US2431162A

US2431162A - Photoflash lamp

Info

Publication number: US2431162A
Application number: US575784A
Authority: US
Inventors: Harold D Blake; Walter J Geiger
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1945-02-02
Filing date: 1945-02-02
Publication date: 1947-11-18
Anticipated expiration: 1964-11-18

Description

Nov. 18, 1947.- H. D. BLAKE ETAL 2,431,162

PHOTOFLASH LAMP Filed Feb. 2, 1945 INVENTORS: HAROLD D. BLAKE, WALTER J. GEIGER,

THEIR ATTORNEY Patented Nov. 18, 1947 PHOTOFLASH LAMP Harold D. Blake and Walter J. Geiger, Cleveland Heights, Ohio, assignors to General Electric 'Company a corporation of New York Application February 2, 1945, Serial No. 575,784

Claims. (CI. 67-31) This invention relates to flash lamps, and especially to lamps in which a more or less compact mass of closely associated combustible and combustion-supporting materials is electrically ignited, usually by means of an electrically heated filament or bridge-wire. Such lamps are much used for photographic purposes. The combustion mass or body may in turn ignite thin metal foil or fine metal wire, in an oxygenous atmosphere, which by its combustion provides some or most of the actinic light or radiation from the lamp as in U. S. Reissue Patent No. 18,678 to Ostermeier; or the combustion mass may itself be relied on for most or substantially all of such radiation, as in U. S. Patent No. 2,291,983 to Pipkin. We have hereinafter explained our invention with particular reference to lamps of this latter type, which are commercially known as "SM photoflash lamps.

For many photographic purposes, a very quick flash of very high peak intensity is desirable. The requirements are so exacting that common variations in commercial grades of combustion materials often render the lamps too slow, or too low in peak intensity, or both; and minor variations in manufacturing procedure which are very difficult to avoid may have a similar effect. However, we have found a way of obviating such defects so as to assure adequate quickness and intensity of flash despite the variations in materials and procedure. We have discovered that by suitable treatment during manufacture, the action can be so improved that the variations whose effects have heretofore been so unfavorable are of no practical consequence. As hereinafter described, the treatment is rather selective in its effects: 1. e., it improves poor lamps more than good ones, thus evening up the level of quality.

As explained in the above-mentioned Pipkin patent, the combustion bodies of SM type flashlamps consist of finely divided combustible material and oxidizing material intimately associated or mixed together, and agglomerated or agglutinated by means of a binder. Suitable combustibles include powders of metals like zirconium, magnesium or aluminum; and suitable oxidizing agents or supporters of combustion are exemplified by oxides or peroxides, and by chlorates including perchlorates. Binders are exemplified by nitrocellulose, which may be used in the form of about a 4% solution in amyl acetate. As mentioned in the Pipkin patent, one suitable composition of the combustion body for a fast lamp, giving a quick, short flash of high intensity, consists of:

Zirconium metal powder grams 3 Magnesium metal powder (325 mesh) do 1 Sodium chlorate powder (C. P., 200 mesh) grams; 1 Potassium perchlorate powder (C. P., 300

mesh) grams 1 4% solution of nitrocellulose in amyl acetate cc 2 A lamp comprising a bead of 50 to grams of this composition and having a filling of oxygen at an absolute pressure of about mm. of mercury gives a total light output of about 5000 lumen-seconds and a flash of some 10 milliseconds duration, the peak occurring about 5 milliseconds after closure of the circuit through the filament.

We have found that the fiash of lamps of this character can be substantially intensified and quickened by treatment usually involving a deposit of oxidizing agent or supporter of. combustion at the surface of the combustion body, generally in the form of crystals more or less isolated or spaced apart. One way of treating the combustion body is to expose the mount including said body to a humid atmosphere: e. 3., such mounts may be kept in ahumidity box at about 100 F. for about 30 min. Another way is to immerse the body in an aqueous solution of soluble oxidizing agent: e. g., such a body may be dipped for about 2 min. in a saturated solution of sodium chlorate at F. Variations in this temperature of'as much as 10 F. either way are not importantly influential on theresult. For this mode of treatment, a sodium chlorate solution has given better results than a potassium perchlorate solution. In the caseof slow, low-peaking lamps, the improvement may increase the peak intensity about 50 to 100%, with a decrease of 50% or more in the interval required to reach the peak after closing the circuit. After treatment of the mounts in either way, they are sealed. into the lamp bulbs or envelopes, and the lamp processing iscompleted (including introduction of oxygen or other oxygen-containing gas) in the usual way.

In both methods of treatment, it is probable that some of the soluble combustion agent (especially the highly soluble sodium chlorate) is dissolved or leached out of the combustion body.

leaving the latter somewhat porous with increased surface exposure to the oxygenous atmosphere, This naturally tends toward faster and more complete combustion, and mayeven be a major factor in the improvement. There is no material decrease in'the total combustion-supporting content of the body in either case, since matter dissolved out is more or less compensated for by matter deposited on the surface of the body.

In the drawings, Fig. l is a side view of a short bulb neck 3, which is mounted in an ordinary bayonet base 4 to whose contact terminals are connected the

inleads

5, 5 through the usual stem-press seal 6. An exhaust tube 1 opening through the seal 6 is itself sealed ofi at 8. Between the inner ends of the

leads

5, 5 is connected the usual igniting filament or bridge-wire 9, and

' on the ends of these leads are shown bead-like bodies I0, In of combustion material, each in contact with the filament 9. Broadly, however, it is immaterial whether the bodies I0, 10 are distinct from one another or merge in a single large bead, as shown in the above-cited Pipkin patent. The glass bulb I may have the usual internal or external coating (preferably both) of transparent or radiation-transmitting lacquer or varnish, and may contain the usual filling of oxygen'at 100 mm. mercury pressure absolute. On the bead surfaces are shown prominences or protuberances formed by isolated white crystal deposits ii of oxidizing agent such as sodium chlorate, which look like fine, circular, rounded white specks. As shown, one of the inleads 5 may carry a fine antenna wire l2 welded thereto and extending nearly to the top of the bulb, as in U. S. Patent 2,342,575 to Elmendorf.

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

1. The combination with a flash lamp mount comprising an igniting filament and a porous body of agglutinated combustible metallic material and supporter of combustion for liberating oxygen in contact with saidfilament, of a rough crystal-like deposit of supporter of combustion on the surface of said body.

2. The combination with a flash lamp mount comprising an igniting filament and a porous body of agglutinated combustible metallic material and supporter of combustion for liberating oxygen in contact with said filament, of a. rough deposit of soluble chlorate on the surface of said body.

3. The combination with a flash mount comprising an igniting filament and a porous body of agglutinated combustible metallic material and supporter of combustion comprising chlorate in contact with said filament for liberating oxygen upon energization of the filament, of isolated chlorate crystals adherent to the surface of said body.

4. A flash lamp mount comprising an igniting filament and a porous body comprising agglutinated combustible metallic material and soluble supporter of combustion in contact with said filament for liberating oxygen upon energization of the filament. characterized by pores in said body formed by leaching out of soluble supporter of combustion.

5. A fiash lamp mount comprising an igniting filament and a'porous body of agglutinated combustible metallic material'and supporter of combustion comprising sodium chlorate in contact with said filament for liberating oxygen upon energization of the filament, characterized by pores and prominences formedby leaching out of the sodium chlorate and by isolated deposits of sodium chlorate adherent to the surface of said body.

6. A fiash lamp comprising a container, an igniting filament in said container, and a porous body of agglutinated finely divided combustible metallic material and soluble supporter of combustion in contact with said filament for liberating oxygen upon energization of said filament, characterized by pores in said body formed by leaching out of soluble supporter of combustion and isolated deposits of soluble supporter of combustion adherent to the surface of said body, and an oxygenous atmosphere in said container, the combustible of said body constituting, in coaction with said atmosphere and the supporter of combustion of thebody, the sole source of actinic radiation from the lamp.

7. A method of intensifying and speeding up the illumination from a flashlamp comprising an igniting filament and a body of agglutinated combustible metallic material and soluble supporter of combustion in contact with said filament, which method comprises leaching said body and forming a rough crystal-like deposit of the supporter of combustion on the surface of said body.

8. A method of improving the illumination from a, fiashlamp comprising an igniting filament and a body of agglutinated combustible and supporter of combustion in contact with said filament, which method comprises immersing said body in a solution of soluble supporter of combustion until adherent crystals of the latter form on said body.

9. A method of improving the illumination from a fiashlamp comprising an igniting filament and a body of agglutinated combustible and soluble supporter of combustion in contact with said filament, which method comprises exposing said body to a humid atmosphere until adherent crystals of said soluble supporter of combustion form on said body.

10. A method of intensifying and accelerating the illumination from a fiashlamp comprising an igniting filament and a body of agglutinated combustible metallic material and a soluble supporter of combustion in contact with said filament for liberating oxygen upon energization of the filament, which method comprises providing said body with a porous surface holding adherent particles of the supporter of combustion.

HAROLD D. BLAKE. WALTER J. GEIGER.

REFERENCES CITED UNITED STATES PATENTS Name Date Bostwick Nov. 30, 1897 Number