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:
Jun. 03, 1980
Filed:
Sep. 20, 1978
Roger D Mickelson, Cedar Rapids, IA (US);
FMC Corporation, San Jose, CA (US);
Abstract
A multiple speed hoisting system has a first fluid circuit, with a maximum effective cross-sectional area for hoisting heavy loads at low speed, and a second fluid circuit, with a smaller effective cross-sectional area for hoisting lighter loads at higher speed. These circuits are separately actuated by a valve that is responsive to a regulating means for selectively positioning the valve. A pressure operated control, that is in flow communication with the second fluid circuit, automatically cancels the influence of the valve regulating means, in response to a predetermined pressure level in the second fluid circuit, and allows the valve to revert to a position actuating the first fluid circuit. Undesirable oscillations within the system between the pressure operated control and the valve regulating means are avoided. In a preferred embodiment of the invention, a pressure switch is the pressure operated control, a solenoid that is actuated by a manual control switch forms the regulating means for selectively positioning the valve, and a relay is provided to stabilize the electrical control circuit, thereby prevent hunting between the pressure switch and the solenoid controlled valve.