is passing to the brake pipe-70 pounds-is also supplied through the rotary valve of the automatic brakevalve to the pipe leading to the equalizing reservoir (green), and its branch to the large duplex gauge, whereon its pressure is registered by the black hand (sometimes called "chamber D pressure," because it is contained in that chamber of the automatic brakevalve).

With both brake-valves in running position, all the rest of the pipes of the equipment are open to the atmosphere, or at least not containing pressure any greater than atmospheric (as in that portion of the "bypass attachment" where it is separated from the brakepipe pressure by the closed cut-out cock, and the checkvalve prevents main-reservoir air from entering), and are given the atmospheric color (orange).

Fig. 9B represents the distributing valve as near like as possible to the sectional view in Fig. 7, and such arbitrary changes in the location of parts and ports as have been made in the interest of a clear understanding have been explained; piston 10 and attachments represent the upper, or application, portion; piston 26 the lower, or equalizing, portion—a triple valve, in effect-while the pressure chamber and application chamber together form the reservoir section, shown as a dark, circular background in Fig. 7. Unreduced mainreservoir pressure enters at MR and fills chamber a;

The E-T Air-Brake Pocket-Book

brake-pipe pressure is represented as entering through the cylinder cap, 23, and is contained in chamber p; the pipe connecting at CYLS is the locomotive brakecylinder pipe; EX is the brake-cylinder exhaust port; II is the connection of the application-cylinder pipe, and IV that of the distributing-valve release pipe.

All parts are in the release and charging (or charged) positions: it is not necessary that the distributing valve shall be in a charged condition for the parts to be in this position, as there is nothing to cause them to change their locations if the air pump should be shut off and the pressures die down; release position of the lower portion will be taken as the result of brake-pipe recharge; of the upper portion, when the automatic and independent brake-valves are both in running position and the equalizing portion of the distributing valve in releasing position, or with the independent brake-valve in release position under any circumstances.

Brake-pipe pressure in chamber p, having forced equalizing piston 26 to the extreme left, finds a passage past the piston through feed-groove u into the compartment surrounding the slide valves, and the pressure chamber (green); and the piston has so placed the graduating valve, 28, that the ports q, r, and z, and cavity are blanked against all other communication; through the ports in equalizing slide valve 31 and the slide-valve seat, application cylinder g, the applica

tion chamber, and the safety valve, are all brought into open communication with each other-as plainly shown by the arrangement, and sequence of color-and also with the application-cylinder pipe which is blanked at the rotary valves of the automatic and independent brake-valves, and with the distributing-valve releasepipe which being routed through both brake valves finds an opening to the atmosphere at the large exhaust port of the automatic brake-valve; hence it is that the greater space of the distributing valve is shown in the subject plates to contain only atmospheric pressure (orange), for with application cylinder g emptied of actuating pressure, any remaining pressure above atmospheric in chamber b would place application piston 10 in the release position as shown, in which the brake-cylinder pressure would escape past the end of the exhaust valve 16 and through port ƒ in that valve, to ports e and d in the seat, and to the atmosphere at EX, and as chamber b is always in direct communication with the brake cylinders the released condition is complete: application slide valve 5 being fixed in its closed position by the engagement of pin 18 which is fitted neat in a socket in a spindle of the application piston.

The edge of piston 26 is made practically air-pressuretight by a metallic packing ring, same as in an ordinary triple valve; and the application piston, 10, also is fitted with a similar packing ring, but, as it is extremely

The E-T Air-Brake Pocket-Book

important that the latter piston shall be as nearly leakage-proof as possible, it also carries a packing leather of the same style as the packing of the brake-cylinder pistons, with the usual expanding ring within it for keeping the bearing surfaces of the leather in permanent contact with the walls of the application cylinder.

It is a common impression that the drain-cock, 38, is for the purpose of draining off the moisture, etc., from the equalizing portion of the distributing valve, because it is located just beneath the lower portion, but it will be seen that it is to drain chamber b and that portion of the cylinder containing piston 10, on the right, the large passage, m, trapping the moisture that is brought in with the main-reservoir air before it can pass on to the locomotive-brake cylinders, and permitting its removal through the drain-cock; if for any reason it should ever become necessary to bleed the locomotive-brake cylinders, it is apparent that this can be done by opening drain-cock 38; and if it should be left open through accident, under ordinary circumstances, it would have the effect of a bad leak of brakecylinder pressure that would keep application valve 5 partly open all the time during a brake application, and represent an undesirable waste of main-reservoir air.

It is hardly necessary to explain that the top side of the large equalizing slide valve, 31, is faced off to form the seat for the small graduating-valve, 28; and that

the latter valve is so closely connected to the equalizing piston as to be, in movement, a part of it, while there is enough slack between the ends of the equalizing valve and the shoulders of the piston spindle to permit of a short independence of movement of the piston, this being identically the same as in the instruction design of a triple valve, Figs. 4 A to 4 D, inclusive.

The spindle of application piston 10 has a tubular end containing the application piston graduating-stem, 19, confined between the graduating-stem nut and the graduating spring, and the duty of these parts is to assist the application mechanism in taking the lap position as the termination of an application movement.

Feed-groove u is of a size that permits the pressure chamber to be charged from the brake pipe in about the same time that is required for the auxiliary reservoirs of the cars to charge-approximately one pound of pressure-chamber increase per second.

It will be considered, in connection with the following charts of the distributing valve and piping diagrams, that the feed valve is adjusted to supply 70 pounds pressure to the brake pipe; that the excess-pressure governor top regulates the pump at 90 pounds in the main reservoir while the automatic brake-valve is in release, running, or holding, positions; that the highpressure governor top has control of the pump when the brake-valve is in positions other than stated, and