US1973082A - Circuit connection for thermionic tubes - Google Patents

Description

Sept. 11.,.1934. L. KRos v 4'CRCUI'I CONNECTION FOR THERMIONIC TUBES Filed may 2s. 192s jnv-renfor 141g 20 J3 lszL /lA/o'ro'ls Patented Sept. 1l, 1934 UNITED STATES PATENT koFFIcI-z Lszl K'rs, Budapest, Hungary Application Mey 2'3, 1929, serial No. 365,324

In Germany June 6, 1928 6 Claims.

tive potential to be used as grid bias.` A furtherobject of` the invention is to produce different constant voltages for several anode circuits supplied from a common feed line. A still further object of the invention is to provide a new potential divider adapted in particular for carry- ,ing out connections according to the inventionl and permitting the taking off from a direct current potential of reduced potentials of lany desired constant value.

According to the invention, a useful potential drop in an anode circuit is produced by connecting inthe anodecircuit aconductor which varies its resistance according to the load at the moment in such manner that the potential drop in it remains practically constant between certain limits of the load.f

As such conductors, tubes filled with rarefled gas, for example, neon, with two or more eleotrodes, cold or heated, or partly cold and partly heated, may be used.

To simplify expressions, such conductors will in the following be described as balance conductors.

It is already known that a constant potential may be taken off the terminals of a discharge tube through which ows a variable current and which represents a balance conductor. Such a discharge tube has also been connected in parallel to an anode Circuit in order to make the poten--l tial of this anode circuit practically independent of the variations of the load. Where, however, it was desired to produce a drop of potential in the anode circuit, that is, in series, with the thermionic tube, ohmic resistances have hitherto been used. This resulted in a drop of potential varying with the load.

By using, in accordance with the invention, a balance conductor for the production of the potential drop desired in the anode circuit, not only i is the independence of the potential drop on the load secured but at the same time numerous other 55 new advantages are obtained which are' of great the above-mentioned distortions are avoided.

(Cl. 25o-27) importance for the correct working of the thermionic tubes. l

A considerable ohmic resistance in the anode circuit represents a high resistance for the modulations of the speaking currents and thereby reduces the sensitiveness or amplifying action of the thermionic tubes. To conduct the modula' tions, a condenser must therefore be connected in parallel to the ohmic resistance, which condenser, however, transmits the various frequeng5 cies in unequal measure and thereby causes distortions in the modulations. In case several anode circuits are connected in parallel, an ohmic` resistance connected in series therewith forms a coupling resistance between the various anode circuits whereby the amplifier tubes are easily put in oscillation, which danger is still further considerably increased if, as usual, grid bias potentials are taken from the coupling resistance.

A balance conductor forms an extremely small resistance for the modulations of the speaking currents, the value of which is furthermore independent of the frequencies. Thanks to this high conductivity for modulation Currents," neither the above-mentioned prejudical effect on the sensitiveness or the amplifying action of the thermionic tubes nor the bad effects of the coupling are to be feared, and due to the independence of the conductivity of the frequencies,

The connection according to the invention is of peculiar practical importance in the taking of a negative grid bias potential from the anode circuit and in the feeding ^of several anode circuits with different potentials from a common feed line. Constant grid bias potentials may be taken from a balance conductor connected behind the nlament or filaments. By the Iconnection of balance conductors in the branches of a common feed line, all of the anodes lying in the several branches may be supplied with constant poten' tials of any desired value if only the potential of the common feed line be made independent of the variations of the load which is possible by bridging over the common feed line by means of a balance conductor, that is, bythe known connection, mentioned at the outset, of afbalance conductor parallel to that anode circuit which is to be supplied with the undivided potential of the common feed line.

The invention also comprises a new potential divider which is adapted in particular for carrying outconnections, according to the invention, with two or more balance conductors. This potential divider ils composed of glow discharge tubes lled 110 or terminals. The different tubes of suchl a potential divider may have a common socket. It is also possible to enclose the electrodes of two or .more glow discharge tubes of a potential divider in a common container or gas space.

In the accompanying drawing- Fig. 1 diagrammatically shows a connection, according to the invention, in which they constant drop of potential in a balance conductor connected behind'the filament is utilized for taking off constant grid potentials.

Figs. 2 and 3 show, also diagrammatically, two forms of construction of another connection, according to the invention, for the supply of several anodes with different potentials from a. common feed line, where the balance conductors connected in series to the anodes lying in the branches of the feed line eiect a distribution oi' the potential independent of the variations of the load.

Fig. 4 shows the combination of the connections according to Figs. 1 and 3.

Figs. 5 and 6 are diagrammatic representations of potential dividers for the connections according to Figs. 2 and 4, respectively.

Fig. 7 shows a further constructional form of the potential divider according to the invention, in diagram, and

Figs. 8 to 10 show in side, top and bottom view,

, a practical construction corresponding to the diagram according to Fig. 7. In the bottom view is also shown the connection of the several glow discharge tubes between each other and with the plug contacts, inndiagram.

In Figs. 5 to 7 and 10, the numberslinserted in the individual glow discharge tubes indicate the constant potential drop taking place in, and being characteristic of, the corresponding tube, while the numbers which in Figs. 5 to 7 are enclosed in brackets under the reference characters for the terminals and according to Fig. 10 are marked 'on the base plate, give the Value of the constant potential which may be taken from the corresponding terminal.

Figs. 11 and 12 show modications of the connections according to Figs. 2 and 4, respectively, in which the' several balance conductors are enclosed in a common container.

In the connection according to Fig. 1, any-desired current source with 'comparatively high internal resistance, lies between 1 and 2, which current source is intended to supply anode and grid potentials for thermionicv tubes (not shown) which are connected with the anodes at 3, and with the iilaments at 4. In thelead between 4 and 2 is connected a balance conductor 5 having a comparatively high ohmic resistance 6 connected as a potentiometer parallel thereto, the balance conductor having 4a negligible ohmic resistance. At the tappings 7 and 8 of the potentiometer 6, grid bias potentials are taken oi for the thermionic tubes supplied. The condensers 9 and 10 serve to conduct the charging anddischarging currents of the grids and of the transformer coils lying thereon. By means `of the condenser 11 the resistance of the anode circuit to alternating current is reduced.

As the potential drop in the balance conductor 5 mainly depends on the constants thereof, remaining practically unaffected by the variations of the current strength i'n the anode circuits,

while from the tappings. of the ohmic poten-A the load in the anode supply line.A As the potenv tiometer 6 only supplies potential and no current is taken therefrom, its resistance may be selected as high as desired.

Itwill be understood that the potentiometer 6 is only necessary for bias potentials which do not reach the working potential of the balance conductor 5. On` the other hand, bias potentials above the working potential of a balance conductor could be taken from several balance conductors connected in series to each other which may be arranged in a common container as in Fig. 12, if desired.

According to Fig. 2 the potential between the terminals 12 and 13 of a known anode mains supply appliance, a so-called B eliminator, represented by coil 14 and condenser 15 is in known manner in so far made independent of the variations of the load by the balance conductor 16 connected in parallel that it cannot appreciably rise over the working potential of the balance conductor 16. So long as the load does not exceed a definite upper limit, the potential between 3 and 4 may therefore be considered as practically constant. By the connection in the sense of the invention of further balance conductors, this potential, available as constant highest potential, may now be reduced to lower anode potentials also constant. In branches of the common feed line between 12 and 3, balance conductors 19 and 20, respectively, are connected in series to anodes to be connected at -17 and 18 whereby each of the anodes connected at 17 and 18 receives a constant potential which is smaller by the potential drop in the balance conductors 19 and 20, respectively, connected in series with the corresponding anode, than the potential between 3 and 4. As ordinary glow discharge tubes having cold electrodes may be made as balance conductors for the most varying potentials over 80 volts, this connection permits of the production and stabili-- zation of any desired potential value for anodes, also under 80 volts, by means of .ordinary glow discharge tubes. The condensers 21 and 22 reduce for higher frequencies the alternating current resistance in the corresponding anode circuits.

The connection according to Fig. 3 differs from that shown in Fig. 2 in that the balance conductors 19','20' and 16' are arranged in potentiometer connection. It needs, of course, no further explanation that in this case the potential between 18' and 4 is less by the sum of the potential drops in 19' and 20' than between 3 and 4, and that the highest value of the potential, between 3 and 4, corresponds to the sum of the working potentials of 19', 20 and 16. Of course, the number of the balance` conductors arranged in series to each other may be chosen as desired.

The combination shown in Fig. 4 of the connections according to Figs. 1 and 3; needs no further description.

Fig. 5 shows a potential divider adapted for the connection according to Fig. 2 and consisting of three glow discharge tubes 16. 19, 20 which have their anodes joined.- The connected anodes have a common terminal b1, whereas each of the three cathodes is provided with a separate "terminal b2, b3, b4. The glow tube 16 which in the connection according to Fig. 2 serves for the bridging over of the common feed line, must have a working potential equal to the potential between 3 and 4, that is, the potential between 3 and 4 must be adjusted to the working potential of the glow tube 16. A potential divider accordi g to the invention permits of this regulation without the use of an instrument. It is sufficient to bring to a glow the glow tube 16 by means of a rheostat connected on the current source. In order that this tube to be observed may be easily distinguished from the other tubes of the potential divider, and still more, in order that the observation may not be interferedfwith by the light effect of the other tubes, which in some cases may glow before, the other tubes are provided with an opaque coating, as is indicated on the drawing by shading.

For the purpose of the connection according to Fig. 2, the glow tubes 19 and 20 of the potential divider are so selected that their working potentials complement the anode potentials desired at 1'7 and 18 up to the workingpotential of the glow tube 16. With the working potentials of the glow tubes as indicated in Fig. 5, the total potential of 200 volts between 3 and 4 is therefore reduced by the glow tubes 19 and 20, the working potentials of which respectively amount to 100 and 180 volts, to 100 and 20 volts respectively, which reduced potentials may be taken from the terminals b2 and b3 respectively. The stability of the potentials taken off the potential divider according to the invention permits the terminals of the potenial divider to be marked once and for all with the values of the potentials to be taken therefrom.

Of course, a potential divider composed of glow tubes in the manner shown in Fig. 5 might comprise only two or also more than three tubes.

Fig. 6 shows a construction of the potential divider according to the invention, which is adapted for the connections according to Figs. 3 and 4. In this case, the several glow discharge tubes 19', 20', 16 and 5 are connected in series est to each other. In the use for the connection according to Fig. 3, the glow tube 5 remains out of working, the points 2 and 4 being connected at the tapping b4 of the potential divider, and the terminal b5 remaining free. In e use for the 'connection according tzr-Figgg4, point 4 is con- Also this regulation may be simply performed by bringing to a glow the tube 161 only.

It will be understood that also in cases where the tubes 19 and 20 serving as potential reducers are connected in series to each other, the bridging over of the total potential may be effected by means of a single tube connected in parallel to the series of potential reducing tubes.

In the potential divider according to Fig. 7,

the two forms of combination of the glow discharge tubes as shown in Figs. 5 and 6 are combined. The tubes a2, a1 and a4'are connected in -series as shown in Fig. 6, while the tube a3 joins this series by its anode being connected to the anode of tube a2. With the use of glow tubes of the potentials indicated, the constant potentials may be` taken from the several terminals b as shown in brackets against the terminals.

In the construction -of the potential divider according to Figs. 8 to 10, corresponding to the diagram of Fig. 7, the four glow tubes a1, a2, a3, a4 are mounted in a common socket d of insulating material shaped as a square base. The tubes are mounted in the top plate, and the terminals b1, b2, b3, b4, b5 constructed in the manner of the known plug contacts, in the bottom of the base d. The vconnection of the tubes betweenv themselves and with the terminals are made in the hollow space of the base d according to the diagram seen in Fig. 10. With this construction the whole potential divider may be manipulated as a single tube.

Of course, a common socket for several tubes does not need to include all the tubes of a potential divider.

The electrodes of two or more or all the glow tubes of a potential divider may also be enclosed in a common container or gas space. Fig. 11 shows, for example, the connection according to Fig. 2 with a potential divider in which the several balance conductors 16,19 and 20 are connected in the same manner as. in Fig. 2 but are enclosed in a common gas space, while in Fig. 12 a form of the connection according to Fig. 4 is shown, in which the several balance conductors are replaced by a single tube potential divider consisting of gaseous discharge paths connected and working in the same manner as the balance conductors 19', 20', 16 and 5 of Fig. 4, except that one of the electrodes, to wit, the most negative cathode, is heated by means of a separate heaterlament 23 supplied with heating current from any desired current source represented by the terminals 24 and 25. Those skilled in the art will readily understand that any other method of heating may be applied -to heat this electrode or any number of the electrodes of the potential divider. The heat so applied results in the diminution of the cathode fall, that is, of the potential drop between the electrodes, .and permits also a regulation of this potential drop by varying the measure of heating. Furthermore ,a discharge tube with heated electrodes may be smaller for a given load. Y

What I claim isz-'- 1. I`n a. system for energizing the grid electrodes of thermionic tubes from a current source of high internal resistance, a discharge device of predominatingly constant potential drop including electrodes in the negative conductor from the cathode to the current source, and means for applying said constant potential drop to the grid. v

2. The system as claimed in claim 1 in which grid biasing potentials are obtained from a potentiometer connected across twoelectrodes of 135 stant the potential ofl the current supplied to the tube.

4. In a system for energizing the anode and 5. The system as claimed in claim 4 in which grid biasing potentials are obtained from a potentiometer connected across two electrodes of said discharge device.

6. The system as claimed in claim 4 in which' anode potentials are obtained from the potential drop across two or more electrodes of said discharge device.

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