Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1998-11-17
2001-06-12
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S491000, C313S492000, C313S493000
Reexamination Certificate
active
06246171
ABSTRACT:
TECHNICAL FIELD
The invention relates to a gas discharge lamp according to the preamble of claim
1
. This gas discharge lamp has a discharge vessel including a gas filling, at least parts of the discharge vessel being transparent to radiation of a desired spectral region. Given a suitable electric supply, a number of anodes and cathodes generates a discharge in the gas filling, which either directly generates the desired radiation, or by means of which radiation emitted by the discharge excites a fluorescent material in the gas discharge lamp, which emits the desired radiation.
In the present case, a gas discharge lamp for so-called dielectrically impeded discharge is considered in which at least the anodes, possibly also the cathodes, are separated from the gas filling by a dielectric interlayer. Furthermore, the invention proceeds from anode and cathode geometries which have strips extending essentially parallel to one another, the term strip-shaped not necessarily implying edges extending parallel to one another. Here, strips means elongated formations which are thin and narrow by comparison with their length. These strips can also have specific structures along their length, as set forth further below, and need not be straight.
Strictly speaking, the terms anodes and cathodes make sense only in unipolar operation of the gas discharge lamp. However, bipolar operation is not excluded here, and in that case the difference between anodes and cathodes becomes blurred and the electrodes must in principle be separated from the gas filling by a dielectric layer. Consequently, the terms “anodes” and “cathodes” in the claims and below also include electrodes for bipolar discharges, which in each case temporarily play the role of an anode or cathode.
It is further to be made clear that the dielectric layer need not be a layer applied to the electrode especially for this purpose, but can also be formed by a discharge vessel wall, for example, if electrodes are arranged on the outside of such a wall or inside the wall.
PRIOR ART
The following documents are named in relation to the prior art:
EP 0 363 832 discloses an UV high-power radiator having elongated electrodes, which are supplied with high voltage in pairs and are separated from a gas filling by dielectric material. The anodes and cathodes are arranged next to one another in alternating sequence, with the result that a configuration of individual discharges which is of the flat type overall is produced in relatively flat discharge vessels.
An operating method for such a discharge lamp follows from WO 94/23442. In this case, specific sequences of pulses of the power supply are specifically tuned to the dielectrically impeded discharge and form overall typical delta-shaped discharges between the anodes and cathodes. In a gas discharge lamp, there are a large number of such individual discharges, which are lined up along the strip-shaped electrodes and, in the event of a suitably designed pulsed mode of operation generate the desired radiation with a very high efficiency.
DE 195 48 003 A1 discloses an appropriate circuit arrangement.
It is described in DE-A 195 26211.5 and WO 94/04625 how the above method can be applied to the previously described UV high-power radiator.
Furthermore, EP 0 607 453 discloses a liquid crystal display having a surface lighting unit composed of a plate-shaped optical conductor and a tubular fluorescent lamp. The fluorescent lamp is bent in this case in such a way that it can be arranged on two or more mutually adjacent edges of the optical conductor plate. The light from the fluorescent lamp can thereby be launched into the optical conductor plate, specifically at at least two edges, and be scattered by the plate surface towards the liquid crystal display. The aim thereby is to improve the uniformity of the illumination by using as far as possible only one fluorescent lamp.
THE INVENTION
The present invention is based on the technical problem of further developing the gas discharge lamp described in the beginning, according to the preamble of claim
1
. The invention thus aims at a method of production for this gas discharge lamp, and at a lighting system having this gas discharge lamp and an electric supply, and also at screen systems in which the lamp according to the invention is combined with a screen.
Overall, the solution to this technical problem takes the form firstly of a gas discharge lamp having a discharge vessel which is at least partially transparent and filled with a gas filling, a number of essentially strip-shaped anodes and cathodes which extend on walls of the discharge vessel and essentially parallel to one another, and a dielectric layer between at least the anodes and the gas filling for a dielectrically impeded discharge in the discharge vessel between neighbouring anodes and cathodes, at least one anode pair being arranged between two cathodes adjacent in each case one anode of the pair.
Furthermore, the invention comprises the method of production according to claim
20
, the lighting system according to claim
21
and the flat screen system according to claim
22
, as well as the respective refinements in the dependent claims.
The advantage of the anode pair between neighbouring cathodes resides chiefly in that in each case only one of the two anodes of the pair is assigned as nearest anode neighbour to one of the cathodes. As a result, no situations can arise in which two equivalent nearest neighbour cathodes are present starting from an anode. To be precise, it has emerged that in this case individual discharges occur in a not exactly predictable way between the anode and one of the two cathodes concerned. This choice of one of the two sides is frequently not uniform over the entire strip length of the electrodes, and can also change with time. Conventional electrode geometries thus do not permit far-reaching spatial and temporal homogenization of the discharge distribution nor, therefore, a truly precise control of the luminous density distribution in the lamp.
“Denser packages” of individual discharge structures can also be produced by the invention as an additional aspect, the result being an improved power density.
In the case of a bipolar operation the terms anodes and cathodes are to be related here in each case to electrodes of one polarity of electric supply. As a result of the exchangeability of the polarities in the bipolar case, the electrodes of both polarities are preferably arranged in pairs in any case given repeated electrode strip arrangements.
However, it holds both for the unipolar and for the bipolar case that the arrangement of electrodes in pairs need not be implemented for the entire gas discharge lamp, but can be dispensed with in the edge regions. Furthermore, it is to be noted that given the alternating arrangement, according to the invention, of pairs of electrodes of the same polarity with the polarity of changing in pairs, electrode pairs exist in each case between which no electrode pair of the other polarity is arranged (specifically, no electrode at all).
In addition to better suitability for bipolar operation, it can be a further advantage of pairwise arrangement of the cathodes as well that the typical delta-shaped discharge structures stand with a tip on the cathodes, and the separation of the cathodes avoids the concentration of two discharge tips at the same point of the same cathode. It is possible thereby to avoid possible thermal problems or stability problems in specific applications.
Preferably the invention is directed to gas dischare lamps having a discharge vessel of electrically non-conductive material and having a flat radiator geometry. Especially with flat discharge vessel geometries the advantages obtained by the invention of an increase in the achievable power density and an improvement of the homogeneity play a role.
In other words, the invention relates in particlar to a flat radiator having an at least partially transparent discharge vessel of electrically non-conductive material that is closed and filled with a gas fill
Hitzschke Lothar
Jerebic Simon
Muecke Jens
Siebauer Rolf
Vollkommer Frank
Clark Robert F.
Day Michael H.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
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