TRIPLE VALVES 221 



pressures will equalize; then the brakes will fully release. 

 The amount of reduction in brake-cylinder pressure for any 

 given graduation depends on the amount of air pressure that 

 is put into the brake pipe each time the brake valve is placed 

 in release, or running, position during such manipulations. 

 This will also determine the rate at which the brake is 

 recharged. 



Emergency Position. When a heavy and sudden reduction 

 in brake-pipe pressure is made by the brake valve or in some 

 other way, the triple valve moves into emergency position. 

 The pressure in chamber H of the triple valve reduces suddenly 

 and the greater auxiliary-reservoir pressure in chamber R 

 causes piston 4 to move rapidly to the extreme left of its 

 chamber, moving the slide valve and graduating valve with it. 

 The graduating spring is compressed and the triple piston 

 rests firmly against the cylinder-cap gasket 22. When the slide 

 valve is in emergency position, the service ports do not register. ' 

 The end of the slide valve uncovers port t in the slide-valve 

 seat, which allows auxiliary -reservoir air to pass into the cham- 

 ber above the emergency piston, forcing this piston down and 

 thus unseating the emergency valve 10. This allows the air 

 in chamber Y to escape to the brake cylinder; then brake-pipe 

 air in passage a raises the check- valve 15 and flows into the 

 brake cylinder in large volume through chambers Y and X 

 and passage C. This produces a local reduction in brake-pipe 

 pressure, which causes the next triple valve to operate quick- 

 action, and so on throughout the train. At the same time 

 port d in the slide valve registers with port c in the seat and 

 allows air in the chamber back of the by-pass piston 25 to escape 

 to the brake cylinder through ports c, d, n, r, and C. The 

 pressure in the chamber back of the by-pass piston 25 will be 

 considerably reduced and the by-pass piston will be moved 

 backwards by the auxiliary -reservoir pressure in the chamber 

 in front of it. This movement of the by-pass piston will unseat 

 the by-pass valve 27 and thus connect the supplementary 

 reservoir with the auxiliary reservoir through ports x, /, and g. 

 This gives, in effect, an auxiliary-reservoir volume approxi- 

 mately three times the size of the one that supplies air to 

 the brake cylinder during a service application of the brake. 



