove 19 the flow velocity of the fluid and the drilling waste flowing inside the groove is increased, and the pressure in the discharge groove 14 is increased by the venturi effect on the tip surface of the inner bit 3.
- the pressure in the front end groove 18 (and the periphery thereof) that opens to the bottom is easily reduced, and the fluid and drilling waste in the front end groove 18 are easily drawn into the discharge groove 14 at a lower pressure. It becomes easy to send to the discharge path 20 on the tool base end side through the discharge groove 14.
- the fluid ejected from the supply hole 13 of the inner bit 3 and the excavation waste generated by the excavation can be efficiently collected in the discharge groove 14 of the inner bit 3 and the discharge is performed. It is possible to stably discharge toward the tool base end side through the groove 14, whereby the excavation work can be proceeded with high efficiency and stability, and the influence on the ground around the excavation hole can be suppressed.
- a tip blow hole 15 is formed in the tip groove 18 formed in the tip surface of the inner bit 3 and communicated with the discharge groove 14, and an outer peripheral blow hole 16 is formed in the outer periphery surface of the inner bit 3 to be a discharge groove. Since it opens in the outer peripheral groove
- At least one of the plurality of tip blow holes 15 opened in the tip surface of the inner bit 3 is a tip blow hole 15A extending so as to be parallel to the axis O, the tip blow hole 15A.
- the fluid ejected from the hole 15A can be prevented from escaping from the distal end surface of the inner bit 3 toward the outer peripheral side, and thereby the ground around the excavation hole can be effectively restrained from loosening.
- the fluid ejected from the tip blow hole 15A easily spreads over the entire tip surface of the inner bit 3, and the excavation efficiency is further improved.
- the tip end surface of the inner bit 3 is arranged so that the position along the axis O direction of the tip end surface of the ring bit 4 is the same as the tip end surface of the inner bit 3.
- the position along the axis O direction of the annular surface which is the foremost part of the front end surface of the ring bit 4 is the same as the outer peripheral edge of the face surface 10 which is the foremost part of the ring bit 4.
- the ring bit 4 surrounds the entire tip portion of the inner bit 3, it is possible to prevent the fluid and drilling waste from leaking radially outward of the ring bit 4, and the fluid and drilling waste are Thus, it is efficiently recovered into the discharge groove 14 located inside the ring bit 4 in the radial direction.
- the chip 8A disposed on the gauge surface 9 is disposed on the face surface 10 with respect to the protruding amount H1 from the gauge surface 9. Since the protruding amount H2 of the chip 8B formed from the face surface 10 is increased, it is easy to secure a space for circulating fluid and excavated debris between the adjacent chips 8B on the face surface 10, and the space It becomes easy to discharge these fluid and excavation waste toward the tip groove 18 and the discharge groove 14.
- an annular chip support portion is projected from the face surface 10 to support the outer peripheral surface of each chip 8B, thereby stabilizing the mounting posture of the chip 8B with respect to the face surface 10.
- the protrusion amount H2 can be secured while increasing the attachment strength. Further, the same member can be used as the chips 8A and 8B while securing the protrusion amount H2 of the chip 8B on the face surface 10 in this way, and the types of components can be reduced.
- the first receding surface 11 and the second receding surface 12 are formed which gradually recede from the outer peripheral edge of the face surface 10 toward the radial center (near the axis O). Since it is easy to secure a gap between the chips 8B and the like on the first receding surface 11 and the second receding surface 12, the retention of fluid and excavation debris on the face surface 10 is effectively suppressed, and the fluid and excavation debris are discharged. Is performed stably. In particular, since the retraction amount of the second retreating surface 12 located at the radial center of the face surface 10 is ensured, the above-described effects can be more easily obtained.
- the positions may be set substantially the same, and in this case, the above-described effects can be obtained without reducing the excavation efficiency of the tip 8B on the second receding surface 12 having a large receding amount.
- the plurality of chips 8B on the face surface 10 are arranged along the circumferential direction, and a plurality of such rows are provided at intervals in the radial direction, for example, an arrow F in FIG. It becomes easy to create the flow of fluid and drilling waste as shown, and these fluid and drilling waste are easily guided into the tip groove 18 along the arrangement of the chips 8B, so that the discharge efficiency is increased.
- channel 18 is extended toward the opposite side (back of the tool rotation direction T) gradually from the front-end blow hole 15 toward the radial direction outer side, there exists the following effect. That is, the tip groove 18 gradually extends toward the rear in the tool rotation direction T from the tip blow hole 15 toward the outer side in the radial direction. Therefore, these fluids and excavated debris easily flow stably from the tip groove 18 into the discharge groove 14.
- the position along the axis O direction of the tip surface of the ring bit 4 is the same as the tip surface of the inner bit 3. It is not limited to.
- FIG. 4 what is shown in FIG. 4 is a modified example of the excavating tool 1 described in the above-described embodiment.
- the axis O of the front end surface of the ring bit 4 with respect to the front end surface of the inner bit 3 is shown.
- a position along the direction is arranged so as to protrude toward the tip side.
- it is arranged so as to protrude to the tip side.
- the ring bit 4 surrounds the entire tip portion of the inner bit 3 as in the above-described embodiment, the intrusion of fluid around the excavation hole is suppressed, and the fluid and excavation debris are ringed. It will be efficiently recovered into the discharge groove 14 located radially inside the bit 4.
- the position along the axis O direction of the front end surface of the ring bit 4 is the same as the front end surface of the inner bit 3 or is disposed so as to protrude toward the front end side”.
- the fact that the bit 4 substantially surrounds the distal end portion of the inner bit 3 indicates that the above-described effects are obtained, and the tip portion of the distal end surface of the inner bit 3 and the ring bit are not necessarily provided. It does not indicate only the relative positional relationship with the foremost part of the tip surface of 4.
- the “tip surface” is a concept including a ridge line portion where two surfaces intersect, for example.
- the ring bit 4 is formed with an annular surface perpendicular to the axis O and two tapered surfaces on the radially inner side and outer side of the annular surface.
- the ridge line on the tip surface of the ring bit 4 with respect to the tip surface of the inner bit 3 is formed.
- the positions along the axis O direction of the portions are the same or are arranged to protrude toward the tip side.
- the position of the tip 8B disposed on the first receding surface 11 in the face O of the inner bit 3 in the direction of the axis O is the tip disposed on the second receding surface 12.
- the tip positions are set to be the same as each other, or the tip of the tip 8B disposed on the first receding surface 11 is retracted to the proximal side from the tip of the tip 8B disposed on the second receding surface 12. It may be.
- first and second receding surfaces 11 and 12 are formed on the face surface 10, either or both of the first and second receding surfaces 11 and 12 may not be formed. . That is, in the above-described embodiment, it has been described that the face surface 10 is retracted stepwise from the gauge surface 9 inward in the radial direction. However, the present invention is not limited to this. The entire surface may be a smooth surface without being retracted. More specifically, as shown in the modification of FIG. 5, the face surface 10 is made smooth without providing the first and second receding surfaces 11 and 12 on the face surface 10, and the face surface 10 is ballistic.
- the protrusion amount H2 may be ensured by implanting a chip 8C (8) formed of a shape (bullet shape) button chip.
- the tip 8C has a longer tip (length along the tip central axis direction) than the above-described chips 8A and 8B, so that the tip 8C protrudes from the face surface 10. It is easy to secure the amount H2.
- the mounting posture of the chip 8C can be stabilized without providing the chip support portion on the face surface 10, the mounting strength is ensured, and the face surface 10 can be easily manufactured.
- the communication hole 17 of the supply hole 13 is branched into a plurality of outer peripheral blow holes 16 at the front end portion of the inner bit 3, and the front end blow holes 15 are further branched from the outer peripheral blow holes 16, respectively. It is not limited to this. That is, the supply hole 13 only needs to include a front end blow hole 15 that opens to the front end surface of the inner bit 3 and an outer peripheral blow hole 16 that opens to the outer peripheral surface of the inner bit 3. May be branched directly from the communication hole 17.
- the tip blow hole 15A extends so as to be parallel to the axis O
- the present invention is not limited to this. That is, the tip blow hole 15 ⁇ / b> A may extend so as to gradually approach the axis O toward the tip side.
- the fluid ejected from the tip blow hole 15A can be prevented from escaping from the tip surface of the inner bit 3 toward the outer peripheral side, thereby effectively preventing the ground around the excavation hole from loosening. Can be suppressed.
- the fluid easily spreads over the entire front end surface of the inner bit 3 and excavation efficiency is improved.
- the outer circumferential groove 19 is inclined and extended toward the proximal end side gradually toward the tool rotation direction T (frontward) from the outer circumferential blow hole 16 toward the discharge groove 14, but the present invention is not limited thereto. Is not to be done.
- the outer peripheral groove 19 may be inclined and extended toward the proximal end side toward the rear of the tool rotation direction T from the outer peripheral blow hole 16 toward the discharge groove 14. That is, in FIG. 3, the outer peripheral groove 19 is located behind the discharge groove 14 in the tool rotation direction T, but instead, the outer peripheral groove 19 is in the tool rotation direction T with respect to the discharge groove 14. It may be arranged in front and communicate with the discharge groove 14. Or the outer peripheral groove
- fluid ejected from the supply hole of the inner bit and excavation waste generated by excavation can be efficiently collected in the discharge groove of the inner bit, and directed toward the tool proximal side through the discharge groove. It is possible to discharge stably, whereby the excavation work can be carried out with high efficiency and stably, and the influence on the ground around the excavation hole can be suppressed. Therefore, it has industrial applicability.
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Abstract
Description
本願は、2013年3月14日に日本で出願された特願2013-052244号に基づき優先権を主張し、それらの内容をここに援用する。
そして、インナービット102に対して軸線O方向の先端側(図6における下側)へ向けた推力及び打撃力、並びに軸線O回りの回転力が与えられることにより、インナービット102及びこれに係合するリングビット103によって地盤が掘削され掘削孔が形成されつつ、これと同時に該掘削孔内にケーシングパイプ101が挿入されて(引き込まれて)ゆく。
そして掘削の際には、供給孔104を通してエア等の流体(噴出媒体)がインナービット102の先端面及びリングビット103の先端面に噴出される一方、排出溝105を通して流体及び掘削により生じた掘削屑(スライム)が工具基端側へ向けて排出されるようになっている。
すなわち、掘削工具100により地盤を掘削して生じる掘削屑は、不図示の掘削装置から供給される流体によって排出されるが、軟弱な地質の地盤では、流体が掘削孔周辺の地盤内部へ浸入してしまい掘削屑が排出できなくなり、掘削屑が掘削孔内に堆積するなどして掘削が安定して行えないことがある。また、場合によっては掘削孔周辺の地盤内部へ浸入した流体が地盤を緩めてしまい、付近の構造物の基礎に影響を及ぼすことがある。
すなわち、本発明の掘削工具の一態様は、地盤を掘削して掘削孔を形成する掘削工具であって、円筒状をなすケーシングパイプと、前記ケーシングパイプ内にその軸線方向に沿って挿通されるとともに、前記軸線方向に沿う先端部が該ケーシングパイプの先端から突出されたインナービットと、円環状をなし、前記ケーシングパイプの先端部に該ケーシングパイプに対して前記軸線回りに回転自在に配設され、前記インナービットの先端部を囲繞するとともに、該インナービットに対しては前記軸線回りに及び前記軸線方向の先端側から係合可能とされたリングビットと、を備え、前記インナービットは、前記インナービット内を通り該インナービットの先端部に開口する供給孔と、前記インナービットの外周面に形成されて前記軸線方向に延びる排出溝と、を備え、前記供給孔は、前記インナービットの先端部の先端面に開口する先端ブロー孔と、前記インナービットの先端部の外周面に開口する外周ブロー孔と、を備え、前記インナービットの外周面には、前記外周ブロー孔と前記排出溝とを連通する外周溝が形成され、前記外周溝は、前記リングビットにより径方向外側から覆われているとともに、前記外周ブロー孔から前記排出溝に向けて、前記軸線回りに向かうに従い漸次前記軸線方向の基端側に向かって延びている。
また外周溝が、その径方向外側からリングビットに覆われていることで、外周ブロー孔からこの外周溝内に噴出した流体が、地盤内部へ浸入するようなことが防止されつつ排出溝内へ向けて効率よく送られて、該排出溝内を流れる流体及び掘削屑の回収効率が向上する。
また、先端ブロー孔がインナービットの先端面(例えば先端溝内)に開口する部分から、該インナービットの外周面の排出溝までの径方向に沿う距離を大きく確保しやすくなり、掘削屑を回収する効率が向上する。
この場合、外周溝内の流体は、インナービットの回転に伴って、外周ブロー孔から排出溝へ向かって軸線方向の基端側へ向けた流れを形成しつつ該排出溝内に流入されることから、排出溝内の流体及び掘削屑が、これに伴って工具基端側へ向けて一層流れやすくなる。
この場合、後退量の大きい第2後退面におけるチップの掘削効率を低減させるようなことがない。
本実施形態の掘削工具1は、二重管式ビットを有するものであり、不図示の掘削装置に連結されて地盤を掘削し掘削孔を形成しつつ、これと同時に該掘削孔内にケーシングパイプ2を挿入してゆくものである。
図1に示されるように、この掘削工具1は、ケーシングパイプ2と、インナービット3と、リングビット4と、を備えている。ケーシングパイプ2は、円筒状をなしている。インナービット3は、ケーシングパイプ2内にその軸線O方向に沿って挿通されるとともに、該インナービット3の軸線O方向に沿う先端部は、ケーシングパイプ2の先端から突出している。リングビット4は、円環状をなし、ケーシングパイプ2の先端部に該ケーシングパイプ2に対して軸線O回りに回転自在に配設され、インナービット3の先端部を囲繞するとともに、該インナービット3に対しては軸線O回りに及び軸線O方向の先端側から係合可能とされている。
ケーシングトップ6は、その基端側部分をパイプ本体5における最先端部の径方向内側に嵌挿した状態で、先端側部分の基端を該パイプ本体5先端に突き合わせるようにして溶接されることにより、パイプ本体5に取り付けられている。
またリングビット4の内周面には、軸線Oに平行に延びる複数条の凹溝4eが、周方向に間隔をあけて、かつリングビット4先端における径方向内側の前記テーパ面に植設されたチップ7と干渉しないように形成されている。これらの凹溝4eは、掘削時の工具回転方向Tの後方部分が図1の右側に示す凹溝4eのようにリングビット4先端の径方向内側の前記テーパ面からテーパ面4cに亘って貫通して形成される一方、工具回転方向Tの前方部分は、その基端側に図1の左側に示す凹溝4eのような壁部4fが形成されてテーパ面4cには開口しないようにされている。
具体的に、本実施形態では、図1及び図5において、インナービット3の先端面のうち、最も先端側に位置する部分(最先部分)である後述するフェイス面10の外周縁(尚、図1においてはフェイス面10の第1後退面11とゲージ面9との間に位置する円環状面)に対して、リングビット4の先端面のうち、前記最先部分である前記円環状面の軸線O方向に沿う位置が、同一である。
従って、凸条3cを凹溝4eに収容してリングビット4の径方向内側に挿入されたインナービット3は、テーパ面3aをテーパ面4cに当接させることによりリングビット4に対して軸線O方向の基端側から係合可能(先端側へ向けて抜け止め状態に係合可能)、かつ軸線O回りに回転させたときには凸条3cが凹溝4eの周方向を向くいずれかの側壁に当接することで、この軸線O回りにも係合可能とされてリングビット4と一体に回転させられる。
図1に示される例では、フェイス面10のうち最も先端側に位置する外周縁に対して第1後退面11が基端側へ後退する後退量よりも、第1後退面11に対して第2後退面12が基端側へ後退する後退量が大きく設定されている。
そして、インナービット3の先端面に突設された複数のチップ8のうち、ゲージ面9に配設されたチップ8Aの該ゲージ面9からの突出量H1に対して、フェイス面10に配設されたチップ8Bの該フェイス面10からの突出量H2が大きくされている。
尚、図1に示される例では、チップ8Bの先端の軸線O方向の位置が、チップ8Aの先端の軸線O方向の位置よりも先端側に配置されている。
また、図3において、フェイス面10には、チップ8Bの外周面を支持するように環状をなすチップ支持部が複数設けられており、これらのチップ支持部は、各チップ8Bの外周面に沿うようにフェイス面10から突設されている。
従って、フェイス面10のうち第1後退面11に配設されたチップ8Bの先端における軸線O方向の位置は、第2後退面12に配設されたチップ8Bの先端における軸線O方向の位置よりも先端側に配置されている。
また供給孔13は、インナービット3の先端部における先端面に開口する先端ブロー孔15と、インナービット3の先端部における外周面に開口する外周ブロー孔16と、これら先端ブロー孔15及び外周ブロー孔16の基端側に連通してこれらの孔15、16に向けて流体を流通させる連通孔17と、を備えている。
供給孔13は、連通孔17、外周ブロー孔16、先端ブロー孔15の順で、内径が小さくされている。
図1及び図2において、先端ブロー孔15は、インナービット3の先端面に複数開口しており、これら先端ブロー孔15のうち少なくとも1つ以上は、軸線Oに平行となるように延在する先端ブロー孔15Aとされている。本実施形態では、インナービット3の先端部に形成された複数の先端ブロー孔15のうち、前記先端ブロー孔15Aが半数以上となっており、具体的には、4つの先端ブロー孔15のうち、2つが前記先端ブロー孔15Aである。また、これら先端ブロー孔15には、前記先端ブロー孔15A以外のものとして、先端側に向かうに従い漸次工具回転方向Tの後方に向かって延びる先端ブロー孔15Bが含まれる。尚、先端ブロー孔15Bは、先端側に向かうに従い漸次僅かに軸線Oから離間するように延在している。
また、先端ブロー孔15は、インナービット3の先端面に形成されて排出溝14に連通する先端溝18内に開口され、外周ブロー孔16は、インナービット3の外周面に形成されて排出溝14に連通する外周溝19内に開口されている。
また外周溝19が、その径方向外側からリングビット4に覆われていることで、外周ブロー孔16からこの外周溝19内に噴出した流体が、地盤内部へ浸入するようなことが防止されつつ排出溝14内へ向けて効率よく送られて、該排出溝14内を流れる流体及び掘削屑の回収効率が向上する。
すなわち、先端ブロー孔15から噴出された流体が、インナービット3の先端面周辺の掘削屑とともに、先端溝18内を通して排出溝14内に効率よく案内されて、これら流体及び掘削屑を回収する効率が高められる。また、外周ブロー孔16が外周溝19内に直接開口していることで、前述した作用効果がより顕著となる。
また、先端ブロー孔15Aがインナービット3の先端面(本実施形態では先端溝18内)に開口する部分から、該インナービット3の外周面の排出溝14までの径方向に沿う距離を大きく確保しやすくなり、先端溝18内を通して掘削屑を回収する効率が向上する。
尚、本実施形態では前記先端ブロー孔15Aが、すべての先端ブロー孔15のうち半数以上とされているので、前述した効果がより顕著に得られやすくなっている。
尚、本実施形態では、フェイス面10に環状をなすチップ支持部が突設されて各チップ8Bの外周面を支持しており、これにより、フェイス面10に対するチップ8Bの装着姿勢が安定させられ取り付け強度も高められつつ、前記突出量H2を確保することができるようになっている。また、このようにフェイス面10のチップ8Bの突出量H2を確保しつつ、チップ8A、8Bとして同一部材を用いることが可能であり、部品の種類を削減できる。
すなわち、先端溝18は、先端ブロー孔15から径方向外側に向かうに従い漸次工具回転方向Tの後方に向かって延びているので、この先端溝18内を流れる流体及び掘削屑の流通が工具の回転によって阻害されにくくなっており、これらの流体及び掘削屑が、先端溝18内から排出溝14内へと安定して流れやすくなる。
ここで、図4に示されるものは前述の実施形態で説明した掘削工具1の変形例であり、この変形例では、インナービット3の先端面に対して、リングビット4の先端面の軸線O方向に沿う位置が先端側へ突出して配置されている。具体的に、インナービット3の先端面のうち最先部分であるフェイス面10の外周縁に対して、リングビット4の先端面のうち最先部分である円環状面の軸線O方向に沿う位置が、先端側へ突出して配置されている。この変形例においても、前述した実施形態と同様にリングビット4がインナービット3の先端部全体を囲繞することから、掘削孔周辺への流体の浸入が抑制され、かつ、流体及び掘削屑がリングビット4の径方向内側に位置する排出溝14内へと効率よく回収されることになる。
尚、本明細書でいう「インナービット3の先端面に対して、リングビット4の先端面の軸線O方向に沿う位置が同一、又は先端側へ向けて突出して配置される」とは、リングビット4がインナービット3の先端部を実質的に囲繞していることにより、前述の効果が得られる状態にあることを表しており、必ずしもインナービット3の先端面における最先部分と、リングビット4の先端面における最先部分との相対的な位置関係のみを指すわけではない。
また前記「先端面」とは、例えば2つの面同士が交差する稜線部分をも含む概念である。すなわち、前述の実施形態では、リングビット4の先端面に、軸線Oに垂直な円環状面と、該円環状面の径方向内側及び外側に2つのテーパ面とが形成されているとしたが、前記円環状面が形成されずに2つのテーパ面同士が交差してなる稜線部分が形成されている場合には、インナービット3の先端面に対して、リングビット4の先端面における前記稜線部分の軸線O方向に沿う位置が同一、又は先端側へ向けて突出して配置されることになる。
また、フェイス面10に第1、第2後退面11、12が形成されているとしたが、これら第1、第2後退面11、12のいずれか又は両方が形成されていなくても構わない。すなわち、前述の実施形態では、フェイス面10がゲージ面9から径方向内側に向かって段階的に後退させられていると説明したが、これに限定されるものではなく、例えば一段のみ後退させられていたり、後退させられることなく全体が平滑な面とされていても構わない。
より詳しくは、図5の変形例に示されるように、フェイス面10に第1、第2後退面11、12を設けずに、該フェイス面10を平滑な面とし、このフェイス面10にバリスチック形(砲弾形)ボタンチップからなるチップ8C(8)を植設することで、突出量H2を確保することとしてもよい。すなわち、チップ8Cは、前述したチップ8A、8Bに比べてその先端部の長さ(チップ中心軸方向に沿う長さ)が長くなっていることから、該チップ8Cがフェイス面10から突出する突出量H2を確保しやすい。またこの構成によれば、フェイス面10にチップ支持部を設けることなくチップ8Cの装着姿勢を安定させることができ取り付け強度も確保されて、フェイス面10の作製が容易である。
尚、前述の実施形態では、複数の先端ブロー孔15のうち、半数以上が前記先端ブロー孔15Aであると説明したが、該先端ブロー孔15Aは、少なくとも1つ以上設けられていれば前述の効果を奏する。ただし、前述した実施形態のように、先端ブロー孔15Aが全体の半数以上設けられた場合には、その効果がより顕著となることから好ましい。さらに、すべての先端ブロー孔15が、前記先端ブロー孔15Aとされることがより望ましい。
従って、産業上の利用可能性を有する。
Claims (9)
- 地盤を掘削して掘削孔を形成する掘削工具であって、
円筒状をなすケーシングパイプと、
前記ケーシングパイプ内にその軸線方向に沿って挿通されるとともに、前記軸線方向に沿う先端部が該ケーシングパイプの先端から突出されたインナービットと、
円環状をなし、前記ケーシングパイプの先端部に該ケーシングパイプに対して前記軸線回りに回転自在に配設され、前記インナービットの先端部を囲繞するとともに、該インナービットに対しては前記軸線回りに及び前記軸線方向の先端側から係合可能とされたリングビットと、を備え、
前記インナービットは、
前記インナービット内を通り該インナービットの先端部に開口する供給孔と、
前記インナービットの外周面に形成されて前記軸線方向に延びる排出溝と、を備え、
前記供給孔は、
前記インナービットの先端部の先端面に開口する先端ブロー孔と、
前記インナービットの先端部の外周面に開口する外周ブロー孔と、を備え、
前記インナービットの外周面には、前記外周ブロー孔と前記排出溝とを連通する外周溝が形成され、
前記外周溝は、前記リングビットにより径方向外側から覆われているとともに、前記外周ブロー孔から前記排出溝に向けて、前記軸線回りに向かうに従い漸次前記軸線方向の基端側に向かって延びている掘削工具。 - 請求項1に記載の掘削工具であって、
前記先端ブロー孔は、前記インナービットの先端面に形成されて前記排出溝に連通する先端溝内に開口され、
前記外周ブロー孔は、前記外周溝内に開口されている掘削工具。 - 請求項1又は2に記載の掘削工具であって、
前記先端ブロー孔は、前記インナービットの先端面に複数開口しており、これら先端ブロー孔のうち少なくとも1つ以上は、前記軸線に平行となるように延在し、又は先端側へ向かうに従い漸次前記軸線に接近するように延在している掘削工具。 - 請求項1~3のいずれか一項に記載の掘削工具であって、
前記インナービットの先端面に対して、前記リングビットの先端面の前記軸線方向に沿う位置が同一、又は先端側へ向けて突出して配置される掘削工具。 - 請求項1~4のいずれか一項に記載の掘削工具であって、
前記インナービットの先端面には、該先端面から突出するチップが複数配設されており、
前記インナービットの先端面における外周縁部は、当該掘削工具の縦断面視で径方向外側に向かうに従い漸次前記軸線方向の基端側へ向かって延びるゲージ面とされており、
前記インナービットの先端面における前記ゲージ面の径方向内側は、フェイス面とされており、
複数の前記チップのうち、前記ゲージ面に配設されたチップの該ゲージ面からの突出量に対して、前記フェイス面に配設されたチップの該フェイス面からの突出量が大きくされている掘削工具。 - 請求項2~5のいずれか一項に記載の掘削工具であって、
前記先端溝は、前記先端ブロー孔から径方向外側へ向かうに従い漸次工具回転方向とは反対側に向かって延びている掘削工具。 - 請求項1~6のいずれか一項に記載の掘削工具であって、
前記外周溝は、前記インナービットの回転方向に向かうに従い漸次前記軸線方向の基端側に向かって延びている掘削工具。 - 請求項5~7のいずれか一項に記載の掘削工具であって、
前記フェイス面は、前記軸線方向の基端側へ後退した第1後退面と、該第1後退面よりも前記軸線方向の基端側へ後退した第2後退面とを有し、
複数の前記チップのうち、前記第1後退面に配設されたチップの前記第1後退面からの突出量と、前記第2後退面に配設されたチップの前記第2後退面からの突出量とが同一である掘削工具。 - 請求項5~7のいずれか一項に記載の掘削工具であって、
前記フェイス面は、前記軸線方向の基端側へ後退した第1後退面と、該第1後退面よりも前記軸線方向の基端側へ後退した第2後退面とを有し、
複数の前記チップのうち、前記第1後退面に配設されたチップの先端における前記軸線方向の位置と、前記第2後退面に配設されたチップの先端における前記軸線方向の位置とが同一である掘削工具。
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