US2521364A - Electron discharge device for high frequency - Google Patents

Description

p 1950 c. E. HALLER 2,521,364

ELECTRON DISCHARGE DEVICE FOR HIGH-FREQUENCY Filed Jan. 4, 1946 INVENTOR fiatenteci Sept.

UNITED STATES PATENT oFFlcE ELECTRON DISCHARGE DEVICE-"FOR; HIGH FREQUENCY Cecil E. Haller, Lititz, Pa., assignor to Radio Cor poration of America, a corporation of Delaware Application January 4, 1946, Serial No. 638,965

1-5 Claims. (01. 25027.5)

a tween which longitudinally extending wires are supported and to which they are welded. At very high frequencies the spacing between the cathode and grid vitally affects the operating characteristics of the tube since this spacing determines the transit time of the electrons between cathode and grid, the greater the spacing the greater the transit time of the electrons and hence the lower the upper frequency of operation. Since the grid wires are ordinarily welded externally to the rings, the grid-cathode spacing is limited by the thickness of the supporting rings or bands. It is, therefore, desirable to provide some means of construction whereby the thickness of the ring or band has no effect on the spacing between the grid wires and the cathode surface.

In tubes of the kind under discussion interelectrode capacities are also of importance. close spacing, however, demanded by high frequency operation increases interelectrode capacities as well as the possibility of electrode shorts and interferes with easy assembly. It is, therefore, desirable to provide a construction permitting close spacing of the working surfaces of the electrodes which will nevertheless minimize interelectrode capacity, reduce liability of shorts 1 and facilitate assembly of the electrode mount.

The 7 Close spacing of electrodes and their supporting structuresalso makes the problem of sealing the envelope, whether by flame or welding if of metal, a difiicult problem. Flames increase the possibility of strains and breakage and the re lease of undesired gases within the tube envelope. With small spacing and a plurality of concentric leads-welding is a difficult problem.

Further, in tubes of this type the inverted cupshaped cathode is usually supported at the end of a tubular supporting member and the heater is inserted, within this tubular member and the cathode. The heater must not only be firmly andrigidly supported within the tubular member but it must be so constructed that the coils of the heater are not shorted on the inner surfaces of the cathode or the supporting sleeve It is, therefore, an object of my invention to provide an electron discharge device useful at ultra high frequencies and of improved design having improved characteristics and promoting;

ease of assembly.

Another object of my invention is to provide a cathode-grid construction in which the desired close spacing can be accomplished without the. limitation normally found with the conventional.

grid construction.

Another object of my invention is to provide; an electron discharge device having a cathodegrid construction minimizing interelectrode ca-" pacities, the liability of interelectrode shorts and which will facilitate electrode assembly.

It is another object of my invention to pro Vide an electron discharge device having such construction that successful seals are facilitated.

and in which the liability of cathode heater shorts is reduced.

The novel features which I believe to be charj acteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a longitudinal section of an electron discharge device made according to my invention and Figure 2 shows-an electron discharge device made according to my invention and shown in Figure 1 utilized in a cavity resonator circuit.

Referring to Figure 1, an electron discharge device made according to my invention co1nprises an inverted cup-shaped cathode ll] of tapering shape surrounded by a, grid ll and an inverted cup-shaped one-piece anode E2 all nested to provide a triode assembly. The anode may be provided with a sleeve I3 to which the radiator comprising an outer collar l5 and radially directed fins M are secured. The tapered cathode is provided with a collar l6 of reduced diameter supported on a tubular member I? having a portion 18 of reduced thickness for reducing heat conduction between the cathode proper and the cathode support. A cathode heater l9 compris-A ing a coil welded at its lower end to the coaxial rod 20 has a lead 2! extending from its upper end and secured to the tubular member 22. Member 22 has the reduced portion 24 and the hermetic seal 23 extends between the reduced portion 24 and the supporting rod 26. The lower end of the tubular member 22 is sealed to the outer tubular member I1 at its lower end by means of high frequency welding. An opening l1 may be provided for degassing purposes.

The grid is provided with an inverted cupshaped cap 25 and a tubular flared-out apron member 2'! between which the vertical grid wires 28 extend and are welded. The lower end of the tubular grid apron and support 2'! is provided with a second flared-outapron member 29. The upper end of the cathode is provided with a pin 32 extending through and contacting only the insulator 30 for centering the upper end of the grid and the cathode, the insulator being retained by cap 3| on the cap 26. It will be observed that since the cap 26 is above the cathode and the upper portion of the tubular member ,2! is be: low the portion 55 of reduced diameter of the cathode, that the thickness of the cap and skirt do not interfere with the close'spacing between the cathode surface and the grid wires as of grid II, this spacing being anything possible within manufacturing limits, Because of the constricted portion :6 of the cathode the cathode surface is'moved away from the grid and the anode and thereby the total inner cathode-grid capacity and cathode-anode capacity is reduced.

'The lower end of the anode is provided with outwardly extending flange 35 and the lower end of the grid skirt 29 with the collar 36 flared upwardly and outwardly. A glass collar 31 is sealed between the flange 35 and the member 36. Members 29 and 36 are radio frequency welded at the lower ends at 38 thus forming a complete envelope for the tube when the transverse seal 33 is madebetween tubular member 24 and the skirt 29.

The heat shields 26' supported on the conductor 20 of the cathode heater assembly reflect the heat back up into the interior of the cathode I0. Should a short occur between the lead 2| and the inner surface of the supporting sleeve l1, no shorting of the cathode heater will occur.

' In assembly, the cathode and grid are assembled as a unit without the heater, the seal being made between the outer tubular member 2 4 and the apron 29 by means of the disc seal 3-3. This permits the grid and cathode to be jigged from a common center, that is the cathode sleeve, thus insuring accurate positioning. The anode l2, collar 31- and collar 36 are assembled as a unit and the cathode and grid assembly inserted within the anode assembly, the anode, grid and cathode being" automatically centered when the apron 28 is received within the collar 36. spacing is insuredby registering the ends of members 22 and 24 and radio frequency welding at 38. The cathode heater is assembled as a unit, the restricted portion 34 insuring a good seal to the support Zilby means of the seal 23. The cathode heater is then inserted into position and a radi frequency weld made at 25.

Thus an electron discharge device having extremely close cathode-grid spacing. low interelectrode. capacity, and improved cathode construction and good seals without the use of fires, which would cause stresses and strains in the insulated portions of the envelope, is insured. The con struction facilitates ready and accurate assembly by utilizing the construction described above.

In Figure 2 I show an electron discharge device made according to my invention utilizing a coaxial line resonator-oscillator circuit. The input circuit comprises the inner tubular memberlfl having a plurality of fingers .0 at the upper end contacting a ring 46 capacityccupledto thev tubular member 11 through the insulating collar Longitudinal 4!. An outer tubular member 42 is electrically connected to inner member 4a to form a resonator by a metallic disc-shaped end member 43. Tuning is accomplished by means of the ring 43 movable longitudinally of the resonator. The resonator is completed by means of the transverse partition member 44 having resilient fingers d5 contacting the grid collar 3.8,. Tuning is accomplished by tuning ring '43.

The output resonator is connected between grid and anode. The upper end of tubular member 42 is continued by means of a tubular member d6 connected with the inner tubular member 41 through conducting disc 5!. Member 41 has spring fingers 48 contacting the collar 49 and are capacity coupled to the anode through insulating collar 50, preferably of mica. resonator between anode and grid is tuned by the longitudinal moving tuning ring member 52. Thus a coaxial line capacity resonator is connected between cathode and grid and between anode and grid. The device may serve as an 08- cillator by providing aperture 54 in the partition M5 and utilizing a coupling loop 53 extending through the aperture and having loops within the two resonators. The load may be taken out or the grid-cathode resonator by means of the coaxial line 56 having the inner loop 56' terminating 0n the partition 44 The cathode heaters may be supplied from the source 5,! and. the anode voltage from the source 58,

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed,

it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forthin the appended claims.

What I claim as new is:

1. An electron discharge device having an elongated hollow tubular cathode assembly closed at one end by an inverted cup-shaped cathode tapered inwardly toward its closed end, an elongated grid assembly positioned over said cathode assembly and coaxial "therewith, said gridassembly including a cup-shaped grid tapered to con.- form to said cathode and positioned over said cup-shaped cathode and closely spaced therefrom, said grid assembly having a skirt-shaped conducting support of outwardly-flared construction and a seal of insulating material extending between said cathode assembly and said skirtshaped conducting support adjacent but spaced" at one end b an inverted cup-shaped cathodetapered inwardly toward-its closed end-and having an annular emitting surface, an elongated grid assembly positionedover said cathode assembly and coaxial therewith, aid grid assembly. including an inverted cup-shaped tapered'grid positioned over said cup-shaped cathode andclosely spaced therefrom, and having a skirtshaped conducting support and, a seal of insulating material extending between said, cathode assembly and said conduct ng, support, said cupshaped grid including a cap, spacedabove the end of said cathode, and longitudinally extending grid conductors extending between said cap; and.

one end of; said conducting support, the portions of said cap and said conducting support to which said grid conductors are secured being positioned outside the projected emitting surface of said cathode whereby said grid conductors may be spaced from said emitting surface a distance less than the thickness of the walls of said cap and said skirt. v

3. A heater for a hollow indirectly heated cathode, said heater including a rod-like conductor, a tubular member coaxial with and surrounding said conductor and an insulating seal extending between said conductor and said tubular member, said tubular member being constricted at said seal, a heater mounted at one end of said rod-like conductor and having one end connected to said conductor and the other end connected to said tubular member, said heater being supported solely by said rod-like conductor and said tubular member.

4. A heater for a hollow indirectly heated cathode, said heater including a rod-like conductor, a tubular member coaxial with and sur rounding said conductor, and an insulating seal extending between said conductor and said tubular member, a heater mounted at one end of said rod-like conductor and having one end connected to said one end 0f said conductor, a second conductor connected to said tubular member, the other end of said heater being connected to said second conductor, and a heat reflecting disc extending transversely of and supported on said rod-like conductor between said heater and said tubular member.

5. A heater for a hollow indirectly heated cathode, said heater including a rod-like conductor, a tubular member coaxial with and surrounding said conductor, and an insulating seal extending between said conductor and said tubular member, a heater mounted at one end of said rod-like conductor and having one end connected to said one end of said conductor and the other end connected to said tubular member, said heater being supported solely by said rod-like conductor and said tubular member.

6. A cathode for an electron discharge device having an elongated conductor, a tubular member coaxial with and surrounding said conductor, and a vacuum-tight seal between said conductor and said tubular member, and a filament supported between said conductor and said tubular member, said filament being supported solely by said elongated conductor and said tubular member.

'1. An electron discharge device having an elongated hollow tubular cathode assembly closed at one end by an inverted cup-shaped cathode tapered inwardly toward its closed end, an elongated grid assembly positioned over said cathode assembly and coaxial therewith, said grid assembly including a cup-shaped grid tapered to conform to the surface of said cathode positioned over said cup-shaped cathode and closely spaced therefrom, said grid assembly having a skirtshaped conducting support, a disc seal of insulating material extending between said cathode and said skirt-shaped conducting support, and a heater within said cathode and comprising an inner conductor and an outer conductor surrounding said inner conductor, and a cathode Y,

filament supported on said inner conductor and connected between said inner conductor and said outer conductor, and a vacuum-tight seal extending between said inner and outer conductors adjacent the open end of said cathode.

8. An .electron discharge device having an elongated hollow tubular cathode assembly closed at one end by an inverted cup-shaped cathode, an elongated grid assembly positioned over said cathode assembly and coaxial therewith, said grid assembly including an inverted cup-shaped grid positioned over said cup-shaped cathode and a conducting supporting member comprising a flared skirt terminating in a straight tubular portion, and. a seal between said conducting supporting member and said elongated tubular member, a collar having a straight tubular portion sealed to the tubular portion of said skirt supporting member and having an outwardly extending flange, an anode positioned over said cathode and grid and having atransversely extending flange and a tubular collar member of insulating material sealed between said flanges for providing an envelope for said cathode and grid.

10. An electron discharge device having an elongated tubular supporting member closed at one end by a cup-shaped cathode, a heater for said cathode including a conductor and a tubular member surrounding one end of said conductor, and a seal between said last tubular member and said conductor and a heater wire within said cup-shaped cathode connected between the conductor and said last tubular member, said last tubular member being heremet ically sealed to the open end oi said elongated tubular member, an inverted cup-shaped grid positioned over said cathode and a conducting supporting member comprising a flared skirt terminating ina straight tubular portion, and a seal between said straight tubular portion and said elongated tubular member, a collar having a straight tubular portion sealed to the end of the tubular portion of said skirt supportingmember and having an outwardly extending flange, an anode positioned over said cathode and grid andhav'ing an outwardly extending flange and a tubular collar member of insulating material sealed between said flanges for providing an envelope for said cathode and grid.

11. An electron discharge device having an elongated hollow tubular cathode assembly closed at one end by an inverted cup-shaped cathode. an elongated grid assembly positioned over said cathode assembly and coaxial therewith, said grid assembly including an inverted cup-shaped grid positioned over said cup-shaped cathode and closely spaced therefrom and having a skirtshaped conducting support, a disc seal of insulating material extending between said cathode assembly and said skirt-shaped conducting support, and an inverted cup-shaped anode nested over said cathode and grid, and an insulating collar member sealed between said anode and the skirt-shaped conducting support of said grid, and a heater within said cathode and comprising estates an inner conductor and-an outer conductor surrounding said inner conductor, and a cathode filament connected and supported between said inner conductor and said outer" conductor; and a vacuum-tight seal extending between said inner and outer conductors adjacent the open end said cathode, and a seal between the outer conduster and the tubular cathode assembly. I

1 2; An electron discharge device having anelongated hollow tubular cathode assembly closed atone end by an inverted cup-shaped cathode, an elongated grid assembly positioned over said cathode assembly and coaxial therewith, said grid assembly including an inverted cup-shaped grid positioned over said cup shaped cathode and closely spaced therefrom and having a skirtshaped conducting support; seal ofinsulating material extending between said cathode assemmy and said skirt-shaped conducting support, and an inverted cup-shaped anode nested over said cathode and grid, and an insulating collar member-sealed between said anode and the skirtshaped conducting support of said grid, and a heater within said cathode and comprising an inner conductor and-an outer tubular conductor surrounding; said innericonductor; and a cathode filament connected and supported between said inner conductor and said outer conductor, and a vacuum-tight" sealextending between said inner conductor and said outer tubular conductor ad'- jacent the open end of said cathode; and a seal between the outer tubular conductor and the tubular" cathode assembly; said outer tubular conductor being constricted at said seal.

13. An electron discharge device having an elongated hollow tubular cathode assembly closed at one end by' an inverted cup-shaped cathode taperediinwardly'towards its closed end and having; an annular emitting; surface, an elongated grid assembly positioned over said cathode assemblyandcoaxial therewith, saidgrid assembly including an inverted: cup-shaped tapered grid positioned over said cup-shaped cathode and closely spaced therefrom and having a tubular conducting support, anda seal of insulating material extending between said cathode assembly and'said conducting support; said-cathode assembly having a smaller-diameter below the. emitting surface of said cathode; whereby'the spacing between; said grid assembly and the restricted por- 8. than the thickness of the said skirt.

l-a Anelectron tube comprising anenvelope having a recessedanode at the upper end and a cathode stem at the lower end, said' stem comprising" an outer tubular member and an inner prong member, a grid terminal ring interposed in the envelope wall between the outer stem member and said anode and providing a cylinwear said cap and drical contact surface, the lower portions of the stem members projecting externally of the en'- vel ope and providing cylindrical contact surfaces coaxial with that of said grid terminal ring, the cylinders defined by said contact surfaceshaving d'ifierent diameters of which'the. inner stern member the smallestthe outerst'em member is next largest and' the grid terminal ring. is'the largest, a cathode element extending into the anode recess and connected to oneof the stem members, a heater for the cathode element connected to the stern members, and a grid disposed about the cathodgelement and connected to said grid terrninal ring.

15. An electron tube comprising an envelope having a recessed anode at the upper end and a. cathode stem at the lower end; said stem comprising an outer tubular member and an. inner. prong member; a gridterminal' ring. interposed in the: envelope wall between the outer stem member and. said anode and providing a cylindizi'cal'- contact surface, the lower portions of the stem members projecting externally of the envelope and providing cylindrical contact surfaces coaxial with that of said grid terminal ring, the cyiinders defined by'sai'd' contact surfaces having differentdi'ameters' of which the inner stem member is'th'e smallest the outer stem member is next largest. and the grid terminal ring is the largest, the envelope wallbeing joined to the tubularstem member above its cylindrical, contact surface. vacuum-tight sealing means disposed between the stem members and" joined to the inner prong member above its cylindrical contact surface, a cathode element extending into the anode recess and connectedto one of the stem. members, a heater for the. cathode element connected tothe stem members, and a grid disposed ahout thecathode eiementand. connected; to said. grid terminal ring.

' CECIL EL REFERENCES (JITED The following references are of record in the file oi this patent;

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