EP1372184A2 - Electrode system for a metal halide lamp and lamp provided with such a system - Google Patents

Abstract

The electrode has an interlocking connection zone (25), formed as a local shaft (16) groove (18)

Description

Technical field

The invention is based on an electrode system for a metal halide lamp and associated lamp according to the preamble of claim 1. These are in particular lamps with an output of at least 20 W, preferably from 100 W, up to powers of 400 W, possibly over 1000 W.

State of the art

EP-A 587 238 describes a metal halide lamp with a ceramic discharge vessel known, in which a two-part implementation in an elongated Stopper capillary by means of glass solder at the end of the Plug is sealed. The outer part of the bushing is permeable Material (niobium stick), the inner part made of halide-resistant material (for example a pen made of tungsten or molybdenum). For higher lamp outputs (up to about 400 W) another solution is used, namely the replacement of the inner Mo pin part with a cermet part. Whose thermal expansion coefficient can be set between that of other metal parts and that of ceramics.

A disadvantage of such solutions is that the connection between the inner part of the bushing and the electrode is very prone to breakage. This applies both to the further processing of the electrode system and in Lifetime behavior of the system when the lamp is in operation. Ultimately, can cause the electrodes to kink to burst the discharge tubes during operation.

WO 01/82331 tries this by a multi-part arrangement of the Bypass implementation. However, this only solves the basic problem insufficient. Generally the diameter of the electrode is smaller than that of the inner part, the two components by melting the End of the inner part and embedding the electrode end therein become. Melting is often done by brazing or laser soldering. The inner part mostly consists of molybdenum or Mo-containing cermet. there but the melting amount on the inner part can not be within the required Accuracy can be ensured reproducibly. Remedy would offer an increase in the melting length. However, that is the limit towards the maximum permissible "welding hump height". So that is an elevation meant in the area of the welding or soldering zone a local accumulation of weld metal or solder results. It can also be act as slag (especially in the case of a cermet compound). The The maximum allowable amount of the cant is determined by the minimum allowable Capillary inner diameter of the discharge vessel determined.

Presentation of the invention

It is an object of the present invention to provide an electrode system to provide the preamble of claim 1, wherein the connection between bushing and electrode is designed to be permanent withstands mechanical and thermal loads.

This object is achieved by the characterizing features of claim 1 solved. Particularly advantageous configurations can be found in the dependent ones Claims.

According to the invention is a means for positive locking, in particular a notch or groove, near the end of the electrode facing the bushing appropriate. It is so close to the end of the shaft that it is from the Material of the bushing from the connection area or melting area is encased. The agent comprises at least one local depression or notch. A circumferential depression is preferred, which is V-shaped or U-shaped, can be designed rectangular or trough-shaped. The notch can for example by grinding or punching.

This notch can be an irregular or regular reduction in the Cross section of the electrode. In particular, it is a circumferential notch or U-shaped or V-shaped groove. When connecting the bushing to the electrode, which is usually done by soldering (hard or laser soldering) or welding, an additional positive connection is now achieved, which is the mechanical Resilience of the connection increased. The committee in a row Inadmissibly large sweat / soldering zone increase is reduced, because now a Reservoir for the excess melt or slag available stands.

An additional advantage is that the recess is a provisional fixation option for a possible coil at the distal end of an extended one Electrode shaft provides by melting the end area the execution is then finally and particularly securely fixed, similar as is known as a fixing option from US-A 5 451 837.

The implementation can be made in one piece, or in two or more parts be constructed by the outer part of niobium or another hydrogen permeable Material, while the inner part has properties, that favors the connection with the shaft (see below). The inner part can be replaced by an extended shaft of the electrode so that the connection technology according to the invention on the connection between the only remaining outer bushing part and accordingly elongated core pin is applied.

The known structure of ceramic discharge vessels also includes a Elongated capillary tube (hereinafter called capillary), where through this capillary an electrically conductive, one or two part Implementation related to the discharge from an inner part and there is an outer pin-shaped part, is passed vacuum-tight. The bushing is usually sealed on the outside of the stopper with glass solder. On the leadthrough an electrode is attached with its shaft, which in the interior of the discharge vessel protrudes.

The lamp power is preferably between 20 and 400 W, however Larger powers (2000 W and more) are also possible.

The attached table shows the dimensions for different lamp powers (35, 70 and 150 W) of the following parts: lamp core pin groove execution Abschmelzbereich power material AD [µm] Depth T [µm] Width B [µm] Final distance [µm] material AD [µm] Length [µm] 35 W 200 30 50 50 Mo or Nb 560 150 70 W 300 50 100 50 Mo or Nb 680 225 70 W 300 60 70 70 Mo or Nb 680 225 150 W 500 70 100 70 Cermet with Mo or Nb 800 270 150 W 500 90 80 70 Cermet with Mo or Nb 800 250 Core pin: material and outer diameter in µm; Groove in the core pin: depth T, width B and distance of the groove from the distal end of the pin, each in µm; Implementation: material and outer diameter in µm; Melting area: Length of the connection area of both components in µm.

The connection between the two components implementation and The core pin is made by laser soldering.

The ratio of the width B of the notch and its depth T in the region is preferred B / T = 1: 1, in particular it should be between 0.8 and 2.2. For reasons of stability should the remaining outer diameter of the core pin in the Area of the notch must be at least 60% of the original diameter, 65 to 75% are preferred.

In the case of a two-part implementation, the inner end region is the Implementation (hereinafter referred to as the melting range), with the electrode in contact, made of Mo, W, or a cermet, the W in one Contains amount that keeps it weldable. The diameter of both to be connected Parts can be approximately the same size in this embodiment. The Electrode is preferably made of tungsten. Your first end is in the connection area embedded, the second end faces the discharge. The Shaft of the electrode can still be used to limit the dead volume Helix, preferably made of molybdenum, be covered, as is known per se.

Alternatively, there is the possibility of the inner part of the current feedthrough by extending the electrode core pin (usually from Tungsten) to the outer lead-through part (usually made of niobium) replace in accordance with EP-A 1 056 115. The elongated shaft of the electrode can also be used with a helix to limit the dead volume, preferably made of molybdenum, as in the case of the two-part Power supply (EP-A 587 238) practiced.

The feedthrough or at least the outer part thereof in the case of a two-part feedthrough consists of an outer part which is adapted to the (aluminum oxide) ceramic and is permeable to H ₂ and O ₂ (in particular a niobium pin or tube, but also the use of Tantalum is possible), which is covered with glass solder and sealed.

In the case of a two-part implementation, the inner part of the implementation consists made of a halide resistant metal (preferably molybdenum or Tungsten or its alloys) or a corresponding cermet. Prefers is the material molybdenum. The inner part is only partly on his outer end covered with glass solder and melted. The inside part is in particular a pen made of cermet or molybdenum or of the higher melting Tungsten. The tungsten can have a rhenium additive either as an alloy or as a plating on the surface. The Rhenium increases the high temperature resistance and corrosion resistance of tungsten. While molybdenum is especially for mercury-containing Suitable fillings, W is advantageous for mercury-free fillings used. In particular, W is also for relatively small watt lamps from 70 W. suitable.

The inner part of the two-part bushing is on one side with the outer Part (niobium stick or tube) and on the other side with the electrode connected. The inner part can itself be constructed in several parts, for example described in WO 01/82331.

The stopper can be made in one part, but also in several parts. For example can in a manner known per se a stopper capillary from an annular Be part of the plug.

Brief description of the drawings

Figur 1

eine Metallhalogenidlampe mit keramischem Entladungsgefäß;

Figur 2

das Elektrodensystem der Lampe der Figur 1 im Detail;

Figur 3

den Verbindungsbereich des Elektrodensystems der Figur 2 mit verschieden geformten Kerben (a bis d);

Figur 4

ein weiteres Ausführungsbeispiel des Verbindungsbereichs;

Figur 5

ein weiteres Ausführungsbeispiel des Verbindungsbereichs;

Figur 6

ein weiteres Ausführungsbeispiel eines Endbereichs.

The invention will be explained in more detail below with the aid of several exemplary embodiments. They show schematically:

Figure 1

a metal halide lamp with a ceramic discharge vessel;

Figure 2

the electrode system of the lamp of Figure 1 in detail;

Figure 3

the connection area of the electrode system of Figure 2 with differently shaped notches (a to d);

Figure 4

another embodiment of the connection area;

Figure 5

another embodiment of the connection area;

Figure 6

another embodiment of an end region.

Preferred embodiment of the invention

A metal halide lamp with an output of 150 W is shown schematically in FIG. It consists of a cylindrical outer bulb 1 made of quartz glass which defines a lamp axis and is squeezed (2) and base (3) on two sides. The axially arranged discharge vessel 4 made of Al ₂ O ₃ ceramic is cylindrical or bulbous in shape and has two ends 6. It is held in the outer bulb 1 by means of two current leads 7, which are connected to the base parts 3 via foils 8. The power supply lines 7 are welded to bushings 9, which are each fitted in an end plug 12 at the end 6 of the discharge vessel. The stopper part is designed as an elongated capillary tube 12 (stopper capillary). The end 6 of the discharge vessel and the stopper capillary 12 are, for example, sintered together directly.

The bushings 9 each consist of two parts. The outer part 13 is designed as a niobium stick and extends up to about a quarter of the length the capillary tube 12 into this. The inner part 14 extends inside of the capillary tube 12 towards the discharge volume. It stops on the discharge side Electrodes 15, consisting of an electrode shaft 16 Tungsten and one pushed onto the discharge end of the shaft Spiral 17. The inner part 14 of the implementation is on the one hand with the Electrode shaft 15 laser soldered and on the other hand with the outer part 13 the execution laser-welded. The niobium stick 13 is approximately 3 mm deep the stopper capillary 12 inserted and sealed by means of glass solder 10.

In addition to an inert ignition gas, the discharge vessel is filled, e.g. Argon, from mercury and additives to metal halides. Is possible for example, the use of a metal halide filling without Mercury, preferably xenon and in particular a high ignition gas Pressure well above 1.3 bar can be selected.

An electrode system is shown in detail in FIG. 2. As implementation 9 is a system consisting of a niobium stick (or tube) as an outer part 13 and a molybdenum pin as the inner part 14.

The niobium pin 13 is on the discharge side with the inner part 14 made of molybdenum butt welded. Inner part 14 is in the same way on the discharge side soldered to the electrode shaft 16.

The alternative is to use an inner part 14 made of cermet with a high proportion of Mo, the remainder Al ₂ O ₃ .

The shaft 16 has a diameter of 0.4 mm. The diameter of the inner Part is 0.8 mm, the outer part is 0.88 mm. The inner part 14 has that is, a 100% larger diameter than the electrode shaft 16.

The principle of the connection according to the invention is shown in FIG. 3a. Depending on the lamp power considered, about 0.5 mm to 2 mm away from the lead-through end of the electrode shaft 16 circumferential groove 18 attached. It also has one, depending on performance Depth of 0.5 to 2 mm and a width of 0.5 to 2 mm. When laser soldering (Arrow), the melting area 25 extends beyond the groove 18, which is here is rectangular, from. The melted molybdenum serves as a solder for embedding the tungsten shaft 16. The groove enables an additional one Form fit and serves as a reservoir for excess melt or the slag generated when segregating cermet.

Alternatively, the groove can also have a circumferential groove with a different shape Have a cross section, in particular a V-shaped recess 26 (Fig. 3b) or a trough-shaped puncture 27 (Fig. 3c). another alternative is a positive locking device that consists of two opposite one another There are notches 28 in the shaft (FIG. 3d).

In a particularly preferred embodiment (Figure 4) is on the shaft 36, which is greatly elongated and therefore replaces the inner lead-through part, a coil 20 for displacement of the dead volume is applied, which is made of molybdenum consists. The last turn 21 is held in the groove 18. While the manufacture becomes a provisional fixation up to laser welding achieved to produce the melting area.

FIG. 5 shows an embodiment in which the bushing 30 (one-piece made of niobium) with the extended core pin 31 made of tungsten or is welded. Both components have approximately the same outside diameter. The means for positive locking is a notch 32. The connection area 33, which can contain material from both components shown here very schematically.

A further embodiment is shown in FIG. 6, in which, in addition to the first Groove 37 remote from the discharge, a second groove 38 in the vicinity of the front, discharge-side End of the shaft 39 ensures that the second Spiral end can be fixed. The helix is not shown. benefits result here in particular from the simplification of the automatic Orientation for the subsequent laser soldering. Both notches 37 and 38 are shaped like a trough with sloping side walls.

Claims (13)

Electrode system for a metal halide lamp, consisting of an electrically conductive feedthrough (9) and an electrode connected to it with a shaft (16), the feedthrough and the electrode having a connection region with melted material, into which the electrode with its end facing the feedthrough Shaft is embedded, and wherein the shaft of the electrode is made of tungsten, characterized in that the electrode within the connection area has a means for positive locking, which consists of an at least local depression on the shaft of the electrode. Electrode system according to claim 1, characterized in that the bushing consists of an inner part (14) and an outer part (13), the electrode being connected to the inner part. Electrode system according to claim 2, characterized in that the inner part consists of a weldable cermet. Electrode system according to claim 1, characterized in that the bushing and the electrode shaft are cylindrical, the diameter of the bushing being 80 to 300% of the diameter of the electrode shaft. Electrode system according to claim 1, characterized in that the means for positive locking consists of two opposing local n or a circumferential recess on the shaft. Electrode system according to claim 5, characterized in that the recess is U- or V-shaped, the bottom of the U or V defining a maximum penetration depth T. Electrode system according to claim 6, characterized in that the maximum penetration depth T is 25 to 40% of the diameter of the shaft. Electrode system according to claim 1, characterized in that the means for positive locking is spaced 0.1 to 2 mm from the end of the shaft facing the bushing. Electrode system according to claim 1, characterized in that the electrode additionally comprises a coil at the end remote from the discharge, which sheaths the shaft, the end of the coil facing the bushing being anchored in the recess on the shaft. Discharge lamp with an electrode system according to claim 1. Discharge lamp according to claim 10, characterized in that the lamp contains a ceramic discharge vessel, in particular made of Al ₂ O ₃ . Discharge lamp according to claim 11, characterized in that the discharge vessel has two ends (6) which are closed with ceramic plugs, each of which contains an elongated capillary tube (12), hereinafter referred to as plug capillary, and through which plug capillary (12) electrically conductive bushing (9) is passed through, an electrode (16) having a shaft (15) being fastened to the bushing and projecting into the interior of the discharge vessel. Discharge lamp according to claim 10, characterized in that the lamp has a metal halide filling.

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