JP3756652B2

JP3756652B2 - Pipe fitting

Info

Publication number: JP3756652B2
Application number: JP01504698A
Authority: JP
Inventors: 和士丸山; 治之永吉; 英司津留
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1998-01-08
Filing date: 1998-01-08
Publication date: 2006-03-15
Anticipated expiration: 2018-01-08
Also published as: JPH11201344A

Description

【０００１】
【発明の属する技術分野】
本発明は、油井管、土木杭管等のテーパねじ継手において、ピンのテーパ雄ねじ部をボックスのテーパ雌ねじ部に垂直方向に差し込み、引き続き回転して締め込む際に、作業性を向上可能な管継手に関する。
【０００２】
【従来の技術】
従来、油（ガス）井の坑井保護、採油及び掘削に使用される油井管（ケーシングパイプ、チュービングパイプ、ドリルパイプ）又は土木用鋼管杭等、施工又は使用時に鋼管を縦方向に継いでいく管用テーパねじ継手に関して、ピンのテーパ雄ねじ部をボックスのテーパ雌ねじ部に垂直方向に差し込み、初期ねじ込みを開始するまでの作業（スタビング性）及びその後のねじ込み作業を容易かつ迅速にする管継手の一例として、図９（Ａ）に示すような形態の管継手５０ａが知られている。管継手５０ａにおいては、管５０のピン５１のテーパ雄ねじ部５２と短管５３のボックス５４のテーパ雌ねじ部５５が嵌合する管用テーパ角ねじ継手が使用されている。この管用テーパ角ねじ継手のねじ込み開始の状況を図９（Ｂ）に拡大図で示している。
管用テーパ角ねじ継手のスタビング性を判りやすく説明するために、テーパ雄ねじ部５２及びテーパ雌ねじ部５５の雄、雌ねじ山５６、５７の形状を同一とし、それぞれの雄、雌ねじ山頂面５８、５９はテーパ面Ｔ_fに平行とする。図に示す嵌合断面図は、まさに雄ねじ山５６が雌ねじ山５７に噛み込もうとするところを示している。つまり、テーパ雄ねじ部５２の雄ねじ山頂面５８を連ねたテーパ面とテーパ雌ねじ部５５の雌ねじ山頂面５９を連ねたテーパ面が丁度競っており、かつ雄ねじ山５６が雌ねじ山５７の谷部６０に位置するように、テーパ雄ねじ部５２の円周方向位置とテーパ雌ねじ部５５の円周方向位置を揃えた図としている。図から明らかなように、このままのねじ形状ではテーパ雄ねじ部５２をテーパ雌ねじ部５５にねじ込むことは不可能である。
【０００３】
ここで、管用テーパ角ねじ継手のスタビング性の正体について明らかにするために、図１０（Ｂ）に示すように、油井管ねじとして広く用いられているＡＰＩバットレスねじ継手の場合を例にして、いかにしてテーパ雄ねじ部６１がテーパ雌ねじ部６２に差し込まれた後、雄、雌ねじ山６３、６４がねじ込まれる仕掛けになっているかを説明する。
ＡＰＩバットレスねじ要素は、テーパＴ＝１／１６（又は６２．５ｍｍ／ｍ、直径に対する変化率）、ピッチＰ＝５．０８ｍｍ、ねじ山高さＨ＝１．５７５ｍｍ、スタビングフランク角η＝１０°、ロードフランク角γ＝３°、雄、雌ねじ山頂面６５、６６の直線部はテーパ面Ｔ_p（即ち、ピッチライン）に平行、雄、雌ねじ山頂面６５、６６のコーナＲ＝０．７６ｍｍ、又は０．２０ｍｍなどを特徴としている。
図１０（Ａ）はテーパ雄ねじ部６１とテーパ雌ねじ部６２がねじ込みのために最も都合の良い周方向に填まり込んだ状況を示している。前記管用テーパ角ねじ継手の場合とは異なり、テーパ雌ねじ部６２の谷部６７の開口部６８は雄ねじ山６３の雄ねじ山頂面６５より幅広くできており、この状態からテーパ雄ねじ部６１を下方に落下させると、テーパ雄ねじ部６１の雄ねじ山６３のコーナ部６９は、テーパ雌ねじ部６２の雌ねじ山６４のコーナ部７０に僅かに載ることができ、その状態からテーパ雄ねじ部６１を回せば、テーパ雄ねじ部６１は螺旋に沿って填まり込んでいくことになる。
【０００４】
また、このようにテーパ雄ねじ部６１がテーパ雌ねじ部６２に填まり込むためには、必ずしも雄ねじ列と雌ねじ列の相対位置は図１０（Ａ）の通りでなくてもよく、雄ねじ山６３のスタビングフランク面７１のコーナＲが雌ねじ山６４のスタビングフランク面７２のコーナＲに接するところまで、テーパ雄ねじ部６１を図１０（Ａ）の位置より下方にずらせた位置でも、テーパ雄ねじ部６１はテーパ雌ねじ部６２に填まり込むことができる。つまり、このずれに相当する周方向角度の分だけ、テーパ雄ねじ部６１をテーパ雌ねじ部６２に差し込んだ時、旨くねじ込むための周方向範囲に裕度を持たせることができる。
通常の差し込み、ねじ込み開始作業では、テーパ雄ねじ部６１をテーパ雌ねじ部６２に差し込み、旨くテーパ雄ねじ部６１の雄ねじ山６３をテーパ雌ねじ部６２の雌ねじ山６４に預けることのできる前記周方向位置まで、テーパ雄ねじ部６１を回転させる。この時は、まだ雄ねじ山６３と雌ねじ山６４は噛み合っていないので、テーパ雄、雌ねじ部６１、６２のそれぞれの軸心が一致していないとかじりを起こすこともあり、直径の大きい鋼管では、回転角が大きいと作業も大変である。従って、雄ねじ山６３と雌ねじ山６４が噛み込める周方向位置の範囲が広い程、適切な場所まで回転させる回転角を小さくすることができ、スタビング性の良いテーパねじ継手といえる。また、テーパ雌ねじ部６２の谷部６７の開口部６８の幅Ｗと雄ねじ山頂面６５の幅Ｖとの隙間Ｇが大きいことの利点は、この隙間Ｇ分だけテーパ雄ねじ部６１を落とし込んでテーパ雌ねじ部６２の雌ねじ山６４のスタビングフランク面７２に預けた時、（管軸方向の隙間Ｇ×テーパＴ）／２の半径方向預け代が確保できるので、安定したねじ込みができることである。
【０００５】
以上の説明から判るように、スタビング性は、テーパ雄ねじ部６１をテーパ雌ねじ部６２に差し込んだ時、その位置からそのままねじ込みを開始することが可能な円周方向の範囲（θ）が広い程、またねじ込みを開始する時、雄ねじ山６３のスタビングフランク面７１を雌ねじ山６４のスタビングフランク面７２に預けている奥行きδ（前記半径方向預け代と同じ）が広い程、良好ということになる。そこで、このスタビング性を支配するθ、δを大きく取るために、従来のテーパねじ継手の形態について幾つかの例で説明する。
まず、ＡＰＩバットレスねじ継手について説明すると、図１０（Ｂ）に示すように、第１にテーパ雄ねじ部６１の雄ねじ山６３のスタビングフランク面７１の角度、即ちスタビングフランク角ηを管軸Ｃに垂直な面から１０°傾けている。このスタビングフランク角ηの傾きが大きい程、填まり込みの隙間Ｇは広くなる。第２に、テーパ雄ねじ部６１の雄ねじ山６３のスタビングフランク面７１のコーナ部６９のＲ＝０．７６ｍｍをとり、さらにこの隙間Ｇを広げている。その他、テーパ雄ねじ部６１を僅かに（直径で０．０３ｍｍ）テーパ雌ねじ部６２より痩せたねじにしたり、雄、雌ねじ山頂面６５、６６とロードフランク面７３、７４とのコーナ部７５、７６のＲを僅かにとる（図１０（Ｂ）ではＲ＝０．２０ｍｍ）ことに依っても僅かに隙間Ｇを広げている。この場合の全ての隙間の総和は約１．７５ｍｍと試算される。これを円周方向の範囲（θ）に換算すると、θ＝（３６０°×１．７５）／５．０８＝１２４°となる。一方、奥行き（δ）はδ＝１．７５／３２＝０．０５５ｍｍとなる。図９の角ねじに比べねじ込みの範囲がでてきているが、積極的にねじ込み易くしているとは言えない。
【０００６】
また、ＡＲＭＣＯ社製のＳＥＡＬ−ＬＯＣＫ継手について説明すると、この特殊継手においては、第１に差し込み側のスタビングフランク角ηを管軸に垂直な面に対して４５°傾けることにより、実質的に雌ねじ山の谷部の幅を広げ、スタビング時、テーパ雄ねじ部の雄ねじ山をテーパ雌ねじ部の谷部に収め易くしている。第２に、雄、雌ねじ山頂面を管軸に平行とし、テーパ雄ねじ部をテーパ雌ねじ部に差し込む時、雄ねじ山と雌ねじ山同士が競るところを少なくしている。
さらに、ＶＥＴＣＯ−ＧＲＡＹ社製の特殊継手においては、４条ねじを適用することにより、一周３６０°の内、４ヶ所のねじ込み可能箇所ができるので、テーパ雄ねじ部をテーパ雌ねじ部に差し込み後、僅かの回転調整にて容易にねじ込みができる。なお、通常の１条ねじでは、ねじ込み可能箇所は１カ所である。さらに、多条ねじ（ｎ条）の最大の特徴は、一旦ねじ込みを開始すると１条ねじに比べ、締まり込み完了までの回転数が１／ｎになることである。このことは、ロープなどで締め込みを行なう大径の継手では非常に重要な要素である。
他の特殊継手として、テーパ雌ねじ部の入り口を長くする（スタビングガイドを設ける）ことにより、テーパ雄ねじ部をテーパ雌ねじ部に差し込む時斜めにならないようにしているものがある。
【０００７】
【発明が解決しようとする課題】
しかしながら、前記従来の管継手においては、未だ解決すべき以下のような問題があった。
１条ねじの形態のものでは、差し込み位置が必ずしもねじ込み開始位置とならず、ねじ込み位置を探るためテーパ雄ねじ部を回転しなければならないという問題があった。
一方、４条ねじを含む多条ねじの形態のものでは、ねじ込み可能箇所が条数だけ存在するので、調整の為の回転を少なくでき、これによって１条ねじに比べてかなりスタビング性は改善されるが、それでもいつも差し込み位置から直ちにねじ込むことは不可能である。
また、スタビングガイドを備えた形態のものでは、ねじの斜め差し込みによるかじりなどのトラブルは防げても、本質的に差し込み後直ちにねじ込みを行なうためのものではない。
【０００８】
本発明はこのような事情に鑑みてなされたもので、多条ねじを有するテーパ雄ねじ部をテーパ雌ねじ部に差し込んだ位置から、そのまま迅速かつ容易にねじ込むことが可能な管継手を提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記目的に沿う請求項１記載の管継手は、管の先端部の外周面にテーパ雄ねじ部を形成したピンと、短管の両端部の内周面に前記テーパ雄ねじ部に螺合するテーパ雌ねじ部を形成したボックスとをねじ込む管継手において、多条ねじを適用し、奇数条の場合は、（条数−１）山おきに配置された高い雄、雌ねじ山と、該高い雄、雌ねじ山間に配置された低い雄、雌ねじ山とからなるねじ列とし、偶数条の場合は、高い雄、雌ねじ山と低い雄、雌ねじ山とを交互に配置したねじ列とするか、又は（条数−１）山おきに配置された高い雄、雌ねじ山と、該高い雄、雌ねじ山間に配置された低い雄、雌ねじ山とからなるねじ列とする。
請求項２記載の管継手は、請求項１記載の管継手において、前記雄ねじ山のねじ山頂面と前記雌ねじ山のねじ山頂面は、角ねじ又は台形ねじのように所定の幅を有し、前記両ねじ山頂面を、管軸に平行な面に対して平行又は、ねじ列テーパ面と反対方向に傾斜させる。
請求項３記載の管継手は、請求項１記載の管継手において、前記雄ねじ山のねじ山頂面と前記雌ねじ山のねじ山頂面は、角ねじ又は台形ねじのように所定の幅を有し、前記両ねじ山頂面の一部を管軸に平行にすると共に、残りの該両ねじ山頂面を前記管軸に平行な面に対してねじ列テーパ面と反対方向に傾斜させる。
【００１０】
請求項４記載の管継手は、請求項１〜３のいずれか１項に記載の管継手において、前記テーパ雄ねじ部を前記テーパ雌ねじ部に差し込む際、前記雄ねじ山のねじ山頂面に接する仮想テーパ面と前記雌ねじ山のねじ山頂面に接する仮想テーパ面とが競り合う状態において、そのまま前記テーパ雄ねじ部を鉛直方向に下げると前記雄ねじ山のねじ山頂面が前記雌ねじ山のねじ山頂面に競ることなく、前記雄ねじ山のスタビングフランク面が前記雌ねじ山のスタビングフランク面に重なることが可能な元の雄ねじ列と雌ねじ列との位置関係を再現できるように、ねじ切り加工時に前記テーパ雄ねじ部及び前記テーパ雌ねじ部の円周方向に符合させる印を付けている。
請求項５記載の管継手は、請求項１〜４のいずれか１項に記載の管継手において、ねじ切り加工時の前記テーパ雄ねじ部及び前記テーパ雌ねじ部のそれぞれのねじ列テーパ面の相対的直径誤差を考慮して、ねじの加工誤差を考慮しない理想的な雄ねじ列及び雄ねじ列の差し込み直後のねじ込みを可能とする所定範囲の適正位置関係の内、前記テーパ雄ねじ部の雄ねじ山のねじ山頂面とスタビングフランク面とのコーナ部の位置が常に適正範囲の中央に来るようにしている。
請求項６記載の管継手は、請求項５記載の管継手において、理想状態において、前記適正範囲が前記ねじの加工誤差より大きい。
請求項７記載の管継手は、請求項１〜６のいずれか１項に記載の管継手において、前記テーパ雌ねじ部の管端部に該テーパ雌ねじ部に続くスタビングガイドを備えている。
【００１１】
本発明は、以下に説明する考え方に基づいてなされたものである。
テーパ雄ねじ部をテーパ雌ねじ部に真っ直ぐ差し込んだ時の態様には以下の３通りの場合がある。第１は、雄、雌ねじ山同士が競ってしまう時、第２は、雄、雌ねじ山が部分的に競ってしまう時、第３は、テーパ雄ねじ部の雄ねじ山のねじ山頂面がテーパ雌ねじ部の雌ねじ山の谷部に重なり引き続きテーパ雄ねじ部の雄ねじ山の側面（スタビングフランク面）が雌ねじ山の側面（スタビングフランク面）に着地するときである。
本発明が目的とする、差し込んだ後直ぐにねじ込みを可能にするためには、テーパ雄ねじ部をテーパ雌ねじ部に差し込んだ後、常に前記第３の状態になるように雄、雌ねじ山の形状やねじ切り加工方法を工夫することが必要となる。本発明では、この第３の状態を常に再現させるために、次の４つの要素技術を採用している。
【００１２】
第１の要素技術は、図２に示すように、テーパ雄ねじ部１１とテーパ雌ねじ部１２の軸方向のねじ山の相対位置が常に第３の状態になるように、ねじ切り加工時にテーパ雄ねじ部１１の先端２０からの雄ねじ山１３のねじ山頂面１４の差し込み側のスタビングフランク面１５のコーナの座標（ｒ、Ｚ_m）を予め決定しておき、それが通過するパイプ１６（又は管と呼ぶ）の円周方向位置に印Ｓ₁（図示せず）を付け、同時に、図２に示すように、雄ねじ山１３のスタビングフランク面１５のコーナが填まり込みを開始する雌ねじ山１７の谷部１８が座標（ｒ、Ｚ_f）になるようにパイプ１９（又は短管と呼ぶ）のテーパ雌ねじ部１２の先端２０ａの円周方向にも印Ｓ₂（図示せず）を付け、差し込み時にそれらの印Ｓ₁、Ｓ₂同士が重なるようにテーパ雄、雌ねじ部１１、１２の円周方向位置を決め、管継手１０のねじ込み作業を行なう。
第２の要素技術は、１リード内の多条ねじ山の一部を他のねじ山の高さより低くすることにより、スタビング時、雄、雌ねじ山同士が競り合う確率を小さくすることである。これは、ねじ山の低い部分を実質的には、１条ねじの谷部とみなすことに等しい。従って、２条ねじの場合は、テーパ雄ねじ部の雄ねじ山のねじ山頂面の幅の３倍の谷部の幅があることになり、スタビング時、雄ねじ山はテーパ雌ねじ部の谷部に容易に収まることになる。
【００１３】
第３の要素技術は、第２の要素技術における高い雄、雌ねじ山同士の競り合いをも回避しようとする考えに基づくもので、高いねじ山頂面をねじ列テーパ面と管軸に対し反対側に傾斜させることにより、雄、雌ねじ山同士が面で接するのを点で接するようにしている。図２に示すように、テーパ雄、雌ねじ部１１、１２の雄、雌ねじ山１３、１７のねじ山頂面１４、２２を管軸Ｃに平行な面Ｄ（図２中破線）より僅かに雄、雌ねじ列の仮想テーパ面Ｔ（図２中２点鎖線）と逆方向のテーパ面Ｅ（図２中実線）とすることである。
第４の要素技術は、図２に示すように、ねじの加工公差を考慮して、理屈の上でテーパ雄ねじ部１１がテーパ雌ねじ部１２に差し込み状態からそのままねじ込める軸方向範囲が、ねじのスタンドオフ公差（又は相対的直径誤差とも呼び、テーパねじの直径公差を長さ方向に換算した値であって、ＡＰＩバットレスねじ継手の場合、１／２ピッチ）より大きくなるようにする。
【００１４】
第２、第３の要素技術が満足されていれば、理屈の上ではテーパ雄ねじ部を円周方向のどの位置で差し込んでも、そのままねじ込みが可能であるが、テーパ雄ねじ部の雄ねじ山のスタビングフランク面をテーパ雌ねじ部の雌ねじ山のスタビングフランク面に安定して着地させるには、ねじのスタンドオフ公差が差し込み後直ぐにねじ込める許容範囲の中心に来るようにし、尚かつスタンドオフ公差の小さい、精度良いねじ加工を行なうようにするのが好ましい。
本発明は、第２、第３の要素技術だけで、３６０°テーパ雌ねじ部１２のどの位置にテーパ雄ねじ部１１を差し込んでも、そのままねじ込むことを可能とするが、実際にはねじの公差、ねじ込み時の僅かなテーパ雄ねじ部１１とテーパ雌ねじ部１２のそれぞれの軸の傾きも考慮して、安定してこのスタビング性を確保できるように、第１の要素技術に示すねじ切り加工時の差し込み位置を指定する印Ｓ₁、Ｓ₂及び第４の要素技術におけるねじのスタンドオフ公差を考慮した最適差し込み位置の考え方をも考慮したものであり、各要素技術を単独もしくは、組み合わせて適用することにより、効果的なスタビング性、迅速締め込み性、継手強度低下の抑制を同時に満足させることができる。
【００１５】
本発明は、雄、雌ねじ部を２段に分けた多条ねじ継手でも、またねじ列のどこかにテーパねじ部を具備する多条ねじ継手でも、それら全てに適用できることは言うまでもない。（図６（Ｃ）及び（Ｄ）参照）。
さらに、既述のスタビングガイドの考えと組み合わせることにより、斜めねじ込み時に予想されるねじのかじり（クロススレッド）を防止し、テーパ雄ねじ部のテーパ雌ねじ部へのスタビングからねじ込みまでの一連の作業を省力化することも可能としている。
【００１６】
【発明の実施の形態】
続いて、添付した図面を参照しつつ、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。
ここに、図１は本発明の一実施の形態に係る管継手が適用されるテーパねじ継手のスタビングフランク面の重なりが最大となる差し込み位置状態を説明する断面図、図２は同テーパねじ継手の差し込み適正範囲の状態を説明する断面図、図３は同テーパねじ継手の嵌合状態を説明する断面図、図４は同テーパねじ継手が３条の場合のねじ形状の断面図、図５は同テーパねじ継手が４条の場合のねじ形状の断面図、図６は本発明の一実施の形態に係る管継手の変形例の断面図、図７は同管継手の実施例の嵌合状態での寸法図、図８は同詳細寸法図である。
【００１７】
図６に示す本発明の一実施の形態に係る管継手が適用されるテーパねじ継手の形状において、（Ａ）は締結ねじのみを備えた管継手、（Ｂ）はねじ嵌合部の先端部に金属シール部を具備する管継手、（Ｃ）は（Ａ）又は（Ｂ）の一様テーパねじ部を２段に分けた管継手、（Ｄ）は（Ａ）又は（Ｂ）の一様テーパねじ部の一部に平行ねじ部を代替した管継手である。雄、雌ねじテーパ部の相対的太さを一定に管理するためには、テーパ雄ねじ部ならば、その先端からある軸方向位置のねじ有効径を一定に加工し、一方テーパ雌ねじ部ならば、継手入口からのある軸方向深さのねじ有効径を一定に加工する。
【００１８】
図１は、一山毎にねじ山高さを変えた、ねじリードＬ（図２を参照）、ピッチｐ（Ｌ／２）の２条ねじからなるテーパ雄、雌ねじ部１１、１２において、雄ねじ山１３、１３ａ、雌ねじ山１７、１７ａが、それぞれのねじ山頂面１４、２２の点と仮想テーパＴが接する状態で、尚かつ雄ねじ山１３のスタビングフランク面１５とねじ山頂面１４とのコーナ部２４が、テーパ雌ねじ部１２の雌ねじ山１７のスタビングフランク面２５とねじ山頂面２２とのコーナ部２７に接した状態、即ち差し込み位置の状態を示している。なお、雄ねじ山１３ａ及び雌ねじ山１７ａにおいて、雄ねじ山１３、雌ねじ山１７の各要素に対応するものには、図に添字ａを付けて説明している。
この状態から、テーパ雄ねじ部１１の雄ねじ山１３のコーナ部２４がテーパ雌ねじ部１２の雌ねじ山１７のコーナ部２７をすり抜ければ、コーナ部２４は管継手１０の管軸Ｃに平行な面Ｄ（破線で示す）に沿って下方に落下し、一つ下の雌ねじ山１７ａを僅かにかわして、その下の雌ねじ山１７のスタビングフランク面２５の点２８に着地する。つまり、高さの低い雄ねじ山１３ａ、雌ねじ山１７ａを、高さの高い雄ねじ山１３が、高さの高い雌ねじ山１７に着地するのに妨げとならない程度に低くしておけばよい。こうして首尾よく、高さの高い雄ねじ山１３のスタビングフランク面１５が、高さの高い雌ねじ山１７のスタビングフランク面２５に重なれば、この時の雄ねじ山１３と雌ねじ山１７の重なりｗは最大となる。
【００１９】
このように雄ねじ山１３のスタビングフランク面１５が旨く雌ねじ山１７のスタビングフランク面２５に着地できるのは、図から明らかなように、一つおきに低いねじ山を配置していることに加え、角ねじ又は台形ねじのように所定の幅を有する雄ねじ山１３のねじ山頂面１４と雌ねじ山１７のねじ山頂面２２とが、差し込み時に競り合うことがないように、管軸Ｃに平行な面Ｄに対してねじテーパ角αと反対側にスタビング逃げ角βを設けて傾斜しているからである。理想的にはこれらねじ山頂面１４、２２は管軸Ｃに平行（図１の破線の補足線）でも競り合うことはないが、テーパ雄ねじ部１１の差し込み時には僅かな傾きがあるので、実際には雄、雌ねじ山１３、１７同士が競り合うこともあり得る。スタビング逃げ角βは大きい方がねじ込み容易性には優れるが、反面大き過ぎると継手引張時に荷重を受け持つロードフランク面２３、２３ａの高さｈが低くなり、テーパ雄ねじ部１１がテーパ雌ねじ部１２から抜け易くなる問題があるので、必要以上に大きくすることは適当でない。特に、雄ねじ山１３、１３ａ、雌ねじ山１７、１７ａの高さを低くすること自体でねじ山高さを犠牲にしているので、ねじ山頂面１４、２２の傾斜角はこの点も考慮して、必要ねじ高さを確保するように決定する。なお、図１及び図２中符号１６はパイプ、１８は谷部、１９はパイプ、２６は雌ねじ山１７のロードフランク面を示す。
【００２０】
図２に示す管継手１０は、雄ねじ山１３のコーナ部２４が仮想テーパ面Ｔに接して止まる位置が、図１の場合に比べて１ピッチＰだけねじ込み方向に進み、図のねじリードＬの中央に位置する状態を示す。テーパ雄ねじ部１１の雄ねじ山１３のコーナ部２４をねじリードＬの中央に設定している理由は、ねじのスタンドオフ公差及び僅かでも傾きを伴ったスタビング作業であっても、雄ねじ山１３のスタビングフランク面１５を安定してテーパ雌ねじ部１２の雌ねじ山１７のスタビングフランク面２５に着地させるためである。ねじのスタンドオフ公差による雄ねじ山１３の雌ねじ山１７に対する相対的ずれの範囲は、スタンドオフ公差をそれぞれｓとすれば、図２に示すｓの範囲となる。
もしコーナ部２４がｓの範囲の上方端に偏れば、雌ねじ山１７のコーナ部２７をすり抜け難い方向となり、一方、反対にｓの範囲の下方端に偏れば、雌ねじ山１７のコーナ部２７までの距離が近くなり、着地時の両方のスタビングフランク面１５、２５の重なりが狭くなるので、安定がよくない方向となる。
【００２１】
従って、ねじ切り時の刃物パス計算においては、雄ねじ山１３と雌ねじ山１７の仮想テーパ面Ｔが接した状態において、図２のコーナ部２４（図中○）が雌ねじ山１７のねじリードＬの中央に位置するようにパスデザインする必要があり、ねじのスタンドオフ公差が小さく、精度の良いテーパねじ加工が必要となる。○を刃物の基準位置と考えれば、それらが雄ねじ切りパスでは、（ｒ、Ｚ_m）を通過するように、一方、雌ねじ切りパスでは、（ｒ、Ｚ_f）を通過するように、ねじ切り開始時の雄ねじ切り刃物、雌ねじ切り刃物とパイプ１６、１９それぞれとの関係を設定し、その時の刃物運動面がそれぞれパイプ１６、１９と交わるパイプ１６、１９の周方向位置に印Ｓ₁、Ｓ₂を付けておく。こうすることで、印Ｓ₁、Ｓ₂の付いたテーパ雄ねじ部１１とテーパ雌ねじ部１２をその印Ｓ₁、Ｓ₂の位置を円周方向に一致させて差し込めば、必ず図２に示す位置関係、即ち雄、雌ねじ山１３、１７のねじ山頂面１４、２２が競ることなく、雄ねじ山１３のスタビングフランク面１５が雌ねじ山１７のスタビングフランク面２５に重なることが可能な元の雄ねじ列と雌ねじ列との位置関係を再現でき、円滑なテーパ雄ねじ部１１の差し込み及びそれに続くねじ込みが可能となる。
【００２２】
図３は管継手１０のテーパ雄ねじ部１１とテーパ雌ねじ部１２とが締め付けを終了した状態、即ち嵌合状態を示している。
本実施の形態に係る管継手１０の場合のテーパねじ形状の特徴は、スタビングフランク面１５、１５ａ、２５、２５ａに比べロードフランク面２３、２３ａ、、２６、２６ａの高さが低くなることである。このことは先に述べたテーパ雄ねじ部１１の抜けを惹起する可能性があるので、その抵抗を高めるために次の２つの方法を採用している。
第１は、図３に示すように、ロードフランク面２３ａ、２６ａを管軸Ｃに対する垂直面Ｖ_sより抜け難い方に角度γだけ傾けることである。
第２は雄、雌ねじ山１３、１７のねじ山頂面１４、２２の全面をスタビング逃げ角βとするのでなく、スタビングフランク面１５、１５ａ、２５、２５ａに近い側のみスタビング逃げ角βとし、残りのロードフランク面２３、２３ａ、２６、２６ａに近い側を平行とするか、逆にスタビングフランク面１５、１５ａ、２５、２５ａに近い側のみ平行とし、残りのロードフランク面２３、２３ａ、２６、２６ａ側にスタビング逃げ角度βを適用することにより、少しでもロードフランク面２３、２３ａ、２６、２６ａの高さｈが低くなるのを回避している。なお、図３中の破線は、ねじ山頂面１４、２２を管軸Ｃに平行にした場合の補足線で、ロードフランク面２３、２３ａ、２６、２６ａの嵌合高さの改善代を示している。
【００２３】
以上、２条ねじの例を詳しく述べてきたが、締め込みは条数が増す程速くなる。そこで、３条ねじ、４条ねじについても、ねじ山の高さの高低の付け方について触れておく。図４（Ａ）は３条ねじで、高いねじ山を２つおき、即ち（条数−１）山おきに配置した場合を示す。
雄ねじ山１３ｃは、雌ねじ山１７ｃをすり抜けた状態で、雌ねじ山１７ｄに着地が見通せる位置にある。スタビングフランク面の重なりも広く取れ、ねじリードＬ内の広い範囲で安定して雌ねじ山１７ｄに着地可能である。しかし、嵌合した状態（二点鎖線）を想像すると、嵌合高さが図示のように狭くなる欠点がを併せ持つことになる。なお、図４（Ａ）中符号１３ｄは高さの高い雄ねじ山を示す。
【００２４】
図４（Ｂ）は、この欠点を解消するため、スタビング位置と着地幅を犠牲にして、高さの高い雌ねじ山１７ｅ、１７ｆの中間の雌ねじ山１７ｇ、１７ｈの高さを高めにしたものである。雄ねじ山１３ｅ、１３ｆはそれぞれ雌ねじ山１７ｈ、１７ｆに着地可能である。なお、図４（Ｂ）中符号１３ｇ、１３ｈも雄ねじ山を示す。
図５（Ａ）は４条ねじで、高いねじ山を１つおきに配置した場合を示す。スタビング性（差し込みからねじ込みまでの作業性）及びねじ嵌合状況を２条ねじと同様とし、ねじ込み速さを２条ねじの倍にできる。雄ねじ山１３ｉ、１３ｋはそれぞれ雌ねじ山１７ｋ、１７ｎに着地可能である。
図５（Ｂ）は４条ねじで、高いねじ山を３つおき、即ち（条数−１）山おきに配置した場合を示す。雄ねじ山１３ｐは雌ねじ山１７ｐをすり抜けた状態で、雌ねじ山１７ｔに着地が見通せる位置にある。図４（Ａ）と同様、スタビング性は良好であるが、継手効率を犠牲にしている。ねじ切り工程で雄ねじ山と雌ねじ山のねじ列相対位置が、制御できるのであれば、図４（Ｂ）及び図５（Ａ）の場合でも、スタビング性には十分余裕があるので、図４（Ａ）及び図５（Ｂ）タイプのねじ山を高低配列したものより、図４（Ｂ）及び図５（Ａ）の方が継手効率も勘案するのであれば、適当である。
【００２５】
また、このように条数を増やしても、スタビング時、雄ねじ山の通り抜けをよくするために、高いねじ山のねじ山頂面にねじ列テーパ面と反対の傾斜を付けたり、丁度いい位置に填まり込むようにねじ加工時、パイプに印を付けておくなどの技術的考え方は、上述の２条ねじの場合と同様である。
【００２６】
【実施例】
続いて、前記実施の形態に係る管継手の実施例について、図７及び図８（Ａ）及び（Ｂ）を参照しながら説明する。図７及び図８は、７インチのＡＰＩバットレスねじ継手を原形とし、前記実施の形態に係る管継手を基にスタビング性及び迅速締め込み性を改良した継手である。なお、図７は管継手の嵌合状態での取り合い寸法を示す断面図である。
ＡＰＩバットレスねじ継手と異なるねじ諸元は、２条ねじとしていること、ピン、ボックスそれぞれの雄、雌ねじ山のねじ山頂面が管軸Ｃに対してねじ列テーパ面ＰＴ、ＢＴと反対側に３°傾斜し、ロードフランク面が管軸Ｃに垂直な面に対して、ＡＰＩバットレスねじ継手の場合とは反対方向に３°傾斜し、さらにスタビングフランク面を３０°傾斜している点である。
【００２７】
このような要領でねじ継手加工を行い、テーパ雄ねじ部をテーパ雌ねじ部に差し込んで、その状態からそのままねじ込みが可能かどうか試した。その結果、管軸Ｃが傾かないようにテーパ雄ねじ部をテーパ雌ねじ部に注意深く挿入すれば、３６０°のどの位置に差し込んでも、そのままねじ込むことが可能であることを確認した。
また、当然であるが、２条ねじとしているため、締め込み回転数も通常のＡＰＩバットレスねじ継手の半分にできた。さらに、軸芯ずれをなくすために、テーパ雌ねじ部の先端（又は管端部とも呼ぶ）に２００ｍｍの円筒をスタビングガイドとして溶接して、同じ作業を実施したところ、芯合わせに神経を使うことなくスタビング、ねじ込みの連続作業が可能であることも確認できた。
【００２８】
【発明の効果】
請求項１〜７記載の管継手においては、多条ねじを適用し、奇数条の場合は、（条数−１）山おきに配置された高い雄、雌ねじ山と、高い雄、雌ねじ山間に配置された低い雄、雌ねじ山とからなるねじ列とし、偶数条の場合は、高い雄、雌ねじ山と低い雄、雌ねじ山とを交互に配置したねじ列とするか、又は（条数−１）山おきに配置された高い雄、雌ねじ山と、該高い雄、雌ねじ山間に配置された低い雄、雌ねじ山とからなるねじ列としているので、１ねじリード内の多条ねじの山形状を工夫することにより、テーパ雄ねじ部の差し込み位置からそのままねじ込むことができると共に、ねじ込み作業を容易かつ迅速に行なうことができる。
特に、請求項２記載の管継手においては、雄ねじ山のねじ山頂面と雌ねじ山のねじ山頂面は、角ねじ又は台形ねじのように所定の幅を有し、両ねじ山頂面を、管軸に平行な面に対して平行又は、ねじ列テーパ面と反対方向に傾斜させているので、テーパ雄ねじ部を３６０°のどの位置で差し込んでも差し込み及びそれに続くねじ込みの連続作業がより円滑に行なえる。
請求項３記載の管継手においては、雄ねじ山のねじ山頂面と雌ねじ山のねじ山頂面は、角ねじ又は台形ねじのように所定の幅を有し、両ねじ山頂面の一部を管軸に平行にすると共に、残りの両ねじ山頂面を管軸に平行な面に対してねじ列テーパ面と反対方向に傾斜させているので、ロードフランク面の高さを大きく保つことができ、抜け難いねじ継手形状にできる。
【００２９】
請求項４記載の管継手においては、テーパ雄ねじ部をテーパ雌ねじ部に差し込む際、雄ねじ山のねじ山頂面に接する仮想テーパ面と雌ねじ山のねじ山頂面に接する仮想テーパ面とが競り合う状態において、そのままテーパ雄ねじ部を鉛直方向に下げると雄ねじ山のねじ山頂面が雌ねじ山のねじ山頂面に競ることなく、雄ねじ山のスタビングフランク面が雌ねじ山のスタビングフランク面に重なることが可能な元の雄ねじ列と雌ねじ列との位置関係を再現できるように、ねじ切り加工時にテーパ雄ねじ部及びテーパ雌ねじ部の円周方向に符合させる印を付けているので、テーパ雄ねじ部の差し込み位置からそのままねじ込むことができると共に、ねじ込み作業をさらに容易かつ迅速に行なうことができる。
請求項５記載の管継手においては、ねじ切り加工時のテーパ雄ねじ部及びテーパ雌ねじ部のそれぞれのねじ列テーパ面の相対的直径誤差を考慮して、ねじの加工誤差を考慮しない理想的な雄ねじ列及び雄ねじ列の差し込み直後のねじ込みを可能とする所定範囲の適正位置関係の内、テーパ雄ねじ部の雄ねじ山のねじ山頂面とスタビングフランク面とのコーナ部の位置が常に適正範囲の中央に来るようにしているので、ねじの加工誤差に無関係にテーパ雄ねじ部の差し込み及びそれに続くねじ込みの連続作業が可能である。
請求項６記載の管継手においては、理想状態において、適正範囲がねじの加工誤差より大きいので、さらにテーパ雄ねじ部の差し込み及びそれに続くねじ込みの連続作業が改善される。
請求項７記載の管継手においては、テーパ雌ねじ部の管端部にテーパ雌ねじ部に続くスタビングガイドを備えているので、テーパ雄ねじ部がスタビングガイドに案内されて、軸芯が出るため、差し込み及びねじ込み作業が容易に実施できる。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る管継手が適用されるテーパねじ継手のスタビングフランク面の重なりが最大となる差し込み位置状態を説明する断面図である。
【図２】同テーパねじ継手の差し込み適正範囲の状態を説明する断面図である。
【図３】同テーパねじ継手の嵌合状態を説明する断面図である。
【図４】同テーパねじ継手が３条の場合のねじ形状の断面図である。
【図５】同テーパねじ継手が４条の場合のねじ形状の断面図である。
【図６】本発明の一実施の形態に係る管継手の変形例の断面図である。
【図７】同管継手の実施例の嵌合状態での寸法図である。
【図８】同詳細寸法図である。
【図９】従来例に係る管用テーパ角ねじを有する管継手のねじ込み開始の状況を説明する断面図及びその拡大図である。
【図１０】ＡＰＩバットレスねじ継手のねじ形状及びこれを使用した管継手ののねじ込み開始の状況を説明する断面図である。
【符号の説明】
１０管継手１１テーパ雄ねじ部
１２テーパ雌ねじ部１３雄ねじ山
１３ａ雄ねじ山１３ｃ雄ねじ山
１３ｄ雄ねじ山１３ｅ雄ねじ山
１３ｆ雄ねじ山１３ｇ雄ねじ山
１３ｈ雄ねじ山１３ｉ雄ねじ山
１３ｊ雄ねじ山１３ｋ雄ねじ山
１３ｍ雄ねじ山１３ｎ雄ねじ山
１３ｐ雄ねじ山１３ｑ雄ねじ山
１３ｒ雄ねじ山１３ｓ雄ねじ山
１３ｔ雄ねじ山１４ねじ山頂面
１４ａねじ山頂面１５スタビングフランク面
１５ａスタビングフランク面１６パイプ
１７雌ねじ山１７ａ雌ねじ山
１７ｃ雌ねじ山１７ｄ雌ねじ山
１７ｅ雌ねじ山１７ｆ雌ねじ山
１７ｇ雌ねじ山１７ｈ雌ねじ山
１７ｉ雌ねじ山１７ｊ雌ねじ山
１７ｋ雌ねじ山１７ｍ雌ねじ山
１７ｎ雌ねじ山１７ｐ雌ねじ山
１７ｑ雌ねじ山１７ｒ雌ねじ山
１７ｓ雌ねじ山１７ｔ雌ねじ山
１８谷部１８ａ谷部
１９パイプ２０先端
２０ａ先端２２ねじ山頂面
２２ａねじ山頂面２３ロードフランク面
２３ａロードフランク面２４コーナ部
２４ａコーナ部２５スタビングフランク面
２５ａスタビングフランク面２６ロードフランク面
２６ａロードフランク面２７コーナ部
２７ａコーナ部２８点[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tapered threaded joint such as an oil well pipe or a civil engineering pile pipe, in which a taper male threaded portion of a pin is inserted into a taper female threaded portion of a box in a vertical direction, and when it is continuously rotated and tightened, the workability can be improved. Related to fittings.
[0002]
[Prior art]
Conventionally, oil pipes (casing pipes, tubing pipes, drill pipes) or steel pipe piles for civil engineering used for well protection, oil extraction and drilling of oil (gas) wells, etc. An example of a pipe joint that makes it easy and quick to insert the taper male threaded part of the pin into the taper female threaded part of the box in the vertical direction and start the initial screwing (stubability) and the subsequent screwing work. As shown in FIG. 9A, a pipe joint 50a having a configuration as shown in FIG. In the pipe joint 50a, a pipe taper angle thread joint is used in which the taper male thread part 52 of the pin 51 of the pipe 50 and the taper female thread part 55 of the box 54 of the short pipe 53 are fitted. FIG. 9 (B) shows an enlarged view of the state of screwing start of the tapered angle threaded joint for pipes.
In order to easily understand the stubbing property of the tapered angle threaded joint for pipes, the male and female thread threads 56 and 57 of the tapered male thread part 52 and the tapered female thread part 55 have the same shape. Tapered surface T _f Parallel to The fitting cross-sectional view shown in the figure shows exactly where the male thread 56 is about to bite into the female thread 57. That is, the taper surface connecting the male screw crest surface 58 of the taper male screw portion 52 and the taper surface connecting the female screw crest surface 59 of the taper female screw portion 55 are just competing, and the male screw thread 56 is in the valley 60 of the female screw thread 57. As shown, the circumferential position of the tapered male threaded portion 52 and the circumferential position of the tapered female threaded portion 55 are aligned. As is apparent from the drawing, it is impossible to screw the tapered male threaded portion 52 into the tapered female threaded portion 55 with the screw shape as it is.
[0003]
Here, in order to clarify the stubbing identity of the tapered angle threaded joint for pipes, as shown in FIG. 10 (B), an example of an API buttress threaded joint widely used as an oil well pipe thread, The following describes how the male and female screw threads 63 and 64 are screwed in after the tapered male screw portion 61 is inserted into the tapered female screw portion 62.
API buttress screw element has taper T = 1/16 (or 62.5 mm / m, rate of change with diameter), pitch P = 0.08 mm, thread height H = 1.575 mm, stubbing flank angle η = 10 ° , Road flank angle γ = 3 °, male and female thread crest surfaces 65, 66 are tapered surfaces T _p It is characterized by a corner R = 0.76 mm or 0.20 mm of the top surfaces 65 and 66 of the male and female threads, ie, parallel to (that is, the pitch line).
FIG. 10A shows a situation where the tapered male screw portion 61 and the tapered female screw portion 62 are fitted in the most convenient circumferential direction for screwing. Unlike the case of the tapered angle threaded joint for pipes, the opening 68 of the valley 67 of the taper female thread 62 is wider than the male thread top surface 65 of the male thread 63. From this state, the taper male thread 61 drops downward. Then, the corner 69 of the male thread 63 of the taper male thread 61 can be slightly placed on the corner 70 of the female thread 64 of the taper female thread 62. If the taper male thread 61 is turned from this state, the taper male thread 61 is turned. The part 61 is inserted along the spiral.
[0004]
In order for the tapered male screw portion 61 to fit into the tapered female screw portion 62 in this way, the relative positions of the male screw row and the female screw row do not necessarily have to be as shown in FIG. Even when the tapered male thread portion 61 is shifted downward from the position of FIG. 10A until the corner R of the bing flank surface 71 contacts the corner R of the stubbing flank surface 72 of the female thread 64, the tapered male thread portion 61 is The taper female thread portion 62 can be fitted. That is, when the taper male screw portion 61 is inserted into the taper female screw portion 62 by an amount corresponding to the circumferential angle corresponding to this deviation, a margin can be given to the circumferential range for screwing in well.
In a normal insertion and screwing start operation, the tapered male screw portion 61 is inserted into the tapered female screw portion 62, and the male screw thread 63 of the tapered male screw portion 61 is moved to the female screw thread 64 of the tapered female screw portion 62 until the circumferential position is reached. The taper male screw part 61 is rotated. At this time, since the male thread 63 and the female thread 64 are not yet engaged with each other, galling may occur if the axes of the tapered male and female thread portions 61 and 62 are not aligned. Work is difficult when the rotation angle is large. Accordingly, the wider the range of the circumferential position in which the male thread 63 and the female thread 64 can be engaged, the smaller the rotation angle to be rotated to an appropriate place, and it can be said that the taper screw joint has good stubbing performance. Further, the advantage that the gap G between the width W of the opening 68 of the valley portion 67 of the taper female screw portion 62 and the width V of the male screw crest surface 65 is large is that the taper male screw portion 61 is dropped by this gap G to reduce the taper female screw. When depositing on the stubbing flank surface 72 of the female thread 64 of the part 62, a deposit in the radial direction of (gap G in the tube axis direction × taper T) / 2 can be secured, so that stable screwing can be achieved.
[0005]
As can be seen from the above description, the stubbing property is such that when the taper male screw portion 61 is inserted into the taper female screw portion 62, the wider the circumferential range (θ) in which the screwing can be started from that position as it is, In addition, when screwing is started, the wider the depth δ (same as the radial deposit allowance) of depositing the stubbing flank surface 71 of the male thread 63 on the stubbing flank surface 72 of the female thread 64 is better. . Therefore, in order to increase θ and δ that govern this stubbing property, the configuration of a conventional tapered screw joint will be described with some examples.
First, the API buttress threaded joint will be described. As shown in FIG. 10B, first, the angle of the stubbing flank surface 71 of the male thread 63 of the tapered male threaded portion 61, that is, the stubbing flank angle η is defined as the tube axis C. It is tilted 10 ° from the plane perpendicular to. The larger the inclination of the stubbing flank angle η, the wider the gap G for filling. Secondly, R = 0.76 mm of the corner portion 69 of the stubbing flank surface 71 of the male screw thread 63 of the taper male screw portion 61 is further widened. In addition, the taper male screw portion 61 is slightly thinner (0.03 mm in diameter) than the taper female screw portion 62, or the corner portions 75 and 76 of the male and female screw crest surfaces 65 and 66 and the load flank surfaces 73 and 74 are formed. The gap G is slightly widened even if R is slightly set (R = 0.20 mm in FIG. 10B). In this case, the total sum of all the gaps is estimated to be about 1.75 mm. When this is converted into a circumferential range (θ), θ = (360 ° × 1.75) /5.08=124°. On the other hand, the depth (δ) is δ = 1.75 / 32 = 0.555 mm. Although the range of screwing has come out compared with the square screw of FIG. 9, it cannot be said that it is making it easy to screw in positively.
[0006]
Further, the SEAL-LOCK joint manufactured by ARMCO will be described. In this special joint, first, the stubbing flank angle η on the insertion side is substantially inclined by 45 ° with respect to the plane perpendicular to the tube axis. The width of the valley portion of the female screw thread is widened so that the male screw thread of the tapered male screw portion can be easily stored in the valley portion of the tapered female screw portion during stubbing. Secondly, the top surfaces of the male and female screw threads are parallel to the tube axis, and when the tapered male screw part is inserted into the tapered female screw part, the place where the male screw thread and the female screw thread compete with each other is reduced.
Furthermore, in the special joint made by VETCO-GRAY, by applying 4 threads, there are 4 places where screwing is possible within 360 ° of the circumference. After inserting the taper male thread part into the taper female thread part, Can be screwed in easily by adjusting the rotation. In addition, in a normal single thread screw, the screwable place is one place. Furthermore, the greatest feature of the multi-thread (n-thread) is that once the screwing is started, the number of rotations until the tightening is completed becomes 1 / n compared to the single thread. This is a very important factor in a large-diameter joint that is tightened with a rope or the like.
As another special joint, there is one that lengthens the entrance of the taper female thread part (provides a stubbing guide) so that the taper male thread part is not inclined when inserted into the taper female thread part.
[0007]
[Problems to be solved by the invention]
However, the conventional pipe joint still has the following problems to be solved.
In the case of the single thread type, there is a problem that the insertion position is not necessarily the screw start position, and the tapered male thread portion must be rotated in order to find the screw position.
On the other hand, in the form of a multi-threaded screw including four-threaded screws, there are as many threadable locations as there are threads, so that the rotation for adjustment can be reduced, which significantly improves the stubbing performance compared to single-threaded screws. However, it is still impossible to screw in immediately from the insertion position.
Further, in the configuration provided with the stubbing guide, troubles such as galling due to the diagonal insertion of the screw can be prevented, but it is not essentially for screwing in immediately after insertion.
[0008]
The present invention has been made in view of such circumstances, and it is intended to provide a pipe joint that can be quickly and easily screwed from a position where a tapered male screw portion having a multi-thread is inserted into a tapered female screw portion. Objective.
[0009]
[Means for Solving the Problems]
The pipe joint according to claim 1, which meets the above object, includes a pin having a tapered male threaded portion formed on the outer peripheral surface of the distal end portion of the tube, and a tapered female threaded portion that is threadedly engaged with the tapered male threaded portion on the inner peripheral surfaces of both ends of the short tube. In a pipe joint for screwing a box formed with a multi-thread, in the case of an odd number of threads, (higher number -1) between the high male and female thread arranged at every other ridge and between the high male and female thread In the case of an even strip, a thread row composed of alternately high males, female threads and low males, female threads, or (number of strips-1) ) A screw train composed of a high male and female screw thread arranged every other mountain and a low male and female screw thread arranged between the high male and female screw threads.
The pipe joint according to claim 2 is the pipe joint according to claim 1, wherein the thread top surface of the male thread and the thread top surface of the female thread have a predetermined width like a square thread or a trapezoidal thread, Both the screw thread top surfaces are inclined parallel to the surface parallel to the tube axis or in the direction opposite to the thread row taper surface.
The pipe joint according to claim 3 is the pipe joint according to claim 1, wherein the thread top surface of the male thread and the thread top surface of the female thread have a predetermined width like a square screw or a trapezoidal screw, A part of the top surfaces of both screw threads are made parallel to the tube axis, and the remaining both screw top surfaces are inclined in a direction opposite to the thread row taper surface with respect to a surface parallel to the tube axis.
[0010]
The pipe joint according to claim 4 is the virtual joint according to any one of claims 1 to 3, wherein when the taper male thread portion is inserted into the taper female thread portion, the virtual taper is in contact with the top surface of the male thread. When the taper male thread portion is lowered in the vertical direction as it is in a state where the surface and the virtual taper surface in contact with the thread top surface of the female thread compete with each other, the thread top surface of the male thread does not compete with the thread top surface of the female thread The taper male thread portion and the taper male thread portion at the time of threading processing can be reproduced so as to reproduce the positional relationship between the original male screw row and the female screw row that can be overlapped with the stubbing flank surface of the female screw thread. The taper female threaded portion is marked to match the circumferential direction.
The pipe joint according to claim 5 is the pipe joint according to any one of claims 1 to 4, wherein the taper male thread part and the taper female thread part have respective relative diameters of the tapered thread surfaces at the time of threading. In consideration of errors, an ideal male screw row that does not take into account screw machining errors, and a screw thread top surface of the male screw thread of the taper male screw portion within an appropriate positional relationship that enables screwing immediately after insertion of the male screw row. And the stubbing flank surface are always positioned at the center of the appropriate range.
A pipe joint according to a sixth aspect is the pipe joint according to the fifth aspect, wherein the appropriate range is larger than a machining error of the screw in an ideal state.
A pipe joint according to a seventh aspect is the pipe joint according to any one of the first to sixth aspects, further comprising a stubbing guide following the tapered female threaded portion at a pipe end of the tapered female threaded portion.
[0011]
The present invention has been made based on the concept described below.
There are the following three cases when the taper male screw portion is inserted straight into the taper female screw portion. The first is when the male and female threads are competing with each other, the second is when the male and female threads are partially competing, and the third is the thread top surface of the male thread of the tapered male thread is the tapered female thread This is when the side surface (stubbing flank surface) of the male thread portion of the tapered male thread portion lands on the side surface (stubbing flank surface) of the female thread thread.
For the purpose of the present invention, in order to enable screwing immediately after being inserted, the shape of the male and female threads and the thread cutting so that the third state is always obtained after the tapered male threaded portion is inserted into the tapered female threaded portion. It is necessary to devise a processing method. In the present invention, in order to always reproduce the third state, the following four elemental technologies are employed.
[0012]
As shown in FIG. 2, the first elemental technique is such that the taper male screw portion 11 is threaded during threading so that the relative positions of the axial threads of the taper male screw portion 11 and the taper female screw portion 12 are always in the third state. The coordinates (r, Z) of the corner of the stubbing flank surface 15 on the insertion side of the thread top surface 14 of the male thread 13 from the tip 20 of _m ) Is determined in advance, and the circumferential position of the pipe 16 (or called a pipe) through which it passes is marked S. ₁ (Not shown), and at the same time, as shown in FIG. 2, the valley 18 of the female thread 17 where the corner of the stubbing flank surface 15 of the male thread 13 starts to fit is coordinates (r, Z _f ) Is also marked in the circumferential direction of the tip 20a of the tapered female threaded portion 12 of the pipe 19 (or short pipe). ₂ (Not shown) ₁ , S ₂ The circumferential positions of the tapered male and female threaded portions 11 and 12 are determined so that they are overlapped with each other, and the screwing operation of the pipe joint 10 is performed.
The second elemental technology is to reduce the probability that the male and female threads compete with each other during stubbing by making a part of the multiple thread threads in one lead lower than the height of the other threads. This is substantially equivalent to considering the low thread portion as a single thread thread valley. Therefore, in the case of double thread, there is a trough width that is three times the width of the thread top surface of the male thread of the taper male thread part. During stubbing, the male thread is easily located in the trough of the taper female thread part. Will fit.
[0013]
The third elemental technology is based on the idea of avoiding the competition between the high male and female screw threads in the second elemental technique, and the high thread top surface is on the opposite side of the thread row taper surface and the tube axis. By inclining, the male and female screw threads are in contact with each other at a point. As shown in FIG. 2, the taper male, the male threads 11 and 12, the thread top faces 14 and 22 of the female threads 13 and 17 are slightly more male than the plane D parallel to the tube axis C (broken line in FIG. 2). The taper surface E (solid line in FIG. 2) is opposite to the virtual taper surface T (two-dot chain line in FIG. 2) of the female thread row.
As shown in FIG. 2, in the fourth elemental technology, the axial range in which the tapered male threaded portion 11 can be screwed into the tapered female threaded portion 12 as it is from the inserted state in consideration of the machining tolerance of the screw is as follows. The standoff tolerance (also called relative diameter error, which is a value obtained by converting the diameter tolerance of the taper screw in the length direction and is 1/2 pitch in the case of an API buttress screw joint).
[0014]
If the second and third elemental technologies are satisfied, it is theoretically possible to screw the taper male screw part at any position in the circumferential direction. In order to stably land the flank surface on the stubbing flank surface of the female thread of the taper female thread, the standoff tolerance of the screw should be at the center of the allowable range that can be screwed in immediately after insertion, and the standoff tolerance is small. It is preferable to perform threading with high accuracy.
In the present invention, it is possible to screw the taper male screw portion 11 into any position of the 360 ° taper female screw portion 12 by using only the second and third element technologies. In consideration of the slight inclination of the respective axes of the tapered male threaded portion 11 and the tapered female threaded portion 12, the insertion position at the time of threading shown in the first elemental technology can be secured so that this stubbing property can be secured stably. Mark S to specify ₁ , S ₂ In addition, the concept of the optimum insertion position in consideration of the standoff tolerance of the screw in the fourth elemental technology is also considered, and effective stubbing and quick tightening can be achieved by applying each elemental technology alone or in combination. It is possible to simultaneously satisfy the suppression of the dropability and the joint strength reduction.
[0015]
Needless to say, the present invention can be applied to both a multi-thread thread joint in which male and female thread portions are divided into two stages, and a multi-thread thread joint having a tapered thread portion somewhere in the thread row. (See FIGS. 6C and 6D).
Furthermore, by combining it with the idea of the stubbing guide described above, it prevents the screw galling (cross thread) expected at the time of oblique screwing, and performs a series of operations from stubbing to screwing into the taper female screw part. It is also possible to save labor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is a cross-sectional view for explaining an insertion position state in which the overlap of stubbing flank surfaces of a taper screw joint to which a pipe joint according to an embodiment of the present invention is applied is maximized, and FIG. FIG. 3 is a cross-sectional view illustrating the fitting state of the joint, and FIG. 3 is a cross-sectional view illustrating the fitting state of the taper screw joint. FIG. 5 is a cross-sectional view of the thread shape when the taper threaded joint has four threads, FIG. 6 is a cross-sectional view of a modified example of the pipe joint according to the embodiment of the present invention, and FIG. 7 is a fitting example of the pipe joint. FIG. 8 is a detailed dimensional diagram in the combined state.
[0017]
In the shape of the taper screw joint to which the pipe joint according to the embodiment of the present invention shown in FIG. 6 is applied, (A) is a pipe joint having only a fastening screw, and (B) is the tip of the screw fitting portion. (C) is a pipe joint in which the uniform taper thread part of (A) or (B) is divided into two stages, and (D) is the uniform of (A) or (B). This is a pipe joint in which a parallel thread part is substituted for a part of the taper thread part. In order to keep the relative thickness of the male and female thread taper parts constant, if it is a taper male thread part, the effective thread diameter at the axial position from the tip is processed to be constant, while if it is a taper female thread part, The effective diameter of the screw at a certain axial depth from the inlet is machined to be constant.
[0018]
FIG. 1 shows a male thread in a tapered male and female threaded portions 11 and 12 each having a thread lead L (see FIG. 2) and a double thread having a pitch p (L / 2). 13, 13 a, female thread 17, 17 a is in a state in which the point of each screw thread top surface 14, 22 is in contact with the virtual taper T, and the corner portion between the stubbing flank surface 15 and the thread top surface 14 of the male thread 13. Reference numeral 24 denotes a state in which the stubbing flank surface 25 of the female thread 17 of the taper female thread portion 12 is in contact with the corner portion 27 of the thread top surface 22, that is, the insertion position. In the male screw thread 13a and the female screw thread 17a, those corresponding to the elements of the male screw thread 13 and the female screw thread 17 are described with a suffix a.
From this state, if the corner portion 24 of the male screw thread 13 of the tapered male screw portion 11 passes through the corner portion 27 of the female screw thread 17 of the taper female screw portion 12, the corner portion 24 is parallel to the surface D parallel to the tube axis C of the pipe joint 10. Along the line (shown by a broken line), it falls downward, slightly evacuates the lower female thread 17a, and lands on the point 28 of the stubbing flank 25 of the lower female thread 17 below. That is, the male screw thread 13a and the female screw thread 17a having a low height may be set low enough not to hinder the high male screw thread 13 from landing on the female screw thread 17 having a high height. In this way, if the stubbing flank surface 15 of the high male thread 13 overlaps the stubbing flank surface 25 of the high female thread 17, the overlap w of the male screw 13 and the female thread 17 at this time Is the maximum.
[0019]
The reason why the stubbing flank surface 15 of the male thread 13 can land on the stubbing flank surface 25 of the female thread 17 is that, as is apparent from the figure, every other low thread is disposed. In addition, the thread crest surface 14 of the male thread 13 having a predetermined width, such as a square screw or a trapezoidal thread, and the thread crest surface 22 of the female thread 17 are parallel to the tube axis C so that they do not compete during insertion. This is because the stub clearance angle β is provided on the side opposite to the screw taper angle α with respect to the surface D and is inclined. Ideally, the thread crest surfaces 14 and 22 do not compete with each other even if they are parallel to the tube axis C (the supplementary line of the broken line in FIG. 1). However, since there is a slight inclination when the tapered male screw portion 11 is inserted, The male and female screw threads 13 and 17 may compete with each other. The larger the stub clearance angle β is, the better the screwing is. However, if it is too large, the height h of the load flank surfaces 23 and 23a that handle the load when the joint is pulled becomes low. Since there is a problem that it is easy to come off, it is not appropriate to make it larger than necessary. In particular, since the height of the screw threads 13 and 13a and the height of the female threads 17 and 17a itself is sacrificed, the height of the screw threads is sacrificed. Decide to secure the screw height. 1 and 2, reference numeral 16 denotes a pipe, 18 denotes a trough, 19 denotes a pipe, and 26 denotes a load flank surface of the female thread 17.
[0020]
In the pipe joint 10 shown in FIG. 2, the position where the corner portion 24 of the male thread 13 stops in contact with the virtual taper surface T advances in the screwing direction by 1 pitch P compared to the case of FIG. Shown in the center. The reason why the corner portion 24 of the male screw thread 13 of the taper male screw part 11 is set at the center of the screw lead L is that even if it is a stubbing operation with a screw standoff tolerance and a slight inclination, This is because the bing flank surface 15 is stably landed on the stubbing flank surface 25 of the female thread 17 of the taper female thread portion 12. The range of the relative displacement of the male thread 13 with respect to the female thread 17 due to the standoff tolerance of the screw is the range of s shown in FIG. 2 where the standoff tolerance is s.
If the corner portion 24 is biased to the upper end in the range of s, the corner portion 27 of the female screw thread 17 is difficult to slip through. On the other hand, if the corner portion 24 is biased to the lower end of the range of s, the corner portion of the female screw thread 17 is Since the distance to 27 becomes short and the overlap of both stubbing flank surfaces 15 and 25 at the time of landing becomes narrow, the direction becomes unstable.
[0021]
Therefore, in the blade path calculation at the time of thread cutting, the corner portion 24 (circle in the figure) of FIG. 2 is the center of the screw lead L of the female thread 17 in a state where the virtual taper surface T of the male thread 13 and the female thread 17 is in contact. It is necessary to design the path so as to be positioned at the position of the screw, and the stand-off tolerance of the screw is small, and the taper screw machining with high accuracy is required. If ○ is considered as the reference position of the blade, it is (r, Z _m ), While in female threaded passes, (r, Z _f ), The relationship between the male thread cutting blade and the female thread cutting blade at the start of threading and the pipes 16 and 19 is set, and the blade motion surfaces at that time are the circumferences of the pipes 16 and 19 where the pipes 16 and 19 intersect. Mark S in the direction position ₁ , S ₂ Add a note. By doing this, the mark S ₁ , S ₂ The tapered male threaded portion 11 and the tapered female threaded portion 12 with the mark S ₁ , S ₂ 2 is always inserted in the circumferential direction so that the positional relationship shown in FIG. 2, i.e., the thread crest surfaces 14 and 22 of the male and female screw threads 13 and 17, do not compete, and the stubbing flank surface 15 of the male screw thread 13. Can reproduce the positional relationship between the original male screw row and the female screw row that can overlap the stubbing flank surface 25 of the female screw thread 17, and smooth insertion of the tapered male screw portion 11 and subsequent screwing are possible.
[0022]
FIG. 3 shows a state where the taper male screw portion 11 and the taper female screw portion 12 of the pipe joint 10 have been tightened, that is, a fitted state.
The feature of the taper screw shape in the case of the pipe joint 10 according to the present embodiment is that the height of the load flank surfaces 23, 23a, 26, 26a is lower than that of the stubbing flank surfaces 15, 15a, 25, 25a. It is. Since this may cause the taper male screw portion 11 to come off as described above, the following two methods are adopted to increase the resistance.
First, as shown in FIG. 3, the load flank surfaces 23 a and 26 a are perpendicular to the tube axis C. _s The angle γ is tilted to the more difficult direction.
The second is not to make the entire surface of the screw thread top surfaces 14 and 22 of the male and female thread threads 13 and 17 the stubbing clearance angle β, but only the side close to the stubbing flank surfaces 15, 15 a, 25 and 25 a is the stubbing clearance angle β, The side close to the remaining load flank surfaces 23, 23a, 26, 26a is made parallel, or conversely, only the side close to the stubbing flank surfaces 15, 15a, 25, 25a is made parallel, and the remaining load flank surfaces 23, 23a, By applying the stub clearance angle β to the sides 26 and 26a, the height h of the load flank surfaces 23, 23a, 26 and 26a is prevented from being lowered as much as possible. The broken line in FIG. 3 is a supplementary line when the thread crest surfaces 14 and 22 are parallel to the tube axis C, and indicates the allowance for improving the fitting height of the load flank surfaces 23, 23a, 26, and 26a. Yes.
[0023]
As described above, the example of the double thread has been described in detail, but the tightening becomes faster as the number of threads increases. Therefore, the method of attaching the height of the thread is also mentioned for the three-thread screw and the four-thread screw. FIG. 4 (A) shows a case where three threads are provided and every two high threads are arranged, that is, every (number of threads-1) threads.
The male screw thread 13c is in a position where the landing can be seen through the female screw thread 17d in a state of passing through the female screw thread 17c. The overlapping of the stubbing flank surfaces can be widened and can stably land on the female thread 17d in a wide range within the screw lead L. However, if the state (two-dot chain line) which fits is imagined, it will have the fault that fitting height becomes narrow like illustration. In FIG. 4A, reference numeral 13d indicates a high male thread.
[0024]
In FIG. 4B, in order to eliminate this drawback, the height of the female screw threads 17g and 17h between the high female screw threads 17e and 17f is increased at the sacrifice of the stubbing position and the landing width. is there. The male screw threads 13e and 13f can land on the female screw threads 17h and 17f, respectively. In FIG. 4B, reference numerals 13g and 13h also indicate male screw threads.
FIG. 5 (A) shows a case where four threads are used and every other high thread is arranged. The stubability (workability from insertion to screwing) and the screw fitting state are the same as those of the double thread, and the screwing speed can be double that of the double thread. Male thread 13i, 13k can land on female thread 17k, 17n, respectively.
FIG. 5 (B) shows a case where four threads are arranged and every three high threads, that is, every (number of threads-1) threads. The male screw thread 13p is in a position where the landing can be seen through the female screw thread 17t while passing through the female screw thread 17p. Similar to FIG. 4A, the stubbing property is good, but the joint efficiency is sacrificed. If the relative positions of the thread rows of the male thread and female thread can be controlled in the threading process, there is a sufficient margin for stubbing even in the case of FIGS. 4 (B) and 5 (A). 4) and FIG. 5 (B) are suitable if the joint efficiency is also taken into consideration, rather than the arrangement of the type B and FIG. 5 (B) type screw threads.
[0025]
Even when the number of threads is increased in this way, in order to improve the threading of male threads during stubbing, the top surface of the thread of the high thread may be inclined opposite to the thread row taper surface, or it may be placed in an exact position. The technical idea such as marking the pipe during threading so as to be stuck is the same as in the case of the above-described double thread.
[0026]
【Example】
Next, examples of the pipe joint according to the embodiment will be described with reference to FIGS. 7 and 8A and 8B. FIGS. 7 and 8 are joints having a 7-inch API buttress threaded joint as an original form and improved stubbing and quick tightening based on the pipe joint according to the embodiment. FIG. 7 is a cross-sectional view showing the mating dimensions in the fitting state of the pipe joint.
The thread specifications that are different from the API buttress threaded joint are two-threaded, and the top of the pin and box male and female threads are 3 on the opposite side of the thread row taper surfaces PT and BT with respect to the tube axis C. The load flank surface is inclined 3 ° in the opposite direction to the API buttress screw joint with respect to the surface perpendicular to the tube axis C, and the stubbing flank surface is further inclined 30 °. .
[0027]
The threaded joint processing was performed in such a manner, and the taper male screw part was inserted into the taper female screw part, and it was tested whether or not the screwing can be performed as it is. As a result, it was confirmed that if the tapered male threaded portion is carefully inserted into the tapered female threaded portion so that the tube axis C does not tilt, it can be screwed in any position at 360 °.
Of course, since it is a two-thread screw, the tightening rotation speed can be half that of a normal API buttress screw joint. Furthermore, in order to eliminate axial misalignment, a 200 mm cylinder was welded as a stubbing guide to the tip (or tube end) of the taper female thread, and the same operation was performed. It was also confirmed that continuous work of stubbing and screwing was possible.
[0028]
【The invention's effect】
In the pipe joint according to any one of claims 1 to 7, a multi-thread is applied, and in the case of an odd-numbered thread, (high number-1) between a high male and female thread arranged at every other thread and a high male and female thread. In the case of an even strip, a thread row composed of alternately high males, female threads and low males, female threads, or (number of strips-1) ) Since the screw row is composed of a high male and female screw thread arranged at every mountain and a low male and female screw thread arranged between the high male and female screw threads, the thread shape of the multi-threaded screw in one screw lead By devising, it can be screwed in as it is from the insertion position of the tapered male screw portion, and the screwing operation can be performed easily and quickly.
In particular, in the pipe joint according to claim 2, the thread top surface of the male thread and the thread top surface of the female thread have a predetermined width like a square screw or a trapezoidal screw, The taper male threaded portion can be inserted at any position of 360 ° and the continuous operation of subsequent screwing can be performed more smoothly. .
In the pipe joint according to claim 3, the thread top surface of the male thread and the thread top surface of the female thread have a predetermined width such as a square screw or a trapezoidal screw, and a part of both the thread top surfaces is connected to the tube axis. In addition, the height of the load flank surface can be kept large since the remaining screw thread crest surfaces are inclined in the opposite direction to the thread row taper surface with respect to the surface parallel to the pipe axis. It can be made into a difficult screw joint shape.
[0029]
In the pipe joint according to claim 4, when inserting the taper male thread part into the taper female thread part, the virtual taper surface in contact with the thread top surface of the male thread and the virtual taper surface in contact with the thread top surface of the female thread compete with each other. If the taper male thread part is lowered in the vertical direction as it is, the male thread stubbing flank surface can overlap the female thread stubbing flank face without competing the male thread thread top surface with the female thread top surface. In order to reproduce the positional relationship between the male screw row and the female screw row, the taper male screw part and the taper female screw part are marked in the circumferential direction at the time of threading, so screw in as they are from the insertion position of the taper male screw part. In addition, the screwing operation can be performed more easily and quickly.
In the pipe joint according to claim 5, an ideal male thread row not considering a thread machining error in consideration of a relative diameter error of each thread row taper surface of the taper male thread portion and the taper female screw portion at the time of threading. In addition, within the predetermined range of appropriate positional relationship that enables screwing immediately after insertion of the male thread row, the corner position of the male thread top surface of the tapered male thread part and the stubbing flank surface is always at the center of the proper range. Thus, the taper male screw portion can be inserted and subsequently screwed continuously regardless of the screw machining error.
In the pipe joint according to the sixth aspect, in the ideal state, since the appropriate range is larger than the screw machining error, the continuous operation of the insertion of the tapered male screw portion and the subsequent screwing is further improved.
In the pipe joint according to claim 7, since the tube end portion of the taper female screw portion is provided with a stubbing guide following the taper female screw portion, the taper male screw portion is guided by the stubbing guide and the shaft core comes out. Insertion and screwing operations can be performed easily.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an insertion position state in which the overlap of stubbing flank surfaces of a tapered threaded joint to which a pipe joint according to an embodiment of the present invention is applied is maximized.
FIG. 2 is a cross-sectional view illustrating a state of an appropriate insertion range of the tapered threaded joint.
FIG. 3 is a cross-sectional view illustrating a fitting state of the tapered threaded joint.
FIG. 4 is a cross-sectional view of a screw shape when the taper threaded joint has three threads.
FIG. 5 is a cross-sectional view of a thread shape when the taper threaded joint has four threads.
FIG. 6 is a sectional view of a modification of the pipe joint according to the embodiment of the present invention.
FIG. 7 is a dimensional diagram of the embodiment of the pipe joint in a fitted state.
FIG. 8 is a detailed dimensional view of the same.
9A and 9B are a cross-sectional view and an enlarged view illustrating a state of screwing start of a pipe joint having a pipe taper angle screw according to a conventional example.
FIG. 10 is a cross-sectional view illustrating a thread shape of an API buttress threaded joint and a state of screwing start of a pipe joint using the API buttress thread joint.
[Explanation of symbols]
10 Pipe joint 11 Taper male thread
12 Taper female thread 13 Male thread
13a Male thread 13c Male thread
13d male thread 13e male thread
13f Male thread 13g Male thread
13h Male thread 13i Male thread
13j Male thread 13k Male thread
13m male thread 13n male thread
13p male thread 13q male thread
13r male screw thread 13s male screw thread
13t Male thread 14 Screw thread top surface
14a Thread crest surface 15 Stubbing flank surface
15a Stubbing flank surface 16 Pipe
17 Female thread 17a Female thread
17c Female thread 17d Female thread
17e Female thread 17f Female thread
17g female thread 17h female thread
17i Female thread 17j Female thread
17k female thread 17m female thread
17n female thread 17p female thread
17q female thread 17r female thread
17s female thread 17t female thread
18 Valley 18a Valley
19 Pipe 20 Tip
20a Tip 22 Thread top surface
22a Thread top surface 23 Load flank surface
23a Road flank surface 24 Corner section
24a Corner 25 Stubbing flank surface
25a Stubbing flank face 26 Road flank face
26a Road flank surface 27 Corner section
27a Corner point 28 points

Claims

In a pipe joint for screwing a pin formed with a tapered male threaded portion on the outer peripheral surface of the distal end of the tube and a box formed with a tapered female threaded portion to be screwed into the tapered male threaded portion on the inner peripheral surface of both ends of the short tube,
When multiple threads are applied, in the case of odd-numbered threads, it consists of (higher number-1) high male and female screw threads arranged at every other thread and lower male and female screw threads arranged between the higher male and female screw threads. A screw row,
In the case of an even number of strips, a high male, a female thread and a low male, a female screw thread is alternately arranged, or (high number-1) high male and female thread arranged at every other thread, A pipe joint characterized by being a screw train composed of a high male and a low male and female thread arranged between female threads.

The thread top surface of the male thread and the thread top surface of the female thread have a predetermined width like a square screw or a trapezoidal screw, and both the thread top surfaces are parallel to a plane parallel to the tube axis or The pipe joint according to claim 1, wherein the pipe joint is inclined in a direction opposite to the thread row taper surface.

The screw thread top surface of the male screw thread and the screw thread top surface of the female screw thread have a predetermined width like a square screw or a trapezoidal screw, and a part of both screw thread top surfaces are made parallel to the tube axis, and the rest 2. The pipe joint according to claim 1, wherein both of the screw thread top surfaces are inclined with respect to a plane parallel to the pipe axis in a direction opposite to the thread row taper surface.

When inserting the tapered male threaded portion into the tapered female threaded portion, in a state where the virtual tapered surface in contact with the thread top surface of the male thread and the virtual tapered surface in contact with the thread top surface of the female thread compete, The original screw thread stubbing flank surface can be overlapped with the female screw thread stubbing flank surface without lowering the screw thread crest surface of the female screw thread when competing with the vertical direction. The mark which matches the circumferential direction of the said taper male screw part and the said taper female screw part at the time of threading so that the positional relationship of a male screw row | line | column and a female screw row | line | column could be reproduced was given. Pipe fittings.

In consideration of the relative diameter error of each taper surface of the tapered male threaded part and the tapered female threaded part at the time of threading, an ideal male threaded line and screwing immediately after insertion of the male threaded line without considering the machining error of the thread The position of the corner portion between the thread top surface of the male thread of the taper male thread portion and the stubbing flank surface is always at the center of the proper range within the appropriate positional relationship within a predetermined range. The pipe joint according to any one of 4.

The pipe joint according to claim 5, wherein the appropriate range is larger than a machining error of the screw in an ideal state.

The pipe joint of any one of Claims 1-6 provided with the stubbing guide following the taper internal thread part in the pipe end part of the taper internal thread part.