US2490769A - Photoflash lamp - Google Patents

Description

fies. 13, 1949 R. E. ANDREA v PHOTOFLAS H LAMP Filed Jan. 2, 1947 INVENTOR. 5

Patented Dec. 13, 1949 PHOTOFLASH LAMP Ralph E. Andrea, Dayton, Ohio Application January 2, 1947, Serial No. 719,647

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) 7 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to a photoflash lamp that is proof against other than intended ignition by electric charges or currents.

One object of the invention is to provide a photofiash lamp that is proof against ignition from induced electrical currents which enter the lamp from sources other than through the base of the lamp.

Another object is to provide a photofiash lamp that is proof against ignition by stray high-frequency and other electric currents or waves. Such phenomena are often present during military usage of photoflash lamps when subjected to electrical transmission from radar and radio stations.

Another object is to provide a sleeve of dry paper or other sheet material to be shipped over the lead-in wires of a foilor wire-filled pht0- fiash lamp during manufacture, thus insulating the filament and primer from any electrical charge which may be present on the foil or wire.

In the drawing:

Fig. 1 is an elevation of my photofiash lamp showing the sleeve in place;

Fig. 2 is an elevation of the sleeve alone; and

Fig. 3 is a cross section of my lamp taken on the line 3-3 of Fig. 1.

In Fig. 1, I0 is a screwor other style base, H is the usual glass envelope or globe. I5 is a filament between the primers l9 and. Hid used commercially in photofiash lamps. I6 is a paper or other material sleeve which I have invented and is mounted over the glass stem l3 and around the lead-in wires Id and I la during the manufacture of the lamp. It has an originally cylindrical form, as shown in Fig. 2, but the shape becomes distorted upon mounting. The reason is that the top of glass stem l3 has an oval cross-section, which the sleeve It assumes.

The sleeve It as shown in the figures has a number of gored areas I! in its upper end, thereby giving that end a deeply crenelated appearance. The areas l'l perform the function of allowing heat from the filament l5 and flame from the filament and primer to reach the foil or wire filling 12 to ignite it. The bulb ll contains oxygen to support combustion of the foil or Wire l2.

The sleeve It may be made of seamless tubing, preferably of paper or permissibly of fiber or plastics. It must be substantially 100 per cent dry.

The preferred form is, however, seamed at [8 (Fig. 3) with a lap seam held with adhesive (not shown) of the pressure-sensitive type. Adhesive is also applied to the base of the sleeve at 20 on the inner edge thereof to assist in maintaining an erect position of the sleeve on the stem l3. The length and stifiness of the sleeve should be such that when it sits firmly on the stem l3, the upper edges will keep the foil or wire l2 from contact with filament. That part of the upper edges which comes above the primers l9 and 19a is preferably bent over them so as to meet or nearly meet in the center. The separation of the gores in length or diameter should not be so great that a prompt ignition cannot be achieved nor should they be longer than one-half the length of the sleeve.

The lamp is operated in the same manner as conventional photofiash lamps. No difiiculty is experienced in igniting the foil or wire filling when the current from standard wiring circuits is used or even when the current source is from a battery of adequate amperage and voltage and enters the lamp through its proper electrical terminals. The current that the battery will give should not be less than that required by the rating of corresponding conventional lamps.

The invention claimed is:

1. In a photofiash lamp, a transparent gastight envelope, a base, a glass stem arising from said base within said envelope, lead-in wires extending through said stem, a filament extending between said lead wires and in contact therewith, ignition means in contact with said filament, a filling of brightly combustible metal, a filling of oxygen in said envelope, a dry sleeve of flexible cellulosic sheet material mounted on the filament-supporting glass stem and supporting said combustible metal filling and preventing contact between said filament and said combustible metal filling, said sleeve being deeply crenelated in a multiplicity of places around its top edge.

2. A photofiash lamp according to claim 1 in which the crenelated portions of the sleeve are of greater width at the top of the sleeve than at their lower ends.

3. A photofiash lamp according to claim 1 in which the crenelated top edges of the sleeve are turned toward the axis of the sleeve.

4. A photofiash lamp according to claim 1 and in addition a coating of pressure-sensitive adhesive on the lower inner edge of the sleeve.

5. A photofiash lamp according to claim 1 in which the sleeve is made of paper.

6. A photoflash lamp according to claim 1 in which the sheet material of which the sleeve is REFERENCES CITED m d i lap-joined t itself t mak a tub The following references are of record in the '7. A sleeve of dry cellulosie sheet material of file of this patent: moderate stifiness having dimensions enabling it 5 to be fitted over and be mounted upon the glass Y UNITED STATES PATENTS filament supporting stem of a. photoflash lamp, Nmnber- Name Date saiol sleeve being deeply multi-crenelated at one 93,275 Johnson Sep 1 1937 end, and coating of pressure-adhesive material 2,178,428 Lammers Oct 31, 1939 on the inner surface of the non-crenelated end 10' 2,230,080 Johnson et 1941 of said sleeve.

RALPH E. ANDREA.

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