US2128236A - Vacuum discharge tube - Google Patents

Description

Aug. 30, 1938. w DALLENBACH 2,128,236

VACUUM DISCHARGE TUBE Filed Oct. 16, 1935 2 Sheets-Sheet 1 mgr Affa/weya Aug. 30, 1938. w. DALLENBACH 2,123,236

VACUUM DISCHARGE TUBE Filed Oct. 16, 1935 2 Sheets-Sheet 2 RQW Affar/ieya Patented Aug. 30, 1938 PATENT oFF cE VACUUM DISCHARGE TUBE Walter Dillenbach, Berlin-Charlottenburg, Germany, assignor to N. V. Machincrieen-en Apparaten'Fabi-ieken "Meat", Utrecht, Netherlands Application October 18, 1935, Serial No. 45,331 In Germany October 19, 1934 11 Claims.

My invention relates to a vacuum discharge tube for exciting ultra-short wave electro-magwnetic oscillations, and particularly to a tube for generating, amplifying or receiving such waves.

In electron tubes for very short electro-magnetic oscillations it is necessary to combine the electrodes, used for excitation immediately, with the resonator. In order to obtain a resonator of low natural damping and thus a tube of a high 19 degree of efliciency, it is further essential to keep Ohms damping losses and, above all, the radiation losses of the resonator, down as far as possible. Further requirements are: a proper escape of the heat from the electrodes for the purand a high degree of disruptive strength of the insulators between the electrodes, subiected'to different potentials, and the conductors connected therewith.

The abovementioned requirements are met to a very high degree by the vacuum discharge tube described in the following. A hollow space is used as the resonator of the tube, which space is limited all around by walls capable of conducting electricity well. The resonator exhibits but very small ohmic losses, and practically no radiation losses whatsoever. In order to be able to excite this hollow space to oscillations, two or more electrodes are required, which either belong to 30 the hollow body proper limiting the hollow space,

or which may also be disposed within or without the hollow body. Particularly advantageous constructions are obtained by placing at least one electrode (inner electrode) in the interior of the hollow body enclosing the hollow space of the resonator. For the purpose of securely attaching this electrode and insulating it from the walls of the hollow body, it is essential to support the electrode in the hollow body at suitable points by insulators. The insulators are advantageously disposed within potential nodes or relatively cool points in the tube in order to obviate losses. For the same reason, the leads to this internal electrode are so arranged, that they extend through the field space of the resonator and the hollow body encasing the resonator, respectively, in the proximity of potential nodes.

According to the present invention the electrodes adjoining the hollow space of the resonator and serving for excitation form a plane plate condenser closed at its edges by further wall parts. The plane design of the electrodes makes it possible to maintain accurately the distance and yields an extremely favourable excitation.

For a fuller description of my invention refpose of avoiding inadmissibly high temperatures erence is made to the accompanying drawings in which I have illustrated several embodiments of my invention.

Figs. 1, 2, and- 3 are cross-sectional views through tubes-illustrating three'diiferent forms of my invention, and

Figs. 4, 5, and 6 are sectional views on lines IV--IV, V-V, and VI-VI, of Figs. 1, 2, and 3, respectively.

Figs. 1 to 6 all illustrate electron tubes, in which the resonator is limited by walls of a rotary symmetrical metallic casing I and by surfaces of a metallic body 2, also rotary symmetrical in form, enclosed by the casing. The hollow space 3, serving as resonator, continues in a radial direction the space 6 limited by the walls 4 and 5. Excitation takes place in the homogeneous field space 6. In the examples of Figs. 1, 4 and 3 and 6 respectively, the resonator space is of disklike shape, in the example of Figs. 2 and 5 toroidal shape. Figs. 1, ,2, 3 and 6 represent the electron tubesin longitudinal section through the axis of rotation. Figs. 4 and 5am sections perpendicular to the axis of rotation of the arrangements shown in Figs. 1 and 2 respectively.

The employment of a disk-like resonator space renders possible at a given wave length a simple and accurate computation of the dimensions of the resonator. If the disk-like hollow space is excited in such a manner that in the proximity 39 of the axis of symmetry between the walls 4 and 5 a potential loop is formed and at the edge of the disk-like hollow space a potential node of the oscillation, a diiferential equation may be set up for the electric field strength in function of the distance from the axis of rotation which may be solved by the application of Bessels cylinder function of zeroth order. If the distance from the axis, measured in a suitable scale, is called r, Bessels cylinder function of zeroth 40 order will have zero figures for the values 1 :3.405, 33-25-520, x3= 8.654, z:

From the simple relation tr-=21:- .{the radius diameter which is only a little smaller than the inside diameter of the casing. The hollow space,

' limited by the casing, will then be divided up an aerial or a loading resistance with the resonator, if it is observed. that a coupling of the loosest possible nature ofthe load to the resonator is necessary. If the couplin is excessively tight, the resonator will be deprived of too much energy, so that it is strongly damped and its emciency impaired. The loose coupling of the aerial with the resonator can be attained by detuning the high frequency line and aerial and by selecting a small wave resistance of the high frequency line relatively to the resonator. If no use is made of the detuning,the selected' wave resist; ance of the high frequency line must be very small. The high frequency line will then almost form a short-circuit capacity for the resonator.

Such a development of the high frequency line possesses, however, the advantage, that a perfectly sinusoidal (simple harmonic) resonator of great selectivity is obtained. In the tubes described, the wave resistance of the space I, used equal natural frequency, but of differentlygreat wave resistance. In thetube shown in Figs. '1, 4

and'3, 6, the two spaces 3 and 1 have the same natural frequency, because they are of exactly .the same diameter.

In the tubes represented in Figs. 2 and 5, the natural frequencies agree only approximately. I

If the hollow space 3, serving as excited in the first harmonic, in connection with which a potential loop is thus formed in the proximity of the axis and a potential node is formed at the edge of the slit 8, a potential loop will also be formed in the proximity of the axis in the tuned space I which serves as shortcircuit condenser. Owing to the inconsiderable wave resistance of space I the potential amphtudes at this potential loop are essentially smaller than at the potential loop in the resonator space 3.

Space 1, acting almost as short-circuit con-' denser. can now be used as high frequency line in the following manner:

In the wall of the casing limiting the short circuit condenser, an opening 8 is provided in the axis of symmetry and thus in the potential loop, through which an aerial i0, galvanically connected to the enclosed electrode 2, projects. The aerial can be tuned to the resonator, as well as it can be detuned relatively thereto. In view of the fact, that the short-circuit condenser, relatively to the .resonator, exhibits a low, natural wave resistance, a reduction of the potential takes place. The potential amplitudes at the point of resonator, is

Thus high control the other hand, only low alternating potentials for the excitation of the aerial. By properly dimensioning the wave resistance of the high frequency line and by the tuning of highfrequency line and aerial, the aerial can be optimally coupled with the resonator. When using the tube as sender, this adaptation will render it possible to attain a maximum power delivery. when using the tube as an amplifier or as a receiver, the power amplification ratio and th incoming power ratio can be raised to maximum an analogous manner. a

In the represented examples the outer face of the wall casing, the inner face of which is used as part of the. high frequency line, serves as counter poise for the M4 aerial. In order to prevent the outer face of the casing from being subjected to resonance and from emitting. loss radiation, an edge II has further been provided for detuning, thereby enlarging thecasing wall used as counter poise.

Considering, that the metallic body enclosed by the casing serves as an electrode in the proximity of the axis of symmetry, and is forced to maintain a direct current potential which differs from that of the casing, it is supported by insulating elements I! against thecasing in the proximity of the nodal line of the electric field, that is, in the proximity of the annular slit 8. In the same way the metallic body 2, enclosed by the casing, is provided in the nodal line of the electric field with the potential lead it which extends, insulated therefrom, through the metallic casing. For the purpose of insulation and a vacuumtight sealing, a glass-to-metal joint ll is provided.

The plate 4, formed by the wall of the casing, of the plate condenser, is provided with an opening, through which a flow of electrons, serving for excitation, can pass into the field space of the plate condenser. From Fig. 4 it can beseen, that a slit-shaped opening I! is provided there, in which thin grid bars ii are inserted perpendicularly to the direction of the slit. These grid bars regularly consist of a material melting at a high temperature, for example, of tungsten or molybdenum, while the other parts of the condenser plates, as well as the casing, are made from a material of considerable heat conductivity, for example copper or silver. In the tube shown in Figs. 2 and 5, the opening is formed as a simple slit II, as can be seen from the sectional view hot cathode l8, which is heated directly, is provided as electron source. In the examples illustrated in Figs. 2, 3, 5 and 6, band-shaped hot cathodes I 9 are employed. Also indirectly heated oxide cathodes can advantageously be used.

In the represented examples all the cathodes have been accommodated in metal casings 2B which aretuned to a higher natural frequency than that of the resonator being excited. This is necessary, on account of the retardation of the high frequency field through the grid interstices into the grid cathode space. when detuning this space, the alternating current potentials, presenting themselves between grid and cathode, will remain small. Coupling oscillations and disturbances of the excitation respectively will not enter an appearance. Also radiationand leakage-losses along the cathode leads will remain'very small. In the electron tubes shown in Figs. 1, 4 and 3, 5 and 6 respectively a glass sleeve 2| is Joined to the cathode casing for so introducing the heating leads 22, that they are vacuum-tight. The tube shown in Figs. 2 and 5 is provided with vacuum-tight leading-in insulators 23 attached immediately to the cathode casing.

The excitation of the tubes can be effected in any desired connection. Particularly, the brake field connection can'be used. The casing I and with it the condenser plate 4 in the form of an open-work electrode, will then be given a high positive and the electrode 2, enclosed by the casing, a weak positive to negative potential relatively to the cathode.

In order to obtain a space charge control, the electron tube shown in Figs. 3 and 6, is provided with additional control electrodes. From the two axial sectional views of Figs. 3 and 6, perpendicular to each other, it can be seen, that these additional control electrodes consists of two parallelbars 24, situated between cathode and grid aperture and are fitted parallel to the electrodes. They obtain their control potential .from the metallic body 2, to which they are galvanically connected by the straps 25. The straps canfinaturally, also be so placed upon the metallic body 2, as to be insulated therefrom andthey can be given a special biasing potential by a lead. In view of the fact, that the straps 25 are connected to the surface of the metallic body 2 in the proximity of the potential loop, the control electrodes 24 are given a control potential, which is cophasal to the alternating current potential of the internal electrode.

The metallic walls, provided for the purpose of limiting the hollow space resonator, the high frequency line and the cathode space can essentially form the vacuum vessel. The different glass-to-metal joints provided for passing the current leads through so as to be insulated, must then be vacuum-tight. For closing up or sealing the tube so as to be vacuum-tight, the glass sleeve 26 is provided which encloses the aerial and'is joined to the wall of the casing by fusing it thereon.

The tubes according to the present invention are particularly adapted for excitation, especially for the generation of intense, electro-magnetic oscillations of the decimeter and centimeter range.

What I claim, is:

1. A vacuum discharge tube, comprising an evacuated casing electrically conductive on its inner surface, a body within said casing, said body being electrically conductive on its outer surface, insulators supporting said body in said casing .and insulating it therefrom, said casing and said body forming a hollow chamber substantially entirely surrounded by metallic surfaces, the said metallic surfaces defining said hollow chamber forming a resonator, a lead to said body extending through said casing and insulated therefrom, the wall parts of said casing and of the enclosed body facing each other to form a flat plate condenser and constituting electrodes, and a cathode adjacent said casing and chamber.

2. A vacuum discharge tube, comprising an evacuated casing electrically conductive on its inner surface and of rotary symmetrical form, a

body of similar form within said casing and coaxial with respect to said casing, said body being electrically conductive on its outer surface, insulators supporting said body within said casing and insulating it therefrom, said casing and said body forming a hollow chamber substantially surrounded by metallic surfaces, said metallic surfaces defining a resonator, a lead to said body extending through the casing and insulated therefrom, the wall parts of said casing and of the enclosed body facing each other to form a fiat plate condenser adjacent the axis of said casing and said body and constituting electrodes, and a cathode adjacent said casing and chamber.

3. A vaccum discharge tube, comprising an evacuated metallic casing of rotary symmetrical form, a metallic body of rotary symmetrical form co-axially disposed with respect to said casing, insulators supporting the metallic body within the casing to insulate the same therefrom in the proximity of potential nodes, a lead to said metal- 110 body extending through said casing in the proximity of a potential node and insulated from said casing, the wall parts of the casing and of the metallicbody facing each other to form in the proximity of the axis of symmetry, a plane plate condenser and constituting electrodes, the wall part of the casing constituting an electrode being provided with an opening, and a cathode outside the casing in the proximity of said opening.

4. A vacuum discharge tube, comprising an evacuated metallic casing of rotary symmetrical form, a metallic body of rotary symmetrical form co-axially disposed within the casing, insulators supporting said metallic body within'the casing to insulate the same therefrom, a lead to said metallic body extending through the casing and insulated therefrom, said metallic body spaced from one part of the casing wall a large distance and from another part of the casing wall a small distance to divide the casing into two spaces of approximately equal natural frequency at different wave resistances, wall parts of one of said spaces facing each other to form in the proximity of the axis of symmetry a plane plate condenser and constituting electrodes, the space with smaller wave resistance constituting a high frequency line, and a cathode.

5. A vacuum discharge tube, comprising an evacuated metal casing of rotary symmetrical form, a metallic body of rotary symmetrical form co-axially disposed in said casing and forming an inner electrode, insulators supporting said metallic body in'said casing, a lead to said metallic body passing through the casing and insulated therefrom, said metallic body being disposed at a larger distance from a portion of the casing wall than from the other portion, said casing thus having two chambers of approximately the same natural frequency but diiferent wave resistances, wall portions of said chamber being directed toward each other in the vicinity of the axis of symmetry to form a plane plate condenser and constituting electrodes, the space having the smaller wave resistance constituting as a high frequency lead, said metallic casing being of radial extension, the inner electrode being diskshaped and having a diameter but slightly smaller than the inner diameter of the casing, said insulators being disposed in the vicinity of the edge of the inner electrode, the lead to the inner electrode being insulated from and passing through the edge of the casing and connected to the edge of the inner electrode.

B. A vacuum discharge tube as defined in claim 4, in which an opening is provided in the proximity of the axis of symmetryin the casing wall limiting the high frequencyiine, an aerial coupied with the high frequency line through said opening. I

7. A vacuum discharge tube. comprising an evacuated cylindrical .metallic casing of radial extension, a metal disk co-axially disposed within said casing, the diameter of said disk being but slightly smaller than the inner diameter of the casing. insulators and a lead in the proximity of the edge of the disk, said insulators being disposed to hold the disk rigidly within the casing, the distance between the disk and one'face of the casing being larger than the distance between said disk and the other faceto form two disk-shaped hollow spaces, the hollow space of smaller wave resistance constituting a high frequency line, said front wall of the casing limiting the high frequency line'being provided with an opening disposed symmetrically therein. an aerial attached to the axis of the metal disk and projecting through said opening into the outer space,

the front wall of the'casing being provided with an opening in the proximity of the axisof syma,1ss,2so-

-inetry. a second metallic casing outside the casing and adjoining said second opening, the hollow space of said second casing being tuned to a higher natural frequency than that of the hollow space of the resonator. and a cathode in the second casing.

28. A vacuum discharge tube as defined in claim 8, in which the opening in the casing wall is slit-shaped, the cathode outside the casing being disposed parallel to the'siit.

9. A vacuum discharge tube as defined in claim 3, the opening in the casing wall being slitshaped, grid bars in the plane of the slit and perpendicular to the slit, the cathode outside-the casing being disposed parallel to the slit.

10. A vacuum discharge tube as defined in claim 5, the part of the hollow;space radially adjoining the plate condenser being of toroidal shape.

11.'A vacuum discharge tube as defined in claim 3, in which additional control electrodes are disposed in the proximity of the cathode} andconductors connecting said control electrodes to the inner electrode.

WALTER nlinnmmacn.

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