Equalizing-Discharge Valve

and that a cavity through the interior of the rotaryvalve seat (indicated by yellow, dotted semicircles) connects the facing ports, b and c, and through this route the feed-valve pipe pressure (brown) supplies the brake-pipe pressure (yellow). Cavity k in the face of the rotary valve now connects port c with another and smaller port in the seat-port g—that goes straight down into chamber D, and it is through this equalizing port, g, that the brake-pipe and equalizing-reservoir pressures are maintained at an equality while the brakevalve is in running position.

The movement of the brake-valve handle to Lap Position causes the rotary valve to blank all of its separable connections; continuing the movement to Service-Application Position, the blanked state of the ports referred to is maintained; there is no feed of pressure to the brake pipe. Cavity h is cored through the rotary valve from its annular opening that faces the valve seat to the central port, o, that is directly over the exhaust port, EX, in the center of the rotary-valve seat; in service-application position port h in the valve face is in register with the preliminary-exhaust port, e, in the rotary-valve seat that leads down into chamber D, and it is through this connection that the equalizing-reservoir pressure is discharged as the first step in the service discharge of brake-pipe pressure.

By noting closely, it will be seen in both views of the

rotary-valve seat that port e contains a bush just below the level of the seat, with a comparatively small opening drilled through it that so restricts the flow of air from chamber D that the pressure from the 10-inch x 141inch equalizing reservoir will be reduced at the rate of about 5 pounds for each 2 seconds that the brakevalve handle remains in the service-application position.

As the pressure in chamber D begins to reduce, the brake-pipe pressure under the equalizing piston becomes the greater and the piston is forced upward, unseating the equalizing valve through which the brake-pipe air discharges to the atmosphere until its pressure is as low as, or slightly less than, the pressure remaining in chamber D, when the piston will be forced downward again, reseating the equalizing-discharge valve and terminating the reduction.

Although the time taken by the engineman in making a reduction of the equalizing-reservoir pressure always amounts to the same number of seconds to cause a given number of pounds reduction of brake-pipe pressure, regardless of the length of the train, after returning the brake-valve to the lap position the discharge of the latter pressure will continue for a time proportionate to the volume of brake-pipe air; understanding this, and by noting results, the engineman will be able to make a close guess as to the number of air-braked cars

Equalizing-Discharge Valve

under his control by the duration of the brake-pipe exhaust.

The equalizing-discharge feature plays no part in making an emergency application, although in the emergency position of the brake-valve the equalizing-reservoir pressure is exhausted; in that position the brake-pipe air is discharged directly to the atmosphere through large ports in the rotary valve and seat, and this operation will be explained in reference to the rotary-valve charts to follow.

The arrangement of all ports in the rotary valve and seat, and air passages through the body of the brakevalve, should be thoroughly understood before proceeding further than Fig. 23, with the preceding piping diagrams for reference in remembering the pressure connections of the brake-valve.

The (brown) port, d, in the rotary-valve seat is directly connected with the feed-valve pipe, and the (yellow) port, c, with the brake pipe, and the flow of air from the former to the latter in the running position has been explained; the passages leading from ports c and d down to the pipe connections with the pipe bracket are shown in the dotted lines. The very small port, r, in the seat is drilled down to the atmospheric exhaust port, and when the brake-valve is in release position this warning port, r, is connected with port d by another port in the face of the rotary valve, and

the sound of the escaping feed-valve pressure indicates to the engineman that the brake-valve is not in the normal carrying position. Port u in the seat connects with the application-cylinder pipe. Port in the seat connects with the distributing-valve release pipe, and in running position is in register with port h in the rotary valve, through which the application cylinder of the distributing valve has temporary connection with the atmosphere via the large, central ports, o and EX, in the rotary valve and seat, respectively. The small (red) port, þ, in the rotary-valve seat, quite close to the large, central port, EX, leads downward and out to the connection with the pipe to the diaphragm-valve chamber of the excess-pressure governor top; it is given the red color because in release, running and holding positions it receives main-reservoir pressure through port s, which is drilled through the rotary valve and has an extended cavity in the valve face through which the connection in the several positions is maintained.

Of the ports in the rotary valve not yet alluded to, a is cut clear through the valve, and in release position is located directly over port b in the seat, permitting main-reservoir air from over the rotary valve to flow into the large passages to the brake pipe by exactly the same route, from port b onward, as was taken by the feed-valve pressure in running position. Port x is a large opening in the face of the rotary valve, with a wide,

Ports in the Rotary Valve

shallow cavity cored out of the interior of the valve -fan-shaped, as indicated by the dotted lines-that reaches inward to the central exhaust port, o; when the brake-valve is in emergency-application position the facing port, x, is in register with the direct brake-pipe port, c, in the seat, this connection providing the heavy discharge of brake-pipe pressure to the atmosphere that insures quick action of the brakes. Port j goes through the rotary valve, and in release position registers with port g in the seat so that main-reservoir air will be temporarily supplied to chamber D and provide a holding-down pressure above the equalizing piston as great as the pressure flowing to the brake pipe beneath it.

As stated, port k is a cavity in the face of the rotary valve, but it has a thin, fan-shaped extension cored in the interior of the valve, shown by dot-and-dash lines, that connects with the small port, n, and the latter is widened and lengthened to form a larger cavity in the face of the rotary valve; when the brake-valve is in emergency position the facing cavity of port n connects with port u in the seat, the end of cavity k has connected with the narrow extension of the feed-valve port, d, in the seat, and port j is lying over port d; through this combination of ports main-reservoir pressure, entering port j at the top of the rotary valve, finds a connected passage to the application cylinder of the distributing valve as the maintaining pressure heretofore alluded to.