Patent ID: 7955062

Claim:
A vane pump for pumping hydraulic fluid, comprising a body having a chamber, a rotor rotatable within the chamber, the chamber and the rotor being shaped to define one or more rise, fall and dwell regions between walls of the chamber and the rotor, the rotor having a plurality of slots, a plurality of vanes located such that each slot of the rotor has a vane located therein, each of the vanes being moveable between a retracted position and an extended position wherein in the retracted position the vanes do not work the hydraulic fluid and in the extended position the vanes work the hydraulic fluid, an under vane passage extending beneath each of the vanes, one or more inlets for introducing relatively low pressure hydraulic fluid into the one or more rise regions, one or more outlets for discharging relatively high pressure hydraulic fluid from the one or more fall regions, at least one flow passage for supplying hydraulic fluid at outlet pressure to the under vane passages of the vanes located in the fall region, and intermediate pressure supply means for supplying hydraulic fluid of an intermediate pressure to the under vane passages of the vanes located in and passing through the rise region, wherein the intermediate pressure is lower than the outlet pressure but higher than the inlet pressure of the hydraulic fluid.