US1995018A - Gas filled tube - Google Patents

Description

Mafch 19, 1935. l H. J. sPANNx-:R

GAS FILLEDy TUBE Filed Feb. 20, 1930 UTPUT l 0.6.

xNvENToR 17a/2s .lbf/Da/z/Ze/4 ATTQRNEYS 2 rect current output.

Patented Mar. 19, 1935 oFFfIfcE i y A,

GAsFrLLED'rUBE Y j.

Hans J'. Spanner, Berlin-Wvi-lmersdorf, Germany, assigner to Electrons, Inc., a corporation of Delaware ,App1iation1rebrury`20, i930, serial No. 429,889 Y In Germany March 4, ,-1929 e Claims. (o1. 25o-27.5)

This invention relates togas filled tubeshaving means for controlling either the time at which ionization begins within the tube, orV the'rate at which ionization proceeds. Due to tlieirfopera-l '5 tion, and arrangement of parts hereinafter described, tubes constructed in accordance with my invention are particularly adapted to control relatively large quantities of power.V

The invention provides a structure in4 Which the control means employed is preferably Without the tube and results Vin a device Which'may be easily manufactured, and which is relatively inexpensive. Thepositioningoi the control electrode outside the tube also screens the electrode from particles sputtered oi by the cathode.

The invention alsoaffords 'a means for variar cycle begins, at which the'tube will rectify alter-y natingvcurrenhthereby varying its average di- The arrangement disclosed also `results in an eicient relay for use with direct-currents. Y' The features and operation of the Ainvention Will -be apparent from the following description and the accompanyingdrawing, in which A I Fig. `1 illustrates-Aa preferred construction'in accordance with-myinvention; Y

Fig. 2 shows the -inventionas applied to .another forni of tube; Y Fig. S-Shews the distributienet potential Vdrop Y obtained, both before andfafte'r ionization starts; andV -1 Fig. 4 illustratesgraphically hovv the inventionV may be used to control the average value 315 ofthe direct current output in an'v alternating current rectier. f v, J v

In myfinvention the amount' of negative space chargewhich is neutralized'by the positive ions of the gas within the-tube may be controlled and thereby the strength of the current ilovv varied so as togpermit the tube to function asacontrol means for relatively 'large currents, which Acurrents may be either 'alternating or direct in character.`

YReferring to Fig. 1, a gas filled tube 1 is shown connected in such manner as to rectify alternating current. An anode 2 and a cathode 3 in the form of a lament are sealed Within the tube. A metallic shield 4 is provided for con- A trolling the point at which ionization of the tube begins. This shield or controlinember 4 is in the form of a cylinder which closely fits the eX- Y terior of the tube and extends over the distance y alternatingcurrentto give 'the eect shown-inl ous from the followingdescription thaty various other forms may be used.

If afsource of alternating'current is supplied to .therinput ,of the tube, thelatter serves as a rectifier to deliver directf'current toits output 5 terminals. The filament may be energized from the secondary 5 of a transformer, the pri marylof which may be connected either to the inputor other desired source of alternating vcurrent-A connection 'lis madeto the electrical center ofA the filament circuitand lservesto connect one. sideof the V'input circuit and alsothe. control.. circuit tothe `iilarnentA circuit. r`The SourceS oi control voltage may be 'obtained from a battery,.as shown, or it may be obtained from an alternating currentsource. "Ihe other side of :thecontr'ol circuit is connected. thru a potential vcontrolling device 9 tothe controlr electrode 4. The 'plate'Z is connected to oney of the direct `current. output L terminals, the vother Youtput Y terminal beingl connected to the alternating current sourcelasfshown. Theqscherne oi'fconnections is illustrative only,'.and may be Widely'variedlfor different purposes-by Athose skilled in the art. L A l I In thelforegoingarrangement the potential of member fiwill control thepoint at which ionization .starts on.each.positive half-'cycle of the Figlll, `which result Yis obtained by neutralizing the positive eld of the plate inthe neighborhoodv ofthe lament. .The resultant relectrostatic eld about the filament is thereby reduced and the electronsemittedby the iilament do not acquire suhicient velocity toionize the gas' and start the discharge until the input voltage reaches the desired value. Once ionization starts, however,

the resistance oi' the-gas path-between the Vvfila-VVV *l Vtery, this potential may be :obtained from any other suitable source of supply, and anysuitable'V means for controlling its potential may be used.r Due to the lfact that the exterior shield or .55

seal.

control element is separated from the tube electrodes by the insulating wall of the tube, various of the disadvantages of the conventional grid element within a tube are obviated. With'an inside grid, even though it may have the same potential as the iilament, the grid in service often becomes an emitting element itself due to Acondensation on its surface'of the emissive coating materialof the lament which is thrownr oi. An inside grid may also acquire suiicient heat from the filament to cause it to become emissive, and any emission on the part of the control element will cause ionization to take place. The instant that any ionizationoccurs'the cut-oi or control function of the tube is seriously impaired.

An important advantage of an exterior con# trol member lies in the fact that it can be comit controls, if so desired. The use of an exterior control member also provides a simplicity of construction and reduces vthe difficulty of making a An inside grid also occludes a considerable quantity of gas, and as it is an expensive undertaking to drive out all of vthe 'occluded Vgas in a large quantity of metal, my construction overcomes this disadvantage."

Fig. 2 illustrates another form of my tube having different shaped electrodes, and connected tocontrol a direct current circuit, but each of the tubesmay be used withA either direct or alternating currents. As connected in Fig. 2, when a direct current voltage is applied. tothe tube the gas is continuously ionized, and in such case the current flow can be varied dependent upon the number of ions inthe discharge path. This ionization can be controlled vby choosing the proper gas densityand varying the'potentialv of the control member. Thus, whenftheshield is very negative with respect to the filament, it attractsl a large number of ions 'fromthedischarge path and thereby permits the building vup of a space charge which decreases the direct current output. Asthe shield is made less negative the ions are released to neutralize the space charge and thereby increase the direct current output. Itis particularly advantageous toV have a large surface for the control electrode when using the same with direct current toneutralize a large quantity of ions, and my arrangement presents thisV advantage.

[Whenrused with direct current circuits, the `gas pressure is an important factor to givel the critical relay action desired. The pressure should be so chosen that with no potential on the control member there will be approximately enough ions present in the discharge stream' to just neutralize the spacecharge to prevent an appreciable space charge drop. The proper gas pressure will ,de-V pend upon various factors, such as the current flow, the size ofthe electrodes, and the configuration of the tube. There are various methods known to those in the art by which the proper density for a given gas may be determined. A

very simple method is to decrease the gas density until the voltage drop across the tube begins to rise above the ionizing voltage and at this point the gas pressure will be suiicient for all practical purposes. The pressure may, however, vary within certain limits, and generally can be somewhat higher because it will be decreased in every instance by .occlusione It Amay be desirable to deliver additional ions in certain quantities from either an auxiliary electrode within the tube, by varying the pressure of the gas within the portion of the tube adjacent the' electrodes, or by introducing the desired ions from external sources.

AIt will be appreciated from the foregoing by those skilled in the art that my tube may be 'utilizedas a valve to efficiently rectify or control -relatively large quantities of power, and may be pletely insulated from the power circuit which" used to replace circuit breakers, motor starters, rheostats, .and various other control apparatus. The tube Ymay, also be used as an oscillator since it has all ofthe. elements necessary to control the oscillation of a tube in the well-known manner. ,'Manyl other and varied uses will be obvious to those skilled in the art Without departing fromv the spirit of my invention, and Ido not wish to be limited except as indicated by the scope of the appendedY claims.

1. In a discharge tube, an. anode, a heatable electron emissive cathode and a gaseous medium, the cathode being subjected to disintegration of electropositive substances, a control electrode ofv large surface surrounding the total length of the discharge path outside of the wall of the tube and adapted tocontrol Vthe amount `of positive ionization in thedischarge iield, the saidgaseous mediumv having apressure which, with no potential on the Ycontrol electrode, gives a voltage drop fromvlanode' to cathodel slightly higher than the ionization potential of said medium.

2. In a; discharge tubeL an anode, a heatable emissive cathode, an ionizable medium at a pressure which gives anoperating voltage drop across the vtube, above 4the ionizing voltage, the cathode being subjected to disintegration of electropositive substances, and a `controlrelectrode of large surface extending along substantially the total length ofthe discharge path andprotected at its surface from said disintegrated substances, said control electrode cooperating with said medium tocontrol `the spacecurrentilow. K

3. In a discharge tube, an anode, a fixed thermionic catho defV and, a gaseous medium, the cathode being subjected to disintegration of elecf tropositive substances, and the density of Vsaid medium being such that the voltage drop across the `tubeisv slightly above Vthe ionizing voltage, and a control electrode substantiallysurrounding the dischargev path and protected at its surface lfrom disintegrated cathode materiaL, said controlelectrodebeing adapted to attract positive ions thereto and thereby control then amount of positive ionization in the discharge'eld HANS' J. SPANNER."`

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