JP6759726B2

JP6759726B2 - Drilling tool

Info

Publication number: JP6759726B2
Application number: JP2016112040A
Authority: JP
Inventors: 中村　和由; 和由中村; 泰隆富田
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2016-06-03
Filing date: 2016-06-03
Publication date: 2020-09-23
Anticipated expiration: 2036-06-03
Also published as: JP2017218744A

Description

本発明は、先端に掘削部が設けられた工具本体と、この工具本体の先端部外周に配設されるケーシングパイプとを備え、工具本体の軸線方向先端側に向けて工具本体に与えられる打撃力および推力と軸線回りの回転力とにより、上記掘削部によって掘削孔を形成するとともに、この掘削孔に上記ケーシングパイプを挿入してゆく掘削工具に関するものである。 The present invention includes a tool body provided with an excavation portion at the tip and a casing pipe arranged on the outer periphery of the tip portion of the tool body, and a blow applied to the tool body toward the tip side in the axial direction of the tool body. The present invention relates to an excavation tool in which an excavation hole is formed by the excavation portion by a force and a thrust force and a rotational force around an axis, and the casing pipe is inserted into the excavation hole.

このような掘削工具として、例えば特許文献１には、掘削装置に接続される掘削ロッドの先端に連結された工具本体の先端部に、工具本体の軸線から偏心した位置に回転軸を有するビットヘッドが掘削部として取り付けられるとともに、工具本体の先端部の後端側は外周側に突出する段部が形成され、またケーシングパイプの先端には、ケーシングパイプの内径よりも小さい内径のケーシングトップが取り付けられて、ケーシングパイプの後端側から挿入された工具本体の上記段部が、このケーシングトップの後端面に当接可能とされた、いわゆる拡径ビットが記載されている。 As such an excavation tool, for example, in Patent Document 1, a bit head having a rotation axis at a position eccentric from the axis of the tool body at the tip of the tool body connected to the tip of the excavation rod connected to the excavation device. Is attached as an excavation part, and a step portion is formed on the rear end side of the tip end portion of the tool body so as to project to the outer peripheral side, and a casing top having an inner diameter smaller than the inner diameter of the casing pipe is attached to the tip end of the casing pipe. A so-called diameter-expanding bit is described in which the step portion of the tool body inserted from the rear end side of the casing pipe can be brought into contact with the rear end surface of the casing top.

このような掘削工具では、こうして段部をケーシングトップの後端面に当接させた状態で、工具本体の上記段部よりも先端側の部分やビットヘッドはケーシングトップの先端から突出し、工具本体を軸線回りに掘削時の工具回転方向に回転させつつビットヘッドを地盤に押し付けることにより、回転の反力によってビットヘッドが上記回転軸回りに工具回転方向とは反対側に回転して拡径した状態で位置決めされる。そこで、工具本体に軸線方向先端側への打撃力と推力を与えることにより、ビットヘッドによって掘削孔が形成されるとともに、段部と当接したケーシングトップおよびケーシングパイプが掘削孔に挿入されてゆく。 In such an excavation tool, with the step portion in contact with the rear end surface of the casing top, the portion of the tool body on the tip side of the step portion and the bit head protrude from the tip of the casing top, and the tool body is pressed. By pressing the bit head against the ground while rotating it around the axis in the tool rotation direction during excavation, the bit head rotates around the rotation axis in the direction opposite to the tool rotation direction due to the reaction force of the rotation, and the diameter is expanded. Positioned with. Therefore, by applying a striking force and a thrust to the tip side in the axial direction to the tool body, an excavation hole is formed by the bit head, and the casing top and the casing pipe in contact with the step portion are inserted into the excavation hole. ..

また、所定の深さまで掘削孔が形成されてケーシングパイプが挿入された後は、工具本体を掘削時の上記工具回転方向とは反対側に回転させることにより、やはり回転の反力によってビットヘッドが上記回転軸回りに工具回転方向Ｔに回転して縮径し、ケーシングトップの内径よりも小さな外径となる。そこで、掘削ロッドを後退させて工具本体を引き抜くことにより、ケーシングパイプを掘削孔に残したまま工具本体およびビットヘッドを回収することができる。なお、ビットヘッドは、工具本体に挿入された係止ピンによって回転自在に係止され、係止ピンはやはり工具本体に取り付けられる固定部材によって抜け止めされている。 Further, after the excavation hole is formed to a predetermined depth and the casing pipe is inserted, the tool body is rotated in the direction opposite to the tool rotation direction at the time of excavation, so that the bit head is also generated by the reaction force of the rotation. The diameter is reduced by rotating around the rotation axis in the tool rotation direction T, and the outer diameter becomes smaller than the inner diameter of the casing top. Therefore, by retracting the excavation rod and pulling out the tool body, the tool body and the bit head can be recovered while leaving the casing pipe in the excavation hole. The bit head is rotatably locked by a locking pin inserted into the tool body, and the locking pin is also prevented from coming off by a fixing member attached to the tool body.

特許第４９５７４４０号公報Japanese Patent No. 4957440

ここで、工具本体の上記段部の外径は、ケーシングパイプの内径よりも小さくなければ工具本体をケーシングパイプ内に挿通させることができず、またケーシングトップの外径よりも大きくなければ段部をケーシングトップの後端面に当接させて打撃力や推力を伝達することができない。また、この段部よりも先端側の工具本体の外径は、ケーシングトップの内径よりも小さくなければ、段部よりも先端側をケーシングトップ内に挿通して掘削部をケーシングトップ先端に突出させることができない。 Here, the outer diameter of the step portion of the tool body must be smaller than the inner diameter of the casing pipe to allow the tool body to be inserted into the casing pipe, and the step portion must be larger than the outer diameter of the casing top. Cannot transmit striking force or thrust by contacting the rear end surface of the casing top. Further, if the outer diameter of the tool body on the tip side of the step portion is not smaller than the inner diameter of the casing top, the tip side of the step portion is inserted into the casing top to project the excavated portion to the tip of the casing top. Can't.

しかしながら、上述のように掘削孔に残されるケーシングパイプの外径は、地盤に形成すべき掘削孔の内径によって様々である。そして、ケーシングパイプやケーシングトップの肉厚を必要以上に厚くしたり薄くしたりすることもできないので、これらケーシングパイプやケーシングトップの内径も、掘削孔の内径に応じて様々な大きさとなる。 However, as described above, the outer diameter of the casing pipe left in the excavation hole varies depending on the inner diameter of the excavation hole to be formed in the ground. Further, since the wall thickness of the casing pipe and the casing top cannot be made thicker or thinner than necessary, the inner diameters of these casing pipes and the casing top also have various sizes depending on the inner diameter of the excavation hole.

従って、このようなケーシングパイプやケーシングトップの内径に対応するために、掘削工具の工具本体も、ケーシングトップの後端面に当接させられる上記段部の外径や、ケーシングトップ内に挿通される段部よりも先端側の部分の外径が異なるものを用意する必要がある。このため、これらの外径が異なる複数種の工具本体を掘削孔の内径に応じて揃えておかなければならず、工具本体の管理が煩雑となるとともに、工具本体の製造コストも高騰することが避けられない。 Therefore, in order to correspond to the inner diameter of the casing pipe and the casing top, the tool body of the excavation tool is also inserted into the outer diameter of the step portion to be brought into contact with the rear end surface of the casing top and the inside of the casing top. It is necessary to prepare a portion having a different outer diameter on the tip side than the step portion. For this reason, it is necessary to arrange a plurality of types of tool bodies having different outer diameters according to the inner diameter of the excavation hole, which complicates the management of the tool body and increases the manufacturing cost of the tool body. Inevitable.

本発明は、このような背景の下になされたもので、一種の工具本体により、様々な内外径のケーシングパイプやケーシングトップに挿通、当接可能であり、工具本体管理を容易にするとともに工具本体の製造コストも抑えることが可能な掘削工具を提供することを目的としている。 The present invention has been made under such a background, and it is possible to insert and contact casing pipes and casing tops having various inner and outer diameters by a kind of tool body, which facilitates tool body management and tools. The purpose is to provide a drilling tool that can reduce the manufacturing cost of the main body.

上記課題を解決して、このような目的を達成するために、本発明は、軸線回りに回転される円柱状の工具本体の先端に掘削部が設けられるとともに、上記工具本体の先端部の外周にはケーシングパイプが配設され、上記工具本体の先端部の後端側には外周側に突出する第１段部が設けられるとともに、上記ケーシングパイプの先端内周部には内周側に突出する第２段部が設けられ、上記第１段部の先端面と上記第２段部の後端面との間には、上記第１段部の外径より小さく、この第１段部よりも先端側の上記工具本体の外径より大きい内径と、上記第２段部の内径より大きく、この第２段部よりも後端側の上記ケーシングパイプの内径よりは小さな外径とを有する環状部材が介装されており、上記環状部材が予め上記第１段部に当接させられた状態で、上記工具本体が上記ケーシングパイプに挿入可能とされていることを特徴とするものである。 In order to solve the above problems and achieve such an object, in the present invention, an excavation portion is provided at the tip of a cylindrical tool body rotated around an axis, and an outer circumference of the tip portion of the tool body is provided. Is provided with a casing pipe, a first step portion projecting to the outer peripheral side is provided on the rear end side of the tip end portion of the tool body, and the tip inner peripheral portion of the casing pipe projects to the inner peripheral side. The second step portion is provided, and between the front end surface of the first step portion and the rear end surface of the second step portion, the outer diameter of the first step portion is smaller than that of the first step portion. An annular member having an inner diameter larger than the outer diameter of the tool body on the tip side and an outer diameter larger than the inner diameter of the second step portion and smaller than the inner diameter of the casing pipe on the rear end side of the second step portion. Is interposed , and the tool body can be inserted into the casing pipe in a state where the annular member is brought into contact with the first step portion in advance .

このように構成された掘削工具では、工具本体の外周側に突出する第１段部は、ケーシングパイプの先端に設けられた内周側に突出する内径の小さいケーシングトップのような第２段部に、環状部材を介して当接して軸線方向先端側への打撃力と推力を伝達する。従って、たとえ第１段部の外径が第２段部の内径より小さかったとしても、環状部材の外径を、第２段部の内径よりも大きくすることにより、これら打撃力と推力を確実に伝達することができる。 In the excavation tool configured in this way, the first step portion protruding toward the outer peripheral side of the tool body is a second step portion such as a casing top having a small inner diameter protruding toward the inner peripheral side provided at the tip of the casing pipe. In contact with the ring member, the striking force and the thrust to the tip side in the axial direction are transmitted. Therefore, even if the outer diameter of the first step portion is smaller than the inner diameter of the second step portion, by making the outer diameter of the annular member larger than the inner diameter of the second step portion, these striking forces and thrusts are ensured. Can be communicated to.

そして、この環状部材を、ケーシングパイプやケーシングトップの内径に合わせた外径のものに交換することにより、一種の工具本体によって様々な内外径のケーシングパイプやケーシングトップに対応することが可能となる。このため、環状部材よりも構造が複雑となる工具本体の管理を容易とすることができるとともに、製造コストも抑えることが可能となる。 Then, by replacing this annular member with one having an outer diameter that matches the inner diameter of the casing pipe or casing top, it becomes possible to correspond to casing pipes and casing tops having various inner and outer diameters with a kind of tool body. .. Therefore, it is possible to easily manage the tool body, which has a more complicated structure than the annular member, and it is possible to suppress the manufacturing cost.

また、上述のように第１段部の外径が第２段部の内径より小さい場合は勿論、第１段部の外径が第２段部の内径より大きくても、ケーシングパイプの内径よりは著しく小さい場合などには、このケーシングパイプの内径に合わせて、環状部材の外径を、工具本体における上記第１段部の外径よりも大きくすることにより、ケーシングトップの後端面への打撃力や推力の伝達面積を大きくして効率的にケーシングパイプを掘削孔に挿入してゆくことができる。また、こうして環状部材の外径を大きくすることにより、環状部材を打撃する第１段部への応力を分散して第１段部の破損等も防ぐことができる。 Further, as described above, not only when the outer diameter of the first stage portion is smaller than the inner diameter of the second stage portion, but also when the outer diameter of the first stage portion is larger than the inner diameter of the second stage portion, it is larger than the inner diameter of the casing pipe. When is extremely small, the outer diameter of the annular member is made larger than the outer diameter of the first step portion of the tool body in accordance with the inner diameter of the casing pipe to hit the rear end surface of the casing top. It is possible to increase the transmission area of force and thrust and efficiently insert the casing pipe into the drilling hole. Further, by increasing the outer diameter of the annular member in this way, it is possible to disperse the stress on the first step portion that strikes the annular member and prevent the first step portion from being damaged.

さらに、このように構成される掘削工具においては、上記環状部材を、工具本体の硬度以下の硬度の材質によって形成することにより、工具本体に与えられる打撃力や推力、回転力による工具本体の摩耗を、環状部材の摩耗に置き換えて抑制することができる。上述のように工具本体は環状部材よりも構造が複雑であるので、そのような工具本体の摩耗を抑制することにより、工具寿命の延長を図って一層低コストで安定した掘削作業を行うことが可能となる。 Further, in the excavation tool configured as described above, by forming the annular member with a material having a hardness equal to or lower than the hardness of the tool body, the tool body is worn due to the striking force, thrust force, and rotational force applied to the tool body. Can be suppressed by replacing the wear of the annular member. As described above, the structure of the tool body is more complicated than that of the annular member. Therefore, by suppressing the wear of the tool body, it is possible to extend the tool life and perform stable excavation work at a lower cost. It will be possible.

さらにまた、上記環状部材に、上記第１段部よりも先端側の上記工具本体の外周面と上記第２段部の内周面との間に配設される円筒部を備えことにより、この円筒部の内外周面を第１段部よりも先端側の工具本体の外周面と第２段部の内周面に摺接させて工具本体を支持することができる。従って、特に第１段部よりも先端側の工具本体の外径が第２段部の内径よりも著しく小さい場合でも、掘削時の工具本体の振れを抑えて直進度の高い掘削孔を形成することが可能となる。 Furthermore, the annular member is provided with a cylindrical portion disposed between the outer peripheral surface of the tool body on the tip side of the first step portion and the inner peripheral surface of the second step portion. The inner and outer peripheral surfaces of the cylindrical portion can be slidably contacted with the outer peripheral surface of the tool body on the tip side of the first step portion and the inner peripheral surface of the second step portion to support the tool body. Therefore, even when the outer diameter of the tool body on the tip side of the first step portion is significantly smaller than the inner diameter of the second step portion, the runout of the tool body during excavation is suppressed to form an excavation hole having a high degree of straightness. It becomes possible.

以上説明したように、本発明によれば、一種の工具本体によって様々な内外径のケーシングパイプやケーシングトップに対応することが可能となって内径の異なる掘削孔にケーシングパイプを挿入することができ、工具本体の管理を容易とするとともに、工具本体の製造コストの抑制を図ることが可能となる。 As described above, according to the present invention, it is possible to correspond to casing pipes and casing tops having various inner and outer diameters by a kind of tool body, and it is possible to insert the casing pipes into drilling holes having different inner diameters. It is possible to facilitate the management of the tool body and reduce the manufacturing cost of the tool body.

本発明の一実施形態を示す工具本体先端部の側断面図である。It is a side sectional view of the tip part of the tool body which shows one Embodiment of this invention. 図１に示す実施形態において掘削部（ビットヘッド）が拡径した状態を示す正面図である（ただし、ケーシングパイプとケーシングトップは図示が略されている。）。It is a front view which shows the state which the excavation part (bit head) has expanded the diameter in the embodiment shown in FIG. 1 (however, the casing pipe and the casing top are not shown). 図１に示す実施形態において取付部材（ビットヘッド）が縮径した状態を示す正面図である（ただし、ケーシングパイプとケーシングトップは図示が略されている。）。It is a front view which shows the state which the diameter of the mounting member (bit head) was reduced in the embodiment shown in FIG. 1 (however, the casing pipe and the casing top are not shown). 図１に示す実施形態の取付部材（ビットヘッド）の（ａ）正面図、（ｂ）側面図である。It is (a) front view and (b) side view of the mounting member (bit head) of the embodiment shown in FIG. 図１に示す実施形態の工具本体および取付部材の図１における平面Ａに沿った断面図である。FIG. 5 is a cross-sectional view taken along the plane A in FIG. 1 of the tool body and the mounting member of the embodiment shown in FIG. 図１に示す実施形態の工具本体を、図１に示した実施形態よりも内外径の大きなケーシングパイプおよびケーシングトップに挿入した状態を示す部分側断面図である。It is a partial side sectional view which shows the state in which the tool body of the embodiment shown in FIG. 1 is inserted into a casing pipe and a casing top having a larger inner and outer diameters than those of the embodiment shown in FIG.

図１ないし図６は、本発明の一実施形態を示すものであって、この実施形態は、本発明を上述したような拡径ビットに適用した場合のものである。本実施形態において、工具本体１は、このような拡径ビットのデバイスであって、軸線Ｏを中心とした外形略多段の円柱状をなしており、その後端部（図１および図６における右側部分）は最も小径のシャンク部１Ａとされている。 1 to 6 show an embodiment of the present invention, and this embodiment is a case where the present invention is applied to the enlarged diameter bit as described above. In the present embodiment, the tool body 1 is such a device with an enlarged diameter bit, and has a columnar shape having substantially multiple stages in outer shape centered on the axis O, and the rear end portion (right side in FIGS. 1 and 6). The portion) is the shank portion 1A having the smallest diameter.

このような掘削工具は、上記シャンク部１Ａに連結される図示されないダウンザホールハンマによって工具本体１に軸線Ｏ方向先端側（図１および図６における左側）への打撃力が与えられるとともに、このダウンザホールハンマに掘削ロッドを介して連結される掘削装置から工具回転方向Ｔへの軸線Ｏ回りの回転力と軸線Ｏ方向先端側への推力が与えられ、地盤（岩盤）等を掘削して掘削孔を形成する。 In such an excavation tool, a down-the-hole hammer (not shown) connected to the shank portion 1A applies a striking force to the tip side of the tool body 1 in the O-direction (left side in FIGS. 1 and 6), and the down-the-hole hammer. A rotational force around the axis O in the tool rotation direction T and a thrust toward the tip side in the axis O direction are given from the excavator connected via the excavation rod to excavate the ground (rock) and form an excavation hole. To do.

工具本体１のシャンク部１Ａよりも先端側の先端部には、その後端側に工具本体１において最も大きな外径の外周側に突出する環状の第１段部１Ｂが形成されるとともに、この第１段部１Ｂよりも先端側には、第１段部１Ｂより一段小径とされた一定の外径を有する円柱部１Ｃが形成されている。また、工具本体１の先端部の軸線Ｏ方向の長さは、円柱部１Ｃが最も長く、これよりも第１段部１Ｂは短い。 At the tip of the tool body 1 on the tip side of the shank portion 1A, an annular first step portion 1B protruding toward the outer peripheral side of the largest outer diameter of the tool body 1 is formed on the rear end side, and this first step portion 1B is formed. A columnar portion 1C having a constant outer diameter, which is one step smaller than that of the first step portion 1B, is formed on the tip side of the first step portion 1B. Further, the length of the tip portion of the tool body 1 in the axis O direction is the longest in the cylindrical portion 1C and shorter in the first step portion 1B.

さらに、工具本体１の外周には、第１段部１Ｂの外径よりも大きな内径を有する軸線Ｏを中心とした円筒状のケーシングパイプＰが配設されるとともに、このケーシングパイプＰの先端には、ケーシングパイプＰの内径よりも小さく、円柱部１Ｃよりは大きな内径を有する多段円筒状のケーシングトップＱが、その後端部をケーシングパイプＰの先端部内周に嵌め入れた状態で接合されて取り付けられている。このケーシングトップＱのケーシングパイプＰ内周側に突出した部分が、本実施形態におけるケーシングパイプＰの先端内周部の第２段部とされており、図１に示す実施形態では、ケーシングトップＱの内径は第１段部１Ｂの外径よりも小さくされている。 Further, a cylindrical casing pipe P centered on the axis O having an inner diameter larger than the outer diameter of the first step portion 1B is disposed on the outer periphery of the tool body 1, and at the tip of the casing pipe P. Is attached by joining a multi-stage cylindrical casing top Q having an inner diameter smaller than the inner diameter of the casing pipe P and a larger inner diameter than the cylindrical portion 1C with its rear end fitted into the inner circumference of the tip portion of the casing pipe P. Has been done. The portion of the casing top Q protruding toward the inner peripheral side of the casing pipe P is the second stage portion of the inner peripheral portion of the tip of the casing pipe P in the present embodiment. In the embodiment shown in FIG. 1, the casing top Q The inner diameter of the first step portion 1B is smaller than the outer diameter of the first step portion 1B.

工具本体１の先端面は軸線Ｏに垂直な平坦面とされ、掘削時にはケーシングトップＱの先端よりも先端側に位置するように配設される。また、この先端面から第１段部１Ｂの後端にかけての工具本体１先端部外周には、掘削時に発生する掘削屑を排出するための排出溝１Ｄが、周方向に等間隔に３条形成されている。これらの排出溝１Ｄの外周側を向く底面は、工具本体１の先端面から後端側に向かうに従い軸線Ｏから離間するように傾斜した後、軸線Ｏに平行に延びて第１段部１Ｂの後端に達している。 The tip surface of the tool body 1 is a flat surface perpendicular to the axis O, and is arranged so as to be located on the tip side of the tip of the casing top Q during excavation. In addition, three discharge grooves 1D for discharging excavation debris generated during excavation are formed at equal intervals in the circumferential direction on the outer periphery of the tip of the tool body 1 from the tip surface to the rear end of the first stage portion 1B. Has been done. The bottom surface of these discharge grooves 1D facing the outer peripheral side is inclined so as to be separated from the axis O from the front end surface of the tool body 1 toward the rear end side, and then extends in parallel with the axis O of the first stage portion 1B. It has reached the rear end.

さらに、工具本体１の先端面には、周方向において上記排出溝１Ｄの間に、先端面から後端側に向けて延びる取付孔部２が、やはり周方向に等間隔に３つ形成されており、これらの取付孔部２は、軸線Ｏに平行で軸線Ｏから外周側に偏心した孔部中心線Ｌ１を中心とした一定内径の断面円形に形成されている。なお、工具本体１の後端からは軸線Ｏに沿って掘削時に圧縮空気等を噴出するブロー孔３が形成されており、このブロー孔３は工具本体１の先端部で分岐して、先端面の中央と、排出溝１Ｄの傾斜した底面と、円柱部１Ｃの後端側の外周面と、そして上記取付孔部２の底面とに開口している。 Further, on the tip surface of the tool body 1, three mounting holes 2 extending from the tip surface toward the rear end side are formed between the discharge grooves 1D in the circumferential direction at equal intervals in the circumferential direction. These mounting holes 2 are formed in a circular cross section having a constant inner diameter centered on the hole center line L1 which is parallel to the axis O and eccentric from the axis O to the outer peripheral side. A blow hole 3 for ejecting compressed air or the like during excavation is formed from the rear end of the tool body 1 along the axis O, and the blow hole 3 branches at the tip of the tool body 1 and has a tip surface. Open to the center, the inclined bottom surface of the discharge groove 1D, the outer peripheral surface on the rear end side of the cylindrical portion 1C, and the bottom surface of the mounting hole portion 2.

本実施形態では、このような取付孔部２に取付軸部４が挿入されて、上記拡径ビットのビットヘッド５が工具本体１に着脱可能に装着されており、このビットヘッド５の先端部には掘削部６が一体に形成されている。この掘削部６の先端面と外周面には、鋼材等からなる工具本体１やビットヘッド５よりも高硬度の超硬合金等からなる掘削チップ７が埋め込まれて多数配設されており、これらの掘削チップ７によって地盤が破砕されて掘削が行われる。 In the present embodiment, the mounting shaft portion 4 is inserted into such a mounting hole portion 2, and the bit head 5 of the enlarged diameter bit is detachably mounted on the tool body 1, and the tip portion of the bit head 5 is detachably mounted. The excavation portion 6 is integrally formed in the area. A large number of excavation tips 7 made of a cemented carbide or the like having a hardness higher than that of the bit head 5 and the tool body 1 made of a steel material are embedded in the tip surface and the outer peripheral surface of the excavation portion 6. The excavation tip 7 of the above crushes the ground and excavates.

取付軸部４は、軸部中心線Ｌ２を中心とした円柱軸状であって、その外径が取付孔部２の内径よりも僅かに小さくなるように形成されるとともに、その長さは取付孔部２の深さと略等しくなるように形成されている。従って、この取付軸部４は取付孔部２に摺動可能に嵌め込まれて軸部中心線Ｌ２が孔部中心線Ｌ１と同軸に挿入され、その後端面が取付孔部２の底面に当接したところで、掘削部６の後端面が工具本体１の先端面に当接することになり、こうして取付軸部４を取付孔部２に挿入した挿入状態でビットヘッド５は孔部中心線Ｌ１回りに回転自在とされる。 The mounting shaft portion 4 has a cylindrical shaft shape centered on the shaft portion center line L2, and is formed so that its outer diameter is slightly smaller than the inner diameter of the mounting hole portion 2, and its length is mounted. It is formed so as to be substantially equal to the depth of the hole 2. Therefore, the mounting shaft portion 4 is slidably fitted into the mounting hole portion 2, the shaft portion center line L2 is inserted coaxially with the hole center line L1, and the rear end surface abuts on the bottom surface of the mounting hole portion 2. By the way, the rear end surface of the excavation portion 6 comes into contact with the tip end surface of the tool body 1, and the bit head 5 rotates around the hole center line L1 in the inserted state in which the mounting shaft portion 4 is inserted into the mounting hole portion 2. Be free.

掘削部６は、図２、図３および図４（ａ）に示すように先端視において概略扇形をなしており、すなわち互いに１２０°の鈍角で交差する２つの側面と、これらの側面の両端を結ぶ凸円弧面状または凸円弧面と平面とを組み合わせた凸側面とを有している。２つの側面は軸部中心線Ｌ２に平行な平面状であって、先端視において一方は長い側面（長側面）、他方は短い側面（短側面）とされ、また凸側面のうち長側面に連なる部分は後端側に向かうに従い軸部中心線Ｌ２側に向かうように僅かに傾斜している。 As shown in FIGS. 2, 3 and 4 (a), the excavation portion 6 has a substantially fan shape in a tip view, that is, two side surfaces that intersect each other at an obtuse angle of 120 ° and both ends of these side surfaces. It has a convex arc surface or a convex side surface that is a combination of a convex arc surface and a flat surface. The two side surfaces are planar parallel to the axis center line L2, and in front view, one is a long side surface (long side surface), the other is a short side surface (short side surface), and is continuous with the long side surface of the convex side surfaces. The portion is slightly inclined toward the rear end side and toward the shaft center line L2 side.

このような掘削部６は、ビットヘッド５が軸部中心線Ｌ２回りに工具回転方向Ｔとは反対側に回転させられたときには、図２に示すように周方向に隣接するビットヘッド５同士で、１つの掘削部６の上記短側面が、工具回転方向Ｔとは反対側に隣接するビットヘッド５の掘削部６における長側面の短側面側の部分に当接して位置決めされる。このとき、凸側面の長側面に連なる部分は、ケーシングパイプＰやケーシングトップＱの外径よりも大きく工具本体１の外周側に突出して拡径し、先端視において軸線Ｏを中心とした円弧をなすように配設される。 When the bit head 5 is rotated around the shaft center line L2 in the direction opposite to the tool rotation direction T, the excavation portion 6 is formed between the bit heads 5 adjacent to each other in the circumferential direction as shown in FIG. The short side surface of one excavation portion 6 abuts on the short side surface side portion of the long side surface of the excavation portion 6 of the bit head 5 adjacent to the side opposite to the tool rotation direction T and is positioned. At this time, the portion connected to the long side surface of the convex side surface is larger than the outer diameter of the casing pipe P and the casing top Q and protrudes toward the outer peripheral side of the tool body 1 to expand the diameter, and an arc centered on the axis O is formed in the tip view. It is arranged so as to form a casing.

また、ビットヘッド５が軸部中心線Ｌ２回りに工具回転方向Ｔに回転させられたときには、図３に示すように周方向に隣接するビットヘッド５同士で、１つの掘削部６の上記短側面が、工具回転方向Ｔとは反対側に隣接するビットヘッド５の掘削部６における長側面の凸側面側の部分に当接して位置決めされることにより縮径させられる。この縮径した状態では、凸側面は、軸線Ｏから最も離れた部分が、ケーシングトップＱの内径よりも小さく、円柱部１Ｃの外径よりは大きな直径の軸線Ｏを中心とした円筒面上に位置するように配設される。 Further, when the bit head 5 is rotated in the tool rotation direction T around the shaft center line L2, as shown in FIG. 3, the bit heads 5 adjacent to each other in the circumferential direction are connected to each other and the short side surface of one excavation portion 6. However, the diameter is reduced by being positioned in contact with the convex side surface side portion of the long side surface of the excavation portion 6 of the bit head 5 adjacent to the side opposite to the tool rotation direction T. In this reduced diameter state, the convex side surface is on the cylindrical surface centered on the axis O having a diameter that is smaller than the inner diameter of the casing top Q and larger than the outer diameter of the cylindrical portion 1C at the portion farthest from the axis O. Arranged to be located.

さらに、このようなビットヘッド５の取付軸部４の外周面には、軸部中心線Ｌ２に直交する平面Ａ、すなわち上記挿入状態における孔部中心線Ｌ１に直交する平面Ａに沿って凹溝４Ａが形成されている。この凹溝４Ａは、本実施形態では図４（ｂ）および図５に示すように軸部中心線Ｌ２を中心として取付軸部４の外周を１周する環状溝とされており、軸部中心線Ｌ２に沿った断面では、軸部中心線Ｌ２方向に延びる半割長円状に形成されている。なお、凹溝４Ａは、このような環状溝とするのに代えて、例えば軸部中心線Ｌ２方向から見て掘削部６の長側面側に形成されて、軸部中心線Ｌ２に直交する上記平面Ａに沿った断面が略１２０°に折れ曲がったＬ字状に形成され、ただしこのＬ字に折れ曲がる部分は、その両側の直線状に延びる部分に接する軸部中心線Ｌ２を中心とした凸円弧状に形成されていてもよい。 Further, on the outer peripheral surface of the mounting shaft portion 4 of the bit head 5, a concave groove is provided along a plane A orthogonal to the shaft portion center line L2, that is, a plane A orthogonal to the hole center line L1 in the inserted state. 4A is formed. In the present embodiment, the concave groove 4A is an annular groove that goes around the outer circumference of the mounting shaft portion 4 around the shaft portion center line L2 as shown in FIGS. 4 (b) and 5 and is the center of the shaft portion. In the cross section along the line L2, it is formed in a half elliptical shape extending in the direction of the shaft center line L2. Instead of forming such an annular groove, the concave groove 4A is formed on the long side surface side of the excavation portion 6 when viewed from the direction of the shaft portion center line L2, and is orthogonal to the shaft portion center line L2. The cross section along the plane A is formed in an L shape bent at approximately 120 °, but the portion bent in the L shape is a convex circle centered on the axis center line L2 in contact with the linearly extending portions on both sides thereof. It may be formed in an arc shape.

一方、工具本体１には、同じく上記挿入状態における孔部中心線Ｌ１に直交する上記平面Ａに沿って有底のピン孔８が形成されている。このピン孔８は、本実施形態では断面円形のものであって、３つの取付孔部２の内周面にそれぞれ工具回転方向Ｔの反対側から接して軸線Ｏに直交する接線をピン孔中心線Ｃとして延び、工具本体１の円柱部１Ｃの外周面に開口するように形成されている。従って、これらのピン孔８は、ピン孔中心線Ｃが取付孔部２の内周面に接する部分で、この取付孔部２の内周面に部分的に開口することになる。 On the other hand, the tool body 1 is formed with a bottomed pin hole 8 along the plane A orthogonal to the hole center line L1 in the inserted state. The pin hole 8 has a circular cross section in the present embodiment, and the center of the pin hole is a tangent line that is in contact with the inner peripheral surfaces of the three mounting holes 2 from the opposite side of the tool rotation direction T and is orthogonal to the axis O. It extends as a line C and is formed so as to open on the outer peripheral surface of the cylindrical portion 1C of the tool body 1. Therefore, these pin holes 8 are portions where the pin hole center line C is in contact with the inner peripheral surface of the mounting hole portion 2, and are partially opened to the inner peripheral surface of the mounting hole portion 2.

また、ピン孔８の半径は、取付軸部４の外周面から凹溝４Ａの溝底までの深さと略等しくされている。さらに、このピン孔８には、ピン孔８の内径よりも僅かに小さな外径の円柱軸状の係止ピン９が円柱部１Ｃの外周側から挿入されており、上述のように取付孔部２の内周面に部分的に開口した部分でビットヘッド５の取付軸部４における凹溝４Ａに係止されて、工具本体１の軸線Ｏ側におけるピン孔８の底面に当接させられている。なお、このようにして係止ピン９がピン孔８の底面に当接したところで、係止ピン９の工具本体１外周側の端面は、円柱部１Ｃの外周面と面一となるように形成されている。 Further, the radius of the pin hole 8 is substantially equal to the depth from the outer peripheral surface of the mounting shaft portion 4 to the groove bottom of the concave groove 4A. Further, a cylindrical shaft-shaped locking pin 9 having an outer diameter slightly smaller than the inner diameter of the pin hole 8 is inserted into the pin hole 8 from the outer peripheral side of the cylindrical portion 1C, and the mounting hole portion is described as described above. It is locked to the concave groove 4A in the mounting shaft portion 4 of the bit head 5 at a portion partially opened on the inner peripheral surface of 2, and is brought into contact with the bottom surface of the pin hole 8 on the axis O side of the tool body 1. There is. When the locking pin 9 comes into contact with the bottom surface of the pin hole 8 in this way, the end surface of the locking pin 9 on the outer peripheral side of the tool body 1 is formed so as to be flush with the outer peripheral surface of the cylindrical portion 1C. Has been done.

そして、工具本体１の第１段部１Ｂの先端面と、第２段部であるケーシングトップＱの後端面との間には、第１段部１Ｂの外径より小さく、この第１段部１Ｂよりも先端側の円柱部１Ｃの外径より大きい内径と、ケーシングトップＱの内径より大きく、このケーシングトップＱよりも後端側の上記ケーシングパイプＰの内径よりは小さな外径とを有する環状部材１０が介装されている。なお、本実施形態では、環状部材１０の外径は第１段部１Ｂの外径と略等しくされている。また、このような環状部材１０は、同じ鋼材によって形成されるにしても、工具本体１の材質の硬度に対して同等の硬度または例えばＨＲＣ５程度までの低い硬度の材質によって形成される。 The distance between the tip surface of the first step portion 1B of the tool body 1 and the rear end surface of the casing top Q, which is the second step portion, is smaller than the outer diameter of the first step portion 1B, and this first step portion An annular shape having an inner diameter larger than the outer diameter of the cylindrical portion 1C on the tip side of 1B and an outer diameter larger than the inner diameter of the casing top Q and smaller than the inner diameter of the casing pipe P on the rear end side of the casing top Q. A member 10 is interposed. In the present embodiment, the outer diameter of the annular member 10 is substantially equal to the outer diameter of the first stage portion 1B. Further, even if such an annular member 10 is formed of the same steel material, it is formed of a material having a hardness equal to that of the material of the tool body 1 or a material having a hardness as low as, for example, about HRC5.

さらに、本実施形態の環状部材１０は、上述のような内外径を有する後端側の環状部１０Ａと、この環状部１０Ａと内径が等しく、ケーシングトップＱの内径よりも僅かに小さな外径を有して先端側に延びる円筒部１０Ｂとが同軸に一体に形成されており、従ってこの円筒部１０Ｂは、工具本体１の第１段部１Ｂよりも先端側の上記円柱部１Ｃの外周面とケーシングトップＱの内周面との間に配設されることになる。また、環状部材１０の軸線Ｏ方向の長さは、図１に示すように環状部１０Ａを第１段部１ＢとケーシングトップＱに当接させた状態で、円筒部１０Ｂの先端面がケーシングトップＱの先端面と面一となるように設定され、工具本体１の円柱部１Ｃの長さよりは十分短く設定されている。 Further, the annular member 10 of the present embodiment has an inner diameter equal to that of the annular portion 10A on the rear end side having the inner and outer diameters as described above and the annular portion 10A, and has an outer diameter slightly smaller than the inner diameter of the casing top Q. A cylindrical portion 10B extending to the tip end side is coaxially and integrally formed. Therefore, the cylindrical portion 10B is formed with the outer peripheral surface of the cylindrical portion 1C on the tip end side of the first stage portion 1B of the tool body 1. It will be disposed between the inner peripheral surface of the casing top Q. Further, the length of the annular member 10 in the axis O direction is such that the tip surface of the cylindrical portion 10B is the casing top in a state where the annular portion 10A is in contact with the first stage portion 1B and the casing top Q as shown in FIG. It is set so as to be flush with the tip surface of Q, and is set sufficiently shorter than the length of the cylindrical portion 1C of the tool body 1.

さらにまた、この環状部材１０の円筒部１０Ｂには、同じく図１に示すように環状部１０Ａを第１段部１Ｂに当接させた状態で、軸線Ｏ方向においてピン孔８の開口部の後端側に部分的に重なり合う位置に、断面円形の３つの貫通孔１１が、周方向に等間隔に形成されており、これらの貫通孔１１には、係止ピン９をピン孔８に挿入した状態で該貫通孔１１を封止する封止部材１２が取り付けられている。さらに、円筒部１０Ｂの外周面には、各貫通孔１１に連通するように凹所１３がそれぞれ形成されており、この凹所１３には、封止部材１２を固定する固定部材１４が配設されている。 Furthermore, as shown in FIG. 1, the cylindrical portion 10B of the annular member 10 is behind the opening of the pin hole 8 in the axis O direction in a state where the annular portion 10A is in contact with the first stage portion 1B. Three through holes 11 having a circular cross section are formed at equal intervals in the circumferential direction at positions where they partially overlap each other on the end side, and locking pins 9 are inserted into the pin holes 8 in these through holes 11. A sealing member 12 that seals the through hole 11 in this state is attached. Further, recesses 13 are formed on the outer peripheral surface of the cylindrical portion 10B so as to communicate with each through hole 11, and a fixing member 14 for fixing the sealing member 12 is arranged in the recess 13. Has been done.

貫通孔１１の円筒部１０Ｂの内外周面における開口部の直径は、ピン孔８の直径と等しく設定されている。なお、ピン孔８の円柱部１Ｃにおける開口部は、は、上述のように環状部１０Ａを第１段部１ＢとケーシングトップＱに当接させた状態で、円筒部１０ＢとケーシングトップＱの先端面よりも後端側に位置して、これら円筒部１０ＢおよびケーシングトップＱに覆われるように配設されている。また、凹所１３は、本実施形態では貫通孔１１の外周側開口部の軸線Ｏ方向後端側に連通するように形成されており、ただし環状部材１０の内周面に貫通してはいない。 The diameter of the opening on the inner and outer peripheral surfaces of the cylindrical portion 10B of the through hole 11 is set to be equal to the diameter of the pin hole 8. The opening of the pin hole 8 in the cylindrical portion 1C is such that the annular portion 10A is in contact with the first stage portion 1B and the casing top Q as described above, and the tip of the cylindrical portion 10B and the casing top Q is formed. It is located on the rear end side of the surface and is arranged so as to be covered by these cylindrical portions 10B and the casing top Q. Further, in the present embodiment, the recess 13 is formed so as to communicate with the rear end side of the outer peripheral side opening of the through hole 11 in the axis O direction, but does not penetrate the inner peripheral surface of the annular member 10. ..

さらに、凹所１３は、貫通孔１１の外周側開口部がなす円の直径と等しい幅で工具本体１の後端側に延びる延出部１３Ａと、この延出部１３Ａの後端側に位置して貫通孔１１の中心線と平行な中心線を有する貫通孔１１よりも大径の円形部１３Ｂとを備えている。なお、円形部１３Ｂの中心線と貫通孔１１の中心線との間隔は、円形部１３Ｂの半径と貫通孔１１の外周側開口部の半径との和よりも僅かに大きく設定されている。 Further, the recess 13 is located at the extension portion 13A extending toward the rear end side of the tool body 1 with a width equal to the diameter of the circle formed by the outer peripheral side opening of the through hole 11 and at the rear end side of the extension portion 13A. A circular portion 13B having a diameter larger than that of the through hole 11 having a center line parallel to the center line of the through hole 11 is provided. The distance between the center line of the circular portion 13B and the center line of the through hole 11 is set to be slightly larger than the sum of the radius of the circular portion 13B and the radius of the opening on the outer peripheral side of the through hole 11.

また、これら貫通孔１１と凹所１３の内周部には、環状部材１０の内外周面との間に僅かな間隔をあけて溝が形成されており、このうち貫通孔１１の内周部に形成された溝は封止部材１２を係止する係止部１１Ａとされている。さらに、凹所１３のうち円形部１３Ｂの内周に形成された溝は固定部材１４の係止部１３Ｃとされるとともに、延出部１３Ａに形成された溝はスライド溝１３Ｄとされている。 Further, in the inner peripheral portion of the through hole 11 and the recess 13, a groove is formed with a slight gap between the inner peripheral surface of the annular member 10 and the inner peripheral portion of the through hole 11. The groove formed in is a locking portion 11A for locking the sealing member 12. Further, the groove formed on the inner circumference of the circular portion 13B in the recess 13 is a locking portion 13C of the fixing member 14, and the groove formed in the extending portion 13A is a slide groove 13D.

これら係止部１１Ａ、１３Ｃおよびスライド溝１３Ｄは、ピン孔中心線Ｃに直交する１つの平面に沿うように形成されていて、すなわちピン孔中心線Ｃ方向を向いて互いに対向する２つの溝壁面は、それぞれ係止部１１Ａ、１３Ｃおよびスライド溝１３Ｄ同士で面一に形成されている。さらに、これら２つの溝壁面はピン孔中心線Ｃに垂直に延びるように形成されるとともに、これらの溝壁面の間の貫通孔１１と凹所１３の内周側を向く溝底面は、溝壁面に垂直すなわちピン孔中心線Ｃに平行に延びるように形成されていて、係止部１１Ａ、１３Ｃ、およびスライド溝１３Ｄはピン孔中心線Ｃに沿った断面が矩形状に形成されている。 The locking portions 11A, 13C and the slide groove 13D are formed along one plane orthogonal to the pin hole center line C, that is, two groove wall surfaces facing each other in the pin hole center line C direction. Are formed flush with each other by the locking portions 11A and 13C and the slide groove 13D, respectively. Further, these two groove wall surfaces are formed so as to extend perpendicular to the pin hole center line C, and the groove bottom surface facing the inner peripheral side of the through hole 11 and the recess 13 between these groove wall surfaces is the groove wall surface. It is formed so as to extend perpendicular to the pin hole center line C, that is, parallel to the pin hole center line C, and the locking portions 11A, 13C, and the slide groove 13D have a rectangular cross section along the pin hole center line C.

なお、これら係止部１１Ａ、１３Ｃおよびスライド溝１３Ｄがなす溝の溝深さ、すなわち貫通孔１１と凹所１３の延出部１３Ａおよび円形部１３Ｂの内周から上記溝底面までの深さは、係止部１１Ａとスライド溝１３Ｄとで互いに等しい一定の深さとなるように形成されている。これに対して、凹所１３の係止部１３Ｃは、これら係止部１１Ａおよびスライド溝１３Ｄの溝深さよりも浅い一定の溝深さとなるように形成されている。 The groove depth formed by the locking portions 11A, 13C and the slide groove 13D, that is, the depth from the inner circumference of the through hole 11 and the extending portion 13A of the recess 13 and the circular portion 13B to the bottom surface of the groove is , The locking portion 11A and the slide groove 13D are formed so as to have a constant depth equal to each other. On the other hand, the locking portion 13C of the recess 13 is formed so as to have a constant groove depth shallower than the groove depths of the locking portion 11A and the slide groove 13D.

このうち、貫通孔１１の係止部１１Ａに取り付けられる上記封止部材１２は、工具本体１やビットヘッド５と同じく鋼材等の剛性体により、外径が２段の円盤状に一体形成されており、このうち外径が大径となる部分はスライド溝１３Ｄを通して貫通孔１１の係止部１１Ａに嵌め入れ可能な大きさに形成されている。また、封止部材１２の外径が小径となる部分は、環状部材１０の外周面における貫通孔１１の開口部に嵌め入れ可能な大きさに形成されている。 Of these, the sealing member 12 attached to the locking portion 11A of the through hole 11 is integrally formed in a disk shape having a two-stage outer diameter by a rigid body such as a steel material like the tool body 1 and the bit head 5. Of these, the portion having a large outer diameter is formed in a size that can be fitted into the locking portion 11A of the through hole 11 through the slide groove 13D. The portion of the sealing member 12 having a small outer diameter is formed to have a size that allows it to be fitted into the opening of the through hole 11 on the outer peripheral surface of the annular member 10.

一方、凹所１３に配設される固定部材１４は、ウレタンゴム等の合成ゴムのような弾性体により、やはり外径が２段の円盤状に一体形成されており、このうち外径が大径となる部分は僅かに縮径するように弾性変形させられた状態で凹所１３の係止部１３Ｃに嵌め入れ可能とされ、小径となる部分は環状部材１０の外周面における凹所１３の開口部に嵌め入れ可能な大きさとされている。さらに、上記大径の部分は、係止部１３Ｃに嵌め入れられた状態で、上述のように係止部１１Ａに嵌め入れられた封止部材１２の大径の部分の外周に弾性変形しつつ密着可能な大きさとされている。 On the other hand, the fixing member 14 arranged in the recess 13 is integrally formed in a disk shape having a two-stage outer diameter by an elastic body such as synthetic rubber such as urethane rubber, of which the outer diameter is large. The portion having a diameter can be fitted into the locking portion 13C of the recess 13 in a state of being elastically deformed so as to be slightly reduced in diameter, and the portion having a small diameter is the portion of the recess 13 on the outer peripheral surface of the annular member 10. It is sized so that it can be fitted into the opening. Further, the large-diameter portion is elastically deformed to the outer periphery of the large-diameter portion of the sealing member 12 fitted into the locking portion 11A as described above in a state of being fitted into the locking portion 13C. It is said to be large enough to adhere.

次に、このような掘削工具を組み立てる場合について説明する。まず、工具本体１にビットヘッド５が取り付けられておらず、またケーシングパイプＰおよびケーシングトップＱが配設されていない状態から、工具本体１先端部の円柱部１Ｃに先端側から環状部材１０を嵌め入れて、３つの貫通孔１１が３つのピン孔８と同軸となるように配置する。次いで、取付孔部２に取付軸部４を挿入して掘削部６が工具本体１の先端面に当接するようにビットヘッド５を工具本体１の先端部に配設する。このとき、各ビットヘッド５は、その掘削部６が上述の縮径した状態とされる。 Next, a case of assembling such an excavation tool will be described. First, from a state in which the bit head 5 is not attached to the tool body 1 and the casing pipe P and the casing top Q are not arranged, the annular member 10 is attached to the cylindrical portion 1C at the tip of the tool body 1 from the tip side. It is fitted and arranged so that the three through holes 11 are coaxial with the three pin holes 8. Next, the mounting shaft portion 4 is inserted into the mounting hole portion 2, and the bit head 5 is arranged at the tip portion of the tool body 1 so that the excavation portion 6 comes into contact with the tip surface of the tool body 1. At this time, each bit head 5 is in a state in which the excavated portion 6 has a reduced diameter as described above.

また、貫通孔１１はピン孔８と同軸とされて連通可能な位置に配設されているので、工具本体１の外周側から貫通孔１１を通して係止ピン９をピン孔８にそれぞれ挿入し、取付軸部４の凹溝４Ａに係止する。次に、環状部材１０の外周から凹所１３に封止部材１２を挿入し、スライド溝１３Ｄに沿って貫通孔１１の開口部に位置させて係止部１１Ａよって係止し、さらに凹所１３の係止部１３Ｃに固定部材１４を嵌め入れて封止部材１２を固定する。 Further, since the through hole 11 is arranged coaxially with the pin hole 8 at a position where it can communicate with each other, the locking pin 9 is inserted into the pin hole 8 from the outer peripheral side of the tool body 1 through the through hole 11. It is locked in the concave groove 4A of the mounting shaft portion 4. Next, the sealing member 12 is inserted into the recess 13 from the outer periphery of the annular member 10, positioned at the opening of the through hole 11 along the slide groove 13D, locked by the locking portion 11A, and further locked by the recess 13. The fixing member 14 is fitted into the locking portion 13C of the above to fix the sealing member 12.

こうして係止ピン９と封止部材１２、固定部材１４が取り付けられたなら、ビットヘッド５の掘削部６を縮径させたまま、工具本体１をケーシングパイプＰの後端側から挿入して、ビットヘッド５の掘削部６と工具本体１の円柱部１Ｃの先端部をケーシングトップＱの内周を通して先端に突出させ、第１段部１Ｂを環状部材１０の後端面に、環状部１０Ａの先端面をケーシングトップＱの後端面に当接させ、第１段部１Ｂの先端面と第２段部であるケーシングトップＱの後端面との間に、環状部材１０の環状部１０Ａを介装する。 When the locking pin 9, the sealing member 12, and the fixing member 14 are attached in this way, the tool body 1 is inserted from the rear end side of the casing pipe P while the excavation portion 6 of the bit head 5 is reduced in diameter. The tip of the excavated portion 6 of the bit head 5 and the cylindrical portion 1C of the tool body 1 are projected to the tip through the inner circumference of the casing top Q, and the first step portion 1B is on the rear end surface of the annular member 10 and the tip of the annular portion 10A. The surface is brought into contact with the rear end surface of the casing top Q, and the annular portion 10A of the annular member 10 is interposed between the front end surface of the first step portion 1B and the rear end surface of the casing top Q which is the second step portion. ..

このとき、環状部材１０は、上述のように貫通孔１１とピン孔８とが同軸の位置から相対的に工具本体１の後端側にずらされ、ピン孔８の開口部の先端側部分が部分的に環状部材１０とケーシングトップＱによって被覆されるので、このピン孔８に挿入された係止ピン９はこれら環状部材１０とケーシングトップＱによって抜け止めされて固定される。なお、係止ピン９をピン孔８に挿入した後は、予め環状部材１０を第１段部１Ｂに当接させてから、工具本体１をケーシングパイプＰに挿入してもよい。 At this time, in the annular member 10, the through hole 11 and the pin hole 8 are relatively shifted from the coaxial position to the rear end side of the tool body 1 as described above, and the tip end side portion of the opening of the pin hole 8 is formed. Since the annular member 10 and the casing top Q are partially covered, the locking pin 9 inserted into the pin hole 8 is fixed by the annular member 10 and the casing top Q. After inserting the locking pin 9 into the pin hole 8, the annular member 10 may be brought into contact with the first stage portion 1B in advance, and then the tool body 1 may be inserted into the casing pipe P.

このようにして組み立てられた掘削工具に、軸線Ｏ方向先端側への打撃力および推力と工具回転方向Ｔへの回転力を与えて掘削を行うと、図１および図２に示すようにビットヘッド５が回転力による反力によって工具回転方向Ｔとは反対側に回転して拡径し、掘削部６の外径がケーシングパイプＰよりも大きくなるので、掘削部６によって形成された掘削孔にケーシングパイプＰを挿入しつつ掘削を行うことができる。 When excavation is performed by applying a striking force and a thrust force toward the tip end side in the axis O direction and a rotational force in the tool rotation direction T to the excavation tool assembled in this manner, the bit head is shown in FIGS. 1 and 2. 5 rotates in the direction opposite to the tool rotation direction T due to the reaction force due to the rotational force to expand the diameter, and the outer diameter of the excavation portion 6 becomes larger than that of the casing pipe P. Therefore, in the excavation hole formed by the excavation portion 6. Excavation can be performed while inserting the casing pipe P.

また、所定の深さまで掘削孔が形成されてケーシングパイプＰが挿入されることにより掘削が終了した後は、工具本体１を工具回転方向Ｔとは反対側に回転させることにより、その反力によってビットヘッド５は工具回転方向Ｔに回転し、図３に示したように掘削部６が縮径するので、ケーシングパイプＰを掘削孔に残したまま工具本体１を引き抜いて回収することができる。 Further, after the excavation is completed by forming the excavation hole to a predetermined depth and inserting the casing pipe P, the tool body 1 is rotated in the direction opposite to the tool rotation direction T by the reaction force. Since the bit head 5 rotates in the tool rotation direction T and the excavation portion 6 has a reduced diameter as shown in FIG. 3, the tool body 1 can be pulled out and recovered while leaving the casing pipe P in the excavation hole.

ここで、図１ないし図５に示した実施形態では、第１段部１Ｂの外径がケーシングトップＱの内径よりも大きいので、環状部材１０の特に環状部１０Ａがなくても第１段部１Ｂを直接ケーシングトップＱの後端面に当接させて軸線Ｏ方向先端側への打撃力および推力をケーシングパイプＰに伝達し、掘削孔に挿入してゆくことができるが、大径の掘削孔を形成する場合に、ケーシングパイプＰおよびケーシングトップＱも、拡径した掘削部６の外径以下の範囲で外径の大きなものを使用するときには、これらケーシングパイプＰおよびケーシングトップＱの肉厚を必要以上に厚くすることはコスト高を招くので、ケーシングパイプＰおよびケーシングトップＱの内径も大きくせざるを得ない。 Here, in the embodiment shown in FIGS. 1 to 5, since the outer diameter of the first step portion 1B is larger than the inner diameter of the casing top Q, the first step portion of the annular member 10 even if the annular portion 10A is not particularly provided. 1B can be brought into direct contact with the rear end surface of the casing top Q to transmit the striking force and thrust toward the tip end side in the O direction of the axis to the casing pipe P and inserted into the drilling hole, but the drilling hole has a large diameter. When using a casing pipe P and a casing top Q having a large outer diameter within the range equal to or less than the outer diameter of the expanded excavation portion 6, the wall thickness of the casing pipe P and the casing top Q is increased. Since increasing the thickness more than necessary leads to high cost, the inner diameters of the casing pipe P and the casing top Q must also be increased.

このため、そのようなときには、場合によっては第１段部１Ｂの外径よりも第２段部としてのケーシングトップＱの内径が大きくなって、打撃力および推力をケーシングパイプＰに伝達することができなくなるおそれがある。また、第１段部１Ｂの外径がケーシングトップＱの内径より大きくても、その差が小さい場合には、打撃力および推力をケーシングパイプＰに確実かつ十分に伝達することができなくなり、掘削効率が著しく低減してしまう。 Therefore, in such a case, in some cases, the inner diameter of the casing top Q as the second stage portion becomes larger than the outer diameter of the first stage portion 1B, and the striking force and the thrust force may be transmitted to the casing pipe P. It may not be possible. Further, even if the outer diameter of the first stage portion 1B is larger than the inner diameter of the casing top Q, if the difference is small, the striking force and the thrust cannot be reliably and sufficiently transmitted to the casing pipe P, and excavation Efficiency is significantly reduced.

そこで、そのようなときでも、図１ないし図５に示した工具本体１と同じ工具本体１を用いて掘削を行うには、図６に示すように環状部材１０を外径の大きなものに交換する。すなわち、この図６に示す環状部材１０は、その環状部１０Ａと円筒部１０Ｂの内径は、図１ないし図５に示した実施形態と同じく第１段部１Ｂの外径より小さく、この第１段部１Ｂよりも先端側の円柱部１Ｃの外径よりは大きくて、工具本体１の円柱部１Ｃが嵌め入れ可能な大きさとされているが、円筒部１０Ｂの外径は、内径が大きくされたケーシングトップＱの内周に嵌め入れ可能な大きさであり、環状部１０Ａの外径は、ケーシングトップＱの内径よりも大きく、内径が大きくされたケーシングパイプＰに嵌め入れ可能な大きさとされていて、第１段部１Ｂの外径よりも大きい。 Therefore, even in such a case, in order to perform excavation using the same tool body 1 as the tool body 1 shown in FIGS. 1 to 5, the annular member 10 is replaced with a member having a large outer diameter as shown in FIG. To do. That is, in the annular member 10 shown in FIG. 6, the inner diameters of the annular portion 10A and the cylindrical portion 10B are smaller than the outer diameter of the first step portion 1B as in the embodiment shown in FIGS. 1 to 5, and the first step portion 1B is formed. It is larger than the outer diameter of the cylindrical portion 1C on the tip side of the step portion 1B so that the cylindrical portion 1C of the tool body 1 can be fitted, but the outer diameter of the cylindrical portion 10B is increased in inner diameter. The size is such that it can be fitted into the inner circumference of the casing top Q, and the outer diameter of the annular portion 10A is larger than the inner diameter of the casing top Q and can be fitted into the casing pipe P having a larger inner diameter. It is larger than the outer diameter of the first stage portion 1B.

従って、上記構成の掘削工具によれば、工具本体１の第１段部１Ｂの外径と、ケーシングパイプＰの第２段部であるケーシングトップＱの内径との差が小さい場合はもとより、たとえケーシングトップＱの内径が第１段部１Ｂの外径よりも大きい場合でも、一種の工具本体１を用いて、工具本体１に与えられる軸線Ｏ方向先端側への打撃力および推力を、第１段部１Ｂから環状部材１０の環状部１０Ａを介して確実にケーシングパイプＰに伝達することができる。このため、外径の異なる複数種の工具本体を用意する必要がなくなって、構造が環状部材１０よりは複雑な工具本体１の管理が容易となるとともに、工具本体１の製造コストの削減を図ることができる。 Therefore, according to the excavation tool having the above configuration, even if the difference between the outer diameter of the first step portion 1B of the tool body 1 and the inner diameter of the casing top Q which is the second step portion of the casing pipe P is small, Even when the inner diameter of the casing top Q is larger than the outer diameter of the first step portion 1B, a kind of tool body 1 is used to apply a striking force and a thrust force applied to the tool body 1 toward the tip end side in the axis O direction. It can be reliably transmitted from the step portion 1B to the casing pipe P via the annular portion 10A of the annular member 10. Therefore, it is not necessary to prepare a plurality of types of tool bodies having different outer diameters, it becomes easier to manage the tool body 1 having a more complicated structure than the annular member 10, and the manufacturing cost of the tool body 1 is reduced. be able to.

また、第１段部１Ｂの外径がケーシングトップＱの内径より小さい場合は勿論、第１段部１Ｂの外径がケーシングトップＱの内径より大きくても、ケーシングパイプＰの内径に対しては大幅に小さい場合などには、このケーシングパイプＰの内径に合わせて、環状部材１０の環状部１０Ａの外径を第１段部１Ｂの外径よりも大きくすることにより、ケーシングトップＱの後端面への打撃力や推力の伝達面積を大きくすることができる。従って、効率的にケーシングパイプＰを掘削孔に挿入することができるとともに、環状部材１０を打撃する第１段部１Ｂの応力集中による破損等も防ぐことができる。 Further, not only when the outer diameter of the first step portion 1B is smaller than the inner diameter of the casing top Q, but also when the outer diameter of the first step portion 1B is larger than the inner diameter of the casing top Q, the inner diameter of the casing pipe P is not affected. When the size is significantly smaller, the outer diameter of the annular portion 10A of the annular member 10 is made larger than the outer diameter of the first step portion 1B in accordance with the inner diameter of the casing pipe P, so that the rear end surface of the casing top Q is formed. It is possible to increase the transmission area of the striking force and the thrust force. Therefore, the casing pipe P can be efficiently inserted into the excavation hole, and damage due to stress concentration of the first stage portion 1B that hits the annular member 10 can be prevented.

さらに、本実施形態においては、環状部材１０が工具本体１の材質の硬度以下の硬度の材質によって形成されており、工具本体１に与えられる打撃力や推力、回転力による摩耗を、工具本体１ではなく環状部材１０に多く生じるようにすることができる。従って、上述のように環状部材１０よりも構造が複雑な工具本体１の摩耗を抑制して工具本体１の長寿命化を図ることができるので、長期に亙って安定した掘削作業を一層低コストで行うことが可能となる。 Further, in the present embodiment, the annular member 10 is formed of a material having a hardness equal to or lower than the hardness of the material of the tool body 1, and the tool body 1 is subjected to wear due to a striking force, a thrust force, and a rotational force applied to the tool body 1. It can be made to occur more in the annular member 10 instead. Therefore, as described above, it is possible to suppress wear of the tool body 1 having a more complicated structure than the annular member 10 and extend the life of the tool body 1, so that stable excavation work can be further reduced over a long period of time. It will be possible to do it at a cost.

さらにまた、本実施形態では、環状部材１０の先端側に、工具本体１の第１段部１Ｂよりも先端側の円柱部１Ｃに嵌め入れ可能な内径とケーシングトップＱの内周に嵌め入れ可能な外径を有し、これら円柱部１Ｃの外周面とケーシングトップＱの内周面との間に配設される円筒部１０Ｂが形成されている。従って、この円筒部１０Ｂを介して工具本体１の円柱部１ＣをケーシングトップＱにより支持することができるので、特に円柱部１Ｃの外径がケーシングトップＱの内径よりも著しく小さい場合でも、掘削時の工具本体１およびビットヘッド５の掘削部６の振れを抑えることができ、直進度の高い掘削孔を形成することが可能となる。 Furthermore, in the present embodiment, the tip side of the annular member 10 can be fitted into the inner diameter that can be fitted into the cylindrical portion 1C on the tip side of the first stage portion 1B of the tool body 1 and the inner circumference of the casing top Q. A cylindrical portion 10B having a large outer diameter and arranged between the outer peripheral surface of the cylindrical portion 1C and the inner peripheral surface of the casing top Q is formed. Therefore, since the cylindrical portion 1C of the tool body 1 can be supported by the casing top Q via the cylindrical portion 10B, even when the outer diameter of the cylindrical portion 1C is significantly smaller than the inner diameter of the casing top Q, during excavation. It is possible to suppress the runout of the excavation portion 6 of the tool body 1 and the bit head 5 and to form an excavation hole having a high degree of straightness.

一方、本実施形態では、ビットヘッド５を回転自在に係止する係止ピン９が挿入される工具本体１のピン孔８の開口部の少なくとも一部が、上述のように工具本体１とは別部材である環状部材１０の円筒部１０Ｂによって被覆可能とされており、こうしてピン孔８の開口部の一部を円筒部１０Ｂによって被覆することにより、係止ピン９を抜け止めして固定することができる。 On the other hand, in the present embodiment, at least a part of the opening of the pin hole 8 of the tool body 1 into which the locking pin 9 for rotatably locking the bit head 5 is inserted is different from the tool body 1 as described above. It is possible to cover with the cylindrical portion 10B of the annular member 10 which is a separate member, and by covering a part of the opening of the pin hole 8 with the cylindrical portion 10B in this way, the locking pin 9 is prevented from coming off and fixed. be able to.

このため、例えば特許文献１に記載された掘削工具のように、ビットヘッドを回転自在に係止する係止ピンが工具本体に直接取り付けられた固定部材によって抜け止めされるのに比べ、工具本体に与えられる打撃力による衝撃によって固定部材が振動して摩耗することにより、固定部材に緩みやがたつき、破損が生じるような事態を防ぐことができる。そして、これに伴い係止ピン９の脱落を防止して、長期に亙ってビットヘッド５を安定的に取付孔部２に取り付けて円滑な掘削を行うことが可能となる。 Therefore, as compared with the excavation tool described in Patent Document 1, for example, the locking pin that rotatably locks the bit head is prevented from coming off by the fixing member directly attached to the tool body. It is possible to prevent a situation in which the fixing member is loosened, rattled, or damaged due to vibration and wear of the fixing member due to the impact of the striking force applied to the fixing member. Along with this, the locking pin 9 can be prevented from falling off, and the bit head 5 can be stably attached to the attachment hole 2 for a long period of time to perform smooth excavation.

また、本実施形態では、ピン孔８が開口する工具本体１の外面が、工具本体１の円柱部１Ｃの外周面であって、孔部中心線Ｌ１に平行な軸線Ｏを中心とする円筒面状に形成されているのに対し、環状部材１０の円筒部１０Ｂはこの外周面に対向する内周面を有する円筒状に形成されているので、円筒部１０Ｂへの嵌め入れ精度を確保し易く、さらに確実に打撃力による衝撃が円筒部１０Ｂに作用するのを避けることができる。 Further, in the present embodiment, the outer surface of the tool body 1 through which the pin hole 8 opens is the outer peripheral surface of the cylindrical portion 1C of the tool body 1 and is a cylindrical surface centered on the axis O parallel to the hole center line L1. While the annular member 10 is formed in a cylindrical shape, the cylindrical portion 10B of the annular member 10 is formed in a cylindrical shape having an inner peripheral surface facing the outer peripheral surface, so that it is easy to secure the fitting accuracy into the cylindrical portion 10B. More reliably, it is possible to prevent the impact of the striking force from acting on the cylindrical portion 10B.

なお、本実施形態では、環状部材１０は初めから円筒環状に一体形成されているが、例えば円筒を周方向に複数に分割した分割体を溶接等により接合し、または周方向の突き合わせ部に係合部を設けて係合させて円筒状に形成してもよい。このような場合には、ビットヘッド５を取り付けて係止ピン９を挿入した後でもピン孔８の開口部を被覆することができ、環状部材１０に貫通孔１１や凹所１３を形成したり、封止部材１２や固定部材１４を取り付けたりする必要もなくなる。 In the present embodiment, the annular member 10 is integrally formed in a cylindrical annular shape from the beginning. For example, a divided body obtained by dividing a cylinder into a plurality of parts in the circumferential direction is joined by welding or the like, or is engaged with a butt portion in the circumferential direction. A joint portion may be provided and engaged with each other to form a cylindrical shape. In such a case, the opening of the pin hole 8 can be covered even after the bit head 5 is attached and the locking pin 9 is inserted, and the annular member 10 may be formed with a through hole 11 or a recess 13. , It is not necessary to attach the sealing member 12 or the fixing member 14.

また、本実施形態では、環状部材１０に、ピン孔８の開口部に連通可能な位置に貫通孔１１が形成されており、この貫通孔１１には該貫通孔１１を封止する封止部材１２が取り付けられている。従って、特に上述のように環状部材１０を円筒状に形成した場合でも、貫通孔１１を通して係止ピン９を容易にピン孔８に挿入することができるとともに、上述のようにこの環状部材１０をずらすことによって貫通孔１１の少なくとも一部を被覆して係止ピン９を抜け止めすることができる。さらに、貫通孔１１の残りの部分に係止ピン９が露出していても、封止部材１２によって貫通孔１１を封止することにより、掘削時に生成された掘削屑である繰り粉が貫通孔１１に入り込んで係止ピン９を摩滅させるような事態を防ぐことができる。 Further, in the present embodiment, the annular member 10 is formed with a through hole 11 at a position capable of communicating with the opening of the pin hole 8, and the through hole 11 is a sealing member for sealing the through hole 11. 12 is attached. Therefore, even when the annular member 10 is formed in a cylindrical shape as described above, the locking pin 9 can be easily inserted into the pin hole 8 through the through hole 11, and the annular member 10 can be inserted into the pin hole 8 as described above. By shifting, at least a part of the through hole 11 can be covered to prevent the locking pin 9 from coming off. Further, even if the locking pin 9 is exposed in the remaining portion of the through hole 11, the through hole 11 is sealed by the sealing member 12, so that the excavation dust generated during excavation is released into the through hole. It is possible to prevent a situation in which the locking pin 9 is worn out by entering the 11.

従って、本実施形態の上記構成は、このように掘削時に工具本体１に打撃力が与えられて衝撃が生じる、工具本体１が軸線Ｏ回りに回転されるデバイスであって、その先端部の軸線Ｏから偏心した位置に上記取付孔部２が開口するとともに、ピン孔８は工具本体１の外周面に開口しており、上記取付孔部２に取り付けられるのは、掘削チップ７が配設された掘削部６が取付軸部４の先端に設けられたビットヘッド５であって、工具本体１の回転に伴い掘削部６の軸線Ｏからの半径が拡縮径するように軸部中心線Ｌ２回りに回転する拡径ビットのような掘削工具に適用して効果的である。 Therefore, the above configuration of the present embodiment is a device in which the tool body 1 is rotated around the axis O, in which a striking force is applied to the tool body 1 during excavation to generate an impact, and the axis of the tip thereof. The mounting hole 2 is opened at a position eccentric from O, the pin hole 8 is opened on the outer peripheral surface of the tool body 1, and the excavation tip 7 is arranged to be mounted on the mounting hole 2. The excavated portion 6 is a bit head 5 provided at the tip of the mounting shaft portion 4, and the axis portion center line L2 is rotated so that the radius of the excavated portion 6 from the axis O is expanded or contracted as the tool body 1 rotates. It is effective when applied to excavation tools such as diameter-expanding bits that rotate in.

ただし、本実施形態では、このような拡径するビットヘッド５を有する拡径ビットに本発明を適用した場合について説明したが、本発明は、その工具本体１が、先端部に拡径しない掘削部を有してケーシングトップＱ（ケーシングパイプＰ）の先端に突出する円盤状のインナービットであるとともに、ケーシングトップＱ（ケーシングパイプＰ）の先端部にはこのインナービットと同軸に一体回転する環状のリングビットが取り付けられた、いわゆる二重管式ビットに適用することも可能である。 However, in the present embodiment, the case where the present invention is applied to the diameter-expanding bit having such a diameter-expanding bit head 5 has been described, but in the present invention, the tool body 1 does not expand the diameter to the tip portion. A disk-shaped inner bit that has a portion and projects to the tip of the casing top Q (casing pipe P), and an annular shape that rotates integrally with the inner bit at the tip of the casing top Q (casing pipe P). It is also possible to apply to a so-called double pipe type bit to which the ring bit of the above is attached.

さらに、本実施形態では、工具本体１先端部の円柱部１Ｃの外周に、ケーシングパイプＰの先端部に取り付けられた円筒状のケーシングトップＱが配設されており、このケーシングトップＱの内径が、工具本体１の第１段部１Ｂの外径よりも小さくされるとともに、環状部材１０の円筒部１０Ｂの外径は、このケーシングトップＱの内径よりも小さくされているので、ケーシングトップＱの内周面と円柱部１Ｃの外周面との間に環状部材１０の円筒部１０Ｂが配設されることになる。 Further, in the present embodiment, a cylindrical casing top Q attached to the tip of the casing pipe P is arranged on the outer periphery of the cylindrical portion 1C at the tip of the tool body 1, and the inner diameter of the casing top Q is The outer diameter of the cylindrical portion 10B of the annular member 10 is smaller than the inner diameter of the casing top Q, so that the outer diameter of the first step portion 1B of the tool body 1 is smaller than that of the casing top Q. The cylindrical portion 10B of the annular member 10 is arranged between the inner peripheral surface and the outer peripheral surface of the cylindrical portion 1C.

このため、本実施形態によれば、掘削時に生成された繰り粉がケーシングトップＱの内周面と円柱部１Ｃの外周面の間に入り込むこと自体を環状部材１０によって防ぐことができ、ケーシングトップＱや円柱部１Ｃの摩耗も防ぐことができる。しかも、掘削時に環状部材１０の環状部１０Ａを工具本体１の第１段部１ＢとケーシングトップＱに当接させた状態で、環状部材１０の貫通孔１１と工具本体１のピン孔８とは、軸線Ｏ方向においてケーシングトップＱの先端面よりも後端側に配設されるので、上記繰り粉が貫通孔１１やピン孔８に入り込んで封止部材１２や係止ピン９を摩滅するのも確実に防ぐことが可能となる。 Therefore, according to the present embodiment, the annular member 10 can prevent the milling powder generated during excavation from entering between the inner peripheral surface of the casing top Q and the outer peripheral surface of the cylindrical portion 1C, and the casing top. It is also possible to prevent wear of Q and the cylindrical portion 1C. Moreover, the through hole 11 of the annular member 10 and the pin hole 8 of the tool body 1 are in a state where the annular portion 10A of the annular member 10 is in contact with the first step portion 1B of the tool body 1 and the casing top Q during excavation. Since it is arranged on the rear end side of the casing top Q in the axis O direction from the front end surface, the milling powder enters the through hole 11 and the pin hole 8 and wears out the sealing member 12 and the locking pin 9. Can be reliably prevented.

１工具本体
１Ａシャンク部
１Ｂ第１段部
１Ｃ円柱部
１Ｄ排出溝
２取付孔部
３ブロー孔
４取付軸部
４Ａ凹溝
５ビットヘッド
６掘削部
７掘削チップ
８ピン孔
９係止ピン
１０環状部材
１０Ａ環状部
１０Ｂ円筒部
１１貫通孔
１２封止部材
１３凹所
１４固定部材
Ｏ工具本体１の軸線
Ｔ工具回転方向
Ｐケーシングパイプ
Ｑケーシングトップ（第２段部）
Ｌ１孔部中心線（取付孔部２の中心線）
Ｌ２軸部中心線（取付軸部４の中心線）
Ａ軸部中心線Ｌ２に直交する平面
Ｃピン孔中心線 1 Tool body 1A Shank part 1B 1st stage part 1C Cylindrical part 1D Discharge groove 2 Mounting hole part 3 Blow hole 4 Mounting shaft part 4A Concave groove 5 Bit head 6 Excavation part 7 Excavation tip 8 Pin hole 9 Locking pin 10 Ring member 10A Circular part 10B Cylindrical part 11 Through hole 12 Sealing member 13 Recessed part 14 Fixing member O Axis of tool body 1 Tool rotation direction P Casing pipe Q Casing top (second stage part)
L1 hole center line (center line of mounting hole 2)
L2 shaft center line (center line of mounting shaft 4)
Plane orthogonal to A-axis center line L2 C Pin hole center line

Claims

An excavation part is provided at the tip of a columnar tool body that is rotated around the axis, and a casing pipe is arranged around the tip of the tool body.
A first step portion projecting to the outer peripheral side is provided on the rear end side of the tip portion of the tool body, and a second step portion projecting to the inner peripheral side is provided on the inner peripheral portion of the tip of the casing pipe.
Between the front end surface of the first step portion and the rear end surface of the second step portion, the outer diameter of the tool body is smaller than the outer diameter of the first step portion and is closer to the tip side than the first step portion. An annular member having a larger inner diameter and an outer diameter larger than the inner diameter of the second step portion and smaller than the inner diameter of the casing pipe on the rear end side of the second step portion is interposed .
An excavation tool characterized in that the tool body can be inserted into the casing pipe in a state where the annular member is brought into contact with the first stage portion in advance .

The excavation tool according to claim 1, wherein the outer diameter of the annular member is larger than the outer diameter of the first stage portion of the tool body.

The excavation tool according to claim 1 or 2, wherein the annular member is formed of a material having a hardness equal to or lower than the hardness of the tool body.

The annular member is characterized by including a cylindrical portion disposed between the outer peripheral surface of the tool body on the tip side of the first step portion and the inner peripheral surface of the second step portion. The excavation tool according to any one of claims 1 to 3.