Low tire pressure warning circuit for a tractor/trailer combination

• US 4,065,750 A
• Filed: 10/18/1976
• Issued: 12/27/1977
• Est. Priority Date: 10/18/1976
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Duncan, Eugene G., Spaniola, James W.
• Primary Examiner(s): Waring, Alvin H.
• Application Number:
  US05/733,346
• Time in Patent Office: 435 Days
• Field of Search: 340/52 F, 340/52 R, 340/53, 340/58, 180/103, 307/10 R
• US Class Current: 340/442
• CPC Class Codes: B60C 23/009 having wheels on a trailer
• CPC Class Codes: B60C 23/0406 Alarms noticeable from outside the vehicle, e.g. indication in side mirror, front light or audible alarms B60C23/0403, B60C23/0405 take precedence
• CPC Class Codes: B60C 23/0425 Means comprising permanent magnets, e.g. Hall-effect or Reed-switches

Abstract

A circuit is provided for a tractor/trailer combination to provide a warning in the tractor of an event such as low tire pressure occurring at the trailer utilizing only conventional wiring connections between the tractor and trailer. When low tire pressure occurs, a flasher circuit on the trailer flashes the trailer marker lamps which are normally energized so that the flashing lamps are visible to the operator. The electrical pulses in the marker lamp circuits are sensed by a detector in the tractor to illuminate an indicator lamp in the tractor. A time delay circuit controlling the flasher circuit for providing a self-check function, and for allowing manual flashing of the lamps without triggering the self-check operation.

Claims

1. In a tractor/trailer electrical circuit having an electrical power supply carried by the tractor and signal lamps carried by the trailer, a low tire pressure warning circuit for indicating in the tractor a low tire pressure event occurring in a trailer tire comprising

a conductive path for supplying electrical power from the power supply to energize the signal lamps,

means for sensing a low tire pressure event occurring in a trailer tire at each revolution of the low pressure tire and providing a corresponding pulsed event signal,

a flasher circuit connected to the said conductive path and effective when enabled for repetitively opening and closing the conductive path to periodically energize the lamps, whereby each time the lamps are energized a current pulse is produced in the conductive path,

a time delay means repsonsive to the pulsed event signal for continuously enabling the flasher circuit for a preset time after an event signal so that the flasher circuit operation continues without interruption during tire rotation, and

means in the tractor for indicating the said low tire pressure event occurring the trailer including an indicating lamp and means responsive to each of the said current pulses for flashing the indicating lamp.

2. In a tractor/trailer electrical circuit having an electrical power supply carried by the tractor and signal lamps carried by the trailer, a warning circuit for indicating in the tractor an event occurring in the trailer comprising

a conductive path for supplying electrical power from the power supply to energize the signal lamps, and switch means in the conductive path to controllably apply power through the path,

means for sensing an event occurring in the trailer and providing a corresponding event signal,

flasher means responsive to the event signal and connected to the said conductive path for repetitively opening and closing the conductive path to flash the lamps, whereby each time the lamps are energized a current pulse is produced in the conductive path,

means in the tractor for indicating the said event occurring in the trailer including an indicating lamp and means responsive to the said current pulses for energizing the indicating lamp, and

a self-check circuit effective for a first short interval after the switch means is initially closed to operate the warning circuit comprising means for energizing the flasher means as soon as the switch means is closed and time delay means having a first timing period for disabling the energizing means upon expiration of the said short time interval, whereby several flashes of the indicating lamp will occur when power is initially applied to the warning circuit to verify operability of the warning circuit.

3. In a tractor/trailer electrical circuit having an electrical power supply carried by the tractor and signal lamps carried by the trailer, a warning circuit having a self-check circuit according to claim 2 wherein the time delay means has a second timing period effective when the said switch means is opened to maintain the energizing means in a disabled condition for a second short interval whereby the switch means may be quickly opened for an interval less the said second short interval and then closed to provide flashing of the signal lamps without actuating the self-check circuit.

4. In a tractor/trailer electrical circuit having an electrical power supply carried by the tractor and signal lamps carried by the trailer, a low tire pressure warning circuit for indicating in the tractor a low tire pressure event occurring in a trailer tire comprising

a conductive path for supplying electrical power from the power supply to energize the signal lamps, manually operated switch means serially connected in the conductive path to control lamp energization,

means for sensing a low tire pressure event occurring in a trailer tire at each revolution of the low pressure tire and providing a corresponding event signal,

a flasher circuit connected to the said conductive path and effective when enabled for repetitively opening and closing the conductive path to periodically energize and de-energize said lamps, whereby each time the lamps are energized a current pulse is produced in the conductive path,

a time delay circuit for enabling the flasher circuit, the time delay circuit including

a. a capacitor

b. a capacitor charging path through a first resistor to provide a first time delay to enable the flasher circuit during the first time delay to effect self-check operation of the flasher upon initial closure of the manually operated switch means,

c. a first capacitor discharging path through a second resistor operable when the flasher circuit is disabled to provide a second time delay after opening of said manually operated switch means to momentarily prevent the said self-check operation to permit, during the interval of the second time delay, manual flashing of the signal lamps,

d. a second capacitor discharging path through a third resistor to discharge the capacitor without significant time delay after each event signal to enable or maintain enabling of the flasher circuit, and

means in the tractor for indicating the said low tire pressure event occurring in the trailer including an indicating lamp, and means responsive to each of the said pulses for flashing the indicating lamp.