JP2004277922A

JP2004277922A - Terminal fixture for cable and method for producing the terminal fixture

Info

Publication number: JP2004277922A
Application number: JP2003070272A
Authority: JP
Inventors: Yasushi Kishi; 靖岸; Shigeru Mizuguchi; 茂水口
Original assignee: Shinko Wire Co Ltd
Current assignee: Kobelco Wire Co Ltd
Priority date: 2003-03-14
Filing date: 2003-03-14
Publication date: 2004-10-07
Anticipated expiration: 2023-03-14
Also published as: JP3692123B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminal fixture for cable, affording high tensile strength without specially extending the axial length of the cylindrical body. <P>SOLUTION: The terminal fixture comprises as the constituent part the cylindrical body 10 having a smaller-diameter hole 12a opened on the opposite side to the tail end part and a larger-diameter hole 12b adjoining the smaller-diameter hole 12a. A cable 24 is inserted from the smaller-diameter hole 12a side followed by making a shrink processing of the cylindrical body 10 to effect pressure contact of the inner circumferential surface of the smaller-diameter hole 12a against the circumference of the cable 24, and the wires at the end 24a of the cable 24 are disaggregated and made divergent inside the larger-diameter hole 12b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、吊り橋や建築物等の構造物に使用されるケーブルの端末を当該構造物に定着させるための端末定着部及びその製造方法に関するものである。
【０００２】
【従来の技術】
従来、前記のようなケーブルの端末定着部として、下記特許文献１，２に示されるものが知られている。
【０００３】
まず、特許文献１の第１図には、中心にフラット孔をもつ鋼製スリーブ内にケーブル端末を挿入してから当該スリーブを縮径加工して当該スリーブ内周面を前記ケーブル端末に圧着したものが示されている。さらに、同文献の第３図には、前記スリーブの前側部であって前記フラット孔よりも前側の部分に当該フラット孔よりも大径のテーパー状孔を形成しておき、このテーパー状孔内に硬化性樹脂を充填して当該樹脂の付着力と前記圧着による付着力の双方でケーブル端末に前記筒体を固定したものが示されている。
【０００４】
【特許文献１】
特開昭５９−８８９８６号公報（第１〜３頁，第１図，第３図）
また、特許文献２の図１には、繊維複合材ケーブルやワイヤロープ等の端部を定着する手段として、テーパー孔部を有する筒体内にケーブル端末を挿入するとともに、その末端部分の素線をばらした状態で前記テーパー孔部内に格納しておき、その筒体内に充填材を充填して硬化させることにより、当該充填材の付着力で前記ケーブル端末に前記筒体を固定するようにしたものが開示されている。
【特許文献２】
特開平１０−８２１７８号公報（第３〜５頁，図１）
【０００５】
【発明が解決しようとする課題】
前記特許文献１の第１図に示される定着部は、筒体の縮径加工による圧着力のみでケーブル端末に筒体を固定するものであるので、固定力の増強には限りがあり、高い引張強度が得られにくい欠点がある。また、同文献１の第３図に示される定着部は、前記圧着部よりも前側に硬化性樹脂の充填による固定部を設けているものの、当該固定部と圧着部とは単に軸方向に並んでいるだけで相乗効果がなく、引張強度の著しい向上は期待できない。
【０００６】
一方、特許文献２に示される定着部は、硬化性樹脂の接着力のみで筒体とケーブルとの固定を行うものであるため、例えば多数本の鋼製素線を拠り合わせたスパイラルロープのように高い緊張力が求められるケーブルの端末定着部に適用することは困難である。また、仮に前記接着力のみで必要強度が得られたと仮定しても、火災等によって端末定着部が異常加熱された場合には前記硬化性樹脂が変質して定着力を失うおそれがある。
【０００７】
すなわち、いずれの文献に記載されるものも、引張強度の増強にはかなりの制限があり、当該強度を確保するためには筒体の軸長を相当長くしなければならないという課題がある。
【０００８】
本発明は、このような事情に鑑み、筒体の軸長を特に延長させることなく高い引張強度が得られるケーブルの端末定着部及びその製造方法を提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記課題を解決するための手段として、本発明は、複数本の素線が撚り合わされたケーブルの端末の周囲に当該ケーブルよりも外径の大きな筒体が固定された端末定着部であって、前記筒体は、その尾端部と反対の側に開口する小径孔と、この小径孔の尾端側に隣接し、かつ、当該小径孔よりも大きな内径をもつ大径孔とを有し、前記小径孔側から前記大径孔内に至るまで前記ケーブルの端末が挿入された状態で当該ケーブルの周囲に前記小径孔の内周面が縮径圧着され、かつ、前記大径孔の内側でケーブル端末の素線がばらされて広がっているものである。
【００１０】
なお、ここでいう筒体の「尾端部」とは、端末定着部が形成された状態でその末端となる側の端部を意味する。また、「素線がばらされて」とは必ずしも各素線同士が完全に独立して平行状態となるまで撚りを解くものに限定する意味ではなく、少なくとも筒体の大径孔内でケーブル末端が広がる形状を形成する程度まで素線同士の間に隙間を生じさせるものであればよい。
【００１１】
この端末定着部によれば、筒体における小径孔の縮径圧着によってケーブルと筒体とが固定されるのに加え、その縮径圧着部分よりも尾端側の大径孔内でケーブル端末の素線がばらされて広がっているため、その広がり部分が前記縮径圧着部分へ逆行することが確実に防がれる。従って、筒体を特に長くしなくても端末定着部の引張強度（筒体からのケーブルの抜けを阻止する強さ）を飛躍的に向上させることが可能である。
【００１２】
特に、前記小径孔が、前記ケーブルの端末が挿入可能な内径をもつ円筒状内周面を有し、前記大径孔は前記小径孔の内周面から前記尾端部に向かうに従って拡径するテーパー状内周面を有し、前記ケーブル末端でばらされた素線が前記テーパー状内周面に沿うように広がっているものとすれば、前記円筒状内周面の縮径によってケーブル端末との圧着状態が安定する一方、ケーブル末端の広がり部分とテーパー状内周面との間のくさび効果によって引張強度が著しく向上する。
【００１３】
さらに、前記筒体内における素線同士の間に素線同士の滑りを抑止する滑り止め樹脂が浸透して硬化しているものとすれば、素線の本数が多いケーブルであっても、当該素線同士の間の滑りを前記滑り止め樹脂で抑止することによって高い引張強度を維持することができる。また、この場合においても、ケーブルと筒体との連結力は主として筒体の縮径圧着によって賄われているので、万が一、火災等による加熱で前記滑り止め樹脂が変質しても、ケーブルの連結状態を維持することが可能である。
【００１４】
さらに、前記筒体内における素線同士の間に多数の粒状体が混入されており、かつ、これら粒状体が前記滑り止め樹脂により拘束されている構成とすれば、前記多数の粒状体の混入によってケーブル末端部分（素線がばらされた部分）の広がり形状を保つことができ、これによって高い引張強度をより確実に得ることができる。
【００１５】
また、前記筒体が前記テーパー状内周面よりもさらに尾端側の位置に固定具が螺着されるねじ孔を有するものであれば、当該ねじ孔を利用して前記固定具を螺着することにより、構造物への据付けをより容易に行うことができるとともに、前記テーパー状内周面を塞いでケーブル末端部分を保護することができる。
【００１６】
また本発明は、複数本の素線が撚り合わされたケーブルの端末定着部を製造する方法であって、尾端部と反対の側に開口する小径孔及びこの小径孔に隣接して当該小径孔よりも大きな内径をもつ大径孔を有する筒体内にその小径孔側から前記ケーブルの端末を挿入する挿入工程と、その挿入状態で前記筒体を縮径加工することにより、当該筒体の小径孔の内周面を前記ケーブルの周囲に縮径圧着しかつ前記大径孔内でケーブル端末の素線をばらして広がらせる縮径工程とを含むものである。
【００１７】
この方法によれば、前記筒体内にケーブル端末を挿入した状態で当該筒体を縮径加工することにより、当該筒体の小径孔内周面と前記ケーブルとが強力に圧着されるのに加え、当該縮径加工による圧力で前記大径孔内において素線がばらされて広がることになり、その広がり部分によって引張強度を飛躍的に増大させることができる。
【００１８】
この方法においても、前記筒体として、前記小径孔が前記ケーブルの端末が挿入可能な内径をもつ円筒状内周面を有し、かつ、前記大径孔が前記小径孔の内周面から前記尾端部に向かうに従って拡径するテーパー状内周面を有するものを用い、前記縮径工程で前記ケーブル末端でばらされた素線を前記テーパー状内周面に沿うように広がらせることが、より好ましい。
【００１９】
また、前記縮径工程後、前記筒体の尾端側からケーブル端末に軸方向の圧縮力を加えて当該端末の素線のばらしを促進するようにすれば、筒体内に圧縮力を作用させるだけの簡単な工程で、前記広がり部分の形成をより確実なものにして信頼性をさらに高めることができる。
【００２０】
また、前記縮径工程後、前記筒体内における素線同士の間に液状の滑り止め樹脂を浸透させてから当該樹脂を硬化させることにより、ケーブルの素線の本数が多い場合でも高い引張強度を確保できる定着部を簡単な工程で製造することができる。
【００２１】
さらに、前記滑り止め樹脂の注入前に予め前記ケーブルの端末の素線同士の間に多数の粒状体を侵入させておき、その後に当該素線間に前記滑り止め樹脂を浸透させて硬化させるようにすれば、当該滑り止め樹脂で前記粒状体を拘束することにより、ケーブル末端の広がり形状をより確実に保つことができ、これによって引張強度をさらに高めることができる。
【００２２】
また本発明は、かかる製造方法に好適な筒体であって、その尾端部と反対の側に開口し、その開口から前記ケーブルの端末が挿入可能な円筒状内周面をもつ小径孔と、この小径孔の円筒状内周面から尾端側に向かうに従って拡径する形状のテーパー状内周面を有する大径孔と、このテーパー状内周面よりも尾端側に位置し、当該尾端側からねじ軸が挿入可能なねじ孔とを有し、かつ、前記テーパー状内周面の内側に外部から液状の滑り止め樹脂を注入するための注入口が周壁に設けられているものである。
【００２３】
この筒体によれば、前記縮径工程後、ねじ孔にねじ軸等を螺着して当該ねじ孔を塞いだ状態で前記注入口から滑り止め樹脂を注入することにより、当該樹脂を円滑に素線間へ浸透させることができる。
【００２４】
【発明の実施の形態】
本発明の好ましい実施の形態を図面に基づいて説明する。
【００２５】
まず、本発明にかかるケーブル端末定着部を製造するにあたり、図１（ａ）に示すような筒体１０を成形する。
【００２６】
この筒体１０の中心孔は、その尾端部（図１（ａ）では右端部）と反対の側（同図左側）から順に、小径孔１２ａ、テーパー孔（大径孔）１２ｂ、及びねじ孔１２ｃとなっている。
【００２７】
小径孔１２ａは、前記尾端部と反対の側に開口し、かつ、この開口側から後述のケーブル２４が若干の隙間をもって挿入可能な一定の内径の円筒状内周面を有しており、図例では、筒体尾端部と反対側の端部から筒体１０の軸長の半分以上の長さにわたって延びている。また、その開口端部には前記ケーブル２４の挿入を円滑にするための誘い込み部分として面取り部（誘い込みテーパー部）１２ｄが形成されている。この誘い込み部分は、省略してもよいし、あるいは図示のものよりもかなり長くしてもよい。要は、小径孔１２ａの軸長を確保できる範囲で、ケーブル挿入側の端部の形状は自由に設定が可能である。
【００２８】
テーパー孔１２ｂは、筒体１０の軸方向中間部に形成され、前記小径孔１２ａの内径と同等の最小径を有し、かつ、当該小径孔１２ａから筒体尾端部に向かうに従って拡径するテーパー状内周面を有している。ねじ孔１２ｃは、前記テーパー孔１２ｂの最大径と略同等の内径を有し、かつ、その内周面に雌ねじが螺刻されたものである。
【００２９】
一方、この筒体１０の外周面は、その尾端部（図１（ａ）では右端部）と反対の側（同図左側）から順に、円筒状外周面１４ａ、テーパー状外周面１４ｂ、及び円筒状外周面１４ｃとなっており、これら外周面１４ａ，１４ｂ，１４ｃの軸方向の位置は、それぞれ、前記小径孔１２ａ、テーパー孔１２ｂ、及びねじ孔１２ｃの軸方向の位置に概ね対応している。
【００３０】
円筒状外周面１４ａの外径は円筒状内周面１４ｃの外径よりも大きく、両外周面１４ａ，１４ｃの間に位置するテーパー状外周面１４ｂは前記円筒状外周面１４ａから円筒状外周面１４ｃに向かうに従って縮径する形状となっている。円筒状外周面１４ｃの外径は後述の縮径工程における押し出し加工の目標径（すなわち当該押し出し加工で用いられるダイスのダイス径）と同等に設定されており、従って、両外周面１４ａ，１４ｃの外径差が当該加工の加工しろとなっている。また、円筒状外周面１４ａの縁（尾端部と反対側の縁）には前記押し出し加工用のダイス内に筒体１０を円滑に挿入するための面取り部１４ｄが形成されている。
【００３１】
さらに、この筒体１０の周壁には、その外部とテーパー孔１２ｂ内とを径方向に連通する注入口１６が設けられている。
【００３２】
次に、この筒体１０を用いたケーブル端末定着部の製造方法例を示す。
【００３３】
１）ねじ軸２０の装着
図１（ｂ）に示すように、前記筒体１０のねじ孔１２ｃに、雄ねじが外周面に螺刻されたねじ軸２０を筒体尾端側から挿入し、螺着する。このねじ軸２０は、後述の押し出し加工において押棒として機能するとともに、端末定着部完成後は固定具としても利用できるものである。また、このねじ軸２０の端部のうち筒体１０へ挿入される側の端部（図では左側端部）の端面には、図示のように後述のケーブル２４の末端が挿入可能な凹部２２を形成しておくことが好ましい。
【００３４】
２）挿入工程
前記ねじ軸２０と反対の側から（すなわち尾端部と反対の側から）ケーブル２４の端末を小径孔１２ａの内側に挿入し、その末端をテーパー孔１２ｂの内側にまで至らせる。図例のようにねじ軸２０の端部に凹部２２を形成している場合には、当該凹部２２にケーブル末端２４ａが入り込むまで深く挿入する。
【００３５】
この挿入の際、予め前記ケーブル末端２４ａを軽く溶接しておけば、筒体１０内へのケーブル２４の挿入の際に当該ケーブル２４の素線の撚りが解けてしまうのを抑止でき、その分、完成後の定着部の引張強度を高めることが可能である。ただし、前記溶接によって撚り状態をあまり強く拘束すると、次の縮径工程でケーブル端末２４ａの広がり効果が得られなくなってしまうので留意を要する。
【００３６】
３）縮径工程
ねじ軸２０を前記筒体１０と反対の側から押すようにして筒体１０を図略の押し出し加工用ダイス内に挿入し、当該筒体１０の押し出し加工すなわち縮径加工を行う。ここで、ねじ孔周囲の円筒状外周面１４ｃの外径は前記押し出し加工用ダイスのダイス径と同等であるため、実際に縮径加工されるのは当該円筒状外周面１４ｃよりも前側の部分すなわち円筒状外周面１４ａ及びテーパー状外周面１４ｂが形成された部分のみとなる。
【００３７】
この縮径加工により、図２に示すような状態となる。すなわち、筒体１０の小径孔１２ａの円筒状内周面がケーブル２４の外周面に圧着されるのに加え、当該ケーブル２４の末端２４ａは当該小径孔１２ａが形成されている筒体部分（ねじ孔よりも前側の部分）の軸方向の伸びによってねじ軸２０の凹部２２からテーパー孔１２ｂ内へ離脱し、さらに前記押し出し加工による圧力で端末２４ａの素線がばらされて前記テーパー孔１２ｂのテーパー状内周面にほぼ沿って広がる形状となる。このような広がり部分の形成により、ケーブル２４の末端２４ａが縮径後の小径孔１２ａ内へ逆行することは著しく困難な状態となり、その結果、定着部での引張強度が効果的に高められることとなる。
【００３８】
一方、ねじ孔１２ｃが形成されている部分については実質上押し出し加工が施されていないので、ねじ軸２０とねじ孔１２ｃとの螺合は正常に保たれる。
【００３９】
４）圧縮力の付加
前記ねじ孔１２ｃからねじ軸２０を一旦取り外し、当該ねじ孔１２ｃを図３（ａ）に示すように上側に向けて当該ねじ孔１２ｃから押棒を挿入することにより前記素線のばらしを促進する。この工程は必要に応じて行えばよく、前記押し出し加工のみでも素線が十分に拡散している場合には適宜省略すればよい。
【００４０】
５）粒状体の投入
前記ねじ孔１２ｃから筒体１０内に多数の粒状体（例えば鋼球）２６を投入し、さらに筒体１０を揺する等して前記粒状体２６をケーブル２４を構成する素線同士の間に侵入させる。この粒状体２６は、ケーブル末端２４ａにおける素線同士の間に介在することによって当該末端２４ａの広がり形状を保持するためのものであって、各粒状体２６の径は素線径や素線同士の隙間に応じて適宜設定すればよい（一般には１ｍｍ程度が好適）。また、具体的な材質も問わず、鋼以外の金属材料、セラミック材料、硬質樹脂等の適用が可能であり、広がり形状の保形に寄与するものであればよい。形状についても球形に限らず、例えば不特定な形状であってもよい。
【００４１】
この工程も、ケーブルの構造によっては適宜省略が可能である。また、４）５）の両工程を省略する場合には、ねじ軸２０の取り外し作業も不要となる。
【００４２】
６）滑り止め樹脂の注入
前記ねじ孔１２ｃにねじ軸２０を装着して当該ねじ孔１２ｃを塞いだ状態で、図３（ｂ）に示すように前記ねじ軸２０側を下にし、注入口１６から滑り止め樹脂を注入する。この滑り止め樹脂は、注入当初は良好な流動性を有し、かつ、その後に硬化するものであればよく、例えばエポキシ系のものが好適である。
【００４３】
この滑り止め樹脂の注入量も適宜設定可能であるが、好ましくは当該樹脂が少なくとも筒体１０の上端から溢れるまで注入するのが好ましい。図例では、ケーブル２４の外周面のうち筒体１０と隣接する部分にシールテープ２８を貼着するとともに、そのケーブル側の筒体端部に円筒状の樹脂受け３０を固定しておき、前記梱包テープ２８から溢れた樹脂３２が樹脂受け３０の内側に溜まるようにしている。
【００４４】
このようにして注入された樹脂が硬化することにより、その接着力で素線同士の軸方向の滑りが抑止されるとともに、装填された粒状体２６の動きが拘束され、その結果、定着部の引張強度はさらに高められることになる。なお、この樹脂注入工程についても、ケーブル２４の素線本数が少ないときは適宜省略が可能である。
【００４５】
７）施工例
前記のようにして得られた定着部の施工例を図４に示す。図では、橋梁等の構造物に設けられた定着壁３４に貫通孔３６が設けられ、この貫通孔３６に前記ねじ軸２０が挿通された状態で当該ねじ軸２０の端部に抜け止め用のダブルナット３７，３８が装着されている。この状態でケーブル２４に高い張力が発生しても、当該張力に十分に対抗する（筒体１０からのケーブル２４の抜けや素線同士の滑りを阻止することが可能である。
【００４６】
なお、本発明の実施形態は前記のものに限定されず、例として次のような形態をとることも可能である。
【００４７】
（１）本発明において、ねじ孔１２ｃの省略は可能である。その場合、テーパー孔１２ｂを筒体の尾端部に位置させてもよい。
【００４８】
（２）本発明に使用されるケーブル２４の具体的な種類は問わず、複数本の素線が撚り合わされたものについて広く適用が可能である。ただし、本発明は素線本数の多いスパイラルロープやストランドロープに特に有効となる。
【００４９】
（３）縮径加工は前記押し出し加工に限らず、例えばクランプ加工や引き抜き加工を用いてもよい。ただし、ケーブル２４が筒体１０に接続されている関係上、押し出し加工の方が操作が容易である。特に、図例のように筒体１０の尾端側にねじ軸２０を締結した場合には、当該ねじ軸２０を押棒として利用することにより、押し出し加工はより容易なものとなる。
【００５０】
（４）本発明に係る筒体の「小径孔」及び「大径孔」の内周面形状は図示のものに限られず、例えば小径孔を大径孔に向かうに従ってきわめてなだらかに縮径するテーパー状としてもよいし、逆に大径孔の内周面を小径孔よりも大径の円筒状内周面としてもよい。ただし、図示のような形状とすれば、小径孔１２ａの円筒状内周面とケーブル２４とを軸方向に均一な圧着力で安定して圧着できる一方、大径孔であるテーパー孔１２ｂの内周面に沿うようにケーブル末端２４ａを広がらせることにより、いわゆるくさび効果を用いて引張強度を効果的に高めることが可能になる。
【００５１】
【実施例】
素線数６１本、外径３２ｍｍのスパイラルロープを前記図１（ａ）に示した形状で最大外径８３ｍｍの筒体内に挿入し、この筒体をその外径が７４ｍｍとなるまで押し出し加工したものについて引張試験を行った。その結果を表１に示す。
【００５２】
同表に示されるように、ケーブル端末と筒体とを単なる圧着のみで連結しただけの比較例に比べ、筒体１０のテーパー孔１２ｂ内で素線末端をばらした実施例１によれば、引張強度（筒体からのケーブルの抜けを阻止する強さ）が１５５ｋＮ（６５５ｋＮ−５００ｋＮ）まで向上することが確認できた。
【００５３】
そして、筒体内に滑り止め樹脂を注入すると引張強度は８３０ｋＮまで増大し、さらにケーブル挿入前にその端末を軽く溶接して撚りの戻りを規制すると引張強度はケーブル破断強度である９６０ｋＮ以上に達することが確認された。
【００５４】
【表１】

【００５５】
【発明の効果】
以上のように本発明は、ケーブルの端末定着部に関するものであって、小径孔及び大径孔をもつ筒体に小径孔側からケーブルの端末を挿入した状態で当該筒体を縮径加工することにより、当該筒体の小径孔の内周面を前記ケーブルの周囲に縮径圧着しかつ前記大径孔内でケーブル端末の素線をばらして広がらせるようにしたものであるので、筒体の軸長を特に延長させることなく高い引張強度を得ることができる効果がある。
【図面の簡単な説明】
【図１】（ａ）は本発明に係る筒体の断面図、（ｂ）は当該筒体にねじ軸を装着しかつケーブル端末を挿入した状態を示す断面図である。
【図２】前記筒体を押し出し加工した後の状態を示す断面図である。
【図３】（ａ）は前記ねじ軸を外して筒体内に粒状体を投入した状態を示す断面図、（ｂ）は当該ねじ軸を装着して注入口からテーパー状内周面内に樹脂を注入する工程を示す断面図である。
【図４】本発明に係る端末定着部の施工例を示す一部断面図である。
【符号の説明】
１０筒体
１２ａ円筒状内周面
１２ｂテーパー状内周面
１２ｃねじ孔内周面
１６注入口
２０ねじ軸（固定具と兼用）
２４ケーブル
２４ａケーブル末端
２６粒状体
３２滑り止め樹脂[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a terminal fixing unit for fixing a terminal of a cable used for a structure such as a suspension bridge or a building to the structure, and a method of manufacturing the terminal fixing unit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a terminal fixing section of a cable as described above, those shown in Patent Documents 1 and 2 below are known.
[0003]
First, in FIG. 1 of Patent Document 1, a cable end is inserted into a steel sleeve having a flat hole at the center, and then the sleeve is reduced in diameter and the inner peripheral surface of the sleeve is crimped to the cable end. Things are shown. Further, in FIG. 3 of the same document, a tapered hole having a larger diameter than the flat hole is formed in a front side portion of the sleeve and on a front side of the flat hole. In this case, a curable resin is filled, and the tubular body is fixed to the cable terminal by both the adhesive force of the resin and the adhesive force by the pressure bonding.
[0004]
[Patent Document 1]
JP-A-59-88986 (pages 1-3, FIG. 1, FIG. 3)
In FIG. 1 of Patent Document 2, as a means for fixing an end of a fiber composite material cable, a wire rope, or the like, a cable terminal is inserted into a cylinder having a tapered hole, and a wire at the end is inserted. The cylindrical body is stored in the tapered hole portion in a separated state, and the cylindrical body is filled with a filler and cured so that the cylindrical body is fixed to the cable terminal by the adhesive force of the filler. Is disclosed.
[Patent Document 2]
JP-A-10-82178 (pages 3 to 5, FIG. 1)
[0005]
[Problems to be solved by the invention]
The fixing unit shown in FIG. 1 of Patent Document 1 fixes the tubular body to the cable end only by the crimping force by the diameter reduction processing of the tubular body. There is a disadvantage that it is difficult to obtain a tensile strength. In addition, the fixing unit shown in FIG. 3 of the document 1 has a fixing portion filled with a curable resin in front of the crimping portion, but the fixing portion and the crimping portion are simply arranged in the axial direction. , There is no synergistic effect, and a remarkable improvement in tensile strength cannot be expected.
[0006]
On the other hand, the fixing unit disclosed in Patent Literature 2 fixes the cylindrical body and the cable only by the adhesive force of the curable resin, and thus is, for example, a spiral rope based on a large number of steel wires. It is difficult to apply to a terminal fixing portion of a cable which requires a high tension. Further, even if it is assumed that the required strength is obtained only by the adhesive force, if the terminal fixing portion is abnormally heated due to a fire or the like, the curable resin may deteriorate and lose the fixing force.
[0007]
That is, in any of the documents, there is a considerable limitation in enhancing the tensile strength, and there is a problem that the axial length of the cylindrical body must be considerably long in order to secure the strength.
[0008]
In view of such circumstances, an object of the present invention is to provide a terminal fixing portion of a cable capable of obtaining a high tensile strength without particularly extending the axial length of a cylindrical body, and an object of the present invention is to provide a method of manufacturing the same.
[0009]
[Means for Solving the Problems]
As a means for solving the above problems, the present invention is a terminal fixing unit in which a cylindrical body having a larger outer diameter than the cable is fixed around a terminal of a cable in which a plurality of strands are twisted, The cylindrical body has a small-diameter hole that opens on the side opposite to the tail end thereof, and a large-diameter hole adjacent to the tail end of the small-diameter hole and having an inner diameter larger than the small-diameter hole, The inner peripheral surface of the small-diameter hole is reduced-pressure-bonded around the cable in a state where the terminal of the cable is inserted from the small-diameter hole side to the inside of the large-diameter hole, and inside the large-diameter hole. The wires of the cable terminal are separated and spread.
[0010]
Here, the “tail end” of the cylindrical body means an end on the side which is the end in the state where the terminal fixing portion is formed. In addition, the term “the wires are separated” does not necessarily mean that the wires are untwisted until they are completely independent of each other and are in a parallel state. At least, the cable ends in the large-diameter hole of the cylindrical body. Any shape may be used as long as a gap is formed between the strands to such an extent that the shape of the wire is widened.
[0011]
According to this terminal fixing part, in addition to the cable and the cylindrical body being fixed by the reduced diameter crimping of the small diameter hole in the cylindrical body, the cable terminal of the cable terminal in the large diameter hole at the tail end side of the reduced diameter crimped portion. Since the wires are separated and spread, the spread portion is reliably prevented from going back to the reduced diameter crimping portion. Therefore, it is possible to dramatically improve the tensile strength of the terminal fixing portion (the strength of preventing the cable from being pulled out of the cylindrical body) without particularly lengthening the cylindrical body.
[0012]
In particular, the small-diameter hole has a cylindrical inner peripheral surface having an inner diameter into which the end of the cable can be inserted, and the large-diameter hole increases in diameter from the inner peripheral surface of the small-diameter hole toward the tail end. Having a tapered inner peripheral surface, assuming that the wires separated at the end of the cable are spread along the tapered inner peripheral surface, a cable terminal is formed by reducing the diameter of the cylindrical inner peripheral surface. While the crimped state of the cable is stable, the tensile strength is significantly improved by the wedge effect between the widened portion of the cable end and the tapered inner peripheral surface.
[0013]
Furthermore, if it is assumed that the non-slip resin that suppresses slippage between the wires between the wires in the cylinder is hardened by penetration, even if the cable has a large number of wires, High tensile strength can be maintained by suppressing the slip between the wires with the anti-slip resin. Also in this case, since the connection force between the cable and the cylinder is mainly provided by the reduced-diameter crimping of the cylinder, even if the non-slip resin is deteriorated by heating due to a fire or the like, the connection of the cable may be performed. It is possible to maintain the state.
[0014]
Furthermore, if a large number of granular materials are mixed between the wires in the cylindrical body, and if these granular materials are configured to be constrained by the non-slip resin, mixing of the large number of granular materials The spread shape of the cable end portion (the portion where the wires are separated) can be maintained, so that high tensile strength can be obtained more reliably.
[0015]
In addition, if the cylindrical body has a screw hole into which a fastener is screwed at a position further on the tail end side than the tapered inner peripheral surface, the fastener is screwed using the screw hole. By doing so, installation to a structure can be performed more easily, and the end portion of the cable can be protected by closing the tapered inner peripheral surface.
[0016]
The present invention also relates to a method for manufacturing a terminal fixing portion of a cable in which a plurality of strands are twisted, the small-diameter hole opening on the side opposite to the tail end portion, and the small-diameter hole adjacent to the small-diameter hole. An insertion step of inserting the end of the cable from the small-diameter hole side into a cylinder having a large-diameter hole having a larger inner diameter, and reducing the diameter of the cylinder in the inserted state, thereby reducing the diameter of the cylinder. Reducing the diameter of the inner peripheral surface of the hole around the cable and reducing the diameter of the wire of the cable terminal in the large-diameter hole.
[0017]
According to this method, the diameter of the cylinder is reduced while the cable end is inserted into the cylinder, so that the inner peripheral surface of the small-diameter hole of the cylinder and the cable are strongly crimped. The wire is separated and spreads in the large-diameter hole due to the pressure caused by the diameter reducing process, and the expanded portion can dramatically increase the tensile strength.
[0018]
Also in this method, as the cylindrical body, the small-diameter hole has a cylindrical inner peripheral surface having an inner diameter into which the terminal of the cable can be inserted, and the large-diameter hole extends from the inner peripheral surface of the small-diameter hole. Using a tapered inner peripheral surface that expands in diameter toward the tail end, the wires separated at the cable end in the diameter reducing step are spread along the tapered inner peripheral surface, More preferred.
[0019]
Further, after the diameter reducing step, if a compressive force in the axial direction is applied to the cable terminal from the tail end side of the cylindrical body to promote the unwinding of the wires of the terminal, the compressive force acts on the cylindrical body. With only simple steps, the formation of the spread portion can be made more reliable, and the reliability can be further improved.
[0020]
Further, after the diameter reducing step, by curing the resin after penetrating the liquid anti-slip resin between the wires in the cylinder, a high tensile strength is obtained even when the number of wires of the cable is large. The fixing unit that can be secured can be manufactured by a simple process.
[0021]
Further, before the injection of the anti-slip resin, a large number of granular materials are infiltrated between the wires of the terminal of the cable in advance, and then the anti-slip resin is permeated between the wires and cured. By restraining the granular material with the non-slip resin, the spread shape of the cable end can be more reliably maintained, and the tensile strength can be further increased.
[0022]
Further, the present invention is a cylindrical body suitable for such a manufacturing method, and has a small-diameter hole having a cylindrical inner peripheral surface which is opened on the side opposite to the tail end thereof and from which the terminal of the cable can be inserted. A large-diameter hole having a tapered inner peripheral surface having a shape that increases in diameter toward the tail end from the cylindrical inner peripheral surface of the small-diameter hole, and is located closer to the tail end than the tapered inner peripheral surface. A screw hole into which a screw shaft can be inserted from the tail end side, and an inlet for injecting a liquid non-slip resin from outside inside the tapered inner peripheral surface is provided in the peripheral wall. It is.
[0023]
According to this cylindrical body, after the diameter reducing step, a non-slip resin is injected from the injection port in a state where a screw shaft or the like is screwed into the screw hole and the screw hole is closed, so that the resin is smoothly moved. It can penetrate between the strands.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the present invention will be described with reference to the drawings.
[0025]
First, in manufacturing the cable terminal fixing section according to the present invention, a cylindrical body 10 as shown in FIG. 1A is formed.
[0026]
The center hole of the cylindrical body 10 is arranged in order from the side opposite to the tail end (the right end in FIG. 1A) (left side in FIG. 1), the small diameter hole 12a, the tapered hole (large diameter hole) 12b, and the screw. It is a hole 12c.
[0027]
The small-diameter hole 12a has an opening on the side opposite to the tail end, and has a cylindrical inner peripheral surface having a constant inside diameter from which a cable 24 described later can be inserted with a slight gap from the opening side. In the illustrated example, it extends from the end opposite to the end of the cylindrical body over a length equal to or more than half the axial length of the cylindrical body 10. Further, a chamfered portion (introduced tapered portion) 12d is formed in the opening end portion as an inviting portion for facilitating insertion of the cable 24. This lure may be omitted or may be significantly longer than shown. In short, as long as the axial length of the small-diameter hole 12a can be ensured, the shape of the end on the cable insertion side can be freely set.
[0028]
The tapered hole 12b is formed at an axially intermediate portion of the cylindrical body 10, has a minimum diameter equal to the inner diameter of the small-diameter hole 12a, and expands in diameter from the small-diameter hole 12a toward the tail end of the cylindrical body. It has a tapered inner peripheral surface. The screw hole 12c has an inner diameter substantially equal to the maximum diameter of the tapered hole 12b, and has a female screw threaded on the inner peripheral surface thereof.
[0029]
On the other hand, the outer peripheral surface of the cylindrical body 10 has a cylindrical outer peripheral surface 14a, a tapered outer peripheral surface 14b, and a cylindrical outer peripheral surface 14b in order from the side opposite to the tail end (the right end in FIG. The outer

peripheral surfaces

14a, 14b, and 14c have axial positions substantially corresponding to the axial positions of the small-diameter hole 12a, the tapered hole 12b, and the screw hole 12c, respectively. I have.
[0030]
The outer diameter of the cylindrical outer peripheral surface 14a is larger than the outer diameter of the cylindrical inner peripheral surface 14c, and the tapered outer peripheral surface 14b located between the outer

peripheral surfaces

14a, 14c is separated from the cylindrical outer peripheral surface 14a by the cylindrical outer peripheral surface. The shape is such that the diameter is reduced toward 14c. The outer diameter of the cylindrical outer peripheral surface 14c is set to be equal to the target diameter of the extrusion in the diameter reduction step described later (that is, the die diameter of the die used in the extrusion). The difference in outer diameter is a margin for the processing. A chamfered portion 14d for smoothly inserting the cylindrical body 10 into the extrusion die is formed at an edge (an edge opposite to the tail end) of the cylindrical outer peripheral surface 14a.
[0031]
Further, an injection port 16 is provided on the peripheral wall of the cylindrical body 10 to radially communicate the outside with the inside of the tapered hole 12b.
[0032]
Next, an example of a method of manufacturing a cable terminal fixing section using the cylindrical body 10 will be described.
[0033]
1) Attaching the screw shaft 20 As shown in FIG. 1 (b), a screw shaft 20 having a male screw threaded on the outer peripheral surface is inserted into the screw hole 12c of the cylindrical body 10 from the tail end side of the cylindrical body. To wear. The screw shaft 20 functions as a push rod in an extrusion process described later, and can be used as a fixing tool after completion of the terminal fixing unit. A recess 22 into which the end of a cable 24 to be described later can be inserted is provided on an end face of an end (left end in the figure) of the end of the screw shaft 20 which is inserted into the cylindrical body 10 as shown in the drawing. Is preferably formed.
[0034]
2) Insertion Step The end of the cable 24 is inserted into the inside of the small-diameter hole 12a from the side opposite to the screw shaft 20 (that is, from the side opposite to the tail end), and its end is brought into the inside of the tapered hole 12b. . In the case where the concave portion 22 is formed at the end of the screw shaft 20 as in the illustrated example, the screw shaft 20 is inserted deeply until the cable end 24a enters the concave portion 22.
[0035]
If the cable end 24a is lightly welded in advance at the time of this insertion, it is possible to prevent the strand of the cable 24 from being untwisted when the cable 24 is inserted into the cylindrical body 10, and accordingly, In addition, it is possible to increase the tensile strength of the fixing unit after completion. However, if the twisted state is excessively restrained by the welding, attention must be paid to the fact that the effect of expanding the cable terminal 24a cannot be obtained in the next diameter reduction step.
[0036]
3) Diameter reduction step The cylindrical body 10 is inserted into an unillustrated extrusion die so that the screw shaft 20 is pushed from the side opposite to the cylindrical body 10, and the cylindrical body 10 is extruded, that is, reduced in diameter. Do. Here, since the outer diameter of the cylindrical outer peripheral surface 14c around the screw hole is equal to the die diameter of the extrusion die, the actual diameter reduction processing is performed on a portion in front of the cylindrical outer peripheral surface 14c. That is, it is only the portion where the cylindrical outer peripheral surface 14a and the tapered outer peripheral surface 14b are formed.
[0037]
By this diameter reduction processing, a state as shown in FIG. 2 is obtained. That is, in addition to the cylindrical inner peripheral surface of the small diameter hole 12a of the cylindrical body 10 being crimped to the outer peripheral surface of the cable 24, the distal end 24a of the cable 24 has a cylindrical portion (screw) in which the small diameter hole 12a is formed. The portion extending from the recess 22 of the screw shaft 20 into the tapered hole 12b due to the axial extension of the portion (the portion on the front side of the hole), and the wire of the terminal 24a is separated by the pressure of the extrusion process, so that the taper of the tapered hole 12b It has a shape that extends almost along the inner peripheral surface of the shape. Due to the formation of such a widened portion, it is extremely difficult for the end 24a of the cable 24 to move backward into the small-diameter hole 12a after the diameter reduction, and as a result, the tensile strength at the fixing portion is effectively increased. It becomes.
[0038]
On the other hand, the portion where the screw hole 12c is formed is not substantially extruded, so that the screwing between the screw shaft 20 and the screw hole 12c is kept normal.
[0039]
4) Applying compressive force The screw shaft 20 is once removed from the screw hole 12c, and the screw wire 12c is turned upward by inserting a push rod from the screw hole 12c upward as shown in FIG. 3A. Promote dissemination. This step may be performed as needed, and may be appropriately omitted if the strands are sufficiently diffused only by the extrusion processing.
[0040]
5) Injection of granular material A large number of granular materials (for example, steel balls) 26 are introduced into the cylindrical body 10 from the screw holes 12c, and the granular body 26 is formed into a cable 24 by shaking the cylindrical body 10 or the like. Let it penetrate between the lines. The granules 26 are provided between the wires at the cable end 24a so as to maintain the spread shape of the ends 24a. (Approximately 1 mm is generally preferable). In addition, regardless of the specific material, a metal material other than steel, a ceramic material, a hard resin, or the like can be used, and any material can be used as long as it contributes to shape retention of the spread shape. The shape is not limited to a spherical shape, and may be, for example, an unspecified shape.
[0041]
This step can also be appropriately omitted depending on the structure of the cable. When both steps 4) and 5) are omitted, the work of removing the screw shaft 20 is not required.
[0042]
6) Injection of anti-slip resin With the screw shaft 20 attached to the screw hole 12c and closing the screw hole 12c, the screw shaft 20 side is turned down as shown in FIG. Inject a non-slip resin from. The non-slip resin only needs to have good fluidity at the beginning of injection and be cured thereafter. For example, an epoxy-based resin is suitable.
[0043]
Although the injection amount of the anti-slip resin can be set as appropriate, it is preferable to inject the resin until at least the resin overflows from the upper end of the cylindrical body 10. In the illustrated example, a seal tape 28 is attached to a portion of the outer peripheral surface of the cable 24 adjacent to the cylindrical body 10 and a cylindrical resin receiver 30 is fixed to an end of the cylindrical body on the cable side. The resin 32 overflowing from the packing tape 28 accumulates inside the resin receiver 30.
[0044]
As the resin injected in this way cures, the adhesive force prevents the wires from slipping in the axial direction, and the movement of the loaded granular material 26 is restrained. The tensile strength will be further increased. Note that this resin injection step can also be omitted as appropriate when the number of strands of the cable 24 is small.
[0045]
7) Application Example FIG. 4 shows an application example of the fixing unit obtained as described above. In the figure, a through hole 36 is provided in a fixing wall 34 provided in a structure such as a bridge, and the screw shaft 20 is inserted into the through hole 36 to prevent the screw shaft 20 from coming off at an end thereof.

Double nuts

37 and 38 are mounted. Even if a high tension is applied to the cable 24 in this state, the cable 24 sufficiently opposes the tension (it is possible to prevent the cable 24 from slipping out of the cylindrical body 10 and to prevent slippage between the wires).
[0046]
Note that the embodiment of the present invention is not limited to the above-described embodiment, and may take the following forms as an example.
[0047]
(1) In the present invention, the screw holes 12c can be omitted. In that case, the tapered hole 12b may be located at the tail end of the cylindrical body.
[0048]
(2) Regardless of the specific type of the cable 24 used in the present invention, it can be widely applied to a cable in which a plurality of strands are twisted. However, the present invention is particularly effective for spiral ropes and strand ropes having a large number of strands.
[0049]
(3) The diameter reduction process is not limited to the extrusion process, but may be, for example, a clamp process or a drawing process. However, since the cable 24 is connected to the cylindrical body 10, the operation is easier in the extrusion process. In particular, when the screw shaft 20 is fastened to the tail end side of the cylindrical body 10 as shown in the example of the drawing, the extrusion process becomes easier by using the screw shaft 20 as a push rod.
[0050]
(4) The shape of the inner peripheral surface of the “small-diameter hole” and “large-diameter hole” of the cylindrical body according to the present invention is not limited to the illustrated shape. Alternatively, the inner peripheral surface of the large-diameter hole may be a cylindrical inner peripheral surface having a larger diameter than the small-diameter hole. However, if the shape shown in the drawing is used, the cylindrical inner peripheral surface of the small-diameter hole 12a and the cable 24 can be stably crimped with a uniform crimping force in the axial direction. By extending the cable end 24a along the peripheral surface, it is possible to effectively increase the tensile strength by using a so-called wedge effect.
[0051]
【Example】
A spiral rope having 61 wires and an outer diameter of 32 mm was inserted into a cylindrical body having a maximum outer diameter of 83 mm in the shape shown in FIG. 1A, and the cylindrical body was extruded until the outer diameter became 74 mm. Those were subjected to a tensile test. Table 1 shows the results.
[0052]
As shown in the table, according to the first embodiment in which the ends of the wires are separated in the tapered hole 12b of the cylindrical body 10 as compared with the comparative example in which the cable terminal and the cylindrical body are merely connected by simple crimping, It was confirmed that the tensile strength (strength for preventing the cable from coming off from the cylinder) was improved to 155 kN (655 kN-500 kN).
[0053]
When the anti-slip resin is injected into the cylinder, the tensile strength increases to 830 kN, and if the end of the cable is lightly welded to prevent the return of twist before inserting the cable, the tensile strength reaches 960 kN or more, which is the cable breaking strength. Was confirmed.
[0054]
[Table 1]

[0055]
【The invention's effect】
INDUSTRIAL APPLICABILITY As described above, the present invention relates to a terminal fixing portion of a cable, and reduces the diameter of a cylindrical body having a small-diameter hole and a large-diameter hole in a state where the cable end is inserted from the small-diameter hole side. By doing so, the inner peripheral surface of the small-diameter hole of the cylindrical body is reduced-pressure-bonded to the periphery of the cable and the wires of the cable end are spread and spread in the large-diameter hole. This has the effect that a high tensile strength can be obtained without particularly extending the axial length.
[Brief description of the drawings]
1A is a cross-sectional view of a cylindrical body according to the present invention, and FIG. 1B is a cross-sectional view showing a state where a screw shaft is mounted on the cylindrical body and a cable terminal is inserted.
FIG. 2 is a cross-sectional view showing a state after extruding the cylindrical body.
FIG. 3A is a cross-sectional view showing a state in which the screw shaft has been removed and a granular material has been put into a cylindrical body, and FIG. FIG. 4 is a cross-sectional view showing a step of injecting a semiconductor.
FIG. 4 is a partial cross-sectional view showing a construction example of a terminal fixing unit according to the present invention.
[Explanation of symbols]
10 Cylindrical body 12a Cylindrical inner peripheral surface 12b Tapered inner peripheral surface 12c Screw hole inner peripheral surface 16 Injection port 20 Screw shaft (also used as fixture)
24 Cable 24a Cable end 26 Granular material 32 Non-slip resin

Claims

A terminal fixing portion in which a cylindrical body having a larger outer diameter than the cable is fixed around a terminal of a cable in which a plurality of strands are twisted, and the cylindrical body is on a side opposite to a tail end thereof. A small-diameter hole to be opened, and a large-diameter hole adjacent to the tail end side of the small-diameter hole and having an inner diameter larger than the small-diameter hole, from the small-diameter hole side to the inside of the large-diameter hole. In a state where the end of the cable is inserted, the inner peripheral surface of the small-diameter hole is reduced-diameter crimped around the cable, and the wires of the cable terminal are separated and spread inside the large-diameter hole. Characteristic terminal fixing part of cable.

The terminal fixing portion of the cable according to claim 1, wherein the small-diameter hole has a cylindrical inner peripheral surface having an inner diameter into which the terminal of the cable can be inserted, and the large-diameter hole is formed from the inner peripheral surface of the small-diameter hole. A cable terminal having a tapered inner peripheral surface that expands in diameter toward the tail end, wherein a strand separated at the end of the cable is extended along the tapered inner peripheral surface. Fixing section.

3. The cable terminal fixing section according to claim 1, wherein a non-slip resin that suppresses slippage of the wires between the wires in the cylinder penetrates and is hardened. Terminal fixing unit.

4. The terminal fixing portion of a cable according to claim 3, wherein a number of particles are mixed between the wires in the cylinder, and the particles are restrained by the non-slip resin. The terminal fixing section of the cable.

5. The terminal fixing portion of the cable according to claim 1, wherein the cylindrical body has a screw hole at a tail end side of the large-diameter hole, into which a fixing tool is screwed. 6. The terminal fixing section of the cable.

A method of manufacturing a terminal fixing portion of a cable in which a plurality of strands are twisted, wherein a small-diameter hole that opens on the side opposite to the tail end and an inner diameter larger than the small-diameter hole adjacent to the small-diameter hole are formed. An insertion step of inserting the end of the cable into the cylindrical body having the large-diameter hole from the small-diameter hole side, and reducing the diameter of the cylindrical body in the inserted state, thereby forming the inner peripheral surface of the small-diameter hole of the cylindrical body. Reducing the diameter of the cable at the periphery of the cable and reducing the diameter of the wire of the cable terminal in the large-diameter hole.

7. The method of manufacturing a terminal fixing portion of a cable according to claim 6, wherein the small-diameter hole has a cylindrical inner peripheral surface having an inside diameter into which the terminal of the cable can be inserted, and the large-diameter hole is formed as the cylindrical body. A tapered inner peripheral surface whose diameter increases from the inner peripheral surface of the small-diameter hole toward the tail end portion. A method for manufacturing a terminal fixing portion of a cable, wherein the terminal fixing portion is spread along a surface.

The method for manufacturing a terminal fixing portion of a cable according to claim 6 or 7, wherein after the diameter reducing step, an axial compressive force is applied to a cable terminal from a tail end side of the cylindrical body to separate the element wires of the terminal. A method of manufacturing a terminal fixing portion of a cable, comprising:

The method for manufacturing a terminal fixing portion of a cable according to claim 7 or 8, wherein after the diameter reducing step, a liquid non-slip resin is permeated between wires in the cylinder, and then the resin is cured. A method of manufacturing a terminal fixing portion of a cable, which is characterized by the following.

10. The method for manufacturing a terminal fixing portion of a cable according to claim 9, wherein after the step of reducing the diameter, a large number of granular materials are allowed to penetrate between the wires of the terminal of the cable, and then the sliding is performed between the wires. A method for manufacturing a terminal fixing portion of a cable, wherein the granular material is constrained by the anti-slip resin by infiltrating and curing the anti-slip resin.

A tubular body that constitutes a terminal fixing portion of the cable by being fixed around the terminal of the cable in which a plurality of strands are twisted, and is opened on the side opposite to the tail end thereof, from the opening. A small-diameter hole having a cylindrical inner peripheral surface into which the end of the cable can be inserted, and a large-diameter hole having a tapered inner peripheral surface whose diameter increases from the cylindrical inner peripheral surface toward the tail end of the small-diameter hole. And a screw hole that is located closer to the tail end than the tapered inner peripheral surface and into which a screw shaft can be inserted from the tail end side, and that a liquid that is externally liquid inside the tapered inner peripheral surface is provided. A cylindrical body, wherein an inlet for injecting a non-slip resin is provided on a peripheral wall.