Vehicle steering system of the fluid power type and spring centered, spring modulated control cylinder therefor

Claim 1

In a vehicle of the type having a frame and at least a pair of spaced apart steerable wheel assemblies and each assembly including a yoke pivotally mounted in said frame and a ground wheel rotatably mounted in each of said yokes, apparatus for angularly rotating each of said yokes to effect steering of said vehicle, each of said apparatus comprising, a double acting fluid power cylinder mounted on said frame and having a connection with its respective yoke for rotating the latter in either direction and to an extent determined by the amount of extension and contraction of said power cylinders, each of said power cylinders having servo-valve means for determining the amount of fluid admitteD to its power cylinder and the direction of fluid through said cylinders, and an extensible control cylinder connected with each of said servo-valve means for actuation thereof, said control cylinders having resilient means for retarding movement of its control cylinder in one direction to thereby vary the amount of contraction of said control cylinder in respect to its extension, whereby said control cylinders are operated in opposite directions and consequently said servo-valve means are actuated in different amounts to cause said power cylinders to simultaneously produce angular rotation of said yokes in like direction but to different degrees.