US3638062A

US3638062A - Support for composite electrode structure

Info

Publication number: US3638062A
Application number: US83307A
Authority: US
Inventors: James E Beggs
Original assignee: General Electric Co
Current assignee: General Electric Co; INDIANA NATIONAL BANK
Priority date: 1970-10-23
Filing date: 1970-10-23
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25

Abstract

An electron discharge device of the planar electrode-type and having a bonded heater-cathode control electrode assembly, employs two garter springs which engage peripheral grooves in the assembly to support rigidly the assembly in the tube structure and at the same time provide low-inductance connections to the control and cathode electrodes. Springs for making contact to the heater of the assembly also force one of the garter springs into engagement with a stop to achieve desired positioning.

Description

United States Patent Beggs [4s 1 Jan. 25, 1972 [54] SUPPORT FOR COMPOSITE Primary Examirrer-David Schonberg EL TR T Assistant Examiner-Paul A. Sacher C 0 E S RUCTURE A!t0rney-Paul A. Frank, John F. Ahern, Julius J. Zaskalicky, [72] Inventor: James E. Beggs, Schenectady, NY. Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [73] Assignee: General Electric Company [57] ABSTRACT [22] Filed: 1970 An electron discharge device of the planar electrode-type and [21] A l. No; 83,307 having a bonded heater-cathode control electrode assembly, employs two garter springs which engage peripheral grooves in the assembly to support rigidly the assembly in the tube [5.2] U.S.Cl ..3l3/337, 3l3/250, 3l3/252, Structure and at the Same time provide low inductance com 313/269 5 3l 3/348 nections to the control and cathode electrodes. Springs for [51] '3" Cl 1/20 H013 19/14 H013 H46 making contact to the heater of the assembly also force one of [58] Field ofSearch "313/250, 252,283,337, 269, the garter springs into engagement with a Stop to achieve 313/348 desired positioning. [56] References Cited 10'Claims, 2 Drawing Figures UNITED STATES PATENTS 3,573.535 4/1971 Hughes ..3l3/348 i a --l5 a a s a a s p p l6 O fz c c a flo a 1: 020 o W ExiS 0 0 0 5 5 i y z n ia a?) 0 D0 n 0 :CCW2O W i\\\\\= q u 23 24 k4 k I? k I 1 \l PATENTEUJANZSIQYZ 8,638,062

[n vent or? James 15'. Begga #2915 A 6 orney SUPPORT FOR COMPOSITE ELECTRODE STRUCTURE My invention relates to electron discharge devices of the planar electrode type and in particular to features of the device to facilitate the manufacture and provide mechanical stability and improved electrical characteristics. The invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Army. Electron discharge devices which are used for either the generation or amplification of microwaves require short direct connections to the control electrode and the cathode to minimize inductance in such connections. Also, for efficient operation of the cathode, head loss through any such connection must be as low as possible. In my copending application Ser. No. 39,284, filed May 21, 1970, and assigned to the assignee of this present invention, there is disclosed an electron discharge device which is easily manufactured, the assembly operation being shortened by use of a garter spring arrangement to snap a unitary cathode, grid, and heater assembly into position in the device. While such an arrangement facilitates the assembly of an electron discharge device, it is always desirable to eliminate insofar as possible the steps of positioning electrodes within a device as well as making contacts between electrodes and external connections. Also, it is desirable in fabricating such devices to eliminate or at least minimize the use of sealing material, such as brazing materials, which during operation of the device may adversely affect the electrical characteristics of the device and its ultimate life.

It is a principal object of my invention to provide a new and improved arrangement for making contacts to cathode and control electrodes of an electron discharge device which provide low-inductance connections to such electrodes.

It is another object of my invention to provide a structure for an electron discharge device in which the number of manufacturing steps is reduced.

It is another object of my invention to provide a new and improved contact-making arrangement for an electron discharge device which provides a rigid support for a control electrodecathode structure relative to the enclosing envelope of the device.

One of the features of my invention consists in employing in an electrondischarge device a bonded heater, cathode, control electrode assembly which is circular in configuration and provided with a pair of peripheral grooves and employing an electrode support and contact-making arrangement in the form of a pair of conductive garter springs which fit into the grooves of the electrode structure to provide low inductance conductive contacts between the cathode and control electrode and contact rings for the respective electrodes which extend through the envelope of the device to provide external connections to the electrodes.

Another feature of the invention consists in employing a pair of conductive springs for making contact to the heater of the electrode structure, permanent connection between such springs, the heater and base contacts being formed during the final exhaust operation for the device, the springs also serving to move the bonded assembly into engagement with a stop and assure desired positioning of the assembly in the device.

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

FIG. 1 is a vertical sectional view of an electron discharge device embodying my invention, and

FIG. 2 is an exploded view of the device of FIG. 1 which illustrates assembly steps employed in the manufacture of the device.

The device illustrated in FIGS. 1 and 2 comprises a composite anode structure 1, a cathode 2, a perforate control electrode 3, and a heater 4. All of these elements are of the planar electrode type and for proper operation of the device must be maintained in accurate, rigidly spaced relation.

The composite anode includes an electron receiving surface 5 which may be formed of a suitable material, such as, for example, molybdenum, and an annular member 6 which may be formed of a metal having excellent gettering properties, such as, for example, titanium. Member 6 is provided with an outwardly extending flange 7 for making external contact to the anode.

The cathode, control electrode, heater assembly is a bonded structure of the type disclosed and claimed in my copending application Ser. No. 39,284, filed May 2|, i970, and assigned to the assignee of this present invention. This unitary structure comprises a disk 8 of a porous refractory metal, such as tungsten. To obtain thermionic emission from the cathode, the pores of the cathode disk are filled with a suitable mixture of oxides, such as, for example, a mixture of barium, calcium, and aluminum oxides. After excess oxide is removed from the surface of disk 8, a layer 10 of insulation, such as, for example, boron nitride, is formed, preferably by chemical deposition over the surface of the cathode disk. Perforate control electrode 3 is formed on the upper surface of the disk by first depositing a layer of tungsten over the insulated coated cathode disk. Perforations are then formed in layer 3 by placing a master grid in contact with the layer and using a blast gun to discharge particles to erode through the portions of layer 3 not covered by the master-grid and through insulating layer 10. In this erosion step, penetration of the openings in the master grid is deep enough to erode through film 3 and insulating layer 10 to reach the surface of cathode disk 2 and form a replica of the control electrode pattern on the surface of the cathode.

The pattern of a heater 1 1 is formed on the reverse or lower side of the coated cathode disk by using essentially the same procedure. In this step, however, the erosion is stopped as soon as the overcoating metal layer surface is penetrated. By so doing, a continuous sheet of insulation remains between heater ll-and the cathode disk. The layer of insulation thus provides high heater-cathode breakdown voltage and also prevents electrons from the cathode from penetrating to the heater. 1

Cathode disk 2 contains two

peripheral grooves

12, 13 which provide means for positioning and rigidly supporting the cathode in the electron discharge device. During the erosion steps previously mentioned, the portion of insulating layer 10 over groove 13 is removed to provide a low-conductive contact region to the cathode.

The structure of the electron discharge device and its envelope is completed by cylindrical insulator 15 positioned between annular member 6 and an externally available control electrode contact member 16, a cathode contact ring 17, and insulating base member 18. Insulator 15 may be formed of a spinel or forsterite and an additional member 19 may be sealed between the lower end of insulator l5 and control electrode contact ring 16. Member 19 and control electrode ring 16 both may be formed of titanium. Cathode contact ring 17 likewise may be formed of titanium and is separated from control electrode contact ring 16 by an input insulator 20 and a metal spinning 21. Spinning 21 is provided on its inner surface with an upwardly extending flange 22, and, preferably, is formed of titanium.

Base member 18 is provided with a pair of

apertures

23, 24 across which are sealed

heater contact buttons

25, 26. These buttons may be of any suitable metal, such as titanium, which can be sealed to the spinel or forsterite base member 18. A ring 27 of titanium is positioned between the upper surface of base insulator 18 and contact ring 17.

In accordance with my invention, a pair of

garter springs

30, 31 are positioned respectively between control electrode contact ring 16 and groove 12 in the control electrode-cathode assembly, and between spinning 21, conductively sealed to cathode contact ring 17 and groove 13 in the control electrode-cathode assembly.

Garter springs

30, 31 preferably comprise coiled helical turns of a suitable metal, such as, for example, tungsten or a tungstenrhenium alloy, so that they provide a good conductive connection between the control electrode-cathode assembly and contact rings l6, 17. Contact ring l6 is provided with a stop 32 in the form of a shoulder on grid contact ring 16 for receiving garter spring 30 and limiting its upward movement. Control electrode 3 extends over the upper edge of insulating layer 10 to form an edge portion or contact region 34 which engages garter spring 30. In this manner, garter spring 30 makes a low resistance, low-inductance contact between control electrode 3 and control electrode contact ring 16. Similarly, garter spring 31 which contacts uninsulated groove 13 and the inner portion 22 of spinning 21, which together with ring 17 forms the cathode contact ring, provides a low resistance, low-inductance connection between the cathode and the cathode contact ring.

I also provide an easily assembled, low-resistance connection between

heater contact buttons

25, 26 and

heater input terminals

35, 36. This connection comprises a pair of

contact springs

37, 38 positioned respectively between button 25 and terminal 35 and between button 26 and terminal 36. Contact

springs

37, 38 are formed of a suitable metal which will retain its resilience even at high temperatures and may be formed, for example, of a tantalum-tungsten alloy.

In assembling the electron discharge device disclosed, as shown in FIG. 2 the anode assembly, together with insulator and titanium member 19 are assembled and sealed together as a unit. The bonded control electrode heater unit is fabricated separately. Finally, the base assembly comprising insulator l8,

heater contact buttons

25, 26 and titanium ring 27 are sealed together as a unit. Thereafter, the bonded control electrode, cathode, heater assembly is snapped into position within the control electrode and cathode contact rings. The anode assembly, the control electrode-cathode contact assembly, and the base assembly are then stacked together with

heater contact springs

37, 38 being positioned between button and terminal 35 and between button 26 and terminal 36. The heater contact springs provide firm contact to the heater terminals and input buttons, and also maintain the heater-cathode control electrode assembly in desired position against stop 32. Also, very thin shims (not shown) of a suitable metal, such as nickel, may be placed between members l6, l9 and

members

17, 27 to assist in sealing these members together during the heating step. The assembled unit is then exhausted and heated to a temperature of the order of l,000 C. At this temperature the heater contact springs and the garter springs sinter sufiiciently to provide good electrical contact respectively to

heater terminals

35, 36 and input buttons 25 26 and to the control electrode and cathode rings 16, 22.

The resultant electron discharge device has an extremely long life, is rugged and is suitable for operation in the microwave region. Long life is obtained by the use of titanium surfaces in many places within the sealed structure to provide a continuous gettering function. The absence of all high vapor pressure materials such as solders and braze materials in contact with the cathode, grid, and heater electrodes assures that there will be no sublimation of such materials during operation of the tube to adversely affect the electrical characteristics of the device or shorten the life of the device. Lowcontact resistance and low-inductance connections are provided by the short direct connections between the grid and cathode electrodes and their external connections, these short low-inductance connections being made through the use of garter springs 30, 31, contacting respectively control electrode 3 and its external connection and cathode 2 and its external connection.

One of the advantages of my structure is that the generous use of titanium in the structure, together with the ceramics employed, provides an ideal enclosure for a long life, grid control amplifier tube. All of the envelope parts, the titanium, ceramic and shim materials can be degassed in vacuum at temperatures of at least l,200 C. They permit the completed tube upon assembly to be exhausted and sealed at approximately l,000 C. This high temperature processing, coupled with the excellent gettering properties of the clean titanium metal, provides an essentially gas-free operating environment for the thermionic cathode.

The clean materials assure that excellent conductive connections are made and maintained at all contact points within the evacuated device. These points are the contact regions of

springs

37, 38 with

terminals

35, 36 and

buttons

25, 26, the points of engagement of the turns of garter spring 30 with region 34 of electrode 3 and ring 16, and the points of engagement of the turns of garter spring 31 with groove 13 of cathode 2 and flange 22.

While I have shown and described a specific embodiment of my invention, it will be obvious to those skilled in the art that many changes and modificatons may be made without departing from my invention in its broader aspects and I, therefore, intend the appended claims to cover all such changes and modificatons 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. In an electron discharge device having an envelope, a bonded heater, cathode, control electrode assembly positioned within said envelope and comprising a circular porous conductive member impregnated with an electron emissive material and having a pair of planar surfaces and a pair of spaced circumferential grooves,

a perforate control electrode supported on one of the surfaces and having an edge portion adjacent one of the grooves, and a heater supported on the other surface,

an electrically insulating material disposed in said one groove and interposed between said porous member and said edge portion, the other of said grooves providing electrical connection to said porous member,

an electrode support and contact-making arrangement concentrically encircling said porous member comprising spaced, electrically insulated, annular control electrode and cathode rings extending through said envelope and providing external contacts, and a pair of conductive garter springs in the two grooves of said porous member, one of said springs conductively contacting said edge portion and said control electrode ring, the other of said springs conductively contacting said porous member and said cathode ring.

2. The arrangement of claim 1 in which said envelope includes a base member having a pair of spaced openings, contact members sealed across said openings, and conductive resilient members positioned between the contact members and input contacts on the heater.

3. The arrangement of claim 2 in which said resilient members are formed of a tantalum-tungsten alloy.

4. The arrangement of claim 1 in which spring stop means is attached to one of said rings.

5. The arrangement of claim 1 in which all portions of said porous member with the exception of the one of said grooves contacted by said other spring and those portions of the porous member underlying perforations in the control electrode are covered with a layer of inorganic insulation.

6. The arrangement of claim 1 in which said garter springs comprise coiled helical turns of metal wire, the metal of said wire being selected from the group consisting of tungsten and an alloy of tungsten and rhenium.

7. The arrangement of claim 6 in which the control electrode and cathode rings consist'of titanium.

8. In an electron discharge device of the planar electrode type having a planar anode and an enclosing envelope, the combination comprising a unitary control electrode, cathode, and heater assembly comprising a porous refractory metal disk impregnated with electron emissive material,

a layer of inorganic insulation coating said disk, said coated disk having parallel outer surfaces,

a perforated control electrode formed on the one of said surfaces opposed to said anode, said insulation layer having openings corresponding to perforations in said electrode,

' 9. in the device of claim 8, a base in said envelope, a pair of contacts in said base, said heater having'a pair of terminals,

and resilient conductive members positioned between respective of said contacts and corresponding of said terminals.

10. In the device of claim 9, a stop on one of said electrode rings, said resilient conductive members moving one of said garter springs into engagement with said stop.

Claims

1. In an electron discharge device having an envelope, a bonded heater, cathode, control electrode assembly positioned within said envelope and comprising a circular porous conductive member impregnated with an electron emissive material and having a pair of planar surfaces and a pair of spaced circumferential grooves, a perforate control electrode supported on one of the surfaces and having an edge portion adjacent one of the grooves, and a heater supported on the other surface, an electrically insulating material disposed in said one groove and interposed between said porous member and said edge portion, the other of said grooves providing electrical connection to said porous member, an electrode support and contact-making arrangement concentrically encircling said porous member comprising spaced, electrically insulated, annular control electrode and cathode rings extending through said envelope and providing external contacts, and a pair of conductive garter springs in the two grooves of said porous member, one of said springs conductively contacting said edge portion and said control electrode ring, the other of said springs conductively contacting said porous member and said cathode ring.

7. The arrangement of claim 6 in which the control electrode and cathode rings consist of titanium.

8. In an electron discharge device of the planar electrode type having a planar anode and an enclosing envelope, the combination comprising a unitary control electrode, cathode, and heater assembly comprising a porous refractory metal disk impregnated with electron emissive material, a layer of inorganic insulation coating said disk, said coated disk having parallel outer surfaces, a perforated control electrode formed on the one of said surfaces opposed to said anode, said insulation layer having openings corresponding to perforations in said electrode, a heater formed on the other of said surfaces, said disk having a pair of spaced circumferential grooves, a pair of insulatingly spaced electrode rings encircling said unitary structure, and a pair of garter springs positioned in said grooves, a first of said springs contacting said control electrode and one of said electrode rings, the other of said springs contacting said porous metal disk and the other of said electrode rings.

9. In the device of claim 8, a base in said envelope, a pair of contacts in said base, said heater having a pair of terminals, and resilient conductive members positioned between respective of said contacts and corresponding of said terminals.