Patent GB-475112-A (GB)
Title: Improvements in and relating to braking equipment for railway and other vehicles
IPC: B60T13/68
Filed: 1936-05-13
Abstract: 475,112. Vehicle brakes. WESTING- HOUSE BRAKE & SIGNAL CO., Ltd. May 13, 1936, No. 13550. Convention date, June 13, 1935. [Class 103 (i)] Fluid - pressure, electrodynamic and electric track brakes are applied by movement of a control pedal 32 and the fluid-pressure brake application is delayed under the control of the electrodynamic braking and the degree of application of the fluid pressure brake is controlled by the electrodynamic and electric track brakes. The foot pedal 32, Fig. 1, by means of cams 320, 318, 316 controls a controller 22 for the electrodynamic brake 20, a controller 28 for the track brake and a driver's valve 42, Fig. 1A, for the fluid-pressure brake. The cams are designed to delay operation of the track brake and to continue operation of the valve 42 beyond that of the two controllers. The valve 42 supplies fluid to a relay valve 34, through a delay valve 40, and a compensating valve 38. The valve 34 is adapted to supply the brake cylinder 10. A winding 133, Fig. 2, of the compensating valve 38 is energized on the application of the electrodynamic brakes and this valve closes the connection between the valves 42, 34. The delay valve 40, energized by initial movement of controller 22, closes this connection first, in order that the current energizing the coil 133 should have time to close the valve. Fluid flows from the valve 42 to a pneumatic switch 275, Fig. 1A, which it eventually opens to break the circuit of delay valve 40 which opens to allow fluid from the valve 42 to flow beneath a diaphragm 127 of valve 38. The valve 38 is thus subject to the opposing forces of the coil 133 and the fluid supplied from the valve 42 but remains closed as long as electrodynamic braking is effective to a desired degree. Further depression of the pedal 32 causes increased action of the electrodynamic brake and the valve 42 and also application of the track brake which energizes another coil 132 of the valve 38. The valve 38 thus remains closed as long as the vehicle speed is above a predetermined low value. Further depression of pedal 32 increases the pressure of the supply from the valve 42 until diaphragm 127 and slide valve 126 of valve 38 are raised allowing fluid to flow from valve 42 to valve 34, which thereupon supplies the brake cylinder. Fluid also flows above the diaphragm 127 to reclose the valve 38 and produce only a light fluid-pressure brake application. As the vehicle slows, a further opening of the valve 38 and a further fluid-pressure brake application is produced. The electric and fluid-pressure braking are thus balanced against one another and if the electric brakes should fail the fluid pressure brakes will be applied to a degree equivalent to the degree of application of the electric brakes. The valve 42 is adapted to be held in applied position by a passenger standing on the door step when leaving or entering the vehicle, which causes fluid to be supplied to a cylinder 179 having a piston connected to the lever 172. An emergency valve 12 is operated to supply fluid by port 365 to the relay valve 34 which supplies the brake cylinder, when the emergency pipe 196 is vented by the release of both a hand valve 18, Fig. 1, and a port valve 16. Release of one of these valves alone produces no venting. Pipe 196 may also be vented by vent valve 198 or rear end valve 252, This venting also releases fluid from a cylinder 191 actuating locking members 189, 190 for valve 42. The emergency valve also makes a connection to sanding apparatus by cavity 392, and also to pneumatic switch devices 354, Fig. 1, 275, Fig. 1A; the former brings about application of the track brakes and the latter breaks the circuit of delay valve 40 which is thus prevented from closing. When a certain service brake pressure has been attained by valve 42, a cut-off valve 14, Fig. 1A, closes pipe 196 by valve 232 so that the operator can release both valves 16, 18 without causing emergency application. Valve 232 is operated by fluid supplied by valve 42 which raises a valve 235 at a certain pressure and acts on diaphragm 233. The relay valve 34 comprises a supply valve 54 and exhaust valve 70 operated by a piston 84 operated by the fluid supplied below it by the valve 42 and returned to lap position by fluid supplied to the chamber 48 above it to which the brake cylinder is connected. The supply valve is operated through a pilot valve 65 which is adapted to release fluid from above the valve which normally holds the valve seated. The exhaust valve also has a pilot valve 75 adapted to admit pressure fluid from the chamber 48 to the chamber above the exhaust valve to assist in opening it. The driver's valve 42 comprises a piston 15 adapted to return the valve to lap position and containing an exhaust valve 152 operated by lever 164 which also operates the supply valve 145. The lever 164 is mounted on a pivot carrier 165 operated by a cam 170 on the shaft 171 operated by the brake pedal. The control spring 159 of the piston 150 is adjustable by means of a member 160 and the position of the piston by a screw 161. The track brakes 24, Fig. 1A, are held raised from the track by fluid-pressure cylinders 288, controlled by electro-magnetic valve 26 operated by initial movement of controller 28 further movement of which controls the electric current in the shoes. The track brake controller 28 on brake operation is adapted to close circuit for a relay 388 which forms a byepass circuit around the controller with only a portion of the resistance 307 in circuit thus effecting maximum energization of the brake shoes. This relay also opens contacts 281 causing the current to winding 132 to pass through resistance 343. This smooths the action of the valve 38. Spring plunger 350 moved by foot pedal engages stop 348 during latter part of movement to ensure uniform resistance to pedal.