and z, and to the atmosphere through the release valve; in the latter case, the release valve must be kept open

until all of the pressure in the auxiliary reservoir and brake cylinder has been discharged.

RUDIMENTS OF THE DISTRIBUTING VALVE.

Owing to its automatic character, the unimproved air-brake can not be depended upon to stay applied for any considerable length of time, as the auxiliary reservoir-the local base of pressure supply—is cut off from recharge by the act of applying the brake, and the inevitable piston packing-leather leakage may be expected to waste away the air from the brake cylinder and auxiliary reservoir; but the locomotive-the heaviest unit of the train, and equipped with a brake equaling in calculated power the brakes of several modern freight cars carries the main-reservoir pressure, and in the E-T type of locomotive-brake equipment a way has been found to supply pressure to the engine and tender-brake cylinders directly from the main reservoir and yet to retain the automatic action and brakepressure-graduation in harmony with the triple-valveoperated cars of the train.

The distributing valve is the central figure of this new equipment, and before taking up the description and explanation of its mechanism in technical detail, a diagrammatic figure will be used to exemplify the principle on which the brake-cylinder pressure is supplied and the automatic graduation of same is performed. In Fig. 5, we have a triple valve precisely similar to

the one described, but here denominated the equalizing valve, an auxiliary reservoir changed in name to pressure chamber, and a sealed vessel containing the same volume as would be in the pressure end of the brake cylinder of Fig. 4 A with the brake piston moved out to its normal travel, but called the application chamber; and these, with the addition of the case containing the small piston and valve at the left of the application chamber, constitute the application features of the distributing valve in an ideal form.

The same explanation as given of Figs. 4 A, 4 B, 4 C, and 4 D will apply to the action of the equalizing valve as the result of brake-pipe pressure reductions and recharge; full main-reservoir pressure enters and is contained in chamber a, as indicated, and serves to hold application valve 5 seated; from chamber b, a pipe leads and branches to all brake cylinders of the engine and tender; therefore, application piston 10 has whatever pressure may be in the locomotive-brake cylinders on one side of it, and the pressure of the dummy-brake cylinder, or application chamber, on the other side.

If a brake-pipe reduction of 10 pounds should be made, the equalizing valve operating as a triple valve will permit air to flow from the pressure chamber to the application chamber until the pressure of the former has been also reduced to a fraction less than that

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