Drilling device for directionally accurate drilling

摘要

For directionally accurate drilling, the drill bit (38) is mounted in a pendulous manner at the front end of the inner pipe string (23) so that it can tilt upon striking against an obstacle (46). The blows of a tubular hammer (33) are transmitted via an anvil (36) to the shank (37) of the drill bit (38). When the drill bit (38) tilts, the blow-transmission surfaces (36a, 37a) form an angle so that the blows act in such a way as to align the drill-bit axis (47) with the drilling axis (A). <IMAGE>