The E-T Air-Brake Pocket-Book

in chamber p being somewhat the stronger pushed piston 26 to the left until the right-hand shoulder of its stem striking equalizing valve 31 the piston was stopped in the position shown; equalizing valve 31 was not moved, and the short, back lash of the piston effected nothing directly except to move graduating valve 28 "on lap," the latter valve closing port z to cut off further increase of application-cylinder pressure, and closing communication between the application cylinder and the safety valve by cutting off port r from port s in the equalizing valve. (It is unnecessary for the safety valve to be cut in to the application-cylinder pressure when there is no chance for that pressure to increase, as in the lap position; and if the safety valve were not cut out at this time, an obstruction between the valve and valve-seat would result in complete loss of the application-cylinder pressure and consequent release of the locomotive brakes.)

Referring to the upper portion of the figure: In the preceding chart the pressures were increasing on both sides of the application piston, 10, and 25 pounds had accumulated in application cylinder g when its further increase was stopped by the closing of the graduating valve (lower portion); when that occurred, main-reservoir air from chamber a continued to flow to chamber b and the locomotive brake cylinders until the pressure in the latter was probably a little greater than that in cylin

der g, when the reaction of the coil spring in the end of the spindle of piston 10 moved the piston and application valve 5 to the left, cutting off the communication between chambers a and b, as shown, and which temporarily closes off pressure supply to the brake cylinders. The leftward movement of piston 10 ceased just as the application valve came to its lapped position, partly because the frictional resistance of exhaust valve 16 under the air pressure of chamber b was met with, and at that point the extending force of the coil spring was checked by the shoulder of graduating stem 19 striking the graduating-stem nut.

I said that the supply of air to the brake cylinders was temporarily closed off, because any subsequent leakage of the locomotive brake-cylinder pressure will permit the application piston to move again to the right to application position, and the brake cylinders to be resupplied at the original pressure; or, if any further reduction of brake-pipe pressure shall be made, both the upper and lower portions of the distributing valve will assume the positions shown in the service-application chart, following with the service-lap position in which the only difference from the subject chart will be suggestive-lower brake-pipe and pressure-chamber pressures, and higher application-cylinder and brakecylinder pressures.

When the brake-pipe pressure has been reduced

The E-T Air-Brake Pocket-Book

by 20 pounds, the contents of the pressure chamber will equalize fully with the application-chamber and application-cylinder at a pressure of 50 pounds; any further reduction will be of no effect on the locomotive brakes, although a 25-pound reduction is necessary to insure the full-on application of all car brakes; further than that, any reduction of the brake-pipe pressure is a waste of air, and in such cases the lower portion of the distributing valve will take the same position as will be shown in Fig. 12 B, emergency position, next to follow.

Emergency-Application Position.

Figs. 12 A and 12 в represent an emergency application as the result of placing the automatic brakevalve in emergency position, although the distributing valve would assume identically the same position from a service brake-pipe reduction of 25 pounds, or more -with the exception that in the latter case the safety valve would probably not be unseated.

Referring first to the piping diagram, Fig. 12 A, the movement of the automatic brake-valve to emergency position has effected a quick and heavy reduction of the brake-pipe pressure, as indicated by the broken color lines, and the effect on the distributing valve is to cause it to supply main-reservoir air to the locomotive-brake cylinders; the supply of main-reservoir pressure to