Patent ID: 8360751

Claim:
A fluid apparatus comprising: a pump barrel forming at least a portion of a sealed spring chamber for containing a compressible fluid and 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 liquid spring biasing element comprising the sealed spring chamber, and a displacing element received in the sealed spring chamber for reducing the volume of the sealed spring chamber, the displacing element being coupled to at least one of the first and second pistons, wherein the sealed spring chamber comprises a portion of the first barrel section of the pump barrel; 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; and a connector between the first and second pistons, the connector being operably configured 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 chamber through the inlet check valve while causing energy to be stored in the liquid spring biasing element, the stored energy in the liquid spring 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 chamber through the outlet check valve.