158 



• KNOWLEDGE ♦ 



[Are. 22, 1884. 



brakes are very rapidly dying out, and in all probability 

 will soon become things of the past, so far at least as rail- 

 way working is concerned. The continuous brakes may bo 

 subdivided into two sections, which may be denominated 

 automatic and non-automatic, terms sufficiently clear to 

 explain themselves. It is to the automatic that attention is 

 now drawn, and the Westinghouse is taken as the specimen, 

 although, as will be seen presently, it is nearly without a 

 peer. 



The Westinghouse Automatic Brake, named after the 

 pateiitee, is worked by air pressure. A small, but powerful, 

 air-pump is ])laced on the engine, and with the aid of steam 

 d-rived from the locomotive boilers, air is forced either 

 into a re.'-ervoir under the foot-plate of the engine, or 

 through a one-inch pipe extending throughout the length of 



coupling with similar pipes on the adjoining vehicles. A 

 branch-pipe connects E with an essential and eminently 

 interesting piece of apparatus called the Triple Valve, 

 F, which is in reality the controlling piece of 

 mechanism, and of which Fig. 2 is an enlarged view. 

 Enclosed in a case, 1, is a piston, 5, carrying with it a slide- 

 valve, 6, which covers the port, a, to the brake cylinder, and 

 iu the position shown establishes a communication between 

 a and the atmosphere by the exhaust-cavity h and passage c. 

 Compressed air from the main pipe E enters the lower 

 part of the case, and forcing up the piston, 5, feeds past it 

 into an auxiliary reservoir (G, Fig. 1) through the groove d 

 (Fig. 2) and the outlet C. This reservoir is thus filled 

 with air under a high pressure (the same as that in the 

 main pipe), and as things now are, this air cannot escape. 



Fiff. J 



the train. The pnmp is entirely under the control of the 

 engine-driver, and he is at liberty, by simply turning a 

 handle, to connect it with his reservoir (T with the pipe. 

 He is also able t > connect the pipe with the external atmo- 

 sphere, so as to reduce more or less completely the air- 

 pre^sure in the pipe, which nominally is about 701b. to the 

 square inch. The pump and its appurtenances, however, 

 need not furtlier detain us, as notliing essential to the 

 proper working of the system is involved ; all that is re- 

 quired being a means of rapidly raising the pressure in the 

 pipe, of easily exhausting it, and of spt edily re-establishing 

 it. 



Let us turn our attention to the brake proper. The 

 acconi]ianying illustration will materially help «s. Fig. 1 

 is a general representation of the apparatus as applied to 

 every individual vehicle. A one-inch pipe, E, which rnns 

 the length of the carriage, is connected by an ingenious 



At the same time, the slide-valve (6) covers the port a, 

 leading to the "brake" cylinder (H, Fig. 1), and is in 

 such a position that air from the latter may exhaust 

 through h and c into the atmosphere. In the brake 

 cylinder are two pistons, which are pressed inwards and 

 almost together by sfiiral springs ; but when the air enters 

 from a (Fig. 2), through the short connecting-pipe shown 

 in Fig. 1, it passes into the small space separating the 

 pistons, and drives them outwards. To each piston is 

 attached a rod, which, acting on a lever, presses a friction 

 block against each side of the wheel. 



So long as an equal pressure is maintained in the 

 reservoir, triple valve, and brake-pipe, the brakes are off, 

 the brake cylinder being in direct comniuiiication with the 

 air, and the spring.'^, therefore, effectually keeping the 

 pistons near each other, and consequently the friction-blocks 

 clear of the wheels ; but on the pressure in the main 



