Patent ID: 8011901

Claim:
A fluid apparatus comprising: a pump barrel having a first barrel section in fluid communication with a fluid source and a second barrel section in fluid communication with a discharge conduit; a first piston housed in the first barrel section for axial movement therein; a second piston housed in the second barrel section for axial movement therein in response to application of an actuating pressure to the discharge conduit, the first and second pistons defining a variable volume chamber between the first and second pistons; a biasing element coupled to at least one of the first and second pistons; an inlet check valve operable to permit fluid to flow from the fluid source into the variable volume chamber; an outlet check valve operable to permit fluid to flow from the variable volume chamber into the discharge conduit; a bypass passageway having an inlet end in fluid communication with the fluid source and an outlet end in fluid communication with the discharge conduit, the bypass passageway being in fluid communication with the variable volume chamber, and wherein the inlet check valve is disposed at the inlet end of the bypass passageway and operable to permit fluid to flow through the bypass passageway into the variable volume chamber and the outlet check valve is positioned at the outlet end of the bypass passageway and operable to permit fluid to be discharged from the variable volume chamber through the bypass passageway; and means for connecting the first and second pistons to cause movement of the first piston in response to movement of the second piston caused by the actuating pressure, the respective movements of the first and second pistons being operable to increase the volume of the variable volume chamber thereby drawing fluid into the variable volume chamber through the inlet check valve while causing energy to be stored in the biasing element, the stored energy in the biasing element being subsequently operable to cause respective return movement of the first and second pistons when the actuating pressure is decreased, the respective return movement of the first and second pistons being operable to reduce the volume of the variable volume chamber thereby causing fluid to be discharged from the variable volume chamber through the outlet check valve.