EP0080820A2 - Entladungslampe - Google Patents

Entladungslampe Download PDF

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Publication number
EP0080820A2
EP0080820A2 EP82306041A EP82306041A EP0080820A2 EP 0080820 A2 EP0080820 A2 EP 0080820A2 EP 82306041 A EP82306041 A EP 82306041A EP 82306041 A EP82306041 A EP 82306041A EP 0080820 A2 EP0080820 A2 EP 0080820A2
Authority
EP
European Patent Office
Prior art keywords
lamp
dose
electrode
lamp according
wick
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.)
Withdrawn
Application number
EP82306041A
Other languages
English (en)
French (fr)
Other versions
EP0080820A3 (de
Inventor
Frank Lawrence Whittaker
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.)
Thorn EMI PLC
Original Assignee
Thorn EMI PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Thorn EMI PLC filed Critical Thorn EMI PLC
Publication of EP0080820A2 publication Critical patent/EP0080820A2/de
Publication of EP0080820A3 publication Critical patent/EP0080820A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J61/28—Means for producing, introducing, or replenishing gas or vapour during operation of the lamp
    • 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
    • H01J61/34—Double-wall vessels or containers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr

Definitions

  • the present invention relates to discharge lamps and is particularly, although not exclusively, related to high pressure discharge lamps such as high pressure sodium lamps and mercury lamps.
  • Discharge lamps comprise a sealed discharge or arc tube of a light transmitting material having electrodes at opposite ends and containing a fill comprising a dose of substances which emit light when a discharge is struck between the electrodes.
  • the dose may comprise: mercury; mercury with the addition of metal halides to improve the spectrum of the light emitted; a sodium/mercury amalgam in the case of high pressure sodium lamps or other more complex mixtures.
  • the fill also includes an inert gas to act as a starter for the discharge.
  • a high pressure discharge lamp including a light transmitting arc tube having, sealed into the ends thereof, electrodes each comprising at least an electrode shank and within the arc tube a dose suitable to be liquid at least in part at the working temperature of the lamp, the lamp further including a reservoir region adapted to collect the liquid dbse when the lamp is appropriately orientated and transfer means arranged to be in contact with the liquid dose when the lamp is appropriately orientated and constructed so that, in operation, at least part of the liquid dose is moved to a hotter part of the tube by the action of surface tension.
  • a high pressure discharge lamp including: a light-transmitting arc tube; two electrodes, each comprising at least an electrode shank sealed into opposing ends of the arc tube; within the arc tube a dose suitable to be liquid at least in part when the lamp is in operation; and transfer means disposed in the region of at least one of said electrode shanks and made of a material which will be wetted by the liquid dose at the operating temperature of the lamp so that in operation, with the lamp appropriately orientated, the transfer member is capable of moving some of the liquid dose to a hotter part of the lamp by the action of surface tension.
  • the device comprises a sealed container with a condensable vapour therein.
  • Capillary means transports the condensed vapour from a cooler region to a hotter region where it evaporates to be transferred to the cooler region by the vapour pressure gradient and there to condense.
  • a heat transfer cycle is set up.
  • the heat pipe shows that surface tension can be used to move liquids to regions of higher temperature, even against the force of gravity, and it is now proposed to use heat pipe technology in a new form of discharge lamp.
  • the electrodes In discharge lamps the electrodes generally comprise a metal, usually tungsten, electrode shank often overwound with a coil which may be impregnated with electron emitter.
  • wick A particularly convenient form of wick for this purpose is a braid of tungsten wire wrapped around the electrode shank.
  • Figure 1 shows a fused silica discharge tube 1, in this example of a type used in a 1000 watt mercury metal halide lamp, and having an internal volume of about 30cm 3 .
  • a conventional electrode at one end comprises a tungsten shank 2, which may optionally contain a small proportion of thorium, with a tungsten coil overwind 3. Electrical connection to the electrode is through a molybdenum foil 4 in a conventional pinch seal 5.
  • the electrode comprises a tungsten shank 6 surrounded by a tungsten wick 7. Electrical connection is also by a molybdenum foil 4 in a pinch seal 5.
  • the wick 7 extends down the shank 6 to the pinch and if the tube is_ operated vertically as shown in Figure 1 a liquid reservoir 8 of the dose forms.
  • wetting may be defined as the achievement of a wetting angle 6 defined by 0° ⁇ 0 ⁇ 90°.
  • a wick should be a material which will be wetted by a metal or metal compound dose at a temperature above the melting point x°C of the dose.
  • the temperature x should preferably be lower than 1000°C and for polycrystalline alumina arc tubes the temperature x should preferably be lower than 1100 C.
  • the wick 7 may take different forms suitable to transport the liquid dose by surface tension. It is considered that a wick of pore radius of about 0.1mm would suit a worst case of a liquid with the density of mercury.
  • a convenient form is a braided tungsten wire which is used as an electrode overwind in some forms of high pressure mercury fluorescent lamps. It is difficult to wind a braid directly on the electrode shank 6 as mandrel because of difficulties in cutting the ends and with the braid springing away from the mandrel. Moreover, multiple layers of braid are desirable.
  • the braid may however be wound in conventional manner on a molybdenum wire as mandrel, the mandrel being dissolved out and the braid fitted on to the electrode shank as a coiled coil. Alternatively, the molybdenum primary mandrel may be replaced by tungsten wire which is left in situ to strengthen the braid and reduce the pore size.
  • Sodium iodide is known as a dose in metal halide lamps but in such lamps the partial pressure of sodium is low because of the low vapour pressure of sodium iodide.
  • each tube was dosed with 3.67mg cm-3 of mercury and 3.Omg cm -3 anhydrous sodium iodide and 15 torr cold fill pressure of argon as a starter gas. This relatively high dose of sodium iodide was in part chosen to ensure the formation of a liquid pool.
  • the tubes were operated vertically at 1000 watts.
  • the capillary action can be made continuous by moving the cool spot nearer to the base of the wick.
  • One means of achieving this which may be used in some production lamps is to provide a close fitting silica sleeve around all but the bottom 5 to 20mm (but preferably the bottom 10mm) of the tube.
  • This is illustrated in Figure 4 in which a 30mm diameter silica tube 11 is fitted around the arc tube 1.
  • Such a tube should have an internal diameter such that a gap between 3 and 10mm (but preferably about 4mm) separates it from the arc tube on all sides.
  • a lamp such as A or B can be operated with a colour appearance similar to a high pressure sodium lamp.
  • Figure 5 shows such a lamp, based on the arc tube 1 of a 1000 watt mercury-metal halide lamp and with the outer silica tube 11, mounted in a conventional glass outer envelope 12. It is supported in the manner of a metal halide lamp by a metal framework and electrical connections in the conventional manner to an end cap in. this example a "Goliath Edison screw" (GES) cap 13.
  • This lamp may be started by a high frequency pulse applied externally to the arc tube.
  • Figure 5A shows a 1000W lamp similar to that of Figure 5 but having starting electrodes at both ends. This lamp is about 400mm long overall with a 90-95mm arc gap.
  • the sodium iodide vapour pressure given by the dose described hereinbefore is too great for a practical lamp, as evidenced by the instability which is typical of metal halide lamps with excessive halide vapour pressure and it is envisaged that the lamp of Figure 5 should have between one tenth and one half of that sodium iodide vapour pressure.
  • the vapour pressure can be reduced by employing the invention to a more limited extent : for example, by shortening the wick or using a larger effective pore radius.
  • mercury-metal halide lamps may be dosed with other halides, such as rare earth halides, which liquefy at typical arc tube temperatures but which have low vapour pressures.
  • the invention may be used with high pressure sodium lamps, enhancing the vapour pressure of other metals to modify the colour.
  • the invention is particularly advantageous for metal vapour lamps such as high pressure sodium since it is especially desirable to increase the vapour pressure of metals or their alloys to improve colour while many metal halides (as used in mercury-metal halide lamps of the prior art) have sufficiently high vapour pressures at the operating temperatures of arc tube envelopes.
  • the sodium may also be omitted, to give new types of high pressure metal vapour-mercury lamps. It should be noted that mercury is notoriously reluctant to wet wicks but better wetting of metal wicks can be obtained with amalgams than with pure mercury.
  • the invention may be used with horizontal burning lamps with suitable wick design.
  • This may be with a metallic or insulating wick along the tube wall or may be with a tube design as shown in Figure 6 in which the tube has the conventional electrodes at the ends and in the wall a depression 14 which may hold a reservoir of liquid 8 when it is at the bottom.
  • a wick 7 is placed in this depression to provide the required heat- pipe action.
  • Figure 7 shows a preferred arrangement for a polycrystalline alumina discharge tube 1 having an end plug 15, which is also of polycrystalline alumina.
  • a niobium tube 16 supporting an electrode shank 2 with a tungsten braid 18 serving both as overwind and as wick.
  • the end of the braid 18 nearest to the electrode top may optionally be impregnated with an electron emissive substance.
  • the end plug 15 is shaped to be concave and the niobium tube 16 is also positioned so as to provide a reservoir for the liquid dose 8. Gravitational forces thus assist in the creation of a liquid pool at the base of the wick.
  • Figure 8 shows a similar arrangement except that the end plug 19 is made of a ceramic-metal (cermet). Where, as in Figure 8 the cermet is electrically conducting, the tungsten shank of the electrode need not pass completely through the plug 19. A metal wire 17, preferably of doped molybdenum, is sintered into the exterior side of the plug, for electrical connection.
  • cermet ceramic-metal
  • Figure 9 shows a further alternative for an alumina arc tube in which the electrode shank 2 carries a braid wick 18 similar to those of Figures 7 and 8.
  • the electrode 2 is sintered into the boss of a conducting cermet end plug 20, which is sealed by a glass frit 21 to the polycrystalline alumina plug 15.
  • the lead wire 17 is preferably of molybdenum and can be brazed or, preferably, sintered into cap 20. For sintering it is preferable to use doped molybdenum which is more ductile.
  • Figure 10 shows how a wick in the form of a tungsten braid 18 may be fitted around an electrode shank 2 so that it might, when sealed into, for example, a fused silica tube, contact the reservoir of liquid dose.
  • a wick in the form of a tungsten braid 18 may be fitted around an electrode shank 2 so that it might, when sealed into, for example, a fused silica tube, contact the reservoir of liquid dose.
  • a conventional electrode overwind 3 is used. This comprises a primary coil overwound with a secondary coil.
  • Figure 11 is an alternative as used in Figure 7 in which the braid 18 extends over a longer part of the shank 2, without a separate conventional overwind.
  • Figure 12 shows the manner in which an electrode as in Figure 10 may be sealed into a fused silica tube 1 so that the wick braid 18 meets the pinch seal 5. In this manner it extends to the very lowest point and will be immersed in any liquid dose which collects there.
  • the pinch seal preferably has a smaller radius of curvature near the base of the wick.
  • the primary (inner) coil of a conventional lamp electrode overwind may be used as a wick.
  • a suitable coil is the primary coil of a 400 watt SON (high pressure sodium) lamp.
  • An example of a coil wick of this form is shown at 26 in Figure 13, mounted on a shank 2 supported on a niobium tube in the manner of Figure 7.
  • Figure 14 shows (but not to scale) a lamp in which a polycrystalline alumina arc tube 24, 113mm long and 7.4mm internal diameter, a size commonly used for 400W high pressure sodium lamps, is mounted inside an evacuated elliptical outer glass bulb 25.
  • the lower end of the arc tube has a braided wick on the electrode and concave plug, both of the type described with reference to Figure 7.
  • the upper end has a conventional electrode 3 and shape of plug commonly used in high pressure sodium lamps.
  • the lamp is dosed with about 40mg sodium and 160mg mercury in the form of an amalgam with 15 torr xenon cold fill pressure.
  • a cap 22 of niobium metal was placed around the top.
  • lamps generally similar to that of Figure 14 have been made, having at one end braided tungsten wicks of various lengths (3mm, 5mm and 7mm) on electrodes with conventional overwinds in the manner of Figure 10.
  • Figure 16 is a graph of the potential difference across the lamp at a constant power of 400 watts as a function of wick braid length, the partial pressure of sodium being strongly correlated with the potential difference.
  • metal vapour lamps suitable for general illumination.
  • metals such as: sodium, thallium and mercury; sodium, thallium, cadmium and mercury; lithium, thallium and mercury can be used to make metal vapour lamps suitable for general illumination.
  • wick electrode and tube shapes to receive it and provide at least some reservoir of liquid dose will be apparent to those skilled in the art.
  • wick forms may be suitable for certain applications:
  • An effective wick may be provided by texturing or contouring the electrode shank surface provided the criteria for capillary action are satisfied. This may be achieved for example by a helical groove which is almost closed at the surface providing opposing surfaces for the capillary action, although at present such a surface would be difficult to produce.
  • tubes have been described with one conventional electrode and one wick electrode it is envisaged that successful tubes may have two electrodes both of which are wick electrodes. However at any time only one such electrode may be operative in a heat pipe mode depending on the tube orientation.
  • the illustrated embodiments show a wick disposed around the electrode shank it will be realised that it may be adjacent or in the region of the shank, perhaps disposed around an auxiliary electrode, providing it is wetted by the liquid dose.
EP82306041A 1981-11-27 1982-11-12 Entladungslampe Withdrawn EP0080820A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8135910 1981-11-27
GB8135910 1981-11-27

Publications (2)

Publication Number Publication Date
EP0080820A2 true EP0080820A2 (de) 1983-06-08
EP0080820A3 EP0080820A3 (de) 1983-12-14

Family

ID=10526224

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82306041A Withdrawn EP0080820A3 (de) 1981-11-27 1982-11-12 Entladungslampe

Country Status (2)

Country Link
EP (1) EP0080820A3 (de)
JP (1) JPS5897251A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2161286A (en) * 1984-07-07 1986-01-08 Ushio Electric Inc Controlled light emission
EP0315445A2 (de) * 1987-11-05 1989-05-10 Ge Lighting Limited Bogenentladungslampe
EP0722183A2 (de) * 1995-01-13 1996-07-17 Ngk Insulators, Ltd. Hochspannungsentladungslampen
EP1507276A2 (de) * 2003-08-15 2005-02-16 Osram Sylvania Inc. Halterung für Bogenentladungsgefäss in Entladungslampen

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1463568A (fr) * 1966-01-13 1966-06-03 Lampes Sa Dispositif applicable aux lampes à décharge électrique contenant des iodures métalliques en vapeur saturante notamment de l'iodure de sodium
US3604972A (en) * 1970-02-25 1971-09-14 Us Army Metal vapor lamp with alkali metal reservoir means
FR2255703A1 (de) * 1973-12-19 1975-07-18 Philips Nv
FR2363187A1 (fr) * 1976-08-26 1978-03-24 Gen Electric Lampe a vapeur metallique haute pression perfectionnee

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1463568A (fr) * 1966-01-13 1966-06-03 Lampes Sa Dispositif applicable aux lampes à décharge électrique contenant des iodures métalliques en vapeur saturante notamment de l'iodure de sodium
US3604972A (en) * 1970-02-25 1971-09-14 Us Army Metal vapor lamp with alkali metal reservoir means
FR2255703A1 (de) * 1973-12-19 1975-07-18 Philips Nv
FR2363187A1 (fr) * 1976-08-26 1978-03-24 Gen Electric Lampe a vapeur metallique haute pression perfectionnee

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2161286A (en) * 1984-07-07 1986-01-08 Ushio Electric Inc Controlled light emission
EP0315445A2 (de) * 1987-11-05 1989-05-10 Ge Lighting Limited Bogenentladungslampe
EP0315445A3 (de) * 1987-11-05 1991-01-23 Ge Lighting Limited Bogenentladungslampe
EP0722183A2 (de) * 1995-01-13 1996-07-17 Ngk Insulators, Ltd. Hochspannungsentladungslampen
EP0722183A3 (de) * 1995-01-13 1996-10-30 Ngk Insulators Ltd Hochspannungsentladungslampen
US5783907A (en) * 1995-01-13 1998-07-21 Ngk Insulators, Ltd. High pressure discharge lamps with sealing members
EP1507276A2 (de) * 2003-08-15 2005-02-16 Osram Sylvania Inc. Halterung für Bogenentladungsgefäss in Entladungslampen
EP1507276B1 (de) * 2003-08-15 2008-01-02 Osram Sylvania Inc. Halterung für Bogenentladungsgefäss in Entladungslampen

Also Published As

Publication number Publication date
JPS5897251A (ja) 1983-06-09
EP0080820A3 (de) 1983-12-14

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Inventor name: WHITTAKER, FRANK LAWRENCE