Patent GB-190711239-A (GB)
Title: Improvements in Air Brakes.
Inventor: LAKE HAROLD WILLIAMSON
Filed: 1907-05-14
Granted: 1908-05-07
Abstract: 11,239. Lake, H. W., [St. Clair Air Brake Co.]. May 14. Brakes.-A compressed-air brake, which can be used in a train with the ordinary automatic compressed-air brake, is normally applied by springs and held out of action by fluid pressure, so that it is applied if the pressure supply fails ; when the brake is applied, some of the opposing fluid pressure is transferred to the other side of the brake piston to assist the application-springs ; and arrangements are provided whereby, when a train is on a long gradient, some of the brakes may be kept continuously applied while the others can be operated as usual.. The brake. cylinder comprises an air chamber 16 and a spring chamber 17, separated by the brake piston 18 which is acted upon by a compression spring or springs 21 tending to force it to the end 22 of the chamber 16 to put the brake on. A valve chamber 23 on the end of the brake cylinder is connected to the train-pipe at 51 and contains a piston 25. A ring 29 is arranged in a circumferential recess in the piston 25 so as to leave an annular chamber 29<1> between the ring and the piston, and the ring can move axially in the recess relatively to the piston. In the running position, Figs. 3 and 8, train-pipe pressure moves the piston 25 up to the left-hand end of the chamber 23, the ring 29 being at the right-hand side of the recess in the piston. Air then passes from the train-pipe to the chamber 16 through a passage 38, 39 in the wall of the chamber 23, a valve-controlled passage 37 through the ring 29, the chamber 29', and a port 29<11> in the piston 25, and moves the brake piston 18 to the release position, Fig. 2 ; and a cavity 36 in the ring connects the spring chamber 17 to atmosphere through passages 42, 41, 40, 44, and 45. On a reduction of train-pipe pressure to apply the brakes, the piston 25 moves to the position shown in Fig. 4, the ring 29 passing to the left-hand side of the piston recess. The passage 37 is thus moved out of register with the passage 39, so that the chamber 16 is shut off from the train-pipe ; the spring chamber 17 is shut off from the exhaust ; and a right-angled passage 35 in the ring 29 is uncovered, allowing air from the chamber 16 to pass to the chamber 17, through the port 29<11>, chamber 29<1>, and passages 35, 40, 41, 42, and assist the springs to apply the brakes. When the pressure in chamber 16 has fallen sufficiently, the train-pipe pressure will move the piston 25 back till it closes the righthand end of the passage 35 in the ring, this being the lap position of the valve. By further reducing the train-pipe pressure, the brake pressure can be increased. If a greater braking pressure than that exerted by the springs is required, the train-pipe pressure is further reduced, whereby the piston 25 is moved to the right-hand end of the chamber 23, and the chamber 16 is connected to atmosphere through port 29<11>, chamber 291, and passages 35, 44, 45, so that the pressure of the springs is augmented by the air pressure in the spring chamber 17. To retain some of the brakes in operation while the train is on a gradient, a certain number of the exhaust pipes 45 are closed by cocks, so that the brakes on those vehicles will not be released with the others. They can, however, be released by increasing the train-pipe pressure sufficiently to overcome the pressure of the springs and the air in the chamber 17 ; but after all the brakes have been subsequently applied, and trainpipe pressure again increased to the normal to release them, the brakes with the closed exhaust pipes will remain 'on.' Hand-operated means may be provided for taking the brakes off irrespectively of the air pressure.