TO PREVENT CREEPING ON OF BRAKES.
To prevent the application of the brakes, from a slight reduction of pressure caused by leakage in the brake-pipe, a semicircular groove is cut in the body of the car-cylinder, 9/64 of an inch in width, 5/64 of an inch in depth, and extending so that the piston must travel three inches before the groove is covered by the packing leather. A small quantity of air, such as results from a leak, passing from the triple valve into the car-cylinder, has the effect of moving the piston slightly forward, but not sufficiently to close the groove, which permits the air to flow out past the piston. If, however, the brakes are applied in the usual manner, the piston will be moved forward, notwithstanding the slight leak, and will cover the groove. It is very important that the groove shall be three inches long, and shall not exceed in area the dimensions given above. Heretofore leakage valves have been used, and also a leakage hole. These leakage holes have been found to be too uncertain in their operation; and consequently it is recommended that these holes should be closed, and the grooves in the cylinders substituted, as rapidly as possible.
When the handle of the four-way cock 13 is turned down, there is a direct communication from main brake-pipe to the brake-cylinder, the triple valve and auxiliary reservoir being cut out; and the apparatus can be worked as a non-automatic brake, by admitting air into the main brake-pipe and brake-cylinder, to apply the brakes. When from any cause it is desirable to have the brake inoperative on any particular car, the four-way cock is turned to an intermediate position, which shuts off the brake-cylinder and reservoir, leaving the main brake-pipe unobstructed to supply air to the remaining vehicles.
The drain-cup A collects any moisture that may accumulate, and is drained by unscrewing the bottom nut.