JP3937267B2

JP3937267B2 - Upper thread tension applicator for sewing machine

Info

Publication number: JP3937267B2
Application number: JP14794098A
Authority: JP
Inventors: 雅夫小川
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1998-05-28
Filing date: 1998-05-28
Publication date: 2007-06-27
Anticipated expiration: 2018-05-28
Also published as: JPH11333171A

Description

【０００１】
【発明の属する技術分野】
本発明はミシンの上糸張力付与装置に関し、特に、副張力付与機構の付勢手段による弾性付勢力を、第１，第２付勢力に択一的に切換え可能な付勢力切換え機構を設けた上糸張力付与装置に関する。
【０００２】
【従来の技術】
従来のミシンには、通常、糸駒（上糸供給源）から天秤に至る上糸経路における上糸に張力を付与し、その張力を調整ダイヤル等で調整可能な糸調子器等の主張力付与機構が設けられている。この主張力付与機構としては、糸調子器等の他に、パルスモータの出力軸に固着された駆動ローラと従動ローラとの間で上糸を挟持し、縫製速度に対するパルスモータ（駆動ローラ）の回転量、つまり上糸の供給量（繰出し量）を制御することで、上糸に付与する張力を調整するものが実用に供されている。
【０００３】
通常、主張力付与機構に糸掛けを行う場合、主張力付与機構を開放させ上糸に張力を付与しない状態に切換える必要があり、従来のミシンには、主張力付与機構を押え足を昇降させる操作部材に連動させ、押え足が上った状態では主張力付与機構が開放し、また、押え足が下った状態では主張力付与機構が閉鎖して上糸に張力を付与するように構成したものが多い。
【０００４】
ところで、縫製時、繰出される上糸が主張力付与機構により捩じられて、主張力付与機構よりも上糸供給源側の上糸にヨリが発生する場合があり、その上糸のヨリが主張力付与機構に進入し、更に主張力付与機構よりも下流側へ引出されると糸が弛み、縫製不良が起きる虞がある。そこで、主張力付与機構よりも糸駒供給源側に、上糸に数gf〜数10gfの張力を付与することにより、上糸のヨリを戻す副張力付与機構（通称、ヨリ戻し）を設けたミシンが広く実用に供されている。
【０００５】
一般的な副張力付与機構は、ベース板とこのベース板に面接触する張力付与板とを有し、その間に上糸が通過する張力付与部が形成され、バネ等の付勢部材により張力付与板をベース板の方へ弾性付勢することで、張力付与部から上糸に張力が付与される。従来の副張力付与機構は、通常、上糸に常時張力を付与するように構成されており、副張力付与機構により上糸に付与する張力をある程度高めの値（例えば、５〜10gf）に予め設定しておくことで、ヨリが発生し易い刺繍糸等にも対応して、上糸のヨリを確実に戻すことが可能になる。
【０００６】
主張力付与機構と副張力付与機構を有するミシンに糸掛けを行う場合には、糸駒から延びる上糸の端部を持って、先ず、副張力付与機構にベース板と張力付与板との間を通して糸掛けを行い、次に、開放された主張力付与機構に糸掛けを行い、その後、天秤に糸掛けを行ってから縫針の目孔に上糸を通して完了する。
【０００７】
一方、本出願人は、縫針の目孔付近の位置に上糸を案内する上糸案内機構と、案内された上糸を目孔内へ取込んで糸通し動作を実行する糸通し機構等を有し、上糸の目孔への糸通しを容易に行うことができる糸通し装置（特公平７−７１５９６号公報参照）を提案し実用化している。この糸通し装置により上糸の目孔への糸通しを確実に行う為には、少なくとも、糸通し機構の作動の際、上糸案内機構で案内された上糸をピンと張った状態に保持しておくことが必要である。
【０００８】
【発明が解決しようとする課題】
従来の主張力付与機構と副張力付与機構を備えたミシンでは、副張力付与機構が上糸に常時張力を付与するように構成され、副張力付与機構により上糸に付与する張力を調整することができないため、各種条件に応じて、副張力付与機構により上糸に付与する張力を予め設定しておかなければならない。
【０００９】
しかし、上糸のヨリを確実に戻す為に、副張力付与機構により上糸に付与する張力をある程度高めの値（例えば、５〜10gf）に設定すると、糸掛けの際、副張力付与機構のベース板と張力付与板との間に上糸を通しにくくなること、副張力付与機構に糸掛けされると上糸を引出しにくくなること等により、上糸の糸掛け作業が大変になる。更に、糸通し装置により縫針の目孔への糸通しを行う場合には、上糸の張力が大きすぎて、天秤側から上糸を引出し目孔に十分な長さの上糸を通すことができないという虞もある。
【００１０】
逆に、上糸の糸掛け作業を容易に行い、糸通し装置による糸通しを確実に行えるように、副張力付与機構により上糸に付与する張力をある程度低い値（例えば、２〜４gf）に設定すると、縫製時、上糸のヨリを確実に戻すことができなくなり、上糸のヨリが主張力付与機構に進入し、更に主張力付与機構よりも下流側へ引出されて弛み、縫製不良が起きるという問題がある。
【００１１】
尚、副張力付与機構において、縫製時には上糸に張力を付与し、糸掛け時には開放して上糸に張力を付与しないように切換え可能に構成することもできるが、糸掛け時に上糸に全く張力が付与されていない状態になるため、糸掛けの際に糸駒から上糸が過剰に引出される可能性があり、オペレータの糸掛け作業が大変になること、また糸通し装置により糸通しを行う場合、上糸案内機構により上糸をピンと張った状態で縫針の目孔付近の位置に案内できないため、縫針の目孔への糸通しを確実に行えないこと等の問題がある。
【００１２】
本発明の目的は、ミシンの上糸張力付与装置において、副張力付与機構により上糸に付与する張力を糸掛け時と縫製時に分けて２段階に調整できるように、副張力付与機構の付勢手段による弾性付勢力を第１，第２付勢力に択一的に切換え可能にし、糸掛け時の糸掛け作業を簡単且つ確実に行い且つ縫製時の上糸のヨリを確実に戻すこと、等である。
【００１３】
【課題を解決するための手段】
請求項１のミシンの上糸張力付与装置は、ミシンの上糸供給源から天秤に至る上糸経路における上糸に張力を付与する上糸張力付与装置において、上糸に張力を与えその張力を調整可能な主張力付与機構と、この主張力付与機構よりも上糸供給源側に設けられベース板と張力付与板との間に上糸が通過する張力付与部を形成してなる副張力付与機構とを備え、前記副張力付与機構に、張力付与板をベース板の方へ弾性付勢する付勢手段と、付勢手段による弾性付勢力を第１付勢力とこの第１付勢力よりも大きな第２付勢力とに択一的に切換え可能な付勢力切換え機構とを設け、前記付勢力切換え機構は、押え足を昇降させる操作部材に連動して作動し、押え足が上った状態では付勢手段による付勢力を第１付勢力に切換え、押え足が下った状態では付勢手段による付勢力を第２付勢力に切換えることを特徴とするものである。
【００１４】
この上糸張力付与装置では、ミシンの上糸供給源から天秤に至る上糸経路における上糸に、主張力付与機構と、主張力付与機構よりも上糸供給源側に設けられた副張力付与機構とにより張力を付与することができる。副張力付与機構においては、付勢手段により張力付与板がベース板の方へ弾性付勢され、ベース板と張力付与板の間に形成された張力付与部から上糸に張力が付与される。
【００１５】
副張力付与機構の付勢手段による弾性付勢力は、付勢力切換え機構により、糸掛け時には第１付勢力に切換えられ、縫製時には第２付勢力に切換えられる。ここで、第１付勢力は、糸掛け作業（糸通し作業を含む）を簡単且つ確実に行える張力（例えば、２〜４gf）を上糸に付与するように設定される。また、縫製時に主張力付与機構の張力付与作用によって主張力付与機構よりも上糸供給源側の上糸にヨリが発生するが、第２付勢力は、その上糸のヨリを確実に戻すことができる張力（例えば、５〜10gf）を上糸に付与するように設定される。
【００１６】
このように、副張力付与機構の付勢手段による弾性付勢力を第１付勢力とこの第１付勢力よりも大きな第２付勢力とに択一的に切換え可能な付勢力切換え機構を設けたので、副張力付与機構により上糸に付与する張力を糸掛け時と縫製時に分けて２段階に簡単に調整することができ、第１付勢力を上記のように設定することで、糸掛け時の糸掛け作業が容易に行えるようになるため、オペレータの糸掛け作業の負荷を軽減することができる。
【００１７】
特に、縫針の目孔に糸通しを行う糸通し装置を設けた場合にも、第１付勢力を糸通し装置に応じた張力で上糸に付与するように設定できるため、その糸通し装置により上糸の目孔への糸通しを簡単且つ確実に行うことが可能になる。しかも、第２付勢力を上記のように設定することで、縫製時の上糸のヨリを確実に戻すこができるため、上糸のヨリが主張力付与機構に進入し、更に主張力付与機構よりも下流側へ引出されて弛み、縫製不良が起こるのを防止できる。
【００１８】
【００１９】
しかも、この上糸張力付与装置では、操作部材を操作して、押え足を上げると付勢手段による付勢力を第１付勢力に切換えることができ、押え足を下げると付勢手段による付勢力を第２付勢力に切換えることができる。このように、押え足を昇降させる操作部材に連動して、付勢力切換え機構が作動するように構成したので、オペレータの操作負荷を軽減でき、また、付勢力切換え機構の構造を簡単化し製作コストを低減できる。
【００２０】
請求項２のミシンの上糸張力付与装置は、請求項１の発明において、前記主張力付与機構は、押え足が上った状態では上糸に張力を付与しないように構成したことを特徴とするものである。
【００２１】
この上糸張力付与装置では、押え足を昇降させることにより、主張力付与機構の状態を、上糸に張力を付与する状態と付与しない状態とに切換えることができるため、オペレータの操作負荷を一層軽減することができる。また、押え足が上った状態では、主張力付与機構が開放されているため、その主張力付与機構に糸掛けを容易に行うことができ、更に、副張力付与機構だけで上糸に張力を付与している状態になるため、前記第１付勢力を、糸掛け作業を容易に行える張力を上糸に付与するように設定し易くなる。
【００２２】
請求項３のミシンの上糸張力付与装置は、請求項１の発明において、前記付勢手段は張力付与板をベース板の方へ弾性付勢する第１，第２付勢部材を含み、第１付勢部材は張力付与板を常時付勢するとともに、前記付勢力切換え機構は、第２付勢部材を張力付与板を付勢する付勢位置と張力付与板を付勢しない付勢解除位置とに亙って切換えることを特徴とするものである。
【００２３】
この上糸張力付与装置では、付勢力切換え機構により、第２付勢部材が付勢解除位置に切換えられると、第１付勢部材だけで張力付与板が第１付勢力でベース板の方へ弾性付勢され、また、第２付勢部材が付勢位置に切換えられると、第１，第２付勢部材の両方で張力付与板が第２付勢力によりベース板の方へ弾性付勢される。即ち、第１付勢部材の弾性付勢力が第１付勢力になり、第１，第２付勢部材の弾性付勢力の和が第２付勢力になる。このように、付勢手段による弾性付勢力を第１，第２付勢力に簡単に切換えることができるとともに、付勢手段と付勢力切換え機構を簡単且つ小型に構成でき、製作コスト的にも有利になる。
【００２４】
請求項４のミシンの上糸張力付与装置は、請求項１の発明において、天秤の先端の糸取上部に糸掛けを許可する許可位置と糸掛けを禁止する禁止位置に切換わる天秤シャッターを備え、前記付勢力切換え機構は、天秤シャッターが許可位置に切換えられた状態では付勢手段による付勢力を第１付勢力に切換え、天秤シャッターが禁止位置に切換えられた状態では付勢手段による付勢力を第２付勢力に切換えることを特徴とするものである。
【００２５】
この上糸張力付与装置では、天秤シャッターが許可位置に切換えられると、天秤の先端の糸取上部に糸掛けを行える状態になるとともに、付勢力切換え機構により、付勢手段による付勢力が第１付勢力に切換えられるため、天秤の糸取上部への糸掛けを含む糸掛け作業を容易に行うことができ、また、天秤シャッターが禁止位置に切換えられると、天秤の糸取上部に糸掛けを行えない状態になるとともに、付勢力切換え機構により、付勢手段による付勢力が第２付勢力に切換えられるため、縫製時の上糸のヨリを確実に戻すこができる。
【００２６】
請求項５のミシンの上糸張力付与装置は、請求項１の発明において、前記天秤シャッターが許可位置又は禁止位置に切換えられた状態を検出する検出手段を設けたことを特徴とするものである。この上糸張力付与装置では、検出手段により天秤シャッターが許可位置又は禁止位置に切換えられた状態を検出することにより、その検出手段から得られる検出情報に基づいて、付勢力切換え機構を作動させることが可能になる。
【００２７】
請求項６のミシンの上糸張力付与装置は、請求項１の発明において、前記付勢手段は張力付与板をベース板の方へ弾性付勢する第１，第２付勢部材を含み、第１付勢部材は張力付与板を常時付勢するとともに、前記付勢力切換え機構は、第２付勢部材を張力付与板を付勢する付勢位置と張力付与板を付勢しない付勢解除位置とに亙って切換えることを特徴とするものである。
【００２８】
この上糸張力付与装置では、付勢力切換え機構により、第２付勢部材が付勢解除位置に切換えられると、第１付勢部材だけで張力付与板が第１付勢力によりベース板の方へ弾性付勢され、また、第２付勢部材が付勢位置に切換えられると、第１，第２付勢部材の両方で張力付与板が第２付勢力でベース板の方へ弾性付勢される。即ち、第１付勢部材の弾性付勢力が第１付勢力になり、第１，第２付勢部材の弾性付勢力の和が第２付勢力になる。このように、付勢手段による弾性付勢力を第１，第２付勢力に簡単に切換えることができるとともに、付勢手段と付勢力切換え機構を簡単且つ小型に構成でき、製作コスト的にも有利になる。
【００２９】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照して説明する。
本実施形態は、ミシンの上糸供給源から天秤に至る上糸経路における上糸に張力を付与する上糸張力付与装置に、本発明を適用したものである。図１に示すように、ミシンＭは、ベッド部１、ベッド部１の右端部分に立設された脚柱部２、脚柱部２の上端部分からベッド部１と対向して左方へ延びるアーム部３等を有する。
【００３０】
ベッド部１は、その左端部分に片持ち状のフリーベッド部４（通称、フリーアーム）と、フリーベッド部４に着脱可能に装着される補助テーブル５とを有し、図示していないが、フリーベッド部４から補助テーブル５を取外すと、フリーベッド部４全体が現れ、このフリーベッド部４を袋物や袖等の筒物に挿通させこれら袋物や筒物を縫製するのに便利になる。
【００３１】
アーム部３の前面には液晶ディスプレイ７が設けられ、この液晶ディスプレイ７に、縫い方（実用縫いや文字等の模様縫い）、ミシンの使い方、糸調子等の各種情報が表示される。液晶ディスプレイ７の表面部にはタッチキーが設けられ、液晶ディスプレイ７に表示された画面に基づいてタッチキーをタッチ操作することで、例えば、液晶ディスプレイ７に表示された複数の縫い方の中から所望の縫い方を選択したり、糸調子の強弱を調整することができる。
【００３２】
液晶ディスプレイ７の左下側においてアーム部３の前面には調整部材８が設けられ、この調整部材８を左右にスライド操作して縫製速度を調整することができる。アーム部３の頭部６の下部には、縫製開始スイッチ、縫製終了スイッチ、布送りＵターンスイッチ、自動糸切りスイッチ等の複数（例えば、４つ）のスイッチ９が設けられている。
【００３３】
アーム部３の後側には、糸駒１１を装着可能な取付け軸１０が設けられ、取付け軸１０に装着された糸駒１１の上糸１２が、糸駒１１から天秤１３に至る上糸経路を経由して針棒１４の下端に装着された縫針１５に供給される。頭部６の下端部分には、ベッド部１のベッド面に載置された布を押える昇降可能な押え足１６と、基端部分が前後方向向きの枢支軸１７ａ（図２参照）に回動自在に支持された操作部材１７が設けられ、操作部材１７を枢支軸１７ａ回りに回動操作し押え足１６を昇降させることができる。
【００３４】
図示していないが、ベッド部１の内部には、回転釜を及び回転釜を駆動する釜駆動機構と、ベッド面上の布を布送り方向（前後方向）へ送る布送り機構等が設けられ、頭部６の内部には、天秤１３を略上下に揺動駆動する天秤駆動機構と、針棒１４を上下駆動する針棒上下駆動機構と、針棒１４を左右に揺動駆動する針棒揺動駆動機構等が設けられている。尚、これらの部材や機構は周知のものであるため、それらの詳細な説明を省略する。
【００３５】
さて、このミシンＭには、前記種々の部材や機構の他に、取付け軸１０に装着された糸駒１１から天秤１３に至る上糸経路における上糸１２に張力を付与する上糸張力付与装置２０（図２〜図７参照）と、天秤１３の先端の糸取上部に糸掛けを許可する許可位置と糸掛けを禁止する禁止位置に切換わる天秤シャッター７５（図３、図６参照）と、前記上糸経路を経由して天秤１３から縫針１５側へ延びる上糸１２の端部付近を縫針１５の目孔１５ａへ糸通しする糸通し装置８０（図８〜図１２参照）が設けられている。
【００３６】
上糸張力付与装置２０について説明する。
図１〜図７に示すように、上糸張力付与装置２０は、上糸１２に張力を与えその張力を調整可能な主張力付与機構２１と、この主張力付与機構２１よりも上糸経路の糸駒１１側に設けられベース板５０と張力付与板５１との間に上糸１２が通過する張力付与部を形成してなる副張力付与機構２２とで構成され、これら主張力付与機２１と副張力付与機構２２はアーム部３の頭部６の内部に設けられている。
【００３７】
先ず、主張力付与機構２１について説明する。
図２〜図４に示すように、主張力付与機構２１は、パルスモータ３０と、パルスモータ３０の出力軸３０ａに固着された駆動ローラ３１と、駆動ローラ３１に当接可能な１対の従動ローラ３２，３３と、１対の従動ローラ３２，３３を駆動ローラ３１に当接する作動位置（図２に実線で示す）と駆動ローラ３１から離隔する非作動位置（図２に鎖線で示す）とに亙って切換えるローラ位置切換え機構３４等で構成されている。
【００３８】
パルスモータ３０はミシン機枠に固着されたフレーム部材３５の鉛直の取付部３５ａの右面部に取付けられ、パルスモータ３０の出力軸３０ａは取付部３５ａを挿通して前方へ延び、その前側において出力軸３０ａに駆動ローラ３１が固着されている。取付部３５ａの左側には可動板３６が配設され、この可動板３６に１対の従動ローラ３２，３３が回転自在に支持されている。尚、可動板３６には駆動ローラ３１が挿通する長孔３６ａが形成されている。
【００３９】
ローラ位置切換え機構３４は、前記可動板３６、可動板３６の後側においてミシン機枠に左右方向向きの軸心回りに回動自在に枢支され且つ略周方向等間隔に形成された３本のレバー部４０ａ，４０ｂ，４０ｃを有する回転体４０、鉛直向きに配設された連結部材４１、押え足１６の操作部材１７の付近においてミシン機枠に左右方向向きの軸心回りに回動自在に枢支された側面視くの字型のリンク部材４２、操作部材１７に一体的に設けられたカム４３を有する。
【００４０】
可動板３６の後下端部に、回転体４０のレバー部４０ａの先端部が回転可能に連結され、回転体４０のレバー部４０ｂの先端部に連結部材４１の上端部が回動可能に連結され、連結部材４１の下端部にリンク部材４２の右端部が回動可能に連結され、リンク片４２の押動部４２ａにカム４３が当接している。回転体４０はバネ部材（図示略）により図２のｄ方向へ回動付勢され、これにより、従動ローラ３２、３３を作動位置に移動させ駆動ローラ３１に接触させる。
【００４１】
操作部材１７が図４の実線の姿勢のとき押え足１６は下降した状態になり、この状態で、カム４３の小径部がリンク片４２の押動部４２ａに当接し、１対の従動ローラ３２，３３が作動位置に位置する。この状態から、操作部材１７を図４のａ方向に回動操作して鎖線で示す姿勢に切換えると、押え足１６が上昇するとともに、カム４３とリンク部材４２と連結部材４１を介して回転体４０が図２のｃ方向に回動され、可動板３６とともに１対の従動ローラ３２，３３が移動して非作動位置に切換えられる。
【００４２】
ここで、例えば、１対の従動ローラ３２，３３は作動位置側へ付勢され、リンク部材４２の押え部４２ａがカム４３に常時当接する状態になる。即ち、１対の従動ローラ３２，３３が非作動位置に位置する状態から、図４の鎖線で示す操作部材１７をｂ方向に回動操作して実線で示す姿勢に切換えると、押え足１６が下降するとともに、回転体４０が図２のｄ方向に回動され、可動板３６とともに１対の従動ローラ３２，３３が作動位置に切換えられる。
【００４３】
１対の従動ローラ３２，３３が非作動位置に切換えられると、１対の従動ローラ３２，３３が駆動ローラ３０から離隔するため、所定の糸掛け手順で駆動ローラ３１の外周部に上糸１２を掛けることができる。駆動ローラ３１の外周部に上糸１２が掛けられた状態で、１対の従動ローラ３２，３３が作動位置に切換えられると、駆動ローラ３１と１対の従動ローラ３２，３３との間で上糸１２が挟持され、制御装置（図示略）により、縫製速度に対するパルスモータ３０（駆動ローラ３１）の回転速度、つまり上糸１２の供給量（繰出し量）を制御することで、上糸１２に付与する張力を調整できるようになっている。
【００４４】
尚、フレーム部材３５には取付部３５ａの下側において取付片３５ｂが一体形成され、この取付片３５ｂに糸案内部材３５ｃが設けられ、主張力付与機構２１に糸掛けされた上糸１２は、主張力付与機構２１から下方へ延び、糸案内部材３５ｃに案内されてＵターンして略上方に位置する天秤１３へ延びている。
【００４５】
次に、副張力付与機構２２について説明する。
図２、図３、図５〜図７に示すように、副張力付与機構２２は、鉛直のベース板５０と、ベース板５０の左面に面接触する鉛直の張力付与板５１と、張力付与板５１をベース板５０の方（右方）へ弾性付勢する付勢機構５２と、付勢機構５２による弾性付勢力を第１付勢力とこの第１付勢力よりも大きな第２付勢力とに択一的に切換え可能な付勢力切換え機構５３等で構成されている。
【００４６】
ベース板５０は、前記フレーム部材３５の後部に固着された水平な取付け部材５４の左後端部分にボルト５０ａで固着されている。ベース板５０にはその後上端部から中央部分へ延びる案内スリット５５が形成され、ベース板５０の上端部には後方へ延出する糸案内部５６が形成されている。糸掛けの際に所定の糸掛け手順を行うことで、上糸１２は糸案内部５６により案内スリット５５の外端側に案内されてから、案内スリット５５によりその内端部の糸掛け部５７へ案内されて完了する。糸掛けされた上糸１２はこの糸掛け部５７からベース板５０と張力付与板５１の間の張力付与部を通過して主張力付与機構２１の駆動ローラ３１へ延びている。
【００４７】
ベース板５０には左右方向向きの軸部材６０，６１が装着され、軸部材６０はその右端部をベース板５０に固着してベース板５０から左方へ延び、軸部材６１はその左端部分をベース板５０に摺動自在に挿通させてベース板５０から右方へ延びている。軸部材６１の中央部分は、ベース板５０と一体形成されたガイド部材６２を摺動自在に挿通し、このガイド部材６２とベース板５０により、軸部材６１は左右方向へ移動可能にガイド支持されている。
【００４８】
軸部材６０の左端部にはリング６３が外嵌固着され、軸部材６１には、ベース板５０よりも左側に位置する左端部と、ベース板５０とガイド部材６２の間の部分に、リング６４，６５が夫々外嵌固着されている。張力付与板５１は略矩形状に形成され、張力付与板５１を軸部材６０，６１が摺動自在に挿通し、これら軸部材６０，６１により張力付与板５１が支持されている。
【００４９】
付勢機構５２は張力付与板５１を右方へ弾性付勢する第１，第２圧縮コイルバネ６６，６７を有し、第１圧縮コイルバネ６６は、軸部材６０に張力付与板５１とリング６３の間において外装され、第２圧縮コイルバネ６７は、軸部材６１にベース板５０とリング６５の間において外装されている。ここで、第１圧縮コイルバネ６６は張力付与板５１を直接右方へ付勢するのに対して、第２圧縮コイルバネ６６は軸部材６１を右方へ付勢し、その軸部材６１とリング６４とを介して張力付与板５１を右方へ付勢するようにしてある。
【００５０】
さて、第１圧縮コイルバネ６６は張力付与板５１を常時右方へ付勢するとともに、第２圧縮コイルバネ６７は、付勢力切換え機構５３により、張力付与板５１を右方へ付勢する付勢位置と張力付与板５１を付勢しない付勢解除位置とに亙って切換えられ、第２圧縮コイルバネ６７を付勢解除位置に切換えると、第１圧縮コイルバネ６６だけで張力付与板５１が第１付勢力により右方へ弾性付勢され、第２圧縮コイルバネ６７を付勢位置に切換えると、第１，第２圧縮コイルバネ６６，６７の両方で張力付与板５１が第２付勢力により右方へ弾性付勢される。即ち、第１圧縮コイルバネ６６の弾性付勢力が第１付勢力になり、第１，第２圧縮コイルバネ６６，６７の弾性付勢力の和が第２付勢力になる。
【００５１】
付勢力切換え機構５３について詳細に説明する。
付勢力切換え機構５３は、押え足１６を昇降させる操作部材１７に連動して作動し、押え足１６が上った状態では付勢機構５２による付勢力を第１付勢力に切換え、押え足１６が下った状態では付勢機構５２による付勢力を第２付勢力に切換えるように構成されている。
【００５２】
図２、図３、図５〜図７に示すように、付勢力切換え機構５３は、前記ローラ位置切換え機構３４と共通の回転体４０と連結部材４１とリンク部材４２とカム４３と、取付け部材５４に垂設された支軸７０に回動自在に枢支された作動部材７１と、支軸７０の右側において取付け部材５４に垂設された支軸７２に回動自在に枢支された押動部材７３を有する。
【００５３】
作動部材７１は平面視コの字型の大小２つの係合部７１ａ，７１ｂを有し、係合部７１ａに回動部材４０のレバー部４０ｃの先端部が下側から係合している。押動部材７３は略直交する連結部７３ａと押動部７３ｂとを有し、連結部７３ａの先端部が作動部材７１の係合部７１ｂに係合し、押動部７３ｂにより軸部材６１の右端部を左方へ押動可能になっている。
【００５４】
作動部材１７が図５（図２）の実線の姿勢のとき押え足１６は下降した状態になり、この状態で、カム４３ａの小径部がリンク片４２の押動部４２ａに当接し、第２圧縮コイルバネ６７が付勢位置に位置する。この状態から、操作部材１７を図５のａ方向に回動操作して鎖線で示す姿勢に切換えると、押え足１６が上昇するとともに、カム４３とリンク部材４２と連結部材４１を介して回転体４０が図２のｃ方向に回動され、押動部材７３が作動部材７１を介して図３のｅ方向に回動される。
【００５５】
すると、図７に示すように、押動部材７３の押動部７３ｂにより軸部材６１が左方へ押動されて、軸部材６１とリング６４とを介して第２圧縮コイルバネ６７の弾性付勢力が張力付与板５１に伝達されなくなり、第１圧縮コイルバネ６６だけで張力付与板５１が右方へ付勢された状態になる。尚、この状態の第２圧縮コイルバネ６７の位置が付勢解除位置になる。
【００５６】
また、第２圧縮コイルバネ６７が付勢解除位置に位置する状態から、図５の鎖線で示す操作部材１７をｂ方向に回動操作して実線で示す姿勢に切換えると、押え足１６が下降するとともに、回転体４０が図２のｄ方向に回動され、押動部材７３が作動部材７１を介して図３のｆ方向に回動される。すると、第２圧縮コイルバネ６７がその弾性付勢力により付勢解除位置から付勢位置に復帰し、図３、図５に示すように、第１，第２圧縮コイルバネ６６，６７の両方で張力付与板５１が右方へ付勢された状態になる。
【００５７】
次に、天秤シャッター７５について説明する。
天秤シャッター７５は、付勢力切換え機構５３の作動部材７０と一体形成され、作動部材７０の下端部から左方へ延び、張力付与板５１の左側において上方へ屈曲し更に前方斜め上がりに延び、その先端部に水平のシャッター板７５ａが一体形成されている。
【００５８】
図３に示すように、付勢力切換え機構５３により第２圧縮コイルバネ６７が付勢位置に切換えられると、シャッター板７５ａが天秤１３の先端の糸取上部の上側に位置し（図１参照）、天秤シャッター７５が天秤１３の糸取上部に糸掛けを禁止する禁止位置に切換えられる。また、図７に示すように、付勢力切換え機構５３により第２圧縮コイルバネ６７が付勢解除位置に切換えられると、図３に鎖線で示すように、天秤シャッター７５は支軸７０回りに水平揺動し、天秤１３の糸取上部に糸掛けを許可する許可位置に切換えられ、シャッター板７５ａが天秤１３の糸取上部の上側に位置しなくなる。
【００５９】
このように、天秤シャッター７５は付勢力切換え機構５３に連動して作動し、付勢力切換え機構５３により、天秤シャッター１３が許可位置に切換えられた状態では、第２圧縮コイルバネ６７が付勢解除位置に切換えられ、付勢機構５２による付勢力が第１付勢力になり、天秤シャッター７５が禁止位置に切換えられた状態では、第２圧縮コイルバネ６７が付勢位置に切換えられ、付勢機構５２による付勢力が第２付勢力になる。
【００６０】
次に、糸通し装置８０につい説明する。
図８〜図１２に示すように、針棒１４と隣接する糸通し軸８１が、針棒台１９に上下動自在に支持され、その上端部分が２又部材８２の隙間を挿通して配設されている。糸通し軸８１の中段よりも上側に水平ピン８３が固定され、糸通し軸８１の下端部分に操作レバー８４と、操作レバー８４よりも下側に位置するフック８５（図１１参照）及び糸案内板８６，８７が固定されている。針棒１４には位置決め部材８８が外嵌固定されている。
【００６１】
糸通し軸８１には、縦方向に所定長さを有する内側の第１ガイド部材９０と外側の第２ガイド部材９１とが２重構造として昇降可能に挿通されている。第１ガイド部材９０は、糸通し軸８１が挿通する上下１対の水平部９０ａと、これら水平部９０ａの略左半部分を連結する側壁部９０ｂ等を一体形成してなり、側壁部９０ｂの左側面部には、糸通し軸８１のピン８３を昇降可能に案内する縦向きのスリット９０ｃが形成され、上側の水平部９０ａには、後側に突出し位置決め部材８８の突出部８８ａに上側から当接する当接部９０ｄが形成されている。
【００６２】
第２ガイド部材９１は、糸通し軸８１が挿通する上下１対の水平部９１ａと、これら水平部９１ａの略左半部分を連結する側壁部９１ｂ等を一体形成してなり、側壁部９１ｂの左側面部には、その上端部において左方向きのピン部材９２が固着され、針棒台１９の側壁部１９ａには、ピン部材９２を昇降可能に案内する縦向きのスリット１９ｂが形成されている。更に、側壁部９１ｂのピン部材９２の下側には、ピン８１を昇降可能に案内する縦向きのスリット９１ｃと、スリット９１ｃの下端部に連通しピン８１を水平方向に移動可能に案内するスリット９１ｄが形成されている。
【００６３】
糸通し軸８１の上端のリング９３と針棒台１９の上支持部１９ｃとの間の糸通し軸８１に、糸通し軸８１を上方へ付勢する圧縮コイルバネ９４が外装され、針棒台１９の下支持部１９ｄと第２ガイド部材９１の下側の水平部９１ｃとの間の糸通し軸８１に、第１，第２ガイド部材９０，９１を上方へ付勢する圧縮コイルバネ９５が外装されている。圧縮コイルバネ９５のバネ力は圧縮コイルバネ９４のバネ力よりも大きく設定され、通常、図９、図１０に示すように、糸通し軸８１は上限位置に位置し、操作レバー８４の基端部が下支持部１９ｄに下側から当接している。
【００６４】
糸通しに際しては、操作部材１７を図４、図５の鎖線で示す位置に回動操作することにより、押え足１６を上昇位置に切換え、上糸張力付与装置２０においては、主張力付与機構２１を開放させるとともに、副張力付与機構２２だけで上糸１２に張力を付与する状態で行う。先ず、操作レバー８４とともに糸通し軸８１を上限位置から下降させる。このとき、ピン８３がスリット９０ｃ，９１ｃに案内されるため、糸通し軸８１は回動しない。また、第１，第２ガイド部材９０，９１は圧縮コイルバネ９５により夫々上限位置に保持される。
【００６５】
糸通し軸８１が押し下げられ、第１ガイド部材９０の当接部９０ｄが位置決め部材８８の突出部８８ａに当接すると、ピン８３がスリット９１ｄに対応する高さ位置になり、このとき、図１１、図１２に示すように、糸駒１１から前記上糸経路を経て天秤１３から延びる上糸１２を、糸案内板８６に係合させその下側を通して、縫針１５の手前を通るように右方へ水平状に引き出しておく。
【００６６】
次に、操作レバー８４を平面視にて時計回り方向に、ピン部材８３がスリット９１ｄの端部に移動するまで回動させると、上糸１２は二股状の糸案内板８７で糸通し位置に位置決めされ、フック８５が縫針１５の目孔１５ａに挿通して上糸１２を引っ掛ける。その後、操作レバー８４を平面視にて反時計回り方向に回動させることにより、上糸１２を目孔１５ａに糸通しすることができる。その後操作レバー８４の操作を止めることにより、操作レバー８４とともに糸通し軸８１は圧縮コイルバネ９４により上限位置まで上昇する。
【００６７】
上糸張力付与装置２０の作用・効果について説明する。
この上糸張力付与装置２０では、ミシン１の上糸供給源である糸駒１１から天秤１３に至る上糸経路における上糸１２に、主張力付与機構２１と、主張力付与機構２１よりも糸駒１１側に設けられた副張力付与機構２２とにより張力が付与することができる。副張力付与機構２２においては、付勢機構５２により張力付与板５１がベース板５０の方へ弾性付勢され、ベース板５０と張力付与板５１の間に形成された張力付与部から上糸１２に張力が付与される。
【００６８】
副張力付与機構２２の付勢機構５２による弾性付勢力は、付勢力切換え機構５３により、糸掛け時には第１付勢力に切換えられ、縫製時には第２付勢力に切換えられる。第１付勢力は、糸掛け作業（糸通し作業を含む）を簡単且つ確実に行える張力（例えば、２〜４gf）を上糸に付与するように設定され、縫製時に主張力付与機構２１の張力付与作用によって主張力付与機構２１よりも糸駒１１側の上糸１２にヨリが発生するが、第２付勢力は、その上糸１２のヨリを確実に戻すことができる張力（例えば、５〜10gf）を上糸に付与するように設定される。
【００６９】
つまり、この上糸張力付与装置２０によれば、副張力付与機構２２の付勢機構５２による弾性付勢力を第１付勢力とこの第１付勢力よりも大きな第２付勢力とに択一的に切換え可能な付勢力切換え機構５３を設けたので、副張力付与機構２２により上糸１２に付与する張力を糸掛け時と縫製時に分けて２段階に簡単に調整することができ、第１付勢力を上記のように設定することで、糸掛け時の糸掛け作業を容易に行えるようになるため、オペレータの糸掛け作業の負荷を軽減することができる。
【００７０】
特に、縫針１５の目孔１５ａに糸通しを行う糸通し装置８０を設けても、第１付勢力を糸通し装置８０に応じた張力を上糸に付与するように設定することができるため、その糸通し装置８０により上糸１２の目孔１５ａへの糸通しを簡単且つ確実に行うことが可能になる。しかも、第２付勢力を上記のように設定することで、縫製時の上糸１２のヨリを確実に戻すこができるため、上糸１２のヨリが主張力付与機構２１に進入し、更に主張力付与機構２１よりも下流側へ引出されて弛み、縫製不良が起こるのを防止できる。
【００７１】
操作部材１７を操作して、押え足１６を上げると付勢機構５２による付勢力を第１付勢力に切換えることができ、押え足１６を下げると付勢機構５２による付勢力を第２付勢力に切換えることができる。このように、押え足１６を昇降させる操作部材１７に連動して、付勢力切換え機構５３が作動するように構成したので、オペレータの操作負荷を軽減でき、また、付勢力切換え機構５３の構造を簡単化し製作コストを低減できる。
【００７２】
押え足１６を昇降させることにより、主張力付与機構２１の状態を、上糸１２に張力を付与する状態と付与しない状態に切換えることができるため、オペレータの操作負荷を一層軽減することができ、また、押え足１２が上った状態では、主張力付与機構２１が開放されているため、その主張力付与機構２１に糸掛けを容易に行うことができ、更に、副張力付与機構２２だけで上糸に張力を付与している状態になるため、前記第１付勢力を、糸掛け作業を容易に行える張力を上糸に付与するように設定し易くなる。
【００７３】
付勢力切換え機構５３により、第２圧縮コイルバネ６７を付勢解除位置に切換えると、第１圧縮コイルバネ６６だけで張力付与板５１が第１付勢力により右方へ弾性付勢され、また、第２圧縮コイルバネ６７を付勢位置に切換えると、第１，第２圧縮コイルバネ６６，６７の両方で張力付与板５１が右方へ弾性付勢される。このように、付勢機構５２による弾性付勢力を第１，第２付勢力に簡単に切換えることができるとともに、付勢機構５２と付勢力切換え機構５３を簡単且つ小型に構成でき、製作コスト的にも有利になる。
【００７４】
天秤シャッター７５を許可位置に切換えると、天秤１３の先端の糸取上部に糸掛けを行える状態になるとともに、付勢力切換え機構５３により、付勢機構５２による付勢力が第１付勢力に切換えられるため、天秤１３の糸取上部への糸掛けを含む糸掛け作業を容易に行うことができ、また、天秤シャッター７５を禁止位置に切換えると、天秤１３の糸取上部に糸掛けを行えない状態になるとともに、付勢力切換え機構５３により、付勢機構５２による付勢力が第２付勢力に切換えられるため、縫製時の上糸１２のヨリを確実に戻すこができる。
【００７５】
前記実施形態を部分的に変更した変更形態について説明する。
１〕天秤シャッター７５が許可位置又は禁止位置に切換えられた状態を検出する検出センサを設けてもよい。この場合、検出センサにより天秤シャッター７５が許可位置又は禁止位置に切換えられた状態を検出することにより、その検出センサから得られる検出情報に基づいて、付勢力切換え機構５３を作動させることが可能になる。
【００７６】
２〕主張力付与機構２１においては、前記説明したものに限らず、例えば、糸調子皿を有する糸調子器等、種々の主張力付与機構を適用可能である。
３〕糸通し装置８０においても、前記説明したものに限らず、例えば、本出願人が出願した片手操作可能な糸通し装置等、種々の糸通し装置を適用可能である。
４〕前記実施形態は一例を示すものにすぎず、本発明の技術思想を逸脱しない範囲で種々の変更を加えて勿論実施し得る。
【００７７】
【発明の効果】
請求項１のミシンの上糸張力付与装置によれば、副張力付与機構の付勢手段による弾性付勢力を第１付勢力とこの第１付勢力よりも大きな第２付勢力とに択一的に切換え可能な付勢力切換え機構を設けたので、副張力付与機構により上糸に付与する張力を糸掛け時と縫製時に分けて２段階に簡単に調整することができる。
【００７８】
その結果、第１，第２付勢力を適切な値に設定することで、糸掛け時の糸掛け作業が容易に行えるようになり、オペレータの糸掛け作業の負荷を軽減することができ、特に、糸通し装置を設けた場合にも、第１付勢力を糸通し装置に応じた張力で上糸に付与するように設定することで、その糸通し装置により上糸の目孔への糸通しを簡単且つ確実に行うことが可能になるし、縫製時の上糸のヨリを確実に戻すこができるため、上糸のヨリが主張力付与機構に進入し、更に主張力付与機構よりも下流側へ引出されて弛み、縫製不良が起こるのを防止できる。
【００７９】
しかも、操作部材を操作して、押え足を上げると付勢手段による付勢力を第１付勢力に切換えることができ、押え足を下げると付勢手段による付勢力を第２付勢力に切換えることができる。押え足を昇降させる操作部材に連動して、付勢力切換え機構が作動するように構成したので、オペレータの操作負荷を軽減でき、また、付勢力切換え機構の構造を簡単化し製作コストを低減できる。
【００８０】
請求項２のミシンの上糸張力付与装置によれば、押え足を昇降させることにより、主張力付与機構の状態を、上糸に張力を付与する状態と付与しない状態に切換えることができるため、オペレータの操作負荷を一層軽減することができ、また、押え足が上った状態では、主張力付与機構が開放されているため、その主張力付与機構に糸掛けを容易に行うことができ、更に、副張力付与機構だけで上糸に張力を付与している状態になるため、前記第１付勢力を、糸掛け作業を容易に行える張力を上糸に付与するように設定し易くなる。
【００８１】
請求項３のミシンの上糸張力付与装置によれば、付勢力切換え機構により、第２付勢部材を付勢解除位置に切換えると、第１付勢部材だけで張力付与板が第１付勢力によりベース板の方へ弾性付勢され、また、第２付勢部材を付勢位置に切換えると、第１，第２付勢部材の両方で張力付与板が第２付勢力でベース板の方へ弾性付勢される。このように、付勢手段による弾性付勢力を第１，第２付勢力に簡単に切換えることができるとともに、付勢手段と付勢力切換え機構を簡単且つ小型に構成でき、製作コスト的にも有利になる。
【００８２】
請求項４のミシンの上糸張力付与装置によれば、天秤シャッターを許可位置に切換えると、天秤の先端の糸取上部に糸掛けを行える状態になるとともに、付勢力切換え機構により、付勢手段による付勢力が第１付勢力に切換えられるため、天秤の糸取上部への糸掛けを含む糸掛け作業を容易に行うことができ、また、天秤シャッターを禁止位置に切換えると、天秤の糸取上部に糸掛けを行えない状態になるとともに、付勢力切換え機構により、付勢手段による付勢力が第２付勢力に切換えられるため、縫製時の上糸のヨリを確実に戻すこができる。
【００８３】
請求項５のミシンの上糸張力付与装置によれば、天秤シャッターが許可位置又は禁止位置に切換えられた状態を検出する検出手段を設けたので、検出手段から得られる検出情報に基づいて、付勢力切換え機構を作動させることが可能になる。
【００８４】
請求項６のミシンの上糸張力付与装置によれば、付勢力切換え機構により、第２付勢部材を付勢解除位置に切換えると、第１付勢部材だけで張力付与板が第１付勢力によりベース板の方へ弾性付勢され、また、第２付勢部材を付勢位置に切換えると、第１，第２付勢部材の両方で張力付与板が第２付勢力によりベース板の方へ弾性付勢される。このように、付勢手段による弾性付勢力を第１，第２付勢力に簡単に切換えることができるとともに、付勢手段と付勢力切換え機構を簡単且つ小型に構成でき、製作コスト的にも有利になる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係るミシンの正面図である。
【図２】上糸張力付与装置の左側面図である。
【図３】上糸張力付与装置の平面図である。
【図４】上糸張力付与装置の主張力付与機構の正面図である。
【図５】上糸張力付与装置の副張力付与機構の正面図である。
【図６】副張力付与機構の斜視図である。
【図７】副張力付与機構の部分平面図である。
【図８】糸通し装置の分解斜視図である。
【図９】糸通し装置の正面図である。
【図１０】糸通し装置の左側面図である。
【図１１】図９のXI−XI線断面図である。
【図１２】糸通し装置の部分正面図である。
【符号の説明】
Ｍミシン
１１糸駒
１２上糸
１３天秤
１５縫針
１６押え足
１７操作部材
２０上糸張力付与装置
２１主張力付与機構
２２副張力付与機構
５０ベース板
５１張力付与板
５２付勢機構
５３付勢力切換え機構
６６，６７第１，第２圧縮コイルバネ
７５天秤シャッター
８０糸通し装置[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an upper thread tension applying device of a sewing machine, and more particularly, an urging force switching mechanism capable of selectively switching an elastic urging force by an urging means of a sub-tension applying mechanism to a first urging force and a second urging force is provided. The present invention relates to an upper thread tension applying device.
[0002]
[Prior art]
  In conventional sewing machines, tension is usually applied to the upper thread in the upper thread path from the thread spool (upper thread supply source) to the balance, and the assertive power of a thread tensioner, etc. that can be adjusted with an adjustment dial, etc. A mechanism is provided. In addition to the thread tensioner and the like, this assertive force imparting mechanism includes an upper thread sandwiched between a drive roller and a driven roller fixed to the output shaft of the pulse motor, and a pulse motor (drive roller) for the sewing speed. A device that adjusts the tension applied to the upper thread by controlling the amount of rotation, that is, the supply amount (feeding amount) of the upper thread, has been put to practical use.
[0003]
  Normally, when threading the assertion force imparting mechanism, it is necessary to open the assertion force imparting mechanism and switch it to a state where tension is not applied to the upper thread. In conventional sewing machines, the assertion force imparting mechanism is moved up and down the presser foot. When the presser foot is raised, the assertion force application mechanism is opened when the presser foot is raised, and when the presser foot is lowered, the assertion force application mechanism is closed to apply tension to the upper thread. There are many things.
[0004]
  By the way, at the time of sewing, the upper thread fed out isTwistedThe twist of the upper thread supply source side of the upper thread supply source than the assertive force imparting mechanism may occur, and the upper thread twist enters the assertive force imparting mechanism and further downstream of the assertive force imparting mechanism. When the thread is pulled out, the thread may loosen and sewing failure may occur. Therefore, a sub-tension applying mechanism (commonly called twist return) for returning the upper thread twist by applying a tension of several gf to several tens of gf to the upper thread on the yarn piece supply source side from the assertive force applying mechanism is provided. Sewing machines are widely used in practical use.
[0005]
  A general subtension applying mechanism has a base plate and a tension applying plate that comes into surface contact with the base plate, a tension applying portion through which the upper thread passes is formed, and tension is applied by a biasing member such as a spring. By tensioning the plate toward the base plate, tension is applied to the upper thread from the tension applying portion. Conventional sub-tension applying mechanisms are usually configured to always apply tension to the upper thread, and the tension applied to the upper thread by the sub-tension applying mechanism is set to a somewhat higher value (for example, 5 to 10 gf) in advance. By setting, it is possible to reliably return the twist of the upper thread in correspondence with the embroidery thread or the like where the twist is likely to occur.
[0006]
  When threading a sewing machine having a main tension applying mechanism and a sub tension applying mechanism, hold the end of the upper thread extending from the thread spool, and first, the sub tension applying mechanism is placed between the base plate and the tension applying plate. Then, the released assertion force imparting mechanism is threaded, and then the balance is threaded, and then the upper thread is passed through the eye of the sewing needle.
[0007]
  The present applicant, on the other hand, has an upper thread guide mechanism that guides the upper thread to a position near the eye of the sewing needle, a threading mechanism that takes the guided upper thread into the eye hole, and executes a threading operation. And a threading device (see Japanese Patent Publication No. 7-71596) that can easily thread the upper thread through the eye hole is proposed and put into practical use. In order to ensure the threading of the upper thread into the eye hole by this threading device, at least when the threading mechanism is operated, the upper thread guided by the upper thread guiding mechanism is held tight. It is necessary to keep it.
[0008]
[Problems to be solved by the invention]
  In a sewing machine equipped with a conventional assertion force application mechanism and subtension application mechanism, the subtension application mechanism is configured to always apply tension to the upper thread, and the subtension application mechanism adjusts the tension applied to the upper thread. Therefore, the tension applied to the upper thread by the sub tension applying mechanism must be set in advance according to various conditions.
[0009]
  However, in order to reliably return the twist of the upper thread, if the tension applied to the upper thread by the sub tension applying mechanism is set to a somewhat high value (for example, 5 to 10 gf), It becomes difficult to thread the upper thread between the base plate and the tension applying plate, and it becomes difficult to pull out the upper thread when threaded by the sub tension applying mechanism. Furthermore, when the threading device is used to thread the needle through the needle hole, the upper thread tension is too high, and the upper thread can be pulled out from the balance side to pass the upper thread long enough. There is also a fear that it cannot be done.
[0010]
  On the contrary, the tension applied to the upper thread by the sub tension applying mechanism is lowered to a certain level (for example, 2 to 4 gf) so that the threading operation of the upper thread can be easily performed and the threading by the threading device can be surely performed. If set, the upper thread twist cannot be reliably returned at the time of sewing, the upper thread twist enters the assertion force application mechanism, and is further pulled downstream from the assertion force application mechanism, causing looseness and poor sewing. There is a problem of getting up.
[0011]
  The sub-tensioning mechanism can be configured so that it can be switched so that tension is applied to the upper thread during sewing and is released during threading so as not to apply tension to the upper thread. Since the tension is not applied, there is a possibility that the upper thread will be pulled out excessively from the thread spool when threading, which will make the operator's threading work difficult, and the threading device will perform threading. When the upper thread guide mechanism is used, the upper thread is not tightly guided by the upper thread guide mechanism, so that there is a problem that the threading of the sewing needle through the eye hole of the sewing needle cannot be performed reliably.
[0012]
  An object of the present invention is to urge the sub tension applying mechanism in the upper thread tension applying device of the sewing machine so that the tension applied to the upper thread by the sub tension applying mechanism can be adjusted in two stages at the time of threading and sewing. The elastic urging force by the means can be selectively switched between the first and second urging forces, the threading operation at the time of threading is easily and reliably performed, and the twist of the upper thread at the time of sewing is reliably returned, etc. It is.
[0013]
[Means for Solving the Problems]
  The upper thread tension applying device of the sewing machine according to claim 1 is an upper thread tension applying device that applies tension to the upper thread in the upper thread path from the upper thread supply source of the sewing machine to the balance, and applies tension to the upper thread. Adjustable assertive force imparting mechanism and subtension imparting formed by forming a tension imparting portion that is provided closer to the upper thread supply source than the assertive force imparting mechanism and through which the upper thread passes between the base plate and the tension imparting plate A mechanism for elastically urging the tension applying plate toward the base plate, and the elastic urging force by the urging means is greater than the first urging force and the first urging force. An urging force switching mechanism that can be switched alternatively to the large second urging force is provided.The urging force switching mechanism operates in conjunction with an operation member that raises and lowers the presser foot. When the presser foot is raised, the urging force by the urging means is switched to the first urging force and the presser foot is lowered. Then, the urging force by the urging means is switched to the second urging force.Is.
[0014]
  In this upper thread tension applying device, the upper thread in the upper thread path from the upper thread supply source of the sewing machine to the balance is applied to the assertion force application mechanism and the sub tension applied to the upper thread supply source side of the assertion force application mechanism. Tension can be applied by the mechanism. In the sub tension applying mechanism, the tension applying plate is elastically biased toward the base plate by the urging means, and tension is applied to the upper thread from the tension applying portion formed between the base plate and the tension applying plate.
[0015]
  The elastic urging force by the urging means of the sub tension applying mechanism is switched to the first urging force at the time of threading by the urging force switching mechanism, and is switched to the second urging force at the time of sewing. Here, the first urging force is set so as to apply a tension (for example, 2 to 4 gf) that can easily and reliably perform the threading operation (including the threading operation) to the upper thread. In addition, twisting of the assertion force applying mechanism during sewing causes a twist in the upper thread supply source side upper thread from the assertion force applying mechanism, but the second urging force can reliably return the twist of the upper thread. It is set so that tension (for example, 5 to 10 gf) that can be applied is applied to the upper thread.
[0016]
  As described above, the biasing force switching mechanism capable of selectively switching the elastic biasing force by the biasing means of the sub-tension applying mechanism between the first biasing force and the second biasing force larger than the first biasing force is provided. Therefore, the tension applied to the upper thread by the sub-tensioning mechanism can be easily adjusted in two stages for threading and sewing, and by setting the first urging force as described above, This makes it possible to easily perform the threading operation of the operator, thereby reducing the load on the operator.
[0017]
  In particular, even when a threading device for threading the stitch needle is provided, the first biasing force can be set to be applied to the upper thread with a tension according to the threading device. It becomes possible to easily and reliably thread the upper thread into the eye hole. Moreover, since the twist of the upper thread at the time of sewing can be reliably returned by setting the second urging force as described above, the twist of the upper thread enters the assertive force imparting mechanism, and further the assertive force imparting mechanism It is possible to prevent the occurrence of poor sewing by being pulled out to the downstream side and loosening.
[0018]
[0019]
  Moreover,In this upper thread tension applying device, when the operation member is operated to raise the presser foot, the urging force by the urging means can be switched to the first urging force, and when the presser foot is lowered, the urging force by the urging means is changed to the first urging force. It can be switched to 2 biasing forces. In this way, the urging force switching mechanism is operated in conjunction with the operation member that raises and lowers the presser foot, so the operation load on the operator can be reduced, and the structure of the urging force switching mechanism is simplified and the manufacturing cost is reduced. Can be reduced.
[0020]
  Claim2The upper thread tension applying device of the sewing machine of claim1In the invention, the assertion force applying mechanism is configured so as not to apply tension to the upper thread when the presser foot is raised.
[0021]
  In this upper thread tension applying device, by raising and lowering the presser foot, the state of the assertive force applying mechanism can be switched between a state in which tension is applied to the upper thread and a state in which the upper thread is not applied. Can be reduced. In addition, when the presser foot is raised, the assertion force application mechanism is open, so that the assertion force application mechanism can be easily threaded, and the sub-tension application mechanism alone can tension the upper thread. Therefore, the first urging force can be easily set so as to apply a tension capable of easily performing the threading operation to the upper thread.
[0022]
  Claim3The upper thread tension applying device of the sewing machine of claim1'sIn the present invention, the biasing means includes first and second biasing members that elastically bias the tension applying plate toward the base plate, and the first biasing member constantly biases the tension applying plate and The force switching mechanism is characterized in that the second urging member is switched between the urging position for urging the tension applying plate and the urging release position for not urging the tension applying plate.
[0023]
  In this upper thread tension applying device, when the second urging member is switched to the urging release position by the urging force switching mechanism, the tension applying plate is moved toward the base plate by the first urging member only by the first urging member. When the second urging member is switched to the urging position, the tension applying plate is elastically urged toward the base plate by the second urging force by both the first and second urging members. The That is, the elastic biasing force of the first biasing member becomes the first biasing force, and the sum of the elastic biasing forces of the first and second biasing members becomes the second biasing force. Thus, the elastic urging force by the urging means can be easily switched to the first and second urging forces, and the urging means and the urging force switching mechanism can be easily and compactly configured, which is advantageous in terms of manufacturing cost. become.
[0024]
  Claim4The upper thread tension applying device of the sewing machine according to claim 1 further comprises a balance shutter that switches between a permitted position for allowing threading and a prohibited position for prohibiting threading at the upper part of the thread take-up at the tip of the balance. The force switching mechanism switches the biasing force by the biasing means to the first biasing force when the balance shutter is switched to the permitted position, and the biasing force by the biasing means when the balance shutter is switched to the prohibited position. It is characterized by switching to an urging force.
[0025]
  In this upper thread tension applying device, when the balance shutter is switched to the permitted position, the thread can be hooked on the upper part of the thread take-up at the tip of the balance, and the urging force by the urging means is first applied by the urging force switching mechanism. Since it can be switched to the urging force, threading work including threading on the upper part of the thread take-up of the balance can be easily performed, and when the balance shutter is switched to the prohibited position, threading on the upper part of the thread take-up of the balance is possible. The urging force switching mechanism switches the urging force by the urging means to the second urging force, so that the twist of the upper thread at the time of sewing can be reliably returned.
[0026]
  Claim5The upper thread tension applying device of the sewing machine of claim1In the invention, a detecting means for detecting a state in which the balance shutter is switched to a permission position or a prohibition position is provided. In this upper thread tension applying device, the urging force switching mechanism is operated based on detection information obtained from the detecting means by detecting the state in which the balance shutter is switched to the permitted position or the prohibited position by the detecting means. Is possible.
[0027]
  Claim6The upper thread tension applying device of the sewing machine of claim1In the invention, the urging means includes first and second urging members that elastically urge the tension applying plate toward the base plate, and the first urging member constantly urges the tension applying plate, and The urging force switching mechanism is characterized in that the second urging member is switched between an urging position for urging the tension applying plate and an urging release position without urging the tension applying plate.
[0028]
  In this upper thread tension applying device, when the second urging member is switched to the urging release position by the urging force switching mechanism, the tension applying plate is moved toward the base plate by the first urging force only by the first urging member. When the second urging member is switched to the urging position, the tension applying plate is elastically urged toward the base plate by the second urging force by both the first and second urging members. The That is, the elastic biasing force of the first biasing member becomes the first biasing force, and the sum of the elastic biasing forces of the first and second biasing members becomes the second biasing force. Thus, the elastic urging force by the urging means can be easily switched to the first and second urging forces, and the urging means and the urging force switching mechanism can be easily and compactly configured, which is advantageous in terms of manufacturing cost. become.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
  In this embodiment, the present invention is applied to an upper thread tension applying device that applies tension to an upper thread in an upper thread path from an upper thread supply source of a sewing machine to a balance. As shown in FIG. 1, the sewing machine M extends to the left facing the bed portion 1 from the bed portion 1, the pedestal portion 2 standing on the right end portion of the bed portion 1, and the upper end portion of the pedestal portion 2. It has arm part 3 grade.
[0030]
  The bed portion 1 has a cantilevered free bed portion 4 (commonly called a free arm) and an auxiliary table 5 that is detachably attached to the free bed portion 4 at the left end portion, and is not shown in the figure. When the auxiliary table 5 is removed from the free bed portion 4, the entire free bed portion 4 appears, which is convenient for inserting the free bed portion 4 into a tubular object such as a bag or a sleeve and sewing the bag or tubular object.
[0031]
  A liquid crystal display 7 is provided on the front surface of the arm 3, and various information such as how to sew (practical sewing and pattern sewing such as letters), how to use the sewing machine, and thread tension are displayed on the liquid crystal display 7. A touch key is provided on the surface portion of the liquid crystal display 7, and the touch key is touch-operated based on the screen displayed on the liquid crystal display 7, for example, from among a plurality of sewing methods displayed on the liquid crystal display 7. It is possible to select a desired sewing method and adjust the strength of the thread tension.
[0032]
  An adjustment member 8 is provided on the front surface of the arm 3 on the lower left side of the liquid crystal display 7, and the sewing speed can be adjusted by sliding the adjustment member 8 left and right. A plurality of (for example, four) switches 9 such as a sewing start switch, a sewing end switch, a cloth feed U-turn switch, and an automatic thread trimming switch are provided below the head portion 6 of the arm portion 3.
[0033]
  On the rear side of the arm portion 3, an attachment shaft 10 to which a thread spool 11 can be attached is provided, and an upper thread 12 of the thread spool 11 attached to the attachment shaft 10 extends from the thread spool 11 to the balance 13. To the sewing needle 15 attached to the lower end of the needle bar 14. At the lower end portion of the head 6, a presser foot 16 that can be raised and lowered to press the cloth placed on the bed surface of the bed portion 1, and a proximal end portion that rotates around a pivot shaft 17 a (see FIG. 2) in the front-rear direction. An operation member 17 that is movably supported is provided, and the presser foot 16 can be moved up and down by rotating the operation member 17 around the pivot shaft 17a.
[0034]
  Although not shown, the bed portion 1 is provided with a rotary hook, a hook drive mechanism for driving the rotary hook, and a cloth feed mechanism for feeding the cloth on the bed surface in the cloth feed direction (front-rear direction). The head 6 has a balance driving mechanism for swinging the balance 13 substantially vertically, a needle bar vertical drive mechanism for driving the needle bar 14 up and down, and a needle bar for swinging the needle bar 14 left and right. A swing drive mechanism or the like is provided. Since these members and mechanisms are well known, detailed description thereof will be omitted.
[0035]
  In addition to the various members and mechanisms described above, the sewing machine M has an upper thread tension applying device that applies tension to the upper thread 12 in the upper thread path from the thread spool 11 mounted on the mounting shaft 10 to the balance 13. 20 (see FIGS. 2 to 7), and a balance shutter 75 (see FIGS. 3 and 6) that switches between a permitted position for allowing threading to the upper thread take-up portion of the balance 13 and a prohibited position for prohibiting threading. A threading device 80 (see FIGS. 8 to 12) for threading the vicinity of the end of the upper thread 12 extending from the balance 13 toward the sewing needle 15 through the upper thread path to the eye hole 15a of the sewing needle 15 is provided. ing.
[0036]
  The upper thread tension applying device 20 will be described.
  As shown in FIG. 1 to FIG. 7, the upper thread tension applying device 20 includes an assertion force applying mechanism 21 capable of applying tension to the upper thread 12 and adjusting the tension, and an upper thread path more than the asserting force applying mechanism 21. It is composed of a subtension applying mechanism 22 that is provided on the yarn spool 11 side and that forms a tension applying portion through which the upper thread 12 passes between the base plate 50 and the tension applying plate 51. The sub tension applying mechanism 22 is provided inside the head 6 of the arm 3.
[0037]
  First, the assertive force imparting mechanism 21 will be described.
  As shown in FIGS. 2 to 4, the assertive force applying mechanism 21 includes a pulse motor 30, a drive roller 31 fixed to the output shaft 30 a of the pulse motor 30, and a pair of followers that can contact the drive roller 31. Roller 32, 33, an operating position where a pair of driven rollers 32, 33 are brought into contact with the driving roller 31 (shown by a solid line in FIG. 2), and a non-operating position which is separated from the driving roller 31 (shown by a chain line). It is composed of a roller position switching mechanism 34 and the like that are switched over.
[0038]
  The pulse motor 30 is attached to the right surface portion of the vertical attachment portion 35a of the frame member 35 fixed to the sewing machine frame, and the output shaft 30a of the pulse motor 30 extends forward through the attachment portion 35a and is output on the front side thereof. A driving roller 31 is fixed to the shaft 30a. A movable plate 36 is disposed on the left side of the mounting portion 35a, and a pair of driven rollers 32 and 33 are rotatably supported by the movable plate 36. The movable plate 36 is formed with a long hole 36a through which the driving roller 31 is inserted.
[0039]
  The roller position switching mechanism 34 includes three movable plates 36, which are pivotally supported by the sewing machine frame on the rear side of the movable plate 36 so as to be rotatable about an axis in the left-right direction and are formed at substantially equal intervals in the circumferential direction. The rotating body 40 having the lever portions 40a, 40b, and 40c, the connecting member 41 arranged in the vertical direction, and the operating member 17 of the presser foot 16 are rotatable around the axis center in the left-right direction on the sewing machine frame. A link member 42 having a cross-sectional view, which is pivotally supported by the actuator, and a cam 43 provided integrally with the operation member 17.
[0040]
  A distal end portion of the lever portion 40a of the rotating body 40 is rotatably connected to the rear lower end portion of the movable plate 36, and an upper end portion of the connecting member 41 is rotatably connected to the distal end portion of the lever portion 40b of the rotating body 40. The right end portion of the link member 42 is rotatably connected to the lower end portion of the connecting member 41, and the cam 43 is in contact with the pushing portion 42 a of the link piece 42. The rotating body 40 is urged to rotate in the direction d in FIG. 2 by a spring member (not shown), thereby moving the driven rollers 32 and 33 to the operating position and bringing them into contact with the driving roller 31.
[0041]
  When the operating member 17 is in the posture shown by the solid line in FIG. 4, the presser foot 16 is lowered, and in this state, the small diameter portion of the cam 43 abuts against the pushing portion 42 a of the link piece 42 and a pair of driven rollers 32. , 33 are in the operating position. From this state, when the operation member 17 is rotated in the direction a in FIG. 4 and switched to the posture shown by the chain line, the presser foot 16 is raised, and the rotating body is rotated via the cam 43, the link member 42, and the connecting member 41. 40 is rotated in the direction c of FIG. 2, and the pair of driven rollers 32 and 33 are moved together with the movable plate 36 to be switched to the inoperative position.
[0042]
  Here, for example, the pair of driven rollers 32, 33 are urged toward the operating position, and the pressing portion 42 a of the link member 42 is always in contact with the cam 43. That is, when the operation member 17 indicated by the chain line in FIG. 4 is rotated in the b direction to switch to the posture indicated by the solid line from the state where the pair of driven rollers 32 and 33 are located at the non-operating position, the presser foot 16 is moved. While descending, the rotating body 40 is rotated in the direction d in FIG. 2, and the pair of driven rollers 32 and 33 are switched to the operating position together with the movable plate 36.
[0043]
  When the pair of driven rollers 32 and 33 are switched to the non-operating position, the pair of driven rollers 32 and 33 are separated from the drive roller 30, so that the upper thread 12 Can be multiplied. When the pair of driven rollers 32 and 33 are switched to the operating position in the state where the upper thread 12 is hung on the outer peripheral portion of the drive roller 31, the upper thread is moved between the drive roller 31 and the pair of driven rollers 32 and 33. The thread 12 is clamped and the rotational speed of the pulse motor 30 (drive roller 31) with respect to the sewing speed, that is, the supply amount (feed amount) of the upper thread 12 is controlled by a control device (not shown). The tension to be applied can be adjusted.
[0044]
  An attachment piece 35b is integrally formed on the frame member 35 below the attachment portion 35a. A thread guide member 35c is provided on the attachment piece 35b, and the upper thread 12 threaded on the assertion force applying mechanism 21 is The main tension applying mechanism 21 extends downward, is guided by the yarn guide member 35c, makes a U-turn, and extends to the balance 13 positioned substantially upward.
[0045]
  Next, the sub-tension applying mechanism 22 will be described.
  As shown in FIGS. 2, 3, 5 to 7, the subtension applying mechanism 22 includes a vertical base plate 50, a vertical tension applying plate 51 that is in surface contact with the left surface of the base plate 50, and a tension applying plate. An urging mechanism 52 for elastically urging 51 toward the base plate 50 (rightward), and an elastic urging force by the urging mechanism 52 into a first urging force and a second urging force larger than the first urging force. It is constituted by an urging force switching mechanism 53 or the like that can be switched alternatively.
[0046]
  The base plate 50 is fixed to the left rear end portion of the horizontal mounting member 54 fixed to the rear portion of the frame member 35 with a bolt 50a. The base plate 50 is then formed with a guide slit 55 extending from the upper end portion to the central portion, and the base plate 50 is formed with a yarn guide portion 56 extending rearward. By performing a predetermined threading procedure at the time of threading, the upper thread 12 is guided to the outer end side of the guide slit 55 by the thread guide part 56 and then the threading part 57 at the inner end part by the guide slit 55. To be completed. The threaded upper yarn 12 passes from the yarn hooking portion 57 through the tension applying portion between the base plate 50 and the tension applying plate 51 and extends to the drive roller 31 of the assertion force applying mechanism 21.
[0047]
  Left and right shaft members 60 and 61 are mounted on the base plate 50. The shaft member 60 has its right end fixed to the base plate 50 and extends leftward from the base plate 50, and the shaft member 61 has its left end portion. The base plate 50 is slidably inserted and extends from the base plate 50 to the right. A central portion of the shaft member 61 is slidably inserted into a guide member 62 integrally formed with the base plate 50, and the shaft member 61 is guided and supported by the guide member 62 and the base plate 50 so as to be movable in the left-right direction. ing.
[0048]
  A ring 63 is fitted and fixed to the left end portion of the shaft member 60, and a ring 64 is attached to the shaft member 61 at a left end portion located on the left side of the base plate 50 and between the base plate 50 and the guide member 62. , 65 are externally fitted and fixed. The tension applying plate 51 is formed in a substantially rectangular shape. The tension applying plate 51 is slidably inserted into the shaft members 60 and 61, and the tension applying plate 51 is supported by the shaft members 60 and 61.
[0049]
  The urging mechanism 52 includes first and second compression coil springs 66 and 67 that elastically urge the tension applying plate 51 to the right. The first compression coil spring 66 is connected to the shaft member 60 between the tension applying plate 51 and the ring 63. The second compression coil spring 67 is packaged between the base plate 50 and the ring 65 on the shaft member 61. Here, the first compression coil spring 66 directly biases the tension applying plate 51 rightward, whereas the second compression coil spring 66 biases the shaft member 61 rightward, and the shaft member 61 and the ring 64 are biased. The tension applying plate 51 is urged to the right via
[0050]
  The first compression coil spring 66 constantly urges the tension applying plate 51 to the right, and the second compression coil spring 67 urges the tension applying plate 51 to the right by the urging force switching mechanism 53. When the second compression coil spring 67 is switched to the bias release position, the tension applying plate 51 is first attached by the first compression coil spring 66 alone. When the second compression coil spring 67 is switched to the urging position by the urging force, the tension applying plate 51 is elastically moved to the right by the second urging force. Be energized. That is, the elastic biasing force of the first compression coil spring 66 becomes the first biasing force, and the sum of the elastic biasing forces of the first and second compression coil springs 66 and 67 becomes the second biasing force.
[0051]
  The urging force switching mechanism 53 will be described in detail.
  The urging force switching mechanism 53 operates in conjunction with the operation member 17 that raises and lowers the presser foot 16. When the presser foot 16 is raised, the urging force by the urging mechanism 52 is switched to the first urging force. In a state in which the urging force is lowered, the urging force by the urging mechanism 52 is switched to the second urging force.
[0052]
  As shown in FIGS. 2, 3, 5 to 7, the urging force switching mechanism 53 includes a rotating body 40, a connecting member 41, a link member 42, a cam 43, and a mounting member that are common to the roller position switching mechanism 34. An actuating member 71 pivotally supported by a support shaft 70 suspended from 54 and a pusher pivotally supported by a support shaft 72 suspended from an attachment member 54 on the right side of the support shaft 70. A moving member 73 is provided.
[0053]
  The actuating member 71 has two engaging portions 71a and 71b that are U-shaped in a plan view, and the distal end portion of the lever portion 40c of the rotating member 40 is engaged with the engaging portion 71a from below. The pushing member 73 has a connecting portion 73a and a pushing portion 73b that are substantially orthogonal to each other, and the distal end portion of the connecting portion 73a is engaged with the engaging portion 71b of the actuating member 71. The pushing portion 73b causes the shaft member 61 to move. The right end can be pushed to the left.
[0054]
  When the actuating member 17 is in the solid line posture of FIG. 5 (FIG. 2), the presser foot 16 is lowered, and in this state, the small diameter portion of the cam 43a abuts on the pushing portion 42a of the link piece 42, and the second The compression coil spring 67 is located at the biasing position. From this state, when the operation member 17 is rotated in the direction a in FIG. 5 and switched to the position shown by the chain line, the presser foot 16 is raised, and the rotating body is rotated via the cam 43, the link member 42, and the connecting member 41. 40 is rotated in the direction c of FIG. 2, and the pushing member 73 is rotated in the direction e of FIG.
[0055]
  Then, as shown in FIG. 7, the shaft member 61 is pushed leftward by the pushing portion 73 b of the pushing member 73, and the elastic biasing force of the second compression coil spring 67 is interposed via the shaft member 61 and the ring 64. Is not transmitted to the tension applying plate 51, and the tension applying plate 51 is urged to the right only by the first compression coil spring 66. Note that the position of the second compression coil spring 67 in this state is the bias release position.
[0056]
  When the operation member 17 indicated by the chain line in FIG. 5 is rotated in the b direction to switch to the posture indicated by the solid line from the state where the second compression coil spring 67 is located at the bias release position, the presser foot 16 is lowered. At the same time, the rotating body 40 is rotated in the direction d in FIG. 2, and the pushing member 73 is rotated in the direction f in FIG. Then, the second compression coil spring 67 returns from the bias release position to the bias position by its elastic biasing force, and tension is applied by both the first and second compression coil springs 66 and 67 as shown in FIGS. The plate 51 is biased to the right.
[0057]
  Next, the balance shutter 75 will be described.
  The balance shutter 75 is integrally formed with the actuating member 70 of the biasing force switching mechanism 53, extends leftward from the lower end of the actuating member 70, bends upward on the left side of the tension applying plate 51, and further extends obliquely forward. A horizontal shutter plate 75a is integrally formed at the tip.
[0058]
  As shown in FIG. 3, when the second compression coil spring 67 is switched to the biasing position by the biasing force switching mechanism 53, the shutter plate 75a is positioned above the upper portion of the thread take-up at the tip of the balance 13 (see FIG. 1). The balance shutter 75 is switched to a prohibit position for prohibiting threading on the upper portion of the thread take-up of the balance 13. Further, as shown in FIG. 7, when the second compression coil spring 67 is switched to the bias release position by the biasing force switching mechanism 53, the balance shutter 75 swings horizontally around the support shaft 70 as shown by a chain line in FIG. It moves to a permission position that permits threading to the upper part of the thread take-up of the balance 13, and the shutter plate 75a is no longer positioned above the upper part of the thread take-up of the balance 13.
[0059]
  Thus, the balance shutter 75 operates in conjunction with the urging force switching mechanism 53, and when the balance shutter 13 is switched to the permitted position by the urging force switching mechanism 53, the second compression coil spring 67 is moved to the urging release position. In the state where the urging force by the urging mechanism 52 becomes the first urging force and the balance shutter 75 is switched to the prohibited position, the second compression coil spring 67 is switched to the urging position, and the urging mechanism 52 The biasing force becomes the second biasing force.
[0060]
  Next, the threading device 80 will be described.
  As shown in FIGS. 8 to 12, the threading shaft 81 adjacent to the needle bar 14 is supported by the needle bar base 19 so as to be movable up and down, and its upper end portion is disposed through the gap between the bifurcated member 82. Has been. A horizontal pin 83 is fixed above the middle stage of the threading shaft 81, an operation lever 84 at the lower end portion of the threading shaft 81, a hook 85 (see FIG. 11) positioned below the operation lever 84, and a thread guide. The plates 86 and 87 are fixed. A positioning member 88 is fitted and fixed to the needle bar 14.
[0061]
  An inner first guide member 90 and an outer second guide member 91 having a predetermined length in the vertical direction are inserted into the threading shaft 81 in a double structure so as to be movable up and down. The first guide member 90 is integrally formed with a pair of upper and lower horizontal portions 90a through which the threading shaft 81 is inserted, and a side wall portion 90b connecting the substantially left half of the horizontal portion 90a. A vertical slit 90c that guides the pin 83 of the threading shaft 81 so as to be movable up and down is formed on the left side surface portion, and the upper horizontal portion 90a projects rearward and contacts the projecting portion 88a of the positioning member 88 from above. An abutting portion 90d that contacts is formed.
[0062]
  The second guide member 91 is integrally formed with a pair of upper and lower horizontal portions 91a through which the threading shaft 81 is inserted, a side wall portion 91b that connects the substantially left half of the horizontal portion 91a, and the like. A left-side pin member 92 is fixed to the left side surface portion at an upper end portion thereof, and a vertical slit 19b for guiding the pin member 92 to be movable up and down is formed in the side wall portion 19a of the needle bar base 19. . Further, on the lower side of the pin member 92 of the side wall portion 91b, a longitudinal slit 91c that guides the pin 81 so as to move up and down, and a slit that communicates with the lower end portion of the slit 91c and guides the pin 81 so as to move horizontally. 91d is formed.
[0063]
  A compression coil spring 94 that urges the threading shaft 81 upward is provided on the threading shaft 81 between the ring 93 at the upper end of the threading shaft 81 and the upper support portion 19 c of the needle bar base 19. A compression coil spring 95 that urges the first and second guide members 90 and 91 upward is provided on the threading shaft 81 between the lower support portion 19d and the lower horizontal portion 91c of the second guide member 91. ing. The spring force of the compression coil spring 95 is set to be larger than the spring force of the compression coil spring 94. Normally, as shown in FIGS. 9 and 10, the threading shaft 81 is located at the upper limit position, and the base end portion of the operation lever 84 is It contacts the lower support portion 19d from below.
[0064]
  At the time of threading, the presser foot 16 is switched to the raised position by rotating the operation member 17 to the position shown by the chain line in FIGS. 4 and 5. In the upper thread tension applying device 20, the assertive force applying mechanism 21. And the tension is applied to the upper thread 12 only by the sub tension applying mechanism 22. First, the threading shaft 81 is lowered from the upper limit position together with the operation lever 84. At this time, since the pin 83 is guided by the slits 90c and 91c, the threading shaft 81 does not rotate. The first and second guide members 90 and 91 are held at the upper limit positions by the compression coil springs 95, respectively.
[0065]
  When the threading shaft 81 is pushed down and the abutting portion 90d of the first guide member 90 abuts on the protruding portion 88a of the positioning member 88, the pin 83 is at a height position corresponding to the slit 91d. 12, the upper thread 12 extending from the thread spool 11 through the upper thread path and extending from the balance 13 is engaged with the thread guide plate 86 and passes through the lower side so as to pass right before the sewing needle 15. Pull out horizontally.
[0066]
  Next, when the operation lever 84 is rotated clockwise in plan view until the pin member 83 moves to the end of the slit 91d, the upper thread 12 is moved to the threading position by the bifurcated thread guide plate 87. The hook 85 is inserted into the eye hole 15 a of the sewing needle 15 and hooks the upper thread 12. Thereafter, the upper thread 12 can be threaded through the eye hole 15a by rotating the operation lever 84 counterclockwise in plan view. Thereafter, when the operation of the operation lever 84 is stopped, the threading shaft 81 is raised to the upper limit position by the compression coil spring 94 together with the operation lever 84.
[0067]
  The operation and effect of the upper thread tension applying device 20 will be described.
  In the upper thread tension applying device 20, the assertion force applying mechanism 21 and the assertion force applying mechanism 21 are applied to the upper thread 12 in the upper thread path from the thread spool 11, which is the upper thread supply source of the sewing machine 1, to the balance 13. Tension can be applied by the sub-tension applying mechanism 22 provided on the piece 11 side. In the subtension applying mechanism 22, the tension applying plate 51 is elastically biased toward the base plate 50 by the biasing mechanism 52, and the upper thread 12 from the tension applying portion formed between the base plate 50 and the tension applying plate 51. A tension is applied to the.
[0068]
  The elastic urging force by the urging mechanism 52 of the sub tension applying mechanism 22 is switched to the first urging force at the time of threading by the urging force switching mechanism 53 and switched to the second urging force at the time of sewing. The first urging force is set so as to apply a tension (for example, 2 to 4 gf) that can easily and reliably perform the threading operation (including the threading operation) to the upper thread, and the tension of the assertion force applying mechanism 21 at the time of sewing. The twisting action causes a twist in the upper thread 12 on the yarn spool 11 side of the assertion force imparting mechanism 21, but the second urging force is a tension that can reliably return the twist of the upper thread 12 (for example, 5 to 5). 10gf) is set to be applied to the upper thread.
[0069]
  That is, according to the upper thread tension applying device 20, the elastic urging force by the urging mechanism 52 of the sub-tension applying mechanism 22 is alternatively selected as the first urging force and the second urging force larger than the first urging force. Therefore, the tension applied to the upper thread 12 by the sub-tension imparting mechanism 22 can be easily adjusted in two stages separately during threading and sewing. By setting the force as described above, the threading work at the time of threading can be easily performed, so that the load of the threading work of the operator can be reduced.
[0070]
  In particular, even if the threading device 80 for threading the eye 15a of the sewing needle 15 is provided, the first biasing force can be set to apply a tension according to the threading device 80 to the upper thread. With the threading device 80, the threading of the upper thread 12 into the eye hole 15a can be performed easily and reliably. Moreover, since the twist of the upper thread 12 at the time of sewing can be reliably returned by setting the second urging force as described above, the twist of the upper thread 12 enters the assertion force applying mechanism 21 and further asserts. It is possible to prevent the sewing failure from being caused by being pulled downstream from the force applying mechanism 21 and being loosened.
[0071]
  When the operation member 17 is operated and the presser foot 16 is raised, the urging force by the urging mechanism 52 can be switched to the first urging force, and when the presser foot 16 is lowered, the urging force by the urging mechanism 52 is changed to the second urging force. Can be switched to. As described above, since the urging force switching mechanism 53 is configured to operate in conjunction with the operation member 17 that moves the presser foot 16 up and down, the operation load on the operator can be reduced and the structure of the urging force switching mechanism 53 can be reduced. Simplify and reduce manufacturing costs.
[0072]
  By raising and lowering the presser foot 16, the state of the assertive force application mechanism 21 can be switched between a state in which tension is applied to the upper thread 12 and a state in which the upper thread 12 is not applied, so that the operation load on the operator can be further reduced. In addition, when the presser foot 12 is raised, the assertion force application mechanism 21 is open, so that the assertion force application mechanism 21 can be easily threaded, and only the subtension application mechanism 22 is used. Since tension is applied to the upper thread, the first urging force can be easily set so as to apply tension to the upper thread that facilitates the threading operation.
[0073]
  When the second compression coil spring 67 is switched to the bias release position by the biasing force switching mechanism 53, the tension applying plate 51 is elastically biased to the right by the first biasing force only by the first compression coil spring 66, and the second When the compression coil spring 67 is switched to the biasing position, the tension applying plate 51 is elastically biased rightward by both the first and second compression coil springs 66 and 67. As described above, the elastic urging force by the urging mechanism 52 can be easily switched to the first and second urging forces, and the urging mechanism 52 and the urging force switching mechanism 53 can be configured easily and in a small size, so that the manufacturing cost can be reduced. Will also be advantageous.
[0074]
  When the balance shutter 75 is switched to the permitted position, it becomes possible to thread the thread take-up portion at the tip of the balance 13, and the urging force by the urging mechanism 52 is switched to the first urging force by the urging force switching mechanism 53. Therefore, the threading operation including threading on the upper part of the thread take-up of the balance 13 can be easily performed, and when the balance shutter 75 is switched to the prohibited position, the upper part of the thread take-up of the balance 13 cannot be threaded. At the same time, the biasing force by the biasing mechanism 52 is switched to the second biasing force by the biasing force switching mechanism 53, so that the twist of the upper thread 12 at the time of sewing can be reliably returned.
[0075]
  A modified form in which the embodiment is partially modified will be described.
1) A detection sensor for detecting a state in which the balance shutter 75 is switched to the permitted position or the prohibited position may be provided. In this case, by detecting the state where the balance shutter 75 is switched to the permitted position or the prohibited position by the detection sensor, the urging force switching mechanism 53 can be operated based on the detection information obtained from the detection sensor. Become.
[0076]
2] The assertion force applying mechanism 21 is not limited to the above-described one, and various assertion force applying mechanisms such as a thread tension device having a thread tension plate can be applied.
3] The threading device 80 is not limited to the one described above, and various threading devices such as a one-hand operable threading device filed by the present applicant can be applied.
4] The above embodiment is merely an example, and various modifications can be made without departing from the technical idea of the present invention.
[0077]
【The invention's effect】
  According to the upper thread tension applying device of the sewing machine according to claim 1, the elastic urging force by the urging means of the sub tension applying mechanism is alternatively selected as the first urging force and the second urging force larger than the first urging force. Since the urging force switching mechanism that can be switched to is provided, the tension applied to the upper thread by the sub-tension imparting mechanism can be easily adjusted in two stages at the time of threading and sewing.
[0078]
  As a result, by setting the first and second urging forces to appropriate values, it becomes possible to easily perform the threading operation during threading, and the load on the operator can be reduced. Even when a threading device is provided, by setting the first urging force to be applied to the upper thread with a tension according to the threading device, the threading device can thread the upper thread into the eye hole. Can be performed easily and reliably, and the twist of the upper thread at the time of sewing can be reliably returned, so that the twist of the upper thread enters the assertion force applying mechanism and further downstream of the assertion force applying mechanism. It can be prevented that it is pulled out to the side and loosens, resulting in poor sewing.
[0079]
  Moreover,When the operation member is operated and the presser foot is raised, the urging force by the urging means can be switched to the first urging force, and when the presser foot is lowered, the urging force by the urging means can be switched to the second urging force. . Since the urging force switching mechanism operates in conjunction with the operation member that raises and lowers the presser foot, the operator's operation load can be reduced, and the structure of the urging force switching mechanism can be simplified and the manufacturing cost can be reduced..
[0080]
  Claim2According to the upper thread tension applying device of the sewing machine, the state of the assertive force applying mechanism can be switched between a state in which tension is applied to the upper thread and a state in which the upper thread is not applied by raising and lowering the presser foot. The load can be further reduced, and when the presser foot is raised, the assertion force imparting mechanism is open, so that the assertion force imparting mechanism can be easily threaded. Since the tension is applied to the upper thread only by the tension applying mechanism, the first urging force can be easily set so as to apply a tension that can easily perform the threading operation to the upper thread..
[0081]
  Claim3According to the upper thread tension applying device of the sewing machine, when the second urging member is switched to the urging release position by the urging force switching mechanism, the tension applying plate is moved to the base plate by the first urging force only by the first urging member. When the second urging member is switched to the urging position, the tension applying plate is elastically urged toward the base plate by the second urging force in both the first and second urging members. Be forced. Thus, the elastic urging force by the urging means can be easily switched to the first and second urging forces, and the urging means and the urging force switching mechanism can be easily and compactly configured, which is advantageous in terms of manufacturing cost. become.
[0082]
  Claim4According to the upper thread tension applying device of the sewing machine, when the balance shutter is switched to the permitted position, it becomes possible to thread the thread take-up portion at the tip of the balance, and the urging force by the urging means is applied by the urging force switching mechanism. Is switched to the first urging force, so that the threading operation including threading on the upper part of the thread take-up of the balance can be easily performed, and when the balance shutter is switched to the prohibited position, the thread is placed on the upper part of the thread take-up of the balance. The urging force switching mechanism switches the urging force by the urging means to the second urging force, so that the upper thread twist during sewing can be reliably returned..
[0083]
  Claim5According to the upper thread tension applying device of the sewing machine, since the detecting means for detecting the state in which the balance shutter is switched to the permitted position or the prohibited position is provided, the biasing force switching mechanism is based on the detection information obtained from the detecting means. Can be activated.
[0084]
  Claim6According to the upper thread tension applying device of the sewing machine, when the second urging member is switched to the urging release position by the urging force switching mechanism, the tension applying plate is moved to the base plate by the first urging force only by the first urging member. When the second urging member is switched to the urging position, the tension applying plate is elastically urged toward the base plate by the second urging force in both the first and second urging members. Be forced. Thus, the elastic urging force by the urging means can be easily switched to the first and second urging forces, and the urging means and the urging force switching mechanism can be easily and compactly configured, which is advantageous in terms of manufacturing cost. become.
[Brief description of the drawings]
FIG. 1 is a front view of a sewing machine according to an embodiment of the present invention.
FIG. 2 is a left side view of the upper thread tension applying device.
FIG. 3 is a plan view of an upper thread tension applying device.
FIG. 4 is a front view of an assertion force applying mechanism of the upper thread tension applying device.
FIG. 5 is a front view of a sub-tension applying mechanism of the upper thread tension applying device.
FIG. 6 is a perspective view of a sub-tension applying mechanism.
FIG. 7 is a partial plan view of a sub tension applying mechanism.
FIG. 8 is an exploded perspective view of the threading device.
FIG. 9 is a front view of the threading device.
FIG. 10 is a left side view of the threading device.
11 is a cross-sectional view taken along line XI-XI in FIG.
FIG. 12 is a partial front view of the threading device.
[Explanation of symbols]
M sewing machine
11 Ikoma
12 Upper thread
13 Balance
15 Sewing needle
16 Presser foot
17 Operation members
20 Upper thread tension applying device
21 Main tension mechanism
22 Sub-tensioning mechanism
50 base plate
51 Tension applying plate
52 Energizing mechanism
53 Energizing force switching mechanism
66, 67 First and second compression coil springs
75 Balance shutter
80 Threading device

Claims

In the upper thread tension applying device that applies tension to the upper thread in the upper thread path from the upper thread supply source of the sewing machine to the balance,
An assertion force application mechanism that can adjust the tension by applying tension to the upper thread, and tension application that allows the upper thread to pass between the base plate and the tension application plate that is provided on the upper thread supply source side of the assertion force application mechanism A subtension applying mechanism formed by forming a part,
The sub-tension applying mechanism includes an urging means for elastically urging the tension applying plate toward the base plate, an elastic urging force by the urging means as a first urging force, and a second urging force larger than the first urging force And a biasing force switching mechanism that can be switched alternatively ,
The urging force switching mechanism operates in conjunction with an operation member that raises and lowers the presser foot. When the presser foot is raised, the urging force by the urging means is switched to the first urging force, and when the presser foot is lowered. Switching the biasing force by the biasing means to the second biasing force;
An upper thread tension applying device of a sewing machine characterized by the above.

The upper thread tension applying device according to claim 1 , wherein the assertion force applying mechanism is configured not to apply tension to the upper thread when the presser foot is raised.

The urging means includes first and second urging members that elastically urge the tension applying plate toward the base plate, and the first urging member constantly urges the tension applying plate and the urging force switching mechanism. the top of the sewing machine according to claim 1, characterized in that switching over the second biasing member biasing position and urging release position with biasing city tensioning plate which urges the tensioning plate Yarn tension applying device.

A balance shutter that switches between a permitted position that permits threading and a prohibited position that prohibits threading is provided at the top of the thread take-up at the tip of the balance, and the urging force switching mechanism is attached when the balance shutter is switched to the permitted position. 2. The sewing machine according to claim 1, wherein the urging force by the urging means is switched to the first urging force, and the urging force by the urging means is switched to the second urging force when the balance shutter is switched to the prohibited position. Upper thread tension applying device.

The upper thread tension applying device according to claim 1 , further comprising detection means for detecting a state in which the balance shutter is switched to a permission position or a prohibition position.