GB1213315A - An assembly for use in hydraulic servo mechanisms - Google Patents

Abstract

1,213,315. Power-assisted steering valves. SERVOMECANISMOS S.A. 28 Dec., 1967 [31 Dec., 1966], No. 58920/67. Heading B7H. An assembly for an hydraulic servo-steering mechanism comprises a resilient torsion bar 4 connected at one end to and enveloped by a rotor 3 having external slots 26, 27 and connected at the other end to a worm or other steering gear input member 5, a sleeve 2 which has orifices 21, 22, 25 and axial internal slots 15, 16 co-operable with the slots 26, 27 is coupled to the member 5 to rotate therewith but be axially movable relative thereto and lies around the rotor 3, one or more pairs of pistons 37, 38 for controlling feel and a casing 1 which lies around the sleeve 2 and has an inlet duet 20, an outlet duct 29, two other servomotor duets 23, 24 and annular grooves 17, 18, 43, 44, each communicating with one of the duets 20, 23, 24, each of the other ducts 23, 24 communicating with one piston of the or each pair thereof, the arrangement being such that, when the rotor 3 is rotated in one sense relative to the sleeve, pressure fluid from the inlet duct flows selectively through the grooves, slots and orifices to one of the servomotor ducts 23, 24 and thereby acts on one piston of the or each pair to turn the rotor in the opposite sense thereby providing feel. On relative rotation of the valve rotor 3 and sleeve 2 pressure fluid from the inlet port 20 and the annular groove 17 in the casing 1 passes through three radial orifices 21 and either through slots 26 and 15, orifices 22 in the sleeve 2 and annular groove 18 and a duct 23 in the casing to one side of the servo-piston (not shown) or through slots 26 and 16, orifices 25 in the sleeve 2 and a duct 24 to the other side of the servo-piston. At the same time fluid is exhausted from the opposite side of the servopiston through the corresponding ones of the slots and orifices to an exhaust port 29. The neutral position of the valve is adjustable either by rotation of an eccentric-headed screw 30 of the sleeve 2 in a slot 31 of a sleeve 32 secured to the worm 5, a lock screw 33 being provided, or, in a modified construction, by rotation of a pin 34 which is mounted in the worm 5 and has an offset finger 35 in engagement with a radial slot 36 of the sleeve 2 (Fig. 5). Steering feel is provided by the torsion bar 4 and by two pairs of pistons 37, 38 which act on lugs 48 of the rotor 3 and are subject to the pressure on a respective side of the servo-piston. The pistons 37 communicate (Fig. 2) through orifices 41 in the sleeve 32, the annular groove 43 in the casing and a duct 45 with the duct 23 to the servomotor and the pistons 38 communicate (Fig. 3, not shown) with the duct 24.