GB1305003A - - Google Patents

Abstract

1305003 Track apparatus TELEFONAKTIEBOLAGET L M ERICSSON 20 April 1971 [22 April 1970] 10299/71 Heading B7N [Also in Division G1] To detect a flat 18 (Fig. 1) on the rim of a wheel 13 of a rail vehicle, the two wheels 12, 13 on one axle 14 are used to close a test circuit which includes part of the rails 10, 11, which circuit is broken by the flat section 18 as the wheels rotate, for a period indicative of the length of the flat section. The connecting points 21, 22 to the rails 10, 11 are longitudinally offset by not more than the distance between consecutive axles. The voltage source 19 may be D.C., when the rail sections containing connecting points 21, 22 are insulated from the rest of the rails, or A.C., when the test circuit is made resonant at the test frequency to limit the effects of parallel paths through other wheel pairs. In one A.C. embodiment (Fig. 2A), the test circuit including wheels and axle b, c fed via transformer 33 is normally in series resonance at the supply frequency, whereby the voltage picked up at impedance 34 is sufficient to trigger unit 37 except when a wheel flat is present. The duration of the break in the output of unit 37 is compared with the time interval between the operation of fixed switches SK1, SK2, to determine the length of the flat and to operate an alarm 39 if it exceeds a preset value. In an alternative arrangement the current in the test circuit is sensed by coils linked to the rails 10, 11 or to the wheel axle b, c, which automatically eliminate the effects of rail currents produced by other wheel pairs. In another embodiment (Fig. 5A), short auxiliary rails 40, 41 are mounted adjacent the main rails 10, 11 and each wheel of a pair 43, 44 completes a separate test circuit in which a flat section produces an open circuit.