. Air brake text for engineers and firemen; . l preliminary exhaust port h, whereby air is dis-charged from chamber D to the atmosphere. The resultant re-duced pressure in chamber D and the equalizing reservoir permitsthe greater brake pipe pressure below the equalizing piston toraise it, unseating the brake pipe discharge valve. The brake pipeair then discharges through passage n into the atmosphere untilthe pressure becomes a trifle less than the pressure remaining inchamber D, which forces the piston downward, reseating thevalve. Emergency Application Position. While the brake valveis in th
. Air brake text for engineers and firemen; . l preliminary exhaust port h, whereby air is dis-charged from chamber D to the atmosphere. The resultant re-duced pressure in chamber D and the equalizing reservoir permitsthe greater brake pipe pressure below the equalizing piston toraise it, unseating the brake pipe discharge valve. The brake pipeair then discharges through passage n into the atmosphere untilthe pressure becomes a trifle less than the pressure remaining inchamber D, which forces the piston downward, reseating thevalve. Emergency Application Position. While the brake valveis in this position, cavity c of rotary valve 13 overlaps both the ENGINEERS BRAKE VALVES. 41 large direct application and supply port / and direct applica-tion and exhaust port k. A large direct passage is thus pro-vided for quickly, discharging brake pipe pressure to the atmos-phere, and the resulting sudden reduction of brake pipe pressurecauses an emergency application of the brake. Port e is slotted to the right (Plate 14), this slot being pro-. D-S ENGINEERS BRAKE VALVE. Release Position. PLATE 16. vided in order that there may be no position between the releaseand running positions, in which communication between themain reservoir and the brake pipe is wholly cut off. If therotary valve is so moved that port ; is above the space betweenports e and /, main reservoir air can still feed through the slottedport into chamber D, thence through port g, into cavity c of therotary valve and through passage / into the brake pipe at Y. 42 ENGINEERS BRAKE VALVES. Port e also serves to allow the main reservoir pressure to reachchamber D above the equalizing piston when the valve handle isbeing moved to release position. The connection is establishedas soon as port / in the rotary valve comes into register withslotted port e in the rotary valve seat. Pressures. When the brake valve is in full release positionthere is one large direct opening leading from the main reservoirto the brake pipe, a
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