Patents for the Westinghouse automatic air-brake were granted in March, 1872. During the succeeding winter, trials of the brake were made by the Pennsylvania Railroad; and it was shortly afterwards adopted by the Philadelphia and Reading Railroad Company as their standard brake for passenger trains. The example of that company was soon followed by the St. Louis, Kansas City and Northern, the Chicago and Alton, the Toledo, Wabash and Western, and the St. Louis, Iron Mountain and Southern Railroads, all of which companies equipped their passenger rolling stock with the automatic air-brake within a few months.
ESSENTIAL PARTS OF THE WESTINGHOUSE AUTOMATIC AIR-BRAKE.
The prominent features of the Westinghouse automatic air-brake consist of the following leading parts: An air-pump, placed on the locomotive, is operated by a steam cylinder, which forces air into an iron drum or reservoir placed under the deck, or in any other convenient part about the engine. The air is compressed to the density considered necessary for the kind of train the locomotive usually pulls.
In the cab, located conveniently to the hand of the engineer, is the engineer’s brake-valve, commonly called the “three-way cock,” which regulates the flow of air from the main reservoir into the main brake-pipes for supplying the auxiliary reservoirs with air. This valve applies the train-brakes by letting the air escape from the main brake-pipes, and releases them by again admitting the pressure of air into the pipes.
From the main reservoir, the main brake-pipe connects with the engineer’s valve, and thence along the train, supplying all the brakes with the air required.
Under the floor of each car is fastened an auxiliary reservoir, which holds a supply of air necessary for operating the brakes on that car. So each car carries its own supply of air.
Connected with each car-truck is a brake-cylinder, in which is operated a piston that applies the brake. The brake-levers connect with the piston-rod in such a manner, that, when the piston is forced out by the air-pressure, the brake is applied.
Attached to the auxiliary reservoir is the triple valve, whose action connects the air-cylinder with the auxiliary reservoir.
THE AIR-PUMP.
When the air-brake was first invented, the distribution of steam within the cylinder was effected differently from what it is in modern pump-cylinders. The steam-valve consisted of a double piston, the heads having ports on their edges which admitted and released the steam. This valve did not move up and down, but received an oscillatory motion from a small auxiliary engine placed on the top of the steam cylinder-head. The movements of the auxiliary engine were regulated by a reversing-rod (popularly known as a kicker-rod), working inside the main piston-rod. This arrangement of steam distribution was somewhat complicated, and liable to get out of order; and it was superseded by the differential steam-valve movement now in use.