Patent GB-236048-A (GB)
Title: Compressed air brake for railway vehicles
IPC: B60T15/18
Filed: 1924-07-14
Abstract: 236,048. Kasantzeff, F. July 14, 1924. Fluid-pressure. - In compressed-air brakes of the type using two train pipes, the valve supplying air from the main reservoir to the feed pipe which supplies the auxiliary reservoirs is arranged, when the driver effects a reduction of pressure in the main pipe, to increase the pressure in the feed pipe, so that the brakes are applied rapidly and with increased power; whilst release is assisted on restoring the pressure in the main pipe, by equalizing the pressure in the feed pipe and auxiliary reservoirs with the pressure in the main pipe through the distributors, which are of special construction. A special form of driver's valve is also used. Fig. 1 shows the general arrangement on the locomotive and one vehicle. The main reservoir 1 is connected by a pipe 11 to the regulating-valve 2 and by a pipe 12 with the driver's valve 3, which is also connected by a pipe 19, cock 4 and branch 16 to the main train pipe 17, and by a pipe 20 and branch 14 with the feed pipe 15 supplying the auxiliary reservoirs 10, which are connected through distributors 5, 6 with brake cylinders 7. The valve 2 is also connected by a pipe 18 to passages in the cock 4 communicating with the branch 16, so that any changes in pressure in the main pipes are transmitted to it. As shown in Fig. 2, the valve 2 comprises a pair of differential pistons 27, 29 controlling communication between a passage 25 leading from the main reservoir and a passage 26 leading to the pi pes 14, 15. The upper face of the piston 29 is subject to a constant pressure, the value of which is determined by the spring loading of a diaphragm 31 controlling a supply valve 33 and the chamber 36 below the piston 27 is subject to the main pipe pressure through the pipe 18 and cock 4. When the main pipe is fully charged, the valve 2 maintains the normal pressure in the feed pipe, any losses due to leakage being made up through the feed passage 28, whilst on a reduction of main pipe pressure, the pistons 27, 29 descend to increase the pressure in the feed pipe and auxiliary reservoirs until the upward pressure on the piston 29 is sufficient to compensate the loss of pressure beneath the piston 27. As shown in Fig. 3, the driver's valve 3 comprises a chamber 38 connected by an aperture the size of which may be adjusted by a screw 40 to the pipes 20, 14, 15, and a second chamber 47, connected by the pipe 19 through the cock 4 to the main pipe 17, and by diaphragm controlled valves 49, 52 respectively with the atmosphere and the passage 51 connected to the pipe 12 from the main reservoir. By controlling the exhaust from the chamber 38 through a restricted passage 45 and past a needle valve 41 to exhaust ports 42, the driver can vary the pressure in the chamber 38, when the movement of the diaphragms 50, 53 effects corresponding pressure variations in the main pipe, whilst any loss by leakage is automatically made up by a further supply of air through the valve 52. Fig. 5 shows the distributor 5 on the locomotive, which comprises a piston 66 subject on one side to auxiliary reservoir pressure at 67, and on the other side to main pipe pressure supplied through a passage 65, the piston being adapted to slide on a bearing 69 through which slides a valve stem 71 controlling an opening 68 which provides communication between the passage 65 and the auxiliary reservoir through a channel 70. The stem 71 is connected to a piston 72 subject on its right hand face to brake cylinder pressure. Normally the parts occupy the position shown, so that the brake cylinder exhausts through a passage 77, but on a reduction of pressure in the main pipe, the piston 66 moves to the right to close the opening 68 and thereafter auxiliary reservoir pressure, augmented by the increased pressure in the feed pipe, moves the piston further to close the exhaust 77 and open the valve 78 to supply air to the brake cylinder through the passages 79, 74 until the brake cylinder pressure is sufficient to move the parts to a middle position with all the ports closed. When the main pipe pressure is restored, the parts return to the position slaown, so that the feed pipe and auxiliary reservoir pressures equalize with that in the main pipe to secure an effective release of the brakes. The distributor on each vehicle comprises, as shown in Fig. 6, a central diaphragm 80 and a pair of differential diaphragms 81, 82, the main pipe, auxiliary reservoir, and brake cylinder being connected respectively to the passages 65, 67 and 74. In this form, communication between the main pipe and the auxiliary reservoir is effected through an opening 85 in the diaphragm 80 controlled by a valve 86, which is always closed unless the part 87 contacts with the valve casing. All the diaphragms are carried on a member 89 having an exhaust passage 90 controlled bv a valve 91. When the main pipe is fully charged, the diaphragm 80 is flexed to the left, as the diaphragm 82 is smaller than the diaphragm 81, and the passage 85 opened so that the pressures on each side of the diaphragm 80 are equalized, whilst the brake cylinder exhausts through the passages 74. 93. 90. When the main pipe pressure is reduced, the diaphragm 80 moves to the right to close ,the. passage 85, and auxiliary reservoir pressure, augmented by the increased feed pipe pressure, moves the, whole diaphragm system further to the right to close the passage 90 and move the valve 91 off its second seat to supply air from the auxilary reservoir through passages 67, 92, 74 to the brake cylinder until the back pressure therein moves the system to a neutral position. In the event of leakage from the brake cylinder, both distributors 5, 6 will automatically restore the braking pressure. The cock 4, Fig. 1, which normally connects the main pipe to the driver's valve may be turned to exhaust the main pipe rapidly to give an emergency brake application; or to connect the feed pipe to the main pipe for a rapid release; or, in the case of double heading, to isolate the driver's valve from both train pipes. Specification 236,049 is referred to.