| 主权项 |
1. A steering system for turning multiple sets of steerable wheels comprising:
a first steering gear operatively connected to a steering wheel and to a first set of steerable wheels to effect turning of the first set of steerable wheels in response to rotation of the steering wheel, the first steering gear including a first control valve assembly, the first control valve assembly directing pressurized fluid to a first hydraulic motor and allowing fluid to return from the first hydraulic motor, the first hydraulic motor being operatively connected to the first set of steerable wheels; and a second steering gear operatively connected to the first set of steerable wheels and fluidly connected to the first steering gear to assist in turning of the first set of steerable wheels in response to rotation of the steering wheel, the second steering gear including a second control valve assembly, the first control valve assembly being fluidly connected to the second hydraulic motor such that the first control valve assembly directs pressurized fluid to a second hydraulic motor and allows fluid to return from the second hydraulic motor, an output shaft of the second steering gear rotating in response to movement of the first control valve assembly when a torque below a predetermined value is applied to the output shaft, the second control valve assembly remaining in a neutral condition when said torque below a predetermined value is applied to the output shaft, the output shaft rotating to cause the second control valve assembly to assume an actuated condition to direct pressurized fluid away from the second hydraulic motor when a torque above the predetermined value is applied to the output shaft of the second steering gear. |
