US2037101A - Flash lamp - Google Patents

Description

Apri M, 1936. J.' A. M. VAN LIEMPT FLASH LAMP Filed April 28, 1954 Patented Apr. 14, 1936 UNITED STATES FLASH LAMP Johannes Antonius Maria van Liempt, Eindhoven, Netherlands, assignor to N. V. Philips Gloeilampenfabrieken, lands Eindhoven, Nether- Application April 28, 1934, Serial No. '123,009 In Germany December 1933 13 Claims.

My present invention relates to flashlamps and more particularly to ilashlamps as used for photographic purposes. Such ashlamps usually comprise a sealed transparent bulb in which is enclosed a readily combustible material together with a substance-usually a. gas filling-which, upon ignition, enters into a reaction with the combustible material with the emission of actinic light.

The combustible materials which have been found most suitable forA this purpose are aluminium and magnesium, which metals in proper form and thickness, when ignited in an oxygen or oxygen-containing atmosphere, have a rapid combustion with the emission of a substantial amount of actinic light.

However, neither aluminium nor magnesium, as used in known ashlamps, gave` a fully satisfactory solution of the problem.

Aluminium is comparatively diflicult to ignite and its ignition in flashlamps could only be effected in case the aluminium was in the form of foils of extreme thinness, namely, of the order of 2 microns and even less.

The rolling of such thin aluminium foils entails considerable diiilculty, and there is a high percentaged variation in the thickness between the several foils. Due to such variations in the, thickness of the foils, the time of combustion and the time and amount of actinic radiation, may vary for the individual fiashlamps.

Furthermore, the handling of such thin aluminium foils and their insertionv into the bulbs are comparatively difficult and requires careful manual operations. 'I'his together with the relatively high price of the thin aluminium foil, makes such lamps fairly expensive. This is a serious drawback as such ashlamps can be used only for a single exposure.

The handling and mounting of aluminium wire is much simpler, and aluminium being an easily drawable metal it would seem, that instead of aluminium sheets, aluminium could be used in flashlamps in the form of wire. This, however, is not the case.

While aluminium can be drawn with comparative ease to a diameter of about 40 to 50 microns, this is still too thick a wire to be ignited, and aluminium wire of such diameter cannot be ignited by the passage of current therethrough, and cannot even be ignited if separate explosive ignition mixtures are provided in the lamp.

To obtain aluminium wire which can be ignited it would be necessary to draw aluminium far below the diameter to which it has been practical to draw it, which would give considerable difliculties in manufacturing same and, even if this were feasible, such wire would be mechanically very weak.

Magnesium is a metal which ignites with considerably greater ease than does aluminium under identical circumstances. However, in the past magnesium wire below diameters of about 500 microns could not be produced, and the only method by which such wires of larger diameters could be obtained was by the squirting process. Such thick squirted wires however have practically vtoo long a flash time.

In my copending United States application Serial No. 723,007, led April 28, 1934, I have described a novel process by means of which it is possible to draw magnesium and magnesium alloys of a high magnesium content into wires or bands of small cross-sectional perimeters, and in my copending United States application Serial No. 723,008, led April 28, 1934, I have described the use of said thin drawn Wires and bands for ilashlamps.

The present invention is based on the idea of combining the useful properties of aluminium with those of magnesium, and I have found that certain magnesium-aluminium alloys constitute an excellent combustible material for flashlamps. More particularly I have found, that two series of magnesium-aluminium alloys are adapted for this purpose, these being the series of such alloys which comprise up to 13% of magnesium, the balance being aluminium, and the series of alloys which comprise more than 85% of magnesium, the balance being aluminium. All of the percentages given herein are per weight. I have also found that the series of magnesium-aluminium alloys containing from 13% to 85% magnesium is unsuitable as a material for ilashlamps in the form of wires, bands or foils, as the alloys having such a magnesium content are not adapted to be subjected to mechanical operations, as drawing or rolling.

Considering rst the series having less than 13% magnesium content and adapted to be used 45 inflammable and moreover, it may be easily drawn cold, for instance at speeds of 100 m. per minute and a narrowing of the drawing dies up to 20% in diameter per die. In order to ensure the same infiammability, a foil of this alloy need not be rolled to such a thinness as aluminum foil. i

However the time of actinic radiation is shorter as more magnesium is added. An alloy of aluminum and 7 to 8% magnesium, for instance, has already a time of radiation substantially corresponding to that "of pure magnesium.

Regarding the second series of the magnesiumaluminum alloys, namely those containing or more magnesium, these alloys have similar properties as the magnesium, both in regard to inammability and time of actinic radiation, as well as in regard to their behaviour when subjected to mechanical working.

In my above referred to copending application Serial No. 723,007 I have dcribed a novel process by means of which pure magnesium, as well as high percentaged magnesium alloys, can be drawn into small diameter wires and bands of a small perimeter, and this process also applies to the series of magnesium-aluminum alloys which comprise 85% or more magnesium, the balance being aluminum.

Pure aluminum, as stated, can be readily drawn: this being accomplished in a cold state and with a high draft. The addition of magnesium to the aluminum makes drawing somewhat more difficult, and with increasing magnesium content the speed of drawing and the draft have to be reduced, however up to a magnesium content of about 13%, cold drawing of the alloy is feasible. Thus e. g. a magnesium-` aluminum alloy having 5% magnesium and 95% aluminum is readily inflammable and can be conveniently drawn cold in the ordinary sense of this word at speeds of about meters per minute, and with a draft up to about 20%. Such wire, even when having diameters of about 300 microns, is suillciently inflammable; however to obtain a short time of actinic radiation I prefer to use smaller diameters e. g. 50 microns or less. This same material in foils having thicknesses of 5 microns or less can be similarly used.

The time of actinic radiation, by which is meant the time required for the light to produce blackening of the light-sensitive material (after its development, is also shorter in the case of Such magnesium-aluminum alloys than in the case of pure aluminum (brought into an inflammable form), under similar conditions.

Such magnesium alloys could not be drawn prior to my invention, and the only process by means of which wires of such alloys could be produced, was by heating such alloys and squirting them in a plastic or molten state through a heated die. However, squirted wires had still too great thickness to be usable for flashlamps.

A magnesium-aluminum alloy comprising more than 85% magnesium can be suitably dra-wn into a thin wire or band in accordance with the process described in my above referred to application Serial No. 723,007. According to said process the alloy, by means of casting or squirting, is formed, for instance, into a rod having a diameter of about 6 mm. and then gradually reduced in perimeter in successive steps either solely by drawing or first by swaging and then by drawing. In this process the successive steps in the reduction oi' the cross-sectional perimeter of the wire are to be kept quite small, and the acamoi draft, i. e. the reduction in perimeter between successive dies,should be 1 to 6%. Thereby the initial stages of swaging or drawing the draft is between 1 to 3% and in the latter stages between 3 to 5%, and should nbt exceed 6% in any stage of the operations.

Furthermore, while passing the dies', the `wire is to be heated to a temperature of about 350 C. This can be achieved, for instance, by heating the drawing die to such a temperature. For diameters above 300 microns, the wire is preferably preheated to a temperature of about 450 C. before reaching the die. Further details are described in the above referred to application Serial No. 723,007.

High percentage magnesium-alloy can ,be drawn into a wire having an improved mechanical strength and to a diameter as low as 100 microns and less. A thin drawn wire of such alloys can be similarly obtained by first drawing the magnesium wire to a suitably small diameter and then flattening the wire, for instance by means of a rolling operation, or by using in the last steps of the drawing operation, suitably shaped dies which flatten the wire.

In such a manner bands having a perimeter less than 300 microns can be obtained.

Drawn magnesium-aluminum alloy (comprising 85% or more magnesium) wires and bands obtained in such a manner have a fine crystalline 1 structure and show, on their surface, characteristic longitudinal stripes due to the drawing process. Such wires and bands are easy to ignite, have a. short actinic reaction time and give a more intensive radiation in comparison with a drawn magnesium wire of the same dimensions.

Such magnesium-aluminum alloys can also be formed in the shape of thin foils having a thickness of about 5 microns or less.

'Ihe new type of flashlamps made according to my invention and using the magnesium-aluminum alloys of the above two series, especially if used in the form of wire or band, havethe advantage of great uniformity in performance,

and can be manufactured by standard methods and on the standard machines used in the manufacture of electric incandescent lamps. Also the danger of combustion in the sealing of such lamps is greatly reduced as compared with the 'same operation for ilashlamps using thin aluminum foils. Furthermore, such lampscan be made in smaller bulbs than the flashlamps presently used for the same or even a greater amount of actinic radiation. I

The novel flashlamps according to my invention comprise a magnesium-aluminum alloy within the percentaged limits previously defined, in the form of a drawn magnesium wire or ribbon of a perimeter preferably below 300-microns, e. g. microns or in the form of a thin foil, suitably supported ln a transparent bulb.

A suitable lling is provided in the bulb and upon the passage of a current through the magnesium-aluminum alloy, or upon igniting same by other means, a very rapid combustion of the magnesium-aluminum alloy is produced with a very effective means of actinic radiation.

Various advantages of my invention and various embodiments and modifications thereof will be described with respect to the accompanying drawing in which:

Figure 1 vis a partly sectionized side elevation of a flashlamp according to my invention in which a drawn magnesium-aluminum wire is supported on a suitable frame and is ignited by means of a suitable primer.

Fig. 2 is a partly sectionized side view of a flashlamp showing a modification of my invention in which the magnesium aluminum wire or ribbon is arranged in the form of a clew.

Fig. 3 is a partly sectionized side view of a flashiamp showing a still further modification, in which the magnesium aluminum wire is arranged in zigzag manner similar to the filaments of. incandescent lamps and is connected to lead-in wires.

Fig. 4 is a partly sectionized side view of a lamp showing a still further modification in which the magnesium-aluminum wire is arranged in the form of a helical coil.

Fig. 5 is a. partly sectionized side view of a fiashlamp according to my invention, which is provided with fuses in the lead-in Wire.

Fig. 6 is a partly sectionized side view of a flashlamp showing a still further modification of my invention in which a thin magnesium-aluminum foil is provided in the bulb.

As a rule I prefer to use a magnesium-aluminum alloy wire or band as the combustible body.

The magnesium-aluminum alloy used, as stated. is one of the two series of which the first comprises less than 13% magnesium, (the balance being substantially aluminum) and the other of which comprises at least 85% magnesium, the balance being substantially aluminum.

The magnesium-aluminum-alloy as used in the fiashlamps according to my invention, may be in the form of a drawn wire or drawn band, or again it may be in the form of a thin foil. As a rule I prefer to use a thin drawn magnesium-aluminium wire or a band having a circumference or perimeter of the order of 300 microns or less e. g. 100 microns.

The transparent bulb of the lamp may have the general shape of an incandescent lamp bulb and may be, as a rule, smaller than the bulbs used for fiashlamps of previously used types.

According to one embodiment of the invention the bulb is provided with a gaseous filling which, upon ignition, enters into an actinic reaction with the magnesium-aluminium alloy. Such a gas may be, 4for instance, oxygen or nitrogen monoxide. The amount of gas used is preferably larger and e. g. about twice the amount theoretically required to complete the chemical reaction. While a lesser amount of gas will not substantially prolong the time of reaction, I prefer to provide such an excess of gas to complete the combustion of the magnesium-aluminium alloy so as to insure a uniform performance of the lamps.

Referring to Figure 1, the lamp there illustrated comprises a vitreous transparent bulb I of the general type used in electric incandescent lamps, and is provided with a stem 2 which supports a button rod 30. Secured to the buttons 32-32 of the rod 30, are supports 5-5 forming a. frame for the magnesium-aluminium wire 6, wound around the same. kThe supports 5-5 may be either of metal or of insulating material.

A small filament 4, the two ends of which are connected to lead-in wires 3-3 sealed into the stem and leading to the outside of the bulb, together with a small piece of aluminium foil 1 prol vided on the filament 4, form ignition means to the wire I by means bf a binder such as a nitro cellulose lacquer or in a mechanical way.

I'he lamp shown in Fig. 2 is similar to that shown in Fig. 1 except, that the magnesium-aluminium wire or band I3, instead of being provided on a frame, is loosely arranged and supported in the bulb in the form of a clew. If thicker wires e. g. more than 60 microns are used. care should be taken that the magnesium-aluminium alloy wire should be at a sufficient distance from the wall of the bulb, and be so secured that no portions of the wire may touch the bulb and cause its cracking when the reaction takes place. This can also be effected by coating the inner surface of the envelope with a thin transparent coating 35 of a lacquer e. g. of acetylcellulose.

To start the reaction a separate igniter or primer is again provided, this being shown in the drawing as a filament I2 to which is applied, for instance by coating, an explosive mixture II. A suitable explosive mixture is, for instance, a paste which comprises a mixture of a metal powder, of an oxidizing agent and of a binding agent. Suitable meials. for example are pulverized zirconium or aluminum, and suitable oxidizing agents are, for example, lead dioxide, manganese dioxide, poassium chlorate and praseodymium oxide. whereas nitrate cellulose acetyl cellulose or sili- Cous varnish are suitable binders.

In case such a combustion mixture ls used, preferably a. gas filling consisting of oxygen or of a gas containing oxygen is used.

The flashlamp of Fig. 3 has the general consruction of an electric incandescent lamp havinf,r a straight filament in zig-zag arrangement, a construction used in some types/of incandescent straight filament vacuum lamps. The magnesium-aluminlum wire or band I1 forms a filament which is supported in known manner on the i hooked ends of the supports 3i, supported on the buttons 32--32 of the button rod 30. The free ends of the magnesium-aluminium wire I l are connected to the sealed in lead-in wires IG-IS in the same manner as is the filament of an incandescent lamp. In this arrangement' no special ignition means are provided and the magnesiumaluminium wire is ignited directly by passing current through same.

Fig. 4 shows a similar embodiment, except that nl the magnesium-aluminium wire forms a coiled lament 2|, supported by and connected to the two ends of the lead-in wires 2li- 20. 'I'his is also a well-known construction for incandescent lamps and ignition again takes place by the passage of current through the magnesium-aluminium wire.

In Fig. 5 an arrangement similar to that of Fig. 2 is shown, except that the primer is shown as a filament 28 which is secured by means of a paste to the free ends of the lead-in wires 24 and 25, and a fuse 25 is provided in the lead-in wire 25; the fuse forming part of this lead-in Wire being made of a suitable material, for instance, of constantan wlre.

Fig. 6 shows a further modification of my invention in' which, instead of a drawn magnesiumaluminium wire or band, a thin magnesium-aluminium alloy foil 33 is provided having a thickness of about 5 microns or less. A suitable primer 34 is also provided. This construction is similar to that used in fiashlamps using thin aluminium foil. However. my invention permits the use`of a considerably heavier foil with a smaller bulb, under similar circumstances.

The lamps with constructions without fuse as Cil shown in Figs. 3 and 4, where the ignition is ei'- i'ected by the passage of the current through the magneslum-aluminium wire or band are adapted to be used for comparatively high voltages, for instance, at the usual supply voltages of 110 to 220 volts.

However, if the lamp is to be used for voltages below 10 volts, for instance with a 4-volt dry battery, as may be required in outdoor photography, I prefer to provide primers or ignition means. Such means may be for instance, one or more small, low voltage incandescible filaments suitably provided in the bulb, or other type of primers already described in connection with the drawing may be used. Instead of such primers or in conjunction therewith, I may also use an explosive gaseous mixture, for instance, carbon disulphide and oxygen, carbon disulphide' and nitrogen oxide, or again, carbon disulphide and laughing gas. The ignition of the magnesium-aluminium wire is then caused by the heat produced by the explosion of the gas mixture, whereby the reaction of this mixture may or may not contribute to the emission of actinic light.

I prefer also to provide a. fuse in the lamps, as illustrated in Fig. 5, especially when the lamps .are suitable for both low and high voltages. 'I'he fuse preferably forms part of the lead-in wires, as shown in Fig. 5, and may be provided either within the bulb or outside thereof.

The character of the actinic light radiated by the lamp, and thus its photographic effect, can be modied by the use of colored bulbs 'or of bulbs which are selectively transparent, for instance, selective to ultra-violet or ultra-red light; or chemical substances, for instance salts, modifying the photographic properties of the actinic light, may be applied to the magnesium-aluminum alloy. Such substances may be, for instance, strontium-calcium-sodiumor mercury-salts, Or a salt like potassium chlorate (KCl Os) may be used, which not only iniluences the light emission, but also produces oxygen.

It should be Well understood that while the chief constituents of the magnesium-aluminum alloys used in my invention are the metals mag-` nesium and aluminum, the alloy may contain a small percentage of other metals; for instance, a few percents of zinc and a few tenths of a percent of maganese or cesium, will not substantially eil'ect either the mechanical or the actinic properties of the magensium-aluminum alloy.

While my invention is preferably applied to` ilashlamps having sealed containers, the magneslum-aluminum alloys described may also be used for flashers to be combusted in the open air in the presence of well-known oxidizing materials, for instance, potassium chlorate.

It should also be well understood that the illustrated embodiments merely give typical examples, and various other structures can be employed. Furthermore, that features shown in the construction of one figure, may be used in connection with the constructions of other gures; for instance, the fuse indicated in Fig. 5 can be equally well used with the construction of any of the other figures; or again, the primer in Fig. 1 can be used with the construction of Fig. 2 and vice versa; etc.

While I have described my invention in connection with specific embodiments and specific application, I do not Wish to be limited thereto, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim as new and desire to secure by Letters Patent is:

1. A flashlamp comprising a sealed container, a solid body consisting substantially entirely of magnesium and aluminum, the magnesium c ontent by weight being from 1% to 13%, and a substance which upon ignition enters into an actinic reaction with said body.

2. A ilashlamp comprising'a sealed container, a solidbody in the container consisting substantially entirely of magnesium and aluminum, the magnesium content by weight being from 85% to 99%, and a substance which upon ignition enters into an actinic reaction with said body.

3. A ilashlamp comprising a sealed container, a solid body within said container, said body being of an aluminum-magnesium alloy other than the series of alloys containing 13% to 85% magnesium by weight, the magnesium content by weight being not less than 1% and less than 99%, and a substance in the container adapted to enter upon ignition into -an actinic reaction with said body.

4. A ashlamp comprising a sealed container, a solid body in the container, said body being of an alloy consisting substantially entirely of magnesium and aluminum and other than the series of alloys containing from 13% to 85% magnesium, the magnesium content by weight being not less than 1% and less than 99%, and a gaseous filling adapted to enter upon ignition into an actinic reaction with said body.

5. A ilashlamp comprising a sealed container, an elongated solid body in the container, said body being an aluminum-magnesium alloy other than the series of alloys containing from 13% to 85% magnesium by weight, the magnesium content rby weight being not less than 1% and less than 99%, lead-in wires sealed into said container and serving as supports and electrical 'connections for said body, and a gaseous illling adapted to enter into an actinic reaction with said body upon the passage of current through said wires and body.

6. A ashlamp comprising a sealed container, a solid body in the container, said body being an alloy substantially entirely of magnesium and aluminum and other than the series of alloys containing from 13% to 85% magnesium by weight, the magnesium content by weight being not less than 1% and less than 99%, ignition means comprising a filament in the container, and lead-in wires hermetically sealed into said container and serving as electrical connections for said filament, application of less than 10 volts across said wires causing heating up of said filament and ignition of said body accompanied by an actinic reaction.

7. A flashlamp comprising a sealed container, a solid body in the container consisting substantially entirely of magnesium and aluminum, the magnesium content by weight lying within the ranges deilned by the limits 1% to 13% and 85% to 99%, a gaseous filling adapted to enter into an actinic reaction with said body, and ignition means for initiating said actinic reaction, said means comprising a nlament and a small aluminum foil provided thereon, said foil having a thickness of about 1 micron and a weight from about 1/2 to 1 mg.

8. A ilashlamp comprising a sealed container, a solid body in the container consisting substantially entirely of magnesium and aluminum, the magnesium content by weight lying within the ranges deiined bw the limits 1% to 13% and 85% to 99%, an explosive gaseous mixture in the container, and an incandescible lament in the container, passage of current through said lament causing an explosion of said mixture and the combustion of said body with an emission of actinlc radiation.

9. A ashlamp comprising a sealed bulb, an elongated drawn body in the bulb consisting substantially entirely of magnesium and aluminum, the magnesium content by weight lying within the ranges dened by the limits 1% to 13% and 85% to 99%, said body upon ignition causing the emission of actinic light, and means to support said body and to prevent direct contact between the body and the bulb.

10. As a asher material for a ashlamp, a solid body consisting substantially entirely of magnesium and aluminum, the magnesium content by weight lying within the ranges defined by the limits 1% to 13% and 85% to 99%.

11. As a flasher material for a ashlamp, an elongated drawn body consisting substantially entirely of aluminum and magnesium, the magnesium content by Weight lying within the interrupted range defined by the limits 1% to 13% and 85% to 99%.

12. A ashlamp comprising a. sealed bulb, an elongated drawn member arranged in the shape of a clew within said bulb and consisting substantially entirely of magnesium and aluminum, the magnesium content by weight lying within the ranges defined by the limits 1% to 13% and 85% to 99%, said body upon ignition causing the emission of actinic light.

13. A flashlamp comprising a sealed container, a foil in the container consisting substantially entirely of magnesium and aluminum, the mage nesium content by weight lying within the ranges defined by the limits 1% to 13% and 85% to 99%, and a substance in the container adapted to enter upon ignition into an actinic reaction with said body.

JOHANNES ANTON'IUS MARIA VAN LIEMPT.

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