JP3786037B2

JP3786037B2 - Backflow prevention device

Info

Publication number: JP3786037B2
Application number: JP2002069305A
Authority: JP
Inventors: 有里子永島
Original assignee: 有里子永島
Priority date: 2001-12-14
Filing date: 2002-02-07
Publication date: 2006-06-14
Anticipated expiration: 2022-02-07
Also published as: JP2003240146A

Description

【０００１】
【発明の属する技術分野】
本発明は上流から下流に流れる流れの逆流を防止する逆流防止装置に関する。特に上水と雑水の回路を接続するような場合に利用される逆流防止装置に関する。
【０００２】
【従来の技術】
従来、雑水路と上水を接続する場合にはシスターンを用い上水を一旦シスターンで受け落差、ポンプ等により雑水側に送水する手段が行われていた。しかし設備の自動化、小型化が進みそれに対応する逆流防止装置として、水路に二つの逆止弁を直列に配し、該逆止弁間の下流室に通水圧が加わると閉じ、通水圧がなくなると開いて水路を大気開放する開放弁を設けた大気開放弁、水路に二つの逆止弁を直列に配し、該逆止弁間の下流室に一次側水圧と下流室水圧の差圧で開閉して下流室を大気開放する開放弁を設けた減圧式逆流防止器等が使用されるようになってきた。
【０００３】
【発明が解決しようとする課題】
前述の大気開放弁は図１０に示すように図示しない一次側の開閉弁を開弁すると、一次側の第一逆止弁５０の弁体Ａ１０が通水圧によりバネＡ１６に対抗して押し下げられるに伴い、弁体Ａ１０に弁軸１５で連結接続された開放弁５１の弁体Ｂ１２も下降して、開放弁５１を閉弁して外部への流出をなくし、下流室６に流入した流水は二次側の第二逆止弁２１を押し開けて下流に流出する。一次側の開閉弁を閉弁すると、通水圧がなくなるので弁体Ａ１０、弁体Ｂ１２はバネＡ１６により押し上げられ、開放弁５１を開弁すると共に第一逆止弁５０を閉弁する。第二逆止弁２１も通水圧がなくなるので閉弁して下流からの下流室６への逆流をなくする構造となっている。
【０００４】
前述の減圧式逆流防止器は図１１に示すように一次側流路３に流入した流水はバネＡ１６に対抗して第一逆止弁５０の弁体Ａ１０を押し下げ開弁して下流室６に流入し、さらに二次側に装設された第二逆止弁２１を押し開け二次側流路４より流出する。導孔４０により一次側流路３とダイアフラム左室４１とが連通されているので一次側流路３の流水はダイアフラム７を右方向（開放弁５１を閉弁する方向）に加圧する。一方導孔４２によりダイアフラム右室４３と下流室６が連通されているので下流室６の流水はダイアフラム７を左方向（開放弁５１を開弁する方向）に加圧する。従って開放弁５１はダイアフラム７に加わる一次側流路３の水圧と下流室６の水圧とダイアフラム７を左方向（開放弁５１を開弁する方向）に附勢するバネＢ２７の力の関係で開閉する。従って、一次側流路３が低圧になると第一逆止弁５０と第二逆止弁２１が閉じ、開放弁５１が開弁し下流室６を大気に開放し逆流を防止する。二次側流路４が高圧になった場合、第二逆止弁２１が逆流を防止するが、第二逆止弁２１に漏れ等が生じると下流室６の圧力が高くなり開放弁５１が開弁して下流室６を大気に開放し逆流を防止する。第一逆止弁５０に漏れ等が生じると下流室６と一次側流路３の圧力差がなくなるので開放弁５１が開弁し逆流の危険を未然に防止する構造である。
【０００５】
前者大気開放弁は一次側流路水圧と下流室水圧を弁体Ａ１０で感知するので感圧力が小さく第一逆止弁５０は主に通水圧（動圧）で開閉されていると共に弁体Ａ１０と弁体Ｂ１２が連結され、第一逆止弁５０と開放弁５１は一方が開弁すると他方が閉弁する構造である。従って流水の開閉は上流一次側でしなければならない。
【０００６】
後者減圧式逆流防止器は第一逆止弁５０と開放弁５１が個別で開閉するので開放弁５１が正常時に開弁しないように一次側流路３と下流室６の圧力差を大きくする為に第一逆止弁５０のバネＡ１６を強くし通水抵抗を大きくしなければ成らないと共に一次側流路３と下流室６の水圧を感知し開放弁５１を開閉するダイアフラム７を別途装設しなければ成らず形状が大きくなり高価である。
【０００７】
【課題を解決するための手段】
前述の問題を解決するために本発明は、上流側から下流側へ流れる流れの逆流を防止する逆流防止装置において、一次側流路と二次側流路の間の流路に弁室を設け、ダイアフラムにより弁室を一次側流路側の上流室と二次側流路側の下流室に水密に仕切り、前記ダイアフラムの軸心部に上流室と下流室を連通する透孔を開口し、上流室側に前記透孔を囲む弁座Ａを形成し、下流室に大気に連通する開放孔を開口し、弁座Ａと中心軸を同じとする前記開放孔を囲む弁座Ｂを形成して、上流室側から弁座Ａに弁体Ａを対向させて第一逆止弁を構成すると共に弁体Ａに弁軸により弁体Ｂを連結して弁座Ｂに対向させて開放弁を構成し、附勢手段Ａにより常時弁体Ａを弁座Ａに附勢し、前記ダイアフラムを附勢手段Ｂにより常時上流室側に附勢し、第一逆止弁を開閉するダイアフラムと開放弁を開閉するダイアフラムを兼用することで第一逆止弁と開放弁が連係して開閉するようにした逆流防止装置であって、
【０００８】
その作動は図示しない開閉弁を開弁すると、一次側流路から流入した流水はダイアフラムを押圧し、附勢手段Ｂに対抗してダイアフラムが附勢手段Ａにより閉弁した状態の第一逆止弁を下流室側に動かし開放弁を閉弁する。さらに流水は開放弁が閉弁すると弁軸により弁体Ｂに連結された弁体Ａが移動できなくなるので、附勢手段Ａと附勢手段Ｂに対抗しダイアフラムに形成された弁座Ａを動かして第一逆止弁を開弁し、下流室に流入し、二次側流路より流出する。図示しない開閉弁を閉弁すると、ダイアフラムを押す圧力が小さくなるので、附勢手段Ａと附勢手段Ｂにより第一逆止弁が閉弁する。一次側流路側で負圧等が起こりダイアフラムを押す力がさらに小さくなると、附勢手段Ｂによりダイアフラムは閉弁した状態の第一逆止弁を上流室側に移動し、開放弁を開弁して下流室を大気に開放する。下流室の圧力が上昇すると、附勢手段Ｂによりダイアフラムは閉弁した状態の第一逆止弁を上流室側に移動し開放弁を開弁して下流室を大気に開放する。
【０００９】
従って開放弁を開閉するダイアフラムを上流室と下流室の間の流路に装設し、そのダイアフラムに第一逆止弁の弁座を形成し、第一逆止弁を開閉するダイアフラムとして兼用し、第一逆止弁と開放弁の開閉を連係させているので第一逆止弁の通水抵抗を大きくしなくても、正常時に開放弁が開弁する事がなく安全性が高く又小型で安価な逆流防止装置となる。
【００１０】
第２の発明は、上流側から下流側へ流れる流れの逆流を防止する逆流防止装置において、一次側流路と二次側流路の間の流路に弁室を設け、ダイアフラムにより弁室を一次側流路側の上流室と二次側流路側の下流室に水密に仕切り、前記ダイアフラムの軸心部に上流室と下流室を連通する透孔を開口し、上流室側に前記透孔を囲む弁座Ａを形成すると共に上流接続口流路の上流室流入口周囲に弁座Ａと中心軸を同じとする前記流入口を囲む弁座Ｃを形成し、下流室に大気に連通する開放孔を開口し、弁座Ａと中心軸を同じとする前記開放孔を囲む弁座Ｂを形成して、上流室側から弁座Ａに弁体Ａの他面に一体的に弁体Ｃを形成又は装着した弁体Ａを対向させて第一逆止弁を構成し、弁体Ｃを弁座Ｃに対向させて第三逆止弁を構成すると共に弁体Ａに弁軸により弁体Ｂを連結して弁体Ｂを弁座Ｂに対向させて開放弁とし、附勢手段Ａにより常時弁体Ａを弁座Ａに附勢し、前記ダイアフラムを附勢手段Ｂにより常時上流室側に附勢し、第一逆止弁を開閉するダイアフラムと開放弁を開閉するダイアフラムを兼用することで第一逆止弁と開放弁と第三逆止弁が連係して開閉するようにした逆流防止装置であって、
【００１１】
前述の発明に加え上流室流入口に第三逆止弁を設けることで、下流側からの逆圧、上流側に於ける負圧等によりダイアフラムを押す力が小さくなり、附勢手段Ｂによりダイアフラムが閉弁状態の第一逆止弁を移動し開放弁を開弁し、さらに移動すると第三逆止弁が閉弁して二重の安全を図るものである。
【００１２】
第３の発明は弁体Ａを常時弁座Ａに附勢する附勢手段Ａに関し、弁体Ａを常時弁座Ａに附勢する附勢手段Ａをダイアフラムと弁体Ａ又は弁体Ａと一体的に接続された部材の間、又は弁箱と弁体Ａ又は弁体Ａと一体的に接続された部材の間のいずれか又は両方に附勢した請求項１，請求項２記載の逆流防止装置であって、附勢手段Ａをダイアフラムと弁体Ａ又は弁体Ａと一体的に接続された弁軸又は弁軸と一体的に接続された部材との間に附勢させた場合には、第一逆止弁を開弁する際、附勢手段Ａと附勢手段Ｂに対抗して開弁する事となり、附勢手段Ａを弁箱と弁体Ａ又は弁体Ａと一体的に接続された部材の間に附勢させた場合には、第一逆止弁を開弁する際、附勢手段Ａの関与がなくなり附勢手段Ｂのみに対抗して開弁する特長があるので目的により選択する事で性能の良い逆流防止装置の設計が出来る。
【００１３】
第４の発明は弁体Ｂに加わる下流室圧力による力とほぼ同じ大きさの下流室圧力による力が弁体Ｂへの作用と対向方向に作用する弁体又はピストンを弁体Ｂに一体的に連結装設した請求項１，請求項２、請求項３記載の逆流防止装置であって、下流室の圧力が弁体Ｂを閉弁する方向に加圧される為に附勢手段Ｂを強くしなければならず、又附勢手段Ｂは弁体Ａを開弁する際の附勢力ともなっているので、通水抵抗にも影響することとなり自由な設計を制限される。弁体Ｂと有効面積をほぼ同一とする弁体又はピストンを下流室圧力が弁体Ｂと対向方向に作用するように弁体Ｂと一体的に装設する事により弁体Ｂに加わる下流室圧力の影響を打ち消し前記課題を解消し、自由な設計を出来るようにするものである。
【００１４】
第５の発明は弁体Ａ又は弁体Ｂ又は弁体Ａと弁体Ｂを連結する弁軸又は弁体Ａと一体的に連結された弁体若しくはピストンの動きを検知し電気信号を出力する検知装置を装設して、弁体Ｂの動きを検知し得るようにした請求項１，請求項２，請求項３、請求項４記載の逆流防止装置であって、流路の異常により逆圧の危険が生じ開放弁が開弁する事態になった場合に、信号を出し警報ランプを点滅する等により逆圧の危険、発生を知らせ、逆流を未然に防止するものである。
【００１５】
【実施例】
以下、本発明の実施例を図面に基づき説明する。
【００１６】
図１は本発明に係る逆流防止装置の一実施例の縦断面図で弁体Ａを常時弁座Ａに附勢する附勢手段Ａをダイアフラムと弁体Ａの間に附勢した例で非流水時を示している。弁箱を一次側流路３と端面にダイアフラム取付面を形成した一次側流路３と連通する上流室５を設け、上流室内面上部に弁体Ａ１０の上昇移動で弁体Ａ１０の上部が衝合し弁体Ａ１０を停止させる突起２０を上流室流入口１８の周囲に形成した弁箱Ａ１と二次側流路４と端面にダイアフラム取付面を形成した二次側流路４と連通する下流室６を設け、下流室底部には大気に連通する開放孔１９を開口し、端面に取付けるダイアフラム７と中心軸を同じとする前記開放孔１９を囲む弁座Ｂ１１を形成した弁箱Ｂ２とで構成する。
【００１７】
ダイアフラム７にはダイアフラム７の軸心部に軸心部に弁軸１５を貫通する貫通孔１４とその貫通孔１４の周囲に上流室５と下流室６を連通する透孔１３を設け透孔１３の上流室側に透孔１３を囲む弁座Ａ９を形成した弁座金具８を水密に一体的に取付け、ダイアフラム７の上流室側から弁体Ａ１０を弁体Ａ１０に一体的に取付けた弁軸１５を前記貫通孔１４に貫通して装設して弁座Ａ９に弁体Ａ１０を対向させて第一逆止弁５０とし、弁軸１５外周に一端を弁座金具８に懸架してバネＡ１６を附勢して弁軸１５の他端に弁体Ｂ１２を連結する。弁体Ｂ１２と弁軸１５は水密に連結するだけでも良いが、本実施例では弁体Ｂ１２を開弁し易くするパイロット弁を付与した方式とした。弁軸１５の下部を細くし弁軸細部２５とし、段差部に弾性体よりなる弁体Ｄ２３を形成し、弁体Ｂ１２の軸心部に弁軸細部２５が貫通する貫通孔２４を設け貫通孔２４の弁室側周囲を弁座Ｄ２２として、弁軸細部２５を貫通孔２４に貫通して弁体Ｄ２３が弁座Ｄ２２を離れ開弁する余裕を持たせて弁体Ｂ１２をＣ型止め輪２６で弁軸１５に連繋する。この場合前述と異なり、バネＡ１６は弁軸１５の弁体Ｄ２３上方部にバネ座１７を止着し前記バネ座１７と弁座金具８の間に附勢する。以下パイロット弁部については説明を割愛し弁体Ｂとして説明する。
【００１８】
前述のように組付けたダイアフラム７を弁箱Ｂ２と弁座金具８の間にバネＢ２７を附勢させ、弁体Ｂ１２を弁座Ｂ１１に対抗させて開放弁５１を構成し、弁箱Ａ１と弁箱Ｂ２のダイアフラム取付面で挟み弁箱Ａ１と弁箱Ｂ２を組み付ける。ダイアフラム７の可動距離と弁体Ａ１０と弁体Ｂ１２の連結距離はダイアフラム７の下流室側への動きで開放弁５１が閉弁してから第一逆止弁５０が開弁し、上流室側への動きで第一逆止弁５０が閉弁して開放弁５１が開弁する距離とする。二次側流路側に装着した第二逆止弁２１は開放弁５１が開弁した時下流から下流室６への逆流を防止するもので装着しない場合もある。ダイアフラムストッパー３８はダイアフラムに加わる力が大きい場合のダイアフラム保護としてダイアフラムの下流室側への動き制限するもので省く場合もある。突起２０は弁体Ａ１０の上流室側への動きを制限するもので第一逆止弁５０の閉弁性を良くするのとダイアフラム保護の働きをするもので省く場合もある。
【００１９】
以上のように構成した逆流防止装置の作動は図示しない開閉弁を開弁すると上流室５に流入した流水の水圧によって、ダイアフラム７は閉弁状態の第一逆止弁５０をバネＢ２７に対抗して下流室側に移動し開放弁５１を閉弁する。開放弁５１が閉弁すると弁体Ｂ１２と弁軸１５により連結されている弁体Ａ１０は移動できないのでダイアフラム７のみがバネＡ１６とバネＢ２７に対抗し下流室側に動き第一逆止弁５０を開弁して、流水が下流室６に流入し二次側流路側に装着した逆止弁２１を押し開けて下流に流出する図２に示す状態となる。
【００２０】
図示しない開閉弁を閉弁すると第二逆止弁２１が閉弁すると共に、流水の水圧によるダイアフラム７に作用する力が小さくなるので、バネＡ１６とバネＢ２７によりダイアフラム７が上流室側に動き第一逆止弁５０を閉弁して図１状態となる。
【００２１】
上流側で負圧等が起こりダイアフラム７に作用する力がさらに小さくなるとバネＢ２７によりダイアフラム７は閉弁した状態の第一逆止弁５０を上流室側に移動し開放弁５１を開弁して下流室６を大気に開放する。又下流側の圧力が高くなると第二逆止弁２１で逆流は防止されが、第二逆止弁２１に塵等により漏れが起こると下流室６の圧力が上昇してバネＢ２７によりダイアフラム７は閉弁した状態の第一逆止弁５０を上流室側に移動し開放弁５１を開弁して下流室６を大気に開放する図３の状態となる。
【００２２】
他の実施例を図４に示す。本実施例は前述の例に対し、突起２０に代えて弁箱Ａ１の上流室流入口１８の周囲に弁座Ａ９と中心軸を同じにする前記流入口１８を囲む弁座Ｃ２８を形成し、弁体Ａ１０の他面に弁体Ｃ２９を形成して弁座Ｃ２８に対向させ第三逆止弁５２を構成したものであり、又本実施例では前述の弁体Ｂ１２を開弁し易くするパイロット弁を付与した方式に代えて弁体Ｂ１２と弁軸１５を水密で僅かに動くように連結して弁体Ｂ１２と弁座Ｂ１１の閉弁性を良くする考慮をした実施例とした。その他の構成については前述の実施例と変わらない。
【００２３】
その作動は上流の負圧、下流の圧力上昇等が起きた場合に、バネＢ２７によりダイアフラム７は閉弁した状態の第一逆止弁５０を上流室側に移動し開放弁５１を開弁して下流室６を大気に開放し、さらに移動すると第三逆止弁５２を閉弁し、さらなる安全性を高めるものである。その他の作動は前述の実施例と変わらない。
【００２４】
他の実施例を図５に示す。本実施例は前述の例に対し、弁体Ａ１０を弁座Ａ９に附勢するバネＡ１６を弁箱と弁体Ａの間に附勢した実施例でありバネＡ１６が流れを阻害しないようにする為、弁箱Ａ１の一次側流路３に周囲を流路３１として軸心部にバネ座３２を設け、弁体Ａ１０の他面に形成された弁体Ｃ２９上部と前記バネ座３２との間にバネＡ１６を附勢するようにしてある。この場合、バネＡ１６は開放弁５１を閉弁する方向に附勢し、バネＢ２７は開放弁５１を開弁する方向に附勢するので、開放弁５１に作用するバネの力はバネＡ１６とバネＢ２７の差力となると共に、バネＡ１６はダイアフラム７に作用しないので、第一逆止弁５０の開閉に作用するバネの力はバネＢ２７のみとなる。而して第一逆止弁５０の通水抵抗を小さくする場合に有効である。その他の構成、作動は前述の実施例と変わらない。
【００２５】
さらに他の実施例を図６に示す。本実施例は下流室６の圧力が弁体Ｂ１２に作用しなくした実施例であり、下流室６の流水を導孔４４により下流室６と開放孔１９を挟んで対向する位置の感圧室４５に連通して、感圧室４５と開放孔１９との貫通穴４６に弁座Ｂ１１と中心軸を同じとする摺動筒４７を形成し有効面積を弁体Ｂ１２と約同じとするピストン４９を水密的に摺動可能に嵌装して、弁体Ｂ１２を連結している弁軸１５に止め輪４８又はネジで水密に連結する。
【００２６】
そしてその作動は下流室６の圧力が弁体Ｂ１２を図示で下方に加圧するのに対して、導孔４４を通して感圧室４５に導かれた下流室圧力はピストン４９を図示で上方に加圧するので両者の力は相殺される事になり下流室圧力は弁体Ｂ１２に作用しない。簡単な力関係で設計しやすくなる。
【００２７】
さらに他の実施例の部分詳細図を図７に示す。本実施例は弁体Ａ１０と弁体Ｂ１２を連結する弁軸１５の下端に磁石３３を装着し、排水孔１９の側壁にホール素子又はリードスイッチ３４を取付け弁軸１５が動き、弁体Ｂ１２が開弁する位置又は開弁する危険位置に来た時に磁石３３の磁力変化をホール素子又はリードスイッチ３４が検知し電気信号を出力するようにしたものである。弁体Ｂ１２が開弁又は開弁の危険を生じたときに警報が発せられるので、逆流の危険を察知して対策防止が出来る。
【００２８】
第三逆止弁５２の他の実施例の部分詳細図を図８に示す。第三逆止弁５２は常時開弁状態を保ち逆流が起きた時に確実に閉弁する非常弁であるので、塵噛み等のない確実に閉弁する弁が望まれる。本実施例は前述の目的を達成する為に成されたものであり、弁座Ｃ２８をテーパー弁座とし、それに対向する弁体Ｃ２９を球状として塵が付きにくくすると共に弁体Ｃ２９のシート面を柔らかいゴム又は内部を発泡体あるいは空気層としたゴム等の弾性体３５とし、多少の塵があってもシールを可能にし、テーパー弁座と柔らかい球状弁体により塵の付きにくいシール性の良い逆止弁としたものである。本実施例では弁体Ｃ２９を球状としたが円錐等凸状の流線型にしても良い。又弁体Ａ１０と弁体Ｃ２９を別体にして互いが僅かに動くように取り付けて、弁座Ｃ２８に対して弁体Ｃ２９が馴染みやすくして逆止弁のシールを良くすることも出来る
【００２９】
図９は本発明の逆流防止装置の上流側に開閉弁として電磁弁３６を一体的に装設した例である。もちろん本発明の逆流防止装置の下流側に開閉弁として電磁弁を一体的に装設する場合もあり、この場合は、第二逆止弁２１を省略しても良い。
【００３０】
【発明の効果】
以上のように請求項１によれば上流室と下流室の圧力を感知して開放弁を開閉するダイアフラムを上流室と下流室の間の流路に装設し、そのダイアフラムに第一逆止弁を形成したので、開放弁と第一逆止弁が連係して開閉し、第一逆止弁の通水抵抗を小さくしても開放弁が誤作動しない、小型で簡単な構造になると共に、第一逆止弁の開閉性能が良くなり、請求項２によれば一次側流路の上流室入口の周囲に弁座Ｃを形成し、弁体Ａの他面に弁体Ｃを形成して、前記弁座Ｃに対向させ第三逆止弁として、開放弁が開弁した場合に第三逆止弁を閉弁するのであるから逆流をさらに確実に防止でき、請求項３によれば弁体Ａを常時弁座Ａに附勢する附勢手段Ａの附勢の仕方で、附勢手段Ａを第一逆止弁の開閉に寄与させる、させないの選択が可能であり、目的にあった設計が可能となり、請求項４によれば弁体Ｂに加わる下流室圧力による力を相殺する弁体又はピストンを装設して弁体Ｂへの下流室圧力影響をなくすのであるから、力関係が簡単となり、請求項５によれば大気に連通する開放孔を開閉する弁体Ｂ、弁軸等の動きで信号を出力して、警報を発して未然に逆流の危険を除けるようにするのであるから、小型で通水抵抗の小さな安全性の高い安価な逆流防止装置となる。本発明ではダイアフラムを使用したが、圧力を感知して水密に動くダイアフラムと同等のものであれば何ら問題ない。
【図面の簡単な説明】
【図１】本発明に係る逆流防止装置の一実施例縦断面図であり非流水時を示す。
【図２】同実施例縦断面図の流水時を示す。
【図３】同実施例縦断面図の開放弁開弁時を示す。
【図４】本発明に係る同装置の他の実施例縦断面図であり非流水時を示す。
【図５】本発明に係る同装置の他の実施例縦断面図であり非流水時を示す。
【図６】本発明に係る同装置の他の実施例縦断面図であり流水時を示す。
【図７】本発明に係る同装置の他の実施例部分詳細図である。
【図８】本発明に係る同装置の他の実施例部分詳細図である。
【図９】本発明に係る同装置に電磁弁を装設した一実施例縦断面図である。
【図１０】従来の逆流防止装置の一例の縦断面図である。
【図１１】従来の逆流防止装置の一例の縦断面図である。
【符号の説明】
１−−弁箱Ａ２−−弁箱Ｂ７−−ダイアフラム
９−−弁座Ａ１０−−弁体Ａ１１−−弁座Ｂ
１２−−弁体Ｂ１３−−透孔１５−−弁軸
１６−−バネＡ２１−−第二逆止弁２７−−バネＢ
２８−−弁座Ｃ２９−−弁体Ｃ３３−−磁石
３４−−ホール素子又はリードスイッチ３５−−弾性体
３６−−電磁弁３８−−ダイアフラムストッパー
５０−−第一逆止弁５１−−開放弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backflow prevention device that prevents backflow of a flow that flows from upstream to downstream. In particular, the present invention relates to a backflow prevention device used when connecting a circuit of clean water and miscellaneous water.
[0002]
[Prior art]
Conventionally, when connecting a miscellaneous channel and clean water, a means is used to receive the clean water once in the systern using a cis-turn and to feed the sewage to the miscellaneous water side by a pump or the like. However, as the automation and miniaturization of equipment progresses, as a backflow prevention device corresponding to it, two check valves are arranged in series in the water channel and closed when the water flow pressure is applied to the downstream chamber between the check valves, the water flow pressure disappears An air release valve with an open valve that opens the water channel to the atmosphere and two check valves are arranged in series in the water channel, and the downstream chamber between the check valves has a differential pressure between the primary water pressure and the downstream chamber water pressure. A decompression backflow preventer or the like provided with an open valve that opens and closes to open the downstream chamber to the atmosphere has come to be used.
[0003]
[Problems to be solved by the invention]
As shown in FIG. 10, when the above-described atmospheric opening valve is opened, the valve element A10 of the primary check valve 50 is pushed down against the spring A16 by the water pressure. Along with this, the valve body B12 of the release valve 51 connected to the valve body A10 by the valve shaft 15 is also lowered, the release valve 51 is closed to prevent outflow to the outside, and the flowing water flowing into the downstream chamber 6 is two. The second check valve 21 on the next side is pushed open and flows downstream. When the primary on-off valve is closed, the water pressure is lost, so the valve body A10 and the valve body B12 are pushed up by the spring A16, thereby opening the release valve 51 and closing the first check valve 50. Since the second check valve 21 also has no water flow pressure, the second check valve 21 is closed so that the backflow from the downstream to the downstream chamber 6 is eliminated.
[0004]
In the above-described decompression type backflow preventer, as shown in FIG. 11, the flowing water flowing into the primary side flow path 3 pushes down and opens the valve element A10 of the first check valve 50 against the spring A16 to enter the downstream chamber 6. Then, the second check valve 21 installed on the secondary side is further opened to flow out from the secondary side flow path 4. Since the primary side flow path 3 and the diaphragm left chamber 41 communicate with each other through the guide hole 40, the flowing water in the primary side flow path 3 pressurizes the diaphragm 7 in the right direction (direction in which the release valve 51 is closed). On the other hand, since the diaphragm right chamber 43 and the downstream chamber 6 communicate with each other through the guide hole 42, the flowing water in the downstream chamber 6 pressurizes the diaphragm 7 in the left direction (direction in which the release valve 51 is opened). Accordingly, the opening valve 51 opens and closes in relation to the water pressure of the primary flow path 3 applied to the diaphragm 7, the water pressure of the downstream chamber 6, and the force of the spring B27 that urges the diaphragm 7 in the left direction (the direction in which the opening valve 51 opens). To do. Therefore, when the primary side flow path 3 becomes low pressure, the first check valve 50 and the second check valve 21 are closed, and the release valve 51 is opened to open the downstream chamber 6 to the atmosphere to prevent backflow. When the secondary side flow path 4 becomes a high pressure, the second check valve 21 prevents a back flow. However, when leakage or the like occurs in the second check valve 21, the pressure in the downstream chamber 6 increases and the release valve 51 The valve is opened to open the downstream chamber 6 to the atmosphere to prevent backflow. When leakage or the like occurs in the first check valve 50, the pressure difference between the downstream chamber 6 and the primary side flow path 3 disappears, so that the release valve 51 is opened to prevent the risk of backflow.
[0005]
Since the former air release valve senses the primary flow path water pressure and the downstream chamber water pressure with the valve body A10, the pressure sensitivity is small, and the first check valve 50 is opened and closed mainly by the water flow pressure (dynamic pressure) and the valve body A10. And the valve body B12 are connected, and the first check valve 50 and the release valve 51 are configured such that when one is opened, the other is closed. Therefore, opening and closing of running water must be done on the upstream primary side.
[0006]
In the latter depressurization type backflow preventer, the first check valve 50 and the release valve 51 are individually opened and closed, so that the pressure difference between the primary side flow path 3 and the downstream chamber 6 is increased so that the release valve 51 does not open during normal operation. In addition, the spring A16 of the first check valve 50 must be strengthened to increase the water flow resistance, and a diaphragm 7 that opens and closes the release valve 51 by sensing the water pressure in the primary flow path 3 and the downstream chamber 6 is separately installed. Otherwise, the shape becomes large and expensive.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention provides a backflow prevention device for preventing a backflow of a flow flowing from the upstream side to the downstream side, and providing a valve chamber in the flow path between the primary flow path and the secondary flow path. The diaphragm is water-tightly divided into an upstream chamber on the primary flow path side and a downstream chamber on the secondary flow path side by a diaphragm, and a through-hole communicating the upstream chamber and the downstream chamber is opened in the axial center of the diaphragm, and the upstream chamber Forming a valve seat A surrounding the through hole on the side, opening an open hole communicating with the atmosphere in the downstream chamber, forming a valve seat B surrounding the open hole having the same central axis as the valve seat A; A valve body A is made to face the valve seat A from the upstream chamber side to constitute a first check valve, and a valve body B is connected to the valve body A by a valve shaft so as to face the valve seat B to constitute an open valve. The urging means A always urges the valve body A to the valve seat A, the urging means B always urges the diaphragm to the upstream chamber side, A backflow prevention device diaphragm and an open valve by also serves as a diaphragm for opening and closing the first check valve open valve has to be opened and closed in conjunction to open and close the check valve,
[0008]
When the opening / closing valve (not shown) is opened, the flowing water flowing in from the primary flow path presses the diaphragm, and the first check in a state where the diaphragm is closed by the urging means A against the urging means B. Move the valve to the downstream chamber side and close the release valve. Furthermore, since the valve element A connected to the valve element B by the valve shaft cannot move when the open valve is closed, the flowing water moves the valve seat A formed on the diaphragm against the urging means A and the urging means B. The first check valve is opened, flows into the downstream chamber, and flows out from the secondary flow path. When the on-off valve (not shown) is closed, the pressure for pushing the diaphragm is reduced, and the first check valve is closed by the urging means A and the urging means B. When negative pressure or the like occurs on the primary flow path side and the force pushing the diaphragm is further reduced, the biasing means B moves the first check valve in the closed state to the upstream chamber side and opens the release valve. Open the downstream chamber to the atmosphere. When the pressure in the downstream chamber rises, the diaphragm is moved to the upstream chamber side by the biasing means B, and the diaphragm is moved to the upstream chamber side to open the release valve to open the downstream chamber to the atmosphere.
[0009]
Therefore, a diaphragm that opens and closes the release valve is installed in the flow path between the upstream chamber and the downstream chamber, and a valve seat for the first check valve is formed on the diaphragm, and also serves as a diaphragm that opens and closes the first check valve. Since the opening and closing of the first check valve and open valve are linked, even if the water resistance of the first check valve is not increased, the open valve will not open during normal operation, which is highly safe and compact. And an inexpensive backflow prevention device.
[0010]
According to a second aspect of the present invention, in the backflow prevention device for preventing the backflow of the flow flowing from the upstream side to the downstream side, a valve chamber is provided in a flow path between the primary side flow path and the secondary side flow path, and the valve chamber is provided by a diaphragm. The upstream channel on the primary channel side and the downstream chamber on the secondary channel side are partitioned in a watertight manner, a through hole is formed in the axial center of the diaphragm to connect the upstream chamber and the downstream chamber, and the through hole is formed on the upstream chamber side. A valve seat A that forms the surrounding valve seat A and surrounds the inlet having the same central axis as the valve seat A is formed around the upstream chamber inlet of the upstream connection channel, and the downstream chamber communicates with the atmosphere. A valve seat B surrounding the open hole having the same central axis as the valve seat A is formed, and the valve body C is integrally formed on the other surface of the valve body A from the upstream chamber side to the valve seat A. The formed or mounted valve body A is opposed to form a first check valve, the valve body C is opposed to the valve seat C to form a third check valve, and the valve A valve body B is connected to A by a valve shaft, and the valve body B is opposed to the valve seat B to be an open valve. The urging means A constantly urges the valve body A to the valve seat A, and urges the diaphragm. The first check valve, the open valve, and the third check valve are linked by means of means B that is always energized to the upstream chamber side and serves as a diaphragm that opens and closes the first check valve and a diaphragm that opens and closes the open valve. A backflow prevention device that opens and closes,
[0011]
In addition to the above-described invention, by providing the third check valve at the upstream chamber inlet, the force for pushing the diaphragm is reduced by the reverse pressure from the downstream side, the negative pressure at the upstream side, etc. Moves the first check valve in the closed state to open the open valve, and further moves to close the third check valve to double safety.
[0012]
The third invention relates to the urging means A for constantly urging the valve body A to the valve seat A, and the urging means A for constantly urging the valve body A to the valve seat A includes the diaphragm and the valve body A or the valve body A. The reverse flow according to claim 1 or 2, wherein the reverse flow is urged either between the members connected integrally or between the valve box and the valve body A or the member integrally connected to the valve body A. When the biasing means A is biased between the diaphragm and the valve body A or a valve shaft integrally connected to the valve body A or a member integrally connected to the valve shaft. When opening the first check valve, the biasing means A and the biasing means B will be opened against the biasing means A and the biasing means B, and the biasing means A is integrated with the valve box and the valve body A or the valve body A. If the first check valve is opened, the urging means A is not involved and the valve is opened only against the urging means B when the first check valve is opened. Because It is the design of the performance of good backflow prevention device by selecting the target.
[0013]
In the fourth aspect of the invention, the valve body or piston in which the force due to the downstream chamber pressure applied to the valve body B is approximately the same as the force exerted on the valve body B acts in the opposite direction to the action on the valve body B. The backflow prevention device according to claim 1, 2 or 3, wherein the biasing means B is connected to the downstream chamber so that the pressure in the downstream chamber is increased in the direction in which the valve body B is closed. The urging means B also has an urging force when the valve body A is opened, so that it affects the water resistance and restricts the free design. A downstream chamber that is added to the valve body B by mounting a valve body or piston having an effective area substantially the same as that of the valve body B so as to be integrated with the valve body B so that the downstream chamber pressure acts in a direction opposite to the valve body B. The object of the present invention is to cancel the influence of pressure to solve the above-mentioned problems and to allow free design.
[0014]
The fifth aspect of the invention detects the movement of the valve body A or the valve body B or the valve shaft connecting the valve body A and the valve body B or the valve body or piston integrally connected to the valve body A and outputs an electric signal. The backflow prevention device according to claim 1, wherein the detection device is installed so that the movement of the valve body B can be detected. When there is a risk of pressure and the open valve opens, a signal is output and a warning lamp blinks to notify the danger and occurrence of reverse pressure, thereby preventing backflow.
[0015]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
FIG. 1 is a longitudinal sectional view of an embodiment of a backflow prevention device according to the present invention, and shows an example in which a biasing means A for constantly biasing a valve body A to a valve seat A is biased between a diaphragm and a valve body A. Shows running water. The valve box is provided with an upstream chamber 5 that communicates with the primary flow path 3 and the primary flow path 3 having a diaphragm mounting surface at the end face. The upper part of the valve body A10 is opposed to the upper surface of the upstream chamber by the upward movement of the valve body A10. The downstream of the valve box A1 having the projection 20 for stopping the joint valve body A10 formed around the upstream chamber inlet 18, the secondary channel 4 and the secondary channel 4 having a diaphragm mounting surface at the end surface. A chamber 6 is provided, and an opening hole 19 communicating with the atmosphere is opened at the bottom of the downstream chamber, and a diaphragm 7 attached to the end surface and a valve box B2 formed with a valve seat B11 surrounding the opening hole 19 having the same central axis. Constitute.
[0017]
The diaphragm 7 is provided with a through hole 14 that penetrates the valve shaft 15 in the axial center of the diaphragm 7 and a through hole 13 that communicates the upstream chamber 5 and the downstream chamber 6 around the through hole 14. A valve shaft 8 in which a valve seat A8 having a valve seat A9 surrounding the through hole 13 is integrally attached to the upstream chamber side in a watertight manner, and the valve body A10 is integrally attached to the valve body A10 from the upstream chamber side of the diaphragm 7. 15 is inserted through the through hole 14 and the valve body A10 is opposed to the valve seat A9 to form the first check valve 50. One end of the valve shaft 15 is suspended on the valve seat bracket 8 by the spring A16. And the valve body B12 is connected to the other end of the valve shaft 15. The valve body B12 and the valve shaft 15 may be simply connected in a watertight manner, but in this embodiment, a pilot valve is provided to facilitate opening of the valve body B12. The lower part of the valve shaft 15 is narrowed to form a valve shaft detail 25, a valve body D23 made of an elastic body is formed in the stepped portion, and a through hole 24 through which the valve shaft detail 25 passes is provided in the axial center of the valve body B12. A valve seat D22 is defined around the valve chamber side of the valve 24, and the valve body B12 is allowed to open from the valve seat D22 by passing through the valve shaft detail 25 through the through-hole 24 so that the valve body B12 can be opened. To be connected to the valve shaft 15. In this case, unlike the above, the spring A16 attaches the spring seat 17 to the upper part of the valve body D23 of the valve shaft 15 and biases it between the spring seat 17 and the valve seat fitting 8. Hereinafter, the pilot valve portion will be described as a valve body B without description.
[0018]
The diaphragm 7 assembled as described above is energized with a spring B27 between the valve box B2 and the valve seat bracket 8, and the valve body B12 is opposed to the valve seat B11 to form an open valve 51. The valve box A1 and the valve box B2 are assembled by being sandwiched between the diaphragm mounting surfaces of the valve box B2. The movable distance of the diaphragm 7 and the connecting distance between the valve element A10 and the valve element B12 are the movement of the diaphragm 7 to the downstream chamber side, the first check valve 50 is opened after the release valve 51 is closed, and the upstream chamber side. The distance at which the first check valve 50 is closed and the release valve 51 is opened by the movement toward is. The second check valve 21 mounted on the secondary flow path side prevents the reverse flow from the downstream to the downstream chamber 6 when the release valve 51 is opened, and may not be mounted. The diaphragm stopper 38 may be omitted because it restricts the movement of the diaphragm toward the downstream chamber as a diaphragm protection when the force applied to the diaphragm is large. The protrusion 20 restricts the movement of the valve body A10 to the upstream chamber side, and may be omitted because it improves the closing performance of the first check valve 50 and functions to protect the diaphragm.
[0019]
The operation of the backflow prevention device configured as described above is such that when the on-off valve (not shown) is opened, the diaphragm 7 opposes the closed first check valve 50 against the spring B27 by the water pressure of the flowing water flowing into the upstream chamber 5. Then, it moves to the downstream chamber side and closes the release valve 51. When the release valve 51 is closed, the valve element A10 connected by the valve element B12 and the valve shaft 15 cannot move, so that only the diaphragm 7 moves to the downstream chamber side against the springs A16 and B27, and the first check valve 50 is moved. When the valve is opened, the flowing water flows into the downstream chamber 6 and the check valve 21 mounted on the secondary channel side is pushed open to flow downstream as shown in FIG.
[0020]
When the on-off valve (not shown) is closed, the second check valve 21 is closed and the force acting on the diaphragm 7 due to the water pressure of the flowing water is reduced, so that the diaphragm 7 moves to the upstream chamber side by the spring A16 and the spring B27. The check valve 50 is closed to the state shown in FIG.
[0021]
When negative pressure or the like is generated on the upstream side and the force acting on the diaphragm 7 is further reduced, the first check valve 50 in a state in which the diaphragm 7 is closed is moved to the upstream chamber side by the spring B27 and the release valve 51 is opened. The downstream chamber 6 is opened to the atmosphere. When the pressure on the downstream side increases, the backflow is prevented by the second check valve 21, but when the second check valve 21 leaks due to dust or the like, the pressure in the downstream chamber 6 rises and the diaphragm 7 is moved by the spring B27. The first check valve 50 in the closed state is moved to the upstream chamber side, the release valve 51 is opened, and the downstream chamber 6 is opened to the atmosphere as shown in FIG.
[0022]
Another embodiment is shown in FIG. In this embodiment, in place of the projection 20, a valve seat C28 surrounding the inlet 18 having the same central axis as the valve seat A9 is formed around the upstream chamber inlet 18 of the valve box A1 instead of the protrusion 20. A valve body C29 is formed on the other surface of the valve body A10 and is opposed to the valve seat C28 to constitute a third check valve 52. In this embodiment, a pilot that makes it easy to open the valve body B12 described above. In place of the system provided with the valve, the valve body B12 and the valve shaft 15 are connected in a watertight manner so as to move slightly, and the valve body B12 and the valve seat B11 are considered to improve the closing performance. Other configurations are the same as those in the previous embodiment.
[0023]
In the operation, when an upstream negative pressure, a downstream pressure increase or the like occurs, the first check valve 50 in a state in which the diaphragm 7 is closed by the spring B27 is moved to the upstream chamber side and the release valve 51 is opened. Then, the downstream chamber 6 is opened to the atmosphere, and when it further moves, the third check valve 52 is closed to further increase safety. Other operations are the same as those in the previous embodiment.
[0024]
Another embodiment is shown in FIG. This embodiment is an embodiment in which a spring A16 for urging the valve body A10 to the valve seat A9 is urged between the valve box and the valve body A in order to prevent the spring A16 from obstructing the flow. For this reason, a spring seat 32 is provided in the axial center portion of the primary flow path 3 of the valve box A1 with the periphery as a flow path 31, and between the upper part of the valve body C29 formed on the other surface of the valve body A10 and the spring seat 32. The spring A16 is biased to the bottom. In this case, the spring A16 biases the opening valve 51 in the closing direction, and the spring B27 biases the opening valve 51 in the opening direction. Therefore, the spring force acting on the opening valve 51 is the same as that of the spring A16 and the spring A16. Since the spring A16 does not act on the diaphragm 7, the spring force acting on the opening and closing of the first check valve 50 is only the spring B27. Thus, it is effective in reducing the water flow resistance of the first check valve 50. Other configurations and operations are the same as those in the previous embodiment.
[0025]
Yet another embodiment is shown in FIG. This embodiment is an embodiment in which the pressure in the downstream chamber 6 does not act on the valve body B12, and the pressure sensitive chamber is located at a position where the flowing water in the downstream chamber 6 is opposed to the downstream chamber 6 and the opening hole 19 by the guide hole 44. 45 is formed in a through hole 46 between the pressure sensing chamber 45 and the opening hole 19 to form a sliding cylinder 47 having the same central axis as the valve seat B11, and a piston 49 having the same effective area as the valve body B12. Is slidably fitted in a watertight manner and is watertightly connected to the valve shaft 15 connecting the valve body B12 with a retaining ring 48 or a screw.
[0026]
In the operation, the pressure in the downstream chamber 6 pressurizes the valve body B12 downward in the figure, whereas the downstream chamber pressure guided to the pressure sensing chamber 45 through the guide hole 44 pressurizes the piston 49 upward in the figure. Therefore, both forces cancel each other, and the downstream chamber pressure does not act on the valve body B12. It becomes easy to design with a simple force relationship.
[0027]
FIG. 7 shows a partial detailed view of still another embodiment. In this embodiment, a magnet 33 is attached to the lower end of the valve shaft 15 that connects the valve body A10 and the valve body B12, a hall element or a reed switch 34 is attached to the side wall of the drain hole 19, and the valve shaft 15 is moved. The Hall element or the reed switch 34 detects a change in magnetic force of the magnet 33 and outputs an electrical signal when the valve is opened or a dangerous position is opened. Since the alarm is issued when the valve element B12 is opened or there is a risk of opening the valve, it is possible to detect the risk of backflow and prevent countermeasures.
[0028]
FIG. 8 shows a partial detailed view of another embodiment of the third check valve 52. Since the third check valve 52 is an emergency valve that is always opened and is surely closed when a backflow occurs, a valve that reliably closes without dust biting is desired. The present embodiment is made to achieve the above-described object. The valve seat C28 is a tapered valve seat, the valve body C29 opposite to the valve seat C29 is made spherical to prevent dust from being attached, and the seat surface of the valve body C29 is formed. Soft rubber or elastic body 35 such as rubber with foam or air inside, enabling sealing even if there is some dust, and with a tapered valve seat and soft spherical valve body it is difficult to get dust and the reverse of good sealing performance It is a stop valve. In this embodiment, the valve body C29 is spherical, but it may be a streamlined convex shape such as a cone. Further, the valve body A10 and the valve body C29 are separated and attached so as to move slightly, so that the valve body C29 can be easily adapted to the valve seat C28 and the check valve seal can be improved. ]
FIG. 9 shows an example in which an electromagnetic valve 36 is integrally installed as an on-off valve on the upstream side of the backflow prevention device of the present invention. Of course, an electromagnetic valve may be integrally provided as an on-off valve on the downstream side of the backflow prevention device of the present invention. In this case, the second check valve 21 may be omitted.
[0030]
【The invention's effect】
As described above, according to the first aspect of the present invention, the diaphragm that opens and closes the open valve by sensing the pressure in the upstream chamber and the downstream chamber is installed in the flow path between the upstream chamber and the downstream chamber, and the first check is attached to the diaphragm. Since the valve is formed, the open valve and the first check valve open and close together, and the open valve does not malfunction even if the water flow resistance of the first check valve is reduced. The opening and closing performance of the first check valve is improved, and according to claim 2, the valve seat C is formed around the upstream chamber inlet of the primary side flow path, and the valve body C is formed on the other surface of the valve body A. Thus, as the third check valve facing the valve seat C, the third check valve is closed when the open valve is opened, so that backflow can be prevented more reliably. It is possible to select whether or not the biasing means A contributes to the opening and closing of the first check valve by the biasing method of the biasing means A that always biases the valve body A to the valve seat A. Yes, the design suitable for the purpose is possible, and according to claim 4, a valve body or a piston that counteracts the force caused by the downstream chamber pressure applied to the valve body B is installed to eliminate the influence of the downstream chamber pressure on the valve body B. Therefore, the force relationship is simplified, and according to claim 5, a signal is output by the movement of the valve body B, the valve shaft, etc. that opens and closes the open hole communicating with the atmosphere, and an alarm is issued to cause a risk of backflow. Therefore, a low-cost backflow prevention device with a small size, a small water resistance, and a high safety can be obtained. In the present invention, a diaphragm is used, but there is no problem as long as it is equivalent to a diaphragm that senses pressure and moves in a watertight manner.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an embodiment of a backflow prevention device according to the present invention, showing a non-flowing state.
[Fig. 2] Fig. 2 shows a water flow in the longitudinal sectional view of the embodiment.
FIG. 3 shows the open valve in the longitudinal sectional view of the embodiment.
FIG. 4 is a longitudinal sectional view of another embodiment of the same apparatus according to the present invention, showing a state of non-flowing water.
FIG. 5 is a longitudinal sectional view of another embodiment of the same apparatus according to the present invention, showing a state of non-flowing water.
FIG. 6 is a longitudinal sectional view of another embodiment of the same apparatus according to the present invention, and shows the time of running water.
FIG. 7 is a partial detail view of another embodiment of the apparatus according to the present invention.
FIG. 8 is a partial detail view of another embodiment of the apparatus according to the present invention.
FIG. 9 is a longitudinal sectional view of an embodiment in which a solenoid valve is installed in the apparatus according to the present invention.
FIG. 10 is a longitudinal sectional view of an example of a conventional backflow prevention device.
FIG. 11 is a longitudinal sectional view of an example of a conventional backflow prevention device.
[Explanation of symbols]
1--Valve box A 2--Valve box B 7--Diaphragm 9--Valve seat A 10--Valve A 11--Valve seat B
12--Valve B 13--Through hole 15--Valve shaft 16--Spring A 21--Second check valve 27--Spring B
28--Valve seat C 29--Valve C 33--Magnet 34--Hall element or reed switch 35--Elastic body 36--Solenoid valve 38--Diaphragm stopper 50--First check valve 51-- Release valve

Claims

In the backflow prevention device for preventing the backflow of the flow flowing from the upstream side to the downstream side, a valve chamber is provided in the flow path between the primary side flow path and the secondary side flow path, and the valve chamber is arranged upstream of the primary flow path side by the diaphragm. A water-tight partition between the chamber and the downstream chamber on the secondary flow path side, a through hole communicating with the upstream chamber and the downstream chamber is opened in the axial center of the diaphragm, and a valve seat A surrounding the through hole is formed on the upstream chamber side Then, an open hole communicating with the atmosphere is opened in the downstream chamber, a valve seat B surrounding the open hole having the same central axis as the valve seat A is formed, and the valve element A is inserted into the valve seat A from the upstream chamber side. The first check valve is configured to face the valve body A and the valve body B is connected to the valve body A by a valve shaft so as to face the valve seat B to form an open valve. A diaphragm that biases the valve seat A, constantly biases the diaphragm to the upstream chamber side by the biasing means B, and opens and closes the first check valve; Backflow prevention device first check valve and an open valve by also serves as a diaphragm was made to open and close in conjunction to open and close the Houben.

In the backflow prevention device for preventing the backflow of the flow flowing from the upstream side to the downstream side, a valve chamber is provided in the flow path between the primary side flow path and the secondary side flow path, and the valve chamber is arranged upstream of the primary flow path side by the diaphragm. A water-tight partition between the chamber and the downstream chamber on the secondary flow path side, a through hole communicating with the upstream chamber and the downstream chamber is opened in the axial center of the diaphragm, and a valve seat A surrounding the through hole is formed on the upstream chamber side In addition, a valve seat C surrounding the inlet having the same central axis as the valve seat A is formed around the upstream chamber inlet of the upstream connection channel, and an open hole communicating with the atmosphere is opened in the downstream chamber. A valve body in which a valve seat B surrounding the open hole having the same central axis as the seat A is formed, and a valve body C is integrally formed or mounted on the other surface of the valve body A from the upstream chamber side to the valve seat A A is made to face the first check valve, the valve body C is made to face the valve seat C to make the third check valve, and the valve body A is attached to the valve shaft. The valve body B is connected to be opposed to the valve seat B to be an open valve, and the urging means A constantly urges the valve body A to the valve seat A, and the urging means B constantly brings the diaphragm to the upstream chamber side. Energized and combined with the diaphragm that opens and closes the first check valve and the diaphragm that opens and closes the relief valve, the first check valve, the release valve, and the third check valve are linked to open and close to prevent backflow apparatus.

The urging means A for constantly urging the valve body A to the valve seat A is provided between the diaphragm and the valve body A or a member integrally connected to the valve body A, or the valve box and the valve body A or the valve body A. 3. The backflow prevention device according to claim 1, wherein the backflow prevention device is biased to either or both of the members connected to each other.

A valve body or piston in which the force due to the pressure in the downstream chamber applied to the valve element B acts in the opposite direction to the action on the valve element B is connected to the valve element B integrally. The backflow prevention device according to claim 1, claim 2, or claim 3.

A detection device for detecting the movement of the valve body A or the valve body B or the valve shaft connecting the valve body A and the valve body B is installed, and the movement of the valve body B leaving the valve seat B is detected. 5. The backflow prevention device according to claim 1, wherein the backflow prevention device outputs an electrical signal.