Device for coupling the pistons to the rotor in a radial-piston hydraulic motor

In a radial-piston hydraulic motor of the type having a rotor eccentrically mounted to a drive shaft within a motor housing, wherein the rotor has a spherical circumferential surface and oppositely disposed flat annular end surfaces normal to the longitudinal axis of said shaft, the motor having a plurality of pistons radially disposed around the rotor, each piston being enclosed within a radial cavity formed with the motor housing, each cavity having a radially disposed inner wall formed with a bearing seat, each piston having one end in permanent oscillating contact with said bearing seat and the other end in sliding contact with the spherical surface of said rotor, a device for coupling each of said pistons to said rotor, said device comprising:

• an annular shoulder formed on said other end of said piston;
• an auxiliary annular element formed with a circular aperture, said aperture being enclosed by a shoulder formed to mate with said shoulder on said piston, said auxiliary element being loosely concentrically mounted on said piston with said piston extending through said aperture;
• a pair of oppositely disposed lateral flanges on said auxiliary element, said flanges being arranged adjacent and generally parallel with said end surfaces of said rotor, each said lateral flange being formed with a recess defined by a cylindrical arc surface concentric with said rotor and a surface adjacent to said cylindrical arc surface parallel with the adjacent rotor end surface whereby said recess is open in a direction parallel with the axis of said shaft;
• and
• a pair of coupling rings disposed in said recesses of all of said auxiliary elements thereby holding said pistons against the spherical surface of said rotor.