Importance

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Abstract

A hydraulic control valve for a power assisted steering system for a vehicle, of generally conventional construction, the essential features of the valve being a sleeve having a bore in the surface of which are longitudinal extending grooves separated by lands, and a valve core fitting closely within the bore of the sleeve so as to be rotatable in the sleeve and having a second set of longitudinal grooves also separated by lands, each groove of the sleeve lying opposite a land of the core. The width of some at least of the grooves or lands vary along their lengths and the arrangement is such that relative rotation between the valve core and the sleeve member acts to vary the effective width and therefore the area of orifices defined by adjacent edges of opposing grooves and lands, thus controlling the restriction to flow of hydraulic fluid within the valve and thus the power assistance provided to the system, wherein the sleeve member and the valve core are relatively movable axially whereby the lengths of the orifices and thus the areas available for the flow of hydraulic fluid may be changed and the degree of assistance thus altered.

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First Claim