GB844661A - Improvements relating to vacuum braking systems for railways - Google Patents

Abstract

844,661. Vacuum brakes for railway vehicles. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. April 14, 1959 [April 14, 1958], No. 11742/58. Class 103 (1). An accelerator valve for the passenger-operable emergency mechanism of a railway vacuum braking system comprises a valve body 1 having a first port 2 for connection to the train pipe 3 and a second port 4 for connection to atmosphere, the interconnection of said ports being controlled by a check-valve 6 capable of being opened in response to a flexible diaphragm 8 subject opposingly to the degree of vacuum in chamber 21 connected via pipe 20 to the train pipe 3 and to the degree of vacuum in chamber 11 connected via passage 15 to a vacuum reservoir 10, a port 14 controlled by a valve member 16 movable by the flexing of the diaphragm 8 is normally in communication with the vacuum reservoir 10 and is connected to a magnet valve means 13 operable by movement of the driver's brake valve to a brake-applying position to open the vacuum reservoir 10 to the train pipe 3; the valve member 16 being movable by the flexing of the diaphragm 8 to close the port 14 when the train pipe vacuum is reduced. due to the operation of the passenger-operable mechanism. So that the driver can have proper control over brake applications by the operation of the driver's brake valve, the accelerator valve is rendered inoperative by a magnet valve 13 when the driver's brake valve (not shown), is moved away from its " running " position towards its " service application " position and thereby opens the vacuum reservoir 10 to the train pipe 3. However, once the check valve 6 has been opened by a reduction in vacuum in the train pipe 3 the valve member 16 closes port 14 and cuts off the connection between chamber 11 and magnet valve 13, thereby ensuring that the driver cannot over-ride the accelerated venting of the train pipe. A manually-operable release valve 17 (Fig. 2), in communication with the vacuum reservoir 10 is provided such that it cannot be operated until the train is stationary. The reservoir 10 is charged (i.e. evacuated) through pipe connection 15, chamber 11, and equalizing check valve 19, joined to the train pipe 3. A modification is disclosed in the Specification wherein a latch mechanism is provided to maintain the check valve 6 in the open position until the train has stopped so that the driver must descend from his cab to manually release the latch mechanism and release the brakes.