Patent GB-190819353-A (GB)
Title: Improvements in and relating to Air-brakes.
Inventor: LAKE WILLIAM EDWARD
Filed: 1908-09-15
Granted: 1909-03-25
Abstract: 19,353. Lake, W. E., [St. Clair Air Brake Co.]. Sept. 15. Brakes.-Relates to compressed - air brakes for railway &c. vehicles, of the type described in Specification No. 11,239, A.D. 1907, in which the brakes are held off by fluid pressure against the action of springs, and, during application, part of the fluid pressure can be transferred to the opposite side of the piston to assist the springs, and consists in providing an improved valve for allowing a predetermined local venting of the train-pipe during service applications, for permitting gradual release and applications, and also for permitting a local venting of the train-pipe in emergency applications. Fig. 1 shows the general arrangement, in which the brake cylinder is divided by the piston 22 into chambers 20, 21 which are connected by a passage 25 through the valve 29. A valve chamber 27, Fig. 3, is connected to the train-pipe at 66 and contains a piston 31. The valve ring 29 is mounted in a recess in the piston so as to leave an annular space 30 between the ring and the piston, and the ring can move axially in the recess relatively to the piston. Mounted at each side of the piston 31 is a buffer plunger 35, 40 pressed outwards by springs, and the chamber 20 is open to the interior of the valve ring through an opening in the end of the plunger casing 35 and a passage 39. The valve ring 29 contains an L-shaped port 42 for connecting the interior of the valve to the passage 25 when the brakes are to be applied, and also a cavity 47 for connecting the passage 25 to the exhaust port 46 when the valve is in running position as shown in Fig. 3. The cavity 47 is connected by a passage 64', Fig. 9, to a cavity 64 which normally registers with a port 62, Fig. 10, in the valve seat 27<1>. The port 62 leads to a venting-chamber 60, Fig. 3, so that the latter is open to the exhaust port 46 in the running-position of the valve. The valve 29 contains also a port 50 having an extension 50<1>, Fig. 12, which, in normal position of the valve, registers with a port 51 so that the interior of the valve 29, and consequently the chamber 20, is in communication with the train-pipe passage 66 through a passage 52 and port 53. The inner end of the port 42 is extended at 42<1>, Fig. 9, in order to register with the port 51 when the valve is in emergency application position, and thus locally exhaust the train-pipe. In the head of the valve chamber is a perforated partition 67 carrying a bushing 69, which is formed with an annular port 70 leading to the passage 25. A valve 73 normally closes the port and is held in position by a spring 75 which is stronger than the spring 41. In operation, assuming the parts to be under no air pressure, the springs, shown in Fig. 1, will move the piston 22 to its extreme position, applying the brakes. Train-pipe pressure introduced at 66, Fig. 3, forces the valve piston 31 and valve 29 to the left and compresses the buffer spring 36, so that the air passes through the port 53, the passage 52, and the ports 51, 50 into the interior of the valve 29, whence it passes through the openings 39 into the chamber 20. When the pressures on the two faces of the piston 31 are nearly equal, the spring 36 moves the piston and valve slightly to the right to the position shown in Figs. 3 and 12, so that communication between the two sides of the piston takes place only by the restricted portion 50<1> of the port 50. At the same time the port 47 connects both the venting- chamber 60 and the passage 25, leading to the forward end of the cylinder, to the exhaust port 46. For a service application, the driver's valve is slightly opened to reduce the train-pipe pressure sufficiently to cause the piston 31 in the leading coach to move the valve ring 29 until the buffer 40 comes against a stop. In this position, a cavity 63, Fig. 9, in the valve ring connects the ports 51, 62, Fig. 10, and the train-pipe discharges into the chamber 60, thereby producing a reduction of train-pipe pressure sufficient to cause the operation of the succeeding valve. At the same time the chamber 20 discharges through the L-shaped port 42 into the passage 25 to equalize the fluid pressure on both sides of the piston and allow the spring to apply the brakes. As soon as the pressure in the chamber 20 falls below the pressure in the train-pipe, the piston 31 moves to the left and closes the outer end of the port 42. When the fluid pressures on the two sides of the brake piston have equalized, a further reduction of train-pipe pressure causes the piston 31 to move to compress the spring 41, and in this position of the valve the port 42 partly registers with the exhaust port 46, so that the fluid in the chamber 20 escapes to the atmosphere and allows the fluid in the chamber 21 to assist the springs in the application of the brakes. In an emergency application, the train-pipe pressure is greatly reduced and the piston and valve 29 move to the right, compressing both of the springs 41, 75, Fig. 6, and unseating the valve 73. In this position of the valve, the air in the chamber 20 passes through passages 80, 81 into the chamber 65 and thence through the port 70 and passages 71, 25 into the forward end of the brake cylinder. The chamber 20 is also connected to the exhaust port 46 through the port 42, and the extension 42<1> of the port 42 registers with the port 51 to vent the train-pipe to atmosphere.