GB279905A - An improved servo brake - Google Patents

Abstract

279,905. Compagnie Internationale des Freins Automatiques. Dec. 24, 1925, [Convention date]. fluid-pressure.-Brake apparatus for vehicles provided with an internal combustion engine, wherein the brake is applied by a liquid under the pressure of a gas and is released by the. suction of the engine, as described in Specification 226,380, is provided with a vessel interposed between the suction pipe of the engine and the pipe connected to the brake to ensure that sufficient vacuum is available for releasing the brakes even when the accelerator valve of the engine is open. The apparatus shown comprises a differential piston 4<1>, 5<1> connected to the brakes, the part 5<1> of the piston being subject to fluid under pressure in the vessel 6 for applying the brakes. Release of the brakes is effected by connecting the chamber 3 of the piston by the pipe 2 to a vessel 71 which communicates past a non-return valve 72 with the suction pipe 1 of the engine. The valve device for controlling the application and release of the brakes comprises spring closed valves 7, 8 adapted to connect the pipe 2 respectively to the vacuum vessel 71 and to the atmosphere and operated by a lever 74 engaging a sliding member 73 secured to a diaphragm 32 which is subject on one side to atmospheric pressure and on the other side to the vacuum in the chamber 3 and to the pressure of a spring 29. Normally the spring 29 holds open the valve 7 and the brakes are released. To apply the brake the diaphragm 32 is depressed by the pedal lever 24 acting through a spring 75 so as to close the valve 7 and open the valve 8. When the pressure in the chamber 3 acting on the diaphragm 32 has risen sufficiently to overcome the spring 75 the diaphragm moves to permit the closing of the valve 8 and the brakes are thus applied to a degree dependent upon the amount of air admitted by the valve 8. Further depression of the lever 24 re-opens the valve 8 and the braking pressure is thus increased. The brakes may be released step by step in a similar manner bv the return movement of the lever 24, the valve 7 being opened at each stage. According to the Specification as open to inspection under Sect. 91 (3) (a) the brake may be applied by a spring or by a solenoid. This subjectmatter does not appear in the Specification as accepted.