DE1571501C3 - Process for the production of a discharge envelope for an electric alkali metal vapor discharge lamp - Google Patents

Description

The invention relates to the production of electrical ΛikalimelaI! Vapor discharge lamps with a tubular piston made of a material with a high aluminum content, d. H. made of a refractory oxide material with an aluminum content exceeding 85 percent by weight, and in particular the manufacture of closures for the ends of such pistons during manufacture of institutions of the aforementioned 'Art.

It has been suggested that the bulbs of electric alkali metal vapor discharge lamps and in particular Manufacture of electric sodium vapor discharge lamps from tubes that are made of a translucent ceramic material with a high aluminum content exist, as this material against is highly resistant to the attack of the hot alkali metal vapor. Such lamp bulbs can, for. B. in the A way to produce that very finely divided aluminum, possibly with the addition of small amounts other refractory oxides, e.g. B. is compressed up to 1% Magncsia, after which the compressed Powder is sintered. The invention provides a method of making a termination for such a tube, which is also highly resistant to attack by alkali metal vapor.

British patent specification 961 070 describes an electric alkali metal vapor discharge lamp with a bulb in the shape of a tube made of translucent, high-density polycrystalline aluminum oxide, the ends of which are hermetically sealed by niobium caps that pass through to the ends of the tube a layer of glass are sealed, whose coefficient of thermal expansion is practically the same as that of niobium and that of the pipe material, preferably a calcium aluminate glass, matches. Niobium caps are beneficial because niobium is hot alkali metal vapor resists and also has a coefficient of thermal expansion very close to that of aluminum oxide comes close, so that seals with a closure part made of niobium withstand temperature cycles particularly well resist.

According to the present invention is a method of making a discharge bulb for an electrical Alkali metal vapor discharge lamp, which consists of a tube made of translucent, refractory oxide material, which contains greater than 85 weight percent alumina, and from each end of the tube sealing closure parts made of niobium or of a refractory niobium alloy, each Closure member is hermetically sealed to one end of the tube by a layer of sealing material which is arranged between the closure part and the pipe end and with the closure part and the pipe is connected, characterized in that the layer of sealing material is made of one or consists of several metals of the group formed by titanium, zirconium, vanadium and hafnium, and that the connection of the sealing layer with the closure member and the tube is achieved by combining the closure part, tube and intervening Sealing layer compresses while assembling at such a temperature is heated so that the metal of the sealing layer is alloyed with the niobium of the closure part and firmly adheres to the alumina pipe.

The present invention provides an improved method of sealing the niobium end caps with the tube of alumina in the manufacture of a lamp as described in British Patent '961,070

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described type. The use of one or more of metals from the group of titanium, zirconium, vanadium and hafnium, with or without niobium, as The sealing layer provides a strong, hermetic seal due to the fact that when heated, the Metals of the group form alloys with the niobium of the end caps and thereby solidly with the caps get connected. In addition, the sealing layer adheres especially when titanium and / or zirconium are contained at the end of the pipe due to the reaction with the aluminum oxide. In addition, resist the metals of the group and therefore also the seals made with them to the hot alkali metal vapor.

The joining of titanium and zirconium with ceramics Materials including alumina are known. The German Auslegeschrift 1 004 989 discloses the use of titanium, zirconium, and titanium-zirconium alloys to seal Nikkei or copper on refractory ceramic material in the manufacture of vacuum-tight pistons, such as / .. B. of electron tube flasks. The German Auslegeschrift 1 126 991 describes a noble gas high pressure discharge lamp, in particular a xenon lamp, with a tubular bulb made of sintered, polycrystalline Aluminum oxide hermetically sealed at both ends by metal end caps. In the In special embodiments, the end caps are made of nickel-chromium-iron and nickel-cobalt-ice alloys and are sealed to the pipe ends by titanium rings or washers. None of these However, descriptions suggest that titanium or zirconium can be used to seal niobium parts to aluminum oxide.

With »refractory niobium alloy« an alloy is to be referred to, which one or more further ones contains refractory metals such that the coefficient of thermal expansion of the alloy differs from that of niobium itself is not very different, e.g. B. a niobium alloy with one or more metals that consisting of the elements tantalum, tungsten, rhenium, titanium, molybdenum, zirconium, vanadium and hafnium Group are selected.

Each closure member may conveniently be in the form of a disk which forms the end of the piston tube covered, or it may be in the form of a cap that fits over the pipe end and with the surface rounded is sealed around the pipe end. Usually an electrode is placed along the axis of the tube carried by each closure part. If it is appropriate, a closure part with an opening be provided and carry another part, e.g. B.! A pump attachment carrying an electrode, which the Opening in the closure part closes, this further part with the closure part either in front of or after sealing the plug to the aluminum oxide tube is sealed.

The method of the invention is particularly suitable for closing the ends of a pipe made of sintered polycrystalline aluminum oxide with or without small additions of other refractory oxides such as Magnesia. However, the tube can also be made from other forms of alumina, e.g. B. essentially from a single crystal of alumina, or crystalline alumina, composed of the vapor phase is precipitated.

The sealing layer may consist of a thin disc of the metals titanium, zirconium, vanadium or hafnium, which is inserted between the tubular piston and the closure member so that it surrounds the pipe end, after which the assembly is pressed together and heated to a suitable temperature. However, these metals all have very high melting points, so that a very high and cumbersome temperature may have to be used to create a seal with a single metal, e.g. Example, when using titanium at the sealing layer, in which case the arrangement must be heated to a temperature of 1800-1850 ⁰ C. It is therefore preferable to use a suitable alloy of two or more of these metals, that is, an alloy which forms a satisfactory bond with the material of the piston, since the seal can be made at lower temperatures with these alloys than with a single metal. A single thin disk made of a suitable alloy can be used or, preferably, an alloy which is manufactured at the point of use in such a way that two or more thin washers each made of a different metal from titanium, zirconium, vanadium, hafnium and also optionally group comprising niobium can be inserted between the piston and the closure member, after which the arrangement is pressed together and heated to a sufficiently high temperature at which the thin disks together form an alloy so that the seal can be produced in a single operation. The heating is preferably carried out in argon or in a vacuum. , ·. . _:

In order to make a satisfactory seal at a comfortable low temperature, is the composition, the sealing layer, preferably chosen so that one at a temperature formed from an alloy which melts not more than 1500 ° C will. For this reason, the sealing layer preferably contains zirconium and vanadium an addition of preferably titanium, whereby the reaction with the surface layers of the aluminum oxide of the piston is promoted. In a preferred method according to the invention, therefore three discs each made of titanium, vanadium and zirconium arranged between the piston and the closure member, the off. Existing titanium disc the aluminum oxide surface and the zirconium.bester existing disc on the closure member. ...

If niobium is initially contained in the sealing layer, the proportion of it should not be so large that that the melting point of the resulting alloy is raised to an undesirable extent. ,,

The drawing shows an embodiment of the invention which is described below.

In the single figure, a sodium vapor lamp is shown partially as a section with a tubular Piston made of translucent aluminum oxide, which is attached at both ends by the method according to the invention is sealed using a sealing layer made of zirconium, vanadium and titanium.

The lamp bulb 1 has the shape of an elongated tube with a length of approximately 120 mm and an inner diameter of 7 mm with a wall thickness of 0.8 mm, which piston in an known way by pressing from finely divided aluminum oxide with an addition of up to 1% magnesia is made. According to the method of the invention to be described below, the tube 1 is on both

Ends with the caps 2, 3 made of niobium and each with a thickness of 0.175 mm, the drawing the caps in readiness for sealing, but not yet with the ends of the alumina tube shows finally connected in order to facilitate the description of the sealing.

By means of titanium 7, an electrode in the form of a siliconized tungsten rod is attached to the cap 2 made of niobium 4 with a length of 15 mm and a diameter of 1.2 mm soldered on, the one winding from a tungsten wire 5 containing a quantity of activation material 6. The tungsten rod 4 extends coaxially to the piston 1. On the outside of the niobium cap 2 is also by means of titanium 9 a Niobium flag 8 soldered on.

The second electrode is carried by the other niobium cap 3 and consists of a siliconized one Tungsten rod 10 with a length of 12 mm, is wrapped with a tungsten wire 11 and with titanium on soldered a molybdenum pin 12, which extends 3 mm into the piston. The pin 12 is through a Passed opening in the middle of the cap 3 and has a shoulder 13, which by means of titanium 14 on the Outside of the cap 3 is soldered. A suction tube 15 is made on the outer end of the molybdenum pin 12 Titanium or niobium on top and at 16 using titanium (with a niobium tube) or using zirconium and vanadium discs (with a titanium tube) soldered on. The molybdenum pin 12 is of a narrow channel 17 traversed, which ends on the side of the pin in the piston 18 and to evacuate the piston and to The filling is used in the manufacture of the lamp.

In the manufacture of the lamp, the caps with the electrodes are first made in the manner described above, including the attachment of the tube 15, all soldering work being carried out in a vacuum or in an inert gas. As shown in the drawing, three ring disks are inserted into each niobium cap, of which the disks 19 and 19 'are made of zircon, the disks 20 and 20' are made of vanadium and the disks 21 and 2V are made of titanium. The ring disks preferably have the following thicknesses: the disks made of zirconium 0.1 mm, vanadium 0.0375 mm and titanium 0.05 mm, while the inner and outer diameters of all ring disks are approximately 6 and 9 mm, respectively. Then the caps with the ring washers attached by spot welding are placed on the tube 1 made of aluminum oxide, as shown, and the entire arrangement is supported vertically, the upper cap being loaded with a weight of 3.5 kg. The assembly is then heated in a vacuum to a temperature of 1400 ± 50 ^c C in about 10 minutes and then allowed to cool. During the heating, the ring disks form an alloy of titanium, vanadium and zirconium, the composition of which is approximately 68% zirconium, 14% vanadium and 18% titanium by weight for the thickness of the ring disks given above. This alloy is alloyed further with the niobium of the caps and establishes a firm connection between these and the ends of the tube 1.

ίο Through the pipe 15 and the channel 17 is in the Flask a filling of sodium and a noble gas, e.g. B. argon, at a pressure of about 20 mm QS let in, after which the tube 15 is closed by squeezing and arc welding in argon will. The discharge tube is inserted coaxially into a cylindrical outer bulb made of glass, which maintains a suitably high operating temperature for the lamp when in use. To the Niobium flag 8 and on the metal tube 15 are elec-

ao tric ladder attached with which the lamp to a Power source can be connected. In the drawing these are the conductors and the glass bulb for the lamp omitted.

In the illustrated embodiment, the seals are at the ends of the discharge bulb highly resistant to the attack of hot sodium vapor when the lamp is in operation and are also of the temperatures occurring in normal operation. turbo fluctuations not influenced.

The lamp described above can be modified in that the discharge bulb is attached at the ends Place the niobium caps can be closed by niobium disks that have the electrode arrangements described wear. Furthermore, the sealing layers between the niobium caps or disks and the ends of the aluminum oxide tube consist of individual ring disks, which consist of one or several of the metals titanium, vanadium, zirconium, and hafnium are made. Will only have a single one at each end Washer made of only one of the metals mentioned is used, so the temperature must be used when heating be slightly higher than the temperature given in the example described and z. B. 1800 to 1850 ° C Use of tilane slices.

Of course, the filling of the lamp can also contain suitable compounds in addition to the sodium, z. B. certain metal iodides, or the sodium can be replaced by another alkali metal or by alkali metal mixtures be replaced, which are suitable for discharge lamps, provided that these additives or Replacement metals do not react with the materials of the piston, caps and sealing washers.

1 sheet of drawings

Claims (9)

Patent claims: 1. Method of making a single charge flask for an electric alkali metal vapor discharge lamp, which consists of a tube made of translucent, refractory oxide material, which contains more than 85 percent by weight of aluminum oxide, and from each end of the tube closing pieces of niobium or of a Refractory niobium alloy, each closure member being hermetically sealed to one end of the tube is sealed by ein.Schicht a sealing material between the closure part and the The pipe end is arranged and connected to the closure member and the pipe, characterized in that that the layer of sealing material made of one or more metals Group consisting of titanium, zirconium, vanadium and hafnium, and that joining the sealing layer with the closure part and the tube is achieved by making the assembly from closure part, tube and intermediate sealing layer, while the assembly is heated to such a temperature that the metal of the sealing layer alloyed with the niobium of the closure member and firmly adhered to the alumina tube. 2. The method according to claim 1, characterized in that that the closure part has the shape of a disc which covers the pipe end. 3. The method according to claim 1, characterized in that the closure part is in the form of a cap that fits over the end of the pipe. 4. The method according to claim 1 to 3, characterized in that one of the closure parts has an opening has and carries another part, which the opening in the lock! hermetically closes. 5. The method according to claim 1 to 4, characterized in that the tube made of sintered, polycrystalline Alumina with or without minor additions of other refractory oxides. 6. The method according to claim 1 to 5, characterized in that that the sealing layer initially also contains niobium. 7. The method according to claim 1 to 6, characterized in that the sealing layer initially of a single thin washer is formed. 8. The method according to claim 1 to 7, characterized in that the sealing layer initially consists of consists of at least two thin washers, each from a different member of the said Group of metals, optionally together with a ring disk made of niobium. 9. The method according to claim 1 to 8, characterized in that three annular discs made of titanium, Vanadium and zirconium exist, initially introduced between the tube and the plug The washer made of titanium on the end face of the tube and the washer made of zirconium be arranged on the closure part.