HYDRAULIC PUMP OR MOTOR DEVICE PLUNGERS

摘要

A plunger for a pump or a motor comprising a plunger body having a hollow interior having a generally cylindrical inner surface and a filler body molded in the interior and prevented from axial, spiral and circumferential displacement relative to the plunger body by two portions of the inner surface differently shaped from each other and also from the generally cylindrical portions. The two portions may be two spiral grooves having different pitches from each other, or a groove having circumferentially varying depth. These grooves are radially deeper than the inner surface at the open end of the hollow interior.