JP3718247B2

JP3718247B2 - Bending method of steel pipe

Info

Publication number: JP3718247B2
Application number: JP30832594A
Authority: JP
Inventors: ▲しげ▼夫堀田
Original assignee: 株式会社サンエツ
Priority date: 1994-11-16
Filing date: 1994-11-16
Publication date: 2005-11-24
Anticipated expiration: 2020-11-24
Also published as: JPH08141658A

Description

【０００１】
【産業上の利用分野】
本発明は、鋼管の曲げ方法に関し、湾曲させた鋼管の被屈曲部分の断面がほぼ真円形を保持する鋼管の曲げ方法に関する。
【０００２】
【従来の技術】
硬質のポリ塩化ビニル（ＰＶＣ）管は、耐薬品性が良好であるので多用されているが、その直径が大きくなればなるほど高圧に耐えることができず、しかも一般に７０℃以上の高温環境では使用することができない。このようなＰＶＣ管の本質的欠陥を回避するため、近年、ＰＶＣと鋼鉄の２層管であるＰＶＣ鋼管が提案され、これは硬質ＰＶＣ管よりも耐圧性及び機械的強度が向上し、ビルやマンションにおける冷暖房設備などの配管に使用されている。
【０００３】
少なくとも鋼管部の内側にＰＶＣ管を密着させるＰＶＣ鋼管は、ＰＶＣ管よりも広範囲の用途に適用できる反面、ＰＶＣと鉄との異質材料の複合管であり、温間加工によって容易に曲げることができない。このため、ＰＶＣ鋼管の配管において湾曲部を有する場合には、従来では２層構造のエルボ部を別個に製造し、これを直線状のＰＶＣ鋼管と接続するのが殆どである。
【０００４】
【発明が解決しようとする課題】
前記のエルボ部は、非常に高価であるうえに管端との接続作業が煩雑であり、該エルボ部とＰＶＣ鋼管の接続部から漏水や腐食が発生するおそれもある。この反面、ＰＶＣ鋼管を直接曲げ加工すると、ＰＶＣ鋼管の被屈曲部分の断面が楕円形に変形しやすく、しかも内側のＰＶＣ管部にひび割れや皺が発生したり、ＰＶＣ管部と外側の鋼管部とが層間剥離する事態が発生しやすい。
【０００５】
本発明者は、ＰＶＣ鋼管に関して曲げ加工するための実験を種々重ねた結果、既に特願平６−１７５９１１号を提案しており、本発明方法はこれをさらに改善したものである。したがって、本発明は、湾曲させたＰＶＣ鋼管の被屈曲部分の断面がほぼ完全な真円形を保持するＰＶＣ鋼管の曲げ方法を提供することを目的としている。本発明の他の目的は、厳冬のような低温期においても曲げ加工の際に内側のＰＶＣ管部にひび割れや皺発生が起こらないＰＶＣ鋼管の曲げ方法を提供することである。
【０００６】
【課題を解決するための手段】
上記目的を達成するために、本発明に係る曲げ方法は、図１及び図２に示すように、鋼管部１の内側にＰＶＣ管部２を嵌め込んで密着させるＰＶＣ鋼管３について適用し、所望に応じて鋼管部の外側にもＰＶＣ管部を嵌合・密着させた３層管（図示しない）であってもよい。用いる鋼管部１は一般に炭素鋼管であるが、ステンレス鋼管などを用いてもよい。また、ＰＶＣ管部２として、ポリエチレン管，ポリプロピレン管なども適用可能である。鋼管部１とＰＶＣ管部２とは、一般に両者を嵌め合わせた後に接着剤で密着させる。
【０００７】
本発明方法を実施するための鋼管曲げ装置４において、直線状のＰＶＣ鋼管３の被屈曲部分３ａ（図２）より前方部３ｂをクランプホルダ５で締め付け、その被屈曲部分をプレッシャホルダ６で圧縮する。プレッシャホルダ６は、ＰＶＣ鋼管３の曲げ半径に対応する外周を有する曲げ型７とともにＰＶＣ鋼管３を挟む。クランプホルダ５，プレッシャホルダ６及び曲げ型７は、ＰＶＣ鋼管３と圧接する面に半円形溝を設け、該半円形溝の断面がやや横長の円形である（図４及び図５参照参照）。
【０００８】
曲げ加工時には、ＰＶＣ鋼管３の後側から管内部へ心金８を押し込み、該心金の内部にヒータ１０を配線することによって内側のＰＶＣ管部２を加熱できる。心金８は、例えば円柱本体１１の先端にワイヤ又はリベットでつないだ変位可能な円盤部１２を有し、該円盤部にもヒータを埋設する。ヒータ埋設の代りに、心金８から熱風が吹き出すように構成し、この熱風を内側のＰＶＣ管部２に吹き付けてもよい。心金８の直径は、図２及び図３に示すように、通常、ＰＶＣ鋼管３の内径つまりＰＶＣ管部２の内径よりも約２ｍｍ小さいと好ましい。
【０００９】
本発明方法では、心金８の代り又は該心金とともに、ＰＶＣ鋼管３の内部に温水１３（図６）のような充填材を加圧充填してもよい。温水１３の充填は、例えばＰＶＣ鋼管３の一端部に盲フランジ１４を取付け、該ＰＶＣ鋼管を垂直に配置してから温水１３を加圧注入し、温水注入後に該鋼管の他端部における盲フランジ１５を閉鎖する。このような充填材としては、加熱した硅砂，ＰＶＣチップ，金属粒片例えば鉛，鉄粉，亜鉛粉，アルミニウム粉，軟ろう材，スチールベルトなどでもよい。これらの充填材の代りに、熱風をＰＶＣ管部２に吹き付けて該管部の被屈曲部分を加熱してから曲げ加工してもよい。
【００１０】
通常、ＰＶＣ鋼管３の被屈曲部分３ａを曲げ型７の外周面に沿って曲げる際に、スライドホルダ１７を前方に押し出すとともに、ＰＶＣ鋼管３をクランプホルダ５の方へ後押しする。ＰＶＣ鋼管３の後押し作動部材は、図示のような油圧作動のチャック１８であっても、又はＰＶＣ鋼管３の後端部を把持する１対のクランプホルダや、スライドホルダ１７の後端突起をＰＶＣ鋼管３の後端面に係止させるような構成であってもよい。
【００１１】
【作用】
本発明の曲げ方法は、クランプホルダ５，プレッシャホルダ６及び曲げ型７がやや横長円形の半円形溝を有することにより、ＰＶＣ鋼管３の被屈曲部分３ａ及びその近傍をやや横長の円形断面に圧縮しながら、該ＰＶＣ鋼管を曲げ型７の外周面に沿って曲げる。この曲げ加工により、ＰＶＣ鋼管３の被屈曲部分３ａはその横断面をやや小径であるがほぼ真円形になるように湾曲させる。被屈曲部分３ａが小径になる程度は、直径６０ｍｍのＰＶＣ鋼管３で約２ｍｍであり、最大でも５ｍｍ前後にすぎないので実用上の問題はない。
【００１２】
また、本発明の曲げ方法では、曲げ加工時にＰＶＣ鋼管３の内部に心金８を押し込んだり又は温水１３などを加圧充填する。押し込まれた心金８は、その内部にヒータ１０を配線することによって内側のＰＶＣ管部２を加熱し、厳冬のような低温期においてＰＶＣ鋼管３の被屈曲部分３ａを曲げ型７の外周面に沿って曲げる際に、内側のＰＶＣ管部２にひび割れや皺が発生することを防止する。
【００１３】
【実施例】
次に、本発明を実施例に基づいて説明する。本発明方法は、図１から図３に例示するようなＰＶＣ鋼管３について適用し、該ＰＶＣ鋼管では炭素鋼管部１の内側にＰＶＣ管部２を嵌め込んで接着剤で密着させる。この場合、鋼管部１の外側にさらにＰＶＣ管部２を嵌合・密着させた３層管でも適用可能である。ＰＶＣ鋼管３は一般に空調配管用又は上水道管用であり、炭素鋼管部１は例えば直径６０.５ｍｍ，厚み４ｍｍ、ＰＶＣ管部２は直径５２.５ｍｍ，厚み１.５ｍｍである。
【００１４】
本発明方法を実施するための鋼管曲げ装置４には、回転可能に設置し且つＰＶＣ鋼管３の曲げ半径に対応する外周を有するほぼ円形平面の曲げ型７を備え、該曲げ型の外周面に環状の半円形溝２１を設ける（図５参照）。曲げ型７には、その外周の一部に切り欠き２２を設け、ここにクランプホルダ５の受け部５ａを嵌めて固着する。クランプホルダ５は、図４から明らかなように、対向面にそれぞれ半円形溝２３，２４を設けた矩形平面の受け部５ａと可動部５ｂとからなり、該受け部の側面は曲げ型７の直径通過線上に位置する。クランプホルダ５は、油圧機構（図示しない）によって可動部５ｂをＰＶＣ鋼管３の方へ押圧することにより、受け部５ａとともに鋼管前方部３ｂを締め付け可能である。クランプホルダ５は、曲げ型７に固着され、適宜の回動機構によって該曲げ型とともに回転する。
【００１５】
図１に示すように、やや横長の矩形平面であるプレッシャホルダ６は、装置の休止状態（図２）においてクランプホルダ５の可動部５ｂと隣接するとともに、半円形溝２５を設けた前面において曲げ型７とともにＰＶＣ鋼管３を挟む。クランプホルダ５，プレッシャホルダ６及び曲げ型７において、ＰＶＣ鋼管３と当接する面に設けた半円形溝２１，２３，２４及び２５は、図４及び図５を参照すると明らかなように、その断面がやや横長の円形である。これらの半円形溝は、例えば、水平方向の直径が６０.５ｍｍであれば垂直方向の直径を５８ｍｍに定める。
【００１６】
一方、スライドホルダ１７は、直線状に摺動可能であってプレッシャホルダ６に近接配置し、その前端面２８が曲げ型７に対して平面から見てほぼ接線方向に延びる。ＰＶＣ鋼管３の座屈を防止するための固定ブロック２９は、平面から見てスライドホルダ１７と向い合う位置に配置し、ＰＶＣ鋼管３の軸方向へ位置替えさせて所定位置で固定できる。スライドホルダ１７の前端面２８及びブロック２９の対応部分３０の内面には、ＰＶＣ鋼管３の外周と対応する半円形溝を形成する。
【００１７】
全体がほぼ円柱形の心金８は、円柱本体１１の先端に円盤部１２をワイヤでつなぎ、該円盤部は曲げ加工時に変位可能である。心金８において、円柱本体１１及び円盤部１２の内部にニクロムヒータ１０を配線し、ＰＶＣ鋼管３の内部に押し込んだ際に内側のＰＶＣ管部２を加熱できる。心金８の直径は例えば４７. ５ｍｍであり、ＰＶＣ鋼管３の内径つまりＰＶＣ管部２の内径よりも２ｍｍ小さい。心金８の後端部に軸方向と平行に連結したリンクバー３３は、チャック１８を通過して、ＰＶＣ鋼管３の軸方向と平行に作動する油圧シリンダ（図示しない）に接続する。また、ＰＶＣ鋼管３の後端部を保持する油圧作動のチャック１８は、被屈曲部分３ａを曲げ型７の外周面に沿って曲げる際にＰＶＣ鋼管３をクランプホルダ５の方へ後押しする。
【００１８】
本発明方法では、ＰＶＣ鋼管３の曲げ加工時に、直線状のＰＶＣ鋼管３の前方部３ｂをクランプホルダ５の受け部５ａと可動部５ｂとで締め付けて把持し、ついで心金８をＰＶＣ鋼管３の後側から管内部へ所定圧力で押し込む。ＰＶＣ鋼管３を水平に保持した状態において、クランプホルダ５でＰＶＣ鋼管３の前方部３ｂをさらに締め付け、プレッシャホルダ６及び曲げ型７で被屈曲部分３ａを圧縮する。この結果、ＰＶＣ鋼管３の前方部３ｂ及びその近傍がやや横長の円形断面に圧縮され、例えば、水平方向の直径が６０.５ｍｍ及び垂直方向の直径が５８ｍｍになる。
【００１９】
この後に、クランプホルダ５及び曲げ型７を図３の矢印方向に回動させ、ＰＶＣ鋼管３の被屈曲部分３ａを曲げ型７の外周面に沿って曲げる。この際に、ＰＶＣ鋼管３の被屈曲部分３ａはやや横長の円形断面に圧縮されながら、曲げ型７の外周面に沿って曲がっていく。また、スライドホルダ１７を前方に押し出すとともに、油圧作動のチャック１８でＰＶＣ鋼管３をプレッシャホルダ６の方へ後押しする。この結果、ＰＶＣ鋼管３は、その被屈曲部分３ａが直径５８ｍｍのように横断面がやや小径であるが、ほぼ真円形になるように湾曲させる。
【００２０】
また、この曲げ方法では、曲げ加工時にＰＶＣ鋼管３の内部に心金８を押し込み。該心金の内部のヒータ１０によって内側のＰＶＣ管部２を加熱する。この結果、厳冬のような低温期においてＰＶＣ鋼管３の被屈曲部分３ａを曲げ型７の外周面に沿って曲げる際に、内側のＰＶＣ管部２にひび割れや皺が発生することがない。このヒータ１０は、作業環境の温度が高くなる夏季においては使用しなくてもよい。
【００２１】
図６に示す変形例では、前記の心金８の代りに、約８０℃の温水１３を圧力ポンプ（図示しない）によって１０〜３０Ｋｇ／ｃｍ²に加圧してＰＶＣ鋼管３の内部に充填する。温水１３の充填は、例えばＰＶＣ鋼管３の一端部に盲フランジ１４を取付け、該ＰＶＣ鋼管を垂直に配置してから温水１３を加圧注入し、温水注入後に該鋼管の他端部における盲フランジ１５を閉鎖した後に水平に戻す。温水１３の他にも、このような充填材として、加熱した硅砂，ＰＶＣチップ，金属粒片例えば鉛，鉄粉，亜鉛粉，アルミニウム粉，軟ろう材，スチールベルトなどが使用可能である。
【００２２】
曲げ加工時にＰＶＣ鋼管３の内部に温水１３を加圧充填しておくと、この加圧温水によって内側のＰＶＣ管部２を約５０〜６０℃まで加熱し、ＰＶＣ管部２を鋼管部１の方へ押し付けるから、被屈曲部分３ａにおいてＰＶＣ管部２が鋼管部１から剥離することを防ぐ。また、厳冬のような低温期において、ＰＶＣ鋼管３の被屈曲部分３ａを曲げ型７の外周面に沿って曲げる際に、内側のＰＶＣ管部２にひび割れや皺が発生することを防止する。
【００２３】
【発明の効果】
本発明に係る曲げ方法において、クランプホルダ，プレッシャホルダ及び曲げ型は、やや横長円形の半円形溝を有する。これによってＰＶＣ鋼管の被屈曲部分及びその近傍をやや横長の円形に圧縮しながら、該ＰＶＣ鋼管を曲げ型の外周面に沿って曲げ、ＰＶＣ鋼管の被屈曲部分をほぼ真円形になるように湾曲させる。したがって本発明の曲げ方法を用いると、ＰＶＣ鋼管を任意の角度に湾曲させた際にその被屈曲部分の断面が常に真円形を保持し、該ＰＶＣ鋼管が潰れることを回避する。この結果、ＰＶＣ鋼管の被屈曲部分における鋼管部の肉厚減少率が小さく、内側の塩化ビニル管部の内曲部に皺発生を防止するとともに、得たＰＶＣ鋼管の機械的強度も大きくなる。
【００２４】
また、本発明に係る曲げ方法では、曲げ加工時にＰＶＣ管部が剥離しないように、ＰＶＣ鋼管の内部に心金を押し込んだり又は温水などを加圧充填する。押し込まれた心金は、その内部にヒータを配線することによって内側のＰＶＣ管部を加熱するともにＰＶＣ鋼管が潰れることを防ぎ、冬のような低温期において内側のＰＶＣ管部にひび割れや皺が発生することを防止する。したがって、本発明の曲げ方法を適用すると、ＰＶＣ鋼管の不良品の発生が少なくなってランニングコストも減らすことができる。
【図面の簡単な説明】
【図１】本発明方法を実施するための鋼管曲げ装置を示す概略平面図である。
【図２】図１の鋼管曲げ装置を示す概略縦断面図である。
【図３】図１の鋼管曲げ装置でＰＶＣ鋼管を曲げ加工した状態を示す図１と同様の概略縦断面図である。
【図４】クランプホルダの受け部及び可動部を示す側面図である。
【図５】プレッシャホルダの側面及び曲げ型の部分横断面図である。
【図６】本発明方法の変形例を示す概略縦断面図である。
【符号の説明】
１鋼管部
２ＰＶＣ管部
３ＰＶＣ鋼管
３ａ被屈曲部分
５クランプホルダ
６プレッシャホルダ
７曲げ型
８心金
１０ヒータ
１７スライドホルダ[0001]
[Industrial application fields]
The present invention relates to a bending method of a steel pipe, the cross-section of the bent portion is about almost bending method of a true circle to that holds the steel tube of the steel tube is curved.
[0002]
[Prior art]
Rigid polyvinyl chloride (PVC) pipes are widely used because of their good chemical resistance, but the larger their diameter, the more they cannot withstand high pressure, and they are generally used in high temperature environments of 70 ° C or higher. Can not do it. In order to avoid such essential defects of PVC pipes, recently, PVC steel pipes, which are two-layer pipes of PVC and steel, have been proposed, which have improved pressure resistance and mechanical strength than rigid PVC pipes, It is used for piping such as air conditioning facilities in condominiums.
[0003]
PVC steel pipes that attach PVC pipes at least to the inside of the steel pipe part are applicable to a wider range of applications than PVC pipes, but they are composite pipes of different materials of PVC and iron and cannot be bent easily by warm working. . For this reason, when it has a curved part in piping of a PVC steel pipe, conventionally, the elbow part of a two-layer structure is manufactured separately, and this is mostly connected with a straight PVC steel pipe.
[0004]
[Problems to be solved by the invention]
The elbow portion is very expensive and the connection work between the elbow portion and the pipe end is complicated, and there is a possibility that water leakage and corrosion may occur from the connection portion between the elbow portion and the PVC steel pipe. On the other hand, if the PVC steel pipe is directly bent, the cross section of the bent portion of the PVC steel pipe is easily deformed into an ellipse, and cracks and wrinkles are generated in the inner PVC pipe, or the PVC pipe and the outer steel pipe. Are likely to delaminate.
[0005]
The inventor has already proposed Japanese Patent Application No. 6-175911 as a result of various experiments for bending a PVC steel pipe, and the method of the present invention further improves this. Accordingly, an object of the present invention is to provide a method for bending a PVC steel pipe in which the cross-section of the bent portion of the bent PVC steel pipe maintains a substantially perfect circular shape. Another object of the present invention is to provide a method for bending a PVC steel pipe that does not cause cracks or wrinkles in the inner PVC pipe part during bending even in a low temperature period such as severe winter.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the bending method according to the present invention is applied to a PVC steel pipe 3 that fits and closely contacts the PVC pipe part 2 inside the steel pipe part 1, as shown in FIGS. Accordingly, a three-layer pipe (not shown) in which the PVC pipe part is fitted and adhered to the outside of the steel pipe part may be used. The steel pipe portion 1 to be used is generally a carbon steel pipe, but a stainless steel pipe or the like may be used. Further, as the PVC pipe portion 2, a polyethylene pipe, a polypropylene pipe, or the like can be applied. The steel pipe part 1 and the PVC pipe part 2 are generally brought into close contact with an adhesive after fitting them together.
[0007]
In the steel pipe bending apparatus 4 for carrying out the method of the present invention, the front part 3b is clamped by the clamp holder 5 from the bent part 3a (FIG. 2) of the straight PVC steel pipe 3, and the bent part is compressed by the pressure holder 6. To do. The pressure holder 6 sandwiches the PVC steel pipe 3 together with a bending die 7 having an outer periphery corresponding to the bending radius of the PVC steel pipe 3. The clamp holder 5, the pressure holder 6 and the bending die 7 are provided with a semicircular groove on the surface in pressure contact with the PVC steel pipe 3, and the semicircular groove has a slightly horizontally long cross section (see FIGS. 4 and 5).
[0008]
At the time of bending, the inner PVC pipe part 2 can be heated by pushing the mandrel 8 into the pipe from the rear side of the PVC steel pipe 3 and wiring the heater 10 inside the mandrel. The mandrel 8 has, for example, a displaceable disc portion 12 connected to the tip of the column main body 11 with a wire or a rivet, and a heater is embedded in the disc portion. Instead of burying the heater, it may be configured such that hot air is blown out from the mandrel 8, and this hot air may be blown onto the inner PVC pipe portion 2. The diameter of the mandrel 8 is preferably about 2 mm smaller than the inner diameter of the PVC steel pipe 3, that is, the inner diameter of the PVC pipe portion 2, as shown in FIGS.
[0009]
In the method of the present invention, instead of the mandrel 8 or together with the mandrel, the PVC steel pipe 3 may be pressurized and filled with a filler such as hot water 13 (FIG. 6). The filling of the hot water 13 is performed by, for example, attaching a blind flange 14 to one end of the PVC steel pipe 3, placing the PVC steel pipe vertically, injecting the hot water 13 under pressure, and then injecting the hot water 13 at the other end of the steel pipe 15 is closed. Such fillers may be heated cinnabar, PVC chips, metal particles such as lead, iron powder, zinc powder, aluminum powder, soft brazing material, steel belt and the like. Instead of these fillers, hot air may be blown onto the PVC pipe part 2 to heat the bent part of the pipe part and then bend it.
[0010]
Normally, when the bent portion 3a of the PVC steel pipe 3 is bent along the outer peripheral surface of the bending die 7, the slide holder 17 is pushed forward and the PVC steel pipe 3 is pushed toward the clamp holder 5. Even if the pushing operation member of the PVC steel pipe 3 is a hydraulically operated chuck 18 as shown in the figure, a pair of clamp holders for gripping the rear end portion of the PVC steel pipe 3 or a rear end protrusion of the slide holder 17 is PVC. The structure which makes it latch on the rear end surface of the steel pipe 3 may be sufficient.
[0011]
[Action]
According to the bending method of the present invention, the clamp holder 5, the pressure holder 6 and the bending die 7 have semi-circular grooves that are slightly horizontally long, so that the bent portion 3a of the PVC steel pipe 3 and its vicinity are compressed into a slightly horizontally long circular cross section. Then, the PVC steel pipe is bent along the outer peripheral surface of the bending die 7. By this bending process, the bent portion 3a of the PVC steel pipe 3 is bent so that the cross section thereof has a slightly small diameter but is almost a perfect circle. The extent to which the bent portion 3a has a small diameter is about 2 mm in the PVC steel pipe 3 having a diameter of 60 mm, and is only about 5 mm at the maximum, so there is no practical problem.
[0012]
Further, in the bending method of the present invention, the mandrel 8 is pushed into the PVC steel pipe 3 at the time of bending, or hot water 13 or the like is pressurized and filled. The pressed mandrel 8 heats the inner PVC pipe portion 2 by wiring a heater 10 therein, and the bent portion 3a of the PVC steel pipe 3 is moved to the outer peripheral surface of the bending die 7 in a low temperature period such as severe winter. When bending along the inner side, the inner PVC pipe portion 2 is prevented from being cracked or wrinkled.
[0013]
【Example】
Next, this invention is demonstrated based on an Example. The method of the present invention is applied to a PVC steel pipe 3 as illustrated in FIGS. 1 to 3, and in the PVC steel pipe, the PVC pipe part 2 is fitted inside the carbon steel pipe part 1 and adhered with an adhesive. In this case, a three-layer pipe in which the PVC pipe part 2 is further fitted and adhered to the outside of the steel pipe part 1 is also applicable. The PVC steel pipe 3 is generally used for air conditioning pipes or water supply pipes. The carbon steel pipe part 1 has, for example, a diameter of 60.5 mm and a thickness of 4 mm, and the PVC pipe part 2 has a diameter of 52.5 mm and a thickness of 1.5 mm.
[0014]
The steel pipe bending apparatus 4 for carrying out the method of the present invention is provided with a substantially circular flat bending die 7 which is rotatably installed and has an outer periphery corresponding to the bending radius of the PVC steel pipe 3, and is provided on the outer peripheral surface of the bending die. An annular semicircular groove 21 is provided (see FIG. 5). The bending die 7 is provided with a notch 22 on a part of its outer periphery, and the receiving portion 5a of the clamp holder 5 is fitted and fixed thereto. As is apparent from FIG. 4, the clamp holder 5 is composed of a rectangular flat receiving portion 5 a and semi-circular grooves 23, 24 provided on the opposing surfaces, and a movable portion 5 b, and the side surface of the receiving portion is the bending die 7. Located on the diameter pass line. The clamp holder 5 can clamp the steel pipe front part 3b together with the receiving part 5a by pressing the movable part 5b toward the PVC steel pipe 3 by a hydraulic mechanism (not shown). The clamp holder 5 is fixed to the bending die 7 and is rotated together with the bending die by an appropriate rotation mechanism.
[0015]
As shown in FIG. 1, the pressure holder 6, which is a slightly oblong rectangular plane, is adjacent to the movable part 5 b of the clamp holder 5 in the resting state of the device (FIG. 2) and is bent at the front surface provided with the semicircular groove 25. The PVC steel pipe 3 is sandwiched with the mold 7. In the clamp holder 5, the pressure holder 6, and the bending die 7, the semicircular grooves 21, 23, 24, and 25 provided on the surface in contact with the PVC steel pipe 3 are cross sections thereof as is apparent with reference to FIGS. 4 and 5. Is a slightly oblong circle. These semicircular grooves define, for example, a vertical diameter of 58 mm if the horizontal diameter is 60.5 mm.
[0016]
On the other hand, the slide holder 17 is slidable in a straight line and is disposed close to the pressure holder 6, and its front end surface 28 extends in a tangential direction with respect to the bending die 7 when viewed from the plane. The fixing block 29 for preventing the buckling of the PVC steel pipe 3 can be arranged at a position facing the slide holder 17 when viewed from above, and can be fixed in a predetermined position by changing the position in the axial direction of the PVC steel pipe 3. A semicircular groove corresponding to the outer periphery of the PVC steel pipe 3 is formed on the front end surface 28 of the slide holder 17 and the inner surface of the corresponding portion 30 of the block 29.
[0017]
The generally cylindrical mandrel 8 as a whole has a disk portion 12 connected to the tip of a column main body 11 with a wire, and the disk portion can be displaced during bending. In the mandrel 8, the nichrome heater 10 is wired inside the cylindrical body 11 and the disk part 12, and the inner PVC pipe part 2 can be heated when pushed into the PVC steel pipe 3. The diameter of the mandrel 8 is, for example, 47.5 mm, which is 2 mm smaller than the inner diameter of the PVC steel pipe 3, that is, the inner diameter of the PVC pipe portion 2. The link bar 33 connected to the rear end portion of the mandrel 8 in parallel with the axial direction passes through the chuck 18 and is connected to a hydraulic cylinder (not shown) that operates in parallel with the axial direction of the PVC steel pipe 3. The hydraulically operated chuck 18 that holds the rear end of the PVC steel pipe 3 pushes the PVC steel pipe 3 toward the clamp holder 5 when the bent portion 3 a is bent along the outer peripheral surface of the bending die 7.
[0018]
In the method of the present invention, when the PVC steel pipe 3 is bent, the front part 3b of the straight PVC steel pipe 3 is clamped and held by the receiving part 5a and the movable part 5b of the clamp holder 5, and the mandrel 8 is then clamped. The tube is pushed into the pipe from the rear side with a predetermined pressure. In a state where the PVC steel pipe 3 is held horizontally, the front portion 3b of the PVC steel pipe 3 is further tightened by the clamp holder 5, and the bent portion 3a is compressed by the pressure holder 6 and the bending die 7. As a result, the front portion 3b of the PVC steel pipe 3 and its vicinity are compressed into a slightly horizontally long circular cross section, for example, the horizontal diameter is 60.5 mm and the vertical diameter is 58 mm.
[0019]
Thereafter, the clamp holder 5 and the bending die 7 are rotated in the direction of the arrow in FIG. 3, and the bent portion 3 a of the PVC steel pipe 3 is bent along the outer peripheral surface of the bending die 7. At this time, the bent portion 3a of the PVC steel pipe 3 is bent along the outer peripheral surface of the bending die 7 while being compressed into a slightly horizontally long circular cross section. Further, the slide holder 17 is pushed forward, and the PVC steel pipe 3 is pushed back toward the pressure holder 6 by a hydraulically operated chuck 18. As a result, the PVC steel pipe 3 is bent so that the bent portion 3a has a slightly small cross section, such as a diameter of 58 mm, but is substantially circular.
[0020]
In this bending method, the mandrel 8 is pushed into the PVC steel pipe 3 during bending. The inner PVC pipe part 2 is heated by the heater 10 inside the mandrel. As a result, when the bent portion 3a of the PVC steel pipe 3 is bent along the outer peripheral surface of the bending die 7 in a low temperature period such as severe winter, the inner PVC pipe portion 2 is not cracked or wrinkled. The heater 10 may not be used in the summer when the temperature of the working environment is high.
[0021]
In the modification shown in FIG. 6, instead of the mandrel 8, hot water 13 at about 80 ° C. is pressurized to 10 to 30 kg / cm ² by a pressure pump (not shown) and filled into the PVC steel pipe 3. The filling of the hot water 13 is performed by, for example, attaching a blind flange 14 to one end of the PVC steel pipe 3, placing the PVC steel pipe vertically, injecting the hot water 13 under pressure, and then injecting the hot water 13 at the other end of the steel pipe Return to level after closing 15. In addition to the hot water 13, heated filler sand, PVC chips, metal particle pieces such as lead, iron powder, zinc powder, aluminum powder, soft brazing material, steel belt, etc. can be used.
[0022]
When the hot water 13 is pressurized and filled in the PVC steel pipe 3 during bending, the inner PVC pipe part 2 is heated to about 50 to 60 ° C. by the pressurized hot water, and the PVC pipe part 2 is connected to the steel pipe part 1. Therefore, the PVC pipe part 2 is prevented from peeling from the steel pipe part 1 at the bent portion 3a. Further, when the bent portion 3a of the PVC steel pipe 3 is bent along the outer peripheral surface of the bending die 7 in a low temperature period such as severe winter, the inner PVC pipe portion 2 is prevented from being cracked or wrinkled.
[0023]
【The invention's effect】
In the bending method according to the present invention, the clamp holder, the pressure holder, and the bending die have semi-circular grooves that are slightly horizontally long. As a result, the bent portion of the PVC steel pipe and the vicinity thereof are compressed into a slightly horizontally long circular shape, and the PVC steel pipe is bent along the outer peripheral surface of the bending die, and the bent portion of the PVC steel pipe is bent so as to be almost a perfect circle. Let Therefore, when the bending method of the present invention is used, when the PVC steel pipe is bent at an arbitrary angle, the cross-section of the bent portion always maintains a true circle, and the PVC steel pipe is prevented from being crushed. As a result, the thickness reduction rate of the steel pipe portion in the bent portion of the PVC steel pipe is small, so that generation of wrinkles is prevented in the inner curved portion of the inner vinyl chloride pipe portion, and the mechanical strength of the obtained PVC steel pipe is also increased.
[0024]
Further, in the bending method according to the present invention, a mandrel is pushed into the PVC steel pipe or hot water or the like is pressurized and filled so that the PVC pipe portion does not peel off during bending. The inserted mandrel heats the inner PVC pipe by wiring a heater inside it and prevents the PVC steel pipe from being crushed, and cracks and wrinkles are formed on the inner PVC pipe in the low temperature period such as winter. Prevent it from occurring. Therefore, when the bending method of the present invention is applied, the occurrence of defective PVC steel pipes is reduced and the running cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a steel pipe bending apparatus for carrying out the method of the present invention.
FIG. 2 is a schematic longitudinal sectional view showing the steel pipe bending apparatus of FIG.
3 is a schematic longitudinal sectional view similar to FIG. 1, showing a state where a PVC steel pipe is bent by the steel pipe bending apparatus of FIG.
FIG. 4 is a side view showing a receiving part and a movable part of the clamp holder.
FIG. 5 is a partial cross-sectional view of a side surface of a pressure holder and a bending die.
FIG. 6 is a schematic longitudinal sectional view showing a modification of the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel pipe part 2 PVC pipe part 3 PVC steel pipe 3a Bending part 5 Clamp holder 6 Pressure holder 7 Bending die 8 Core metal 10 Heater 17 Slide holder

Claims

The front part of the straight steel pipe is tightened with a clamp holder and the bent part is compressed with a pressure holder, and the clamp holder, pressure holder and bending die are provided with a semicircular groove on the surface in pressure contact with the steel pipe. Since the semicircular grooves have a slightly horizontally long cross section, the front portion of the steel pipe is further tightened with the clamp holder while the steel pipe is held horizontally, and the bent portion is compressed with the pressure holder and the bending die. As a result, the bent portion of the steel pipe and the vicinity thereof are compressed and deformed into a slightly horizontally long circular cross section, and then the clamp holder and the bending die are rotated and the slide holder is pushed forward to cross the bent portion of the steel pipe. A method of bending a steel pipe that is curved so that the surface is almost circular.

For vinyl chloride steel pipe on the outside is brought into close contact with fitted portion PVC pipes of steel parts in accordance with the fitting further desired vinyl chloride pipe portion inside of the steel pipe section, ahead of the bent portion of the linear vinyl chloride steel thereby compressing the clamping and the bent portion at the clamping holder by pressure holder the part, pushing the core bar from the rear side of the vinyl chloride steel into the tube portion, the tip of said cardiac gold with wiring the heater inside the said cardiac gold A method of bending a steel pipe, in which a displaceable disk part is connected with a wire and a heater is embedded in the disk part to heat the inner pipe part.

For vinyl chloride steel pipe on the outside is brought into close contact with fitted portion PVC pipes of steel parts in accordance with the fitting further desired vinyl chloride pipe portion inside of the steel pipe section, ahead of the bent portion of the linear vinyl chloride steel thereby compressing the clamping and the bent portion at the clamping holder by pressure holder the part, pushing the core bar from the rear side of the vinyl chloride steel into the tube section, and configured to blow the hot air from said cardiac gold, inside the hot air spraying the PVC pipe section, the method bending of the steel pipe to be bent is heated to be bent portion of the vinyl chloride pipe section.

For vinyl chloride steel pipe on the outside is brought into close contact with fitted portion PVC pipes of steel parts in accordance with the fitting further desired vinyl chloride pipe portion inside of the steel pipe section, ahead of the bent portion of the linear vinyl chloride steel the tightening and the bent portion of the parts in the clamp holder with compressed by pressure holder, and pressure filled with hot water in the interior of the vinyl chloride steel is heated inside the vinyl tube chloride unit, the vinyl chloride steel pipe at a low temperature phase A method of bending a steel pipe that prevents cracking of the vinyl chloride pipe part when the bent part is bent along the outer peripheral surface of the bending die .

Mounting a blind flange at one end of the vinyl chloride steel, hot water from the vinyl chloride steel pipe disposed vertically and injected under pressure, according to claim 4, wherein for closing the blind flange at the other end of the steel tube after the hot water injection Bending method.