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:
Nov. 21, 1978
Filed:
Jul. 08, 1977
Christopher G Kay, Cedar Rapids, IA (US);
Robert A Fritsch, Cedar Rapids, IA (US);
Harnischfeger Corporation, W. Milwaukee, WI (US);
Abstract
An electro-hydraulic control system to enable either simultaneous extension or retraction of all boom sections in a telescopic crane boom or independent extension or retraction of one or more individual boom sections comprises a valve assembly, including solenoid-operated extend and retract valves, on each boom section cylinder; a manually operable three-position (neutral, extend, retract) main control valve for connecting the valve assemblies to a pressurized fluid source and to a reservoir; a relay for energizing all solenoid valves simultaneously when the main control valve is operated to extend or retract positions to thereby effect simultaneous extension or retraction, respectively, of all boom sections; and manually actuatable selector switches, one for each movable boom section, which, when any one selector switch is actuated while the main valve is operated, override the relay and energize only the solenoid valves in a selected valve assembly thereby enabling independent extension or retraction of a selected boom section.