Зображення сторінки
PDF
ePub

This reduction of brake-pipe pressure induces an actuating pressure of about 25 pounds in the application cylinder, which flows into the application-cylinder pipe and to both brake-valves, where the outlets are blanked; the distributing-valve release pipe is no longer in connection with the atmosphere, its outlet at the automatic brake-valve having been closed by the application movement of the rotary valve, and it is also blanked against pressure at the distributing valve, and so retains the atmospheric reference color of orange.

The distributing valve now causes main-reservoir air to flow to the several brake cylinders of the locomotive until their pressure equals that of the application cylinder, the brake-cylinder pressure registering by the red hand of the small duplex gauge.

Having learned the general pressure movements that induce action of the distributing valve we will now refer specifically to that unit of the E-T equipment which automatically graduates and maintains the locomotive braking pressure with such wonderful nicety—the Distributing Valve, Fig. 10 B: The 10-pound reduction of brake-pipe pressure in chamber Þ has permitted the 70 pounds in the pressure chamber to move equalizing piston 26 to the right until its button head strikes the graduating sleeve, 60, in which position it stops, as shown, without completing its maximum travel for

The E-T Air-Brake Pocket-Book

two reasons: first, the resistance of the graduating spring against the graduating sleeve; second, in that position the pressure on the left of piston 26 begins to reduce about as rapidly as the brake-pipe pressure is being discharged, for the movement of the piston has pulled graduating valve 28 to open port z in the big slide valve, 31, and the latter—the equalizing valve -has been drawn by a shoulder of the piston spindle to a position in which port z is in register with port h in the seat through which pressure-chamber air flows to application cylinder g and, in connection with cavity n in the face of the equalizing valve and port w in its seat, to the application chamber whose only purpose is to supply the space necessary for the proper expansion of this actuating and regulating pressure.

Proportionate to the amount of brake-pipe reduction we have 25 pounds pressure in cylinder g, and this has forced application piston 10 the full length of its righthand stroke, compressing the spring in its tubular end when stem 19 strikes the cap nut, and by means of the engagement of pin 18 with the application valve, 5, moving that valve to the right until the large port through it is in even register with the port in the seat; a shoulder of piston 10 has engaged with the exhaust valve, 16, sliding it to the right and closing exhaust ports e and d in its seat; main-reservoir air now flows from chamber a through the port in valve 5 to chamber

[graphic][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][merged small][merged small][merged small]

Fig. 11.— No. 6 Distributing Valve in Automatic

Service Lap Position.

Copyright, 1909, by The Norman W. Henley Publishing Co

b, and thence through port c and the pipe connecting at CYLS to the brake cylinders.

In this position the application-cylinder air has its fullest connection with the safety valve (so arranged specially for High-Speed Brake service), cavity t in the graduating valve, connecting ports r and s in the equalizing valve, through which the pressure from port h flows to passage l and the safety valve, as shown.

The sequence of pressures in the pipes connecting with the distributing valve at II and IV has been explained in Fig. 10 A, and the blanking of the distributing-valve connection of the latter port is here seen in port i and the dead cavity k in the equalizing valve.

Automatic Service-Lap Position.

As the sequence of an automatic-service application the parts within the distributing valve assume the position of service lap, as represented in Fig. II; this phase involves no change in the pressures as indicated in the piping diagram that precedes this chart, and it will only be necessary to refer to certain changes incident to the distributing valve itself.

It was assumed that the brake-pipe pressure had been reduced from 70 to 60 pounds; and when the pressure on the left of equalizing piston 26 had become a trifle less than the latter figure, from loss of air to the application chamber and application cylinder, the pressure

« НазадПродовжити »