US2939986A - Electron tube structures - Google Patents

Description

June 7, 1960 H. A. LANGER ETAL 2,939,935

ELECTRON TUBE STRUCTURES Filed Oct. 15, 1957 3 Sheets-Sheet 1 FIG. I

INVENTORS HELMUT A. LANGER BY ALDO S. TALBAGK AG T June 7, 1960 H. A. LANGER ETAL 2,939,986

ELECTRON TUBE STRUCTURES Filed Oct. 15, 1957 3 Sheets-Sheet 2 INVENTORS HELMUT A. LANGER 2 I AGENT June 1950' H. A. LANGER ETAL 2,939,986

ELECTRON TUBE STRUCTURES I Filed Oct. 15, 1957 3 Sheets-Sheet 3 INVENTORS HELM UT A LANGER BY ZALDO S. TALBACK AGENT ELECTRON TUBE STRUCTURES Heimut A. Longer and Waldo S. Taibach, Stamford,

Conn, assignors, by mesne assignments, to The Machlett Laboratories, Incorporated, Spi'ingdale, Conn, a corporation of Connecticut Filed Oct. 15, 1957, Ser. No. 690,356

Claims; (Cl. 313-247) This invention relates to improvements in electron tubes and has particular reference to electron tubes capable of delivering relatively large amounts of power and to novel electrode structures there-for.

Still more specifically this invention relates to an electron tube of particularly rugged assembly construction and embodying novel arrangements of sub-assemblies, particularly electrode supporting structures, which permit the various electrodes to be quickly and easily mounted in automatically aligned relations with respect to one another without the requirement of additional aligning operations, and wherein the structures are such that the electrodes will maintain their aligned relations throughout long tube life.

This invention is an improvement upon known electron discharge devices wherein the electrodes are insecurely mounted and consequently tend during use to leave their proper prealigned relative positions. Other known devices are of a complicated nature, difficult to manufacture and assemble, and in the manufacture thereof require special cleaning operations to eliminate oxidation formed during brazing processes and the like.

Accordingly, it is a primary object of the present invention to overcome the above and other disadvantages of known electron tubes by the provision of an improved electron tube characterized by a novel rugged construction able to withstand mechanical shock and vibration and having a relatively long life.

Another objectis to provide an electron tube construction which embodies novel sub-assemblies, portions of which may be individually shaped after being fitted together into a unit wherebythe preassembled electrodes will be individually supported in proper and secure relative positions without additional alignment operations.

A further object is to provide a tube wherein the parts which are fixedly and rigidly secured togethere by means such as welded or brazed connections, may be assembled easily and efiiciently in a clean manner.

A still further object is the provision of novel means and method of forming a grid of parallel wire construction wherein the grid wires are securely fixed in place but are allowed to expand in an axial direction to prevent bowing When heated.

Another object is to provide an electron tube of the above character having a novel cathode structure embodying improved heat control means.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings, in which Fig. l is an axial sectional view of an electron tube embodying the invention;

Fig. 2 is an enlarged elevational view partly in section of the electrodes of the tube disclosed in Fig. 1;

Fig. 3 is a horizontal sectional View taken substantidly on line 33 of Fig. 2;

Fig. 4 is an enlarged axial sectional view of the electrode supporting structures;

Fig. 5 is an enlarged vertical sectional view of the joint between the screen grid support and its mounting; and

Fig. 6 is an enlarged vertical sectional view illustrating the connection between the control grid support and its mounting.

Referring more particularly to the drawings, the illustrated tube embodying the invention inciudese a hollow cylindrical anode 10 which forms one end portion of the envelope of the tube. The outer end of the anode is closed and the inner end is connected by a Kovar seal 11 to one end of an annular dielectric bulb 12. Within the bulb 12 is an axially extending tubular support 13 which is of substantial thickness and, thus, relatively rugged. The end of the support 15 opposite the anode is sealed to a terminal ring 14 which is in turn sealed by a Kovar ring 15 to the end of bulb 12.

Within and spaced from the first support 13 is a second tubular support 16 which extends coaxially therewith and is also relatively thick and, therefore, rugged in con-- Support 16 has a terminal ring 17 mounted on its outer end and sealed to support 13 by an annulararrangement consisting of a pair of Kovar rings 18 struction.

and 19 interconnected by a dielectric ring 20, ring 18 being connected directly to terminal ring 17 and ring.

19 being sealed to a third metal ring 21 carried by the inner surface of support 13. Ring 21 has a planar portion the inner edge of which fits relatively snugly about the outer surfaceof support 16 approximately midway thereof, and has its outer peripheral edge sealed to the inner surface of support 13, whereby the supports are maintainedsubstantially parallel.

The envelope of the tube is completed by a reentrant structure embodying another pair of Kovar rings 22 and.

2.3 interconnected by a dielectric ring 24, ring 22 being sealed to terminal '17 inwardly of support 15, and ring 23 being sealed to a platelike member 25 which closes' the end of the tube.

Fixedly mounted on the inner end of support 13 is a relatively heavy deck 26' which is provided on the outer edge of its surface nearest the anode with a shallow annular groove 27 (Figs. 4 and S) which is machined into the deck 26 so as to lie in a plane substantially per-- fectly normal to the axis of the support 13.

The screen grid structure is adapted to be mounted" on the deck 26 and comprises an annular support ring.

28, the lower end of which is turned inwardly to form a flange 29 having an inside diameter of predetermined size whereby the flange 29 fits snugly within the groove 27 in deck 26. The opposite end of the support ring 23 carries an annulus 30 which is initially provided with a plurality of equally spaced openings in which are located the ends of respective axially extending screen grid wires 31. The annulus 30 is preferably made of copper or other relatively soft metal and is provided with a cir-- curnferential groove 32 (Fig. 4) throughout its outer periphery which provides a relatively thin wall 33 between the groove 32 and grid wires 31. sired that the Wires 31 be allowed to expand longitudinally when heated, they are held in place within their Since it is de-- on the ring'28 .to form one sub-assembly. The surface of the flange 29 which is to be positioned upon the groove 27 'in deck 26 is machined to a plane which is substantially perfectly normal to the axis of the screen grid structure. 7

I Then the structure is positioned upon the deck 26 with flange 29 positioned in groove 27, whereupon the grid 'will automatically assume an accurate alignment with the axis of the support 13. To retain the entire screen grid structure in position, the deck 26 is provided with a plurality of threaded openings fo'r'receiving screws 35 (Fig. which carry washers 36. The screws 35 are mounted in the deck close enough to the flange 27 so that the washers 36 will overlie the flange, holding it in the groove 27.. The ring 28 is also provided with openings 3'7 for access to the screws with a screwdriver.

The deck 26 is provided with a central opening in whichis rigidly secured one end of a tubular cathode support 38 which extends upwardly toward the anode. Threaded onto the other end of the cathode support 38 is a mounting ring 39 which has one surface 40 extending slightly into the anode area beyond the adjacent surface of the support 38. Surface 40 is machined so as to lie in a plane substantially perfectly parallel to the plane of the machined groove 27 in deck 26.

A hollow cylindrical cathode 41 is adapted to be carried by the mounting ring 39 and has adjacent one end an inner flat flange-like annular portion 42 which rests firmly upon surface 40 and is adapted'to be retained in position by screws. The surface of portion 42; is also carefully machined, prior to. assembly with ring 39, so as to lie in a plane substantially perpendicular to the axis of the cathode 41. Thus the cathode will be automatically aligned parallel with grid wires 31 when the 45a in the deck in a direction toward the anode. A third deck 46'(Figs'. 1, 4 and 6) is screwed or otherwise mounted upon the ends of the posts 45 and hasi'a 47 which is directed toward the anode. The surface 48- of the deck adjacent the rim 47 is machined to lie in a' plane parallel to the machined surfaces '27 and 40 and provides an annular seat upon which isposition'ed a grid-supporting ring 49. I

A plurality of control'grid wires, are mounted in the ring 49 in a manner similar to'the mounting for screen grid wires 31. Ring 49 is provided with openings in which the wires 50 are positioned and with an outer peripheral groove 51 forming a thin walled portion which permits deformation so as to closely embrace the wires, allowing them to expand longitudinally but restraining them from lateral displacement.

The bottom of groove 51 forms'a lip which is adapted to lie ina plane substantially coextensive with the upper surface of the rim 47 on deck 46 (Fig. 6). Thus a screw 52 can be inserted in rim 47 and a washer 53 thereon will overlie the lip of the groove 51 so as to retain the parts in assembled relation.

The surface of the ring 49 which rests upon surface 48 of deck 46 is, previous to assembly with the deck, machined so as to lie in a plane perpendicular to the axis of the cylinder formed by the grid wires 50. Thus, after the assembly is completed, the screen grid wires 31, control grid wires 50 and cathode 41 will be substantially parallel. f

The unsupported ends of the control grid 50 are rests directly upon the baflle.

secured to a relatively rigid ing 50a (Fig. 1) so as to be maintained in predetermined parallel spaced relation. As shown in Fig. 3, the control grid wires 50 are provided in equal numbers to screen grid wires 21 and are respectively radially aligned therewith between wires 21 and the cathode 41.

The outer surface of thelcathode 41 is provided with a plurality of longitudinally extending spaced grooves 54 in which is placed a selected electron emissive material.

The lands 55 between the grooves 54 are of predetermined shapes and are radially aligned with the grid wires 50 and 21. Thus, when the cathode is heatedand suitable grid and anode' potentials are applied, electrons from the emissive material will be beamed toward the anode through the control and screen grids. The electrode structures and their functions are more fully described in copending US. patent application Serial No. 675,080, filed July 30, 1957, and for more detailsthereof reference should be made to that application.

The cathode 41 is adapted to be heated by a filamentary or mesh type heater 56 (Figs. 1 and 3) which is preferably of cylindrical shape and coaxially mounted within the cathode. The lower end of heater 56 is secured to an annular support 57 which has an outwardly turned flange portion 58 by which the support is secured to the flange 42 of the cathode and to the mounting ring 39 by use of screws 58a.

The other end of the heater 56 is secured to a shallow cup-shaped member 59 (Fig. l) which is adapted to rest upon a bafile 60 which is carried by an axially extending 4 of the heater 56 and terminates adjacent'the end of the assembled electrode structures.

The baflle 60 rests upon a ledge formed by making the end portion of the rod 61 of smaller diameter than the remainder thereof; and the cup-shaped member 59 A group of additional baflles 63 are mounted'on the reduced end portion of the rod 61 and are held in place by a nut 64' threaded onto the end of the rod. Small rings or washers are used to space the baffles from one another and from the member 59.

Annular baflles 65' are also provided at the opposite end of the heater structure and function with baflies 63 to confine .heat to the area within the cathode 41.

Baflle 60 carries a tubular shield 66 which extends axially of the heater 56 and closely therewithin to still further deflect heat toward the cathode. V

A getter device 67, preferably formed of a wire of selected gettering material, encircles rod 61 within shield 66 and has its ends connected directly to the rod.

At the other end of the tube, platelike closure member 25 also carries a relatively thick rod 68 of good heat conductive material whichextends outwardly through the reentrant portion of the envelope and carries on its outer end a plurality of coolingfins 69. This allows cooling of the control grid structure.

The anode 10 is adapted to be directly supplied with suitable electrical potential. The heater 56 is supplied with electrical energy through terminal 17, support 16, deck 62, rod 61, baffle 59and through support 57, ring 39, tubular support 38, deck 26, support 13 and terminal 14. 'The cathode 41 is mounted directly on ring 39 and, therefore, is supplied with potential from terminal 14. The screen grid 31 is adapted to be operated at cathode potential and, therefore, also is suppliedwith potential from terminal 14. The potential for control grid 50 is supplied thereto from rod 68 through closure member 25, deck 44, posts 45, deck 46 and ring 49.

From the foregoing description it will be apparent that we have provided a novel tube structure which embodies a group of sub-assemblies which may be quickly and easily assembled into the final tube structure according to some of the objects of this invention. This tube structure is of especially rugged and durable construction and embodies no brazed or welded joints which must be made within the envelope after sub-assemblies are completed.

Various additions and modifications within the scope of this invention will readily become apparent to one skilled in the art, such as the placing of an annular shield 80 at anode potential between the Kovar seal 11 and the adjacent grid structure at a diiferent potential to prevent damage to the glass-to-metal seal. It is intended, therefore, that all matter shown and described herein be illustrative and not limiting in its scope.

We claim:

1. A high power electron discharge device comprising a dielectric bulb having at one end an outwardly axiallyextending hollow anode and having at the other end three cylindrical metal electrode supports extending inwardly of the bulb in spaced insulated relation one within another and substantially coaxial with the anode, the outermost electrode support having decks on its inner end respectively supporting one end of a first grid and a cylindrical indirectly-heated cathode structure, the grid and the cathode structure both extending coaxially into the anode, the cathode structure being located in spaced relation within the grid and including a cylindrical heater having one end connected with one of said decks, the innermost electrode support having a deck on its inner end carrying a second grid which extends into the anode coaxially with and between the first grid and the cathode structure, and the third electrode support having a deck on its inner end carrying a conductive member which extends coaxially through the cathode structure and heater and is connected to the unsupported end of the heater.

2. A high power electron discharge device as set forth in claim 1 wherein the deck on the innermost electrode support carries a radiator on its outer surface whereby heat from the second grid is dissipated.

3. A high power electron discharge device as set forth in claim 1 wherein the cathode structure comprises a cylindrical hollow cathode proper, an annular base mounted on the cathode-supporting deck within the cathode proper, a mesh type heater of cylindrical shape extending axially of the anode within the cathode proper and having one end fixed to the base, and a disc-like retainer at the other end of the heater and fixed to the conductive member carried by the third electrode support whereby the emitter is retained in extended stretched condition.

4. A high power electron discharge device as set forth in claim 3 wherein the conductive member carries at its free end outwardly of the emitter a baffie device for confining heat to the interior of the cathode proper.

5. A high power electron discharge device comprising a hollow cylindrical anode having a known longitudinal axis and having one end closed, an annular dielectric bulb having one end sealed to the open end of the anode, a hollow indirectly-heated cylindrical cathode structure positioned within the anode, a pair of grid structures mounted one within the other between the cathode structure and the anode, and conductive means supporting the grid and cathode structures comprising first and second hollow cylindrical coaxial electrode terminal supports of different diameters positioned one within another within the bulb and extending coaxial with the axis of the anode toward the grid and cathode structures, the outer ends of the supports being supported by the end of the bulb opposite the anode, the first support having a pair of decks conductively aflixed to its inner end, the second support having a deck conductively affixed on its inner end, each deck being provided with an annular surface preformed to be in a plane perpendicular to the axis of the supports, the grid and cathode structures each embodying annular supporting members having a preformed surface lying in a plane perpendicular to the axis of its respective structure and conductively mounted upon the preformed surface of a respective deck whereby the structures are axially aligned on a common axis, the grid structures each including active grids formed of parallel wires fixedly secured at one end, and the annular supporting members each being provided with an annular row of openings in which the other ends of the respective grid wires are located, the wires being frictionally held within the openings and movable longitudinally therein in response to expansion and contraction caused by thermal variations.

References Cited in the file of this patent UNITED STATES PATENTS 2,513,387 Wei July 4, 1950 2,515,337 Clark July 18, 1950 2,707,757 Agule May 3, 1955

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