| 摘要 |
A downhole back off sub10 comprises a housing 2 couplable with a drive shaft 3, the housing 2 comprising a pair of housing parts 21, 22 rotatable relative to each other about a common rotation axis 23 and engaged together via a kinematic pair, which may be provided by cooperating threads 24 arranged to translate the relative rotation of the housing parts 21, 22 into longitudinal displacement. A transmission mechanism 5, which may be provided by a harmonic drive 51, isarranged to selectively transmit the rotation of the drive shaft 3 to at least one of the pair of the housing parts 21, 22 to induce the relative rotation and the resulting relative longitudinal of the housing parts 21, 22. Rapid reconnection/disconnection can be achieved by interrupting the transmission mechanism 7 and locking one housing part directly to the drive shaft 3.
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