Patent GB-386333-A (GB)
Title: Pneumatic braking apparatus for railway vehicles
IPC: B60T8/18
Filed: 1931-04-16
Abstract: 386,333. Fluid-pressure brakes. ALGRAIN, P., 198, Rue Parmentier, La Croyere, Belgium. April 16, 1931, No. 11292. Convention date, April 23, 1930. [Class 103 (i).] In automatic compressed air or vacuum brakes for railway vehicles in which the braking effort varies automatically with the load carried by each vehicle and with the degree of braking applied to the train, and with the variation of brake cylinder pressure brake cylinder pressure is controlled by valves controlled by the displacement of a single movable element only, the movement of which is controlled by four essential forces, (1) the load carried by the vehicle, (2) train pipe pressure, (3) the power pressure which acts in the brake cylinder or another valve controlling the brake cylinder, and (4) the counter-pressure, i.e. the pressure on the non-working side of the brake piston. The apparatus is shown applied to both vacuum and pressure brakes. The lower working chamber of the vacuum cylinder 2 is connected by a pipe 3 with the chamber 4a of the regulating valve 4 and the upper chamber and vacuum reservoir 17, constituting the counter-pressure are connected by a pipe 13 with a chamber 10d containing the spring 12 the tension of which is regulated by the load of the vehicle. The single element controlling the valves 9, 15 and comprising diaphragms 10g, 10h is acted on by the spring 12, the power pressure air in chamber 4a conveyed through a passage 11 into chamber 10b, the counter-pressure in the chamber 10d and train pipe pressure in the chamber 10k conveyed through a pipe 7a. Rise of train pipe pressure on brake application is conveyed through a pipe 5 and the open valve 9 to the lower chamber of the brake cylinder to apply the brakes and acting in the chamber 10b presses down the diaphragms and allows the valve 9 to close. The passage 11 is restricted by an adjustable plug 11b to allow the rise of pressure to take full effect in the brake cylinder before the valve 9 closes. The valve 9 is opened and closed for each further rise of train pipe pressure. If the valve 9 leaks, excess pressure thus obtained in chamber 10b depresses the diaphragms until a sleeve 15 engages a fixed abutment 16 and opens the pin valve 14 to connect chambers 10b, 10d and equalize the pressures therein when the valve will reclose. Leakage of brake pressure is compensated by opening of the valve 9. On brake release and reduction of train pipe pressure the diaphragms fall, open the pin valve and connect the lower chamber of the brake cylinder to the-vacuum reservoir 17. The consequent fall in the pressure in the chamber 10b allows the diaphragm to rise and open the valve 9 to connect the brake cylinder to the train pipe. The regulating valve is also shown adapted for a compressed air brake, the position of the large and small diaphragms being reversed, a triple valve connected to an auxiliary reservoir being arranged in the pipe 5 and a retaining valve, Fig. 2, being arranged in the pipe 7a. The triple valve connects the auxiliary reservoir normally to the train pipe and the pipe 5 to the atmosphere and on brake application connects the auxiliary reservoir to the pipe 5. The chamber 10d in this modification is connected to the atmosphere which in this case is the counter-pressure. A sufficiently gradual rise of train pipe pressure effects an initial progressive release of the brakes without movement of the triple valve. Train pipe air is supplied to the central chamber 10k through a non-return valve 39, Fig. 2, in the valve 38 of the retaining valve 36. The valve 39 is maintained open by the air acting on a diaphragm 37 until a definite reduced pressure is obtained when it is closed by a spring 40 to prevent excessive fall in pressure in the chamber 10k. The tension of the spring 12, Fig. 1, is adjusted in proportion to the load by a cam 22 in the form of an Archimedian spiral and contained in an airtight chamber 26 containing lubricant. To the pivot 22a of the cam is attached a lever 21 connected at its upper end by a rod 24 to a lever 20, Fig. 7, mounted on a pivot 18. Pivoted at 20b on the lever 20 is a lever 23 which is mounted on a pivot 19. The pivots 18, 19 are mounted on two parts of the vehicle separated by the suspension springs. A spring 25 connects the pivot 20b to the upper end of the lever 21. The levers and rods are provided with screw threaded heads for adjustment. To prevent injury due to shocks the pin 19 is mounted in a slide 23a in the lever 23, adjustable by a screw. 23d. In a modified form of the invention for use in cases where the wagons always run either empty or fully loaded the spring 12 is adjusted by hand and the counter-pressure chamber 10d is connected to the pipe 5 by a pipe in which is provided a cock adapted to connect the chamber 10d either to the counter-pressure when the valve functions as above or to the train pipe when the valve 9 remains permanently open and train pipe air at full pressure has free access to the brake cylinder. The cock is turned by hand or by connections to the suspension system of the vehicle so that the cock is operated in accordance with the load on the vehicle. In the latter case a connection similar to that shown in Fig. 7 is used in which the rod 24 at the end opposite to that at which it is connected to the lever 20 is provided with a pin 24b, Fig. 8, guided in a slide 28 and engaging between the branches 29a of a fork 29 fixed to the pin 26a of the cock. The pin 24b has idle travel at each end of its movement to prevent shocks effecting the cock. In a further modification of the invention, Fig. 3, in which the brake cylinder supply is first rapid and then at a reduced rate in accordance with the load, the regulating valve 4 supplies pressure air to a distributing valve 44 of similar construction which supplies the brake cylinder 2 near which the valve 44 is situated. In charging position the train pipe 7 is connected through the triple valve 8 to the auxiliary reservoir 6 and through a pipe 41 to the valve 4. The valve 4 supplies pressure air through the valve 9, Fig. 1, and a pipe 45 to a chamber 49m of the valve 44 at a pressure in accordance with the load on the vehicle, when this pressure is attained the valve 9 closes. On fall of train pipe pressure on brake application the triple valve 8 connects the auxiliary reservoir 6 to the brake cylinder 2 through the open valve 47 of the valve 44 until the diaphragms are depressed to close this valve. Immediately preceding this closure a valve 53 is opened by a cross bar 53a thereon which engages a shoulder 44d and allows further brake cylinder supply to take place through the valve 9, the pipe 45, the chamber 49m, and a passage 49n in the pin valve 49. This supply is restricted by an adjustable pin valve 45b. The diaphragms are formed of flexible corrugated metal or of leather or rubber and have segmental supports on the side opposite to that on which the maximum pressure acts.