GB1102329A - Improvements in or relating to electro-pneumatic compressed air brake arrangements for rail vehicles - Google Patents

Abstract

1,102,329. Pneumatic brakes for rail vehicles; valves. KNORR-BREMSE G.m.b.H. 9 May, 1966 [7 May, 1965], No. 20528/66. Headings F2F and F2V. [Also in Division H1] A compressed-air braking system for rail vehicles includes both a pneumatic control valve and an electric control comprising an electromagnetic application valve 23 and an electromagnetic release valve 32, both associated with a venting conduit 31 from the brake cylinder 21, the release valve consisting of two valves operated by an electromagnet so constructed as to be energizable in two stages, partial energization of coil 34 attracting a yoke 37 to open a vent 40 so as to allow rapid venting of cylinder 21, and full energization attracting armature 33 to close the venting conduit at 36. Upon de-energization of the release valve the venting conduit is open to atmosphere via restriction 41 so long as application valve 23 is not energized. Energization of the valve 23 causes movement of an armature to close off the venting conduit at 27 and simultaneously open at 26 a conduit 22 for feeding compressed air from a reservoir 9, via chambers 11 and 14 of a triple valve 4, to the brake cylinder 21. The two stages of energization of the release valve 32 are achieved by selective operaton of switches 46, 49 of which the latter connects the full voltage of a battery 45 to the coil of the release valve while the former connects to the coil a portion of this voltage at a tap 47 on the battery, the battery being protected by a diode 48. In use, the following sequence of operations is effected: to brake the train, switches 46 and 50 are closed, the former opening the vent 40 while the latter energizes the application valve 23; when no further increase in braking is desired, switch 49 is closed, whereby armature 33 closes off the venting conduit at 36, and switch 50 is then opened; to release the brake switch 49 is first opened to give rapid release through the vent 40, and towards the end of brake release switch 46 is opened to conserve current, release then being completed via the restriction 41. The arrangement and construction of the triple valve 4 is conventional, the pressure rise in chamber 14 during an electropneumatic brake application maintaining the piston 10 in its lower position in spite of any drop in pressure in control chamber 3 caused by filling of the reservoir 9, while in the absence of electropneumatic control the piston is able to respond to any pressure reduction in the train pipe 1 to apply the brake by opening valve 18, 19 owing to the difference which then occurs between the pressures in chamber 3 and constant pressure chamber 7. Electromagnetic valves.-Fig. 2 shows the construction of the release valve 32. An energizing coil 34 is disposed within a ferromagnetic casing 51 which is discontinued by a paramagnetic ring at 52 and is again discontinued at the ends of the coil. A thin ferromagnetic sleeve 56 interconnects the upper part of the casing with a plug 53 forming the lower part of the casing and extends within the coil 34. This sleeve is capable of containing a limited amount of flux and therefore acts as a partial magnetic short-circuit with respect to armature 33. Armature 37, however, is in series with the sleeve 56 so that partial energization of coil 34 causes armature 37 to be attracted and bridge the ring 52. Full energization of coil 34, however, is necessary before armature 33 will respond, since the sleeve 56 has first to be saturated. In the circuit of Fig. 3 (not shown) which can be used to operate the switches 46, 49, 50 of Fig. 1, switch arms (80, 81) are actuated sequentially by movement of the piston of a second triple valve (86) whose control chamber (85) is fed via a regulator (68) initial operation of which causes closure of a single switch (69). The switches 46, 49, 50 are controlled by relays (63, 64, 65) which are energized through contacts associated with the switch arms (80, 81) so that they respond to the position of the triple valve piston, which includes a reaction piston (92) to respond to the pressure in the brake cylinder. A further relay (76) actuated by closure of switch (69) after a delay gives time for pressure to build up in the control chamber (85) of the triple valve before brake application can occur, and a pressuresensitive switch (66) ensures that the brake is almost fully released before switch 46 opens.