| 摘要 |
A hydraulic actuator and system for driving a subsurface reciprocating pump. The actuator is double acting and comprises a piston reciprocable in a cylinder on a guide tube, so that the maximum volume of the chamber below the piston is greater than that of the chamber above the piston, and the lower working area of the piston is greater than its upper working area. Ports in the cylinder above and below the piston are connected to a valving and control arrangement, and a source and receiver of hydraulic fluid and an accummulator are also provided. The valving arrangement is controlled so that when the piston reaches a lower level of travel fluid is discharged from the upper chamber to the receive, to enable upward movement of the piston, and when the piston reaches an upper limit of travel discharge of fluid from the upper chamber is interrupted and flow of fluid from the lower chamber to the upper chamber and accummulator is enabled. Several valving and control arrangements are disclosed.
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