JP3930285B2

JP3930285B2 - Electric fusion joint

Info

Publication number: JP3930285B2
Application number: JP2001319796A
Authority: JP
Inventors: 紀之森谷
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2001-10-17
Filing date: 2001-10-17
Publication date: 2007-06-13
Anticipated expiration: 2021-10-17
Also published as: JP2003120886A

Description

【０００１】
【発明の属する技術分野】
本発明は、熱可塑性樹脂製管、特にガスや水道用の配管材として好適なポリエチレン管の接続に使用される電気融着継手に関するものである。
【０００２】
【従来の技術】
ポリエチレンは化学的に極めて安定であり、可塑剤も必要としないので、水道用配管材として有用である反面、実質的に非極性であるために、接着剤による接合が至難である。
そこで、図７に示すように、内層１’側に螺旋巻回抵抗線３’を埋め込み、抵抗線端子２’を外層５’に表出させた熱可塑性樹脂製継手、所謂、電気融着継手が使用されることが多い。
この電気融着継手により熱可塑性樹脂管を接合するには、被接合管端部を継手内に挿入し、抵抗線３’を通電発熱させて内層１’と被接合管端部との界面を熱融着させている。
この場合、外層５’は実質上熱溶融されず端子２’の位置が固定であり、端子近傍の抵抗線部分も実質上固定のままとされるが、内層樹脂が熱溶融されて熱膨張により両端子間の中央から各端子に向け流動され、端子に近いほど累積効果により流量が大とされるために、実質上固定の端子近傍の抵抗線部分に前記樹脂の流動に伴い移動されてくる抵抗線部
分が接触し、短絡が生じて上記界面の熱融着を満足に行ない得ないことがある。
【０００３】
そこで、かかる不都合を防止するために、図８の（イ）に示すように、端子２’近傍の抵抗線部分３１’の内筒軸方向に対する角度を他の抵抗線部分３２’よりも小とし、それに応じ他の抵抗線部分３２’の内筒軸方向に対する角度を大きくし、すなわち巻付けピッチを小さくして、図８の（イ）における間隔ｇを相対的に広くすること（特開平４−８９９４号公報、特開２００１−４１３８５号公報）や、図８の（ロ）に示すように、端子２’近傍の抵抗線部分３１’の巻径を他の抵抗線部分３２’よりも大きくすること（前掲の特開２００１−４１３８５号公報）等が提案されている。
【０００４】
【発明が解決しようとする課題】
ところで、電気融着継手として、図９に示すように熱可塑性樹脂製内筒１”の端子受け部１１’に端子２’のピン部２１’を装着し、内筒外面の螺旋溝１２’に抵抗線３’を巻付け、抵抗線３’の各端部と各端子２’のヘッド部２２’の側面とを溶接等により接合し、内筒１”上に熱可塑性樹脂外層５’を射出成形し、外層５’の表面から端子２’のヘッド部２２’を表出させたものが、いわゆる、インナー・アウター式として知られている。
この構成では、内筒表面の溝に抵抗線を巻付けているので、抵抗線の整然・安定な巻付けを保証でき、抵抗線の巻付け時や外層の射出成形に際しての金型組み込み時等での抵抗線の交絡を確実に排除できる。
【０００５】
上記したインナー・アウター式において、端子近傍の抵抗線部分の巻径を他の抵抗線部分よりも大きくするには、所定長さ（通常、１／２周から１／３周程度）の凸条部の上面に溝を設け、この溝に端子近傍の抵抗線部分を巻付けることが、前記した抵抗線の整然・安定な巻付け保証のために要請される。
しかしながら、内筒の外面に、このような凸条部を設けると、外層の射出成形時にエアーが捕捉され易く、気泡が生じ、気泡上の外層箇所の肉厚が薄くなって機械的なウィークポイントとなる畏れがある。
【０００６】
また、端子近傍の抵抗線部分を巻付けるための溝の内筒軸方向に対する角度を、他の抵抗線部分を巻付けるための溝の同角度よりも小さくする構成では、内筒が無流動の液状になって内筒による支持が喪失されたときに、抵抗線の折り曲げ状態をそのまま保持させ得るように抵抗線を折り曲げ塑性加工することが予定されているが、抵抗線をこのように塑性加工して、内筒の溝に巻付けることは、機巻では困難であり、特に抵抗線が鉄クロム線のように剛直な場合には至難である。
【０００７】
更に、前記内筒に設けた端子受け部にピン部を装着した端子のヘッド部と抵抗線との接合には、作業能率上、スポット溶接を使用することが要請されるが、端子のヘッド部が溶接熱で加熱され、端子のヘッド部に接触された端子受け部分が熱軟化され、抵抗線の張力を支えきれなくなって端子が傾き乃至は抜脱されることもある。
【０００８】
本発明の他の目的は、熱可塑性樹脂製内筒に抵抗線が溝において巻付けられ、該内筒上に熱可塑性樹脂外層が射出成形され、該外層に抵抗線端子が埋着されてなる継手において、端子の抵抗線部分を巻付けるための溝の内筒軸方向に対する角度を他の抵抗線部分を巻付けるための溝の同角度に較べて小さくするにもかかわらず、抵抗線を円滑な巻付けで容易に製作できる電気融着継手を提供することにある。
【０００９】
本発明の更なる目的は、前記した目的に加え、端子近傍の抵抗線部分の巻径を大きくするための上面溝付き凸条部を内筒に設けるにもかかわらず、エアー捕捉を防止して充分な継手強度を有する電気融着継手を提供することにある。
【００１０】
本発明の更なる目的は、前記した目的に加え、内筒の端子受け部にピン部を装着した端子のヘッド部と抵抗線とのスポット溶接をスムーズに行ない得る電気融着継手を提供することにある。
【００１１】
【課題を解決するための手段】
本願の請求項１に係る電気融着継手は、熱可塑性樹脂製内筒に抵抗線が溝において巻付けられ、該内筒上に熱可塑性樹脂外層が射出成形され、該外層に抵抗線端子が埋着されてなる継手において、端子近傍の抵抗線部分を巻付ける溝の内筒軸方向に対する角度を他の抵抗線部分を巻付ける溝の内筒軸方向に対する角度よりも小さくするための抵抗線折り曲げ用ボスが設けられ、抵抗線が他の抵抗線部分において内筒表面の溝に巻付けられ、更に、前記ボスにおいて折り曲げられたうえで溝無しの経間部を経て端子近傍の内筒部分の溝に前記の小角度のもとで巻付けられていることを特徴とし、請求項２では、端子近傍の内筒部分の溝が凸条部の上面に設けられており、更に、請求項３では、凸条部がエアー抜き切欠部または孔を備えている。
【００１３】
本願の請求項４に係る電気融着継手では、前記何れかの電気融着継手において、端子のピン部を装着するための端子受け部が内筒に設けられ、端子のヘッド側面に溶接された抵抗線の引っ張りに対し端子のヘッド部を支えるための擁壁が前記端子受け部に設けられている。
【００１４】
【発明の実施の形態】
以下、図面を参照しつつ本発明の実施の形態について説明する。
図１の（イ）は本発明に係る電気融着継手の要部を示す縦断面図、図１の（ロ）は同上要部を示す平面図、図１の（ハ）は同上要部を示す正面図、図１の（ニ）及び（ホ）は図１の（ハ）におけるニ−ニ断面図及びホ−ホ断面図である。
図１において、１は熱可塑性樹脂内筒、例えばポリエチレン内筒、１１は内筒外面の各端部に突設した端子受け部である。２は端子であり、ピン部２１とヘッド部２２を有し、ピン部２１を端子受け部１１に緊嵌状態で装着してある。３は抵抗線、例えば鉄クロム線を示し、端子２近傍の抵抗線部分３１と他の抵抗線部分３２とから成る。１２は他の抵抗線部分３２を巻付けるために内筒１の外面に設けた溝である。４は端子２近傍の抵抗線部分３１の巻径を他の抵抗線部分３２よりも大きくするために設けた凸条部であり、端子２側に至るほど背を漸次に高くし、上面に溝４１を設け、凸条部４の奥端ｅにおける溝４１と内筒外面における溝１２とは、内筒外面に対して同一の高さレベルとしてある。この凸条部４と端子受け部１１との間は、切り欠いてあり、この切欠部４０が後述する外層射出成形時のエアー抜き通路として使用される。
図１において、端子２近傍の抵抗線部分３１が凸条部４の溝４１に巻付けられ、他の抵抗線部分３２が内筒外面の溝１２に巻付けられ、抵抗線３の各端部と各端子２のヘッド部２２の側面とが溶接されている。
５は内筒上に射出成形した熱可塑性樹脂外層であり、端子２のヘッド部２２が表出されている。
【００１５】
図１に示す電気融着継手を製作するには、コア金型上に一旦射出成形によって内筒１を形成し、各端子受け部１１に各端子２のピン部２１を装着し、内筒表面の溝１２に沿い他の抵抗線部分３２を、凸条部４の上面の溝４１に沿い端子２近傍の抵抗線部分３１をそれぞれ巻付け、抵抗線３の各端部と各端子２のヘッド部２２の側面とを溶接し、次いで、外金型をセットし、外金型と内筒との間のキャビティに溶融樹脂をチャージし、チャージ樹脂の冷却固化を待って外層５を成形し、離型することができる。
前記溶融樹脂のチャージ時、前記凸条部４の陰にエアーが溜ろうとしても、凸条部４の切欠部４０がエアー抜き通路となり、そのエアーが継手端部の金型合わせ目の隙間より容易に排出される。そして、継手が厚肉であるために、キャビティが相当に厚く、チャージ
圧がほぼ０であるために、上記金型合わせ目の隙間からの樹脂の漏出もよく防止できる。従って、充分な機械的強度を有する電気融着継手を良好な作業性で製作できる。
【００１６】
上記実施例では、凸条部４の高所側に切欠部４０を設けているが、低所側の高さが実質的に０、高所側が端子受け部に連設された凸条部の基本型に対し、図２の（イ）〜（チ）に示すように、エアー抜きとして有効な切欠部または孔を設けたものであれば、適宜のものを使用できる。
図２の（イ）において、１１は端子受け部、４は端子受け部１１に連設された凸条部であり、低所側に切欠部４０を設けてある。
図２の（ロ）において、１１は端子受け部、４は凸条部であり、端子受け部１１との間及び低所側に切欠部４０を設けてある。
図２の（ハ）において、１１は端子受け部、４は端子受け部１１に連設された凸条部であり、途中に切欠部４０を設けてある。
図２に（ニ）おいて、１１は端子受け部、４は凸条部であり、端子受け部１１との間及び途中に切欠部４０を設けてある。
図２の（ホ）において、１１は端子受け部、４は凸条部であり、端子受け部１１との間及び途中並びに低所側に切欠部４０を設けてある。
図２の（ヘ）において、１１は端子受け部、４は端子受け部１１に連設された凸条部であり、複数箇の孔４０，…を所定の間隔を隔てて設けてあり、孔４０の形状は限定されず、例えば丸の外、三角形、四角形とすることもできる。孔は、図２の（ト）に示すように、凸条部４の付け根に及ぶ大きさとすることが望ましい。
また、図２の（チ）に示すように、凸条部４の上端に沿い、抵抗線巻付け用溝４１よりも深い切欠溝４０を設けることも可能である。
【００１７】
図１の（ニ）において、端子近傍の抵抗線部分を巻付ける上面溝付き凸条部４の内筒軸方向に対する角度αと、他の抵抗線部分を巻付ける内筒表面の溝１２の内筒軸方向に対する角度βとを請求項１に基づき、α＜βとして端子２近傍の抵抗線部分３１の内筒軸方向に対
する角度を他の抵抗線部分３２の内筒軸方向に対する角度よりも小さくし、前記したように、図８の（イ）において示した間隔ｇを相対的に広くすることによっても、電気融着継手による融着接合時の端子近傍抵抗線の交絡防止の万全を期すことができる。
【００１８】
上記実施例での凸条部においては、端子に至るほど背を漸次に高くしてあるが、背を実質的に全長にわたり等しくし、溝深さ
を端子側に至るほど浅くし、奥側端での溝底面と内筒表面の溝底面とを一致させるようにしてもよい。
【００１９】
図３の（イ）は請求項１に係る電気融着継手の一実施例の内筒を示す平面図、図３の（ロ）は図３の（イ）におけるロ−ロ断面図である。
図３において、１はポリエチレン内筒等の熱可塑性樹脂内筒、１１は内筒の各端部外面に突設した端子受け部である。２は前記と同様にピン部２１及びヘッド部２２を有する端子であり、前記した通り、ピン部を端子受け部１１に緊嵌状態で装着してある。４１は端子近傍の抵抗線部分を内筒軸方向に対する角度αで巻付けるために内筒端部の外面に設けた溝、１２は他の抵抗線部分を内筒軸方向に対する角度βで巻付けるために内筒外面に設けた溝であり、内筒１の外径をｄ、端子２近傍の抵抗線部分を巻付ける溝４１のピッチをＰ、他の抵抗線部分を巻付ける溝１２のピッチをｐとすれば、
[数１]
tandα＝πｄ／Ｐ
[数２]
tandβ＝πｄ／ｐ
が成立し、傾斜角αが傾斜角βより小であることによるピッチＰの増大に相応してピッチｐを狭くすることにより、継手長さを一定に保持してある。
１３は溝４１と溝１２との間に設けた経間であり、内筒１の溝無し外面のままにしてある。１４は抵抗線を前記傾斜角βから傾斜角αに折り曲げるためのボスであり、溝１２の端に、前記折り曲げに対する曲げ内側に突設してある。このボス１４は、前記の鉄ニクロム線のような高剛性の抵抗線でも折り曲げ得る強度を有するものであればよく、円柱の外、多角柱も使用可能である。
【００２０】
抵抗線は図示してないが、前記他の抵抗線部分が溝１２に巻付けられ、ボス１４で折り曲げられ、更に、端子近傍の抵抗線部分が溝端のガイドボス１５１、１５２によりガイドされて溝４１内に納められ、端子２のヘッド部２２の側面に溶接される。
前記折り曲げ用ボス１４による抵抗線の折り曲げ時、経間１３の抵抗線部分にも曲げモーメントが作用し、図３の（イ）において、折り曲げ用ボスに当接された抵抗線箇所ａに作用する曲げモーメントをｍ0、当接圧力をｆとすると、経間のある位置ｘにおける曲げ
モーメントｍxは
[数３]
ｍx＝ｍ0−ｆ・ｘ
で与えられ、経間１３の抵抗線部分がこの曲げモーメントｍxにより湾曲される。
而るに、この湾曲された経間抵抗線部分が溝無しの内筒表面上にあり、溝に巻付ける必要がないから、仮りに、経間に溝が存在して湾曲経間抵抗線部分をその溝に納めなければならない場合に較べ、内筒全体への抵抗線の巻付けを容易に行うことができる。
【００２１】
上記において、折り曲げ用ボス１４による抵抗線の折り曲げ角は前記した傾斜角αに等しくすることが理想的であるが、実際は、αよりもやや小さいか、若しくはやや大きくなる。αよりもやや小さいときは、ガイドボス１５１の内面で端子近傍の抵抗線部分が溝４１内にガイドされ、αよりもやや大きいときは、他方のガイドボス１５２の内面で端子近傍の抵抗線部分が溝４１内にガイドされる。
したがって、折り曲げ用ボス１４による抵抗線の折り曲げを、内筒軸方向に対する角度を前記の角αより小さくするように行ない、一方のガイドボス１５１のみを設けること、または、内筒軸方向に対する角度を前記の角αより大きくするように行ない、他方のガイドボス１５２のみを設けるようにしてもよい。
なお、ガイドボスには、溝底へのガイド面を設けることが好ましい。このガイドボスには、円柱や多角柱を使用できる。
【００２２】
上記請求項１の実施例では、端子近傍の内筒部分の表面に設けた溝に端子近傍の抵抗線部分を巻付けているが、請求項２に基づき、端子近傍の内筒部分に凸条部を設け、この凸条部の溝に端子近傍の抵抗線部分を巻付けて端子近傍の抵抗線の巻径を他の抵抗線部分よりも大きくすることもできる。この場合、凸条部においては、前記したように、端子に至るほど背を漸次に高くし、上面に一様深さの抵抗線巻付け用溝を設けてもよく、また、背を実質的に全長にわたり等しくし、溝深さを端子に至るほど浅くし、奥側端での溝底面と内筒表面の溝底面とを一致させるようにしてもよい。後者の場合、図４の（イ）及び（ロ）〔図４の（イ）の正面図〕に示すように、前記したガイドボスを省略し、端子近傍の抵抗線部分を巻付ける凸条部４の奥側端ｅでの深溝の内面にテーパガイド面１５０を設けることができる。
【００２３】
更に、請求項３に基づき、凸条部にエアー抜き切欠部または孔を設け、前記と同様に、熱可塑性樹脂外層の射出成形工程での外型と内筒との間のキャビティへの溶融樹脂のチャージ時、凸条部の陰に溜ろうとするエアーを凸条部のエアー抜き切欠部または孔を経て継手端部の金型合わせ目の隙間から排出することもできる。
【００２４】
上記請求項１〜３の何れの実施例でも、製作においては、内筒表面の両端側の各端子受け部に端子のピン部を装着し、一方の端子のヘッド部側面に抵抗線の一端をスポット溶接し、この端子近傍の抵抗線部分の巻付け、他の抵抗線部分の巻付けをそれぞれ行なったのち、他方の端子近傍の抵抗線部分の巻付けを行ない、ついで、抵抗線の他端側と他方の端子のヘッド部側面とをスポット溶接し、而るのち、外層を射出成形することが必要であり、スポット溶接の際、端子受け部の端子ヘッド部に対する接触部位の熱軟化が避けられないが、請求項４によれば、この熱軟化にもかかわらず、端子を充分安定に保持できる。
【００２５】
図５の（イ）は請求項４の実施例の端子受け部を示す平面図、図５の（ロ）は同じく側面図、図５の（ハ）は同じく正面図である。
更に、図６の（イ）は同端子受け部に装着される端子を示す側面図、図６の（ロ）は同端子の底面図であり、電源端子に着脱自在に接続されるヘッド部２２の下面にピン部２１を備えている。
図５において、１１１は熱可塑性樹脂内筒に一体に設けた端子受け躯体、１１２は躯体上端の端子ヘッド受け面であり、中央に端子ピン部挿通穴１１３を設け、受け面１１２の外郭を端子ヘッド２２の裏面外郭に一致させてある。１１４及び１１５は端子ヘッド受け面１１２の前後に設けた擁壁及び後壁であり、内側面を端子ヘッド２２の外面（円柱面）に一致した曲面としてある。１１６，１１６は端子ヘッド部を両サイドからスポット溶接電極（ピン電極）で挾むことを可能とする開口であり、この開口のための躯体の欠切は、端子ヘッド受け面１１２よりも下方位置に及んでいる。
【００２６】
図５の（ニ）は端子受け部１１に端子２を装着し、端子２のヘッド部２２の側面に抵抗線３をスポット溶接した状態を示し、抵抗線３の引っ張りに対して端子ヘッド部２２を擁壁１１４で支えることができるから、前記端子受け部１１の端子ヘッド部２２に対する接触部位の熱軟化にもかかわらず、端子２を充分安定に保持でき、従って、抵抗線の巻付け状態を安定に維持できる。
【００２７】
図５の（ニ）において、擁壁１１４には抵抗線３の引っ張りに対し剪断反力が発生し、後壁１１５は抵抗線３の引っ張りで端子２が傾くのを阻止するモーメント反力を擁壁１１４とで発生するが、支持の主体は、前者の剪断反力であり、後壁１１５は省略することもできる。
【００２８】
【実施例】
〔実施例１〕
ポリエチレン製片受けソケット２００であり、端子近傍の抵抗線部分の長さを１／２周、ピッチを１本／１２ｍｍ、最大巻径を２２０ｍｍとし、他の抵抗線部分の巻径を２１７ｍｍ、巻付けピッチを１本／６ｍｍとするように、端子近傍の抵抗線部分を巻付けるための上面溝（溝深さ２ｍｍ）付きで背を漸次に高くした凸条部、他の抵抗線部分を巻付けるための内筒表面の溝（溝深さ２ｍｍ）、及び端子受け部を内筒に設け、端子受け部と凸条部とは連設し、凸条部の奥端側を削除して経間部を設け、直径５ｍｍの円柱体抵抗線折り曲げ用ボスを突設し、凸条部の溝入口の両側に直径５ｍｍのテーパガイド面付きガイドボスを突設し、抵抗線に直径２ｍｍの鉄クロム線を用い、端子と抵抗線との接合をスポット溶接で行ない、ポリエチレン外層を射出成形した。
【００２９】
〔比較例〕
前記に対し経間部を設けないものを比較例とした。
【００３０】
実施例品１に対し、抵抗線（前記した通り、直径２ｍｍの鉄クロム線を使用）のワィンダーによるコイリングを１５０回行なったところ、１００％の成功率であった。前記比較例品についても、ワィンダーによるコイリングを１０回試みたが、巻くことができなかっ
た。
【００３１】
〔実施例２〕
端子の寸法は、ヘッド部外径が８ｍｍ、ピン部外径が３ｍｍ、ピン部長さが６ｍｍである。
上記端子受け部を図５に示した構成とし、躯体部外径を１２ｍｍ、ピン挿入穴の内径を２．５ｍｍφ、穴深さを６ｍｍ、擁壁及び後壁の各壁厚を２ｍｍ、高さを１ｍｍ、開口下端の位置を受け面の下方３ｍｍとした。
一方の端子のヘッド部側面に抵抗線（前記した通り、直径２ｍｍの鉄クロム線を使用）の一端側をスポット溶接し、スポット溶接３秒後に張力３ｋｇｆで抵抗線をコイリングし、抵抗線の他端側と一方の端子のヘッド部側面とをスポット溶接した。
スポット溶接の電流設定値は、６ｋＡとした。
【００３２】
この実施例品について、試料数を１０個として溶接後の端子の支持状態を調査したところ、異常は観られなかった。
これに対し、擁壁を設けていない比較例品では、試料数１０個中４個に端子抜けが発生した。
【００３３】
【発明の効果】
請求項１に係る電気融着継手においては、端子近傍の抵抗線部分の内筒軸方向に対する角度を他の抵抗線部分の内筒軸方向に対する角度よりも小さくするための抵抗線折り曲げ用ボスを設けて抵抗線を折り曲げ、この折り曲げ箇所に燐在して生じる湾曲抵抗線部分を溝に納める必要がないようにしてあるから、端子近傍の抵抗線部分の内筒軸方向に対する角度を小さくするように抵抗線を折り曲げるにもかかわらず、内筒全体における抵抗線の溝への巻付けを容易に行なうことができ、良好な製造能率の電気融着継手を提供できる。
【００３４】
特に、請求項２の電気融着継手では、端子近傍の内筒部分の溝を凸条部の上面に設けているから、端子近傍の抵抗線部分の巻径を他の抵抗線部分よりも大きくでき、端子の抵抗線部分をピッチのみならず巻径をも大きくでき、電気融着継手による融着接合時の端子近傍抵抗線の交絡防止の万全を期すことができる。
【００３５】
更に、請求項３の電気融着継手では、凸条部にエアー抜き切欠部または孔を設けてあるから、外層射出成形時に凸条部の陰にエアーが捕捉されるのを防止でき、気泡の発生をよく排除でき、充分な継手強度を保証できる。
【００３６】
請求項４の電気融着継手においては、端子のピン部を装着するための内筒の端子受け部に、抵抗線の引っ張りに対して端子のヘッドを支えるための擁壁を設けてあるから、端子受け部の端子ヘッド部に対する接触部位の溶接熱による熱軟化にもかかわらず、端子を充分安定に保持でき、良好な歩留で製造できる電気融着継手を提供できる。
【図面の簡単な説明】
【図１】本発明の一実施例を示す図面である。
【図２】本発明の他の異なる実施例の要部を示す図面である。
【図３】本発明の上記とは別の実施例を示す図面である。
【図４】本発明の上記とは別の実施例の要部を示す図面である。
【図５】本発明の上記とは別の一実施例を示す図面である。
【図６】本発明において使用する端子の一例を示す図面である。
【図７】従来の電気融着継手を示す図面である。
【図８】上記とは別の従来の異なる電気融着継手を示す図面である。
【図９】上記とは別の従来の電気融着継手を示す図面である。
【符号の説明】
１内筒
１１端子受け部
１２他の抵抗線部分を巻付ける溝
１３経間部
１４抵抗線折り曲げ用ボス
２端子
２１端子のピン部
２２端子のヘッド部
３抵抗線
３１端子近傍の抵抗線部分
３２他の抵抗線部分
４凸条部
４１端子近傍の抵抗線部分を巻付ける溝
４０エアー抜き用切欠部または孔
５外層[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to an electric fusion joint used for connecting a thermoplastic resin pipe, particularly a polyethylene pipe suitable as a piping material for gas and water.
[0002]
[Prior art]
Polyethylene is chemically very stable and does not require a plasticizer. Therefore, polyethylene is useful as a plumbing material for water supply, but is substantially non-polar, so that bonding with an adhesive is difficult.
Therefore, as shown in FIG. 7, a thermoplastic resin joint in which a spirally wound resistance wire 3 ′ is embedded on the inner layer 1 ′ side and the resistance wire terminal 2 ′ is exposed on the outer layer 5 ′, a so-called electrofusion joint. Is often used.
In order to join the thermoplastic resin pipe by this electric fusion joint, the end of the pipe to be joined is inserted into the joint, and the resistance wire 3 'is energized to generate heat so that the interface between the inner layer 1' and the end of the pipe to be joined is formed. It is heat-sealed.
In this case, the outer layer 5 ′ is substantially not thermally melted and the position of the terminal 2 ′ is fixed, and the resistance wire portion in the vicinity of the terminal is also substantially fixed, but the inner layer resin is thermally melted and thermally expanded. It flows from the center between both terminals toward each terminal, and the closer to the terminal, the larger the flow rate is due to the cumulative effect. Therefore, it moves to the resistance wire portion near the fixed terminal as the resin flows. In some cases, the resistance wire portions come into contact with each other and a short circuit occurs, so that the thermal fusion of the interface cannot be satisfactorily performed.
[0003]
Therefore, in order to prevent such inconvenience, as shown in FIG. 8A, the angle of the resistance wire portion 31 ′ near the terminal 2 ′ with respect to the inner cylinder axis direction is made smaller than that of the other resistance wire portions 32 ′. Accordingly, the angle of the other resistance wire portion 32 ′ with respect to the inner cylinder axis direction is increased, that is, the winding pitch is decreased, and the interval g in FIG. -8994, JP-A-2001-41385) and (b) of FIG. 8, the winding diameter of the resistance wire portion 31 'in the vicinity of the terminal 2' is larger than that of the other resistance wire portions 32 '. (Japanese Patent Laid-Open No. 2001-41385 described above) and the like have been proposed.
[0004]
[Problems to be solved by the invention]
By the way, as shown in FIG. 9, as the electric fusion joint, the pin portion 21 ′ of the terminal 2 ′ is mounted on the terminal receiving portion 11 ′ of the thermoplastic resin inner tube 1 ″, and the spiral groove 12 ′ on the outer surface of the inner tube The resistance wire 3 'is wound, each end of the resistance wire 3' and the side surface of the head portion 22 'of each terminal 2' are joined by welding or the like, and the thermoplastic resin outer layer 5 'is injected onto the inner cylinder 1 " A so-called inner / outer type is known in which the head portion 22 ′ of the terminal 2 ′ is exposed from the surface of the outer layer 5 ′.
In this configuration, the resistance wire is wound around the groove on the surface of the inner cylinder, so that the resistance wire is ordered and stable, and when the resistance wire is wound or the die is assembled during the outer layer injection molding, etc. It is possible to surely eliminate the entanglement of the resistance wire at.
[0005]
In the inner / outer type described above, in order to make the winding diameter of the resistance wire portion in the vicinity of the terminal larger than that of the other resistance wire portions, a ridge having a predetermined length (usually about 1/2 to 1/3 turn). A groove is provided on the upper surface of the portion, and the resistance wire portion in the vicinity of the terminal is wound around the groove in order to guarantee an orderly and stable winding of the resistance wire.
However, if such a ridge is provided on the outer surface of the inner cylinder, air is easily trapped during the injection molding of the outer layer, bubbles are generated, and the thickness of the outer layer portion on the bubbles is reduced, resulting in a mechanical weak point. There is a drowning.
[0006]
Further, in the configuration in which the angle of the groove for winding the resistance wire portion near the terminal with respect to the inner cylinder axis direction is smaller than the same angle of the groove for winding the other resistance wire portion, the inner cylinder is non-flowing. It is planned that the resistance wire will be bent and plastic processed so that the bent state of the resistance wire can be maintained as it is when it becomes liquid and the support by the inner cylinder is lost. Thus, it is difficult to wind it around the groove of the inner cylinder by machine winding, and it is particularly difficult when the resistance wire is rigid like iron-chromium wire.
[0007]
Furthermore, for the work efficiency, it is required to use spot welding for joining the head portion of the terminal having a pin portion attached to the terminal receiving portion provided in the inner cylinder and the resistance wire. Is heated by welding heat, and the terminal receiving portion in contact with the head portion of the terminal is thermally softened, and the terminal may be tilted or pulled out because the tension of the resistance wire cannot be supported.
[ 0008]
Another object of the present invention is that a resistance wire is wound around a groove on a thermoplastic resin inner cylinder, a thermoplastic resin outer layer is injection-molded on the inner cylinder, and a resistance wire terminal is embedded in the outer layer. Despite the fact that the angle of the groove for winding the resistance wire portion of the terminal with respect to the inner cylinder axis direction is smaller than that of the groove for winding the other resistance wire portion, the resistance wire is smoothed. An object of the present invention is to provide an electric fusion joint that can be easily manufactured by simple winding.
[0009]
A further object of the present invention is to prevent air trapping in spite of providing the inner cylinder with a convex groove with an upper surface groove for increasing the winding diameter of the resistance wire portion in the vicinity of the terminal in addition to the aforementioned object. An object of the present invention is to provide an electric fusion joint having sufficient joint strength.
[0010]
A further object of the present invention is to provide an electric fusion joint capable of smoothly performing spot welding between a head portion of a terminal having a pin portion mounted on a terminal receiving portion of an inner cylinder and a resistance wire in addition to the above-described purpose. It is in.
[0011]
[Means for Solving the Problems]
In the electric fusion joint according to claim 1 of the present application, a resistance wire is wound around the inner tube made of thermoplastic resin in a groove, an outer layer of the thermoplastic resin is injection-molded on the inner tube, and a resistance wire terminal is provided on the outer layer. In a buried joint, a resistance wire for making the angle of the groove for winding the resistance wire portion near the terminal smaller than the angle of the groove for winding the other resistance wire portion with respect to the inner cylinder axis direction. bent boss is provided, the resistance wire is wound in a groove of the inner tube surface at the other resistance wire portion, further, the inner cylinder portion of the terminal near the via through between portions without grooves after having folded in the boss characterized in that the is wound under a small angle of the grooves of the second aspect, the grooves of the inner cylinder portion of the terminal near provided on an upper surface of the convex portion, further, claim in 3, convex portions are provided with air vent notch or hole.
[0013]
In the electric fusion joint according to claim 4 of the present application, in any one of the electric fusion joints, a terminal receiving portion for mounting the pin portion of the terminal is provided on the inner cylinder and welded to the side surface of the head of the terminal. A retaining wall for supporting the head portion of the terminal against the pulling of the resistance wire is provided in the terminal receiving portion.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Longitudinal sectional view of (b) is 1 showing a main portion of the electric fusion coupling according to the present invention, (b) is a plan view showing the same principal portion of Figure 1, in Figure 1 the (c) is same as above main portion FIG. 1 (D) and FIG. 1 (E) are a sectional view and a sectional view of the knee in FIG.
In FIG. 1, 1 is a thermoplastic resin inner cylinder, for example, a polyethylene inner cylinder, and 11 is a terminal receiving portion projecting from each end of the outer surface of the inner cylinder. Reference numeral 2 denotes a terminal, which has a pin portion 21 and a head portion 22, and the pin portion 21 is attached to the terminal receiving portion 11 in a tightly fitted state. Reference numeral 3 denotes a resistance wire, for example, an iron chrome wire, and is composed of a resistance wire portion 31 near the terminal 2 and another resistance wire portion 32. Reference numeral 12 denotes a groove provided on the outer surface of the inner cylinder 1 for winding the other resistance wire portion 32. Reference numeral 4 denotes a ridge provided to make the winding diameter of the resistance wire portion 31 in the vicinity of the terminal 2 larger than that of the other resistance wire portion 32, and the height is gradually increased toward the terminal 2 side, and a groove is formed on the upper surface. 41, the groove 41 at the back end e of the ridge 4 and the groove 12 at the outer surface of the inner cylinder are at the same height level with respect to the outer surface of the inner cylinder. A notch is formed between the ridge portion 4 and the terminal receiving portion 11, and the notch portion 40 is used as an air vent passage during outer layer injection molding described later.
In FIG. 1, the resistance wire portion 31 near the terminal 2 is wound around the groove 41 of the ridge portion 4, and the other resistance wire portion 32 is wound around the groove 12 on the outer surface of the inner cylinder. And the side surface of the head portion 22 of each terminal 2 are welded.
Reference numeral 5 denotes a thermoplastic resin outer layer injection-molded on the inner cylinder, and the head portion 22 of the terminal 2 is exposed.
[0015]
In order to manufacture the electric fusion joint shown in FIG. 1, the inner cylinder 1 is once formed on the core mold by injection molding, the pin portions 21 of the terminals 2 are attached to the terminal receiving portions 11, and the inner cylinder surface is formed. The other resistance wire portion 32 is wound along the groove 12 and the resistance wire portion 31 in the vicinity of the terminal 2 is wound along the groove 41 on the upper surface of the protruding portion 4, and each end portion of the resistance wire 3 and the head of each terminal 2 are wound. Welding the side surface of the portion 22, then setting the outer mold, charging molten resin into the cavity between the outer mold and the inner cylinder, waiting for the charge resin to cool and solidify, and molding the outer layer 5; Can be released.
When charging the molten resin, even if air tends to accumulate behind the ridges 4, the notches 40 of the ridges 4 serve as air vent passages, and the air passes through the gap between the mold joints at the end of the joint. Easily discharged. Since the joint is thick, the cavity is considerably thick and the charge pressure is almost zero, so that leakage of resin from the gap between the mold joints can be well prevented. Therefore, an electric fusion joint having sufficient mechanical strength can be manufactured with good workability.
[0016]
In the above embodiment, the notch 40 is provided on the high side of the ridge 4, but the height of the low side is substantially 0, and the ridge of the ridge that is continuously provided to the terminal receiving part is located on the high side. As shown in FIGS. 2 (A) to 2 (H) with respect to the basic mold, an appropriate one can be used as long as it is provided with a notch or hole effective for air venting.
In FIG. 2A, reference numeral 11 denotes a terminal receiving portion, 4 denotes a protruding strip portion connected to the terminal receiving portion 11, and a notch portion 40 is provided on the lower side.
In FIG. 2B, 11 is a terminal receiving portion, 4 is a protruding portion, and a notch portion 40 is provided between the terminal receiving portion 11 and on the low side.
In FIG. 2C, reference numeral 11 denotes a terminal receiving portion, 4 denotes a protruding strip portion connected to the terminal receiving portion 11, and a notch portion 40 is provided in the middle.
In FIG. 2D, 11 is a terminal receiving part, 4 is a convex part, and the notch part 40 is provided between the terminal receiving part 11 and the middle.
In (e) of FIG. 2, 11 is a terminal receiving part, 4 is a protruding item | line part, The notch part 40 is provided between the terminal receiving part 11, the middle, and the low side.
In FIG. 2 (f), 11 is a terminal receiving part, 4 is a protruding line part connected to the terminal receiving part 11, and a plurality of holes 40,... Are provided at predetermined intervals. The shape of 40 is not limited, and can be, for example, a circle, a triangle, or a rectangle. As shown in FIG. 2G, it is desirable that the hole has a size that extends to the base of the ridge 4.
Further, as shown in FIG. 2 (h), it is also possible to provide a notch groove 40 that is deeper than the resistance wire winding groove 41 along the upper end of the ridge 4.
[0017]
In FIG. 1 (D), the angle α of the convex groove portion 4 with the upper surface groove around which the resistance wire portion in the vicinity of the terminal is wound with respect to the inner cylinder axis direction, and the inside of the groove 12 on the inner cylinder surface around which the other resistance wire portion is wound. The angle β with respect to the cylinder axis direction is based on claim 1, and α <β and the angle with respect to the inner cylinder axis direction of the resistance wire portion 31 near the terminal 2 is smaller than the angle with respect to the inner cylinder axis direction of the other resistance wire portions 32. However, as described above, it is possible to prevent entanglement of the resistance wire near the terminal at the time of fusion bonding by the electric fusion joint also by relatively widening the gap g shown in FIG. Can do.
[0018]
In the ridges in the above embodiment, the back is gradually increased toward the terminal, but the back is substantially equal over the entire length, and the groove depth is shallower toward the terminal side, and the back end The bottom surface of the groove and the bottom surface of the inner cylinder surface may coincide with each other.
[0019]
3A is a plan view showing an inner cylinder of an embodiment of an electrofusion joint according to claim 1 , and FIG. 3B is a cross-sectional view of FIG.
In FIG. 3, 1 is a thermoplastic resin inner cylinder such as a polyethylene inner cylinder, and 11 is a terminal receiving portion projecting from the outer surface of each end of the inner cylinder. Reference numeral 2 denotes a terminal having a pin portion 21 and a head portion 22 as described above. As described above, the pin portion is attached to the terminal receiving portion 11 in a tightly fitted state. 41 is a groove provided on the outer surface of the inner cylinder end portion for winding the resistance wire portion in the vicinity of the terminal at an angle α with respect to the inner cylinder axis direction, and 12 is a coil for winding the other resistance wire portion at an angle β with respect to the inner cylinder axis direction. Therefore, the groove is provided on the outer surface of the inner cylinder, the outer diameter of the inner cylinder 1 is d, the pitch of the groove 41 for winding the resistance wire portion near the terminal 2 is P, and the pitch of the groove 12 for winding the other resistance wire portion. If p is p,
[Equation 1]
tandα = πd / P
[Equation 2]
tandβ = πd / p
The joint length is kept constant by narrowing the pitch p corresponding to the increase in the pitch P due to the fact that the inclination angle α is smaller than the inclination angle β.
Reference numeral 13 denotes a passage provided between the groove 41 and the groove 12, and the outer surface without the groove of the inner cylinder 1 is left as it is. Reference numeral 14 denotes a boss for bending the resistance wire from the inclination angle β to the inclination angle α, and is provided at the end of the groove 12 so as to protrude inside the bending with respect to the bending. The boss 14 only needs to have a strength that can be bent even by a highly rigid resistance wire such as the above-described iron nichrome wire, and a polygonal column or a cylindrical column can also be used.
[0020]
Although the resistance wire is not shown, the other resistance wire portion is wound around the groove 12, bent by the boss 14, and further, the resistance wire portion in the vicinity of the terminal is guided by the guide bosses 151 and 152 at the groove end to become the groove. 41 and is welded to the side surface of the head portion 22 of the terminal 2.
When the resistance wire is bent by the bending boss 14, a bending moment also acts on the resistance wire portion of the warp 13 and acts on the resistance wire portion a in contact with the bending boss in FIG. If the bending moment is m0 and the contact pressure is f, the bending moment mx at a certain position x is
[Equation 3]
mx = m0−f · x
And the resistance line portion of the meridian 13 is bent by this bending moment mx.
Therefore, since this curved meridian resistance line part is on the inner cylinder surface without the groove and it is not necessary to wrap around the groove, there is a groove between the meridians and there is a curved meridian resistance line part. Can be easily wound around the entire inner cylinder as compared with the case where the wire must be placed in the groove.
[0021]
In the above description, it is ideal that the bending angle of the resistance wire by the bending boss 14 is equal to the above-described inclination angle α, but actually, it is slightly smaller or larger than α. When it is slightly smaller than α, the resistance wire portion near the terminal is guided in the groove 41 on the inner surface of the guide boss 151, and when it is slightly larger than α, the resistance wire portion near the terminal on the inner surface of the other guide boss 152. Is guided in the groove 41.
Therefore, the resistance wire is bent by the bending boss 14 so that the angle with respect to the inner cylinder axis direction is smaller than the angle α, and only one guide boss 151 is provided, or the angle with respect to the inner cylinder axis direction is set. Alternatively, the angle α may be larger than the angle α, and only the other guide boss 152 may be provided.
The guide boss is preferably provided with a guide surface to the groove bottom. The guide boss can be a cylinder or a polygonal column.
[0022]
In the embodiment of the first aspect, although wound resistance wire portion of the terminal near the groove formed in the surface of the inner cylinder portion of the terminal near, based on claim 2, projections in the inner cylinder portion of the terminal near It is also possible to provide a portion and wind the resistance wire portion near the terminal around the groove of the protruding portion so that the winding diameter of the resistance wire near the terminal is larger than the other resistance wire portions. In this case, as described above, in the ridge portion, the height may be gradually increased toward the terminal, and a resistance wire winding groove having a uniform depth may be provided on the upper surface. It is also possible to make the groove lengths equal to each other and make the groove depth as shallow as it reaches the terminal so that the groove bottom surface at the back end matches the groove bottom surface of the inner cylinder surface. In the latter case, as shown in FIGS. 4 (a) and (b) [front view of FIG. 4 (a)], the above-described guide boss is omitted, and a ridge portion for winding a resistance wire portion in the vicinity of the terminal. The taper guide surface 150 can be provided on the inner surface of the deep groove at the back end e of 4.
[0023]
Further, according to the third aspect of the present invention, an air vent notch or a hole is provided in the ridge, and in the same manner as described above, the molten resin into the cavity between the outer mold and the inner cylinder in the injection molding process of the thermoplastic resin outer layer. At the time of charging, air to be stored behind the ridges can be discharged from the gap between the mold joints at the end of the joint through the air vent notch or hole of the ridge.
[0024]
In any of the above embodiments of the first to third aspects, in manufacturing, a terminal pin portion is attached to each terminal receiving portion on both ends of the inner cylinder surface, and one end of a resistance wire is attached to the side surface of the head portion of one terminal. After spot welding, winding the resistance wire portion near this terminal, winding the other resistance wire portion, then winding the resistance wire portion near the other terminal, and then the other end of the resistance wire It is necessary to spot weld the side and the side of the head of the other terminal, and after that, it is necessary to injection-mold the outer layer. During spot welding, avoid thermal softening of the contact part of the terminal receiving part with respect to the terminal head. However, according to the fourth aspect , the terminal can be held sufficiently stably despite the thermal softening.
[0025]
5 (a) is a plan view showing the terminal receiving portion of the embodiment of claim 4 , FIG. 5 (b) is a side view, and FIG. 5 (c) is a front view.
6A is a side view showing a terminal mounted on the terminal receiving portion, and FIG. 6B is a bottom view of the terminal, and the head portion 22 is detachably connected to the power terminal. A pin portion 21 is provided on the lower surface of the.
In FIG. 5, reference numeral 111 denotes a terminal receiving housing integrally provided on the thermoplastic resin inner cylinder, 112 denotes a terminal head receiving surface at the upper end of the housing, a terminal pin portion insertion hole 113 is provided in the center, and the outer surface of the receiving surface 112 is connected to the terminal. The rear surface of the head 22 is matched with the outline. Reference numerals 114 and 115 denote retaining walls and a rear wall provided in front of and behind the terminal head receiving surface 112, and the inner side surfaces are curved surfaces that coincide with the outer surface (cylindrical surface) of the terminal head 22. 116 and 116 are openings that allow the terminal head portion to be pinched by spot welding electrodes (pin electrodes) from both sides, and the notch of the casing for this opening is located below the terminal head receiving surface 112. It reaches to.
[0026]
FIG. 5D shows a state in which the terminal 2 is mounted on the terminal receiving portion 11 and the resistance wire 3 is spot welded to the side surface of the head portion 22 of the terminal 2, and the terminal head portion 22 against the pulling of the resistance wire 3. Can be supported by the retaining wall 114, the terminal 2 can be held sufficiently stably despite the thermal softening of the contact portion with respect to the terminal head portion 22 of the terminal receiving portion 11, and therefore the resistance wire is wound. It can be maintained stably.
[0027]
In FIG. 5D, a shear reaction force is generated on the retaining wall 114 against the pulling of the resistance wire 3, and the rear wall 115 holds a moment reaction force that prevents the terminal 2 from being tilted by the pulling of the resistance wire 3. The main body of support is the former shear reaction force, and the rear wall 115 can be omitted.
[0028]
【Example】
[Example 1]
This is a single piece socket 200 made of polyethylene, the length of the resistance wire portion in the vicinity of the terminal is 1/2 turn, the pitch is 1/12 mm, the maximum winding diameter is 220 mm, and the winding diameter of the other resistance wire portion is 217 mm. Wrapping the ridges and other resistance wire parts with a top groove (groove depth 2mm) for winding the resistance wire part near the terminal and gradually increasing the back so that the attachment pitch is 1 / 6mm A groove on the surface of the inner cylinder (groove depth 2 mm) to be attached and a terminal receiving part are provided in the inner cylinder, the terminal receiving part and the protruding line part are connected to each other, and the back end side of the protruding line part is deleted. A boss for bending a cylindrical resistance wire with a diameter of 5 mm is provided, a guide boss with a tapered guide surface with a diameter of 5 mm is provided on both sides of the groove entrance of the ridge, and an iron with a diameter of 2 mm is provided on the resistance wire. Using chromium wire, the terminal and resistance wire are joined by spot welding, and the outside of the polyethylene It was injection-molded.
[ 0029]
[Comparative Example]
In contrast to the above , a comparative example was provided without a meridian part .
[0030]
Against the Example product 1, (as described above, using the iron-chromium wire having a diameter of 2 mm) resistance wire was subjected 150 times to coiling by Wainda of was a 100% success rate. For the comparative product, coiling with a winder was attempted 10 times, but could not be wound.
[0031]
[Example 2]
As for the dimensions of the terminals, the head part outer diameter is 8 mm, the pin part outer diameter is 3 mm, and the pin part length is 6 mm.
The terminal receiving portion has the configuration shown in FIG. 5, the outer diameter of the housing portion is 12 mm, the inner diameter of the pin insertion hole is 2.5 mmφ, the hole depth is 6 mm, the wall thickness of the retaining wall and the rear wall is 2 mm, and the height. Was 1 mm, and the position of the lower end of the opening was 3 mm below the receiving surface.
Spot welding one end of a resistance wire (using a 2mm diameter iron chrome wire as described above) on the side of the head of one terminal, coiling the resistance wire with a tension of 3kgf 3 seconds after spot welding, The end side and the head part side surface of one terminal were spot-welded.
The current setting value for spot welding was 6 kA.
[ 0032]
About this example product, when the number of samples was 10, and the support state of the terminal after welding was investigated, no abnormality was observed.
On the other hand, in the comparative example product not provided with the retaining wall, terminal loss occurred in 4 out of 10 samples.
[0033]
【The invention's effect】
In the electrical fusion joint according to claim 1 , a resistance wire bending boss for making the angle of the resistance wire portion near the terminal with respect to the inner cylinder axis direction smaller than the angle of the other resistance wire portion with respect to the inner cylinder axis direction is provided. It is necessary to bend the resistance wire, and it is not necessary to place the curved resistance wire portion that is formed in the bent portion into the groove, so that the angle of the resistance wire portion near the terminal with respect to the inner cylinder axis direction is reduced. In spite of the bending of the resistance wire, the resistance wire in the entire inner cylinder can be easily wound around the groove, and an electrofusion joint with good manufacturing efficiency can be provided.
[0034]
In particular, in the electric fusion joint according to claim 2 , since the groove of the inner tube portion near the terminal is provided on the upper surface of the protruding portion, the winding diameter of the resistance wire portion near the terminal is larger than the other resistance wire portions. In addition, not only the pitch but also the winding diameter of the resistance wire portion of the terminal can be increased, and it is possible to make sure that the resistance wire near the terminal is prevented from being entangled at the time of fusion bonding by the electric fusion joint.
[0035 ]
Furthermore, in the electric fusion joint according to claim 3 , since the air vent notch or hole is provided in the ridge, it is possible to prevent air from being trapped behind the ridge during the outer layer injection molding. Generation can be well eliminated and sufficient joint strength can be guaranteed.
[0036]
In the electric fusion joint according to claim 4 , since the retaining wall for supporting the head of the terminal against the pulling of the resistance wire is provided in the terminal receiving portion of the inner cylinder for mounting the pin portion of the terminal, In spite of thermal softening due to welding heat at the contact portion of the terminal receiving portion with respect to the terminal head portion, it is possible to provide an electrofusion joint that can hold the terminal sufficiently stably and can be manufactured with a good yield.
[Brief description of the drawings]
FIG. 1 is a drawing showing an embodiment of the present invention .
FIG. 2 is a view showing a main part of another embodiment of the present invention .
FIG. 3 is a drawing showing another embodiment of the present invention .
FIG. 4 is a view showing a main part of another embodiment of the present invention different from the above .
FIG. 5 is a drawing showing another embodiment of the present invention .
FIG. 6 is a drawing showing an example of a terminal used in the present invention.
FIG. 7 is a view showing a conventional electric fusion joint.
FIG. 8 is a drawing showing another conventional electric fusion joint different from the above.
FIG. 9 is a view showing a conventional electric fusion joint different from the above.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inner cylinder 11 Terminal receiving part 12 Groove which winds another resistance wire part 13 Passage part 14 Resistance wire bending boss 2 Terminal 21 Terminal pin part 22 Terminal head part 3 Resistance wire 31 Resistance wire part 32 near the terminal 32 Other resistance wire portion 4 Projection strip portion 41 Groove for winding the resistance wire portion near the terminal 40 Notch or hole for air vent 5 Outer layer

Claims

In a joint in which a resistance wire is wound around a groove in a thermoplastic resin inner cylinder, a thermoplastic resin outer layer is injection-molded on the inner cylinder, and a resistance wire terminal is embedded in the outer layer, a resistance wire near the terminal A resistance wire bending boss is provided to make the angle of the portion with respect to the inner cylinder axis direction smaller than the angle of the other resistance wire portion with respect to the inner cylinder axis direction. In addition, after being bent at the boss, it is wound around the groove of the inner tube portion near the terminal through the gap portion without the groove at the small angle. Electric fusion joint.

Electrical welding joint according to claim 1, wherein the groove for winding the resistance wire portion of the terminal near is provided on the upper surface of the ridge.

The electrofusion joint according to claim 2, wherein the protruding portion has an air vent notch or a hole.

A terminal receiving portion for mounting the pin portion of the terminal is provided in the inner cylinder, and a retaining wall for supporting the terminal head against the pulling of the resistance wire welded to the side surface of the terminal head is provided in the terminal receiving portion. The electric fusion joint according to claim 1 .