GB997065A - Hydraulically operated vehicle steering mechanisms - Google Patents

Abstract

997,065. Power-assisted steering mechanism. BURMAN & SONS Ltd., and W. H. BRIGGS. June 4, 1964 [July 22, 1963], No. 28851/63. Heading B7H. In a power-assisted steering mechanism controlled by a rotary valve comprising a first valve element 10 having splines 12 for connection to a driver operable shaft and a second valve element 11 connected to the input worm of the steering gear, relative rotation of the valve elements 10, 11 from a neutral position produces axial movement of the element 10 against the restoring force of a spring 17, and fluid pressure acts on the end face 39 of the element 10 to partially counteract the force of the spring 17 under conditions requiring high steering effort. Axial movement of the first valve element 10 is effected by balls 25 disposed between cam surfaces 26 in dogs 27 projecting from second element 11 and cam surfaces 24 in a collar 23 engaging lugs 22 on a second collar 21 connected to a ring 18 secured on the splines 12 by a second ring 20 which engages the collar 21 and the ring 18 by means of two unequal sets of serrations, thereby providing a vernier adjustment for the valve element. Dogs 28 on the first valve element 10 engage the dogs 27 on the second element 11 after a predetermined relative rotation to provide manual steering. An adjustable abutment 16 for the spring 17 is carried by a rod 15 fixed at its other end (not shown). In the neutral position of the valve elements 10, 11 (Fig. 2), oil from an engine driven pump flows through an annular passage 29 around the rod 15 to radial holes 30 in the element 10, thence to grooves 31, 32 and around lands 33, 34 to passages 37, 38 leading to a sump or reservoir. When the element 10 is turned, communication between the grooves 31, 32 and the passages 37, 38 is interrupted by the lands 33, 34 and the oil flows through ports 35 or 36 to one side of a piston 31. A pressure depending on the steering resistance will thereby be exerted on the piston 13 and will be transmitted through the annular passage 29 to act on the end face of the piston 39 and counteract the restoring force of the spring 17.