US2191594A - Controlled gaseous discharge device - Google Patents

Description

Feb. 27, 1940. P. L. SPENCER 2,191,594

CONTROLLED GASEOUS DISCHARGE DEVICE Filed Feb. 5, 1938 :5 Sheets-Sheet 1 l App/fed Volfoye PERCY L. SPENCER Feb. 27, 1940. P. L. SPENCER 2,191,594

CONTROLLED GASVEOUS DISCHARGE DEVICE Filed Fel o. 5 193a aspeets-sneet 5 [nae/22 w I I I RCYLS J E I Feb. 27, 1940 um'rso STATES 2,191,594 PATENT OFFICE 7 3,191,804 OONTBOIJID GASEOUB DISCHARGE DEVICE. .rercy L. Spencer, West Newton, Mass sssignor to Baytheon Manufacturing Company, Newton, loss, a corporation of Delaware Application February 5, 1938, Serial No. 188,88!

8Claim This invention relates to controlled gaseous discharge devices, and more particularly to such devices in which the time of starting of an ionizing discharge between the electrodes is controlled by means of a magnetic field.

An object of my invention is to produce such a device which will operate as an alternatin current switch.

Another object is to produce such a device I. which will control the magnitude of alternatin currents fiowing through it.

A further object is to devise such a tube which will selectively rectify in opposite directions.

An additional object is to devise such a selecli tivcly rectifying tube in which the magnitude of the resultant direct current may be controlled.

A still further object is to produce the foregoing results by means of a magnetically-controlled tube.

3 "the foregoing and other objects of my invention will be best understood from the following description of exemplifications thereof, reference being bad to the accompanying drawings where- Fig. l is a cross-sectional view of one embodimeat of my invention showing my novel discharge tube together with a diagrammatic. representation of a circuit whichmay be used therewith;

Figs. 2, 3 and- 4 are curves for analyzing the relationships between the current voltage and magnetic variations existing under various conditions of operation of Fig. l; and

Figs. 5, 6 and 'l are diagrammatic representations of various types of control current supply tor Fig. 1.

In Fig. 1, i.represents a hermetically-seal envelope, preferably of glass, having enlarged end chambers 2 at each end thereof, said enlarged chambers being connected by a tubular intermediate section 3. In each enlarged chamber 2' is mounted an electrode 4 which may act either as a cathode or as an anode, as will be hereinafter described. Interposed' between the two electrodes 4 and surrounding the discharge path between them is provided a conductive tubular intermediate electrode 5. The electrode 5 is preferably made of non-magnetic material and may comprise a cylinder of thin sheet metal, such as,

for example, non-magnetic nickel or tantalum. The electrodelmaybeofanyother suitable form, such as, for example, a-wire mesh or a metallic deposit on the walisof the tubular section i. Alsoitispoasihlctomakeit'sothatitdoesnot completely'surround the discharge path within 56 it.

'meeuvelope I ispmvidedwitha reentrant stemtateachendthereoL-sehofwhichsteins sopportsoneottheelectrode'sl. 'iheelectrodel preferablycufllotahollowmetalmcmberl povidedwlthawflhternalradially-dilc1. era-21.5)

posed metal fins 8. The metal fins and also the interior of the hollow member 1 are coated with an electron-emissive material, such as, for example, alkaline earth oxides. In order to heat the surfaces of the electrode 1 to temperature of thermionic emission, a heating filament 9 is disposed within the hollow member I. The heater 9 may consist of a single helix of a refractory conductor, such as, for example, tungsten, and may be electrically connected at its upper end to the hollow member 1 by being welded to one of the fins 8. In, order to prevent excessive radiation of heat from the hollow member I, it is surrounded by means of a heat shield Ill. The electrode assembly 4 is supported on the stem 6 by means of a pair of conducting standards II which are sealed in the press 6. One of the standards II is sealed through said press so as to provide an external electrical connection to the electrode 4. The lower end of the filament heater 8 is provided with a lead l2 whichis likewise sealed through the press 6 so as to provide an external electrical connection thereto. In Fig. 1 it will be seen that the electrode l at the right-hand end is shown in cross-section. However, it is to be understood that the electrode 4 at the left end is of identically the same structure as that shown at the right-hand end. In the interest of simplicity, however, the electrode 4 at the left-hand end is not shown in cross-section.

In order to support the intermediate electrode 5 in position between the electrodes 4, it is provided with a pair of conducting electrode stan dards I! which may be sealed in one of the presses 6; 'for example, the left-hand press. One of the standards I3 is sealed through the press 6 so as to provide an external electrical connection to the intermediate electrode 5.

The envelope I containing the construction as described above, after being thoroughly evacuated in accordance with the usual practice, is filled with some suitable ionizable medium. This medium may be, for example, a metallic vapor, such as mercury vapor, or a gas, such as one of the noble gases, or a mixture of such gases. when mercury vapor is used, pressures in the range of one to one hundred microns are preferred, while in the case of a noble gas, such as argon,

a pressure of the order of one millimeter or less is preferred. In any event, the gas pressure is of a suitable value so that when a discharge occurs between the electrodes I, the gas or vapor becomes ionized and current flows at a relatively low voltage drop.

In order to supply power to the device, there is provided a supply transformer it having a. primaryiiandasecondary l6. Theprimary II is adapted to be connected to some suitable source of alternating current. A conductor ll connsctsonesndofthesecondarylt-toaconductor Ii, and thus to the right-hand electrode 4. A conductor It extends from the opposite end of the secondary It to a load 9. The other side of the load is connected by means of a lead 20 5 to the other conductor II, and thus to the left- 10 temperature.

between the two electrodes 4. This potentiometer has a sufliciently high resistance to prevent an excessive current from flowing through it, and may be, for example, about 1000 ohms. Said po- 5 tentiometer is provided with a center tap 22 connected through a high resistance 23 to the intermediate electrode 5, whereby the potential said electrode is maintained substantially midway between thepotential of the two electrodes 4.

20 In order to prevent any substantial amount of current from flowing in the intermediate electrode circuit, the resistance 23 is preferably of a high value; for example, a megohm.

Upon supplying heating current to each pair of 25 conductors H and iii, the filament 9 and consequently the coated surfaces of each electrode 4 will be raised to a temperature at which said coated surfaces emit a copious supply of electrons thermionically. As each electrode 4 be- 30 comes positive, electrons emitted from the oppo- 35 between said two electrodes 4. Thus it will be.

site electrode 4 will travel toward said positive electrode, producing an intense ionization of the gas within the envelope, whereupon a flow of current with a relatively low voltage drop will occur seen that each electrode 4 acts alternately as a cathode and as an anode as the potential impressed upon it reverses in polarity. Under such conditions, therefore, alternating current will 0 flow freely through the discharge tube, and such alternating current will likewise flow through the load l9. As more fully described and claimed in my copending application, Serial No. 612,235, filed May 19, 1932, now Patent No. 2,124,682, for

45 an improvement in Electrical gaseous discharge devices, a discharge of the type which I have .described above is prevented from starting when a magnetic field of a predetermined magnitude, intercepting the direction of said discharge, is

v 50 impressed across the space within the intermediate electrode 5. This transverse magnetic field may be applied in any suitable manner. For example, I have shown a pair of magnetic pole pieces 24 disposed on opposite sides of the tubular 5 portion 3, surrounding the intermediate electrode 5. The magnetic pole pieces 24 may form part of the unitary core structure. In order to energize said core structure and said magnetic pole pieces, energizing coils 25 are provided. These coils 25 are fed with current through a control device 26 which may be energized through any suitable source. As indicated in Fig. 1, this source may be the transformer l4, in which case the input to the control device 26 is connected by means of a pair of conductors 21 to the opposite sides of the secondary l6.

When the control device 26 is so adjusted that the current flowing through the coils 25 is below a predetermined value, and thus the flux im- 7 pressed upon the tube is likewise below a prede- 75 For practical purpo termined value, the starting of the discharge between the electrodes 4 is not delayed, and there-' of flux may be considered as substantially zero. If, however, the control device 26 is adJusted so that the current supplied to the coils 25 produces a flux which is always above a predetermined value, the discharge between the electrodes 4 is eflectively prevented from starting through- 25, whereby the requisite amount of. flux is impressed upon the discharge tube. Under these conditions, by switching the control device 26 on and oil, alternating current flowing through the discharge tube is likewise switched on and oil. Consequently the alternating current flowing through the load I9 is connected or disconnected, depending upon the position in which the switch 28 is set. Under these conditions, the arrangement as shown in Fig. 1 acts as an alternating current switch. V

Inasmuch as the discharge tube which I have described can handle large amounts of current and withstand considerable magnitudes of voltage, the switching device which I have described eliminates the disadvantages inherent in the use of electrical contacts for switching purposes under similar conditions.

If instead of operating the arrangement as shown in Fig. 1 as a switch, it is desired to control the magnitude of the altemating current flowing in the load IS, the conditions as exemplified by Fig. 2 may be utilized. Under these conditions the control device 26, instead of supplying a particular predetermined value of current and therefore of flux to the control tube,is constructed to vary the amount of. current supplied to the energizing coils 25. For this purpose the rectifier of Fig. 5 is made adjustable. In Fig. 2 the voltage applied to the anodes 4 is represented by the sine wave X. In a practical case the flux control characteristic of the discharge tube may be represented by the curve Y. This curve represents the limiting value of flux above which a discharge will be prevented for each instantaneous value of voltage applied to the electrodes 4. I! under these conditions the current supplied to the coils 25 is of such a value as toproduce a-' flux of the value indicated by the dotted line Flux A, this value of flux will intersect the control characteristic Y at the point A. Therefore, a discharge will start at the pointA on the applied voltage curve and conduction will continue until the'end of the half. cycle in which said discharge is initiated. As indicated in Fig. 2, this initiation of current occurs in both halves of the applied voltage wave, and'therefore under these conditions alternating current of a predetermined magnitude will flow through the load l9. If, however, the control device '26 (Fig. 5) is adjusted so as to supply a higher value of current to the coils 25, producing a higher value-of flux, as indicated in Fig. 2 by Flux B, then this value of flux will intersect the control characteristic Y at another point B. It will be noted that the point B occurs later in the applied voltage cycle than does the point A. Under these latter conditions, a discharge will be initiated at point B on theapplied voltage curve at a later. time than in the case of the lower value of flux.

1 the value of the current supplied to the coils 25 through the control device 26, the value of alternating current supplied to the load l9 may likewise be varied.

Instead of controlling the magnitude of the alternating current supplied to the .load I! by varying the magnitude of the current suppli to the coils 25, a similar efiect can be produced by supplying alternating current to said control coils and varying the phase of said alternating current with respect to the voltage applied to the anodes 4. Under these conditions the control device 25 would not be constructed as a rectifier but would constitute a phase-shifting network,

as represented in Fig. 6. The conditions of oper-- ation of such an arrangement are exemplified in Fig. 3. 'In this figure the voltage applied to the anodes is again represented by the curve Xi Since alternating current is supplied to the energizing coils 25, the flux set up by those coils will likewise be an alternating flux and is represented in Fig; 3 by the curve Z. The conditions of operation of the discharge tube for this type of ,operation are assumed to be such that a discharge is prevented whenever the flux is appreciably greater than zero. Actually this condition can readily be obtained in a practical device. If, as shown in Fig. 3, the control device 26 (Fig. 6) is so adjusted that the flux curve Z leads the voltage curve by a certain phase angle, the flux will be substantially greater than zero at the beginning of each half cycle, and therefore the starting of a discharge will be delayed. The flux curve Z, however, passes through a zero value later on in said half cycle. As the flux passes through zero, a discharge is initiated through the discharge tube and the conduction continues until the endof that half cycle. Further, as indicated in Fig. 3,

such delay and initiation of the discharge occurs in each half cycle, and therefore an alternating current of a predetermined value will flow through the load l9. As the control device 28 is adjusted to increase the angle of lead between the flux curve Z and the applied voltage X, the curve Z will pass through zero earlier in the applied voltage cycle, initiation of the discharge will occur earlier in said applied voltage cycle, and the value of alternating current flowing through the load I! will be increased. As the phase angle between the flux and the applied voltage is decreased, initiatioh of the discharge occurs later in the cycle, and the value of currents througlr the load it is decreased. The limiting conditions in either case exist when the flux curve Z passes through a valueat which it is in phase with the applied voltage. As this transition takes place, the alternating current through the load I! will suddenly shift from zero to maximum value, or from its maximum value to zero, depending upon the direction in which the change occurs.

The foregoing conditions of operation in each case deliver an alternating current to the load --be provided by making the magnetic structure,

includingthepolepieces,intheformofapermanentmasnethavingapredeta-mineddegree of m etization. As illustrated in Fig. 4, this flux bias may be represented by the horizontal dotted line V. Instead of. biasing the magnetic structure by having it inflie form of a permanent magnet, the control device II, as represented in Fig. I, may have an auxiliary rectifying arrangenient 29 therein, and in addition an adjustable phase-shifting network II for supplying alternat-' ing current to the coils 25. The rectifier 29 superimposes on the alternating current supplied by the phase-shifting device 3!, a predetermined value of direct current. Under these conditions likewise the flux bias may also be represented by the horizontal dotted line V in Fig. 4. In either of the arrangements as indicated, the control device 26 supplies to the coils 25 an alternating component of current which sets up an alternating component of flux, as indicated by the curve W in Fig. 4. Since the magnetic field is biased by the value as represented by the line V, the variable component of flux W will vary around the flux bias V as an axis. Preferably the alternating component of flux W a adjusted so that its peak value is substantially equal to the flux bias value. Under these conditions, as indicated in Fig. 4, the resultant flux will periodically drop to a zero value. When this occurs, the discharge which was prevented from starting prior to the flux reaching said zero value will be initiated. If, for example, the phase of the variable flux component W is adjusted so that its zero value occurs at the beginning of one-half of the applied voltage wave, the discharge will be initiated at that point and the tube will conduct current substantially throughout that half cycle of applied voltage. This is the condition as illustrated in Fig. 4. When this occurs, however, the resultant flux remains greater than its zero value throughout the other half cycle of the applied voltage, and therefore a discharge is never initiated during said other half cycle. The result of this arrange- -ment is that the discharge tube conducts current in but one direction, and therefore a direc current will flow through the load l9.

If it is' daired, however, to reverse the direction in which the direct current flows through the load i9, it is merely necessary to shift the phase of the alternating flux component, W through 180 degrees. This might well be accomplished by providing a reversing switch 3| in Fig. '7, to reverse the connections to the leads-extending to the energizing coils 25. when the alternating component of flux is thus shifted through 180 degrees, conduction will occur during the half cycle in which it was previously inhibited,- and a discharge will be inhibited throughout that half cycle in which conduction previously occurred. The result of such a change, therefore, would be to reverse the direction of the direct current which flows through the load l9.

instead of permitting a 'simple reversal of direct current through the load IS, the arrangement can also be operated so as to control the value of the direct current in each case. Referring again to Fig. 4, if the alternating component offluxwisshiftedinphasetotheleftsoas to bring said alternating component more nearly in phase with the applied voltage, the zero point these conditionsthe current would flow. for a I short'erperiod during each conducting half cycle,

occur continuously to zero as the component W was-shifted through 180 degrees. As the current passed its zero value, the alternating component 'W would be displaced 180 degrees from the position shown in Fig. 4, and the direction of the direct current through the load 18 would suddenly reverse and rise to its maximum value, as described above. Therefore, as the phase relationship between the alternating component W and the applied voltage was continuously varied, the direct current passing in one direction would gradually decrease to zero and suddenly rise to a maximum value in the opposite direction, and

again gradually decrease to zero. A reversal in the direction of the phase shift would merely reverse the direction of the variation in the direct current supplied to the load.

The invention is not limited to the particular details of construction or operation as described above as many equivalents will suggest themselves to those skilled in the art. For example, the electrodes 4 might take a variety of diilerent forms as long as these electrodes could alternately act as a cathode and anode as described above. Furthermore, various combinations of the types of operation as described above could likewise be utilized. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In combination, an electrical space dis charge device comprising an envelope containing two electrodes, each adapted to operate as-a cathode, an intermediate electrode mounted adjacent the discharge path between said cathodes, and

an ionizable medium at a pressure under operatthe direction of the discharge between said cath-,

odes.

3. In combination, an electrical space discharge device comprising an envelope containing two electrodes, each adapted to operate as a cathode, an intermediate electrode mounted adjacent the discharge path between said cathodes, and an ionizable medium at a pressure under operating conditions sufiicient to supp copious ionization upon the passage of a discharge, means for producing a magnetic field which is transverse to the direction of the discharge between said cathodes, means for connecting a source of alternating current between said cathodes, and

means for adjusting the value of said magnetic field.

4. In combination, an electrical space discharge device comprising an envelope containing two electrodes, each constructed as a thermionic cathode, an intermediate electrode mounted adjacent the discharge path between said cathodes, and an ionizable medium at a pressure under operating conditions suflicient to supply copious ionization upon the passage of a discharge, means for producing a magnetic field'which is transverse to the direction of the discharge between said an ionizable medium at a-pressure under operat-' ing conditions suiiicient. to supply copious ionization upon the passage of a discharge, means for connecting a. source of alternating current between said cathodes, means for producing a magnetic field periodically'varying at, the frequency of said source, which field is transverse to the direction of the discharge between said cathodes, and means for adjusting the phase angle between said magnetic field and said source.

6. In combination, an electrical space discharge device comprising an envelope containing two electrodes, .each' constructed as a thermionic cathode, an intermediate electrode mounted adjacent the discharge path between said cathodes, and an ionizable medium at a pressure under operating conditions sufiicient to supply.

charge, means for connecting a source of a'Jternating current between said cathodes, means for producing an alternating magnetic field which is transverse to the direction of the discharge between said cathodes, and means for adjusting the phase angle between said magnetic field and said source.

7. In combination, an electrical space discharge device comprising an envelope containing two electrodes, each constructed as a thermionic cathode, an intermediate electrode mounted adjacent the discharge path between said cathodes, and an ionizable medium at a pressure under operating conditions sufiicient to supply copious ionization upon the passage of a discharge, means for connecting a sourcsilof alternating current be-.

tween said cathodes,means for producing a magnetic field having a unidirectional bias component and an alternating component, said field being transverse to the direction of thedischarge between said cathodes, and means for adjusting the value of said unidirectional bias.

8. In combination, an electrical space discharge device comprising an envelope containing two electrodes, each constructed as a thermionic cathode, an intermediate electrode mounted adjacent the discharge path between said cathodes, and an ionizable medium at a pressure under operating conditions sufficient to supply copious ionization upon the passage of a discharge, means for connecting a source of alternating. current between said cathodes, means for producing a magnetic field having a unidirectional bias component and an alternating component, said field being transverse to the direction of the discharge between said cathodes, and means for adjusting the phase angle between said alternating component and said source.

' PERCY L. SPENCER.

Images