US 1247068 A
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Description (OCR text may contain errors)
B. L. BENBOW.
APPLICATION FILED ocr. 4, 1913.
1,247,068. Pafented NOV. 20, 1917.-
]EYYEHTUR .BUHJYIE LEE EL'NB 01W, ay-
I H15 A2 TaRNEy.
UNITED STATES PATENT OFFICE.
BUB-HIE LEE BEITBOW, 0F CLEVELAND, OHIO, ASSIGNOB TO GENERAL EECTBIG comm, A CORPORATION OF NEW YORK.
Specification 0! Le r a e I Patented NOV. 20, 191'? Application filed October 4, 1913. Serial No. 798,286.
Be it known that I, Bumnn LEE BENBOW,
a citizen of the United States, residing at Cleveland, -county of Cuyahoga, State of Ohio, have invented certain new and useful Improvements in Filaments, of which the following is a. specification.
My invention relates to filaments for incandwcent lamps and more particularly to filaments of that character composed of metal such as tungsten. The object of my invention is to produce a filament of a highly concentrated form and of such consistency that it will require comparatively few supports in the lamp.
In producing my improved filament, I wind a straight fine filament wire of the roper diameter to produce the requisite 'ght under voltage conditions of the circuit in which it is to be used, into a coil or helix of comparatively small diameter. The small diameter of the coil renders the difference in otentialbetween successive turns when the filament is in use very small and the wire may be wound with the turns very close together without danger of the current jumpintilzsrcross between turns. The winding of coil is referably done on a mandrel of quite sm diameter and the winding stres is such that the material is stressed be 0nd its elastic limit into a permanent h The filament thus produced is then wound into another helix, the winding stress also exceeding the elastic limit of the material. This may be done on the same mandrel upon which the first helix was wound. The result is what may be termed a double helix 0: a helix wound into a helix. In order that the turns of the second wound helix may be properly spaced from each other a spacing wire may be wound therewith and afterward removed.
In the drawing Figures 1 and 2 are views partially in sectlon showing two forms of incandescent lamp each containing a filament'embodying my invention, and Fig. 3 is a detail view on an enlarged scale of a por tion of the said filament.
The lamp shown in Fig. 1 has a filament consisting of a straight portion 1 and a double helical portion 2. A support 3 composed of any metal commonly used for supports and of such size that it is comparatively rigid extends from the stem 4 into which it is sealed and is provided at the tip and eyelet 6. The filament 1, 2 is twisted around the said eyelet and it extends from the same to the lead-in wires 7. It will be readily seen that by this construction a considerable length of filament may be concentrated in a comparatively small length of lamp. This aflords a very useful construction especially where the lamp is to be used to illuminate show-cases and in other locations where it is desired to direct a very brilliant light over a comparatively extensive area.
In Fig. 2 is shown a filament embodying my invention mounted in a lamp having a spherical bulb 8. The filament 9 is concentrated around the center of the bulb and is draped between the supporting hooks 10 and 11 which are mounted in the glass stem 12. Owing to the compact structure of the filament only a very few supports are required. Such a lamp as-that shown in Fig. 2 is especially adapted for use where it is desired to direct light by means of a reflector or reflecthereof with the supporting hook 5 having tors to a comparatively small area. Lamps of this kind are especially adapted for use in connection with stereopticon apparatus, search lights, signal lights, and also for headlights for vehicles.
In Fig. 3 is shown on an enlarged scale a section of a filament embodying my invention. In mounting the filament it may be stretched somewhat. The process of winding, during which the wire is stressed beyond its elastic limit, seems to increase its strength. The completed filament is very elastic and may, be handled very roughly without danger of breaking. After it is in use the filament sets and loses much of its elasticity. For this reason it is preferable not to stretch it in mounting; in other words, to wind it in substantiall which it will be used in the amp.
What I claim as new and desire to secure by Letters Patent of the United States, is
1. In an electric incandescent lamp, a plurality of supports and a metal light emitting filament having the shape of a helix, the turns of which are made 'up of helices, strlmg between the said supports, said filament possessing a permanent shape independent of said supports.
2. In an electric incandescent lamp, a li ht emitting filament having the shape 0 a helix, the turns of which are made up of helices, and means engaging only widely septhe shape in ereted portions of the said filament for supporting the same.
, 3. In an electric incandescent lamp, e light emitting filament haivin the she e of e 5 helix, the turns of whic are me 0 up of helices.
4. In an electric incandescent lamp, a li ht emitting filament having the she e o a helix, the turns of which are med e up of 10 helices, saicl filament wire being support/e61 incense at only at few points in its length nndl being otalierwise free of contaict'with other meter]. s.
In witness whereof, l have hereunto set my henci this first clay of @ctoloer, 1913.
BURNIE LEE BENBOW.