Patent ID: 7128086

Claim:
A valve, comprising: a valve body having an inlet, an outlet, a flow passageway coupling the inlet to the outlet, and a cavity intersecting the flow passageway, the cavity having a first chamber and a second chamber, the second chamber having a generally hollow configuration; a piston assembly including a hollow piston body, a support member coupled to the hollow piston body, and a poppet coupled to the support member, the hollow piston body being disposed in the second chamber, the support member and the poppet being disposed in the first chamber; a seal having a section separating the first and second chambers, the section defining a first effective inner area; a biasing member configured to urge the hollow piston body toward the first chamber; a reference pressure passageway in fluid communication with the outlet and the second chamber; and a piston seat positioned to selectively engage the poppet, the piston seat enclosing a second effective inner area at least approximately equal to the first effective inner area; wherein the hollow piston body has an inner wall defining a third inner area greater than or egual to the first effective inner area.