Patent GB-195752-A (GB)
Title: Improvements in and relating to combined compressed air and vacuum brake systems
IPC: B60T13/60
Filed: 1922-01-06
Abstract: 195,752. British Thomson-Houston Co., Ltd., (General Electric Co.). Jan. 6, 1922. Fluid-pressure. - In a fluid-pressure brake system of the kind in which a compressed-air brake, on the locomotive for instance, is controlled by the vacuum brake pipe of vacuum brakes with which the vehicles of the train are provided, the distributor valve for the compressed-air brake comprises a pair of pistons one of which is subject to a constant vacuum on the one side and to the variable brakepipe vacuum on the other side, and the other piston to brake cylinder pressure on the one side and to atmospheric pressure on the other side; further, the compressedair brake and the vacuum brakes may also be independently controlled. The locomotive equipment shown includes a straight air driver's valve 5 for the compressed air brake, a second driver's valve 8 for controlling all the brakes by the vacuum brake pipe 7 which extends to the vacuum brakes on the train, a pipe 2 directly connected to the compressed-air reservoir 1, a straight air pipe 3 extending between the driver's valves and the brake cylinders 4 and a pipe 6 connected to an exhauster. The distributor valve for the compressed-air brake comprises a piston 11 subject on both faces to the vacuum in the train pipe 7, a non-return valve 13 being interposed in the connection to the upper face; a second piston 15 connected to the piston 11 by members 14, open at its under face to atmosphere and at its upper face to the pressure in the brake cylinders by the pipe 17; a valve 18 actuated by piston 15 and controlling an exhaust port 51 connected to pipe 19 and a valve 22 also actuated by the stem of the piston 15 and controlling the compressed-air supply from pipes 2, 21 through a valve 30 adapted to out off this supply in certain positions of the driver's valves. With the valves 5, 8 in running position, the brake pipe 7 is connected to the exhauster pipe 6 and the vacuum. on the faces of piston 11 being equal the pistons and valve 18 will assume the position in which the exhaust port 51 is uncovered. The brake cylinders 4 will thus be open to atmosphere by way of pipes 17, 19, passages 39 of valve 5, pipe 40, passage 41 of valve 8, and pipe 42. As pipes 19, 33 are open to exhaust, the cut-off valve will be held open. as shown by the pressure in main-reservoir pipe 2, 21. To effect an application of the compressed-air brakes only, the driver's valve 5 is moved to service position thereby connecting the main reservoir pipe 2 to the pipe 3 and the brake cylinders. To effect a service application of the compressed-air and vacuum brakes simultaneously, the driver's valve 8 is moved to the desired service position, thereby venting the vacuum brake pipe 7 by passage 46 and pipe 47. The increased brakepipe pressure acting beneath the piston 11 of the locomotive distributor valve, causes the pistons to rise and open the valve 22 so as to admit compressed air to the brake cylinders 4 by way of pipes 21, 17 until the pressure in these cylinders and valve chamber 16 is sufficient to return the pistons and permit the valve 22 to close. All the brakes may be released by returning the valve 8 to the running position. To release the vacuum brakes only, the valve 8 is moved from lap to release position whereby the brake pipe 7 is connected to the exhauster pipe 6 by passages 37, but the pipe 40 being blanked the brake cylinders 4 cannot exhaust. To release the locomotive brakes only, the straight air valve 5 is moved to release position thereby connecting the brake cylinders 4 to exhaust by pipes 3, passage 45 and pipe 44. In this position of the valve 5 also the pipes 19 and 33 are connected by passage 48 to the main-reservoir pipe 2, thereby causing the valve 30 to out the main-reservoir connection 21 to the distributor supply valve 22, opening of which consequent upon the fall of pressure in the chamber 16 and the brake cylinders is thus ineffective. To apply the vacuum brakes only, the straight air valve 5 is moved to lap position so that the pipes 19 and 33 are connected to the main-reservoir pipe as just described, thereby equalizing the pressure on the two sides of the piston 31 so that it is closed by the spring 32; the valve 8 is then moved to service position. When the valve 8 is moved to emergency position the main-reservoir pipe 2 is connected to the straight air pipe 3 by a large passage 49 in the valve 8 and the brake pipe 7 is connected to the exhaust pipe 47 by a large part of passage 46.