DE3137076A1 - HIGH PRESSURE DISCHARGE LAMP - Google Patents

Description

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Lawyer file: 31 800

description

The invention relates to a high-pressure discharge lamp according to the preamble of claim 1.

High pressure sodium lamps and metal halogen lamps are in has been used extensively for exterior lighting. Compared to high pressure mercury vapor lamps, which are almost have been used exclusively for outdoor lighting, and in comparison with metal halide lamps is the Lamp power of the high pressure sodium lamp about twice or 1.5 times. Hence it is also because of its energy saving Properties an increasingly stronger use. expected use of high pressure sodium lamps.

In general, the conventional high pressure sodium lamp has a translucent alumina discharge or light Arc tube on. The discharge tube is generally straight and its ends are end capped with alumina closed, which are connected to the tube with a ceramic cement or adhesive. "A bushing, such as a niobium tube with an electrode attached to the front end thereof extends through the End cap and is with this with a ceramic cement or -Adhesive connected. The discharge tube is filled with sodium amalgam and for starting with a rare gas, such as a so-called "Penning" gas, which consists of neon and argon,

^ÖW filled and is held in an outer glass jacket, which is provided with a lower part or foot.

The vapor pressure in the discharge tube depends on the temperature at the coldest point behind the electrode

End of the tube. In a conventional high pressure discharge lamp is the heat capacity of the end part of the discharge

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manure pipe relatively high, so that the temperature rise is slow at the coldest point. Consequently will the rise time, one of the lamp characteristics, is longer. aside from that the heat loss at the end portions of the discharge tube is so high that the lamp efficiency becomes lower. Furthermore, because of the difference in heat capacity between the end cap and the end portion of the alumina discharge tube, with which the end cap is closed, the end parts are very sensitive to cracking. 10

In addition, the conventional high pressure discharge lamp has problems with aging because sodium is lost through the gaps between the end caps and the ends of the discharge tube. To eliminate this difficulty, is. it has been proposed to lengthen the terminal end parts of the discharge tube, that is, the end parts _y with which the end caps are closed. However, a greater length of the end cap results in an increase in the heat capacity, and consequently the difference in heat capacity between the sealed end portion of the discharge tube and the end cap becomes even greater, so that the end portions of the tube are more sensitive to one Are cracking. Consequently, the sealing end parts of the discharge tube must not be elongated beyond a certain value.

The invention is therefore intended to provide a high pressure discharge lamp which has a short rise time and a high lamp output and their high performance

shows a minimal decrease initially over its life or useful life. In addition, according to the Invention, a high-pressure discharge lamp can be created in which cracks form on the sealing end parts an alumina discharge or arc tube and a loss or disappearance of sodium the discharge tube is essentially eliminated According to the invention, this is the case with a high-pressure discharge lamp

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according to the preamble of claim 1 by the features in

The characterizing part of claim 1 is achieved. Beneficial

Further developments of the invention are given in the subclaims. · ■

.

According to a preferred embodiment of the invention, the inside diameter of the discharge tube is a high-pressure discharge lamp in its central part, i.e. in the middle between the ends of the tube, is greatest and increases in size ! O ends off. Further, the ends of the discharge tube are relative Feedthroughs that carry an electrode at their front or inner end, immediately closed and sealed.

The invention is described below on the basis of preferred embodiments explained in detail with reference to the accompanying drawings. Show it?

Fig. 1 is a side view of a first embodiment the invention;

Fig. 2 is a sectional view of a discharge tube;

3 shows rise time characteristics of the first embodiment and a conventional high-pressure discharge lamp;

Fig. 4 is a side view of a second embodiment

the invention;
30th

Fig. 5 is a sectional view of a discharge tube; :

Fig. 6 shows a comparison between the rise time characteristic of the second embodiment and a conventional one High pressure discharge lamp, and

-δ-1 Fig. 7 shows a comparison between the operating time curves of the second embodiment and a conventional high pressure discharge lamp.

In the individual figures are the same or corresponding to one another Parts are denoted by the same reference numerals. The inventors have conducted extensive studies and experiments in order to eliminate the aforementioned difficulties with conventional high pressure discharge lamps, and

10 have found that if instead of the conventional straight alumina discharge tube, a discharge or arc tube is used, the inner diameter of which is used is largest in the middle and decreases towards the ends, the above-mentioned task with the invention can be solved.

Referring to Figure 1, there is a first embodiment of the invention, i.e. a high pressure sodium lamp with a discharge or arc tube 2, which is held in an outer bulb 1, which is like a conventional discharge lamp made of glass and evacuated. In the outer bulb 1, the discharge tube 2 is through holding lines 3 and 4, tube supports 5 and 6 and an insulating rod 7 supported. One end of the lower tube support 5 is welded to the holding line 3, and its other end carries one or the lower end of the insulating rod 7. The other or upper end of the insulating rod 7 is loose in a Feedthrough 8 introduced, which is electrically connected to the holding line 3 via a conductor wire 9. An end of the upper tube support 6 is welded to the holding line 4 and the other end is welded to a bushing 10. the Holding lines 3 and 4 extend through a glass base 11 and are with. a socket 13 or a ground contact 14 connected.

Referring to Fig. 2, the structure of the discharge or arc tube is illustrated 2 described in detail. The discharge

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manure tube 2 has an aluminum oxide tube or casing 15 and bushings or niobium tubes 8 and 10 on which inserted into the linden of the alumina tube or sheath 11 and with this airtight by ceramic cement or adhesive are connected. The alumina tube or shell 15 has in the middle between its ends or in its middle Part the largest inner diameter, gradually increasing towards the ends decreases. Electrodes or tungsten windings 16 and are held at the front ends of the feedthroughs 8 and 10. The discharge tube 2 is covered with sodium amalgam 18 (about 78 mol% sodium) and filled with xenon or a so-called "Penning" gas made of neon and argon. ·

With a 150 W lamp of the type shown in FIG. 2 and a wall load of about 18 W / cm ^a (ie the input power divided by the inner surface of the discharge tube between the electrodes), the change in the lamp voltage after starting was investigated. The results are shown in FIG. In the invention, the rise time is significantly shortened, as shown by curve A. Curve B shows the rise characteristic of a conventional discharge lamp which has the same nominal values and in which the end caps are attached to the ends of a straight aluminum oxide ceramic tube. A rapid increase in lamp voltage means that the luminous flux and other parameters increase rapidly.

The tests have shown that in comparison to the conventional discharge lamp, the performance of the invention Charge lamp has increased by about 6% with the same wall load. With a conventional 150W lamp with a wall load of around 18W / cm ' the lamp power is 52 Im / W, while the Lamp capacity of the corresponding discharge lamp

according to the invention to about 55 lm / W (at a color temperature of about 250 ⁰ KJ. The increase in lamp performance is likely to be due to the lower loss.

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-δι due to heat conduction between the middle and the ends the discharge tube.

The dimensions and lamp performance of the invention Discharge lamps are listed below.

Lamps d Dimensions in mm 0
^F e 1 Lamp power
in. W 17th 4.0 6th efficient.
ability in
lm / W 10 50 31 K 6.5 6th 37 150 43 6.0 7.5 6th 55 250 58 10.0 9.5 6th 58 400 12.0 61 15th 15.0

0 and 1 become on Fig. 2

Regarding the abbreviations d, 0
referenced. The wall load was about 18 W / cm ^{2 and} the average color temperature was 2500 ^° K.

A conventional alumina ceramic discharge tube has difficulty because sodium is present at the ends of the Tube is lost and the tube itself is damaged; these difficulties are completely eliminated in the invention. Even if the sealing length 1 (see FIG. 2) of the bushing 8 is increased, in contrast to FIG conventional discharge tube does not increase the heat capacity of the sealing member. Consequently, the length 1 can be reduced to a value (which goes beyond about 3mm) so that the sodium loss can be avoided. In addition, the wall thickness of the niobium tube or the bushing 8 can be reduced so that the difference in the coefficient of thermal expansion between niobium and aluminum oxide is kept to a minimum can be decreased and hence the alumina discharge tube 15 can be prevented from being damaged at its ends will.

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In the case of the conventional discharge tube, thermal protection layers how to apply metal coatings to the ends of the pipe to obtain a higher level of color rendering; with the invention, a higher degree of color rendering can be achieved can be obtained without thermal protection layers. '

During the tests, the diameter 0 in the middle and the diameter 0 at the ends (see Fig. 2) were changed in order to investigate the luminance distribution. If the diameter 0 is very much smaller than the diameter 0 _c _ •, the absorption layers of vaporized sodium at the ends of the tube become very thin, so that the color temperature becomes more reddish at the ends than in the middle. Care must therefore be taken that the diameter 0 _e 15 · is not very much smaller than the diameter 0. The search results have shown that preferably 0> 0.6

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A second embodiment shown in FIG. 4 has a discharge or arc discharge tube 20 shown in FIG. 5. The discharge tube 20 has an alumina clad 21 whose inner diameter is uniform along the discharge part but becomes smaller at the ends. Compared with a conventional discharge tube, the heat capacity of the end part of the tube which is the coldest point is lower, so that "the temperature at the coldest point rises rapidly when the lamp is turned on, and hence the rising time is shortened as shown in Fig In Fig. 6, curve C represents the characteristic value ^{3 (3 of} the second embodiment according to the invention and curve B that of a conventional lamp.

The movement of sodium amalgam was observed when the lamp is turned on and after it is turned off where is the heat capacity, i.e. the volume Q 'of the part is changed with the smaller diameter or the sealed end part of the discharge tube. Around the volume Q '

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-ΙΟΙ to change, the length I ¹ and the wall ^{thickness t 1 of} the sealed end part (see Fig. 5) are changed. It has been found here that if the volume Q ^{1 is} less than twice the volume Q of the discharge space with a length 1, the amalgam can always be held at the coldest point. That is, if -Q '<2, OQ, the amalgam can be prevented from moving toward the electrode after the discharge lamp has been turned off. As a result, the phenomenon which takes a long time before the arc site is stabilized when the discharge lamp is turned on again can be substantially eliminated. The same is true of the discharge or arc tube shown in FIG. Thus, in comparison with a conventional discharge lamp, "the discharge lamp according to the invention has an advantageous performance during the service life, since the increase in lamp voltage due to aging can be reduced or minimized, as shown in FIG. .7 is shown.

In Fig. 5, x 0 is the inner diameter and where t is the wall thickness of the part of the discharge tube having the large diameter and. with 0 ¹ denotes the inner diameter of the sealed end part or of the part with the smaller diameter. The following then applies:

Q = π 1 (t ² + 0 t) and
Q ¹ = η I ¹ (f ² + 0 't \).

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The curve D in FIG. 7 shows the behavior or the power during the service life of a 400 W lamp in which the distance between the electrodes is 82 mm, 0 = 7.6 mm, t = 0.78 mm, .I ¹ = 6 mm, 0 ¹ = 4.1mm and t ¹ = 1.2mm. Q and Q ¹ are then 123,2mm ³ and 119.8 mm ^3. The curve E in Fig. 7 ■

is the curve of a 400W lamp of the corresponding conventional one Lamp type.

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It was also found that if the wall load is the same for a high pressure sodium lamp with the in

. 4, the lamp output capacity is about 4% higher than that of the corresponding conventional discharge lamp. If, for example, the wall ^{load is around 18W / cm 2} and the lamp power is 150W, the lamp power of the conventional lamp is 52 lm / W, while that of the discharge lamp according to the invention is 541 m / W (with a color temperature of

about 2500 ^T 'K). As in the first embodiment, the increase in lamp performance can be attributed to the lower loss due to heat conduction from the central part to the ends of the discharge tube.

As described above in connection with the first embodiment, even if the length I ^{1 of} the sealed end increases, the heat capacity of the sealed end does not increase. "Consequently, the length 1 'can be increased to such an extent that during the lamp life a.

Loss of sodium can be avoided. There is also the difference in the heat capacity or in the coefficient of thermal expansion between the shell or the piston 21 and the implementation 8 are reduced to a minimum the formation of cracks at the sealed ends can be substantially avoided.

In addition to a high-pressure sodium lamp, the invention can just as well be used with other discharge lamps, such as metal-halogen lamps. By the inventors, a discharge lamp was prepared, as shown in Fig. 4 ,, except that the ^En tladungsröhre 20 was silver filled with a mixture of NaI, SCI and Sc, and mercury as a buffer gas. In order to avoid that the bushings are attacked by halogen elements or connections, the inner wall surfaces, which with respect to the discharge

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1 exposed space, coated with metal molybdenum. The effects are essentially the same as described above.

End of description

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Claims (6)

Claims ' High-pressure discharge lamp in which an envelope or a bulb a discharge tube made of aluminum oxide, electrode assemblies, each having a bushing with an electrode attached to its front end Ends of the shell or the bulb are arranged, and the shell or the bulb with at least one or more light-emitting Materials and one or more rare gases for starting is filled, characterized in that the inner diameters of the ends of the sheath or of the piston (2; 20) are smaller than the diameter of the central part, and gradually become smaller towards the ends, and that tubular bushings (8,10). at the front end of each one an electrode is attached, at the ends of the shell (2; 20) directly " are sealed. 2. High-pressure discharge lamp according to claim 1, characterized in that g e k e η η-records, that the light emitting material is sodium. 3. High pressure discharge lamp according to claim 1, characterized in that that each of the bushings (8, 10) is a niobium tube _ 2 - having. Telegrams: VII / XX / Ktz BERGSTAPF PATENT Munich © (089) 988272 TELEX: 988273 0524560 BERG d 988274 983310 · '" ^: '"'"'■" ·· "· ^: - 3 Ί 37076 —9— 4. High-pressure discharge lamp according to claim 1, characterized marked is that the inner diameter of the shell or of the piston (2) with increasing distance from the Middle gradually becomes smaller, and that the light emitting material is sodium. 5. High pressure discharge lamp according to claim 1,. characterized, that the shell or the piston (20) is designed so that its inner diameter is in ■ 10 uniformly to the part which defines the discharge space • remains and becomes smaller towards the ends. 6. High-pressure discharge lamp according to one of claims 4 or 5, characterized in that the volume of the end part of the shell or of the piston (2, -20), which the Bushing (8,10) seals, is smaller than twice the volume of the part of the shell or of the piston (2; 20), which defines the discharge space, the two parts being the same length. '-