US2825853A - Gaseous discharge devices - Google Patents

Description

March 1958 SlN-PlH FAN GASEOUS DISCHARGE DEVICES Filed Aug. 30, 1954 INVENTOR SIN-PIH FAN United tates Patent't') GASEOUS DISCHARGE DEVICES Sin-'Pih Fan, PhiladelphiapPa assignor' to Burroughs Corporatiom-Detr'oit; Michi, a corporation-of Michigan Application August 30, 1954, Serial No.=453,038 6 Claims. (CL 315-168)" This invention "relates generallyto gaseous discharge devices.*"-Mor'e particularly the invention relatesto bi stable state gaseous tubes.

Gaseous tube bistable state devices "havebeen' proposed in the prior 'art. Such devices'are exemplified-by glow discharge circuits of the H. P. BoswauPate'nt No. 2,142,- l06or theR; S. Cre'nshaw, Jr; Patent'-No.' 2,541,041. These" devices have-relied upon differences in -ionization andde'ionization potentials in response to-eXternal pulses for "both fixing and extinguishing the discharge." 3 Thus, the elements have been sensitive to gas pressure and im- 2 condition" results equilibrium 'is'reache'd between ion' and-electroncurrent flow. Ibis-position depends upon gas pressure'and circuit parameters. It has been determinedthat'withlowpressure tubesthe positive ion current flow to'the grid is a function of both the electric fieldintensity'about'the gridand the positive ion density;

' Thusf-witlt less elcctricfield intensity, the positive'ions purities t'o the extent that reliable operationwithin close tolerances is difiicult'without special'selection'of' tubes;

Furthermore; it" is" difficult to positively triggerthe prior art devices in both-of 'thefstable conditions with-similar control pulses.

Thei'efore;"an'object"of the presentirivention is-'-to produce reliable bistab'le'" state operation with" gaseous disch'argetubes."

A further object of the invention'is to provid'e'novel gaseous 'tube's'tructure.

A generalobject of the inventionis to provide-im proved gaseous discharge devices.

In general any gaseous discharge device including" a control electrode may-be operated in accordance "with themethods proposed by the present invention to aiford bistable output characteristics.

Ina specific embodiment-of the invention-a special electron discharge device is constructed comprising'an hermetically sealed envelope with at least one bistable state compartment within said envelope.- Each of the compartmentscomprises a cathode, an anode, and two spaced control grid electrodes forming an isolated area between'the cathode and'the anode of each compartment. A gaseous atmosphere is provided within said envelope. External power-supply means and-associated circuitry is 'c'onnected'to' the electrodes to bias the control -eletrodesandcreate an electric field about the cathode of such magnitude'that no appreciable amount of electrons"wil1-fiow"from' the cathode to the anodein the presenceof the grid bias. Load circuits such as resistors areindividually'connected with each of the grids and the'anode to develop respectively input and output potentials'.

If this tube is operated with a positive voltage pulse applied to a grid electrode or the anode one of said sections or conversely if a negative voltage pulse appliedto' th'e'cath'ode of one of the compartments, it will establish "electron flow, which in turn will generate positive ions. The' positive ions will'flow to the biased grid electrodes which are normally maintained at a negative potentialandcause-the grid voltage to rise, thus-allowing'more'clectrons' to flow to the anodewhich in turn will generate more ions. Efiectively, this is a negative resistance action which will continue and cause the "grid voltage" to become 'morepositive 'until 'a limiting'saturation condition results; after which electron flow to thegridagainreduces the 'potential."' A conductive stable will how at lower'speed tothe grids 'than'with greater field intensiqrb' .Accordinglwa reduction of field intensity wilhreduc'etheibn currentrfiow tothe grid; A lowering of gridion current wilhdebrease' the field intensity and finally cause a 'non=conductive stable grid; voltagestate: In order to cause a reversible action, the tube parameters must be s'uclrtliatthe grid 'do'es-not 'lose'control. One way of assuring'thisis to providea: low pressure" gaseous atmosphere such 'tlia't "the ions are sparse enough "to b'e' unablntoformthe plasma sheath of usual gaseous tubes which causesthet'gridy-tb"lose '-control." By means of thisfeature' of 'the invehtiondherefore'; the'field intensity may be controlled to establish either -one'of'the -two stable statesJ In accordance with another embodiment of the iuven n'on the tube compartments are stacked in such a' manner thateach co'mpartmentserves to prime'the adjacent com partmentfor conduction in-*-response to an external signal; Grid electrodemeans separate-the electrodes ofeach tube section." Thiis'jeach'gi-id except-the first and' the last grid"in"the ,stack'mrefunctionally common to the two adjacent anode cathdde'electrode assemblies; The -'elec-" fiodefirst in-order alongdhe'stacked compartments-is ordinarily" maintained"at"' a more-positive potential than any"of tlfe succeeding" electr'odes:-=If then "there "is a simnltaneousinput' pulse 'appliedtdall the gl'idST'0fih tube, only the firsteompartment" of thetube'cOntaininQ the more positive grid will conduct; The magnitude and duration' of the input pulse' is "so chosen '-that there 'is no possibility of "causing' the othertube" compartments to conduct: Then',"1the'"next' input signal-will cause-"the above"operation"to-proceedto the' next adjacent *tube 'section',=etc. 'Inpursignalsmay' be-impressed respectively until all' tubesections are simultaneously conducting. Thereafter, 'the tube compartments; beginning 'with 'the last "one-in said stacked'arrangement can be made-to become non-conducting by the application-"of a further series of signals such'as negative pulses applied to the grid electrodes. "Alternative operation maybe provided with a large amplitude-pulsed respective polarity being usedtocut-ofioffire all compartments simultaneously. It the'amplitude -isless and"thepulse'-width longpthe switching-of the individual compartments maybe done in quick succession:

In accordance-'wvithstill another embodimentof the invention, an' "electron "discharge" device comprises i i a hermeticallysfealed' envelope; a' cathode positioned-within said envelopey'a pluralityofanode electrodes arranged ina substantiallyconcentric manner about the cathode and spacedsubstantiallyequidistant apart, and' a series of single control gridelectrodes located between adjacent anode electrodes-." -These anodes canarbitrarily be designated as runningconsecutively'from-a first position toan Ntlf'position"whe're 'there are-N anodes." The'N resulting grid' electrodes'comprise'plate-like electrodes, which extendbetweeneach anode to a point near to' and' radial with the cathode. *An additional 'grid electrode whichis maintained at a lower potential may be positioned between the Nth anode'a'nd theNth' grid electrode so that initially the first anodeandthe cathode 'will form-"u conductive path =r'atherthan the Nth' anode and the cathode.

In accordance*with-onefeatureof the inventiorr'the tubes may-be stepped in either'direction*along the compartments of the tube. This *resultsbecause the tube may be made to proceed at will to either of its stable conditions. Thus, the gaseous matter within the device is maintained at low pressure, so that complete ionization in a tube section will not isolate the grid action. Otherwise potentials established at the grid electrodes would not control the flow of electrons in the tube sections, and the switching process would be irreversible.

Although several special tubes are constructed to take advantage of operational characteristics taught by the invention, any low pressure gaseous tube having control electrodes may be operated by the novel methods of the invention to produce bistable state characteristics.

Other objects and features of the invention will be more fully understood from the following detailed description thereof when read in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagrammatic sketch of a gaseous tube and associated circuitry comprising a bistable device constructed in accordance with the invention;

Figs. 2 and 3 are schematic sketches of embodiments of the invention employing a gaseous tube with a cascaded or stacked arrangement of individual bistable state tube sections; and

Fig. 4 is a graph showing curves representative of the mode of operation of the invention. Referring now to Fig. 1, the electron emitting cathode is positioned within an hermetically sealed envelope 17 and connected to ground potential through a resistor 15. An electron receiving anode 11 is also positioned with the envelope 17 in spaced relationship with the cathode 10 and is connected to ground potential through the series combination of resistor 14 and positive potential source 16. Two grid electrodes 12 and 13 stationed on either side of a compartment containing the anode and cathode are individually connected in series arrangement with resistors 18 and 19, which have a common terminal extending to the negative potential source 21. The positive terminal of potential source 21 is connected to ground potential through a load resistor 20. Input terminals 22, 23, and 24 are associated respectively with the two commonly connected grid electrodes, the anode 11, and the cathode 10. It is to be noted that although operation of the device may be obtained through the application of properly poled input signals of suitable magnitude and duration to any of the input leads 22, 23, or 24, reference will be hereinafter made principally to positive signals at input lead 22.

Referring now to Fig. 2, a. series of grids 26 through 32 are arranged substantially parallel to each other such that their normal projections will be substantially coincident. The grids 26 through 32 each define one bound of a tube compartment, and physically comprise a platelike member substantially parallel to a plane passed through a separate anode and cathode located in each compartment. The anodes 33 through 37 are spaced along a line normal to the plane of any of the grid electrodes. The anodes 33 through 37 are commonly connected to the positive terminal of potential source 45 by way of resistor 43. Cathodes 38 through 42 are also positioned in a line normal to the plane of any of the grid electrodes and each cathode is spaced laterally from the corresponding anode. All of the cathodes 38 through 42 are commonly connected to ground through a resistor 44. Each of the grid electrodes 27 through 31 are connected to the series combination of a resistor 57 and the negative terminal of potential source 53 through respective ones of individual resistors 48 through 52. The positive terminal of potential source 53 is connected to ground.

A double pole-double throw switch 55 has one pole adapted to connect a further negative potential source 56 directly to the first grid electrode 32 in one position, and directly to the last grid electrode 26 in the other position. The other pole respectively connects the potential source 53 through resistor 54 to the first grid electrode 32 or the last grid electrode 26.

Referring now to Fig. 3 plate-like grid electrodes 61 through 70 are arranged concentrically around and radially extending from the cathode 78. Each of the grid electrodes 61 through 7 0 are contained within hermetically sealed envelope 60. Separate anodes 59 and 71 through 77 are also arranged concentrically around cathode 78 and are individually spaced between adjacent grid elec-.

trodes, except that no anode is positioned between grid electrodes 61 and 70. The purpose of this is to isolate the two tube sections represented by anodes 59 and 77 from each other so that the direction of rotation of ionization of tube sections can be controlled. This will become more readily understood from the description of operation appearing later in this specification. Separate resistors 79 through 86 respectively connect grid electrodes 62 through 69 to a common conductor 99. The series combination of load resistor 97 and the negative potential source 96 connects the said common conductor 99, and therefore the grid electrodes, to ground potential. The double pole-double throw switch 98, however, in one position connects the further negative supply potential source to grid electrode 61 through a resistor 90, and simultaneously connects grid electrode 70 to common conductor 99 through a resistor 87. Alternatively in the other position switch 98 will connect negative battery source 95 to grid 70 through resistance 90 and will connect grid 61 to common conductor 99 through resistance 87. The function of the switch 98, which is much the same as the function of the switch 55 of Fig. 2 is to permit a choice of the direction in which the tube may be made to count in response to a series of successive input pulses.

All of the anodes 59 and 71 through 77 are connected to a common positive potential source 94 through resistor 88. The cathode 78 is connected to ground through a resistor 89. Separate terminals 91, 92, and 93 are associated respectively with the anodes, the cathode, and the grid electrodes. As described with respect to Figs. 1 and 2, any of the three injut terminals may be utilized to insert operating pulses to the circuit, but in the description of operation contained herein, emphasis will be placed on utilization of positive pulses at the input terminal 93 associated with the grid electrodes.

Referring to operation of the tube of Fig. 1, assume that there is no appreciable electron flow from the cathode 10 due to the negative voltage bias on grid electrodes 12 and 13. If now a positive voltage pulse of the proper magnitude is applied to input terminal 22 connected to grids 12 and 13 through resistors 18 and 19, it will raise the potential of the grid electrodes 12 and 13 to a point where some electrons will flow from cathode 10 towards anode 11. Some of these electrons will hit gas molecules in the tube and thus create positive ions which will be attracted to the grids 12 and 13. This will raise the potential of the grids 12 and 13 which will permit more electrons to flow from the cathode which, in turn, will create more positive ions. The potential of the grid voltage will finally rise to a point where it will begin to collect electrons as well as positive ions, thus decreasing the rate at which the grid potential is rising. The rate of collection of electrons by the grid electrodes 12 and 13 will continue to increase until equilibrium is reached as the negative electric charge they represent approaches the positive charge on the positive ions collected by said grid electrodes. Stability is reached when the grid currentgrid voltage curve 102 of Fig. 4 intersects the load line at point 100. It is to be noted that curve 102 has a negative resistance portion and that a further stable condition exists at point 103 when the tube section is in a nonconducting condition. Point 104 is a non-stable point as can be seen from the curve 102. Curve 105 of Fig. 4 represents the anode current to anode 11 as the potential of grids 12 and 13 increases in a positive direction. It is clear from this that an output potential may be taken from the tube anode at terminal 23 indicating the bistable condition of the tube. The stable operating point is -enough to avoid sheathing the grid agene gsis's attained since the gaseous matter in the tubeisnot forced into complete isolation of the grid. This is p'ossiblewhen the difference of potential between the cathode and the grid electrodes or the cathode and the anode electrode is kept below a critical value or the gas pressure is low during complete ionization. The tube may therefore be cut off or removed from its conductive stable state to its non-conductive stable state by applying a negative pulse to the grids at terminal 22.

Operation of the circuit of Fig. 2 is similar except that several units are cascaded within a single envelope. Further structural details are included for controllin'g'the direction of propagation of information alongthe several cascaded units. Thus, assume that the double pole-double throw switch 55 is in the upper position so that the negative terminal of potential source 56 is connected to the lowermost grid 32 and that the negative terminal of' potential source 53 is connected to the uppermost grid 26 through resistance 54. Potential source 53 maintains grid 26 at a lower potential than potential source 56 maintains grid 32.

Thus, if a positive input voltage pulse of the proper magnitude is now applied to input terminal 106, electron current will be caused to flow from cathode 42 towards anode 37. In accordance with the curve 102 of Fig. 4, this tube section (herein identified as the first tube section) will leave the stable condition identified by point 103 and become conductive at stable point 100. It is to be noted that the aforementioned positive pulse applied to input terminal 106 was applied to all the grid electrodes 26 through 32 but that only the first tube section became conductive. This is due to the fact that grid electrode 32, prior to the application of said positive input pulse, is made more positive than the remaining grids 26 through 31 and thus becomes primed to conduct with a lower magnitude input pulse than grids 26 through 31. In the conductive state of the first tube section the grid 31 will be more positive than the remaining grids 26 through 30 because of current fiow through resistor 52 resulting from positive ions bombarding the grid 31.

The application of a second positive voltage input pulse upon terminal 106 similarly causes electron current to flow from cathode 41 towards anode 36 in what herein is defined as the second tube section. The second tube section will therefore be driven into the bistable condition of point 100 as well as the first tube section. This results because ionization within the first tube section causes the adjoining grid 31 to be primed more positive than grids 26 through 30.

In a similar manner the remaining tube sections can be caused to attain the conductive state in consecutive order until all the sections are simultaneously conductive. In this condition, all the grid electrodes except grid 32 and grid 26 receive positive ions from two tube sections. It is further to be noted that grid 32 is biased more positively by battery source 56 (when the switch 55 is closed in its uppermost position) than are any of the other grid electrodes. Consequently, the tube sections can be caused to become extinguished one by one beginning with the last tube section containing cathode 38 by further application of successive negative voltage input pulses upon input terminal 106. More specifically, a first negative voltage input impressed upon input terminal 106 will cause only the tube section containing cathode 38 to become extinguished because of the less positive potential of grid 26 caused by receiving ions from the single tube section. Then grid 27 will be collecting positive ions from only one tube section. Therefore, a second negative input pulse upon terminal 106 will cause only the tube section adjacent the said last tube section to become extinguished. The last tube section to become extinguished will be that section containing cathode 42.

The direction of propagation along the sections of the device shown in Fig. 2 can be reversed by changing the position of switch 55" so that negative-battery supply iti is connected to grid electrode 26 and negative battery source 53 is connected to grid 32 -throu'gh=resistbnc'e 54.

In the structure'shown in Fig:- 3', similar: operation results. Assume thatth'e' doublepole double'throwswitch 98 is positioned so that'negative battery source -is connected to-grid-61and-negativebatterysource 96 connected to grid 70 through resistance 97. By placing grid 61 at a more positive potential than any of-th'e' other grids 62 through 70'=with thep'dtential source 95, apositive voltage input pulse of'the proper'magnitude' applied to input terminal 93 'will cause thetub'e' section-comprising anode 59' to b'ecomecbnductive, thus causing grid 62 to become-"more positivethan-grids 63-through 70'; Another positive-pulse'applied to=input terminal 93 will cause the tube sectioncorfiprising anode 71"to become conductive. Subsequent positive" pulses will cause consecutive tube sections to 'become conductiveuntirall the tubesection are condtictin'g Millie-condition; grid 70 collects positive ions from only the tube section comprising anode 77. Additionally, it should be noted that grid 61, which also collects positive ions from only one tube section, is biased more positively by battery source 95 than is grid 70 by battery source 96. Consequently, a series of negative pulses applied to input terminal 93 will consecutively cause the tube sections to become nonconductive beginning with the tube section comprising anode 77.

If switch 98 is positioned so that battery source 95 is connected to grid 70 through resistance 90, and grid 61 is connected to battery source 96 through resistance 87, the direction of propagation about the cathode 78 will be reversed in that the tube section containing anode 77 will be the first to become conductive and the tube section containing anode 59 will be the last to become couductive. Thus, it is seen that the tube may be readily used as a reversible counting device or arithmetic register.

Certain variations may be made from the specific embodiments of the invention. For example, by using con ventional gaseoustube structure with specified gas pressure, operating methods similar to those described here inbefore may be effected to attain the desired bistable state characteristics. Having, therefore, described the operational features of the invention, claims are appended which are believed descriptive of the nature and scope of the invention.

What is claimed is:

1. A gaseous discharge device and accompanying system comprising a hermetically sealed envelope, cathode means positioned with said envelope, a plurality of anodes spaced apart from said cathode means, a plurality of grid electrodes each extending from said cathode means and along a point substantially midway between adjacent ones of said anode means, a bias potential coupled to said grid electrodes, a first potential source connected between the cathode means and each anode of such magnitude that the electric field from this source alone between said cathode means and said plurality of anodes will not support electron flow fom said cathode means in the presence of said bias potential, at second potential source coupled to at least one grid electrode to alter the electric field surrounding said cathode means to support electron current flow from said cathode to a corresponding one of said anodes upon initiation by an external pulse, gaseous means within said hermetically sealed envelope adapted to produce positive ions when bombarded with electron flow, and means coupled to individual grid electrodes to reduce the bias potential in response to ion collection.

2. A gaseous discharge device in accordance with claim 1 in which said cathode means comprises a plurality of cathodes arranged substantially in a row, each one of said cathodes being associated with an individual one of said plurality of anodes, said plurality of grid electrodes individually separating each associated anode and cathode from each other associated anode and cathode elec- 1 in which said cathode means is a single electrode, a plurality of anodes are positioned concentrically around said cathode means and in which each of said plurality of grid electrodes extends radially from the vicinity of said cathode means through a point substantially midway between adjacent ones of said anodes.

4. A bistable state device comprising in combination, a gaseous discharge tube having at least a control electrode, cathode and anode, means biasing the control electrode, means establishing a potential between said cathode and said anode of such magnitude that discharge is not supported between the anode and cathode in the presence of control electrode bias, means coupled with the control electrode to reduce the bias upon collection by ions, and means reducing the bias in response to an external signal in such magnitude that conduction is supported between the anode and cathode and is main tained by ion collection upon the control electrode.

5. A gaseous discharge device comprising, an anode a cathode spaced from said anode, and a pair of grid. electrodes stationed on opposite sides of the anode receive ion current in response to a glow discharge an: extending substantially the entire distance between the cathode and anode to form a compartment capable of su; taining a glow discharge.

6. A device as defined in claim 5 wherein the grid elec trodes are connected with series resistors of such value that ion current flowing therethrough during glow dis charge will maintain the device in a stable conductive condition.

References Cited in the file of this patent UNITED STATES PATENTS 2,593,109 Craft Apr. 15, 1952

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