The micro motion drive unit is a highly refined screw-driven hydraulic jack.

微形传动装置是一个极精制的螺杆用液压作动筒。

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However, the study in the hydraulic top drive only used in the service machine, poor-boy rig, also there have no research on deep and ultra-deep series of hydraulic top drive unit in China.

然而，对液压顶驱的研究，还停留在修井机、和浅井钻机上。国内目前还没有深井和超深井系列的液压顶驱装置。

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A coupler drive system for pumping unit is developed by using the theory of hydraulic drive of coupler.

运用耦合器液力传动原理，研制成功抽油机耦合器传动系统。

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The front and rear cabs (5) are steered by hydraulic rams and a drive unit links the two halves so the rear trailer can be steered independently and is not simply dragged behind the front unit.

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