Circuit for operating warning lights

• US 6,507,154 B1
• Filed: 09/21/2001
• Issued: 01/14/2003
• Est. Priority Date: 09/21/2001
• Status: Expired due to Fees

• Current Assignee: The Fire Products Company
• Original Assignee: The Fire Products Company
• Inventors: Menke, W. Kenneth
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): TRAN, THUY V
• Application Number:
  US09/961,215
• Time in Patent Office: 480 Days
• Field of Search: 315/83, 315/82, 315/185.R, 315/189, 315/193, 315/362, 307/10.6, 307/10.8
• US Class Current: 315/83
• CPC Class Codes: B60Q 1/2611 Indicating devices mounted on the roof of the vehicle

Abstract

The present invention pertains to an electrical circuit for operating warning lights that are commonly used on emergency and service vehicles. The electric circuit enables the use of pairs of 21 volt DC halogen lamps on a light bar installed on an emergency vehicle equipped with a 42 volt electrical system.

Claims

1. An electric circuit for illuminating incandescent lamps comprising:

an input for connection to a source of electric power;

a first lamp;

a first resistor;

a second lamp;

a second resistor; and

means for switching the circuit between a start up circuit where a series connection of the first lamp and first resistor is connected in parallel with a series connection of the second lamp and second resistor, and an operation circuit where the first lamp is disconnected from the first resistor and the second lamp is disconnected from the second resistor and the first lamp is connected in series with the second lamp, the switching means being operable to switch the circuit from the start-up circuit to the operation circuit after the first and second lamps reach incandescence.

2. The circuit of claim 1, further comprising:

each of the first and second resistors has a resistance and the first resistor resistance is substantially equal to the second resistor resistance.

3. The circuit of claim 1, further comprising:

each of the first and second lamps has a voltage rating and the first lamp voltage rating is substantially equal to the second lamp voltage rating.

4. The circuit of claim 1, further comprising:

the source of electric power connectable to the circuit has a voltage that is equal to a sum of the first and second lamps voltages.

5. The circuit of claim 4, further comprising:

the source of electric power voltage is 42 volts DC and each of the lamps voltages is 21 volts DC.

6. The circuit of claim 1, further comprising:

each of the first lamp and second lamp has a lamp resistance when illuminated and the first lamp resistance is substantially equal to the second lamp resistance, and the first lamp resistance is substantially equal to the second resistor resistance.

7. The circuit of claim 6, further comprising:

each of the first and second lamps have a voltage drop that are substantially equal immediately after the circuit is switched from the start-up circuit to the operation circuit and the source of electric power is applied to the operation circuit.

8. The circuit of claim 1, further comprising:

the switching means comprises means to apply the source of electric power to the start-up circuit when one of the first and second lamps fails.

9. The circuit of claim 1, further comprising:

the switching means comprises means to apply the source of electric power to the start-up circuit when one of the first and second lamps is removed from the circuit.

10. An electric circuit for illuminating incandescent lamps comprising:

a first junction for connection to a source of electric power;

a second junction for connection to an electric ground;

a first electrically conductive path connecting in series the first junction, a first lamp, a first switching device and the second junction;

a second electrically conductive path connecting in series the first junction, the first switching device, a second lamp and the second junction; and

a third electrically conductive path connecting in series the first junction, the first lamp, the first switching device, the second lamp and the second junction.

11. The electric circuit of claim 10, further comprising:

the first electrically conductive path and the second electrically conductive path are connected in parallel between the first junction and the second junction.

12. The electric circuit of claim 10, further comprising:

a first resistor connected in series with the first electrically conductive path.

13. The electric circuit of claim 12, further comprising:

the first resistor being connected in series between the first switching device and the second junction.

14. The electric circuit of claim 12, further comprising:

a second resistor connected in series with the second electrically conductive path.

15. The electric circuit of claim 14, further comprising:

the second resistor being connected in series between the first junction and the first switching device.

16. A method of converting a light assembly having one or more lamps that are each operative at a first voltage for operation at a second voltage that is greater than the first voltage, the method comprising:

providing a first junction for electrical connection to a source of electric power of one lamp of the light assembly;

providing a second junction for electrical connection to an electric ground of the one lamp;

connecting the first junction in a first series circuit with a first lamp, a first switching device and the second junction;

connecting the first junction in a second series circuit with the first switching device, a second lamp and the second junction; and

connecting the first junction in a third series circuit with the first lamp, the switching device, the second lamp and the second junction where the switching device is operable to complete at least two of the first, second and third series circuits independently of each other.

17. The method of claim 16, further comprising:

alternating completing the first series circuit and the third series circuit by the switching device.

18. The method of claim 16, further comprising:

alternating completing the second series circuit and the third series circuit by the switching device.

19. The method of claim 16, further comprising:

simultaneously completing the first series circuit and the second series circuit in parallel with each other by the switching device.

20. The method of claim 16, further comprising:

alternating completing the first series circuit and the second series circuit simultaneously in parallel with each other and completing the third series circuit by the switching device.

21. The method of claim 16, further comprising:

connecting a first resistor in the first series circuit between the first lamp and the first switching device.

22. The method of claim 21, further comprising:

connecting a second resistor in the second series circuit between the first junction and the switching device.