Patent ID: 7322808

Claim:
In a hydraulic device utilizing rotor valving with inner and outer commutation grooves in an orbiting rotor interconnecting two ports to expanding and contracting gerotor cells through a stationary manifold in the housing on pressurizing one side of the rotor away from the manifold, the improvement of a pressure compensation mechanism, said pressure compensation mechanism including a balancing plate, said balancing plate being connected to the housing between the rotor and the housing on the other side of the rotor than the manifold, said balancing plate having a pressure chamber, a shuttle valve compartment, said shuffle valve compartment being fluidically connected to said pressure chamber, said shuffle valve compartment having two openings, said two openings being connected to the two ports respectively, a shuttle valve, said shuttle valve being in said shuttle valve compartment, said shuttle valve being moveable within said compartment to seal one of said two openings upon relative pressurization of the other of said two openings to provide for the pressurization of said pressure chamber and thus pressure compensation for the device.