Patent ID: 8082734

Claim:
A drive assembly for a reciprocating pump, comprising: a support structure; a linear actuator mounted on the support structure, the linear actuator having a stationary portion and a movable ram portion, the stationary portion of the linear actuator including a rotating screw with a travelling nut which carries the movable ram portion; at least one direction altering cable guide mounted to the movable ram portion of the linear actuator; at least one cable having a first end and a second end, the first end being anchored to one of the support structure or the stationary portion of the linear actuator, the second end being adapted for attachment to a polish rod of a reciprocating pump; a reversible motor which alternatively rotates the screw in a clockwise and a counter-clockwise direction to initiate movement of the travelling nut which carries the movable ram portion, such that the movable ram portion moves the cable and cable guide which results in the polish rod reciprocally moving a multiple of the distance travelled by the moveable ram portion of the linear actuator; and a pair of fluid cylinders positioned on opposed sides of the rotating screw, the fluid cylinders acting as shock absorbers to slow the descent of the travelling nut which carries the moveable ram portion and, in particular, the otherwise uncontrolled descent of the travelling nut which occurs in the event of a power failure.