Patent ID: 6932107

Claim:
A flow control valve for providing a substantially constant flow of fluid through the 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; a hollow piston movably disposed in the cavity adjacent to the flow passageway; a seal positioned in the cavity proximate to the piston and sealably separating the cavity into first and second chambers, the seal having at least a section exposed to the fluid in the first chamber, the section of the seal having an inner perimeter portion defining a first effective inner area within the hollow piston; a biasing member configured to urge the hollow piston; a reference pressure passageway in fluid communication with the inlet and the second chamber; and a member positioned at least proximate to the piston and the flow passageway, the member having an orifice with a second inner effective area at least approximately equal to the first effective inner area defined by the section of the seal, the piston being movable relative to the member to vary a portion of the flow passageway.