Patent GB-271049-A (GB)
Title: Improvements relating to fluid pressure braking apparatus
IPC: B60T15/04
Filed: 1927-03-31
Abstract: 271,049. Westinghouse Brake & Saxby Signal Co., Ltd., (Assignees of Thomas, T. H., and Cook, E. S.). May 14, 1926, [Convention date]. Fluid-pressure. - In valve mechanism for venting the train-pipe of a fluid-pressure brake system, wherein an initial light reduction of the train-pipe pressure is automatically followed by a further reduction, the time interval between the end of the first reduction and the beginning of the second is automatically varied in accordance with the time taken to effect the first reduction. The interval between the two pressure reductions is thus caused to depend upon the length of the train and the second reduction is effected only after the slack of the train has run in. The apparatus comprises an electromagnetically operated valve E which when deenergized in certain traffic conditions causes a valve A to connect the equalizing reservoir 12 of the engineers valve 1 to one reduction reservoir 59 which after an interval determined by a timing reservoir is connected by the operation of valve mechanism B, C to a second reduction in train-pipe pressure. In running conditions, as shown, air from the reservoir 34 is supplied by pipe 35 and passage 37 to the piston chamber 15 of this valve so that the valve is held by a spring 39 in the position shown. The chamber 18 of the valve B is connected to atmosphere by the pipe 42 and the port 41 in the engineers valve 1; the chamber 19 of the valve B is connected to the train pipe 14 and the chamber 24 of this valve is open to atmosphere by the passages 43, 44, 46, pipe 47, the valve A and post 50. The valve B is thus held in the position shown by the train-pipe pressure acting on the piston 21. The chamber 25 of the valve C is connected to atmosphere by the passages 53 the valve B passage 55 and the port 50. As the other chamber 27 of the valve C is open to atmosphere by the port 58 this valve is held in the position shown by the spring 57. The reduction reservoirs 59, 60 are connected together by the pipe 61, the valve C and pipe 65 and to exhaust by the pipe 61 and the valve A. The timing reservoir 66 is open to atmosphere through the valve B by the port 56. When the valve E is de-energized it opens the chamber 15 of the valve A to atmosphere by the pipe 33 and port 70 and the valve A is thus shifted downwardly to connect the equalizing reservoir 12 and chamber 11 of the train-pipe discharge valve 10 to the reduction reservoir 59. The valve 10 is thus opened and the train-pipe 14 vents through the passage 40 and restricted port 41. The pressure which builds up in the passage 40 and in the chamber 18 of the valve B connected thereto by pipe 42 causes this valve to shift downwardly thereby connecting the chamber 25 of the valve C with the main reservoir 34 through a reducing valve 75, and passages 74, 53. The valve of the device C is thus moved to the right to cut off the passage 62 from the passage 64 so that only the reduction reservoir. 59 is connected to the equalizing reservoir 12 for the first reduction of train-pipe pressure. Air from the main reservoir also flows into the timing reservoir 66 by the passage 53 and restricted passage 68. With the valve B in its lower position the chamber 24 thereof is vented to atmosphere by the port 79. When after this first reduction in train-pipe pressure, the valve 10 closes, the pressure in the chamber 18 of the valve B falls due to its connection with the exhaust port 41, and the valve returns to its upper position thereby connecting the chamber 25 of the valve C and the timing reservoir 66 to the restricted exhaust port 56 through the passages 53, 55. When the pressure in the timing reservoir has fallen to a predetermined degree the spring 57 returns the valve C so as to connect the passages 62, 64 and thus the second reduction reservoir 60 to the reservoir 59 and the equalizing reservoir 12. The trainpipe discharge valve 10 is thus again opened to effect the second pressure reduction. The time interval between the end of the first reduction and the second is dependent upon the degree of pressure built up :in the timing reservoir 66 through the restricted passage 68 and therefore upon the time during which the discharge valve 10 remains open in effecting the first reduction. If as by reason of a particle of material getting between the valve 10 and its seat, the valve fails to close sufficiently after the first pressure reduction to effect the operation of the valve B, the continuous discharge from the trainpipe will be sufficient to cause a full application of the brakes. When the valve B is in its lower position during the first reduction, a lock up reservoir 52 is connected to the train-pipe 14 by cavities in this valve and the valve A. This reservoir is connected to the chamber 24 of the valve B in its upper position and the pressure therein thus prevents the valve from moving downwards again during the second stage of the pressure reduction. When the valve E is again energized the valve A returns to the normal position shown. An acknowledging valve 5 is provided.