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Sensor for railcar wheels

  • US 6,663,053 B1
  • Filed: 08/30/2002
  • Issued: 12/16/2003
  • Est. Priority Date: 08/30/2002
  • Status: Active Grant
First Claim
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1. A detector for the presence of a train wheel on a train track comprising:

  • a) at least one electromagnetic field generator sensor comprising;

    an inductance-capacitance (L/C) loop tank circuit that develops an alternating current at a natural resonance frequency to provide an electromagnetic field when the L/C tank circuit is electrically charged;

    a charging circuit that provides an electrical charge to the tank circuit when amplitude of the frequency drops below a predetermined level; and

    a feed back from the tank circuit to the charging circuit at the resonance frequency permitting the charging circuit to determine when the amplitude of the frequency has dropped below the predetermined level;

    said L/C tank circuit and charging circuit being incapable of maintaining the predetermined amplitude of the frequency when a ferromagnetic material of the mass of a train wheel is located in a center of the field;

    b) at least one means for holding the electromagnetic field generator proximate a train rail so that the electromagnetic field extends through a spatial area through which a train wheel travels and so that the field is affected to cause a drop in the frequency amplitude below a second threshold level that is below the predetermined level when a train wheel is located on the rail so that it partially affects the field, and so that there is a further drop in frequency amplitude below a third threshold level below the second threshold level when the train wheel is located so that it filly affects the field;

    c) at least one means for detecting an increase in frequency amplitude above a first threshold level above the predetermined level indicating that the electromagnetic field generator is no longer in a proper position relative to the train rail, for detecting the drop in frequency amplitude below the second threshold level to indicate approach of the train wheel, and for detecting the drop in frequency amplitude below the third threshold level to indicate the presence of the train wheel; and

    d) a means for compensating for drift of frequency amplitude from the predetermined level when the drift is between the first and third threshold levels and for ceasing such compensating when the frequency amplitude is above the first threshold level or below the second threshold level.

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