168 TRIPLE VALVES 



OPERATION OF QUICK-ACTION TRIPLE 



The quick-action triple contains two distinct sets of mechan- 

 ism. One of these, consisting of the triple piston 4 with stem, 

 slide valve 3, and graduating valve 7 with graduating stem 21 

 and graduating spring 22, is used in making service stops and 

 in releasing brakes; it is often called the service part of the 

 triple. The other set, consisting of the emergency piston 8, 

 emergency valve 10, and brake-pipe check- valve 15, is only 

 brought into use in an emergency application of the brakes; 

 hence, it is often called the emergency or quick-action part of 

 the triple. 



Release Position. The operation of the quick-action triple 

 in released position is the same as that of the plain triple. The 

 slide valve of the quick-action triple is shown in release posi- 

 tion in the figures. In this position, any air that may be 

 in the brake cylinder can pass through the slide valve, out 

 through the exhaust port to the. atmosphere, thus releasing 

 the brake. At the same time, brake-pipe air can pass the main 

 piston 4 through the feed -groove, thus recharging the auxiliary 

 reservoir. 



Service Position. The operation of the quick-action triple 

 in service application is the same as that of the plain triple. 

 When a service application of the brakes is made, the triple 

 piston 4 moves out until the knob touches the graduating 

 stem, after which any further movement is prevented. The 

 exhaust port closes first, and the service port and graduating 

 port of the slide valve connect with the brake cylinder by way 

 of the brake-cylinder port. As the graduating valve 7 opens 

 before the slide valve moves forwards, air passes from the 

 auxiliary reservoir through this graduating port to the brake 

 cylinder until auxiliary pressure is reduced just a trifle below 

 brake-pipe pressure, when the triple piston moves to lap 

 position and the graduating valve 7 is closed. During suc- 

 ceeding reductions, the graduating valve simply opens and 

 closes without moving the slide valve, as in the plain triple. 



