PC PASSENGER-BRAKE EQUIPMENT 301 



Release and Charging Position. In the release and charging 

 position of the control valve, the parts are in position to release 

 the brake and to charge the pressure chamber and the emer- 

 gency and the service reservoir. In charging the equipment, 

 air enters at the brake-pipe connection and passes through port 

 a into chamber B and chamber A , thereby forcing the equal- 

 izing piston 20 to release position. This causes port b' of the 

 equalizing slide valve to register with port b' of the valve seat 

 and permits brake-pipe air to pass from chamber B, through 

 port b, the equalizing check-valve 16, and ports b', into chamber 

 D. It will be noted that there is no feed-groove for piston 20. 

 Also, port c' of the slide valve registers with port c' in the seat, 

 so that air from chamber D flows through ports c', raises 

 the emergency-reservoir check- valve 16 a, and passes through 

 port c to chamber R and to the emergency reservoir. Some 

 of the air that passes the check-valve 16a flows through port e 

 of the slide valve 22 and port e of the valve seat to the direct- 

 and graduated-release cap 18, thence through port e in the 

 release slide valve into chamber E, as shown. In passing 

 through port e of the slide valve 22, part of the air branches 

 off at port v and passes through chamber H of the service- 

 reservoir charging valve and port g to the service reservoir 

 and to chamber 2V in the application portion. 



From chamber B, brake-pipe air also flows through the feed- 

 groove s* into chamber E, so that this chamber charges by two 

 paths. Air from chamber E passes through port y, thence 

 through port / of the slide valve 22 and through port / of 

 the valve seat direct to the pressure chamber Z, charging 

 this chamber to brake-pipe pressure. Part of the air passing 

 through port y of slide valve 22 passes through port x of the 

 slide valve and seat into chamber K below the large piston of 

 the service-reservoir charging valve. This gives brake-pipe 

 pressure in both chambers G and K and a service-reservoir 

 pressure, which is much lower, in chamber H, so that the 

 service-reservoir charging valve is held in the position shown 

 until recharging is completed by the greater upward pressure 

 on the large piston. The chamber K is relatively small and 

 the ports leading to it are large enough to charge it more 

 quickly than the chambers G and H. 



