Patent ID: 6240961
Filing Date: 2001-06-05
Classification: B62D,Y10T

Abstract:
Apparatus comprising:first and second relatively rotatable valve members having a common axis, said valve members being configured to direct hydraulic fluid to flow between said valve members from inlet ports to outlet ports;said valve members having radially opposed lands and grooves defining orifices that enlarge and orifices that constrict upon relative rotation of said valve members from neutral positions through a range of movement of said valve;a pair of said constricting orifices being located in parallel between said inlet ports and said outlet ports, each of said pair of parallel constricting orifices being defined by a chamfered corner of a corresponding one of said lands;said valve members comprising means for providing back pressure at selected orifices between said outlet ports and said inlet ports, said selected orifices including both of said pair of parallel constricting orifices;said means for providing back pressure comprising a third land which is spaced from said pair of lands, said third land defining a third orifice located in series with said pair of parallel constricting orifices;said third orifice having a constant size for all relative positions of said first and second valve members through said range of movement of said valve.