US2997617A

US2997617A - Electric incandescent lamp

Info

Publication number: US2997617A
Application number: US706828A
Authority: US
Inventors: William F Hodge
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1958-01-02
Filing date: 1958-01-02
Publication date: 1961-08-22
Anticipated expiration: 1978-08-22

Description

Aug. 22, 1961 W. F. HODG E ELECTRIC INCANDESCENT LAMP Filed Jan. 2, 1958 lnventov: WiLLiam F l-lod cgga, b WW;

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United States Patent 2,997,617 ELECTRIC INCANDESCENT LAMP William F. Hodge, Lyndhurst, Ohio, assignor to General Electric Company, a corporation of New York Filed Jan. 2, 1958, Ser. No. 706,828 3 Claims. (Cl. 313-278) My invention relates to electric incandescent lamps or similar devices comprising a sealed envelope containing an incandescible filament for emission of radiant energy. More particularly, the invention relates to lamps having an elongated envelope containing a straight wire filament which is required to be maintained taut during operation.

The use of long filaments of straight tungsten wire, which expand and sag under their own weight upon being heated to incandescence, requires the provision of means which will maintain the filament taut under all conditions and, at the same time, will permit of ready expansion and contraction of the filament without subjecting it to undue strains. It is an object of this invention to provide a unique and especially advantageous, inexpensive and reliable spring tension means for performing that function.

Further objects and advantages of my invention will appear from the following description of a species thereof and from the drawing wherein:

FIG. 1 is a side view, partly in section, of a lamp embodying the invention; and

FIG. 2 is a fragmentary perspective as viewed from the line 2-2 in FIG. 1 and showing the connection of the filament to the tensioning spring means.

Referring to the drawing, the lamp illustrated therein comprises an elongated tubular envelope 1 of glass or quartz preferably containing a filling of inert gas, such as argon at a pressure of several hundred millimeters. The envelope is sealed at both ends of compressed or flattened pinch seal portions 2 in which are embedded portions of lead-in or current supply conductors 3. When the envelope 1 is of quartz, the conductors 3 preferably consist of wires of molydenum having extremely thin intermediate flattened or foliated portions 4 hermetically sealed in the seal portions 2. The envelope 1 also contains an incandescible filament 5, preferably of straight tungsten wire, which is fixedly secured as by welding, at one end to the inner end of the lead-in conductor 3 at the left in FIG. 1.

In accordance with the invention, there is provided at the opposite or right hand end of the lamp a spring tension means comprising a wire helix 6 preferably of tungsten. The diameter of the helix 6 is a little less than the inside diameter of the envelope 1, allowing it to slide freely therein. One end of the helix 6 is secured, as by welding, to the adjacent lead-in conductor 3. The other, or remote, end of the helix 6 rests against a retaining means which is fixed relative to the envelope 1 and which is here illustrated as a pair of opposed inward protuberauces 7 formed by indentations or constructions in the wall of the envelope.

The right hand end of the filament is supported from a point on the helix 6 intermediate its ends. As herein illustrated, the end of the filament is welded directly to a part of one of the turns of the helix which has been distorted, as shown at 8, to bring it substantially across the axis of the envelope 1. During assembly of the lamp, the seal 2 at the right is made first. The lead-in conductor 3 at the left, previously welded to the filament, is then pulled down into sealing position to thereby compress the part 9 of the helix against the protuberances 7. Suflicient compression is introduced to make sure that expansion of the filament, when heated to incandescence, will be taken up by the spring action of the part 9 with suflicient residual tension to keep the filament taut.

During operation of the lamp, current flows through the part 10 of the helix to the filament 5. The wire sizes employed for the helix 6 and filament 5 are so proportioned that the design current necessary to heat the filament to desired operating temperature will heat the part 10 of the helix to a red heat. At this temperature the helix portion 10 is relatively soft and acts as aflexible current conductor. However, the spring portion 9 of the helix does not carry current and, therefore, it is not softened and maintains the necessary tension on the filament to keep it straight.

In a specific lamp designed for infrared radiation, the envelope 1 may be of quartz tubing having an inside diameter of 7.75 mm., the filament 5 may be a tungsten wire of .013 inch diameter and 11% inch overall length, to operate at a color temperature of approximately 3400" K. at a current of about 14.05 amperes from a source of 52.5 volts across the lamp terminals, and the helix 6 may be of tungsten wire of about .019 inch diameter with the portion 10 heated to a red heat during passage of the current therethrough.

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

1. An electric incandescent lamp comprising a sealed tubular envelope, a pair of current supply conductors sealed in opposite ends of said envelope and extending thereinto, a helical compression spring of slightly smaller diameter than said envelope located adjacent one end of the envelope, retaining means fixed relative to the envelope and engaged by the end of said spring remote from said one end of the envelope, a straight wire incandescible filament securely connected at one end to the current supply conductor at the other end of the envelope, said filament extending longitudinally of the envelope and into the interior of said spring and supported at its other end from a part of said spring spaced from its said remote end, the spring being held, by said filament against said retaining means under compression suflicient to take up the expansion of the filament when heated to incandescence and maintain the filament taut, and flexible conductor means electrically connecting the said other end of the filament with-the current supply conductor at the said one end of the envelope.

2. An electric incandescent lamp comprising a sealed tubular envelope, a pair of current supply conductors sealed in opposite ends of said envelope and extending thereinto, a helical compression spring of slightly smaller diameter than said envelope located at one end of the envelope and having a proximate end secured to the current supply conductor at said end of the envelope, retaining means engaged by the remote end of said spring and fixed relative to said envelope, a straight wire incandescible filament securely connected at one end to the current supply conductor at the other end of the envelope, said filament extending longitudinally of the envelope and into the interior of the said remote end of said spring and supported at its other end from and electrically connected to a part of said spring intermediate the ends of the spring, the portion of said spring between said retaining means and the part secured to said other end of the filament being under compression suflicient to take up the expansion of the filament when heated to incandescence and maintain the filament taut, the remainder portion of said spring serving as a flexible current supply conductor.

3. An electric incandescent lamp comprising a sealed tubular envelope, a pair of current supply conductors sealed in opposite ends of said envelope and extending thereinto, a helical compression spring of slightly smaller diameter than said envelope located at one end of the envelope and having a proximate end secured to the current supply conductor at said end of the envelope, retaining means engaged by the remote end of said spring and 3 fixed relative to said envelope, a straight Wire incandescible filament securely connected at one end to the current supply conductor at the other end of the envelope, said filament extending longitudinally of the envelope and into the interior of the said remote end of said spring and supported at its other end from and electrically connected to a part of said spring intermediate the ends of the spring, the portion of said spring between said retaining means and the part secured to said other end of the filament being under compression sufficient to take up the expansion of the filament when heated to incandescence and maintain the filament taut, the remainder portion of said spring serving as a flexible current supply conductor and being proportioned relative to said filament so that the design current necessary to heat said filament to its 15 2,731,579

normal operating temperature will heat said remainder portion of the spring to a red heat and thereby minimize the tension therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,745,181 Mischler Jan. 28, 1930 1,975,499 Braselton Oct. 24, 1934 2,078,360 Ziegenbein Apr. 27, 1937 2,342,044 Foote Feb. 15, 1944 2,521,315 Victoreen Sept. 5, 1950 2,521,682 Backer etal Sept. 12, 1950 2,523,033 Leighton Sept. 19, 1950 2,532,956 Simpson Dec. 5, 1950 Weiss Jan. 17, 1956