Patent GB-468355-A (GB)
Title: Control mechanism for power operated devices
IPC: B62D5/24
Filed: 1935-11-01
Abstract: 468,355. Fluid-pressure servomotors. MANLY CORPORATION. Nov. 1, 1935, No. 30217. Convention date, Nov. 12, 1934. [Class 135] Control mechanism for power - operated devices comprises a manually rotatable shaft, a driving member, e.g. a worm, rotatable with and axially movable on the shaft, a driven member coacting with the worm, power-operated means for actuating the driven member, and control mechanism for the poweroperated means actuated by the axial movement of the worm, the bearing members for the worm or the shaft acting as stops to limit the axial movement of the worm in either direction so as to cause the driven member to be actuated manually. As applied to a steering gear of a motor vehicle, the steering shaft 10, Fig. 1, is supported at its lower end within a casing 14 by roller bearings 18, 19 located in hubs 20, 21. A worm 31, employed both for actuating the control apparatus and for manual steering should the power fail, is keyed to an enlarged part 25 of the shaft 10 so as to be movable axially thereon to actuate the control valve mechanism. For manual steering, the axial movements of the worm are limited by stops consisting of the inner races of the ball bearing members 18, 19. The worm meshes with a sector 36 keyed to a shaft 37 connected to the wheels. The power apparatus, which includes a follow-up device, consists of a cylinder 40, a double-acting piston 44 in which is connected to the sector 36. The movements of the piston are controlled by a valve 65, Figs. 2, 3, slidably fitted in a bore 50 in the cover 41 of the cylinder, and adapted to be moved against the pressure of a spring 79 by a lever 77, Figs. 1, 2, pivoted at 78 and engaged by a pin 75 adapted to be moved by the worm 31. Pressure fluid is admitted by a pipe 53, Fig. 3, to a passage 52 with port 51, and exhaust takes place through plug 55 and pipe 56. Passages 61, 63, Fig. 2, leading to the upper and lower faces respectively of the piston terminate in ports 59, 60 located on opposite sides of the port 51. The control valve has three heads 66 ... 68 separated by reduced portions 69, 70. A longitudinal passage 71 extends through the valve as far as the part 69 where it meets a cross passage 72. Movement of the valve to the right, from the neutral position shown, admits pressure fluid to passage 63 and opens passage 61 to exhaust, and vice versa. Rotation of steering-shaft 10 rotates worm 31 over sector 36 and produces axial movement of the worm which actuates the control valve. When piston 44 moves, it moves sector 36 and the wheels and, during this movement, returns the worm, the rate of return depending on the relative movements of sector 36 and rotation of worm, thus giving the follow-up effect. The apparatus gives and maintains a definite position of piston 44 for every position of the steering control members. If the power fails, the worm is moved until it strikes the inner race of either of the ball bearings 18, 19 and then manual steering is possible in the usual manner. In a modification, the hydraulic cylinder, instead of being attached to the casing 14 as in Fig. 1, is separate therefrom and is hinged at one end to the vehicle frame. The axial movement of the worm is provided for by forming the outer face so that the rolling members of the bearing have limited axial movement thereon, and the pin for actuating the control valve is moved by the inner race. The control valve is located at the lower end of the worm casing and is connected by pipes to the appropriate ends of the power cylinder. The control valve described in both forms is of the type in which, in its neutral position, both ports are cut off, but it may be of the type in which both ports are open.