US2656479A

US2656479A - Mount for electron discharge devices

Info

Publication number: US2656479A
Application number: US182011A
Authority: US
Inventors: William B Brown
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-08-29
Filing date: 1950-08-29
Publication date: 1953-10-20
Anticipated expiration: 1970-10-20
Also published as: DE896686C; NL90094C; GB692239A; FR1038769A

Description

Oct. 20, 1953 w B. BROWN MOUNT FOR ELECTRON DISCHARGE DEVICES Filed Aug. 29, 1950 INVENTOR 1111mm B.BR0111N Patented Oct. 20, 1953 UNITED 2,656,479 MOUNT- F oR ELECTRON IiIsoiiARGE DEVICES William *B; Brown, Hasbroucli Heights; N; .L, as signor toRadio Corporation ofrAmerica;a;'-:cor-= poration of Delaware:

Application August 29, 1950;,sena1 N6. ration- 8 Claims; 1

Conventional filamentsupporthooks" or anchors" do not function well when the filamentary oathod e is impressed withrelatively high voltages an'dacquires ahigh temperature, due to their" relatively small cross sections; Such small" cross" sections do not-provide the necessaryhotstrength for an adequate support function: Furthermore,- whentheanode is hell shaped with one end closed, the support of the end'ofthe-fil'ament remote from-the end of the device fromwhich the filament lead-ins extend, involves use ofa' support member disposedbetweemthe filament and the anode-and coextensive with the filament axially of the anode. This member istherefore an effective shield between a portion ofthefilament and a portion of the anode.- the other end of the filament involves a" structure that has no portion extendingbetween-the fila ment-and-theanode. Consequently-whenvoltage disfferences between the filament and'anode are relatively high, the filament-will tend to flex'to=- wardsthe anode in adirectiomopposite to that in"-Which'- the coextensivesupport lies." Repeated: flexures of the filament in this manner will weak-en it and cause ultimate rupture" thereof;

The shielding effect of the coextensive support referredtrr is also objectionable inthatit interferes with the electron-emission pattern-between the filament and the anode: This pattern should be symmetrical for bestoperation of the device;

Accordingly it is an object of the invention to" providean improved electron discharge device:

further obj ect is to" provide -an'- improved sup'-- port structure for afil'amentary cathode:

Another object: is to provide a'nelectron dis charge? device: of; improved electrode stability under relatively high: voltage; excitation;

A further object-is to'provide'a'support structure for a filamentary cathode that: will be effective' in the. presence of relatively high voltage energization of the cathode.

Support" of 30 Another object is to provide a relatively strong supportfor-a filamentary cathodein the presence of relatively high temperatures of the cathode."-

A} further obj ecif-i's to provide a comhined sup port andshield for-a filamentary cathode? Another object is-to provide a' relatively stro support fora fil'amentarycathode that ii'rad tion serves as a shield to neutralize attrac we forces between the cathode"- and air associated anode.-

r h Obiefct t ef d sub ert a e: filamentary cathode that 'efiectivelycaincels elf N, trical forces tending to" deflect-the" cathode W-itll' respect toa'notlier associated electrode.-

Another object isto'provide a'ruggedrri'echa cal support for a'fi-lament'ary' cathodetha also serves to preserve thecathode'from -movem M t" response toa relatively" high voltage differe ce v, betweenthecathode and" another associated electrode. e I I x A further obj set isto provide a} combined-flay menta'rycathode and a rugged fixed'f sup'portf therefor wherein the structure of a cathode and the support contribute to 1 good operation of tan electron dischargedevice at" relatively high" oper-' ating voltage: I a 7 According to one" feature of the inventiong af filan'rerit'a rycathode adapted for relatively high? voltage energization is made in'f a' fiexiblef form such; asa helix and is supported between two? relatively" ma ssive and? rugged supports; 'Ihi sf renders thesuppOrt's effective forsupportingthei' filament in the presence of relatively high tem-v peratures reached by the filament during*opera= tion. Themassiveness of: thesupports 'cl'eprlves them of appreciable flexibility However} the? mechanical temperature response of the filament; finds release in the inherent. flexihility; of the v filament form.

According to another aspect of the invention a coiled filamentary" cathode; is supported at its-- ends within a tubular anode-in spacediplanes parallel to" a, transversesaxis: of the anode by;

I supports that are coextensivewith the filamentalongthe longitudinalaxisof the anodee This: support structure balances the forces of. attrac tion hetweenthe filament" and-the anode and pre serves the filament against deflections. with; re-.

-;spect to the anode. This isflparticularly. adva n \J movement or fiexure of the filament relative to the anode.

Further objects and advantages of the invention will appear as the description proceeds.

While the invention is pointed out with particularity in the appended claims, it will best be understood from a consideration of a specific embodiment thereof taken in connection with the appended drawing, in which:

Figure l is an elevation partly in section of an electron discharge device employing the invention and;

Figure 2 is a transverse section along the line 2-2 of Figure 1 and depicts a preferred support arrangement of a filamentary cathode in accordance with the invention.

Referring to the drawing in more detail, there is shown in Figure 1 an electron discharge device including an enevelope ill having at one end thereof a base i l through which extend lead-ins Within the envelope referred to is disposed an anode l4 having a tubular portion closed at one end and open at the other. The anode is supported at its closed end by a lead-in I5 extending through the end of the envelope remote from the base I i and terminating in an external contact cap [6.

A filamentary cathode I! which is preferably of coiled or helical form is supported within the anode I4 and transversely of both the longitudinal axis and a transverse axis of the anode, on support rods or bus bars l8, 19, as by welds. This manner of supporting the filament permits maximum coextension of the filament with the longitudinal axis of the anode l4 and desired spacing between the support rods I8, Hi. This separation should be appreciable when the filament is energized by a relatively high voltage source to avoid undesired electrical interference between the support rods. Support rod It! may be connected to lead-in l3 and support rod l9 may be connected to lead-in l2.

When the filamentary cathode I1 is operated at a relatively high voltage, it acquires a relatively high temperature. To be serviceable in the presence of such high temperature, support rods l8, l9 are relatively massive for increased ruggedness and strength. Due to their massive character the support rods possess very little flexibility. Therefore they are unable to respond in movement to expansions and contractions of the filament caused by on and off conditions. However, by constructing the filament in such a manner as to confer inherent flexibility thereto, the expansions and contractions referred to may be absorbed readily by the filament itself. One form that the filament may take in accordance with the invention is that of a coil or helix.

While a flexible form of the filament I 4 is therefore required because of the rigid character of the filament support rods I 8, 19 it has resulted in serious difficult because of the readiness with which the filament responds to an unbalanced force of attraction between the filament and the anode. Such unbalance would occur if the support rods l 8, I9 terminated at their points of contact with the filament H. In this event the support rod I8 would be coextensive with the filament axially of the anode and would shield one side of the filament from the anode. Support rod I9, however, would terminate at the lower end of the filament and would include no portion extending between the filament and the anode. The opposite side of the filament would therefore be unshielded. The attractive force between the anode I4 and the opposite side referred to of the filament would therefore be stronger than that between the shielded side of the filament and the anode. This would result in a fiexure of the filament away from support rod [8 and towards the anode. This fiexure is objectionable particularly when the filament is at a relatively high temperature as results from high voltage excitation. This is because the filament is relatively weak when hot and because the force of attraction is increased with filament voltage. Eventual rupture of the filament is likely to occur as a consequence of these conditions.

To overcome this difliculty I have made the support rod [9 coextensive with support rod 18. Since both support rods i8, 18 are of equal thickness, an equal shielding of the filament from the anode at opposite sides thereof is accomplished. The forces of attraction between the filament and anode are therefore balanced and the filament is preserved from fiexure.

A further contribution to the balance of the forces of attraction between the anode and the filament is effected by the manner in which the filament is affixed to support rods (8, i9, according to the invention. As shown more clearly in Figure 2, the filament coil terminates in relatively

straight legs

20, 2|, extending parallel to the axis of the filament coil ll. If the legs referred to were fixed to the support rods at sides of the rods facing a common direction, a complete balance of the forces acting on the filament would not occur. This is because a major portion of the filament would extend beyond the space defined by and between the two support rods referred to. This extension of the filament would lack symmetry with respect to the plane of the support rods so that a portion of the filament would be shielded and another and opposite portion would lack shielding. This would result in an unbalance in the attractive forces between the filament and anode resulting in some deflection of the filament.

To overcome this difficulty I prefer to mount the filament in such a way that the

legs

20, 21 thereof engage sides of the support rods (8, 19 facing opposite directions as shown in Fi ure 2. This results in a symmetrical disposition of the filament coil with respect to the space between the support rods, and balances the forces of attraction on the filament from opposite directions. It will be apparent that with this arrangement a force of attraction on the filament in any diametric direction is effectively neutralized by a force in the opposite direction. This mounting arrangement of the cathode filament on the support rods therefore contributes to a further reduction in fiexure of the filament.

Many additional advantages result from the filament support structure of the invention. For example, since both support rods I 8, I9 are of equal length, manufacture of the device is simplified. This is because no critical selection of the appropriate support rod is necessary. One receptacle can supply both support rods required for the support structure of the invention. Furthermore, since fiexure of the filament is reduced longer life of the device is obtained. In addition, the electrical characteristics of the device are maintained constant due to the preservation of a critical spacing between the filament and anode.

While the filament support Structure of the invention is particularly useful when a relatively high voltage difference exists between the filament and another electrode of a device, it is also beneficial when relatively low voltages are used. While deflection of the filament due to low voltages are not of as large a magnitude as when high voltages are employed, any deflection at all of the filament in some critical uses of electron discharge devices is objectionable. Thus the invention has a wide range of utility.

While one example has been chosen for illustrating the invention it will be obvious to persons skilled in the art that modifications may be .made therein without departing from the spirit of the invention and it is accordingly desired to include such modifications within the spirit of the appended claims.

I claim:

' 1. A high voltage electron discharge device having a stem, a tubular anode having'an open end adjacent said stem, a filamentary cathode structure of relatively small cross-section within said anode extending longitudinally and transversely thereof, whereby one end of said cathode is closer to said open end than the other end of said cathode, two spaced rod-like supports having equal length extending from said stem into said anode and each having an appreciable crosssectional area in relation to the cross-section of said cathode structure, one end of said cathode being fixed to one end of one of said supports, the other end of said cathode being fixed to the other of said supports at a portion thereof intermediate its ends, whereby said cathode is shielded by said supports from said anode in opposite directions for preventing fiexure of said cathode.

2. A high voltage electron discharge device including a hollow anode, a filamentary cathode Within said anode and having a predetermined cross-sectional area, said cathode being angularly disposed with respect to a transverse axis of said anode, support rods for engaging the ends of said cathode, each of said rods having a cross-sectional area appreciable in relation to said predetermined cross-sectional area, one end of said cathode being disposed to one side of one of said rods, and the other end of said cathode being disposed to the opposite side of the other of said rods, said rods being coextensive axially of said anode, whereby a symmetrical shielding of said cathode from said anode is effected for preventing lateral fiexure of said cathode.

3. A high voltage electron discharge device comprising an envelope, a tubular anode supported at one end of the envelope, two spaced and coextensive rigid supports fixed to the opposite end of said envelope and extending into said anode in axial parallel relation therewith, a filamentary cathode having a flexible form fixed to said supports, one end of said cathode engaging the free end of one of said supports, the other end of said cathode engaging the other of said supports at a portion thereof appreciably spaced from its free end, the ends of said cathode engaging opposite sides of said supports, each of said supports having a cross-sectional area that is appreciable in relation to the crosssectional area of said cathode, whereby said cathode is symmetrically shielded from said anode to prevent fiexures in said cathode.

4. A high voltage electron discharge device comprising an envelope, an anode having opposite wall portions, two support rods extending from one end of said envelope and between-said wall portions, and a cathode structure supported diagonally across said support rods, said support rods being coextensive with said cathode structure in the direction axially of said anode and each of said support rods having a cross-sectional area substantially equal to the crosssectional area of said cathode structure,where= by shielding of said cathode by: said rods is substantially balanced and lateral fiexure ofthe cathode is minimized. w

-5. A high voltage electron discharge device comprising an elongated envelope, atubular anode within and coaxial with said envelope, 2. filamentary cathode within said anodeand extending diagonally across the anode axis, whereby one end of said cathode is closer thanthe other to one end of said envelope, a lead-in ex-v tending from said one end of the envelope and fixed to said other end'of said cathode, whereby said lead-in extends between said anode and one side of said cathode and shields said one side from attractive forces generated between said cathode and anode during operation of said device, a second lead-in extending from said one end of the envelope and fixed to said one end of the cathode, said second lead-in extending from said one end of the cathode toward the other end of said envelope and between the anode and the side of said cathode opposite said one side thereof for providing a balanced shielding of said cathode from said attractive forces, whereby said cathode is preserved from harm resulting from an unbalance of said forces on said cathode.

6. A high voltage electron discharge device comprising an elongated envelope, an anode having spaced opposite wall portions extending parallel to the axis of said envelope and defining a space therebetween, two parallel rectilinear and coextensive lead-ins and support wires extending into said space from an end of and in axial parallel relation with said envelope and terminating in free ends in said space, said wires extending between said opposite wall portions of the anode and. being disposed in a plane parallel to said envelope axis and including said opposite wall portions of the anode, whereby said wires define a space therebetween that is shielded from electrostatic forces from said opposite wall portions during operation of said device, and an elongated filamentary cathode in said shielded space, one end of said cathode being fixed to and adjacent a free end of one of said wires, the other end of said cathode being fixed to the other of said wires at a region thereof spaced from the free end thereof, whereby said cathode extends diagonally between said wires and is shielded from said opposite wall portions of the anode, said anode having other portions on opposite sides of said shielded space, said other portions producing electrostatic forces that are of equal magnitude on each of said opposite sides of the shielded space, whereby the electrostatic forces acting on said cathode are balanced for preventing fiexure of said cathode.

7. A high voltage electron discharge device comprising an elongated envelope, a filamentary cathode and a tubular anode in said envelope of relatively high voltage difference in operation of said device, said cathode being within and extending diagonally across the axis of said anode, and two supports fixed to the ends of said cathode and extending from one end of the envelope and axially parallel to said anode, one

or said suDP rts having a tree end fixed to one end of said cathode and being coextensive with said cathode and disposed between one side of said cathode and said anode for shielding said side from said anode, the other of said supports including a portion extending from said one end of. the envelope to the other end of said cathode for supporting and leading electrical energy to said cathode, said other of said supports including a portion extending from said other end of the cathode in a direction away from said one end of the envelope in coextensive relation to said cathode axially of said anode for shielding from said anode the side of said cathode oppositeztosaid one side thereof, for providing balanced shielding or said cathode from said anode to prevent flexures of said cathode in response to electrostatic forces between said cathode and anode.

\ 8; An electron discharge device having a filamcntary cathode, a pair of supports for said cathode, an anode surrounding said cathode, said supports having parallel portions including 8 free ends lying within said anode, said portions being coextensive with each other, said cathode being positioned diagonally of the axes of said anode and said supports, one end of said cathode being secured to one of said supports adjacent the free end thereof, and the other end of said cathode being secured to the other of said supports at a location thereon removed from the free end thereof, whereby said supports equally shield opposite sides of said cathode from said anode for preventing flexures of said cathode resulting from unequal shielding of opposite sides thereof.

WILLIAM B. BROWN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,987,338 Heintz Jan.- 8, 1935 2,158,308 Saohtleben May 16, 1939 2,244,070 Kurtz June 3, 1941 2,247,268 Witbeck June 24, 1941