US2145157A - Incandescent electric lamp - Google Patents

Description

INCANDES CENT ELECTR I C LAMP Filed June 20, 1938 Inventor; William-T Cowhig, by HIM/75 His Att orney Patented Jan. 24, 1939 PATENT OFFICE INCANDESCENT ELECTRIC LAMP William '1. Cow l l;

General Electric New York Application June 20,

Bus y, Com

En land,

asslgnorto puma onol 1938, Serial No. 214,824

In Great Britain July 13, 1937 4 Claims.

The present invention relates to incandescent electric lamps and more particularly to such 'lamps in which a relatively short coiled filament of a refractory metal such as tungsten is mounted within and sealed into an envelope consisting of a tube of quartz or other like strong, heat resisting transparent or translucent vitreous material so as to lie axially within the tube.

One of the dlfiiculties which arise when atungsten filament is mounted in a small quartz or glass envelope has been that the filament sags during operation and approaches the wall of the envelope. It is not convenient to introduce a support along the length of the lamp owing to the small diameter of the envelope, so that it is desirable to eliminate this sag by drawing the iilarhent taut after it has been flash aged during the lamp exhausting operation.

One object of my invention is to provide a method of mounting the filament of an electric incandescent lamp so that it may be easily drawn taut without weakening the lamp envelope.

According to the invention, the sealing of the leading-in wiresinto the drawn-down ends or neck portions of the tubular envelope is eflected at points somewhat spaced from the body of the envelope, and after the envelope has been sealedoil the portion of one or both of the drawn-down ends of the envelope, adjacent the body thereof,

is heated to soften it, and the leading-in wires,

Referring to the drawing, there is shown a typical double-ended lamp comprising a filament I mounted within a small tubular envelope 2 preferably of quartz or other high heat-resistant glass. The filament I is disposed substantially axially of the tubular envelope 2 which is of relatively small internal diameter. Opposite ends of the filament are connected to current supply or leading-in wires sealed into reduced end or neck portions 2' of the lamp envelope 2, each of said wires comprising a length of molybdenum wire 3 secured to the filament l, a strip of molybdenum foil attached to the wire 3, and a section of molybdenum strip 5 secured to the foil 4. The

;, actual seal between the quartz lamp envelope 2 and the current supply wires is made at the foil 4.

The filament assembly is sealed into the quartz or glass envelope 2 in the usual way, using the above-described molybdenum strip seal. In the 5 usual method of making these lamps, the seals are at a relatively short distance, such as 1 or 2 mm.', from the body of the lamp envelope 2. According to my invention, however, the seal is made at a considerably greater distance from 10 the body of the lamp envelope, preferably at a distance of about to 1 cm. therefrom, as shown in the drawing. The lamp envelope is then exhausted through the exhaust tube Ii after which the filament is then burned or flash aged in the .customary manner until recrystallization processes, etc., are complete. The exhaust tube 6 having been tipped, the envelope neck portion A immediately adjacent the body of the envelope 2 is then softened and the filament I drawn taut by a pulling-out or stretching operation. One or both of the envelope neck portions A between the body of the envelope and the current supply wire seal may be softened to permit this drawing-out Q or stretching of the filament.

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

1. The method of mounting a longitudinally extending coiled filament, having leading-in wires connected to its opposite ends, within a tubular glass envelope having reduced end portions, which comprises sealing said leading-in wires into said reduced end portions, at least one of said leading-in wires'being sealed at a point considerably removed from the body of said envelope to thereby provide an extended neck portion between the body of, said envelope and the said seal, softening said extended neck portion of said envelope, and then drawing the said filament' taut while the said extended neck por- 40 tion is still plastic.

2. The method of mounting .a longitudinally extending coiled filament, having leading-in wires connected to its opposite ends, within a tubular glass envelope having 'reduced end portions, which comprises sealing said leading-in wires into said'reduced end portions'at pointsconsiderably removed from the body 'of said-envelope tothereby provide extended neck per-- tions between the body of said envelope and the said seals, softening at least one of said extended neck portions,- and then-drawing the said fila-' ment taut while the said extended neck portion is still plastic.

3. The method of mounting a longitudinally 56 extending coiled filament, having leading-in wires connected to its opposite ends, within a tubular glass'enveldpe having reduced end portions, which comprises sealing said leading-in:

wires into said reduced end portions, at least one of said leading-in wires being sealed at a point considerably removed from the body of said envelope to thereby provide an extended neck portion between the body of said envelope and the said seal, exhausting said envelope and operating said filament until recrystallization thereof is-complete, softening said extendedi-neck portion of said envelope, and then drawing the said filament taut while the said extended neck portion is still plastic.

4. The method of mounting a longitudinally extending coiled filament, having leading-in V wires connected to its opposite ends, within a tubular glass envelope having reduced end por-.

ment taut while the said extended neck portion a is still plastic.

WILLIAM '1. COWHIG.

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