| 摘要 |
An improved pump jack assembly for reciprocating a sucker rod in a well bore is disclosed. The pump jack assembly includes a walking beam pivotally mounted for free swinging motion on a Sampson post. The walking beam includes a fixed counterweight mounted on one end and a horsehead mounted on the opposite end. The walking beam is driven in up-and-down pumping motion by a pair of balance weights which are coupled for coordinated reciprocal movement along the walking beam. The balance weights are linked together for concurrent movement and are driven by a hydraulic cylinder mounted on the counterweight end of the walking beam. The weights are so positioned that while one weight is being raised by the hydraulic cylinder, the other weight is falling due to gravity. Thus the weights help each other and greatly reduce the power requirement. The downward stroke of each end of the walking beam is limited by saddle weights which are pivotally coupled to the walking beam on opposite sides of the Sampson post. A pedestal disposed in the path of movement of each saddle weight engages the saddle weight and limits its downward movement as the walking beam nears the limit of its downward stroke.
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