Hydraulically powered steering system for a vehicle having multiple

Abstract

A load transporting vehicle has a plurality of independently steerable wheel sets, each of which incorporates a turntable having a downwardly extending strut and a pivotally mounted trailing arm that carries a pair of wheels. The turntable is rotatably mounted on the vehicle frame. A pair of double acting piston and cylinder assemblies are coupled to rotate the turntable via a rack and pinion. A hydraulic control valve, having a control spool actuated by a boden type cable, controls the flow of hydraulic fluid to the piston and cylinder assemblies. The linear movement of the boden cable is programmed and controlled by rotatable cams. Three or four sets of cams, each set of which controls a different mode of steering, are mounted on a rotatable shaft. Each set of cams has a single cam to a given boden cable and associated wheel set. The sets of cams are interleaved to form groups corresponding to each wheel set. By axially shifting the shaft, a cam follower connected to the boden cable disengages from one cam and engages a next adjacent cam to change from one mode of steering to another. A cam follower lifting mechanism is provided to raise the followers from the cam surfaces during the shifting procedure.