DE1764961A1 - Short arc high pressure lamp - Google Patents

Description

Patent-Treuhand-Gesellschaft for electric light bulbs mbH, Munich

"Short arc high pressure lamp"

The invention relates to a short-arc high-pressure lamp with an approximately spherical Vessel with two main electrodes facing each other at a distance that is small compared to the diameter of the bulb especially high pressure mercury vapor lamps. The electrode stabilized short arc of these lamps achieves luminance levels of around 20 - 200 ksb and serves as an almost point-like light source in optical Devices. The mercury vapor pressure reaches values during operation from 10 to 100 at.

These lamps are to be distinguished from high-pressure mercury vapor lamps for street and hall lighting, etc., which have an approximately tubular vessel, a wall-stabilized arch exceeding the diameter of the vessel Have length and significantly lower luminance levels.

Because of their use in optical devices, it is necessary that the mercury pressure lamps have the least possible arc unrest and that the optical quality of the vessel wall is improved during its normal service life due to the deposition of nebulization products not significantly deteriorated. Although the current ones

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BATH ORIGINAL

109883/0445

Lamps of this type with their electrodes consisting of hammered and ground volfram rods have a high level of perfection arc unsteadiness and blackening require further improvement for particularly high demands or for lamps operated with alternating current. This aim is achieved according to the invention achieved in that both electrodes consist of sintered bodies, the 20 wt. $ to 90 wt.% Tantalum carbide and 80 wt 10 wt. ^ Tungsten and / or contain the metals rhenium, molybdenum, tantalum.

™ In the case of emission layers activated with thorium oxide, in particular for electron tubes, it is already known to add various metal carbides that serve as reducing agents (DBP 967 660). In order to reduce the heat emitting properties of high pressure lamps To improve the electrode surface, this was also the case already provided with a layer of sintered tantalum carbide (DBP 1 182 743). Finally, a neon tube is also known, the electrodes of which consist of tantalum carbide, which are only slightly sputtered (USA patent 1 909 68O). These publications however, do not give any indication that sintered electrodes made of tantalum carbide and tungsten are designed as compact self-supporting bodies or another high-melting metal, the arc unrest and blackness

fc tion for short-arc high-pressure lamps operated in particular with alternating current can decrease. Rather, lengthy investigations were required to find out whether and by what measures the Electrodes further improve the operating properties of Short arc high pressure lamps can be achieved.

The invention is explained using an example.

The bulb 1 of the high-pressure mercury vapor lamp for alternating current operation consists of quartz glass free of bubbles and streaks and forms a spherical or egg-shaped discharge space. Di · electrode core pins J

109883/0445 _BAD original

4 and 4 consist of hammered and ground tungsten, have a diameter of 1.5 mm and carry the sintered electrode bodies 5 and 6 at their front ends. According to the invention, these consist of a mixture of 60 Jd tantalum carbide and 40% tungsten; it originally also contains a binding agent, eg 2 % camphor. The rear part of the sintered electrodes has a cylindrical shape, while the front part, which is used for the arch attachment, tapers off in a conical or truncated cone shape. Both electrode core pins 3 and 4 carry electrode coils 7 and 8 made of tungsten wire with a diameter of 0.4 mm, closely behind the sintered electrode bodies 5 and 6, which consist of μ two layers of turns wound one on top of the other and fit tightly on the electrode pins. The lower layer is tightly wound and consists of four turns. The wire is then wound back over this helix in such a way that an upper layer of three turns is created, each of which is 0.1 mm apart. These electrode coils 7 and 8 are used to hold the emitter, which is preferably made of thorium. This emitter is only used to facilitate ignition, but it cannot be ruled out that some thorium may get into the arc attachment area during operation, mainly due to surface migration. The sintered bodies of the electrodes preferably contain no emitter additive, apart from traces that reach them in very small quantities through migration. After the coils have been filled with the emitter paste, are pushed i Kernatifte the 3 and 4 in it. The upper electrode core pin is additionally provided with a getter coil 9 made of tantalum wire with a diameter of 0.5 mm, which is pulled onto the rod behind the electrode coil 7. With 10 and 11 the fusible lines are designated, with 12 and 13 the two bases of the lamp.

On the piston wall is on the annular zone between the discharge space and melting, as well as a mirror coating 14 applied to the melted, pressed-in pump tip.

1 09883 / 0A 45

In the production of the electrode sintered bodies 5 and 6, one goes from a mixture of tantalum carbide powder and tungsten powder, which with dissolved in diethyl ether. Camphor stirred up for so long until the solvent has evaporated. Cylindrical compacts are then placed in a mold at a pressure of 300 to 320 kp manufactured, which has a blind hole for receiving the electrode core pin own. The compacts are then pre-sintered for 10 minutes at 150 ° C. in forming gas. Afterward the tip of the cone is turned. The finished sintered bodies are placed on the core pins provided with electrode coils and pushed through Annealing in a forming gas atmosphere is shrunk on.

The filling of the lamp consists of about 35 Torr of argon as ignition gas and an amount of mercury that evaporates completely during operation.

Dimensions of the electrodes and power consumption of the lamp are like that coordinated that a small melting surface is formed on each electrode in the base area of the arc, on which the bow is generally stable without contraction. It is believed that the high stability of the arch is due to its constancy the work function across the enamel surface, maybe is also favored by a particularly low work function. The surprisingly small despite the presence of two Scheelz surfaces Blackening of the lamp bulb - especially when using electrodes made of a sintered material, 60% by weight of tantalum carbide and 40% by weight of tungsten - can be made from the "soft", i.e. understand the uncontracted arch attachment that covers practically the entire enamel surface evenly. This is how it comes about in spite of the high electrode load necessary to maintain a stable burning arc is necessary, not to the high local heating that occurs when the arc is contracted at the point where the arc is attached can be observed and make a significant contribution to

1 09883/0445

vaporization or atomization of the electrode material and thus for Provide blackening of the discharge tube.

Maintaining the specified mixing ratio of tungsten and tantalum carbide is of great importance. An increase in the proportion of tantalum carbide leads to an increased blackening, while an increase in the proportion of tungsten leads to the appearance of individual sparkling pearls favored, which lead to a restless bow stand.

While the invention contains only mercury in addition to ignition gas Ultra-high pressure lamp has been described, bring the new electrodes even with those, preferably operated with alternating current Short-arc high-pressure lamps have corresponding advantages that are metal halide in addition to mercury or as the sole light-generating filling contain. The properties of xenon short-arc lamps for AC operation are also determined by sintered electrodes made of tungsten and tantalum carbide improved.

- patent claims -

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Claims (9)

Claims Short-arc high-pressure lamp with an approximately spherical vessel, in the middle of which there are approximately two main electrodes at a distance oppose, which is small compared to the piston diameter, characterized in that both electrodes consist of sintered bodies containing 20% by weight to 90% by weight of P tantalum carbide and 80% by weight to 10% by weight of tungsten and / or Contains rhenium, molybdenum, tantalum. 2. Short-arc high-pressure lamp according to claim 1, characterized in that that the electrode sintered body consists of about 60% by weight Tantalum carbide and about 40 wt.% Tungsten. 3 * short-arc high-pressure lamp according to claim 1 and 2, characterized in that that the mixture of tantalum carbide and tungsten used for the production of the electrode sintered body still contains an admixture of binding agent, e.g. 2% camphor. 4. Short arc high pressure lamp according to claim 1 to 3 »characterized in that that the electrode sintered bodies 5 and 6 have a rear cylindrical and a front, the arc approach serving, conical or frustoconical part and that they are made of electrode core pins 3 and 4 hammered and ground tungsten. 5. Short-arc high-pressure lamp according to claim 4, characterized in that that close behind the electrode sintered bodies 5 and 6 on the electrode core 3 and 4 electrode coils 7 and 8 made of tungsten wire sit, consisting of a lower tightly coiled layer of turns and made 1098 * 370445 an upper layer of turns that have mm from each other a distance of about O ₁ I exist and which serve for retaining the emitter. 6. Short arc high pressure lamp according to claim 5 »characterized in that that the electrode core pin 3, which is upper during operation, has a getter coil 9 behind the electrode coil 7 . Wears tantalum wire. 7 short-arc high-pressure lamp according to claims 1 to 6, characterized by * indicates that the filling, in addition to an ignition gas, has a pressure of 10 to 100 at contains the amount of mercury that generates it. 8. short arc high pressure lamp according to claim 1 to 7 * characterized in that that the lamp filling contains metal halides as the component to be excited. 9. short-arc high-pressure lamp according to claim 1 to 8, characterized in that that the dimensions of the electrodes and the Power consumption are coordinated so that g forms a small melting surface in the area where the bow is attached. Dr.Be/Wg. S 81 ( Blank page