JP2004344903A

JP2004344903A - Method for forming projecting part of pipe insertion port and separation-preventing joint

Info

Publication number: JP2004344903A
Application number: JP2003142766A
Authority: JP
Inventors: Mutsuo Uchida; 睦雄内田; Shinichiro Tanaka; 進一郎田中
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2003-05-21
Filing date: 2003-05-21
Publication date: 2004-12-09
Anticipated expiration: 2023-05-21
Also published as: JP4412916B2

Abstract

<P>PROBLEM TO BE SOLVED: To easily and inexpensively form a projecting part at an insertion port, and to obtain a pipe joint which can surely exert separation-preventing functions when used as a separation-preventing joint. <P>SOLUTION: The protruding part of the insertion port at the insertion port 2 of a pipe 6 for the separation-preventing pipe joint is provided to the outer periphery of the pipe. The outer periphery is heated to a temperature at which the pipe 6 made of cast iron can be plastically deformed and cementite is not crystallized to the pipe wall structure after rapid cooling. Next, the pipe 6 for the pipe joint is compressed to the pipe axis direction. The heated pipe wall is expanded and plastically deformed 11 in the pipe outer diameter direction. It is cooled as it is. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は管挿し口突部成形方法及び、この挿し口突部を有する挿し口を用いた離脱防止継手に関する。
【０００２】
【従来の技術】
ダクタイル鋳鉄管の離脱防止を図った管継手として図１３に示す管継手１が知られている。
【０００３】
この管継手１は、突部３を形成した挿し口２を、内面に一つ割りロックリング（以下単にロックリングという。）５を配置した受口４に挿入し、管継手１に抜け出し力が作用した場合、挿し口突部３とロックリング５とを係合させて抜け出しを防止するようにしたものである。
【０００４】
図中、２ａはシール用ゴム輪、５ａはロックリングの芯出しゴムを示す。
ところで、一般に鋳鉄管、ダクタイル鋳鉄管は遠心力鋳造法によって成形されるから鋳造時に挿し口突部３を一体成形するのは製法上無理で、鋳造後にリング部材を溶接により後付けすることによって挿し口突部３を設けることが行なわれる（特許文献１）。
【０００５】
【特許文献１】
特開平１１−３５００４２公報
【０００６】
【発明が解決しようとする課題】
しかしながら、挿し口突部３を挿し口２に溶接するには、挿し口リング部材を正確に加工しなければならず、その溶接作業も慎重に行う必要があり、製造コストが高価になる問題があった。
【０００７】
さらに、挿し口リング部材を溶接する際、溶接箇所の管壁が一旦溶融され、ついで急冷されるので溶接箇所の管壁に硬くて脆いセメンタイトが晶出し、管壁の材質が硬くて脆くなり、瞬間的に大きな外力が作用すると破壊されやすくなるといった問題もある。このため、焼鈍工程が新たに必要になるなど製造に手間とコストがかかる問題もあった。
【０００８】
この発明は、上記問題を解消し、挿し口に容易かつ安価に挿し口突部を形成でき、しかも離脱防止継手として用いた場合に、確実に離脱防止機能を発揮し得る管継手を得ることを課題としてなされたものである。
【０００９】
【課題を解決するための手段】
即ち、この発明の管挿し口突部成形方法は、離脱防止管継手用管の挿し口の挿口突部を設ける外周を、該管を構成する鋳鉄が塑性変形し得る温度であって、放冷しても管壁組織に組織変化が生じない程度の温度まで加熱し、次いで前記管継手用管を管軸方向へ圧縮し、前記加熱した管壁を管外径方向へ膨出塑性変形させ、その状態のまま放冷するものである。
【００１０】
この方法により挿し口突部を形成すれば、挿し口リングが不要となるうえ、加熱後管を軸方向に圧縮力を付加するだけで突部が形成されるので、従来に比べ非常に容易に挿し口突部を形成することができる。また、加熱温度が、放冷しても管壁組織に組織変化が生じない程度の温度とされているので加工後に改めて焼鈍工程を必要とすることがなく、しかも塑性変形後の管壁組織は、例えばフェライトからパーライト化されるなど適度に材質が硬くされ、抜け出し防止を計る膨出部のロックリングとの接触による変形も防止される。
【００１１】
請求項２の発明は、上記製法で製造された挿し口を用いた離脱防止継手に関し、管受口内面のロックリング収納溝の溝深さが、管奥方側より管受口開口側へ向け２段にわたって段状に浅くなるように変化され、管奥方側の深い溝の深さが、一つ割りロックリングの径方向厚さと請求項１に記載された挿し口外面の膨出変形量とを加えた量の深さ、管受口開口側の浅い溝の深さが前記挿し口外面に密着した前記ロックリングの外面をほぼ隙間なく受容できる深さとされ、該受口内に収納した前記ロックリングに挿口を挿入し、受口内へと挿入していくことで管奥方側の収納溝内で前記一つ割りロックリングを拡径させて挿し口の前記膨出部を通過させ、管受口奥方へと挿入して接続し、挿し口に引抜き力が作用したときに、挿し口外面に密着させた前記ロックリングを受口開口側の浅い溝部分に移動させ、浅い溝の開口側端に前記ロックリングを当接させるとともに前記ロックリングの管受口奥方側端に挿し口の膨出部を当接させることで抜け出し防止が図られるようにしたものである。
【００１２】
接続した離脱防止管継手に抜け出し方向へ外力が加わったとき、ロックリングは浅いロックリング収納溝へと移動し、そこで管受口内面によって軸方向への移動が防止され、抜け出ようとする挿口は、膨出部をロックリングの管受口奥方側端に接するが、ロックリングは、浅いロックリング収納溝内面に支えられて拡径変形しないように保持されるので、滑らかな膨出部が接触してもロックリングが拡径して乗り越えてしまうことはない。したがって、挿口突部が滑らかな膨出部とされていても確実に抜け出し防止が図られるのである。
【００１３】
請求項３は、請求項２のロックリング収納溝の溝深さの変化する境界部分がテーパ面とされ、さらに浅い溝の受口開口側内面がロックリングの管受口開口側端面に形成したテーパ面と傾斜がほぼ合致するテーパ面とされたものである。
【００１４】
挿し口に抜け出し力が作用した場合、これとともに抜け出し方向へ移動するロックリングは、テーパ面との接触により縮径方向に力が加わり、これによってロックリングが強く挿し口外周に巻きつくようになり、膨出部のすり抜けがさらに防止される。
【００１５】
【発明の実施の形態】
次に、この発明の実施の形態を説明する。
図１はこの発明の管挿し口突部成形方法を実施する装置の断面図である。
【００１６】
図１において、６は挿し口２と受口４を有する鋳鉄管を示す。この鋳鉄管６の挿し口２側であって、挿し口突部を形成する部分の外周に加熱装置７、例えば高周波誘導過熱コイル７を配置し、この加熱装置７により加熱温度を、挿し口２が容易に塑性変形可能であり、一方、放冷しても管壁組織変化があまり生じない温度まで加熱する。
【００１７】
具体的には鋳鉄管の場合は、８００℃〜１０００℃の温度に加熱する。
ここに上記温度範囲とするのは、８００℃以下では温度が低すぎ膨出変形には強大な力を要して成形が困難となり、１０００℃を超えると塑性変形の容易性の点では好都合であるが冷却時に管壁組織変化が生じ、例えば管壁組織にセメンタイトが晶出し易くなるなど、鋳鉄管の表面硬度が局部的に増し組織が脆くなって強度的に不都合を生じるためである。
【００１８】
そして、鋳鉄管６の挿し口２側端にストッパ８が、また受口４側端には、押し板９を介して軸方向圧縮力が付加できるようにされている。
この押し板９に対する圧縮力は、油圧装置（図示せず）のピストンロッド１０により付加される。
【００１９】
また、鋳鉄管６は、支持ロール１５上に支持されている。
次に、上記装置により挿し口突部を形成する方法について説明する。
まず図１に示すように鋳鉄管６の挿し口２を高周波誘導過熱コイルなどの加熱装置７内に挿入し、ストッパ８に挿し口端を押し当てて位置決めし、次いで加熱装置７を作動させ、挿し口２が容易に塑性変形可能であり、一方、管壁組織がパーライト化してもセメンタイトが晶出しない温度、具体的には上述した８００℃〜１０００℃に加熱する。
【００２０】
そして、加熱すれば図２に示すように押し板９に軸方向押圧力を付加して鋳鉄管６に軸方向押圧力Ｆを付加する。
すると軸方向押圧力Ｆにより加熱部分３ａが膨出変形し、図３にも拡大して示すように、挿し口突部１１が形成される。その状態のまま冷却し、以後焼きなましなどの熱処理などの後処理をすることなく使用に供されるのである。
【００２１】
なお、上記実施の形態として、軸方向押圧力Ｆを加えて加熱部分３ａを膨出変形させる場合、図４に示すように加熱部分３ａに成形用外型１２を外嵌しても良い。
【００２２】
この成形用外型１２は、二つ割りのリング１４とされ、内面に膨出変形すべき挿口外周の径方向と軸方向幅の空間を内包するような溝１３が形成され、割り部１４ａに設けた、てこ１４ｂやフック１４ｃを利用した迅速に固定できる固定装置１４ｄにより挿し口管２外周に環状に取り付けるように構成されている。
【００２３】
また、上記挿し口突部１１の膨出形成手段として、高周波誘導過熱コイルを用いた場合を示したが、これに限らず図５に示すように管６を駆動装置（図示せず）を備えた支持ローラ１５、１５上に載せて軸周囲に回転可能に支持し、管６を回転しつつ挿し口端２をプラズマトーチ１６で加熱し、目的温度にまで加熱されれば図６に示すように押し板９で軸方向へ押圧し、ストッパ８を兼ねる突部成形治具８ａにより図７に示すように膨出部の膨出量が一定となるように膨出変形させるようにしても良い。
【００２４】
なお、図５〜図７に示した装置は、加熱装置、ストッパの構造が異なるだけで他は図１〜図３に示した装置と同じであるため、同一部分又は相当する部分については同一符号を付して詳細な説明は省略する。
【００２５】
次に、上記挿し口２を離脱防止継手の挿し口管として使用した場合について説明する。
図８は、膨出部１１を形成した挿し口２を使用した場合の離脱防止継手の要部拡大断面図を示したものである。
【００２６】
図８において、受口４内面に形成されるロックリング収納溝１７は、管奥方側１７ａより管受口開口側１７ｂへ向け図示のように二段にわたって段状に浅くなるように変化され、管奥方側の深い溝１７ａの深さが、ロックリング５の径方向厚さＨと挿し口に形成した膨出部１１の高さｈの和に等しい深さとされ（図９参照）、管受口開口側の浅い溝１７ｂの深さは挿し口２外面に密着したロックリング５をほぼ隙間なく受容できる深さ（図１１参照）とされている。
【００２７】
また、深い溝１７ａから浅い溝１７ｂへ変化する境界部分は図示のようにテーパ面１７ｃとされ、さらに浅い溝１７ｂの受口開口端側の内面１７ｄは、ロックリング５の受口開口側端面に形成したテーパ面５ａと傾斜がほぼ合致するテーパ面１７ｄとされている。
【００２８】
図中２ａはシール用ゴム輪、４ａは受口内面に形成されたシール用ゴム輪の収納溝を示す。
そして、この受口４に挿し口２を挿入する場合、図８に示すように受口４内にシール用ゴム輪２ａとロックリング５をそれぞれ収納溝４ａ、１７に収納し、矢印で示すように挿し口２を受口４内へ挿入する。
【００２９】
挿し口２の突部となる膨出部１１は、シール用ゴム輪２ａを圧縮して受口４奥方へと入り込み、やがてロックリング５と係り合ってロックリング５を収納溝１７奥方へと押し込んでいく。
【００３０】
ロックリング５は図９に示すように収納溝奥方の壁１７ｅに当接し、それ以上奥方へは進めないので、膨出部１１によって拡径変形される。また、収納溝奥方の溝深さはロックリング５の径方向厚さＨと、膨出部１１の高さｈとの和とされているので、挿し口２の膨出部１１はロックリング５を拡径変形させ、同時にその内部をすり抜けて受口４の奥方へ挿入されていく。そして、図１０に示すように挿し口２の開口端２ｂから受口奥端４ｂまでの距離Ｓ_１と、膨出部１１からロックリング収納溝１７の受口開口端側端面１７ｄに当接したロックリング５の奥端までの距離Ｓ_２までの間が伸縮用の隙間となる。
【００３１】
次に、継手に抜け出し方向の外力が作用し、挿し口２が受口４から抜け出ようとした場合は、図１１に示すように、挿し口２とともにロックリング５が受口４の開口方向へ移動し、浅い溝１７ｂへ入っていく。
【００３２】
やがて、ロックリング５は浅い溝１７ｂの開口側端１７ｄに当接し、テーパ面同士の接触により、ロックリング５は縮径作用を受け、この結果ロックリング５は挿口２外面に抱きつくように縮径変形しようとする。
【００３３】
したがって、ロックリング５の内側を挿し口２が滑り移動しようとしても、膨出部１１がロックリング５の奥端側に接触し、抜け出しを阻止する。
また、膨出部１１の立ち上がり部が滑らかな湾曲面とされていても、ロックリング５は浅い溝１７ｂに殆ど隙間なく入り込まされているので拡径変形することができず、前述の縮径作用と相俟って膨出部１１を通過させない。
【００３４】
一方、膨出部１１は、放冷しても管壁組織に組織変化が生じない程度の温度、例えばパーライト化してもセメンタイトが晶出しないような温度に加熱されているので、成形後の膨出部１１は適度な硬さと強度を有し、容易に復元収縮したり破壊されることもない。
【００３５】
したがって、強大な引抜き力が作用しても挿し口２が受口４から抜け出てしまうことはなく、離脱防止機能が発揮されるのである。
【００３６】
【発明の実施例】
次にこの発明の実施例を説明する。
小口径管〜中口径管の管厚８．５ｍｍのスリップオンタイプの離脱防止管継手に付いて実施した。この種離脱防止管継手の挿口突部における膨出量ｈは、ほぼ３ｍｍ前後である。したがって、この膨出量とするための軸方向押圧力と加熱温度との関係を測定した。表１にその結果を示す。
【００３７】
【表１】

表１より明らかなように挿し口の加熱温度が７００℃では、５００〜１０００ｋＮであっても０．８〜１．４ｍｍと膨出部の十分な高さが得られず、８００℃、３００ｋＮで３．０ｍｍと目的の高さｈが得られることが判った。
【００３８】
また、１０００℃を超え１１００℃とした場合は管が溶融し突部形成が不可能となった。以上より、加熱温度は８００℃〜１０００℃が好適な範囲であることが判明した。
【００３９】
次に、挿し口突部となる膨出部の高さｈと引抜力との関係を図１２に示す試験装置で試験した。
図１２に示した試験装置２０は、管６の外径にほぼ等しい内径の挿入孔２１を有する基台２２に膨出部１１を有する挿口２を、受口４側（図示せず）を切り取った管中央側端６ａから挿入し、基台２２の貫通孔２１内面に膨出部１１を係止させるようにしたもので、基台２２は、支柱２６に支持された基盤２５上に基台２２が支持されている。
【００４０】
そして、挿口２内に反力板２３を溶接し、加圧ロッド２４の先端を反力板２３に当接し、矢印方向への軸方向圧縮力を加えて膨出部１１が基台２２の貫通孔２１をすり抜けるか、又は膨出部１１が破壊されるまでに要する力を測定した。その結果は表２の結果となった。
【００４１】
【表２】

【００４２】
これによるとｈが１．５ｍｍ以下の場合は目標値である３ＤｋＮ（Ｄは管直径）に達するまでにすり抜けが発生し抜け出し防止が機能しなかったが、ｈ＝２．０〜３．０ｍｍの場合は、６ＤｋＮの引抜き力でも異常がなく、耐震用離脱防止継手として十分な性能を発揮できることが確認された。
【００４３】
【発明の効果】
この発明は以上説明したように、挿口に抜け出し防止のための突部を形成する場合、挿口を加熱した後管軸方向に一定押圧力で圧縮するだけで形成されるので、従来のように溶接などといった面倒な工程は不要となり、突部の成形が容易となる。また、加熱温度が、放冷しても管壁組織に組織変化が生じない程度の温度例えば、冷却後管壁組織がフェライトからパーライトへ変化してもセメンタイトが晶出しない、いわゆる焼鈍を要しない温度とされているので成形後の熱処理も不要で、それだけ安価に製造できるのである。
【００４４】
しかも、冷却後は管壁組織が、例えば、フェライトからパーライトへと変化するといったことはあり、このような変化の場合は膨出部に適度な硬度が備えられ、したがって強大な引抜き力が作用しても膨出部がロックリングにしごかれてもとの径に復元変形してしまうといったことも防止され、確実な抜け出し防止効果が発揮されるのである。
【００４５】
また、抜け出し時、滑らかな膨出部とされた挿口突部によりロックリングに拡径力が作用しても、ロックリングは受口の浅い溝部分で拡径しないように外径から支えられているので、ロックリングの拡径変形に起因する抜け出しも確実に防止されるといった効果を有する。
【図面の簡単な説明】
【図１】この発明の方法の実施状態を示す要部破断断面図である。
【図２】この発明の方法の実施状態を示す要部破断断面図である。
【図３】この発明の方法の実施状態を示す要部拡大断面図である。
【図４】この発明の方法を実施する装置の一例を示す要部拡大断面図である。
【図５】この発明の方法の他の実施状態を示す要部拡大断面図である。
【図６】この発明の方法の他の実施状態を示す要部拡大断面図である。
【図７】この発明の方法の他の実施状態を示す要部拡大断面図である。
【図８】この発明の方法により成形された挿し口を用いた離脱防止継手の要部断面図である。
【図９】この発明の離脱防止継手の接合過程を示す要部断面図である。
【図１０】この発明の離脱防止継手の接合完了状態を示す要部断面図である。
【図１１】この発明の離脱防止継手の離脱防止状態を示す要部断面図である。
【図１２】この発明の離脱防止継手の離脱防止機能を試験する装置の断面図である。
【図１３】従来の離脱防止継手の断面図である。
【符号の説明】
２挿し口
３ａ加熱部分
４受口
５ロックリング
６鋳鉄管
７加熱装置
８ストッパ
９押し板
１０ピストンロッド
１１膨出部
１２成形用外型
１５支持ローラ
１６プラズマトーチ
１７ロックリング収納溝
Ｆ軸方向押圧力[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pipe insertion port forming method and a separation prevention joint using an insertion port having the insertion port projection.
[0002]
[Prior art]
A pipe joint 1 shown in FIG. 13 is known as a pipe joint for preventing detachment of a ductile cast iron pipe.
[0003]
In this pipe joint 1, the insertion port 2 having the projection 3 is inserted into a receiving port 4 in which a lock ring (hereinafter simply referred to as a lock ring) 5 is arranged on the inner surface, and the pipe joint 1 is pulled out. When operated, the insertion projection 3 and the lock ring 5 are engaged to prevent slipping out.
[0004]
In the drawing, reference numeral 2a denotes a rubber ring for sealing, and 5a denotes a centering rubber of the lock ring.
By the way, since a cast iron pipe and a ductile cast iron pipe are generally formed by a centrifugal casting method, it is impossible to integrally form the insertion projection 3 at the time of casting, and after the casting, a ring member is retrofitted by welding. Provision of the protrusion 3 is performed (Patent Document 1).
[0005]
[Patent Document 1]
JP-A-11-350042 [0006]
[Problems to be solved by the invention]
However, in order to weld the insertion port projection 3 to the insertion port 2, the insertion port ring member must be accurately machined, and the welding operation must be carefully performed, resulting in an increase in manufacturing cost. there were.
[0007]
Further, when welding the insertion ring member, the pipe wall at the welding location is once melted and then rapidly cooled, so that hard and brittle cementite crystallizes on the pipe wall at the welding location, and the material of the pipe wall becomes hard and brittle, There is also a problem that it is easily broken when a large external force acts momentarily. For this reason, there has been a problem that the production is troublesome and costly, for example, a new annealing step is required.
[0008]
The present invention solves the above-described problems, and provides a pipe joint that can easily and inexpensively form an insertion port projection in an insertion port and that can reliably exhibit a separation prevention function when used as a separation prevention joint. This was done as an issue.
[0009]
[Means for Solving the Problems]
That is, the pipe insertion port forming method of the present invention is characterized in that the outer circumference of the insertion port of the pipe for the pipe for preventing separation is provided with a temperature at which the cast iron constituting the pipe can be plastically deformed. The pipe wall is heated to a temperature at which no structural change occurs in the pipe wall structure even when it is cooled, and then the pipe for fitting is compressed in the pipe axis direction, and the heated pipe wall is expanded and plastically deformed in the pipe outer diameter direction. , And is allowed to cool as it is.
[0010]
If the insertion port projection is formed by this method, the insertion port ring becomes unnecessary, and since the projection is formed only by applying a compressive force to the pipe after heating, it is very easy compared to the conventional method. An insertion projection can be formed. In addition, since the heating temperature is set to such a level that the structure of the tube wall does not change even if it is allowed to cool, there is no need for a new annealing step after processing, and the tube wall structure after plastic deformation is For example, the material is appropriately hardened, for example, by changing from ferrite to pearlite, and deformation due to contact with the lock ring of the bulging portion for preventing escape is also prevented.
[0011]
The invention according to claim 2 relates to a disengagement prevention joint using an insertion port manufactured by the above-mentioned manufacturing method, wherein the groove depth of the lock ring storage groove on the inner surface of the pipe receiving port is set from the inner side of the pipe toward the opening side of the pipe receiving port. The depth of the deep groove on the inner side of the pipe is changed to be stepwise shallower over the step, and the depth of the groove in the radial direction of the split lock ring and the amount of bulging deformation of the outer surface of the insertion opening according to claim 1 are determined. The depth of the added amount and the depth of the shallow groove on the pipe receiving port opening side are set to a depth capable of receiving the outer surface of the lock ring closely contacting the outer surface of the insertion port with almost no gap, and the lock ring housed in the receiving port. By inserting the insertion hole into the receiving opening, the split lock ring is expanded in the receiving groove on the back side of the pipe by passing through the bulging portion of the insertion opening, and the pipe receiving opening is inserted. Insert the cable into the back and connect it. The lock ring is moved to the shallow groove portion on the receiving opening side, and the lock ring is brought into contact with the opening end of the shallow groove, and the bulge portion of the insertion port is inserted into the pipe receiving deep end of the lock ring. The contact is prevented from slipping out.
[0012]
When an external force is applied to the connected anti-disengagement fitting in the pull-out direction, the lock ring moves to the shallow lock ring storage groove, where it is prevented from moving in the axial direction by the inner surface of the pipe socket, and the insertion hole that tries to pull out The bulge contacts the end of the lock ring on the back side of the pipe socket, but the lock ring is supported by the inner surface of the shallow lock ring storage groove and held so as not to expand and deform. Even if the lock ring comes into contact, the lock ring does not expand and get over. Therefore, even if the insertion projection is a smooth bulge, it is possible to reliably prevent the projection from coming off.
[0013]
According to a third aspect of the present invention, the boundary portion where the groove depth of the lock ring storage groove of the second aspect changes is a tapered surface, and the inner surface of the shallow groove on the receiving opening side is formed on the end surface of the lock ring on the receiving opening side. This is a tapered surface whose inclination almost matches the tapered surface.
[0014]
When the exit force acts on the insertion port, the lock ring that moves in the exit direction along with this force is applied in the radial direction by contact with the tapered surface, which causes the lock ring to wind strongly around the insertion port outer periphery. In addition, slip-through of the bulging portion is further prevented.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described.
FIG. 1 is a sectional view of an apparatus for carrying out a method for forming a pipe insertion port projection according to the present invention.
[0016]
In FIG. 1, reference numeral 6 denotes a cast iron pipe having an insertion port 2 and a receiving port 4. A heating device 7, for example, a high-frequency induction heating coil 7 is arranged on the outer periphery of a portion forming the insertion port protrusion on the side of the insertion port 2 of the cast iron pipe 6, and the heating temperature is set by the heating device 7. Can be easily plastically deformed, while being heated to a temperature at which a change in the structure of the tube wall hardly occurs even if it is left to cool.
[0017]
Specifically, in the case of a cast iron tube, it is heated to a temperature of 800 ° C to 1000 ° C.
Here, the above-mentioned temperature range is set at 800 ° C. or lower because the temperature is too low and a large force is required for bulging deformation, and molding is difficult, and when it exceeds 1000 ° C., it is convenient in terms of easiness of plastic deformation. However, this is because the surface hardness of the cast iron tube is locally increased, for example, cementite is easily crystallized in the tube wall structure, and the structure becomes brittle, causing a problem in strength.
[0018]
A stopper 8 is applied to the end of the cast iron pipe 6 on the side of the insertion opening 2, and an axial compression force can be applied to the end of the cast iron pipe 6 via a pressing plate 9.
The compression force on the push plate 9 is applied by a piston rod 10 of a hydraulic device (not shown).
[0019]
The cast iron tube 6 is supported on a support roll 15.
Next, a method of forming the insertion port protrusion by the above-described device will be described.
First, as shown in FIG. 1, the insertion port 2 of the cast iron pipe 6 is inserted into a heating device 7 such as a high-frequency induction heating coil, the insertion port is pressed against a stopper 8 for positioning, and then the heating device 7 is operated. The insertion port 2 can be easily plastically deformed, while the pipe wall is heated to a temperature at which cementite does not crystallize even if the pipe wall structure becomes pearlite, specifically, the above-mentioned 800 ° C. to 1000 ° C.
[0020]
Then, when heated, an axial pressing force is applied to the pressing plate 9 as shown in FIG. 2 to apply an axial pressing force F to the cast iron pipe 6.
Then, the heating portion 3a swells and deforms due to the axial pressing force F, and the insertion port protrusion 11 is formed as shown in an enlarged manner in FIG. It is cooled in that state, and then used without any post-treatment such as heat treatment such as annealing.
[0021]
In the embodiment described above, when the heating portion 3a is expanded and deformed by applying the axial pressing force F, the outer mold 12 for molding may be externally fitted to the heating portion 3a as shown in FIG.
[0022]
The outer mold 12 is formed into a split ring 14, and a groove 13 is formed on the inner surface so as to include a space in a radial direction and an axial width of an outer periphery of an insertion opening to be swollen and deformed. In addition, it is configured so as to be annularly mounted on the outer periphery of the insertion port tube 2 by a fixing device 14d that can be quickly fixed using the lever 14b and the hook 14c.
[0023]
Further, the case where a high-frequency induction heating coil is used as the bulge forming means of the insertion port protrusion 11 has been described. However, the present invention is not limited to this, and the pipe 6 is provided with a driving device (not shown) as shown in FIG. The supporting end is mounted on the supporting

rollers

15 and 15 so as to be rotatable around the shaft, and the insertion end 2 is heated by the plasma torch 16 while rotating the tube 6, and when heated to the target temperature, as shown in FIG. Alternatively, the protrusion may be pressed in the axial direction by the push plate 9 and may be swelled and deformed by the protrusion forming jig 8a also serving as the stopper 8 so that the swelling amount of the swelling portion is constant as shown in FIG. .
[0024]
The devices shown in FIGS. 5 to 7 are the same as the devices shown in FIGS. 1 to 3 except for the structure of the heating device and the stopper, and therefore, the same or corresponding parts have the same reference characters. And a detailed description is omitted.
[0025]
Next, a case in which the insertion port 2 is used as an insertion pipe of a separation prevention joint will be described.
FIG. 8 is an enlarged sectional view of a main part of the separation-preventing joint when the insertion port 2 having the bulging portion 11 is used.
[0026]
In FIG. 8, the lock ring housing groove 17 formed on the inner surface of the receiving port 4 is changed so as to be stepwise shallow in two steps as shown in the drawing from the inner side 17a of the pipe toward the opening 17b of the receiving port. The depth of the deep groove 17a on the back side is set to a depth equal to the sum of the radial thickness H of the lock ring 5 and the height h of the bulging portion 11 formed in the insertion port (see FIG. 9). The depth of the shallow groove 17b on the opening side is set to a depth capable of receiving the lock ring 5 closely contacting the outer surface of the insertion opening 2 with almost no gap (see FIG. 11).
[0027]
The boundary portion where the deep groove 17a changes to the shallow groove 17b is a tapered surface 17c as shown in the figure, and the inner surface 17d of the shallow groove 17b on the receiving opening end side is formed on the receiving opening opening end surface of the lock ring 5. The tapered surface 17d is formed so that its inclination substantially matches the formed tapered surface 5a.
[0028]
In the drawing, reference numeral 2a denotes a sealing rubber ring, and 4a denotes a storage groove for the sealing rubber ring formed on the inner surface of the receiving port.
When the insertion port 2 is inserted into the receiving port 4, the sealing rubber ring 2a and the lock ring 5 are stored in the receiving

grooves

4a and 17 in the receiving port 4 as shown in FIG. The insertion port 2 is inserted into the reception port 4.
[0029]
The bulging portion 11 serving as a projection of the insertion opening 2 compresses the sealing rubber ring 2 a and enters the receiving hole 4 deep, and eventually engages with the lock ring 5 and pushes the lock ring 5 deep into the storage groove 17. Go out.
[0030]
As shown in FIG. 9, the lock ring 5 abuts against the wall 17 e on the inner side of the storage groove and cannot be further advanced, so that the bulging portion 11 expands and deforms the diameter. Further, since the groove depth at the back of the storage groove is the sum of the radial thickness H of the lock ring 5 and the height h of the bulging portion 11, the bulging portion 11 of the insertion opening 2 is Is enlarged and deformed, and at the same time, slips through the inside and is inserted into the back of the receptacle 4. Then, as shown in FIG. 10, the distance S ₁ from the opening end 2 b of the insertion opening 2 to the receiving end 4 b and the end surface 17 d of the locking ring storage groove 17 from the bulging portion 11 to the receiving opening end. until the distance S ₂ to the back end of the lock ring 5 is clearance for expansion and contraction.
[0031]
Next, when an external force is applied to the joint in the pull-out direction and the insertion opening 2 tries to slip out of the receiving opening 4, as shown in FIG. 11, the lock ring 5 moves in the opening direction of the receiving opening 4 together with the insertion opening 2. It moves and enters the shallow groove 17b.
[0032]
Eventually, the lock ring 5 comes into contact with the opening-side end 17d of the shallow groove 17b, and the taper surfaces contact each other, thereby causing the lock ring 5 to undergo a diameter reducing action. As a result, the lock ring 5 is shrunk so as to be held on the outer surface of the insertion opening 2. Try to deform radially.
[0033]
Therefore, even if the insertion opening 2 tries to slide inside the lock ring 5, the bulging portion 11 comes into contact with the deep end side of the lock ring 5, thereby preventing the lock ring 5 from slipping out.
Further, even if the rising portion of the bulging portion 11 has a smooth curved surface, the lock ring 5 cannot enter into the shallow groove 17b with almost no gap, so that the lock ring 5 cannot be expanded and deformed. In combination with this, the bulging portion 11 is not allowed to pass.
[0034]
On the other hand, the swollen portion 11 is heated to a temperature at which the structure of the tube wall structure does not change even when the tube is allowed to cool, for example, a temperature at which cementite does not crystallize even if it is pearlitized. The protrusion 11 has appropriate hardness and strength, and is not easily restored and shrunk or broken.
[0035]
Therefore, the insertion opening 2 does not fall out of the reception opening 4 even if a strong pulling force acts, and the detachment prevention function is exhibited.
[0036]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Next, an embodiment of the present invention will be described.
The test was carried out on a slip-on type detachment prevention fitting having a thickness of 8.5 mm for small to medium diameter pipes. The bulging amount h at the insertion projection of this kind of separation prevention pipe joint is about 3 mm. Therefore, the relationship between the axial pressing force and the heating temperature for obtaining the swelling amount was measured. Table 1 shows the results.
[0037]
[Table 1]

As is clear from Table 1, when the heating temperature of the insertion port is 700 ° C., even if it is 500 to 1000 kN, a sufficient height of the bulging portion is not obtained as 0.8 to 1.4 mm, and at 800 ° C. and 300 kN. It was found that a desired height h of 3.0 mm was obtained.
[0038]
Further, when the temperature was higher than 1000 ° C. and 1100 ° C., the tube was melted and it was impossible to form a projection. From the above, it was found that the heating temperature is preferably in the range of 800 ° C to 1000 ° C.
[0039]
Next, the relationship between the height h of the bulging portion serving as the insertion port protrusion and the pull-out force was tested using a test device shown in FIG.
The test apparatus 20 shown in FIG. 12 includes a base 22 having an insertion hole 21 having an inner diameter substantially equal to the outer diameter of the tube 6, the insertion port 2 having the bulging portion 11 on the base 22, and the receiving port 4 side (not shown). The bulging portion 11 is inserted into the cut center end 6a of the tube and locked on the inner surface of the through hole 21 of the base 22. The base 22 is mounted on a base 25 supported by a support 26. A table 22 is supported.
[0040]
Then, the reaction force plate 23 is welded into the insertion opening 2, the tip of the pressure rod 24 abuts on the reaction force plate 23, and an axial compressive force is applied in the direction of the arrow, so that the bulging portion 11 The force required to slip through the through hole 21 or break the bulging portion 11 was measured. The results are shown in Table 2.
[0041]
[Table 2]

[0042]
According to this, when h is 1.5 mm or less, slip-through occurs until the target value of 3DkN (D is the pipe diameter) is reached, and the slip-out prevention does not function, but h = 2.0 to 3.0 mm. In this case, there was no abnormality even with a pull-out force of 6 DkN, and it was confirmed that the joint could exhibit sufficient performance as an anti-separation joint for earthquake resistance.
[0043]
【The invention's effect】
As described above, according to the present invention, when a projection is formed in an insertion opening to prevent the insertion, the insertion opening is formed by simply compressing the insertion opening at a constant pressing force in the axial direction after heating the insertion opening. No complicated steps such as welding are required, and the projections can be easily formed. Further, the heating temperature is a temperature at which the structure of the tube wall does not change even if it is allowed to cool, for example, the cementite does not crystallize even if the tube wall structure changes from ferrite to pearlite after cooling, so-called annealing is not required. Since the temperature is set, heat treatment after molding is not required, and the production can be performed at a lower cost.
[0044]
Moreover, after cooling, the tube wall structure may change from, for example, ferrite to pearlite. In such a case, the bulging portion is provided with an appropriate hardness, and therefore a strong drawing force acts. Even when the swelling portion is squeezed by the lock ring, it is prevented from being restored to the original diameter, and a reliable slip-out preventing effect is exhibited.
[0045]
Also, at the time of escape, even if the expanding force acts on the lock ring due to the smooth bulged insertion projection, the lock ring is supported from the outer diameter so as not to expand in the shallow groove portion of the receiving port. Therefore, the lock ring can be surely prevented from coming out due to the radial expansion deformation of the lock ring.
[Brief description of the drawings]
FIG. 1 is a fragmentary cross-sectional view showing an embodiment of a method according to the present invention.
FIG. 2 is a fragmentary cross-sectional view showing an embodiment of a method according to the present invention.
FIG. 3 is an enlarged sectional view of a main part showing an embodiment of the method of the present invention.
FIG. 4 is an enlarged sectional view of a main part showing an example of an apparatus for carrying out the method of the present invention.
FIG. 5 is an enlarged sectional view of a main part showing another embodiment of the method of the present invention.
FIG. 6 is an enlarged sectional view of a main part showing another embodiment of the method of the present invention.
FIG. 7 is an enlarged sectional view of a main part showing another embodiment of the method of the present invention.
FIG. 8 is a cross-sectional view of a main part of a detachment prevention joint using an insertion port formed by the method of the present invention.
FIG. 9 is a fragmentary cross-sectional view showing the joining process of the separation preventing joint of the present invention.
FIG. 10 is a cross-sectional view of a main part showing a completed joint state of the separation preventing joint of the present invention.
FIG. 11 is a cross-sectional view of a main part showing a state of preventing a separation of the separation prevention joint of the present invention.
FIG. 12 is a cross-sectional view of an apparatus for testing the function of a separation prevention joint of the present invention.
FIG. 13 is a cross-sectional view of a conventional separation prevention joint.
[Explanation of symbols]
2 Insertion opening 3a Heating portion 4 Receptacle 5 Lock ring 6 Cast iron tube 7 Heating device 8 Stopper 9 Push plate 10 Piston rod 11 Swelling portion 12 Outer mold 15 Supporting roller 16 Plasma torch 17 Lock ring storage groove F Axial pressing pressure

Claims

The temperature at which the cast iron constituting the pipe is plastically deformed, and the outer periphery of the outer circumference of the insertion protrusion of the pipe for the pipe for the separation prevention pipe fitting, is such that the structure of the pipe wall structure does not change even if it is allowed to cool. Then, the pipe for fittings is compressed in the axial direction of the pipe, and the heated pipe wall is swelled and plastically deformed in the outer diameter direction of the pipe. Method.

The groove depth of the lock ring storage groove on the inner surface of the pipe socket is changed so that the depth of the deep groove on the inner side of the pipe is changed so that the depth of the deep groove on the inner side of the pipe is A depth obtained by adding the radial thickness of the split lock ring and the amount of bulging deformation of the outer surface of the insertion port according to claim 1, and the depth of the shallow groove on the opening side of the pipe receiving port is equal to the outer surface of the insertion port. The outer surface of the lock ring that is in close contact with the lock ring has a depth that can be received with almost no gap, and an insertion hole is inserted into the lock ring housed in the socket, and the insertion groove is inserted into the socket so that the storage groove on the back side of the pipe. In the inside, the split lock ring is expanded in diameter and passed through the bulging portion of the insertion port, inserted and connected to the inside of the pipe receiving port, and when a pulling force is applied to the insertion port, the outer surface of the insertion port. The lock ring, which is brought into close contact with the groove, is moved to the shallow groove portion on the receiving opening side, and the opening side end of the shallow groove is moved. Separation preventing joint so as to prevent escape by causing contact bulges of inserting port into the tube socket deeper end of the locking ring is brought into contact with said locking ring is achieved.

3. The tapered surface of the lock ring storage groove according to claim 2, wherein the boundary portion where the groove depth changes is a tapered surface, and the inner surface of the shallow groove on the opening side of the receiving opening is formed on the end surface of the locking ring on the opening side of the receiving opening. The anti-separation joint has a tapered surface that almost matches the slope.