Articulated vehicle servo assisted hydrostatic steering - with twin control pumps for enhanced manual steering with servo failure

摘要

Steering has two hydraulic pumps (10, 11) driven by the steering wheel, via gearing (13). The control valves operate in such a way that when the servo pump is functioning then only a small application of the steering wheel operates the steering, while for purely manual control the wheel has to be turned more. - The outputs fromt he two pumps are coupled either in series or in parallel depending on the node of operation, and the state of the servo pump.