NO. 6 ET LOCOMOTIVE BRAKE 261 



would be compressed and the parts would assume emergency 

 position. 



Air passing from the pressure chamber into the application 

 cylinder builds up a pressure on the left side of the application 

 piston 10, which forces this piston to the right. This movement 

 of piston 10 also moves the application valve 5 and exhaust 

 valve 16 over to the right. The graduating stem 19 strikes the 

 cap nut, and the graduating spring 20 is compressed. When 

 the exhaust valve 16 moves to the right, it first closes the 

 exhaust ports e and d, and thus cuts off the brake cylinders from 

 the exhaust port Ex and the atmosphere. Application valve 5 

 then connects chamber a with port b, and thus allows main-reser- 

 voir air to flow from chamber a through port b into the exhaust- 

 valve chamber, thence through port c to the brake cylinders. 



If the reduction in the brake-pipe pressure is not great enough 

 to equalize the pressures in the application cylinder, the applica- 

 tion chamber, and the pressure chamber, air from the equalizing- 

 valve chamber will continue to flow through ports z and h until 

 the pressure on the pressure-chamber side of the equalizing 

 piston 26 is a trifle less than that remaining in chamber p and 

 the brake pipe. The greater pressure in chamber p will then 

 move the equalizing piston 26 and graduating valve 28 to the 

 left, until the graduating valve closes the upper end of port z, 

 stopping the flow of air from the pressure chamber to the 

 application chamber and the application cylinder, thus pre- 

 venting any further increase in application-cylinder pressure. 

 The graduating valve has also closed the top end of port s and 

 cut off communication between the application cylinder and 

 the safety valve, so that if the safety valve leaks, the leak cannot 

 reduce the pressure in the application cylinder. 



Air from chamber a will continue to flow to the exhaust-valve 

 chamber and out through port c to the brake cylinders until the 

 pressure in the exhaust-valve chamber slightly exceeds that 

 in the application cylinder, when the greater pressure in the 

 exhaust-valve chamber, assisted by the graduating spring 20 

 and stem 19, will move piston 10 to the left far enough to close 

 port b and stop the flow of air from chamber a to the exhaust- 

 valve chamber. This position, is called automatic service lap 

 position. 



