| 摘要 |
A wellhead top drive is provided that includes a driving gear, a driven gear , and a movable member. The movable member has a first intermediate gear toward a first end and a second intermediate gear toward a second end. The movable member is movable between a first position and a second position, such that in the first position, the driving gear drives the driven gear via the first intermediate gear, and in the second position, the driving gear drives the driven gear via the second intermediate gear.
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