US3817683A

US3817683A - Photoflash lamps

Info

Publication number: US3817683A
Application number: US00302756A
Authority: US
Inventors: K Weber; P Pike
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-02-05
Filing date: 1972-11-01
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18

Abstract

Minature photoflash lamps with a borosilicate glass envelope of less than 1 cc internal volume, a filling of hafnium or hafnium containing filamentary material and combustion supporting gas, giving integrated light outputs on flashing in the ranges of approximately 14,000 lumen seconds per cubic centimeter of bulb volume to 32,500 lm sec/cc.

Description

[451 June 18, 1974 United States Patent [19] Weber PHOTOFLASHLAMPS 3,506,385 4/1970 Weberetal.......................... 431/95 [751 Inventor: Km H-WebenPepperPikeOhio 312321833 $1133; ifla'iii iifiii1331;311:1313:Z3332 [73] Assignee: General Electric Company,

Schenectady, NY.

Nov. 1, 1972 [21] Appl. No.: 302,756

[22] Filed:

Related US. Application Data [63] Continuation of Ser. No.

[57] ABSTRACT Minature photoflash lamps with a borosilicate glass 112,9l3, Feb. 5, 1971,

abandoned.

envelope of less than 1 cc internal volume, a filling of hafnium or hafnium containing filamentary material and combustion supporting gas, giving integrated light outputs on flashing in the ranges of approximately 14,000 lumen seconds per cubic centimeter of bulb volume to 32,500 lm sec/cc.

References Cited UNITED STATES PATENTS 3,303,674 Anderson.......................... 431/94 X 5 Claims, 8 Drawing Figures PHOTOFLASH LAMPS CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation, of application Ser. No. 112,913, filed Feb. 5, 1971 and now abandoned.

Reference is made herein to Ser. No. 42,245 filed June 1, 1970, now abandoned by H. J. Bowers and J. C. Sobieski entitled Method and Apparatus for Filling Flashlamp Bulbs with Filamentary Combustible Material and assigned to the same assignee of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improved miniature photoflash lamps, generally of the all-glass type, the envelope of which contains a filling of filamentary combustible material composed of essentially hafnium and a combustion supporting gas, such as oxygen, at high pressure.

2. Description of the Prior Art As originally introduced on the market, commercial photoflash lamps of the miniature type such as the wellknown all-glass (AG1) photoflash lamp, which utilize zirconium shredded foil and oxygen in a clear glass envelope of less than 2 cc volume and which are completely safe in operation, i.e., free from shattering, produced an integrated quantity of light in the range of 6,500 lumen seconds per cubic centimeter of bulb volume. Such lamps are disclosed in US. Pat. No. 2,982,119 Anderson. As subsequently developed, such allglass miniature photoflash lamps were improved, while maintaining their safety of operation, to provide, in the case of lamps adapted for use is the wellknown flashcube, an integrated light output of approximately 7,400 lumen seconds per cubic centimeter of bulb volume and, in the case of the photoflash lamp commercially known as the AG3 lamp, an even higher integrated light output of about 8,400 lumen seconds per cubic centimeter of bulb volume. Further gain in light output per unit volume, while still maintaining safety of lamp operation, has been achieved in such allglass miniature photoflash lamps by employing zirconium shredded foil fillings and high oxygen gas pressures in conjunction with a borosilicate glass envelope having a low coefficient of expansion and high heatresistance as disclosed in US. Pat. No. 3,506,385, Weber et al., such photoflash lamps having an integrated light output of at least 12,500 lumen seconds per cubic centimeter of bulb volume. Although zirconium has been employed for the filamentary combustible material of such prior miniature type fiashlamps, other combustible metals such as aluminum, hafnium and thorium have been used or proposed as filamentary light-producing material for fiashlamps generally as disclosed in US. Pat. No. 3,303,674.

SUMMARY OF THE INVENTION In accordance with the present invention, a significant and further increase in the integrated light output of miniature fiashlamps has been achieved while still affording complete safety of operation. High and uniformly dispersed loadings of filamentary hafnium as the combustible material have been used in combination with a high heat-resistant, low coefficient of expansion,

glass envelope, of a type giving an excellent seal with the ignition means, together with increased filling pressures of the combustion supporting gas, to provide a flashlamp producing a manyfold increased integrated light output per cubic centimeter of bulb volume in the range of from approximately 14,000 lumen seconds/cc to 32,500 lm sec./cc and in some instances somewhat higher.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view of an all-glass photoflash lamp of the invention having a high uniformly distributed loading of hafnium filamentary material;

FIG. 2 shows an all-glass lamp of the invention similar to FIG. 1 but having an AGI type base;

FIG. 3 shows an all-glass lamp of the invention similar to FIG. 1 but having percussive-type ignition means;

FIG. 4 illustrates an all-glass lamp of the prior art utilizing a fill of filamentary material;

FIG. 5 illustrates the configuration of the filamentary strands of combustible material which may be employed in the fiashlamps of FIGS. 1 to 3, and which are kinked or bent according to one aspect of the present invention;

FIG. 6 illustrates a conventional flashcube in which the lamps of either FIGS. 1 or 3 are mounted;

FIG. 7 is a graph comparing the greatly increased integrated light output achieved by photoflash lamps of the present invention with prior art flash lamps, and

FIG. 8 shows curves of instantaneous light output per internal bulb volume for prior art lamps and photoflash lamps of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, several different embodiments of the invention are shown by way of example. In FIG. 1, the flashlamp 10 comprises a sealed envelope or bulb ll of clear drawn glass tubing having an internal volume of less than 1 cubic centimeter and which is closed at one end by an integral flattened stem press or pinch seal 12 and at the other end by an exhaust tip 13. Strands of combustible material 14 are dispersed within the lamp envelope and chemically react on lamp ignition with a combustion supporting gas in the envelope, such as oxygen, to provide a flash of actinic light.

The lamp is provided with suitable flash ignition means, which in the case of the lamp of FIG. 1 comprises a pair of lead-in wires 15 sealed in the stem press 12 and connected near their inner ends by a filament 16 in the form of a short length of fine tungsten wire of approximately 0.6 mil diameter. Beads of fulminating or primer material 17 coated on the ends of the lead-in wires 15 and in contact with the filament 16 are ignited by heat from the filament when energized by electric current to initiate combustion of the filamentary combustible material 14. An insulating support 18, such as I a glass bead, ties the two lead wires 15 together and as- FIG. 2 illustrates an AGl type of flashlamp in which the stem press or pinch 12 may be enlarged somewhat and provided with a transverse groove 21 with the ends of the lead wires 19 being folded back over the stem press with their free ends re-entering and embedded in the press to provide, in effect, a lamp base for mounting the flashlamp in a socket. Such a base construction is shown by VandenBoom US. Pat. No. 3,0l6,727.

One alternative form of ignition means, i.e., a socalled percussive type ignition means for the photoflash lamp is illustrated by FIG. 3 in which an anvil rod 22 carrying a coating 23 of percussively ignitable fulminating material over part of its length is located centrally within a deformable metal tube 24 depending from and sealed to one end of the lamp envelope 10 with the tube being closed at its outer end. The lamp of FIG. 3 is percussively flashed by striking the tube 24 with a hammer or spring at a region opposite the fulminating material 23 to ignite such material which is then expelled out of the open inner end of the tube into the lamp envelope to ignite the combustible material in the lamp. Lamps of the percussively ignitable type may be incorporated into a flashcube with appropriate designs of mechanically operated spring hammers for flashing the lamps as is known in the art.

Other alternative means may be used for igniting the flashlamps, such as piezoelectric crystals or lasers, as is known in the art.

Photoflash lamps of the general design constructions shown on enlarged scales by FIGS. 1, 2 and 3 are well known. By following the teachings of the present invention, the design parameters and constructions have been modified and combined in a new way to provide flashlamps having greatly increased integrated total light output for a given size of lamp envelope such increases being on the order of a factor of 2 or more. The teachings are especially applicable to the newer miniature all-glass flashlamps and flashcubes in which the internal volume of the lamp envelope is less than 1 cubic centimeter.

In the preferred form of the present invention, and to utilize the invention to the fullest extent possible, the lamp envelope 11 of less than 1 cc volume is made of a bore-silicate glass having a low coefficient of thermal expansion to afford increased strength for containing and withstanding the thermal and mechanical shock incident to lamp flashing and to provide an excellent hermetic seal with the lead-in wires 15. The ignition mount lead-in wires 15 are made of metal or alloy substantially matching the expansion of the glass, a suitable lead-in wire being made from an iron-nickel-cobalt alloy. A suitable glass is disclosed in the aforementioned Weber and Cressman US. Pat. No. 3,506,385, in which the glass consists essentially of the following constituents in about the ranges stated by weight: 60 to 75% SiO 10 to 25% B 1 to 10% A1 0 4 to 10% total alkali oxides, and 0 to 5% BaO, the glass having a mean coefficient of linear thermal expansion, between 0 and 300C, in the range of about 40 to 50 times per degree C. Although not dependent upon the compositions of the borosilicate glasses used, examples of suitable wall thicknesses of glass tubing from which the envelopes 11 are made would range from about 10 mils to 50 mils.

Combined with use of the borosilicate glass tubing of the envelope having the characteristics mentioned is a filamentary combustible fill 14 of hafnium or an alloy consisting essentially of hafnium. The filamentary material 14 may be cut from hafnium foil in a manner well understood in the art to form a shredded foil with the thickness of the hafnium foil ranging from about 0.5 to 1.5 mils and with the cut width of the individual strands ranging from about 0.5 to 3.0 mils. The quantity of filamentary combustible material loaded into the lamp envelope ranges from 60 to 200 milligrams per cubic centimeter of internal lamp volume.

To assist in distributing the stranded hafnium material in an exceptionally uniform and dense manner throughout the interior of the envelope, as in the showing of FIGS. 1, 2 and 3, the strands are sharply bent or kinked along their lengths at sharp angles on the order of 60 as is already known. As an example, a strand length of about 4 inches is kinked with about 20 to 40 sharp bends located at intervals of about one-eighth inch along the strand length. The kinking takes place after the individual filamentary strands are cut from the sheet of foil and prior to insertion of the strands into the lamp envelope. The mechanism for kinking the strands is disclosed in copending patent application Ser. No. 42,245, filed June 1, 1970, by J. J. Bowers and J. C. Sobieski and assigned to the same assignee as the instant application. The sharp bends or kinks in the strands give the strands a closely bunched or crinkled appearance, as shown at 25 in FIG. 5. When loaded into an envelope 11, the kinked strands form point contact with the inner wall of the envelope, as shown in FIGS. 1, 2 and 3. This is distinguished from the sub stantial lengths of a relative large open loop configuration with gradual bends lining the envelope wall as in the prior stranded metallic fillings of prior art lamps as shown at 26 in FIG. 4. As a result of the kinking as described above, the quenching action of the wall envelope on the speed of combustion on lamp flashing is reduced and the combustion efficiency is increased with more light output. Moreover, the uniform distribution and density of fill of the foil resulting from the sharply bent and kinked strands makes possible a better oxygen reaction throughout the bulb on flashing with the combustion proceeding at a uniform rate throughout the volume of combustible material. With the strands in a kinked form, it is believed that there is less selfabsorption of the generated light by the filamentary material within the envelope and more useful light emitted on flashing.

A combustion supporting gas, for example oxygen, is introduced into the lamp envelope prior to the tipping off thereof in amounts and at pressures to provide from to percent of the quantity of gas necessary for a stoichiometric chemical reaction with the hafnium filamentary material 14 on lamp ignition in terms of an idealized chemical reaction in which Hf 0 HfO Such gas pressures will range from about 8 to 30 atmospheres. With hafnium, the combustion proceeds comparatively slowly over the five to ten millisecond period following ignition as the chemical reaction between the high molecular weight hafnium and oxygen gains impetus. As combustion accelerates, the finely kinked condition of the strands facilitates a very uniform and high rate of chemical reaction to take place giving an unusually high light output over the entire burning cycle of the lamp. As a result, the instantaneous light output per unit of lamp volume of lamps of the instant invention closely follows the output of prior art flashcube lamps up to about a 13 millisecond time interval following energization of the lamp ignition filament 16, as shown by the graph of FIG. 8 wherein the curve designated Lamp Type A is representative of a flashlamp constructed according to the invention. This means that flashlamps of the invention are suitable for use with cameras calling for the operating characteristics of previous commercial flashlamps, for example, the flashcube of which the output is illustrated in FIG. 8.

The hafnium metal itself, and the hafnium oxide formed on flashing, have boiling points of approximately 5,400 C at atmospheric pressure. With the higher gas pressures within the envelope, the boiling temperature will increase by well-known physical laws so that the increased thermal intensity and light output of the hafnium-oxygen reaction is contained at high loadings within the borosilicate glass envelope to give a greatly increased light output in photoflash lamps of commercial production without envelope shatter. Photoflash lamps constructed in accordance with the invention will provide an integrated light output of at least 14,000 lumen seconds per cubic centimeter of lamp volume and in some instances as high as 32,500 1m sec/cc.

Many thousands of photoflash lamps of the invention have been constructed and successfully flashed with safety using design parameters and giving results as set forth in the table below. Such lamps have utilized hafnium filamentary combustible material and, as specific examples, have been tabulated in four groups as lamp types A, B, C and D giving the light outputs as stated without color correcting coatings.

(Ave. 29,500)

To provide an additional measure of protection against shattering of the glass bulb on lamp flashing, the bulb is dipped, sprayed, or otherwise provided with a heatresisting high-strength coating, an example being cellulose acetate lacquer. ln appropriate instances, the coating may be provided with coloring material to restrict or correct radiation emitted on flashing of the lamp to provide proper color correction for the photographic film being exposed, as is well understood.

FIG. 7 graphically illustrates the greatly increased light output of the novel miniature all-glass lamps herein disclosed by curves of the integrated light output per cubic centimeter of lamps A, B, C and D in comparison with the conventional No. 5, M3, AGl and flashcube lamps, all without colored lacquer or colored 6 covers or shields to restrict or correct the light output. As shown by such curves, the total integrated lumen seconds per cubic centimeter of bulb volume for the different lamp types are approximately as follows and in the case of Lamp Types A, B, C and D the average light output from the preceding table is listed.

Thus, photoflash lamps may be manufactured in accordance with the invention which will give a substantially higher light output per unit of bulb volume with excellent product safety. Specifically, the flashlamps described herein as exemplifying the invention give a light output per unit bulb volume from approximately two to as high as approximately five times higher than has heretofore been reached with flashlamps of the prior art. As used in the claims, the term envelope should be interpreted to mean an envelope which may, or may not be, provided with a containing coating, depending upon the flashlamp design, as is well understood in the art. In both tables the total integrated light outputs of the flash-lamps have been rated at 40 milliseconds, which corresponds to substantially all the useful light output of the lamps although, as shown in FIG. 7, there is a very small and minor increment of light available for photographic purposes for an additional ten seconds out to approximately 50 milliseconds.

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

1. A flash lamp comprising, in combination,

a borosilicate glass light-transmitting envelope consisting essentially of the following constituents in ranges by weight of to SiO 10 to 25% B 0 1 to 10% A1 0 4 to 10% total alkali oxides and 0 to 5% BaO and having a coefficient of thermal expansion of about 40 to 50 times 10 per degree C and a volume of less than 1 'cc,

a quantity of stranded combustible material consisting essentially of hafnium distributed within said envelope in an amount from 28 to 52 mgs, said strands being minutely kinked into bends at a multiplicity of closely spaced points along the lengths of the strands corresponding to about 20 to 40 bends per 4-inch length of strand,

a quantity of a combustion supporting gas at a pressure of from 10 to 26 atmospheres within said envelope and in an amount from about to of the stoichiometric quantity required for chemical reaction with the combustible material, and

ignition means for igniting said combustible stranded material mounted within said envelope by means comprising a metallic member having a coefficient of expansion substantially matching that of the glass and being sealed to the glass envelope,

said flash lamp upon flashing generating a total integrated light output of from 14,000 to 32,500 lumen seconds per cubic centimeter of envelope volume at approximately 40 milliseconds after ignition.

2. The combination of claim 1 in which the envelope volume is from 0.55 to 0.65 cc, the quantity of combustible material is from 42 to 52 mgs, the quantity of combustion supporting gas is from 10 to 12 atmospheres and the integrated light output per cubic centimeter of bulb volume is between 14,000 and 17,000.

3. The combination of claim 1 in which the envelope volume is from 0.3 to 0.35 cc, the quantity of combustible material is from 28 to 36 mgs, the quantity of combustion supporting gas is from 13 to 17 atmospheres and the integrated light output per cubic centimeter of bulb volume is between 17,000 and 21,400.

4. The combination of claim 1 in which the envelope volume is from 0.3 to 0.35 cc, the quantity of combustible material is from 42 to 46 mgs, the quantity of combustion supporting gas is from 17 to 20 atmospheres

Claims

1. A flash lamp comprising, in combination, a borosilicaTe glass light-transmitting envelope consisting essentially of the following constituents in ranges by weight of 60 to 75% SiO2, 10 to 25% B2O3, 1 to 10% Al2O3, 4 to 10% total alkali oxides and 0 to 5% BaO and having a coefficient of thermal expansion of about 40 to 50 times 10 7 per degree C and a volume of less than 1 cc, a quantity of stranded combustible material consisting essentially of hafnium distributed within said envelope in an amount from 28 to 52 mgs, said strands being minutely kinked into bends at a multiplicity of closely spaced points along the lengths of the strands corresponding to about 20 to 40 bends per 4-inch length of strand, a quantity of a combustion supporting gas at a pressure of from 10 to 26 atmospheres within said envelope and in an amount from about 80% to 150% of the stoichiometric quantity required for chemical reaction with the combustible material, and ignition means for igniting said combustible stranded material mounted within said envelope by means comprising a metallic member having a coefficient of expansion substantially matching that of the glass and being sealed to the glass envelope, said flash lamp upon flashing generating a total integrated light output of from 14,000 to 32,500 lumen seconds per cubic centimeter of envelope volume at approximately 40 milliseconds after ignition.

4. The combination of claim 1 in which the envelope volume is from 0.3 to 0.35 cc, the quantity of combustible material is from 42 to 46 mgs, the quantity of combustion supporting gas is from 17 to 20 atmospheres and the integrated light output per cubic centimeter of bulb volume is between 21,800 and 26,600.

5. The combination of claim 1 in which the envelope volume is from 0.22 to 0.26 cc, the quantity of combustible material is from 36 to 44 mgs, the quantity of combustion supporting gas is from 20 to 26 atmospheres and the integrated light output per cubic centimeter of bulb volume is between 26,500 and 32,500.