US2495259A - Taut grid electrode for electron tubes - Google Patents

Description

G. s. JACKSON 2,495,259

r:AUT GRID ELECTRODEFOR ELECTRON TUBES Jian. 24, 1950 Fi1ed Nov. 14, 1945 sheets-sheet 1 GEORGE SAMUEL JACKSON Jan., 24, 1950 G. s. JACKSON 2,495,259

TUT GRID ELECTRODE4 FOR ELECTRON TUBES Filed NOV. 14, 1945 2 s heS-Sheet 2 v uh'lIIAllll FVG. /O v GEORGE SAMUEL JACKSON Patented Jan. 24, 1950 VTAU'I GRID ELECTRODE "FOR ELECTRON ATUBES George Samuel Jackson, y'UnitedfStatesNavy Application November 14, 1945.,.Serial'No. 628;630

(Granted under "the act of .March f3, 18'8'3, as amended April 30, 1928; S370 0. G. T757) 112 Claims.

L1 This invention .relates to a .mount for an electrode of an electron .tube to .-prevent deformation `on heating. .More particularly, this invention relates to a mount for :a planar rgridconstructed to keep the grid AWires taut at .hghoperating temperatures The use of higher frequencies in radio transmission has brought .about radical changes in design of .the .electron 'tubes used .in radio irequency circuits. yOne .outgrowth of the use of 1higher frequencies is the so-called planar type tube .in .which the .electrodes are arranged in :a series of `parallel planes. Concurrently With the use of .higher frequencies, steps have ybeen taken to decrease .the size of -the tube. This `has resuited in operating temperatures higher than those previously encountered.

Because of the higher frequencies and the higher operating temperatures, frequency .drift caused by the deformation of tube electrodes, particularly the grids, has become more pronounced. The deiormationof the grid caused .by Y

the heat generated in the tube elongates the grid wires thus permitting them to sag. 'This disturbs the spacing relationship .between the grid and the other electrodes, and causes undesired changes in 'the operation characteristics of the electron tube. Notonly is such .deformation disadvantageous in the operationof the electron tube when it is used in a static mount, but the altered characteristics become still more objectionable when the .tube is subject to shock .and vibration. The increasinguse of electron 'tubes on 4moving vehicles especially fior military purposes, makes it necessary that the grid structure be kept taut, and therefore less subject to deformation upon shock and Vibration. It is Van object of my invention to provide Supporting structure for a grid or other electrode which keeps such electrede .taut at elevated temperatures.

it isa further object of my invention to provide a mount for an electrode Whichpermits the electrode to expand to equal or greater extent than the mount when subi ect to an increased temperature,

It is another object o'f my invention toprovide an electrode-supporting 'structure which enables expansion to take place upon an increase in .temperature Without afecting the ability of the support to conduct high-frequency currents and/.or the heat generated in the tube when in operation.

It is still another object of my 'invention to provide an electrode mount which isresistant to deformation caused by shock and vibration particularly under 'high temperature conditions,

.In the drawing.:

.Figure lisa sectional vliew .of .an electron tu'be to which my .structure .is .particularly applicable.

Figure 2 shows a .grid structure consisting o'f oppositelydisposedlbowed members.

Figure 43 isa .sectional 'view v.taken on .section v3`3 ofligurefl.

Figure 4 shows `a `ring support `for a grid maintained Sin place by `diametri'callyplaceii .support- .-ing tabs.

lFigure "5 .shows 2a modification of 'the structure ,shoWnlnlFigure 4.

.Figure 6 shows the use :of an l"expansive ring resiliently supported. I

Figure 7 is a sectional view taken 1m section support 'with the `a'dclition of 'an 'annular conducting member between thesnpport'irrgring land 'the base.

Figure 12 is a sectional View takenon section |2I 2 of'Figure lfl.

In Figure '1 a sectional 'View o'f a modern type vof so-called "oilcan tube 'construction is shown in `simplified I"fori-n. The "tube consists of a. cathode '20 `which produces @radiation y'from --the 'circular end portion 22. Thefca'thode is heated fby means "of a heater `2`4 supplied through 'terminal 26. A cylindrical conductor '238 is ihermeti'cally 'sealed to the cathode by means of the annular glass seal 3l). VThe cylindrical conductor as Tin :the Ausual tube of thistype `lsrigiil-y 'connected t'oth'e y'gridsupporting 'metal ring 32 J'and to fthe 4anode 934 by l-means o an annular -gl'ass sea'l 35. 'It will be noted that the cathode, sanctieandrgridzareplanar surfaces in vertically spaced relation. Additional grids may beinterpcsed hetweenath'ecathode and the Vanode .in yaccordance with the tube characteristics desired. It will be seen that the grid wires fare in tclose thermal Yrelation with respect to lthe .heated cathode -20 jand the iheat :generating anode `surf ace .3.1. The l'ieating produced thereby causes the grid wires ltoexpand and to sag, especially with the aid oi gravity unless provision is .made for .keeping .the wires taut. As .-above stated, the change in ,position loi .the .grid wires -undesirably varies the .electrical o1.= era'ting char@ acteristics of .the tube.

`wire A4UA attached thereto.

In Figure 2 is shown one construction which insures that the grid wires shall remain taut even under conditions of elevated temperature. The mount, referring to the assembly, comprises a metal grid frame which consists of two oppositelydisposed bowed members 38. These members are mounted in an aperture provided in the base or supporting member 32. The grid wires 40 are fastened to the frame members 3S and are arranged in a direction perpendicular to the extension 42 at which the frame member is supported on the base member. Members 38 serve not only as mechanical supportsand electrical connections to the grid wire but .also provide through extension 42 a good path for conduction of heat from them to external metal shell 28.

It will be seen that the frame members 38 form a roughly circular grid space. The frame members 38 are formed of a metal having a coeicient of expansion equal to or greater than the grid Y However, the base member 32 is constructed of a metal having a low temperature coe'icient of expansion. Thus, as the temperature of the assembly is increased and the length of the grid wires becomes greater, expansion taking place in the frame members 38 increases the amount of "bow thus keeping the grid wires taut. Preferably the frame members 38 should have a temperature coeicient of expansion which produces elongation of the grid wires slightly greater than that due alone to their elevated temperature. The diierential expansion should preferably not be sulciently great to impart to the grid wires a permanent elongation or set under the temperatures encountered in service although this condition may be obtained if desired.

Figure 4 shows the use of a grid supporting ring 44 constructed of material having suitably high temperature coeicient of expansion. The ring frame 44 is in turn supported by diametrically placed metal bridging tabs 46 which are rigidly attached, for example by welding, to the base 32 and to the ring. The expansion characteristics of the tabs is not critical although it is preferable to use material which has a low temperature coeicient of expansion. In operation an increase of temperature causes the ring 44 to expand in the direction of lateral freedom thereby compensating for the linear expansiontaking place in the grid wires and otherwise causing them to sag. The grid wires may be attached to the supporting ring by any desired means, for example by welding.

terior of the tube.

Figure shows another embodiment of my invention in which the rings are replaced by expansion members 48 joined by end pieces 50 of low-expansion coecient material to which the grid wires 40 are attached.

' Figures 6 and 7 show a resilient form of metallic connectors 52 joining the grid ring 44 with the supporting base 32. This construction permits the grid ring to expand freely in all directions Yand yet maintains the desired fixed planar relationship between the grid ring and the supporting base. Connectors 52 also serve to conduct heat from the grid structure to the exterior of the tube.

l In Figure SI have shown a structure in which the grid-supporting ring 54 and a supportingbase 5G are formed integrally from the same piece of metal. Integral tabs 53 serve the purposes of ex- 'Iabs 4S also provide paths for conduc- H tion of heat from the grid structure to the exlill tension 42, Fig. l, tabs 46, Figs. 4 and 5 and connectors 52, Figs. 6 and 7.

In Figure 9 the supporting ring 60 overlaps the base 62. The ring and the base are fastened together for example, by means of a tack weld at points 64. This structure has the advantage that the thermal path is shortened by reason of the close proximity of the supporting base and the grid ring. It has the further advantage of providing a means for minimizing the capacitance and inductance effect of the separate grid ring and supporting base structure of Figures 2, 4, 5, 6 and 8.

In Figures 11 and 12 improved thermal contact between the base member 62 and the grid ring 60 is provided by joining the base and grid ring by an annular conductor 66. This conductor is made of thin ilexible material of suitable thermal and electrical characteristics. If desired, a rib or convolution may be formed in this conductor as shown at 68 in order to take up the diierential expansion occurring between the ring 69 and the base 52. The diametrically placed tabs 46 are joined to the grid ring 6U and the base 62, for example, by means of tack welds. rIhese tabs maintain the grid ring and the base $2 in ilxed planar relationship.

It will be seen in Figures 6 and l1 that the gridsupporting structure which I propose is equally suitable for a grid composed of mutually perpendicular wires in the form of a network or screen. The screen type of grid is also applicable in the structures of a network or screen. The screen type of grid is also applicable in the structures shown in Figures 2, 4, 5, 8 and 9 since the tautness of the wires running in one direction will result in the maintaining in place of the mutually perpendicular wires.

While I have, for the sake of ready understanding, described my electrode supporting structures with particular reference to a grid, it will be obvious to one skilled in the art that this structure is applicable to any electrode or multiple electrodes within an electron tube in which it is necessary to maintain a planar surface in spite of use over a wide temperature range.

It will be obvious to one skilled in the art that a number of grids in accordance with my construction may be placed in superposed relation to maintain constant overall tube characteristics even at elevated temperatures.

While the electrode supporting structure is particularly applicable to use in the tube having vertically stacked electrodes such as the lighthouse or oil can type, my invention is applicable in other types of tubes where it may be desired to maintain the shape of the electrode or to compensate for expansion under conditions of elevated temperatures.

While the invention admits various additional modifications and alternative constructions, I have shown in the drawings and have described only the preferred embodiments. It is to be understood, however, my invention is of scope dened by the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What I claim is:

l. A mount for a planar electrode comprising a base having an aperture, a pair of oppositelydisposed bowed thermally expansive members secured in said aperture, the ends of said bowed members engaging said base, and a metallic electrode consisting of a plurality of conductors in a plane, the ends of said electrode conductors engaging said bowed members.

2. The subject matter as claimed in claim 1, said base member being provided with diametrically-opposed notches receiving the ends of said bowed members.

3. An electron tube including a mount for a planar electrode comprising a ring member designed normally to expand upon being subject to increased temperature, a planar electrode fastened at displaced points thereof to said ring, said electrode consisting of material having a thermal coefcient of expansion not greater than that of said ring, a base member, and supporting tabs engaging said ring and said base member at least at two diametrical points of said ring to allow expansion of said ring.

4. An electronic device comprising, a base ring,

a frame composed of bowed members in confronting relationship defining an opening, the ends of the bowed members attached to the base ring and defining bridging means between the frame and base ring, and a filamentary grid connected to the bowed members and spanning the opening perpendicularly of the direction of the extensions.

5. In an electron tube, a base ring, a frame member centered in respect to the base ring and consisting of end pieces and oppositely bowed confronting expansion members connected by the end pieces to define an opening, extension tabs attaching the expansion members to the base ring and forming bridging means between the frame and base ring, and a filamentary grid attached to said frame member and spanning the frame opening perpendicularly to the direction of the extension tabs.

6. An electronic device of the class described, comprising a metal ring and a rigid mounting therefor, a thermo-expansive apertured frame disposed parallel to said ring with its aperture substantially aligned with the hole of the ring, a plurality of parallel grid wires secured at their ends to opposite sides of the frame, and means rigidly securing said frame to said ring in two diametrically opposite zones that are aligned in a direction perpendicular to the grid wires.

'7. An electrode comprising, a Afirst annular metallic member, a grid consisting of a plurality of substantially parallel wires the opposite ends of which are attached to opposite sides of said annular member, and a pair of sole supporting members for said annular member, said supporting members being attached to opposite sides of said annular member at points which form a line substantially perpendicular to said parallel wires, and a second annular metallic member which is relatively xed surrounding said first annular member, said second annular member being attached to said supporting members to restrain ex.. pansion of said first annular member in a direction substantially perpendicular to said parallel wires.

8. In an electronic device having a mount for a planar electrode comprising a ring of conducting material, a plurality of wires fastened at their ends to said ring, forming a grid, said wires being constructed preferably of material having a thermal co-eflicient of expansion not greater than that of said ring, a rigid base member, and ring supporting elements attached to said base member and engaging said ring at diametrically located points whereby expansion of the ring relative to the base is facilitated.

9. In an electronic device, a base ring, a ringlike frame centered within and in respect to said base ring and consisting of diametrically located heat expansible members and diametrically located end pieces joining the ends of the expansible members, supporting tabs attaching the'expansion members to said base ring at the approximate central points of the respective expansion members, and a iilamentary grid connected at its ends to said end pieces, said end pieces having a heat expansibility less than that of said expansion members.

10. An electronic device comprising a rigid support element, a heat-expansible, curvilinear, elongated frame secured xedly at displaced points to said support element, and a grid wire attached to said frame and extending perpendicularly to a line joining said displaced frame points, said grid having a co-efcient oi. thermal expansion not greater than that of said frame whereby the grid is held taut irrespective of variation in operating temperatures of the device.

11. In an electronic device having a mount for a planar electrode comprising a ring of conducting material, a plurality of wires fastened at their ends to said ring, forming a grid, said wires being constructed preferably of material having a thermal co-efcient of expansion not greater than that of said ring, a rigid base member, and ring supporting elements attached to said base member and engaging said ring at diametrically located points whereby expansion of the ring relative to the base is facilitated, said base member and ring being coplanar and integral.

12. An electronic device as described in claim 6 modified in that the frame surrounding the frame aperture overlies the inner edge of the base ring.

GEORGE SAMUEL JACKSON.

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

UNITED STATES PATENTS Number Name Date 2,153,949 Varian Apr. 11, 1939 2,163,156 Samuel June 20, 1939 2,261,154 Hansen et al. Nov. 4, 1941 2,367,331 Bondley Jan. 16, 1945

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