Patent GB-648791-A (GB)
Title: Improvements in or relating to brake control apparatus
IPC: B60T8/32
Filed: 1948-02-04
Abstract: 648,791. Vehicle brakes. AMERICAN BRAKE SHOE CO. Feb. 4, 1948, No. 3250. Convention date, July 24, 1939. [Class 103 (i)] [Also in Group XXXV] An apparatus for preventing wheel slip in railway vehicle braking systems comprises electrical means for comparing the speeds of rotation of two adjacent axles so that if the speed of one axle with respect to the other should begin to fall, due to wheel slip, relays will be operated that actuate a valve that serves 'to reduce the pressure in the brake cylinder for the slipping wheel so as. to bring the two. axle speeds back into synchronism. In the system shown in Figs. 1, 2, 3 and 4 the rotation of the two axles FA and RA is transmitted by flexible drives 48 and 53 to the elements R1 and R2 in the switch-box S. The element R2 has a set of spring-loaded brushes 95 that contact in succession separate upper and lower sector plates 90 and 91 so that circuits are thus completed as follows : lead in 72, plate 78, brushes 95, sector plates 90 or 91, leads out 62 or 64. Lead 72 is connected to one terminal of battery B2, Fig. 2, and the circuit is returned from leads 62 and 64 by way of slowto-release relays SR1 and SR2 respectively. Should the speeds of the two axles fall out of synchronism to such an extent that the armature 98 of the relay SR1 has not been released by the time armature 101 of relay SR2 is closed, a further circuit will be completed which energizes a further relay SR3 controlling a circuit supplied by battery B1. In the circuit of battery Blare two coils 30 and 31 operating check and release valves 28 and 29 on the fluid pressure supply lines to the brake cylinders 12, 13 and 14, 15. In order that the correct pair 12, 13 or 14, 15 shall be operated to correct for the wheel slip, provision is made as follows for operating a change-over switch 36, 39, 40 according to which of the axles FA or RA is rotating most rapidly. In the switchbox S, the lead 86 on element R2 is connected by a conductor 83 with a sector plate 81 which is located in spaced relation between the ends of the arcuate plate 78, as shown in Fig. 4. Plate 78 has secured to it a pin 108 projecting into a segmental space 107 formed in the insulating core 105 of element R1. According to whether the speed of the element R 1 or R2 is the greater, the pin 108 will move to one end of the other of slot 107 so that the gap between the plates 78 and 81 may or may not be bridged by the conductor 110. By this means a circuit that follows the path, battery B2, lead 72, plate 81, element 83, lead 86, relay 41, lead 88, battery B2 may or may not be completed to selectively actuate relays 30 or 31 according to the relative speeds of the axle. The operation of the pin-and-slot mechanism 107, 108 just described requires that the vehicle shall be driven in one direction only if the system is to function correctly. To avoid this limitation a change-over switch may be fitted which is actuated by a pulley according to the direction of rotation of the element R2 in the switchbox 5. In a further modification, a similar system is operated by means of commutator switches fitted directly on the ends of the wheel axles, instead of being remotely driven in a switch-box S.