Patent ID: 8668475

Claim:
A linear rod pumping apparatus, for imparting reciprocating substantially vertical motion to a polished rod of a sucker-rod pump having a pump stroke, the apparatus comprising: a linear mechanical actuator arrangement, having a substantially vertically movable member attached to the polished rod of the sucker-rod pump for imparting and controlling vertical motion of the polished rod of the sucker-rod pump the linear mechanical actuator arrangement comprising; a rack and pinion gearing arrangement, with the rack being disposed for operation in a substantially vertical direction for reciprocating motion; the rack being operatively connected in gear mesh relationship with the pinion, and the pinion being operatively connected to the rotating output of a reversible motor, such that rotation of the reversible motor in a first direction is accompanied by a substantially vertically upward motion of the rack, and such that a substantially vertically downward motion of the rack is accompanied by rotation of the motor rotatable element in a second direction opposite the first direction; the rack also being operatively connected to the polished rod of the sucker-rod pump for imparting vertically upward motion to the polished rod of the sucker-rod pump along the pumping axis when the rack is moving downward; and the rack further being operatively connected to the polished rod of the sucker-rod pump such that the polished rod of the sucker-rod pump exerts a substantially vertically upward directed force on the rack, during a portion of the pump stroke; the reversible motor operatively connected to the substantially vertically movable member of the linear mechanical actuator arrangement with the pinion operatively coupled to the rotating output of the motor establishing a fixed relationship between the rotational position of the motor and the vertical movement of the vertically movable member; a pulley; and a cable which is operatively connected to both the rack and the polished rod of the sucker-rod pump, wherein the cable passes over the pulley.