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Publication numberUS3626236 A
Publication typeGrant
Publication dateDec 7, 1971
Filing dateFeb 25, 1970
Priority dateMar 25, 1969
Also published asDE2013573A1, DE2013573B2
Publication numberUS 3626236 A, US 3626236A, US-A-3626236, US3626236 A, US3626236A
InventorsFenn Henry Alfred, Robinson Kenneth Buckley
Original AssigneeThorn Lighting Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Tungsten-halogen lamps
US 3626236 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Kenneth Buckley Robinson; Henry Alfred Fenn, both of London, England Feb. 25, 1970 Dec. 7, 1971 Thorn Lighting Limited London, England Mar. 25, 1969 Great Britain [72] Inventors App]. No. Filed Patented Assignee Priority TUNGSTEN-HALOGEN LAMPS 13 Claims, 2 Drawing Figs.

U.S. C1 313/316, 313/222, 313/276 Int. Cl HOIlt 9/00 FieldofSearch 313/115, 222, 223, 315, 316

{ 56] References Cited UNITED STATES PATENTS 1,483,449 2/1924 Johnson 313/315 3,441,774 4/1969 Stone et a1. 313/316X Primary Examiner-Raymond F. Hossfeld Alr0rneyLaurence Burns ABSTRACT: A tungsten halogen incandescent lamp having two planar filaments which are spaced further apart at one pair of edges of the planes than at the other pair, one filament being of lower efficiency than the other filament so that in use the lamp can be orientated with the filaments further apart at the upper edges and the filament of lower efficiency uppermost whereby the temperature gradient between the top and the bottom of the filaments is reduced.


LEY ROBINSON KENNETH BUCK HENRY ALFRED FENN INVENTORS ATTORNEY TUNGSTEN-HALOGEN LAMPS The present invention relates to improvements in tungstenhalogen incandescent lamps.

A tungsten-halogen studio lamp consisting of two parallel planar filaments mounted in a silica envelope, has the disadvantage that the filaments are necessarily large, which causes the size of the envelope to be larger than the optimum size for the operating temperature of the lamp. To reduce the size of the envelope and hence its cost the dimensions of the filaments and the spacing between the filaments are reduced as much as possible. Notwithstanding these reductions, a large envelope is still required, and due to the risk of an explosion when a large envelope is filled to a high pressure, the envelope is only filled to a relatively lowpressure. The filaments of the lamps thus produced are particularly prone to arcing, especially when the lamp is burnt with the filaments at an angle of about 45 to the horizontal, which is an orientation commonly used in the studio.

It has been found that most of the arcing occurs at the top of the filament which is uppermost in use. Normally it is the rear filament that is uppermost.

The arcing has been attributed to two causes. Firstly the upper filament runs at a temperature 3050 C. higher than the lower filament, due to its position. Additionally there is a temperature gradient from the bottom to the top of each filament. Thus the top of the upper filament is the hottest part of the lamp and consequently the filament evaporates more rapidly there than at the rest of the filament. The tungsten halide which decomposes near the filament replaces tungsten on the filament but not necessarily on the hot spots. These hot spots of the filament become thinner more rapidly than elsewhere, their electrical resistance becomes relatively high and hence these parts become still hotter. The evaporation is enhanced and it has been found that a 30 C. rise in the original filament-temperature causes a reduction of 25 percent in the life of the lamp. The hotter a wire becomes the more likely it is to emit ionizing particles which may start arcmg.

Secondly in the region of the Langmuir sheath, whose dimensions are controlled bythe temperature and pressure of the lamp, and the viscosity and density of its fill, convection does not occur and only laminar gas flow is evident. In doublefilament tungsten-halogen studio lamps the Langmuir sheaths may overlap. Impurities such as iron in the lamp can combine with the halogen and eventually find their way back to the filament. They may then be flashed off as ionizedparticles. The laminar flow tends to transfer the ionized particles from the lower filament to the top of the upper filament increasing the likelihood of arcing.

In this specification a planar filament means a filament which is large in two dimensions and relatively small in the third dimension. Thus the term "planar filament" includes, for example, a a biplanar filament.

According to the present invention a tungsten-halogen incandescent lamp comprises two planar filaments located one in front of the other, and the spacing between the filaments being greater at one pair of edges of the planes of the filaments than at the opposite pair of edges.

In a preferred form of the present invention one of the filaments is of a lower efficiency than the other.

By using the lamp with the ends which are spaced further apart at the top and the filament of lower efficiency uppermost the life time of the lamp can be increased and may be greater than a similar lamp of the type described above.

The temperature gradient between the top and bottom of each filament is reduced and may be eliminated since there is less heat transfer between the filaments at the top than at the bottom. The temperature difference between the front and rear filaments is reduced and in some cases eliminated by the wider spacing which gives less heat transfer and by the lower efiiciency of the upper filament. The spacing at the top may be made sufficient to separate the Langmuir sheaths there and the convection between the filaments tends to prevent ionized gas being transferred from one filament to the other.

A embodiment of the invention will now be described with reference to the accompanying drawings of which:

FIG. l is a front elevation of a tungsten-halogen-studio lamp; and

FIG. 2 is a side elevation of the lamp of FIG. 1.

Two tungsten filaments 11 and 12 are mounted in a silica envelope 13. The filaments are made up of substantially parallel coiled sections 14 which are connected] in series and which are supported by hooks 15 from silica bridges l6. Metalrods 17 support the silica bridges 16. These rods pass through a flat silica disc 18 which forms the base of the envelope 13. Two silica tubes 19 surround the rods 17 on the side of .the disc 18 which is not enclosed by the envelope 13. The tubes 19 are sealed with pinched seals 20 and metal foils 21 are included in the seal electrically to connect the rods M7 to terminal wires 22.

The ends 23 of the wires of the filaments are wound round the rods 17 so as to provide electrical connection between the filaments II and 12 and the terminal wire 22.

The upper ends of the rods 17 are provided with coils 24 which are located in tubes 25 on the inside ofthe envelope 13.

The lamp is made by bending the rods 17 into the shape required by the spacing of the filaments and the tubes l9with the seals 20 are welded into the flat silica disc 18. The filaments II and 12 are mounted on the rods 17 and the envelope I3 is then sealed aroundthe filaments. The fill of the envelope includes inert gas and small quantities of a halogen either as the element or in a compound.

The filament 12 has a lower efficiency than the filament l1 and the rods 17 are so bent that the filaments are further apart at the top than at the bottom.

In normal use the filaments are 45 to the horizontal with the filamentlZ above and to the rear of the filament 11. In this way the temperatures of the filaments are approximately the same and the tendency for arcing is less than for similar lamps with parallel filaments of equal efficiencies.

Each filament of the lamp described is a planar filament made up of parallel coiled-wire sections connected in series. However, it is possible to have other forms of planar filament such as, for example, one made upof a zigzagarray of coiled sections connected in series, or a biplanar filament, that is a filament in which alternate sectionsare displaced out of the plane of the other sections into, a second plane. Furthermore the coiled filament may be a coiled coil.

What is claimed is:

l. A tungsten-halogen incandescent lamp comprising: an, envelope; a fill of inert gas and halogen; lamp terminals; two planar tungsten filaments located one in front of the other inside the envelope, the spacing between the said filaments being greater at one pair of edges of the planes of the filaments than at the opposite pair of edges; and lead-in conductors connecting the filaments to the terminals.

2. A lamp as claimed in claim 1 wherein one of the filaments is of lower efficiency than the other.

3. A lamp according to claim 2 in which the filament of lower efficiency is the rear filament.

4. A lamp according to claim I in which the filaments are made up of parallel coiled wire sections.

5. A lamp according to claim 4 in which the sections are suspended between bridge means.

6. A lamp according to claim 5 in which the bridge means are of silica.

7. A lamp according to claim 5 including hooks, the sections being suspended from the bridge means by the hooks.

8. A lamp according to claim 5 in which the lead-in conductors are metal rods, the bridge means being supported in the envelope by the metal rods.

9. A lamp according to claim 8 including coils and corresponding tubes the coils being mounted at one end of each of the rods and engaging the corresponding tubes which are provided on the inside of the envelope, the rods passing through and being-sealed in the envelope.

10. A lamp according to claim 1 in which the filaments are further apart at the edges most distant from the lamp terminals.

11. A lamp according to claim oriented during use with said edges uppermost.

12. A lamp according to claim 2 oriented during use with the filament of lower efficiency uppermost.

13. A lamp according to claim 1 in which each filament is 5 made up of filament sections which lie substantially in the plane of the filament.

# 1C i i

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1483449 *Sep 15, 1921Feb 12, 1924Westinghouse Lamp CoElectric lamp for projection apparatus
US3441774 *Dec 12, 1966Apr 29, 1969Gen ElectricHalogen-cycle incandescent lamp with planar filament
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3968395 *Mar 28, 1975Jul 6, 1976Siemens AktiengesellschaftTwo filament electric bulb traffic light
US3986067 *Dec 12, 1974Oct 12, 1976U.S. Philips CorporationElectric incandescent lamp with support structure for a planar filament
US4023060 *Nov 28, 1975May 10, 1977Gte Sylvania IncorporatedRuggedized, high power tungsten-halogen lamp
US4720653 *Oct 20, 1986Jan 19, 1988Gte Products CorporationElectric lamp with bridge support member providing both compressive and axial support
US5159235 *Aug 10, 1990Oct 27, 1992Gte Products CorporationHollow lamp bridge
US5896007 *Dec 22, 1994Apr 20, 1999Patent Treuhand Gesellschaft Fur Elektrische Gluehlampen MbhHalogen incandescent lamp with heat transfer by conduction
US7107676Nov 5, 2003Sep 19, 2006Fridrich Elmer GOne piece foliated leads for sealing in light sources
US7322870Nov 5, 2003Jan 29, 2008Fridrich Elmer GApparatus and process for finishing light source filament tubes and arc tubes
US7811148Dec 5, 2007Oct 12, 2010Halogen Technologies, Inc.Light source bodies for filament tubes and ARC tubes
USB531929 *Dec 12, 1974Jan 20, 1976 Title not available
U.S. Classification313/579, 313/276
International ClassificationH01K1/54, H01K1/18, H01K1/00
Cooperative ClassificationH01K1/54, H01K1/18
European ClassificationH01K1/54, H01K1/18