Patent GB-152057-A (GB)
Title: Improvements in and relating to air brake equipments
IPC: B60T13/66
Filed: 1919-05-06
Abstract: 152,057. British Thomson - Houston Co., (General Electric Co.). May 6, 1919. Fluid-pressure. - In fluid-pressure braking- apparatus adapted to reduce the brake cylinder pressure automatically with the speed, a. release valve is opened at one end of a number of speeds according to the initial pressure applied. The initial pressure is determined by the position of the motorman's valve. The apparatus shown comprises a motorman's valve 1 controlling pipe connexions of which the pipe 2 is connected to the main reservoir 3, the pipe 5 leads to the brake cylinder past a valve 7, the pipe 8 leads directly to the brake cylinder 19, and the pipe 9 is open to atmosphere. A drum moving with the valve 1 carries contacts 10, 11, 12 for connecting the trolly 16 to wires 17, 18 connected respectively to the contacts 24, 27 of pressure-actuated switches A, B, the cylinders of which are open to the brake cylinder 19. Each switch A, B comprises a spring 36, extending between arms 32, 38 connected respectively to the piston 28 and to the switch proper whereby, when the piston reaches either extreme position, the switch is closed or opened. The switches A and B are adapted to connect the wires 17, 18 respectively to the valve 7 by the contacts 23, 26 and wire 48. The magnet 46 of a release valve 40 is in two circuits, one of which includes the wires 17 and 51 and is controlled by the switch 3 and a relay 43 and the other of which includes the wire 18 and wire 49 and is controlled by the switch B and the relay 42. The relays 42, 43 are adapted to be connected by a relay 44 to the armature 41 of the propelling motor when the power supply is cut off. The relays 42, 43 respond to different strengths of current and therefore to different predetermined speeds of the vehicle. In the normal condition shown, the brake cylinder is open to exhaust pipe 9 by both of the pipes 5, 8 and the motorman's valve, the valve 7 being de-energized and open. The relays 42, 43 are connected by the wire 45 to the trolly 16 and hold open the circuits of the release valve 40 so that the valve is closed. In making an application of the brakes at low speeds, the motorman's valve is moved to the first service position whereby the brake cylinder 19 is supplied by the pipes 2, 5 and 6. When the pressure in the brake cylinder reaches a value sufficient to actuate the switch A, the valve 7 is connected by the wire 48 and contacts 23, 24 to the wire 17 which at this time is connected by the motorman's valve to the trolly 16. The valve 7 is therefore closed. The relay 44 is similarly energized and connects therelays 42, 43 in the circuit of the motor armature 41. When the speed falls sufficiently, the relay 43 closes the circuit of the release valve 40 through the wire 17, switch A, and wire 51 whereby the valve 40 is opened and the brake cylinder air leaks away through the restricted passage of the valve until it is sufficient only to keep the brake blocks in contact with the wheels. At this point a loaded valve 60 prevents further escape of air, and the complete release of the brakes is effected by the motorman's valve. When the brake cylinder pressure has fallen below the value at which the valve 60 closes, the switch A opens and the parts return to the normal position. If the vehicle is travelling at a higher speed, the motorman's valve is moved to the second service position in which the brake cylinder is supplied by the pipes 2, 5, 6 as before. The wire 18 however is connected to the trolly 16 in this position of the valve, and the switch A though closed is ineffective. When the brake cylinder pressure reaches the higher value sufficient to close the switch B, the wires 18, 48 are connected, thereby closing the valve 7 and connecting the relays 42, 43 in the circuit of the motor armature 41 as before. When the speed falls to the value at which the relay 42 is arranged to act, the circuit of the release valve 40 is closed through the wire 49, switch B and wire 18, and the release valve is thereby opened to reduce the brake cylinder pressure as before. To make an emergency application, the motorman's valve is moved to the position E in which the brake cylinder is supplied directly by way of the pipes 2 and 8 as well as by way of the pipe 5 and valve 7.