PERCUSSIVE DOWN-THE-HOLE ROCK DRILLING HAMMER AND AN ARRANGEMENT USED THEREIN

摘要

A down-the-hole percussive drill comprises a casing (11), a drill bit (13) mounted at a lower end of the casing, a hollow feed tube (15) fixed within the casing and extending along a center axis (CL) thereof, and a piston (16) mounted for axial reciprocation within the casing for transmitting impacts to the drill bit. Air-conducting passages are formed in the piston and are supplied with pressurized air from the hollow feed tube. The hollow feed tube is mounted to a top sub (14) of the drill by means of pins (44) which are mounted in the top sub and extend radially into a side wall of the feed tube, the pins being situated outside of the central passage. A bushing (45) is mounted on an outer periphery of the feed tube and is pressed radially between the top sub and of the feed tube for stabilizing the feed tube. The invention also relates to an arrangement to be mounted in a top sub.