Patent ID: 7770595

Claim:
A constant-flow valve assembly, comprising: a first fluid passageway configured to carry fluid at a first fluid pressure; a chamber having at least a portion configured to receive fluid at a second fluid pressure less than the first fluid pressure; a second fluid passageway connected to the portion of the piston chamber and configured to carry fluid at the second fluid pressure; a third fluid passageway configured to carry fluid at a third fluid pressure less than the first and second fluid pressures; a piston slideably disposed in the chamber; a biased valve member having a valve seat adjacent to the third passageway, a valve body, and a first biasing member coupled to the piston, and a second biasing member coupled to the valve body being urged by the second biasing member toward the valve seat and configured to provide a substantially constant fluid flow to the third passageway past the valve seat substantially independent of the pressure differentials between the second and third fluid pressures; and an adjustable restrictor assembly between the first and second fluid passageways, the restrictor assembly having an inlet portion, an outlet portion, and a restrictor with a fluid pathway extending therebetween, the inlet portion being positioned to receive fluid at the first fluid pressure from the first fluid passageway and to direct the fluid to the restrictor, and the outlet portion being positioned to receive fluid from the restrictor and direct fluid to the second fluid passageway at the second fluid pressure, the restrictor having an entry portion and an exit portion of the fluid pathway, the restrictor being movable to adjust the position of the entry and exit portions relative to the inlet and outlet portions to adjust a fluid flow rate of fluid through fluid pathway to the second fluid passageway and to automatically adjust the biased valve member for a constant flow rate of fluid through the valve assembly, and wherein the restrictor comprises a sleeve with an interior area and a central member disposed in the interior area, the fluid pathway extends through the sleeve and around the central member.