US2071369A - Flash lamp - Google Patents

Description

Feb. 23, 1937.

H. A. WILLIAMS ET AL FLASH LAY? Filed Jan. 24, 1954 //v1//v r025 1 A735! Y Ally 10L [A M5 FNH/ UE' 5/ ybU/JZZ'IZA 7 MM ,4 7' TOR/V5 Y5 PMs-.1 F.|...-'23, 1937 2,071,369

UNITED STATES PATENT OFFICE FLASH LAMP HarryA. Williams and Enrique G. Touceda,

Albany, N. Y.

Application January 24, 1934, Serial No. 708,081

- 6 Claims. (01. 67-31) In the art of photography, many'pictures are Referring to Fig. 1, our flash lamp, which is taken with the aid of flash lamps. The exposures, indicated generally at I comprises a translucent in this case, should be made during the range bulb 2 having the configuration of an ordinary of maximum brilliancy of light emission in order incandescent lamp. The neck of the bulb is "to obtain a clearly defined image on the film or sealed in a screw base 3 comprising a metallic 5 plate. This can be accomplished with some decasing 4 filled with an insulating compound 5. gree of accuracy under favorable circumstances. The conductors 6 and insulating casings I there- However, the majority of flashlight pictures must for extend from the base upwardly within the be taken under adverse conditions. For exambulb 2 and terminate in spaced relationship with 10 pie, the object may be in motion. Itis known each other to form the terminals of a spark gap, 0 that timed exposures or exposures of ordinary indicated generally at 8. The lower ends of the duration could not-be made in order clearly to conductors 6, indicated at 6a and 6b, are conphotograph an object in motion. On the connected to terminal points of the screw base 3 in -trary, a very short exposure, say of the order the usual manner. The bulb' 2 is filled with a of 1/ 100th or 1/200th of a second, is necessary. readily oxidizable substance 9 preferably compris- 15 Furthermore, in making short exposures where ing a foil which is adapted to emit light upon flash lamps are used as a means of providing an oxidation thereof. Examples of suitable sublight, it is evident that the light emission therestances which may be used as foils are metals, from must be very accurately synchronized or metal alloys and rare earths, such as aluminum, timed with the camera shutter in order to in copper, phosphor bronze, cerium and the like. sure clear and well defined pictures. To aid in the ignition of the oxidizable sub- In the present type of flash lamps, an ignition stance, a small amount of a fulminating subdevice comprising an electrical resistance element stance having rapid flame propagation characis utilized which becomes incandescent when teristics may be suitably disposed within ignition current is supplied thereto and ignites a comrange of the spark gap. By way of example, we bustible or oxidizable substance suitably dishave illustrated a small amount of guncotton posed in the lamp. This type of ignition necesl0 supported by a wire H secured between the sarily involves an appreciable and variable time insulating casings 1 of the conductors (see Fig. 3). element in view of the precision which is de- Oxidation of the light emitting substance may fined by the shutter speed of the camera in contake place in air, but we prefer to evacuate the 30 junction with which it is used. bulb 2 and fill with oxygen at a pressure prefer- Our inventiontherefore has for an object the ably below atmospheric. The inclusion of a provision of a flash lamp for photographic purfulminating substance and the oxygen in our poses which is-endowed with the characteristics lamp aids in producing a flash lamp having the of substantially instantaneous ignition and light characteristics of substantially instantaneous igemission, the operation of which may be readily nition and very rapid oxidation of the foil. and accurately synchronized with the operation In Fig. 4 we have illustrated a modified form of a camera shutter. of spark gap the terminals of which are formed With this and other objects in view, our inof carbon or similar substance which partially vention includes the novel elements and combidisintegrates upon the passage of a spark, eject- 40 nations and arrangements thereof described being particles of incandescent material. The low and illustrated in the accompanying drawejected particles effect a wider ignition range ing in whichand generally aid in the ignition of the oxidizable Fig. 1 is an elevation view of our flash lamp; materials within the bulb. Fig. 2 is a fragmentary, sectional view through In Fig. 5, we have illustrated a wiring diagram 5 the base of the lamp; wherein the preferred means for producing and Fig. 3 is an enlarged, detail view of the spark controlling the energy for activating an oxidation gap terminals illustrating apreferred disposition of the light emitting substance in the lamp is of an oxidizable substance with respectthereto; diagrammatically illustrated. A' source of elec- Fig. 4 is an enlarged, detail view of a modified trical energy, indicated as a battery I4, is con- 50 form of terminals for the spark gap; and nected in series with the controls or switches B Fig. 5 is a wiring diagram of a circuit adapted and C and the primary l5a of an induction coil for use in conjunction with our flash lamp. IS. The connections are made through the con- In the drawing, like reference characters inductors l6, l1, l8 and I9, respectively, as the cirdicate like parts throughout the various figures. cuit is traced from the battery in a clockwise 55 direction. An end of each of the primary and secondary coils, |5a and IE1), respectively, are connected together and the flash lamp 1 embodying our invention may be connected through conductors 20 and 2| across the secondary of coil IS. The battery I4 may comprise a plurality of dry cells providing a source of electrical energy of the order of about 6 volts. Furthermore, a condenser 22 is preferably connected across the switch C to reduce sparking when said switch is opened.

It will be noted that the circuit, above described, may readily be adapted for use with a camera and a description of a practical manner of associating the controls thereof in cooperative relationship with a camera is fully set forth in our copending application Ser. No. 708,082, which was filed in the Patent Oifice on or about the 24th day of January 1934.

The operation of our flash lamp and associated circuit is as follows.

Assuming that the switch C is in closed position, when the switch B is closed, a. circuit is completed through the battery. l4, switches B and C and the primary l5a of the coil l5. This circuit need be maintained only during a sufficient interval of time thoroughly to saturate the magnetic circuit, whereupon the circuit may be opened through an operation of switch C. The sudden opening of the primary circuit produces a surge of high potential in the secondary coil l5b which is substantially instantaneously dissipated in the form of a spark discharge across the terminals of the spark gap indicated at 8, in the flash lamp. The spark discharge activates an oxidation of the foil or similar substance within the globe of the lamp. The fulminating substance, which may comprise a suitable amount of guncotton or the like, aids in producing a substantially instantaneous oxidation or light emission following the operation of switch C in the circuit.

It is evident that when an exposure is made through the operation of a camera shutter, the magnetic circuit may be closed and opened, as above described, in timed relation therewith, producing a light emission from the flash lamp.

It is to be understood that the flash lamp which we have illustrated and described embodies a preferred arrangement of elements collectively forming a lamp adapted to be synchronized with extreme accuracy with the shutter or automatic exposure mechanism of a camera. However, equivalent elements may be substituted for those which we have employed in our lamp and rearrangements made in the relative dispositions thereof without departing materially from the scope of our invention,

Very accurately timed high speed exposures of a falling billiard ball or a white disk attached to the hand of a synchronous clock making sixty revolutions per minute, and illuminated by a flash from the present types of flash lamp indicate three things very clearly; first, that there is a very substantial lag or interval of time between the making of the circuit which ignites the flash lamp and the actual ignition thereof; second, that this interval varies even with different flash lamps of the same manufacture and to such a substantial degree that the illumination cannot be positively synchronized with an exposure of less than l/50th of a second; and third, that once ignition of the material in the flash lamp has actually taken place, maximum illumination is almost instantaneous.

It is obvious from .the foregon. that the defects in the present type of flash "\mp are due primarily to the relatively long a variable period of time which elapses between the closing of the ignition circuit and the actual ignition of the flash light material.

With modern high speed lenses and extremely fast plates or films, exposures as short as 1/1000th of asecond are not unusual and exposures very much shorter than 1/50th of a second (the minimum synchronizing limit of the present flash lamp) are absolutely necessary to obtain clear pictures of an object moving even at moderate speed.

With our apparatus, using a high potential spark as a means for activating a light giving reaction between the oxidizable material and the oxygen of the air or in the bulb of the flash lamp or otherwise, the time differential between the instant of breaking the primary circuit and the ignition of the oxidizable light giving material is not only so very much shortened that it may be said to be substantially instantaneous but it is also made substantially constant. This last characteristic is of the utmost importance because it permits precise synchronization of light with shutter opening. With variations in the above time differential as small as 1/50thof a second which is quite usual in the present type of flash lamp, it is obviously impossible to photograph anything with any degree of certainty with an exposure as short as 1/ 100th of a second because the light, in one case may occur before the shutter has opened, and in the next case after the shutter has closed.

Without any precautions as to standardizing conditions and using ordinary flash light powder in the open air and a small piece of gunootton between carbon spark gap terminals with our apparatus one can readily synchronize the flash with exposures of much shorter duration than has been heretofore successfully accomplished even with flash lamps.

In a flash lamp containing oxygen gas and foil as described, and using carbon spark gap terminals (preferably spongy or porous carbon which will be permeated with the oxygen), and either with or without guncotton or a similar flame propagating substance, the light may be consistently synchronized with exposures of a very much higher speed. In the presence of oxygen alone, the carbon becomes almost explosive and even in the air the spark really partakes of the nature of a flaming arc, and incandescent particles of carbon are projected violently from the terminals which in either case facilitates ignition.

The word light as used in the specification and claims, is to be understood as meaning and including light rays both visible and invisible and by the use of which it is possible to take a photog raph; and the word translucent is to be understood as meaning and including transparent and having the general property of transmitting such light.

While we have described our invention in its preferred embodiments, it is to be understood that the words which we have used are words of description rather than of limitation. Hence, changes within the purview of the appended claims may be made without departing from the true scope and spirit of our invention in its broader aspects.

What we claim is:

1. An electric spark ignited photographic flash lamp having a type of construction characterized by the lapse of a substantially constant interval of time between the instant of electric current application thereto and the instant of full illumination, whereby it is adapted for positive synchronization with camera shutter openings, of the order of 1/100 of a second and shorter, said lamp comprising a gas-tight translucent envelope containing a rapidly oxidizable substance adapted to emit light upon combustion thereof, electrical ignition means comprising terminals disposed in fixed, spaced relation within said envelope to form a spark gap within effective ignition range of said substance, spaced terminals on theexterlor of said envelope, and electrical conductors extending between said spark-gap-form ing terminals and said exterior terminals.

2. An electric spark ignited photographic flash lamp having a type of construction characterized by the lapse of a substantially constant in terval of time between the instant of electric current application thereto and the instant of full illumination, whereby it is adapted forpositive synchronization with camera shutter openings of the order of 1/100 of a second and shorter, said lamp comprising a gas-tight translucent envelope containing arapidly oxidizable substance adapted to emit light upon combustion thereof, electrical ignition means comprising terminals disposed in fixed, spaced relation within said envelope to form a spark gap within effective ignition range of said substance, spaced terminals on the exterior of said envelope, and electrical conductors extending between said spark-gap-forming terminals and said exterior terminals; at least one lamp comprising a gas-tight translucent envelope containing a first rapidly oxidizable substance adapted to emit light upon combustion thereof, electrical ignition means comprising terminals disposed in fixed, spaced relation within said envelope to form a spark gap within effective ignition range of said first substance, a second, readily oxidizable substance having rapid fiame propagation characteristics positioned between said terminals, whereby a spark across said gap will pass therethrough, spaced terminals on the ex-,, v

terior of said envelope, and electrical conductors extending between said spark-gap-forming 'terminals and said exterior terminals.

4. An electric-spark-ignited photographic flash lamp having a type of construction characterized by the lapse of a substantially constant interval of time between the instant of electric current application thereto and. the instant of full illumination, whereby it is'adapted for positive synchronization with camera shutter openings of the order of l/100 of a second and shorter, said lamp comprising a gas-tight translucent envelope containing a gas, a filling of foil in said envelope adapted to emit light upon combustion thereof with said gas, electrical ignition means disposed in fixed, spaced relation within said envelope to form a spark gap, a second, readily oxidizable substance having rapid flame propagation characteristics positioned between said terminals and within effective igniting range of said foil, whereby a spark across said gap will pass therethrough, spaced terminals on the exterior of said envelope,

and electrical conductors extending between said spark-gap-forming terminals and said exterior terminals.

5. An electric-spark-ignited photographic fiash lamp having a, type of construction characterized by the lapse of a substantially constant interval of time between the instant of electric current application thereto and the instant of full illumination, whereby it is adapted for positive synchronization with camera shutter openings of the order of 1/ 100 of a second and shorter, said lamp comprising a gas-tight translucent envelope containing a rapidly oxidizable substance adapted to emit light upon combustion thereof, electrical ignition means comprising terminals of readily combustible material disposed in fixed, spaced relation within said enevelope to form a spark gap within effective ignition range of said substance, spaced terminals on the exterior of said envelope, and electrical conductors extending between said spark-gap-forming terminals and said exterior terminals.

6. An electric spark ignited, photographic,

I flash lighting device comprising a gas-tight, translucent envelope containing a gas, a filling of foil in said envelope adapted to emit light upon combustion thereof with said gas, electrical ignition means comprising terminals disposed in fixed spaced relation within said envelope to form a spark gap within effective ignition range of said foil, a battery, a transformer having its secondary winding in circuit with said terminals, and means for forming a closed circuit through said battery and the primary Winding of said transformer including means controllable by the operator for opening said last mentioned circuit to produce a spark across said gap; devices of the foregoing type being characterized by the lapse of a substantially constant interval of time between the instant of openingsaid primary circuit and the instant of full illumination whereby they are adapted for positive synchronization with camera shutter exposures of the order of 1/ 100 of a second and shorter.

HARRY A. WILLIAMS. ENRIQUE G. TOUCEDA.

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