VEHICLE SIGNAL LIGHTING SYSTEMS

• US 3,840,851 A
• Filed: 06/29/1973
• Issued: 10/08/1974
• Est. Priority Date: 06/30/1972
• Status: Expired due to Term

• Current Assignee: Alastair Kershaw Stevenson, Albert Lewis Fowler
• Original Assignee: Alastair Kershaw Stevenson, Albert Lewis Fowler
• Inventors: Fowler, Albert Lewis, Stevenson, Alastair Kershaw
• Primary Examiner(s): Yusko, Donald J.
• Application Number:
  US05/375,080
• Time in Patent Office: 466 Days
• Field of Search: 340/74,78 315/77,79,82,83
• US Class Current: 340/469
• CPC Class Codes: B60Q 1/2603 Attenuation of the light according to ambient luminiosity, e.g. for braking or direction indicating lamps

Abstract

A vehicle lighting system which provides facility for rearward facing warning lamps such as turn indicators and stop lamps to be automatically dimmed in conditions of poor ambient lighting. Each lamp to be so dimmed has connected in series therewith a switchable device, for example a power transistor, which is caused for normal operation, to remain in a highly conductive state. When the side lamps of the vehicle are turned on, and/or when the ambient lighting falls below a threshold level, an oscillator circuit is energized which causes the transistor to alternate between highly conductive and highly resistive states so as to reduce the electrical energy fed to the lamp. In the event that said lamp is a flashing turn indicator lamp, an expedient is disclosed for causing the flashing rate to remain substantially constant despite the reduction in power consumed by the lamp.

Claims

1. A circuit arrangement for selectively reducing the intensity of illumination of rearward facing turn indicator lamps fitted to a vehicle and arranged to be supplied with electric current, pulsed at a given rate, in response to the actuation of a direction indicator switch, the arrangement comprising a respective device electrically connected in series between the switch and each of said lamps, each of said devices being capable of assuming a first condition, in which it presents substantially no impedance to said current, or a second condition, in which it presents a substantial impedance to said current, control means, operative on said devices, for holding said devices in said first condition to enable the lamps to be illuminated with full intensity and for responding to a control signal to cause said devices to alternate between said first and second conditions so as to interrupt said current at a rate substantially higher than said given rate to enable the lamps to be illuminated with reduced intensity, and the arrangement further comprising frequency selective impedance means associated with said lamps and arranged to present a lower impedance to electrical current interrupted at said higher rate than to electrical current pulsed at said given rate, thereby to provide a leakage current path for said interrupted current in addition to the path through a lamp such that the overall current drawn by the arrangement remains within predetermined limits whether the lamps are illuminated with full or reduced intensity.

2. An arrangement according to claim 1 wherein said frequency selective impedance means comprises a capacitor.

3. An arrangement according to claim 2 wherein said capacitor is connected from the junction of one of said lamps and its series-connected device to the junction of another of said lamps and its series connected device.

4. An arrangement according to claim 1 wherein the said lamps comprise first and second lamps, respectively situated adjacent opposite sides of the vehicle, said vehicle also being fitted with third and fourth lamps which face forwardly thereof and are situated on either side of the vehicle, the third lamp being connected so as to pulse simultaneously with the first lamp and the fourth lamp being arranged to pulse simultaneously with the second lamp;

the third and fourth lamps being connected directly to said direction indicator switch, wherein the vehicle further includes a hazard warning system whereby all four of said lamps can be caused to pulse simultaneously, means being provided for overriding said control means so as to hold both said series connected devices in said first condition when said pulsed current is applied simultaneously to said four lamps.

5. An arrangement according to claim 4 wherein said over-riding means comprises respective unidirectionally conductive means connected from said control means to each of said third and fourth lamps, the arrangement being such that when both of said third and fourth lamps receive pulsed current simultaneously, the operation of said control means is inhibited.

6. An arrangement according to claim 1 including inhibit means for inhibiting the operation of said control means so as to cause each of said series connected devices to remain in said first condition.

7. An arrangement according to claim 6 including warning means for providing an indication when the operation of said control means is inhibited.