Piston-piston rod retaining assembly for a hydraulic piston and cylinder unit

A hydraulic piston and cylinder unit comprising the combination of a cylinder assembly defining a cylindrical chamber, a piston member mounted in the cylindrical chamber for reciprocating movement therein in response to movement of hydraulic fluid under pressure into and out of the chamber, and a piston rod member connected to the piston member for movement therewith and extending from one end of cylinder assembly. The members have meshing threads thereon configured to be meshingly interengaged when the members are rotationally moved into an assembled position relative to one another in one direction. The combination also includes a retaining ring including deformable material configured and positioned with respect to one of the members and with respect to the threads of another of the members such that when the members are moved in the one rotational direction into the assembled position, the threads of the other member are moved into the material of the retaining ring to deform the same and thereby resist relative rotational movement between the members in the opposite direction.