| 摘要 |
A downhole pump drive head assembly for driving the rod string which rotates the rotor of a downhole pump includes a body provided with upper and lower bearings in which is rotatably mounted a drive shaft which carries, for rotation therewith, a polish rod of the rod string. A hydraulic retarder is mounted on the body and includes a stator turbine and a rotor turbine, the rotor turbine being mounted with respect to the shaft, for example, by means of a free wheel mechanism. The hydraulic retarder, therefore, operates to control rotation and prevent back-spin of the rod string.
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