Patent GB-191512155-A (GB)
Title: Improvements in and relating to Fluid Pressure Braking Apparatus.
IPC: B60T15/30
Filed: 1915-08-23
Abstract: 12,155. Westinghouse Brake Co., [Assignees of Turner, W. V.]. May 5, [Convention date]. Fluid-pressure.-To obtain a simultaneous actuation of the brakes throughout the train in emergency applications, a series of devices 3 are interposed in the train-pipe 10, 11, such devices normally giving free communication between the sections 10, 11 and the triple-valve branch 2, but adapted, by the movement of a piston slide valve 12, 15, upon a sudden drop in train-pipe pressure, first momentarily to vent the train-pipe freely to atmosphere by the operation of a quick-action valve 17, the local pressure reduction thus produced effecting the further movement of the slide valve 12, 15, whereby one train-pipe section, say 11, is cut off by a check valve 23 or 24 from its adjacent section 10 and branch 2, a restricted atmospheric vent 57<1> being simultaneously opened to each train-pipe section thus isolated. A uniform rate of pressure reduction is thus established in each train-pipe section and branch 2 connected therewith, and when this pressure reaches a predetermined minimum, a hold-back valve device 34, Figs. 7 and 9, with which the triple-valve 1 is provided, is moved to open the auxiliary reservoir 7 to the brake cylinder 6. The device 3 comprises passages 8, 9 leading from the train-pipe sections 10,11 normally connected with each other by passages 25, 26 and the check-valve chamber 23', and by passage 42 to a chamber 20, into which opens, by passage 27 the triple-valve branch pipe 2. The chamber 20 is also connected by passage 47, 48, 49 with the piston chamber 13, and in the normal position of the piston slide valve 12, 15 shown in Fig. 2, train-pipe air is thus supplied by way of the chamber 13 and passage 50 to the slide valve chamber 16 and a chamber 52 constantly open to it. The chamber 54 is also connected with the chamber 16 by passage 53 and slide-valve passage 56, Fig. 3. When a service or gradual train-pipe pressure reduction is made, the piston 12 moves only as far as the stop 59, and the auxiliary slide valve opens the chamber 16 to the exhaust port 63 until the pressure in the chamber 52, 16 equalizes with that in the train-pipe. Possible movement of the slide valve to emergency position, due to excess pressure in the chamber 52, 16, is thus prevented in service applications. The triple valve 1 is operated in the usual way in a service application. If a sudden reduction of trainpipe pressure is made, either at the driver's valve or by a break-in-two, the piston 12 first moves to the position shown in Fig. 5, comprising the spring stop 59 working in the main stop 55. The quickaction valve piston 17 is then exposed to the pressure in the chamber 52, 16 by the port 64 and passage 65, whereby the chamber 20 and the train-pipe. 10,11,12 is freely vented by the exhaust passage 66. With the sudden fall of pressure thus effected in the chamber 13, the piston 12 moves against the resistance of the main stop 55 sufficiently for the main slide valve to open the chamber 54 of that stop to the exhaust port 63 by the passage 53 and cavity 62, and the slide valve then moves promptly to the position shown in Fig. 3, in which the quickaction valve chamber 18 is opened to the exhaust port 63 by passages 65, 68 62, so that this valve 17 closes. The passage 47 also then connects the chamber 20 and the train-pipe sections 10, 11, 2 open thereto with the chamber 16, 52, and this chamber is opened to a restricted atmospheric exhaust 57<1> by port 69 and passage 57. The passage 57 is open to the underside of the check valves 23, 24, and as there will be a more rapid rate of reduction above the check valve 23 through the passage 9 than below it by restricted passage 57, this check valve lifts to cut off the passage 9 and forward train-pipe section 11 from the rear section 10 and branch 2. If the initial sudden train-pipe pressure reduction takes place on the side of the section 10, the check valve 24 is lifted, instead of the valve 23. The triple valve, which in service applications opens the auxiliary reservoir to the brake cylinder by passages 58, 45, Fig. 7, closes such communication in its extreme right-hand position, assumed after the local venting of the train-pipe by the valve 17, and exposes the upper face of the holdback valve 34 to the auxiliary-reservoir pressure through the passage 41, which, in the emergency position of the piston 30, is open to the reservoir side thereof. The under face of the valve 34 is open to train-pipe pressure through passage 40, and when this pressure falls sufficiently by escape from the restricted vent 57', the valve drops, Fig. 9, and by connecting-passages 41, 37 opens the brake cylinder at 4 to the auxiliary reservoir at 5 and applies the brakes. Prompt opening movement of the valve 3 is ensured by the increased area thereof which becomes exposed to the reservoir pressure through the passage 36 immediately the valve unseats. The waves of pressure reduction which travel back ahead of the serial opening of the quickaction valves 17 are sufficient to open the slide valves 12 of the devices 3 to service position, and so a serially increasing pressure reduction in the chambers 52 is effected in advance of the opening of the valves 17. This assists in the equalization of the pressure throughout the train-pipe and the simultaneous opening of all the hold-back valves 34. The fall of pressure by the vents 57<1> continues after the application of the brakes until there is sufficient reduction to permit the spring 67, Figs. 2 and 3, to return the piston and auxiliary slide valve to the position shown in Fig. 5. The passages 47 and the train-pipe are thus cut off from the chamber 52, 16 and the exhaust 57'. The chamber 52, 16, however, continues to exhaust until the pressure therein is less than that in the train-pipe, whereupon the valves are returned to their normal position, shown in Fig. 2.