GB1114779A - Improvements in control means for hydraulic power-assisted systems,with particular reference to steering gears - Google Patents

Abstract

1,114,779. Power-assisted steering. CAMGEARS (CLEVEDON) Ltd. 18 Oct., 1966 [11 Oct., 1965], No. 43129/65. Heading B7H. A control means for use in an hydraulic power-assisted steering or other hydraulic system has a torsionbar 6 which transmits rotary motion between first and second parts 1a 9 of the system and has valve members 10 formed thereon, which are rotatable with the second part 9 and co-operate with two fluid-flow orifices 11 in a valve body 1 rotatable with said first part 1 to vary the pressure in two opposed hydraulic operating circuits. As shown, the first part 1a is secured to a steering shaft 12, the second part 9 rotates a pinion 22 in mesh with a steering rack 23 and the two opposed hydraulic operating circuits communicate with opposite sides of a servo piston through ports 21. In the neutral steering position pressure fluid-flow from inlet 17 is divided equally by axiallybored shuttle valve 16 and passes to the orifices 11 through respective annular passages 14 and axial passages 13 of the valve body 1. The exhaust from the orifices passes back to the pump supplying the inlet 17. On relative rotation of the valve parts during steering movements (Fig. 4), the portion 10 of the torsion-bar 6 acts as a flap valve producing at the orifices 11 a differential pressure which is communicated through drillings 13 and annuli 14 to the ports 21 to move the servo-piston and through the drillings 14 and ports 18 to the opposite sides of the shuttle valve which moves so as to provide a greater flow to the high pressure side of the servo-piston. In modifications, shuttle valve (30) is provided with bores (34) through the lands and ends which coact with coaxial bores in the valve housing (Fig. 5, not shown), or two constant output fluid supply pumps are provided.