US2178430A

US2178430A - Flash lamp

Info

Publication number: US2178430A
Application number: US133875A
Authority: US
Inventors: Richard S Mackie
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1937-03-30
Filing date: 1937-03-30
Publication date: 1939-10-31
Anticipated expiration: 1956-10-31

Description

Oct. 31, 1939.

R. s. MACKIE 2,178,430

FLASH LAMP Filed March 50, 1937 Inventor: Richard S. Mackie,

by M

His Attorney.

Patented Oct. 31, 1939 UNITED STATE-S PATENT OFFICE FLASH LAMP ration of New York Application March 30, 1937, Serial No. 133,875

7 Claims.

My invention relates to flash'lamps and more particularly to that type of flash lamp used for photographic purposes which usually comprises a sealed transparent bulb in which is enclosed a readily combustible material, such as metal foil or wire, togetherwith a substance, usually a gas filling, which, upon ignition, enters into a reaction with the combustible material with the resulting emission of actinic light.

To initiate the actinic reaction, it is necessary to provide some form of ignition means therefor. The type of ignition means customarily employed for such purpose comprises a resistance element or filament embedded in a bead of ignition paste and supported within the bulb in close proximity to the combustible material by a conventional mount structure. The ignition paste generally used is extremely sensitive, and when the electrical circuit through the filament is energized, the heated filament promptly ignites the bead of ignition paste which in turn ignites the combustible material, thus initiating the actinic reaction.

As a safeguard against explosion of the glass bulb when a lamp of this type is flashed, it is customary to test the same for the presence of air. One desirable method of conducting such a test, known as a coil test, consists in the use of high frequency equipment employing glow tubes.

It has been found, however, that such a method of testing results in the loss of a great number of flash lamps through the premature flashing of the same, termed flash-outs, which is caused by the ignition of the extremely sensitive bead of ignition paste by the high frequency of the test equipment. In addition, accidental smashing or breaking of a flash lamp may ignite the bead of ignition paste so that the lamp catches fire. Furthermore, the bead of ignition paste is very fragile, and frequently cracks or breaks off during shipment or other handling of the lamp. I have accordingly devised a novel form of ignition means or primer head for flash lamps whichprevents the premature flashing of the same, eliminates the danger of such lamps catching fire when smashed or broken, and possesses increased mechanical strength and resistance to cracking and breaking off.

One object of my invention is to provide an 50 improved flash lamp which will not flash prematurely when subjected to various external phenomena, such 'as sparks induced by high frequency, corona. or the like.

Another object of my invention is to provide an improved flash lamp which will not catch flre and burn when accidentally smashed or broken.

Still another object of my invention is the provision of a novel form of ignition means for flash lamps which will not ignite when subjected to various external phenomena, such as sparks induced by high frequency, corona, and the like, or when the lamp is smashed or broken.

A further object of my invention is the provision of a coating of lacquer or other similar non-conducting material on the bead of ignition 10 paste-of a flash lamp, which coating will exclude such paste from various external phenomena normally tending to ignite it.

A still further object of my invention is the provision of a coating of non-conductive ma- 16 terial on the bead of ignition paste of a flash lamp, which coating preferably consists of a lacquer composed of a resin solution, a nitrocellulose lacquer, land a plasticizer.

Another object of my invention is the pro- 20 vision of a coating of thermoplastic material on the primer bead of a flash lamp which coating will cause metal foil or wire of the lamp to adhere to the head during the sealing in operation.

A further object of my invention is the pro- 25 vision of a coating on the primer bead of a flash lamp which will add mechanical strength to the' bead and prevent it from cracking and breaking off.

Other objects and advantages of my invention 30 will appear from the following description of species thereof and from the accompanying drawing, in which:

Fig. 1 is an elevation ofa flash lamp comprising my invention in which the ignition means 5 comprises a bead of ignition paste enclosing the filament and coated with a layer of thermoplastic non-conductive material, and Fig. 2 is an enlarged fragmentary sectional. view of a portion of a bead of ignition paste coated in accord- 40 ance with my invention.

Referring to Fig. 1, the lamp comprises a vitreous bulb l0 containing a small filament H, the ends of which are connected to lead-in wires I2, l2 which extend through a stem Hi to the 5 base I 4. The filament II is embedded in a fulminating substance 15 to thereby form the ignition means for the lamp. A disc I 6, preferably of asbestos, is mounted on the stem I3 to shield the base end of the lamp from the heat of combustion. The bulb I0 is loosely filled with combustible material I], consisting of metal foil or wire, usually of aluminum.

The fulminating substances or primer bead l5 customarily employed in flash lamps of the type described above is composed of an extremely sensitive metal powder l8, such as zirconium metal, together with an oxidizing agent, such as lead peroxide, mixed with a suitable binder, such as lacquer. When a head of this paste dries, the metal powder particles at the surface protrude therefrom, and under the microscope have the appearance of fuzz. It is this fuzz that causes the head of ignition paste to flash when a slight spark or even corona strikes the same. Similarly, the friction apt to be exerted on such fuzz when a flash lamp is accidentally smashed or broken might cause the bead of paste to flash, with the attendant danger of fire. By covering this fuzz or roughened surface with a coating of a suitable non-conductive substance.l9, as shown in Fig. 2, the metal powder I8 is thereby excluded from the action of all external phenomena thereon tendingto ignite the same, such as sparks induced by high frequency, or corona, friction, and the like. In this manner, the premature flashing of the bead of ignition paste [8, and of the flash lamp itself, during test or when broken, is prevented. In addition, the coating i9 definitely adds a considerable amount of mechanical strength to the fragile bead of ignition paste, thereby reducing the danger of the bead cracking and breaking off during shipment and other handling of the lamp.

The coating material l9 may consist of a mixture of a synthetic or natural resin solution with or without nitrocellulose lacquer and with or without a suitable plasticizer, dissolved in suitable solvents. to use is that commercially known as Glyptal varnish, but the resin contained therein may be any other resin having thermoplastic properties. The nitrocellulose lacquer may consist of nitrocellulose dissolved in a suitable solvent or solvents, such as acetone, while the plasticizer may be dibutylphthalate, tricresylphosphate, or some other similar substance. The above mixture of a resin solution, nitrocellulose lacquer and a plasticizer is diluted with a suitable thinner or diluent, preferably that known as Ault and Wibcrg thinner H8349. The coating material may be applied to the fulminating substance or primer bead i5 by simply dipping such bead in the coating material and allowing the latter to dry thereon. During this drying process, the aforementioned thinner or diluent evaporates, leaving a coating of solid material on the fulminating substance consisting of the mixture of a resin solution, nitrocellulose lacquer and a plasticizer referred to above.

The synthetic resin preferably employed in the coating material [9, and commercially known as Giyptal, possesses the property of thermoplasticity; or, in other words, it becomes plastic upon the application of heat thereto. This resin is present in suflicient quantity in the coating 'material iii to impart this property of thermoplasticity to the coating material itself, so that the heat attending the sealing of the mount in the bulb renders such coating material plastic. Any portion of the metal foil or wire I! within the lamp coming into contact with the coating material while the same is in such a plastic state will permanently adhere to such coating material and accordingly to the primer bead. thus insuring positive and instantaneous ignition of the metal foil or wire upon the ignition of the primer bead.

The synthetic resin solution I prefer Although the preferred form of the invention is shown and described herein, it is to be understood that modifications may be made therein, such as the use of coatings of a composition other than those mentioned above, without departing from the spirit and scope of the invention as described herein and as setforth in the appended claims.

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

l. A flash lamp comprising a sealed container,

a quantity of combustible material within said container, and means for igniting said combustible material, said means including a head of highly sensitive fulminating substance comprising readily ignitable metallic powder and coated with a layer of material comprising a mixture of a thermoplastic resin solution and a nitrocellulose lacquer. 2. A flash lamp comprising a sealed container. a quantity of combustible material within said container, and means for igniting said combustible material, said means including a bead of highly sensitive fulminating substance comprising readily ignitable metallic powder and coated with a layer of material comprising a mixture of a thermoplastic resin solution and a plasticizer.

3. A flash lamp comprising a sealed container, a quantity of combustible material within said container, and means for igniting said combustible material, said means including a bead of highly sensitive fulminating substance comprising readily ignitable metallic powder and coated with a layer of material comprising a mixture of a thermoplastic resin solution, a nitrocellulose lacquer, and a plasticizer.

4. A flash lamp comprising a sealed container, a quantity of combustible material within said container, and means for igniting said combustible material, said means including a bead of highly sensitive fulminating substance comprising readily ignitable metallic powder and coated with a layer of thermoplastic lacquer.

5. A flash lamp comprising a sealed container, a quantity of combustible material within said container, and means for igniting said combustible materiahsaid means comprising an electrical translation element embedded in a bead of highly sensitive fulminating substance comprising readily ignitable metallic powder, said bead being coated with a layer of thermoplastic lacquer.

6. A flash lamp comprising a sealed container, a quantity of combustible material within said container, and means including a bead of highly sensitive fulminating substance comprising readily ignitable metallic powder for igniting said combustible material, a portion of said combustible materi: being securely attached'to said bead of fulminating substance by a thermoplastic lacquer.

7. A flash lamp comprising a sealed container, a quantity of combustible material within said container, and means for igniting said combustible material including a bead of highly sensitive fulminating substance comprising readily ignitable metallic powder, said bead having thereon a protective coating of thermoplastic resinous lacquer of sufficient thickness to prevent ignition of said bead upon breakage of the said container.

RICHARD S. MACKIIE.