US2435202A - Electronic tube and control therefor - Google Patents

Description

Feb. 3, 1948.

P. H. CRAIG ELECTRONIC TUBE AND CONTROL THEREFOR Filed May 20, 1942 Us Hl U5 Paz/mer Cra/y Patented Feb. 3, 948

UNITED STATES PATENT OFFICE ELECTRONIC TUBE AND CONTROL THEREFOR Palmer H. Craig, Gainesville, Fla., assignor to Invex Corporation, New York, N. Y., a corporation of New York Application May 20, 1942, Serial No. 443,717

3 Claims. (Cl. 315-268) This invention relates to electronic tubes of the space-discharge rectiiier class.

The tube of this invention comprises in general an evacuated envelope containing an anode and a cathode and ionizable gas at predetermined pressure; and provided with a control electrode. The control electrode is in the form of a loop or band encircling or embracing the discharge path through the tube between the anode and cathode; and in the preferred form is a loop or band on the outside of the envelope, but in some cases it may be disposed within the envelope.

The invention resides in an improved method and means for controlling the discharge current between the anode and cathode by the control electrode.

It is among the objects of the invention:

To provide generally an improved electronic tube of the gaseous discharge rectier class;

To provide an electronic tube of the class referred to having an improved mode of operation;

To provide in connection with an electronic tube of the class referred to, improved means for controlling the discharge current therethrough;

To provide an improved method of controlling the discharge current through an electronic tube of the class referred to.

Other objects will be apparent to those skilled in the art to which my invention appertains.

My invention is fully disclosed in the following description taken in connection with the accompanying drawing in which,

Fig. 1 is a side elevational view with parts broken away of a tube embodying my invention;

Fig. 2 is a diagrammatic view of an electric circuit suitable for operation and control of the tube of Fig. 1;

Fig. 3 is a cross sectional view taken from the plane 3-3 of Fig. 1, through the envelope wall and a control electrode of the tube, and with the thickness of the wall and electrode magnied for illustrative purposes.

Fig. 4 is a diagrammatic view illustrating changes of main tube current which occur upon changing the degree of negative energization of the control electrode of the tube in the practice of the invention.

While my invention is applicable to the type of electronic space-discharge tube having a cathode in the form of a pool of mercury or the like, as well as to the type having a heated thermionic emission cathode, I have chosen to illustrate and describe it herein as applied to the latter type, since the construction and mode of operation of the parts of the tube embodying my invention are otherwise the same in both types of tubes.

Referring therefore to the drawing, I have shown at I a glass tube envelope having on the lower end thereof a metal plug base 2 of the prong type provided with three individual prongs 3, t, and 5, and having above the base a pinch 6 in which are sealed terminal conductors con.- nected to the prongs in the usual manner, the terminal conductors being indicated at 1, 8 and 9. The envelope has been evacuated and contains ionizable gas such as argon therein at a predetermined pressure to be referred to.

In the upper end portion of the envelope I is an anode Il) electrically connected to an external terminal II in the usual manner. The anode may be of graphite, or of molybdenum, or of carbonized nickel, or may be of other materials such as have been used for the anodes of tubes of this type. At I2 is shown generally a cathode of the indirectly heated type, and it may be of any suitable construction. One construction which I have found suitable is that constituting the subject matter of the copending application of Palmer H. Craig and John J. Glauber, Serial No. 338,194, filed May 31, 1940, for Improvements in discharge rectiiier tubes with indirectly heated cathodes, which issued July 14, 1942, as United States Patent No. 2,289,346.

The conductors 1, B and 9 are connected through the pinch 6 to the prongs 3, 4 and 5 respectively. As indicated in Fig. 2, in connection with Fig. 1, the main circuit through the tube is from the anode Il), through the gas as a discharge arc to the cathode I2 and thence by conductor 9 to the prong 5; and the circuit for heating the cathode is from one prong say the prong 4, by Way of the conductor 8 to the heater I3 of the cathode (Fig. 2) and back by conductor 'l to the prong 3.

The envelope may be evacuatedas referred to by well-known processes, including heating of the internal structural parts and flashing of a getter or the like, and then gas such as argon is introduced at the desired pressure.

The general operation of the tube as described is that well-known of tubes of this class. Thermionic coatings on the cathode l2 are heated and emit electrons and these electrons ionize the gas within the envelope causing it to emit other electrons, and when potential is impressed upon the anode and cathode and the anode is positive with respect to the cathode, a ow of electrons and current occurs from the cathode to the anode in the nature of a discharge.

The control electrode is shown at i4 and is in the form of an external band outside of and embracing or encircling the envelope I, and it may be variously constructed. It may be in the form of a separate detachable wire or band of metal; or a band of metal mesh; but preferably 1 provide a band which in effect is fused or sealed into the material of the outer wall of the envelope. The preferred process for applying such a band electrode is that used in ornamenting glassware with metallic bands or the like, for example with platinum bands. A so-called "liquid platinum paint like commercial material is painted in the form of the desired band on the outer surface of the envelope. The glass and the band are then heated, and the band takes on the appearance of metal platinum and has the characteristic of being fused into the glass surface. A band thus made is electrically conductive, and metal parts can be soldered thereto in strong rigid juncture therewith; and accordingly a Ametal `terminal I5 is soldered to the band ld formed as at it for making electrical connection therewith.

lThe electrode Il as shown in Fig. 1 is disposed between the cathode and anode which is its lpreferred position.

When a tube constructed as above described is put into operation and the discharge flows from the cathode tothe anode under Athe impulsion of the -potential th'ereacross, the maximum amount of current flow, or amperage, is of course determined by the Vline potential from which the .cathode-anode potential is derived and by the resistance of the external load circuit; but the actual amperage owing is under the control of the energization of the electrode i4.

Hereinafter when the anode is referred to as of positive sign, it is with the meaning that it is positive with respect to the cathode, and when the control electrode is referred to as negative it is with the meaning that it is negative with respect to the cathode when the anode is positive with respect to the cathode.

Perhapsthe most useful application of the tube is in the lcontrol of alternating current load circuits, -and this will be described as illustrative of its uses, although those skilled in the art will understand how it may be applied to uses with direct current.

`When the potential impressed upon the anode and cathode is alternating, the ow of current -occurs only during those half waves in which the anode is positive as is well-known, and even Without yenergization ofthe control electrode the current is automatically interrupted in each half cycle in which the anode is negative; and therefore with alternating current the tube admits of control of the duration ofthe current or the number of half cycles thereof after it starts by suitably energizing the control electrode, inasmuch as this electrode can at any time be energized suiciently to cut ol the flow of current by preventing the current from starting on the next succeeding positive half cycle; and by establishing a phase relationship between the control electrode venergizing potential and the anode `to .cathode impressed potential, and controlling the degree .of energization of the control electrode at that phase relationship, the control electrode cancontrol the effective amperage owing at any timef'by changing the time of starting in each positive half cycle, to thereby reduce the effective value to a minimum value, and vice versa raise it to a maximum.

I have discovered furthermore that lf the control electrode be energized negatively to a suitable super-negative degree, that is a degree beyond the degree at which it prevents current flow as described, it will cause current again to flow; or if the minimum value of current be flowing it will Vmaintain it flowing or increase it; and that if this super-negative degree of energization be ,further increased, the amperage will be increased Vdirectly or commensurably with the increase of the super-,negative energization, and vice versa, decreased directly commensurably when the supernegative energization is decreased.

The control of Athe current through the tube bynegative electrode energization may therefore be effected by two methods, as follows:

First, vthere is Va high value of negative energization of the control electrode at which the current flow is cut off or reduced to a minimum, as the case may be; and at negative energization below this high value, current dov/'s or increases from the minimum as `the case may be, the current being maxim-um for zero or low electrode energica-tion; and the amperage of the current fiow is inversely commensurable with the degree of negative energization, being greater for lesser degrees and vice versa.

Second, at suitable super-negative-energization beyond the vsaid high value, cu-rrent flows or increases from the minimum as the Vcase may be;

and the amperage of the current flow is directly commensurable with the degree of super-negative energizatiom being greater for Agreater degreees -of super-negative energization and vice versa.

So far as I am aware no gaseous discharge tube has been proposed heretofore the current flow through which lvaries directly commensurably with the degree of negative energization of a control electrode as described above in the second method of operation. f

I have discovered furthermore that as the said super-negative-energization of the control electrode is increased, thefamperage reaches a maximum value again, Aand at still higher degrecs of super-negative energization, vbegins to decrease again.

The above described control, over a range of higherand higher Vdegrees of negative energization `of the control electrode, including the two described methods, .by which the amperage is caused to begin at a first maximum, to decrease toa minimum, and .again'to increase to a second maximum, Amay be considered here as a first phase ofthe control, .and .I have discovered that the control goes through other and successive generally similar phases of control; that is to say, as the negative energization increased higher and higher the amperage decreases from the said second maximum to asecond minimum, and then rises to a third maximum; and then decreases from the third maximum to a third minimum `and then rises to a `fourth maximum; and that .there .are several .of .these successive phases of control,

.The characteristics of the above described changes of amperage occurring upon increasing the negative energization of the control electrode are illustrated in Fig. 4 of the drawing; ordinate values representing amperage, and abscissa values 'representing negative'corrtrol electrode energization.

A more stable and otherwise satisfactory control of the amperage liowing through the tube may be effected if alternating Jvoltage be imr pressed upon the control electrode out of phase with that impressed upon the anode and cathode. To this end the control of the effective amperage by corresponding energization of the control electrode may be effected by varying the phase relationship between the electrode energization and the potential impressed upon the anode and cathode but I prefer to effect this control as referred to by utilizing a fixed angular phase displacement of the control electrode energization and by varying the amount of the potential on the control electrode at this phase displacement.

I have found that a suitable phase displacement is approximately 135 degrees lag of the electrode potential behind the anode potential although this exact displacement is not essential. This xed angle variable potential electrode control is illustrated and described in my Patent No. 2,001,836, issued May 21, 1935, for a single range of discharge current values between a minimum and a maximum only in which the effective amperage varies inversely commensurably with the degree of energization of the control electrode.

In Fig. 2 is illustrated a representative circuit for effecting this type of control with a tube such as has been described above. In this iigure at I is shown the envelope, at Io the anode, at Ill the control electrode, at I2 the cathode, and at i, 8 and e the conductors leading to the cathode. Supply mains I'I and I8 energize the primary I9 of a transformer the secondary Ztl of which supplies alternating current at suitable voltage, such for example as five volts, to the above described lament heating circuit. The supply mains also energize the primary 2! of a transformer having a secondary 22 connected in a Aloop circuit with a resistor 23 and a condenser 24, the said loop circuit being also connected to cathode I2 by a wire 25.

The control electrode Iii is connected as at 2S with the resistor 23 by an adjustable rheostat or potentiometer type of connection for adjusting the potential on the control electrode, the .circuit for the electrode being considered from the wire 25, to the cathode I2, to the electrode I4, to connection 26, through a part of the resistor 23, back to the Wire 25. The condenser 24 may be adjusted to cause the potential on the electrode Il! to be out of phase with the potential across the anode Ill and cathode I2 as described, and at this xed phase displacement, which as stated above is preferably but not necessarily of the order of 135 degrees behind the anode cathode potential, the actual potential on the control electrode Ill may be adjusted by the adjustable connection at 25; and the polarity of this potential, predetermined by the transformer 2 I--22, is negative with respect to the cathode when the anode is positive with respect to the cathode, and is herein referred to as negative with that meaning as mentioned hereinbefore.

As illustrative of suitable quantities for parts of the circuit of Fig. 2, it may be added here that for a rectier as described above having a continuous main current carrying capacity of 2% amperes, the capacity of the condenser 2t may suitably be .019 microfarad; and the resistance in the resistor 23 may suitably be of the order.

of 150,000 ohms; and the voltage across the resistor provided by the transformer secondary 22 may suitably be 600 volts, for supply mains I'I, I8 at 110 volts 60 cycles. With the xed phase displacement referred to, the electrode connection at 26 may be adjusted to zero` electrode potential, at which the full 21/2 amperes will flow in the main load circuit on each half wave, from the cathode to the anode of the tube; and if the negative potential on the control electrode I4 be adjusted to raise it above zero value, the tube will pass current later in each half wave and the effective amperage in the load circuit will be decreased; and at approximately 450 volts on the electrode it the main current will be practically cut off or reduced to a low minimum; and if the potential on the electrode It be adjusted to raise it negatively to a super-negative degree beyond 450 volts, current will again flow and the effective amperagevvill be greater for higher electrode voltages; and vice versa, less for lesser electrode voltages in this super-negative range. It will be noted that the quantities here given are suitable for the above identied first phase of control, and it will be understood by those skilled in the art how to adapt the quantities of the energizing circuit to the higher potentials suitable for the succeeding phases of control.

As mentioned hereinbefore, rectier tubes of the gaseous discharge type are known containing a gas such as argon in the envelope. In the above described tube, I also prefer to employ as stated a gas such as argon but I have found that the pressure of the gas within the envelope should be taken into account. For any pressure utilized the control electrode energization should correspond when control or variation of the current flow by the electrode energization is Wanted. If a low gas pressure is used, the electrode voltage to normally cut off current ovv or reduce it to a minimum is lower and if the pressure is high, it is higher.

I have found that, taking into account the voltage drop and loss of energy through the tube and the optimum control conditions for varying the current by the electrode from zero or a minimum to the maximum discharge current of the tube, a suitable pressure is of the order of to 110 microns of mercury; and I therefore prefer to use that pressure of argon in the tube for ordinary applications.

In alternating current installations in which variation of the flow of current through the tube is not wanted. and all that is wanted is initiation and interruption of the current by electrode energization, the negative electrode may be energized at a phase displacement of degrees with respect to the anode cathode potential. Also while I have described the control of variation of the current flow through the tube by utilizing a control electrode energized negatively out of phase with the anode cathode, and by adjusting the electrode potential by a rheostat at a fixed I phase displacement. it is to be understood that my invention may likewise be practiced by the known means of adjusting the phase displacement of the control electrode energization with respect to the anode-cathode potential.

My invention will operate as described, using a tube constructed as described in connection with Figs. 1 and 3 of the drawing` and as illustrated therein, and having the arrangement and proportion of the described parts shown in these figures of the drawing; and when energized and controlled as described by a circuit such as that of Fig. 2 of the drawing, having the quantitative circuit factors stated in the foregoing description.

My invention is not limited however in every respect to the exact details of construction illustrated and described. inasmuch as changes and modifications thereof may be made within the spirit of my invention Without sacrificing its 75" advantagesfandtwithin:thescope o thefappendedf- Eorrexample'ltheftubeof my invention; may-besnsedcin multiple back-to-back arrangement to..pass'fatfulhwavezof. alternating currenti.

IrThe: method: oit controllingI the current` amperagesin' an` electricrzcircuit; which includes: connectingin; thea-circuit:the:anodeV and thermoemissivefcatlrodeofa; rectier" gaseous Ydischarge electronic: tulo'ef.A comprising at gas iilled envelope inlwhichthe'anodeand-Icathode are spaced apart anda controlxelectrodeinztne form-r of aloand surrounding:V the. envelopetina zone between the anoxi'tandtcathode'; impressing ontheanodeand catliode ffalternatingfpotental -fsuiicientA torcause' tleftubevtopass currentg energizing the control electrodefwitli alternatingipotential atv the frequency of-itli'e impressed-potential, and negative with respeci'r'ltmthe*cathodewhen.the anode is positiveA` withz respecttto 'the cathode; and causing currenti in the-ciicuitltoflirstrdecrease and tlienf: increasey by continuously increasing the energizationoffth'e:control electrode from a value at'wiiichcurrent;y nou/sin` the circuit to a value atl Wlfiicitiscuti'o-'and on througha rangeo valnestlieyondtlie'- cutoi value;

2.-' Tlie method54| of controlling the current' a-nlpera'ge".in3 an `electric` circuit; which includes: cunn'ectiiigy in xtliei circuit ftlie anode and thermoernissi-'ve cathode*ofal rectifier Vgaseous discharge electronic f tubef comprising-f' a gas4 nlled envelope Wnieli-tlieanodeandcathode are spaced apart andT acont'rol'electrode in theform of a band surrounding thief-envelope ina zonneV between the anode and cathode; impressing on the anod'eand catlf'i'oele` alternating potential Y sufficient to cause the tulo'ertopass-current; energizing the control electrode Witli alternating potential at the fre- (fuencyof theimpr-'essedi potential, and negative 35 Number withzrespectztofthezcathodel when the anode isf positiveWitlfrl respect ito the' cathode; and causing. currentin the circuit to first decrease and then increase byenergizing` the control electrode-ata 1 valuezbeyond'the cutoi value to cause a high thetubeto pass current; energizing the control electrodewith alternating potential at the frequencyof. the impressed potential, and negative Withv respect to the cathode when the anode isy positive with respect to the cathode; and causing currentY in the circuit to rst increase and then decrease;y by energizing the control electrode at a value beyondA the cut off Value to cause a lowvalue of'current to flow and continuously increasing the control electrode energization.

PALMERH. CRAIG.

REFERENCES GITED The following references are of record in the le of' this patent:

UNITED STATES PATENTS Name Date Ile Van Nov. l5, 1932 Craig May 21, 1935 Swart Dec. 28, 1937V

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