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 wheel. 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 within its sheath is controlled by a rotatable cam in turn coupled to a steering wheel on the vehicle. The control valve is associated with the turntable for sliding rectilinear movement relative to the axis of rotation of the turntable and is coupled to the turntable via a rack and pinion so that the rotary motion of the turntable is translated to the control valve. When the cable is positioned at a predetermined location via movement of the steering wheel, the valve control spool is moved to initiate flow in a predetermined direction to the piston and cylinder assemblies. When the turntable rotates in response to movement of the piston and cylinder assembly, the control valve moves away from the cable, causing the control spool to recenter in its neutral position to terminate hydraulic fluid flow to the piston and cylinder assemblies.