High-pressure discharge tube

The subject of the invention is a high-pressure discharge llama, equipped with an unloading tank, which covers the unloading space, has a ceramic wall and is sealed at one end with a protruding ceramic plug, which covers with a lumen the current supply lead to the electrode located in the unloading tank and is connected to said pipe gas-tight, by means of a fused ceramic connector at the end remote from the discharge space.

A lamp of the said type, in the form of a high-pressure sodium lamp, is known from GB 2 083 692 and US 4 910 433, and in the form of a metal halide lamp from EP 0 587 238. Other possible constructions are known, for example, from Patent EP-0 587 238.

It has been assumed that one of the following materials is used to make the ceramic wall or plug: monocrystalline metal oxide (e.g. sapphire), homogeneously sintered polycrystalline metal oxide (e.g. Al₂ABOUT₂, YaG) and polycrystalline homogeneously sintered metal nitride (e.g. AlN).

The selected contract is highly suitable for lamps with relatively low power and accordingly small dimensions, in particular having a relatively small electrode distance. To prevent excessively high temperatures on the surface of the fused ceramic connector during lamp operation, the discharge tank seal was constructed as a protruding plug, and the fused ceramic connector was implemented near the end of the protruding plug that is not facing the discharge space.

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The fused ceramic connector between the protruding plug and the power supply cable is formed in the furnace during the firing process. To this end, the protruding plug and the power supply lead are heated together with the molten ceramic mass so that the ceramic material is melted and plastically deforms in the gap between the protruding plug and the power lead. The assembly is then cooled to room temperature and a connector is made between the protruding plug and the power lead. This is the so-called sealing procedure.

The distance at which the fused ceramic material deforms plastically in the gap determines the length over which the gas-tight fused ceramic connector extends. The length of the fused ceramic connector is important for the implementation of good quality lamps. If the length is less than 1 mm, a relatively weak mechanical connection is created, with a serious risk of premature lamp failure.

If the given length is relatively large, the surface area of ​​the fused ceramic connector opposite the discharge surface reaches a much higher temperature during lamp operation, which is undesirable. The result is impacts on the fused ceramic connector by the components filling the discharge tank and changes in the photometric properties of the lamp resulting therefrom (e.g. color of the emitted radiation, lighting efficiency). In addition, this often leads to premature lamp wear.

The production of lamps on an industrial scale necessitates serial production. The production of the known lamp exhibits a wide spread of length over which the embedded ceramic connector extends. This leads to a high percentage of deficiencies in the manufacturing process.

A high-pressure discharge lamp, according to the invention, equipped with an discharge tank, which covers the discharge space, has a ceramic wall and is sealed at one end with a protruding ceramic plug, which covers the lumen with a lumen that leads the current to the electrode located in the discharge tank and is connected to said inlet in a gas-tight manner by means of a fused ceramic connector at the end distant from the discharge space, according to the invention, it is distinguished by the fact that at least the end portion of the protruding ceramic plug adjacent to the end remote from the discharge space is impermeable to light. The protruding ceramic plug is impermeable to light at a distance, preferably at least 1 mm, more preferably at least 3 mm, measured from an end distant from the discharge space.

In another preferred embodiment, the protruding ceramic plug is impermeable to light along its entire length. The protruding ceramic plug is preferably provided with an outer coating.

Preferably, the protruding ceramic plug is formed of a ceramic material that is impermeable to light.

In another preferred embodiment, the protruding ceramic plug is formed of a ceramic material impregnated with optical means.

The solution according to the invention makes it possible to improve the method of controlling the length of the fused ceramic connector.

It has been found that high reproducibility of the current distance of the plastically fused ceramic, and thus also the length of the gas-tight ceramic joint achieved, can be achieved during the sealing procedure. This is attributed to the increased infrared absorption of the end portion of the protruding plug which is impermeable to light. This leads to a more homogeneous heating during the sealing procedure of both the protruding plug as well as the ceramic material deformable, which leads to better control of the length of the fused ceramic connector by time control of the sealing procedure.

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An important advantage of the invention is that a relatively simple measurement in the form of a pre-treatment during the production of components may suffice, while the technology of making existing lamps, in particular the sealing procedure, can be maintained without modification.

The non-transparent end portion has a length of at least 1 mm, preferably at least 3 mm. This has the advantage that heating occurs even during the sealing procedure, over the entire length of the fused ceramic connector to be carried out.

It is advantageous for the simple production of a protruding ceramic plug when it is impermeable to light along its entire length. The duration of the sealing procedure may be reduced due to the significantly increased heat absorption thus generated in the sealing procedure. This is a particularly important advantage in series production.

The protruding ceramic plug may be impermeable to light as a result of the outer coating, for example in the form of Mo, W or C. The coating can be accomplished by vacuum evaporation, chemical vacuum evaporation, brushing (e.g. with a W rod), or dipping in solution ( for example molybdate) previously fired but not yet sintered compact that will form a protruding end cap after sintering. A further possibility is to dispense a viscous solution into the compact (e.g. molybdate), which is also known as painting.

Another possibility to obtain a protruding end plug impermeable to light is to manufacture a protruding end plug from a non-translucent ceramic material. This is possible, for example, because the ceramic material is impregnated with optical agents, e.g. Fe, Cr, Ni, during its manufacture.

The object of the invention, in an embodiment, is explained in more detail in the drawing, in which Fig. 1 schematically shows the lamp of the invention, and Fig. 2 shows in detail the discharge tank of the lamp of Fig. 1.

Figure 1 shows a high-pressure discharge lamp provided with a discharge tank 3 with a ceramic wall covering the discharge space 11. In a practicable embodiment, the discharge tank 3 comprises a filling which, in addition to Hg and the diluted gas, also includes at least a metal halide. The discharge tank 3 is sealed at the end with protruding ceramic plugs 34, 35, which cover the power supply cables with clearance (fig. 2: 40, 41, 50, 51) to the electrode 4,5 located in the discharge tank, which is connected to the gas supply line in a gas-tight manner, by means of a fused ceramic connector 10 (Fig., 2) adjacent to the end distant from the discharge space 11. The discharge tank 3 is surrounded by an outer bulb 1, which is provided with a lamp base 2 at one end. The discharge takes place between the 4.5 electrodes in the operating state of the lamp. The electrode 4 is connected to the first part constituting the electrical contact of the lamp base 2 by a current conductor 8. The electrode 5 is connected to the second part constituting the electric contact of the lamp base 2 by a current conductor 9.

The discharge tank 3, shown in more detail in Fig. 2 (not to scale), has a ceramic wall 31 and is formed by a cylindrical part with an inner diameter ID limited at each end by end wall parts 32a, 32b. Each portion of the end wall 32a, 32b defines the end plane 33b of the discharge space. Each of the end wall parts has an opening in which the protruding ceramic end cap 34, 35 is fixed in a gas-tight portion of the end wall 32a, 32b by means of a sintered connection S. Each of the protruding ceramic end caps 34.35 covers the lumen 40 , 41, 50, 51 to a combined electrode 4, 5 having an end 4b, 5b. The power lead is connected to the protruding ceramic plug 34, 35 in a gas-tight manner from the side remote from the discharge space 11, by means of a fused ceramic joint 10. The protruding ceramic plugs 34, 35 are provided with coatings 64, 65 at their ends distant from the discharge space, that protruding end caps are impermeable to light. The length at which the end part of each of the protruding end caps is impervious to light is 3 mm. The tips of the electrodes 4b, 5b are located with an EA gap.

Each power lead contains a halide resistant part 41, 51, e.g. in the form of a sintered ceramic metal Mo-Al₂ABOUT₃, and the part 40.50 attached to the joined end plug 34, 35 in a gas tight manner by means of a fused ceramic connector 10. The fused ceramic connector 10 extends over a certain length, for example approximately 1 mm, on a ceramic metal sintered Mo 4151. It is possible so that the parts 41, 51 are formed in a different way than from the ceramic-metal sintered Mo-Al₂ABOUT₃. The halide-resistant coil wound around the halide-resistant bolt belongs to the structure that was found to be particularly suitable. Mo is suitable for use as a halogen-resistant material. The 40.50 parts are made of metal, which has a coefficient of thermal expansion strictly corresponding to that of the end plug. For example, it was found that b is a suitable material. Parts 40.50 are connected to conductors 8, 9 in a way that is not shown in detail. The described construction of the guide wire makes it possible for the lamp to be operated as desired in any lighting position.

Each of the electrodes 4,5 includes an electrode rod 4a, 5a, which is provided with a bend 4c, 5c. The electrode ends in the described embodiment are essentially in the end planes 33a, 33b formed by the end wall parts.

The protruding ceramic end caps are made so that they are positioned in the recess at a relative distance a from part of the end walls 32a and 32b, and there are gas tightly sealed there, with a sintered connection S. In a different embodiment of the lamp according to the invention, the protruding ceramic end caps 34, 35 are made without placing in a recess relative to parts of the end walls 32a, 32b. In this case, the electrode ends lie between the end planes defined by the end wall parts.

In the feasible embodiment of the lamp according to the invention, as shown in the figure, the lamp has a rated power of 70 W. The filling of the discharge vessel is 4.4 mg Hg and 8 mg aJ, T1J and (Dy + Ho + Tm) j₃, in a mass ratio of 65:10:25. In addition, the lamp contains Ar as the ignition gas. The lamp is designed for a color temperature of 3000 K with color point coordinates (x, y: 437.404) and for the general color split index Ra above 80. The discharge vessel is made of polycrystalline aluminum oxide and has an internal diameter of ID 6.85 mm and a distance between 7 mm EA electrode tips. The protruding end caps are impermeable to light at the ends coming out of the discharge space for a length of 3 mm due to the coating of W. The coating is made so that the compact is painted with brush W, after which the compact is sintered to achieve gas impermeability. The protruding end caps are sintered towards part of the end walls at a distance of 1 mm from the end planes defined by the end wall parts. The end wall parts have a height of 3 mm, so that the sintered connection with the end plugs extends over a length of 2 mm. It has been found that this sintered joint length is in practice sufficient to realize a sufficiently strong and gas-tight fastening between the end wall portion and the protruding end cap, also for large scale mass production. The electrode ends lie in the end planes. Each electrode includes a W rod provided with a W bend at the end.

Then, the gas-tight fused ceramic connector was shaped in a known manner between each protruding ceramic plug and the connected power supply cable. The fused ceramic connector 10 extends from 3 to 3.5 mm from the end of the protruding plug distant from the discharge space.

For comparison, data from prior art lamps are provided. Here, the length at which the fused ceramic connector extends between the protruding end cap and the power supply cable changes from 3 to 7.5 mm, but in many cases the length does not

180 621 can be unambiguously determined because the current distance of the fused ceramics varies along the circumference of the current lead.

In a further possible embodiment of the lamp shown, the coating is made of Mo. For this purpose, the previously shaped protruding end caps were immersed at one end in an aqueous Na solution₂MoO₄ and glycerin. After drying, the protruding end caps were sintered to be gas-tight and simultaneously sintered to part of the end walls. The use of a gas-tight connection of fused ceramics between the protruding ceramic plug and the connected power supply cable, made in the same way as for a lamp equipped with a W coating on protruding ceramic plugs, led to a comparable end result.

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35 FIL-50

FIG.1

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FIG.2

UP Department of Publications. Circulation of 60 copies

Price PLN 2.00