GRUPPO DI LEVE DI COMANDO PER TRASMISSIONE DI CAMBIO DI POTENZA E FRIZIONE DI MODULAZIONE

摘要

The power train of a crawler tractor comprises a hydraulically operated modulating main clutch (operated by a clutch control valve) for transmitting motive power from the tractor engine to a hydraulically operated reversible multi-speed range power shift transmission (operated by a shift selector valve) for varying the speed at the output shaft of the transmission. A control lever assembly at the tractor operator's station comprises a manually operable gear selector lever and a manually operable safety lever. The gear selector lever is pivotally mounted on an oscillatable shaft and movable laterally in opposite directions from a centered neutral position to rotate the oscillatable shaft and thereby operate the shift selector valve (connected to the oscillatable shaft) and shift the transmission to either first or second speed ranges in either forward or reverse direction. The gear selector lever extends through a slot in a U-shaped bracket which is mounted for fore and aft pivotal movement and is connected by specially-shaped cam means to operate the clutch control valve. The gear selector lever is also pivotally movable fore and aft in any selected speed range to effect corresponding fore and aft movement of the bracket and thereby operate the clutch control valve to cause transmission output shaft speed to vary in the speed range selected. An adjustable friction assembly imposes drag on the gear selector lever to provide control "feel" for the operator. The safety lever is pivotally mounted for fore and aft movement between engine-start and engine-run position and, when placed in engine-start position, actuates an electric safety switch which enables the tractor engine to be started. Interlock means connected to and between the gear selector lever and the safety lever ensure that the safety lever cannot be placed in engine-start position unless the shift selector lever is placed in neutral.