| 摘要 |
A load cell is mounted on a polished rod between a rod clamp and a hanger bar. The polished rod is connected to a string of sucker rods that drive a reciprocating pump for lifting fluid from a borehole. The load cell includes a tubular body which is fitted with strain gauges for measuring compressional forces applied to the cell. The ends of the tubular body are shaped with annular spherical surfaces which mate with corresponding surfaces on washers at each end. Each of the washers tightly surrounds the polished rod and as a result of the loading on the polished rod, the washers and rod are forced into coaxial alignment with the load cell. Optionally, the polished rod can receive a centralizing sleeve which forces it to be centered within the tubular body of the load cell or the washers at either end thereof. As a result of the centralized placement of the polished rod, the loading across the cross sectional area of the load cell is made substantially uniform thereby enhancing the operation and life of the load cell.
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