314 PC PASSENGER-BRAKE EQUIPMENT 



partly or wholly. The first path, however, insures direct con- 

 nection to the atmosphere. 



There are two outlets from the application chamber to the 

 exhaust in direct-release position, while there is only one outlet 

 when cap 18 is turned so as to give graduated release. The 

 capacity of the release port, therefore, is greater for direct 

 release than for graduated release, and thus gives a more rapid 

 release with the direct-release adjustment, which is desirable. 



Quick- Action Valve Venting. Either a brake-pipe reduction 

 that is too fast or a reduction so heavy that it reduces brake- 

 pipe pressure below the pressure of equalization of the pressure 

 chamber and the reduction-limiting chambers will produce a 

 differential pressure on pistons 3 and 20 that will move them to 

 their emergency positions. 



With the slide valve 4 in emergency position, emergency- 

 reservoir air passes through port c direct into chamber E, thence 

 through port r to the space below the quick-action closing valve 

 139. Chamber T, above valve 139, is connected by port s 

 with port o and the emergency-brake cylinder, which is con- 

 nected to the atmosphere through port o, the cavity in the 

 emergency slide valve, port o', and the emergency-cylinder 

 exhaust; consequently, the quick-action clasing valve 139 is 

 raised from its seat and emergency-reservoir air flows into the 

 chamber W above the quick-action piston 131. This forces 

 down piston 131 and opens the quick-action valve 133 against 

 the brake-pipe pressure in the chamber V that vents brake-pipe 

 air to the atmosphere through chamber V, port qx, and the 

 quick-action exhaust, thereby producing a local drop in brake- 

 pipe pressure that transmits the quick-action serially through- 

 out the train. 



Air from the emergency cylinder, after flowing to chamber 

 E, passes through port I direct to chamber C and the appli- 

 cation chamber. This forces piston 78 back into application 

 position, which closes the exhaust ports k and opens the appli- 

 cation-valve port wide, thus allowing the service reservoir and 

 the service-brake cylinder to equalize through port g, chambers 

 N and O, and port n. 



The movement of the slide valve 4 to emergency position 

 also opens the chamber P above the large emergency piston 



