Patent GB-366495-A (GB)
Title: Improvements in and relating to railway brakes
IPC: B60T15/30
Filed: 1930-09-27
Abstract: 366,495. Fluid - pressure brakes. MATROSOFF, I. K.; 26/2, Ulica Truda, Dietskoje Scelo, Leningrad. Sept. 27, 1930, No. 29028. [Glass 103 (i).] Control valve mechanism for automatic compressed air brakes comprises an auxiliary valve controlled directly by the train-pipe pressure and adapted in applying the brakes, to cut off the control chamber of the main valve from the train pipe and to connect it to the brake cylinder. The main valve is subject to direct control by the brake cylinder pressure. The time taken for the brake cylinder pressure to reach a predetermined pressure is the same irrespective of the capacity of the auxiliary reservoirs or brake cylinders. The brake cylinder pressure obtained by a given train-pipe pressure reduction may be varied. Fig. 1 is a view of the apparatus in normal release position and Fig. 3 a diagrammatic view in maximum application position. The auxiliary valve piston 1 connected to the slide valve 2 is subject to the trainpipe pressure in chamber 15 and to that in a chamber 19 which is also one control chamber of the main valve piston 3. The other side of the piston 3 is open to a control reservoir 22. The piston 3 actuates the rod 6 of a slide valve 4 by means of an inclined slot 46 on the piston-rod and a pin on the valve rod. A second valve 9 rides upon the valve 4 and is connected to a piston 8 the left-hand chamber 34 of which is permanently connected to the brake cylinder 26 by passages 35, 26<1> while the other side of the piston abuts on springs 11, 12. The spring 12 may be rendered inoperative to give a lower brake cylinder pressure for a given train-pipe pressure reduction as on a lightly loaded vehicle by turning the cap 13 which has a helical slot engaged by fixed pins to impart to it an axial movement. Normally air from the train pipe is supplied from chamber 15 through the groove 16 and port 18 to chamber 19 thence through the passage 20 around the piston 3 to the chamber 21, 22. The auxiliary reservoir 25 is charged by passages 43, 42 in the valve 2 and also by way of the chamber 19 and through ports 23, 25<1> in the valve 4. The brake cylinder 26 is open to exhaust through ports 26<1>, 27, 28, 29, 31, 32 in the valves 4, 9. When the trainpipe pressure is reduced to apply the brakes, the piston 1 moves to the right and the valve 2 (1) connects the train pipe to atmosphere through passages 41, 45, 40 in valve 2 and ports 401, 32 in valve 4, (2) vents the chamber 19 to the brake cylinder through passages 36, 27, 26<1>. The piston 3 therefore rises closing the chamber 21, 22 and shifting the valve 4 to a position such that (1) the passage 40<1> is covered, disconnecting the train pipe from the atmosphere, (2) the auxiliary reservoir supply port 23 is covered, (3) the port 28 is moved from beneath the passage 29 to beneath the passage 38 so that the brake cylinder is cut off from the exhaust port 32 and connected by the port 28 and passages 24, 251 to the auxiliary reservoir 25, (4) the venting of the chamber 19 to the brake cylinder is continued but through a restricted passage 33 in the valve 4. When the brake cylinder pressure acting on the piston 8 is sufficient to overcome the initial stressing of the springs 11, 12 this piston and the valve 9 commence to move to the right. If the trainpipe pressure reduction is stopped, the valve 2 returns to close the vent passage . 36 of the chamber 19 when the pressure in this chamber has equalized with the train-pipe pressure. The piston 3 rises to a position corresponding to the reduced train-pipe pressure by reason of the expansion of the air in chamber 21, 22 and when the brake cylinder pressure has reached a value sufficient to displace the piston 8 and valve 9 to an extent equal to the displacement of the valve 4 the supply from the auxiliary reservoir to the brake cylinder is cut off. The rate at which the brake cylinder pressure rises is dependent upon the speed of movement of the valve 4 for if the pressure rises too rapidly so that the valve 9 overruns the valve 4 the port 28 tends to become closed to the supply passage 38 and may come to register with the passage 29 to release any excess of pressure and if the pressure rises too slowly the port 28 opens more widely to the passage 38. The speed of the valve 4 is dependent upon the calibre of the restricted venting passage 33 for the chamber 19 and upon the inclination of the slot 46 in the rod of the piston 3. The rate of rise of the braking pressure and the time taken to reach the maximum pressure is thus the same for all sizes of brake cylinders and any desired curve of braking pressure may be obtained. The maximum brake cylinder pressure is determined by the movement of the piston 3 to the top of its cylinder. The release of the brake cylinder pressure may also be graduated by raising the train-pipe pressure in stages, the supply through the port 18 in the piston 1 causing the return of the piston 3 and valve 4 and the consequent movement of the valve 9 and exhaust of the brake cylinder through the passages 29, 32. The rate at which the brakecylinder pressure falls is determined by the size of the port 18. The upper part of the slot 46 is parallel to the axis of the rod of the piston 3 so that the brake-cylinder pressure is completely released somewhat before the pressure in the train pipe and auxiliary reservoir has reached the normal value.