DE1139207B - Electric incandescent lamp with a filament made of a refractory carbide - Google Patents

Description

The invention relates to gas-filled electric incandescent lamps, the incandescent body of a refractory metal carbide, such as TaC, HfC, ZrC, NbC, or from mixed crystals of carbides consists.

Electric incandescent lamps with a carbide incandescent body are known per se. When operating such Lamps evaporate carbon from the carbide of the incandescent body. Tried this vaporizing to prevent the incandescent body by using a gas filling, which in addition to an inert Gas (neon, argon, krypton, xenon or nitrogen) hydrocarbon or hydrogen or both together contains. In the vicinity of the hot mantle, the hydrocarbon decomposes and gives off its carbon on the incandescent body. In this way, the incandescent body can be completely Regenerate consumption of hydrocarbons. In some cases, hydrocarbons can be found in the gas space the lamp from the vaporized carbon and the hydrogen, which is added to the gas filling or that was formed by the decomposition of hydrocarbons, regress; however remains the extent of this reaction within very modest limits, since at temperatures above 900 ° C the Equilibrium partial pressure of the hydrocarbon is far below 1% of the hydrogen partial pressure, even under the thermodynamically most favorable conditions in the formation of methane over solid Carbon. It should be noted that it is inexpedient is to choose the partial pressure of the hydrogen higher than 5% of the total pressure. A higher one Content causes an increased thermal conductivity of the gas filling and thus considerable energy losses of the Incandescent body. In addition, the service life of the lamp is reduced in this case. Apparently the Hydrocarbon formation in the gas space does not reach the equilibrium by far, so that the concentration of hydrocarbons in the vicinity of the incandescent body is insufficient for carburization but there is excess hydrogen, which removes carbon from the incandescent body, and the higher the hydrogen partial pressure, the faster. It also makes itself felt at higher hydrogen contents In the closed gas space of the +5 lamp the thermal diffusion is noticeable by itself the lighter hydrogen is preferred in the vicinity of the hot glow body, the heavier hydrocarbon but stops further away at the colder parts of the lamp, so that the decarburization continues to accelerate will.

Below 900 ⁰ C is the reaction speed electric incandescent lamp with an incandescent body made of a high-melting carbide

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative: Dipl.-Ing. H. Auer, patent attorney,
Hamburg 1, Mönckebergstr. 7th

Diploma Phys. Gerhard Wollank,

Dr. Peter Eckerlin and Josef Stute, Aachen,

have been named as inventors

Density so small that no noteworthy hydrocarbon formation in the gas space or above separated Carbon can take place.

For these reasons it is understandable that lamps with carbide incandescent bodies and the aforementioned Gas fillings at luminous body temperatures above 3600 ° K are strongly influenced by the interior after a short time Carbon fog and only have a limited lifespan between 5 and a maximum of 25 hours.

However, the service life is significantly longer for an incandescent lamp with an incandescent body from one high-melting carbide or mixed carbide and a gas filling, which is wholly or partly hydrogen or hydrocarbon or both together with or without inert gas and the invention a catalyst for the reaction between carbon and hydrogen to form hydrocarbons contains.

This catalyst is said to promote the formation of hydrocarbon of carbon and hydrogen at temperatures at which hydrocarbons, especially methane, in larger ones. Amounts besides hydrogen are present in equilibrium, and this at such a rate that all the carbon evaporating from the luminous element is converted.

The electric incandescent lamp is expediently designed so that the entire inner surface the lamp is covered by a catalyst layer. It is necessary that these parts have a temperature achieve at which the catalyst is effective

209 680/146

is. In this way it is prevented that there are places inside the lamp on which the Carbon can settle and is thus withdrawn from the cycle. Above all, it is sufficient on the glass piston such a thin catalyst layer that no significant light absorption occurs through it

The catalyst consists ζ. B. from one of the metals of the transition series of the periodic table or an alloy of these metals, preferably made of nickel, cobalt or iron. With the latter Metals, the desired reaction proceeds with sufficient speed at temperatures above 250 ° C. For technical reasons, temperatures above 600 ° C will be avoided. Also, at such high levels Temperatures the catalyst is slightly deactivated and the equilibrium pressure of the hydrocarbons, especially methane, too small for the desired cycle.

The production of the catalyst layer can be done in that the inner lamp parts with the Catalyst or a compound of the catalyst are vaporized. If you choose a connection, so this must be converted into the actual catalyst by a chemical process. The vapor deposition can be done before assembling the lamp parts; however, it is expediently done later. The catalyst can, for example, be applied separately or by impregnation in the melt Incandescent body or an additional heating conductor, whichever made of tungsten, tantalum or other material, applied and evaporated under vacuum will.

The invention is explained in more detail with reference to FIGS. 1 and 2.

Figs. 1 and 2 show cross sections of lamps according to the invention.

1 metal disc as a carrier, 2 glass bulbs, using the technique of glass-metal fusion connected to 1, 3 incandescent bodies made of TaC, 4 power supply lines, 5 insulating gas seal, 6 carrier tubes for the incandescent body 3 and the power supply 4, 7 soldering points, 8 connecting pieces to 3, 4 and 6.

In Fig. 1, the catalyst 9 is applied to the incandescent body 3, in Fig. 2 on a heating conductor 10, which can be heated via the metal disk 1 and one of the carrier tubes 6 and is thus attached is that when the catalyst evaporates with certainty all points of the lamp from Catalyst can be achieved.

After assembling the lamp according to FIG. 1 or 2, it is baked out in the usual way. After cooling, with the high vacuum pump running, the luminous element 3 (FIG. 1) or the heating wire 10 (FIG. 2) is placed on the for evaporation of the catalyst b2w. its connection required temperature. After any post-treatment of the vapor deposition layer or renewed heating, the flask can be filled with the gas mixture. The gas filling can, for. B. except for the inert gas to 1 percent by volume of hydrogen and 3 percent by volume of methane or 2% of hydrogen and 2% of ethane or ethylene. The ratio of H ₂ to CH ₄ should be chosen so that at the chosen temperature of the lamp surface there is an excess of hydrogen over the hydrocarbon in a ratio of at least 2: 1 over the content at thermodynamic equilibrium; because large parts of the gas are at temperatures at which practically all hydrocarbons are decomposed, and the carbon released in the process, together with the carbon coming from the luminous element, must be captured in the parts of the gas space near the wall and converted into hydrocarbons. For the reasons mentioned above, the maximum limit for hydrogen is 5 percent by volume.

The service life achieved with lamps produced in this way is 30 to 90 hours at burning temperatures over 3600 ° K. The service life is at least doubled compared to lamps without a catalyst. The blackening curve also provides an even greater advantage. While with the Lamps without a catalytic converter that blacken shortly after start-up remain the same Catalyst lamps clear until shortly before their end. Set as a result of deactivation of the catalyst If the carbon is deposited, it only takes a short time for the incandescent body to burn through.

Claims (5)

PATENT CLAIMS: 1. Electric incandescent lamp with an incandescent body made of a refractory carbide or mixed carbide and a gas filling which consists entirely or partially of hydrogen or hydrocarbon or both together with or without inert gas, characterized in that the lamp is a catalyst for the reaction between carbon and hydrogen Contains formation of hydrocarbons. 2. Incandescent lamp according to claim 1, characterized in that the entire inner surface of the Lamp is covered by a catalyst layer. 3. Incandescent lamp according to claim 1 or 2, characterized in that the catalyst layer from metals of the transition series of the periodic table or their alloys, preferably Nickel, cobalt or iron. 4. Incandescent lamp according to claim 1 or the following claims, characterized in that the The lamp contains no more than 5 percent hydrogen by volume. 5. A method for producing an incandescent lamp according to claim 1, 2 or 3, characterized in that the inner lamp parts with the Catalyst or a compound of the catalyst are vaporized. 1 sheet of drawings 1 209 680/146 10.62