Failsafe speed control for tractor transmission - has valve to inhibit clutch engagement with highest gears in high ratio range

摘要

The tractor transmission has a gear box in line with a high and low ratio box. The gears are engaged in conjunction with hydraulically operated clutches with the clutch operation inhibited for the higher gears in the high ratio setting. The inhibit control uses a valve to limit the top speed of the tractor and prevent damage to the transmission. The inhibit control operates by venting the servo line to the clutch in the forbidden gear combinations.