Emergency lighting system for gaseous-discharge lamps

• US 4,091,307 A
• Filed: 01/02/1974
• Issued: 05/23/1978
• Est. Priority Date: 03/06/1972
• Status: Expired due to Term

• Current Assignee: Esquire, Inc. (New York) (The Hearst Corporation)
• Original Assignee: Esquire, Inc. (New York) (The Hearst Corporation)
• Inventors: McNamara, Albert C. Jr.
• Primary Examiner(s): Dahl, Lawrence J.
• Application Number:
  US05/429,991
• Time in Patent Office: 1,602 Days
• Field of Search: 315/86, 315/87, 315/88, 315/89, 315/91, 315/92, 315/93, 315/116, 315/129, 315/135, 315/136, 315/182, 315/192
• US Class Current: 315/92
• CPC Class Codes: H05B 41/46 Circuits providing for substitution in case of failure of the lamp

Abstract

This invention pertains to an emergency lighting circuit that operates with a high pressure, gaseous-discharge lamp and associated ballast. When the gaseous-discharge lamp goes out, after once being ignited, sufficient current is supplied to an incandescent light or lights to maintain illumination to the area normally illuminated by the lamp. The device for providing this current may vary, but generally incorporates a voltage breakdown means that receives higher voltage from the ballast when there is failure of the gaseous-discharge lamp than when the arc therein is struck. A preferred embodiment also lights the incandescent lights during initial warm-up of the gaseous-discharge lamp. The incandescent lights may also be used in a cold environment to maintain the gaseous-discharge lamp sufficiently above an ambient temperature level to make possible initial striking of the arc in the lamp when ambient temperature conditions might otherwise prevent it. Further, half-cycles of ballast output voltages are blocked by diodes and capacitors are used to increase the applied voltage to enhance restriking of the gaseous-discharge lamp in additional embodiments.

Claims

1. In combination with a gaseous-discharge lamp having

a first main electrode and

a second main electrode, and

a current-limiting ballast means connected to at least one of said first and second main electrodes,

an emergency heating circuit, comprising

voltage breakdown means having a threshold level greater than the normal operating voltage across the gaseous-discharge lamp and less than the necessary peak starting voltage applied to the gaseous-discharge lamp, and

heat-producing resistive means connected to form a series combination with said voltage breakdown means, said series combination being connected in parallel across the gaseous-discharge lamp,

operating voltage applied across the ballast means and the gaseous-discharge lamp establishing a voltage across said voltage breakdown means below its threshold level while there is conduction between the first and second main electrodes,

momentary interruption of operating voltage causing a period of cessation of such conduction resulting in voltage being applied across said voltage breakdown means above its threshold level, thereby heating up said resistive means, said resistive means being housed adjacent the gaseous-discharge lamp so as to build up the ambient temperature thereof above the required temperature level for starting the gaseous-discharge lamp.

2. Lighting system comprising, in combination,

a source of alternating current,

a gaseous discharge lamp connected to said source,

ballast means connected to said source including impedance means connected in series with said gaseous discharge lamp,

an incandescent lamp connected to said source, and

actuating means connected to said ballast means and said incandescent lamp for rendering said incandescent lamp inoperative during operation of said discharge lamp and for automatically rendering said incandescent lamp operative when said discharge lamp ceases operating,

said actuating means comprising controlled semiconductor switch means in series with said incandescent lamp, and triggering means connected across said gaseous discharge lamp and to said semiconductor switch means for rendering the latter means conductive when said discharge lamp ceases operation.

3. Lighting system as defined in claim 2, said triggering means comprising voltage-sensitive switch means.