SELF-PULSING TRANSMITTER FOR VEHICLE TIRE PRESSURE INDICATION SYSTEM

• US 3,805,229 A
• Filed: 09/15/1972
• Issued: 04/16/1974
• Est. Priority Date: 09/15/1972
• Status: Expired due to Term

• Current Assignee: John C. Murphy
• Original Assignee: John C. Murphy
• Inventors: Murphy, John C.
• Primary Examiner(s): Waring, Alvin H.
• Application Number:
  US05/289,698
• Time in Patent Office: 578 Days
• Field of Search: 340/58 200/61.22,61.25,61.26 325/15,111,117
• US Class Current: 340/447
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0433 Radio signals

Abstract

A self-pulsed oscillator or transmitter and a pneumatic tire low pressure monitoring and warning system using same is provided wherein the transmitter comprises a transistor having base, emitter, and collector electrodes with the electrodes being operatively connected to a DC power source. The transmitter has oscillating means connected between the base electrode and the collector electrode establishing the frequency of the oscillator and employs a simple and inexpensive device to provide a selfpulsing action.

Claims

1. An RF transmitter for a pneumatic tire low pressure monitoring and warning system comprising:

means sensing a low pressure condition in a pneumatic tire supported on an associated vehicle by a rotatable support;

a self-pulsed transmitter having one active element, said transmitter carried by said rotatable support and being rotatable therewith;

said transmitter being actuated by said sensing means and providing pulse modulated output signals in response to said low pressure condition;

selective means for receiving said pulse modulated RF signals and insuring positive recognition of said pulse modulated RF signals generated by said RF transmitter wherein false alarms in an environment of high atmospheric and man-made electromagnetic interfering signals are eliminated;

said active element comprising a transistor having base, emitter and collector electrodes;

means connecting said electrodes to a DC power source;

oscillating means connected to said base and collector electrodes and to said emitter electrode for establishing the operating frequency of said transmitter; and

inactive means providing a self-pulsing action and establishing the pulse repetition rate.

2. An RF transmitter for a monitoring and warning system as set forth in claim 1 in which said inactive means providing self-pulsing action comprises a capacitor having a poor dissipation factor in parallel with a resistor, said capacitor and resistor operatively connected between the circuit ground for said oscillating means and said emitter electrode, said capacitor adapted to be charged to a maximum potential until current flow through said emitter electrode stops to thereby stop oscillation of said oscillating means, and when said capacitor is discharged to a potential less than said maximum potential then current flow through said emitter electrode again commences to thereby enable oscillation in said oscillating means, wherein the emitter potential which will start oscillation in said oscillating means is lower than the emitter potential required to stop oscillation thereof;

said resistor and said capacitor having a time constant which establishes the desired pulse repetition rate.

3. An RF transmitter for a monitoring and warning system as set forth in claim 2 in which said capacitor has a dissipation factor greater than 0.1 per cent.

4. An RF transmitter for a monitoring and warning system as set forth in claim 1 and further comprising an RF filter separating said DC power source from said transistor electrodes.

5. An RF transmitter for a monitoring and warning system as set forth in claim 2 in which said transistor is an NPN transistor.

6. An RF transmitter for a monitoring and warning system as set forth in claim 1 wherein said oscillating means is a tank circuit including a coil which is unshielded and unobstruCted to establish an alternating near field and thereby permit the use of said coil as a transmitting antenna which couples to said receiving means.