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:
Apr. 19, 1977
Filed:
Mar. 17, 1975
Wilburn Kelly Brown, Morton Grove, IL (US);
Pettibone Corporation, Chicago, IL (US);
Abstract
The invention may be used with a boom or the like which is raised and lowered by double-acting hydraulic cylinder means provided with a pilot-actuated safety valve at its bottom such that the boom can only go down when pilot pressure (normally from the downthrust line) is applied to this safety valve. The main manual valve has a four-position spool which provides a float position reached by moving through the lowering position. As the main valve is moved to the float position, its manual actuation mechanism actuates an auxiliary valve to supply pilot pressure to the safety valve to open the safety valve to allow the cylinder to achieve the desired floating action. This pilot pressure supply is through a shuttle valve which alternatively lets pilot pressure be applied to this safety valve as here stated or, from the downthrust, without ever connecting the two sources.