Patent GB-295988-A (GB)
Title: Improvements in release valves for single chamber air pressure brakes
IPC: B60T15/54
Filed: 1928-07-03
Abstract: 295,988. Hardy Maschinenfabrik und Giesserei Akt.-Ges. Geb. Aug. 22, 1927, [Convention date]. Fluid-pressure. - Release valves for single chamber fluid pressure brakes for use in combination with the usual triple or like valve and of the kind controlled by the difference between the initial and actual trainpipe or auxiliary reservoir pressures and the brake cylinder pressure comprise a lift valve controlled by coaxial pistons or diaphragms on which these pressures and that of the atmosphere act. The pistons may also actuate a valve for giving a supplementary supply to the brake cylinder. Fig. 4 shows one construction comprising a piston 16 subject on its lower and upper faces to the atmospheric pressure and the initial pressure in the auxiliary reservoir or train-pipe respectively through the pipe 15 and the pipe 12 and non- return valve 14. The rod of the piston 16 engages a differential piston 18 the under faces of which are subject respectively to the actual auxiliary or train-pipe pressures and the brake cylinder pressure through the pipes 12, 5. The pipe 5 may be connected directly to the brake cylinder or to the exhaust port of the usual triple valve. The brake cylinder is connected by the pipe 5<1> to the supply port of the triple valve. The piston 18 is provided with a bore 19 with which co-operates a fixed closing disc 20. Under running conditions the ports are in the position shown so that the brake cylinder is open to exhaust through tht pipes 5, 15. When the brakes are applied by the operation of the triple valve, the reduction of pressure in the chamber 23 causes the pistons to move downwardly and the pressure in the brake cylinder which acts on the piston 18 if the chamber a is directly connected thereto is insufficient to raise the pistons. When after an application, the train pipe and auxiliary reservoir pressures are raised a predetermined amount, the pistons are raised and the brake cylinder pressure is reduced until equilibrium of the pressures is established..The brake cylinder pressure may thus be reduced step by step. The 'brakes on an uncoupled vehicle may be released by lifting the valve 14. This may be done by lifting a second valve 33 which also serves to exhaust the auxiliary reservoir. Instead of the piston 18 being of differential form it may have faces of equal area. Fig. 5 shows a construction in which this is the case and which is adapted in addition to releasing the brakes to supply compressed air to the brake cylinder if the prsesune therein should due to leakage or other cause fall below a value corresponding to a given train-pipe pressure. The valve disc 20 is attached to a slidable stem which also carries a second valve disc 25 pressed upwardly by a spring 27 so as normally to close an opening by which compressed air is supplied from the auxiliary reservoir 3 by pipe 29 to the brake cylinder 2 by a pipe 5. The chambers above and below the piston 16 are connected to the train-pipe 8, in one case by way of the non- return valve 14. The triple valve 30 having the usual connections is provided. When the brakes are applied the train-pipe pressure difference acts downwardly on the piston 16 and if this pressure is sufficient to overcome the pressures of the springs 21, 27 and that in the brake cylinder, the valve 25 is opened and air is supplied through it to the brake cylinder.