US3662209A

US3662209A - Electron discharge device with helical conductor providing swap fit

Info

Publication number: US3662209A
Application number: US39284A
Authority: US
Inventors: James E Beggs
Original assignee: General Electric Co
Current assignee: General Electric Co; INDIANA NATIONAL BANK
Priority date: 1970-05-21
Filing date: 1970-05-21
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09

Abstract

An electron discharge device which is easily manufactured and assembled consists of three concentric cylinders, unitary cathode grid and heater assembly, a garter spring arrangement for snapping the assembly into position with respect to one of these cylinders, and arrangements for making connections to the heater, the cathode, and the control grid as the assembly is snapped into position. In one version, the device is open to the atmosphere so that it can be used in space environment to take advantage of the extremely high vacuum conditions existing in such environment.

Description

O United States Patent [151 3,662,209 Beggs 1 May 9, 1972 54] ELECTRON DISCHARGE DEVICE 3,262,002 7/1966 Kreplin ..313 93 x WITH HELICAL CONDUCTOR 3,403,297 9/l968 Crouch ..307/l 18 X 1,508,486 9/1924 Tharaldsen ..3l3/238 X [72] Inventor: James E. Beggs, Schenectady, NY. Primary Examiner-David Schonberg Assistant Examiner-Joby H. Kusmer [73 1 Asslgnee: General Electnc Cnmpany AtmrneyPaul A. Frank, John F. Ahern, Julius J. Zaskalicky, [22] Filed; May 2] 1970 Frank L. Neuhauser. Oscar B. Waddell and Joseph B. Forman [21] Appl, No.: 39,284 [57] ABSTRACT An electron discharge device which is easily manufactured [52] U.S. Cl ..313/237, 313/238 and assembled consists of three concentric cylinders, unitary [5 l 1 Int. Cl. ,.H0lj 1/00 cathode grid and heater assembly, a garter spring arrangement [58] Field of Search ..313/236-238; for sn pp ng the assembly into po ition with respect to one of 307/] 18 these cylinders, and arrangements for making connections to the heater, the cathode, and the control grid as the assembly is 56] References Cited snapped into position. In one version, the device is open to the atmosphere so that it can be used in space environment to UNITED STATES PATENTS take advantage of the extremely high vacuum conditions existing in such environment. 2,932,755 4/1960 Jeppson ...3l3/237 UX 3,327,156 6/1967 Gerlach ..313/237 X 9 Claims, 3 Drawing Figures ELECTRON DISCHARGE DEVICE WITH HELICAL CONDUCTOR PROVIDING SWAP FIT My invention relates to electron discharge devices of the planar electrode type and, in particular, to structural features of such devices which facilitate their manufacture while imparting mechanical stability and long life electrical characteristics to the devices.

Electron discharge devices of the planar electrode type require accurate spacing of a cathode, a control electrode, and an anode. Such devices are extremely small in size and the control electrode is a small delicate structure which must be accurately spaced with respect to a cathode and an anode. Furthermore, the structure must be one which must operate satisfactorily over a broad range of operating temperatures during which it may be subject to all types of thermal and mechanical shocks. Manufacturers have long sought to find ways to facilitate the manufacture of such devices so that the cost of assembly and production of the devices could be reduced without impairing the operating characteristics of the device while, if possible, elongating the life of the device.

In the past, such devices usually have been used under a wide variety of terrestrial conditions. It would be desirable, however, that the construction of such devices would be of a nature that with slight modification, the devices could be used in space environment to take advantage of the extremely high vacuum present in space. By exposing the tube structure to the space environment, gases that evolve would be continually pumped during the entire life of the device.

It is an object of my invention to provide new and improved electrode structures for an electron discharge device of the planar electrode type to facilitate manufacture and assembly of such devices.

It is another object of my invention to provide a new and improved structure for an electron discharge device of the planar electrode type in which insulating surfaces are placed in regions remote from the cathodes to minimize electrical leakage on surfaces of such insulation.

It is another object of my invention to provide a new and improved electron discharge device of the planar electrode type which has improved mechanical stability and long electrical life characteristics.

In accordance with my invention, an electron discharge device of the planar electrode type is formed of a plurality of concentric cylinders which can be assembled in fixed, spaced relation, one of the cylinders being constructed to receive a unitary heater, cathode, control grid structure which is snapped into position with respect to the electrode by using a garter spring to surround the electrode structure and make contact with the cylinder, the assembly operation automatically making contact simultaneously with the heater, cathode, and control grid of the electrode structure, An important feature of the device is the construction by which all insulating surfaces are positioned in regions remote from the cathodes so that electrical leakage is not developed on surfaces of the insulation. Such a structure permits its use not only under normal terrestrial conditions, but also in space environment so that advantage can be taken of the extremely high vacuum present in space. For such uses, the tube structure is exposed to the space environment so that gases that evolve are continually pumped during the entire life of the device. In this manner, final exhaust or sealing is not required and the device can be operated after a period of exposure to its space environment. A pressure sensitive switch may be included in the circuit to the device to prevent its operation until the tube structure has been exposed to the high vacuum conditions present in space.

While this specification concludes with claims particularly pointing out and distinctly claiming what is regarded as the present invention, the details of the preferred embodiments of the invention may be more readily ascertained from the following detailed description when read in conjunction with the accompanying drawings in which:

FIG. 1 is an exploded view, partly in section, of an electron discharge device embodying my invention;

FIG. 2 is a vertical, sectional view of a modification of the device of FIG. 1; and

FIG. 3 is a vertical sectional view of the device of my invention, modified for use in space environment.

The device of FIG. 1 comprises three concentric cylinders l, 2, 3. Cylinder 1, preferably, is of a ceramic insulating material, such as a spinel, and supports an anode 4 which comprises a copper body 5, and an active refractory metal electrode surface 6 which may be formed, for example, of molybdenum. The massive body 5 is secured to the active electrode surface 6 in any conventional manner, such as by brazing or welding. Cylinder 1 is secured to electrode 6 by an interposed seal in the form of a ring 7 of titanium positioned between the upper end of cylinder 1 and the outer surface of member 6.

Cylinder 2 is formed of a refractory metal which also may serve as a gettering material for the device and for this purpose may be formed of titanium. At its bottom portion, cylinder 2 is provided with an integral flange 8 which functions as an externally accessible contact for cylinder 2. In assembly, flange 8 is sealed to cylinder 1 by means of an interposed ring 9 of titanium. At its upper end, cylinder 2 is provided with a shoulder 10.

Inner cylinder 3 is likewise provided at its bottom portion with an outwardly extending flange ll spaced from flange 8 of cylinder 2 by means of an insulating ring 12 which may comprise, for example, forsterite. Cylinder 3 and its attached flange portion 11 may be formed of any suitable refractory metal such as, for example, titanium.

I provide a ceramic base 13 for the device which is sealed to flange 11 and which may be formed of a suitable ceramic material such as, for example, forsterite. A pair of

heater terminals

14, 15 extend through apertures provided in base 13 and are suitably sealed to that base.

Terminals

14 and 15 may be formed of titanium and each is provided at its upper end with a coil 16 of a refractory wire such as tungsten or an alloy of tungsten and tantalum. The coil 16 surrounds a central guide pin 17 formed on the tops of

terminals

14, 15.

A unitary heater, cathode, control grid structure 18, whose construction and function is disclosed in detail and claimed in my concurrently filed application Ser. No. 39,463 and assigned to the assignee of this present invention, comprises a porous cathode 19, a control grid 20, and a heater element 21. Cathode 19, preferably, is formed of porous tungsten and is suitably impregnated with a mixture of conventional electron emissive oxides. Cathode 19 is covered by a layer 22 of inorganic insulating material, such as, for example, boron nitride or alumina. Control grid 20 and heater 21 are formed by layers of a suitable refractory metal deposited on insulation layer 22 in accordance with a predetermined pattern. A plurality of openings 23 are formed through control grid 20 and insulating layer 22 on the upper surface of cathode 19 to permit electrons from the cathode to pass through openings 23 and control grid 20 to anode 6. Cathode 19 and its encasing insulating layer 22 are provided with a peripheral groove 24 arranged to receive a resilient conductive helix 25 supported in shoulder 10 on cylinder 2. Resilient conductor 25 may be formed of a suitable refractory metal such as, for example, a coil of tungsten wire, the ends of which are fastened together to form a garter spring. Extending into the bottom portion of cathode 19 are a plurality of contacts in the form of pins 26, having heads 27 which assure their being embedded in the cathode and retained in position by means of insulating layer 22. Pins 26 extend vertically downwardly and are adapted to be received in a plurality of openings 28 in cylinder 3. To insure good conductive contact between pins 26 and cylinder 3 which forms the cathode contact for the device, a small loop 29 of a suitable metal, such as nickel or copper, may be placed around each pin before the assembly operation.

In assembling the electron discharge device of FIG. 1, the

cylinders

2, 3, base 13 and insulating ring 12, together with

terminals

14 and 15 are assembled and sealed by heating to a suitable temperature. Thereafter, garter spring 25 is placed in position in groove 24 of cathode l9 and the unitary heater,

cathode, control grid structure 18 is pressed downwardly until garter spring 25 snaps into shoulder 10 of cylinder 2. In so doing, garter spring 25 makes contact with an edge portion 20 of control grid 20 thus assuring contact between the control grid and the externally accessible flange 8 of cylinder 2. Contact is likewise made between springs 16 at the upper end of

terminals

14, 15 and

terminals

30, 31 of heater 2]. Simultaneously, pins 26 enter openings 28 in cylinder 3.

Anode structure 4 is likewise assembled as a unit by sealing

rings

7 and 9 to ceramic cylinder 1 and anode electrode 6. The anode assembly is placed in position over the previously assembled

cylinders

2, 3 and unitary electrode structure 18 supported in contact with cylinder 3. The assembled device is thereafter exhausted and heated to a temperature such that ring 9 seals to flange 8 and loops 29 seal pins 26 to cylinder 3. At the same time, springs 16 sinter to

terminals

30, 31.

The electron discharge device of FIG. 2 is similar in construction to the device of FIG. 1 with the exception that cylinder 2 is curved inwardly at its upper end to form a flange 35 which extends over groove or shoulder 10 to retain garter spring 25. An alternative method of contacting cylinder 3 with cathode 19 is likewise shown in the form of a continuous loop of wire 36 formed preferably of a refractory metal such as tungsten and which is placed in groove 37 at the upper end of cylinder 3. Upon assembly, when unitary electrode structure 18 with its encircling garter spring 25 is snapped in position by snapping garter spring 25 into shoulder 10, the loops of wire 36 make resilient positive contact at a plurality of points between the cathode and cylinder 3. FIG. 2 also utilizes a slightly different contact for the terminals of heater 21. In this modification, the heater input leads comprise

lengths

38, 29 of a tungsten or tungsten tantalum wire having a plurality of coiled turns 40 which form springs in the wire for assuring positive pressure on

terminals

30, 31 of the heater.

The device of FIG. 3 illustrates a modification of my electron discharge device which is adapted for use in space environment. In this device anode 40, which may comprise, for example, molybdenum, has an annular cylindrical outer wall 41 which is provided with a plurality of vent openings 42. Grid contact cylinder 43, in the form of a ring of titanium, is sealed to the bottom of cylinder 41 by means of a ceramic ring 44 of a suitable material such as forsterite. Cathode cylinder 45 at its upper end is provided with an inner groove 46 which receives garter spring 25. Cathode cylinder 45 has an outwardly extending cylindrical portion 47 which is spaced from and sealed to control grid cylinder 43 by means of a ceramic ring 48 of forsterite. Cylinder 45 is likewise provided with a plurality of vents or openings 49. A suitable insulator 50 is sealed across a central opening 51 in cylinder 45 for supporting

heater terminals

52, 53. These terminals may comprise lengths of tungsten tantalum wire having a few coiled turns to provide a spring action and assure positive resilient contact with heater 21. In the device of FIG. 3, garter spring 25 is shown as making contact with an uninsulated peripheral groove 55 in cathode 19. Grid contact cylinder 43 is provided with an inwardly extending plurality of fingers 56 which contact control grid 20. A vent opening 57 is likewise provided in insulator 50 to assure that when the device is subjected to a space environment the entire interior of the device is brought to the extremely high vacuum present in space.

In using the device of FIG. 3 in space environment, a protective circuit may be employed to assure that the heater is not energized until proper vacuum conditions have been attained. This circuit includes a pressure sensitive switch 60 connected in circuit between a battery 61 used for supplying energy to heater 21. Pressure sensitive switch may comprise a sylphon bellows type switch or any other conventional pressure sensitive switch element. Alternatively, the heater energizing circuit may be programmed so that it is not completed or closed until proper vacuum conditions are achieved in the device.

In operation, the region in the device of FIG. 3 defined by opposed surfaces of cylinder 43 and

cylinders

45, 47 functions as an input circuit or microwave cavity, while the region defined by the upper surface of cylinder 43, control grid 20, and anode structure 40 functions as an output circuit or cavity.

Dielectric members

44, 48 with cylinder 43 operate as a dc blocking capacitance in these circuits.

In the various embodiments of my improved electron discharge device, the insulating members which comprise portions of the device are located in regions both remote from and shielded from the cathode unit, in this fashion minimizing the electrical leakage that might otherwise develop on surfaces of the insulation. In the case of the device of FIG. 3, prior to it being sent into space, heater, cathode, grid unit 18 and the various circuit parts are cleaned and degassed in a manner similar to that employed for preparation of parts used in sealed-off tubes. However, no final exhaust or scaling is required. The device can be operated after a period of exposure to its space environment, either a pressure-sensitive switch or programming being employed to assure no operation until such conditions are attained.

While I have shown and described several embodiments of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from my invention in its broader aspects and 1, therefore, intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electron discharge device comprising three concentric cylinders, a planar anode member supported by the outer of said cylinders, a unitary cathode, grid, and heater assembly being contained within said outer cylinder and being sup ported by one of said remaining cylinders, said assembly comprising a disk having two parallel outer surfaces and a peripheral groove, one of said remaining cylinders having an inner groove and a garter spring comprising a resilient helical conductor encircling said assembly and in snap-fitting engagement with both said grooves, said helical conductor resiliently supporting said unitary assembly from said one remaining cylinder and providing a low conductive path between an electrode on said assembly and said one remaining cylinder, said helical conductor also positioning said assembly along the axis of said cylinders and in predetermined relation with respect to said planar anode member.

2. The device of claim 1 in which said disk includes a porous refractory member between two parallel outer surfaces which comprises a cathode electrode, said outer surfaces being electrically insulated from said cathode electrode, one of said outer surfaces comprising a control electrode and being in spaced parallel relation with said anode member, said one remaining cylinder providing an externally available contact for one of said electrodes and said other remaining cylinder contacting the other of said electrodes.

3. The device of claim 2 which includes a base and leads for said heater are contained within the inner of said cylinders and extend through said base.

4. The device of claim 3 which includes resilient members in said leads for said heaters to facilitate contact thereto.

5. The device of claim 1 in which said one remaining cylinder comprises the central of said three cylinders and said helix contacts said grid electrode.

6. The device of claim 2 in which said one remaining cylinder comprises the inner of said three cylinders and said helix contacts said cathode electrode.

7. The device of claim 1 in which said outer cylinder has an opening therein whereby the interior of said device is subjected to ambient pressure.

8. The device of claim 7 which includes leads for supplying operating potentials to said device, said leads having a pressure responsive switch connected in series therewith to facilitate operation of said device in outer space.

9. The device of claim 7 in which the two innermost of said cylinders comprise a first microwave cavity whereby input signal may be supplied between said two innermost cylinders,

the outer and central cylinders comprise a second microwave cavity, said central cylinder forming a portion of a direct current blocking capacitance in the circuits of said first and second cavities.

:u rax a 5 2922330 UNITED STA'IICS PA'IEN'I OFFICE CERTIFICATE (II CGIIRECIIQN Patent No. 3, 662, 209 Dated May 9, 1972 Inventor(s) James E. Beggs It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE TITLE After "PROVIDING" delete 'SWAP" and substitute therefor SNAP IN THE SPECIFICATION Col. 3, line 52 After "tungsten" insert or tungsten Signed and sealed this 12th day of September 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOI'TSCHALK Attesting Officer Commissioner of Patents

Claims

1. An electron discharge device comprising three concentric cylinders, a planar anode member supported by the outer of said cylinders, a unitary cathode, grid, and heater assembly being contained within said outer cylinder and being supported by one of said remaining cylinders, said Assembly comprising a disk having two parallel outer surfaces and a peripheral groove, one of said remaining cylinders having an inner groove and a garter spring comprising a resilient helical conductor encircling said assembly and in snap-fitting engagement with both said grooves, said helical conductor resiliently supporting said unitary assembly from said one remaining cylinder and providing a low conductive path between an electrode on said assembly and said one remaining cylinder, said helical conductor also positioning said assembly along the axis of said cylinders and in predetermined relation with respect to said planar anode member.

9. The device of claim 7 in which the two innermost of said cylinders comprise a first microwave cavity whereby input signal may be supplied between said two innermost cylinders, the outer and central cylinders comprise a second microwave cavity, said central cylinder forming a portion of a direct current blocking capacitance in the circuits of said first and second cavities.