TRIPLE VALVES 185 



Retarded-Release Position. If, when releasing the brakes, 

 the brake-pipe pressure is 3 Ib. or more in excess of the auxil- 

 iary-reservoir pressure as is usually the case on the head cars 

 of a train, the triple piston, instead of stonging when it strikes 

 the retarding stem SI, will compress the retarding spring 33 

 and move to retarded-release position, taking the slide and 

 graduating valves with it. 



When in this position, the ridge on the back of the triple 

 piston is against the end of the slide-valve bushing, with which 

 it makes an air-tight joint except at the feed-groove. Brake- 

 pipe air therefore passes the triple piston through the feed- 

 groove; thence through the feed-groove in the shoulder of the 

 piston to the auxiliary reservoir. As the feed-groove in the 

 shoulder of the pisfon has only about half the area of the feed- 

 groove in the bushing, the auxiliary reservoir will be recharged 

 much more slowly when the triple valve is in retarded-release 

 position than when it is in full-release position. The feed-port 

 in the slide-valve seat is covered by the slide valve in retarded- 

 release position, so that the auxiliary reservoir can get no air 

 from that source. 



In this position of the triple valve, the exhaust passage is 

 through a restricted passage through the body of the slide 

 valve, so that brake-cylinder air escapes very slowly to the 

 exhaust port and the atmosphere. When the difference of 

 pressure between the brake-pipe and auxiliary reservoir is 

 less than the tension of the retarded-release spring by an 

 amount sufficient to compensate for the friction of the parts , 

 the triple piston and slide valve will be moved back to full- 

 release position by the spring. 



Emergency Position. The emergency application of the K 

 triple valves is the same as for all other types of triple valves. 



COMPARISON OF TYPES K AND H-l (F-36) TRIPLE 

 VALVES 



In the accompanying table are given the results of compara- 

 tive tests of types K and H-l (F-36) triple valves; the table 

 shows the pressures in the brake cylinder with different piston 

 travels and reductions. There was 15 Ib. in the brake cylinder 

 when the second reduction was made. 



