| 摘要 |
A pumping unit such as used on an oil well, the unit having a base, an upright sampson post supported on the base, a drum rotatably supported to the sampson post, the drum being rotatable about its horizontal axis, a lever arm pivoted to the base and in a direction to and away from the vertical sampson post, a weight arm pivotally affixed at one end to the upper end of the lever arm, a counterweight affixed to the outer end of the weight arm, a cable extending over the drum having one end secured to the lever arm and the other end hanging in a vertical position from the drum and adapted to be attached to pumping equipment such as an oil well polish rod, a gearbox driven crank arm connected by a pitman arm to the lever arm to pivot the lever arm back and forth towards and away from the sampson post to thereby cause the cable to reciprocate over the drum and a linkage connected to the weight arm to cause it to pivot as the lever arm is pivoted so that the counterweight reacts to offset the weight of pumping equipment attached to the cable.
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