Air pressure indicator for a vehicle tyre
First Claim
1. A device for indicating safety limits of air pressure in tires of at least two wheel assemblies of a vehicle, the device including for each of the at least two wheel assemblies of the vehicle a first conductive surface, a second conductive surface, a third conductive surface and a fourth conductive surface, a first pair of conductive surfaces including said first and second conductive surfaces, said first pair of conductive surfaces being mounted onto an insulated base fixed onto a rotating portion of each wheel assembly, and a second pair of conductive surfaces including said third and fourth conductive surfaces, said second pair of conductive surfaces being mounted onto an insulated base fixed onto a nonrotating shaft of each wheel assembly, a pair of air capacitors being formed between said first pair and said second pair of conductive surfaces, an electronic circuit which includes a high frequency oscillator, an amplifier, a magnitude and phase comparator, a sequential circuit, two diodes, and a bridge circuit with three resistors and four capacitors which are connected with said nonrotating conductive surfaces for each of said at least one pair of wheels, a detection circuit that also includes a pulse generator, a comparator, RLC sinusoidal wave transformer, and a signal display and a tire pressure sensor including means for converting air pressure variations in the tires into displacement of a semiconductor membrane to thereby operate as an ON-OFF switch which shorts out said first with second conductive surfaces with a metallic frame of the wheel assembly when in an ON position when air pressure in a tire is abnormal, said pair of air capacitors being adapted to operate as a variable capacitor in said electronic circuit wherein a first frequency range is produced by said pair of air capacitors when the ON-OFF switch is in an OFF position, and a second frequency range is produced by said pair of air capacitors when the ON-OFF switch is in the ON position which results in said electronic circuit activating the signal display to thereby reflect a tire with abnormal air pressure.
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Accused Products
Abstract
The present invention relates to a device which indicates the safety limits of the air pressure in each one of the pneumatic tires of a vehicle by transmitting appropriate information from the wheels to the driving control board. Transmission of information is based on the capacitive coupling between rotating and non-rotating conductive annular surfaces (2-5, 12-19, 72-75) which are mounted into channels of insulated bases (6-9) fixed in the available space between the bearing flange, the braking system and the wheel bearings (66) and are forming cylindrical and plane capacitors. An electronic circuit incorporates these capacitors as basic elements for its operation, and also an AC bridge (20) to give an automatic compensation by measuring the differential capacitance for each pair of the wheels to avoid faulty indication due to causes like humidity, temperature, etc. Also a simple electronic circuit can be used for each one of the wheels. A tire pressure sensor (1) comprises a semiconductor membrane (30) with an electrode (33) which is shorting out the rotating conductive surfaces (2, 3, 12, 13, 16, 17, 72, 73) when the tire pressure deviates from the safety limits resulting in a change of the original frequency and giving visual display or audio indication.
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Citations
8 Claims
- 1. A device for indicating safety limits of air pressure in tires of at least two wheel assemblies of a vehicle, the device including for each of the at least two wheel assemblies of the vehicle a first conductive surface, a second conductive surface, a third conductive surface and a fourth conductive surface, a first pair of conductive surfaces including said first and second conductive surfaces, said first pair of conductive surfaces being mounted onto an insulated base fixed onto a rotating portion of each wheel assembly, and a second pair of conductive surfaces including said third and fourth conductive surfaces, said second pair of conductive surfaces being mounted onto an insulated base fixed onto a nonrotating shaft of each wheel assembly, a pair of air capacitors being formed between said first pair and said second pair of conductive surfaces, an electronic circuit which includes a high frequency oscillator, an amplifier, a magnitude and phase comparator, a sequential circuit, two diodes, and a bridge circuit with three resistors and four capacitors which are connected with said nonrotating conductive surfaces for each of said at least one pair of wheels, a detection circuit that also includes a pulse generator, a comparator, RLC sinusoidal wave transformer, and a signal display and a tire pressure sensor including means for converting air pressure variations in the tires into displacement of a semiconductor membrane to thereby operate as an ON-OFF switch which shorts out said first with second conductive surfaces with a metallic frame of the wheel assembly when in an ON position when air pressure in a tire is abnormal, said pair of air capacitors being adapted to operate as a variable capacitor in said electronic circuit wherein a first frequency range is produced by said pair of air capacitors when the ON-OFF switch is in an OFF position, and a second frequency range is produced by said pair of air capacitors when the ON-OFF switch is in the ON position which results in said electronic circuit activating the signal display to thereby reflect a tire with abnormal air pressure.
- 7. A device for indicating safety limits of air pressure in tires of at least two wheel assemblies of a vehicle, the device including for each of the at least two wheel assemblies of the vehicle a first conductive surface, a second conductive surface, a third conductive surface and a fourth conductive surface, a first pair of conductive surfaces including said first and second conductive surfaces, said first pair of conductive surfaces being mounted onto an insulated base fixed onto a rotating portion the each wheel assembly, and a second pair of conductive surfaces including said third and fourth conductive surfaces, said second pair of conductive surfaces being mounted onto an insulated base fixed onto a nonrotating shaft of the wheel assembly, a pair of air capacitors being formed between each said first pair and said second pair of conductive surfaces, an electronic circuit which includes a bridge circuit having a first branch connected to a first of said air capacitors associated with a first of said at least two wheel assemblies and a second branch connected to the other of said air capacitors associated with the other of said at least two wheel assemblies, an output of said bridge circuit being in a balanced state with respect to a reference signal into said bridge circuit when input signals from said pair of air capacitors to said first and second branches are equal but being in an unbalanced state when the signal inputs from said pair of air capacitor are not equal such that an output of said bridge circuit generates an output signal in phase relationship to said reference signal as an indication of abnormal air pressure in one of the tires of said at least one pair of wheel assemblies, an air pressure sensor mounted to each of the tires, said air pressure sensors being connected to said first pair of conductive surfaces such that if an abnormal air pressure is sensed in one of the tires, at least one of said first and second conductive surfaces becomes shorted whereby the input signal from one of said pair of air capacitors to said bridge circuit is changed relative to the input signal from the other of said pair of air capacitors, and display means connected to said electronic circuit for displaying when an abnormal air pressure is sensed in one of the tires.
Specification