Patent GB-235543-A (GB)
Title: Improvements in air pressure brakes for railways
IPC: B60T15/18
Filed: 1925-05-19
Abstract: 235,543. Rihosek, J., and Hardy Maschinenfabrilt und Giesserei Akt.- Ges. Geb. June 12, 1924, [Convention date]. Void [Published under Sect. 91 of the Act]. Fluid-pressure.-A graduated release valve for compressed-air brakes comprises a slide valve 17 controlled by a piston 7 subject on one side to train pipe pressure and on the other to the pressure in the slide valve chamber, and the pressure of a spring 18 or to gravity, and a piston 2, subject on one side to brake cylinder pressure. and on the other to atmospheric pressure, and having a stem 5 which projects into the piston chamber of the piston 7. When the brakes are fully released, the pressures on the two sides of the piston 7 are equalized through a passage 12 and a port 20 in the slide valve, so that the spring 18 holds the parts in the position shown, and the triple valve exhaust port is connected to atmosphere by a passage 10, slide valve ports and passage 24, 21, 23 aud exhaust passage 11. When train pipe pressure is reduced to apply the brakes, the pressures on opposite sides of the piston 7 are kept equal by flow from the valve chamber past non-return valve 14 and passage 13, so that brake cylinder pressure acting on the piston 2 moves the piston 7 and slide valve to the right. thereby interrupting communication between the passages 10. 11 and between the passage 12 and port 20. If, after an application, train pipe pressure is raised, either continuously or intermittently, to effect a graduated release, excess pressure on the left side of the piston 7 moves the piston and slide valve still further to the right, so that the passages 10. 11 are again connected through ports and passages 22, 21, 24 and the brake cylinder begins to exhaust. The two sides of the piston 7 are, however, now connected by the passage 12 and a port 19 in the slide valve, and when the pressures on its opposite sides have equalized, the piston and slide valve are moved to the left to cut off the exhaust and throw the port 19 out of register with the passage 12. When, on the return of the parts to this position, brake cylinder pressure on the left side of the piston 2 is insufficient to overcome that of the spring 18, the whole system returns to the position shown in Fig. 1, and complete release is effected. The passage 13 is preferably provided with a nozzle 15, so that when train pipe pressure is increased, a suction effect is set up tending to draw air past the valve 14, whereby the movement of the piston 7 to the right is facilitated. A more delicate operation of the device is ensured by the arrangement shown in Fig. 5, wherein the passage 12 has a branch passage 32, the port 20 is replaced by ports 28, 30, and the exhaust passage 11 has a branch passage 26. With the slide valve in the normal position shown, a projection 29 on the valve rod 16 closes the port 28, whilst when the slide valve moves to the right during a brake application, the projection closes the port 30 and a partition 27 closes the passage 12. On raising train pipe pressure for a graduated release, the slide valve moves still further to the right, and the port 28 passes over and beyond the passage 26, whereby the valve chamber is momentarily vented to atmosphere to assist the movement of the parts. The passage 32 is thus connected to the port 19, so that the pressures on opposite sides of the piston 7 equalize and the spring 18 returns the slide valve to mid-position, the projection 29 serving to close the port 28 during this movement, and the two sides of the piston 7 being connected by the passage 12 and port 30 until the partition 27 covers the passage 12.