GB847213A - Improvements in or relating to power assisted steering mechanism for mechanically propelled vehicles - Google Patents

Abstract

847,213. Vehicle power steering. BISHOP, R., and JOHNSTON, R. H. Aug. 10, 1956 [Aug. 11, 1955], No. 23236/55. Class 79(5). In a power assisted steering mechanism having a fluid pressure operated piston and cylinder servomotor acting in association with a manually operable steering gear the steering shaft comprises parts 1, 2 capable of limited, relative rotary motion, the shaft parts carrying elements, a helical slot formed in each element, the slots 38, 40 being oppositely inclined and engaging a pin 42, whereby the relative rotary motion causes rotary and axial movement of the pin 42 relative to the steering shaft and consequential axial displacement relative to the steering shaft of means engaged by the pin 42 for controlling the supply and exhaust of the pressure fluid. As shown the element secured to the part 1 by a nut 15 comprises concentric sleeves 10, 12 interconnected by a radial wall 11. The sleeve 12 has tongues 13, 14 projecting through slots 22, 23 in a radial wall 20 interconnecting concentric sleeves 19, 21 forming the element secured to the shaft part 2 by a nut 24, a rubber sleeve 45a or a helical spring urging the walls 12, 20 apart. Tongues 26, 27 on the sleeve 21 and the tongues 13, 14 are engaged by springs 30, 31 carried by pegs 28, 29 on the wall 20. The slots 38, 40 are formed in each side on the sleeves 12, 21 and the pins 42 are carried by a sleeve 44 having circumferential flanges 46, 47. An extension 51 on each leg of a V-shaped member 52 engages the flanges 46, 47, and the member 52 is pivoted at 50 to a casing 6 and is connected at 53 to the movable member of a valve 54 controlling power assistance to the steering. In operation manual rotation of the shaft part 1 causes by means of the lost motion between the tongues 13, 14 in the slots 22, 23 against the action of the springs 30, 31 movement of the sleeve 44 due to the pin and slot connections 38, 40, 42. The axial part of the movement of the sleeve 44 is transmitted through the member 52 to operate the valve 54. In the event of hydraulic failure manual steering is maintained by taking up the lost motion between the fingers 13, 14 and the slots 22, 23 or by the slots 38, 40 being closed at both ends. Specifications 745,202 and 779,647 are referred to.