US1967009A - Space discharge tube construction - Google Patents

Description

] Filed July 27, 1932 a Sheets-Sheet 1 V INVENTOR August Hunfl BY 7 ATTORNEY Jl lly 17, 1934. HUND SPACE DISCHARGE TUBE CONSTRUCTION s sheets-Shea 2 Filed July 27, 1932 m Y T M m m Wm ,w l A WW H 8 5 0 m R Q MUJH July 17, 1934.

HUND SPACE DISCHARGE TUBE CONSTRUCTION 3 Sheets-Sheet 5 Filed July 27. 1 95;

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240 280 l/O/ZS 12 0 200 Work anode p0 zenf/a/ 5 d m R mH m E VLl m 0 2 Eu M 0 m H n om I w 6 om 4H .r W W l I0 8 BY fi W "1. ATTORNEY Patented July 17, 1934 UNITED STATES SPACE DISCHARGE TUBE CONSTRUCTION August Hund, West Orange, N. J., assignor to Wired Radio, Inc.,' New York, N. Y., a corporation of Delaware Application July 27, 1932, Serial No. 624,920

10 Claims. (Cl. 250-27.5)

This invention relates to glow discharge tubes and has particular reference to the structural details thereof and to the adaptation of such tubes for a wide range of uses in electrical circuits generally.

An object of my invention is to provide a glow discharge tube of this character comprising a plurality of electrodes of conformity suitable to the peculiar manner of activating such tubes.

Another object of my invention is to provide a tube of the class described which functions so as to exhibit a primary and a secondary glow discharge, thereby rendering it suitable in a variety of circuits; for example, as in an oscillator, a del tector or an amplifier.

Another object of my invention is to so proportion the respective activated areas of the electrodes and to envelop the electrodes in a suitable gas at a suitably attenuated pressure so that optimum conditions may be obtained for the operation of such tubes.

Another object of my invention is to provide a glow discharge tube of the class described, in which the electrodes are suitably disposed in a j medium of attenuated gas or mixture of gases so as to exhibit a high degree of power gain between the input and output circuits of the tube, a minimum wattage consumption being required in the ionizing circuit, as well as in the work circuit.

These and other objects are attained by a novel construction of the glow discharge tube, as will be more fully understood from the following description and by reference to the accompanying drawings, in which:

Fig. 1 depicts in elevation one embodiment of a glow discharge tube having its ionizing electrodes disposed internally of the work electrode system;

Fig. 2 is a sectional view of the electrodes along the line 2-2 of Fig. 1;

Fig. 3 is an alternative embodiment of the glow tubes of my invention showing the ionizing electrodes disposed externally of the work electrode system;

Fig. 4 is a plan view of the electrode system '1 shown in the tube of Fig. 3;

Fig. 5 shows a modified tube somewhat similar to that of Fig. 1, but having a work anode of cylindrically crimped formation;

Fig. 6 shows the work anode crimped in a plane; and

Figs. '7, 8 and 9 are curve diagrams illustrating some of the operating characteristics of one of the glow tubes of my invention.

In my copending application, Serial No. 590,- 561, filed February 3, 1932, I have shown several ionization electrodes independent of the other electrodes called work electrodes. The tubes of my invention as herein disclosed, while adapted to function in a similar manner, have certain improvements of structural detail as compared with the tubes of the aforementioned application.

In my copending application, Serial No. 613,- 710, filed May 26, 1932, one of the uses of a tube of the class herein described and its manner of operation in an oscillator circuit is illustrated. It will be understood, however, that these tubes may be used in a great variety of diiierent circuits for the achievement of new and desirable results.

The herein described tubes may be distinguished from those of my above-mentioned copending application, Serial No. 590,561, in that the electrodes are differently formed and otherwise characterized so as to set up a glow, or secondary ionization, in the region of the work anode, provided a suitable potential is applied to the latter.

My discovery, which resulted from the con-. struction and manner of operation herein shown, appears to go directly contra to previously accepted theories, in that the operating characteristics of glow tubes such as mine are greatly improved when this secondary ionization takes place. In the space between the primary and secondary ionization a control electrode may be suitably disposed so that very considerable space currents'passing toward the work anode may be controlled by a very small Voltage variation impressed upon the control electrode.

Referring now to Figs. land 2, a glow discharge tube is shown having a suitable envelope 1, and base 3 of well-known type. The several electrodes of the tube are connected by leads 4 with the prongs 5. The'leads are suitably insulated as by the'glass tubes 6, so as to prevent the possibility of ionization in unwanted regions.

In the embodiment of my invention as shown in Fig. 1, there are provided an ionizing cathode '7 and an ionizing anode 8, each of which consists preferably of one or more convolutions of a simple wire helix. In place of the helix construction, however, it is within the scope of'the invention to employ either solid or hollow cylinders or-electrodes having other suitable shapes. In general, however, the eifective working area of the ionization cathode 7 is usually greater than that of the ionization anode 8. This area relationship provides the advantage that an excess of negatively charged ions and electrons is available at the ionizing cathode 7 for building up the space current toward the work anode 10. This space current may then be suitably modulated as it passes through the mesh of the control electrode 9, when variations of potential are applied to the latter. I v

A preferred form of control electrode 9 is that of a simple wire helix. The work anode 10 may, if desired, be a round or flat wire ring and its location is found to be satisfactory when the plane of the ring substantially bisects the working area of the cathode 7.

As shown in Fig. 1, each of the electrodes is of' circular formation and they are arranged concentrically with respect to one another.

Referring now to Figs. 3 and 4,- the embodiionizing cathode'll and the ionizing anode 12.

This ionization, however, ismore or less localized in those regions where thebends in the anode 12 approach the cathode ll. Theeffective working area of the cathode 11 is, therefore, greater 1 than that of the anode l2 notwithstanding the fact that the two rings have substantially the same diameter and an even greater developed length of wire is used in the anode 12 than in the cathode 11.. Due to this construction; therefore, it is possible toset up a stream of negatively charged ions and electrons in the region of, primary glow discharge, which stream is centripetally projected through the mesh of the control electrode 14 and toward the centrally disposed work anode 13, where secondary ionization takes place Y The results obtained from the operation of the tube as shown in Figs. 3 and 4 are comparable with those hereinbefore described with respect to Figs. 1 and 2. The operation ofboth tubes will, therefore,'be understood in View of the foregoing description. 7

Referring now toFig. 5, a third modification of my invention is shown wherein the ionizing electrodes 7 and 8 are centrally disposed andsurrounding them is the control electrodeQ, ,the same as shown in Fig. 1. In this embodiment, however, a crimped formation of the work anode l5is provided. The zig-zag pattern may becylindrically crimped as shown in Fig. 5, or, alter-- natively, it' may conform to .aqplane as in Fig. 6.;

In the embodiments of my invention shownin Figs. 1 2, 5 and 6, primary ionization takes place as before mentioned between the centrally-disw posed ionizing electrodes, whence streams .of

negativelycharged ions and electrons are centrifugally projected through the mesh of -t he'control electrode and toward the outwardly disposed work anode 10, 15 or 16, as the case maybe. Secondary ionization takes placev in allcases, in the region of the work anode. The operation of the tubes of these. modifications .is, therefore, similar to that ofthe tube embodiments previ-, ously described.

In order to illustrate some of .the operating .the curves of Figs. 7, 8 and 9 were plotted, the 'gas within the envelope was nitrogen at a pressure of 24' mm. mercury. Across the ionizing electrodes was a drop of 308 volts with an ionization current of 35 mill'iamperes. The ionization power was, therefore, only 10.8 watts.

Fig. 7 shows the relation between the workanode potential and the work-anode current when a bias E3 of 27 volts is impressed upon the'control electrode with respect to the potential-of the positive ionization electrode. Due to the scale on which the currentvariations were plotted, the curve appears to start at O and ascends very slightly to the point a. Careful measurements, however, showed that, with no external voltage applied between the work anode and the positive ionization electrode, a minute flow of current could be observed which apparently is dueto the primary ionization pressure (or spill) towards the work anode. This minute currentis comparable in magnitude with that customarilyfound in thermionic tubes when the plate is directly connectedto the filament, i. e., without plate battery. It. is of; no significance in the ordinary uses of these ,tubes. 1

At about 84 volts of workanode potential the current curve jumps suddenly between the points a and b; thatis, approximately from 0.25 to 3.8 m.,a. This is due to the commencement of a secondary glow discharge in the region of the work anode. With further increases .in the work-anode potential, the. work-anode current increases rapidly up tothe point d, wherea streamer dis chargesets in between-the work anode and the control electrode. The unstable condition of the tube between a and b, and again, the streamer discharge above the point (2 determine the useful ranges for operating thetube as anordinary detector or amplifier. The useful ranges are-between 1) and (1, also between 0 and a. The former is much to be preferred, however, since it is possibleto control so much more output power with a given fluctuation of input potential applied to the control electrode.

NVhere the tube is intended to function as a threshold amplifier or trip relay, the operating characteristic ,inay be swung over the range which straddles the critical points a and b or else above the point d, so that a large current may trigger off withvery slight variation in the control potential.

Fig.8 shows a number of curves corresponding withthatof Fig. -..'7,i but on an enlarged scale and confined to the normal operating range b'-d. .Thedifferent curves were obtained underlthe conditions of control electrodebias as shown. The dot-and-dashline runningthrough the operating point'c indicates the region in which the best operating conditions prevail. "It is near the region of saturation and not far from the region of streamer-discharge d.

The extraordinarypower gain which results from-operating'these tubes in the manner shown will be. betterunderstood when it, is .considered that the primary flow of negative ions passing through the mesh of the control electrode is increased many fold by the production of new and additional ions as the stream approaches the work anode. Thus, the current flowing towards the work anode is greatly increased by virtue of the secondary ionization and with no need for a corresponding increase in the input power applied to the control electrode.

As was brought out above, streamers set in at the point at. Beyond this point the control electrode becomes flooded with a streamer glow and the tube can no longer function as an amplifier of voice and carrier currents. Many experiments were therefore carried on to shift the point d as far out on the characteristic as possible.

It may be of interest to note here that success in this direction did not result from attempts to completely surround the control electrode, as by a hollow cylinder. The reason for this was that streamers would be set up between the cylinder wall and the control electrode even when very low voltages were applied between the work anode and the ionization anode. Hence the round wire or fiat metal ring shaped work anode 10, or the crimped wire work anode l5 and 16 were found to be preferable, as they tend to move the point 11 practically into the saturation region, thus providing a very powerful output. Substantially the same advantage also accrues from the use of an axially disposed work anode 13, as shown in Fig. 3. For some purposes, however, the wavy ring construction as shown either in Fig. 5 or Fig. 6 is to be preferred.

Fig. 9 gives curves for the control electrode current in relation to the work anode potential. This diagram, when considered in connection with the curves of Fig. 8, provides the means for computing the dynamic plate resistance Tp, the mutual conductance gm, the amplification factor and the dynamic input resistance Tc.

The load line may be drawn as shown in Fig. 8, passing through the operating point e, and at such an inclination as to avoid distortion in the amplified output current variations. Furthermore, this load line does not extend beyond the streamer points of the several characteristic curves plotted for different control electrode potentials.

The computations show that the dynamic resistance is as low as 5420 ohms, while the amplification factor ,u. for this particular tube is as high as 20.65. Hence the mutual conductance gm is as high as 3815. With some of my tubes it is an easy matter to produce a mutual conductance as high as 10,000. Some of my tubes have an amplification factor a as high as '70 or 80, the dynamic plate resistance being not greater than 10,000 ohms. With a tube of this type, therefore, a very high degree of power amplification is obtainable, while preserving a very low dynamic plate resistance along with a high dynamic input resistance. A further advantage to be had in these tubes is the avoidance of the necessity for adding another control electrode such as found in the so-called pentode tubes for producing a low output resistance.

I claim:

1. A gaseous discharge tube comprising an ionizing cathode, an ionizing anode the activated surface of which is relatively smaller than that of said cathode an output circuit anode for localizing a glowing ionization discharge in a region other than that in which ionization is produced by said ionizing cathode and anode, and an openly constructed control electrode interposed between the two regions of ionization, said output circuit anode being of a crimped ring formation surrounding said other electrodes.

2. A gaseous discharge tube comprising an ionizing cathode of closely wound helical formation, an ionizing anode the activated surface of which is relatively smaller than that of said cathode, an output circuit anode for localizing a glowing ionization discharge in a region other than that in which ionization is produced by said ionizing cathode and anode, and an openly constructed control electrode interposed between the two regions of ionization.

3. An electrical discharge tube comprising a plurality of electrodes enveloped in an attentuated gas two of said electrodes being suitably positioned for setting up a primary ionization discharge therebetween, an output circuit anode suitably arranged to localize a secondary ionization discharge therebetween and a control electrode interposed between the regions of primary and secondary ionization respectively, said output circuit anode being of crimped ring formation surrounding the other electrodes.

4. An electrical discharge tube comprising a plurality of electrodes enveloped in an attenuated gas, one of said electrodes being an ionizing cathode, another of said electrodes being an ionizing anode, said two electrodes being suitably positioned for setting up a primary ionization discharge therebetween, said ionizing cathode being of closely WOlllld helical formation, a third electrode being suitably arranged to localize a secondary ionization discharge thereabout and a control electrode interposed between the regions of primary and secondary ionization respectively.

5. A gaseous discharge tube comprising a pair of ionizing electrodes, an openly constructed control electrode externally disposed with respect to said ionizing electrodes, and means including an output circuit anode of crimped wire ring formation for localizing a glowing ionizing discharge exterior to said control electrode.

6. A gaseous discharge tube in accordance with claim 5 in which said output circuit anode is crimped so as to conform substantially to a cylindrical surface.

'7. A gaseous discharge tube comprising, a pair of ionizing electrodes, an openly constructed control electrode operatively disposed with respect to said ionizing electrodes, and means including an output circuit anode of crimped wire ring formation for localizing a glowing ionizing discharge adjacent said control electrode.

8. A gaseous discharge tube in accordance with claim '7 in which said output circuit anode is crimped so as to conform substantially to a cylindrical surface.

9. A gaseous discharge tube comprising a plurality of electrodes enveloped in an attenuated gas, two of said electrodes being ionizing electrodes and another a control electrode operatively related to said ionizing electrodes and one of said plurality of electrodes being in the form of a crimped ring encircling said control electrode.

10. An electrical discharge tube comprising an envelope containing an attentuated gas, a plurality of electrodes within said envelope between certain of which a space current may be established, a control electrode operatively related to said space current electrodes and one of said plurality of electrodes being in the form of a crimped ring surrounding said control electrode.

AUGUST HUND.

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