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:
Aug. 08, 1995
Filed:
Nov. 22, 1993
Gerald P Simmons, Morton, IL (US);
Caterpillar Inc., Peoria, IL (US);
Abstract
In many transmission control systems, electro-hydraulic valves have been used to condition the various clutches in the transmission. It is desirable to have a system where the clutches remain engaged in the event of an electrical malfunction in the system. In the subject invention, a separate electro-hydraulic interlock system is provided to control each one of a plurality of hydraulically actuated speed and directional clutches. Each of the electro-hydraulic interlock systems includes a pilot operated valve which operates to proportionally control one of the hydraulically actuated clutches in response to receipt of a pilot signal from an electro-hydraulic proportional valve that is proportionally controlled in response to a first electrical control signal. A solenoid operated valve is also provided to selectively communicate the pressurized fluid from the one hydraulically actuated clutch to a pressure responsive section of the electro-hydraulic proportional valve so that in the event of an electrical failure in the system, the pressurized fluid from the one hydraulically actuated clutch acts on the pressure responsive section holding the electro-hydraulic proportional valve in the fluid passing condition. This holds the pilot operated valve in a position to maintain the one hydraulically actuated clutch engaged.