Piston for swash plate pump

Claim 1

In a swash plate pump including a cylinder, the improvement comprising a piston assembly for reception in said cylinder in order to minimize lateral dynamic thrust wear of the piston and cylinder, said assembly comprising an elongate piston body having an enlarged piston head for sliding contact with the cylinder, and a cylindrical bearing sleeve mounted on said piston body in axial spaced relation to said piston head for sliding contact with the adjacent portion of the cylinder, means for providing a fulcrum engagement between said bearing sleeve and said piston body to allow overall flexure of said piston body while maintaining said bearing sleeve substantially coaxial relative to the bore surface of said cylinder so that the load from the piston is distributed substantially uniformly over the external bearing area of the sleeve, a predetermined radial clearance being provided between the piston body and the sleeve in order to permit relative pivotal movement therebetween, said means for providing a fulcrum engagement comprising an enlarged land portion on said piston body adjacent said sleeve for contact with the central portion of said sleeve upon lateral movement of said piston body taking up said radial cLearance, said land portion having an axial length less than the axial length of the sleeve so that lateral loads on said piston are transferred to said sleeve within the central portion of the sleeve.