Patent Application
20060066245
The present invention relates to a dielectric barrier discharge lamp together with an appropriate electronic ballast for operating the lamp. This sentence will be referred to below as “illumination system”. Dielectric barrier discharge lamps are understood to mean discharge lamps in which at least the anodes or, in the case of bipolar operation, even all of the electrodes, are isolated from a discharge medium in the discharge vessel by a dielectric layer. This results in automatic quenching of the discharge by internal counterpolarization as a result of the dielectric layer on the anode or the electrode, which in this phase acts as the anode, being electrically charged. Lamp operation therefore takes place finally by means of a dense row of very short discharge flashes.
Dielectric barrier discharge lamps have been disclosed in different ways in the prior art and are of interest, owing to various advantageous technical properties, in particular for backlighting displays, for example computer monitors and television screens, or for office automation applications. In the lastmentioned case, lamp shapes which are in the form of elongate rods are generally used which can be used to illuminate documents in scanners, fax machines, copiers or the like. Those discharge lamps having a discharge vessel which is elongate in the form of a tube are likewise already known and accessible. They may also be of interest for other applications, for example as UV radiators for specific technical processes. The present invention is not restricted to a specific application.
Dielectric barrier discharge lamps cannot be operated using a direct current owing to the discharge mechanism which has been outlined in brief, but are operated either using unipolar power supply pulses or using bipolar power supply pulses. The frequencies used are generally of the order of magnitude of a few 10 kHz.
In the prior art, both designs having inner electrodes and those having outer electrodes are known. Outer electrodes generally provide for more simple production but tend towards certain minimum thicknesses of the dielectric layer between the electrode and the discharge medium since the discharge vessel wall itself acts as said dielectric layer. In principle, variants having inner and outer electrodes are also conceivable.
It is already known to fit such electrodes, in the case of inner electrodes, by means of dispension, i.e., for example, spread-coating, and, in the case of outer electrodes, by means of adhesive bonding or by means of transparent foil sleeves covering the entire discharge lamp.
Inner electrodes are conventionally passed to the outside in a gas-tight manner through an outer wall of the discharge vessel. There, contact is generally made with the electrodes, whether they be outer electrodes or inner electrodes passed through, by means of soldering or so-called crimping connections. Contact is made with cables which produce a connection to a ballast for the purpose of operating the discharge lamp. In addition, the conventional dielectric barrier discharge lamps and associated ballasts are mounted independently of one another and are connected to one another merely by a connection cable.
The invention is based on the technical problem of specifying an illumination system which is advantageous as regards the connection between the discharge lamp and the ballast and comprises a dielectric barrier discharge lamp having a discharge vessel which is elongate in the form of a tube and an appropriate electronic ballast. The invention is also intended to specify a corresponding method for connecting the discharge lamp to the ballast.
This technical problem is solved by an illumination system comprising
In addition, the invention relates to a method for connecting the discharge lamp to the electronic ballast, in which the discharge lamp with an end having contacts to an electrical connection of the lamp, as the plug connection element, is inserted into a plug connection element, which is designed to be complementary thereto and is fixedly connected to the housing of the ballast.
Preferred refinements are specified in the dependent claims and are explained in more detail in the text which follows. The disclosure in this case relates implicitly both to the illumination system and the method without a distinction explicitly being drawn in detail between these categories.
The basic idea of the invention consists in a dielectric barrier discharge lamp having a discharge vessel which is elongate in the form of a tube to a certain extent being regarded as the plug connection element itself. For this purpose, the discharge lamp has contacts fitted at one end for the electrical connection and is connected with this end to a correspondingly designed, complementary plug connection element which is fixedly connected to the ballast, i.e. to the housing of said ballast. In this case, it is naturally possible for the ballast-side plug connection element to be connected to a printed circuit board of the ballast via a cable, but a direct mechanical connection between the lamp and the ballast should be created by the plug connection.
It is preferable in this case for the ballast-side plug connection element to not only be fixedly connected to the housing but to be integrated in the housing. In other words, the plug connection element should not be fixed. A flexible cable between the ballast housing and the lamp in the form of a flexible mechanical connection therebetween is therefore dispensed with. It is preferable for the plug connection element to be integrated flat in the ballast housing, i.e., for example, to be in the form of a recess in an otherwise, for example, parallelepipedal housing, into which recess the tubular lamp itself can be inserted with one end. For illustrative purposes, reference is made to the exemplary embodiment.
The ballast-side plug connection element is preferably a plug socket, i.e. a female element in relation to the tube shape of the lamp.
In addition, it is particularly preferable for the electrodes to be in the form of rods and to be in the form of a plug connection element at one end. The basic idea of this refinement consists in the outer electrodes being in the form of rods and in the process being used as plug connection elements at one end. In this case, rod-shaped means that the electrodes have a certain intrinsic dimensional stability, and can thus be used as the plug connection element, i.e. are not foil electrodes. In particular, in this case the length and width of the electrodes transverse to the longitudinal extent should be comparable in terms of order of magnitude, for example should not differ from one another by more than a factor of 5.
In this case, the electrodes should be designed such that they can be connected to a complementary plug connection element in a form which can preferably be detached mechanically, i.e. can be isolated again without any fundamental damage. In this case, a plug connection is understood to mean a force-fitting connection, which takes place whilst maintaining the essential shape of the plug connection elements, of largely dimensionally stable elements. The plug connection is thus intended to be delimited by, for example, crimping connections, in the case of which contact is made with foil-like electrodes with a substantial change to the shape of said electrodes and without using dimensional stability.
The use of the electrodes themselves as plug connection elements provides a simple design, markedly simplifies the contact-making method and combines this contact-making method in an advantageous manner with the mechanical connection between the ballast and the lamp.
In particular, the electrodes may be simple round rods and, in this case, either have a tube end as the so-called female element of the plug connection or end as a round rod as the so-called male element. The tube end, which is designed to accommodate a round rod, can therefore be present as the female plug connection element both on the electrode side and on the ballast side. Corresponding designs are naturally also possible with cross sections other than the round cross section, but the round cross section is preferred.
Preferred in principle is not only a plug connection which can be detached without any damage being caused but also a plug connection which can be produced by means of a purely translatory movement. Such plug connections are simple in design terms and allow for a particularly simple contact-making method.
Favorable geometric designs for the plug connection elements on the electrodes or the complementary plug connection elements are configured such that one element at least partially surrounds the complementary element. For example, with the connection described between a rod end and a tube end, the rod end is completely surrounded by the tube end. If, however, a widened flat end of a rod is inserted into a slot in a complementary element, the flat end is now only surrounded on two sides, i.e. only partially, by the complementary element. This means that one element bears on at least two sides of the other element “laterally” in relation to the longitudinal direction.
In this case, the electrode ends and the associated ballast-side plug connection elements for the electrode ends can be allocated the female or the male role as desired.
It is preferable for the electrode ends to be used as the plug connection elements to protrude beyond the discharge lamp, i.e. to be capable of being introduced into corresponding receptacles on insertion in which the complementary plug connection elements for the electrodes are provided. The ballast-side plug connection element for the lamp itself in this case does therefore not need any projecting structures in order to make contact with the electrodes, which is advantageous even in terms of protection against touching contact.
The frequencies used during operation of the discharge lamp are generally of the order of magnitude of a few 10 kHz, with the result that such discharge lamps produce interference radiation in EMC-sensitive conditions. In a further refinement, this problem is particularly advantageously solved by a conductive metallic shield which partially surrounds the discharge vessel and in the process leaves an angle of opening free for light radiation purposes, at least one shielding face, limiting the angle of opening, of the shield being remote from the discharge vessel at its outermost end by a distance which is at least as great as half the average diameter of the discharge vessel transverse to the longitudinal extent.
Tubular discharge lamps of this type have a so-called aperture along their longitudinal extent, i.e. a longitudinally extending strip, from which light emerges from the lamp. In order to ensure good efficiency, this aperture should if possible not be covered directly by a shield, for which purpose known shields also leave the aperture completely free. However, the lamp then radiates over the entire region which is left free at the corresponding spatial angles. The shielding face provided by the invention delimits the spatial angle of this radiation and thus also defines an angle of opening of the light radiation. This angle of opening can be optimized in terms of the technically desired application, i.e. in an individual case the angle of opening may also be markedly smaller than is actually possible in the case of the aperture provided. In this case, however, the shielding face would not impair the luminous efficiency at the spatial angle relevant to the application, but would markedly improve shielding.
The basic idea of the invention thus consists in the shield not being limited to a conductive envelope, known per se, of the discharge vessel outside the angle of opening but the shield having at least one shielding face which extends away from the discharge vessel and in the process limits the angle of opening. The shield should therefore to a certain extent have a “screen” along at least one lateral boundary of the angle of opening. Corresponding shielding faces are preferably provided at both boundaries of the angle of opening, but a shielding face could also be dispensed with, for example, if the shield in the other direction is not important or is already provided for other reasons, for example by a metallic wall which is provided there in any case. The shielding face in this case does not necessarily need to run along its entire extent along the boundary of the angle of opening, i.e. does not necessarily need to extend substantially radially. At least its outermost end preferably limits the angle of opening. This outermost end is moreover remote from the discharge vessel in accordance with the invention at least by half the average diameter of the discharge vessel.
Moreover, it is also not absolutely necessary for the shield to surround the entire rest of the circumference of the discharge vessel apart from the angle of opening. Here too, owing to the lack of significance of the electromagnetic interference radiation in a specific direction or shielding elements which are provided there in any case, the reasons for a shield may be absent and/or there may be other physical reasons which allow a gap in the shield to appear advantageous.
However, it is preferable in the context of this invention for the shield to surround and shield the discharge vessel and therefore to a certain extent to form a sleeve over more than half of the circumference of said discharge vessel. As is described in more detail below, this sleeve may also have advantageous properties as a mounting aid or holder.
The mentioned sleeve preferably has, over part of the circumference of the discharge vessel, particularly preferably over the remaining part, apart from the shielding face(s), a relatively small distance from the discharge vessel, to be precise in comparison with half the average diameter of the discharge vessel. The remaining part of the shield then forms the mentioned shielding face. For illustrative purposes, reference is made to the exemplary embodiments.
Although the shielding face according to the invention of the shield can limit the light radiation of the lamp and thus define an effective angle of opening at least towards one side, in many cases it is desirable to utilize as much as possible of the radiated light. If the extent of the aperture is based on the central point of the discharge vessel in cross section with respect to the longitudinal direction and this is considered to be the angle of opening, the angle of opening of the light radiation, based on the same central point, of the shield will preferably be greater than that of the aperture. In this case, the shielding face can moreover screen light radiated from the aperture, since the light radiation in the lamp also takes place from parts of the inner sheath which are closer to the aperture, with the result that the effective light radiation angle of the aperture is greater than the angle of opening when viewed radially.
In addition, the shield can also contain further shielding elements in the region of the angle of opening in addition to the shielding face(s), in particular flat shielding parts which extend substantially radially in cross section and further divide the angle of opening. The shield can thus also be slightly improved in the direction of the light radiation. Examples will be explained further below.
It may be important for the sleeve, if it is electrically conductive or contains electrically conductive parts, to be coupled to the electrode(s) in a manner which is not excessively capacitive. It is in this case preferred for an assumed radial thickness dD between the metallic sleeve and the outer electrode, i.e. approximately the thickness of the mentioned insulation layer within the metal shield, and a dielectric constant ∈D of this layer and a thickness dB of the dielectric barrier between the electrode and the discharge medium at a corresponding dielectric constant ∈B to overall fulfill the following relationship:
dD/∈D≧F×dB/∈B,
where the factor F is at least 1.5, preferably at least 2 and particularly preferably at least 2.5. Reference is made to U.S. Pat. No. 6,304,028 B1 for further details in which it is also explained, inter alia, that the corresponding sum of the individual quotients of thickness and dielectric constant must be used in this relationship in the case of multilayer composites.
One simple and preferred possibility consists in at least one, preferably two end-side bases being provided on the lamp which are dimensioned to be radially slightly larger than the discharge vessel itself. If, in this case, the shield is fitted so as to bear against the base and is preferably mounted and held also in this form, the radial difference between the base and the discharge vessel gives the desired distance.
A further preferred refinement of the base relates to flattened sections on its cross-sectional shape (perpendicular to the longitudinal extent of the discharge vessel) which are provided so as to also match the shield, for example a correspondingly shaped metal sheet. In this case, when mounting the shield on the bases, the alignment of the flattened sections provides a correct orientation, i.e. in particular an alignment of an aperture of the lamp with the angle of opening defined by the shield. In this case, the base can naturally also contain further latching devices which match the shield. However, a latching or clamping action may also be provided by the sleeve shape alone, i.e. by the interlocking connection of the shield itself.
Furthermore, with the invention, at least one outer electrode can be fitted to the discharge vessel by means of an interlocking connection with a sleeve surrounding the electrodes, said sleeve partially surrounding the circumference of the discharge vessel perpendicular to the longitudinal extent but in the process leaving an aperture free for light radiation purposes.
This refinement also relates to a corresponding production method in which at least one electrode is fitted to a discharge vessel which is elongate in the form of a tube by means of an interlocking connection with a sleeve surrounding the electrode such that the electrode lies along the longitudinal extent of the discharge vessel, the sleeve leaving an aperture free for light radiation purposes.
The basic idea in this case consists in using a sleeve for the purpose of mounting the at least one electrode or preferably the two or more outer electrodes. The sleeve is in this case a device which has sufficient intrinsic dimensional stability for holding the electrodes by means of an interlocking connection. The sleeve can therefore be used, so to speak, as a clip or clamping device. This makes it possible for an aperture to be left free in order for the discharge lamp to radiate light, with the result that the sleeve does not need to be transparent or particularly thin. The sleeve also does not need to be adhesively bonded. Furthermore, it allows for stabilization and/or protection of the discharge vessel against external effects and can therefore also contribute to a reduction in the wall thicknesses of the discharge vessel which is desired for weight reasons and for preventing voltages which are too high. In particular, the electrode can be mounted on the discharge vessel by simply being clipped onto or inserted into the sleeve such that production of the discharge lamp is markedly simplified and accelerated at this point.
Preferred features of the invention are the fact that only the mentioned interlocking connection holds the electrode, i.e. said electrode is not also adhesively bonded to the discharge vessel or fixed in another way, and also the fact that the sleeve is prestressed for this purpose, i.e. still maintains a certain contact pressure even in the mounted state.
In addition, it is also preferred for the sleeve itself to be held on the discharge vessel only by means of an interlocking connection or else a force-fitting connection as a result of its intrinsic stability, i.e. to bear against said discharge vessel freely. It should therefore likewise not additionally be adhesively bonded.
Primarily as regards the stabilization and protective function of the sleeve already mentioned, it is preferred, but not absolutely necessary in the context of the invention, for the sleeve to extend substantially along the entire discharge vessel. In an individual case, one or more sleeves may also be used which make up only part of the longitudinal extent of the discharge vessel.
In addition, the above explanation relating to the interlocking connection and the intrinsic dimensional stability of the sleeve should not be understood in such a way that they need necessarily be integral. Within the context of a particular refinement of the invention, in contrast provision is made for an at least two-part sleeve to be used. In this case, there may also be a functional differentiation, for example in the form of an outer shielding plate according to the explanations above and an electrical insulation lying therein between at least the electrode and the shielding plate. In such cases, the insulation itself need not necessarily be dimensionally stable although it should be understood to be part of the sleeve.
A further possibility for a two-part sleeve comprises two parts which have been split along the longitudinal extent of the discharge vessel and are adjacent and fixedly connected to one another in the mounted state, said parts producing an interlocking or force-fitting connection with respect to the discharge vessel in the connected state. Such parts can therefore also be placed on the discharge vessel without an interlocking and force-fitting connection and then connected to one another for the purpose of producing the interlocking or force-fitting connection. Possible connections are, in particular, clip connections between the two parts, preferably also undetachable clip connections. This embodiment is particularly suitable for sleeves which are not made from a substantially elastic material.
Preferred applications of the illumination system according to the invention are not only in office automation but also in UV radiators. Such UV radiators can be used for various technical processes. Of particular interest in the context of this invention is the illumination of catalyst surfaces for photocatalysis of reactions. A preferred example of an application is one in air purification, in particular in vehicles, for example motor vehicles. In this case, air pollutants can be converted by a photocatalytic process and thus eliminated, and the vehicle interior can thus be supplied with air having a much better quality than that in the outside world.
The invention will be explained in more detail below with reference to the exemplary embodiments, it being possible for the individual features also to be essential to the invention in other combinations.
a shows a schematic, perspective view of one end of the discharge lamp shown in
b shows a variant of
Firstly, reference is made to U.S. Pat. No. 6,304,028 B1 which has already been mentioned above for the purpose of illustrating the design of a typical dielectric barrier discharge lamp having a tubular discharge vessel. Explanations which have already been given in this document are not repeated below. Instead, the description of the exemplary embodiments concentrates on the differences from this prior art.
The figure shows the fact that a substantially linear dielectric barrier discharge lamp 2 having two laterally protruding shielding faces 3 is inserted into the rear region of that side of the ballast 1 which is on the right in
It can be seen in
The axial electrode ends 4 are the ends, on the left-hand side in
That part of the lamp 2 which reaches beyond the shielding faces 3 is a plastic base 7 which holds, together with a second base 8 which can be seen in
In
Since in this case the insulating layer between the electrodes and the shielding plate 10 is at the same time in the form of a base corresponding to the base 7 in
In both cases, the embodiment in
b shows one variant of
The base 7 shown in
In contrast to
The bent shape of the shielding faces 3′ can in this case take physical conditions in the environment into consideration, for example if the illumination system (in the sense of
Finally,
| Number | Date | Country | Kind |
|---|---|---|---|
| 102004047373.0 | Sep 2004 | DE | national |
