| 摘要 |
A jacking apparatus comprises a rail having a plurality of pairs of vertical slots longitudinally spaced apart. A sled slides along this rail and has cross members to which are pivotably attached ends of hydraulic cylinders, the other ends of the hydraulic cylinders being pivotably attached to cross heads which also slide along the rail. The cross heads have bevelled latches, slidable vertically, and longitudinally reversible for engagement with the slots in the rail; so that repetitive, reciprocal movement of the hydrauic cylinder pistons will cause successive, incremental movements of the sled and a load selectively pushed or pulled by the sled along the rail.
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