| 摘要 |
An improved pumping jack is provided for particular use in oil fields for driving oil well pumps, but which has general utility. The pumping jack of the invention includes a member mounted for angular movement about a particular axis, and which defines first and second fluid chambers on either side of the said axis. A pump and valve combination selectively introduces and discharges fluid to and from the first and second fluid chambers to cause the aforesaid member to oscillate about the axis so as to achieve the desired reciprocal pump driving action.
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