| 摘要 |
<p>The invention provides a down-the-hole drill assembly (21 ) comprising an assembly of a bit (9) and co-operating chuck (19) including a bit (9) mounting with an external sleeve (4) surrounding the bit (9) mounting, the sleeve (4) during operation of the drill being clamped between the chuck (19) and the bit head (9). The sleeve (4) provides a shield against ingress of debris into the bit and chuck assembly, and provides control of exhaust from the assembly. The sleeve (4) further provides control of a pin (107) releasably engaging the bit (9) to the chuck (19).</p> |
