DE1081568B - Low pressure mercury vapor discharge lamp and method for making the same - Google Patents

Description

GERMAN

The invention relates to low pressure mercury vapor discharge lamps with preheatable electrodes, their coils with an alkaline earth compound are covered and carried by wire or rod-shaped electrical leads, where 5 Parts of the electrical lead wires serve as anodes when the lamp is in operation. In particular the invention relates to fluorescent lamps of this type.

The known discharge lamps have a tendency to have spots or blackening at the ends of the Lamp bulb next to the electrodes to form. The analytical investigation has shown that this Patches are mainly made up of barium, which collects the mercury and causes the blackening. It is believed that this barium emanates from the emission mixture produced by the Electrodes, as this is often the only source of barium found in the lamp.

Such spots and blackening usually occur after some time in operation of the lamp and become stronger over time; the discoloration makes the lamp unsightly and weakens the light emitted.

The invention is based on the object of eliminating this disadvantage.

Electrical discharge tubes with gas and / or steam atmosphere and activated, coiled ones are known Electrodes with cooling blades running in the direction of the discharge path, which are close to the inlet entry point of the associated holder into the interior of the discharge vessel and at least up to The fastening point of the electrode coil on the holder is sufficient. The task of these cooling blades is the Counteract the formation of cathode spots and glow discharges. Meanwhile, these cooling blades are used Solution of the task of the invention unsuitable. The heat distribution on the cooling blades is always uneven, because the parts of the cooling blades that are closest to the corresponding parts of the cooling blades the opposite. Electrode are located, take over the function of the anode, to which the electrical Arc crosses. They are therefore excessively heated, so that a transport of. Barium compounds the lamp bulb must enter. Furthermore, the cooling fins of the known design have sections that are relatively close to the lamp bulb and not only radiate heat to the lamp bulb, but also release barium ions, which are conveyed across the cooling fins by a creeping process will.

Furthermore, the cooling fins narrow and blacken due to the proximity of parts of the same Lamp bulb, the fluorescent layer by over-low-pressure mercury vapor

Discharge lamp
and methods of making the same

Applicant:

Westinghouse Electric Corporation,
East Pittsburgh, Pa. (V. St. A.)

Representative: Dipl.-Ing. F. Weickmann

and Dr.-Ing. A. Weickmann, patent attorneys,

Munich 2, Brunnstr. 8/9

Claimed priority:
V. St. ν. America June 13, 1956

Albert W. Wainio, Pompton Plains, N.J.,

and Frederic E. Sutter, West Caldwell, N. J. (V. St. A.),

have been named as inventors

moderate thermal radiation in the immediate vicinity of these fluorescent layers.

And finally, the attachment of such cooling fins requires an additional manufacturing process and additional assembly; these measures make series production more difficult and expensive.

The invention solves the problem of preventing the formation of dark precipitates in that on the lamp bulb at least the parts of the lead wires serving as anode by a pretreatment obtain a stable, rough surface with a dark, matt color.

The lamps according to the invention are manufactured in such a way that a plating of dark chromium vanadium in a composition of 100 to 9.5 parts by weight of chromium to 1 part of vanadium is applied to the leads. The vanadium is preferably _{plated as V 2} O ₃ and the chromium is partially oxidized with the proviso that the ratio of the chromium atoms to the oxygen atoms combined with chromium is from 2: 1 to 100: 1.

A coating of an aluminum-iron alloy can be applied to the supply lines be applied, which has a roughened surface with a dull gray color. So the supply lines can be at least partially

OOJ 5091/179

consist of iron coated with the aluminum-iron alloy.

Another embodiment of the lamp is that on the supply lines a coating of carbonized Nickel is applied from a rough surface and matt dark color. Are the leads from Iron, at least the supply line parts serving as anode can be produced by reaction of the iron with a a small amount of molybdenum can be made rough and dull dark. The matt dark color and the rough ίο but can also be generated in that at least the supply line parts serving as anode Aluminum is vapor deposited.

The figures explain the invention using an exemplary embodiment. It shows:

1 shows a fluorescent lamp designed according to the invention in a view and partially in section,

2 shows the cross section of a conductor which is provided with a heat-emitting coating,

3 shows a plating installation for applying a highly heat-radiating coating to the Lead wires,

4 shows a modified embodiment of a conductor wire.

The invention is primarily intended for use on fluorescent lamps, i. H. on low-pressure mercury vapor discharge lamps, which have a fluorescent coating on the inner surface of the lamp envelope; the embodiments shown refer to this type of lamp. However, the invention can be used in the same way for low-pressure mercury-vapor discharge lamps without a fluorescent coating on the inner surface of the Bulbs of the type commonly used as ultraviolet light sources.

The fluorescent lamp 10 shown as an example has a tubular enveloping vessel 12 with the Ends of welded feet 14; the envelope vessel ends in caps 16, which the holder and the facilitate electrical connections of the lamp. Each foot 14 carries leads 18, which into the interior of the Envelope vessel protrude. At the ends of the envelope between the inwardly directed ends of the lead wires 18 are electrode coils made of tungsten or other suitable, still melting metal arranged, which are coated with electron-emitting alkaline earth oxide. The alkaline earth oxide consists for example from 60 percent by weight BaO, 30 percent by weight CaO and 10 percent by weight SrO. The electron-emitting coating can, however, only consist of barium oxide or a mixture of Barium oxide and strontium oxide or of barium oxide and calcium oxide exist. Such emitting Mixtures are known; in conventional lamps, the main component is the Mixture of barium oxide.

The lead wires 18. which go into the interior of the Lamp bulbs protrude and carry the filament 20 by welding or in some other way with the in the Glass fused conductors22 connected; the latter usually consist of so-called dumet wire. Dumet wire is a wire with a copper sheath over a nickel or iron core; he is particularly suitable for sealing in glass. These wires 22 are for example copper wires with the usual Base pins 24 conductively connected. In the case of a fluorescent lamp, the envelope vessel is on his inner surface provided with a phosphor layer 26, e.g. B. with activated by manganese zinc silicate for the purpose of converting the ultraviolet radiation given off by the discharge of the lamp into visible radiation to transform. Such phosphor material is known in many ways. If the lamp is used as a Ultraviolet source is used, the fluorescent coating is dispensable. The lamp also includes a weak filling of inert, ionized gas, such as argon, at a pressure of 4 mm of mercury, to make it easier to get started; also a small charge of mercury 28. Other inert, Ionizable gases at different pressures are used, as is also the case in the relevant technology known.

Fluorescent lamps are usually designed for use with alternating current; In this operation, the coils provided with electron-emitting material serve as the cathode in each half-cycle. While the filament at one end of the lamp works as an electron-emitting cathode, the lead wires 18 and filament 20 at the opposite end of the lamp serve as an anode. In normal operation, those parts of the lead wires 18 which are closest to the associated coils 20 act as an anode. These wire parts, which work as anodes, get very hot during lamp operation, as a result of the I ² R losses through the wire, the bombardment with positive ions and the heat carried by the hot cathode. This leads to the wire cross-sections in the vicinity of the helix being designed in such a way that they operate at a relatively high temperature. Temperatures up to 880 ° C come into consideration.

The reason jarium is transferred from the coils 20 to the lamp envelope 12 in the form of spots is not clarified. It used to be assumed that either a most direct transmission from the coils on the piston or possibly a direct transmission · takes place via the conductor wires. Attempts to eliminate these end spots moved in the direction of the emitting To improve the mixture in terms of its stability. However, it has been shown that by changing the Lead wires or at least those parts of the lead wires, which serve as anodes during lamp operation, preventing the formation of end spots can be. This is achieved in a known manner in that the outer surfaces at least the parts of the wires that work as anodes are given a matt dark color and roughened to increase the heat radiation of at least these anode parts. Practically one becomes that whole part of the lead wire 18, which protrudes into the interior of the piston 12, with such a matt dark Coating and provided with a roughened surface.

The ability of heat absorption or heat radiation is the same; that means that a body that is a good absorber is at the same time a good radiator. Certain substances, such as lamp soot, mixed in water glass, have an emissivity of about 95% of a perfectly black Body, while commercially available, polished copper or ordinary, bare aluminum have an emissivity of less than 5% (compared to an absolutely black body). Of the the most important factor in terms of heat radiating ability is the condition of the surface, which should be etched or otherwise roughened. While color is also important, it is of secondary importance. In the example case it was found that the lead wires or at least the during operation parts of the same working as anodes

should be provided with a roughened surface and a matt dark color. The advantage according to the invention can be achieved by using wires of a matt gray color and a roughened surface, as well as with wires of a matt black color and a roughened surface. But other colors also lead to success, provided they are only matt and dark. It should be emphasized that normally any surface that is etched or otherwise roughened is due to a lack of it
owns.

When operating lamps that have matt-colored and surface-roughened wires, a part the heat emitted by the hot cathode

wires or the precipitation of barium from the lead wires on the lamp bulb is prevented will. What is certain, however, is that the barium precipitate on the wall of the fluorescent tube was largely prevented will.

The preferred embodiment of a matt dark colored and roughened surface of the lead wires is a black plating of a chrome and Vanadium composition ranging from 100 up to

of the spectral effect, a matt appearance can vary from 9.5 parts by weight of chromium to 1 part by weight of vanadium. The vanadium is conveniently _{plated as V 2} O ₃ (this is a black fabric). The plated chromium is precipitated partially oxidized, with a ratio of chromium atoms to

absorbed by these wires, and such an amount of heat is emitted from the oxygen atoms, in conjunction with chromium, as explained later 2: 1 to 100: 1. This matte black plating will be. Meanwhile, a substantial part of the amount, on a metal wire, for example iron or that to the wires by conduction from the hot. Nickel, made; the wire has z. B. a cathode by / ² 2? Losses and by positive ion diameter of 0.5 mm. The thickness of the coating bombardments emitted by the wires is not critical as long as the outer surface has the properties mentioned by which these operate in a much cooler condition; In the case of the wires of the conventional design, it is, for example, 1.25 microns. Such a coating is shown in FIG. 2, typically made of nickel or nickel-plated iron.

passed, relatively bright and, what of particular- Fig. 3 shows a device for plating a

whose meaning is, were bare. Measurements have 25 wire with black chrome vanadium for the result that the embodiment according to the invention works un- Use on fluorescent lamps according to the experience 100 ° C cooler than connecting wires up to now manure. The wire to be plated is withdrawn from a customary type. Winding roll 30, runs over two tensioning rolls Tank 36 partially noticeable decrease in appearance from end-to-end fills. The wire is observed through rollers 38 and 40 spots. This results in better kept below the liquid level. When leaving explanation for the cause of the formation of such, the wire is anodically cleaned in this solution, in case of stains. Apparently the barium is sublimed or a current density of approximately 0.4 amperes per cm ² reaches the wire surface in some other way from the coils. Electrical contact with the wire wires. From these, the barium is then brought about on the _w i _r d via the contact rollers 34 and 42. The lamp bulb is transferred where it collects mercury. The wire overflows from the alkaline solution and appears as dark spots. Thereby, contact roller 42 through spray water 44 and over one that the wires were forced to work in substantially contact roller 46 in the acid solution of a tank 48th cooler condition, apparently the first ₄₀ before and after passage through the spray water reaction, in which barium The wire grinds down the wires 44 via scrapers made of rubber blades which are attached to a drainage trough 50 in order to remove excess liquid from the surface of the wire. In the tank 48 the wire is under

avoided. This explanation is only theoretical; 45 the liquid level held by rollers 51., 52, What is certain, however, is the fact that if the wire is anodically cleaned in this solution, at a

Current density of about 0 ', 4of to 0.55 amps per cm ² wire surface. The electrical contact with the wire is achieved by contact rollers 46 and 54.

the lead wires is physical and chemical _go places. From the acid bath, the wire runs over con stability and sufficient adhesion to the timing rollers 54 and spray water 56 as well as a con

is beaten, or the second reaction, in which barium is deposited from the wires onto the piston is prevented and so the formation of stains

surface is designed according to the invention, the formation of end stains is drastically prevented. Condition for the implementation according to the invention

clock roller 58 in a tank 60 with a chrome vanadium plating solution. Before and after passing through the spray water 56, the wire is at

Wire, under the normal working conditions of the lamp.

Tests have shown that the surface can be coating temperatures up to 750 ° C and higher excluded ₅₅ 62 Γη catfish same as at 50 is excess, the interior of the lamp freed liquid piston can stand under a partial vacuum. at
Electron tubes is the use of heat

emitting coatings known on the elements.

In. the tank 60 is the wire below the liquid level held by rollers 63 and 64. He also passes under a contact rail 66. Of the

The purpose here is to wire the elements of the tube in the 60's with a clinging precipitate

Operation to cool the so-called counter-electrolytic with a black chrome-vanadium-

electron emission, because conductor materials often when heated to very high temperatures become electron emissive. With fluorescent lamps

Precipitation provided, at a current density of 0.75 to 1.2 QA-Cm- ² wire surface area; contact is made with the wire passing through

According to the present invention, the proportions 65 are contact roller 58 and contact bar 66. Fundamentally different from the plate compared to electron tubes; With this machine, the wire runs over the tension roller 68 and the lead wires become a black one
Emitter adjusted to prevent precipitation

Interrupt barium. The open question is

and along the surface of a washing sponge 70, which is carried by a drainage trough 72. Water is sprayed onto the wire surface from nozzles 74.

if the precipitate of the Eariums _7o sprayed on the combined input; the sponge washes away the chemicals.

Finally, the wire passes under a dry lamp 76 before it is wound.

The solution in the alkaline bath 36 is preferably an aqueous solution of an alkaline cleaner, for example 37.5 g sodium hydroxide per liter. Optionally, a commercially available alkaline Cleaner can be used and this solution is kept at a temperature of approximately 60 'to 65 ° C held. The acid solution in tank 48 is preferably a 50% aqueous solution more concentrated Sulfuric acid; this solution is kept at room temperature.

The chromium-vanadium plating bath can be an aqueous solution of the following composition: chromium trioxide - 200 grams per liter; Ammonium metavanadate - 200 g per liter; Glacial acetic acid - 6.5 cm ³ per liter. This plating bath can be used at about room temperature; however, the solution may need to be cooled if the process is extended over a long period of time.

The concentration of chromium and vanadium salts in the electrolyte is preferably kept in the ratio of about 12 parts of chromium to 1 part of vanadium; however, this ratio can vary from 100: 1 to 9.5: 1. Instead of acetic acid, other organic acids, such as formic acid or citric acid, can be used; the proportion of organic acid in the bath can also vary from 3 to 20 cm ³ per liter.

The wire, which is provided with a black chrome-vanadium coating, shows a magnification of 2000 times a very fine crystal structure with a multitude of very fine initial cracks or cracks, which result in a very strong surface roughening. The chromium and vanadium compounds are not visible under the microscope as separate crystals, but appear as a dark mass a homogeneous crystal structure. Analysis shows that the black coating on the Wire has approximately the same percentage composition in terms of vanadium and chromium, in which these elements were present in the electrolyte from which the coating was formed.

After plating, the wire is cut to the desired length and tied with the Dumet wire conductive, e.g. B. by welding, connected before the lamp base is produced. The foot and the Lamps are then manufactured according to the usual process. Albeit a black coating Chrome vanadium is preferred, but good results can also be achieved with an iron wire, which is coated with a compound of aluminum and iron. When producing such a coating aluminum powder can be wiped onto the iron wire and the iron wire provided with aluminum then heated, for example, to 800 ° C in hydrogen or other non-oxidizing atmosphere will. But there can also be other methods of applying the aluminum, e.g. B. Hang up or Plating find use. An iron-aluminum alloy is thus obtained on the surface which has a has a matt gray appearance and a roughened surface. The emissivity is approximately 85 per cent of the emissivity of a blackbody. The strength of the order of the aluminum-iron alloy can for example be between 0.025 and 0.0125 mm. There were also according to the invention other types of matt dark and rough coatings applied, such as carbonized nickel. This coating, too, resulted in a considerable improvement over the relatively low-emission ones Coatings of a previously known design. However, this improvement is not of the degree which can be achieved with chrome-vanadium or iron-aluminum alloys. Carbonized nickel raises the problem of good adhesion. This problem can be experimentally solved without difficulty master.

FIG. 4 shows a modified embodiment of the lamp shown in FIG. In this embodiment 4, the conductors are above where they are attached to the coil 20 are elongated and then bent in the longitudinal direction of the helix so that they are parallel or axially parallel run to this. The anodes 78, which are formed by the extension of the wires 18, are preferably located are, and the filament 20 in a plane perpendicular to the axis of the lamp envelope 12, so that the path the mercury discharge is not changed while the lamp is operating.

In this embodiment, at least the anode parts 78 are matt dark and roughened Surface provided in the sense of the present invention.

Life tests were carried out for a large number of lamps of the embodiment according to the invention employed; and it became the point in time at which the discoloration occurred first, recorded. The table below shows the results of these tests for 500 hours, 1000 hours and 1500 hours.

The percentages given mean what percentage of the lamps examined after the ones mentioned Hour numbers was still free of discoloration. It can be seen that the discoloration of the invention Lamp becomes practically negligible.

Ladder type

Operating time in hours I 1000 I.

1500

Lamps with ladders with a matt dark and roughened surface

Comparison lamp - conductor made of nickel-plated iron

Claims (9)

Claims: 6s 1.Low-pressure mercury vapor discharge lamp with preheatable electrodes, the filaments of which are covered with an alkaline earth compound and of wire or rod-shaped electrical 95%
77% 85 to 92%
50% 73 to 85% 38% Leads are worn, with parts of the electrical lead wires in operation of the Lamp used as anode, in particular fluorescent lamp of this type, characterized in that to prevent the formation of dark deposits on the lamp bulb at least as. Parts of the lead wires that serve anode are given a stable, rough surface through a pretreatment darker, dull color. 2. Lamp according to claim 1, characterized in that a plating on the leads of dark chrome vanadium in a composition of 100 to 9.5 parts by weight of chrome 1 part vanadium is applied. 3. Lamp according to claim 2, characterized in that the vanadium is mainly _{plated as V 2} O ₃ and that the chromium is partially oxidized with the proviso that the ratio of the chromium atoms to the oxygen atoms combined with chromium is from 2: 1 to 100: 1 is. 4. Lamp according to claim !, characterized in that a coating on the leads an aluminum-iron alloy is applied, which has a roughened surface of matt gray Has color 5. Lamp according to claim 4, characterized in that the leads from at least partially consist of iron coated with the aluminum-iron alloy. 6. Lamp according to claim 1, characterized in that a coating is made on the leads carbonized nickel with a rough surface and matt dark color is applied. 7. Lamp according to claim 1, characterized in that the leads are made of iron and that at least the supply line parts serving as anode by reaction of the iron with a small amounts of molybdenum are made rough and dull dark. 8. Lamp according to claim 1, characterized in that the leads are made of iron and that at least the supply line parts serving as anode are made by vapor deposition of aluminum are dull dark colored and made rough. 9. Lamp according to one of the preceding claims, characterized in that the useful The outer surface of the anode of the leads is enlarged in a manner known per se by the Ends of the lead wires from the points where they are connected to the electrode coils are to be bent in such a way that these ends are at a certain distance from the helix and run essentially parallel next to it by at least with the axis of the helix lie approximately in a plane which is perpendicular to the longitudinal axis of the lamp envelope. Considered publications: German patents No. 718 479, 868 026,
858; German patent application S 21295 VIIIc / 21f
(announced April 30, 1952); French Patent No. 967,217; H. Steyskal: "Working methods and material science of high vacuum technology, technology of electron tubes" from the series: "Physikalische Schriften", Heft 3, Physik-Verlag, Mosbach / Baden, 1955, p. 97 to 98; Espe-Knoll: »Materials science of high vacuum technology«, Springer-Verlag, Berlin, 1936, pp. 154 to 156. 1 sheet of drawings © 009 509/179 5.