Butterfly valve

Claim 1

A valve comprising a valve seat having a passageway therethrough and a valve element movable into and out of engagement with said valve seat for opening and closing said passageway, one of said valve seat or element being formed of an elastomeric material and the other thereof being formed of a relatively rigid material; actuating means operatively connected to said valve element for moving said valve element to and from a closed position in which said valve element engages said valve seat and said passageway is closed by said valve element; a motor having a fluid responsive diaphragm movable between first and second positions; a connecting element fixed to and movable with said diaphragm; an arm having one end slidingly engaging said connecting element for movement in two directions back and forth thereon, and an opposite end connected to said actuating means; first stop means adjacent said diaphragm and second stop means spaced therefrom for limiting the sliding movement of said arm relative to said connecting element in both said directions; and a preloaded compression spring operatively disposed between said arm and said second stop means for biasing said arm against said first stop means, whereby movement of said diaphragm to its first position will cause said first stop means to move said arm in a direction to cause said actuating means to move said valve element to its open position, and movement of said diaphragm to its second position will cause said second stop to push against said spring to move said arm in a direction to cause said actuating means to move said valve element to its closed position, with said spring limiting the amount of force which can be exerted by said diaphragm on said valve element in a direction tending to move the latter to said closed position, the preload on said spring and the arrangement of parts being such that on closing said valve element engages said valve seat prior to said diaphragm reaching said second position, whereby said spring is at least partially compressed when said valve is closed, the compession of said spring being sufficient to provide a valve closing force which results in a slight compression of said elastomeric material.