Patent GB-645497-A (GB)
Title: Improvements in and relating to the steering of trucks and like wheeled vehicles
IPC: B62D7/02
Filed: 1947-10-20
Abstract: 645,497. Vehicle steering. PRODUCTION FACILITIES (FILMS), Ltd., RAWNSLEY, D. W., GREEN, E. R., and TICEHURST, G. N. Oct. 20, 1947, No. 28019. [Classes 79 (iii) and 79 (v)] [Also in Group XXIX] A truck comprises four steerable ground wheels, each mounted for independent swivelling movements, a power-operated steering unit for each wheel, and steering control mechanism controlling the supply of power to the units whereby the wheels can be swivelled so that either different pairs of wheels can be locked with their axles aligned while the remaining two wheels are coupled together for related steering movement or all the wheels can be locked with their axles disposed radially to a common centre within the truck when it is desired to rotate the truck about this centre. The truck may have pairs of steering wheels forming units disposed at each corner, each pair being capable of swivelling about a vertical axis. The units are controlled from the steering control mechanism by hydraulic means, but according to the provisional specification the control may be mechanical, electrical or hydraulic. The control mechanism controls the units for three methods of steering as shown in Fig. 1, in the first of which the axles of all the wheels are aligned to cause rotation of the truck about a central vertical axis, in the second the two rear wheel units are held immovable and steering is obtained by movement of the front units during forward or rearward movement of the truck and in the third method two side wheel units are held against swivelling and the other units are controlled for steering during lateral movement of the truck. As shown each pair of wheels 2 can swivel about a king pin 4 and may be driven from an electric motor 5 and through a differential gear 3. Integral with each king pin 4 is a pinion 9 operated by racks 8 each connected to a plunger in a single acting twin cylinder hydraulic ram. Secured to one of the racks 8 is a cable 10 leading to the steering control mechanism 11, to which also lead delivery and return pipes for the ram of each steering unit. The hydraulic system comprises a header tank 25, a pump 27 with a delivery pipe 29, a by-pass relief valve 28 and a low pressure return pipe 30. The pump 27 delivers pressure fluid through a control valve 31 and pipes 32 to jacks 6 situated at each corner of the truck, operation of which jacks supporting the truck when static, and a hydraulic control valve 16 in the control mechanism 11 for each of the steering units. The steering control mechanism 11 comprises a steering shaft 12 having secured to it a steering wheel or tiller bar (not shown) and cams 13. A roller 18 on a spring-loaded lever 17 follows each cam 13, the levers 17 controlling the hydraulic valves 16. Another roller 18 on the lever 17 follows a cam 15 rotatably mounted on a shaft 14, the cams 15 being controlled by the cables 10. Secured on the shaft 12 is a sector plate 20 having three cut-away portions corresponding to the above-mentioned three methods of steering. A movable plunger 21, which can be interlocked with the switch controlling the electric motors to prevent any accidental driving of the truck during the change over from one method of steering to another, engages the required portion of the sector plate 20 permitting angular movement of the shaft 12 within that portion. Movement of the shaft 12 which is damped by a hydraulic dashpot 33 causes actuation of the appropriate hydraulic valves 16 (dependent upon the method of steering required) through the respective cams 13 and lever 17, the valves 16 in turn actuating the plungers of the appropriate steering units. This movement cf transmitted from the steering units by the cables 10 to the cams 15 which operates the levers 17 causing a centralising and closing of the associated valves 16. Change over from one steering method to the other is effected by appropriately shaping the cams, eccentric portions of each cam 13 causing the requisite movement of each wheel unit on rotation of the shaft 12 between one cut-away portion of the plate 20 and the next.