Patent GB-190428183-A (GB)
Title: Improved Means for use in Operating Continuous Brakes by a Vacuum or Compressed Air.
Inventor: HOLCROFT HAROLD
Filed: 1904-12-23
Granted: 1905-11-23
Abstract: 28,183. Holcroft, H. Dec. 23. Brakes, pneumatic-pressure and vacuum. In trains which have to run both on a line on which pressure brakes are used and one on which vacuum brakes are used, and which have, consequently, to be fitted with the two kinds of brakes, the necessity for providing both a pressure and a vacuum cylinder on each coach is avoided by fitting the ordinary vacuum cylinder with a converting-valve whereby it is made to serve also as a pressure cylinder. The converting-valve may be operated by hand or automatically. In the arrangement shown in Fig. 2, the ordinary vacuum cylinder A is fitted with a hand-operated converting-valve B, which is shown on a larger scale in Fig. 3. In the position shown, the valve is set for working with pressure. When the pressure in the Westinghouse train-pipe H is reduced, air from the auxiliary reservoir E flows through the triple valve F as usual to the inlet d of the converting-valve, whence it passes up to the bottom of the piston through the valve recess i and the passage b, the upper side of the piston being open to atmosphere through the valve passages a, g, e. If the vacuum system is to be employed, the plug of the converting-valve B is turned through a right-angle so as to shut off the pressuresystem inlet d and open communication between the vacuum pipe attached to the inlet f and the bottom of the piston through the passage b. The usual ball valve of the vacuum cylinder is shown at c. In order to prevent too great a pressure in the cylinder in the event of a rupture of the train-pipe while the pressure system is in use, a reducing-valve is fitted between the triple valve and the converting-valve, as shown at G. Fig. 5 shows an arrangement in which the converting-valve is operated automatically so as to change from one system to the other. As shown, the pressure system is in use, air from the triple valve passes through the inlet d<1>, valve ports i<1>, and passage b<1> to the bottom of the piston A, the upper side of the piston being open to the vacuum train-pipe at f<1> through the passage a<1>. To change to the vacuum system it is only necessary to produce a vacuum in the train-pipe at f<1>, when the valve pistons C<1>, D<1> will be moved to the right so that the pressure inlet d' will be shut off, the passage a' will be closed by a valve g<1> on the valve piston C', and the vacuum train-pipe at f will be open to the bottom of the piston through the passage b<1>. The usual ball valve is shown at c<1>. The reducing-valve for limiting the pressure in the cylinder is combined with the converting-valve. It consists of a spring-opened valve, the stem of which passes throught an axial hollow in the converting-valve and is attached to a diaphragm r at the back of the piston C'. When the pressure is excessive, the diaphragm moves from the piston and closes the valve. The converting-valve may otherwise be operated by hand by a lever K. For effecting rapid release of the brakes after an application with the pressure system, the cylinderexhaust valve shown in Fig. 8 may be introduced between the triple valve, connected at N, and the converting-valve, connected at O. Air passes from N through holes T in the diaphragm S and past the flap valve U to the converting-valve to apply the brakes, but, when the pressure at N is lowered in releasing the brakes, the air from O lifts the diaphragm and the attached valve Q, which opens the cylinder to atmospheric ports.