US2233768A - Converter - Google Patents

Description

E. BRUCHE March 4, 1941.

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Patented Mar. 4, 1941 UNITED STATES PATENT OFFiCE assignor to General Electric Company, Schenectady, N. Y., a corporation of New York Application August 25 1939, Serial No. 291,842

In Germany September '13, 1938 Claims.

This invention relates to an electron discharge device, particularly such a device adapted to generate a D. 0. potential which is higher than an alternating potential applied to the tube.

The principal object of my invention is to provide an electron discharge device and circuit by which an alternating voltage can be converted into a direct voltage of higher potential.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figures 1, 2 and 3 are diagrams illustrating the principles of operation of my invention, Figure 4 is a schematic diagram of an electron discharge device made according to my invention and Figures 5, 6 and 7 are modifications of the device shown in Figure 4.

First the principle underlying the invention shall be set forth. Referring to the schematic diagram of Figure 1, the planar electrodes I and 2 are in the form of reticulate (grid or grate) structures, while planar target or impact electrodes 3 and 4 are solid. All of these electrodes are positioned at right angles to the plane of the drawing. Within the highly evacuated space between the electrodes, electrons shall be assumed to be midways between electrodes I and 2 and distance shall be measured by a coordinate 8. Suppose also that at the time t=0, an electron of zero speed shall be in the plane 8 0. At the same time and for some time thereafter, the potential of grid I shall be V, the potential of grid 2 value -V, while the common potential of 3 and 4 shall be of a constant and negative value U as represented in Figure 3. The potentials of the various electrodes referred to are with respect to a plane in space parallel to the grids I and 2 and passing between the point 0 midway between the electrodes I and 2. This plane is the reference plane and assumed to have a zero potential at the beginning of the movement of the electron from point 0 to and through the various electrodes as the voltages on these electrodes change with respect to this reference point. The dependence upon time t of the coordinate s of the electrons moving subject to the influence of the electric fields generated by the electrodes is shown graphically in Figure 2. Initially, the electron travels towards the electrode I, reaching the latter at the instant in. At this moment, the potentials at the grids I and 2 shall be assumed to change in sign. The electron is decelerated in the space between electrodes I and 3 since electrode 3 is at a greater negative potential than the electrode I, is reversed and on passing the electrode I it possesses the same rate of speed which it had when first traveling through this grid. Inasmuch as the field set up between I and 2, at time t1, has changed its direction, the electron is again accelerated in the space between I and 2 because of the negative potential on grid I and the positive potential on grid 2, that is, up to instant 752 when it enters the space between 2 and 4. In this space it is retarded, but this time, because of its greater speed, it enters to a greater depth than previously into the space confined between I and 3. Upon its return to electrode 2, it gathers the same rate of velocity as upon its first passage through electrode 2. In the meanwhile, at instant t2, the potential at electrodes I and 2 has reversed in sign so that the electron is accelerated again. This cycle is continued, in fact, the change in potential at I and 2 occurs always just at the time when the electron enters in one of the spaces between I and 3 or 2 and 4 (at instants t1 t2 t3 M) with the result that the electron is invariably accelerated in the space between I and 2, enters ever greater depths in the spaces causing its retardation and finally reaches the target or impactor electrode 4 (though it might just as well be 3). Hence, during its travel the electron has been able to absorb from the alternating electric field so much energy that, in spite of the potential U retarding or braking it, it was enabled to impact upon the target electrode. It is noted that this effect by no means is conditioned by the fact that the electron, at time i=0 was of zero speed and that it happened to be in the plane 8:0. Generally speaking, the alternating field sorts out a group from among the electrons traveling in it which deprive'it of so much energy that they impact upon the impactor electrodes.

Thus, if a sourceof electrons happens to be in the plane s=0 then the cycle described may be repeated by causing the alternating potential again to follow a course which it had during the time i=0 up to the time T when the electron impacted upon the electrode 4. This means that a periodic alternating potential is impressed across electrodes I and 2 the periods of which would correspond to the rectangular voltage curve between 0 and T shown in Figure 3. In this manner electrons will always reach the impactor electrodes with the result that the potential U thereof'becomes increasingly more negative. Thus, if the electrodes 3 and 4 originally are assumed to have possessed any desired potential at all, it is always possible to obtain a condition where, by application of a convenient alternating potential, a D. C. potential of a value being high in contrast to the applied alternating potential is secured between the target electrodes and the cathode giving off the electrons.

In other words, according to the invention an electron discharge tube for the purpose of creating a D. C. voltage which is high compared with its working potentials, is provided with a high frequency alternating potential which serves the purpose of so accelerating the electrons that the latter will cause an impactor electrode to be charged up to the D. C. voltage to be produced.

It will be understood that the value of the D. C. voltage to be so produced is a function of the geometric conditions of the electrode assembly, and of the form and the frequency of the alternatin potential. As a matter of fact, it is not feasible to produce D. C. voltages of any desired value at all with the alternating potential shown in Figure 3, for the optimum shape of this potential depends upon the potential U which by virtue of charging assumes increasingly more negative values. In other words, the form of the period or cycle of the alternating potential and its frequency will suitably have to be chosen to provide a given D. C. voltage which is to be generated. The form of the voltage is to a certain extent immaterial for the reason that each and every alternating field will produce a sorting of electrons as hereinbefore described as a result of which a certain group of electrons will abstract from the field so much energy that it is possible to charge up the impactor electrode. Hence, it will be expedient to produce the alternating field, say, by pure sinusoidal or periodic rectangular potentials for the reason that the production of potentials of this sort may, in certain circumstances, require less elaborate technical means than the production of potentials being of .a very definite curve shape would require.

Figures 4 to 7 illustrate exemplified embodiments of a discharge vessel according to the invention partly in schematic form.

The arrangement illustrated in Figure 4 is predicated upon an organization of the kind shown in Figure 1. In other words, two planar electrodes in the form of grates or grid-like structures are placed opposite each other. They are, in turn, surrounded by two impactor electrodes 3 and 4. The source of the electrons consists of a rod-shaped cathode 5 mounted between I and 2, the said cathode 5 being connected by way of a source of D. C. voltage 1 with the source of alternating potential 6 impressed upon I and 2, the action of the same being that the mean potential of l and 2 is positive in reference to the cathode. This measure will, fundamentally speaking, alter nothing in the principle underlying the invention as set forth above; but it may serve to raise the efficiency and, on the whole to determine the working point of the arrangement. Inasmuch as electrodes 3 and 4 are conductively connected, the ensuing D. C. voltage is taken oil, for instance, from 4 and cathode 5 across the leads 8 connected to load L by way of a resistancefl servingto prevent short-circuiting of the tube. The cathode indicated at 5 may be either of the thermionic or of the photo-cathode type. The electrodes are housed within evacuated envelope E.

Figure 5 shows an assembly presenting cylindric symmetry. Also in this case, the cathode 5 is in the form of a cylindrical rodlet. It is mounted in the space bounded by the two-semicylindrical grids I and 2. The impactor electrodes 3 and 4 shown in Figure 4 are in this embodiment combined to form a single cylindrical electrode 3 surrounding the electrodes l and 2. The circuit organization is the same as that shown for the arrangement Figure 4.

The organization illustrated in Figure 6 differs from that shown in Figure 4 in so far as the electrodes la, 2a, 3a and 4a are formed and disposed trumpet-shaped rather than planar. What has here been added are two electrodes 6a and 1a which are impressed with a D. C. voltage so that a field is set up which accelerates the electrons in the direction towards the larger opening or the flared end of the system. For instance, an electron which reaches the electrode 311, will then describe a path, say, as indicated at 8. The reason underlying this modification is explained by reference to Figure 3. It will be seen that the alternating voltage curve there shown is not a purely periodic rectangular potential wave. It is shown that the various rectangular cycles between t1 and t2, t2 and ts, etc., become increasingly broader or longer for the reason that the various alternations of the st curve shown in Figure 2 become of increasingly greater duration or length. Now, by the measures before indicated conditions are made so that these semicycles will practically become of like duration so that the alternating potential in Figure 3 becomes really a periodic rectangular potential. In other words, the arrangement Figure 6 offers the advantage over that shown in Figure 4 that its optimum working potential normally becomes of constant frequency. Thus, the first named arrangement insures a higher eliiciency if both arrangements are operated with this alternating potential.

In the arrangement illustrated in Figure 7, an electron issuing from the cathode l8 travels through a row of successive cylinders ll, l2, l3, and finally impacts upon the target electrode [4. In this scheme, cathode l and electrode 12, and cylinders II and I3 are at the same potentials, whereas the alternating voltage source I is connected between cathode IO and cylinder II. It it known that certain electrons on fiying through these cylinders are able to absorb an amount of energy from these cylinders which will enable them to buck against a D. C. voltage which is high compared with the working alternating potential. As a result these electrons charge the impactor electrode i 4 to a high negative potential, the ensuing D. C. potential may be taken off at l4 by means of the leads 15.

According to another object of the present invention, .a discharge tube as here disclosed may be combined with a generator tube, that is a Barkhausen (oscillating-electron) tube, to generate high frequency oscillations in such a way that the generator furnishes the working alternating potential for the tube. The discharge tube may then be used for the generation of D. C. voltages which are of a value which is high in comparison with the working D. C. potential on the generator. It is also expedient to unite the electrode assemblies of both tubes within the same vessel. What thus results is a tube which, upon the impression of certain low D. C. working potentials, will produce a high D. C. voltage by self-excitation.

While I have indicated the preferred embodiments of my invention of Which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed Without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device for converting an alternating voltage into a direct voltage of higher potential and including means for supplying electrons, and an output electrode for receiving said electrons, electrodes positioned between said electron supplying means and said output electrode through which electrons pass to said output electrode, and a load circuit including connections for maintaining the output electrode at a potential substantially that of the electron supplying means, means for applying an alternating voltage between the electron supplying means and the electrodes positioned between said electron supplying means and said output electrode to cause the electrons to receive successively greater energy from the electrodes positioned between the electron supplying means and the output electrode to cause said electrons to strike said output electrode whereby the applied alternating voltage is converted to direct voltages in the load circuit.

2. An electron discharge device for converting an alternating voltage into a direct voltage of higher potential, including a cathode for supplying electrons and an output electrode for receiving said electrons, foraminous electrodes positioned between the cathode and the output electrode through which electrons pass to said output electrode, a load circuit including connections for maintaining the output electrode at a potential substantially that of the cathode, means for applying an alternating voltage between the cathode and each of said foraminous electrodes for causing electrons to receive successively greater energy from the foraminous electrodes to cause said electrons to strike said output electrode whereby the applied alternating voltage is converted to direct voltage in the load circuit.

3. An electron discharge device for converting an alternating voltage into a direct voltage of higher potential, including a cathode for supplying electrons and a tubular output electrode around said cathode for receiving said electrons,

semi-cylindrical grid electrodes positioned between the cathode and the output electrode through which electrons pass to said output electrode, a load circuit including connections for maintaining the output electrode at a potential substantially that of the cathode, means for applying an alternating voltage between the cathode and each of said grid electrodes for causing electrons to receive successively greater energy from the foraminous electrodes to cause said electrons to strike said output electrode whereby the applied alternating voltage is converted to direct voltage in the load circuit.

4. An electron discharge device for converting an alternating voltage into a direct voltage of higher potential and including a straight thermionic cathode, a pair of grid-like electrodes positioned on opposite sides of the cathode, the spacing between the cathode and the grid electrodes increasing from one end of the cathode to the other, an output electrode having portions on opposite sides of the cathode and outside of said grid-like electrodes and similarly shaped to said grid electrodes, an electrode positioned at each end of the grid-like and output electrodes, means for applying an alternating voltage between the cathode and the grid-like electrodes and a load circuit including connections for maintaining the output electrode at a voltage substantially that of the cathode, means for maintaining the electrode at the end of the gridlike electrodes closer to the cathode at a negative potential with respect to the cathode and the electrode at the other end at a positive potential with respect to the cathode.

5. An electron discharge device for converting an alternating voltage into a direct voltage of higher potential and including a cathode for supplying electrons and an output electrode for receiving said electrons, and a plurality of tubular electrodes positioned between said cathode and output electrodes through which electrons pass, a connection between the cathode and one of said tubular electrodes, another connection between tubular electrodes on opposite sides of the tubular electrode connected to the cathode, means for applying an alternating potential between the cathode and the interconnected tubular electrodes, and a load circuit connected between the cathode and the output electrode and including connections for maintaining the output electrode at a potential substantially that of the cathode.

ERNST BRUCHE.

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