US2013093A - Electron discharge device - Google Patents

Description

Sept. 3, 1935. s, G; FRANTZ ELECTRON DISCHARGE DEVICE 2 sheets-sheet 1 Filed May 22, 1930 5 4 o r 000 omwb o 0o 00 o o INVENTOR SAMUE FRANTZ ATTORN EY Sept. 3,1935. FRANTZ 2,013,093

ELECTRON DI SCHARGE DEVICE Filed May 22, 1930 2 Sheets-Sheet 2 o o o 3 o 4, o 1 o 3 o q i o o 0 0 o O 4 4 0 O INVENTOR SAMUE G. FRANTZ ATTORNEY Patented Sept. 3, 1935 PATENT OFFICE ELECTRON"DISCH ARGE DEVICE Samuel G; Frantz, Princeton, N. J., assignor to I Radio Corporation of America, a corporation of Delaware ApplicationMay22, 1930, Serial No; 454,533

i1 Claim. (01. 2 50-27.5)

This invention relates to electron discharge devices and more particularlyto a method of controllingv the flow of electrons. i v

' The invention comprises a novel method of, an

i means for, controlling theflow of electrons in an electron discharge device, and depends upon I the proposition that a current flowing through a conductor produces a magnetici'field around the conductor, and also that an electron in motion is similar to current flow in a conducto'ra If a conductor is-positioned in an electron discharge device and carries current, the magnetic field around the conductor will tend to deflect or control the electronieflow injthe discharge device. These phenomena are utilized by the invention in several forms; forexample, current is madeto flow through the grid of a thermionic valve, and

valves and high power rectifiers, and in avoiding the effect, often objectionable, of secondary, emission from the anode or electron collector. In my arrangement, an auxiliary electrode is positioned close to the plate or electron collector, and current is passed through this auxiliary electrade; at the same time a high potential is supplied to this auxiliary electrode to accelerate the flow of" electrons from thecathode toward the auxiliary electrode. The magnetic 'field created bythe current flowing in the auxiliary electrode will deflect the electronic'flow to an extent sufficient to repelthem from the auxiliary electrode, and at the"same time the high velocity of the 40' electrons accelerated by the high positive potentional electrode is employedto accelerate the tiallof the auxiliary electrode will be suiiicientto bring the electrons to the anode or electroncollector.

Otheraspects ofrthe invention will appear fur ther in the specification.

The invention will be more clearly understood 1 with the aid of the accompanying drawings.

Figure lrepresents a schematic/showing of a simple form of my invention as appliedto the ordinary three electrode vacuumtube.

Figure 2 represents a schematic. showing of another form of'my invention, in which an addielectrons. i l

Figure 3 is a schematic showing of amodifica- V Figure 3.

tion of my invention, in which the magnetic field for deflecting the electrons is produced by a.

, electron discharge device;

, Figure 6, shows another View of the structure illustrated in Figure 5. p e

' Figure 7 shows another form of my invention in which the accelerating electrode itself carries the current for producing the magnetic field' which. deflects the electrons; I l i Figure 8 shows another view of the structure 11- lustrated in Figure '7. l

* Figure 9 shows schematically another form of my invention similar to that of Figures 7 and 8 except that in FigureQ the accelerating electrode which carries the current is positioned within the anode or electron collector. it

-Figurel0 is another view of the structure illustrated in Figure. 9.

Figure 11 shows schematically another modification in which the accelerating electrode which carries the deflecting current is positioned entirely around the anode or electron collector and- Figure 12 shows another view, of' the structure illustrated in Figure l1.- I

Inordinary three electrode tubes, the three electrodes comprise a hot electron-emitter or cathode; a cold electron-collector or anode, and an inputor control electrodeknown as the grid. When the cathode is heated sufficiently and when a proper potential difference is applied between theanode and the cathode, electrons will flow from the cathode to the anode, as is well known. The control electrode or grid is impressedwith the control voltages to affectthe flow of electrons from the cathode to the anode, or in other words, to control the flow of current from the anode to the cathode. Since the control electrode is usually positioned between the cathode and the anode, and since the control grid would normally be positive sometimes with respect to the cathode,

trode. .This flow of electrons to and throughthe control electrode has given rise toseveral difficul ties, and many attempts have been made to eliminate or reduce this flow. The common "3,; combination of these.

method is to apply to the control grid a potential or bias which is negative with respect to the cathode. This tends to reduce or eliminate the attraction which the control grid has for the electrons flowing from the cathode. This, however, does not entirely eliminate the flow of electrons to and through the grid, because notwithstanding this negative bias, the fluctuations in control voltages make the control electrode more positive at times than the negative biasing potential applied to it, and this reduces or neutralizes the repulsion which the control grid should exert on the electrons. Too much grid 'bias will stop operation of the tube. Moreover, the position of the control grid between the cathode and the anode subjects the control grid to bombardment by the electrons, and many of them enter the control electrode.

I have found that I can exert a greater repulsion on the electrons tending to enter the grid than has heretofore been accomplished by the negative grid biasing potential.

A simple form of my apparatus is illustrated in Figure I which shows a three electrode tube adapted to the purposes of my invention. In this figureQthe cathode or filament l is shown as a straight wire, although it is obvious that it may be the hairpin type or cylindrical type of filament or the indirectly heated cathode type. Surrounding the cathode I is the control electrode or grid 2, which is here shown schematically as a helix, although it may have other forms, the main requisite being that the elements of the grid be spaced apart to permit the electrons to pass therethrough on their Way to the electron collector or anode 3. This anode is shown as a cylinder concentric with the cathode I and the grid 2, although it is apparent that it may have other forms, and may comprise a plate, a wire, or any Enclosing the whole may be an envelope of glass or metal 6, indicated diagrammatically in Figures 1, 2, and 3.

During operation of the tuba-the cathode l is heated to emit electrons, and the potential of the anode 3 is such as to attract the electrons. The grid 2 is impressed with the signal voltages to control the number of electrons passing through to the anode 3. This is the usual process of operating the tube. In addition, I pass a current through the grid 2 during the operation of the tube. As is well known, a wire which carries cur rent produces lines of force around it, the direc tion of which may be determined by the right hand rule. The control grid 2, therefore, will at all times during operation have a magnetic field which will have a direction perpendicular to the plane of the figure. As the electrons approach the grid 2 on their way to the anode 3 which attracts them, the magnetic field produced by the current in the grid 2 will exert a repelling eifect on the electrons. An electron will consequently be induced to take the path shown by the broken line in the figure. The path will approximate the shape of a spiral, the degree of which will depend on the voltage diiference between the cathode and the anode and on the force of the magnetic field produced by the current in the grid 2. The magnetic field and the current which produces it will not aifect the electron emitting tendencies of the cathode, but on the other hand thelnput voltages on the control electrode 2 will act in the normal manner to control the flow of electrons, and the anode will act in the usual manner to attract the electrons in its vicinity. The grid 2, however, will not receive electrons because the local magnetic field in the immediate vicinity of the grid wires will repel the electrons. My device, therefore, will be such as to eliminate or substantially reduce the flow of electrons in the control grid and this will be accomplished without the aid of the grid biasing potential.

Figure 2 shows another form of my invention in which an additional electrode is employed to accelerate the electrons from the cathode to the anode. In this figure, the cathode I is shown schematically as a cylinder, although as pointed out in connection with Figure 1, it may have other forms and shapes. Surrounding the cathode l is the control grid 2, and surrounding the control grid 2 is the electron collector or anode 3. Positioned between the grid 2 and the anode 3 is an additional electrode 4 which acts to accelerate the flow of electrons from the cathode l to the anode 3. The electrode 4 is given a high potential to attract the electrons from the cathode l and this potential is so high that the momentum attained by the electrons I will be suflicient to cause them to pass through the accelerating electrode 4 and strike the anode 3, even though the potential of the anode be less than that of the accelerating electrode 4. This will permit the use of lower plate potentials. In addition, the accelerating electrode 4 may carry a current which induces a magnetic field to pre-i vent the electrons from entering it. If desired,

the control grid 2 may also have a. current traversing it to prevent any of the electrons from entering it, or both the grid 2 and the accelerating electrode 4 may carry currents.

In the ordinary tube, the anode may be said to have two functions. The first is to provide the necessary accelerating electro-static field by acting as the high potential plate of a condenser, the other plate being the cathode. The second function is to act as the receiving electrode which collects the electrons so that they may be removed from the tube as current through a wire provided for the purpose. In the ordinary tube, the combining of these two functions results in the following two serious disadvantages: The anode is bombarded by high velocity electrons accelerated by the high potential of the anode, and the kinetic energy of these electrons appears in the anode as heat. In power tubes the limit of power capacity is determined by the ability of the anode to dissipate this heat. Among the methods adopted to dissipate this heat are watercooling, air-cooling, oil-cooling, large surface for the anode, and others. The second undesirable result is the electrical power loss in the circuit, which loss is equal to E1. That is, some of the power which might ideally appear in the output circuit is lost sofar as useful work is concerned. This power loss, E1, is the potential difference E between the cathode and the anode, times the electron current I between the cathode and the anode. This energy represents the kinetic energy given to the electrons which finally appears in the anode in the form of heat and is entirely lost so far as useful work is concerned.

In one aspect of my invention, I separate the two functions of the anode. For example, in the device illustrated in Figure 2, the anode is used solely as the electron collector, and to accelerate the electrons I provide the additional electrode 4 which is kept at a high potential to attract the electrons. kept at a very' high potential; in fact, it maybe kept at a much lower potential than the auxiliary accelerating electrode, and acts toreceivemost The anode 3, therefore, need not beof the electrons which have been discharged from 4 the cathode.

illustrated as a straight filament, although it is obvious that a hairpin or helical filament or indirectly heated cathode may be employed. The anode or electron receiving electrode 3 is shown here diagrammatically as straight vanes, although it is obvious that other forms may be used, and in fact it" is necessary only that the anode be appropriately apertured, as will hereafter appear. The accelerating electrode 4 is in the form of a cylinder surrounding the anode 3, although it is apparent that the accelerating electrode 4 may have other forms to suit the appropriate design. In this modification, the external solenoid 5 surrounding the accelerating electrode 4 is used to produce the magnetic field, which in this instance will acton the electrons in the direction shown by the arrows. The electrons emitted by the cathode I will be directed toward the accelerating electrode 4 on account of the centrically positioned about the cathode I.

latters high potential, but the magnetic field produced by the external solenoid 5 will be just,

sufficient to deflect the electrons so that they strike the face of the anode-or electron collecting electrode 3. The path of the electrons is shown by the broken lines in Figures 3 and 4.

In another modification illustrated in Figures 5 and 6, the cathode l is utilized as the genera tor of the magnetic field by passing current through it or an adjacent wire,'and the magnetic field will deflect the electrons so that they strike the anode 3 rather than the accelerating elec trode 4. The path of the electrons is illustrated by the broken lines in Figures 5 and 6.

In another modification of my invention, the accelerating electrode itself carries current which produces all or part of the magnetic field to defiect the electrons. One form of this modification is shown in Figures 7 and 8. Here I is the cathode, as before; 4 is the high potential accelerating electrode; and 3 is the anode or electron receiving electrode. The anode 3 and the accelerating electrode 4 are given the form of intermeshing helices of thesame diameter and con- The accelerating electrode 4 is made to carry a current counter-clockwise, and the anode 3 is made to carry current clockwise, the current in 4 being greater than the current in 3. The magnetic field between the cathode v I and the intermeshing helices will therefore be up. As the electrons leave the cathode l and flow toward the anode 3, they will receive a tangential component of velocity in a counter-clockwise direction, substanlill tially horizontal as viewed in Figure 8, until they approach the helices. magnetic field will exert a vertical force on" the electrons having counter-clockwise movement and tend to move them away from 4 toward 3, as shown by the broken lines in Figure 8. The electrode 4 will thereby act only as an accelerating electrode, without receiving any of the electrons which it is desired that the anode 3 receive.

In another form'of this modification, illustrated in Figures 9 and 10, the device is made in the form of the usual three electrode tube, with the addition of a helix 4 which acts as the accelerating electrode; As shown, this helix 4 is positioned relatively close to the anode 3. Current is passed Near the wires 4 and 3, the

through the accelerating electrode 4, as above discussed, and the electrons in their path from the cathode l to the anode 3 will receive a counterclockwise velocity as shown in Figure 9. The current flow in the accelerating electrode 4 is counter -clockwise, as before, and the magnetic field induced by this current will tend to deflect the electrons in their path before they reach the helix 4 as shown in Figure 10. This deflection will be suflicient to cause the electrons to pass in through the interstices of the helix 4 and collect on the anode 3. As is obvious, the anode 3 may be in other forms than a cylinder.

Since the anode 3 may be at a potential only slightly above that of the, cathode I, in contradistinction to the very. high potentials usedin the present tubes, the kinetic energy of the received electrons in mydevice is small on account of the relatively low velocityof the electrons as they strike the anode 3. The heating of the anode is therefore small and the power capacity of my tube will be relatively great. At the same time the power loss, which as above discussed is equal to E1, is small, and my tube is therefore highly efflcient.

Figures 11 and 12 illustrate another modification of my invention in which the accelerating electrode 4 is given the form of a hollow member surrounding the anode 3.

Current is sent up through the accelerating electrode 4 within the anode 3 as shown by the arrows in Figure 12, and current is sent down through the cathode l.

The magnetic field resulting from the current in the accelerating electrode 4 and the current in the cathode I will be such as to deflect the electrons away from the wires of the accelerating electrode 4 just before they reach the accelerating electrode 4 on their way tothe anode 3.

Not only does my invention reduce the power loss and the heating of the tube but it also reduces the mechanical disintegration of the anode due to the high velocity of the electrons as they strike the anode in the ordinary construction. As is well-known, this disintegration affects the operating characteristics of the tube and in time renders the tube inoperative for its purposes. My

. invention increases the power capacity of the tube, avoids disintegration of the anode, reduces the heating of the anode, avoids expensive and cumbersome cooling means for the anode, avoids the disadvantages of negative grid bias, and in general results in a highly efiicient tube.

I wish it to be understood that the forms shown inthis application are merely illustrative and not definitive, it being apparent that changes may be made in the proportions, shapes, and designs to suit various desired operating conditions.

Having now described my invention, what I desire to claim is,-

An electron discharge device comprising an envelope containing an electron emitting electrode,

an electron collecting, electrode and an accelerating electrode positioned between said other two electrodes and comprising a helix of conducting material wound in the same direction throughout its length, and connections from the two ends only of the helix through the envelope to provide terminals for passing current through the helix to create a magnetic field to protect the helix from bombardment by the electrons.

SAMUEL G. FRANTZ.

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