Patent GB-190715967-A (GB)
Title: Improvements in Air Brakes.
Inventor: DYKE THOMAS HOOKER VAN
Filed: 1907-07-11
Granted: 1908-06-11
Abstract: 15,967. Dyke, T. H. van. July 12, 1906, [date applied for under Patents Act, 1901]. Brakes.-In an air brake of the type in which the slack in the rigging is first taken up by the transfer of compressed air from one side of the main brake piston to act upon an auxiliary piston, and the brakes are then pressed on to the wheels by air being exhausted to the atmosphere from the same side of the main brake piston, the piston is held in the release position without the use of springs ; the train-pipe is vented to the atmosphere at the distributing- valve in emergency applications ; a leak-off valve is provided to permit of the gradual reduction of the initial braking pressure to a certain limit, and subsequent leakages are automatically compensated for ; and a manually-operated valve is provided on the distributing-valve by which the leak-off valve can be cut out of action and the braking pressure can be varied on loaded and unloaded cars. The brake piston has two heads 17, 19, Fig. 1, connected by a rod 18, to which is resiliently connected a sleeve 22, which slides through the end 3 of the brake cylinder 1 and carries a sliding push-rod 27 connected to the rigging. The piston head 17 separates the chamber 31 of the brake cylinder from the chamber 32, and the head 19 separates the chamber 21 from the chamber 31. The distributing-valve 4 is shown in Figs. 1, 4, 5 12, and 14 ; Fig. 1 showing a section on the broken line a b h c, Fig. 4, Fig. 12 a section on the line h c, Fig. 5 a section on the line a d looking in the direction of arrow A, and Fig. 14 a section on the broken line a e f g looking in the direction of arrow B, while Fig. 4 shows a section on the line o p, Fig. 5. This valve contains chambers 5,6 separated by a partition in which is secured a valve seat 7, upon the opposite faces of which are mounted rotary disk valves 8, 9. The parts and cavities in these valves and their seat are shown developed in four different relative positions in Figs. 18, 19, 20, and 21. In the release position, Figs. 1, 14, and 18, air from the train-pipe 49<1> flows past the piston 45 into the chamber 5, and thence, through registering ports 106, 107, 108 in the valve 8, seat 7, and valve 9 respectively, into chamber 6, whence it flows into the chamber 32 of the brake cylinder through a passage 33, Figs. 1 and 14, and into the chamber 31 through a port 41 in the valve 9, a port 35 in the seat 7, and passage 34, Figs. 1 and 12 ; at the same time, the brake-cylinder chamber 21 is connected to the atmosphere through a passage 36, a port 38 in the seat 7, a recess 109 in the valve 8, a port 110 in the seat 7, a recess 111 in the valve 9, and the arm 112 of a bifurcated recess 113, Fig. 12, in the seat 7 which connects to the atmospheric passage 114. When train-pipe pressure is reduced for a service application, the piston 45 moves to the right until its head 57 is arrested by a spring stop 55, cutting off the chamber 5 from the train-pipe. During this motion, the pistonstem 43 swings a bell-crank graduating-valve 40 against a pin 121 on the valve 8, moving the nose of the bell-crank out of a port 58 in a housing 61, which covers ports 59, 60, Figs. 18-21, in the valve 8, and rotating the valve 8 into the position indicated in Fig. 19. In this position, air flows from the chamber 31 to the chamber 21 (which is disconnected from the atmosphere) through the passage 34, port 35, cavities 109, 38, and passage 36, and from the chamber 32 to the chamber 21 through the chamber 6, ports 41, 35, &c., and moves the brake piston out to take up the slack in the rigging ; the chamber 5 is disconnected from the chamber 6, the chamber 21 is connected to a chamber 69 in the triple valve through a passage 37, cavities 39, 73, 72, and passage 71 ; and the chamber 5 is connected to a chamber 63 through ports 58, 59, cavity 62, 79, 77, Fig. 12, and passage 78, and when the pressure in chamber 5 is sufficiently reduced, piston 45 is moved back towards the position shown in Fig. 14 far enough for the nose of the bell-crank 40 to close the port 58 in the housing 61 and shut off the chamber 63 from the chamber 5, but not far enough to move the valve 8. When the pressure in the chamber 69 has risen sufficiently, a piston 70, Figs. 5 and 14, is moved until its stem 66 strikes a piston 82, and in this movement it rotates, for the first time, the valve 9 into the position indicated by Fig. 20. Ports- 35, 41 are then disconnected, so that the brake-cylinder chamber 32 is shut off from the chamber 31 ; and the chamber 32 is connected to the atmosphere through the chamber 6, ports 122, 123, recess 124, recess 74, and passage 75. As the air escapes from chamber 32, the pressure in the chambers 21, 31 presses the brake blocks on to the wheels. By means of a hand valve 100, Fig. 4, the chamber between the pistons 82, 83, Figs 5 and 14, can be connected to, or disconnected from, the chamber 63. For a loaded car, these chambers are disconnected, so that the pressure in the chamber 63 acts on the larger piston 83 ; for an empty car they are connected, and the effective pressure in chamber 63 then acts upon the smaller piston 82. When the pressure in the chambers 6, 32 has fallen sufficiently for the air in the chamber 69 to move the piston 70 to the inner end of the chamber 69 in opposition to the pressure in the chamber 63 on the piston 82 or 83, the valve 9 will be further rotated into the position shown in Fig. 21, moving the ports 122, 123 out of register, and stopping the exhaust from the brake-cylinder chamber 32. The brakes will then be held on with the distributing-valve in lap position, and any leakage of air past the brake piston head 17 from the chamber 31 to the chamber 32 will move the piston 70 to reconnect the ports 122, 123 and allow air to escape from the chamber 32 to compensate for the leakage. To allow the initial braking pressure to leak off to a certain limit, the hand valve 100, Fig. 4, can be set to connect the brake - cylinder chamber 31 to the chamber 32 through a passage 94, Fig. 5, valve chamber 87, passage 95, and passage 98, Fig. 4. The pressure in the chamber 31 moves the spring- pressed piston valve 88, Fig. 5, to the left, and passes to chamber 32 through grooves 93 ; as the pressure in chamber 31 falls, the spring 92 moves the piston 88 over a deeper part of the groove, so that the brake pressure falls at an increasing rate to a certain limit, when the piston-valve 88 is seated. In emergency applications, the spring 54, Fig. 14, is compressed, and the valve 8 is rotated sufficiently to connect the train-pipe to the atmosphere through the passage 116, cavities 117, 118, port 119, cavity 120, and the arm 115 of the bifurcated cavity 113, and air flows from the chamber 5 to the chamber 63 through the port 60 as well as the port 59. When the train-pipe pressure is increased to release the brakes, the piston 45 and valve 8 are returned to the position shown in Figs. 14 and 18, and since the valve 9 remains in the position shown in Fig. 21, air passes from the chamber 21 to the chamber 32 through the cavities 38, 109, ports 110, 125, and chamber 6, and the increased pressure in the chamber 6 returns the valve 9 to the position shown in Fig. 18, in which the chambers 63, 69 are connected to the exhaust. The air remaining in chambers 31, 32 permits a second application of the brakes to be made without recharging the system.