| 摘要 |
Clutch-clutch-brake steering unit having hydraulically actuated cylinders for controlling same to control rotation of a track-drive sprocket in a crawler tractor. Specifically, one of the clutch cylinders and a brake cylinder provided in the unit have an inlet-outlet port in common, and are so arranged on a spring-applied-brake, hydraulically-applied-clutch basis that a single pressure signal in the inlet-outlet port alternately operates the cylinders to apply the brake and release the one clutch, to apply the one clutch and release the brake or, by proper modulation, to partially engage either, i.e., slip the clutch or drag the brake to intermediate degrees as desired. And, to nearly the same extent, the other clutch cylinder and the brake cylinder provided in the unit have inlet-outlet ports in common and are similarly arranged that the absence or presence of a single pressure control signal in their inlet-outlet ports alternately operates the cylinders to apply the brake and release the other clutch, or to apply the other clutch and release the brake.
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