| 摘要 |
A self-energizing, positive engagement safety mechanism for long stroke, well pumping units, whether powered mechanically or hydraulically, and which employ a lift belt and counterweight. Upon failure of the sucker rod, polish rod or lift belt, a latching mechanism is actuated to engage a rack on both sides of the counterweight thereby to arrest and lock the counterweight against free fall. Actuation of the latching means is controlled by sensing belt tension below the counterweight thereby to enhance the sensitivity and reliability of the safety mechanism.
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