Variable output vane pump

A variable output vane pump comprising

• a pump housing having a circular bore;
• a rotor supported rotatably within said housing;
• a plurality of vanes fitted in the outer circumference of said rotor, said vanes being displaceable radially into and out of said rotor;
• a ring having first and second sides supported pivotally by a pivot portion, said pivot portion connecting the circular bore of said housing to the outer circumference of said ring and enclosing said rotor and said vanes;
• inlet and outlet ports formed in said housing, first and second pressure chambers for pivotting said ring being formed between the circular bore of said housing and the outer circumference of said ring by means of a plurality of seal pins fitted in a plurality of axial grooves formed in the outer circumference of said ring and opening into the circular bore of said housing, said ring being urged by the action of a spring fitted in said housing in a direction opposite to that of the pressure built up by said pressure chambers, said direction being such that the axis of said ring is displaced from the axis of rotation of said rotor;
• and
• an elastic member fitted in the bottom of each of said plurality of axial grooves, each of said elastic members urging the seal pin fitted in the same groove both toward the circular bore of said housing and at the same time toward one of the side walls of said axial groove, the urging direction of said elastic member and a tangential line, on which said seal pin is tangential to the circular bore of said housing, being at an acute angle with respect to each other;
• wherein said first pressure chamber communicates with said outlet port and encloses the pivot portion of said ring for generating a force urging said ring toward said pivot portion against the internal pressure generated in said ring by a pumping action which is weaker than said internal pressure, and said second pressure chamber is disposed adjacent said first pressure chamber, spaced therefrom by said seal pins and adapted to be supplied with the pump output pressure for generating an urging force against the biasing force of said spring, the region extending between the circular bore of said housing and the outer circumference of said ring other than said pressure chambers communicating with said inlet port.