Patent GB-175271-A (GB)
Title: New or improved compressed air continuous brake system for passenger or goods trains
IPC: B60T15/04
Filed: 1922-02-07
Abstract: 175,271. Bozic, D. Feb. 7, 1921, [Convention date]. Fluid-pressure.-An automatic compressed-air brake system comprises the combination of a driver's valve adapted to maintain the train-pipe pressure at the reduced value against leakage during an application of the brakes with a distributor valve which is controlled both by trainpipe and brake cylinder pressures, the auxiliary reservoir being connected to the train-pipe past a non-return valve, whereby leakage from the brake cylinder is made up from the auxiliary reservoir, the pressure in which cannot fall below that of the established train-pipe pressure. Means may be provided to permit the utilization of the main reservoirs of two coupled engines under the control of a single driver's valve. Springs may be interposed between the pistons of the distributor adjustable manually or automatically by the load on the vehicle to determine the maximum braking pressure on a vehicle or the rate of rise of the braking pressure. The driver's valve, Fig. 1, comprises a piston 15 subject to the pressure of a spring 14 and the pressure in a chamber 5 and actuating a pair of valves 13, 9 controlling communication respectively with the atmosphere through passage 12 and the main reservoir connected at 4. The chamber 5 is connected by passage 18 with the chamber 2 containing a second piston 20, the upper chamber 3 of which is open to the train-pipe. The piston 20 actuates valves 6, 7, 22 which control communication of the train-pipe chamber 3 with the main reservoir chamber 4 and by the passage 23, with the atmosphere. The pressure of the spring 14 can be adjusted by the screw cap 15 to determine and maintain through the operation of the piston 11 and valves 9, 13, the desired pressure in the chambers 5 and 2 and the pressure in these chambers similarly determines the pressure in the train-pipe by the piston 20 and valves 6, 7, 22. As shown, the train-pipe supply valve comprises two valves 6, 7 the larger one 6 being opened by a projection 18 on the valve rod, subsequently to the valve 6, whereby a large opening is opened at the commencement of the feed to the train-pipe. The pressure in the chambers 2, 5 acts only on part of the area of the piston 20, so that the train-pipe pressure will always be inferior to the main reservoir pressure. A cock 16 enables the chambers 2, 5 to be connected through a passage 19 with the chambers 2 of the valve on a second locomotive, the cock 16 on the second locomotive being in position to cut off the chamber 5 thereon. The distributor, Fig. 2, comprises a piston 32 fitting in the chambers 28, 29 and immersed in a liquid such as oil. The chamber 29 is connected by passages 31 to a chamber 29a containing air in its upper part. The piston 32 is subject to the train-pipe pressure in the chamber 28, and the rod 34 thereof abuts against a member 35 which may have several faces with different profiles as indicated in Fig. 2a, whereby it raises a second piston 36 under the action of the piston 32 either directly or through one or two springs 37, 38. The piston 36 is subject to brake cylinder pressure in the chamber 27, and actuates a pair of valves 42, 43 which respectively control the exhaust by passage 39 and the supply from the auxiliary reservoir at 26. The valve 43 has a cylindrical extension 45 to regulate the flow, and the exhaust passage 39 is partly obstructed by a winged part 40 in such a manner that the flow is greater as the springs 37, 38 are less compressed. In charging, the air flows from the train-pipe chamber 28 past the non-return valve 30 to the auxiliary reservoir, and the piston 32 uncovers the passage 31 so that the pressures in chambers 28 and 29, 29a equalize. If the train-pipe pressure is reduced to apply the brakes, the piston 32 raises the piston 36, whereby the valve 43 is opened to supply the brake cylinder. If the profile I, Fig. 2a, is effective so that this piston engages the piston 36 without the intervention of the springs 37, 38 the valve 43 remains open until the brake cylinder pressure on the piston 36 is able to overcome the difference in pressure in the chambers 28, 29 acting on the piston 32. If the profile II, Fig. 2<a>, of the member 35 is in operative position, the spring 37 is effectively interposed so that when the brake cylinder pressure on the piston 36 is sufficient to overcome the spring, the piston can. descend sufficiently relatively to the piston 32, to allow the collar 45 to restrict the supply to the brake cylinder. With profiles III and IV of the member 35 effective, the springs 37, 38 are successively and simultaneously compressed and the descent of piston 36 relatively to the piston 32 is sufficient to effect the closing of the valve 43, thus limiting the brake cylinder pressure independently of the train-pipe pressure reduction. The brake cylinder pressure is automatically maintained against leakage, and if the auxiliary reservoir pressure tends to fall below that of the train-pipe, air is supplied to this reservoir from the train-pipe past the valve 30 and to the train-pipe from the main reservoir. The brakes may be wholly or partly released by raising the train-pipe pressure, thereby causing the exhaust valve 42 to be opened by descent of the pistons 32, 36. Figs. 4 and 5 show a forked spring member 350 interposed between the piston rod 34 and a pin 370 upon which and the piston 36 bears a spring 37. An initial compression is given to the spring 350 by a piece 351. In an application of the brakes, first the spring 37 and then the spring 350 is compressed and the valve 43 closes. The spring 350 may be connected to the vehicle springs so that it may automatically be moved horizontally to vary the maximum braking pressure with the load. In a further modification the member 35 is replaced by a lever having a fulcrum adapted to slide upon a fixed bearing. Springs are interposed between this lever and the piston 36 and the piston rod 34, and by sliding the lever longitudinally on its fulcrum the line of action of the spring is varied so that the brake cylinder pressure obtained with a given train-pipe pressure reduction as well as the maximum pressure can be varied. This adjustment of the lever can be effected automatically by variation of the load as above described. The Specification as open to inspection under Sect. 91 (3) (a) describes also the following subject-matter :-The piston 32 may be bell-shaped to form the chamber 29a. The adjustment of the spring 350, Figs. 4 and 5, may be effected automatically so as to diminish the braking pressure with the diminishing speed of the train. The projection 352 may be provided on the spray 350 for engagement with the piston rod 36 to render the springs inoperative. Accelerating valves may be provided adapted to vent the trainpipe and to be re-closed by opening the control chamber freely to the train-pipe. One form of accelerator comprises a loosely-fitting piston 53, Fig. 4 (Cancelled), so that the pressure in the train-pipe connected at 52 normally equalizes from the chamber 50 into the chamber 51. A rod 54 secured to the piston 53 carries a valve 55 normally held closed by the spring 56. A valve 57 in the piston 53 is normally seated by a spring 59. When the train-pipe pressure is suddenly reduced, the upward movement of the piston 53 first unseats the valve 55 to vent the train-pipe and subsequentlv the engagement of the spring 59 with the lower conical part 58 of the valve 57 causes this valve rapidly to open to equalize the pressure in the chambers 50, 51 and thereby effect the closing of the valve 55. The spring 59 mav be fixed to the valve 57 and have lower ends engaging coned parts on the base of the chamber 51. In the modification shown in Fig. 10 (Cancelled), ports or passages 510, 511, 512 which may be slightly open in the normal position of the piston 53 are opened or further opened when the piston rises. A port 514 may also be provided. This subject-matter does not appear in the Specification as accepted.