US3672814A - Photoflash lamp with yttrium combustion filling - Google Patents

Abstract

AN IMPROVED COMBUSTIBLE PHOTOFLASH LAMP IS DESCRIBED WHEREIN THE COMBUSTIBLE METAL FOIL IS YTTRIUM METAL. THE RISE TIME CHARACTERISTIC TO PEAK LIGHT OUTPUT IS SIGNIFICANTLY IMPROVED BY THE USE OF THE YTTRIUM COMBUSTIBLE METAL. THE ADDITION OF VARYING AMOUNTS OF YTTRIUM METAL TO

STANDARD COMBUSTIBLE METAL SUCH AS ZIRCONIUM ALSO IMPROVES THE RISE TIME TO PEAK LIGHT OUTPUT CHARACTERISTIC FOR THESE LAMPS.

Description

June 27, 1972 K. F. ANDREW ETAL 3,672,814

PHOTOFLASH LAMP WITH YTIRIUM COMBUSTIBLE FILLING Filed Oct. 30, 1970 LE L 22 MILLISECONDS United States Patent Ofice 3,672,814 Patented June 27, 1972 3,672,814 PHOTOFLASHLAMP WITH COMBUSTION FILLING Kenneth F. Andrew, East Pittsburgh, and Richard L. Tallman and Earl A. Gulbransen, Pittsburgh, Pa., assiguors to Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed Oct. 30, 1970, Ser. No. 85,513

Int. Cl. F21lr 5/02 U.S. Cl. 431-95 6 Claims ABSTRACT OF THE DISCLOSURE An improved combustible photoflash lamp is descirbed, wherein the combustible metal foil is yttrium metal. The rise time characteristic to peak light output is significantly improved by the use of the yttrium combustible metal. The addition of varying amounts of yttrium metal to standard combustible metal such as zirconium also improves the rise time to peak light output characteristic for these lamps.

BACKGROUND OF THE INVENTION One type of standard photoflash lamp in use for the last several years is a zirconium shreaded foil combustible, super-pressure, oxygen-filled photofiash lamp. Such lamps have continuously been reduced in size while providing adequate light output to make picture-taking very convenient.

The characteristic light output curve for photofia sh lamps to a certain extent determines their utility with various camera systems. The zirconium shredded foil flash lamp exhibits a light output characteristic curve which rises at a fairly rapid rate from the initiation of light output to the peak light output in a period of about 8 milliseconds, and then exhibits a gradual decay over approximately 30 milliseconds. It is desirable for certain camera systems that a flash lamp be provided which has a light output characteristic curve which exhibits as short a time for rise to peak light output as is possible.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view in section of a photofiash lamp embodiment of the present invention.

FIG. 2 is a plot of the light output characteristic curves for both the yttrium lamp of the present invention, and for a standard zirconium flash lamp. The relative light output is measured along the ordinate, and the time in milliseconds is plotted along the abscissa.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention can be better described by reference to the exemplary embodiment as shown in FIG. 1, and by the light output characteristic curves shown in FIG. 2. In FIG. 1, photoflash lamp 10 comprises an hermetically sealed, light-transmissive glass envelope 12, ignition means which by way of example comprises an electrically conductive filament 18, for example formed of tungsten. A readily combustible conventional primer 20, such as a several milligram mixture of powder zircohium and potassium perchlorate is deposited on filament 18, or on the ends of lead- ins 14 and 16, proximate filament 18. The electrically conductive lead- ins 14 and 16 are sealed through the envelope 12 and electrically connected to the ignition filament 18. A conventional blue lacquer coating 24 is generally disposed on the exterior envelope 12 to improve the color characteristic of the light output and to prevent ruptureof the envelope 12. The primary combustible material is a shredded metal 22 which comprises yttrium metal. For a photofiash lamp with a volume of about 0.6 cubic centimeter, the shredded yttrium is preferably included in an amount of about 30 milligrams, which is about 5.7X10- gram-atom of yttrium per cubic centimeter of lamp volume. The lamp is tipped-off and sealed containing an oxygen fill of about 8 atmospheres, although this can readily be varied from five to ten atmospheres, for example. The yttrium combustible metal is preferably in the form of shredded foil, and as an example, the dimensions of the foil shreds are similar to those of the conventional zirconium foil shreds. Measuremerits of burning rates for yttrium foil of conventional foil dimension, i.e. about 1.8 square mils cross section, indicate that the yttrium burns about twice as fast as conventional zirconium foil.

The yttrium combustible content can be varied with a decrease in light intensity as the amount is decreased and as a practical limit the yttrium content is at least about 3.7 -10- gram-atom per cubic centimeter of lamp volume. The oxygen content can be widely varied, but is generally in the range of 70-100% stoichiometry with respect to the yttrium in forming yttrium oxide during combustion.

The typical light output characteristic curve for the lamp described above is shown in FIG. 2 as curve A. Relative light output is plotted along the ordinate against the time in milliseconds. The first portion of curve A which runs along the zero axis is indicative of the time from the application of electrical potential to filament 18 until the primer is ignited and the combustible is burning to produce light output. This time is largely determined by the nature of the ignition system, i.e. for an electrical system such as described above it is about 3-4 milliseconds. It is the portion of curve A which extends from the initial production of light output at the end of this 3-4 milliseconds ignition period, to the peak light output value, which is referred to as the rise time to peak light output in this application. As is readily seen in FIG. 2, the rise time to peak light output for the lamp of the present invention is about 4 milliseconds. The light output then gradually decays over approximately 30 milliseconds. Comparative data for a zirconium flash lamp is shown by curve B of FIG. 2. The ignition time of about 3 to 4 milliseconds is about the same, but the time to peak light output from initiation of light output is about 8 milliseconds, or about double the time which is observed for the lamp of the present invention.

It has also been discovered that yttrium metal can be added to zirconium metal as the combustible to provide a flash lamp with an improved time peak light output characteristic curve. For example, for the lamp size described above with a 20 milligram shredded foil filling which is zirconium and at least 20 atom percent yttrium the time to peak light output from'initiation of light output is reduced to approximately 5 milliseconds. The use of a hafnium metal combustible foil is disclosed in copending application S.N. 46,378 filed June 15, 1970, owned by the assignee of the present invention. The addit of e t 1. 2.,a m1i .tetr t tiymu ththsm i memaas mthe.an e s.smea s. s t afl si t gravid; hafnium combustible results in an improvement of rise time over that attained with only hafnium so that the peak lightoutputhoccurs about 6 milliseconds after initia; tion of light output. It is thus seen that relativelysmall amounts of yttriumin combination with other conventionally used combustible metals results in an improved light output characteristic.

The invention has been described with a conventional ignition system but is not limited thereto. A percussive ignition system can be utilized in igniting the improved combustible light-producing metal.

We claim as our invention: H p

1. A photoflash lamp combination comprising an hermetically sealed light-transmissiveenvelope, ignition means within said envelope adapted to be activated to initiate combustion, a combustion supporting atmosphere substantially comprising oxygen at a predetermined pressure enclosed by said envelope, wherein the improve: ment consists of an improved gombustible metal com: prising at least 4 atompercentfyttrium, whereby the rise time to peak light outputis shortfened,

2. The combination as specified in claim l, 'wherein said yttrium is present. in anamount of at [least about 55.7}{10 gram-atom cubic centimeter of lamp vol- 7i) 1 0(l% stoichiometry with respect to the yttrium in forming yttrium. oxide durihg combustion. V

3. The combination as specified r in claim 2, wherein said yttrium is preferably included in an amount of about 5.7 l0 gram-atomper cubic centimeter-of lamp volume, and the oxygen press ure is about 8 atmospheres.

4.'The combination as specified in claim 1-, :wherein i said combustible metal consists essentially ofryttrium;

5. Thecombinatiomas specified inclaim 1, wherein said combustible-metal substantially comprises zirconium l,

and the yttrium contentis at least about..20 atom percent of the total combustible metal.

6. The combination as specifiedin claim 1, wherein said combustible metal substantially comprises hafnium and the yttrium content is at least about 4 atom percent of the total combustible metal.

v v References Cited UNITED STATES PATENTS EDWARD J. MICHAEL, Primary Examiner

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