| 摘要 |
<p>The percussive drilling arrangement (1) uses compressed air to transport chips of material cut by a drill to the surface for collection. The drill head assembly (4) is characterised by a cover means (32, 33) limiting the length of air channels (10, 11) in the drill head assembly (4) exposed to the bore hole before the drill cutting face (13). The air is directed from the channels (10, 11) about the drill bit (5), across the cutting face (13) and into collection ducts (14, 15), picking up the material chips and carrying them to the surface.</p> |
