| 摘要 |
A hydraulically-operated percussive device comprises a piston/striker reciprocable in a housing and valve means adapted to intermittently pressurize a working area of the piston/striker to produce forward working strokes thereof. The housing contains a chamber adapted to be pressurized by the hydraulic working fluid to apply a continuous return force to a differential return area of the piston/striker which has a step arranged to enter a dashpot cavity at one end of the chamber to damp forward movement and thereby limit overstroking of the piston/striker. The piston/striker has an intermediate flanged portion which is a close sliding fit in the chamber end regions of which are interconnected through a conduit so that both annular end faces of the flanged portion are subject to the fluid pressure. The end faces are of different efective areas with the difference providing said differential return area and the larger end face providing the step. |
