US2122776A - Electron discharge tube - Google Patents

Description

July 5, 1938. K. MATTHIES ELECTRON DISCHARGE TUBE Filed May 2, 1936 6'(D/ElECTR/C) CAPACITANCE H 6 CYl/NDRICAZ CAPACITOR-EZFCTRODE Mm WR 00 CAPACITANCE l2 INVENTOR KURT MATTH I ES ANODE 3 BY g 'A'TToRNEY Patented July 5, 1938 UNITED. STATES PATENT OFFICE ELECTRON DISCHARGE TUBE Application May 2, 1936, Serial No. 77,517 In Germany May 2, 1935 8 Claims.

This invention relates to a tube generator for short waves, and more particularly to an electron tube having a suitable structure for minimizing the deleterious effects of inter-electrode capacitances. Utility for such a tube is to be found in radio apparatus, medicinal oscillators, and ultrashort wave devices generally.

In oscillatory circuit design using electron tubes for generating short waves, it is known that the electrode capacitances play a part that must be taken into account. The capacitances in question are those between anode and grid, between grid and cathode, and between anode and cathode. In like manner, in case of very short waves the inductances of the lead-ins to the tubes and the leads within the tube proper, can no longer be neglected. For this reason it has heretofore been suggested that tube generators for short waves, might be so constituted that the oscillatory circuits should be confined to the tube capacities and tube inductances. While in general the tube capacities are comparatively large, in the majority of cases, the tube inductances alone are insufiicient to obtain an oscillatory circuit. In these cases, a special circuit coil is required which is arranged outside the tube and forms together with the tube capacities the oscillatory circuit. In rendering the induction of this oscillatory circuit coil variable this offers at the same time the possibility of tuning the oscillatory circuit.

In generator tubes for producing short waves for medicinal purposes no possibility of tuning for varying the produced frequency is required, since in the applications to be considered a definite wave length need not be adjusted to. But the produced oscillation energies must in general be of relatively high frequency and high amplitude for these purposes, so that for such generator tubes a high efliciency is of great importance.

In accordance with the invention, in order to attain this end, the oscillating circuit coil, in a short wave tube generator especially if designed for medicinal purposes, and which is to supply a wave length of, for instance, below 300 cm. is placed in the tube proper. In this manner leadins to the coils are dispensed with while otherwise due to the skin effect at the high frequencies, large losses would be caused. On the other hand, where the oscillatory circuit coil is placed in the tube proper according to the invention, the highvacuum of the tube serves as dielectric for the coil thus reducing the dielectric losses in the coil insulation to zero. In a tube generator according to the invention, the oscillatory circuit coil placed in the tube proper together with the tube capacities and a special blocking capacity form the oscillatory circuit. The blocking capacity is likewise arranged in the interior of the tube, whereby the anode serves as one layer of this blocking capacity, while the other layer is formed by a special auxiliary electrode surrounding the anode completely or partially. In order to prevent too great a reduction of the heat delivery of the anode, this auxiliary electrode is preferably formed as screen or net. Hence in a tube generator according to the invention, the conducting parts of the oscillatory circuit are placed entirely within the envelope of the tube. The production of the energy takes place by way of induction through a coil coupled to the oscillatory circuit coil, likewise accommodated within the tube.

The accompanying drawing, Fig. 1, shows, by way of example, a tube generator in accordance with the invention, and

Fig. 2 shows a circuit diagram for such a tube. Fig. 1 shows the tube assembly. Within the tube there are arranged in the known manner, the incandescent cathode I, the grid 2, and the anode 3. The oscillatory circuit coil is represented by the coil 4 placed between grid and auxiliary electrode 6. This auxiliary electrode 6 together with the anode 3 form the blocking capacity in series to the oscillatory circuit coil. The reduction of the energy takes place through coil 5 coupled to the oscillatory circuit coil 4, and across the leads 8 and 9. In order to maintain the inductance of the through leads 8 and 9 as low as possible, the latter may be disposed so that the one surrounds concentrically the other one. A sealed-in lead I 0 may be connected to the grid 2 through which any desired biasing potential may be impressed upon the grid in order that the working point be properly adjusted on the tube characteristic. In order to reduce the losses within the oscillatory circuit as much as possible, the connection line between grid and oscillatory circuit coil is insulated from the auxiliary electrode 6 by means of a quartz insulator l.

The mechanical structure of the tube is pref-,- erably such that the anode and the grid form. concentrical cylinders in whose center the incandescent cathode is arranged. In this case, the auxiliary electrode 6 is formed into a cylinder or part of a cylinder surrounding the anode completely or partially. The quartz insulator 1 carrying the auxiliary electrode is likewise preferably shaped as a hollow cylinder. In order to obtain a favorable insulation of the anode against the other electrodes, and to render the mechanical structure as simple as possible, the anode is fastened to a place on the tube bulb lying opposite to the press of the tube in which the other electrodes are mounted.

Fig. Z represents the circuit of the tube generator shown in Fig, l. Herein, item I again represents the incandescent cathode, while 2 is the grid, and item 3 the anode. The oscillatory circuit coil 4 is connected to the anode across the blocking capacity formed by the auxiliary electrode and the anode. In this circuit the interelectrode capacitances are labeled thus: ll represents the anode-grid capacitance, I2 is the gridcathode capacitance, and I3 the anode-cathode capacitance. A capacitive reactance between the anode 3 and the outer electrode 6 exists across the dielectric 6'. As can be'seen, the voltage in the oscillatory circuit will be divided by the tube capacities ll, l2, and I3, so that one part of thevoltage of the oscillatory circuit is always applied to the grid 2. It is in this manner that the oscillations in the oscillatory system are sustained. The reduction of energy takesnplace across coil 5 coupled to the oscillatory circuit coil 4. Between grid 2 and the cathode there is placed a grid resistor l5 in series to the choke coil 14 serving for blocking the high frequency oscillation, and a condenser I6 is placed in parallel to said grid resistor.

I claim:

1. An electron discharge tube having a concentric system of electrodes including a. cathode, two auxiliary electrodes and an anode interposed between said auxiliary electrodes, an inductive reactance mounted within the tube envelope and having terminals each connected to one of said auxiliary electrodes respectively, said inductive reactanc'e in combination with the inherent interelectrode capacitances constituting a resonant circuit tuned to the frequency of the, oscillations to be generated, a grid. biasing lead connected to one of said auxiliary electrodes and an output coil coupled to said inductive reactance.

An electron discharge tube having acathode and a plurality of cold electrodes coaxially disposed about the cathode, an. inductively reactive element mounted within the envelope of said tube and interconnecting the outermost withthe innermost cold electrode, an output coil inductively coupled to said reactive element, and means supporting one of said cold electrodes in capacitively reactive relation to the outermost and innermost cold electrodes, said means being located at an end of the tube envelope opposite the means of support for the remaining electrodes.

3. An electron discharge device comprising a container and electrodes therein, said electrodes including a centrally disposed cathode, a grid, an anode and an auxiliary electrode surrounding the anode, an oscillation circuit within said container comprising an. inductance connected in series from said grid to said auxiliary electrode and comprising the inherent capacity between said electrodes, and ,a secondary inductance within said container coupled to said first inductance and having output leads directly connected: there- 4. An electron discharge device comprising a container and concentric electrodes therein, said electrodes including a centrally disposed cathode, a grid, an anode and an auxiliary electrode exterior to the anode, and an oscillating circuit Within the tube comprising an inductance in series from the grid to said auxiliary electrode and the inherent capacities between said grid, anode and auxiliary electrode.

5. An electron discharge device comprising a container having electrodes therein, said elec-,

trodes comprising a cathode, a grid surrounding said cathode, an anode surrounding said grid, an auxiliary electrode surrounding said anode, and a resonant circuit Within said container constituted by the .inherentcapacitance between said anode and said auxiliary electrode and by an inductance connected between said grid and said auxiliary electrode. 7

6. An electrical discharge device comprising a container having electrodes therein, said electrodes comprising an incandescible cathode, a cylindrical grid surrounding said cathode, a cylindrical anode surrounding said grid and a cylindrical auxiliary electrode surrounding said anode, and an inductance in series between said grid and said auxiliary electrode.

7. An oscillation generator comprising an electron discharge tube including a centrally disposed cathode, a control grid surrounding the cathode, an anode surrounding the control grid and a fourth electrode surrounding the anode; means including an inductance and a capacitor within the envelope of said-tube for establishing reso-' nance at an ultra-high frequency,said inductance being disposed in circuit between the grid and said fourth electrode and said capacitor, the other electrode of said capacitor being constituted by said fourth electrode and a portion of said anode in juxtaposition thereto, and an inductive conductor within the envelope of said tube and cou-' pled to. the inductance of said resonant circuit.

8. An electron discharge tube having a concentric system of electrodes including a cathode, an anode and two other electrodes, said anode being supported from one end of said tube and the other electrodes being supported from the opposite end thereof and a resonant circuit mounted within the envelope of said tube, said resonant circuit including a capacitive portion formed by two electrodes within the envelope, one of said electrodes being the anode proper and the other being an electrode exterior to the anode, and said resonant circuit including an inductive element interconnecting two electrodes, one internally and one externally of said anode.

KURT MATTHIES.

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