US2212645A - Electron tube - Google Patents

Description

ug-27 G. A. MORTON 2,212,645

ELECTRON TUBE 2 Sheets- -Sheqt 1 Filed May 29, 1937 16 l K I PICTURE SIG/V195 INPUT T Bnventor George H.M0rt0n (Ittorneg Au 27, 1940; .G. A. MORTON ELECTRON TUBE Fi led May 29, 1937 2 Sheets-Sheet 2 Ill PICTURE GIGNHL l/VPU 7' Zinbentorv .Morton Geo-rye H attorney Patented Aug. 27, E940 UNITED sTATes eATs- T OFFICE George A, Morton, Audubon, N, J.,' assignor-to Radio Corporation of America, a corporation of Delaware 1 Application May 29,1937, Serial No. 145,413 1 l 10 Claims. '(ollzsm-zv).

My invention relates to electron tubes wherein r the phenomenon of secondary emission is utilized for control purposes.

If an insulated element is bombarded by an electron beam, it must assume an equilibrium potential such that as many electrons leave the element as reach it.= If it emits nosecondary electrons, it will go sufficiently negative to prevent any primaryelectrons from reaching it. If it emits secondary electrons, it will assume a potential such that the ratio of primary to secondary electron is unity. :The potential of the bombarded element will in this case be determined by the potential of the element in the tube which collects the secondary electrons, or which -controls the field around the elementbeing bombarded. Therefore, by regulating the potential of this controlling element, the potential of the bombarded elementcan be adjusted to any desired value, or varied at will.

If the element is not insulated, but is connected to some other point in such a way that the ourrent leaving it is small compared with the beam current, the same method can be applied. If

the current leaving or reaching the element' through this connection is comparable with the beam current, its potential may be controlled in the same way, but the equilibriumsecondary emission ratio will not be unity. This method may be applied'to'a single element in the tube,

of' said electrodes remain at this potential for av certain period of time.

From the foregoing discussion, it'will be apparent that an object of my invention is to provide an improved electron. discharge tube wherein the potential of an electrode is to be con trolled.

A further object of my invention is to provide an improved method of controlling the potential of an electrode in an electric discharge device. 1

A further object of my invention is to provide an improved electricdischarge tube wherein the potentials of a plurality of electrodes are controlled successively.

A still further object of my invention is to provide an improved methodof and. means for controllingthepotential of an insulated electrode.

The invention" mu be better understood fromv the. following description, taken in connection with the accompanying drawings, in which 1 Figures 1 "and 2 are diagrams of electronic tubes and associated circuits-embodying my invention, 1

Figures 3 and 4 show electronic tubes embodying a preferred form of my invention, whichare connected in. a television receiver having'a bank or mosaic of lamps to form the receiver screen,

and l I Figure 5 is 'a view of another embodiment of my invention.

Referring to Fig. 1, this particular embodiment of my invention comprises 'a highly evacuated envelope 3| having therein an electron gun comprising an'indirectly heated cathode 2, a control electrode 3, an anode-.4 and a second anode 5. At the opposite end of the envelope there is an electrode 6, the' potential of which it isdesired to control. A

A ring electrode 1, which is maintained at a slightlyihigher positive potential than the anode 5, by means of a'battery 8, functions as a collector of secondary electrons emitted from electrode 6 when it is bombarded by a beam of electrons from the electron gun. The electrons in this beam, which is represented by the broken line 9, will be referred to as the primary electrons, as distinguished from the secondary electrons resulting from. bombardment of the elec 'trode 6 by the primary electrons.

- ondary electrons leaving it equals the number of primary electrons reaching it. It follows that by controlling then'umber of secondary electrons leaving the electrode 6, the potential of this electrode is controlled. I

Thus, by impressing picture signals, for ex- .ample, upon electrode 1 through a transformer it, the potential of electrode 6 is varied in accordancev with the picture signal, and the light emitted from glow lamp I2 also varies with the picture signal. The lamp [2 may be located behind a scanning disc, such as a Nipkow disc, to reproduce a television picture in awell known manner.

potential of electrode 6, it will be apparent that,

as electrode 1 lsmade more negative by an incoming signal, it will draw fewer secondary electrons from electrode '6. Thus electrode 6 be- ,comes more negative until a suflicient number of the primary electrons are beingrepelled to make the ratio ofrprimar'y electrons to secondary 818(5- trons unity.

In Fig. 2,where parts similar to those in Fig. 1 are indicated by like reference numerals, my electron tube is the same as in Fig. 1, except that;

an additional control electrode l'l isprovided.

This control electrode may be one of any shape placed near the electrode 6, but in a preferred form it is in the shape of a ring surrounding electrode 6 and has a screen portion located between electrode 6 and the electron gun. Thepotential of electrode 6 is varied as previously described,

theiin'comingi signal being applied to electrode l'l. vInzFigxB thereis 'illustratedone of the preferred". embodiments of my invention wherein the potentials of a plurality of electrodes may .berchanged inrapid succession in accordance with a -picture signal or thelike. In Fig. 3, parts similar to thoseinFi'g. l are indicated by like reference numerals.

In my electronic tube shown in Fig. 3, there are a'pluralityof electrodes 60, 6b, 5c, 6d, etc. In. the particular application of this. tube indicatedrin Fig.3, thatis, inla television receiver having a screen 2| comprising a mosaic of'glow lamps 22,'the envelope l contains many more 5 electrodes, such as 6w, than indicated, andthey,

like the lamp 22, are arranged as a mosaic.

'A control electrode 23 is located between the electrodes 611,621, etc., and the electrongun, this electrode controlling thelpotentials of electrodes @61 6b, etc., in the same way that: electrode ll .in-Fig.--2l controls the potential of electrode 5. ,The electrode 23 may be in the form'of a screen as indicated. Preferably, metalplates 23a, which may be in the form of a honeycomb structure, are provided to prevent secondaryelectrons from going froma bombarded-electrode such as 5b, toan adjacent electrode such as 611, instead of toithe collector electrode lmAs'indicated, the partitionxplates 23a and thescreen formingthe mainp'art of electrode 23 are electrically conthrough an amplifier 21'.

The gas lamps 22 are in the plate circuits of amplifier tubes 26a, 2%, etc; whereby they are lighted to a brilliance"depending upon the'potentials of the amplifier tube grids, the potentials. of

,these 'gri-ds in turn dependupon the potentials of transmitter in any well known'manner. a

For the purpose or explanation, it will be as- .fjsumed that the ray 9 is-b-eing deflected rapidly in. the plane of the paper and over the row of electrodes-6a, =61), etc., and that it is being deflected; comparatively slowly in a plane perpendicular to the plane of the paper, As the cathode ray is deflected over the row of electrodes to,

61), etc., the upper row of lamps 22 will light up, the action being as follows:

At the instant that the cathode ray strikes the electrode Ea, the control screen 23 is at a certain potential, determined by the incoming The electrode 6a emits secondand it strikes electrode 6?), the potential of scannedbythe cathode ray. When scanned the second timeythe action is repeated.

It will be apparent that the grids of tubes 26a,

.261), etc., assume. the potentials of electrodes 6a, 6b, etc,, whereby each of the lamps 22 glows with anintensity depending ;upon the illumination of a correspondingpicture element of the subject being transmitted. Each glow lamp remains lighted-,and glows with unchanging intensity until itsintensity. is changedby the next scanningcyclepf the cathode ray 9. l

It should benoted that in my above-described tubes the potential of the control electrode with respect to, thebombarded electrode (the potential ,.of electrode 23 with respect to electrode 6a in Fig.3, for example) determines the number of secondary electrons leaving the bombarded element only during the period that the bombarded element is acquiring a new equilibrium potential. As soon as the new, equilibrium potential is reached, the-ratioof primary electrons to secondary electrons is again unity and the number .of secondary electrons leaving the bombarded element is the same as before.

In Fig. 4,,where parts similar tothose in Fig. 3 are indicated by the same reference numerals, I have illustrated an electronic tube similar to that shown in Fig. 3, but which has the picture signals applied to the secondaryelectroncollector electrode'l as described in connection with Fig. 1.

The, operation of this television receiver is the same as'that of the receiver in Fig. 3.

InFig. there is shown .a-nembodiment of my invention in which a plurality of electrodes are bombarded simultaneously by electrons sprayed from an electron gun. It comprises an evacuated envelopes! having therein an electron gun comprising a cathode 32 and an anode 33. An additional anode 34 is provided for accelerating the electrons and'for collecting secondary electrons. A'plurality of output electrodes 36a, 3617, etc., are located at the end of the'envelope 3| where they are-bombarded .by the primary electrons from, the electron gun.

Each of the output electrodes is provided with a control electrode, as indicated at 31a, 31b, etc. It will be evident that the potentials of the: 'output electrodes may be changed'simultaneously for control purposes by varying the potentials of the electrodes 31a, 3111, etc., whereby aplurality of circuits may be controlled simultaneously by the single control tube 3|.

By the 5 expression secondary emission equilibrium potential, used=in the claims, is meant the potential of an ele'ctrodebein'g bombarded with a beam of primary electrons with respect to an electrode determining theratio of secondary electrons leaving the first electrode to the number of electrons in the said beam, said beam being such that the number of said secondary electrons equals the number of saidprimary electrons.

. I claim as my invention:

1. In an electric discharge device having aninsulated or floating electrode to be controlled and a control electrode, the method of causing said first electrode to assume any one of a plurality of desired potentials which comprises bombarding said first electrode witha beam of primary electrons with suiflcient velocity to release a quantity of secondary electrons therefrom such that the ratio of secondary electrons-to primary electrons may be greater than unity,

said control electrode to make said first electrode 7 prises bombarding said electrode with primary electrons with sufficient velocity to release a quantity of secondary electrons therefrom such that the ratio of secondary electrons to primary electrons may be greater than unity and whereby said electrode assumes substantially secondary emission equilibrium potential and controlling the instantaneous electric field in the region of said electrode to control the instantaneous ratio of secondary electrons to primary electrons whereby sa d electrode assumes a different potential which is substantially secondary emission equilibrium potential.

3. An electric discharge tube comprising an evacuated envelope having therein means for generating a beam of electrons having a certain velocity, a plurality of insulated or floating electrodes capable of secondary electron emission and positioned to be bombarded by said beam with sufiicient velocity torelease a quantity of secondary electrons therefrom such that the ratio of secondary electrons to primary electrons may be greater than unity, each of said electrodes having an output conductor extending outside said envelope, and means for controlling the number of secondary electrons leaving said electrodes for the purpose of controlling their potentials.

4.'The invention according to claim 3 char-- acterized in that said last means includes a control electrode common to said plurality of electrodes.

5, In combination, an electric discharge tube 7 comprising an evacuated envelope having therein means forgenerating a beam of electrons having a certain velocity, a plurality of insulated or floating electrodes capable of secondary electron emission and positioned tobe scanned by said 7 beamwith sufiicient velocity to release a quantity of secondary electrons therefrom such that the ratio of secondary electrons to primary electrons maybe greater than unity, means for deflecting said beam across said electrodes, each of said electrodes having an output conductor extending outside said envelope, and means for controlling the number of secondary electrons leaving said' electrodes for the purpose of controlling their potentials.

6. The invention according to claimfi characterized in that said last means includes a control electrode common to said plurality of electrodes. i

'7. In combination, an electric discharge tube comprising an evacuated envelope having therein means for generating a beam of electrons havof said electrodes having an output conductor extending outside said envelope, an electrode for collecting said secondary electrons, and means for controlling the number of secondary electrons leaving said electrodes for, the purpose of controlling their potentials.

8. The invention according to claim 7 characterized in that said last means includes a control electrode common to said plurality of electrodes.

. 9. An electric discharge tube comprising an evacuated envelope having therein means for generating a beam of electrons, a plurality of electrodes positioned to be bombarded by said beam, each of said electrodes being substantially insulated or floating whereby it may acquire sub stantially a secondaryemission equilibrium potential, each of said electrodes being adapted to be connected to an element for controlling its potential, and means for controlling the number of secondary electrons leaving said electrodes and thereby causing them to acquire a new potential which is substantially the secondary emission equilibrium potential.

10. In combination, an electric discharge tube comprising an evacuated envelope having therein means for generating a beam of electrons, a

' plurality of electrodes positioned to be bombarded having an output connection, means for controlling the number of secondary electrons leaving said electrodes for the purpose of controlling their potentials, and electric discharge means comprising a plurality of electrically insulated electrodes, each of said output connections being connected to one of said last-named insulated electrodes, said output connections being the sole connections to said last named electrodes;

GEORGE A. MORTON.

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