| 摘要 |
An oil well has a rotary pump driven by a rod string. The rod string is driven by a well head drive including a prime mover, such as an internal combustion engine, a variable ratio transmission and a drive shaft. The system eliminates the high initial cost and high losses associated with hydraulic drives. The drive speed is readily changed using the variable ratio transmission. A shear pin is incorporated in the drive shaft to limit the torqueapplied to the pump drive.
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