Cranked rod pump apparatus and method

A cranked rod pumping (CRP) apparatus, for imparting reciprocating substantially vertical motion to a polished rod of a sucker-rod pump having a pump stroke, the CRP apparatus comprising:

• a cranked mechanical actuator arrangement, having a substantially vertically movable member attached to the rod of the sucker-rod pump for imparting and controlling vertical motion of the rod of the sucker-rod pump, the cranked mechanical actuator arrangement further includes, a frame, a crank element and an articulating link element such that
• the frame has a base thereof adapted for attachment to the wellhead of a well, and having one or more linear guide rails extending vertically upwardly from the base when the base is attached to the wellhead, with the vertically movable member being slidably mounted on the linear guides and constrained by the guides for substantially linear reciprocating vertical movement along the linear guide rails;
• and
• a motor having a right angle gear box with a rotatable element thereof operatively connected to the substantially vertically movable member of the linear mechanical actuator arrangement in a manner establishing a fixed relationship between the rotational position of the rotatable element of the motor and the vertical movement of the vertically movable member, with
• the crank element being operatively coupled at a first attachment point thereof to the rotatable element of the motor for rotation in a fixed drive ratio with the rotatable element of the motor, with
• the motor being disposed on one side of the one or more linear guide rails above the base of the frame, and the vertically movable member being slidingly disposed on an opposite side of the one or more linear guide rails;
• the articulating link element has first and second attachment points thereof disposed at a spaced relationship from one another along the articulating link element, with
• the first attachment point of the articulating link element being pivotably joined to the crank element at a second attachment point of the cranked element spaced eccentrically radially outward from the first attachment point of the cranked element with the second attachment point of the articulating link element being pivotably attached to the vertically movable member, with
• the crank element and the articulating link element having respective lengths of the CRP apparatus, and the vertical location of the first attachment point of the crank element above the base of the frame being cooperatively selected so that the vertically movable member is constrained to always hang below the first attachment point of the articulating link in any angular position of the crank element during operation of the CRP apparatus, in such a manner that gravitational force will cause the vertically movable member to be slidingly held in contact with the one or more linear guide rails as the motor is controlled to impart reciprocating motion to the vertically movable member along the one or more linear guide rails.