| 摘要 |
A downhole sucker rod pump especially well adapted for use in pumping thick oils and oils containing particles of sand or rock includes helical grooves or apertures for producing an intermittent unidirectional rotation of the plunger without appreciably restricting the flow of oil through the pump. This rotation distributes wear more uniformly around the plunger. In a first embodiment, helical apertures are provided in the cage portion at the upper end of the plunger. Because of their large axial extent, these apertures collectively provide an outlet of large area for the oil, and thus restrict the flow only slightly. Because of their inclination these apertures produce a torque on the cage and plunger. In a second embodiment, a second plunger is attached to the upper end of the cage. The second plunger includes helical grooves in its cylindrical outer surface. The lower portion of the cage is provided with apertures that permit the oil to flow from the interior of the cage into a space between the cage and the pump barrel, this space being closed at its upper end by the second plunger. To continue its upward movement, the oil must flow through the helical grooves of the second plunger, thereby imparting a torque to the cage. As in the first embodiment, a swivel connection is provided to permit rotation of the cage and plunger with respect to the pull rod.
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