218 TRIPLE VALVES 



ports j, nt, and k at the top of the slide valve, shutting off 

 communication between the auxiliary and supplementary 

 reservoirs, chamber F, and the slide-valve chamber R, and 

 between the brake cylinder and the atmosphere. It also 

 uncovers port z, and cavity v in the graduating valve connects 

 ports / and o. As the main piston 4 continues to move, the 

 shoulder on the end of its stem engages the slide valve; all 

 these parts then move together until the knob on the main 

 piston 4 strikes the graduating sleeve; the triple valve is then 

 in quick-service position. In this position port k in the slide 

 valve is moved away from port x, which leads to the supple- 

 mentary reservoir; port z registers with port r, and the aux- 

 iliary-reservoir air can pass to the brake cylinder through 

 ports z and r and passage C; ports y and o register so that brake- 

 pipe air from chamber F passes to the brake cylinder through 

 ports y and o, cavity v in the graduating valve, port I, cavity q, 

 port r, and the passage C. 



The pressure in chamber F being reduced, check- valve 15 

 will rise and allow brake-pipe air from passage a to be supplied 

 to this chamber as fast as it passes out through port y. This 

 local reduction in brake-pipe pressure will assist in applying 

 the brakes, but will not cause an emergency application, 

 because the air must pass through the restricted port /. The 

 tendency to produce quick action is also guarded against 

 by proportioning the valves and locating the ports so that 

 the service port z will not fully register with port r while port y 

 is connected to port o, and any movement tending to compress 

 the graduating spring will increase the opening of the service 

 port z and decrease the opening through port y. This grad- 

 ually increases the rate of discharge from the auxiliary reser- 

 voir, and decreases the rate of discharge from the brake pipe, 

 until port z is opened its full extent and port y is entirely 

 closed. When this takes place, the triple valve is said to be 

 in full-service position. Triple valves in a short train will 

 usually assume this position, because the reduction in a short 

 brake pipe is more rapid than that in a long brake pipe. 

 When in either quick-service or full-service position, cavity q 

 in the slide valve connects the brake-cylinder port r with 

 port b, thus connecting the brake cylinder with the safety 



