US2570208A

US2570208A - Electronic switch

Info

Publication number: US2570208A
Application number: US778574A
Authority: US
Inventors: Trevor H Clark
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1939-08-21
Filing date: 1947-10-08
Publication date: 1951-10-09
Anticipated expiration: 1968-10-09
Also published as: BE442708A

Description

Oct. 9, 1951 CLARK 2,570,208

ELECTRONIC SWITCH Filed Oct. 8, 1947 DEFLE ON a VOL GE S RCE A TTOPNE'Y Patented Oct. 9, 1951 UNITED STATES TENT OFFICE I ELECTRONIC SWITCH Application October 8, 1947, Serial No. 778,574 In France August 21, 1939 Section 1, Public Law 690, August 8, 1946 Patent expires August 21, 1959 8 Claims.

The present invention relates to electronic discharge devices and more particularly to electronic discharge devices in which the discharge is concentrated in one or more beams.

In devices of this kind it is often desirable to modify the beams after their formation, for example, by deviation, or in some other way and, consequently, it is desirable to have beams which can easily be controlled. With this object it is of interest that the beam or beams should consist of electrons having velocities comprised with in the narrowest possible range, and as uniform a direction of velocity as possible. These conditions have been realised in the majority of cathode ray tubes and related devices by using only a small proportion of the cathode to emit the electrons and amongst these electrons only those are used which seem to have velocities whose directions and magnitudes are suitable for the desired object. Arrangements of this kind have the great disadvantage of decreasing useful electron currents to a very low value. For example, a cathode with a normal oxide coating usually emits a thermionic current of 50-100 milliamperes per heating watt. A cathode of this type employed in a valve with beams controlled by deviation and heated with an energy of 2.5 watts would have a useful emission of only 125 milliamperes and, moreover, in consequence of the speed conditions to be satisfied, only about 1 per cent of this emission can be used in the usual type of structures which form electron beams.

The invention has in consequence for its principal object the provision of means for the production of one or more electron beams in which the velocities of the electrons are substantially parallel in directions and of magnitudes comprised within a narrow range of values, whilst reducing the los in energy to a considerable extent, in other words by markedly increasing the useful current of electrons emitted by the cathode, and consequently the resultant output of the discharge device.

Further, if electronic discharge devices where the beam or beams of electrons are to be subjected after their formation to means of deviation, whereby they are deflected as desired to one or other of a certain number of targets, or collector electrodes, while the focus obtained on one of the targets is assured. it is desirable to maintain this focus substantially constant, irrespective of the target on which the beam is made to fall. In order that the focusing action of the deflecting means shall be substantially uniform independently of the deviation imposed on the beam, or beams, these means of deflection should have the maximum action possible on the electrons of the beams, that is to say that the speeds of the electrons at the locations where means of deflection begin to act in the completed structure of the discharge device should be as slow as possible. Moreover, as it is obvious that these means of deflection will not act in a uniform manner on the electrons of a beam of relatively large transversal dimension, the beam or beams generated should be concentrated as much as possible so as to reduce to a minimum the differences of the forces of deflection on the various electrons of the beam.

The invention has, consequently for another of its objects, the provision of means to produce one or more electron beam comprising at their output from the emissive and beam focusing structure, electrons of substantially uniform velocities of low values, and of directions which are substantially parallel, concentrated in a very small transversal section, and all these accomplishments using a reduced number of electrodes in the generator structure of the beam, or beams.

The beam electronic discharge device in accordance with the present invention comprises means for the limitation of the discharge of a cathode according to one or more determined beams, means to ensure theflow of the electrons from the said cathode, and to give them a velocity and direction which is substantially uniform, and means for slowing down the electrons in such a way as to ensure at the output of the emissive and beam focusing structure a point of concentration of each beam at which the electrons have a minimum speed and this preferably in such a manner that the point where each beam converges should also be a point where the paths of the electrons emitted by the surface of the corresponding cathode cross one another, that is to say, a point where the electrons emitted by the portion on the left of the emissive surface pass substantially to the right of the beam, and vice versa.

In a more specific manner an electrode structure according to certain characteristics of the invention which generates one or more electron beams comprises an electrode which is an emitter of electrons or a cathode, and a oollimating electrode around this cathode having one or more openings for the passage of the electrons intended to form the beam, or beams, an accelerating electrode around the first two electrodes, and an electrode surrounding the first three and having one or more openings in alignment with those of the collimating electrode arranged to reduce the speed of the electrons without essentially modifying the direction of their velocities which are in the desired direction of propagation. The voltages of these electrodes are regulated in such a manner as to ensure a point of'convergence of electron path and preferably of intersection in a location situated in the immediate vicinity of the opening, or openings of the electrode which retards the electrons. The collimating electrode is brought to a negative potential, or zero with relation to the cathode, the accelerator electrode serving to ensure that the electrons will be withdrawn from the immediate vicinity of the cathode is carried to a positive potential with relation to the cathode and the electrode which retards the electrons is brought to a potential lower than that of the accelerator electrode, this potential being positive, negative or zero with relation to that of the cathode, to determine the crossover point of the beam, or beams and depending upon the desired mean speed of the electrons.

In accordance With another characteristic of the invention, the accelerator electrode comprises an electrode in the form of a grid with large meshes or other structure having large openings, having the plane or substantially plane portion of their surface in front of those portion of the surface of the cathode which emit the useful electrons.

In accordance with another characteristic of the'invention, the accelerator electrode comprises portions which are substantially plane, and have large openings placed in front of each active portion of the cathode, these portions being electrically independent of one another, and may be employed to accelerate or block the corresponding electron by variations in the potentials which are individually applied thereto.

In accordance with another characteristic of theinventior nthe collimating electrode is an integral part of the cathode, which therefore has non-emissive portions so arranged as to play the part of the collimating electrode in relation to the emitting portions. I

The invention, will, moreover, be explained in detail in the followingdescription of examples of embodiments exemplified by the attached drawings, in whichf v I v Figure 1 shows an electrode structure incorporating characteristics of the invention shown by way of illustration as being part of a structure of an electronic discharge device withradial deviation or deflection of the electronic beam.

Figure 2 shows a modification of the electrode structure as an object of the invention;

Figure 3 shows an electrode structure according to the characteristics of the invention for the production of two opposed electron beams and;

Figure 4 shows a modification of the structure of Figure 3 comprising, in accordance with another characteristic of the invention, means to control independently of the two electron beams produced by the structure.

Figure 1 shows schematically a generating structure of a beam of electrons incorporating certain characteristics of the invention to be employed in a radial deviation device with low potential. It is clear, nevertheless, that the invention is in no way limited to the type of deviation which is shown here, only to give an example of the application in practice of such an electrode structure. A 7

In the different figures, moreover, the corresponding element are indicated by the same reference numbers.

An electrode or cathode emitting electrode, either of the direct heating type or indirect heating type is shown schematically in 4. This electrode is surrounded partially by an electrode I having one or more openings such as 8, Figure 1, or S and 8, Figures 3 and 4. As shown, thi electrode I may consist either of a cylinder or a sphere open at 8 and centered on the cathode 4 as in Figure 1, or in several cylinder or spherical portions centered on the cathode according to the number of electronic beams desired. Therefore, Figures 3 and 4 show this electrode divided in two portions because these examples of embodiments have been chosen in the case where it is desired to obtain two opposed beams.

This electrode I, or collimating electrode, is taken to a negative potential with respect to the cathode in order to ensure the concentration of the electrons emitted by the cathode along the paths of its opening 8, or of its openings 8 and 8-.

Around these two electrodes is arranged an accelerator electrode 2 taken to a positive potential with respect to the cathode, in such a way as to create a large gradient of potential in the desired direction of displacement of electrons, in other words, in such a way as to ensure that the electrons will be removed from the immediate vicinity of the cathode surface and to avoid the formation of an electronic space charge in front of the surface of the cathode 4, at the same time giving to the electrons a component of speed in this direction which is great with respect to the speeds of any directions in which they have been emitted.

In order not to impede the paths of the electrons emitted by' the'c'athode 4, this accelerator electrode 2 has wide openings, forexample, consisting of alarge mesh grid, or an assembly of wires Whichare relatively thin in 'relation to their spacing. This accelerator electrode 2 is arranged so as to have a substantially plane surface 9 in front of the active portion of the cathode, the rest of the electrode is of cylindrical or spherical form as shown in Figure 1, or symmetrical with relation to the'lat'eral supporting rods H) as shown in Figure 2, or again having two

plane surfaces

9 and 9" in front of the active portions of the cathode, as shown in Figure 3. In a general way the accelerator electrode will have as many substantially plane surfaces as there are electron beams in the beam forming structure.

An electrode 3 consisting of a cylinder or of a sphere, or other suitable form provided with openings ll, Figures 1 and 2, and ll'-l'l, Figures 3 and 4 in" alignment with the openings of the electrode I surrounds the preceding electrodes. This electrode 'is taken to a lower potential than that of the electrode 2,a potential which may be positive, negative or zero with respect to that of the cathode 4 according to the choice of potentials of theelectrodes I and 2, of the diameter of electrode 3, and of the dimension of the opening or of the

openings

8, 8 andlLH. 'H

With such an electrode structure the beam or beams at the outlet of the structure has a marked focal point for the electrons which have slow speeds and uniform or substantially uniform direction and which will be particularly suitable for. further control such as a deviation. For example, as shown in Figure l, the electron paths which are extremely narrow and concentrated 5 at 12, as indicated in dotted lines at 13 are focused by the choice of potentials applied to the electrodes I to 3 to such a degree that the electrons emitted from the right side of the surface of the cathode 4 and passed to the left side of the beam and vice versa, can then be subjected to a radial deviation field, between the electrodes 5 and E. This radial field is established by applying potentials in such a way as to re-accelerate the electrons and may be created by carrying the electrode 5 to a potential which is very positive with respect to the cathode and simultaneously the electrode 6 to a potential below that of the electrode 5, and which may even be zero or negative with respect to the cathode 4. The direction of the velocities of the electrons of the beam at the outlet of the structure I to 4 is substantially tangential to the cylindrical electrode 5 and the beam is concentrated at 127 approximately from the point 12 and thus on one of the collector electrodes la to Fe according to the potential of the cylindrical electrade 6 as is known in the art. In the applicants embodiment, for example, a current of 2 milliamperes was transmitted to the collector electrodes 7 when a voltage of 360 volts was applied to the electrodes 5 and I, a normal zero voltage to the electrode 8, +15 volts on the electrode 3, +25 volts on the electrode 2, and 250 volts on the electrode I. This electronic current was confined to 1 mm. in width at the point of impact. If the potentials were adjusted in such a way that the width of the beam was 2 mm. a current of 5 milliamperes could be passed to the collecting electrode. intensity of its current do not depend upon the voltage of the electrode 6, even though this voltage determines the point of impact on the beam on the electrodes Ia-4e.

Instead of creating a crossover of the electrons of the beam at the point of convergence l2, it is clear that in certain cases a very high concentration assuring a slow electron beam which is extremely narrow may sufiice, as indicated in It and I4 on Figure 3.

The modification shown in Figure 2 of the structure 1 of Figure 1 is characterised by the fact that the collimating electrode l of Figure 1 has been incorporated with the cathode 4, that is to say, that the cathode 5 has been provided in such a form that it constitutes at the same time an emitting cathode of electrons on a portion 15 at the side A of the structure, and a collimating electrode for the emitted electrons created for example, by the projecting portions [6 of each side of the emissive portion IS. The rest of the cathode on the side B of the structure is not coated with emissive substance. This modification of the structure is evidently not limited to that shown on Figure 2, but it may be seen that it may be applied to structures with multiple beams, and that there may be a great number of suitable forms of cathodes.

The width of the beam and the iii) In Figure 4 has been represented an accelerator electrode in two

parts

2 and 2 which are mechanically independent. These two parts may well be electrically independent if desired, which may permit chosen potentials to be a p ied to them in different ways. In particular these potentials may be such that one of the portions. 2 or 2 mav act in order to accelerate the electrons emitted by the side corre ponding to cathode 4, whilst the other portion substantially impedes the pa sa e of the electrons emitted by the other side of the structure. Such an arrangement, which may be extended to devices with beams of a greater number than two may be employed particularly advantageously in electronic switching systems or equipments of the push-pull type, and the like.

It is clear that the invention is not limited to examples of embodiments shown and described, but may on the contrary be capable of many modifications, in particular, in the form of the electrodes shown, these electrodes being able to be square, rectangular, cylindrical, ellipsoidal, oval or other forms without changing the operation of the modified structure. It is also clear that it may be employed in devices with any number of electron beams, and is moreover, not limited to its use with radial deflection structures as already stated. Still other modifications and adaptations will become apparent to the expert without departing from the scope of the invention.

What is claimed is:

1. An electron discharge device comprising a cathode, means for assisting the emission of electrons from said cathode, a collimatric electrode positioned around said cathode and having an opening for the passage of electrons to form a beam, an accelerating electrode positioned around said cathode and collimatric electrode and held at a given positive potential with respect to said cathode, and an electron retarding electrode held at a potential lower than said accelerating electrode surrounding said cathode and last two electrodes and having an opening in alignment with the opening in said collimatric electrode to reduce the speed of the electrons passing through said openings without modifying the direction of those electrons which have the desired direction of propagation.

2. An electron discharge device according to claim 1, in which said collimatric electrode is held no more positive than said cathode.

3. An electron discharge device according to claim 1, in which the accelerator electrode is in the form of a grid with large meshes and having a substantially plane surface in front of the cathode.

4. An electron discharge device according to claim 1, in which the collimating electrode is an integral part of the cathode but is non-emissive.

5. An electron discharge device according to claim 1 in which said collimatric electrode and said retarding electrode each have an additional opening substantially oppositely disposed with respect to said first mentioned openings to form an additional electron beam of reduced electron velocity adjacent said additional openings.

6. An electron discharge device according to claim 1 in which said retarding electrode has an additional opening substantially oppositely disposed with respect to said first mentioned openings, and said accelerating electrode comprises two electrically isolated portions each positioned in line with a respective opening in said retarding electrode.

'7. In an electron discharge device, a cathode,

beam forming means for limiting the emissionof electrons to a given portion of said cathode and to focus the beam through a crossover adjacent said cathode, electron retarding means positioned adjacent said crossover and spaced further from said cathode than from said beam forming means for reducing the velocity of said electrons approaching said crossover, electron accelerating means positioned between said cathode and said crossover, a plurality of electron collecting elements positioned to one side of said cathode, two partially cylindrical coaxial electrodes having difierent radii the opposing arcuate surface of which define an arcuate space to receive the beam, first voltage means for establishing a steady potential difference between said coaxial electrodes, and second voltage means for applying a varying potential difference between said coaxial electrodes to direct said beam to selected ones of said collecting elements.

8. In an electron discharge device, a cathode, beam-forming means including an accelerating electrode for limiting emission of electrons to a given portion of said cathode and to focus the beam through a crossover adjacent said cathode, electron retarding means positioned adjacent said crossover and spaced further from said cathode than from said beam-forming means for reducing the velocity of said electrons approaching said crossover, electron-accelerating means positioned between said cathode and said crossover, a plurality of electron collecting elements positioned to one side of said cathode, two partially cylindrical co-axial electrodes having different radii the opposing arcuate surfaces of which define an arcuate space to receive the beam, positioned so the crossover occurs between said surface and a source of varying D. C. voltage connected between said partially cylindrical electrodes to direct said beam to selected ones of said collecting elements.

TREVOR H. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,979,392 Lubcke Nov. 6, 1934 2,100,701 Schlesinger Nov. 30, 1937 2,107,520 Schade Feb. 8, 1938 2,144,085 Rothe et al Jan. 17, 1939 2,159,765 Jonker et a1. May 23, 1939 2,197,033 Diels Apr. 16, 1940 2,252,580 Rothe et al Aug. 12, 1941 2,254,096 Thompson Aug. 26, 1941 2,380,225 Fleming-Williams July 10, 1945 FOREIGN PATENTS Number Country Date 475,106 Great Britain Nov. 12, 1937 498,167 Great Britain Jan. 4, 1939