Patent ID: 7334597

Claim:
A bypass valve assembly selectively operated to bypass a delivery fluid, comprising: a housing assembly having a fluid inlet, a bypass fluid outlet and a pressure inlet; a cage assembly slidably supported within the housing and having a plunger end and a piston retaining end, the plunger end forming with the housing an interior chamber in fluid communication with the pressure inlet; a piston assembly slidably supported by the cage assembly; first biasing means for biasing the piston assembly to a closed position in which fluid flow is prevented between the fluid inlet and the bypass fluid outlet; second biasing means biasing the plunger toward the pressure inlet; and wherein the piston assembly is slidable from the closed potion to one of a first open position and a second open position, the piston assembly biased to the closed position when the delivery system pressure is between an upper first threshold pressure value and a lower second threshold pressure value, to the first open position when the delivery system pressure exceeds the first threshold pressure value whereby fluid flow is permitted from the fluid inlet through the bypass fluid outlet, and to the second open position when the delivery system pressure is less than the second threshold pressure value whereby fluid flow is permitted from the fluid inlet through the bypass fluid outlet.