US2171490A - Electric discharge device - Google Patents

Description

Aug. 29, 1939. H. F. DALPAYRAT 2,173,4fi

ELECTRIC DISCHARGE DEVICE Filed Dec. 2, 1936 2 Sheets-Sheet 1 1 gm d.

2,3 HAQiB Aug. 29, 1939. H. F. DALPAYRAT ELECTRIC DISCHARGE DEVICE Filed Dec. 2, 1936 2 Sheets-Sheet 2 Patented Aug. 29, 1%39 2,171,490 ELECTRIC DISCHARGE DEVKCE Henri F. Dalpayrat, New York, N. Y., assignor to Radio Corporation of America, a. corporation of Delaware Application December 2, 1936, Serial No. 113,927

10 Claims.

My invention relates to electric discharge devices and more particularly, to devices of the socalled electron beam type as well as to utilization circuits therefor.

In accordance with art prior to my invention, electron-control in vacuum tubes was usually obtained through the use of helical or solenoid grids concentric with a thermionic cathode or partially inclosing the cathode and disposed between the said cathode and the anode. Furthermore, it was customary to utilize slotted or perforated controlelectrodes through the openings in which electrons pass and from which many of them were accidentally reflected or caused the liberation of secondary electrons. In accordance with my experiments and experience, such control electrodes are a fruitful source of tube noises, and prevent the attainment of higher degrees of amplification, while causing most of the technical difficulties encountered in well known vacuum tube amplifiers.

In addition, wound wire grids, or slotted or perforated structures between the cathode and the anode cause the reflection of electrons emitted from the cathode, and also emit interfering secondary electrons, thus reducing the amplification obtainable and the efiiciency of the tube.

A still further disadvantage of conventional thermionic tubes heretofore known is the absorption of electrons by tube parts, such as the control grid, the screen-grid, or other grids, causing undesirable potential variations or excessive currents in such parts that seriously interfere with their normal purposes and functions. That feature also prevents the attaining of maximum amplification and is a source of noise and distortion of the signal. Also, as is now quite well known, relatively high inter-electrode capacities exist in conventional thermionic tubes which prevent proper-amplification of the higher modulation frequencies and militate against the efficiency of the tubes for the amplification of ultra-short waves.

Another well-known disadvantage of grid- 7 tubes is due to the fact that, near the surface of the output anode, the electrostatic positive field density of the anode per unit area is much greater than the negative electrostatic field density of the electron streams reaching that surface, which prevents the cathode-electrons from repelling the secondary-electrons liberated by the anode when the latter receives cathode electrons.

Furthermore, in thermionic tubes of the multigrid type, secondary electrons emitted from the output anode are accelerated by the screen grid and are caused to impinge upon and pass through the control grid, in a direction contrary to the direction of flow of the useful electrons, thus reducing the effectiveness of the control grid and tending to lower the electron emission from the cathode. Such anode secondary emission obviously increases with increase in signal amplitude, giving rise to non-linear amplification and consequent distortion.

It is also evident that the suppressor grid cannot be given a sufficiently negative potential to repel all secondary electrons emitted by the anode, unless it is made so negative as to also prevent electrons emitted from the cathode from reaching the anode. This, in my estimation, is a serious fault which is partly overcome by applying a quenching frequency to the suppressor, but,

.as is well known, super-regeneration circuits cannot be used satisfactorily for all amplification purposes.

From the manufacturing standpoint, in thermionic tubes of the type wherein wound wire grids are utilized, it is diflicult to obtain perfection. That is to say, when an attempt is made to so align the various grids, in order to reduce the objectionable features hereinbefore referred to, tube production must necessarily be slowed up or else the percentage of rejections increases.

Conventional tubes of the types under discussion are inevitably microphonic to a greater or less extent. The microphonic noises may be caused by heat emitted from the cathode which alters the various electrode-structures rigidity with consequent changes in inter-electrode capacities affecting the sensitivity or amplification factor.

Another disadvantage of grid-tubes, especially at short Wave lengths, is their inefficiency when they are used for multiple functions, such as a mixer tube for superheterodyne operation, due to unwanted capacity couplings existing between the various electrodes.

Another disadvantage of grid tubes is that when it is attempted to obtain a greater isolation of different functions within one tube, through the use of separate amplifying units or complicated electrode arrangements within a single envelope, the tube becomes more bulky, more fragile, more expensive, and more complicated to manufacture, while the unusual number of circuit connections at the base of the tube is a marked inconvenience, or a detriment to satisfactory short-wave reception and complicates the circuit wiring at this point.

Still another disadvantage of grid-tubes, of ordinary inexpensive types, is their inability to deliver full undistorted power-output, especially when a low positive voltage is applied to the anodes.

A still further disadvantage of grid-tubes is the constant variation in electronic field density existing between the cathode and the signal input control-grid, rendering this grid temporarily less effective for low amplitude modulations or higher signal frequencies, immediately after the liberation of a large percentage of the cathode-tocontrol-grid space charge, by high amplitude signal modulations.

Even in multi-grid tubes of the so-called beam type, entirely satisfactory operation cannot be obtained because of the fact that the various horizontal electron beams, shaped by the grid wire turns, constantly vary in cross sectional area according to the signal voltages impressed upon these grids, while the anode potential is varied only by the quantity of electrons flowing through its circuit. This 'discrepancycauses a higher electronic velocity of the compressed beams when the grid is more negative, thus directly opposing or counteracting in various irregular amounts the full effectiveness of the signal voltage variations received by the signal control grid. Although this type of uneven amplification cannot be de termined by simultaneous observation of the wave-forms of all audible frequencies, through oscilloscope analysis, the effect, nevertheless, prevents obtaining natural and genuinely realistic audible reproduction, as it is in the case when amplitudes are distorted or a large precentage of harmonics are generated.

Another disadvantage of grid-tubes is that the anode potential exerts a variable attraction upon the electrons emitted by, and in the immediate vicinity of the cathode, which variable attraction constantly counteracts, in various amounts, the action of the control grid. For example, when the control grid becomes more negative, fewer electrons reach the anode which then draws less current and whose voltage thereof increases. The increasing anode voltage augments the attraction by the anode of the electrons that are near the cathode, thereby partially defeating the purpose of the negative potential applied to the grid, thus preventing it from repelling the proper number of electrons from the emitting cathode.

Referring to the prior art, and particularly to the phenomenon well known as space charge, that is an accumulation of low velocity electrons which form an electron cloud hovering around the emitting cathode and which greatly decrease the controlling actions of the modulation grid as well as lowering the amplification and impairing the efficiency of single and multiple grid tubes.

Although it is well known that an electrode charged with a low positive potential can be placed between the cathode and the input modulation grid, for the purpose of absorbing the space charge and increasing the controlling action of the modulation grid upon the electrons being emitted by the cathode. It is also known that such a positive absorption electrode must be placed very near the cathode, carry a very low positive charge, and offer a minimum physical obstruction to the useful modulated electron stream.

One difiiculty in this method is that the space charge removing electrode cannot be placed too near the cathode without incurring danger of short circuit. Another difiiculty is that as the distance between the cathode and the modulation grid is increased, the percentage of modulation of this grid is decreased enormously due to venting the establishment of larger main anode output currents.

Therefore, it is another object of my invention to simultaneously absorb the space charge, increase the electronic emission and transfer, accelerate and direct electrons by control electrodes capable of modulating the electron beams which it shapes and directs.

Referring again to the prior art, and particularly to the so-called gridless tubes of the single cathode ray variety, it is well-known that an electron beam can be formed, modulated, accelerated, directed towards, and collected by two output anodes equidistant from the cathode. It is also known that modulation of the output currents can be accomplished by deflecting the electron beam through electrostatic means, which may be modulated at signaling frequencies, thus varying the number of electrons collected by each anode as the beam sweeps in oscillatory manner over the surface of these anodes. While a device of this type can be used for amplitude selection or automatic stabilization purposes, it has several objectionable features. For example, in order not to offset the action of the beam deflecting plates, it is necessary to produce and maintain a uniform electronic density throughout the cross-sectional area of the beam, and therefore a similar value of potential must be applied to both output anodes.

It might be said in passing that I am thoroughly familiar with the use, for amplification purposes, etc., of tubes of the so-called cathode ray type, wherein an electron beam is emitted from an electron gun and is caused to be deflected over a plurality of output electrodes. The number of useful electrons, in such devices, however, is small and the anode current is generally insufficient for the majority of purposes. Also, high anode potentials must be used and one or more focusing, dispersing, or accelerating electrodes must be disposed between the gun and the output electrodes, thus causing diminution of the electron stream, increasing the number o terminals required and rendering the tube unduly bulky for use in radio receivers.

Referring again to the prior art, and more particularly to systems wherein amplitude selection is obtained through the use of hghly negatively biased control grids or other electrodes, or through reverse feed-back, a signal of relatively high amplitude must be present before the control is effective. One disadvantage in using grid tubes for that purpose is that the anode attraction upon the cathode electrons is ever present and necessitates the use of very high negative bias on the controlling grids, which high negative bias is not always easily obtainable. Even with high negative bias a grid is not an efficient barrier for the electrons in transit within the tube, because of the relatively wide spaces between the turns, which cannot be made much less without completely blocking the passage of all electrons, regardless of the operating C bias used.

Another objection is that a high negative bias cannot be obtained through the conventional cathode lead resistor method without greatly decreasing the anode output current and lower ing the efficiency of the tubes, as well as causing distortion.

Referring again to the prior art and more particularly to the method of obtaining modulation in electric dischargedevices, especially those in which grids are completely eliminated and the cathode electronic emission is under the constant attraction of the positive anode, and where a so-called absorption anode is placed behind or near the cathode, to be used as controlling element by robbing more or less electrons from the useful electron stream.

One objection to this method is the ineflicient control thus provided over the cathode to anode electron stream.

Another objection is the signal distortion produced by the increases of current in the absorption anode when such is used for modulation.

In my invention this method of modulation by electronic absorption is greatly improved by my new tube designs and operating principle, in which (1) the interfering electronic space charge is prevented from accumulating and (2) the absorption currents in some electrodes are decreased by the voltage variations of other modulation electrodes and (3) whereas a greater control is attained over the electrons in transit between cathode and anode through the unbalancing of the electrical equilibrium existing between the various electrodes controlling the cathode emission,

Referring again to the prior art and particularly to multi-grid tubes, where some grids are used for the sole purpose of absorbing the space charge and other grids are used to accelerate and propel towards the anode a modulated electron stream.

An objection to these methods is that when the order of utilization is changed for the various grids, the grid then being used for modulation is too far from the cathode to control large numbers of electrons, and, furthermore, due to the presence of the positively charged spacecharge grid between the cathode and the control grid, the electrons acquire sufiicient velocities to impinge upon or shoot through the control grid irrespective of its original voltage variations or bias.

Another objection is, in multi-grid tubes, the position of the acceleration element or so-calledscreen grid, whose current increases with the increased liberation of electrons by the modulation grid which gives rise to lower anode currents, distortion of original amplitudes, the generation of harmonics and the decrease of potential of this screen-grid element exactly at the time when, on the contrary, a raise in this potential would be highly beneficial to coordinate with the actions of the modulation grid.

In my invention these several objections are substantially corrected or prevented. For example, when the controlling electrodes (here called compressors) turn more positive and allow a wider-spray of electrons over the anode surface, the collectors (absorption anodes) receive less electrons, and as the positive voltage of these elements is thus increased, an increase in electronic velocity is obtained, for the electrons shooting towards the openings between the collectors and the compressors.

Another advantage of my invention is that acceleration of the modulated electron stream increases with the signaling amplitudes (according to circuit design, if desired) while simultaneously through the same acceleration. element, the space charge isbeing constantly absorbed.

Another objection present in all multi-grid tubes is that the modulation grid must be maintained at a negative bias sufficiently high to repel electrons emitted by the cathode, when no input signal is present. While the action of the screen grid, due to its positive field attraction, counteracts in varying proportions this repulsion and also causes the liberation of a number of electrons much larger than the number of electrons being repelled when the modulation grid turns more negative. Thus partial detection of the signal is caused and said detection current causes many objectionable cross-modulations, or interferences, or parasitic noises, distorting the frequencies of the signal wanted.

In my invention the undesirable effects are greatly minimized because the rate of cathode emission (as controlled by the increase of potential of some electrodes and an exact decrease of the potential of some other electrodes) maintain the total electrostatic attraction fields constant and permanently stable.

I wish to make it clear at this point that, in my invention, unlike any other electronic device, modulation is accomplished by deflecting simultaneously several electron beams over the surfaces of several absorption elements, thus passing more or less electrons to the main output anode, while at the same time, these absorption and deflection elements are so disposed near the cathode as to maintain its electronic emission rate and electronic field density stable and constant,thus preventing the degenerative effects due to excessive C bias variations through cathode resistor as for low frequencies in A F amplifiers.

An object of my invention, therefore, is to provide an improved electric discharge tube wherein electron control is obtained without resorting to a multiplicity of wound or perforated grids, thus obviating at a singlestroke many of the disadvantages of conventional tubes.

Another object of my invention is to provide an electric discharge tube, suitable for detection, amplification and other well-known purposes, and of such type that, through its use, and simple electric circuits, and without resorting to critical interstage feed-back circuits, automatic volume control, noise limitation, etc., may be obtained.

Another object of my invention is to provide an improved electric discharge tube of the type under discussion that shall, by reason of its construction, be extremely versatile and capable of a wider range of applications and greater usefulness than conventional tubes.

Another object of my invention is to eliminate solenoid grids or their perforated equivalents and to provide a tube that shall be even more efficient, for certain purposes, than tubes wherein grids of such types are utilized.

Another object of my invention is to provide a tube, devoid of electron control elements of conventional types, that shall itself provide automatic self-limitation, automatic signal amplitude selection, automatic voltage or current regulation, and shall be adaptable to a plurality of uses, such as detection and/or rectification and/or signal amplification.

Another object of my invention is to provide a thermionic tube wherein electron beam action may be obtained without resorting to conventional control grids, thus obviating many of the disadvantages heretofore pointed out.

Another object of my invention is to provide an improved electric discharge tube based upon an operating principle applicable for use in electric power rectifier circuits, line voltage regulation circuits, line telephone systems, radio receivers, transmitters and amplifiers, or for the purpose of maintaining constant the rate of vibration or rotational speed of various electrical and/or electrically operated mechanical devices.

Another object of my invention is to provide novel utilization circuits for my improved elec- ,tric discharge device, whereby it may be utilized for multiple functions, such as, a combination diode detector and automatic noise suppressor tube, or a combination power rectifier and automatic voltage stabilizer tube, or ,a combination radio frequency amplifier .and volume control tube, or a combination heterodyne frequency changer and noise level limiting tube, etc. Said utilization circuits form the subject matter of a specification now being prepared for separate filing.

Another object of my invention is to provide an electric discharge device wherein inter-electrode capacities are greatly reduced, thus rendering this device practical and efllcient for the amplification of high audio or radio frequencies, or the generation of oscillations of constant frequency and amplitude. I

Another object of my invention is to provide an improved electric discharge device wherein a plurality of functions may be obtained without interference one with another.

Another object of my invention is to provide an electric discharge device that shall be simple in construction, and inexpensive to manufacture.

Another object of my invention is to provide an electric discharge device that shall be capable of delivering high undistorted power output with minimum positive potential applied to the output electrode or electrodes.

Another object of my invention is to provide an electric discharge device that shall be relatively free from microphonic noises.

Another object of my invention is to provide an electric discharge device of such type that the useful electron stream is not robbed of electrons by the presence of an undue number of positively charged electrodes, whereby distortion in the output current is reduced.

Another object of my invention is to provide an electric discharge device that shall require minimum negative C bias for threshold voltage control, thus obviating the necessity for utilizing a cathode resistor of large magnitude.

Another object of my invention is to provide an electric discharge device wherein oneor more electron beams may be formed from the full cathode emission without resorting to the use of electron guns or the like.

Another object of my invention is to provide an electron tube of the general type under discussion, wherein utilization may be made of secondary electron emission for obtaining higher voltage or current amplification, if desired.

Another object of my invention is to provide an electric discharge device such that zero current may be obtained, in the no signal condition, without resorting to unduly high negative biasing potentials.

Another object of my invention is to provide an electric discharge device of such type that the main output electrode is incapable of exerting any accelerating influence upon the electrons immediately leaving the cathode.

Another object of my invention is to provide an electric discharge device so constructed as to prevent accidental secondary electronic emissions from opposing, interfering, or repelling the main cathode emission, or from affecting the operating voltages of the various beam-controlling or beam-collecting electrodes.

Another object of my invention is to provide an electric discharge device wherein secondary emission control is obtainable through variation of the cross-sectional area of a primary electron stream impinging upon a secondary cathode.

Another object of my invention is to provide an electric discharge device of the beam type, wherein the control electrodes are so shaped and positioned as to divide the total electron emission from a cathode into a plurality of electron beams while, at the same time, said electrodes exert electro-static control upon such beams either simultaneously or individually, or alternately.

Another object of my invention is to provide an improved electric discharge device wherein larger cathode emissions may be utilized, wherein neither electron guns nor conventional grids are employed, and one that can be operated with a plurality of varying potentials upon the individual electrodes thereof, in order to provide for a new variety of circuit combinations.

Another object of my invention is to provide an electric discharge device wherein the cathode is electrically and physically shielded from the output electrodes.

Another object of my invention is to provide an improved electric discharge device wherein control of a plurality of electric beams may be accomplished 'through the utilization of rigid electrodes substantially incapable of positionchange during operation thereof, whereby tube noises are minimized and uniform manufacturing production may be secured.

Another object of my invention is to provide a novel electric discharge device having such electrode arrangement that it may be operated with either high or low vacuum, with a gaseous content or with metallic or non-metallic vapors.

A still further object of my invention is to provide an improved electric discharge device devoid of grids or the like, wherein the rate of the cathode electronic emission does not depend entirely upon the potentials applied to the output electrodes or anodes.

My improved electric discharge device operates upon an entirely new principle, insofar as I am aware. Basically, my new thermionic tube includes a central cathode, around and closely adjacent to which are disposed a plurality of beam forming elements. A- plurality of output electrodes are within the tube, preferably coaxial with the cathode, the said output elements being in such position as to be normally shielded from the cathode by the first mentioned electrodes, both physically and electrically by reason of proper potentials'that may be applied thereto during operation of the device.

The function of the electrodes immediately adjacent to the cathode is to cause the formation of a plurality of concentrated electron beams, which beams, as hereinafter will be pointed out, may be completely focused upon absorption electrodes, here called collectors, and prevented from reaching the output anodes, or maybe permitted to reach the said output anodes to a greater or less extent, depending upon the variable spreading of these electron beams by modulation or other potentials applied to the said beam shaping electrodes.

More specifically stated, in my improved tube,

the electrons leaving the cathode are subjected simultaneously to two electrostatic fields, one positive and the other negative, the negative field cooperating with the positive field to compress the electrons into beams which impinge, more or less, upon the electrodes supplying the positive field in the absence of control or modulation potentials. As the ratio between the several field strengths is varied by reason of modulation potentials and the like, the beams so expand and contract as to fall, to a greater or less extent, upon the output anodes. Also, in accordance with my invention, one or more of the beam controlling electrodes may be coated with barium oxide, caesium, or the like, whereby they emit secondary electrons upon bombardment by primary electrons, thus increasing the amplification obtainable.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of certain specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a perspective view of a thermionic tube constructed according to my invention,

Figs. 2, 3 and 4 are diagrammatic sectional views of the electrode structure to which reference will be made in explaining the operation of the device,

Fig. 5 is a perspective view of the electrode structure in an alternative embodiment of my invention,

Figs. 6 and '7 are views in cross-section of the electrode structure of the device shown in Fig. 5 and a slight modification thereof,

Figs. 8 and 9 are diagrammatic cross-sectional views of the electrode structure in a tube constructed according to my invention and in which use is made of secondary emission,

Fig. 10 is a cross-sectional view of the electrode structure in a tube somewhat similar to that exemplified by Fig. 8,

Fig. ll'is a view in perspective of the electrode structure of a preferred embodiment of my invention,

Figs. 12, 13 and 14 are cross-sectional views of the electrode structure in a tube of the type exemplified by Fig. 11, to which reference will be made in explaining the operation thereof,

Fig. 15 is a cross-sectional view of the electrode structure in a tube analogous to the tube shown in Fig. 11, except that the cathode is circular rather than square in cross-section,

Fig. 16 is a diagrammatic view of a circuit of a preferred form for utilization of a tube of the general type exemplified by Figs. 11 to 15, inelusive,

Fig. 1'7 is a diagrammatic view of a circuit somewhat analogous to that exemplified by Fig. 16, except that the circuit associated with the tube is such that the said tube functions not only as detector but as an audio-frequency amplifier, and,

Figs. 18 and 19 are diagrammatic cross-sectional views of still further modified electrodeassemblies.

' plates II, and a thermionic cathode I3.

In all figures of the drawings, similar elements are similarly designated.

Referring now to Fig. 1 of the drawings, an embodiment of my invention -is constituted by an evacuated envelope l in the lower end of which is sealed a press 3 of semi-conventional type. The press, together with a plurality of mica separators 5 and 1, serves to support an electrode assembly comprising an anode 9, a plurality of collector The cathode may be constituted'by a cylinder of insulating material having an internal heaterand provided with a conductive sheath externally coated with rare earth oxides. As, perhaps, more clearly shown in Figs. 2, 3 and 4, a compressor electrode I5 is mounted between the collector plates at each side of the cathode and parallel thereto. These compressor electrodes, together with the collector electrodes, eifectively shield the cathode physically and electrically from the output electrode or anode, during operation of the tube.

As shown in Fig. 1 of the drawings, the collector electrodes may be [connected together and the anode or output electrode may be a single cylinder. Also as shown in Fig. 1, the compressor electrodes may be connected by a bridge I! from which a lead extends through the envelope of the tube to an external metallic cap 19. It is to be quite clearly understood, however, that each of the collector electrodes may be supplied with separate externally extending connections and that the anode or output electrode may be constructed as. shown in Figs, 2, 3 and 4, whereby each half thereof is electrically independent of the other and also may be supplied with an individual connection, and which design is recommended for detector, or automatic voltage stabilization purposes. H

In the operation of the device illustrated in Fig. 1 of the drawings, the collector electrodes and the anode are maintained at a positive potential with respect to the cathode, the potential of high negative bias on the compressor rods is necessary.

If the collector plates 1 l are made slightly more positive or the compressor rods slightly less negative than the balanced condition, the electron beams tend to spread toward the edges of the collector plates, as indicated in Fig. 3. A further decrease in the negative potential applied to the compressor rods or a further decrease in the positive potential applied to the collector plates reduces the compression of the electron beams and permits them to spread beyond the surfaces of the collector plates and to impinge upon the anodes 9 in the form of four electron beams, as exemplified in Fig. 4 of the drawings. The beams, of course, extend vertically for the full length of the anode plate 9 or plates.

By varying the potential applied to the compressor rods or by varying the potential applied to the collector plates, the electron beams may be caused to vary in cross-section and the number of electrons reaching the anode plate or plates be caused to change in proportion.

It is understood in the event that my improved tube be utilized as a detector, that the ratio between the collector electrode potential and the compressor rod potential either may be so chosen that in the no-signal condition no electrons reach the anode or the maximum number reach the anode. In the first condition, the tube is utilized as an anode bend detector, while in the second mentioned condition it is utilized similarly to a grid-leak-condenser operated tube of conventional design.

Also, when my improved tube is utilized in a class B amplifier circuit or a push-push circuit, the electrodes are so biased that only positive half cycles of an in-coming signal cause electrons to reach the anode.

When my improved tube is utilized only as an oscillator or as an amplifier, the potential ratio mentioned is so chosen that substantially half of the available electrons in the beams impinge upon the anode in the zero signal state. Such being the case, both positive and negative half cycles of the modulation potentials cause proportionate variation in the output from the tube.

My improved tube, therefore, functions entirely differently from beam tubes of the grid type in that during its operation the actual cross-sectional area of the electron beams is al- I and that secondary emission of the anode, per

unit'area, cannot repel orcounteract these electrons, whereas a high amplitude voltage will cause the spreading of the beam over a wider area of the anode surface and thus offer a lower electronic negative field density per unit area of the anode, which thus reduces through secondary emission distortions or blasting caused by excessively high signal amplitudes.

Referring once more to Fig. 1 of the drawings, it will be noted that a small diode plate is supported from the press and surrounds the lower end of the cathode.

The diode plate is of value in A. V. C'.,circuits. Referring now to Figs. 5,dand Z of the drawings, which is the form recommended for radio frequency amplification, the collector electrodes may be replaced by a plurality of vertical rods ll disposed around the cathode and parallel thereto and the compressor electrodes may be replaced by a plurality of similar rods l 5 or plates similarly disposed, the compressor electrodes being connected together internally of the tube and being provided with a lead which extends to the metallic cap 19, while the collector electrodes are also similarly connected and are pro- ;ilded with a common externally extending lead When proper positive and negative potentials are supplied to the collector and compressor electrodes, respectively, the electrons leaving the cathode may be formed into a plurality of beams equal in number to the number of collector electrodes. The formation of such beams is clearly exemplified by Figs. 6 and 7.

This modification of my improved tube functions in substantially the same manner as the tube illustrated in Fig. 1.

Figs. 8 and 9 exemplify a still further modification of my invention, wherein the collector electrodes ll, instead of being flat plates as in the device shown in Fig.1, are so bent that the vertical edges thereof are much farther away from the compressor electrodes l5 than in the first described device. In addition, parts of the surfaces of the collector electrodes, preferably adjacent the said free vertical edges, are coated with secondary-electron emissive material, such as barium oxide, caesium, or the like, while the parts of the said electrodes closest to the cathode are uncoated and absorb primary electrons emitted from the said cathode.

In the operation of the device shown in Figs. 8 and 9, and more particularly as exemplified by Fig. 9, when the compressor electrode potential is rendered less negative than normal, the electrons impinge upon the coated portions of the collector plates and cause the liberation of secondary electrons that, in turn, travel to the anodes.

The last referred to embodiment of my invention functions in a slightly different manner from the embodiment shown in Fig. 1. That is to say, it is my belief that the primary electrons from the cathode cannot reach the anodes if the proper value of positive potential is applied on the secondary cathodes. Instead, they merely spread to a greater or less extent over the surfaces of the collector electrodes, in this case called secondary cathodes, causing, through variation in the angle of incidence, as well as the movement from uncoated to coated portions of the said collector electrodes, the liberation of more or less secondary electrons.

A somewhat similartube is exemplified by Fig. 10 of the drawings, in which a single troughshape coated collector plate II is disposed at one side of the cathode and a single flat compressor electrode I5 and a semi-cvlindrical anode 9 (in the order given) are disposed at its opposite side. Preferably, the portions of the collector plate closest to the anode are coated with amaterial capable of emitting secondary electrons which augment the primary electrons received by the anode when the compressor electrode potential is less negative than normal.

It may, of course, so happen that both primary and secondary electrons reach the anode in the devices exemplified by Figs. 8, 9 and 10. I can, however, state definitely that the amplification factor of the tube is improved through utilization of secondary emission, and that it appears to function in accordance with the same principle as that involved in the functioning of the tube shown'in Fig. 1, i. e., the obtaining of electron beam control through alteration of the cross-section thereof, rather than through diminution of the electron density, as in conventional tubes.

In Figs. 11, 12, 13 and 14, I have illustrated what seems to me at the present time to be' the preferred embodiment of my invention. In this embodiment the cathode I3 is square in cross-section and two collector electrodes H are disposed in parallel relation and closely adjacent thereto, respectively opposite diametrically located edges thereof, while two compressor electrodes l5 are disposed in similar relation opposite and adjacent the remaining edges. V The electrode assembly is surrounded by a single anode 9 that is exposed to the four sides of the cathode through the spaces between the collector and compressor electrodes.

Although, in Fig. 11, I have illustrated the' anode 9 as being a continuous cylinder, it may be constituted by two or four separate and electrically distinct electrodes, from each of which an individual connection extends to the exterior of the tube. Since such modification is obvious, it has not been illustrated. a

In addition, I have illustrated the collector electrodes 1 I as being inter-connected within the tube and being supplied with a common external lead and have shown similar connections for the compressor electrodes I5. These several eletrodes, as well, may be electrically distinct and may be provided with individual external connections in the event that it is desired to-provide a multiple-function electrode assembly within the same glass or metal envelope, serving, for example, as a push-pull amplifier.

The operation of the tube exemplified by Fig. 11 is clearly evident from an inspection of Figs. 12, 13 and 14; it is substantially the same as the operation of the tubes hereinbefore described.

Although I prefer, in a tube of the type shown in Fig. 11 of the drawings, to utilize a cathode square in cross-section, it is not to be inferred that my invention is limited thereto. In fact, as shown in Fig. 15, I may make use of a conventional cylindrical cathode.

\ In the event that it is desired to utilize a tube of the type exemplified by Fig. 11 for amplification, a circuit such as that shown in Fig. 16 may advantageously be employed. As illustrated in the said figure, the compressor electrodes l may be connected to an input circuit constituted by an inductor 23 shunted by a condenser 25, and normal negative bias may be supplied thereto from a self-bias resistor 21 included in the cathode circuit. As is customary, the self-bias resistor is shunted by a bypass condenser 29.

The collector electrodes are supplied with positive potential from a bleeder resistor 3| interposed between the positive terminal of a high potential source (not shown) which supplies potential to the anode 9. For tone control purposes, a resistor 33 may be included in the potential supply lead to the collector electrodes and an adjustable tap on the resistor may be connected to the cathode through a capacitor.

The primary winding of a transformer 31 may be included in the output circuit, as shown, of the tube, if being used for audiTF-frequency amplification may be impedance or resistance-coupled to a subsequent amplifying stage.

A coupling capacitor 39 is connected between the input circuit and the collector electrodes.

In the operation of the circuit exemplified by Fig. 16, it is my present understanding that each half-cycle of an incoming signal, whether at audio or at radio frequency, causes a differential potential to be applied to the compressor and collector electrodes. Such being the case, the normal balanced condition is disturbed and the potentials of the said electrodes are so altered that the electron beams are caused to spread to a greater or less extent. That is to say, the presence of the coupling condenser between the compressor and collector electrodes causes, at one time, an increase of the repelling action of the compressors simultaneously with an increase of the attraction of the collectors, thus causing a decrease of current to the anode and at a later time, a decrease in the repelling action of the compressors and a decrease of the attraction of the collectors, with consequent increase in anode current. At any rate, an incoming signal, whether at audio or radio frequency, when applied to both the compressor and collector electrodes in the manner exemplified by the figure of the drawings under discussion causes the output current to the anode 9 to be modulated accordingly.

Whether the device is used for audio or radio frequency amplification, the position of the tap on the bleeder resistor 3! determines the gain. If the circuit is being used for audio frequency amplification, the variation of the point of connection of the capacitor 35 to the series resistor 33 serves as a tone control and if the circuit is being used for radio frequency amplification, it serves as a sensitivity control.

I also find it sometimes desirable for special ultra-short waveoperation to place the compressor electrodes just as close to the cathode as is possible without incurring any risk of a short circuit, but such limited spacing is unnecessary for ordinary purposes. A spacing of one millimeter or less is desirable, and can easily be. obtained through careful workmanship, but is not essential.

In Fig. 17, I have disclosed another circuit suitable for utilization of a tube of the type exemplified by Fig. 11. In this circuit the collector plates II are connected through the input circuit 23-25 to the cathode over a coupling resistor 39 which, in turn, by means of an adjustable tap and a capacitor M, is connected to the compressor'electrodes l5.

Negative bias is supplied to the compressor electrodes from a cathode lead resistor t3, the supply circuit including an isolating resistor 35.

When a signal is applied to the collector plates,

which function as diodes, the potentials set up,

in which the anode is perforated in the device,

shown in Fig. 1. Such openings, or windows, or perforations decrease interelectrode capacities and generally improve the performance of the tube at high frequencies. 1

Referring to Fig. 18, the tube exemplified thereby is quite similar to that exemplified by Figs. 1 to 4, comprising a plurality of main anodes 9, an oval cathode I3, a plurality of collector electrodes, and a plurality of electron beam compressor electrodes. The compressor electrodes preferably take the form of hollow cylinders extending parallel tothe cathode, the spacing being such that when a negative potential of the proper value is applied thereto, all of the electrons emitted from the cathode may be caused to impinge upon the collector electrodes.

By properly choosing the ratio between the negative potential applied'to the compressors and the positive potentials applied to the anodes and to the collectors, the electron beams may be caused either to partially reach the anodes or to be entirely absorbed by the collectors, depending upon the type of operation desired.

The electrode assembly diagrammatically shown in cross-section in Fig. 19 is substantially the same as that shown in Fig. 18, except that each main output anode 9 is provided with a vertically extending bay of sufficient Width to accommodate a collector electrode ll. By reason of the curvature of the cathode surface, the collector electrodes-are nearer .thereto than are the output anodes; consequently, they are enabled to function satisfactorily at a lower poten tial than the normal anode potential. The device, however, is substantially the same in operation as all of the devices hereinbefore described.

To minimize secondary emission, the main anodes 9 as well as the supplementary anodes, or collectors l i, may be provided with a plurality of quite fine, vertically extending corrugations.

It will be apparent from the foregoing description of a preferred embodiment of my improved electric discharge tube, of several alternative embodiments thereof, and a number of utilization circuits therefor, that it is versatile and well adapted to the uses to which reference was first herein made.

Although I have chosen certain embodiments of my invention for purposes of illustration and description, many modifications thereof will at once be apparent to those skilled in the art to which it pertains. My invention, therefore, is not to be limited, except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In an electric discharge device, a cathode of the equi-potential type square in cross-section, an anode surrounding said cathode and substantially coaxial therewith, at least two 'compressor electrodes disposed adjacent to the oathode and parallel therewith, at least two collector electrodes disposed adjacent to the cathode and also parallel therewith, the said compressor and collector electrodes being so spaced around the cathode that the faces of the latter are mainly exposed to the anode.

2. An electron discharge device having a straight thermionic cathode, a pair of flat collector electrodes positioned on opposite sides of said cathode, a pair of compressor electrodes disposed on opposite sides of said cathode between said flat collector electrodes, output elec trodes parallel to said cathode and positioned opposite the space between said fiat electrodes, said collector electrodes and said output electrodes receiving electrons from said cathode in accordance with the voltage applied to said compressor electrodes.

- 3. In an electric discharge device a cathode, an anode, supplemental anodes capable of absorbing the cathode space charge and disposed closer to the cathode than the first mentioned anode, and means for subjecting electrons from the cathode to a beam shaping field to cause them to impinge principally upon the supplemental anodes, the cathode being oval in a crosssection and the supplemen'al anodes being disposed opposite the oval surfaces.

4. In combination, an electric discharge device having a cathode, a main anode, a plurality of supplemental anodes interposed between the cathode and the main anode, a plurality of beam shaping electrodes disposed adjacent to the supplemental anodes, an input circuit connected between the beam shaping electrodes and the cathode, means for normally biasing the beam shaping electrodes negatively, coupling means between the input circuit and the supplemental anodes and an output circuit connected to the main anode.

5. An electron discharge device having a straight thermionic cathode, a pair of elongated fiat electrodes positioned on opposite sides of said cathode for receiving electrons from said cathode, a-rOd-like compressor electrode parallel to said cathode and positioned between said elongated fiat electrodes adjacent the longitudinal edges thereof on each side of the cathode and oppositely disposed arcuate shaped electrodes positioned opposite the space between said elongated fiat electrodes and parallel tosaid cathode, the current from said cathode dividing between said elongated fiat electrodes and said arcuate shaped electrodes in accordance with the variable voltage applied to said rod-like electrodes during operation of the electron discharge device.

6. An electron discharge device having a straight thermionic cathode, a pair of collector electrodespositioned on opposite sides of said cathode and having the surfaces facing said cathode coated with emitting material for releasing secondary electrons when primary electrons from said cathode strike said coated surfaces, a pair of elongated compressor electrodes one positioned on each side of said cathode between said coated electrodes, and output electrodes positioned outside of said other electrodes and opposite the space between said coated electrodes for receiving electrons from said cathode and from said coated electrodes in accordance with the variable 1 voltage applied to said compressor electrodes during operation of said electron discharge device.

7. An electron discharge device having a straight thermionic cathode of elliptical cross section, a pair of straight compressor electrodes adjacent the longitudinal edges of said cathode, collector electrodes on opposite sides of and parallel to the elliptical faces of said cathode, and output electrodes positioned on the outside of said collector electrodes. the current to said collector electrodes and to said output electrodes dividing in accordance with the variable voltage applied to said compressor electrodes.

8. In an electric discharge device a cathode, an anode, a supplemental anode capable of absorbing the cathode space charge and disposed closer to the cathode than the first mentioned anode, and means for subjecting electrons from the cathode to a beam shaping field to cause them to impinge principally upon the supplemental anode, the cathode being substantially oval in cross-section, and the beam shaping means being disposed adjacent those portions of the cathode having the least emission.

9. In combination an electric discharge device having a cathode, an anode, ,a plurality of supplementary anodes interposed between the cathode and the anode, a plurality of beam shaping electrodes disposed between the cathode and the first mentioned anode and adjacent to the supplemental anodes, an input circuit connected between the beam shaping electrodes and the cathode, means for applying a normal negative bias to the beam shaping electrodes, an impedance device included in the input circuit and a connection including a capacitor between the impedance and the supplemental anodes, wheresupplemental anodes disposed adjacent to the beam forming electrodes and the cathode for receiving electrons from said cathode, the supplemental anodes having portions extending toward the first mentioned anode and a coating of material capable of emitting secondary electrons upon the surface of the supplemental anode exposed to the cathode electronic emission.

HENRI F. DALPAYRAT.

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