Patent GB-318940-A (GB)
Title: Improvements in or relating to single chamber compressed air brakes
IPC: B60T15/18
Filed: 1928-06-11
Abstract: 318,940. Hildebrand, W. June 11, 1928. Fluid-pressure. - In a single chamber compressed air brake with a secondary control valve controlled by a primary control valve influenced by train pipe pressure and effecting the regulation of the pressure in the brake cylinder and influenced by the pressure in a regulating container, the pressure in the brake cylinder and the pressure in a control chamber and the variation of pressure in the regulating container is effected by a primary control valve highly sensitive to pressure variations. The piston of the primary control valve S', Fig. 1, is provided with split packing rings and is connected with the train pipe L and the regulating container, divided by a piston K into two parts A, B. The counter piston k<5> ensures a diminished pressure in the chamber A, A<2> to allow train pipe pressure to return the valve S<1> to release position. The chamber B is charged through the valve S' and the chamber A by leakage past the piston K. When train pipe pressure falls, on brake application, the valve S<1> moves to open to an exhaust port 0, the chamber B and also a chamber B' of the secondary control valve S<2>. The consequent fall in pressure in the chamber B<1> allows the pressure in the control chamber A', fed from the auxiliary reservoir H, to move the valve S<2> to open the brake cylinder C to the auxiliary reservoir H by pipes c<2>, d<1>. When the fall of train pipe pressure is stopped, this pressure moves the valve S' against the pressure in the chamber A<2> to close the exhaust port O, and brake cylinder pressure and a spring acting on a piston k<11> closes the supply to the brake cylinder by the valve S<2>. A graduated brake application is thus obtained, and on increase of train pipe pressure a graduated release is obtained. In a modified construction, the regulating container is not divided, is charged by a groove past the valve piston, and is exhausted to the brake cylinder through a non-return valve. The exhaust port of the valve S<2> is also controlled by the valve S'. In a further modification, Fig. 3, the regulating container B is supplied through a non-return valve R and supplies the control chamber A by means of a duct g and an aperture m in a valve v. On reduction of train pipe pressure the brake cylinder is first supplied from the container B through the valve S<1> and duct b<2> and a restriction D and then by movement of the valve S<2> through the duct b<2> due to the fall in pressure in the chamber A' which also causes the closing of the valve v by the superior pressure in the chamber A. The valve v maintains the pressure in the chamber A substantially constant. The differential piston of the valve S<2> is divided, the play between the parts K<2>, K<3> being taken up when the valve S<2> moves on brake application. The piston K<3> does not act on the slide valve in release position. The exhaust duct d<1> of the valve S<2> is controlled also by the valve S<1> which connects this duct to an exhaust port O when train pipe pressure is increased, which increases the pressure in the container B and moves the valve S<2> to connect the brake cylinder duct b<2> to the duct d<1>. An arrangement is also shown for connecting a standard single chamber brake into one embodying the invention. This brake comprises a brake cylinder arranged on one side of the auxiliary reservoir which acts as the regulating container and the standard control valve on the other side which acts as the valve S'. An intermediate piece is arranged between the valve S' and the container and is provided with a four-way cock, in the connection between the control valves and the brake cylinder, having passages of different diameters in order that the brake may be used for goods or passenger trains. Specifications 29120/04 and 278,111 are referred to.