PC PASSENGER-BRAKE EQUIPMENT 313 



and this action will be repeated. The gradual release of the 

 brake can be continued until the emergency reservoir and the 

 pressure chamber equalize at a pressure about 5 Ib. below nor- 

 mal brake-pipe pressure. 



Release Position Charging Pressure Chamber and Emer- 

 gency and Service Reservoirs. The recharging of the pressure 

 chamber to within 5 Ib. of brake-pipe pressure is accomplished 

 with emergency-reservoir air. By the time this is accomplished 

 the service-brake cylinder is entirely released, and the final 

 stage of recharging the pressure chamber and the emergency 

 and service reservoirs is accomplished by the use of air from 

 the brake pipe. 



Direct- Release and Charging Position. The direct-release 

 position is the same as the graduated-release position, except 

 that the direct and graduated-release cap 18 is turned to the 

 position for the direct release of the brake. With cap 18 in 

 this position, the brake cannot be graduated off. 



Changing the position of cap 18 cuts off the connection 

 between the emergency reservoir and the application chamber 

 and chamber E. During direct release, therefore, the cham- 

 bers E and Z are recharged from the brake pipe through the 

 feed-groove s' past the piston 3. There is direct connection 

 between chambers E and Z through port y, ports y and / of 

 slide valve 22, and port / of the valve seat. As chamber E 

 charges from chamber B, chamber- E pressure cannot increase 

 above chamber- B pressure; therefore, piston 3 cannot be moved 

 to graduated lap position and the brake cannot be gradu- 

 ated off. 



The chambers C and X are open to the atmosphere through 

 port I, ports / and q of slide valve 4, port q, cap 18, port /', 

 and the application-chamber exhaust. This affords an exhaust 

 outlet for chamber X, which cannot be closed as long as the 

 release slide valve 4 remains in release position. A second path 

 from the application chamber to the exhaust leads through 

 port /, port I in slide valve 4, cavity dw in the graduating valve 

 6, ports /' in the slide valve and seat, and the application-cham 

 ber exhaust. It is possible, however, for this path to be partly 

 restricted or, perhaps, entirely closed by the piston 3 moving 

 the graduating valve 6 so as to close port / in the slide valve 4 



