Patent GB-190611459-A (GB)
Title: Improved Devices for Controlling Brake Cylinder Pressure in High Speed Brakes
Inventor: TURNER WALTER VICTOR
Filed: 1906-05-16
Granted: 1906-08-30
Abstract: 11,459. Turner, W. V. May 26,1905, [date appliedfor under Patents Act, 1901]. Brakes.-Valve devices for controlling brakecylinder pressure, which limit the pressure in service applications and permit of a higher initial pressure in emergency applications, described in Specification No. 29,040, A.D. 1904, are adapted to hold this higher pressure for the en tire period o f an emergency stop or to permit of its being gradually reduced to the maximum service pressure, or to a pressure higher than this, with or without an initial predetermined period of full emergency pressure. In the arrangement shown in Fig. 1, the brakecylinder connexion 1 leads into a chamber 2 in which works a slide valve 8 operated by the common stem 5 of two pistons 6,7, which are normally kept in the position shown by springs 11, 14 and stems 12, 13. In service applications, the pressures equalize on both sides of the pistons, and no movement takes place unless the brake-cylinder pressure, acting through a passage 10 on a diaphragm 16, rises sufficiently to overcome an adjustable spring 26 and move a stem 30 to open a valve 17. In this case, the chamber 3 is exhausted, and the pistons move to the left to bring a port 31 in the slide valve over an exhaust port 9, through which the brake-cylinder pressure leaks off to the maximum permitted by the spring 26. In emergency applications, the sudden increase of pressure acting upon the larger piston 7 moves the slide valve 8 to cover the port 10, whereby the regulating-device 16, 26, 30 is cut out until the pressures have substantially equalized, through a passage 23 in the piston 7, in the chamber 2 and chambers 4, 25, when the slide valve is moved back and the port 10 uncovered. The high pressure thus suddenly admitted against the diaphragm 16 opens wide the valve 17, and the pistons and slide valve are moved to their extreme left-hand position, the port 31 travelling over and beyond the port 9, so that substantially the full braking pressure is retained in the cylinder during the stop; or the port 9 may be arranged to be slightly opened, allowing the brake-cylinder pressure to leak off to the value for which the spring 26 is set. The slide valve may be adapted to connect the ports 10, 9 while the regulating-device 16, 26, 30 is cut out, to prevent an accidental accumulation of pressure against the diaphragm 16. To obtain in emergency applications a final pressure of higher value than the maximum allowed in service applications, there may be provided in the slide-valve seat a port 33 leading to a valve 27. This valve controls the communication to an exhaust port 29, and is normally held closed by a spring 28 which can be set to any desired pressure. The port 33 is normally closed, but is opened when the slide valve moves to its extreme left-hand position, in which the port 9 is covered, after the predetermined initial period of full emergency cylinder pressure. In a modified construction, when the pistons and slide valve are first moved to the right in emergency applications, the chambers 4, 25, as well as the passage 10, are connected to atmosphere through a cavity in the slide valve, the passage 23 in the piston 7 being omitted. The slide valve thus remains in this position, in which the port 33 is uncovered, so that the cylinder pressure at once commences to leak off to a degree depending upon the compression of the spring 28. In the device shown in Fig. 5, the brake-cylinder pressure, in service applications, can readily equalize around the piston 7 through passages 10, 101, and the passage 10, leading to an ordinary low-pressure blow-off valve 81, remains uncovered so that the cylinder pressure is limited by an adjustable spring 261. The port 33, leading to a high-pressure blow-off valve 27, is constantly open. In emergency applications, the piston 7 is moved over against its gasket 21, cutting out the low-pressure valve and connecting the right-hand slide of the piston to the atmosphere through passages 101, 10, 32, 9. The cylinder pressure is then governed by the high-pressure valve 27, and may be reduced at any required rate by adjusting the size of the ports.