220 TRIPLE VALVES 



pass to the brake cylinder either from the auxiliary reservoir 

 through port z or from the brake pipe through port y. 



If the triple valve is in full-service position when the reduc- 

 tion of brake-pipe air at the brake valve ceases, it will assume 

 lap position in the same manner as just explained, but the 

 triple piston will be assisted in its movement to lap position 

 by the graduating spring, which was slightly compressed, and 

 the piston will be stopped in full-service lap position instead 

 of in quick-service lap position. 



Graduated Release. The triple assumes full-release posi- 

 tion in discharging air from the brake cylinder to the atmos- 

 phere during a graduated release of the brakes. To graduate 

 the release of the brakes, the brake-pipe pressure should be 

 increased just enough to move the main piston, slide valve, 

 and graduating valve to release position, and the brake valve 

 should then be returned to lap position, which will prevent 

 any further increase in brake-pipe pressure. As the main 

 piston and the slide and graduating valves have been moved to 

 release position, brake-cylinder air 'escapes to the atmosphere 

 through ports C, r, n, cavity w, port m, and the exhaust port p; 

 but, as the increase in brake-pipe pressure has ceased on 

 account of the brake valve being lapped and as air from the 

 supplementary reservoir still flows through ports x and k into 

 chamber R, the pressure on the auxiliary-reservoir side of 

 piston 4 is increased sufficiently above that on the brake-pipe 

 side to move piston 4 and graduating valve 7 to graduated- 

 release lap position. In this position, piston 4 closes the feed- 

 groove * and the graduating valve closes ports m, j, and k, 

 on the back of the slide valve. This cuts off the flow of air 

 from the brake pipe to the auxiliary reservoir through the 

 feed-groove i and the port j and from the brake cylinder to 

 the atmosphere through port m, as well as from the supple- 

 mentary reservoir to the auxiliary reservoir through port k. 

 In this way the brakes are only partly released, as only a 

 portion of the brake-cylinder air is allowed to escape to the 

 atmosphere. 



In releasing the brake, a series of such graduations may be 

 made until the brake-pipe pressure has been restored to the 

 pressure at which the auxiliary and supplementary-reservoir 



