Abstract: A rotary valve of a hydraulic power steering gear includes an input-shaft journalled within a sleeve. In the bore of the sleeve, an array of eight axially extending blind-ended slots and an array of two primary and two secondary axially extending return channels are formed. The primary return channels are diametrically opposed, and the secondary return channels are diametrically opposed. The return channels extend to at least one axial extremity of the bore to communicate hydraulic fluid to a return port. Further, the radial depth of the secondary return channels is substantially less than the radial depth of the primary return channels at or near the axial extremity.

Abstract: A low noise rotary valve for a hydraulic power steering gear that offers flexibility in the design of its boost characteristic has inlet ports to receive hydraulic fluid from a pump, return ports to return hydraulic fluid to the pump, and cylinder ports to communicate the hydraulic fluid to left and right-hand cylinder chambers of the hydraulic power steering gear. The valve has an input-shaft with a plurality of axially extending grooves separated by lands. A sleeve that has in its bore an array of axially extending slots that circumferentially align with the lands on the input-shaft is journalled on the input shaft. The interfaces between the coacting input-shaft grooves and sleeve slots define axially extending orifices which open and close when relative rotation occurs between the input shaft and the sleeve. These orifices are ported as a network such that they form primary and secondary hydraulic Wheatstone bridges each having right and left-hand inlet orifices and return orifices.

Abstract: A low noise rotary valve for a hydraulic power steering gear offering flexibility in the design of the boost characteristic has inlet ports to receive hydraulic fluid from a pump, return ports to return hydraulic fluid to the pump, and cylinder ports to communicate the hydraulic fluid to left and right-hand cylinder chambers of the hydraulic power steering gear. The valve has an input-shaft with a plurality of axially extending grooves separated by lands. A sleeve that has in its bore an array of axially extending slots that circumferentially align with the lands on the input-shaft is journalled on the input-shaft. A torsion bar residing in a bore of the input-shaft compliantly connects the input-shaft to a driven member. The interfaces between the co-acting input-shaft grooves and sleeve slots define axially extending orifices which open and close when relative rotation occurs between the input shaft and the sleeve.