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:
Sep. 19, 1978
Filed:
Sep. 09, 1977
Minoru Saruwatari, Calgary, CA;
Canadian Foremost Ltd., Calgary, CA;
Abstract
A pump jack, such as the type capable of use in pumping crude oil from an oil well, the pump jack including a double acting piston and cylinder motor with the piston rod of the motor being adapted to be connected to the polished rod projecting upwardly from a well head. A variable displacement hydraulic pump, which is driven by a motor or engine, is included in a closed hydraulic loop wherein conduits are connected to a pair of output ports of the pump. A pump control means controls the direction and volume of flow in the loop so as to establish the stroke of the piston rod. A compressible fluid counterbalance is provided for accumulation of energy during a down stroke of the piston rod so that the energy may be returned to the piston during the up stroke. An economical and versatile unit may be produced by mounting a counterbalance cylinder coaxially above the motor and providing the counterbalance with an additional closed chamber in fluid communication with a charged chamber of the counterbalance. The additional chamber may be provided in hollow structural members forming a support portion of a pump jack tower. The tower can be mounted on a portable base or deck by way of a pivot connection so that the tower can be swung down to a horizontal transportation position.