EP0907961B1 - Lampe a mercure a basse pression - Google Patents

Lampe a mercure a basse pression Download PDF

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Publication number
EP0907961B1
EP0907961B1 EP98903250A EP98903250A EP0907961B1 EP 0907961 B1 EP0907961 B1 EP 0907961B1 EP 98903250 A EP98903250 A EP 98903250A EP 98903250 A EP98903250 A EP 98903250A EP 0907961 B1 EP0907961 B1 EP 0907961B1
Authority
EP
European Patent Office
Prior art keywords
screen
electrodes
low
pressure mercury
lamp
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP98903250A
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German (de)
English (en)
Other versions
EP0907961A1 (fr
Inventor
Wilhelmus Maria Petrus Van Kemenade
Pieter Joseph Clara Van Der Wel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
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Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Priority to EP98903250A priority Critical patent/EP0907961B1/fr
Publication of EP0907961A1 publication Critical patent/EP0907961A1/fr
Application granted granted Critical
Publication of EP0907961B1 publication Critical patent/EP0907961B1/fr
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/30—Vessels; Containers
    • H01J61/35—Vessels; Containers provided with coatings on the walls thereof; Selection of materials for the coatings
    • 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
    • H01J61/10—Shields, screens, or guides for influencing the discharge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/70—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr
    • H01J61/72—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr having a main light-emitting filling of easily vaporisable metal vapour, e.g. mercury

Definitions

  • the invention relates to a low-pressure mercury discharge lamp provided with a tubular discharge vessel having a tube axis and enclosing a discharge space containing a filling of mercury and one or several rare gases in a gastight manner, current supply conductors extending from outside the discharge vessel to electrodes arranged inside the discharge vessel, which electrodes each have a first and a second fastening, while at least one of said electrodes is surrounded by a screen which has a smallest width W, transverse to the direction from the first to the second fastening, and in a plane transverse to the tube axis, which width is smaller than a distance D between said fastenings.
  • Such a low-pressure mercury discharge lamp also referred to as lamp hereinafter, is known from US 4,891,551.
  • the discharge vessel has an electrode on either side in a commercially available lamp of this type.
  • Each of the electrodes is surrounded by a screen having a smallest width W of 7 mm and a length L of 5 mm.
  • the electrodes are fastened to their current supply conductors, the distance D between the first and the second fastening being 10 mm.
  • Such lamps may be integrated with a supply unit so as to form a lighting unit, or alternatively it may be possible for them to be detachably coupled to a supply unit.
  • a supply unit which ignites the lamp in the cold state is attractive on account of its simplicity. Moreover, the lamp emits light immediately in the case of cold ignition.
  • the low-pressure mercury discharge lamp is for this purpose characterized in that the screen has a length L, in the direction of the tube axis, which lies between once and three times the smallest width W.
  • the inventors have experimentally ascertained that a length L within said range results in a considerable decrease in the mercury consumption in the case of cold ignition. This is surprising, the more so as the length L of the screen was found to have no appreciable influence during nominal operation.
  • a possible explanation is the following: many metals, for example Ca, Sr, and Ba whose oxides are used in emitter materials for electrodes are capable of forming amalgams with mercury. Reduction of these oxides to the respective metals is found to take place in practice, for example during activation of the electrodes.
  • Zr which is often used as an additive in emitter material, also is an amalgam-forming metal. Mercury bound to such metals on the electrode is released again during lamp operation, when the electrodes are hot.
  • a practical embodiment of the low-pressure mercury discharge lamp according to the invention is characterized in that the ratio L/W of the screen lies between 1,2 and 2.5.
  • the reduction in the mercury consumption is comparatively limited for a ratio below 1.2.
  • For a ratio above 2.5 no appreciable further reduction in the mercury consumption is realized, while the screen darkens the discharge vessel locally.
  • the circumference of the screen is preferably at most four times the distance D.
  • each of the electrodes has a screen as described above.
  • the electrodes of the lamp according to the invention may each have only a single current supply conductor in the case of cold ignition.
  • the electrodes may have a first fastening to said current supply conductor and a second fastening to a wire fused into the wall of the discharge vessel.
  • the electrodes each have a first and a second current supply conductor, to which they have their respective first and second fastenings.
  • the electrodes may have additional fastenings between the first and the second fastening.
  • a favourable embodiment of the low-pressure mercury discharge lamp according to the invention is characterized in that the discharge vessel is provided with a protective layer at an inner surface.
  • a protective layer for example made from a metal oxide such as aluminum oxide or yttrium oxide, counteracts reactions between mercury and the discharge vessel wall. It also contributes to the maintenance of the luminous flux during lamp life.
  • the end portions of the discharge vessel may also be provided with a protective layer.
  • the discharge vessel may have a luminescent layer for converting UV radiation into visible radiation, for example in lamps for general lighting purposes, or for converting UV radiation into UV radiation of greater wavelength, for example in suntanning lamps.
  • a luminescent layer may be absent, for example in lamps for disinfection purposes.
  • Figs. I and 2 show a low-pressure mercury discharge lamp, here for general lighting purposes, provided with a tubular discharge vessel 10 having a tube axis 11.
  • the discharge vessel 10 has a length of 120 mm and an inner diameter of 25 mm.
  • the discharge vessel 10 encloses in a gastight manner a discharge space 12 which contains a filling of 1 mg mercury and a mixture of argon and krypton (25/75 vol%) with a filling pressure of 2 mbar.
  • Current supply conductors 20a, 20a', 20b, 20b' extend from outside the discharge vessel 10 through end portions 17a, 17b of the discharge vessel to a first and a second electrode 21a, 21b arranged in the discharge space.
  • the electrodes 21a, 21b each have a first current supply conductor 20a, 20b and a second current supply conductor 20a', 20b' to which they have respective first fastenings 22a, 22b and second fastenings 22a', 22b'.
  • the electrodes 21a, 21b are coated with an emitter material which comprises barium oxide, strontium oxide, and calcium oxide.
  • the electrodes 21a, 21b are each surrounded by a screen 23a, 23b, made of iron in the present case.
  • the screens 23a, 23b in the lamp shown, identified with "inv1" hereinafter, have a smallest width W of 7 mm transverse to the direction from the respective first 22a, 22b to the second fastening 22a', 22b' and in a plane transverse to the tube axis 11 and .
  • the smallest width W of the screens 23a, 23b is smaller than the distance D between the fastenings of the electrode, which is 10 mm.
  • the screens 23a, 23b have a circumference of 36 mm, which is less than four times the distance between the fastenings.
  • the screen 23a of the first electrode 21a has a length L of 15 mm in the direction of the tube axis 11, ie 2.14 times the smallest width W.
  • the length L thus lies between once and three times the smallest width W.
  • the ratio L/W lies between 1.2 and 2.5.
  • the length L of the screen 23b of the second electrode 21b is 5 mm.
  • the discharge vessel has a protective layer 14 of finely distributed aluminum oxide with a coating weight of 55 ⁇ g/cm 2 on its inner surface.
  • the aluminum oxide particles of the protective layer have a median diameter of approximately 0.013 ⁇ m, and a specific area of approximately 100 m 2 /g.
  • the protective layer 14 is provided directly on the inner surface 13 of the discharge vessel 10.
  • the protective layer is supported by a layer repelling alkali metals, for example made of silicon oxide.
  • a layer repelling alkali metals counteracts the migration of alkali metals, such as sodium, from the discharge vessel wall into the discharge space, where they will form amalgams with mercury, or lead to mercury consumption in some other way.
  • the protective layer 14 here supports a luminescent layer 16 with a coating weight of 1.8 mg/cm 2 which is composed of a mixture of green-luminescing cerium-magnesium aluminate activated by terbium, blue-luminescing barium-magnesium aluminate activated by bivalent europium, and red-luminescing yttrium oxide activated by trivalent europium.
  • the mercury consumption was measured for the lamp "inv1" according to the invention as described above, for a further lamp “inv2” according to the invention, and for a lamp “ref” not according to the invention.
  • Both electrodes in lamp inv2 have a screen of 10 mm length.
  • Both electrodes of lamp ref have a screen of 5 mm length.
  • the ratio L/W of the screens of the lamps inv2 and ref is accordingly 1.43 and 0.71, respectively.
  • the lamps inv2 and ref correspond to the lamp inv1 in all respects other than those mentioned.
  • the lamps were operated at high frequency by means of a supply unit which ignites in the cold state during the endurance test.
  • the lamps were switched on for 15 min and off for 5 min periodically during this.
  • the mercury consumption as a function of the number of switching-on operations was ascertained by the method described in EP 725 977, the displacement of free mercury during DC operation being measured.
  • the remaining percentage by weight of free mercury (% Hg ) as a function of the number of cold ignition operations (N) is plotted in Fig. 3. It is apparent from Fig. 3 that the mercury present in the discharge space of lamp ref has been substantially used up after 3750 switching-on operations. A substantial portion of the mercury was still free for lamp operation at that moment in the lamps inv1 and inv2 according to the invention.
  • the lamps according to the invention were also found to consume comparatively little mercury compared with lamps not according to the invention in the case of dimmed operation, where the current through the discharge space is reduced.
  • the mercury consumption of lamps according to the invention and lamps not according to the invention is approximately the same during nominal operation.

Landscapes

  • Vessels And Coating Films For Discharge Lamps (AREA)

Abstract

L'invention concerne une lampe à mercure à basse pression comprenant une enceinte tubulaire (10) de décharge dotée d'un axe (11) de tube. L'enceinte (10) de décharge délimite un espace (12) de décharge étanche aux gaz. Des électrodes (21a, 21b) disposées dans cet espace comportent une première fixation (22a, 22b) et une seconde fixation (22a, 22b). L'une des électrodes (21a) est entourée d'un écran (23) d'une largeur minimale W, sur un plan transversal par rapport à l'axe (11) du tube et transversal par rapport à l'axe joignant la première fixation (22a) à la seconde fixation (22a), et dont la largeur est inférieure à la distance D qui sépare les fixations (22a, 22a'). L'écran (23a) est caractérisé par une longueur L, dans le sens de l'axe (11) de tube, égale à trois fois la largeur W minimale. La lampe consomme relativement peu de mercure dans le cas d'un allumage basse température.

Claims (5)

  1. Lampe à décharge dans la vapeur de mercure à basse pression munie d'une enceinte à décharge tubulaire (10) présentant un axe de tube (11) et enfermant un espace à décharge (12) contenant d'une façon étanche au gaz un remplissage de mercure et d'un ou plusieurs gaz rares, des entrées d'alimentation de courant (20a, 20a', 20b, 20 b') s'étendant à partir de extérieur de l'enceinte à décharge à des électrodes (21a, 21b) disposées jusque dans l'enceinte à décharge, lesquelles électrodes présentent chacune une première fixation (22a, 22b) et une deuxième fixation (22a', 22b'), alors qu'au moins l'une desdites électrodes (2 la) est entourée d'un écran (23a) qui présente une largeur minimale W transversale par rapport à la direction à partir de la première fixation à la deuxième fixation et dans un plan transversal à l'axe de tube et, laquelle largeur est inférieure à une distance D comprise entre lesdites fixations, caractérisée en ce que dans la direction de l'axe de tube, l'écran (23a) présente une longueur L, qui se situe entre une et trois fois la largeur minimale W.
  2. Lampe à décharge dans la vapeur de mercure à basse pression selon la revendication 1, caractérisée en ce que le rapport L/W de l'écran (23a) se situe entre 1.2 et 2.5.
  3. Lampe à décharge dans la vapeur de mercure à basse pression selon la revendication 1 ou 2, caractérisée en ce que la circonférence de l'écran (23a) est égale à au moins quatre fois la distance D.
  4. Lampe à décharge dans la vapeur de mercure à basse pression selon l'une des revendications 1, 2 ou 3, caractérisée en ce que chacune des électrodes est munie d'un écran comme défini dans la revendication en question.
  5. Lampe à décharge dans la vapeur de mercure à basse pression selon l'une des revendications précédentes, caractérisée en ce que l'enceinte à décharge (10) est munie d'une couche protectrice (14) appliquée à une surface intérieure (13).
EP98903250A 1997-03-27 1998-03-02 Lampe a mercure a basse pression Expired - Lifetime EP0907961B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP98903250A EP0907961B1 (fr) 1997-03-27 1998-03-02 Lampe a mercure a basse pression

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP97200921 1997-03-27
EP97200921 1997-03-27
EP98903250A EP0907961B1 (fr) 1997-03-27 1998-03-02 Lampe a mercure a basse pression
PCT/IB1998/000265 WO1998044537A1 (fr) 1997-03-27 1998-03-02 Lampe a mercure a basse pression

Publications (2)

Publication Number Publication Date
EP0907961A1 EP0907961A1 (fr) 1999-04-14
EP0907961B1 true EP0907961B1 (fr) 2002-08-07

Family

ID=26146294

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98903250A Expired - Lifetime EP0907961B1 (fr) 1997-03-27 1998-03-02 Lampe a mercure a basse pression

Country Status (2)

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EP (1) EP0907961B1 (fr)
WO (1) WO1998044537A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6534910B1 (en) 2000-09-06 2003-03-18 Koninklijke Philips Electronics N.V. VHO lamp with reduced mercury and improved brightness

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3549937A (en) * 1968-02-03 1970-12-22 Tokyo Shibaura Electric Co Low pressure mercury vapour discharge lamp including an alloy type getter coating
US4891551A (en) * 1988-05-31 1990-01-02 North American Philips Corporation Fluorescent lamp with grounded and fused electrode guard
DE19521972A1 (de) * 1995-06-16 1996-12-19 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Verfahren zur Herstellung eines Kappenbandes für Entladungslampen

Also Published As

Publication number Publication date
EP0907961A1 (fr) 1999-04-14
WO1998044537A1 (fr) 1998-10-08

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