Abstract: An improved lifting system is disclosed for pumping liquid such as oil from a subterranean pump using a band-and-pulley assembly. The device uses a single-piece band shaped in the form of an elongated loop. Both intermediate lengths of the looped band are draped together over a rotating pulley assembly mounted near the top of a derrick. The loop formed by one end of the band supports a first end-roller assembly coupled to the polished rod assembly, which is in turn coupled to the subterranean pump. The loop formed by the other end of the band supports a second end-roller assembly coupled to the counterweight assembly The counterweight assembly is reciprocated vertically by a drive motor, thereby driving the intermediate lengths of the band over the top, supporting pulley. The end rollers have sufficient diameter and rotational freedom to permit movement of the band, and the bearing of great weights, without damaging the band.

Abstract: New apparatus and methods are disclosed for controlling the operation of a rod-pumped oil well. The load on and position of the rod string are measured, an integration calculation related to the work done during a portion of the downstroke is performed, and the result is compared to a reference value, to detect a pumped-off condition in the well.