US2419578A - Electron discharge device - Google Patents

Description

April 9, 1947. c. v. LlTTON ELECTRON DISCHARGE DEVICE Filed July 9, 1943 AT 61mm Patented Apr. 29, 1947 ELECTRON DISCHARGE DEVICE Charles V. Litton, Redwood City, Calif., assignor to Federal Telephone and Radio Corporation, Newark, N. J a corporation of Delaware Application July 9, 1943, Serial No. 494,043

14 Claims.

This invention relates to improvements in electron discharge devices, and more particularly to a novel vacuum tube structure adapted for use at extremely high frequencies.

An object of the present invention is to provide an improved vacuum tube of optimum geometry of parts for ultra-high frequency application.

Another object of this invention is to provide a vacuum tube in which the product of the inductance and capacitance of the grid and anode leads is minimized to the greatest possible extent.

A further object of this invention'is to provide a vacuum tube embodying an improved geometry of parts, which at the same time may be built and assembled in a relatively simple manner.

Generally speaking, this invention may be defined as comprising the constructions and combinations recited in the annexed claims and il lustrated in certain embodiments in the drawings accompanying and forming a part of this application, wherein:

Fig. 1 is a longitudinal cross-sectional view of a preferred form of vacuum tube according to the present invention,

Fig. 2 is a partial longitudinal cross-sectional view illustrating a slightly modified form of construction;

Fig. 3 is a partial longitudinal cross-sectional view illustrating another modified detail;

Fig. 4 is a partial longitudinal cross-sectional view illustrating another modified detail of construction;

Fig. 5 is a partial longitudinal cross-sectional view illustrating a still further modified structural detail.

In the preferred form of tube according to this invention, illustrated in Fig. 1, the construction will embody a general bell-shaped envelope III of insulating material, preferably glass. This envelope will be formed in two sections, an upper section I2 carrying the cathode and grid elements of the tube, and an anode-carrying lower section I4, joined together by a thin metal ring l6. This ring provides means for effecting a joint between the upper and lower sections of the glass envelope by the use of high frequency heating and may have a coefficient of expansion substantially the same as that of the glass envelope; for example, such a ring may be made of Allegheny Sealmet or an equivalent chromium iron alloy. This will permit heating at the juncture point without overheatin the previously formed grid and anode seals.

The bottom of the bell-shaped envelope I is covered by the anode structure generally indicated at Hi. This anode may be provided with a hollow core section 20 connected to the outside through an annular passage 22 whose inner sur face forms the anode electrode itself. The outside of one end of the anode l8 beginning with the upper edge of the annular passage 22 is formed with a downwardly-extending frustoconical surface 24 with an integral conical continuation 26 sealed to the lower rim of the envelope. A connector ring 28 may be attached to the projecting end of the edge outside of the envelope. If desired, a cooling fin structure (not shown) may be attached to the outer end of the anode structure by screwing it into the threaded bore 30 and soldering or brazing it thereto. The upper portion ll of the envelope carries a grid support which may consist of a grid cone 32 having attached thereto at its smaller end a substantially cylindrical grid 34 positioned within the anode-electrode forming passage 22, and an upper frusto-conical cone seal 36 projecting through the walls of the upper envelope section l2. In accordance with the preferred form of construction illustrated in Fig. 1, a flat backing ring 38 is positioned within the cone seal 36, the smaller end of the cone seal 36 and the large end of the grid cone 32 being bent inwardly to form adjacent juncture surfaces which are attached to one another and to the backing ring 38 by suitable means such as screws 40. This arrangement has the advantage that the heads of the screws are enclosed within the conical grid support but in such case the grid cone must be provided with suitable openings 42 through which the screws can be inserted and tightened. A connector ring 44 may be attached to the wide end of the cone seal 36, outside of the envelope.

Before describing further details of the vacuum tube structure of the present invention, attention is particularly directed to the relationship between the conical grid support and the adjacent frusto-conical anode surface. The angle formed between these two conical sections is illustrated as being approximately an arrangement which minimizes the product of inductance and capacitance of these two leads. If the angle is substantially smaller than 90, the grid-anode capacitance between the leads will gradually increase, whereas if the angle is substantially greater than 90 the grid-anode inductance will increase. The arrangement described, therefore, permits the optimum relationship between thegrid and anode leads while still permitting the construction of a strong conical rid support and good mechanical arrangement of the anode.

In the form of tube taken by way of example, I have utilized an indirectly heated cathode 46 attached to the end of a cathode supporting structure 48 which, at its upper end is attached, in turn, to a generally frustro-conical cathode cone seal 50. The connection may be made in any suitable manner as by screws 52. To the outer end of the cone seal 50 is preferably attached an externally threaded connector ring 54, by means of which connection may be made to a tubular line (not shown). The heating cOil 56 within the cathode electrode 46 will be attached at one end to the electrode proper and at its other end is provided with an upstanding lead 58 positioned substantially centrally within the envelope. At the upper end of the envelope is positioned a ringlike structure 60 having an extending annular knife-edge 64. To the latter may be sealed the glass tubulation 66. The upper end of the lead 58 will be attached to the ring-shaped member 60 as by conductor 68. The latter may be removably attached to the top of the lead as by connector III which, it will be noted, is positioned directly beneath the tubulation 66. Accordingly, after the ring-shaped member 60 with attached conductor 68 is sealed to the top of the envelope II], the other end of conductor 68 is still accessible for connection to the lead 58 through the top of the tube, and through the open tubulation 66 after this connection is made, evacuation of the tube may follow. The outside of the ring-shaped member 60 may be threaded, as shown, for attachment to a tubular line.

Fig. 2 illustrates a slightly different form of grid support which is of slightly simpler construction than that shown in Fig. 1. In this case the adjacent edges of the grid cone I32 and the cone seal I36 are not bent flat but merely overlap. A strengthening ring I33 is positioned within this overlapping section, and the overlapping sections plus the ring I38 may be rigidly connected together by means such as screws I40.

In Fig. l the ring-shaped member was illustrated as a single integral piece of metal in which the annular knife edge 64 was formed on a reversally-bent back and inwardly-directed portion of the ring proper. In Fig. 3, on the contrary, the ring 260 is formed with downwardly directed annular knife edge 262 and an upwardly directed knife edge 264, to whose inner surface the tubulation 266 is sealed. In this case the cathode lead 53 may extend further upwardly to a slight degree and will be directly connected to the ring 260 through the conductor 268. Again, however, the connection between conductor 268 and the lead 58 is readily accessible, being directly below the tubulation 266.

Fig. 4 shows a still further modified form of cathode lead-in construction. In this case the ring-shaped member is in the form of a hollow half toroid 360, with an annular knife-edge extension 362 forming a sealing connection with the upper portion I2 of the glass envelope. The internal, smaller annular-knife edge 364 also projects downwardly and the glass tubulation 366 is sealed to its inner surface. The conductor 368 from the lead 58 may, in this case, project directly Into and form electrical connection with the body of the half-toroid 360, which also may be provided with a threaded socket 380 for the reception of a threaded cathode conductor.

The construction illustrated in Fig. 5 is quite similar to that shown in Fig. 4, except that in this case the half-toroid end member 460 is not as thick as that shown in Fig. 4 and the conductor 468 from the lead 58 may extend directly through the end member 460. In this case, the larger-diameter knife edge 462 will be sealed to the upper portion I2 of the glass envelope, while the smaller annular knife edge 464 is sealed to the tubulation 365. If the end member 460 is made relatively thin as compared to the end member 360 of Fig. 4,

it is preferably formed of a suitable metal which has the same coefficient of expansion as the glass of the envelope. In the construction illustrated in both Figs. 4 and 5, the accessibility of the lead 58 for the purposes of connecting a conductor thereto, will be clear as shown in Figs. 1, 2 and 3.

While I have described above the principles of my invention in'connection with specific apparatus and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and the accompanying claims.

I claim:

1. An electron discharge device comprising a. hollow insulating envelope open at both ends, an anode structure closing one end of said envelope, said anode structure comprising a metallic mass having a cylindrical central bore in one end the outer surface of said mass about said bore sloping downwardly in all directions forming a generally frusto-conical face, and integral extensions on said conical face projecting through and forming a sealing connection with the edge of the oneend of said insulating envelope, a grid positioned within said cylindrical bore, a genereraily inverted irusto-conical metallic grid support attached at its smaller end to said grid and extending upwardly and outwardly through the walls of said envelope, a cathode positioned within said grid, and cathode support means closing the other end of said envelope.

2. The combination according to claim 1, in which the angle between the inverted frusto-conical grid support and the frusto-conical anode surface'is approximately 3. The combination according to claim 1, in which said insulating envelope is divided into upper and lower sections, the upper section holding the grid and cathode supports, and the lower section the anode structure, and means including a thin metallic ring sealing the two sections of the envelope together.

4. An electron discharge device comprising a generally bell-shaped insulating envelope, an anode structure closing the bottom of said bellshaped envelope, said anode structure comprising a solid metallic mass having a relatively large hollow core and a cylindrical central passage through one end of said mass communicating with said hollow core, the outer surface of said mass about said passage sloping downwardly in all directions forming a generally frusto-conical face, and an integral extension on said conical face projecting through and forming a sealing I conical grid support and the irusto-conical anode said two turned over flat rings and positioned inside of the cone seal.

7. The combination according to claim 4, in which said grid support comprises a hollow i'rusto-conical grid cone having its smaller end attached to said cylindrical grid, and a hollow frusto-conical cone seal having its smaller end overlapping the larger end 01' the grid cone and its larger end extending through the envelope, and means attaching the overlapping ends together, said means including a strengthening ring positioned at the joint within the overlapping ends s. The combination according to claim 4, in which said bell-shaped envelope is divided into upper and lower sections, the upper section holding the grid and cathode supports and the lower section the anode structure, and means including a thin metal ring having substantially the same coeiiicient or expansion as the envelope material, sealing the two sections 01' the envelopes together. 9. The combination according to claim 4, in combination with a first connector ring attached outside of the envelope to the larger end of the grid support, and a second connector ring attached outside 01' the envelope to the P jectingintegralertensions oi'saidanodestructure.

10. The combination according to claim 4. in combination with an externally threaded connector ring positioned outside of said envelope and attached to the projecting p rtions or said cathode support.

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one end thereof, the outer surface or said mass about said bore sloping downwardly in all directions forming a generally irusto-conical face, and integral extensions on said conical face projecting through and forming a sealed connection with the lower edge of said bell-shaped envelope, a grid positioned within said bore, an inverted generally irusto-conical metallic grid support attached at its smaller end to said grid and extending upwardly and outwardly through said envelope, a cathode positioned within said grid, cathode support means extending through the top of th bell-shaped envelope, a cathode lead rising substantially upwardly from said cathode to the top of said bell-shaped envelope, a generally ring-shaped metal member. 01' substantial thickness having an externally downwardly extending annular kniie edge sealed to the top of said envelope, positioned substantially coaxially with respect to said lead and an inner annular knife edge of smaller diameter than said first knii'eedge, a conductor attached at one end to said metal ring-shaped member, means connected to the other end or said conductor to the upper end or said centralLv positioned cathode lead and sealing means across said annular knife edge.

12. The combination according to claim 11, in which said sealing means comprises a glass envelope sealed to the inner surface of said smaller annular knife-edge.

13. The combination according to claim 11, in which said conductor extends outwardly through said ring-shaped member.

14. The combination according to claim '11. in which said ring-shaped member is in the form of a hollow hall-toroid.

CHARLES V. LI'I'ION.

css 0mm The rollowingreierences areoi'recordinthe file 01' this patent:

UNITED STATES PATENTS Number Name.

2,345,794 Chevigny Apr. 4, 1044 FOREIGN PAmTB Number Country Date 849,405 Italian June 18, 103'!

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