| 摘要 |
<p>UNDERREAMER WITH DEBRIS FLUSHING FLOW PATH Abstact of the Disclosure An underreamer having a plurality of drilling arms hingedly attached to a tubular body for movement between a retracted position and an extended position for drilling. The underreamer includes a central wash pipe for delivering drilling mud to remove cuttings and debris from the hole during drilling and an alternate flow path, generally through the body for delivering drilling fluid to the vicinity between the arm and the body to flush debris therefrom which would prevent the arms from retracting to their normal position for withdrawal from the borehole.</p> |
