US2471424A

US2471424A - Electron discharge device

Info

Publication number: US2471424A
Application number: US557880A
Authority: US
Inventors: John J Glauber
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC; Federal Telephone and Radio Corp
Priority date: 1944-10-09
Filing date: 1944-10-09
Publication date: 1949-05-31
Anticipated expiration: 1966-05-31

Description

May 31,1949. 7 J. J. GLAUBER 2,471,424

ELECTRON DISCHARGE DEVICE Filed Oct. 9, 1944 2 Sheets-Sheet l INVENTO JOHN J'- GZ/IUB ATTORNEY May 31, 1949. .1. J. GLAUBER ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed Oct. 9, 1944 IN V EN TOR.

JO/l/V J: 61/7056)? A TTURNFY Patented May 31, 1949 ELECTRON DISCHARGE DEVICE John .I. Glauber, West Orange, N. J., assignorto Federal Telephone andR'adio Corporation; New York, N. Y., a corporation of Delaware .Qpplication October 9, 1944, Serial No. 557,889

17 Claims. (01. 250-275) This invention relates generally to electron discharge devices and particularly to thegrid-cathode structures thereof.

In such devicesaroing to the cathode is undesirable and is particularly deleterious where such arcing occurs to a cathode surface having a coating of emissive materials. Such coated surfaces are more susceptible to injury than uncoated surfaces since arcing tends to cause the coating to peel on or disintegrate, and to cause some of the coating materials to evaporate there by making the electrondischarge device more sassy. The additional gases or vapors thus introduced, particularly in the case of vacuum type tubes, change the mode of operation of said devices, and further tend to cause more arcing since a low-resistance arcing path is provided by the ions formed-inthe path of the discharge.

An object of the present invention is the provision of means ,ior preventing or at least minimizing the possibility oizarcing to :the surface of an electrode structure suscep ible ,to injur cause of said arcing.

Another object of the present invention is the provision of means for preventing arcing to the coated surface of a cathode.

Certain grid structuresconsist of a'plurality of longitudinal members arranged parallel to each other and secured together. Otherforms of grid structures arecomprised of ,a spiral wire supported by longitudinal members. In electron discharge devices employing either of such types of grid structures there is a tendency, forjthe lonitudinal members to bow at some point intermediate the ends thereof towardsthe' cathode. The bowed portion of said members tends to vary the characteristics of the electrondischarge .device, makes arcing. more likely, and in extreme cases may touch the cathode rendering the electron discharge device completely inoperative as well as causing damage to associated equipment. To prevent this bowing, ithas heretofore been known to utilize a ring or similar element ar ranged around the outer sidesof said longitudinal members, that is, the sides away from the oathode, and. Welding said ring. to said sides. This proves inadequate, however, in many cases, par ticularly where a. great deal of heat is generated inside the electron. discharge device. The tendency or" the longitudinal members to bow places a tension upon the lwelds andthe, heat also tends to weaken them. Consequently, the longi udinal members break away ,fromtheir restraining rings, with the deleterious results heretofore mentioned.

A still further 'object prme pifesent invention is the provision of an improved means and arrangement for" preventing bowing of said longitudinal members.

Still another object of the present invention is the provision of meansfor'preventing bowing of said longitudinal members which means also serve to prevent arcing to selected portions'of the cathode. e

In accordance with a feature of the present invention, the inward bowing of said longitudinal members is prevented by arranging one or more metallic rings or similar elementswhich are relatively incompressible,"intermediate the endsof said longitudinal members and in between said members, with portions of saidelementsabutting the inner sides of said longitudinal members and welded thereto. Consequently, when the longitudinal members tend to bow inwardly they push against said element and since said element is relatively incompressible, the inward bowing is inconsequential.

Further, in accordance with a feature of my invention, said elements are employed to provide a safety spark gap or' arcing path to an uncoated portion of the cathode and-thus toprevent injury to the cathode coating-by arcing. This is accomplished by making thedistance between said element and the uncoated portion of the cathode shorter than the distances between said element and the coated portion of the cathode or between any portion of the grid structure and the coated portion of the cathode.

Other and further objects of the present invention will become apparent and the foregoing will be best understoodfrom the following description of embodiments of my invention, reference being had to the drawings in which:

Fig. l is a longitudinal sectional view of an electron discharge device embodying my invention; I l

Fig. 2 is an enlarged detailed view of a portion of the cathode-grid structure; and

Fig. 3 is an elevational view of an electron discharge device partly broken away to give a view of a modified form of cathode grid structure embodying my invention.

Referring now'to Fig. 1 the numeral I generally designates an electron discharge device having an envelope generally designated as 2 including insulating portions 3, '4 and 5, with portions 3 and 4 connected by an annular ring 6, and portions 4 a'ndli connected by a similar annular grid ring 7.

Rings

6 and 1 are provided with feather edged flanges 8 sealed to the ends of the insulating portions therea'djacent.

The envelope is completed by an anode block 9 of the reentrant type having a feather edge l provided at the outside thereof sealed to the lower end of insulating portion 5. The active port-ion of the anode is a cylindrical anode surface H which may be formed by boring a hole in the end of the copper block.

Arranged within said cylindrical anode surface ii is a cylindrical cathode l2 surrounded by a cylindrical grid l3.

Passing through and sealed in the insulating portion 3 of the envelope are the heater support members l4, l5 and I6. The cathode l2 illustrated in Figs. 1 and 2 is of the indirectly heated type and supports M, l5 and H5 are also employed as current-carrying leads for heating the heating element ii. The cylindrical coated emitter E8 of cathode i2 is supported from and electrically connected with ring 6 by means of a tubular member i9.

Grid 53 is of the type comprised of a plurality of longitudinal rods or members 20. The longitudinal rods of grid [3, are welded at one end to a fiared tubular support member 2! which, in turn, is supported from grid ring 1 while at the other end said rods are welded to a spacing and supporting member 22.

As will be seen more clearly in Fig. 2, in accordance with a feature of the present invention, there is provided means for preventin the longitudinal rods 29 of grid Hi from bowing inwardly. These mean-s2 consist of a plurality of relatively incompressible annular elements 23 which are arranged around the cathode, spaced therefrom and in accordance with the present invention arranged intermediate the ends of the longitudinal rods and inwardly thereof between said rods. Elements 23 are preferably made of metal and may be in the form of rings. Elements or rings 23 abut the inner surfaces or the inner sides of the longitudinal rods, that is' the sides facing the cathode, and are welded to said sides at the point of contact. Th elements or rings 23 are thus suspended from the longitudinal rods.

It will be seen that'when the longitudinal rods 20 tend to bow inwardly, they will press against the relatively incompressible rings 23, without, however, putting tension upon the welds and consequently without tending to pull said welds apart.

Further, in accordance with a feature of this invention, means are provided for preventing arein to the surfaces of the cathode coated with emissive materials. For this purpose, the cathode is provided with uncoated portion 2% adjacent the rings 23 supporting grid l3, these uncoated portions 241 separating coated portions 25 of said cathode. The various elements are so arranged that the distance from any ring 23 to its adjacent uncoated portion 2&- is less than the distance between said rin and the nearest point of the coated portion 25. Likewise the distance between'any ring 23 and the cathode I2 is less than the distance between any other point of the grid structure and the cathode structure. By the terms grid structure and cathode structure, as well as electrode structure, I refer in this specification as well as in the claims not only to the grid, cathode, or electrode itself, but also to its leads and supports with the exception of the rings or elements 23.

Consequently it will be seen that when the potential between the cathode structure and grid structure rises to the point at which arcing is likely to occur, the arcing will occur between the ring 23 and the uncoated portion 24 thereby preventing arcing to coated portions 25 of the cathode. t will thus be seen that rings 23 serve a dual function: to support the longitudinal rods, and to provide a safety arcing path or gap to the uncoated portions of the cathode.

While I have described my invention in connection with one form of grid and an indirectly heated type of cathode, it apparent that it may also be employed with other types of cathode, such as for example, the filamentary type of coated cathode, and other types of grid structure such as, for example, the spiral wire type. One form of the cathode and one form of the grid specifically mentioned immediately hereinabove are illustrated in Fig. 3 wherein a tube as includes a cathode Zl comprised of a plurality of parallel bars, strands or filaments 28 arranged in the form of a cylinder and connected at opposite ends to rings 22% and 3! respectively which are connected to a source of filamentary heating current (not shown). The cathode 2'1 is surrounded by a cylindrical grid is! comprised of a spiral grid wire 32 supported by longitudinal rods Or grid laterals 33. To prevent said laterals from bowing inwardly, elements or rings 23, such as those described in Figs. 1 and 2, are arranged in relation to longitudinal rods 33 in the same manner as rings 2;} of Figs. 1 and 2 are arranged in relation to longitudinal rods 20. The filament bars or strands 23 of cathode 2'! are provided with uncoated portions 3t, and portions 35 coated with emissive materials. The distances and dimensions of the various elements are selected as described in relation with Figs. 1 and 2 to provide a safety sparking gap between rings 23 and the uncoated portions 3 3' of the filaments 2d.

Accordingly, it will be seen that my invention may be employed with various types of gridcathode structures, and 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 of my invention and the accompanying claims.

I claim:

1. An electron discharge device comprising a pair of adjacent electrode structures, one of said structures having a plurality of surfaces, one of said surfaces bein more susceptible to injury by arcing thereto than the other of said surfaces, and a conductive member electrically integrally connected with the surface of said other structure and spaced from said less susceptible surface a distance less than the distance between said other structure and said more susceptible surface.

2. An electron discharge device according to claim 1 wherein said conductive member is separated from said less susceptible surface a distance less than the distance between said member and said more susceptible surface.

3. An electron discharge device, comprising a pair of adjacent electrode structures, one or" said structures having a surface susceptible to injury by arcin thereto, and a conductive member electrically integrally connected with the surface of said other structure and spaced at a shorter dis tance from said one structure than said other electrode to provide a shorter path between said other structure and a point on the one structure remote from said susceptible surface having less resistance to arcing than the path between said other structure and said surface.

4. A discharge device according to claim 3, wherein said one structure includes a cathode having a coating of emissive material on said surface and said point is at an uncoated portion of said cathode.

5. An electron discharge device, comprising a cathode and another electrode structure adjacent said cathode structure, said cathode having a surface coated with emissive materials and an uncoated surface, and a conductive member electrically integrally connected to the surface of said electrode structure and spaced from said uncoated surface a distance less than the distance between said other electrode and said coated surface to provide a path between said electrode structure and the uncoated surface of the cathode having less resistance to arcing than the path between said electrode structure and the coated surface.

6. An electron discharge device comprising a pair of adjacent electrode structures, one of said structures having a plurality of surfaces, one of said surfaces being more susceptible to injury by arcing thereto than the other of said surfaces,

and means reinforcing th other structure, and

arcing thereto, and means reinforcing the other structure, and providing a shorter arcing path to the less susceptible surface than to the more susceptible surface.

8. An electron discharge device, comprising a cathode having a portion of its surface coated with emissive material and an uncoated portion, a grid structure including a plurality of longitudinal members mounted around said cathode, and a relatively incompressible ring-shaped conductive element mounted around said cathode adjacent said uncoated portion, spaced therefrom, and electrically mounted directly on the surface of said members, the distance between said element and the uncoated portion bein less than the distance between said longitudinal members and the coated portion.

9. An electron discharge device, comprising a cathode having a portion of its surfaces coated with emissive material and an uncoated portion, a grid surrounding said cathode, a plurality of grid laterals supporting said grid and a relatively incompressible ring-shaped conductive element mounted around said cathode adjacent said uncoated portion, spaced therefrom, and fixed to said laterals, the distance between said element and the uncoated portion being less than the distance between the grid and the cathode.

10. An electron discharge device, comprising a cathode having a portion of its surface coated with emissive material and an uncoated portion, a grid surrounding said cathode comprising a plurality of longitudinal members surounding said cathode, and a relatively incompressible annular conductive element mounted around said cathode adjacent said uncoated portion, spaced therefrom, and fixed to said members, the distance between said element and the uncoated portion being less than the distance between the grid and the coated portion of the cathode.

11. An electron discharge device, comprising a cathode having a portion of its surface coated with emissive material and an uncoated portion, a grid structure surrounding said cathode, said grid structure including a plurality of longitudinal members mounted around said cathode, and a ring-shaped metallic ring mounted around said cathode adjacent said uncoated portion and spaced therefrom, said ring being mounted inwardly of said longitudinal members and welded to and suspended from the inner surface thereof, said ring being closer to the uncoated portion of said cathode than to the coated portions of said cathode, and also closer to the cathode than any portion of the grid is to the cathode.

12. An electron discharge device comprising a pair of electrode structures mounted one within the other, the inner structure having a plurality of surfaces, one of said surfaces being more susceptible to injury by arcing than the other of said surfaces, the other of said structures including a plurality of longitudinal members and means prevent ng said members from bowing inwardly, said preventing means comprising a relatively incompressible element mounted between said members intermediate the ends of the electrode structure and abutting and fixed to the inner surfaces of said members, said element being spaced from said less susceptible surface a distance less than the distance to said more susceptible surface.

13. An electron discharge device according to claim 12 wherein said element is mounted from said outer electrode structure.

14. An electron discharge device according to claim 12 wherein said element is metallic and is sealed to the inner surface of the outer electrode structure.

15. An electron discharge device according to claim 12 wherein said incompressible element is ring-shaped.

16. An electron discharge device according to claim 12 wherein said inner electrode structure is a cathode and said outer electrode structure is a grid.

17. An electron discharge device according to claim 12 wherein said outer electrode structure comprises a plurality of grid laterals and a grid wire wound around said laterals, and said incompressibl element is mounted around said inner electrode structure at a distance therefrom, abutting and fixed to the inner surface of said laterals.

JOHN J. GLAUBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,444,438 White Feb. 6, 1923 2,130,280 Knoll Sept. 13, 1938 2,198,323 Wagner Apr. 23, 1940 2,254,095 Thompson Aug. 26, 1941 2,358,542 Thompson Sept. 19, 1944 FOREIGN PATENTS Number Country Date 457,090 Great Britain Nov. 16, 1936