| 摘要 |
A fluid operated power steering system having a control motor for actuating a steering valve which, in turn, actuates a fluid operated steering motor, the system including manually operable control means for delivering fluid under pressure from a pump to opposite ends of the control motor selectively. The control motor includes a control cylinder having axial cylindrical recesses at its ends, and includes a control piston having on opposite sides thereof complementary axial cylindrical plungers respectively insertable into the recesses so that fluid trapped in the recesses provides hydraulic stops for the control piston at the ends of its stroke. A relief valve discharges fluid from the recesses into a reservoir in the event excessive pressures are developed in the recesses due to external forces, such as the encountering of obstructions by the steerable wheels of the vehicle on which the system is installed. Under such conditions, the control system overrides the hydraulic stops and encounters mechanical stops at the ends of the control cylinder. With this construction, the hydraulic stops normally limit the travel of the control piston, but can be overcome if necessary to permit overtravel of the steerable wheels. Under such conditions, the hydraulic stops have a cushioning effect on the control piston and limit the severity of contact with the mechanical stops.
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