A valve unit to control the flow of high-pressure fluid comprising a housing having a fluid inlet and a fluid outlet; a flow port in the housing communicating between the inlet and outlet, and a seat about the flow port; stem structure in the housing, and a stopper carried by the stem structure to be...http://www.google.com/patents/US5638862?utm_source=gb-gplus-sharePatent US5638862 - Diaphragm valve
