Abstract: 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.

Abstract: A yo-yo variety reciprocating drive for long stroke, well pumping units, which employ a flexible element as the operative link between the winding drum and the polish rod of the well pump. Reversal from an upstroke to a downstroke is cushioned by mechanism which provides a power source off dwell period of predetermined duration during the aforesaid stroke exchange and is adjustable to control the length of stroke of the pumping unit. A velocity control senses the velocity of the polish rod during such dwell period and re-energizes the power source when a predetermined velocity is achieved following reversal of direction.