Variable displacement vane pump having low actuation friction cam seal

A durable, vane pump comprising:

• (a) a rotor member having journal ends and a cylindrical central vane section comprising a plurality of radial vane slots uniformly spaced around the central circumference thereof, said vane slots being elongate in the axial direction and having a central vane-supporting portion with axial vane slot extensions at each end thereof, extending beyond said central vane section;
• (b) a plurality of vane elements, each slidably-engaged within the central vane-supporting portion of a said slot for radial movement therewithin, leaving said vane slot extensions at each end thereof;
• (c) an adjustable unitary cam member having a uniform width and opposed faces and a bore therethrough forming a cam chamber having a continuous interior cam surface, the central vane-supporting portion of the cylindrical vane section of said rotor member being supported within said cam chamber so that the outer tip surfaces of all of the vane elements make contact with said continuous interior cam surface during rotation of said rotor member between a low pressure inlet arc segment, a high pressure outlet arc segment and intermediate seal arc segments of said cam chamber;
• the opposed faces of said cam member having at least one liquid inlet groove in the low pressure inlet arc segment thereof, and arcuate slots in corresponding areas of the high pressure outlet arc segments thereof, each said slot containing an elongate arcuate sealing member which is biased outwardly from its slot, said vane slot extensions of the rotor member extending axially beyond said cam chamber;
• (d) an outer cylindrical cam enclosure or spacer having a larger diameter than the cam member and having a width which is slightly greater than the width of the cam member;
• (e) an opposed pair of bearings rotatably supporting the journal ends of said rotor member;
• and
• (f) an opposed pair of cylindrical cam seal elements, one each between a said bearing and a face of said cam member, each said seal element having an outer radial face surface which tightly engages an edge of said cam enclosure or spacer to support an inner radial face surface of each cam seal element closely spaced from a face of said cam member except in the area of the high pressure outlet arc segments of each seal element, where the radial face surfaces of each cam seal element make sealing engagement with said arcuate sealing members on the opposed faces of the cam member, each cam seal element having an inner circumferential surface which overlaps the vane slot extensions of the central vane section of the rotor member;
• each said seal element further including liquid-conveying passages which open to the vane slot extensions and communicate with the cam chamber, the first said passage being located in the inlet arc segment of each seal element and being open to at least one said liquid-inlet groove in the surface of the cam faces, and the second said passage being located in the discharge arc segment of each seal element and being open to a liquid discharge conduit, to permit the continuous supply and pressure discharge of a liquid through said pump while minimizing leakage thereof, whereby the adjacent faces of the cam seal elements and of the cam member are fixed in closely-spaced, friction-free relation, except in the areas of engagement between said arcuate sealing members and said opposed faces of the cam member, to provide a low actuation force, variable displacement pump.