. Official proceedings . to reducethe pressure in the auxiliarv reservoir as fast as the pressure isreducing in the brake pipe, when the train is of considerablelength. Put if the brake-pipe reduction is miire raj^d than thatof the auxiliary, the difference in pressures on the two sides ofpiston 4 soon becomes sufficient to slightly compress the graduat-ing spring, and niove the slide valve to the position shown inFig. 3, called Full Scnicc: In this position, quick service porty is closed, so that no air flows from the brake pij^e t(T the brake Ouick-Service Trii)lc Xalvc. 237. Fig. 3. Full-Sc
. Official proceedings . to reducethe pressure in the auxiliarv reservoir as fast as the pressure isreducing in the brake pipe, when the train is of considerablelength. Put if the brake-pipe reduction is miire raj^d than thatof the auxiliary, the difference in pressures on the two sides ofpiston 4 soon becomes sufficient to slightly compress the graduat-ing spring, and niove the slide valve to the position shown inFig. 3, called Full Scnicc: In this position, quick service porty is closed, so that no air flows from the brake pij^e t(T the brake Ouick-Service Trii)lc Xalvc. 237. Fig. 3. Full-Scrvi cylinder; the brake-pipe reduction being- sufficiently rapid, thereis no need of the additional quick-service reduction, so the triplevalve cuts it out. Also, ports r and r are fully open, and allowthe auxiliarv-reservoir pressure to reduce more rapidly, so as tokeep pace with the more rapid brake-pipe reduction. Lap Position—When the brake-pipe reduction ceases, aircontinues to flow from the auxiliary reservoir through ports 3and r to the brake cylinder, until the pressure in the chamberR becomes enough less than that of the brake pipe to cause pis-ton 4 and graduating valve 7 to move to the right until theshoulder on the piston stem strikes the left-hand end of slidevalve 3. As the friction of piston and graduating valve is muchless than that of the slide valve, the difference in pressure whichwill move the piston and the graduating valve, will not be suf-ficient to move all three; consequently, the piston stops in theposition shown in Fig. 4. This movement has
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