| 摘要 |
<p>A check valve (10) is provided to maintain fluid flow in a single desired direction through a conduit. The check valve (10) requires a greater fluid pressure to open the check valve to allow fluid to pass in a desired direction than an amount of pressure required to keep the check valve in its open position. This variable opening force performance is provided by providing a closure arm (340) exerting a closure force on a flapper (120) urging the flapper toward its closed position. Contact between the closure arm (340) and the flapper (120) occurs between a follower (360) on the closure arm (340) and a cam surface (126) on the flapper (120). A contour of the cam surface on the flapper, and especially a hump (124) on the cam surface causes the closure arm (340) to exert a variable amount of force on the flapper (120) depending on the position of the flapper. When the flapper (120) is closed a relatively large amount of force is exerted on teh flapper. When the flapper (120) is open a relatively smaller amount of force is exerted on the flapper by the closure arm (340). The dimensions and contours of the follower (360) and the cam surface (126) can be customized to provide desired closure arm force exerting characteristics for the check valve (10) of this invention.</p> |
