GB781751A - Improvements in or relating to power-assisted steering gear for mechanically-propelled vehicles - Google Patents

Abstract

781,751. Vehicle power steering. BISHOP R., JOHNSTON, R. H., WHITLOCK, G. B. R. and JOHNSTON, K. J. R. May 18, 1953 [May 16, 1952], No. 12492/52. Class 79(5) [Also in Group XXIV] A vehicle steering gear comprises a steering shaft 47 connected to the steering wheel and carrying a rotary, cylindrical valve member 40, a screwed shaft 14 connected to the shaft 47 by a spring-centred, rotary, lost-motion connection 51, and a nut 11 on the shaft 14 integral with a piston 27. The nut is connected by a link 9 and crank 4 to an output shaft 3. The lostmotion connection is such that the initial part of the movement of the steering shaft 47 turns the valve member 40 to place one end of the cylinder 1 in which the piston 27 reciprocates in communication with a pressure fluid supply chamber 42 and the other end of the cylinder with an exhaust chamber 43, the valve member and a surrounding sleeve 29 having radial drillings for this purpose. The consequent fluidpressure bias on the piston assists further rotation of the steering shaft, after the lost-motion has been taken up, to rotate the shaft 14. The part of the lost-motion connection fixed to the shaft 14 has radial extensions 53 engaging the sleeve 29 whereby the further rotation of the steering shaft 47 after the lost-motion is taken up does not result in movement of the valve member relative to the sleeve. The exterior of the sleeve has a circumferential groove 30.....35 for each radial drilling to place the latter permanently in communication with the corresponding port in the casing, i.e. the inlet and exhaust ports D, A and four other ports connecting with the ends of the cylinder. The piston 27 may have a small through passage to permit actuation in the event of failure of the pressure fluid supply. Specification 745,202 [Group XXIX] is referred to.