Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01K—ELECTRIC INCANDESCENT LAMPS
  • H01K3/00—Apparatus or processes adapted to the manufacture, installing, removal, or maintenance of incandescent lamps or parts thereof
  • H01K3/22—Exhausting, degassing, filling, or cleaning vessels
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
  • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
  • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
  • H01J7/183—Composition or manufacture of getters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01K—ELECTRIC INCANDESCENT LAMPS
  • H01K1/00—Details
  • H01K1/28—Envelopes; Vessels
  • H01K1/32—Envelopes; Vessels provided with coatings on the walls; Vessels or coatings thereon characterised by the material thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01K—ELECTRIC INCANDESCENT LAMPS
  • H01K1/00—Details
  • H01K1/52—Means for obtaining or maintaining the desired pressure within the vessel
  • H01K1/54—Means for absorbing or absorbing gas, or for preventing or removing efflorescence, e.g. by gettering
  • H01K1/56—Means for absorbing or absorbing gas, or for preventing or removing efflorescence, e.g. by gettering characterised by the material of the getter

Definitions

• Our invention relates to a method of coating the inner wall of a vessel, for example the bulb of an incandescent lamp with a getter layer consisting of a metal or a mixture of metals of the group formed by magnesium, calcium, strontium and barium.
• a getter is usually employed for binding unwanted residual gases in a vessel in order to improve the vacuum or to maintain the same or to avoid the presence of gases which are harmful to filament wires and the like provided in the vessel.
• Phosphorus is applied for this purpose to the filament wire or to another place in the lamp, where a temperature is reached sufficient for the phosphorus to be evaporated. After exhausting at a raised temperature and after filling with inert gases, if desired, the lam-p is sealed. By burning the lamp the phosphorus is evaporated and any residual gases in the lamp, for example residual oxygen and water vapor are bound.
• the use of phosphorus as a getter involves a few disadvantages.
• the temperature of the lamp during the sealing process and the exhausting must, for example, not exceed the evaporation temperature of phosphorus or the temperature at which phosphorus burns spontaneously in air. This means in practice that the evacuation is carried out at a temperature, which lies 100 C. to 200 C. below the softening temperature of the glass of the bulbs of incandescent lamps for general use.
• a further disadvantage resides in that the quantity of phosphorus must be applied in an accurately defined measure, since otherwise yellow-brown deposits may be formed of the wall of the bulb, so that the light output of the lamp is reduced.
• alkali-earth metal oxide or such a carbonate may be heated in the vessel in contact with a reducing agent.
• the reducing agent may be formed by the metal of the filament Wire of an incandescent lamp.
• the invention has for its object to overcome these difficulties and to provide a more felicitous method and a better defined product.
• getter layers can be obtained using, as a getter, a substance formed by a compound of the gross formula: (MeO) XO wherein Me is Mg, Ca, Sr, Ba or a mixture of the same, X is a metal for example W, Mo, Ti and m is equal to the valency of the metal X divided by 2, the said difficulties being thus avoided.
• the metal X may be formed by 3,266,861 Patented August 16, 1966 one or more metals of the fifth, sixth and seventh group of the Periodical System.
• the oxides of metals of these groups are capable of forming compounds with alkali-earth metal oxides, in which case in the said gross formula 11 is higher than 1. It is advisable to choose such compounds in incandescent lamps that the metal X cannot form alloys with the metal of the filament wire during burning likely to shorten the lifetime of the filament wire.
• the compounds are at most slightly hygroscopic and are not at all reactive or only slightly reactive with carbon dioxide, so that they can be better handled than the oxides and carbonates of the alkali-earth metal oxides, particularly the barium oxide and barium carbonate. It has been found that the compounds are dissociated, in general, at temperatures in excess of 1300 C. in contact with metals such as tungsten, molybdenum, tantalum, zirconium, alkali-earth metal being set free, which is evaporated at this temperature.
• the group of compounds particularly suitable within the scope of the invention includes inter alia Ba WO Ba CaMoO Ba TiO other suitable compounds are, for example, Ba TaO BaSr MOO Ba LaTaO
• the compound can be obtained by heating a mixture of an oxide or a carbonate of the desired alkali-earth metal with a metal such as tungsten, molybdenum and others, an oxide of such a metal or an alkali-earth metal compound with the metal oxide for example alkali-earth tungstenate, molybdate and others.
• the alkali-earth compounds may be mixed with a reducing substance, for example zirconium, tungsten and others. It has been found that already with a quantity of one third of the theoretically required quantity an appreciable elfect is obtained, when the mixture is disposed on a heated metal surface. The reduction of the alkaliearth compound is then performed more rapidly and more completely.
• a reducing substance for example zirconium, tungsten and others.
• the compounds may be applied for example in the form of suspensions, if necessary with a binder or they may be formed by pills, grains or other bodies, by molding.
• alkali earth compounds may be advantageous to use alkali earth compounds together with phosphorus. Some advantages of the use of the alkali-earth compounds alone are then sacrificed, it is true, but this may be compensated for by other advantages, which may render the use of the combined compounds of alkali-earth metal and phosphorus desirable, which will be explained more fully hereinafter.
• the method according to the invention is particularly suitable for coating the inner wall of the bulb of an incandescent lamp.
• the filament wire of tungsten Prior to or sub-sequent to the mounting in the base of a lamp the filament wire of tungsten is coated with Ba WO To this end a suspension of Ba WO in an organic solvent, if necessary with a binder is applied to the filament wine by dipping, painting, spraying, by cataphoretical agency or by a further method. Then the filament wire is mounted in a bulb; the lamp is exhausted and degasified at a higher temperature.
• the value of the degasifying temperature is limited, with the use of Ba WO and other alkali-earth compounds as the sole source of getter material, only by the prop erties of the material of the incandescent lamp, particularly by the softening temperature of the glass of the bulb of said lamp.
• This "temperature lies, in general, below the reduction temperature and decomposition temperature of the getter-producing compounds. Degasification may therefore be carried out at a higher temperature than in the case in which phosphorus is used as a getter.
• the lamp is then sealed and the cap is applied.
• the lamp is then burnt at a voltage which is usually to higher than the voltage to be normally used for the lamp.
• the decomposition and the reduction of the getterproducing compounds according to the invention are usually carried out in excess of 1300 C.
• barium tungstenate BaWO is also evaporated and deposited on the wall of the bulb.
• BaWO or other compounds released when other getter-producing substances according to the invention are used is disturbing either on the wall or on the filament wire.
• said compounds have a favorable effect as blackening getters such as cryolith.
• a favorable quantity of the getter-producing alkali-earth compound amounts to not more than about 2% by Weight of the weight of the filament wire.
• the quantity of metal required for the reduction is so small that it can be withdrawn from the filament wire in most cases Without any troublesome effects. This quantity is, in most cases, within the Weight tolerances of the filament wire.
• the quantity of metal to be Withdrawn from the filament wire may be further reduced by mixing the getterproducing alkali-earth compound with tungsten, Zirconium or a different reducing agent in the form of powder; this provides in addition the great advantage of a higher reaction speed and an improved accomplishment of the reaction due to the larger contact surface of the reacting substances.
• the gas discharge in the lamp may take too much time in certain cases, particularly when the temperature of the filament wire does not rise rapidly above this value. This may involve the risk of an are being struck, so that the lamp becomes defective. Such a fatal gas discharge may be avoided by mixing a small quantity of phosphorus with the getter-producing alkaliearth compound.
• An advantageous ratio between the phosphorus and the alkali-earth compound lies between and 1.
• a suitable suspension of Ba WO contains for example 6% by weight of Ba WO and 0.4% by weight of acrylate resin in xylene. To this suspension may be added 0.6 to 6% by weight of phosphorus and, if desired, a powdery reducing agent, for example a metal powder in a quantity lying between /3 of the theoretical quantity and the theoretical quantity required for the reduction of the Ba WO5.
• the number of lumens per Watt was about 8 and in the second case about 7, measured on the new lamp. In the first case there was found a smaller difference in lifetime.
• the method according to the invention may be employed advantageously with vacuum lamps and gas-filled lamps, when said gases are not bound by the metal getter employed.
• a method of coating the internal wall of a closed vessel with a getter layer comprising the step of heating a compound within the vessel having the formula (MeO) XO in which Me is a metal selected from the group consisting of Mg, Ca, Sr, Ba, and mixtures thereof, X is a metal selected from the group consisting of metals in the fifth, sixth, and seventh group of the periodic table of elements, It has a value greater than 1, and m is equal to the valence of the metal Me divided by 2, in contact with a reducing substance to a temperature at which the said compound is decomposed releasing the metal Me which is deposited on the wall of the vessel.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Discharge Lamp (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Luminescent Compositions (AREA)
• Gas Separation By Absorption (AREA)
• Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=19754127

Family Applications (1)

Country Status (9)

Cited By (4)

Families Citing this family (2)

• 0
  • BE BE637608D patent/BE637608A/xx unknown
  • NL NL283516D patent/NL283516A/xx unknown
• 1963
  • 1963-09-11 US US308101A patent/US3266861A/en not_active Expired - Lifetime
  • 1963-09-18 CH CH1149263A patent/CH434461A/de unknown
  • 1963-09-18 GB GB36759/63A patent/GB1013704A/en not_active Expired
  • 1963-09-18 AT AT749663A patent/AT238313B/de active
  • 1963-09-18 DK DK438663AA patent/DK105817C/da active
  • 1963-09-18 SE SE10204/63A patent/SE304555B/xx unknown
  • 1963-09-19 ES ES291801A patent/ES291801A1/es not_active Expired

Non-Patent Citations (1)

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