Power steering mechanism for automotive vehicles

Claim 1

A power steering mechanism comprising a steering shaft, a driven shaft, a cylinder, a piston mounted for reciprocation in said cylinder, a worm shaft mounted coaxially within said piston, a helical screw connection between said worm shaft and said piston whereby rotation of said worm shaft effects reciprocation of said piston in one direction or the other depending upon the direction of rotation of said worm shaft, a torsion bar connecting said steering shaft and said worm shaft whereby torque applied to the former is distributed to the latter therethrough, pilot means for piloting one end of said steering shaft on said worm shaft, said torsion bar being adapted to yield to permit limited angular displacement of said steering shaft with respect to said worm shaft upon application of steering torque to said steering shaft, a geared connection between said driven shaft and said piston whereby the latter is rotated upon reciprocation of said piston, a valve housing connected to said cylinder, a valve sleeve in said valve housing coaxially arranged with respect to said worm shaft, a valve spool slidably situated in said valve sleeve, said valve spool and said valve sleeve having cooperating annular valve lands, a pressure inlet passage, pressure outlet passages extending to opposed sides of said piston, said valve lands cooperating with said passages to control the degree of communication between said inlet passage and each of the said outlet passages, an internal helical cam groove formed in a valvE portion connected to said valve sleeve, a groove formed in said steering shaft, a ball cam element registering with said grooves, means for urging said valve spool into engagement with said ball cam element whereby axial displacement of the latter effects valve adjustment of said valve spool with respect to said valve sleeve, bearing means for journalling the other end of said steering shaft in said valve housing, said valve sleeve being piloted at one end thereof in said valve housing at a location proximate to said steering shaft bearing means and an articulated mechanical connection between said valve sleeve and said worm compensating for angular displacement of said steering shaft with respect to said worm shaft thereby tending to maintain said sleeve and said shaft in generally parallel disposition, a radial clearance being provided between an outer surface of said valve sleeve and the surrounding valve housing to accommodate radial displacement of said valve sleeve do to said angular displacement upon rotation of said steering shaft.