Variable displacement vane pump with vane tip relief

A durable, single action, variable displacement vane pump capable of pumping of liquids comprising:

• (a) a cylindrical rotor member having journal ends and a 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 each having a central vane-supporting portion;
• (b) a plurality of vane elements, each slidably-engaged within the central vane-supporting portion of a said vane slot for radial movement therewithin to form vane bucket areas therebetween;
• (c) a unitary cam member having opposed faces and a circular transverse bore therethrough forming a cam chamber having an interior cam surface, the central vane section of said rotor member being supported axially and non-concentrically within said cam chamber so that the outer tip surfaces of all of the vane elements make contact with said interior cam surface during rotation of said rotor member, except at the rotational center of said interior cam surface where each said vane tip surface or said cam surface is provided with a central recess or groove which spaces said vane tip surfaces from said interior cam surface along a narrow central area around the entire interior cam surface in the direction of rotation of said rotor member, which narrow central area is open to the circulation of liquids being pumped, to prevent stagnation and overheating of said liquids;
• (d) an opposed pair of bearing seals rotatably supporting the journal ends of said rotor member, each said bearing seal having a face surface which contacts a face surface of said cam member and encloses the central vane-supporting portion of said rotor member within said cam chamber, each bearing seal having an inlet arc segment comprising means for admitting fluid to expanding vane bucket areas of the rotating vaned rotor and through said central recesses or grooves, and into said vane slots and undervane areas, and a discharge arc segment comprising means for discharging pressurized fluid from contracting vane bucket areas and through said central recesses and grooves of the rotating vaned rotor and from undervane areas as the vanes are depressed into the vane slots during rotation through the discharge arc, said cam member being adjustable relative to said vaned rotor to vary the extent of eccentricity therebetween for varying the displacement capacity of said vane pump.