GB979377A - Improvements in power-assisted steering mechanisms - Google Patents

Abstract

979,377. Power-assisted steering. HYDROSTEER Ltd. Feb. 12, 1963 [Jan. 26, 1962], No. 3119/62, Heading B7H. In a power-assisted rack-and-pinion steering mechanism a manually operable input shaft 22 is connected to the pinion 1 with provision for a limited degree of relative angular motion which is resisted by a resilient bias acting radially and actuates valve means controlling the power assistance. The input shaft 22 is provided with lugs 28 engaging with limited clearance in a groove 27 extending across a transmission member 24 connected to the pinion 1. Balls 32, 33 carried in openings 34, 35 in the shaft 22 are urged by a spring-loaded ball 30 into engagement with grooves 37, 38 in a valve sleeve 25 which engages the transmission member 24 by means of dogs co-operating with the groove 27 and rotates therewith. Axial channels 40, 41 in the surface of the input shaft 22 and ports 42, 43 in the sleeve 25 co-operate with negative lap so that when the shaft 22 is in a neutral position relative to the sleeve 25, fluid supplied by a duct 49 through the pinion 1 to the channels 41 flows across the ports 42, 43 to the channels 40 which communicate with a return chamber 50. When the input shaft 22 is rotated fluid from the channels 41 flows through one pair of ports 42 or 43 to one of grooves 44, 45 communicating therewith, the other pair of ports 42 or 43 being connected to the return chamber 50 via the channels 40. The grooves 44, 45 are connected by flow lines 19, 20 and annular passages 17, 18 to the ends of a fluid pressure cylinder containing a double-acting piston secured to the rack bar 4.