SIGNALLING SYSTEM FOR LOW TIRE CONDITION ON A VEHICLE

• US 3,665,387 A
• Filed: 08/31/1970
• Issued: 05/23/1972
• Est. Priority Date: 08/31/1970
• Status: Expired due to Term

• Current Assignee: Robert S. Enabnit
• Original Assignee: Robert S. Enabnit
• Inventors: Enabnit, Robert S.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/068,445
• Time in Patent Office: 631 Days
• Field of Search: 340/58,213,52H,52D,384E,52R 307/1R,118 200/83H,83K,83N,83R,61.25 180/103 73/146.5 331/181,65 336/30
• US Class Current: 340/448
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver

Abstract

A fail-safe low tire pressure warning system adaptable for any number of wheels of a vehicle and providing dashboard indications of system operation and low pressure conditions while the vehicle is in motion. A pair of coils mounted on each wheel are interconnected under normal conditions by a switch responsive to tire pressure and periodically, due to wheel rotation, quench an oscillator circuit by reversing the normal magnetic field occurring in a second pair of coils in the oscillator. Pulses generated as a result of the quenching are accumulated to form a signal for controlling lamp indicator circuits. A low pressure condition or inoperativeness of the circuit is recognized by a red lamp indication or absence of any indication. A minimal warning system for a multiple wheeled vehicle using diode logic is described as are tire pressure switches for truck and passenger car applications.

Claims

1. A tire pressure indicating system for vehicles, comprising a pair of magnetically coupled coils on the relatively stationary portion of the vehicle, means responsive to the magnetic coupling of said pair of coils for developing an oscillatory signal, means on a wheel of the vehicle for reversing the magnetic coupling in said pair of coils to affect the oscillatory signal when the pressure in the tire is at a predetermined level, and circuit means operatively connected with said signal developing means for providing indications representative of the state of the oscillatory signal.

2. The system as set forth in claim 1 wherein said magnetic coupling reversing means comprises a pressure switch mounted for movement with the wheel of the vehicle for monitoring air pressure in the tire, and a movable pair of coils interconnected by said pressure switch, said movable pair of coils movable with the wheel in a path of travel adjacent said magnetically coupled coils on the relatively stationary portion for periodically reversing the magnetic coupling of the latter.

3. The system as set forth in claim 2 wherein said movable pair of coils comprises a loop of conductive wire folded in a figure eight for reversal of a received magnetic field, said pressure switch being connected in said loop to provide electrical continuity at the predetermined tire pressure level.

4. The system as set forth in claim 2 wherein said movable pair of coils comprises first and second multiple turn coils having substantially parallel coil axes, mounted on the rim of the wheel adjacent one another and aligned substantially parallel with the wheel axle, said pressure switch being in series connection with said multiple turn coils.

5. The system as set forth in claim 1 wherein said magnetic coupling reversing means on the wheel of the vehicle periodically affect the magnetic coupling in said magnetically coupled pair of coils due to wheel rotation when the vehicle is in motion, said circuit means comprising means for developing a pulse each time the magnetic coupling is so affected, means for accumulating the pulses from said pulse developing means, and a signal circuit responsive to said accumulating means for providing visual indications of the presence and absence of accumulated pulses.

6. The system as set forth in claim 5 wherein said accumulating means comprises a charging circuit having a time constant sufficiently long to develop a predetermined DC level from the periodically occurring pulses caused by wheel rotation, said signal circuit comprising an amplifier and a signal lamp, said amplifier being responsive to such DC level to cause illumination of said signal lamp.

7. The system as set forth in claim 5 wherein said pulse developing means comprises a detector circuit for providing a signal representative of the oscillatory signal, a reference source of voltage, and a comparator operatively coupled to said detector circuit and said reference source for providing a pulse output when the magnetic coupLing is reversed.

8. The system as set forth in claim 7 wherein said reference source of voltage comprises a charging circuit coupled to said detector circuit for developing a reference voltage therefrom.

9. A system for signalling conditions between movable and relatively stationary members, comprising a switch on the movable member responsive to the conditions, magnetic field reversing modulating means in connection with said switch for establishing a magnetic field when said switch is in a closed state, an oscillator on the relatively stationary member, said oscillator being magnetically coupled with said modulating means and affected by the magnetic field thereof to provide a modulated output, demodulator means responsive to said oscillator output for developing the modulation signal, means for converting the modulation signal to a control signal, and means responsive to said control signal for providing visual indications representative of the presence and absence of the modulation signal.

10. Apparatus for signalling low tire pressure conditions on a vehicle, comprising a pressure switch and coil combination in each monitored wheel of the vehicle, an oscillator and circuit means associated with each said switch and coil combination, said oscillators being periodically quenched under normal tire pressure conditions due to wheel rotation, said circuit means being operative to form control signals indicative of such periodic quenching, a circuit for illuminating indicator lamps, and means for combining the control signals from said circuit means for energizing said illuminating circuit to provide signals of normal pressure conditions on all wheels and low pressure conditions on any single wheel.

11. Apparatus as set forth in claim 10 wherein said combining means comprises a diode logic circuit receiving as inputs the control signals from said circuit means and providing an output signal to said illuminating circuit.

12. Apparatus as set forth in claim 11 wherein said illuminating circuit comprise a pair of transistor amplifiers for energizing a pair of said indicator lamps, said amplifiers being interconnected to alternately energize said lamps.

13. Apparatus as set forth in claim 10 wherein said combining means comprises a diode logic circuit for receiving control signal inputs from a plurality of wheels of the vehicle, and a selector switch receiving as inputs such control signals and the output signal from said logic circuit, said switch providing individual and common control of said illuminating circuit.

14. Apparatus for signalling tire pressure conditions of a vehicle wheel, comprising an oscillator on the relatively stationary portion of the vehicle, said oscillator having a primary coil and a feedback coil in normal magnetically coupled relationship for producing oscillation, a pressure switch, a pair of coils interconnected with said pressure switch and mounted on the wheel of the vehicle for movement to a position of magnetic coupling with said oscillator primary and feedback coils, said pair of coils reversing the direction of induced magnetic coupling and providing magnetic feedback from said primary coil to said feedback coil differing from the normal phase relationship and in a phase relationship tending to prevent oscillation, and means for providing signals indicative of the state of oscillation of said oscillator.

15. The apparatus of claim 14, wherein the pressure switch includes a pair of electrical contacts, a flexible diaphragm disposed in spaced relation from the contacts and movable in response to changes in air pressure within the tire, a contact plate movable in unison with the diaphragm for placing the contacts in electrical communication, means for biasing the contact plate in a direction away from the contacts, and a lubricant interposed between the diaphragm and contact plate for maintaining the contact plate in free floating relation on the diaphragm.

16. The apparatus of claim 15, wherein the lubricant comprises oIl which is electrically non-conductive and has no deleterious effect on the diaphragm.

17. The apparatus of claim 16, wherein the lubricant is silicone oil.