US2497910A - Flash lamp - Google Patents

Description

Feb. 21, 1950 c. E. RANSLEY FLASH LAMP Filed Nov. 15, 1945 INVENTOR Y Y E E N s R N O HL CM m S EM 5 E m Am H C Passes Feb. 21, 1950 FLASH LAMP Charles Eric Ransley, Sudbury, England, assignor to General Electric Company, a corporation of New York Application November 15, 1945, Serial No. 628,900 In Great Britain November 27, 1944 Claims.

My invention relates to flash light lamps of the type used for photographic purposes wherein a combustible metal burns in an oxygen containing atmosphere within a sealed transparent envelope. The combustion of the metal is usually initiated by means of a primer ignited by an electric current supplied from outside the envelope, but the invention is not limited to this particular method of igniting the metal.

In flash lamps of the type specified it is essential that the combustion of the metal be rapid in order that the required flash of light may be produced. This imposes a severe limitation on the nature and form of metals that can be used. Thus, aluminum and magnesium are the only really practicable metals and these are most suitably used in the form of thin foil or ribbon or fine wire.

Inasmuch as flash light lamps are mainly used for photographic purposes, it is desirable that the flash should have good characteristics, i. e., that the curve relating light intensity to time should be of approximately square wave form. It is also usually desirable, and particularly with synchronized cameras having high speed shutters, that the flash should attain a workable intensity at an accurately predetermined time after the initial ignition of the metal and that this time should be substantially the same for difierent lamps.

It is an object of the present invention, therefore, to improve the characteristics of such type flash lamps in both of the above-mentioned respects.

According to the invention, the above object is achieved by the introduction within the sealed transparent envelope of a substance which reacts with the metal oxide formed during the combustion of the metal. vCarbon tetrachloride is a suitable substance but carbonyl chloride and other halogen compounds of carbon, silicon, phosphorus, etc., that react with the metal oxide are possible alternatives. The explanation of this effect is probably that the added substance reacts with and removes the film of oxide formed on the surface of the metal during combustion and thereby promotes more uniform burning of the metal.

My invention therefore consists broadly in the inclusion, Within the sealed envelope of a flash ligh lamp of the type specified, of a substance, preferably in the form of a gas, which will combine with the oxide of the combustible metal formed when the metal is ignited.

Further objects and advantages of my invention will appear from the following description of a species thereof and from the accompanying drawing which illustrates, in elevation, a flash lamp comprising my invention.

Referring to the drawing, the flash lamp there shown comprises a sealed light-pervious envelope 0 of glass or similar material containing a charge of a combustible light-giving solid material 2 for generating, on ignition, a flash of actinic light. The combustible material 2 may be in the form of thin foil or ribbon or fine wire made of a'suitable metal, such as aluminum or magnesium or alloys thereof, and distributed loosely within the envelope or bulb l. Mounted within the envelope l, within efiective ignition range of the combustible material 2, is a small filament 3 the ends of which are connected to leading-in wires 8, t. In the particular type of flash lamp illustrated wherein the combustible material 2 is in the form of wire, ribbon or foil loosely distributed within the bulb, a small quantity of a suitable fulminating substance 5 is provided within the envelope l in contact with the filament 3 to thereby form the ignition means for the ;combustible material. The fulminating material 5 is preferably applied to the leading-in wires l in the form of separate coatings or beads thereon. The envelope l is profvided with a re-entrant stem 6 through which the leading-in wires 4 are sealed and are connected to the terminals of a conventional type lamp base 1. To support the combustion of the combustible material 2, the envelope l is filled with oxygen or oxygen-containing gas at a suitable pressure.

In accordance with the invention, the flash characteristics of the lamp are improved by the introduction into the envelope l of a substance, preferably in the form of a gas, which reacts instantaneously with the metallic oxide formed when the combustible metal 2 is ignited. Carbon tetrachloride is a suitable substance for this purpose, but carbonyl chloride and other halogen compounds of carbon, silicon, phosphorus, etc., 'that react with the metal oxide are possible alternatives.

The improved flash characteristics obtained by the use of the invention renders it possible to use, for the combustible metal 2, alloys of aluminum and magnesium (with each other or with other metals) hitherto considered not practicable but which would otherwise be desirable, for example for ease of drawing into the form of flne wire. Thus we have found it possible to use an alloy of aluminum with 4% copper in the form of 35,11. (1.4 mil) diameter wire. In the experiment in which this wire was used, the volume of the sealed envelope 8 was 120 cc., the weight of wire 2 used was 60 mgms, the oxygen pressure within the envelope was 300 mm. mercury and carbon tetrachloride to a pressure of so mm. mercury was included within the envelope.

The use of the invention also renders it possible to use satisfactorily foils, ribbons or wires of greater thickness than the maximum considered practicable hitherto, thus considerably simplifying the problems of producing suitable foils, ribbon or wire.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A flash lamp comprising a sealed lighttransmitting envelope, a combustible solid metallic material within the envelope for generating on ignition a flash of actinic light, means within said envelope for igniting the metallic material therein, and a combustion-supporting atmosphere in said envelope comprising an oxygenous gas and a gaseous compound which reacts with the metallic oxide formed within the lamp upon combustion of the metallic material to thereby promote uniform burning thereof and which consists of a halogen compound of an element of the group consisting of carbon, silicon and phosphorus.

2. A flash lamp comprising a sealed lighttransmitting envelope, a combustible solid metallic material within the envelope for generating on ignition a. flash of actinic light, means within said envelope for igniting the metallic material therein, and a combustion-supporting atmosphere in said envelope comprising an oxygenous gas admixed with carbon tetrachloride.

3. A flash lamp comprising a sealed lighttransmitting envelope, a combustible solid metallic material within the envelope for generating on ignition a flash of actinic light, meanswithin said envelope for igniting the metallic material therein, and a combustion-supporting atmosphere in said envelope comprising an oxygenous bustion-supporting atmosphere in said envelope 3 comprising an oxygenous gas and a gaseous compound which reacts with the metallic oxide formed within the lamp upon combustion of the metallic material to thereby promote uniform burning thereof and which consists of a. halogen compound of an element of the group consisting of carbon, silicon and phosphorus.

5. A flash lamp comprising a sealed lighttransmitting envelope, a combustible within said envelope comprising a loose filling of fine wire of an alloy of aluminum with about 4% copper, means within said envelope for igniting the wire therein, and a combustion-supporting atmosphere in said envelope comprising an oxygenous gas admixed with carbon tetrachloride.

CHARLES ERIC RANSLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,011,771 Miller Aug. 20, 1935 2,037,101 Van Liempt Apr. 14, 1936 2,272,779 Sarbey Feb. 10, 1942

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