Patent ID: 8678082

Claim:
A hydraulic oil well pumping apparatus, comprising: a) a hydraulic cylinder having cylinder body and a piston that is movably mounted to the cylinder to travel between a upper and lower piston positions; b) a pumping string that extends downwardly from the piston, the string being configured to extend into an oil well and including one or more sucker rods for pumping oil from the well; c) a variable displacement hydraulic pump; d) a prime mover that is connected to and that powers the pump; e) a directional control valve that moves between open flow and closed flow positions; f) a first flow line connecting the pump and the hydraulic cylinder, the directional control valve being positioned in the flow line so that it can control flow between the hydraulic pump and hydraulic cylinder; g) a proportioning valve; h) a hydraulic fluid reservoir for containing hydraulic fluid to be supplied to the hydraulic pump; i) a second flow line that transmits hydraulic fluid from the hydraulic cylinder to the reservoir via the proportioning valve; j) a control system that controls movement of the piston as it moves between the upper and lower piston positions by controlling the directional control valve and the proportioning valve wherein the control system generates an electrical signal that opens and closes the proportioning valve; k) a control of piston movement being enabled when the rod changes direction at a lower position of the piston l) wherein the proportioning valve is choked to lower flow through it as the piston is descending from the upper toward the lower position; and m) wherein the control system changes pump displacement to a lower displacement when the piston is lowering and a higher displacement when the piston is elevating.