US2642548A - Cold cathode discharge tube - Google Patents

Description

June 16, 1953 M. w. WALLACE 2,642,548

COLD CATHODE DISCHARGE TUBE Filed 061;. 26, 1951 J g I v VEN IN TOR M/LNER W. WALLACE ATTORNEY Patented June" 16, 1953 COLD CATHODE DISCHARGE TUBE Milner W. Wallace, Westwood, N. J., assignor to v Federal Telecommunication Laboratories, Inc., a

Nutley, N. J a'corporation of Delaware I Application October 26, 1951, Serial No. 253,284

13 Claims. (Cl. 313-196) This invention relates to electron switchin and counting devices and. more particularly to multi-gap cold cathode discharge tube for use in such devices.

In multi-gap tubes heretofore proposed for switching and counting devices, one anode and several cathodes are provided to form a number of cathode-anode gaps. In the use of these tubes it is desired that the gaps discharge in a given order. It is also desirable that the discharge transfer reliably from one gap to another particular gap, in some definite prescribed sequence. Heretofore attempts have'been made to accomplish desired sequence of discharge by providing intermediate cathodes or special'transfer electrodes together with external circuits or by shaping the cathodes to include transfer elec trodes for unidirectional counting operation.

Where the cathodes are specially shaped to effect directional transfer from gap to gap, such shaping tends to slow down the operation" since special shaping increases de-ionization time or requires progression of the glow from the initial point of discharge to a point adjacent the next gap to be discharged. If rapid counting operation is not desired, then the slow shift of the glow across the shaped cathode is not troublesome. Howeper, if rapid count is important, then special shaping of the cathode impedes the operation and is, therefore, undesirable. Where additional cathodes or transfer electrodes are provided between counting cathodes, such arrangements add complications to the tubestructure and the associated circuitry, and the time element required for each transfer again slows down the operation of the tube.

One of the objects of this invention is to provide a multi-gap cold cathode gas filled tube which avoids the use of specially shaped electrodes and/or the addition of transfer electrodes.

Another object of the invention is to provide a multi-cathode counting and switching device for use with a cathode biasing circuit capable of high speed counting and switching op= e'ration.

One of the features of the invention is the simplicity of construction of the tube, the cathodes or transfer electrodes. Instead, I have found itpreferable to have all cathode-anode gaps as simple and as nearly identical as possible and to relyon circuit biasing and adjacent gap priming for unidirectional operation.

Another feature of the invention is the pro- 7 vision of means for controlling or limiting the cathodes so that they have substantially equal active areas. I accomplish this by placing a barrier, which may comprisea shield or control electrode extending over adjacent the part of the cathode to be maintained inactive. .The active portion of the cathode is then the end portion that protrudes beyond this barrier. Where an apertured shield or. control electrode plate is used as a barrier, another feature involved is the manner and method employed to support and align the cathodes in spaced axially extension through such apertures.

The above-mentioned and other features and objects of this invention will become more ap-v parent by reference to the following descrip tion taken in conjunction with the accompanying drawings, wherein:

Fig. l is a vertical sectional view of a multigap tube according to'the present invention; Fig. 2 is a schematic illustrationof the tube together with a biasing circuit'for the cathodes thereof;

Fig. 3 is a fragmentary view of a modified cathode-anode assembly with parts/shown in section;

Fig. 4 is a fragmentary view of another embodiment of the cathode-anode'assembly with parts showninsection; andf v Fig. '5 is a plan view of the assembly shown in Fig. l. V

Referring to Fig. 1 of the'drawing the tube comprises an envelope I mounted in a base 2 which is provided with terminals 3 for reception in a socket. The terminals 3 are connected by 'leads 4 through the envelope I to corresponding electrodes of the tube.' The baseand envelope are secured together by cement 5. One of the electrodes 7 contains at least'in part an electrode assembly, and the electrode assembly as a whole is supported'by'the leads 4 which are sealed throughthe envelope l as indicated are shown. The cathode pins are supported in' at 6. The electrode 1 is in'the form of a ho1-' low body, one part 8 being in the form of a hol-, low cylinder while asecond part 9 is in the form 1' of an end flange. The end flange 9 extends m-; wardly and comprises a barrier for determinin Y The flangev 9" an insulating web 2| which extends crosswise of the body 8 to which it is secured. This web may comprise glass or other insulating material. In order to insure proper alignment of the cathode pins axially of the apertures 0, the following operation is found satisfactory The cathode pins and the body 8 are pro-oxidized so that the cathode pins are just large enough to fit into the apertures Ills -The oxide layers act as spacers to locate the pins centrally of the apertures; After the application of the glass web.- bi ng 2| the oxides are removed by a cleaning operation including a water rinse and a dip in a solution of sulfuric and nitric acid, thus centering the cathode pins in spaced relation in the apertures ID. The clearance 'betwefen'the pins and the sides of the apertures is preferably within 0.002 to 0.004 inch. I

A central stem 22 is provided for supporting a cylindrical anode 23. The stem 22 is beaded as indicated at 24 and made integral with the webbing 2} by known glass welding technique. This welding operation also secures the webbing 2'! to the cylindrical portion of the electrode 1 which is preferably of Kovar. The cathode pins as well as the anode stem 22 are of Kovar which has a coeificient of expansion similar to glass. The anode 23 is supported by wires 25 which are Welded to the anode and to the anode stem 22.

The member 1 which comprises the support for the assembly as well as the shield for defining the active areas of the cathodes is connected by a lead 26 by which the member may be raised to a desired potential. The member thus biased acts as a control electrode for the cathodes and limits the active areas thereof.

Referring to Figs. 3, 4, and of the drawing, twoalternative elements for the cathode-anode assembly are shown. In Fig. 3 the anode is indicated as a wire rin 31 which is disposed con:- centrically 0f the series of cathodes H to 20. The cathodes extend through apertures con tained a control electrode plate 33, similarly as ill str te n are. r. It W b d aploaroht to tho e s il i tho r a e anode 2'! may be of various shapes so long as an anode urfac is spac o oivo di t ho m ho this s rfa o he cat odes- F r e m le h he 2'! ma vo hio'the ends of th at o esas ho jio to l in i o t ma h dis s wit n the circle defined byt'he' cathodes.

in F s 4 and 5. h ohtrolj l to 2 is posed as a hollow cylinder without the end flange show i He n th s form. h apertur d atod 30 are dis d ci c e hu may boih her uration if s e in h wall ff o oyh do oh ho h e s ch. s nd catedattl, are turned at their ends so that the cti e a dons a: are d s ed a l h h the apertures 30. The anode 33 in the form of a ringis -disposed concentrically of the control olootrod 29 h o o si a on to t e nds o he a i ly d os d hoda hi e I a e shown r ss b-lo catho eho l ss mbl arr n e nt in. ig a ne 5, i ill be c ar ha manyv o her a ran e:

m h u i z n ho.. rhp o a de-anod r laa tionship and the assembly features of the present invention'are possible. The cathodes, for errample, may be arranged in a straight line or if desired in'an irregular fashion so long as the anode is spacedjequally from each of the oathd The u d ntal e rem n is tha the a o o a s h v s st tiall identica operating characteristics.

The gaseous atmosphere preferred for the tube is a mixture of neon, argon and hydrogen, the percentage of which may be varied widely depending upon the gas pressure, the electrode voltages and the electrode geometry of the tube; and also the break-down voltage point desired. When hydrogen gas is used in small percentages the hydrogen accelerates .dGs-iQIliZfitiQIl and is, therefore,.desirab le. The amount of hydrogen preferred is between 5 and 10 per cent. Argon is used principally to reduce the breakdown voltage point and is not critical. The percentage of argon is preferably between about 1 and 3 per .cent. The remaining percentage of the gasmixture is neon. The gas pressure is not critical, but relative high pressures in the neighborhood of mm. of mercury are preferred. The higher pressures favor rapid de-ionization and also give a wider spread between normal striking and maintaining voltages.

Referring particularly to Fig. 2 of the drawing, the cathodes H to 20 have associated therewith a bias control system comprising a plurality of cathode circuits 34 to (33 coupled to-. gether as a re-entrant circuit by rectifiers as indicated at 44. Each bias control circuit includes a pair of resistors 45 and 45 connected together in series and to one of the cathodes, such as cathode I5, together with'a condenser 41 con.- nected in parallel across the two resistors. The cathode biasing circuits are connected to ground as indicated at 38. The anode 23 has a source of positive potential connected thereto through resistor 49. The pulse input to be counted is applied, when the input pulses are of positive potential, through capacitor .50'to the anode circuit. Should the source of input pulses be of negative potential the ground connection 43 would then be provided with a resistor and the negative input pulses" applied thereacross. An output connection 52 is connected to the cathode 20. A positive bias is applied over connection 53 to the control electrodes.

for purposes of illustration of the present invention, other forms of bias control. circuits may be d: r dd tiona information on b as con trol circuits reference may be had. to the co.- p hd g application o J- La r ase 2 Se ia No. 248,999, filed September 29 i. o o cribin the ope a ion of the tub attention s oll ol t tho' rm primin When there e v l goes. in a ow tuba. oo ddc: n i one gap il odho the s i in or breakow ge o tho'oth s- Th red ction is known as priming? A gap closely adjacent n t is onduct n will o prim d mor ha a s m lar sap th r awa To initiate operation of-rthe tube a high voltage s appl ed t theah'ode ci cuit ca g one of th 45 and 45. Part of thisvoltage will appear on the nest cathode l5 to the right" through the..con-. oot e rectifi r. Y

I I I I I A sn aller positivevoltage 1S d l o on ho ec nd. around the series of cathodess'o that the cathode I3 to the left of the one) conducting has. aeroor nearly zero volta e @QQIQ S itsresistors with the rectifier between it and" the conducting cathode appearing as a high resistance, Thus, the potenal ol hoo hot oh thi's eft nd th no e g ater hanthat bet ee a th r ca h andam d h s. a he fact While only one bias control circuit is shown thode l6. and so onv adjacent cathode.

to the newly fired cathode, the system is ready to receive a new input pulse. The bias voltage on the successive cathodes varies in stair-step fashion except possibly for the last two or three cathodes to the left of the firing cathode and these may be substantially equal.

The speed of counting ranges from less than one pulse per second to a rate well exceeding one hundred thousand pulses per second. In tests, the rate of one hundred thousand pulses per second has proved to be accurate but as the rate was increased, the counting became erratic as the rate of two hundred thousand pulses per second was approached. While the tube illustrated is shown to have only ten cathodes, it will be clear that a less or greater number of cathodes may be pro vided, as may be desired. It should also be understood that tubes made in accordance with the present invention have definite advantages over hard vacuum tubes. For example, the present tube saves space and weight and requires about /6 of the power required for a comparable circuit using hard tubes. The life of the present tube also far exceeds the life ofthe hard tube. Tubes operating at 100 kc./ s. are found to be very useful in many applications, such as counting,

switching and frequency division.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made by way of example only and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A cold multi-cathode-anode gap discharge device comprising an envelope containing a gaseous atmosphere, an anode, a plurality of cathodes spaced apart and from said anode to form cathode-anode gaps of substantially equal operating characteristic and means equalizing substantially the active areas of said cathodes.

2. A device according to claim 1, wherein the A means for equalizing the active areas of the cathodes include a barrier disposed in association with the cathodes to limit the active areasthereof.

3. A device according to claim 1, wherein the cathodes are in the form of pins and the means for equalizing the active areas of the cathodes include a barrier to limit the activity of each cathode to the tip portion only of the cathode pin.

4. A device according to claim 3, wherein the barrier includes a control tions disposed adjacent the ends of the cathode axially of said body pins and means for applying a potential bias to said control electrode.

5. A device according to claim 3, wherein the barrier comprises a shield having apertures therethrough and said cathode pins are disposed with posed in substantially equal spacedrelationship with respect to said cathode pins.

7. A device according to claim 6, wherein the active portion of the anode is in the form of a ring and the cathode pins are disposed radially with respect to said anode ring.

8. A device according to claim 1, wherein said means for equalizing the active areas of the oathodes includes a hollow body havingaperturesin a wall thereof, and said cathodes comprise a group of pins disposed in said body with the ends thereof protruding through said apertures, and a web of insulating material disposed crosswise of said body to support said pins.

9. An electrode assembly for a cold multicathode-anode gap discharge device comprising a hollow body having a plurality of apertures through a wall thereof, means carried by said body to support a plurality of cathode pins with the end portions thereof protruding" through said apertures whereby said body limits the active areas of said cathodes to the parts protruding outside said body.

10.- An electrode assembly according to claim 9,

wherein said body is cylindrical and the means for supporting said cathodes includes a web of insulating material carried by the inner surface 13. An electrode assembly according to claim 10 further including an anode and an anode stem supporting said anode, said stem being disposed and supported by said web.

References Cited in the file of thispatent UNITED STATES PATENTS electrode having por I "MILNER W. WALLACE.

Depew Dec. 18, 1951

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