POWER STEERING SYSTEM

摘要

A power steering system for a wheeled agricultural tractor includes a pump circulating oil through a known steering-wheel-operated hydrostatic steering unit. A double-acting hydraulic cylinder communicates via conduits with the steering unit and is connectible to the tractor frame. A piston having a rod which projects from one end only of the cylinder is connectible to steer the tractor. A valve block interposed in the conduits causes oil displaced from the piston-rod end of the cylinder to flow to its other end when oil under pressure is supplied to said other end, and causes oil displaced from said other end to return directly to the steering unit when oil under pressure is supplied to the pitson-rod end of the cylinder. This enables the steerable wheels of the tractor to be steered through equal angles in both directions in response to equal angular movements of the steering wheel in the corresponding directions, despite the unequal end-face areas of the piston.