Patent Application
20230402274
The invention relates to a gas discharge lamp, in particular a deuterium lamp, with a high local radiance. Gas discharge lamps of this kind are used for example for spectroscopy applications.
In the case of deuterium lamps, the current designs on the market for generating high radiance levels are based on an elongated, channel-like diaphragm. However, this embodiment has the disadvantage that the lamp is difficult to ignite in the case of a single long channel. The arc voltage of the lamp is also significantly increased by the long diaphragm channel as compared to a standard deuterium lamp with a single, flat diaphragm, this having a negative effect on the service life.
In order in particular to compensate for the effect of more difficult ignition, additional electrodes must be introduced into the lamp, which increase complexity in the design and in the electrical control of the lamp.
From DE 196 28 925 A1 a UV discharge lamp is known, comprising a lamp bulb made of quartz glass and an electrode housing arranged therein, which contains an anode and a cathode. Between the two electrodes there is a diaphragm arrangement composed of a plurality of optical diaphragms made of high-melting material. The diaphragm opening serves to constrict the arc discharge generated between the electrodes. The multiple-diaphragm arrangements lead to a strong increase in or multiplication of the radiance by the formation of several plasma spheres with relatively little outlay. In a preferred embodiment, three diaphragms are provided, each of which is individually connected to the voltage supply of the electrodes via controllable switches, wherein the diaphragms are ignited one after the other. In this case, the diaphragms perform an auxiliary anode function which enables a stepwise ignition of the deuterium lamp, which results in increased ignition reliability.
EP 1 437 760 A1 describes a deuterium lamp with a gas-tight lamp bulb made of glass with a lamp foot (base) and cylindrical side wall, one part of which serves as a light-emitting window. A light-emitting assembly (electrode insert), which has an electrically conductive housing made of nickel, is accommodated in the lamp bulb. A shaft, which is connected to the lamp foot, is welded to the distal housing end. The light-emitting assembly comprises a disk-shaped anode, and a plurality of diaphragms which delimit the discharge path. The anode is welded to the distal end of an upright pin, which in turn is fastened to the lamp foot. The diaphragms consist of molybdenum or tungsten and have a diaphragm opening with a diameter of approximately 0.5 to 1 mm. They are each fastened to the housing via a metal support plate. In addition, a metallic front cover with a light passage opening in the direction of the optical axis is fastened to the housing. The cathode is accommodated a cathode chamber of the housing laterally in relation to the optical axis. This prevents material sputtered off or vaporized by the cathode from being deposited on the light-emitting window.
DE 10 2014 105 028 A1 discloses a deuterium lamp with a gas-filled lamp bulb which surrounds an electrode insert. The electrode insert comprises a diaphragm between anode and cathode and a housing partition wall made of ceramic. The cathode, a cathode window and a light emission window are arranged on one side of the housing partition wall, and the anode is arranged on the other side.
As a result of the multiple diaphragms, known gas discharge lamps have a comparatively high radiance. However, their electrode inserts are composed of a plurality of individual components. During assembly and adjustment of these components, distances and orientation in relation to one another and in relation to the optical axis must be maintained exactly and reproducibly, which is particularly problematic when the components have to be positioned by means of retaining rods and welded connections. Especially in the case of strict demands on the dimensional accuracy and precision of the gas discharge lamps, the manufacturing effort in terms of duration and costs as well as the reject rate is high.
It is thus the object of the invention to provide a gas discharge lamp having a high radiance, which is characterized by a simple structural design and at the same time good ignition and low arc voltage.
This object is achieved by a gas discharge lamp, in particular a deuterium lamp, a gas-filled lamp bulb which surrounds an electrode insert with the features of claim 1. The electrode insert comprises:
The electrode insert is the component group which generates the light of the arc discharge between anode and cathode and emits it through the light emission window onto the lamp bulb of the discharge lamp. The electrode insert comprises a partition wall made of an electrically insulating material, such as, for example, ceramic and in particular aluminum oxide ceramic. On its one wall side (referred to here as “front side”), the partition wall carries a cathode-side assembly and on the other wall side (here referred to as “rear side”) carries an anode-side assembly.
The anode-side assembly comprises the anode and at least one diaphragm, preferably at least two diaphragms. Optionally, the diaphragms are spaced apart from one another and electrically insulated from one another, so that each of the diaphragm openings leads to a constriction of the arc discharge and causes the formation of a plasma ball and a “halo” in front of and behind the diaphragm opening. This creates additional radiance.
At least the diaphragm and the anode are combined to form a common component ensemble, preferably a stacked component ensemble, which is also referred to below as a “component stack”.
A retaining profile for retaining the component ensemble projects from the rear side of the partition wall. The retaining profile is, for example, at a right angle to the partition wall rear side. It is preferably an integral component of the partition wall or is connected directly or indirectly to the partition wall via an intermediate element. The retaining profile consists of a single retaining element, for example a cylindrical or conical profile element, or is composed of a plurality of retaining elements, for example a plurality of cylindrical and/or conical profile elements. These are distributed, for example, over the rear side of the partition wall in such a way that they define a receiving space around the optical axis that is laterally more or less closed, which serves to accommodate the component ensemble. This receiving space has, for example, a cylindrical internal geometry, but it can also widen conically from the rear side at least over a part of its extension length. The walls of the profile elements facing the receiving space can be straight in plan view or they can be curved, preferably they have, in plan view, a U-shaped, V-shaped, C-shaped or horseshoe-shaped cross-section, for example. In a particularly preferred embodiment, the retaining profile comprises at least two tube-shell-shaped profile parts which are arranged around the optical axis with their open sides opposite one another.
The component ensemble is accommodated in the retaining profile or on the retaining profile. Apart from the at least one diaphragm and the anode, the component ensemble may comprise other components, such as at least one further diaphragm and spacer elements or insulating elements. All components of the ensemble can be connected to one another in a force-fitting, friction-fitting or form-fitting manner, so that the component ensemble as a whole is retained in or on the retaining profile. For this reason individual components of the ensemble, in particular of the stack, need not be retained separately. This already facilitates the installation of the electrode insert.
In the case of a stacked component ensemble, these components generally have a disk or ring shape and, by being placed above or next to each other, form an essentially cylindrical component stack with plane-parallel contact surfaces. Pressing the contact surfaces against one another creates a friction-fitting or force-fitting connection. This arrangement of the components simplifies assembly and increases the accuracy of positioning the components relative to one another.
When the at least one diaphragm is designed as an electrically active component with a separately adjustable electrical potential, a particularly simple electrical contacting is facilitated if at least one of the diaphragms, preferably the foremost diaphragm, has a contact for an electrical connection pin.
The contact is preferably designed as a socket for receiving the connection pin, for example with elastic deformable walls which resiliently encompass and fasten the connection pin.
In the case of a component ensemble designed as a component stack, as regards the interplay of the component stack and the retaining profile, an embodiment is preferred in which the component stack has a stack height and a stack circumference and the retaining profile at least partially encloses the stack circumference over the stack height.
The retaining profile projecting from the partition wall rear side consists of one profile element or a plurality of profile elements distributed around the optical axis which define a space around the optical axis which serves to receive the component stack. The space is closed laterally or is more or less open laterally. The height of this space is determined by the length of the profile elements, i.e. by the distance of the free end of the shortest retaining profile from the partition wall rear side. This height is greater than the stack height, so that the component stack can be completely accommodated in the retaining profile receptacle.
It proves advantageous here if the component stack comprises a spring element which is designed to press the component stack against the partition wall.
The spring element exerts a compressive force in the direction of a component-stack center axis. As a result of the pressure of the spring element, all components of the stack which are located between the partition wall rear side and the spring element are pressed against one another, and thus fixed both in their axial position and in their radial position by friction- or force-fitting connection.
Installation by means of a spring element, for example a spring washer or a spring clip, moreover has the advantage that it can be implemented quickly and easily.
The spring element thus contributes to the simplification of assembly and to the reproducibility of component positioning. It is usually—but not necessarily—the outermost component of the component stack. It rests against an abutment which is located outside the component stack, for example on a retaining bracket.
In a preferred embodiment of the gas discharge lamp, the component ensemble comprises insulating elements and at least one spacing compensation element.
The insulating elements are used, on the one hand, for the electrical insulation of the diaphragms from one another or from other components which are at a different electric potential. On the other hand, they enable—due to their thickness alone—an exact adjustment of the desired distance between adjacent diaphragms.
The spacing compensation element serves to set a prespecified height of the component stack.
In the case of the component ensemble explained above, at least one disk-shaped diaphragm, preferably two or more disk-shaped diaphragms and the anode and also other components are combined to form a component stack. This component stack, regardless of how it is retained, the arrangement of the components of the ensemble with respect to one another and any advantageous embodiments of individual components, represents an invention which can be used in a gas discharge lamp.
In the case of a component ensemble that is at least partially enclosed laterally within a receptacle of the retaining profile, there may be a certain mechanical play in the retaining profile receptacle. However, in particular, the diaphragm opening or the diaphragm openings should lie as exactly as possible on the optical axis. In order to improve the radial positioning of the individual diaphragm or the axial alignment of the diaphragms in the component stack, at least one of the diaphragms has—preferably all of the diaphragms have—spring elements which are supported, for example, on the retaining profile in a preferred embodiment.
The spring elements are ideally integral components of the diaphragm. They can be produced, for example, by cutting more or less peripherally into the diaphragm material on two opposite sides of the diaphragm starting from the diaphragm edge, as a result of which an elongate bracket is formed at the diaphragm edge, which remains connected to the remaining diaphragm material and which is elastically deformable within the bounds of the kerf width.
Optionally, the at least one diaphragm is designed as a diaphragm disk, wherein the integral spring elements are designed by flexible brackets created by peripheral disk-edge incisions on opposite sides of the diaphragm disk.
Optionally, abutments on which the spring elements are supported are assigned in the retaining profile receptacle. The spring force generated as a result of the elastic deformation is absorbed by another contact point which is located on the opposite side of the receptacle as seen in the direction of force. Overall, the two spring elements for the diaphragm result in four defined contact points within the retaining profile receptacle and thus a reproducible and exact four-point mounting of the diaphragm in the receptacle. This contributes to a simple assembly and precise adjustment of the diaphragm openings in the optical axis.
In embodiments of the component ensembles with a plurality of disk-shaped diaphragms and when using the diaphragms with other disk-shaped components in a component stack, all diaphragms are preferably equipped with such spring elements. As a result, the diaphragm openings of the diaphragms arranged axially spaced apart from one another and each mounted in the receptacle by means of a four-point mounting are aligned on the optical axis\. By pressing the flat sides of the disk-shaped components of the stack, a joining connection of the components of the stack is also achieved solely by frictional connection (=non-positive connection) and thus an exact positioning of the component stack overall.
Regardless of the manner of its arrangement in a component stack or other possible advantageous embodiments of the diaphragm, the above-explained embodiment of the diaphragm with integral spring elements represents an invention which can be used in a gas discharge lamp.
In a further preferred embodiment of the gas discharge lamp, a mounting plate is arranged on the rear side of the partition wall, which mounting plate is provided with through-holes through which connection elements for establishing an electrical connection to the cathode-side assembly and to the anode-side assembly extend.
The partition wall and the mounting plate are preferably designed as one piece. The mounting plate projects, for example, at a right angle from the partition wall rear side.
Electrical connections to the cathode-side assembly and to the anode-side assembly are guided through the through-holes of the mounting plate. This allows electrical potentials at the anode, cathode and other components, such as a diaphragm, to be adjusted by connecting to a voltage source outside the lamp bulb.
In addition, retaining rods which serve for fastening the electrode insert in the lamp bulb can engage in the mounting plate.
In addition, the mounting plate can be connected to a hollow mounting base which in the installed state extends in the direction of a lamp foot of the gas discharge lamp.
The mounting base preferably consists of ceramic and can serve for additional mounting of the electrode insert on the lamp foot of the lamp bulb. Since the mounting base is hollow on the inside, electrical connection pins or lines and/or retaining rods can also be guided through electrically insulated from one another.
The partition wall, the mounting plate and the mounting base are preferably designed as one piece. This avoids component gaps which can lead to electrical flashovers during ignition of the discharge.
In a particularly preferred embodiment of the gas discharge lamp, the anode-side assembly comprises an anode housing which surrounds the retaining profile and a component stack retained thereon, and the cathode-side assembly comprises a cathode housing for receiving the cathode.
The additional enclosure of the assemblies shields the discharge arc from the environment, prevents parasitic secondary discharges and thus supports the routing of the discharge arc through the diaphragm opening
In particular with regard to a simple and accurate assembly of the gas discharge lamp, it has proven to be particularly advantageous if the cathode housing is composed of a plurality of molded parts which are connected to one another by means of a plug-in connection, in particular an interlocking connection consisting of insertion tab and slot.
If the cathode housing has bendable insertion tabs which correspond to longitudinal slots in the partition wall this will also contribute to the simple and dimensionally accurate assembly of the gas discharge lamp.
The assembly process for fastening the cathode housing to the partition wall comprises inserting the insertion tabs through the longitudinal slots and bending over the insertion tabs.
The anode housing is preferably provided with longitudinal slots which, in the installed state, extend coaxially with the longitudinal slots of the partition wall. As a result, during the assembly of the cathode housing the anode housing can also be mounted on the partition wall in one operation by inserting the plug-in tabs not only through the longitudinal slots of the partition wall but also through the longitudinal slots of the anode housing and bending them over. In this embodiment of the gas discharge lamp, three components, namely the partition wall, the anode housing and the cathode housing, are connected to one another simultaneously and with dimensionally accurate positioning by means of the interlocking connection of insert tab and slot.
In a particularly preferred embodiment of the gas discharge lamp, this comprises a glass foot plate, mounted in the lamp bulb, on which a plurality of retaining rods and a plurality of electrical connection pins are mounted, wherein the foot plate, the retaining rods and the connection pins form a prefabricated assembly which are electrically and mechanically connected to the electrode insert. The mounting plate is preferably locked on the retaining rods by widening the retaining rod regions directly above and/or below the mounting plate. Additionally or alternatively, the locking is effected above the mounting plate by slitting the upper retaining rod end and bending over the slit ends.
The invention is explained in more detail below with reference to an exemplary embodiment and a patent drawing. The following are shown in detail:
The directional cross drawn above the exploded view of the electrode insert according to
The central component of the electrode insert 1 is a ceramic partition wall 2 serving as a carrier assembly for a plurality of components. From the rear side 21 of the ceramic partition wall 2, two structurally identical, substantially cylindrical, and in plan view C-shaped retainers 3 project vertically, which are face one another with their open C-sides and which are also referred to below as “C-towers” 3. The C-towers 3 define an essentially cylindrical intermediate space extending coaxially with the optical axis 11. This serves to receive and retain a stack of a plurality of components arranged one after the other, which overall is assigned the reference number 4, and which is also referred to below as a “diaphragm stack”. In the exemplary embodiment, the substantially cylindrical intermediate space has an almost circular cross-section with a minimum inner diameter of 8 mm.
A plurality of diaphragms are combined in the diaphragm stack 4; in the exemplary embodiment, there are three diaphragms 51, 52, 53 made of molybdenum, which are separated and electrically insulated from one another by spacer rings 61, 62 made of ceramic. Adjoining to the rear is an anode 7, bounded on both sides by ceramic disks 81, 82, with central hole 7a and connection tabs 7b. The diaphragm stack 4 is outwardly completed by a spring washer 9. For fastening the diaphragm stack 4 between the C-towers 3, a retaining bracket 10 made of molybdenum is used, which is guided through holes 10a in the C-towers 3. It serves as an abutment for the spring washer 9, which by its spring force presses the diaphragm stack 4 forwards in the direction of the ceramic partition wall rear side 21. The spacer rings 61, 62 and the ceramic disks 81, 82 are circular and have a diameter of 7.9 mm. Any regions of the other components 51, 52, 53, 7, 9 projecting beyond the circular shape extend through a free gap between the two C-towers 3, thus likewise fitting into the intermediate space; they are used to support the alignment of the components during assembly and contribute to protecting against rotation.
The diaphragms 51, 52, 53 each have a diaphragm hole 51a, 52a, 53a with a diameter of 0.3 mm, wherein the center points of the diaphragm holes 51a, 52a, 53a lie on the optical axis 11. The foremost diaphragm 51 is also provided with contact legs 51c for receiving an electrical connection pin (26), via which an additional auxiliary ignition pulse can be applied to the foremost diaphragm 51. Otherwise, it is the task of the diaphragms 51, 52, 53 to constrict the plasma of the deuterium lamp and thus to produce a plasma with high local radiance, said plasma being precisely localized.
The diaphragms 51, 52, 53 each have two elastically resilient, integral brackets, which are produced by a lateral peripheral incision in the diaphragm edge, and which are referred to below as “spring legs” 51b, 52b, 53b. In the installed state, the spring legs 51b, 52b, 53b exert a force directed in the direction perpendicular to the optical axis 11 onto the diaphragms 51, 52, 53 and press them against two contact beads 31 in the upper half of the C-towers 3. The two spring legs 51b, 52b, 53b support themselves against two other contact beads 32 in the lower half of the C-towers 3, so that all diaphragms 51, 52, 53 are retained between the C-towers 3 with a total of four contact points (four-point mounting). The two contact beads 31 in the upper half of the C-towers 3 lie on the same radius starting from the optical axis 10. This ensures a centering of all diaphragms 51, 52, 53 of the diaphragm stack 4 on the optical axis 11 of the deuterium lamp without further aids, which is important for an optimal radiance of the deuterium lamp.
The diaphragms 51, 52, 53 of the diaphragm stack 4 aligned on the optical axis 11 of the deuterium lamp form a channel on the projection of the optical axis 11, the diameter of which channel corresponds to that of the individual diaphragm holes 51a, 52a, 53a. The disadvantage of a correspondingly long individual channel in relation to ignition behavior is avoided by the separation of the diaphragms 51, 52, 53 by means of the ceramic spacer rings 61, 62.
The diaphragms have thicknesses in the range of 0.1 to 1 mm; in the exemplary embodiment it is 0.5 mm. The ceramic spacer rings 61, 62 determine the diaphragm spacing and have thicknesses in the range of 0.1 to 1 mm; in the exemplary embodiment, it is 0.25 mm. The front ceramic disk 81 is arranged behind the last diaphragm 53 and has a thickness in the range of 0.1 to 1 mm, in the exemplary embodiment it is 0.8 mm. The thickness of the rear ceramic disk 82 is designed such that a total length of 4 mm results for the diaphragm stack 4 (without spring washer 9 and retaining bracket 10). An electrical connection pin 26 (anode pin) is welded to the anode pin of the lamp foot at the connection tabs 7b of the anode 7.
During operation, the deuterium lamp heats up to an operating temperature above room temperature. The thickness of the spring washer 9 at 0.2 mm and its bending radius at 6 mm are designed such that, on the one hand, the components in the component stack 4 cannot slip and that, on the other hand, the thermal expansion of the component stack 4 can be compensated during operation of the deuterium lamp. Despite the absence of play, the spring-loaded mounting of the diaphragms 51, 52, 53 also enables a compensation for the different thermal expansions of ceramic (of the spacer disks and insulating disks) and molybdenum (of the diaphragms). The choice of molybdenum as the diaphragm material ensures a spring property over the entire temperature range.
Thickness and number of diaphragms and the diaphragm opening diameter influence the ignition behavior, the arc voltage and the radiance of the deuterium lamp. With increasing number and thickness of the diaphragms and decreasing diameter of the diaphragm opening, ignition of the lamp becomes more difficult and the arc voltage rises. The total length of the diaphragm channel is predetermined by the diaphragms 51, 52, 53 including the spacer disks 61, 62. For a defined total length of the diaphragm channel, it has proven to be more advantageous to use a plurality of thin diaphragms than a few thick diaphragms. In this case, ignition takes place more reliably and the arc voltage is lower. This was demonstrated in tests. The hole diameter of the diaphragms is usually less than 0.5 mm (in the exemplary embodiment it is 0.3 mm); a diaphragm thickness of 0.5 mm, a diaphragm spacing of 0.25 mm (thickness of the spacer disks 61, 62) and a diaphragm number of 3 result in a total channel length of 2.00 mm.
For plasma guidance, both the diaphragm stack 4 on the rear side 21 and the cathode on the front side 22 of the ceramic partition wall 2 are each enclosed by a housing 100, 200.
Insofar as the same reference numbers are used in
The metal front 201 is curved in a U-shape and has two rearwardly pointing tabs 201c, by means of which it is fastened to the front side 22 of the ceramic partition wall 2. Here, the two tabs 201c are inserted through two corresponding slots (reference numeral 2b in
On the rear side 21 of the partition wall 2, the diaphragm stack 4 together with the anode 7 is enclosed by an anode housing 100, the rear wall 101 of which has a hole 102 on the optical axis 11 and enables a combined use of the deuterium lamp according to the invention with an incandescent lamp. In this case, the light of the incandescent lamp radiates through the deuterium lamp (shine-through operation) in order to produce a combined UV/VIS spectrum. The anode housing 100 reduces secondary discharges, i.e. discharges which do not lead through the channel of the diaphragm stack 4. The anode housing 100 can be made of metal or ceramic. Preferably, it consists of metal in order to keep the weight and the costs of the deuterium lamp low.
For fastening to the partition wall 2, the anode housing 100 is provided with two laterally protruding wings 103, in each of which a longitudinal slot 103a extends from top to bottom. For fastening, the tabs 201c of the front assembly 200 are also inserted through these longitudinal slots 103a.
The design principle of inserting tabs through slots and then fastening them by bending enables a play-free mounting of the entire housing structure in a simple and cost-effective manner.
Integral components of the ceramic partition wall 2 are a mounting plate 23 pointing at right angles to the rear and a mounting base 24. For mounting the ceramic partition wall 2 on a foot plate 181 (shown in
For fastening, the free ends of the retaining pins 25 are crimped, welded, pinched or bent over. In particular by bending over above the mounting plate 23, a play-free mounting of the ceramic partition wall 2 against the lower support points on the foot plate 181 can be realized. This is important for the exact localization of the plasma in lamp operation.
In an alternative embodiment, the retaining pins 25 are pinched on the underside of the mounting plate 23 in order to produce support points here which define the height of the ceramic partition wall 3 above the foot plate 181. The support points are located on the retaining pins 25 directly below the mounting plate 23. They can either be crimped as sleeves onto the retaining pins or the retaining pins 25 themselves are pinched so that material projects beyond the actual diameter of the retaining pins 25, which serves as a bearing surface.
In a further alternative embodiment, the retaining pins 25 are not bent over on one side above the mounting plate 23, but are slit in the center and the slitted ends are bent symmetrically in two directions.
Further through-holes of the mounting plate 23 serve for the electrical contacting of the electrodes (anode, auxiliary anode and cathode (with two terminals)). For this purpose, electrical connection pins 26 extend on the one hand through the through-holes of the mounting plate 23 to the corresponding electrodes, and on the other hand right through through-holes of the foot plate to electrical connection elements of the deuterium lamp.
Further details can be seen from the views of the electrode insert 1 in
From the plan view of the retaining profile 3 with the foremost diaphragm 51 inserted therein according to
The photograph of
The photograph of
The part (c) is a housing 700 for the anode-side assembly, and the part (d) is a housing 800 for the cathode-side assembly. For the purpose of mounting on the ceramic partition wall 72, the housing 700 is provided with a double slot 701, and the housing 800 is provided with a double tab 801. For this purpose, the ceramic partition wall 72 likewise has a suitable double slot 72a.
The sketch of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 128 643.0 | Oct 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/074290 | 9/2/2021 | WO |
