| 摘要 |
A pump jack for traveling up and down a pole. The pump jack includes a frame member supporting a lower shackle member which includes front and rear clamping bars which can apply a coupling force for gripping the pole. A pump arm is pivotally coupled to the frame member and further pivotally supports an upper shackle member having a front helical rod and a rear clamping bar for also applying a clamping force for gripping the pole. The two shackle members are suitably biased to alternately position one of the shackle members in gripping relationship with the pole. The pump arm is used to step upwardly the pump jack along the pole. A release mechanism is coupled to the lower shackle for disengaging it from the pole. An over the center spring loaded handle coupled to the helical rod is used to roll the pump jack down the pole. The handle prevents accidental downward rolling during the upward stepping of the pump jack along the pole.
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