Diaphragm valve

Claim 1

A valve for controlling flow in response to downstream pressure variation, said valve including a housing having means at least partially defining a flow passageway having a port surrounded by a valve seal, said port separating an upstream portion of said flow passageway from a downstream portion, a diaphragm mounted on said housing and being movable relative to said port between a port closing position and a port opening position, said diaphragm including a first side subject to atmospheric pressure producing a first force urging said diaphragm toward said port opening position, and a second side cooperating with said housing to assist in completing said flow passageway and subject, in part, to the pressure condition in said downstream portion of said flow passageway, a diaphragm support engaging at least a portion of said diaphragm and having a cupped middle portion and movable in common with said diaphragm, and a spring engaged with said support and urging said diaphragm toward said port closing position, whereby, when said downstream passageway portion is subject to a pressure condition below atmospheric pressure, such sub-atmospheric pressure produces a second force which acts in common with said first force and in opposition to said spring so as to displace said diaphragm toward said port opening position, and whereby, when said downstream flow passageway portion is subject to a pressure higher than sub-atmospheric pressure, such higher pressure produces a second force acting counter to said first force and said spring displaces said diaphragm toward said port closing position.