| 摘要 |
A dual steering system for use on a material handling vehicle having a chassis with front steerable wheels and an upperstructure movably supported from the chassis for rotary movement about a connecting center pin. The vehicle has a main truck cab on the chassis, from which the vehicle may be driven over road to a selected site, and an operator cab on the upperstructure from which the excavator vehicle may be operated and also driven for short distances. When the vehicle is driven over road, the vehicle is steered from a steering wheel in the main truck cab, and hydraulic power is provided by a hydraulic power supply mounted on the chassis. When the excavator is controlled from the operator cab, the vehicle is steered with a joy stick and hydraulic power is supplied from an alternate hydraulic supply on the upperstructure. Thus, two alternate but interconnected sources of hydraulic fluid are utilized to provide power to a hydraulically powered, mechanically controlled steering gear. Operatively connected to the mechanical input of the chassis steering gear is the output of a tee gear box which has two rotary mechanical inputs for controlling the output. One rotary input to the tee gear box is from the steering wheel located in the main truck cab on the chassis. A second rotary input to the tee gear box is provided by a hydraulic torque motor which is controlled through the joy stick steering device in the operator cab on the upperstructure.
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