Drilling device with tubular outer drill stem through which injection drill stem extends

摘要

A ring drill crown is fixed at the front end of the outer drill stem (10) and a central drill crown is coupled to the outer drill stem to rotate with it and to receive strokes. The central drill crown is axially movable relatively to the injection drill crown (24) and has a non-round outer profile, which for rotary drive engages in a corresponding inner profile of the ring drill crown.