As the hydraulic drive system rotates the chains, the gripper blocks feed the tubing string into, or out of the well.
当液压传动系统使链转动时，夹块将挠性管柱送入井内或将它从井内带出。
2
The electro-hydraulic proportional control valve uses the proven force feed-back system for improved hysteresis, repeatability, and response.
电液比例控制阀使用的证明力反馈改善滞后性，重复性系统和响应。
3
The paper introduces the main functional design of a kind of small cutting coal machine with hydraulic fork lift as feed power and chain-saw cutting knives driven by generator as working head.