US1993767A - Space discharge device and method of making it - Google Patents

Description

T UN-I EDsTATES PA OF PatentedMar; 12, 1935 srAcE DISCHARGE nEvIcE METHOD I or MAKINGIT *VictorO. Allen, Madison, N. J; assignor, by mesne' assignments, toRadio Corporation of America,

' a corporation of Delaware r No pr ing. Application April 4, 193b,

' fI'his invention relates to methods and means 51 members.

devices as audions, rectifiers, ;etc it is the usual I practicetoemploy so called getters,.andclean-up agents itoj expedite the evacuation oi the devices :1 It has: alsobeen proposed to employ Chemical agents which are left permanently within the device to act as'ikeepers so far as'occluded and residualzgases within the device are concerned.

Nothoroughly satisfactory single chemical; agent may beemployed as both getter. and fkeeperf with different types of electron emitters-.' I

heretofore to employ as a getter, magnesium.

. However the utility ofmagnesium is limited in a its advantagesto devices employing emitters of the thoriated tungsten type. In orderthat the.

magnesium may' be rendered effective itis necessary'to subject it to a flashing operation whereby it becomes vaporized. Substantially the en- 5"; tire. clean-up action of the magnesium is therefore eiiective only while it is in a vaporized condition; Aside from this limitation there isanother disadvantagewhich of course is common to all: vaporizable getters, name y that it is difiicult n ztheiormof a non-transparentfmirror on the walls and other partsbf-the device. Ithas been{ .5;. proved'by many tests that after. the manufacture ot the magnesiumis almostentirely..-negligible} ci a deviceand while itds in use theeffectiveness Devices have been actuallymade without employing the magnesium. getter and said devices have been found to-possess as good a life andoperating characteristics includingffreedom from gases as with devices employing magnesium;

1 Accordingly it isyanothenimportant object of the present invention to provide -a chemical agent or agents for; electron discharge devices and; possessing all the advantages of the usual 'jmagnesium getter and without the above noted and other disadvantages incident to the use of magnesium. v j y Another object of the invention is to; provide a -nove1 chemical :clean-up agent for expediting '7 the evacuation'of electron discharge deviceswhich agent'also acts asan effective .keeperf duringthe entire life of the device.

n Another object isto; providel a'nOnEVaporiZabIe.

I pjAnother feature of the invention relates to Applicantgis aware that it has been proposed cal; agent capable tion not specifically enumerated will be appar-' billing with carbon dioxide, carbon monoxide;

Serial No.1 l41,703

14 Claims. "(o1.250+g'1.5);...

chemical agent which acts as an effective getter of manufacturing space discharge. devices and with particularity to a novel method of manu facturing devices employingwelectron emissiveand keeper while inthe non-vaporized state. Another object of the invention is to provide a novel typeof. clean-up agent having 'a' greater.

v g capacity to absorb or adsorb residual gases both 5. is well known in the manufacture ofsuch V duringthe manufacture'and during the life of thedevice. V l Another object of the invention is toemploy as a getter or clean-up agent thesame material which .canbe used for electron emissive pur 10 DOSES. V V r A feature of the invention relates to the use of a compound of the alkali earthgroup and the alkali metal group containing oxygen, as a getter and PkeeperF.

the'method of producing agetter and ;keeper within an electron discharge device.

7 Another feature of the invention relates to the method-of treating acarbonate of the alkali earth group to produce'a chemical agent which acts both as getter and keeperj g A further feature-of theinvention relates to the method of producing a non-vaporized'chemiof acting as a getter" and keeper..- j 1 V a A further feature relates to, the method of subjecting a chemical agent. within an electron discharge device to successive treatments wherebysaid agent isfirst decomposed to produce an v oxide which acts as a cleanup agent and" also liberates the gas or gases acting to flush. out

any air or other gas within'the device.

V of the alkali or alkali earth groups to producean oxide. .by decomposition without liberating any oxidizing gases or vapors. 7 -.Other features and advantages of: the invenent after a consideration of the following detail; descriptions and the appended claims. 1

.It is a well-known fact that the oxides -of the V alkali earth group have a great affinity for com- Water; vapor and 'rnany other gases which 'asis well knowninterfere with the proper evacuation and operation of electron discharge devices;

This characteristic is so marked that these oxides cannot be exposed under ordinary; conditions to the atmosphere without being immediately. attacked; ,7 I j 1 i It is. also known that the addition of carbon to barium or strontium carbonates considerably lowers the temperature required for decomposition of such carbonates, and that during this reaction carbon monoxide is liberated instead of carbon dioxide, as is shown by the following eq uation I In the manufacture of such devices. as audions or the like it is recognized that carbon monoxide gas being a strong reducing agentis an ideal gas for flushing out the devicebefore the final clean up agent. vention therefore it is proposed to employ any In accordance with the-present insuitable salt either of the alkali metal or the alkali earth groups.

of the invention; These salts are mixed withan organic material or any material containing organic carbon either in the freeor 'associatedi states and subjected to heat. Thus in manufacturing audions, lamps, or vacuumtubes generally the following procedurehas actually been employed and found to produce very good re sults. A mixture of barium and strontium carbonatesWit-h organic" carbon is mounted at any convenient point withintheenvelopeof the device. Preferably this mixture is mounted in the device at such a point that its temperature is not surlic'iently raised torenderit electronically active. Thus the mixture may be compressed within a small cup or container andfthis container mountedat' a distance from'the heater elementor filament off the device;

The device with the chemical thus mounted therein is placed on the pump andfsubjected to simultaneously raised to a-relatively high tern perature, preferably by induced radio-frequency currents in-the usual manner, and during this heat treatment the evacuation is continued and completed in the regular manner. When the evacuation hasbeen' proceeded with to-the re quired extent the device is'sealed oi? the pump.

Consequently. there is retained within the de-- vice a: comparatively large quantity of barium and strontiurn oxide which function 'as-ke'epers' during. the actual life of the device: to react with gases liberated from the elements and surfaces within the device. I r

From the foregoing it will be seen that there is produced a chemical agent which acts during the initial stages of evacuation to expedite the evacuating time and also remains within the deviceto act as keeper and since the keeping action of the agent is substantially entirely independent of its vaporization it is efiecthis at all times during the life of the device regardless or the operating temperature thereof.

Inasmuch as the barium and strontium oxides resulting from the decomposing process hereinabove described are themselves electronically emissive and are the same materials that are ordinarily employed for electron emissive cathodes, it is necessary to mount the chemical agents I For :example oxalatesor carbonates of barium and/or, strontium are particularly advantageous in achieving the objects above described at such a point within the device that they do not become hot, to render them electronically active during the life of the tube. What is claimed is: V

1. The method of evacuating the enclosing envelope: of an electron discharge device having an electron emitting cathode which comprises heating apart from the cathode a stable salt of the alkali earth group in the presence of a reducing agent to produce an alkali earth oxide,

subjecting'the envelope to a pumping operation during said heating, and 'resubjecting the oxide 'to-heat to eifect a final evacuation.

2. The method. of evacuating an electron dis-- charge device having an electron emissive cathode,. which includes the step of heating apart fromsaid'cathode, a carbonate of an alkali earth metal'i'n the presence of a reducing agent with- .in the device:

3. The method of evacuating an electron discharge device-having an electron emissive cathode which includes the' step of heating apartfrom- 'sa-id cathode, a carbonate of an alkali earth metal inthe presence of organic carbon within the device. 7 I v I 4.' The methodof evacuating an electron dis charge device having an electron emissive cathode which includes thejstep of heating apart from said" cathode, a mixture or arium carbonate'in' the presence of'a reducing agent within the device:

5;. The-method ofevacuating an electron dis-' charge device having an electron emissive cathode which includes the step of heating apart from said cathode, a mixture of barium carbonate in the presence of organic carbon within the device to reduce the barium carbonate to bariumpxide and then heating the barium oxide to complete the evacuation. V v

c 6. The method of evacuating an electron discharge device having an electron emissive cath ode which comprises mounting a mixture of barium and strontium carbonates together with organic carbon at a suitable location within the device where it will not be materially afiected" by-cathode heat, reducing said carbonates to their oxides, subjecting the oxides to heat and simul-- taneously subjecting the device to exhaustion; j

7. The method of completing the evacuation'of a partially evacuated electron discharge device which comprises heatinga stable salt of the alkali earth group to liberate a quantity of carbon mon oxide within the device and to reduce said salt to the oxide, removing said carbon'monoxide, and then heating said oxide to effect a final clean-up.

8.- The method of completing the evacuation of a partially evacuated electron discharge device which includesheating a-carbonate of the alkali earth'group' to evolve a'quantity of carbon m'onoxide within the device and to reduce said salt to the'o'xidaremoving said carbon monoxide,

' and then heating said oxide to effect a final cleanl An electron'discharge devi'ce'havingon' the interior thereof an electron emissive cathode and a separate quantity of a carbonate of the alkali earth group situated within the device at a point where it will not be materially affected by the cathode heat.

10. An electron discharge device having onthe interior thereof an electron emissive member and a separate quantity ofmaterial apart from said member comprising a mixture of barium and strontium'carbonates and organic carbon.

1l. The method of evacuating an electron discharge device having an electron emitting cathode which comprises mounting a mixture of an oxalate ofthe alkali earth group and organic carbon within'the device and subjecting said mixture to heatapart from said cathode;

12. The method of evacuating an electron'discharge device having anelectronemitting cathode which comprises mounting a mixture of an oxalate of an alkali metal and organic carbon within the device and subjecting said mixture to heat apart from said cathode.

13. The method of manufacturing an electron discharge device having an evacuated envelope which comprises subjecting a mixture of a salt of the alkali earth group and a reducing agent placed withinthe envelope to heat to effect a reaction therebetween to form an oxide of the metal of thesalt' and carbon monoxide and evacuating the envelope during the reaction;

14. The method'of evacuating an electron discharge device having an electron emitting cathode therein which includes the step of heating a mix- 'ture of barium and strontium carbonates in the presence of organic carbon within the device and apart from said cathode to efiect a reaction there-- between to provide'barium and strontium oxides within said device. VICTOR 0. ALLEN.