GB732031A - Improvements relating to vacuum brake apparatus for railway and like vehicles - Google Patents

Abstract

732,031. Vacuum brake apparatus. GRESHAM & CRAVEN, Ltd. July 29, 1954 [Oct. 15, 1953], No. 28451/53. Class 103 (1). In a vacuum brake apparatus for railway and like vehicles in which an exhauster produces vacuum in the exhaustion pipe communicating through an automatic isolating valve with a vacuum relief valve and with the vacuum side of the locomotive brake cylinders, the exhaustion pipe also communicates with the train pipe via the driver's brake valve so that under normal bracking application, the relief valve operates to keep the exhaustion pipe vacuum below a predetermined maximum (e.g. 20 or 21 inch mercury) and under emergency brake application the isolating valve closes when the train pipe vacuum falls below a predetermined value (e.g. 5 inch mercury) to raise the vacuum at the vacuum side of the locomotive brake cylinders in order to increase the braking power of the locomotive. In the arrangement shown in Fig. 1, the usual brake valve a controls the connection between the exhaustion pipe b leading to the exhauster c and the train pipe d which has a connection e to the locomotive brake cylinders f. The pipe b has connections via the non-return valve g with the pipe h which leads to the vacuum side of each locomotive brake piston in its cylinder f and to the vacuum chamber i. The pipe b is also connected with the automatic isolating valve k and the vacuum relief valve m via the connection j (Fig. 2). The automatic isolating valve k is normally held open by spring n so that the upper side of the diaphragm o is in contact with the pressure in the pipe j and communication is established between the pipe j and the vacuum relief valve m which prevents the vacuum rising above 20-21 inch mercury by admitting air to the system. Pipe p connects the underside of the diaphragm o with the train pipe d. In a normal service brake application, the isolating valve k remains open and the vacuum in the pipe b and in the vacuum side of the brake operating cylinders f is maintained at 20-21 inch mercury. When an emergency application is made and the vacuum in the train pipe d falls below 5 inches mercury, the pressure on the lower side of the diaphragm o overcomes the pressure of the spring n and the valve k shuts; thus isolating the relief valve m from the pipe j. The exhauster c can now increase the vacuum in the pipe h and at the vacuum side of the pistons in the locomotive brake cylinders f to give increased braking power for heavy or emergency applications. When the brakes are released by operation of the brake valve a, the vacuum in the train pipe d is restored and the isolating valve k is opened, allowing the vacuum relief valve m to reduce the high vacuum at the vacuum sides of the pistons of the locomotive brake cylinders f to a normal figure.