| 摘要 |
A hydraulic oil well pumping arrangement employs a compensating type hydraulic pump, a directional valving arrangement and a proportioning valving arrangement. When the directional valve is energized, oil is directed to the rod end of the hydraulic cylinder. The rod or piston part of the hydraulic cylinder will then elevate until a first limit switch is actuated which then will de-energize the directional valve and send a current signal to the proportional valve. This current signal to the proportional valve forces it to open to a point at which the cylinder rod would extend at the desired velocity until it reaches a second limit switch. The second limit switch is near the bottom (for example, 1 foot, or 0.30 meters) of travel of the rod or piston. The current signal to the proportional valve is then decreased, creating a choking arrangement that forces the cylinder rod to decelerate. The cylinder rod then reaches another limit switch. Upon reaching the third limit switch, the signal is removed from the proportional valve so that it closes. This halts a draining of fluid from the hydraulic cylinder. At the same time, a voltage signal is sent to the directional valve opening it so that pump flow again travels from the pump to the hydraulic cylinder and once again elevates the rod and the connected pumping string or sucker rod.
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