JP3750437B2

JP3750437B2 - Drilling tools

Info

Publication number: JP3750437B2
Application number: JP26020599A
Authority: JP
Inventors: 猛林; 仁也久田; 和由吉田
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 1999-09-14
Filing date: 1999-09-14
Publication date: 2006-03-01
Anticipated expiration: 2019-09-14
Also published as: JP2001082063A

Description

【０００１】
【発明の属する技術分野】
本発明は、工具本体の先端部に掘削ビットが取り付けられた掘削工具に関するものである。
【０００２】
【従来の技術】
この種の掘削工具としては、工具本体の先端部外周に内周側に凹むように形成された凹部に、この工具本体の中心軸線に対して平行に偏心した中心線回りに回転可能に拡径ビットが取り付けられるとともに、この工具本体の先端部中央には上記軸線に沿って取付孔が形成され、円盤状に形成されたビット本体の後端側に取付軸部が形成された掘削ビット（パイロットビット）が、この取付軸部を上記取付孔に挿入して取り付けられたものが提案されている。しかして、かかる掘削工具では、上記掘削ビットのビット本体の先端面と拡径ビットの先端面とに、超硬チップが植設されるなどして切刃が設けられており、工具本体を上記軸線回りに回転させるとともに該軸線方向先端側に打撃力を与えることにより、この軸線からの外径が拡径するように上記拡径ビットを回転させた状態で上記切刃によって掘削を行う一方、掘削終了時にはこの掘削時の回転方向とは反対向きに工具本体を回転させることにより、上記拡径ビットを縮径させた状態として工具本体を削孔から引き抜くことができる。
【０００３】
【発明が解決しようとする課題】
ところで、このような従来の掘削工具において、上記取付孔に取付軸部を挿入して掘削ビットを工具本体に取り付ける際には、一般に取付孔の内周に雌ネジ部を形成するとともに取付軸部外周には雄ネジ部を形成してこれら雌雄ネジ部を螺合させる方法が採られている。そして、この雌雄ネジ部の捩れの向きは、掘削時の工具本体の回転によって取付軸部が緩んで掘削ビットが外れたりすることがないように、この掘削時の回転方向の後方側に向かうに従い後端側に向かうように形成されている。
【０００４】
しかしながら、このような捩れの向きに掘削ビットの取付軸部が工具本体の取付孔に螺合させられた掘削工具では、掘削時に掘削ビットに作用する荷重によって取付軸部は取付孔にきつくねじ込まれて締め付けられることとなり、摩耗などが生じた際にこの掘削ビットを取り外して交換するのに、きわめて多くの労力と時間とを要する結果となってしまう。その一方で、このような締め付けが生じることのないように、例えば断面円形の取付孔に円柱状の取付軸部を嵌挿した上で止めネジやピンで固定したりした場合には、工具本体の回転に対する掘削ビットの取付剛性を確保することができなくなって、掘削ビット先端の切刃による掘削が不可能となるおそれがある。
【０００５】
本発明は、このような事情を鑑みてなされたもので、このように取付軸部を取付孔に挿入して掘削ビットを工具本体に取り付けた掘削工具において、工具本体を回転させて掘削を行う場合でも掘削ビットの取付剛性を十分に確保しつつ、交換時等には掘削ビットを工具本体から容易に取り外すことが可能な掘削工具を提供することを目的とする。
【０００６】
【課題を解決するための手段】
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工具本体の先端部に、先端側に切刃が設けられるとともに後端側に取付軸部が形成された掘削ビットが、上記工具本体の先端部中央に開口して上記軸線に沿って延びる取付孔に上記取付軸部を挿入させて取り付けられた掘削工具において、まず第１に、上記取付孔の内周に、上記軸線に平行に延びる凹溝を形成するとともに、上記取付軸部の外周には、その両側面が上記凹溝の両内壁に密着する突条を形成し、また上記工具本体の先端部外周には内周側に凹む凹部を形成するとともに、この凹部には、先端側に切刃が設けられた拡径ビットを上記軸線に平行に偏心した中心軸回りに回転可能に収容し、上記掘削ビットには、先端面に上記切刃が設けられた円盤状のビット本体を備えるとともに、このビット本体の後端面には、上記拡径ビットの先端部を回転可能に支持する支持部を設け、この支持部を、上記ビット本体の後端面に形成された支持孔または支持軸として、上記拡径ビットの先端には上記支持孔に嵌挿される取付軸または上記支持軸を嵌挿可能な取付孔を形成したことを特徴とし、また第２には、上記取付孔に、上記軸線に直交する断面が多角形状をなす嵌合部を形成するとともに、上記取付軸部には、その側面が嵌合部の内壁に密着する断面多角形状の被嵌合部を形成し、また上記工具本体の先端部外周には内周側に凹む凹部を形成するとともに、この凹部には、先端側に切刃が設けられた拡径ビットを上記軸線に平行に偏心した中心軸回りに回転可能に収容し、上記掘削ビットには、先端面に上記切刃が設けられた円盤状のビット本体を備えるとともに、このビット本体の後端面には、上記拡径ビットの先端部を回転可能に支持する支持部を設け、この支持部を、上記ビット本体の後端面に形成された支持孔または支持軸として、上記拡径ビットの先端には上記支持孔に嵌挿される取付軸または上記支持軸を嵌挿可能な取付孔を形成したことを特徴とする。従って、このように構成された掘削工具では、いずれの場合も取付軸部の側面が取付孔の内壁に周方向に密着した状態で取付軸部が取付孔に嵌合させられるので、上述のような雌雄ネジ部による螺合によらずとも、工具本体の回転に対する掘削ビットの取付剛性を十分に確保することができる。
【０００７】
ここで、上記凹溝を、上記凹部が内周側に最も凹む部位を避けるように形成したり、あるいは上記軸線に直交する断面において、上記嵌合部の内壁がなす上記多角形の辺を、この凹部の壁面のうち該凹部が内周側に最も凹む部位に位置する壁面部と平行となるように形成したりすれば、この凹部と上記取付孔との間に大きな肉厚を確保して、掘削ビットの取付剛性の一層の向上を図ることができるとともに、この工具本体先端部の凹部と取付孔との間に損傷が生じたりするのを防ぐことができる。
【０００８】
そして、本発明では、上記掘削ビットを、先端面に上記切刃が設けられた円盤状のビット本体を備えたものとするとともに、このビット本体の後端面に、上記拡径ビットの先端部を回転可能に支持する上述のような支持部を設けることにより、この拡径ビットについてもその取付剛性を十分に確保することが可能となる。さらに、上記工具本体に、上記取付孔に開口するようにピン取付孔を穿設するとともに、このピン取付孔には係合ピンを上記取付孔内に突出して上記取付軸部に係合するように取り付ければ、取付軸部が工具本体の先端側から取付孔に嵌挿されて取り付けられることとなる掘削ビットを確実に抜け止めすることができ、工具本体に軸線方向に打撃力が与えられる場合でも、その衝撃によって掘削ビットが外れたりするような事態を防ぐことができる。
【０００９】
【発明の実施の形態】
図１ないし図３は、本発明の第１の実施形態を示すものである。本実施形態において工具本体１は、外形形状が先端側（図１において左側）に向かうに従い段階的に拡径する概略多段円柱状に形成されていて、その縮径した後端部がシャンク部２とされており、このシャンク部２に図示されないハンマ等が取り付けられることにより、該工具本体１は掘削時にその中心軸線Ｏ方向先端側に向けて打撃力を受けるとともに、この軸線Ｏ回りに図２に符号Ｔで示す工具回転方向に回転させられる。さらに、このシャンク部２の後端面から先端側に向けては軸線Ｏに沿って掘削時に圧縮空気等が供給される貫通孔３が形成されていて、この貫通孔３は途中で３方向に分岐させられるとともに、その先端側の部分が拡径して工具本体１の先端面１Ａの中央に開口させられることにより、本実施形態における取付孔４とされており、この取付孔４に掘削ビットとしてパイロットビット５が取り付けられている。また、この工具本体１の先端部の外周には、内周側に凹むように３つの凹部６…が周方向に等間隔に形成され、これらの凹部６…にはそれぞれ上記軸線Ｏに平行に偏心した中心軸Ｘ回りに回転可能に拡径ビット７が取り付けられている。
【００１０】
上記パイロットビット５は、工具本体１の外径よりもやや小さな外径の円盤状をなすビット本体８の後端面に該ビット本体８の中心線に沿って取付軸部９が一体に突設された形状をなしており、この取付軸部９が上記取付孔４に挿入されることにより、該パイロットビット５は上記中心線を工具本体１の軸線Ｏと同軸として該工具本体１の先端部に取り付けられる。また、この取付軸部９には軸線Ｏに沿って排気孔１０が形成されており、この排気孔１０は先端側のビット本体８部分において分岐して、すり鉢状をなすこのビット本体８の先端面に放射状に形成された排気溝１１…に開口させられる一方、ビット本体８の外周面には軸線Ｏ方向に向けて延びる掘削屑の排出溝１２が周方向に間隔を開けて複数条形成されていて、上記排気溝１１…はこのうち一部の排出溝１２…に連通させられている。さらに、このビット本体６の先端面と外周面の先端側とには、超硬合金等の硬質材料よりなるチップ１３が上記排気溝１１…および排出溝１２…を避けるようにして多数植設されており、これらのチップ１３…によってパイロットビット５の先端側に設けられる切刃が構成されている。
【００１１】
一方、このパイロットビット５の上記取付軸部９は、その外径が後端側に向かうに従い３段に縮径する略多段円柱状とされており、このうち最後段の小径部９Ａの外周面には、断面略半円弧状をなす環状溝１４が中段の中径部９Ｂ側に形成されるとともに、この中段の中径部９Ｂの外周面には、軸線Ｏに平行に延びる突条１５が周方向に間隔を開けて複数条（本実施形態では６条）同形同大に形成されている。これらの突条１５…はそれぞれ、本実施形態では取付軸部９の最先段の大径部９Ｃとの間に僅かな間隔を開けた位置から中段の中径部９Ｂの全長に亙って延びるように形成され、軸線Ｏを含む平面による断面が図１に示すように該軸線Ｏに対する径方向に偏平した等脚台形状をなしている。また、この突条１５は、軸線Ｏに直交する断面においては、図４に示すように中径部９Ｂの外周面から突出する半円の突端部を平面または凸曲面によって切り欠いたように形成され、すなわちこの突条１５の周方向を向く一対の側面１５Ａ，１５Ａが、上記平面または凸曲面によって切り欠かれて形成された該突条の外周面１５Ｂ側に向かうに従い凸曲しつつ互いに接近する円弧面とされた、略等脚台形状の断面をなすように形成されている。
【００１２】
さらに、本実施形態におけるこれら６条の突条１５…は、図４に示すように取付軸部９の周方向において、互いに近接する一対の突条１５，１５が、該一対の突条１５，１５間の間隔よりも大きな間隔を開けて等間隔に３対配設された配列をなしており、各対の突条１５，１５のうち周方向の一方の側（本実施形態では上記工具回転方向Ｔの後方側）の突条１５の上記外周面１５Ｂには、軸線Ｏに対する径方向に凹む凹孔１６がそれぞれ形成されている。なお、これらの突条１５…が形成される上記中径部９Ｂは、その軸線Ｏ方向の長さが上記小径部９Ａや大径部９Ｃよりも長くされていて、突条１５の長さもこれらより長くされている。また、この大径部９Ｃは、その外径が突条１５の上記外周面１５Ｂがなす外径と略同径とされ、軸線Ｏを含む断面においてパイロットビット５のビット本体８の後端面８Ａに凹曲面を介して滑らかに連なるように形成されている。さらに、このビット本体８の後端面８Ａの外周側には、先端側に凹む断面円形の３つの支持孔１７…が周方向に等間隔に形成されており、これらの支持孔１７…は、当該パイロットビット５を工具本体１に取り付けた状態において上記中心軸Ｘと同軸となるように配設されていて、本実施形態における支持部とされている。
【００１３】
一方、工具本体１の上記凹部６は、該工具本体１の先端面１Ａから後退して先端側を向く底面１８と、この底面１８の周縁から軸線Ｏに平行に先端側に延びて上記先端面１Ａに達する壁面１９とにより画成されており、底面１８はさらに、該底面１８の工具回転方向Ｔの後方側に広がって工具回転方向Ｔ側に向けて内周側に延在する軸線Ｏに垂直な平坦面状の底面部１８Ａと、この底面部１８Ａの工具回転方向Ｔ側にあって外周側に向かうに従い後端側に傾斜する底面部１８Ｂとにより構成されていて、上記底面部１８Ａには上記中心軸Ｘを中心とした断面円形の支持孔２０が形成されるとともに、上記傾斜面部１８Ｂには、上記貫通孔３から３方向に分岐させられた分岐孔３Ａがそれぞれ開口させられている。また、この分岐孔３Ａの途中からはさらに小径孔３Ｂが分岐させられて軸線Ｏに平行に先端側に向けて延びており、この小径孔３Ｂは底面１８の上記底面部１８Ａ，１８Ｂの交差稜線部に開口させられている。さらに、工具本体１の外周には軸線Ｏに平行に延びる掘削屑の排出溝２１が各凹部６に対して２条ずつ形成されており、これらの排出溝２１，２１は上記底面部１８Ｂの外周側において工具回転方向Ｔ側とその後方側とに開口させられている。
【００１４】
これに対して、上記壁面１９は、図２に示すように先端側からみて、工具本体１の外周面に鋭角に交差するように上記底面部１８Ａの工具回転方向Ｔ後方側に屹立して工具回転方向Ｔ側を向く壁面部１９Ａと、この壁面部１９Ａに滑らかに接する上記中心軸Ｘを中心とした凹円弧面状の壁面部１９Ｂと、この壁面部１９Ｂにさらに滑らかに接して上記壁面部１８Ａに対し鋭角をなすように工具回転方向Ｔ側に真っ直ぐに延び、工具本体１の内周側に最も凹んで上記取付孔４に近接する壁面部１９Ｃと、この壁面部１９Ｃに連なる段差状の壁面部１９Ｄと、この壁面部１９Ｄを介して上記壁面部１９Ｃに対し工具回転方向Ｔ側に一段後退し、かつ該壁面部１９Ｃに平行に真っ直ぐ延びて工具本体１の外周に至る、工具回転方向Ｔの後方側を向く壁面部１９Ｅとから構成されている。
【００１５】
このように構成された凹部６に取り付けられる上記拡径ビット７は、そのビット本体２２が先端側からみて、上記壁面部１９Ｃ〜１９Ｅにそれぞれ略密着可能とされた段差状に連なる側面２２Ａ〜２２Ｃと、このうち側面２２Ａ，２２Ｃに平行に延びる側面２２Ｄと、側面２２Ａ，２２Ｄに滑らかに接する凸半円弧面状の側面２２Ｅと、側面２２Ｃ，２２Ｄ間に形成された凸曲面状の側面２２Ｆとを備えた羽根型をなしており、凸円弧面状の側面２２Ｅの半径は凹円弧面状の上記壁面部１９Ｂに密着可能な大きさとされている。また、このビット本体２２の先後端面には、側面２２Ｅがなす凸円弧の中心軸と同軸に延びる断面円形の取付軸２３，２４が該ビット本体２２に一体に形成されていて、先端側の取付軸２３はパイロットビット５の上記支持孔１７に、後端側の取付軸２４は凹部６の支持孔２０にそれぞれ嵌挿可能とされており、こうして取付軸２３，２４が支持孔１７，２０に嵌挿されて支持されることにより、当該拡径ビット７は、上記側面２２Ｅが壁面部１９Ｂに摺接しながら上述のように上記中軸Ｘを中心に回動可能とされている。
【００１６】
しかして、この拡径ビット７のビット本体２２は、該拡径ビット７が先端側からみて中心軸Ｘ回りに工具回転方向Ｔ側に回転したときには、図１の左下側に示された拡径ビット７のように上記側面２２Ａ〜２２Ｃが壁面部１９Ｃ〜１９Ｅに略密着して凹部６内に収容され、その軸線Ｏからの外径が縮径させられる一方、中心軸Ｘ回りに工具回転方向Ｔの後方側に回転したときには、図１の上側に示された拡径ビット７のように側面２２Ｄが壁面部１９Ａに当接して該ビット本体２２の側面２２Ｆ側が工具本体１の外周面よりも外周側に突出し、その軸線Ｏからの外径が拡径するようになされている。さらに、この側面２２Ｆは、こうして拡径ビット７が拡径した状態において上記軸線Ｏを中心とした凸円弧面をなすようにされており、この側面２２Ｆの先端側と上記側面２２Ｃの先端側、およびこの拡径状態で上記パイロットビット５よりも外周側に突き出すビット本体２２の先端面部分とには、やはり超硬合金等の硬質材料よりなるチップ２５が多数植設されていて、これらのチップ２５によってこの拡径ビット７の先端側に設けられる切刃が構成されている。
【００１７】
さらにまた、パイロットビット５の上記取付軸部９が挿入される上記取付孔４は、該取付軸部９の形状に合わせてその内径が工具本体１の先端面１Ａ側から上記貫通孔３に向けて３段に縮径するように形成されており、最も後端側の貫通孔３に連なる小径部４Ａは取付軸部９の小径部９Ａが、中段の中径部４Ｂは取付軸部９の中径部９Ｂが、先端面１Ａ側の大径部４Ｃは取付軸部９の大径部９Ｃが、それぞれ嵌挿可能な径および深さに形成されている。そして、このうち中径部４Ｂから大径部４Ｃにかけては、その内周に、軸線Ｏに平行に延びる上記突条１５と同数（すなわち６条）の凹溝２６が、周方向に該突条１５…と等しい間隔および配列で形成されている。これらの凹溝２６…は、それぞれ軸線Ｏに直交する断面においてその内壁２６Ａが、上記突条１５の両側面１５Ａ，１５Ａが密着可能な大きさの半円状をなして中径部４Ｂの内周面から凹むように形成され、また軸線Ｏからその溝底までの深さは上記大径部４Ｃの半径よりも大きくされており、従って大径部４Ｃにおいてもこれらの凹溝２６…は図２および図３に示すようにその溝底側が残されたまま軸線Ｏに平行に延び、先端面１Ａに達して開口させられる。
【００１８】
さらに、上記突条１５…と等しい配列とされたこれらの凹溝２６…は、周方向に互いに近接する一対の凹溝２６，２６が３対、これら対をなす凹溝２６，２６間の間隔よりも大きな間隔で周方向に等間隔に配列されることとなるが、ここで本実施形態では、これら３対の凹溝２６間の間隔が大きく開けられた部分が、図２に示すように上記凹部６の壁面１９のうち内周側に最も凹む壁面部１９Ｃ側に位置するように、すなわちこの内周側に最も凹む壁面部１９Ｃを避けて凹溝２６が形成されるようになされている。より具体的には、先端側からみて図１に示すように軸線Ｏと凹部６が内周側に最も凹む部位とを通る仮想直線（本実施形態では軸線Ｏを通って壁面部１９Ｃに直交する直線）Ｌ上に凹溝２６が形成されていないのが望ましい。
【００１９】
さらにまた、本実施形態では工具本体１に、その上記各凹部６の壁面１９のうち段差状の壁面部１９Ｄから、取付孔４の上記各対をなす凹溝２６，２６のうち工具回転方向Ｔの後方側の凹溝２６に向けて、軸線Ｏに対する径方向に工具本体１を貫通するようにピン取付孔２７が穿設されて取付溝４内に開口させられており、このピン取付孔２７は軸線Ｏ方向においては、パイロットビット５のビット本体８の後端面を工具本体１の先端面１Ａに密着させて取付軸部９を取付孔４に挿入した状態で、突条１５の外周面１５Ｂに形成された上記凹孔１６と等しい位置に配置されている。一方、工具本体１にはさらに、軸線Ｏに直交する平面内において該工具本体１の外周面から取付孔４の小径部４Ａの内周の接線方向に延び、該取付孔４に接して断面半円状に開口するようにピン取付孔２８が形成されており、このピン取付孔２８は、軸線Ｏ方向においては小径部４Ａの中径部４Ｂ側の部分を通過し、上記取付軸部９を取付孔４に挿入した状態でこの取付軸部９の小径部９Ａの断面半円状の上記環状溝１４と一致して断面略円形をなすように形成されている。そして、これらのピン取付孔２７，２８には、その大きさおよび深さに合わせた係合ピン２９，３０が外周側から挿入されてスペーサやスナップリングにより固定され、その先端部がパイロットビット５の上記凹孔１６および環状溝１４に係合させられている。
【００２０】
このような本実施形態の掘削工具は、まず上記支持孔２０に取付軸２４を嵌挿して凹部６…に拡径ビット７…をそれぞれ収容した上で、突条１５…を凹溝２６…に嵌合させるようにして取付孔４に取付軸部９を嵌挿するとともに拡径ビット７の取付軸２３を支持孔１７に嵌挿してパイロットビット５を工具本体１の先端部に装着し、さらに上記ピン取付孔２７，２８に係合ピン２９，３０を挿入して凹孔１６および環状溝１４に係合させることにより、組み立てられる。そして、掘削時には上記ハンマによって工具本体１に打撃力が与えられるとともに該ハンマを介して工具本体１が工具回転方向Ｔ側に回転させられることにより、拡径ビット７…が拡径してその先端側の切刃とパイロットビット５先端側の切刃とによって地盤等に削孔が形成され、さらに例えばこの削孔内に、工具本体１が挿通可能な内径と拡径時の拡径ビット７の外径よりも僅かに小さな外径とを有するケーシングパイプＰが挿入されてゆく。また、掘削終了後には、工具本体１が掘削時の工具回転方向Ｔとは逆回転させられることにより、拡径ビット７…が縮径するので、ケーシングパイプＰ内を通してパイロットビット５および拡径ビット７…ごと工具本体１を引き抜いてケーシングパイプＰだけを削孔内に残すことができる。
【００２１】
しかして、上記構成の掘削工具においては、この工具本体１の先端部に掘削ビットとして取り付けられるパイロットビット５が、上述のようにその取付軸部９を工具本体１の取付孔４に挿入するに際して、この取付軸部９の中径部９Ｂに形成された突条１５…を取付孔４の中径部４Ｂに形成された凹溝２６…に嵌合させて、この突条１５の両側面１５Ａ，１５Ａを凹溝２６の内壁２６Ａに密着させているので、掘削時の工具本体１の回転に伴ってパイロットビット５に作用する荷重をこの側面１５Ａ，１５Ａに密着する内壁２６Ａによって確実に受け止めることができ、このパイロットビット５の取付剛性を十分に確保することが可能となる。しかも、突条１５の両側面１５Ａ，１５Ａが凹溝２６の内壁２６Ａに直接密着しているので、取付孔４と取付軸部９との間に周方向にがたつきが生じるようなことも少ない。
【００２２】
そして、その一方で、これら突条１５…および凹溝２６…は工具本体１の軸線Ｏに平行に形成されているので、従来の雌雄ネジ部による螺合のように工具本体１の回転によって取付軸部９が取付孔４にきつく締め付けられるようなことはなく、パイロットビット５の交換時などにおいては、上記係合ピン２９，３０を抜き取ることにより、容易にパイロットビット５を取り外すことが可能である。なお、本実施形態では上記凹溝２６…を断面半円状に形成するとともに突条１５の側面１５Ａ，１５Ａをこの凹溝２６の内壁２６Ａに密着可能な円弧面状に形成しているが、突条１５を、外周面１５Ｂを平面や凸曲面で切り欠くことなくその全周に亙って凹溝２６の内壁面２６Ａに密着可能な断面半円状に形成したりしてもよく、またこのような半円形の断面ではなくとも、例えばこれら突条や凹溝の断面をその両側面と内壁とが互いに密着可能な方形状や台形状に形成したり、あるいはこれら両側面や内壁の断面がインボリュート曲線をなすように形成したりしてもよい。
【００２３】
また、本実施形態の掘削工具では、その工具本体１の先端部外周に形成された凹部６に拡径ビット７が中心軸Ｘ回りに回転可能に収容されており、掘削時にはこの拡径ビット７を拡径させることによって工具本体１よりも径の大きい削孔を形成可能とし、かつ掘削終了後には該拡径ビット７を縮径させることにより、上記削孔内に挿入したケーシングパイプＰ内を通して工具本体１を引き抜き可能としているが、このような拡径ビット７を収容する凹部６を形成するに際して、この凹部６の壁面１９のうち取付孔４に最も近接する壁面部１９Ｃにおいては、該取付孔４の内周に上記凹溝２６が形成されてはおらず、すなわちこの凹溝２６は、凹部６が工具本体１の内周側に最も凹む部位を避けるように形成されている。このため、本実施形態では、この凹部６と取付孔４との間に十分な肉厚を確保することが可能となって、これによっても掘削ビットとしてのパイロットビット５の取付剛性を確実に確保することができるので、このパイロットビット５に高い荷重が作用するような掘削条件下でも安定した掘削を促すことが可能となる。
【００２４】
さらに本実施形態では、このように拡径ビット７が工具本体１の先端部外周に回転可能に取り付けられるのに際して、上記パイロットビット５のビット本体８の後端面に支持部として支持孔１７…が形成されていて、これらの支持孔１７…に先端の取付軸２３をそれぞれ嵌挿して各拡径ビット７…が取り付けられており、すなわち該拡径ビット７はその両端が支持された状態で工具本体１に取り付けられるので、本実施形態によればこれら拡径ビット７についても高い取付剛性を確保することができ、一層安定した掘削作業を促すことが可能となる。なお、本実施形態では、このようにパイロットビット５のビット本体８後端面に支持孔１７を形成して拡径ビット７の取付軸１７を嵌挿しているが、逆にビット本体８の後端面に支持部として支持軸を形成するとともに拡径ビット７先端にはこの支持軸を嵌挿可能な取付孔を形成して拡径ビット７を支持するようにしてもよい。
【００２５】
さらにまた、本実施形態では、上記取付軸部９の６条の突条１５…のうち周方向に等間隔に位置することとなる半数の３条の突条１５…の外周面１５Ｂに凹孔１６がそれぞれ形成されるとともに、該取付軸部９の小径部９Ａには環状溝１４が形成され、工具本体１に形成されたピン取付孔２７…，２８に挿入した係合ピン２９…，３０をこれら凹孔１６…および環状溝１４に係合させることにより、軸線Ｏ方向先端側に取付軸部９が取付孔４に支持されている。従って、本実施形態によれば、例えば掘削時に上記ハンマから与えられる打撃力による衝撃などによって取付軸部９が取付孔４から抜けてパイロットビット５が外れてしまうようなこともなく、このパイロットビット５および拡径ビット７…を確実に保持して円滑な掘削作業を執り行うことができる。なお、この掘削時にパイロットビット５に作用する軸線Ｏ方向の荷重は、このパイロットビット５のビット本体８の後端面が工具本体１の先端面１Ａに密着することでこの先端面１Ａによって受け止められるので、上記係合ピン２９…，３０にかかる荷重が作用して損傷が生じるようなことはない。
【００２６】
次に、図５ないし図７は本発明の第２の実施形態を示すものであり、また図８および図９は本発明の第３の実施形態を示すものであって、いずれも図１ないし図４に示した第１の実施形態と共通する部分には同一の符号を配して説明を省略する。このうち、図５ないし図７に示す第２の実施形態は、第１の実施形態と同様に工具本体１の先端部外周に形成された３つの凹部６…のそれぞれに拡径ビット７が収容可能とされているものであって、取付孔４に上記凹溝２６が形成される代わりに断面正６角形状の嵌合部３１が形成されるとともに、掘削ビットとしてのパイロットビット５の取付軸部９には、上記突条１５に代えてこの嵌合部３１に嵌合可能なやはり断面正６角形状の被嵌合部３２が形成されていることを特徴とする。そして、さらにこの第２の実施形態では、軸線Ｏに直交する断面において図６に示すように、嵌合部３１の内壁３１Ａ…がなす正６角形の６辺のうち、周方向に１つおきに位置する３辺が、上記凹部６の壁面１９のうち該凹部６が内周側に最も凹む部位に位置する上記壁面部１９Ｃとそれぞれ平行となるように形成されている。
【００２７】
また、この第２の実施形態では、上記係合孔２７よりも後端側において、図７に示すように一対の上記ピン取付孔２８，２８が軸線Ｏに直交する一の平面上で取付孔４を挟むように互いに平行に工具本体１に形成されており、これらのピン取付孔２８，２８は上記一の平面に沿った断面において、嵌合部３１の内壁３１Ａ…がなす正６角形の６辺のうち互いに対向する２辺に沿って延びて各内壁３１Ａに断面半円形の溝状に開口するようにされている。これに対して取付軸部９の上記被嵌合部３２には、当該パイロットビット５を取り付けた状態において上記一の平面の位置に、この一の平面に沿った断面において該被嵌合部３２の側面３２Ａ…がなす正６角形の６辺のうち互いに対向する２辺に沿って平行に延びるように断面半円状の溝３２Ｂ，３２Ｂが形成されており、取付軸部９を取付孔４に挿入することにより、これらの溝３２Ｂ，３２Ｂと上記内壁３１Ａ，３１Ａに開口したピン取付孔２８，２８の断面半円形の溝とが一致して該ピン取付孔２８，２８に連通する断面円形の孔がそれぞれ画成され、これらの孔にピン取付孔２８，２８を通して係合ピン３０，３０がそれぞれ嵌挿されて取り付けられ、取付軸部９に係合させられている。
【００２８】
一方、図８および図９に示す第３の実施形態においては、工具本体１の先端部外周に４つの凹部６…が周方向に等間隔に、すなわち９０°おきに形成され、従って該凹部６…の各壁面部１９Ａ〜１９Ｅも互いに周方向に９０°おきに配設されていて、これらの凹部６…にそれぞれ拡径ビット７が収容される構成とされており、これに対して取付孔４には断面正８角形状の嵌合部３３が形成されるとともに、パイロットビット５の取付軸部９にはこの嵌合部３３に嵌合可能なやはり断面正８角形状の被嵌合部３４が形成されている。そして、さらにこの第３の実施形態では、上記嵌合部３３の内壁３３Ａ…がなす正８角形の８辺のうち、周方向に１つおきに位置する４辺が、上記凹部６の壁面１９のうち該凹部６が最も内周側に凹む部位に位置する上記壁面部１９Ｃとそれぞれ平行となるように形成されている。
【００２９】
また、この第３の実施形態でも、工具本体１の上記係合孔２７より後端側の軸線Ｏに垂直な一の平面上に、図９に示すように一対の上記ピン取付孔２８，２８が、上記嵌合部３３の内壁３３Ａ…がなす正８角形の８辺のうち互いに対向する２辺に沿って延びて該内壁３３Ａ，３３Ａに断面半円弧形に開口するように形成されるとともに、取付軸部９の被嵌合部３４には、その側面３４Ａ…の断面がなす正８角形の８辺のうち互いに対向する２辺に沿って、これらピン取付孔２８，２８の開口部分と一致して断面円形の孔を画成する断面半円弧状の溝３４Ｂ，３４Ｂが形成されている。そして、こうして形成される上記断面円形の孔に、ピン取付孔２８，２８を通して係合ピン３０，３０がそれぞれ嵌挿されて固定されることにより、該係合ピン３０，３０が取付軸部９に上記軸線Ｏ方向に係合させられている。
【００３０】
しかして、このような第２、第３の実施形態においても、取付孔４の上記嵌合部３１，３３の内壁３１Ａ…，３３Ａ…に、取付軸部９の被嵌合部３２，３４の各側面３２Ａ…，３４Ａ…が密着することにより、取付軸部９の軸線Ｏ回りの周方向の回動が拘束されるので、該取付軸部９を取付孔４に高い剛性で取り付けてパイロットビット５を工具本体１の先端部に保持することができ、また雌雄ネジ部による螺合のように掘削時に作用する荷重によって取付軸部９が取付孔４にきつく締め付けられることもない。しかも、上記第２の実施形態では３つの凹部６…の上記各壁面部１９Ｃ…が周方向に等間隔に配置され、すなわち１２０°おきに配置されているのに対して、断面正６角形状をなす嵌合部３１の内壁３１Ａ…は６０°おきに配置されて、そのうち１つおきの内壁３１Ａ…が上記壁面部１９Ｃに平行に配置され、また第３の実施形態では４つの凹部６…の各壁面部１９Ｃ…が９０°おきに配置されているのに対して、断面正８角形状をなす嵌合部３３の１つおき（９０°おき）の内壁３３Ａ…が各壁面部１９Ｃに平行に配置されており、従ってこれら壁面部１９Ｃと内壁３１Ａ，３３Ａとの間の間隔を一定に保って取付孔４周辺の剛性を確保することができる。
【００３１】
加えて、これら第２、第３の実施形態では、上記ピン取付孔２７よりも後端側に一対のピン取付孔２８，２８が形成されており、これらのピン取付孔２８，２８は軸線Ｏに垂直な上記一の平面において、取付孔４の嵌合部３１，３３の内壁３１Ａ…，３３Ａ…の断面がなす多角形の互いに対向する２辺に沿って、該取付孔４を挟み込むように形成されるとともに、取付軸部９の被嵌合部３２，３４には、その側面３２Ａ…，３４Ａ…の断面がなす多角形の互いに対向する２辺に沿って溝３２Ｂ，３２Ｂおよび溝３４Ｂ，３４Ｂが形成されていて、上記ピン取付孔２８，２８に嵌挿されて取り付けられた係合ピン３０，３０にこれらの溝３２Ｂ，３２Ｂや溝３４Ｂ，３４Ｂが係合させられている。従って、第１の実施形態のように断面円形の取付孔４および取付軸部９の接線方向に沿って形成された一のピン取付孔２８に係合ピン３０を取り付けて係合させる場合に比べ、係合ピン３０の数が増えるのは勿論、係合ピン３０と取付軸部９との係合長さを延長させることができるため、これら第２、第３の実施形態によれば、パイロットビット５のさらに確実な抜け止めを図ることができる。
【００３２】
なお、これら第２、第３の実施形態では、取付孔４の嵌合部３１，３３と取付軸部９の被嵌合部３２，３４とをそれぞれ互いに嵌合可能な断面正６、８角形状に形成しているが、嵌合部３１，３３を断面正６、８角形状とした場合には、例えば被嵌合部３２，３４を、嵌合部３１，３３の内壁３１Ａ…，３３Ａ…に密着可能な側面３２Ａ…，３４Ａ…を有する断面正１２、１６角形状や偏１２、１６角形状に形成したり、一つおきの内壁３１Ａ…，３３Ａ…に密着可能な側面３２Ａ…，３４Ａ…を有する偏６、８角形状に形成したりしてもよい。また、逆に被嵌合部３２，３４を断面正６、８角形状とした場合には、例えば嵌合部３１，３３を、被嵌合部３２，３４の一つおきの側面３２Ａ…，３４Ａ…に密着可能な内壁３１Ａ…，３３Ａ…を有する断面偏６、８角形状や、あるいは断面正３角形状、正方形状に形成したりしてもよく、特に後者の場合には、互いに隣接する内壁３１Ａ…，３３Ａ…同士が交差する隅部を、側面３２Ａ…，３４Ａ…に干渉しない範囲で凹曲面状に形成したりしてもよい。さらに、このような正６、８角形以外でも、取付孔の嵌合部に取付軸部の被嵌合部が嵌合可能であれば、他の多角形状の断面を採用することも可能である。
【００３３】
【発明の効果】
以上説明したように、本発明によれば、第１に、取付孔の内周に工具本体の中心軸線に平行に延びる凹溝を形成するとともに、掘削ビットの取付軸部の外周には、その両側面が上記凹溝の両内壁に密着する突条を形成することにより、また第２には、取付孔に上記軸線に直交する断面が多角形状をなす嵌合部を形成するとともに、取付軸部にはその側面が嵌合部の内壁に密着する断面多角形状の被嵌合部を形成することにより、掘削ビットの工具本体への取付剛性を確保して安定した掘削作業を図ることができるとともに、雌雄ネジ部による螺合などの場合のように掘削時の荷重によって掘削ビットの取付軸部が工具本体の取付孔にきつく締め付けられるようなことがなく、掘削ビットの交換等をきわめて容易かつ短時間に行うことが可能となる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態を示す側断面図である。
【図２】図１に示す実施形態を先端側からみた正面図である。
【図３】図１におけるＹＹ断面図である。
【図４】図１におけるＺＺ断面図である。
【図５】本発明の第２の実施形態を示す側断面図である。
【図６】図５におけるＹＹ断面図である。
【図７】図５におけるＺＺ断面図である。
【図８】本発明の第３の実施形態を示す、図５におけるＹＹ断面に相当する図である。
【図９】本発明の第３の実施形態を示す、図５におけるＺＺ断面に相当する図である。
【符号の説明】
１工具本体
４取付孔
５パイロットビット（掘削ビット）
６凹部
７拡径ビット
８パイロットビット５のビット本体
９取付軸部
１３，２５チップ（切刃）
１４環状溝
１５突条
１５Ａ突条１５の側面
１６凹孔
１７，２０支持孔
１９Ｃ凹部６の壁面１９の壁面部（凹部が内周側に最も凹む部位）
２３，２４拡径ビット７の取付軸
２６凹溝
２６Ａ凹溝２６の内壁
２７，２８ピン取付孔
２９，３０係合ピン
３１，３３嵌合部
３１Ａ，３３Ａ嵌合部３１，３３の内壁
３２，３４被嵌合部
３２Ａ，３４Ａ被嵌合部３２，３４の側面
３２Ｂ，３４Ｂ溝
Ｏ工具本体１の中心軸線
Ｘ拡径ビット７の中心軸
Ｔ掘削時の工具回転方向[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an excavation tool in which an excavation bit is attached to a distal end portion of a tool body.
[0002]
[Prior art]
As this type of excavating tool, the diameter of the tool main body is increased in diameter so that it can be rotated around a center line that is eccentric in parallel to the central axis of the tool main body, in a recess formed on the outer periphery of the tip end of the tool main body. A drill bit (pilot) in which a mounting hole is formed in the center of the tip of the tool body along the axis, and a mounting shaft is formed on the rear end side of the disk-shaped bit body. Bits) are proposed in which the mounting shaft portion is inserted into the mounting hole. Thus, in such a drilling tool, a cutting edge is provided by, for example, implanting a cemented carbide tip on the tip surface of the bit body of the drilling bit and the tip surface of the diameter-expanding bit, While rotating around the axis and applying a striking force to the tip end in the axial direction, excavation is performed with the cutting blade while the diameter expansion bit is rotated so that the outer diameter from the axis is expanded, At the end of excavation, the tool main body can be pulled out of the drilling hole in a state where the diameter expansion bit is reduced by rotating the tool main body in the direction opposite to the rotation direction at the time of excavation.
[0003]
[Problems to be solved by the invention]
By the way, in such a conventional excavation tool, when the excavation bit is attached to the tool body by inserting the attachment shaft portion into the attachment hole, generally, an internal thread portion is formed on the inner periphery of the attachment hole and the attachment shaft portion. A method is adopted in which a male screw part is formed on the outer periphery and these female and male screw parts are screwed together. And the direction of twisting of this male and female screw part is as it goes to the rear side of the rotation direction at the time of excavation so that the mounting shaft part does not loosen due to the rotation of the tool main body at the time of excavation and the excavation bit is detached. It is formed to face the rear end side.
[0004]
However, in a drilling tool in which the mounting shaft portion of the drilling bit is screwed into the mounting hole of the tool body in such a twisting direction, the mounting shaft portion is tightly screwed into the mounting hole by a load acting on the drilling bit during drilling. As a result, it takes a lot of labor and time to remove and replace the excavation bit when wear occurs. On the other hand, in order to prevent such tightening, for example, when a cylindrical mounting shaft is inserted into a mounting hole having a circular cross section and then fixed with a set screw or pin, the tool body There is a risk that the mounting rigidity of the excavation bit with respect to the rotation of the excavation bit cannot be secured, and excavation with the cutting edge at the end of the excavation bit becomes impossible.
[0005]
The present invention has been made in view of such circumstances, and in such an excavation tool in which the attachment shaft portion is inserted into the attachment hole and the excavation bit is attached to the tool main body, excavation is performed by rotating the tool main body. Even in such a case, an object of the present invention is to provide an excavation tool capable of easily removing the excavation bit from the tool body when replacing the excavation bit while sufficiently securing the attachment rigidity of the excavation bit.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve such an object, the present invention provides a cutting edge on the tip side of the tool body rotated about the axis and a mounting shaft portion on the rear end side. In the excavation tool in which the excavation bit in which the excavation bit is formed is installed by inserting the attachment shaft portion into the attachment hole that opens in the center of the tip portion of the tool body and extends along the axis, first, the attachment A concave groove extending in parallel to the axis is formed on the inner periphery of the hole, and ridges whose both side surfaces are in close contact with both inner walls of the concave groove are formed on the outer periphery of the mounting shaft portion. In addition, a concave portion that is recessed toward the inner peripheral side is formed on the outer periphery of the tip end portion of the tool body, and in this recess, a diameter expanding bit provided with a cutting blade on the tip end side is arranged around a central axis that is eccentric in parallel with the axis. The excavation bit is provided with a disk-shaped bit body with the cutting edge provided on the tip surface, and the tip end portion of the diameter-expanding bit is rotated on the rear end surface of the bit body. A support portion that supports the support body is provided, and the support portion is used as a support hole or a support shaft formed in the rear end surface of the bit body, and a mounting shaft or the above-described attachment shaft is inserted into the support hole at the tip of the enlarged diameter bit. A mounting hole into which the support shaft can be inserted is formed. Second, the fitting hole is formed with a fitting portion having a polygonal cross section perpendicular to the axis, and the fitting shaft portion has a fitting portion whose side surface is a fitting portion. Forming a mating section with a polygonal cross section closely contacting the inner wall In addition, a concave portion that is recessed toward the inner peripheral side is formed on the outer periphery of the tip end portion of the tool body, and in this recess, a diameter expanding bit provided with a cutting blade on the tip end side is arranged around a central axis that is eccentric in parallel with the axis. The excavation bit is provided with a disk-shaped bit body with the cutting edge provided on the tip surface, and the tip end portion of the diameter-expanding bit is rotated on the rear end surface of the bit body. A support portion that supports the support body is provided, and the support portion is used as a support hole or a support shaft formed in the rear end surface of the bit body, and a mounting shaft or the above-described attachment shaft is inserted into the support hole at the tip of the enlarged diameter bit. A mounting hole into which the support shaft can be inserted is formed. It is characterized by that. Therefore, in the excavation tool configured in this way, in any case, the mounting shaft portion is fitted into the mounting hole with the side surface of the mounting shaft portion closely contacting the inner wall of the mounting hole in the circumferential direction. The mounting rigidity of the excavation bit with respect to the rotation of the tool body can be sufficiently ensured without being screwed by the male and female screw portions.
[0007]
Here, the groove is the above Form the recess so as to avoid the most recessed part on the inner circumference side, or In the cross section perpendicular to the axis, Inner wall of the fitting part The sides of the polygon formed by The wall of this recess A wall surface portion located at a portion where the concave portion is most recessed on the inner peripheral side, If it is formed to be parallel, a large thickness can be secured between the recess and the mounting hole, and the mounting rigidity of the excavation bit can be further improved. It is possible to prevent damage from occurring between the recess and the mounting hole.
[0008]
And in the present invention, The excavation bit is provided with a disk-shaped bit body having the cutting edge provided on the tip surface, and the tip end portion of the diameter-expanding bit is rotatably supported on the rear end surface of the bit body. As above Provide support By It is possible to sufficiently secure the mounting rigidity of the diameter expanding bit. Further, a pin mounting hole is formed in the tool body so as to open to the mounting hole, and an engaging pin projects into the mounting hole so as to engage with the mounting shaft portion. If it is attached to the tool body, the excavation bit that will be attached by being inserted into the attachment hole from the tip end side of the tool body can be securely retained, and the tool body is given a striking force in the axial direction. However, it is possible to prevent the excavation bit from coming off due to the impact.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3 show a first embodiment of the present invention. In the present embodiment, the tool body 1 is formed in a substantially multi-stage columnar shape whose outer shape gradually increases in diameter toward the front end side (left side in FIG. 1), and the rear end portion whose diameter is reduced is the shank portion 2. When a hammer or the like (not shown) is attached to the shank portion 2, the tool body 1 receives a striking force toward the front end side in the direction of the central axis O during excavation, and around the axis O, FIG. Are rotated in the tool rotation direction indicated by T. Furthermore, a through-hole 3 to which compressed air or the like is supplied during excavation is formed along the axis O from the rear end surface to the front end side of the shank portion 2, and the through-hole 3 branches in three directions along the way. In addition, the diameter of the distal end side of the tool body 1 is increased and opened in the center of the distal end surface 1A of the tool body 1, thereby forming the mounting hole 4 in the present embodiment. A pilot bit 5 is attached. Further, on the outer periphery of the tip portion of the tool body 1, three recesses 6 are formed at equal intervals in the circumferential direction so as to be recessed toward the inner periphery, and these recesses 6 are respectively parallel to the axis O. A diameter expansion bit 7 is attached so as to be rotatable around an eccentric central axis X.
[0010]
The pilot bit 5 has a mounting shaft portion 9 integrally projecting along the center line of the bit body 8 on the rear end surface of the bit body 8 having a disk shape having an outer diameter slightly smaller than the outer diameter of the tool body 1. When the mounting shaft 9 is inserted into the mounting hole 4, the pilot bit 5 has the center line coaxial with the axis O of the tool body 1 and is attached to the tip of the tool body 1. It is attached. In addition, an exhaust hole 10 is formed in the mounting shaft portion 9 along the axis O, and the exhaust hole 10 branches off at the bit body 8 portion on the distal end side to form a tip of the bit body 8 that forms a mortar shape. On the outer peripheral surface of the bit body 8, a plurality of drilling waste discharge grooves 12 extending in the direction of the axis O are formed at intervals in the circumferential direction. The exhaust grooves 11 are communicated with some of the exhaust grooves 12. Further, a large number of chips 13 made of a hard material such as cemented carbide are implanted on the front end surface and the outer peripheral surface of the bit body 6 so as to avoid the exhaust grooves 11 and the exhaust grooves 12. These chips 13 constitute a cutting blade provided on the tip side of the pilot bit 5.
[0011]
On the other hand, the mounting shaft portion 9 of the pilot bit 5 has a substantially multi-stage cylindrical shape whose outer diameter is reduced to three steps as it goes to the rear end side, and among these, the outer peripheral surface of the last-stage small-diameter portion 9A The annular groove 14 having a substantially semicircular cross section is formed on the middle-diameter portion 9B side of the middle stage, and a protrusion 15 extending parallel to the axis O is formed on the outer peripheral surface of the middle-diameter portion 9B. A plurality of strips (six strips in this embodiment) having the same shape and the same size are formed at intervals in the circumferential direction. Each of these protrusions 15... Extends over the entire length of the middle-diameter portion 9B of the middle stage from a position where a slight gap is provided between the projection shaft 15 and the most large-diameter portion 9C of the mounting shaft 9 in the present embodiment. The cross section by the plane containing the axis O is formed in the isosceles trapezoid shape flat in the radial direction with respect to the axis O as shown in FIG. In addition, in the cross section orthogonal to the axis O, the protrusion 15 is formed such that a semicircular protruding end protruding from the outer peripheral surface of the medium diameter portion 9B is cut out by a flat surface or a convex curved surface as shown in FIG. In other words, the pair of side surfaces 15A, 15A facing the circumferential direction of the ridge 15 approach each other while curving toward the outer circumferential surface 15B side of the ridge formed by cutting out the above-described plane or convex curved surface. It is formed so as to have a substantially isosceles trapezoidal cross section.
[0012]
Further, as shown in FIG. 4, the six ridges 15 in the present embodiment include a pair of ridges 15, 15 that are adjacent to each other in the circumferential direction of the mounting shaft portion 9. Three pairs are arranged at equal intervals with an interval larger than the interval between 15, and one side in the circumferential direction of each pair of ridges 15, 15 (in the present embodiment, the tool rotation described above) On the outer peripheral surface 15B of the protrusion 15 on the rear side in the direction T, a concave hole 16 that is recessed in the radial direction with respect to the axis O is formed. The medium diameter portion 9B in which the protrusions 15 are formed has a length in the direction of the axis O longer than the small diameter portion 9A and the large diameter portion 9C. Have been longer. The large-diameter portion 9C has an outer diameter that is substantially the same as the outer diameter formed by the outer peripheral surface 15B of the protrusion 15 and is formed on the rear end surface 8A of the bit body 8 of the pilot bit 5 in a cross section including the axis O. It is formed so as to be smoothly connected via a concave curved surface. Further, on the outer peripheral side of the rear end surface 8A of the bit body 8, three support holes 17 having a circular cross section recessed in the front end side are formed at equal intervals in the circumferential direction. In a state where the pilot bit 5 is attached to the tool main body 1, the pilot bit 5 is disposed so as to be coaxial with the central axis X, and serves as a support portion in the present embodiment.
[0013]
On the other hand, the concave portion 6 of the tool body 1 has a bottom surface 18 that recedes from the distal end surface 1A of the tool body 1 and faces the distal end side, and extends from the peripheral edge of the bottom surface 18 to the distal end side in parallel with the axis O to the distal end surface. The bottom surface 18 further extends on the axis O extending to the rear side in the tool rotation direction T of the bottom surface 18 and extending toward the inner peripheral side in the tool rotation direction T side. The bottom surface portion 18A has a vertical flat surface shape, and a bottom surface portion 18B which is on the tool rotation direction T side of the bottom surface portion 18A and is inclined toward the rear end side toward the outer peripheral side. A support hole 20 having a circular cross section around the central axis X is formed, and branch holes 3A branched in three directions from the through hole 3 are opened in the inclined surface portion 18B. . Further, a small diameter hole 3B is further branched from the middle of the branch hole 3A and extends toward the front end side in parallel to the axis O. The small diameter hole 3B intersects the bottom surface portions 18A and 18B of the bottom surface 18. It is opened to the part. Further, two cutting grooves 21 are formed on the outer periphery of the tool body 1 so as to extend in parallel to the axis O with respect to the respective recesses 6. These discharging grooves 21 and 21 are formed on the outer periphery of the bottom surface portion 18B. On the side, it is opened to the tool rotation direction T side and the rear side thereof.
[0014]
On the other hand, as shown in FIG. 2, the wall surface 19 is erected on the rear side in the tool rotation direction T of the bottom surface portion 18A so as to intersect the outer peripheral surface of the tool body 1 at an acute angle as seen from the tip side. A wall surface portion 19A facing the rotation direction T side, a wall surface portion 19B having a concave arc surface centered on the central axis X that is in smooth contact with the wall surface portion 19A, and a wall surface portion that is more smoothly in contact with the wall surface portion 19B A wall surface 19C that extends straight in the tool rotation direction T side so as to form an acute angle with respect to 18A, is most recessed on the inner peripheral side of the tool body 1 and is close to the mounting hole 4, and a stepped shape that continues to the wall surface 19C. A wall surface portion 19D, and a tool rotation direction that retreats one step toward the tool rotation direction T with respect to the wall surface portion 19C via the wall surface portion 19D, and extends straight in parallel to the wall surface portion 19C to reach the outer periphery of the tool body 1. Facing the back side of T It is composed of a surface portion 19E.
[0015]
The diameter-enlarged bit 7 attached to the recess 6 configured as described above has side surfaces 22A to 22C that are connected in steps so that the bit body 22 can be substantially closely contacted with the wall surface portions 19C to 19E when viewed from the front end side. Of these, a side surface 22D extending parallel to the side surfaces 22A and 22C, a convex semicircular arc-shaped side surface 22E smoothly contacting the side surfaces 22A and 22D, and a convex curved side surface 22F formed between the side surfaces 22C and 22D, The radius of the side surface 22E of the convex arcuate surface is such that it can be in close contact with the wall surface part 19B of the concave arcuate surface. Further, on the front and rear end surfaces of the bit body 22, mounting shafts 23 and 24 having a circular cross section extending coaxially with the central axis of the convex arc formed by the side surface 22E are formed integrally with the bit body 22, and attached to the front end side. The shaft 23 can be inserted into the support hole 17 of the pilot bit 5 and the mounting shaft 24 on the rear end side can be inserted into the support hole 20 of the recess 6, and thus the mounting shafts 23, 24 can be inserted into the support holes 17, 20. By being inserted and supported, the diameter-enlarged bit 7 is rotatable about the central axis X as described above while the side surface 22E is in sliding contact with the wall surface portion 19B.
[0016]
Therefore, the bit main body 22 of the diameter-enlarged bit 7 has an enlarged diameter shown on the lower left side in FIG. 1 when the diameter-enlarged bit 7 rotates around the central axis X toward the tool rotation direction T when viewed from the tip side. Like the bit 7, the side surfaces 22 A to 22 C are substantially in close contact with the wall surface portions 19 C to 19 E and are accommodated in the recess 6, and the outer diameter from the axis O is reduced. When rotated to the rear side of T, the side surface 22D abuts against the wall surface portion 19A as in the diameter-expanded bit 7 shown in the upper side of FIG. 1, and the side surface 22F side of the bit body 22 is more than the outer peripheral surface of the tool body 1. It protrudes to the outer peripheral side, and its outer diameter from the axis O is increased. Further, the side surface 22F forms a convex arc surface centered on the axis O in a state where the diameter expanding bit 7 is expanded, and the side surface 22F has a front end side and a side end side of the side surface 22C. In addition, a large number of chips 25 made of a hard material such as cemented carbide are implanted in the tip surface portion of the bit body 22 projecting outward from the pilot bit 5 in this expanded diameter state. 25 constitutes a cutting blade provided on the distal end side of the diameter expanding bit 7.
[0017]
Furthermore, the mounting hole 4 into which the mounting shaft portion 9 of the pilot bit 5 is inserted has an inner diameter from the tip surface 1A side of the tool body 1 toward the through hole 3 in accordance with the shape of the mounting shaft portion 9. The small diameter portion 4A connected to the through hole 3 on the rearmost end side is the small diameter portion 9A of the mounting shaft portion 9, and the middle diameter portion 4B of the middle step is the diameter of the mounting shaft portion 9. The medium-diameter portion 9B is formed to have a diameter and a depth at which the large-diameter portion 4C on the distal end surface 1A side can be inserted into the large-diameter portion 9C of the mounting shaft portion 9, respectively. Of the inner diameter portion 4B to the larger diameter portion 4C, the same number of groove grooves 26 as the protrusions 15 extending in parallel to the axis O (that is, six stripes) are provided on the inner periphery thereof in the circumferential direction. 15 is formed with an interval and arrangement equal to 15. Each of the concave grooves 26... Has a semicircular shape in which the inner wall 26A in a cross section orthogonal to the axis O can be in close contact with both side surfaces 15A, 15A of the ridge 15, and the inner diameter of the inner diameter portion 4B. The depth from the axis O to the groove bottom is made larger than the radius of the large-diameter portion 4C. Therefore, these concave grooves 26 ... are also shown in the large-diameter portion 4C. As shown in FIGS. 2 and 3, the groove bottom side is left parallel to the axis O and reaches the front end surface 1A to be opened.
[0018]
Further, these concave grooves 26, which are arranged in the same arrangement as the ridges 15, are composed of three pairs of concave grooves 26, 26 adjacent to each other in the circumferential direction, and the distance between the concave grooves 26, 26 forming these pairs. 2 are arranged at equal intervals in the circumferential direction at a larger interval. Here, in the present embodiment, as shown in FIG. The concave groove 26 is formed so as to be positioned on the side of the wall surface 19C that is most concave on the inner peripheral side of the wall surface 19 of the recess 6, that is, avoiding the wall surface portion 19C that is most concave on the inner peripheral side. . More specifically, as seen from the front end side, as shown in FIG. 1, an imaginary straight line that passes through the axis O and the portion where the recess 6 is most recessed on the inner peripheral side (in this embodiment, passes through the axis O and is orthogonal to the wall surface 19C. It is desirable that the groove 26 is not formed on the straight line L.
[0019]
Furthermore, in this embodiment, the tool main body 1 is provided with a tool rotation direction T of the concave grooves 26 and 26 forming the respective pairs of the mounting holes 4 from the stepped wall surface portion 19D of the wall surface 19 of each of the concave portions 6. A pin mounting hole 27 is formed in the mounting groove 4 so as to penetrate the tool main body 1 in the radial direction with respect to the axis O toward the concave groove 26 on the rear side of the pin. In the direction of the axis O, the outer peripheral surface 15B of the ridge 15 with the rear end surface of the bit body 8 of the pilot bit 5 in close contact with the front end surface 1A of the tool body 1 and the mounting shaft portion 9 being inserted into the mounting hole 4. It is arrange | positioned in the position equal to the said concave hole 16 formed in this. On the other hand, the tool body 1 further extends in the tangential direction of the inner periphery of the small diameter portion 4A of the mounting hole 4 from the outer peripheral surface of the tool body 1 in a plane orthogonal to the axis O, and is in contact with the mounting hole 4 in a half-section A pin mounting hole 28 is formed so as to open in a circular shape, and this pin mounting hole 28 passes through the portion on the side of the middle diameter portion 4B of the small diameter portion 4A in the direction of the axis O, and passes through the mounting shaft portion 9. When inserted into the mounting hole 4, the mounting shaft portion 9 is formed so as to have a substantially circular cross section in alignment with the annular groove 14 having a semicircular cross section of the small diameter portion 9 A. In these pin mounting holes 27 and 28, engagement pins 29 and 30 matching the size and depth are inserted from the outer peripheral side and fixed by spacers or snap rings, and the tip portions are pilot bits 5 The concave hole 16 and the annular groove 14 are engaged.
[0020]
In the excavation tool of this embodiment, first, the mounting shaft 24 is inserted into the support hole 20 to accommodate the diameter-enlarged bits 7 in the recesses 6. The mounting shaft portion 9 is inserted into the mounting hole 4 so as to be fitted, the mounting shaft 23 of the diameter-expanding bit 7 is inserted into the support hole 17, and the pilot bit 5 is mounted on the distal end portion of the tool body 1. Assembling is performed by inserting engaging pins 29 and 30 into the pin mounting holes 27 and 28 and engaging the concave holes 16 and the annular groove 14. Further, at the time of excavation, a striking force is applied to the tool body 1 by the hammer, and the tool body 1 is rotated to the tool rotation direction T side through the hammer, thereby expanding the diameter-expanding bit 7. A cutting hole is formed in the ground or the like by the cutting edge on the side and the cutting edge on the tip side of the pilot bit 5. A casing pipe P having an outer diameter slightly smaller than the outer diameter is inserted. In addition, after the excavation is completed, the tool main body 1 is rotated in the direction opposite to the tool rotation direction T during excavation, so that the diameter-expanding bits 7... 7... Can be pulled out and only the casing pipe P can be left in the drilling hole.
[0021]
Therefore, in the excavation tool having the above-described configuration, when the pilot bit 5 attached as the excavation bit to the distal end portion of the tool body 1 inserts the attachment shaft portion 9 into the attachment hole 4 of the tool body 1 as described above. The protrusions 15 formed on the medium diameter portion 9B of the attachment shaft 9 are fitted into the concave grooves 26 formed on the medium diameter portion 4B of the attachment hole 4, and both side surfaces 15A of the protrusion 15 are fitted. 15A is in close contact with the inner wall 26A of the concave groove 26, so that the load acting on the pilot bit 5 as the tool body 1 rotates during excavation is reliably received by the inner wall 26A in close contact with the side surfaces 15A, 15A. It is possible to sufficiently secure the mounting rigidity of the pilot bit 5. In addition, since both side surfaces 15A, 15A of the ridge 15 are in direct contact with the inner wall 26A of the concave groove 26, there is a possibility that rattling occurs between the mounting hole 4 and the mounting shaft portion 9 in the circumferential direction. Few.
[0022]
On the other hand, since the ridges 15 and the concave grooves 26 are formed in parallel to the axis O of the tool body 1, it is attached by rotation of the tool body 1 like screwing by a conventional male and female screw part. The shaft portion 9 is not tightly tightened in the mounting hole 4, and when replacing the pilot bit 5, the pilot bit 5 can be easily removed by removing the engaging pins 29 and 30. is there. In the present embodiment, the concave grooves 26 are formed in a semicircular cross section, and the side surfaces 15A and 15A of the ridge 15 are formed in a circular arc shape that can be in close contact with the inner wall 26A of the concave grooves 26. The ridge 15 may be formed in a semicircular cross section that can be in close contact with the inner wall surface 26A of the groove 26 over the entire circumference without cutting out the outer peripheral surface 15B with a flat surface or a convex curved surface. Even if it is not such a semi-circular cross section, for example, the cross sections of these ridges and grooves are formed in a square shape or a trapezoidal shape in which both side surfaces and inner walls can be in close contact with each other, or cross sections of these both side surfaces and inner walls May form an involute curve.
[0023]
Further, in the excavation tool of the present embodiment, the diameter expansion bit 7 is accommodated in the recess 6 formed on the outer periphery of the tip end portion of the tool body 1 so as to be rotatable around the central axis X. By expanding the diameter, it is possible to form a drilling hole having a diameter larger than that of the tool main body 1 and, after completion of excavation, by reducing the diameter of the diameter expanding bit 7, the inside of the casing pipe P inserted into the drilling hole is passed through. Although the tool body 1 can be pulled out, when the concave portion 6 for accommodating such an enlarged diameter bit 7 is formed, the wall surface portion 19C closest to the mounting hole 4 among the wall surfaces 19 of the concave portion 6 has the attachment. The concave groove 26 is not formed on the inner periphery of the hole 4, that is, the concave groove 26 is formed so as to avoid a portion where the concave portion 6 is most concave on the inner peripheral side of the tool body 1. For this reason, in this embodiment, it becomes possible to ensure sufficient thickness between this recessed part 6 and the attachment hole 4, and this also ensures attachment rigidity of the pilot bit 5 as an excavation bit. Therefore, stable excavation can be promoted even under excavation conditions in which a high load acts on the pilot bit 5.
[0024]
Further, in the present embodiment, when the diameter-enlarged bit 7 is rotatably attached to the outer periphery of the tip end portion of the tool body 1 as described above, a support hole 17 as a support portion is formed on the rear end face of the bit body 8 of the pilot bit 5. Each of the diameter-enlarged bits 7 is attached to each of the support holes 17 by inserting the attachment shafts 23 at the front ends thereof. That is, the diameter-enlarged bits 7 are supported at both ends thereof. Since it is attached to the main body 1, according to this embodiment, it is possible to ensure high attachment rigidity for these diameter-expanded bits 7 and to promote more stable excavation work. In the present embodiment, the support hole 17 is formed in the rear end surface of the bit body 8 of the pilot bit 5 and the mounting shaft 17 of the enlarged-diameter bit 7 is fitted and inserted, but the rear end surface of the bit body 8 is reversed. In addition, a support shaft may be formed as a support portion, and an attachment hole into which the support shaft can be inserted may be formed at the tip of the diameter expansion bit 7 to support the diameter expansion bit 7.
[0025]
Furthermore, in the present embodiment, a concave hole is formed in the outer peripheral surface 15B of half of the three ridges 15 which are located at equal intervals in the circumferential direction among the six ridges 15 of the mounting shaft portion 9. 16, and an annular groove 14 is formed in the small diameter portion 9 A of the mounting shaft portion 9, and engaging pins 29, 30 inserted into pin mounting holes 27, 28 formed in the tool body 1. Are engaged with the concave holes 16 and the annular groove 14, so that the mounting shaft portion 9 is supported by the mounting hole 4 on the tip side in the axis O direction. Therefore, according to the present embodiment, the pilot bit 5 does not come off from the mounting hole 4 due to the impact of the striking force applied from the hammer during excavation and the pilot bit 5 does not come off. 5 and the diameter-expanding bits 7 can be securely held and a smooth excavation operation can be performed. The load in the direction of the axis O acting on the pilot bit 5 during excavation is received by the tip surface 1A when the rear end surface of the bit body 8 of the pilot bit 5 comes into close contact with the tip surface 1A of the tool body 1. The load applied to the engagement pins 29... 30 does not act to cause damage.
[0026]
Next, FIGS. 5 to 7 show a second embodiment of the present invention, and FIGS. 8 and 9 show a third embodiment of the present invention. Portions common to those in the first embodiment shown in FIG. Among these, in the second embodiment shown in FIGS. 5 to 7, the diameter-enlarged bit 7 is accommodated in each of the three recesses 6 formed on the outer periphery of the distal end portion of the tool body 1 as in the first embodiment. A fitting portion 31 having a regular hexagonal cross section is formed instead of the concave groove 26 in the mounting hole 4 and the mounting shaft of the pilot bit 5 as a drilling bit is provided. The portion 9 is formed with a fitted portion 32 having a regular hexagonal cross section that can be fitted to the fitting portion 31 instead of the protrusion 15. And in this 2nd Embodiment, as shown in FIG. 6 in the cross section orthogonal to the axis line O, every other 6 sides of the regular hexagon formed by the inner wall 31A of the fitting portion 31 in the circumferential direction. 3 sides are formed so as to be parallel to the wall surface portion 19 C located in the portion of the wall surface 19 of the recess 6 where the recess 6 is most recessed on the inner peripheral side.
[0027]
In the second embodiment, the pair of pin mounting holes 28, 28 are mounted on a single plane perpendicular to the axis O as shown in FIG. 4 are formed in the tool body 1 in parallel with each other, and these pin mounting holes 28, 28 are in the shape of a regular hexagon formed by the inner wall 31A of the fitting portion 31 in the cross section along the one plane. It extends along two sides facing each other among the six sides and opens in a groove shape having a semicircular cross section in each inner wall 31A. On the other hand, the fitted portion 32 of the attachment shaft portion 9 is located at the position of the one plane when the pilot bit 5 is attached, and the fitted portion 32 in a cross section along the one plane. The grooves 32B, 32B having a semicircular cross section are formed so as to extend in parallel along two opposite sides of the six sides of the regular hexagon formed by the side surfaces 32A of the side surfaces 32A. The grooves 32B, 32B and the semi-circular grooves of the pin mounting holes 28, 28 opened in the inner walls 31A, 31A coincide with each other so as to communicate with the pin mounting holes 28, 28. These holes are respectively defined, and the engagement pins 30 and 30 are respectively fitted and attached to these holes through the pin attachment holes 28 and 28, and are engaged with the attachment shaft portion 9.
[0028]
On the other hand, in the third embodiment shown in FIGS. 8 and 9, four recesses 6 are formed on the outer periphery of the tip of the tool body 1 at equal intervals in the circumferential direction, that is, every 90 °. The wall surface portions 19A to 19E are also arranged at intervals of 90 ° in the circumferential direction, and the diameter-enlarged bits 7 are accommodated in the recesses 6 respectively, and mounting holes are provided for these. 4 is formed with a fitting portion 33 having a regular octagonal cross section, and a fitting portion having a regular octagonal cross section that can be fitted to the fitting portion 33 on the mounting shaft portion 9 of the pilot bit 5. 34 is formed. Further, in the third embodiment, among the eight sides of the regular octagon formed by the inner wall 33A of the fitting portion 33, four sides positioned every other one in the circumferential direction are the wall surface 19 of the recess 6. Of these, the concave portion 6 is formed so as to be parallel to the wall surface portion 19 C located at the most concave portion on the inner peripheral side.
[0029]
Also in this third embodiment, a pair of the pin mounting holes 28, 28 as shown in FIG. 9 on one plane perpendicular to the axis O on the rear end side of the engagement hole 27 of the tool body 1 is also provided. Is formed so as to extend along two opposite sides of the regular octagonal eight sides formed by the inner wall 33A of the fitting portion 33 and open to the inner walls 33A and 33A in a semicircular arc shape in cross section. In addition, the fitting portion 34 of the mounting shaft portion 9 has an opening portion of these pin mounting holes 28 and 28 along two opposite sides of the eight sides of the regular octagon formed by the cross section of the side surface 34A. The grooves 34B and 34B having a semicircular arc cross section that defines a hole having a circular cross section are formed. Then, the engagement pins 30 and 30 are respectively inserted and fixed in the circular holes formed in this way through the pin attachment holes 28 and 28, so that the engagement pins 30 and 30 are attached to the attachment shaft portion 9. Are engaged in the direction of the axis O.
[0030]
Thus, also in the second and third embodiments, the fitting portions 32 and 34 of the mounting shaft portion 9 are formed on the inner walls 31A and 33A of the fitting portions 31 and 33 of the mounting hole 4. Since the side surfaces 32A, 34A, ... are in close contact with each other, rotation of the mounting shaft portion 9 in the circumferential direction around the axis O is restricted, so that the mounting shaft portion 9 is attached to the mounting hole 4 with high rigidity. 5 can be held at the tip of the tool body 1, and the mounting shaft portion 9 is not tightly fastened to the mounting hole 4 by a load acting during excavation such as screwing by a male and female screw portion. Moreover, in the second embodiment, the wall surface portions 19C of the three recesses 6 are arranged at equal intervals in the circumferential direction, that is, arranged at intervals of 120 °, whereas a regular hexagonal cross section is formed. The inner wall 31A of the fitting part 31 is arranged every 60 °, and every other inner wall 31A is arranged in parallel to the wall surface part 19C, and in the third embodiment, four recesses 6 are formed. Are arranged every 90 °, whereas every other fitting wall 33 having a regular octagonal cross section (every 90 °) has an inner wall 33A ... on each wall portion 19C. Therefore, the space between the wall surface portion 19C and the inner walls 31A and 33A can be kept constant, and the rigidity around the mounting hole 4 can be secured.
[0031]
In addition, in the second and third embodiments, a pair of pin mounting holes 28, 28 are formed on the rear end side of the pin mounting hole 27, and these pin mounting holes 28, 28 have an axis O. The mounting hole 4 is sandwiched along two opposing sides of a polygon formed by the cross-sections of the inner walls 31A, 33A of the fitting portions 31, 33 of the mounting hole 4 in the one plane perpendicular to In addition, grooves 32B and 32B and grooves 34B, which are formed along two opposite sides of the polygon formed by the cross sections of the side surfaces 32A..., 34A. 34B is formed, and the grooves 32B and 32B and the grooves 34B and 34B are engaged with the engagement pins 30 and 30 that are fitted and inserted into the pin attachment holes 28 and 28, respectively. Therefore, as compared with the case where the engagement pin 30 is attached to and engaged with one pin attachment hole 28 formed along the tangential direction of the attachment hole 4 having a circular cross section and the attachment shaft portion 9 as in the first embodiment. Since the number of engagement pins 30 can be increased, the engagement length between the engagement pins 30 and the mounting shaft portion 9 can be extended. Therefore, according to the second and third embodiments, the pilots The bit 5 can be more reliably prevented from coming off.
[0032]
In the second and third embodiments, the fitting sections 31 and 33 of the mounting hole 4 and the fitted sections 32 and 34 of the mounting shaft section 9 can be fitted to each other with regular six and eight cross sections. In the case where the fitting parts 31 and 33 have a regular hexagonal and octagonal cross section, for example, the fitted parts 32 and 34 are connected to the inner walls 31A... 33A of the fitting parts 31 and 33, respectively. The side surfaces 32A ..., 34A ... have side faces 32A ..., 34A ... that can be in close contact with each other ... Alternatively, it may be formed in the shape of a deviation 6 or 8 having 34A. On the other hand, when the fitted portions 32 and 34 have regular hexagonal and octagonal cross sections, for example, the fitted portions 31 and 33 are replaced with the alternate side surfaces 32A of the fitted portions 32 and 34,. May be formed in a cross-sectional deviation 6 or octagonal shape having inner walls 31A ..., 33A ... that can be in close contact with 34A ..., or a regular triangular shape or a square shape, and in the latter case, they are adjacent to each other. The corners of the inner walls 31A, 33A, etc. that intersect each other may be formed in a concave curved surface within a range that does not interfere with the side surfaces 32A, 34A,. Further, other than such regular hexagons and octagons, other polygonal cross sections can be adopted as long as the fitted portion of the mounting shaft portion can be fitted to the fitting portion of the mounting hole. .
[0033]
【The invention's effect】
As described above, according to the present invention, firstly, a concave groove extending in parallel to the central axis of the tool body is formed on the inner periphery of the mounting hole, and the outer periphery of the mounting shaft portion of the excavation bit is provided on the outer periphery thereof. By forming protrusions whose both side surfaces are in close contact with both inner walls of the concave groove, and secondly, a fitting portion having a polygonal cross section perpendicular to the axis is formed in the mounting hole, and the mounting shaft By forming a fitting portion with a polygonal cross section whose side faces are in close contact with the inner wall of the fitting portion, it is possible to secure the attachment rigidity of the excavation bit to the tool body and achieve stable excavation work. In addition, the excavation bit mounting shaft is not tightly tightened to the mounting hole of the tool body due to the load during excavation, as in the case of screwing by male and female screw parts, etc. It can be done in a short time That.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a first embodiment of the present invention.
FIG. 2 is a front view of the embodiment shown in FIG. 1 as viewed from the distal end side.
3 is a YY cross-sectional view in FIG. 1. FIG.
4 is a ZZ cross-sectional view in FIG. 1. FIG.
FIG. 5 is a side sectional view showing a second embodiment of the present invention.
6 is a cross-sectional view along YY in FIG.
7 is a ZZ cross-sectional view in FIG. 5. FIG.
FIG. 8 is a view corresponding to a YY section in FIG. 5, showing a third embodiment of the present invention.
FIG. 9 is a view corresponding to the ZZ cross section in FIG. 5, showing a third embodiment of the present invention.
[Explanation of symbols]
1 Tool body
4 Mounting hole
5 Pilot bit (Drilling bit)
6 recess
7 Expanding bit
8 Bit body of pilot bit 5
9 Mounting shaft
13,25 insert (cutting edge)
14 annular groove
15 ridges
Side of 15A ridge 15
16 concave hole
17, 20 Support hole
19C Wall surface portion of the wall surface 19 of the recessed portion 6 (the portion where the recessed portion is recessed most on the inner peripheral side)
23, 24 Mounting shaft for expanding bit 7
26 Groove
26A Inner wall of recessed groove 26
27, 28 Pin mounting holes
29, 30 engagement pin
31, 33 Fitting part
31A, 33A Inner walls of the fitting portions 31, 33
32, 34 mated part
32A, 34A Side surfaces of mated portions 32, 34
32B, 34B groove
O Center axis of tool body 1
X Center axis of expansion bit 7
T Tool rotation direction during excavation

Claims

An excavation bit having a cutting edge provided at the front end side and a mounting shaft portion formed at the rear end side at the front end portion of the tool main body rotated about the axis opens to the center of the front end portion of the tool main body and opens the axis line. In the excavation tool attached by inserting the attachment shaft portion into the attachment hole extending along the groove, a concave groove extending in parallel with the axis is formed on the inner periphery of the attachment hole. On the outer periphery, ridges whose both side surfaces are in close contact with both inner walls of the concave groove are formed, and on the outer periphery of the tip end portion of the tool body, a concave portion recessed on the inner peripheral side is formed. A diameter-enlarged bit provided with a cutting edge on the distal end side is rotatably accommodated around a central axis that is eccentric in parallel with the axis, and the excavation bit is a disc-shaped bit body having the cutting edge provided on the distal end surface. And the rear end face of this bit body Is provided with a support portion that rotatably supports the tip portion of the diameter-enlarged bit, and the support portion is a support hole or a support shaft formed in the rear end surface of the bit body, An excavation tool characterized in that an attachment shaft to be inserted into the support hole or an attachment hole into which the support shaft can be inserted is formed at the tip of the bit .

The excavation tool according to claim 1, wherein the concave groove is formed so as to avoid a portion where the concave portion is most concave on the inner peripheral side.

An excavation bit having a cutting edge provided at the front end side and a mounting shaft portion formed at the rear end side at the front end portion of the tool main body rotated about the axis opens to the center of the front end portion of the tool main body and opens the axis line. In the excavation tool attached by inserting the attachment shaft portion into the attachment hole extending along the fitting hole, a fitting portion having a polygonal cross section perpendicular to the axis is formed in the attachment hole. The shaft portion is formed with a fitted portion having a polygonal cross section whose side surface is in close contact with the inner wall of the fitting portion, and a recess recessed on the inner circumferential side is formed on the outer periphery of the tip portion of the tool body, In this recess, a diameter-enlarged bit provided with a cutting edge on the distal end side is accommodated so as to be rotatable around a central axis that is eccentric in parallel to the axis, and the excavation bit is provided with the cutting edge on the distal end surface. It has a disc-shaped bit body and this A support portion for rotatably supporting the tip end portion of the diameter-enlarged bit is provided on the rear end surface of the base body, and this support portion is a support hole or a support shaft formed in the rear end surface of the bit body. An excavation tool characterized in that an attachment shaft to be inserted into the support hole or an attachment hole into which the support shaft can be inserted is formed at the tip of the diameter expansion bit .

In the cross section perpendicular to the axis, the polygonal side formed by the inner wall of the fitting portion is parallel to the wall surface portion of the wall surface of the concave portion where the concave portion is most recessed on the inner peripheral side. The excavation tool according to claim 3, wherein the excavation tool is formed.

A pin mounting hole is formed in the tool body so as to open to the mounting hole, and an engagement pin projects into the mounting hole and engages with the mounting shaft portion. drilling tool according to any one of claims 4 to claims 1, characterized in that attached to.