FIG. 1 shows a schematic sectional view of a lamp tube of a high-intensity discharge lamp (UHP lamp) comprising an electrode arrangement.
FIG. 2 shows a schematic sectional view of one embodiment of an electrode according to the invention.
FIG. 3 shows a schematic sectional view of an alternative embodiment (compared to FIG. 2) of an electrode according to the invention.
FIG. 4 shows a schematic sectional view of a further embodiment of an electrode according to the invention.
FIG. 5 shows a schematic sectional view of an electrode according to the invention which comprises a material reservoir.
FIG. 1 schematically shows a sectional view of a lamp tube 1 with a discharge space 2 of a high-intensity discharge lamp (UHP lamp) known from the prior art. The lamp tube 1, which is made in one piece and is usually made of quartz glass and hermetically seals a discharge space 2 filled with a conventional gas, comprises two cylindrical regions of the seals 9, 10 which lie opposite another and between which there is an essentially spherical region having a diameter of approximately 10 mm. The electrode arrangement comprises essentially a first electrode 3 and a second electrode 4, between the opposite electrode heads 7, 8 of which an arc discharge is produced in the discharge space 2, wherein the arc serves as the light source of the high-intensity discharge lamp. The other ends of the electrodes 3, 4, that is to say the electrode bases 5, 6, are connected to the molybdenum wires 13, 14 via the molybdenum tapes 11, 12. The molybdenum wires 13, 14 are also connected to the electrical terminals of the lamp (not shown in FIG. 1), via which the supply voltage required to operate the lamp is fed by a power supply, possibly with a ballast, designed for a general mains voltage.
The electrodes 3, 4 mainly consist of a tungsten material, are of cylindrical shape and are approximately 4 to 8 mm long, and the electrode bases 5, 6 have a diameter of approximately 0.3 to 0.7 mm.
FIG. 2 shows one embodiment of an electrode 3 according to the invention. The electrode base 5 is shaped as a hollow cylinder, wherein its outer diameter is approximately 0.6 mm and its inner diameter is approximately 0.3 mm. The electrode base 5 consists of a tungsten material produced by means of a powder metallurgy process, so that the electrode base 5 has a lower density than the electrode head 7. This tungsten material of the electrode base 5 may be produced for example in a conventional sintering process from tungsten powder having a particle size of approximately 0.4 to 30 μm, wherein the shape of a hollow cylinder is achieved by extrusion. One end of the electrode base 5 is fixedly connected to the electrode head 7, which electrode head is solid and made of tungsten and is of cylindrical shape. In order to cool the electrode 3, a tungsten wire 15 is wound tightly around the electrode 3 a number of times in a known manner.
At least one such electrode according to the invention can be used in high-intensity discharge lamps, in particular UHP lamps, which can be used in a system for projection purposes.
FIG. 3 shows an alternative embodiment to FIG. 2, wherein this once again has the above-described electrode base 5 and a different electrode head 7. This electrode head 7 is spherical and solid and made of tungsten.
The electrode head 7 may be designed and produced for example in accordance with U.S. Pat. No. 6,552,499 B2.
FIG. 4 shows a further embodiment of an electrode 3 according to the invention. The electrode 3 has an electrode base 5 and a solid electrode head 7, wherein at least one element 16 which limits the heat flow in the electrode base is arranged between the electrode head 7 and the electrode base 5. The electrode base 5 and the electrode head 7 are fixedly connected to one another by the element 16, wherein they do not directly touch one another. The element 16, which in this case is a cooling element, is shaped as a hollow cylinder and consists of a tungsten material produced by means of a powder metallurgy process, so that the cooling element has a lower density than the electrode head 7.
The cooling element could alternatively be a wound wire which is fixedly connected to the electrode base 5 and the electrode head 7 and ensures the necessary mechanical stability of the electrode 3.
The electrode base 5 may be solid or hollow, or have at least one region which has a lower thermal conductivity than the electrode head 7.
This electrode head 7 may be cylindrical or spherical and preferably consists of solid tungsten.
FIG. 5 shows in a schematic sectional view an electrode 3 according to the invention which comprises a material reservoir 17 in the region of the electrode base 5.
The electrode 3 is in principle designed in the same way as shown in FIG. 4, but additionally has at least one material reservoir 17. This material reservoir 17 in the form of a cross-sectional expansion or an additionally arranged cylindrical body (component) is arranged in (FIG. 5.1) or on (FIG. 5.2) the region of the electrode base 5 which is subject to increased material removal during operation of the lamp.
Patent Application
20080093970
