256 NO. 6 E T LOCOMOTIVE BRAKE 



cylinder g above or below that in the exhaust-valve cham- 

 ber. The application valve 5 controls or graduates' the flow 

 of main-reservoir air from chamber a to the exhaust-valve 

 chamber and the locomotive brake cylinders when the brakes 

 are being applied by either the automatic or independent 

 brake valves. The exhaust valve 16 opens and closes the 

 brake-cylinder exhaust ports e and d. It is made shorter than 

 the distance between the shoulders on the application-piston 

 stem, so that when the exhaust valve is in lap position, piston 10 

 can move valve 5 far enough to open and close port b without 

 disturbing the exhaust valve. The application-piston guide 47 

 is made nearly an air-tight fit in its bushing, so that in addition 

 to acting as a guide for piston 10, it acts as a dash pot that 

 assists in steadying the movement of the application piston 

 and its slide valves 5 and 16. 



The application graduating stem 9 and spring 20 act as a 

 cushion for piston 10 when it is moved to application position. 

 They also assist the pressure in the exhaust-valve chamber in 

 moving the application piston 10 back to lap position when 

 the pressure in this chamber and that in the application 

 cylinder are nearly equalized. The graduating stem 19 and 

 its spring 20 are held in the stem of piston 10 by the nut 21. 

 The stem 19 touches the cap nut 22 just as the piston 10 

 starts from lap to application position; thus, as piston 10 moves 

 to application position, the spring 20 is compressed, and when 

 the pressure in the exhaust-valve chamber becomes a trifle 

 greater than that in the application cylinder, spring 20 will 

 assist in moving piston 10 back to lap position. 



The equalizing-piston graduating sleeve 44 and spring 46 

 perform the same functions as the graduating stem and spring 

 in a triple valve. They assist in preventing the equalizing 

 piston from moving past service position during a service appli- 

 cation on a short train, and also aid in starting the equalizing 

 piston from emergency position. 



The application piston 10 is provided with a packing 

 leather 13 and a packing-leather expander 12, as well as with 

 a brass packing ring 15. These prevent air from leaking 

 from the application cylinder g into the exhaust-valve chamber 

 during an application of the brakes. 



