US2325667A - Flash lamp - Google Patents

Description

Aug. 3, 1943.

J. H. DE BOER FLASH LAMP Filed Feb. 15, 1943 IN V EN TOR.

ATTORNEY Patented Aug. 3, 1943 FLASH LAMP Jan Hendrik de Boer, London, England, assignor to The Hartford National Bank and Trust Company, Hartford, Coma, as trustee Application February 15, 1943, Serial No. 475,952 In Great Britain May 15, 1941 7 Claims.

My invention relates to flash lamps having an envelope of transparent organic material, such as acetyl-cellulose.

The word "transparent as used herein and in the claims is to be understood to mean that the material transmits those light rays which are used for photographic purposes.

Although flash lamps having envelopes of the above type have several advantages from the production view point, I have found that they have several disadvantages which seriously effect their commercial usefulness. Probably the most serious disadvantage is that there is diffusion of gases through the envelope of organic material and this deleteriously efl'ects the proper functioning of the lamps. More particularly, if the lamp is filled with oxygen at a pressure below at-' mospheric pressure, for instance 42 cm. to 57 cm. Hg, air will gradually diffus into the lamp and form a mixture of oxygen and nitrogen at atmospheric pressure. At first the nitrogen will form a small amount of the mixture, but after some time, due to further diflusion, the mixture within the lamp will approach 20% oxygen and 80% nitrogen.

The above difllculties are very seriou because to secure the desired actinic characteristics it is essential that the filling of a flash lamp comprise only certain gases and that these gases be present in predetermined quantities and at a predetermined pressure. Usually the filling comprises only oxygen at a predetermined pressure, but in some cases other gases such as oxygen-producing gases and insert gases, are added.

In accordance with the invention I overcome the above difllculties by-providing the envelope with a sealing layer of regenerated cellulose. This layer may be formed as an intermediate sandwiched between two layers of transparent organic material, or may be a layer on the inner wall of an envelope consisting of organic material. I prefer to form the envelope of a cellulose derivative which can be partially converted back I into cellulose because this makes it possible to form the layer of regenerated cellulose from a Fisure 1 is a sectionized side-view or a flash lamp embodying my invention,

Fig. 2 is a sectionized side-view of a flash lamp according to another embodiment of the invention, and

Fig. 3 is a sectionized view on an enlarged scale of a portion or the lamp shown in Figure 2.

The flash lamp shown in Figure 1 comprises an envelope having a cup-shaped upper portion I and a plate-shaped bottom portion 2. Portion l is formed of an outer layer-3, an inner layer I and an intermediate layer 4. Layers 3 and I are formed or a transparent organic material, such as a non-inflammable cellulose material which exhibits some elasticity and preferably some flexibility. Suitable materials for this purpose are cellulose acetate, polyvinyl chloride, urea formaldehyde resin, polyacrylic acid or ethers, polyvinyl ethers. V

In accordance with the invention the intermediate layer 4 is formed of regenerated cellulose which has been produced by converting a cellulose derivative into cellulose again. Such a layer is highly resistant to diffusion of gases.

The intermediate layer 4 of regenerated cellulose may be formed by applying regenerated cellulose to the layer 5 and then forming the layer 3 thereon. However, Ipreier to form layer- 4 from a surface portion of either layer 3 or '6. In this case I form layer 3 or 6 of a cellulose derivative which can be partially converted back into cellulose. For instance layer 5 may be of acetylcellulose and a surface portion saponified to form layer 4 of regeneratedcellulose. This saponifl-= cation may be performed by a solution of caustic soda or potassium hydroxide preferably in methylor ethylalcoholic solution.

The bottom portion 2 comprises a layer 8 of an organic material, an intermediate layer 1 of regenerated cellulose and a layer 8 of an organic material. The materials of layers 8 and 8 may be the same as the materials oi layers 3 and 5, whereas the material of layer 1 may be the same as that of layer 4 and may be formed in a similar manner.

The lower end or portion I is provided with an annular flange 9 by which it is sealed to the bottom portion 2. It will be noted that the layers I and 8 do not extend into the flange andthat the seal at the flange is formed between the layers 4 and l of regenerated cellulose. This makes it possible to obtain a tight Joint.

Sealed into the portion 2 are two lead-in wires it which, at their upper ends, support suitable ignition means H, such as a filament provided with a small amount or zirconium, aluminium or phosphorus powder.

The container is provided with a quantity of combustible material 62, shown as a thin wire of aluminium or aluminium-magnesium alloy. Instead of wire,,the usual foils may be used. The lamp also contains a filling of a combustion supporting gas such as oxygen. Due to the use of the sealing layers l and l of regenerated cellulose,.the gas may be at a relatively high pressure, for instance about atmospheres, without danger oi diiTusion, and because of this a very intense flash is obtained and the lamp can be of small size.

I may also place in the lamp solid substances which under the conditions of reaction within the envelope yield oxygen to supplement the gaseous filling. According to the speed at which the oxygen is released, these solid substances may be associated with the primer or with the metal foil, wire or powder. In this way a greater quantity of oxygen is made available for the reaction without a corresponding increase in the maximum pressure generated within the envelope. Certain metallic oxides such as mercuric oxide, silver oxide and cadmium oxide are suitable. Other examples of suitable substances are so called higher oxides or peroxides such as lead-peroxide, red lead, manganese dioxide, barium peroxide, silver peroxide, etc. and salts which are capable of releasing oxygen at rather low temperatures, such as alkali-chlorates, perchlorates, permanganates, bichromates, 'chromates, perborates. Even organic peroxides, such as benzoylperoxide may be used. In the case of mercuric oxide, the mercury vapour released within the envelope during the reaction may asaaeer bustible material within said container, 2. comaugment the actinic value of the light emitted. I

The flash lamp shown in Figure 2 is similar to that shown in Figure 1 and has similarparts indicated by the same reference numerals. However, in the lamp of Figure 2 the inner layers 5 and 8 are omitted. The layers 3. and 5 are preferably made of a cellulose derivative which canbe converted back into cellulose and the layers 4 and l are formed by saponifying a surface portion of layers 3 and 6.

Figure 3 shows a part of the portion 2 of Fig. 2. However, in Fig. 3 a layer of regenerated cellulose extends along the portion of wires in so as to form a seal between these wires and the layer 6.

Although I have described my invention with reference to specific examples and constnuctions, I do not desire to be limited thereto, because obvious medifications will readily present themselves to'one skilled in this'art.

Iclaim:

1. A flash lamp comprising a container, combustible material within said container, a. combustion-supporting gas within said container,

and means for igniting said material, said container comprising a layer of a transparent orbustion-supporting gas within said container, and means for igniting said material, said container comprising two layers of a transparent organic material, and a sealing layer of regenerated cellulose interposed between said first two layers.

3. A flash lamp comprising a container, combustible material within said container, a combustion-supporting gas within said container, and means for igniting said material, said container comprising a layer of a transparent organic material capable of being converted into cellulose and a sealing layer of regenerated cellulose formed from a surface portion of said first layer and covering said first layer.

4. A flash lamp comprising a container hB.V ing two parts, combustible material within said container, a combustion-supporting gas within said container, and means for igniting said material, each part of said container comprising a layer of a transparent organic material and a sealing layer oi regenerated cellulose, said parts being joined together by the layers of regenermaterial, each of said parts comprising a layer of transparent organic material, a sealing layer of regenerated cellulose covering the inner surface of said cup-shaped part and the flange thereof and a sealing layer'of regenerated cellulose covering the surface of said plate-shaped part, said parts being sealed together at said flange by the layers of regenerated cellulose.

-6. A flash lamp comprising a container, combustible material within said container, a combustion-supporting gas within said container, and means for igniting said material including lead-in wires extending through a portion of the container, said portion comprising a layer of a transparent organic material and a sealing layer of regenerated cellulose, said latter layer surrounding the part of the lead-in wires extending through the container.

,7. A flash lamp comprising a container, combustible material within said container, a combustion-supporting gas within said container, and means for igniting said material, said container comprising an outer layer of a transparent organic material capable of being converted into JAN HENDRIK DE BOER.

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