Patent ID: 8235107
Filing Date: 2012-08-07
Classification: E21B,F04B,Y10S

Abstract:
1. A hydraulic oil well pumping apparatus, comprising: a) a hydraulic cylinder having a rod that is movable between a upper and lower rod positions; b) a pumping string that extends downwardly from the rod, the string being configured to extend into an oil well for pumping oil from the well; c) a prime mover; d) a hydraulic pump that is powered by the prime mover, said pump having a compensator that regulates pump flow and pump pressure; e) a directional control valve that moves between open flow and closed flow positions; f) a flow line connecting the pump and the hydraulic cylinder, the 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 flow line that transmits hydraulic fluid from the hydraulic cylinder to the reservoir via the proportioning valve; and j) an electronic control system that controls movement of the rod as it moves between the upper and lower positions by controlling the control valve and the proportioning valve wherein the control system includes an electrical signal that opens or closes the proportioning valve so that a control of rod movement is enabled when the rod changes direction at the lower position of the rod, and wherein the proportioning valve is choked to lower flow through it as the rod is descending from the upper toward the lower position.