US2204306A - Vacuum tube - Google Patents

Description

`w. T. HARls Y 2,204,306

June 11, 1940.

VACUUM TUBE Original Filed Nov. 10, 1938 l 2 Sheets-Sheet 2 l June lul., 1940 vwmmr r. Hmm, `'rmi yResearch Corporation, poration of New York m'igrzul..animera. Y

New York,'N. Y., a corormmi application ummmro, 193s, serial No; f

239,885. Dividedv and this ber 27, 1938, Serial N0. 241,983

application Decora- 1s claims. `(ci. esto-21.5)

This invention relates to vacuum tubes and pary ticularly to vacuum tubes having ,grid elements that draw substantially no current. y'll'he novel tubes are particularlyv adapted for use at ultra high frequencies but may be used to advantage f at lower frequencies.

The tubes now used inultra high frequency circuits are of clumsy shapes and have poorly arranged leads which are responsible for substantial inductance and high frequency resistance in ultra highfrequency circuits that are built around the tubes. The output of the prior tubes has been limited by these faults and by the grid dissipation, i. e. grid currents due toA electrons captured by the grid in their flow from cathode to plate. A recently produced ultra high frequency tube of the water cooled anode .type ex'-l hibits a -grid current oi' from one-fifth to onehalf of the anode current when used as an oscilf golator. The output of this tube tends towards zero as the wavelength is shortened to one meter.

Objects of the present invention are to provide vacuum tubes having grids of novel design that are not bombarded and therefore draw substantiallyno grid current. An object is to provide'k vacuum tubes having elements that maybe directly incorporated into the oscillatory and lthe .water cooling circuits. oi' `V an amplifier ory oscillator. An object is to provide vacuum tubes hav- ;mLing one or more tubular anode elements that y extend through the tube. and assemblies of cathode and grid elements in cylindrical symmetry about the anode tube or tubes. Further objects are to provvide tubes of the type -stated in4 which the grid elements are" located at each side of the I spaces, i. e. the Apathsfof electron. flowbetween 4 thecathode elements and the centrallylocated' hollow anode element.

These and other objects and advantages of the invention will befapparent from the following specification whentaken with the accompanying vdrawings in which: I

Fig. lis a schematic transverse'section through y 1 a tube embodying the invention;

xFig. 2 'isa perspective view of the same;` Figs.' 3 and tare schematic diagrams of-frnul-4 f V:tiple element'water-coo'l'ed tubes;

Fig. 5 is a transverse'sectlonal 'view through a double screen grid tube; y Fig. 6 is a side'elevation of the same; e Fig. 7 is a sectional view substantially on line 'i-'iofFig.6; l

Fig. 8 is an exploded view of the cathode and grid electrodes of the doublel tube; and L Fig. 9 is an enlarged detail view of .the cathode andcathode shield elements.

, Certain features of the invention as applied to tubes for use at ultra high frequencies may be incorporated in simpler tube constructions, as 15 shown in Figs.- l and 2, which may be operated at radio andlower frequencies with elciencies not obtainable with prior tubes.A The tube elements comprise an anode A havingv a semi-cylindrical section which merges into a flat heat-radi- 10 ating flange, a illamentary cathode C, preferably` a ilat strip or ribbon extending parallel to the axis of the semi-cylindrical plate section, an

approximately U-shaped cathode shield .CS at the side of the nlament opposite the anode and 16 located outside of the space between the anode A and `cathode C, and a grid G in the form of a pair of parallel ribbons extending along opposite sides of the space between the cathode and anode. The elements are supported'within an evacuated 20 yenvelope T inthe usual mannery by= their leads,

the control grid ribbon G having a common lead which supports the same and the cathode shield lCS being connected to one ofthe cathode-leads.

'This electrode assembly has the general form, 25 as .viewed in cross-section, of an electronlgun yand the control grid lies outside of the electron stream and is not bombarded during use ofthe ltube as an oscillator. v 'Iubes of this design have been operated at ultra high frequencies with grid currents reduced to the order of 4one one-thousandth of the plate current, thus substantially l eliminating overheating of the grid as a factor limiting eillciency and/or the highest frequency vof operation. With an anode A of tantalum and a construction of substantially the dimensions of the vpatent drawings, the tubes of Figs. 1 and 2 have converted about 75 wattsofpowerk at ultra high frequencies., 'I'hisis equivalent to the performance of prior small ultra high frequency tubes of more complex or expensive construction and operating without cooled anodes.

Tubes of higher power koutput may bev con-` structed, as shown in Fig. 3, by -a multiple assembly of a plurality of electron gun units about a central tubular anode A through which waterk may flow tocool the anode. An assembly of six units, asshown in Fig. 3, has been operated with high emciency at wave lengths of the order of one meter; the'six illaments'being of tungsten 50 0.050" wide, 0.001" thick and 1" long, with the laments equally spaced to define a cylindrical surface of about 0.75" diameter. Amplification constants between 30 and y504 were obtained, and the tube exhibited very linear plate characteristics that intersect the zero current axis smoothly, i. e., they exhibit sharp cut off characteristics. For operating conditions leading to maximum power output, the grid current remained vanishingly small; of the order ofi/1000 of plate current.

Increasing the cathode surface will giveV greater power converting capacities, and such increase in the cathode surface may be obtained through the use of more and/or of longer 'cathode ribbons. Exceedingly compact constructions may be obtained with the electrode geometry shown schematically, and on a larger scale, in Fig. 4. The cathode shield CS' takes the form of a cylinder having radial ribs that define compartments in which the cathode ribbons C are located, the grid G' being formed by ribbons or strips in radial alinement with the ribs of the cathode shield.

Screen grids may be desirable to simplify neutralization problems when modulating over an extended frequency band, asin television transmission, and the screen grid will comprise ribbons or strips in alinement with the control grid ribbons. The incorporation of two sets of electrode assemblies in one envelope is especially advantageous in screen grid tube constructions as this simplies a connection of the two screen grids. by a low impedance conductor. An appropriate design, as shown in Fig. `5, comprises two electrode assemblies that each include the elements shown in Fig. 4 and, in addition, an inner set of grid ribbons constituting a screen grid. The electrode assemblies may be in close proximity since each is within its cathode shield cylinder and the bar connecting the screen grids may therefore be quite short. Y

As shown in Figs. to 9, the hollow anode of the vacuum tube is an oxygen free high conductivity copper tube I that extends centrally through a glass envelope 2 that is preferably of the type designated '10'1DG by the Corning Glass Company. 'Ihe opposite ends of copper tube I extend through and are silver soldered to a rigid sleeve 3 and to a sylphon bellows 4 which, in turn, is soldered to a sleeve 3. These sleeves are Kovar (a glass sealing alloy) and they are connected to the main body 2 of the envelope by intermediate sections 5 of '704AJ glass manufactured by the Corning Glass Company. The

different coeflicients of expansion of the copper and glass necessitates the sylphon bellows or expension joint at one anode seal.

The cathode ribbons are 'connected between rings 6, 1 at the bottom of the assembly and an upper ring 8 that is yieldingly supported from the ring 1 by telescoping connections that each Vcomprise a wire 9 connectedby a hollow glass bead vIll to a wire II having la cupped washer I2 secured thereto to carry alight tungsten spring I3v that bears against a washer Il, the wire II extending freely through washer Il and the looped end of a wire I5 that is attached to the ring 8. The rings G, 1 are preferably formed as lo'ops in the ends of relatively long wires, thus leaving projecting ends 6', 1', respectively, that extend through the envelope 2 to serve as the cathode terminals and to support the cathode assembly. Alternate cathode elements I 6, Ilia extend between ring 8 and rings 6, 1, respectively, the ring 8 being of somewhat smaller diameter than rings 6 and 1,*and short studs 6a, 1a being spot welded to rings 6, 1, respectively, to make connection to the lower ends of the cathode elements. The cathode screen comprises the cylinder I1 and radial ribs I8 which are carried by the ring 1 and terminate short of the upper cathode ring 8.

The control grid assembly comprises upper and lower rings I9 that are connected by a wire support to which the grid lead 2| is attached. The grid elements 22 are secured to the rings I9 in .radial alinement with the shield ribs I8. Similarly, the screen grid assembly includes upper and lower rings 23 that are spaced by a wire 24 and carry short studs 25 between which the screen grid ribbons 28 are connected. In a double assembly tube, the relatively rigid wires 24 of the screen grids are connected by a shorting bar 21 to which the terminal 28 is secured. The cathode shield cylinder I1 is'apertured to pass the terminals 2| and 28 that support the control grid and screen grid, respectively.

This application is a divisionof my copending application" Serial Number 239,885,.filed November 10, 1938.

It is to be understood that the constructions herein shownl and described are illustrative of the invention and that various modifications that may be developed by those skilled in the art fall within the spirit of my invention as set forth in the following claims.

I claim:

1. A vacuum tube comprising an evacuated envelope, an anode, a cathode assembly comprising an electron emitting member and a nonernitting member partially enclosing said emitting member at the side thereof opposite said anode and electrically connected to a point on the emitting member to assume the potential thereof, and means for controlling the intensity of the electron stream between said cathode assembly and said anode; said means comprising paired control gridmembers straddling the space occupied by the electron stream and having surfaces substantially parallel to the general direction of the electric field between said anode and the cathode assembly.

2.v A vacuum tube as claimed in claim l, wherein said electron emitting member is a fiat strip in a plane normal to the path of the electron stream, and said non-emitting member is located outside of the space between said flat strip electron emitting member and said anode.

3. A vacuum tube as claimed in claim 1, wherein said non-emitting member is of approximately U-shape.

4. A vacum tube as claimed in claim 1, wherein said electron emitting element is a flat ribbon in a plane normal to the path of the electron stream, and said non-emitting member is of approximately U-shape and located substantially entirely at the side of said electron emitting member opposite said anode.

5. A vacuum tube comprising an evacuated envelope, an anode, a cathode assembly comprising an electron emitting fllamentary member-and a non-emitting shield member partially enclosing and spaced from the fllamentary member, an electrical connection from said shield member to a point on said lamentary member, and grid means between said anode and cathode assembly to control the intensity of the electron stream; said grid means comprising a pair of members straddling the space occupied by the electron stream and having surfaces substantially parallel to the general direction of the electric lfield between said anode and the cathode assembly, and

a common conductive support and lead for said ment, and a connection within said envelope be element and extending along opposite sides 'of the space between said cathode and anode elements,l an approximately U-shaped cathode shield at the side of said cathode element opposite said anode element and grid element, the

edges of said cathode shield terminating substantially in a plane through the cathode yeletween said cathode shield and iilamentary cathode. i

7. A vacuum tube comprising an evacuated an end of said envelope, a ilat ribbon cathode element, electron accelerating means consisting of a single-anodey element, a grid comprising ilat ribbons extending along each side of the space between said lcathode and anode elements, andan approximately U- shaped cathode shield at the face of said cathode opposite said grid and having side portions'opposed to and in substantial alinement with the respective at ribbons of the grid.

8. A vacuum tube comprising an evacuated envelope, an anode element extending through and to opposite sides of said envelope, a cathode comprising iilamentary members in spaced relation lying in a cylindrical surface substantially coaxial with and surrounding-said anode element, cathodeshield means outside said cathode members and including ribs extending between adjacent cathode members, and grid means comprising at ribbonsradially disposed in alinement with the ribs of said cathode shield means and in the space betweensaid anode and said cathode members. f. v

9. A vacuum tube as claimed in claim`8,\where in said grid means comprises concentrically dis- I DOsed control and screen in radial alinement.

10. A vacuum tube comprising an evacuated envelope, a tubular anode extending through said envelope, a cathode surrounding said tubular grid sets of :dat ribbons anode, and grid means for controlling the intenv sity of the electron ow from said cathode lto said anode; said cathode comprising a plurality of flat ribbons parallel to the axis -oi said anode and in a cylindrical surface coaxial with said anode,a pair of terminal rings surrounding said A anode members.

` both anode members.

anode at one set` of ends of said ribbonasaid ribbons being connected in alternation to said rings,

a ring adjacent the other set of ribbon ends and connected to all of said ribbons, and leads for said cathode extending through said envelope from said pair oi.' rings.v f

11. A' vacuum tube as claimed in claim 10,`in combination with spring means maintaining said ribbons under tension.

12. A-vacuum tube as claimed in claim 10, in combination ywith grid means v'comprising a pluralityof radially disposed ribbonv elements in the vspace between said cathode and saidanode, said ribbon elements being in staggeredrelation to said cathode ribbons. v

' 13. vA vacuum tube as claimed in'claim 10, in combination with a plurality of grids between said anode and rsaid cathodes, each of said grids comprising a plurality of ribbon elements in the space between said cathode and said anode, the ribbon elements of the grids being in radial alinement with respect to said anode and staggered with respect to the ribbons of said cathode. 14.' A vacuum tube as claimed in claimlO, in combination with a cathode shield comprising a cylinder secured to one ofy said rings and .extending along and in'spaced relation to said cathode ribbons, and ribs on said cylinder extending radially between adjacent pairs of the vcatliode ribbons. v j 15. A tubey comprising an evacuated envelope, a pair of tubular anode members extending, in parallel relation through said envelope, an assembly of circumferentially spaced fllamentary cathode members arranged in cylindrical symmetry about each anode member, cathode shield means atthe outer side of each cathode member and extending between adjacent cathode members, and radially disposed'control grid members at opposite sides of the space between the respective cathode members and their associated 16. A tube as claimed in claim 15, in combination with screen grid members in radial alinement with the several control grid members,v and means within the envelope electrically con' necting the screen grid members associated with wrmsua T. nanars.

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