US2300959A - Cathode for discharge devices - Google Patents
Cathode for discharge devices Download PDFInfo
- Publication number
- US2300959A US2300959A US372196A US37219640A US2300959A US 2300959 A US2300959 A US 2300959A US 372196 A US372196 A US 372196A US 37219640 A US37219640 A US 37219640A US 2300959 A US2300959 A US 2300959A
- Authority
- US
- United States
- Prior art keywords
- cathode
- discharge devices
- reducing agent
- discharge
- zirconium
- 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.)
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Links
- 239000003638 chemical reducing agent Substances 0.000 description 13
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 10
- 238000010891 electric arc Methods 0.000 description 10
- 150000001875 compounds Chemical class 0.000 description 9
- 239000008188 pellet Substances 0.000 description 7
- 229910052726 zirconium Inorganic materials 0.000 description 7
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 6
- QKYBEKAEVQPNIN-UHFFFAOYSA-N barium(2+);oxido(oxo)alumane Chemical compound [Ba+2].[O-][Al]=O.[O-][Al]=O QKYBEKAEVQPNIN-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 150000004645 aluminates Chemical class 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 5
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 239000007795 chemical reaction product Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- 239000001856 Ethyl cellulose Substances 0.000 description 2
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 2
- QFFVPLLCYGOFPU-UHFFFAOYSA-N barium chromate Chemical compound [Ba+2].[O-][Cr]([O-])(=O)=O QFFVPLLCYGOFPU-UHFFFAOYSA-N 0.000 description 2
- 229940083898 barium chromate Drugs 0.000 description 2
- 229920001249 ethyl cellulose Polymers 0.000 description 2
- 235000019325 ethyl cellulose Nutrition 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 239000004359 castor oil Substances 0.000 description 1
- 235000019438 castor oil Nutrition 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- ZEMPKEQAKRGZGQ-XOQCFJPHSA-N glycerol triricinoleate Natural products CCCCCC[C@@H](O)CC=CCCCCCCCC(=O)OC[C@@H](COC(=O)CCCCCCCC=CC[C@@H](O)CCCCCC)OC(=O)CCCCCCCC=CC[C@H](O)CCCCCC ZEMPKEQAKRGZGQ-XOQCFJPHSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000003870 refractory metal Substances 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- RLQWHDODQVOVKU-UHFFFAOYSA-N tetrapotassium;silicate Chemical compound [K+].[K+].[K+].[K+].[O-][Si]([O-])([O-])[O-] RLQWHDODQVOVKU-UHFFFAOYSA-N 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
- H01J9/042—Manufacture, activation of the emissive part
Definitions
- My invention relates to cathodes of electric discharge devices and especially of devices wherein, in full operation, the discharge is an unconstricted low-pressure arc discharge and not a high-pressure arc discharge with a constricted column.
- a cathode means, as usual, an electrode which actsas cathode during some part of the operation of the device. If the device is operated from an alternating supply, the cathode will usually act as anode during some part of the cycle.
- Low-pressure arc discharge devices for example ccmmercial lamps coated on their interior surface
- ccmmercial lamps coated on their interior surface With luminescent materials and operating on ordinary supply voltages, are usually provided with activated cathodes heated independently of the discharge during the starting period, though they may be heated by the discharge alone when in full operation. It is neces sary to heat the cathodes independently during the starting period, because otherwise the glow discharge, which first passes, does not transform itself into an arc unless the applied voltage is undesirably high.
- An object of this invention is to provide a cathode which permits this transformation to occur with lower applied voltages than must be used with the cathodes used hitherto.
- the drawing shows in perspective one form of electrode embodying the present invention.
- the cathode of an electric discharge device consists of a pellet, shown at it in the drawing having considerable electrical conductivity, prepared by heating, within the discharge envelope and during the manufacture of the device, a mixture of a not too easily reducible compound of an alkali earth metal like strontium, or preferably barium, with a not too easily volatile reducing agent and, preferably, a binder.
- the compounds preferred are barium aluminate (Ba A1204) or barium chromate (BaCrO4).
- the reducing agents preferred are silicon, zirconium, or commercial ferro-titanium containing some 12 per cent of aluminum. Aluminum alone is usually less suitable on account of its volatility.
- the reducing agent should be in considerable excess, so that after the reduction the remainder of it makes the pellet highly conducting. If the reducing agent does not react readily with water (e. g. silicon) potassium waterglass may be used as a binder.
- water e. g. silicon
- an organic binder maybe used, for example a solution of ethyl cellulose.
- a pellet it! prepared from the mixture is preferably placed within a tungsten helix I l which serves as its support and can be heated during the manufacture of the device so as to cause the compound. and the reducing reagent to react.
- the pellets, before they are heated, are perfectly stable and may be preserved for long periods in a stoppered bottle.
- zirconium is the reducing agent, the pellet must not be heated above 300 C. in the sealing-in of the cathode in order that it may not burn in air.
- the other reducing agents named are less liable to burn.
- cathodes according to the invention appears to arise largely from the roughness of their surface, which leads to the concentration of the glow discharge on one or a few spots and avoids its spreading over a large area, and from their high electrical conductivity.
- Powdered barium aluminate is mixed with an equal weight of zirconium powder; to the mixture is added 15 per cent by Weight of a binder consisting of 17 gm. of ethyl cellulose, 3 gm. of castor oil, and m1. of toluene.
- the resulting paste is formed into a pellet which is dried, placed within a tungsten spiral and introduced into the discharge device. At a suitable stage in the pumping of the device, the tungsten spiral is heated to a temperature (about 1000 C.) high enough to cause the zirconium and barium aluminate to react, but not much higher than is necessary for this purpose.
- the method of manufacturing cathodes for electric arc discharge devices which comprises mixing together the powders of a difficultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and an excess of a diificultly volatile metallic reducing agent, and then heating the mixture to cause a reaction of the ingredients whereby, after the reduction, the remainder of the metallic reducing agent makes the mass highly conductive.
- the method of manufacturing cathodes for electric arc discharge devices which comprises mixing together the powders of a difiicultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a diflicultly volatile metallic reducing agent selected from the group consisting of silicon, zirconium and ferro-titanium containing about 12 per cent of aluminum, and then heating the mixture to cause a reaction of the ingredients.
- the method of manufacturing cathodes for electric arc discharge devices which comprises mixing together approximately equal weights of powdered barium aluminate and zirconium powder with a binder, and then heating the mixture to a temperature of approximately 1000 C. to cause the zirconium and barium aluminate to react.
- a cathode for electric arc discharge devices comprising the reaction product of the powders of a diflicultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a difiicultly volatile metallic reducing agent, the metallic reducing agent being present in an amount appreciably in excess of that required to reduce the difiicultly reducible compound so that the cathode is highly conductive.
- a cathode for electric arc discharge devices comprising the reaction product of the powders of a diificultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a diificultly volatile metallic reducing agent selected from the group consisting of silicon, zirconium and ferrotitanium containing about 12 per cent of aluminum.
- a cathode for electric arc discharge devices comprising the reaction product of approximately equal weights of powdered barium aluminate and zirconium powder.
- a cathode for electric arc discharge devices comprising a coil of refractory metal wire containing and supporting a coherent and substantially homogeneous electron-emissive pellet consisting of the reaction product of a powdered compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a powdered difficultly volatile metallic reducing agent.
Description
Nov. 3, 1942.
M. PIRANI CATHODE FOR DISCHARGE DEVICES Filed Dec. 28, 1940 lnven'toT': I Marcello Fran], b% M HIS A'h'kow'neg.
Patented Nov. 3, 1942 CATHODE FOR DISCHARGE DEVICES Marcello Pirani, Wembley, England, assig'nor to General Electric Company, a corporation of New York Application December 28, 1940, Serial No. 372,196 In Great Britain January 1, 1940 7 Claims. (Cl. 250-275) My invention relates to cathodes of electric discharge devices and especially of devices wherein, in full operation, the discharge is an unconstricted low-pressure arc discharge and not a high-pressure arc discharge with a constricted column. However, since a high-pressure discharge usually starts as a low-pressure discharge, the use of the invention in high-pressure discharge devices is not excluded. A cathode means, as usual, an electrode which actsas cathode during some part of the operation of the device. If the device is operated from an alternating supply, the cathode will usually act as anode during some part of the cycle.
Low-pressure arc discharge devices, for example ccmmercial lamps coated on their interior surface With luminescent materials and operating on ordinary supply voltages, are usually provided with activated cathodes heated independently of the discharge during the starting period, though they may be heated by the discharge alone when in full operation. It is neces sary to heat the cathodes independently during the starting period, because otherwise the glow discharge, which first passes, does not transform itself into an arc unless the applied voltage is undesirably high. An object of this invention is to provide a cathode which permits this transformation to occur with lower applied voltages than must be used with the cathodes used hitherto.
The drawing shows in perspective one form of electrode embodying the present invention.
According to the invention the cathode of an electric discharge device consists of a pellet, shown at it in the drawing having considerable electrical conductivity, prepared by heating, within the discharge envelope and during the manufacture of the device, a mixture of a not too easily reducible compound of an alkali earth metal like strontium, or preferably barium, with a not too easily volatile reducing agent and, preferably, a binder.
The compounds preferred are barium aluminate (Ba A1204) or barium chromate (BaCrO4). The reducing agents preferred are silicon, zirconium, or commercial ferro-titanium containing some 12 per cent of aluminum. Aluminum alone is usually less suitable on account of its volatility.
The reducing agent should be in considerable excess, so that after the reduction the remainder of it makes the pellet highly conducting. If the reducing agent does not react readily with water (e. g. silicon) potassium waterglass may be used as a binder.
If (like zirconium) it does react with water, an organic binder maybe used, for example a solution of ethyl cellulose. A pellet it! prepared from the mixture is preferably placed within a tungsten helix I l which serves as its support and can be heated during the manufacture of the device so as to cause the compound. and the reducing reagent to react. The pellets, before they are heated, are perfectly stable and may be preserved for long periods in a stoppered bottle. If zirconium is the reducing agent, the pellet must not be heated above 300 C. in the sealing-in of the cathode in order that it may not burn in air. The other reducing agents named are less liable to burn.
The merit of cathodes according to the invention appears to arise largely from the roughness of their surface, which leads to the concentration of the glow discharge on one or a few spots and avoids its spreading over a large area, and from their high electrical conductivity.
One method of preparing a cathode according to the invention will now be described by way of example. Powdered barium aluminate is mixed with an equal weight of zirconium powder; to the mixture is added 15 per cent by Weight of a binder consisting of 17 gm. of ethyl cellulose, 3 gm. of castor oil, and m1. of toluene. The resulting paste is formed into a pellet which is dried, placed within a tungsten spiral and introduced into the discharge device. At a suitable stage in the pumping of the device, the tungsten spiral is heated to a temperature (about 1000 C.) high enough to cause the zirconium and barium aluminate to react, but not much higher than is necessary for this purpose.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. The method of manufacturing cathodes for electric arc discharge devices which comprises mixing together the powders of a difficultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and an excess of a diificultly volatile metallic reducing agent, and then heating the mixture to cause a reaction of the ingredients whereby, after the reduction, the remainder of the metallic reducing agent makes the mass highly conductive.
2. The method of manufacturing cathodes for electric arc discharge devices which comprises mixing together the powders of a difiicultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a diflicultly volatile metallic reducing agent selected from the group consisting of silicon, zirconium and ferro-titanium containing about 12 per cent of aluminum, and then heating the mixture to cause a reaction of the ingredients.
3. The method of manufacturing cathodes for electric arc discharge devices which comprises mixing together approximately equal weights of powdered barium aluminate and zirconium powder with a binder, and then heating the mixture to a temperature of approximately 1000 C. to cause the zirconium and barium aluminate to react.
4. A cathode for electric arc discharge devices comprising the reaction product of the powders of a diflicultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a difiicultly volatile metallic reducing agent, the metallic reducing agent being present in an amount appreciably in excess of that required to reduce the difiicultly reducible compound so that the cathode is highly conductive.
5. A cathode for electric arc discharge devices comprising the reaction product of the powders of a diificultly reducible compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a diificultly volatile metallic reducing agent selected from the group consisting of silicon, zirconium and ferrotitanium containing about 12 per cent of aluminum.
6. A cathode for electric arc discharge devices comprising the reaction product of approximately equal weights of powdered barium aluminate and zirconium powder.
7. A cathode for electric arc discharge devices comprising a coil of refractory metal wire containing and supporting a coherent and substantially homogeneous electron-emissive pellet consisting of the reaction product of a powdered compound selected from the group consisting of the aluminate and the chromate of an alkali earth metal and a powdered difficultly volatile metallic reducing agent.
MARCELLO PIRANI,
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2300959X | 1940-01-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2300959A true US2300959A (en) | 1942-11-03 |
Family
ID=10903392
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US372196A Expired - Lifetime US2300959A (en) | 1940-01-01 | 1940-12-28 | Cathode for discharge devices |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2300959A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2782115A (en) * | 1953-08-24 | 1957-02-19 | Wimmer Anton | Process of producing pig iron and steel |
| US2871196A (en) * | 1957-04-29 | 1959-01-27 | Gen Electric | Cathodes and emissive material therefor |
| US2961568A (en) * | 1957-11-14 | 1960-11-22 | Gen Electric | Filament joint for incandescent lamps |
| US3312856A (en) * | 1963-03-26 | 1967-04-04 | Gen Electric | Rhenium supported metallic boride cathode emitters |
-
1940
- 1940-12-28 US US372196A patent/US2300959A/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2782115A (en) * | 1953-08-24 | 1957-02-19 | Wimmer Anton | Process of producing pig iron and steel |
| US2871196A (en) * | 1957-04-29 | 1959-01-27 | Gen Electric | Cathodes and emissive material therefor |
| US2961568A (en) * | 1957-11-14 | 1960-11-22 | Gen Electric | Filament joint for incandescent lamps |
| US3312856A (en) * | 1963-03-26 | 1967-04-04 | Gen Electric | Rhenium supported metallic boride cathode emitters |
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