Patent GB-264197-A (GB)
Title: Improvements in or relating to compressed-air brakes
IPC: B60T15/30
Filed: 1925-08-13
Abstract: 264,197. Drolshammer, I. Aug. 13, 1925. Fluid - pressure.- Valve mechanism for controlling the exhaust or the supply and exhaust of the brake cylinders in an automatic compressed-air brake system comprises a control piston subject to the initial train-pipe pressure, the varying train - pipe pressure and to a spring whereby the piston has a progressive movement corresponding to the variation of the pressure effected in the trainpipe in applying and releasing the brakes, the piston being unaffected by the value of the initial train-pipe pressure. The piston controls through an interposed spring a piston valve subject to the pressure in the brake cylinder for controlling the supply and exhaust and for venting the train-pipe thereto. The apparatus also includes means as described in Specification 214,092 for varying the rate of supply to the brake cylinder. As shown in Fig. 1, the main valve piston K1 is connected to a counterbalancing piston K by a rod d upon which is slidable a piston valve s between which and a collar T1 fixed to the rod d is interposed a spring F1. A spring F2 acts on the piston K1. The train-pipe is connected through a non-return valve and passage E1 to the auxiliary reservoir B and through passages (not shown) in a cock H and a passage o to the chamber R1 above the piston K. Air from the train-pipe also flows to the chamber R below the piston past the packing 9 which serves as a non-return valve. With the valve in the release position as shown the brake cylinder connected at C is open to atmosphere by the passage g and ports h and i. When the pressure in the trainpipe and chamber R1 is reduced to apply the brakes the piston K1 moves upwards against the tension of the spring F2 to a definite position determined by the amount of the pressure reduction, and moves the valve s by the interposed spring F1 to cover the exhaust port hand uncover the port k to which leads the supply passage E from the auxiliary reservoir. The apparatus is provided with a cock H and an arrangement of supply passages for the brake cylinder such as is described in Specification 214,092. With this cock H in the position shown air is then supplied to the brake cylinder at first by the wide port w1 in the cock, passages 1, 2, 3, groove 4, a passage (not shown) in the liner L, the recess k3, port k, recess a and passage g and also by the restricted passage w2 in the cock H and port k. The trainpipe also is vented to the brake cylinder by the pipe x4 and port x1 and if the train-pipe pressure reduction is rapid, also by the pipe x6 and port x2. When the brake cylinder pressure acting on the piston area of the valve s has built up to a value corresponding to the train-pipe pressure reduction, the valve s compresses the spring F1 and moves back to cover the supply ports k, x1, x2. The brake cylinder pressure may thus be progressively increased. It may also be progressively decreased by raising the train-pipe pressure, the valve s being moved at each stage alternately to open and close the exhaust port h. The pressure in the brake cylinder acting through the valve s and spring F1 on the piston K1 is counterbalanced by this pressure acting on the piston K. The chamber R may as shown be connected to the auxiliary reservoir through a non-return valve V3 to prevent leakage from this chamber causing release of the brakes, particularly after an emergency application. In a modification, Fig. 2, adapted to diminish leakage past the valves, the supply valve s1 is separate from the exhaust valve s2 and is connected thereto by a rod m with limited freedom for independent movement. The piston K1 actuates the valves through the spring F1, interposed between plates p, q, the several connections between the parts being of a flexible character. The supply valve s1 is formed with an annular part b adapted to be held against a seating c by the brake cylinder pressure acting on the upper part of the valve through a channel f. In a further form, the exhaust passages r, t, u are replaced by a lift valve arranged in the valve member s2 and opened by abutting against a fixed part. The spring F2 may be dispensed with, the compression of spring F1 alone determining in this case the position of the piston K1. The apparatus may be used as a graduating release valve for use with the Westinghouse brake by connecting the passage c, g to the exhaust port of the Westinghouse valve and by plugging the connection E for the auxiliary reservoir.