Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/04—Electrodes; Screens; Shields
  • H01J61/06—Main electrodes
  • H01J61/073—Main electrodes for high-pressure discharge lamps
  • H01J61/0732—Main electrodes for high-pressure discharge lamps characterised by the construction of the electrode
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/36—Seals between parts of vessels; Seals for leading-in conductors; Leading-in conductors

Definitions

• the invention relates to an electrode for a discharge lamp according to the preamble of claim 1 and a discharge lamp with such electrodes.
• Such an electrode and a discharge lamp with such an electrode are disclosed, for example, in the published patent application WO 03/060947 A2.
• This document describes a two-part electrode with a cylindrical shaft and a cylindrical head, wherein the shaft and the head of the electrode have different diameters and / or consist of different materials.
• This electrode is used in a high-pressure discharge lamp for vehicle headlights.
• the electrode according to the invention has an elongated shaft and a head which is arranged at one end of the shaft, the shaft being flattened according to the invention, so that its dimensions transverse to its longitudinal extent are at most as large as the corresponding transverse dimensions of the head.
• the flattened shaft is easier to weld with other metal parts, especially with molybdenum melting foils, because there is a larger o surface for the welded connection is available.
• the shaft has a lower mass than the head part and thus also a correspondingly lower heat capacity, so that only a comparatively small amount of energy in the form of heat is dissipated from the discharge via the shaft in the form of heat.
• the electrode according to the invention is advantageously only flattened on one side or on two opposite sides.
• the electrode is flattened in the region of the shaft by machining material, preferably by milling or grinding, or by evaporation of material, preferably by laser.
• machining material preferably by milling or grinding
• evaporation of material preferably by laser.
• the electrode according to the invention can also be formed in one piece in the region of the shaft and head, and therefore in particular no welding between the shaft and head is required.
• the electrode according to the invention has improved mechanical stability compared to a multi-part electrode.
• the transition from the head to the shaft of the electrode according to the invention is advantageously made as moderately as possible.
• the transition is preferably carried out by means of a radius, the value of which is preferably in a range from 0.3 mm to 0.5 mm.
• the electrode according to the invention is preferably used as a gas discharge electrode for discharge lamps, in particular high-pressure discharge lamps with a discharge vessel made of quartz glass, which is provided with molybdenum foil seals.
• the dimension of the shaft of the electrode according to the invention preferably has a value in the range from 50 ⁇ m to 350 ⁇ m along a first spatial direction oriented transverse to the longitudinal direction of the electrode and has a second spatial direction oriented perpendicular to the longitudinal direction of the electrode and perpendicular to the first spatial direction is a value in the range from 200 ⁇ m to 450 ⁇ m.
• Such electrodes are suitable for use in metal halide high-pressure discharge lamps for motor vehicle headlights, which have a comparatively se have a low power consumption of approx.
• the electrode according to the invention preferably consists of tungsten, a tungsten alloy or tungsten provided with dopants in order to be able to withstand the high temperatures of a gas discharge in a high-pressure discharge lamp.
• the electrode according to the invention is preferably designed as a pin electrode.
• the head of the electrode can be provided with a helix in order to increase the heat capacity of the head.
• the entire shaft or a section of the shaft of the electrode according to the invention can be coated with ruthenium in order to reduce the risk of cracks or cracks occurring in the region of the discharge vessel in which the shaft of the electrode is closely embedded in the discharge vessel material.
• Figure 1 is a side view of an electrode according to the first embodiment of the invention and a molybdenum foil welded to it in a schematic representation
• FIG. 2 A second side view of the electrode and molybdenum foil shown in FIG. 1 in a view rotated by an angle of 90 degrees around the longitudinal axis of the electrode compared to FIG. 1
• Figure 3 is a plan view of the face of the shaft of the electrode shown in Figure 1
• FIG. 4 shows a side view of an electrode according to the second exemplary embodiment of the invention and a molybdenum foil welded to it in a schematic representation
• FIG. 5 A second side view of the electrode and molybdenum foil shown in FIG. 4 in a view rotated by an angle of 90 degrees around the longitudinal axis of the electrode compared to FIG. 4
• Figure 6 is a side view of an electrode according to a third embodiment of the invention in a schematic representation
• FIG. 7 shows a side view of a high-pressure discharge lamp with the electrodes according to the invention
• the electrodes shown schematically in FIGS. 1 to 6 according to the preferred exemplary embodiments of the invention are intended for use in the high-pressure metal halide discharge lamp shown schematically in FIG.
• the electrode 11 according to the first exemplary embodiment of the invention is designed as a one-piece pin or rod and consists of tungsten, which may have small amounts of the usual dopants, which are either advantageous for processing the tungsten into rods, or which, like in the case of, for example, thorium oxide, improve the ignitability of the high-pressure discharge lamp.
• the electrode 11 has a shaft 11a and a head 11b.
• the head 1 Ib is circular-cylindrical. It has a diameter of 0.35 mm. Its length is 1.2 mm.
• the shaft 11a has a length of 6.3 mm, so that the total length of the one-piece electrode 11 measures a total of 7.5 mm.
• the shaft Ua is welded to a molybdenum foil 103, which is used to seal the discharge vessel 10 of the high-pressure discharge lamp shown in FIG. 7.
• the shaft 11a is flattened on two opposite sides, so that its transverse dimension perpendicular to the molybdenum foil 103 is only 0.20 mm and is therefore smaller than the diameter of the head 11b.
• the transverse dimension of the shaft I Ia parallel to the molybdenum foil 103 is 0.35 mm, which corresponds to the diameter of the head I Ib.
• a tungsten rod is used to produce the electrode 11, the transverse dimension of which in the region of the shaft 11a is adjusted to the desired value by mechanical material removal on two sides, preferably by milling or grinding.
• the electrode 11 in the area of the shaft 11a has an oval or rectangular cross section.
• the surfaces of the shaft 11a resulting from the flattening are particularly well suited for welding to the molybdenum foil 103.
• a simplification of the manufacturing process of the electrodes according to the invention can be achieved in that the electrode in the region of the shaft is flattened only on one side instead of on two sides, as is disclosed in the second exemplary embodiment of the invention and in FIGS. 4 and 5.
• the electrode 11 'according to the second exemplary embodiment likewise consists of tungsten and has an overall length of 7.5 mm. Its circular cylindrical head I Ib 'has a diameter of 0.35 mm and a length of 1.0 mm.
• the shaft I Ia ' has a length of 7.5 mm and its transverse dimension perpendicular to the molybdenum foil 103 is 0.20 mm, while its transverse dimension parallel to the molybdenum foil 103 corresponds to the diameter of the head I Ib'.
• the electrode 11 ' is also made from a circular cylindrical pin or rod with a uniform diameter of 0.35 mm.
• the surface of the shaft 11a 'created by the flattening of the electrode 11' in the region of the shaft 11a ' is welded to the molybdenum foil 103, which is used to seal the discharge vessel 10 of the high-pressure discharge lamp shown in FIG.
• the shaft 11a 'of the electrode 11' has an outline in cross section perpendicular to its longitudinal direction due to the flattening on one side, which is defined by a segment of a circle and a section designed as a chord, as shown schematically in FIG.
• the electrode 1 1 " according to the third embodiment of the invention consists of a bilaterally flattened tungsten rod I Ia" and a tungsten coil I Ib ", which is threaded onto one end of the tungsten rod I Ia" and the head I Ib "of the electrode 1 1" forms.
• the transverse dimension of the tungsten rod I Ia "perpendicular to its flattened surfaces is 0.20 mm. Its transverse dimension parallel to these surfaces is 0.35 mm.
• the tungsten rod I Ia" has an oval or rectangular cross section perpendicular to its longitudinal extent.
• the end of the electrode 11 "equipped with the filament 11b" after it has been installed in the discharge vessel 10 of the high-pressure discharge lamp forms the end of the electrode 11 "on the discharge side 11 "welded to the molybdenum foil 103.
• the high-pressure discharge lamp shown in FIG. 7 and described in more detail below has two identical electrodes which correspond to one of the exemplary embodiments of the electrodes 11, 11 'or 11 "according to the invention described in more detail above.
• the preferred embodiment of the invention is a mercury-free metal halide high-pressure discharge lamp with an electrical power consumption of approximately 35 watts.
• This lamp is intended for use in a vehicle headlight. It has a two-sided sealed discharge vessel 30 made of quartz glass with a volume of 24 mm 3 , in which an ionizable filling is enclosed gas-tight.
• the inner contour of the discharge vessel 30 is circular-cylindrical and its outer contour is ellipsoidal.
• the inside diameter of the discharge space 106 is 2.6 mm and its outside diameter is 6.3 mm.
• the two ends 101, 102 of the discharge vessel 10 are each sealed by means of a molybdenum foil 103, 104 melted or squeezed therein.
• the molybdenum foils 103, 104 each have a length of 6.5 mm, a width of 2 mm and a thickness of 25 ⁇ m.
• the electrodes 11, 12 of the same type which are designed in accordance with the above-described first, second or third exemplary embodiment of the electrodes 11, 11 'or 11''and between which the lamp is used during lamp operation Forms discharge arc responsible for light emission.
• the distance between the electrodes 11, 12 is 4.1 mm.
• the electrodes 11, 12 are each electrically conductively connected to an electrical connection of the lamp base 15, which is essentially made of plastic, via one of the molybdenum foils 103, 104 and via the current supply line 13 remote from the base or via the current return 14 on the base side.
• the overlap B between the electrode 11 and the molybdenum foil 103 connected to it is 1.3 mm + 0.15 mm.
• the discharge vessel 10 is enveloped by an outer bulb 16, which is made of quartz glass or hard glass.
• the quartz glass or hard glass of the outer bulb 16 is provided with the usual UV-absorbing additives.
• the outer bulb 16 has an extension 161 anchored in the base 15.
• the outer diameter of the outer bulb 16 is 9 mm and its wall thickness is 0.9 mm.
• the discharge vessel 10 has on the base side a tubular extension 105 made of quartz glass, in which the base-side power supply 14 runs.
• the electrodes 11, 12, the molybdenum foils 103, 104 and / or current leads 13, 14 can be coated with ruthenium in the region of the sealed ends 101, 102 of the discharge vessel 10.
• the ionizable filling enclosed in the discharge vessel consists of xenon with a cold filling pressure of 11,800 hPa, 0.25 mg sodium iodide, 0.18 mg scandium iodide, 0.03 mg zinc iodide and 0.0024 mg indium iodide.
• the operating voltage U of the lamp is 45 volts.

Landscapes

• Discharge Lamp (AREA)
• Vessels And Coating Films For Discharge Lamps (AREA)
• Circuit Arrangements For Discharge Lamps (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34970339

Family Applications (1)

Country Status (5)

Families Citing this family (2)

Family Cites Families (8)

• 2004
  • 2004-06-15 DE DE102004028562A patent/DE102004028562A1/de not_active Withdrawn
• 2005
  • 2005-05-19 WO PCT/DE2005/000921 patent/WO2005124822A1/fr active Application Filing
  • 2005-05-19 AT AT05752440T patent/ATE435501T1/de not_active IP Right Cessation
  • 2005-05-19 DE DE502005007626T patent/DE502005007626D1/de active Active
  • 2005-05-19 EP EP05752440A patent/EP1756853B1/fr not_active Not-in-force
  • 2005-05-19 US US11/596,572 patent/US20070228981A1/en not_active Abandoned

Non-Patent Citations (1)

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