US2898504A - Electron discharge device - Google Patents

Description

Aug. 1 5 R. L. NORTON 2,898,504

ELECTRON DISCHARGE DEVICE Filed Jan. 17, 1957 2 Sheets-Sheet 1 Aug. 4, 1959 R. L. NORTON ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed Jan. 17, 1957 INVENTOR. flaw/er Z. Wax/"m Arfmewyts' ELECTRON DISCHARGE DEVICE Robert L. Norton, Santa Barbara, Calif., assign'or to Penta Laboratories, Inc., Santa Barbara, Calif., a corporation of California Application January 17, 1957, Serial No. 634,667. 12 Claims. or. 313-299 This invention relates to an electron tube structure and more particularly to electrode configurationswithin electron discharge devices of the type arranged to form concentrated electron beams.

The principalobject of this invention is to provide an electron tube having improved anode efficiency.

Another object of the invention is to provide an electron flow guide arrangement to extend the range wherein the plate current is relatively insensitive to plate voltage fluctuations so that a relatively large plate voltage swing will produce minimal plate current reduction under conditions of low plate voltages and therefore will result in greater plate efliciency.

It has been found in many conditions of use that an electron'tube or discharge device will exhibit superior linear, distortion free characteristics whenthe flow of electronsfrom the cathode to the anode is guided or directed so as to fall upon the anode in substantially concentrated beams. A beam formed concentration of electrons at the anode, for example, improves the linearity in power amplifiers where the plate voltage swing is arranged to fall below the screen voltage.

A further object of this invention is to provide an improved electron flow guide or directing arrangement inan electron, discharge device which provides a higher concentration of emitted electron flow toward certain preselected anode areas. 7 I

' A feature of this invention is that with the improved electron flow guide or direction arrangement the linear operating ranges'are greatly increased.

A more specific object of this invention is toprovide an aligned grid electron tube or discharge device having one set of grids formed with elongate beam deflecting surfaces disposed in alignment with selected interposed grid members. This combination forms spaced electron beam guides that direct a highly concentrated flow of electrons outwardly from the cathode between two adjacent deflecting surfaces so the beam strikes the anode in a direct path of travel.

'A still more specific object of this invention is to provide an electron beam control and directing arrangement to form and direct flow of a concentrated electron beam from cathode to anode by means of spaced pairs of electron defiecting members disposed adjacent the anodeand formed to provide an electron deflecting surface substantially parallel to the direction of electron flow and of greater area than the leading face of the deflecting member adjacent thecathode. V

It is an object of the-invention to provide one group of each class of grid members aligned with the beam deflecting elements and a member or members of another group of each class 'of grid members disposed between selected members of the latter group. H Y Another feature of this invention is thatthebeam control elements are enabled to form the electron beam guide while at cathode potential whereat it isunnecessary' to 7 provide a separate power supply for the guide elements;

ice

- Because of this feature the guide elements may be con-- nected directly to the tubes cathode internally of the tubewithout impairing-materially the efficiency of tube operation. o

Other objects of the present invention will become apparent upon reading the following specification and referring to-the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several'views.

In the drawings:

Fig. 1 is a cut away perspective of a preferred em- H bodiment of the invention.

7 Fig. 2 is a top plan sectional view of the embodiment of Fig. 1 taken at line 2-2. Fig. 3 shows a graphic illustration of plate voltage and plate current and indicates the improved characteristics of a tube of this invention.

Fig. 4 is a diagrammatic view of the electrode structure of'the invention showing the path of electron flow in relation thereto.

:Fig. 5 is a fragmentary perspective of another embodiment of a beam deflecting electrode structure;

-'Fig. 6 is a fragmentary elevational view of another embodiment of the invention.

-Referring now to the drawings and with particular reference to Figs. 1 and 2 there is provideda preferred embodiment of the invention in which an electron discharge device A is formed with an anode cup mounted on a tube base 16. The anode cup and tube base form a sealed envelope 17 which is evacuated to form the hous-' ing for the electrode elements of the tube. In this embodiment anode B functions in a dual capacity as the plate or anode electrode for the tube and also forms structural elements of the envelope 17. It is to be understood, ljowever, other conventional anode or plate structures could be used such as in arrangements where the entire anode is enclosed in an evacuated envelope. The tube A generally comprises a heater 18, a cathode, a control grid, a screen grid and a beam guide means indicated generally r at C,D,'E, and F, respectively.

The heater 18 is housed within the cylindrical cathode C and is arranged in a conventional manner to. be 'con-' nected to a filament power source so as to elevate the temperature of the cathodesufficiently to obtain electron 3 emission therefrom.

l The control grid D comprises a cage like structure which forms members 20 and 21 of control grid which in this embodiment takes the form'of bars arranged in vertical equally spaced parallel alignment 'both in respect to each other and the cathode C.

The screen grid E comprises a similar but somewhat larger cage like structure formed with screen grid bars or members 22 and 23 also arranged in parallel equally spaced alignment with respect to each other and to the I cathodeC. The total number of control and screen grid bars is equal and bars 20 and 21 are radially aligned with bars 22 and 23respectively and with cathode C. i

I The electron beam control means F comprises a cage structure'which comprises parallel equally spaced metal ribbons 37 in parallel equally spaced alignment both with respect to each other and to the cathode. .In this. embodiment of the invention there is provided one ribbon 37 for each aligned pair of. control and screen grid bars 20 and 22 respectively. Each pair of aligned bars 20 and 23 are aligned. with a ribbon 37 and are desig nated as ribbon aligned bars, and the members or bars 7 21 and' 23 between the ribbon aligned bars 20 and22l are designated as intermediate grid bars. v In operation of the tube A, the anode Bis provided with a relatively high positive voltage with respect to the cathode. The screen grid E is energized witha.

Patented Aug. 4, 1959.

positive potential somewhat lower than the plate potential; bias voltage upon which is superimposed a signal or driving voltage which varies the control grid potential. The precise bias voltage value of the control. vgrid is largely dependent upon the class" of operation in which the tube is tobe employed; The beam directional means F may \be arranged at cathode potential so in some tube designs the cathode C and ribbons-'37 may b'ebonnected'together interiorly of the tubeA'; Insome instances the ribbons may be elevated slightly above above specified will operate within an exceedingly widerange of plate voltage swing without substantial. plate current drop in the region of low plate-voltages.

. Further, the range has been found to include the area wherein the screen voltage maybe considerably above:

the plate voltage. The high screen voltage provides a high'plate current without the necessity of driving the grid positive.

The control grid D'is' energized-bya'negative Thus the tube is particularly satisfac-- trons back to the screen grid. In the configuration of Fig: 4 the-relatively'wide'or elongated guide surfaces 38 cause the electrons to be retained within the guide influence of the ribbons 37 until they reach a point where they are directly attracted by the positive anode more than by the screen even where the plate voltage is arranged to swing below the-.screen-voltage. It can be seen that the general path of electron flow against the anode is directed radially-toward the anode and reduces loss by reasonof tangential approach. This reduces the likelihood ofthe electrons being collected by screen grid E before reaching the anode.

Two requirements are believed important to obtain the electron= 'guidecharacteristic above specified. First, the

tory for utility in linear amplifiers suchLasradio frequency power amplifiers for incorporation. in single side band transmissions.

Fig. 3 shows a plot wherein the plate voltage isfindicated by the designation. E and plate current at l The. chart shows an ordinary tetrode havingunaligned grids plotted at 31.

Curve 33 shows that greater plate current can flow with lower plate voltages than heretofore possible V'Withsuppressor grid tubes working under similar conditions-..

The electron flow of this tube structure is illustrated diagrammatically in Fig. 4. In Fig. 4 cathode C; control grid D, screen grid E and beam deflecting elements. F are diagrammaticallly illustrated in a sectional plane.=

In Fig. 4 the number of.

Curve 32 shows a conventional: pentode tube having. aligned grids. Curve 33-shows an. equivalent tube made-in accordance with this invention.-

aligned electron: re-action surfaces 38 must be substantially longer than the surface 41 facing the cathode so the maximum electron deflection surface is immersed in the path of electron flow with both surfaces 38 substantially-parallel with the desired path of electron flow.

The second requirement for the proper operation of each electron gun-is that' there be at least one intermediate control grid member disposed between the ribbon aligned g-ridmembers. The number of intermediate grid members and the-relative spacing-'ofthe' members with respect torelativa distance between cathode and' anode is dependent upon various operational requirements, and also. the intendedvoltage ranges within'which the tube is designed toberoperatedtionthatotherequivalent means ofconstructing such a radially elongate: guide. could also be employed satisfactorily.1 For example referring to Fig. 5, each ribbon 37 could-be replaced with three spaced vertically aligned wiresAS suppliedwith-the same voltage as the ribbons 37. Suchadeviee would operate to provide the elongated-defleeting surfaceand-would function in substantially the same manner as ribbons 37.

. Infthe embodiment of the invention shown in Figs. 1 and-2 the g-rid members 21 have been generally indicated asparallel with respect to the cathode. It is also contemplated-to-be-within. the scope of the invention that Specifically, the relatively tangential paths of eleetron flow are indicated at T as opposed to the relatively radial paths R and the diagram illustrates that the electrons in paths T having large tangential components-of.

velocity are deflected radially toward the anode andare thus not permitted to return to the screen. I

'It is understood that it is within the scope of the invention to include one or more intermediate grid bars 21 and 23 which are disposed between ribbon aligned grid bars 29 and 22. It is preferable that the number of a class of grid members or bars be an integral mul1p e ur ahgned wlth, two wires 46a and 48a of the total number of deflecting elements'and that the members or bars in each class be equally'spaced from one another.

The areas between adjacent electron guide ribbons 37,

is, in effect, an electron gun in which a beam of highly concentrated electron flow is directed againstthe anode B. Electrons emitted from cathode'C are arranged to pass from cathode between control grid bars 20 and21 and are then propelled between screen grid bars 22 and 23. The screen grid'E functions as an accelerating element to project electrons toward anode B. When the electrons are between the electron guide. ribbons 37 there is a general repulsion affected by the'guide ele-' ment ribbons which tend to direct the electrons inwardly toward the mid-point between each two ribbons.

In prior art tubes employing. suppressor grids there is a'tendency for the'suppressor grid'to deflect some electhe electron gun could be oriented horizontally in a. tube structure such asindicatcd in Fig. 6. In Fig. 6 a tube G is provided with two parallel control grid wires 46 and 46 form'ed'in spaced helices circumscribing the cathode47.. A set of screen grid wires 48 and 48 are arrangedlin interposed helices circumscribing the cathode exteriorly of the control grid wires 46 and 46 and withthes'creen grid'wire 48 aligned with the control grid wire 46% and with the screen grid wire 48'? aligned with eontrollg'ridwire 46 A beam deflecting element comprising a ribbon'member 49'i's formed in a helix circumscribing 'sc'reen- 'grid'wire 48*- and with the surface 50 of ribbon 49' aligned to face cathode 47 so that the two flats 51 of the ribbonprovide electron re-action'or guide Guide wires46 an'd 48 form the intermediate grids. The elements of the gridsand guides of the electron gun are thus"formed-by'adjacent' turns of the helix formed by wires'46 'and' 48 and ribbons 49. In this tube embodiinent'there'will'beastream or beam of electrons directed against anode55' of tube 6' formed by an electron gun between'adjacent' turns or folds of the helices. The helical electron beam will be disposed in the gap formed by adjacentturns of ribbon'49 Tube G thus functions insubstantially-thesame'manneras described in Figs: 1 and 2 and illustrated'in' Figs. 3 and 4 except that the electron beam is directed in a helical pattern ratherthan the vertical pattern as before described.

Although the foregoing" invention has been described i in some" detail 'byway of illustration and example for that certain changes and modifications may be practiced within the spirit of the invention as limited only by the scope of the appended claims.

What is claimed:

1. An electron discharge device having a cathode and an anode and a control grid comprising means to channel electron discharge fiow through a selected path from cathode to anode, said means comprising electron deflector elements aligned with selected spaced grid members but not with others and immersed in the flow path of electrons from cathode to anode, said'elements being elongate in the direction of electron flow.

2. An electron discharge device having a cathode and an anode and a control grid comprising spaced means to form a channel of concentrated electron flow through a selected path from cathode to anode with minimal divergence and maximum suppression of secondary emission, said spaced means comprising electron deflector elements aligned with selected spaced grid members and arranged to straddle other of said grid members, said deflector elements immersed in the path of flow of electrons from cathode to anode.

3. In an electron discharge device of the type having a cathode to emit electrons and an anode to receive electrons, the combination of first and second control grid means disposed between the cathode and anode and electron beam deflecting means disposed between said grid means and said anode, said deflecting means having two oppositely facing elongate electron reaction surfaces between the anode and cathode and aligned with said first gn'd means with said first and second control grid means each being substantially equidistantly spaced from said cathode, and said second control grid means disposed between said first grid means.

4. A device according to claim 3 and wherein each said element of said deflecting means comprises a plurality of aligned wires.

5. A device according to claim 3 and wherein each element of said deflecting means comprises a conductive ribbon.

6. A device according to claim 3 and wherein said first and second grid means each comprises a length of wire formed in a helix around the cathode and the members of said first grid means comprising adjacent turns of the helix and wherein said electron beam deflecting means comprises a length of ribbon arranged in a helix formed around the first grid means.

7. In an electron discharge device of the type having a cathode to emit electrons and an anode to receive electrons, the combination of first and second control gn'd means located between the cathode and anode, first and second screen grid means disposed between said control grid means and said anode, electron beam deflecting means arranged between said screen grid means and said anode, each said first control grid means, first screen grid means, and electron beam deflecting means having a pair of members disposed in spaced aligned relation, each member of said deflecting means having two oppositely facing elongated electron reaction surfaces extending between the anode and cathode aligned with a respective member of said first control grid means and said first screen grid means, said first and second control grid means being substantially equidistantly spaced from said cathode, said second control grid means having at least one member disposed between two members of the first control grid means, said first and second screen grid means being substantially equidistantly spaced from said cathode, and said second screen grid means having at least one member flanked by two members of said first screen grid means aligned with a member of said first control grid means.

8. In an electron discharge device of the type having a cathode to emit electrons and an anode to receive electrons, the combination of control grid means disposed between the cathode and anode arranged to control the flow of electrons therebetween, electron beam deflecting means between said control grid means and said anode todeflect electron flow to channel a concentrated electron beam directed toward the anode, said deflecting means comprising a plurality of elements each having two oppositely facing elongate electron reaction surfaces extending'between the anode and cathode to guide electron flow adjacent thereto in a path generally parallel to said surfaces, said control grid having a plurality of spaced apart members with one said member aligned with each deflect-,

deflecting members disposed between said grid members and the anode, each said deflecting member disposed parallel to and aligned with one said first grid member, said deflecting member in cross-section formed with two elongate faces and at least one smaller face, said small face facing said cathode and said elongate faces arranged in alignment with a first grid member and cathode in position so that both faces are immersed in the electron stream flow from the respective sides of the aligned first grid member, and at least one said second control grid member arranged between each two first control grid members and spaced substantially equidistantly therewith from said cathode.

10. The combination according to claim 9 and wherein there is provided first screen grid members aligned between each first control grid member and' aligned deflecting member, and at least one second screen grid member disposed between each first screen grid member and spaced substantially equidistantly from said cathode in alignment with a second control grid member.

11. In an electron discharge device of the type having a columnar cathode to emit electrons and a cylindrical anode circumscribing the cathode to receive electrons, the combination of a plurality of parallel, staggered, equidistantly spaced first and second control grid members arranged to circumscribe the cathode between the cathode and anode and spaced equidistantly from said cath ode; a plurality of parallel, staggered, equidistantly spaced first and second screen grid members arranged to circum-- scribe the cathode between the control grid members and the anode and each spaced substantially equidistantly from said cathode; each said first screen grid member arranged in alignment with a first control grid member and each said second screen grid member arranged in alignment with a second control grid member; a plurality of electron beam deflecting members disposed between said grid members and the anode; each said deflecting member disposed parallel to and aligned with one aligned pair of first screen and control grid members; and each said deflecting member formed with two oppositely facing elongate electron beam reaction surfaces disposed between the cathode and anode and aligned with respectively aligned grid members, and a substantially smaller electron beam reacting surface facing the cathode.

12. In an electron discharge device of the type having a columnar cathode to emit electrons and an anode to receive electrons circumscribing the cathode, the combination of: a first control grid member arranged in a helix circumscribing the cathode; a second control grid member arranged in a helix interposed between turns of the helix formed by said first control grid member; said first and second control grid members equidistantly spaced from said cathode; a first screen grid member formed in a helix circumscribing and aligned with said first control grid member; a second screen grid member formed in a. helix interposed between said first screen grid member and circumscribing said second control grid member and ing said first screen grid member and aligned therewith; said electron beam deflecting member formed with two oppositely facing electron beam reacting surfaces extending between the cathode and anode in alignment with the first screen grid member and first control grid member; and a substantially smaller electron beam reaction surface facing the cathode.

References Cited in the file of this patent UNITED STATES PATENTS

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