GB117647A - Improvements in and relating to Braking Systems for Electrically Driven Vehicles. - Google Patents

Abstract

117,647. British Thomson - Houston Co., (General Electric Co.). June 23, 1917. Electric and magnetic; fluid-pressure. - The simultaneous application of the fluid-pressure and regenerative brakes of an electric locomotive or the like is prevented except in emergency by a valve mechanism adapted to be actuated by current from the regenerative brake and the pressure in the train-pipe to cut off the brake cylinder from its distributing valve and open it to exhaust. The fluid-pressure system shown is of the kind wherein the locomotive brake can be applied independently of the train brakes by the driver's valve 2 or together with these brakes by reducing the pressure in the train-pipe 4 through a second driver's valve 1. A slide valve RV is interposed between the locomotive distributing valve DV and brake cylinder BC, and normally connects the brake cylinder to an exhaust port 23. A brake CV, controlled by current from the regenerative brake, connects the piston chamber 32 of the valve RV to atmosphere when de-energized, as shown. If the regenerative brake is not in operation and the fluid-pressure brake is applied, the pressure air supplied to the pipe 3 moves the valve RV to the lift, thereby cutting off the brake cylinder BC from the exhaust port 23 and feeding into this cylinder. If, while the fluid-pressure brake is thus applied, the regenerative brake is put into operation, the valve CV is moved downwards, thereby cutting off the chamber 32 of the valve RV from atmosphere and connecting it to the train-pipe 4 by the pipe 21. If the locomotive brake only has been applied or a service automatic application of the brakes throughout the train has been made, the train-pipe pressure in the chamber 32, assisted by a spring as shown, if necessary, will be sufficient to overcome the brake cylinder pressure and to return the valve RV to the position shown, so that the locomotive brake will be released. The valve will not be so returned however if the train-pipe pressure has been reduced to the extent necessary to obtain an emergency application of the brakes. Independent application of the locomotive fluid-pressure brake is effected by admitting air from the reservoir MR through the driver's valve 2 and connexions 7, 8, 9, 10 to the application chamber AC and the piston chamber 11 of the distributing valve DV, thereby causing the slide valve 17 to connect the reservoir by pipe 14, chamber 12, valve port 13, and pipe 3 to the valve RV. Air from the trainpipe 4 normally feeds past the piston 25 of the valve DV into a chamber PC. When the trainpipe pressure is reduced by manipulating the valve 1 to'make a service application of the brakes throughout the train, the valve 27 moves to the right and connects the chamber PC to the application chamber AC and the piston chamber 11, and the reservoir MR is connected to the brake cylinder BC, as previously described. The triple valves TV throughout the train will be actuated in the usual manner. An emergency train-pipe pressure reduction causes the valve 27 to move to the extreme right, and the pressure chamber PC is then connected directly to the piston chamber 11 instead of through the restricted port 28. This causes the valve 17 to move to its extreme position and to connect the reservoir and brake cylinder pipes 14, 3 directly instead of through the port 13. The regenerative brake comprises exciter generators G<1>, G<2> for super-exciting the shunt fields F<1>, F<2> of the driving motors A<1>, A<2> during regenerative braking. The generators are excited by shunt fields f<1>, f<2> and series fields S<1>, S<2> connected in series with the driving motors during braking. The excitation of the shunt fields f<1>, f<2> is controlled by the resistance r which is varied by the controller C. The circuit by which the driving motors supply energy to the trolly T when the brake is operative is by way of the earth connexion, the fields S<2>, S<1>, F<2>, the series parallel controller SP, field F<1>, controller SP, armature A<2>, controller SP, and armature A'. In the first position of the controller C for applying the brake, the shunt fields F<1>, F<2> are connected to the supply conductor 6 and the armatures G<1>, G<2> of the exciter generators are connected in multiple to the fields F<1>, F<2>. These connexions are maintained throughout the braking operation. As the controller is advanced, the resistance r is cut out and the excitation of the generators G<1>, G<2>, and thus of the driving motors acting as generators, is increased. The series fields S<1>, S<2> are provided to take care automatically of the fluctuating voltage of the trolly and to give a constant braking effect for each position of the controller C.