EP1849178B1 - Dielectric barrier discharge lamp configured as a double tube - Google Patents

Description

Technical area

The invention is based on a dielectric barrier discharge lamp with a discharge vessel in coaxial double tube arrangement, i. an inner tube is coaxially disposed within an outer tube. Inner tube and outer tube are connected to each other at their two end faces and thus form the gas-tight discharge vessel. The discharge space enclosed by the discharge vessel thus extends between the inner and outer tubes.

This type of discharge lamp typically has a first electrode disposed within the inner tube and a second electrode disposed on the outer surface of the outer tube. Both electrodes are thus outside the discharge vessel. It is in this case therefore a two-sided dielectrically impeded discharge. In the following, for reasons of simplicity, when the internal electrode or inner electrode and outer electrode or outer electrode are occasionally referred to, this term refers only to the spatial arrangement of the relevant electrode with respect to the coaxial double-tube arrangement, i. within the inner tube or on the outside of the outer tube.

This type of lamp is used in particular for UV irradiation in process technology, for example for surface cleaning and activation, photolytics, ozone generation, drinking water purification, metallization, and UV curing. In this context, the term radiator or UV lamps is also common.

The coaxial arrangement of two tubes, such as quartz glass, allows the construction of lamps with very long lengths. Long lamps are for high performance Of importance, since the maximum coupled into the lamp power increases with the length. However, attaching the inner electrode causes problems with long lamps, for example longer than 1 m, as well as lamps with a small inner tube diameter. On the one hand, the inner electrode should rest firmly against the wall of the inner tube, ie without sagging, on the other hand, it should be as easy to assemble. This problem is exacerbated when the discharge vessel is bent, for example, U-shaped.

State of the art

A generic dielectric barrier discharge lamp is in the document DE 196 13 502 A1 described. It is an excimer radiator with a closed discharge space, which is formed as an annular gap between two coaxially arranged quartz glass tubes. The discharge space contains a discharge gas forming excimer under discharge conditions. On the outside of the wall of the outer quartz glass tube is provided an outer electrode in the form of a net, while the inner electrode is formed by a voltage applied to the inside of the wall of the inner quartz glass tube wire spiral. Due to the relatively large distance to the neighboring electrode, the areas of high field strength concentrate in a spatially small area and there is a high field strength gradient at the radiator surface. This can make it easier to form filaments in the area of the wire spiral. When a high voltage is applied between the electrodes, so-called excimers are formed in the filling gas of the discharge space, which emit non-coherent but essentially monochromatic UV radiation, depending on the chemical composition. In the known excimer radiator, however, the inner electrode in the form of the wire spiral can not be mounted very easily.

Radiation generation can be achieved by suitable choice of electrical operation, as in the Scriptures EP 733 266 B1 described, be made more efficient in connection with suitable electrode arrangements. When investing A negative high voltage on the inner conductor (cathode side) form Δ-like discharge structures, the tip of which lies on the cathode side. By applying a closed electrode surface in the inner conductor to reach a substantially diffuse luminous discharge.

From the Scriptures EP 767 484 A1 An embodiment of a dielectric barrier discharge lamp is known, in which the inner electrode is designed in the form of a metal tube with a longitudinal slot extending in the direction of the radiator axis. To assemble the inner electrode, the slotted metal tube is slightly rolled up and then inserted into the inner tube. As a result, a firm abutment of the inner electrode on the wall of the inner tube is achieved, so that the discharge filaments forming numerous discharge filaments are distributed substantially homogeneously. However, with a vertically oriented lamp axis, the filaments tend to migrate along the longitudinal slot.

In Scripture DE 198 56 428 As a inner electrode, a metal band is installed spirally. This has the advantage that the filaments are distributed homogeneously and are spatially fixed even when installed vertically. The disadvantage is still not very simple production of the inner electrode. In addition, delimited areas also appear in the metal strip spiral, where the discharges take place almost exclusively.

Another possibility is the application of conductive coating inside the inner tube. This process is also quite complicated, since long drying and baking times are required. The JPH10241633 A shows a dielectric barrier discharge lamp.

Presentation of the invention

The object of the present invention is to provide a dielectric barrier discharge lamp in a coaxial double tube arrangement with an improved inner electrode.

• o einem Entladungsgefäß, das
  • o ein Außenrohr und ein Innenrohr umfasst, wobei
    • ▪ das Innenrohr innerhalb des Außenrohrs angeordnet ist,
    • ▪ das Innenrohr und das Außenrohr gasdicht miteinander verbunden sind, wodurch zwischen Innen- und Außenrohr ein mit einem Entladungsmedium gefüllter Entladungsraum gebildet ist,
• o einer ersten Elektrode und mindestens einer weiteren Elektrode, wobei
  • o die erste Elektrode innerhalb des Innenrohrs angeordnet ist,

dadurch gekennzeichnet, dass
die erste Elektrode in der Form einer elektrisch leitfähigen Bürste ausgebildet ist.This object is achieved by a dielectric barrier discharge lamp with

• o a discharge vessel, the
  • o comprises an outer tube and an inner tube, wherein
    • The inner tube is arranged inside the outer tube,
    • ▪ the inner tube and the outer tube are connected to one another in a gastight manner, whereby a discharge space filled with a discharge medium is formed between the inner and outer tubes,
• o a first electrode and at least one further electrode, wherein
  • the first electrode is arranged inside the inner tube,

characterized in that
the first electrode is in the form of an electrically conductive brush.

Particularly advantageous embodiments can be found in the dependent claims.

Starting from the dielectric barrier discharge lamp described above, according to the invention, the inner electrode is designed in the form of a conductive brush, which is formed, for example, by weaving thin metal threads, the braid wires or bristles, into two twisted metal wires, also called twisted wires. In this case, the rotary wires in the axial direction and the sizing wires in bristle tufts run radially in the direction of the inner wall of the inner tube and touch with the tips of the inner tube. Alternatively, the trimming wires can also be radially embedded in an elongated axial support. In any case, a very dense and uniform coverage of the internal surface of the radiator with individual electrodes is achieved with the aid of the conductive brush according to the invention as the inner electrode. The homogeneous discharge structure remains because of the large number of possible Discharge points received. In addition, one still has the advantage of a slight local field increase, which reduces the ignition or operating voltage.

In a preferred embodiment, the inner electrode is designed as a round brush. For example, the round brush electrode may be made of fine filaments of conductive material (bristles) woven into two or more spirally wound carrier wires (twisted wires). At least one of the twisted wires is electrically conductive. The bristles are aligned substantially perpendicular to the twisted wires and spiral around the twisted wires in bristle tufts. The outer diameter of the round brush is a little larger than the inner diameter of the inner tube to ensure a secure contact. Due to the larger outer diameter of the brush in the relaxed state compared with the inner diameter of the inner tube, a concern of the bristles or fine metal wires, preferably not only with the tips guaranteed. The diameter in the relaxed state results when the brush is not installed. Under the outer diameter is understood to mean the maximum diameter of the cross section perpendicular to the brush longitudinal axis. By the mentioned minor concern of the bristles also reduces the effect of undesirable excessive local field strength peaks. The spiral shape of the inner electrode prevents unwanted migration of the discharge filaments very effectively regardless of the spatial orientation of the discharge lamp. The preferably elastic deformability of the round brush facilitates installation in the inner tube. In addition, the inner electrode thus formed is also suitable for bent inner tubes.

Advantageously, the distance of the bristles within a bristle tuft in the relaxed state is 0.01 mm to 1 mm. The smaller the gap between the adjacent bristles is chosen, ie with increasing density of the bristles, the more homogeneous the discharge. With denser bristle spacing, however, the deformability of the brush decreases, which is the Assembly difficult. Preferably, the distance is between 0.05 mm and 0.2 mm.

Bristles with a diameter of between 0.005 mm and 0.5 mm, preferably between 0.02 mm and 0.2 mm, have proven particularly useful.

As favorable in view of their elastic deformability, twisted wires have been found with thicknesses between 0.2 mm and 2 mm.

As a material for both the twisted wires and the bristles is preferably stainless steel.

For discharge lamps with a curved inner tube, the inner electrode in the form of a brush according to the invention is particularly well suited. Due to its flexibility, the inner electrode according to the invention can adapt to the bending of the inner tube. The bend can be executed both as a kink and as a continuous curvature. As examples, a circular, semicircular, banana-shaped or U-shaped curvature of the inner tube should be mentioned.

The internal electrode according to the invention combines simple assembly with a uniform occupancy of the inner surface of the inner tube and consequently a homogeneous discharge within the discharge vessel. Plus, it's easy to make.

The at least one further electrode is typically arranged on the outside of the outer tube. As outer electrode, inter alia, both net-like and strip or line-shaped electrodes come into consideration. For a directed radiation, a reflector can be provided on the rear side of the lamp according to the invention, ie on the side opposite to the side intended for the light emission, preferably of aluminum, which can simultaneously act as an earth electrode. Alternatively, the lamp according to the invention can be embedded in a metal block, for example made of aluminum, and also several lamps next to one another. At this Variant, the metal block acts as an outer electrode, preferably at ground potential. In addition, a cooling system can be connected.

Brief description of the drawings

Fig. 1a

eine erfindungsgemäße Entladungslampe mit einer rundbürstenförmigen inneren Elektrode in einer Seitenansicht,

Fig. 1b

eine Querschnittdarstellung des Ausführungsbeispiels aus Figur 1a,

Fig. 2

eine erfindungsgemäße Entladungslampe mit einer segmentierten inneren Elektrode in einer Seitenansicht,

Fig. 3a

eine erfindungsgemäße Entladungslampe mit einer halbrundbürstenförmigen inneren Elektrode in einer Seitenansicht,

Fig. 3b

eine Querschnittdarstellung des Ausführungsbeispiels aus Figur 3a,

Fig. 4

eine U-förmige erfindungsgemäße Entladungslampe mit einer rundbürstenförmigen inneren Elektrode in einer Seitenansicht.

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

Fig. 1a

a discharge lamp according to the invention with a round brush-shaped inner electrode in a side view,

Fig. 1b

a cross-sectional view of the embodiment of FIG. 1a .

Fig. 2

a discharge lamp according to the invention with a segmented inner electrode in a side view,

Fig. 3a

a discharge lamp according to the invention with a semicircular brush-shaped inner electrode in a side view,

Fig. 3b

a cross-sectional view of the embodiment of FIG. 3a .

Fig. 4

a U-shaped discharge lamp according to the invention with a round brush-shaped inner electrode in a side view.

Preferred embodiment of the invention

The FIGS. 1a, 1b show a highly schematic representation of a side view and a cross-sectional view of a first embodiment of the inventive dielectric barrier discharge lamp 1. The elongated discharge vessel of the lamp 1 consists of an outer tube 2 and an inner tube 3 in coaxial double tube arrangement, which define the longitudinal axis of the discharge vessel. The length of the dielectric barrier discharge lamp 1 designed for an electric power consumption of 20 W is 20 cm. The outer tube 2 has a diameter of 40 mm and a wall thickness of 1 mm. The inner tube 3 has a Diameter of 11 mm and a wall thickness of 1.2 mm. Both tubes 2, 3 consist of UV radiation permeable quartz glass. In addition, the discharge vessel is closed at its two end faces such that an elongated, annular gap-shaped discharge space 4 is formed. For this purpose, the discharge vessel has suitably shaped, annular vessel sections 5 at its two ends. In addition, a pumping tube (not shown) is attached to one of the vessel sections 5, with the aid of which the discharge space 4 is first evacuated and then filled with 15 kPa xenon. On the outside of the wall of the outer tube 2, a total of eight uniformly distributed, line-shaped outer electrodes 5 of width 1 mm are arranged parallel to the longitudinal axis of the discharge vessel. Inside the inner tube 3, ie also outside the discharge space 4 enclosed by the discharge vessel, a round brush-shaped inner electrode 6 is arranged. The inner electrode 6 consists of an axial support element 7 (shown here only in simplified form) and numerous bristles 8. The support element 7 is formed from two twisted stainless steel wires (twisted wires), each 1 mm in diameter (not shown). Numerous stainless steel wires, each 0.06 mm in diameter, are woven spirally along the entire length of the carrier element 7 in tufts into these two twisted wires of the carrier element 7, which are oriented radially to the carrier element 7 and act as bristles 8.

FIG. 2 shows a further embodiment, wherein the same features as in FIG. 1a, 1b are provided with the same reference numerals. The dielectric barrier discharge lamp 9 shown schematically there differs from that in FIG FIG. 1a, 1b shown lamp only in that here the inner electrode is divided into five segments 10-14. Within the segments 10, 12 and 14, the carrier element 7 is provided in the entire circumference with radially extending bristles 8. These segments 10, 12 and 14 alternate with the segments 11 and 13, in which there are no bristles. In operation, therefore, the lamp 9 preferably radiates in partial areas the segments 10, 12 and 14, whereas in the segments 11 and 13 no discharge is formed.

The FIGS. 3a, 3b show in a highly schematic representation of a side view and a cross-sectional view of another embodiment. Again, same features as in FIG. 1a, 1b are provided with the same reference numerals. The dielectric barrier discharge lamp 9 shown schematically there differs from that in FIG FIG. 1a, 1b shown lamp in that here the inner electrode is provided only semi-cylindrical with radial bristles 8. In addition, the outside of the wall of the outer tube 2 is half-shell-shaped with an outer electrode 16 made of aluminum, which extends along the entire length of the outer tube 2. In this case, the outer electrode 16 is oriented so that it is directly opposite the semicircular brush-shaped inner electrode. This causes a preferred direction for the radiation. The outer electrode 16 may for example be vapor-deposited, glued or plugged. In addition, the outer electrode may also be formed by a metal block, in which the lamp is partially embedded.

In Figure 5, an embodiment is shown schematically in which the discharge vessel and thus the inner tube 17 and the outer tube 18 are bent in a U-shape. The flexible inner electrode 6 according to the invention is easily able to follow this bend. In addition, due to the flexibility of both the support member and the bristles, the inner electrode 6 is relatively easy to insert into the inner tube.

Claims (15)

1. Dielectric barrier discharge lamp (1), having

   o a discharge vessel, which

   o comprises an outer tube (2) and an inner tube (3),

   ▪ the inner tube (3) being arranged inside the outer tube (2),

   ▪ the inner tube (3) and the outer tube (2) being connected to one another in a gas-tight manner, so that a discharge space (4) filled with a discharge medium is formed between the inner and outer tubes,

   ∘ a first electrode (6) and at least one further electrode (5),

   ∘ the first electrode (6) being arranged inside the inner tube (3),

   characterised in that
   the first electrode (6) is configured in the form of an electrically conductive brush.
2. Dielectric barrier discharge lamp according to claim 1, wherein the brush-shaped first electrode (6) comprises an elongate carrier element (7) and bristles (8), which are arranged essentially radially with respect thereto and extend essentially as far as the wall of the inner tube (3).
3. Dielectric barrier discharge lamp according to claim 1 or 2, wherein the carrier element (7) and the bristles (8) are made of a flexible material.
4. Dielectric barrier discharge lamp according to claim 3, wherein the flexible material is metal, preferably stainless steel.
5. Dielectric barrier discharge lamp according to any one of the preceding claims, wherein the carrier element (7) is provided with bristles over the entire circumference at least in sections, in the manner of a round brush.
6. Dielectric barrier discharge lamp according to claim 5, wherein the diameter of the round brush-like electrode (6) in the extracted state is greater than the inner diameter of the inner tube (3) of the discharge vessel.
7. Dielectric barrier discharge lamp according to any one of the preceding claims, wherein each bristle (8) consists of a wire.
8. Dielectric barrier discharge lamp according to claim 7, wherein the diameter of the bristle wire is from 0.005 mm to 0.5 mm, preferably from 0.02 mm to 0.2 mm.
9. Dielectric barrier discharge lamp according to claim 7, wherein the average mutual separation of the neighbouring bristle wires of the brush-like electrode in the extracted state is from 0.01 to 1 mm, preferably from 0.05 mm to 0.2 mm.
10. Dielectric barrier discharge lamp according to any one of the preceding claims, wherein the carrier element consists of at least two wires twisted into one another.
11. Dielectric barrier discharge lamp according to claim 10, wherein the diameter of each wire is from 0.2 mm to 2 mm.
12. Dielectric barrier discharge lamp according to any one of the preceding claims, wherein the at least one further electrode (5) is arranged on the outer side of the outer tube (2).
13. Dielectric barrier discharge lamp according to claim 12, wherein the at least one further electrode (5) is net-like, or strip-shaped or line-shaped.
14. Dielectric barrier discharge lamp according to any one of claims 1 to 11, which is at least partially embedded in a metal block that functions as a further electrode.
15. Dielectric barrier discharge lamp according to any one of the preceding claims, wherein the discharge tube is curved.

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