Patent ID: 7273205

Claim:
The combination of a discharge piston movable to close a fluid passage and to open the fluid passage and an actuator piston operable to assist with biasing the discharge piston to move to close and to move to open comprising: a discharge piston movable along an axis, a body including a recess, an actuator piston seat, and a fluid vent passageway in fluid communication with said actuator piston seat; an actuator piston associated with said body, said actuator piston including a head and a diaphragm having a first surface and a second surface, said actuator piston being slideable along the axis and with respect to said body between a retracted position and an extended position, said diaphragm being located within said recess of said body such that said diaphragm is slideable within said recess as said piston slides between said retracted position and said extended position, said head adapted to sealingly engage said actuator piston seat when said actuator piston is in said retracted position, said head adapted to be disengaged from said actuator piston seat when said actuator piston is in said extended position; a biasing member located within said recess of said body in operative engagement with said diaphragm, said biasing member adapted to resiliently bias said actuator piston toward said retracted position; and a plunger having a first end and a second end, said plunger being selectively slideable with respect to said body between a retracted position and an extended position, said first end of said plunger adapted to engage said diaphragm, said second end of said plunger adapted to receive a positive displacement force such that said plunger transfers said positive displacement force to said diaphragm; whereby said actuator piston is selectively slideable from said retracted position toward said extended position by selective application of said positive displacement force to said second surface of said diaphragm such that a first fluid passageway extends through said actuator piston seat.