| 摘要 |
<p>The invention concerns an arrangement at a drill for down-the-hole drilling in front of a subsequent lining pipe (58), comprising a drill bit (2) intended to be inserted at its neck (2a) into a chuck in a down-the-hole drill (100), from which impacts are transferred to the drill bit, a control means (5) for guiding the drill and the lining pipe relative to each other and that allows the drill to rotate relative to the lining pipe, a coupling arrangement (24a, 24b; 46, 47) in the form of a bayonet coupling or similar with which the drill can be coupled to the control means (5) in a manner that allows them to be separated and that in its freed condition allows the drill, together with the down-the-hole drill, to be withdrawn through the lining pipe, a flushing passage (32c) for the supply of flushing agent in front of the drill and an evacuation passage for the removal of drilling cuttings together the flushing agent. In order to achieve increased drilling efficiency, it comprises a casing shoe (4) that can be applied at the forward end of the lining pipe (58) and intended to displace the lining pipe forwards and into the borehole through interaction with a contact surface (59a) arranged at the casing shoe and a contact surface (59b) arranged at a stationary part of the down-the-hole drill (100).</p> |
