A HYDRAULIC PERCUSSIVE IN-HOLE ROCK DRILLING MACHINE

摘要

A hydraulic drill string device can be in the form of a percussive hydraulicin-hole drilling machine that has a piston hammer (50) with an axial throughhole (51) into which a tube (35) extends. The tube forms a channel forflushing fluid from a spool valve (62) and the tube wall contains channels(40) with ports (41,42) cooperating with the piston hammer for controlling thevalve.