EP1519407A2 - UV radiator with tubular discharge vessel - Google Patents

Abstract

The radiator has a tubular, quartz-glass discharge vessel filled with xenon at a pressure of 150 mbar. The vessel has a tubular part that is split into two imaginary tube halves (5a, 5b) by an imaginary sectional plane (S). An inner electrode with a 1 mm-thick molybdenum wire is arranged on an inside of the half (5a). Strip-shaped outer electrodes (11a, 11b) made of silver solder, are fitted to the outside of the half (5b).

Description

Technical area

The invention is based on a UV emitter with a for the production of one-sided dielectric barrier discharges designed, essentially tubular, on both sides gas-tight sealed discharge vessel.

The term UV (= U ltra v iolett) emitters are to be understood as emitters which emit electromagnetic radiation during operation with shorter wavelengths than in the visible region of the spectrum (about 380 to 770 nm), ie radiation having wavelengths below 380 nm. In particular, radiation with shorter wavelengths than about 200 nm is included, which is also referred to as VUV (= V akuum u ltra v iolett) radiation Thus, UV lamps for lighting purposes, such as general lighting, unsuitable , Rather, they are used in process technology, especially for surface cleaning and activation, photolytics, ozone generation, drinking water purification, metallization, and UV curing.

In particular, the invention also relates to high power UV radiators, i. long radiators, e.g. with lengths of typically a few 10 cm to about 2 m or more.

UV-emitters based on dielectric have proven to be particularly efficient Barrier discharge proved, especially if they are in accordance with operated according to the pulsed operating method described in US 5,604,410 become.

The term "dielectric barrier discharge" is defined as at least a so-called dielectrically impeded electrode ahead. A dielectric Disabled electrode is opposite the interior of the discharge vessel or of the discharge medium separated by means of a dielectric, for example in which the electrode on the outside of typically out Glass or other dielectric wall of the discharge vessel is arranged. This type of electrodes will be shortened in the following also referred to as "outer electrode".

The present invention relates to a UV emitter comprising at least one outer electrode having the aforementioned type. In addition, the UV lamp includes a tubular, sealed on both sides discharge vessel, which encloses a discharge medium. The discharge medium is an ionizable Filling used, which usually consists of a noble gas, For example, xenon or a gas mixture with additional buffer gas such as neon or halogen additives, for example chlorine, fluorine etc .. Within the discharge vessel is at least one electrode, in the following shortening also referred to as "inner electrode" arranged. This inner electrode is unhindered, i. in direct contact with the discharge medium. It is therefore a UV emitter based on a one-sided dielectric disabled discharge.

In operation, a high voltage is applied between inner and outer electrode (s), thereby generating a gas discharge inside the discharge vessel. Due to the high radiation efficiency, the pulsed operating method described in the already mentioned US Pat. No. 5,604,410 is preferably used, in particular unipolar voltage pulses. For reasons of protection against contact, the outer electrode is preferably connected to earth at zero potential ("earthed"). The inner electrode is supplied with negative voltage pulses, ie acts as a cathode during each voltage pulse. For further details, reference is made again to US 5 604 410. During the gas discharge so-called excimers are formed in the discharge medium. Excimers are excited molecules, such as Xe ₂ *, XeCl *, which emit electromagnetic radiation when they return to the normally unbound or weakly bound ground state. In the case of Xe ₂ * or XeCl *, the maximum of the molecular beam radiation is approximately 172 nm and 308 nm, respectively.

State of the art

The document WO 01/35442 shows a UV radiator with a tubular discharge vessel. Within the discharge vessel is centrally a helical axial Electrode arranged. On the outside of the discharge vessel are evenly distributed with respect to the extent of several parallel to the tube axis extending strip-shaped electrodes. This radiates the radiator substantially uniform over the entire circumference, i. rotationally symmetric, that is undirected from. For flat surfaces to be efficiently irradiated can be used, the use of additional reflectors is necessary, the greatest possible amount of radiation evenly on the surface to be irradiated to steer. In order to produce spotlights with lengths of more than 20 cm, is for the centric inner electrode a holder, for example a provided axial support tube. For very long spotlights, especially longer than about 1 m, the manufacture is due to the increasing Risk of breakage of the support tube, however, more and more difficult. On the other hand must a sagging of the inner electrode can be avoided as this is the uniformity the generation of radiation along the entire radiator negative would affect.

Presentation of the invention

The object of the present invention is to provide a UV radiator with tubular Discharge vessel and non-rotationally symmetric radiation characteristic specify. Other aspects include the possibility of emitters higher Performance, i. to manufacture long spotlights and a high radiation efficiency to achieve.

This object is achieved by a UV emitter with a for generating essentially designed by one-sided dielectric barrier discharges tubular, on both sides gas-tight sealed discharge vessel and in each case at least one elongate, parallel to the longitudinal axis of the discharge vessel oriented inner and outer electrode, characterized that on the inside of an imaginary first half of the tube tubular part of the discharge vessel, the at least one inner electrode and on the outside of an opposite imaginary second one Pipe half which is arranged at least one outer electrode, wherein the two opposite tube halves through a longitudinal axis of the tubular discharge vessel contained imaginary section through the Discharge vessel are defined.

Particularly advantageous embodiments can be found in the dependent claims.

In other words, you can see the tubular part of the discharge vessel mentally by an imaginary longitudinal section into two equal halves to present split. The at least one inner electrode is on the inside the first imaginary pipe half arranged. The at least one Outer electrode is on the outside of the second imaginary pipe half arranged and that at least in the case of an inner and an outer electrode essentially diametrically. Even if it is in the following considerations is not always explicitly mentioned, it should always be remembered that the Division of the discharge vessel into two tube halves not real, but is purely imaginary nature and serves only the arrangement of the interior and To describe external electrodes in more detail.

The substantially diametrical arrangement of inner and outer electrode On the one hand has the advantage of high radiation efficiency due to the relative to the discharge vessel diameter large striking distance for the discharge, as taught by the already mentioned US 5,604,410. On the other hand it opens up the possibility of moving away from a substantially rotationally symmetric and to come to a more directional radiation characteristic.

For this purpose, on the outside of the second tube half of the discharge vessel in the simplest case, either strip-shaped or flat Outer electrode arranged diametrically to the inner electrode. In the latter Case extends in the direction of the circumference of the tubular discharge vessel considered spatial extent of the outer electrode approximately over the entire corresponding spatial extent of the second imaginary pipe half of the discharge vessel. In this case, the flat outer electrode e.g. be realized by a coating or by a suitably shaped metal part into which the outside of the second tube half of the discharge vessel is embedded as it were. The flat design the outer electrode has the advantage that they still at the same time as a reflector can act for the UV radiation, thereby reducing the targeted radiation is further improved. For this purpose must be for the outer electrode a material with sufficient reflection properties for UV radiation, For example, aluminum, to be selected.

As an alternative to the flat external electrode can also more than one, for example Use two, three or more strip-shaped external electrodes become. This allows the emission characteristic of a flat outer electrode approach without their undesirably high capacitive load due having to accept the large electrode area. There are Although the electrodes are not symmetrical with respect to the entire circumference of the Discharge vessel arranged, but preferably symmetrically with respect a plane intersecting the imaginary pipe half which is - in cross-section considered as a perpendicular bisector of the imaginary pipe half corresponding Semicircle represents. In addition, it has been shown that the radiation efficiency with e.g. two strip-shaped outer electrodes higher is, as with a flat outer electrode, for example in the form of a half-mirrored arrangement. In addition, can be a corresponding achieve higher radiation output than with only one strip Outer electrode.

For the latter reason, it may also be advantageous to have more than one inner electrode to use, which is then also symmetrical with respect to the imaginary Tube half cutting plane, which - viewed in cross section - as the perpendicular bisector of the semicircle corresponding to the imaginary pipe half represents, are arranged. If the belonging to the internal electrodes Pipe half is to be used as a radiating surface, i. especially then, if the other half of the tube is largely or even completely with one or is covered by a plurality of external electrodes, the internal electrodes are preferably positioned relatively close to the imaginary cutting plane, but only as far as still sufficient distance to the nearest outer electrode remains. In this way, the largest possible electrode-free radiating surface achieved. However, as a preferred radiating surface quite well the other half of the tube belonging to the outer electrodes can be considered. Which side to give preference depends ultimately on the individual case of the concrete arrangement of all electrodes.

Unlike the external electrodes, there are none for the internal electrodes strip-shaped electrodes, since the latter typically from Leitsilberbahnen or the like. Because the inner electrode for efficiency reasons not covered with an additional dielectric layer and thus is separated from the discharge medium (unilaterally dielectrically impeded discharge), would namely during operation of the lamp low solvent residues and similar volatiles of such an electrode web outgas, thereby entering the discharge medium and the generation of radiation deteriorate unacceptably. Instead, for the inner electrode a metal wire as pure as possible or the like used.

With long radiators, it is usually necessary to have at least one inner electrode on the inside of the first tube half of the discharge vessel to fix. For this purpose, preferably one on the inside of the first Half pipe fastened bracket used. The holder is, for example, depending on the length of the spotlight from one or more narrow Pipe pieces, half pipe pieces or rings, through which the elongated inner electrode threaded through. As a result, the inner electrode on the mentioned Inside of the discharge vessel even with very long lamps, e.g. with more than approx. 1 m length, sufficient hold without significantly sagging. The inner electrode is e.g. trained as a staff, especially simply thread through the "eyelet-like" holder. Alternatively, the inner electrode designed as a helix. This may be a bit more expensive thread through the bracket. However, it offers the advantage that the numerous partial discharges arising in the pulsed operating method at exactly defined preferred points between the helix and the usually strip-shaped outer electrodes and thus very uniform to form distributed. For further details on this, reference is made to US Pat. No. 6,060,828, in particular refer to the description associated with FIGS. 5a-5c. In any case, the at least one inner electrode is made of metal, preferably made of tungsten or molybdenum. In this case, a metal wire into consideration, that with another metal, e.g. coated with platinum. These Variant is especially for halogenated or otherwise corrosive discharge media suitable. The helix does not necessarily have to be rotationally symmetric, i.e. be three-dimensional. Rather, she can also flat, for example like a sinusoid. The flat version even supports nor the goal of a directional radiation characteristic. It is important, that the inner electrode very clean before installation in the discharge vessel because impurities affect the efficiency of UV production.

The holder is made of a temperature-resistant dielectric material, preferably glass, quartz glass or ceramic. The holder is preferred from the same material as the discharge vessel wall. Then lets namely, the holder by simply merging with the discharge vessel attach to the inside. Alternatively, the holder also be fixed by means of glass solder, but because of the before closing the discharge vessel to be expelled solvent of the glass solder paste problematic with regard to contamination of the discharge medium can be.

Brief description of the drawings

Fig. 1a

eine Seitenansicht eines erfindungsgemäßen UV-Strahlers mit einer stabförmigen Innen- und zwei streifenförmigen Außenelektroden,

Fig. 1b

ein Querschnitt des UV-Strahlers aus Fig. 1a entlang der Linie AB,

Fig. 1b

eine Detailvergrößerung des Bereichs C des in Fig. 1b dargestellten Querschnitts,

Fig. 2

ein Querschnitt entsprechend Fig. 1 b durch eine Variante des erfindungsgemäßen UV-Strahlers mit drei streifenförmigen Außenelektroden,

Fig. 3

ein Querschnitt entsprechend Fig. 1b durch eine Variante des erfindungsgemäßen UV-Strahlers mit vier streifenförmigen Außenelektroden,

Fig. 4

ein Querschnitt entsprechend Fig. 1b durch eine Variante des erfindungsgemäßen UV-Strahlers mit fünf streifenförmigen Außenelektroden und zwei stabförmigen Innenelektroden,

Fig. 5

ein Querschnitt entsprechend Fig. 1b durch eine Variante des erfindungsgemäßen UV-Strahlers mit einer flächigen Außenelektrode und einer stabförmigen Innenelektrode,

Fig. 6

eine Detailvergrößerung des Bereichs C entsprechend des in Fig. 1b dargestellten Querschnitts einer Variante des erfindungsgemäßen UV-Strahlers mit einer veränderten rohrförmigen Halterung für die Innenelektrode,

Fig. 7

eine Detailvergrößerung des Bereichs C entsprechend des in Fig. 1b dargestellten Querschnitts einer Variante des erfindungsgemäßen UV-Strahlers mit einer halbrohrförmigen Halterung für die Innenelektrode.

In the following, the invention will be explained in more detail with reference to exemplary embodiments. The figures show:

Fig. 1a

a side view of a UV emitter according to the invention with a rod-shaped inner and two strip-shaped outer electrodes,

Fig. 1b

a cross section of the UV radiator of Fig. 1a along the line AB,

Fig. 1b

a detail enlargement of the area C of the cross section shown in Fig. 1b,

Fig. 2

1 b through a variant of the UV emitter according to the invention with three strip-shaped outer electrodes,

Fig. 3

1 through a variant of the UV emitter according to the invention with four strip-shaped outer electrodes,

Fig. 4

1 through a variant of the UV emitter according to the invention with five strip-shaped outer electrodes and two rod-shaped inner electrodes,

Fig. 5

1 through a variant of the UV emitter according to the invention with a flat outer electrode and a rod-shaped inner electrode,

Fig. 6

an enlarged detail of the region C corresponding to the cross section shown in FIG. 1b of a variant of the UV emitter according to the invention with an altered tubular holder for the inner electrode,

Fig. 7

a detail enlargement of the region C corresponding to the cross section shown in Fig. 1b of a variant of the UV emitter according to the invention with a semi-tubular support for the inner electrode.

Preferred embodiment of the invention

In the following, reference is made to that in Figures 1a - 1c schematically shown side view of a UV lamp 1, the cross-sectional view along the line AB or the detail enlargement of the area C. The UV emitter 1 has a substantially tubular discharge vessel 2 Quartz glass, the first end to a dome-like cap 3 including molten pump tip 3a is formed and that at his other end is sealed gas-tight by means of a pinch seal 4. The discharge vessel 2 is filled with xenon at a pressure of 150 mbar. With a length of about 68 cm forms the tubular part 5 of the discharge vessel the main part of the for an electrical power consumption of approx. 50 W UV lamp 1. The total length of the discharge vessel is about 72 cm. The inner and outer diameter of the tubular Part 5 is 28 mm or 30 mm. In Fig. 1b, the tubular part 5 is through an imaginary sectional plane S, which contains the longitudinal axis L, in two imaginary Pipe halves 5a, 5b split. On the inside of the first half pipe 5a, an inner electrode 6 made of a 1 mm thick molybdenum wire is arranged, which extends over the entire length of the tube half 5a and parallel to Longitudinal axis of the discharge vessel 2 extends. With the help of three as a holder Serving 8 mm long quartz tube pieces 7 (see Fig. 1c) is the rod-shaped Inner electrode 6 is attached to the inside of the first tube half 5a, that the distance to the mentioned imaginary sectional plane S maximum is. The quartz tube pieces 7 are fused directly to the vessel wall. you Inner diameter is only slightly larger than the diameter of the inner electrode 6, so that the inner electrode 6 is still through the already on the Inside the first tube half 5a attached quartz tube pieces 7 therethrough threading, but still reliably fixed. Through the pinch seal 5 through the inner electrode 6 is guided gas-tight to the outside. On the Outside of the second tube half 5b are two strip-shaped each 2 mm wide Outer electrodes 8a, 8b made of silver solder parallel to the longitudinal axis of the Discharge vessel 2 applied. Their mutual shortest distance is 27 mm. With regard to the imaginary sectional plane S, the two outer electrodes 8a, 8b symmetrically positioned such that both are the same Distance to this plane S have. In pulsed operation form two discharge levels consisting of numerous partial discharges (not shown), one each between the inner electrode and each the two outer electrodes. For more details about the partial discharges Reference is made to the already cited US 5,604,410.

Of course, the invention also easily allows longer spotlights to build as shown in Fig. 1a, in which correspondingly more than three Breakpoints are provided (not shown).

In a variant, not shown, the inner electrode does not consist of a rod-shaped wire but rather from a wire helix. To first the support parts, e.g. short pieces of pipe or rings, with the Connected vessel wall and then the wire helix through the support parts threaded.

FIGS. 2 to 5 show variants of the UV emitter according to the invention, which differ only by the respective electrode configuration. The same features are provided with the same reference numerals.

Fig. 2 shows a cross section corresponding to Fig. 1b by a variant of UV emitter according to the invention with three strip-shaped outer electrodes 9a - 9c. Due to the longer impact distance between the inner electrode. 6 and the center outer electrode 9b forms the middle discharge plane (not shown) only at higher coupled-in electrical power, than this for the other two, i. between the inner electrode 6 and the two "outer" outer electrode 9a and 9c lying discharge planes the case is.

Fig. 3 shows a cross section through a variant with four strip-shaped Outer electrodes 10a-10d.

Fig. 4 shows a cross section corresponding to Fig. 1b by a variant of UV emitter according to the invention with five strip-shaped outer electrodes 11a-11e and two rod-shaped internal electrodes 12a, 12b. Both internal electrodes 12a, 12b are for a first polarity and all external electrodes 11a-11e are for a second polarity of the supply voltage intended. Each of the two internal electrodes 12a, 12b is each a half-pipe piece 13a, 13b attached to the inside of the associated pipe half 5a. With increasing coupled power initially forms respectively between an inner electrode 12a, 12b and the next adjacent outer electrode 11a, 11e a discharge plane and then successively each another between inner electrode 12a, 12b and next outer electrode 11b, 11d until finally with sufficiently high power input all discharge planes are formed. The two internal electrodes 13a, 13b are positioned so that between them a relatively large e-electrode-free Radiating surface is.

Fig. 5 shows a cross section corresponding to Fig. 1b by a variant of UV emitter according to the invention with a flat outer electrode 14 and a rod-shaped inner electrode 6 with holder 7. The outer electrode 14 consists of a the entire outside of the associated tube half 5b covering aluminum layer. In operation, it forms between the inner electrode 6 and the entire surface outer electrode 14 is a relatively diffuse Discharge off.

Fig. 6 shows an enlarged detail corresponding to that shown in Fig. 1b Area C of a variant of the UV emitter according to the invention. Here consists of the holder for the inner electrode 6 of a total of three pipe sections 15 (in cross-section only one visible), the inner diameter clearly larger than the diameter of the wire-shaped inner electrode 6 allows the inner electrode 6 easier through the on the inside of the Thread tube half 5a pre-assembled tube pieces 15. Besides, has a bigger one Inner diameter has the advantage of having no or at least less form parasitic Gleitentladungen in the region of the brackets.

FIG. 7 shows a further variant with the only difference compared to FIG. 6, that the holder for the inner electrode 6 as half pipe piece 16th is trained.

Claims (17)

UV radiator having a discharge tube designed to produce one-sided dielectric barrier discharges and having a substantially tubular discharge vessel sealed on both sides and in each case at least one elongated inner and outer electrode oriented parallel to the longitudinal axis of the discharge vessel,
characterized in that
on the inside of an imaginary first pipe half of the tubular part of the discharge vessel, the at least one inner electrode and on the outside of an opposite imaginary second half pipe the at least one outer electrode is arranged, wherein the two opposite pipe halves through an imaginary section through the longitudinal axis of the tubular discharge vessel Discharge vessel are defined. UV radiator according to claim 1, the exact an inner electrode and a Outer electrode which are diametrically positioned to each other. UV emitter according to claim 1, wherein the inner and outer electrodes each symmetrical with respect to a respective imaginary pipe half cutting plane, which - viewed in cross-section - as a perpendicular bisector of the imaginary pipe half corresponding semicircle represents, are arranged. UV radiator according to one of the preceding claims, wherein the at least an inner electrode consists of a rod of metal. UV emitter according to one of claims 1 to 3, wherein the at least an inner electrode consists of a metal spiral. UV emitter according to one of the preceding claims, wherein the at least an inner electrode with a metal, in particular platinum, coated is. UV emitter according to one of claims 4 to 6, wherein the metal is tungsten or molybdenum is. UV radiator according to one of the preceding claims, wherein the at least an inner electrode with at least one holder on the inside the first imaginary pipe half is attached. UV emitter according to claim 8, wherein the at least one holder a Pipe piece, half pipe or ring is. UV lamp according to claim 8 or 9, wherein the holder and the discharge vessel wall made of the same material. UV radiator according to one of the preceding claims, wherein the at least an outer electrode is strip-shaped. UV radiator according to one of claims 1 to 10, wherein the at least an outer electrode is flat. UV emitter according to claim 12, wherein in the direction of the circumference the tubular discharge vessel considered spatial extent the outer electrode approximately over the entire corresponding Spatial extension of the imaginary second half pipe extends. UV emitter according to claim 12 or 13, wherein the at least one outer electrode is designed as a coating. UV emitter according to claim 12 or 13, wherein the at least one outer electrode is designed as a solid metal part, in the outside the imaginary second half pipe of the discharge vessel as it were is embedded. UV lamp according to one of the preceding claims, in operation electromagnetic radiation with wavelengths shorter than about 200 nm emitted. UV lamp according to one of the preceding claims, wherein the discharge vessel is filled with a discharge medium comprising xenon.

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