Patent ID: 6901844

Claim:
In a radial piston pump having a housing defining a central cavity; a drive member mounted for rotation in the cavity about a drive axis; at least one pumping chamber mounting bore extending radially relative to said axis, through the housing to said cavity; a piston oriented radially within the pumping chamber mounting bore and having a radially outer pumping end and a radially inner driven end cooperating with the drive member for reciprocal movement in said pumping chamber mounting bore between top dead center and bottom dead center travel limits; a sliding shoe engaging the driven end of the piston and bearing on the drive member, for providing said cooperation whereby the rotary movement of the drive member is converted to the reciprocal movement of the piston; and a return spring for urging the driven end of the piston toward the shoe and the drive member, wherein the improvement comprises: that the sliding shoe has a central region that engages the driven end of the piston and an outer region surrounding the driven end of the piston and projecting into the pumping chamber mounting bore a distance such that for all positions of the piston relative to the drive member, at least a portion of said outer region remains within the pumping chamber mounting bore, said outer region being radially inwardly spaced from an inside surface of said pumping chamber mounting bore so long as said sliding shoe is engaged with the driven end of said piston.