Alarm device for informing reduction of pneumatic pressure of tire

  • US 4,180,795 A
  • Filed: 12/12/1977
  • Issued: 12/25/1979
  • Est. Priority Date: 12/14/1976
  • Status: Expired due to Term
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First Claim
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1. An alarm device for informing reduction of pneumatic pressure of a tire by converting an abnormal change of the pneumatic pressure into an electric signal and generating an alarm, the device comprising:

  • at least one oscillator means having an oscillation coil fixed on a chassis side of a vehicle and changing its oscillation state of electromagnetic waves in accordance with an abnormal change of the pneumatic pressure;

    a resonator means fixed to the peripheral portion of a wheel having a tire adjacent the oscillation coil and consisting of a resonance coil and a capacitor capable of resonating with the electromagnetic wave radiated from said oscillation coil and a pressure sensing switch for sensing an abnormal change of the pneumatic pressure;

    a signal processing device provided for each oscillator and including a detector means for detecting the output of the oscillator, a comparator means for comparing the present output of the detector with a preceding output of the detector to generate an output pulse, an integrator means for integrating the output pulse of the comparator, and a logic circuit means for logically operating the output of the integrator; and

    an alarm means for generating a warning signal in accordance with the output of the signal processing device.

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