US2256335A - Electron discharge device - Google Patents

Description

Sept. 16, 1941.

' w. H. ALDOUS ETAL ELECTRON DISCHARGE DEVICE Filed May 4, 1939 I NV EN TORS w 3N U m 00 6 0 w T AW Wu TM mm Mu MW M MR F 0 WM Patented Sept. 16, 1941 UNlT f1 ELECTRON DISCHARGE. DEVICE William Herbert Aldous and Geoflrey William Warren, Wembley, England, assignors to M-O Valve Co. Limited, a limited company of Great Britain Application May 4, 1939, Serial No. 271,697 In Great Britain May 5, 1938 5 Claims.

Our invention relates to electron discharge devices, more particularly to improvements in such devices suitable for superheterodyne operation.

Broadly the invention is directed to multielectrode valves of the type in which electrons from a linear cathode pass through an accelerating grid and a retarding control grid, in that order, to an anode. The electrons may pass through other electrodes also, for example a first control grid before the accelerating electrode and a screen grid and a suppressor grid after the retarding control grid. Thus known hexodes and heptodes, such as are used for frequency-changing, belong to this type. As usual, the term grid does not imply that the electrode is grid-like mechanically; it may be a helix or parallel wires or any other known equivalent structure.

In valves of this type some of the electrons approaching the retarding control grid are necessarily turned back towards the accelerating grid. If the controlling potentials have a frequency so high that their period is not long compared with the time of transit of the electrons between the two grids, some of the returned electrons may pass back through the accelerating grid with excess kinetic energy and may be collected by more negative electrodes, for example the first control grid nearer the cathode. They then cause known harmful effects, for example damping in the input circuit associated with the first control grid.

The object of this invention is to provide an electron discharge device which will prevent this return of electrons through the accelerating grid and thus the harmful effects noted.

An electron turned back at a grid does not usually travel along its previous path; it is generally deflected through a considerable angle. If, as has hitherto been usual, the Wires of all the grids are approximately in planes perpendicular to the length of the cathode, the deflections are predominantly in planes passing longitudinally of the cathode. They do not therefore carry the electrons away from the cathode and the inner electrodes surrounding it, they merely move the electrons from one point to another along the length of these electrodes. The principle underlying the invention is to arrange the turned back lie, or at least have substantial components, in these perpendicular planes. The defiections then tend to carry the electrons to one side of the cathode and the inner electrodes.

According to the invention the accelerating grid and the retarding control grid are so arranged relative to each other and to the linear cathode, and to the other electrodes of the valve, that the deflections of the electrons which are turned back at the retarding control grid have a substantial component in planes perpendicular to the length of the cathode.

On method of producing such deflections is to arrange the effective part of the retarding control grid in a plane inclined at a substantial angle to the plane of the effective part of the accelerating grid cooperating with it, so that the normal to the centre of the retarding control grid passes to one side of the cathode, and to provide another electrode, adapted to be maintained positive to the retarding control grid, on this side of the cathode. Deflections will be predominantly in the plane containing this normal and the incident direction; accordingly they contain a component perpendicular to the length of the cathode.

Another method of achieving the same result is to make both the accelerating gridand the retarding control grid in the form of wires parallel to the length of the cathode. Then when an electron is turned back it will be deflected accelerating grid and retarding control grid so.

mainly directed to the cathode, and so that the deflections produced when the electrons are mainly in the plane perpendicular to the length of the cathode.

The novel features which we believe to be characteristic of our 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 diagrammatic transverse sections of electron discharge devices made according to our invention and Figure 4 is a diagram showing electron paths in the tube of Figure 3 during operation of the tube.

In Figure 1 of the drawing accompanying this long as their efiective part is plane, and may be mechanically and electrically connected or separated within the valve. The anode comprises sections 5, 5' associated with grids 4, 4' respectively. These anode sections may also be mechanically and electrically connected or separated within the valve. Theflat collector electrode 8 of sheet material, which may be electrically connected to the accelerator grid 3, or a connection to 6 may be brought out separately so that a suitable positive potential may be applied to it.

It will be noted that the planes of the effective parts of the grid anode systems 4, and 4', 5', are inclined to the plane of the effective part of the accelerating grid 3 and that the normals to these planes are directed to that side of the cathode on which the electrode 6 lies. The electrons returned from 4 and 4 will therefore have a component of velocity parallel to the breadth of the cathode or in a plane transverse to the cathode as indicated by the arrows. At these grids the stream of electrons is divided into two parts, one part going t the anode, and the other part being reflected. The reflected electrons will be collected by the electrode 6. The electrodes are mounted within envelope Id.

In the embodiment of the invention illustrated in Figure 2 the parts functionally similar to those shown in Figure 1 are denoted by the same numerals. Beam-forming electrodes 9, 9' are introduced, which insure that an electron leaving the effective part of the accelerating grid falls on the effective part of the retarding control grid I and, in particular, prevent electrons travelling directly from the accelerating electrode 3 to the collecting electrodes 6, 6. In this example screening grids I, 1', and suppressor grids 8, 8' have been inserted between the retarding control grids 4, 4' and anodes 5, 5'. All these grids are here shown as completely surrounding the anodes 5, 5b, as this may render their manufacture easier. An envelope l9 encloses the electrodes.

When valves of thiskind, having two control grids, are used as frequency changes, it is common practice to place an oscillator valve in the same envelope. This may naturally also be done in valves according to the present invention. This oscillator valve may be of triode, tetrode or pentcde form; it may employ part of the cathode l or it may have a separate cathode.

In the embodiment of Figure 3 the linear cathode I indirectly heated, is surrounded by a helical first control grid 2 and has on opposite sides a beam-forming sheet metal member, these sheet metal members forming an electrode 3 having oppositely disposed apertures and maintained at cathode potential. This electrode concentrates the electrons through the oppositely disposed apertures into ribbon beams lying in a plane passing longitudinally of the cathode. The accelerating grid ll, retarding control grid i2, and second accelerating and screening grid l3 are all wires parallel to the length of the cathode and lying on either side of the electron beams from the cathode. The cylindrical anode l4 surrounds all the other electrodes. An envelope l6 encloses all of the electrodes. Flat sheet members l5 of conducting material which may be madeas extensions on electrode 3' lie parallel to the path of the beams.

With this arrangement, any electron, turned back by the wires l2, if it does not retrace exactly its original path, must be deflected (as shown by the curved dotted lines and, on a larger scale, in Figure 4) in the plane of the drawing and will thus tend to be caught by the accelerating electrode II or concentrating electrode 3 rather than by the first grid 2'.

While we have indicated the preferred embodiments of our invention of which we are now aware and have also indicated only one specific application for which our invention may be employed, it will be apparent that our 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 our invention as set forth in the appended claims.

What we claim as new is:

1. An electron discharge device having a cathode for supplying electrons and an anode for receiving said electrons, a first control electrode between said cathode and said anode, a beam forming electrode for forming electrons from said cathode into a beam and including a sheet member of conducting material lying in a plane parallel to said beam, an accelerating electrode and a second control electrode positioned between said first control electrode and the anode, each of said last two electrodes having portions lying on opposite sides of said beam, said second control electrode being adapted to have varying positive and negative voltages of high frequency applied thereto during operation of said discharge device, said sheet member being adapted to receive any electrons returned by said second control electrode when said second control electrode assumes a negative potential with respect to the cathode.

2. An electron discharge device having a cathode for supplying electrons and an anode for receiving said electrons, a first control grid between said cathode and said anode, a beam forming electrode for forming electrons from said cathode to said anode into a beam, an accelerating electrode and a second control electrode positioned between said first control electrode and said anode, said second control electrode being adapted to have varying high frequency potentials applied thereto and a sheet member of conducting material positioned outside of said accelerating and second control electrodes and lying parallel to said beam and electrically connected to said beam forming electrode for receiving any electrons returned by the second control electrode when high frequency potentials are applied to said second control electrode.

3. An electron discharge device having a cathode for supplying electrons and an anode for receiving electrons, a beam forming electrode having an aperture for forming the electrons into a beam, extensions on said beam forming electrode lying in planes on opposite sides of said beam and parallel to said beam, an accelerating electrode comprising a rod positioned on each side of said beam, and a second control electrode comprising a rod positioned on each side of said beam and adapted to have a potential at high frequency applied thereto, said extensions on said beam forming electrode adapted to receive any electrons returned by said second control electrode during operation of the device.

4. An electron discharge device having a cathode and an anode and a control electrode surrounding said cathode. a beam forming electrode surrounding said cathode and control grid and provided with oppositely disposed apertures for forming the electrons from said cathode into a pair of oppositely disposed beams, extensions on said beam forming electrode lying in planes parallel to said beam, an accelerating electrode comprising rods on opposite sides of said beam and between said beam and extensions and a second control electrode comprising rods positioned on opposite sides of the beam and between the beam and said extensions and adapted to have high frequency voltages applied thereto, said extensions adapted to receive any electrons returned by said second control electrode during operation of the discharge device.

5. An electron discharge device having a cathode for supplying electrons and an anode for receiving said electrons, a first control grid between said cathode and said anode, beam forming means for forming electrons from said cathode to said anode into a beam, an accelerating electrode and

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