The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 02, 1988
Filed:
Jun. 23, 1986
James R Mayer, Englewood, CO (US);
Robert T Sparkman, Jr, Victoria, TX (US);
Other;
Abstract
A well pumping unit comprising a double acting hydraulic cylinder actuator supported on a mast above a wellhead and having a piston rod connected directly to the polish rod of an elongated subsurface pump rod string. A generally cylindrical annular counterweight is disposed around the mast and is interconnected with the cylinder actuator by flexible chains trained over crown sheaves and travelling sheaves connected to the upper piston rod offsetting the weight of the pump rod string and at least a portion of the weight of the fluid column in the well. The pumping unit is controlled by a hydraulic control system including a directional control valve and flow control valves for selectively controlling the strokes of the cylinder actuator. A hydraulic pressure load sensing system measures total load on the rod string and provides for automatic shutdown of the actuator if the fluid level in the well is pumped below a predetermined level. The counterweight includes a tank for receiving a selected amount of liquid which may be pumped into or out of the tank by a reversible motor driven pump controlled by a circuit which senses an imbalance in the working pressures of the hydraulic fluid being supplied to the cylinder actuator to correct the effective weight of the counterweight for changes in fluid density and lifting effort of the actuator.