Patent GB-248728-A (GB)
Title: Improvement in power actuator for brake mechanism for automotive vehicles
IPC: B60T13/24
Filed: 1926-02-17
Abstract: 248,728. Bragg, C. S., and Kliesrath, V. W.. March 5, 1925, [Convention date]. Fluid-pressure.-In a vacuum brake for motor vehicles of the type described in Specification 245,444, intermittent reduction of the brake pressure during prolonged application of the brake is effected by connecting the pressure end of the brake cylinder to the vacuum, without admitting air or other pressure fluid to the vacuum end of the cylinder. The brake, is connected to the hollow piston-rod 5 of a piston 3, through which passes a sleeve 20, connected to the brake pedal, and carries valves 40-43 arranged in pairs separated by compressible rubber cushions 50. In the off position the valves are held to their seats by the expansion of the cushions 50. but both ends of the cylinder are connected to vacuum by means of a valve 542d, which is held open by the contact of the piston hub with pins 542e. The valve controls communications between a pipe 542f from the inlet manifold of the engine, and passages leading to the right-hand end of the cylinder 1 and a pipe 542g to the left-hand end. When the sleeve 20 is moved to the left collars 43a, 41a open the valves 43. 41 by compressing the cushions 50, putting the left-hand end of the cylinder in communication with the vacuum through a port 34, space 17. ports 24, the sleeve 20 and a pipe 67 to the inlet manifold, while the right-hand end of the cylinder is put in communication with the atmosphere through a port 36, space 18, ports 27 and a port 29 in the pistonrod 5. The consequent movement of the piston closes the valves. When the pressure on the brake pedal is reduced the sleeve 20 is moved to the right, whereupon the collar 42a opens the valve 42, thus connecting the right-hand end of the cylinder 1 with the vacuum space 17. When the brake pedal is entirely released the sleeve 20 is moved further to the right, so that the collar 40a on the sleeve 20 opens the valve 40 also, thus connecting the left-hand end of the cylinder 1 with the atmosphere through passages 33, 19 and the space 18. When the stop 26 on the sleeve 20 comes in contact with a nut 21 the cushions 50 expand and close the valves. Set screws 5a in the piston-rod 5 engage with lost motion between collars on the sleeve 20, in order that the brake may be applied by means of the pedal if the vacuum fails, air being then expelled from the left-hand end of the cylinder 1 through a relief valve in the pipe 67. In a modification the valve 542d is dispensed with and the collars 41a, 42a are so arranged that the valves 41, 42 are open in the off position, both ends of the cylinder being then connected to the space 17. The valves 41, 42 may be of rubber with ribbed faces, so that they are normally open but are closed by compression. In a further modification the left-hand end of the cylinder is connected bv a passage in the piston to the seat of the valve 42, so that, when the valve 42 is open, both ends of the cylinder are connected to the vacuum space 17. The spring attached to the brake pedal may be replaced by a spring arranged between a collar on the end of the sleeve 20 and an internal collar in the piston-rod 5, in order that the force used to depress the pedal may be utilized to assist the brake piston. Instead of atmospheric air, the exhaust gases may be utilized for operating the brake. A regulating valve may be inserted in the connection to the inlet manifold to limit the amount of air entering the manifold. Specification 243,332, [Class 8 (ii). Air and gases, Treating &c.], also is referred to.