Dual rotary valve for variable assist power steering gear for automotive vehicles

DETAILED DESCRIPTION Having described a preferred form of my invention, what I claim and desire to secure by U.
S.
Letters Patent is: 1.
In a fluid pressure operated power steering gear mechanism having a fluid flow source, a pressure movable part adapted to be connected to a steering linkage for a vehicle, a drive member connected to said pressure movable part, a driving shaft connected to said drive member; the connection between said drive member and said driving shaft comprising a torsion bar that accommodates angular displacement of said drive member relative to said driving shaft; a rotary valve means situated in and partly defining pressure distribution and flow return passages extending to said pressure movable part and to said fluid flow source to effect pressure differential forces acting on said pressure movable part; said valve means comprising an internal valve member and a surrounding sleeve; said internal valve member having formed thereon two sets of valve lands, one set being axially displaced relative to the other, two sets of internal valve lands formed in said sleeve respectively registering with the valve land sets of said internal valve member; said valve sleeve being connected operatively to said drive member for rotational movement therewith; vehicle speed sensitive valve means for distributing fluid flow only to a first of said sets of valve lands at low vehicle speeds and for distributing fluid flow to both sets of said valve lands at high vehicle speeds; said internal valve member being connected to and rotatable with said driving shaft, the first set of said registering valve lands being adapted to control pressure distribution to said pressure movable part during initial deflection of said torsion bar and being adapted to effectively increase the magnitude of the pressure distributed to said pressure movable part as said torsion bar deflection increases within a first range of deflection during operation at low vehicle speeds and the other set of registering valve lands being adapted to control pressure distribution through said passages to said pressure movable part upon deflection of said torsion bar within a greater range of deflection of said torsion bar as fluid is distributed simultaneously to both valve land sets at high vehicle speeds