Patent GB-295454-A (GB)
Title: Improvements relating to fluid pressure braking apparatus
IPC: B60T13/60
Filed: 1927-05-21
Abstract: 295,454. Winter, H. J., and Westing- house Brake & Saxby Signal Co., Ltd. May 21, 1927. Fluid-pressure.-Fluid-pressure braking apparatus of the combined compressed air and vacuum type comprises a valve for automatically comtrolling the release of fluid under pressure from the compressed air brake pipe under the combined influence of the automatic compressed air brake pipe pressure, the vacuum brake pipe pressure and a constant pressure, in order that an application of the vacuum brake causes a corresponding reduction of the compressed air pipe pressure. An energizing valve may also be provided to release pressure from the compressed air pipe in an emergency application of the vacuum brakes. A diaphragm 2 separates the valve casing into two compartments, a compartment 3 open to the atmosphere through an aperture 5 and a compartment 4 connected to the vacuum brake pipe. A spring 6 presses on the under side of the diaphragm. The diaphragm is provided with a stem 8 the upper part of which is secured to a diaphragm 11 separating chambers 12, 13. The chamber 12 communicates with the atmosphere through an opening 14 and the chamber 13 communicates through a restricted port 17 with the upper side at the piston 18 of the equalizing discharge valve and also through a non-return valve 15 with the compressed air brake pipe 16 which permits recharging thereof. The upper end of the stem 8 is tubular, opening into the chamber 12 by an aperture 21 and carrying in its upper end a valve 22 connected to a spring closed valve 24 controlling communication of the chamber 13 with a passage 26 leading to a feed valve. The pressure of the spring 6 and the atmospheric pressure in chamber 3 in equilibrium with the pressure fluid supplied from the feed valve through the passage 26 maintains the valve closed and the valve 24 open. On admission of air to the vacuum pipe 7 the diaphragms move downwards closing the valve 24, thus cutting off communication between the feed valve and the compressed air pipe 16 and the stem 8 then moves away from the valve 22 opening communication between the atmospheric chamber 12 and the upper side of the piston 18 which moves to vent the compressed air brake pipe 16 through a port 29 and apply the compressed air brakes. When the compressed air brake pipe pressure has been reduced to a predetermined extent the .diaphragms rise again to reclose the valve 22 owing to the reduction of pressure in the chamber 13 and the release of fluid by the piston 18 is interrupted, as pressure acting on the under side of the piston 18 through an aperture 28 is also reduced. During release of the brakes the converse action of the ports takes place. The spring 6 can be adjusted so that the closing movement of the piston 18 takes place at any desired degree of reduction of the compressed air pipe. The emergency valve comprises a reservoir 30 closed by a diaphragm 31 and maintained at the pressure obtaining in the vacuum pipe 7 by a small aperture 33 in the stem 32 of the diaphragm. On complete destruction of the vacuum in the pipe 7 the diaphragm rises and opens the compressed air brake pipe 16 to atmosphere by raising a valve 40 by means of a lever 37 connected to the stem 32. The connection to the pipe 7 is made adjacent the driver's brake valve to render the action of the valve sensitive.