Patent GB-337818-A (GB)
Title: Improvements relating to vacuum braking apparatus for railways and the like
IPC: B60T13/46
Filed: 1929-08-08
Abstract: 337,818. Bird, G., and Westinghouse Brake & Saxby Signal Co., Ltd. Aug. 8, 1929. Fluid-pressure.-Vacuum brake apparatus for railways in which an automatic application of the brakes is arranged to be electrically effected in predetermined traffic conditions comprises control mechanism having a timing reservoir normally maintained at a vacuum and adapted to be placed in communication with the atmosphere in predetermined traffic conditions, this increased pressure after a predetermined interval of time being arranged to effect the opening of a valve whereby an application valve is actuated. The application valve comprises a diaphragm normally subject to the vacuum in the timing reservoir, the pressure on the diaphragm being suddenly increased when the timing reservoir pressure has increased to a predetermined extent when a spring moves the diaphragm to open a valve connecting the brake pipe to atmosphere. An electromagnet 1, when energized mantains a valve 3 closed and valve 4 open so that the timing reservoir 9 is connected through a chamber 11 and a pipe 13 with a train control vacuum reservoir 14 and through non-return valve 15 with the main vacuum reservoir. A diaphragm 18 connected to the reservoir 9 maintains a valve 28, by toggle mechanism 20 in a position to connect the pipe 13 to a pipe 30 and thus maintain vacuum in chamber 54 of a vacuum switch 53 which is thus closed and also to maintain vacuum in the chamber 33, Fig. 2, of the application valve so that the stem 49 is in its upper position, with valves 39, 44 open, thus allowing communication between an atmospheric chamber 34 and a chamber 38. and also between the brake pipe 47 and the ejector pipe 46. De-energization of the electromagnet 1, Fig. 1, allows a spring 6 to close the valve 4 and open the valve 3 thus connecting the reservoir 9 to atmosphere through a vacuum horn 10 which gives a warning note. The reservoir 9 is of such a capacity that a prearranged time elapses before it attains atmospheric pressure.. If the driver closes his acknowledging switch in this time a circuit is closed through the switch 53 and the electromagnet, which is re-energized. Otherwise when the reservoir 9 attains atmospheric pressure the diaphragm 18 and toggle mechanism 20 operates the valve 28 with a snap action to close the connection between pipes 13 and 30 and open the pipe 30 to atmosphere through a port 31. The switch 53 is thereupon opened interrupting the circuit of the electromagnet 1 which can only be restored by a special resetting switch necessitating the breaking of a seal or which is only accessible when the train is at rest. The chamber 33, Fig. 2, is also filled with air and the stem 49 moves down closing valves 39, 44 and opening a valve 43 thus connecting the brake pipe 47 to the chamber 38. Under the brake pipe vacuum thus established in the chamber 38 the relief valve 40 opens to admit air until the vacuum has decreased to the value for which the valve 40 was set, and a service application is effected. The automatic brake operation may be prevented by a latch device 60. The toggle mechanism 20 comprises a spring 29 which maintains the valve 28 in one of two positions and moves the valve rapidly and positively from one position to the other.