Patent GB-253136-A (GB)
Title: Improvements in and relating to braking systems
IPC: B60T13/68
Filed: 1926-06-04
Abstract: 253,136. British Thomson-Houston Co., Ltd., (Assignees of Hamilton, W. S. H.). June 4, 1925, [Convention date]. Fluid-pressure; electric and magnetic. - Brake systems for railway trains comprising an electric regenerative brake on the locomotive and air brakes throughout the train are provided with means whereby, if the regenerative braking effect exceeds a predetermined value, the air brake on the locomotive is cut-out as regards service applications, emergency applications of the air brakes cut out the regenerative brake and failure of the regenerative brake applies the air brake on the locomotive or throughout the train. Instead of the air-brake being cut-out when the regenerative braking effect .exceeds a given value, a de. vice may be provided adapted automatically to regulate the air brake pressure in accordance with the regenerative braking effect so that the combined braking effect does not exceed a value such as would cause slipping of the wheels. The driving motors of the locomotive comprise armatures A1, A2 and field windings F1, F2, arranged to be over-excited by generators G1' G2 preferably driven at a constant speed. The series fields S1, S2, of the generators G1, G2 are. energized by the generated current of the motors A1, A2 and the shunt fields f1, f2 thereof by a battery B through a resistance varied by contactors C under the control of the braking controller BrC. The driving motors A1, A2 are connected for series and parallel driving and regenerative operation by contactors C2, C3, C4 under the control of the main and braking controllers MC, BrC. The air brake sysstem comprises the usual triple valve TV, brake cylinders B, C1 and auxiliary reservoir AR on the cars of the train, controlled by the driver's automatic valve 11 and train-pipe 13. The locomotive brake equipment comprises the distributing valve DV which is subject to control by the driver's valve 10 to apply the locomotive brake alone or bv the driver's valve 11 to apply this brake simultaneously with the train brakes. In effecting an independent application of the locomotive brake by the valve 10 air is supplied from the main reservoir MR by the pipe 12 to the left hand side of the piston 14 which thereupon moves the slide valve 15 to supply air from the. main reservoir by pipes 16, 18 to the brake cylinder BC. When an automatic and simultaneous application of the brakes throughout the train is made by venting the train-pipe 13 through the driver's valve 11, the piston 20 of the locomotive distributing valve operates the .slide valve 19 to supply compressed air from the chamber PC to the chamber AC communicating with the left-hand side of the piston 14 which thus actuates the slide valve 15 to supply the brake cylinder BC as above described. To prevent the application of the locomotive air brakes if the regenerative braking exceeds a given value, the distributing valve DV is provided with an additional piston 21 arranged to oppose the piston 14. A magnet valve 22 when ,energized is adapted to connect the chamber 21<1> of the. piston 21 to the main reservoir to hold the valve 15 in or to return it to the release position. When the valve 22 is de-energized the chamber 21<1> is exhausted to the brake cylinder BC. The circuit of the valve 22 includes contacts 24 controlled by contactor C4, contacts 26 which are closed when the line-breaker LB is closed, contacts 27, 28 on the braking and main controllers BrC, MC, and con. tacts 25 closed in the running and release positions of the driver's valve 10. The provision of the contacts 24, 26, 28 ensure that the valve 22 can only be energized if the regenerative brake is effective and if in these conditions the braking controller is moved beyond its third position the contacts 27 are also closed so that the valve 22 will be energized and a service application of the locomotive air brake effected bv the driver's automatic valve 11 will be prevented. If however an emergency application of the air brakes is effected by the drivers valve 11 air is supplied by pipe 35 to open the switch 34 and thus also the line-breaker LB by de-energizing the winding 36 thereof and thereby to cut-out the regenerative brake. If the regenerative brake should fail due either to overload current or an over-voltage, the line-breaker LB is opened directly in the former case and by means of the relay 43 in the latter case. The opening of the line-breaker opens the contacts 26 to prevent release of the locomotive air brake by the valve 22 and closes contacts 32 to energize valves 29, 30 provided the driver's valve 10 is in the running position so that the lower contacts 25 are closed. The valve 30 closes the release pipe 31 of the distributor DV and the valve 29 connects the main reservoir to the application pipe 12 through a reducing valve 44 to apply the locomotive air brake. Failure of the regenerative brake may instead be arranged to apply the air brakes throughout the train by the energizing of three valves one of which closes the release pipe 31, the second cuts off the main reservoir supply to the driver's valve 11 and the third connects the equalizing reservoir ER to a reduction reservoir. Fig. 3 shows a modified ' system provided with means whereby the pressure in the locomotive brake cylinder BC is regulated in accordance with the regenerative braking effect so that the combined braking effect is maintained at a value such as will prevent slipping of the wheels. For this purpose valves 52, 53 adapted when energized respectively to disconnect the. chamber 21<1> of the additional piston 21 of the distributor DV from the brake cylinder BC and connect it to the main reservoir MR are in a circuit including contacts 24, 26, 27, 28 similar to those of the valve 22, Fig. 1, and also contacts 60, 61, 62 of a relay 54 comprising windings 57<a>, 57<b> arranged on the watt-meter principle and energized responsively to the regenerated current in the motors and the field current thereof. The movable element of the relav carries a contact piece 56 for engagement with the contacts 60, 61, 62 and is connected also to a spring and to a piston 55 subject to the pressure in the brake cylinder BC. Thus. if the torque on the relay due to the regenerative braking effect and the air brake pressure is sufficient to overcome the spring, first the valve 52 and then the valve 53 is energized to admit air from the main reservoir to the chamber 21<1> and thus to reduce the braking pressure until the permissible pressure is reached. Specifications 130,451, and 157,721 are referred to.