| 摘要 |
A drilling apparatus (10) comprises an outer cylinder (12); a drill bit (30); and a piston (32) disposed within the outer cylinder (12) and driven by a working fluid for impacting the drill bit (30). The piston (32) is reciprocable relative to the outer cylinder (12) during operation of the drilling apparatus (10) and has a top end (39) and a bottom or front end (34), each piston end having a bore (33, 35). At least one of the bores (33, 35) has a tapered portion to facilitate movement of the piston (32) over a sealing tube (14, 41) controlling pressure of the working fluid driving reciprocation of the piston (32) relative to the outer cylinder (12) of the drilling apparatus (10). The drilling apparatus may be a down the hole, in the hole or reverse circulation hammer drill (10). |
