Puncture alarm device for a tire

Claim 2

In a puncture alarm for a tire, including sensor means disposed within said tire, said sensor means for providing a change in electrical characteristic in response to the puncturing of said tire by a conductive object, and including an alarm and detection circuit means for producing an output signal in response to said sensor means to activate said alarm, said detection circuit means coupled to said sensor means and alarm, and comprising: a power supply; gate means coupled to said alarm for producing said output signal; and compensation means coupled to said power supply, sensor means and gate means for biasing said gate means such that said output signal is produced only when said electrical characteristic assumes a value outside of a preselected range, said compensation means for allowing a predetermined magnitude of degradation of said electrical characteristic without causing a false alarm.

Claim 3

The detection circuit means of claim 1 wherein: said electrical characteristic is the impedance of said sensor means, said impedance tending to degrade with time and wear.

Claim 4

The detection circuit means of claim 2 wherein: said gate means is a programmable uninjunction transistor; and said compensation means is a network of passive electrical elements coupled between said power supply, said programmable uninjunction transistor, and said sensor means.

Claim 5

The detection circuit means of claim 1 further comprising: latch circuit means for producing a steady output signal in response to transient excursions of said electrical characteristic outside said preselected range.

Claim 6

A detection circuit means in a puncture alarm for a tire, said detection circuit means coupled to an alarm, sensor means for providing a decrease in resistance in response to the puncturing of said tire by a conductive object, said detection circuit for activating said alarm in response to a decrease of said resistance below a preselected value, said detection circuit comprising: a power supply; an uninjunction transistor having a first and second gate and cathode and producing an output signal to activate said alarm whenever said second gate is at a potential less than said first gate, said cathode being coupled to said alarm; a compensation network including a first voltage divider coupled to said power supply and to said first gate, and a second voltage divided coupled to said power supply and said second gate, said sensor means coupled at least in part in parallel with said second voltage divider with respect to said power supply, said first and second voltage dividers proportioning the potential applied to said first and second gates such that said resistance of said sensor may decrease up to a preselected value without altering the operation of said detection circuit.

Claim 7

A detection circuit means in a puncture alarm for a tire, said detection circuit means coupled to an alarm, sensor means for providing a decrease in resistance in response to the puncturing of said tire by a conductive object, said detection circuit for activating said alarm in response to a decrease of said resistance below a preselected value, said detection circuit comprising: a power supply; an uninjunction transistor having a first and second gate and cathode and producing an output signal to activate said alarm whenever said second gate is at a potential less than said first gate, said cathode being coupled to said alarm; a compensation network including a first voltage divider coupled to said power supply and to said first gate, and a second voltage divided coupled to said power supply and said second gate, said sensor means coupled at least in part in parallel with said second voltage divider with respect to said power supply, said first and second voltage dividers proportioning the potential applied to said first and second gates such that said resistance of said sensor may decrease up to a preselected value without altering the operation of said detection circuit.

Claim 8

The detection circuit of claim 5 further comprising: latch circuit means having an input coupled to said cathode and an output coupled to said alarm, said latch circuit means for producing a steady output signal in response to transient reductions of said resistance below said preselected value.

Claim 9

The detection circuit of claim 5 wherein said alarm is coupled to said detection circuit by a telemetric coupling circuit.

Claim 10

The detection circuit means of claim 1 wherein said gate means is a silicon controlled rectifier having an anode and cathode in series circuit with said alarm and power supply and having a gate coupled to said sensor means.