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:
Jul. 12, 1988
Filed:
Mar. 10, 1987
Peter F Maroney, Bixby, OK (US);
Frank C Blalock, Brandon, MS (US);
Crane Carrier, Co., Tulsa, OK (US);
Abstract
A portable workover rig for lowering and raising objects such as pipe into and out of a borehole and includes a mast which can be raised from the horizontal position to a vertical position. a first hydraulic motor drives a sandline drum and a second hydraulic motor drives a mainline drum. A normally closed pilot operated check valve provided in the power hydraulic fluid conduit can be opened to permit freewheeling of the main drum allowing heavy objects to free fall in the wellbore. The mainline drum's motor is controlled by a control valve having a counterbalance feature which when a heavy load is being lowered into the well bore prevents the drum from rotating faster than it would be driven by the power hydraulic fluid. A similar but separate control system is used for the sandline drum.