CONTTNUOUS RAILWAY BKAKES. 



193 



tliaii tlio ])rcssuro iu tlio train-pipe. TJic object of tins will 

 be seen later on. 



When the brakes are " off," the train-pipe pressure is 

 equal to the reservoir pressure, the " triple " valve of each 

 reservoir being held in nndahle balance between the pres- 

 svires. 



When the brakes are " off," the brake-piston is in com- 

 munication with the atmosphere, the piston being kept 

 homo, and the brakes " off," by the " spiral" springs. 



To apply the brakes, the driver discharges air from the 

 brake pipe, the equilibrium of the "triple" valves is thereby 

 destroyed, they fall and open a communication between the 

 auxiliary reservoirs and the brake-cylinders, the air from the 

 reservoir forcing out the brake-pistons and applying the brakes. 



When the brakes are to be released, the driver opens a 

 communication between the main reservoir and the train- 

 pipe, the excess of the air pressure in which admits of its 

 supplying the train-pipe with the air necessary to restore 

 the " triple " valve to its former state of unstable equili- 

 brium. The " triple " valve, being thus raised, cuts off the 

 communication between the auxiliary reservoirs and the 

 brake-cylinders, and jjlaces the latter in communication with 

 the atmosphere through the exhaust passage, thus allowing 

 the brake pistons to be forced home by the springs, and the 

 brakes to bo released. When the triple valve reaches 

 the groove at the end of its travel, air again feeds past 

 It into the auxiliary reservoirs, until the normal pressure in 

 them is again reached. 



In a Paper on Bi-akes, read before the Society of Arts by 

 Mr. W. P. Marshall, M.I.C.E., he stated that the " Westing- 

 house " brake could not, like the Automatic Vacuum Brake 

 and other Differential Pressure brakes, be applied with any 

 desired degree of pressure, and be loft for any length oi' 



