| 摘要 |
<p>The present invention relates to a device which can be used to centralize a polished bar and/or a piston stem of a subsurface pump within a production pipe. The device comprises an elongate, substantially cylindrical body member having a longitudinal axis of symmetry, a plurality of slots in the member, and a plurality of rotatable members eccentrically mounted in the slots with respect to the longitudinal axis of symmetry for permitting simultaneous contact between the rotatable members and the inner wall of a tubular production pipe.</p> |
