Patent GB-150732-A (GB)
Title: Improvements in automatic high speed compressed air brakes
IPC: B60T1/10
Filed: 1920-09-04
Abstract: 150,732. Cesar, V., and Franchimont, E. Sept. 5, 1919, [Convention date]. Void [Published under Sect. 91 of the Act]. Fluid-pressure.-An automatic braking system has combined therewith a compressor on each vehicle actuated by the running wheels and thrown into operation in emergency linking to intensify the braking pressure produced by the auxiliary reservoirs. By the stopping of the compressor if the wheels lock, and the provision of a leak-off passage from the brake cylinder, the brake blocks are applied at about the skidding pressure at all speeds. The leak-off passage may feed the auxiliary reservoirs, and the supply thereto from the train-pipe be thereby rendered unnecessary. The train-pipe may be connected to the brake cylinder in applications, and release of the brakes to effect a braking by train-pipe air alone or in part to accelerate the depression or increase of train-pipe pressure. Release of the brakes may be effected in stages. Movement of the distribution valve may be checked by a dash-pot device. The apparatus shown in Fig. 1 comprises a. main reservoir 1, driver's valve 4, distributor 23, auxiliary reservoir. 27, brake cylinder 33, and compressor 41. In running conditions, the train-pipe 10, 17 is fed through the adjustable valve 12, and the passages 10, 8 of the driver's valve. The auxiliary reservoir is supplied from the train-pipe by the pipe 30 and non-return valve 28. The chambers 18 and 24 of the distributor are open to the train-pipe, there being connexions 60, 22 for the chamber 24. The chamber 25 is connected to atmosphere through an adjustable passage 26 which constitutes a dashpot device for checking the movement of the slide valve 20. The brake cylinder 33 and the compressor chamber 48 are open to atmosphere by the pipes 51, 55 and passages 55<1>, 21, 61. The compressor is adapted to be actuated by the engagement of a roller 46 on a lever 44 with a cam 47 on the wheel axle 39, and is held out of engagement when the compressor chamber is open to exhaust by a. counterweight 44<1> or a spring. For a moderate application of the brakes the train-pipe pressure is reduced sufficiently by connecting the passage 9 of the valve 4 to the pipe 13 to cause the distributor slide 20 to register the passage 21 with the port 58<1> whereby the trainpipe is connected to the brake cylinder 33 through the pipes 58, 55. The chamber 24 of the distributor is cut off from the train-pipe at the pipe 60 when the valve 20 moves down, and the expansion of the air in this chamber together with that of the spring 24<1>, if provided, determines the position taken up by the valve in correspondence with the reduction effected in the chamber 18. The passage 22 and pipe 60 may be dispensed with. With a further reduction of train-pipe pressure for normal braking the passage 21 connects the passages 59', 55', and air is then supplied to the brake cylinder from the auxiliary reservoir 27 by the pipes 30, 59, 55. For emergency braking the train-pipe pressure is further reduced and the port 21 then connects the passages 59<1>, 57<1> so that air from the auxiliary reservoir flows into the compressor chamber 48 and the brake cylinder by the pipes 59, 57, 51 past the non-return valves 49, 50. The pressure in the chamber 48 forces the roller 46 into engagement with the cam 47, and the compressor is then actuated to draw further air from the auxiliary reservoir and force it into the brake cylinder. The pressure in the brake cylinder can leak back into the auxiliary reservoir by the pipe 54, non-return valve 53, and an adjustable passage 52, so that if the braking pressure becomes sufficient to lock the wheel 38, and thereby stop the working of the compressor, the pressure in the brake cylinder falls and the wheel is again unlocked. A cycle of operations is thus established by which the braking pressure is maintained at about the value at which the wheel is locked, this pressure thus diminishing automatically with the speed of the train. When the train has stopped normal braking is automatically reestablished. The condition of normal braking after emergency braking may be re-established during the running of the train upon raising the train-pipe pressure, by connecting the passage 9 of the driver's valve 4 to the supply pipe 11, sufficiently to register the port 21 with the pipes 55, 59, thereby connecting the brake cylinder to the auxiliary reservoir and cutting off the supply to the compressor, the actuating member 44, 46 of which is thereupon maintained out of contact with the cam 47. Further increase of train-pipe pressure moves the distributor to the position in which the brake cylinder is connected to the trainpipe, thus further reducing the braking pressure. According to the arrangement shown in Fig. 2, the compressor 41 is provided with a lower chamber, which is connected to the train-pipe at 72, and a spring 71 further tends to hold the actuating mechanism of the compressor in the inoperative position. The connexion of the auxiliary reservoir 27 and the chamber 24 of the distributor 23 with the train-pipe is by a port 66 in the chamber 18, so that the connexion is cut off when the piston 19 moves downwardly. The chamber 24 is connected to the auxiliary reservoir through an adjustable passage 67, and to the chamber 25 by a passage 65 in the slide valve 20, thus providing a check to the movement of the valve. The passage 65 may be dispensed with, and the chamber 25 be connected to atmosphere at the lower position of the piston 19. The port 21 of the valve 20 normally connects the compressor chamber 48 and the brake cylinder 33 to the exhaust port 61. When the train-pipe pressure is reduced the piston 19 moves to its extreme lower position, the port 21 momentarily connecting the ports 58<1>, 55<1> so as to vent the train-pipe to the brake cylinder by pipes 58, 54 and then connecting the pipes 30, 57 to open the auxiliary reservoir to the compressor chamber 48 and the brake cylinder 33. If only a moderate train-pipe pressure reduction has been made, the compressor remains inoperative, but if the pressure in the train-pipe and thus in the compressor chamber 70 is reduced substantially to atmosphere the pressure in the chamber 48 forces the piston 42 and mechanism 44, 46 into operative engagement with the cam axle 47, thereby giving the maximum braking pressure as previously described. When the trainpipe pressure is raised the compressor is thrown out of action, and the condition of moderate braking restored before the pressure rises sufficiently to return the distributor to normal position for the complete release of the brakes. The connexion of the brake cylinder to the train-pipe by the port 21 during the return movement accelerates the increase of train-pipe pressure. A complementary compressing piston or snifting device may be connected to the chamber 48 adapted to take in air from the atmosphere so as to compensate for losses of air in the system, the auxiliary reservoir having a valve to limit the pressure therein. Means for supplying this reservoir from the train-pipe may in this case be dispensed with.