US2375742A - Photographic flash lamp - Google Patents

Description

May 8, 3945- E. o. KALIL ET AL 2,375,742

PHOTOGRAPHIC FLASH LAMP Filed Sept. 30, 1942 Figa@ @alienated May w45 airain PH'EGRAPMC FLASH LAME? Emil Q. Kalli, Brooklyn, N. Y., and William E. Gleim, Bloomfield, N. Il., assignors to Wabash Appliance Corporation, Brooklyn, N. Y., a corporation oi New York Application September 30, 1942, Serial No. 460,222

7 Claims.

This invention consists in a new and improved photographic ash lamp having certain advantages over those heretofore known and employing in its construction novel compositions of combustible materials not heretofore used for the generation of light in such lamps.

Uniform performance and reliability are the most important characteristics of flash lamps. Not only must the ash always reach the same high intensity of light, but it must follow dependably a predetermined time curve so that it may be synchronized with the opening of the camera shutter or other moving object. Moreover it is desirable that the time curve should provide an appreciable build-up interval before the maximum intensity of the ilash is reached, in order, for example, to allow for actual shutter movement.

The combustible or ignitible material of the lamp must be such that it may be readily and instantaneously ignited or primed by the limited energy of a ash light battery, that it be capable of generating a ilash of high intensity and that its functions should be properly carried out without danger of explosion or formation of toxic gases.

We have discovered that all these desirable results and others that will be hereinafter pointed out may be achieved by properly locating and exposing an area of zirconium within an oxygendlled bulb in proximity to an igniting device responsive to the passage of an electric current. Ln the best form now known to us a paste of- Iinely divided zirconium powder is mixed with a small amount of a powdered oxidizing ingredient and then this paste is spread as a coating -upon any suitable supporting or carrying medium in the bulb. 'I'he supporting medium may be of any iesired shape, but is preferably symmetrical with respect to the bulb, as for example, a ring or col- ,a-lbdisposed concentrically in the axis of the In preparing zirconium for this use, it is de- :irable to reduce the commercially available )lack or black-grey zirconium powder to a ner :tate of subdivision, as by ball milling for several hours, in general controlling the action of he combustible mixture by regulating the paricle size of the metal powder, and then convertng it to the form of paste by adding any suitable inder as nitro-cellulose, gum arabic, or shellac n. solution.

The fulminating or oxidizing agent may take he form of potassium perchlorate, (K010i). laClOs, PbOz, CaOz or MgOz, NH4NO3, PbNe,

BaNs, or any equivalent oxide or fulminating mixture, and by varying the proportions of these agents the shape of the time curve of the lamp may be' controlled and the point of maximum intensity of the iiash may be advanced or delayed as desired for the requirements of the lamp manufactured.

While all the oxides mentioned are satisfactory, certain of them give up their oxygen at a relatively slower `rate than others. For example,

the greater the proportion of MgOz in the paste, the more delayed will be the instant of maximum light intensity of the flash. Preferably and as herein shown the lamp may include an igniting area of relatively slow burning composition leading to a substantial area of relatively fast burning composition.

The major part of the oxygen for combustion is supplied by lling the bulb with oxygen or other oxygeneous gas. Under these conditions the percentage of oxidizing ingredient in the combustible paste is critical. The optimum conditions are such that the zirconium particles should be blasted from their supporting medium into the oxygen atmosphere of the bulb in very finely divided form, approaching a colloidal dispersion in the oxygen, and burn rapidly totally surrounded by oxygen before they strike the wall of the bulb. Accordingly suiiicient KC104 or the like lis added to start the reaction of combustion and to insure removal of the combustible paste from its support and the desired dispersion. 2% to 5% byweight of oxidizer or iulminator results in a very satisfactory mixture. Should the percentage be increased beyond 6% or 7% there is a marked decrease in light for two reasons. Oxidizer present above 5% practically blasts the zirconium directly against the side walls of the bulb. Consequently it does not have time to bum completely and in addition to the loss of light output the walls of the bulb are blackened and a substantial amount of light is lost on that account. By holding the oxidizer or fulminator at or below 5% this excessive blasting effect and blackening of the bulb are both eliminated and a satisfactory time curve is secured.

Zirconium is one of a group of metals which burn freely in oxygen giving off actinic light, and

. is the best of these metals now known to me for purposes of this invention. However, Al, Mg, and alloys thereof have substantially the same properties and may be regarded as equivalent to zirconium when'used as a. substitute for it in the manner above explained.

'These and other features of the invention will be best understood and appreciated from the i'ollowing description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing in which,

Fig. 1 is a view in perspective of the completed lamp,

Fig. 2 is a fragmentary view on an enlarged scale showing the disposition of the combustible material in the lamp, and

Fig. 3 is a characteristic time curve of a lamp of my invention.

The flash lamp herein shown comprises a glass bulb I and metal base II which may be of any desired commercial shape and size. Within the bulb is located the mount comprising the glass stem I2 in which are sealed leads I3. To these are welded extensions of nickel wire offset toward each other above the end of the stem and brought into close proximity and parallel relation at their upper ends. Between these two ends extends a fine filament I of such characteristics that it fuses readily in transmitting a low voltage current. Upon the ends of the nickel extension wires I4 are placed beads I6'of ignitible priming or fulminating compound. The composition of these priming beads consists in zirconium powder prepared as above outlined, blended with KC104 and MgOz or equivalent oxidizers in proportions approximating Per cent zirconium 90 KClO4 2 M302 8 In these beads therefore the slower oxidizer MgOz predominates and the composition is relatively slow burning on this account although well adapted to serve as a priming compound.

As herein shown the combustible light source material is distributed within the bulb upon a ring-shaped supporting medium disposed substantially concentrically with respect to the priming beads and to the bulb, in a plane substantially level with the priming beads. The supporting ring may be made outvof nickel wire or other suitable metaland mounted in the lamp by means of an angle wire I1 which is herein shown as welded to one of the extension wires I4. The ring itself is completely encased in a coating I8 of a paste of zirconium, KClO4 and MgO: in approximately the [following proportion:

Per cent Zirconium 95 KClO4 3.75 MgOz 1.25

These dry ingredients may be mixed in paste form with a liquid binder and the paste applied to the ring by dipping it one or more times below the surface of the paste, and when the paste dries it constitutes a firm coating which may be handled with convenience in the manufacture of the lamp. 250 mg. of a paste having the above formula will produce approximately 30,000 lumenseconds, when flashed in an atmosphere of oxygen at 550 mm, pressure of mercury.

It will be apparent that the priming charge and the flash composition are supported as distinct masses freely exposed to the oxygen atmosphere of the bulb.

In operation the filament I5 is fused by closing a circuit through the leads of the lamp. The priming beads I6 are immediately ignited and within 'a few milliseconds the coating I8 of the ring is uniformly ignited from the burning beads. The faster burning coating is exploded to the extent of blasting the zirconium particles ,it' contains into the oxygen atmosphere of the bulb wherein they burn rapidly with the emission of actinic light.

A typical curve illustrating the action of the lamp is shown in Fig. 3 from which it will be noted that about ve milliseconds is consumed in the fusion of the filament I5 followed by about seven milliseconds for the combustion of the priming beads I6. Combustion of the coating material begins at about the twelve millisecond point and the light intensity runs up on a very steep curve to a maximum of about 1,000,000 lumens at the twenty millisecond mark. -From then on the light intensity falls off on a gradual curve to the sixty-live millisecond Point. It will be understood, of course, that the character of this curve may lbe .varied substantially by varying the composition and amoint of the priming beads and combustible ring coating. For example, the build-up time may be decreased by increasing the percentage of KC104 at the expense of the percentage of MgOz in the priming beads.

The flash lamp herein described represents the most desirable embodiment of the invention now known to me but may be varied in many of its details Within the scope of the invention. While the lead extensions and ring have been described as of nickel it is entirely practicable to employ iron of ferrous alloys. Where metal is used it is desirable to keep the wire diameter of the ring small so that the ring shall not albsorb heat and so lower the lighting efficiency of the compound. The composition of the priming and light source paste has been stated as best adapted for a lamp flashing in `accordance with the specific curve of Fig. 3 and, of course, if a different curve is desired the composition may be correspondingly varied in the manner above suggested.

While We prefer to employ priming or igniting beads having oxydizing ingredients it is necessary for purposes of our invention only that we have available fulminating material generating sumcient heat to ignite the combustible light-generating material upon the supporting medium and for this function barium azide or lead azide are acceptable agents.

It will be understood that there are two distinct phases in the action of the lamp of our invention: rst, driving the combustible material out into the oxygen atmosphere of the bulb quickly, faster than the rate of flame propagations and in very nely dispersed form, and second, burning the oxygen-surrounded particles before they become plastered on the walls of the bulb. This, of course, requires a fine balance of the ingredients used and can be eiected only between critical limits. These limits may be stated as -9'7% zirconium to 20-3% fulminating ingredients.

Having thus disclosed our invention and described in detail an illustrative embodiment thereof, we claim as new and desire to secure by Letters Patent:

l. A photographic flash lamp having a gaslled bulb containing anA ignitible primer adapted to be detonated by an electric current, a ring located concentrically within the bulb and in proximity to said primer and having a coating of powdered zirconium mixed with a fulminating agent in proportions between 809'7%V zirconium to 20 to 3% fulminating agent, the said primer and zirconium coated ring being supported separately and freely in the gaseous atmosphere of the bulb.

2. A photographic ilash lamp having an oxygen# illled bulb containing an ignitible primer and a l carrier exposing in the bulb and adjacent to the primer a substantial area of zirconium mixed with KClOn and 'MgOn in proportions between 80-97% zirconium to 20 to 3% KClO4 and MgOz,

the said zirconium mixture being supported' freely in the oxygen atmosphere oi' the bulb.

3. A photographic ash lamp having an oxygen-illled bulb containing an ignitible primer and a carrier exposing adjacent to the primer a substantial area. or zirconium mixed with an oxidizing agent comprising about 75 parts K010i carrier exposing a substantial area of zirconium n mixed with an oxidizing agent containing a high proportion of KClO4 and a lower proportion of MgOs, andan ignitible primer interposed between said fusible fllament and carrier and comprising a high proportion of MgOs and a lower proportion of KC104, said primer and zirconium mixture being supported separately in the oxygen atmosphere of the bulb.

5. A photographic ilash lamp comprising an oxygen-filled bulb having an ignitible primer therein, and a supporting medium adjacent to the primer coated with a dried paste having `a composition approximating Zr 95%,. K010i 3.75% and MgOz 1.25%. said primer and said paste being separately supported .in the oxygen atmosphere of the bulb. l

6. A photographic ash lamp comprising an oxygen-lled bulb having leads therein support- -ing an ignitible priming charge having a composition approximately Zr 90%, KC104 2%. MgOa 8%, and a supporting ring disposed symmetrically in the bulb adjacent to the priming charge and having a coating of dried paste of a composition approximately` 95% zirconium'in finely divided powder, 3.75% potassium perchlorate and 1.25% magnesium dioxide. the priming charge and the paste composition oi' the said ring being disposed as distinct masses in the oxygen atmosphere of the bulb.

'7. In a photographic flash lamp, supplementary light sources comprising a body comprising approximately 'Zr 90%. KClO4 2% and MgOz, and a second body comprising approximately Zr 95%. KC104 4% and MgOn, the two bodies being supported asdistinct masses and freely exposed within the lamp.

EMIL 0. KALIL. WILLIAM E. GLEIM.

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