Patent ID: 8708679

Claim:
A vane pump for pumping hydraulic fluid comprising: a body having a chamber; and 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, with each slot of the rotor having a vane of the plurality of vanes located therein, each vane being moveable between a retracted position and an extended position˜ with each vane having two intravanes disposed therein, wherein in the retracted position the vanes do not work the hydraulic fluid and in the extended position the vanes work the hydraulic fluid, wherein the chamber defines one or more inlets for introducing relatively low pressure hydraulic fluid, at an inlet pressure, into the one or more rise regions, and wherein the chamber defines one or more outlets for discharging relatively high pressure hydraulic fluid, at an outlet pressure, from the one or more fall regions, wherein the rotor defines an under vane passage extending beneath each vane with the vane resisting fluid flow between the under vane passage and the chamber through the vane, and a plurality of flow passages, each to communicate pressurized hydraulic fluid to a portion of an under vane passage, wherein each vane has disposed therein at least two intravanes located below an upper surface of the vane, and the rotor defines respective flow passages of the plurality of flow passages, each in fluid communication with a respective under vane passage to communicate pressurized hydraulic fluid to the intravanes, wherein in a first mode of operation pressurized hydraulic fluid is delivered to both intravanes regions of a vane when the pump is operating at a relatively low pump speed, and in a second mode of operation pressurized hydraulic fluid is delivered to one intravane of the vane when the pump is operating at a relatively high pump speed.