| 摘要 |
A steering system for a tow tractor having steerable front and rear road wheels is disclosed. The steering system comprises a steering wheel for turning the front road wheels and a hydraulic servo valve for turning the rear road wheels through an angle proportional to the turning of the front road wheels. A rear mechanical push-pull cable is used for signaling a feedback angular quantity of the turning of the rear road wheels to the servo valve. A front mechanical push-pull cable is used for signaling an input angular quantity of the turning of the front road wheels to the servo valve. A hydraulic clutch is used for remotely engaging and disengaging the front mechanical cable and the servo valve to provide a vehicle steering system having at least two steering modes for the front and rear road wheels. A method of operating a vehicle having mechanical controls for steerable front and rear road wheels is disclosed that eliminates the dangers of a failure mode inherent in an electronic control over hydraulic four-wheel steering device. 70670/2/1-1-1/5 |
