GB803194A - Power-assisted steering mechanism for vehicles - Google Patents

Abstract

803,194. Vehicle power steering. MONROE AUTO EQUIPMENT CO. Oct. 2, 1956, No. 30021/56. Class 79(5) In a power assisted steering mechanism the drop arm 16 is formed in two pivoted parts 24, 25, one connected to the hand steering wheel 11 and the other to the steerable wheels, the part 25 carrying a pair of aligned valve assemblies 60, 61 for controlling the operation of the servomotor 47, the part 24 having a member 35 located between the assemblies 60, 61 for actuating them during relative pivotal movement of the parts 24, 25 and the parts engaging with one another through abutment means limiting such relative pivotal movement. As shown, the invention is applied to a vehicle steering mechanism comprising a steering column 10, Fig. 1, carrying the wheel 11 and connected through a steering gear 12 and the drop arm 16 to a drag link 15, which is connected by a track rod 20 and steering arms 19, 21 to stub axles 22. Applied to the mechanism is a pneumatic system comprising a piston and cylinder servomotor 47 interconnecting a bracket 55 on the rod 20 and a bracket 56 fixed to the vehicle, the assembly being supplied from an air storage tank 50 charged by a compressor 48 driven by an electric motor 49. The supply of compressed air from the tank 50 to the assembly 47 is controlled by the valve assemblies 60, 61 and a valve 70, which is a conventional manually operable air pressure regulating valve to vary the amount of power assistance provided for the steering mechanism. The valve assemblies 60, 61 are operated by the drop arm parts 24, 25, Fig. 5, pivoted together at 28 and connected respectively to the output shaft 31 of the gear 12 and to the drag link 15. Pivoting of the parts 24, 25 is resisted by rubber blocks 39 inserted in bores 34a in the part 24 and bearing through metallic caps 39b against adjustable screws 43 carried by lugs 42 on the part 25. Pivoting of the parts 24, 25 is initiated by manual rotation of the column 10 against resistance of the steerable wheels and serves to operate the valve assemblies 60, 61 which are secured by bolts 63 to brackets 45 on the part 25. Each valve assembly 60, 61 comprises a housing forming chambers 72, 73 interconnected by a passage 76, the chamber 72 being connected by conduits 67, 68 to the tank 50 and the passage 76 having ports 77, 78. The motor port 77 of each valve assembly is connected to a respective end of the servomotor 47 by a conduit 57 or 58, and the port 78 is connected to exhaust by a silencer 80. Disposed in each valve housing is a valve member 84 having a head 85 carrying a ball 86 and a bore in the valve stem having ports 93. The member 84 is acted on by a spring 89, which is disposed between the valve housing and a shoulder 88 on the valve head 85. A further spring 94 is disposed between the valve housing and a valve disc 95 which is adapted either to seal the bore in the valve stem as shown in the valve 60 in Fig. 4 preventing compressed air from passing from the chamber 72 up the bore and through the ports 93 to the exhaust port 78 or to seal the passage 76 as shown in the valve 61 in Fig. 4 preventing compressed, air from passing up the passage 76 from the chamber 72 to the motor port 77. The balls 86 are adapted to bear on adjustable screws 37 carried by the lug member 35 on the drop arm part 24. In operation pivoting or " breaking " of the parts 24, 25 causes the valve members 84 to be moved relative to the associated housings thereby connecting one end of the servomotor 47 to pneumatic pressure and the other end to exhaust to give power assisted steering. In the neutral position of each valve assembly 60, 61 the bore in the valve member 84 is isolated from the chamber 72 by the valve disc 95, but the disc does not close the passage 76 permitting pressure to be applied to both ends of the servomotor 47.