US3732455A

US3732455A - Halogen incandescent lamp

Info

Publication number: US3732455A
Application number: US00113980A
Authority: US
Inventors: G Neumann
Original assignee: Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
Current assignee: Osram GmbH
Priority date: 1970-03-03
Filing date: 1971-02-09
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08
Also published as: NL7102433A; GB1341762A; FR2081664A1; FR2081664B1; DE2009916C2; DE2009916A1; BE763594A

Abstract

The halogen incandescent lamp has a tungsten filament and its halogen cycle takes place with fluorine participating therein. To prevent corrosive action of the fluorine on internal lamp components, the inert fill gas contains an additive of perhalogenated low molecular weight hydrocarbons with at least one fluorine atom per molecule in a concentration of from 1 X 10 8 to 1 X 10 6 gram atoms of fluorine, and from 1 X 10 8 to 1 X 10 6 gram atoms of at least one more halogen such as chlorine, bromine, or iodine per cc of bulb volume; preferably, difluorodibromomethane (CF2Br2) is admixed to the fill gas. During lamp operation, a cyclic tungsten-fluorine process takes place close to the filament, the tungsten not included in this cycle is transported back to the filament by the second halogen.

Description

I United States Patent 91 [111 3,732,455 Neumann 1 May 8, 1973 [54] HALOGEN INCANDESCENT LAMP FOREIGN PATENTS OR APPLICATIONS 1 lnvemorl Gerhard Neumann Munich, 954,729 4/1964 Great Britain ..313 223 Germany 898,115 6/1962 Great Britain ..3l3/223 [73] Assignee: Patent-Treuhand-Gesellschaft fur elektrische, Munich, Germany Emmme Ry Lake Assistant ExaminerJames B. Mullms [22] Fled: 1971 Attorney-Flynn & Frishauf [2i] Appl. No.: 113,980

[57] ABSTRACT 30 Foreign Application p i i Data The halogen incandescent lamp has a tungsten filament and its halogen cycle takes place with fluorine Mar. 3,1970 Germany....- ..P 20 09 916.5 participating therfiirL To prevent corrosive action of the fluorine on internal lamp components, the inert fill [52] US. Cl ..313/222, 3 134222 gas contains an additive of perhalogenated low 2; molecular weight hydrocarbons with at least one 1 he 0 care l 31:; fluorine atom per molecule in a concentration of from l X 10- to l X 10 gram atoms of fluorine, and from 1 X 10' to I X 10 gram atoms of at least one more [56] References cued halogen such as chlorine, bromine, or iodine per cc of UNITED STATES PATENTS bulb volume; preferably, difluorodibromomethane (CF Br is admixed to the fill gas. During lamp opera- 3 at 2 tion, a cyclic tungsten-fluorine process takes place 3 3 1111970 z g i f g 31/312 X close to the filament, the tungsten not included in this cycle is transported back to the filament by the second halogen.

9 Claims, 1 Drawing Figure llllllllllr PATENTED 81375 3.732.455

Dr. Gerhard M. Neumann INVENTOR HALOGEN INCANDESCENT LAMP Incandescent electric lamps having tungsten filaments and whose bulb filling of inert gases contains halogen additives are known in the art. With the aid of a halogen additive, a cyclic process takes place inside the lamp during operation thereof, during which the tungsten particles evaporating off the filament and normally depositing on the wall of the bulb are converted at the operating temperature of the lamp envelope to gaseous tungsten halides and are transported back onto the filament. The tungsten halides are decomposed close to the hot filament to free halogens and tungsten, which is deposited onto the filament. Incandescent lamps having halogen additives in the fill gas do not blacken throughout their operating lives, and their light output efficiency remains approximately constant during operational life.

The halogens iodine, bromine, chlorine or fluorine may be used for the described cycle; gaseous mixtures of the halogens have been suggested. (See German Pat. publication No. 1.241.531). If fluorine is added to the inert fill gas of the lamp, the inner wall of the bulb and the other components located inside the lamp, such as, for instance, the filament supports, have to be provided with a coating which is gaseous-fluorine-resistant. Also when using the other halogens, possible attack by the free halogens on the filament ends, the metallic supports and the lead-in wires must be prevented or, at least, delayed. When using bromine, the simultaneous presence of hydrogen within the lamp has proved suitable. The favorable effect of hydrogen is supposed to result from the formation of hydrogen bromide, which inhibits an attack of the elementary bromine on the metallic components. Hydrocarbon bromine compounds are thus added to the inert fill gas supplying bromine and hydrogen (see German Patent publication paper No. 1.489.441).

From investigations of the fluorine cycle in halogen incandescent lamps it is known that with the normally used filament temperatures the rate of decomposition of the tungsten fluorides is higher than the rate of evaporation of the tungsten filament. Consequently, in such a halogen incandescent lamp, the evaporated tungsten from the gaseous phase is conducted as a compound with fluorine to the hottest spots of the filament and is deposited thereon. By this deposition of tungsten, the hottest spots are reinforced, and a temperature balance of the filament is effected. Up to now, this advantage of the tungsten-fluorine cycle could not be utilized, because extraordinarily complicated protective measures were necessary to prevent an attack by the fluorine on the material of the envelope and on the internal lamp components.

It is an object of the present invention to provide a halogen incandescent lamp inside which, during operation the halogen cycle takes place while fluorine is simultaneously present, without necessitating special measures to protect the lamp bulb and also the internal lamp components from an attack by fluorine. Consequently, the invention permits the utilization of the known specific advantages of the tungsten-fluorine cycle, i.e. the redeposition of the evaporated tungsten on the hottest spots of the filament.

The invention thus relates to a halogen incandescent lamp which has a tungsten filament and an additive to the inert fill gas of compounds containing halogens, which during operation of the lamp supply fluorine and at least one more halogen to the halogen cycle to prevent blackening of the lamp bulb.

Subject matter of the invention:

Perhalogenated low molecular weight hydrocarbons which contain at least one fluorine atom per molecule, are admixed to the inert fill gas. The amount of perhalogenated low molecular weight hydrocarbons admixed to the inert fill gas and containing at least one fluorine atom per molecule is so determined that a concentration of from 1 X 10- to 1 X 10 gram atoms of fluorine per cc of bulb volume and a concentration of from 1 X 10- to 1 X 10' gram atoms of at least one more halogen per cc of bulb volume is obtained. A concentration of from 7 X 10- to 4 X 10- gram atoms per cc of bulb volume and a concentration of from 7 X 10' to 4 X 10- gram atoms of at least one more halogen per cc of bulb volume is especially favorable. Preferably, perhalogenated methanes of the general composition CF X are admixed to the inert fill gas, wherein X is chlorine and/or bromine and/or-iodine, m is a whole number at least 1, and n is a whole number at most 3, and the sum of m n equals 4. Also perhalogenated ethanes of the general composition C F X are suitable, wherein X is chlorine and/or bromine and/or iodine, p is a whole number at least 1, q is a whole number at most 5, and the sum of p q equals 6. Most favorable results are obtained with admixtures of difluorodichloromethane (CF Cl and of difluoromonochloromonobromomethane (CF ClBr) and of difluorodibromomethane (CF Br to the fill gas, the aforesaid bromine-containing compounds being distinguished from the chlorine containing compounds in that they form during the dissociation within the lamp elemental bromine which is less corrosive with regard to metal parts. For this reason, the aforesaid bromine containing compounds are preferably used, however, the chlorine containing compounds may also be used and furnish satisfactory results in lamps according to the invention. Furthermore, trifluoromonochloromethane (CF Cl trifluoromonobromomethane (CF Br) monofluorotrichloromethane (CFCl monofluorotribromomethane (CFBr tetrafluorodibromoethane (C F Br and trifluorotrichloroethane (C' F Cl and the corresponding perhalogenated low molecular weight hydrocarbons with atleast one fluorine atom per molecule containing iodine and chlorine, or bromine and, furthermore, containing chlorine and bromine, are satisfactory in use.

As used in this application, hydrocarbons with one and up to about four hydrocarbon atoms per molecule are designated low molecular weight hydrocarbons.

the inert lamp fill gas in the required quantity without any technological difficulties.

Let it be assumed that the cyclic process within the incandescent lamp during operation thereof with the admixture of perhalogenated hydrocarbons according to the invention with at least one fluorine atom per molecule to the inert fill gas, is caused by the chemically and thermally highly resistant compounds which dissociate to a very small extent at above 2,000C close to the highly heated filament and thus supply a small amount of elementary fluorine besides the other halogens present in the molecule. in the presence of, for instance, difluorodibromomethane in the lamp bulb, there may occur the following reversible disproportionation:

2 cigar, CF, CBr, 1

The resulting CF may then dissociate forming However, another disproportionation appears to be possible also:

2CF Br cFBr l-CF Br 3 with the ensuing reactions under formation of perhalogenated ethanes and of elementary halogens:

2 CFBr C,F,Br,+ 2 Br 4 and I 2 CF Br C F Br 2 F 5 2 CF Br C F Br 6 Still more conversions are conceivable, which explain the transient liberation of elementary fluorine and elementary bromine from the difluorodibromomethane admixed to the inert fill gas, as indicated in the equations 1 to 6. Similar considerations apply to perhalogenated hydrocarbons with a higher or lower bromine component than that present in difluorodibromomethane, and with at least one fluorine atom per molecule and, correspondingly, they also apply to perhalogenated hydrocarbons with chlorine atoms and/or iodine atoms and, eventually in addition, bromine atoms and with at least one fluorine atom per molecule. A theoretical thermodynamic explanation of the processes inside the bulb during operation of the lamp is difficult to hypothesise, however, it is not necessary for an understanding of the subject matter of the invention.

According to the invention, the tungsten-halogen cycle in incandescent lamps preventing blackening can proceed with either fluorine or another halogen such as, for instance, chlorine or bromine participating therein. It appears that the tungsten-fluorine cycle only takes place close to the filament. The surprising observation that no corrosion of the lamp bulb occurs during operation points in this direction. The tungsten particles which are not included in the fluorine cycle, are converted by the second halogen present in the lamp and are transported back to the filament.

When using perhalogenated hydrocarbons with at least one fluorine atom as admixture to the inert fill gas, no other measures for protection of the components located inside the lamp, such asthe filament supports, are necessary. The regeneration of the chemically and thermally stable perhalogenated hydrocarbons from the transient dissociation products is consequently rapid and complete.

The accompanying drawing shows a hologen incandescent lamp with an additive to the inert fill gas of perhalogenated hydrocarbons comprising at least one fluorine atom per molecule.

Tungsten filament 1 is located inside lamp envelope 2 of glass, which 'may be, but need not be, quartz glass and is supported by supporting

wires

3, 4. The supporting wires are connected with

molybdenum foils

5, 6, which are hermetically pinch-sealed into the glass, and to which

terminals

7, 8 are welded. The lamp is operated at 24 V and with a power input of 250 W. The lamp envelope contains a filling of inert gases, such as nitrogen, rare gases or mixtures thereof, and an admixture of perhalogenated low hydrocarbons with at least one fluorine atom per molecule andin such a quantity that a concentration of from 1 X l0 to 1 X 10' gram atoms of fluorine per cc of bulb volume and a concentration of from 1 X 10' to l X 10' gram atoms of at least one more halogen per cc of bulb volume results. Preferably, a concentration of from 7 X 10' to 4 X 10- gram atoms of fluorine per cc of bulb volume and from 7 X 1.0 to 4 X 10 gram atoms of at least one more halogen per cc of bulb volume is utilized. The cold fill pressure of the lamp may be, for instance, to 660 torr or even more. f

The lamp envelope should be dimensioned so that during operation of the lamp a wall temperature of at least 250C is attained. Known high-melting glasses, quartz glass hard glasses or even simple glass compositions can be used for manufacturing the lamp envelope. The drawing shows a single-ended halogen incandescent lamp, although the invention is also applicable to halogen incandescent lamps of other envelope shapes, such as tubular or spherical bulbs. The invention is not limited to the lamp described and may be used-with halogen incandescent lamps of other voltage and wattage ratings.

I claim:

1. A halogen-containing incandescent electric lamp having a tungsten metal filament, said lamp having'an inert fill gas and containing as an additive in said inert fill gas, at least one perhalogenated hydrocarbon vconv raining 1-4 carbon atoms, said perhalogenated hydrocarbon containing onlyffluorineand bromine as the halogen atoms and containing at least one fluorine atom-and at least one bromine atom per molecule.

2. Lamp according to claim 1 wherein said hydrocarbon has the formula CF,,,X, wherein -m is a whole number from 1-3, n is a whole number from 1-3, m n equals 4, and X is bromine. i

3. Lamp according to claim 2 wherein said hydrocarbon is added to the inert fill gas in a quantity supplying a concentration of from 7 X 10" to 4 X 10" gram atoms of fluorine per cc of bulb volume and a concentration of from 7 X 10" to 4 X 10 gram atoms of bromine per cc of bulb volume.

4. Lamp according to claim 3 wherein said hydrocarbon is CF,Br,.

5. Lamp according to claim 2 wherein said hydrocarbon is at least one selected from the group consisting of CF Br CF Br, and CFBr 6. Lamp according to claim 1 wherein said hydrocarbon has the formula C F X wherein p is a whole number from 1-5, q is a whole number from 1-5, p q equals 6, and X is bromine.

7. Lamp according to claim 6 wherein said hydrocarbon is C F,,l3r and.

8. Lamp according to claim 6 wherein said hydrocarbon is added to the inert fill gas in a quantity supplying a concentration of from 7 X 10 to 4 X 10" gram atoms of fluorine per cc of bulb volume and a concentration of from 7 X 10' to 4 X 10' gram atoms of bromine per cc of bulb volume.

9. Lamp according to claim 1 wherein said hydrocarbon is added to the inert fill gas in a quantity supplying a concentration of from I X 10 to l X 10' gram atoms of fluorine per cc of bulb volume and a concentration of from 1 X 10- to l X 10' gram atoms of bromine per cc of bulb volume.

Claims

2. Lamp according to claim 1 wherein said hydrocarbon has the formula CFmXn wherein m is a whole number from 1-3, n is a whole number from 1-3, m + n equals 4, and X is bromine.
3. Lamp according to claim 2 wherein said hydrocarbon is added to the inert fill gas in a quantity supplying a concentration of from 7 X 10 8 to 4 X 10 7 gram atoms of fluorine per cc of bulb volume and a concentration of from 7 X 10 8 to 4 X 10 7 gram atoms of bromine per cc of bulb volume.
4. Lamp according to claim 3 wherein said hydrocarbon is CF2Br2.
5. Lamp according to claim 2 wherein said hydrocarbon is at least one selected from the group consisting of CF2Br2, CF3Br, and CFBr3.
6. Lamp according to claim 1 wherein said hydrocarbon has the formula C2FpXq wherein p is a whole number from 1-5, q is a whole number from 1-5, p + q equals 6, and X is bromine.
7. Lamp according to claim 6 wherein said hydrocarbon is C2F4Br2 and.
8. Lamp according to claim 6 wherein said hydrocarbon is added to the inert fill gas in a quantity supplying a concentration of from 7 X 10 8 to 4 X 10 7 gram atoms of fluorine per cc of bulb volume and a concentration of from 7 X 10 8 to 4 X 10 7 gram atoms of bromine per cc of bulb volume.
9. Lamp according to claim 1 wherein said hydrocarbon is added to the inert fill gas in a quantity supplying a concentration of from 1 X 10 8 to 1 X 10 6 gram atoms of fluorine per cc of bulb volume and a concentration of from 1 X 10 8 to 1 X 10 6 gram atoms of bromine per cc of bulb volume.