Piston assembly for a fluid mechanism with reaction plate, complete with slipper block

Claim 1

A piston assembly for use in a pressurized fluid mechanism such as a hydraulic pump or motor equipped with pistons which bear against a reaction plate via slipper blocks, said assembly comprising such a piston and the slipper block associated therewith, which slipper block is coupled to one end of said piston by means of a ball-and-socket joint, the male element of said joint comprising that part of said slipper block opposite the face supporting said slipper block on the reaction plate, and the female element of said joint comprising said end of said piston, said piston including a central cavity issuing at its two axial ends and which has, at said piston end comprising said female element of said joint, a through hole formed by a shoulder of smaller cross-section than the adjacent part of said central cavity and said slipper block including an inner cavity open to the reaction plate and a through hole which connects said inner cavity of said slipper block with said male element of said joint, wherein: a bolt comprising a bolt head and a bolt stem and a nut threaded on said bolt stem hold said slider block to said piston, said stem passes through said through holes and one of said bolt head and said nut is disposed for contact with a supporting surface on said central cavity and the other of said bolt head and nut is disposed for contact with a supporting surface on said inner cavity; said supporting surfaces for said nut and said bolt head on said inner cavity and said central cavity form ball-and-socket joints with said bolt head and said nut; said through holes in said piston and said slipper block form an enclosure in said assembly between said slipper block and said piston closed at the ends thereof by said bolt head and nut; a bore through said bolt stem and bolt head provides hydraulic communication between said central and inner cavities; and said one of said bolt head and nut rests against said shoulder via a bush in said through hole in said shoulder, said bush comprising a head interposed between said shoulder and said bolt head or nut and a pipe connecting said enclosure with said central cavity provided in said bush.