Patent ID: 6962175

Claim:
A fluid exchange device for replacing used fluid from an accessed hydraulic circuit with fresh fluid from a fresh fluid source, said device comprising: a pump having at least four variable volume fluid chambers including a first working fluid chamber, a second working fluid chamber, a first pumping fluid chamber and a second pumping fluid chamber; a control valve, operatively coupled to the pump, said control valve having a first valve position and a second valve position; a first conduit for receiving used fluid from the accessed hydraulic circuit; a second conduit for introducing fresh fluid into the accessed hydraulic circuit; a third conduit operatively coupling the first conduit to the first working fluid chamber when the control valve is in the first valve position, and operatively coupling the first conduit to the second working fluid chamber when the control valve is in the second valve position; a fourth conduit operatively coupling the second working fluid chamber to a used fluid receptacle when the control valve is in the first valve position, and operatively coupling the first working fluid chamber to the used fluid receptacle when the control valve is in the second valve position; a fifth conduit operatively coupling the second conduit to the first pumping chamber when the control valve is in the first valve position, and operatively coupling the second conduit to the second pumping fluid chamber when the control valve is in the second valve position; and a sixth conduit operatively coupling the second pumping fluid chamber to a fresh fluid source when the control valve is in the first valve position, and operatively coupling the first pumping fluid chamber to the fresh fluid source when the control valve is in the second valve position.