| 摘要 |
A downhole drilling tool comprises a drillstring, a drilling head, and a freewheel for transferring drive from the drillstring to the drilling head. The freewheel is positioned between the drillstring and the drilling head and comprises a first race 68, a second race 70, a locking ring 72 interposed between the first race 68 and the second race 70, and at least one locking element 84 retained partly in a recess of the first race 68 and partly in a recess of the locking ring 72. In use, the locking element 84 moves between a locked position in which the locking ring 84 is forced into engagement with the second race 70 and a release position in which the locking ring 84 is released from the second race 70. In a second embodiment, a guide ring is interposed between the first race and the second race. |
