Patent GB-299794-A (GB)
Title: Improvements in and connected with compressed air brakes
IPC: B60T15/04
Filed: 1928-10-31
Abstract: 299,794. Bozic, D. Oct. 31, 1927, [Convention date]. Fluid-pressure.- In drivers control valves for fluidpressure brake apparatus, wherein the train-pipe pressure is varied for operating the brake and maintained at the adjusted value by the pressure of a spring acting on a piston which determines the pressure in one chamber of an equalizing piston arranged to actuate train-pipe supply and exhaust valves, the spring is adapted to be put out of control to effect the opening of an emergency valve for connecting the train-pipe to atmosphere. The piston 9 slidable in the valve body 1 is subject on its upper face to the pressure of a spring 31 and on its lower face to the presseure in a chamber 5 communicating by passage 14 with the lower chamber 2 of the equalizing piston 15, the upper chamber 3 of which connects with the train-pipe 23. A valve 22 controlling the supply of compressed air from the main reservoir pipe 7 to the chamber 3 and the train-pipe carries a small valve 20 and by means of a sliding connection, a larger valve 18, arranged to seat on the exhaust passage 17. Valves 8, 11 control communication of the chambers 5, 2 with the reservoir pipe 7 and an exhaust passage 10. A piston 25 subject on its upper and lower faces respectively to the pressure in chamber 5 and the train-pipe 23 carries an emergency valve 26 by which the train-pipe can be connected directly to the atmosphere. The pressure of the spring 31 is adjustable for operating the brakes by the handle 28 by turning the head 22 which engages a helical groove formed in the valve body 1. The cap 30 may also be turned on the head 27, to adjust the spring for determining the normal pressure in the train-pipe. Compressed air from the pipe 7 seats the valve 11 and passing the valve 8 flows to the chambers 5 and 2, raising the equalizing piston 15 and seating the valves 18, 20 and opening the valve 22 so that compressed air is supplied to the chamber 3 and the train-pipe 23. When the pressure in the chambers 5, 2 is sufficient to overcome the spring 31 the piston 2 rises and the valve 8 closes so that the pressure in the chamber 2 ceases to rise and the rising pressure in the chamber 3 depresses the piston 15 until the valves 22 is seated. Pressure is thus established in the train-pipe corresponding to the pressure of the spring 31. To apply the brakes, the head 27 is turned to reduce the spring pressure, thus unseating the valve 11 and exhausting the chambers 5, 2 by the passage 10 whereby the piston 15 is depressed to unseat the valve 20 or also the valve 18 according as the spring pressure is gradually or abruptly relieved, the train-pipe 23 being thereby exhausted until equilibrium of the pressure is again established. The head 27 may also be turned into a position in which the lugs 29 engage the flange of the piston 9 which is thus directly lifted to open the valve 11, to completely exhaust the chambers 5, 6 causing the piston 25 to lift and open the trainpipe 23 directly to atmosphere to effect an emergency application of the brakes. The piston 9 may also be depressed independently of the spring 31 by the engagement of a lug 290 on the head 27. Specification 175,271 is referred to.