Electro-hydraulic interlock system for a transmission maintains a ratio clutch engaged on supply failure

• Main Author: GERALD P SIMMONS
• Format: Patent
• Language: English
• Published: 24.05.1995
• Edition: 6
• Subjects: BLASTING; ENGINEERING ELEMENTS AND UNITS; GEARING; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVEFUNCTIONING OF MACHINES OR INSTALLATIONS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; HEATING; LIGHTING; MECHANICAL ENGINEERING; TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION; TECHNICAL SUBJECTS COVERED BY FORMER USPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ARTCOLLECTIONS [XRACs] AND DIGESTS; THERMAL INSULATION IN GENERAL; WEAPONS

A separate electro-hydraulic interlock system (50) of a transmission control system controls each one of a plurality of hydraulically actuated speed and directional clutches via supply line (55) and return line (56). Each of the interlock systems includes a pilot operated valve (58) which operates to proportionally control one of the hydraulically actuated clutches in response to receipt of a pilot signal from an electrohydraulic proportional valve (64) that is proportionally controlled in response to a first electrical control signal. A solenoid operated valve (86) is also provided to 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.