| 摘要 |
<p>DRILLING METHOD AND APPARATUS A drill having plural forwardly projecting circumferentially spaced cutting bits includes a hydraulic motor operated at full drilling fluid pressure to drive the cutting bits in unison through a first one-way clutch in a drilling mode. A centrifugal device responding to higher speed rotation of the drill operates a reversing valve connected with the hydraulic motor to reverse it at required times to incrementally advance the cutting bits of the drill in unison to compensate for wear and present a new sharp cutting face on each bit for continued drilling. The reversal of rotation of the bits is transmitted from the hydraulic motor through a second one-way clutch of the single revolution type which drives a pinion common to and in mesh with drive gears individual to the several cutting bits and matching the shapes of their flutes and being axially slidable relative thereto. Locking rings individual to the drill bits and threadedly engaged therewith are coupled through paired clutch springs to the casing of the drill and to clutch sleeves individual to the bits and, in turn, fixed to their driving gears.</p> |
