US3004185A - Electron tube - Google Patents

Description

G. M. ROSE, JR

ELECTRON TUBE Oct. 10, 1961 2 Sheets-Sheet 1 Filed May 26, 1958 Oct. 10, 1961 G. M. RosE, JR

ELECTRON TUBE 2 Sheets-Sheet 2 Filed May 26, 1958 INVENTOR BY Ezuas M. RUSJR. Mfl

United State Patent Ofiics 3,004,l85 Patented Oct. 10, 1961 31,0%,185` ELECTRON TUBE George M. Rose, Jr., Mountain Lakes, NJ., assign'o'r to Radio Corporation of America, a eorporation of Dela- Ware Filed May 26, 1958, Ser. No. 737,785 21 Claims. (Cl. 313-245) The present nvention relates to electron tubes. Particularly, the invention relates to an electron tube Wherein the parts thereof have relatively simple and rugged constructions which not only coact to provide atube having mproved performance efliciency but which also contribute to facility in assembling the parts to form the tube.

One field in which the invention finds particular utility is that of receiving type tubes. Conventional receiving type tubes have relatively complex structural features and require certain Imaterials for the parts thereof. These features and materials impose restrictions which limit further improvement both in performance and in ease of tube assembly. Major attempted improvements thereiu, while retaining the present basic design concepts, Would result in enhanced complexity, and thus increase production shrinkage and =field failures.

One of the consequences of the complex structures of conventional receiving type tubes is the unavoidable establishment of undesired mechanical strains therein, resulting from stresses that are necessarily applied during tube fabrication. Such mechanical strains are objectionable in that they involve forces that tend to change initial relative positions of active tube elements established to secure desired electrical characteristics. Where such forces are of a magnitude suflicient actually to accomplish the change referred to, the tube characteristics are aifected adversely to a degree that may destroy further tube utility. Examples wherein the application of such stresses is unavoidable are found in certain Operations, such as forming lead-in wires to desired Shape for engaging predetermined electrodes, bending connector elements to suitably interconnect spaced tube elements, and joining tube parts by welding. a

Another problem resulting from adherenee to -present basic design concepts in relation to receiving type tubes, involves limitations inherent in the compositions of certain tube parts. For example, appreciable reliance has been placed heretofore on mica plates for service as spacing and insulating elements. However, mica structures are relatvely weak and may be incapable of perforrning a spacing function to a highly critical degree. Mica as a material, is also objectionable because of its tendency to delaminate, vand because of its water content. Some of this water is released during tube processing and some during use of a tube. Such release is deleterious to the emitting coatng employed on cathodes in 'receiving type tubes. Another water holding material, glass, is also commonly used in such tubes for stems and bulbs.

'Ihe use of mica and glass as the composition for elements in receiving type tubes, involves an undcsired restriction on the temperature Vused for tube processing. The glass usually used for stems and bulbs softens at a temperature from 400 to 450 C., and mica releases Water vapor at a temperature of about`600 C. The use of mica and glass components in a tube, therefore, precludes use of higher temperatures, if permitted by tube compositions, is desirable not only in that it would permit a fast'er production schedule With a given capital facility, but also in that a better tube Would be produced in which the metal elements thereof would be' more nearly completely free from occluded Vgasses. Absence o f such occluded gasses' would reduce the need for getters .and in fact may permit a complete absence of getters without adverse effects on tube life. Furthermore, the ability to withstand such higher temperatures, permits higher operating temperatures.

A further problem in relation to receiving type tubes involves manufacturing techniques. Conventional receiving tubes require the production of several sub-assemblies in order to make a tube mount Such sub-assemblies comprise at least a stem and an electrode cage. Each of these sub-assemblies is made in a separate locationand by a different type of facility. Thus a stem'is made on a stem machine capable of heatng and Shaping glass to desired form and of locating lead-in wires in suitable relation to the glass to provide a sub-assembly comprising involving a number of individual welds sequentially made' The making of these welds ,requires the applicationrof force from a number of directions, i and give rise to mechanical stresses of muIti-directional character.:

These complex procedures in tube manufacture vare objection-able in that skilled labor is required and'in that the several stages involved in making the sub-assemblie increase the probability .of shrinkage, because of the necessary handling and transport.

But not only does the practicel of making the subassemblies in tube fabrication involve appreciable' Shrinkage and require skilled labor, but it precludes a desired versatile tube design. The need for sub-assemblies renders `it difficult if not impossible to produce a basic design for tubes of different electrode complements.- Usually each cage is unique and difers in many respects from all fother cages. Hence, common parts and` common jigs cannot be used for several different tube types. This lack of fiexibility in conventional receivin'g tube designs is a serious bar to economics in tube manufacture. I

While the foreg'oing problems are associated with receiving type tubes; it is obvious that they may also characterize other tube types, especially where volume production is involved. g

Accordngly, it is an object of the invention to provide 'an improved electron tube having enhanced performance eificiency. V i

A further purpose is to provide an improved electro tube structure which is characterized by enhanced versatility and simplicity for facility in manufacture.

Further objects in accordance'with the foregoing are:

To provide an electron tube structure substantially free from strains thatv tend to effect adver'sely the sp'acings of electrodes during operation' of a tube at elevated temperatures;

To provide an electron tube having relatvely simple w i 3 parts for contributing to versatility of tube design and resultant economy in manufacture;

To provide an electron tube having parts adapted to withstand relatively high temperatures without adverse effects, thus enabling the use of improved techniques in manufacture;

To provide an electron tube having parts of relatively rugged structure, thereby contributing to the ruggedness of the tube for preserving relatively small spacings between electrodes thereof; p To provide a tube having parts each comprising an integral and relatively simplestructure, thereby contributing to ease of handling by unskilled labor and to the use of mcchanized'techniques for ltheir assembly;

To provide an electron tube having an electrode assembly in which allof the parts thereof are proportioned and designed to provide simplicity of shape and'ruggedness of construction and to enable the parts to be readily assembled into the proper position in a jig and then securred together into a unitary assembly lby a single brazing operation whereby a rugged'and substantially strain freel assembly is obtained. I

To provide 'an electron tube having improved performance eficiency. i

' An electron tube embodying the invention may have a structure comprising a flat wafer or disc made, for example;.of 'aceramic material, and having openings therethrough defined by walls coated with a suitable metal. Wire lead-ins and supports extending through the aforementioned openings, are suitably bonded to the metal coating referred to, for providing a relatively rugged and hermetic seal therewith. The lead-ins and supports aforementioned extend into the envelope of the tube and are fixed as by brazing to tube parts. The tube parts comprise a plurality of concentricicylindrical electrode elements of progressively enlarged cross-section, each having affixed to one end thereof and in coaxial'relation thereto a metal fiange or collar. For reducing capacitance between the lead-inconductors, a relatively large spacing therebetween is insured by a relatively large transverse extent of the collars in relation to the electrode elements to which they are afi'ixed; Furthermore, the collars are stepped both in regard to their transverse extents as well as in a direction along' the axs of the wafer referredl to, for a purpose that will, become clear.

This 'array of the collars aforementioned permits the lead-ins and supports to be arrayed in concentric circles through'the stem wafer, the number of circles being equal to the number of tube elements requiring connection to suitable power or voltage sources outside of the tube. In the case of a triode having'an indirectly heated cathode, theV number of such circles is four. This provides two lead-ins in the innerrnost circle for the cathode heater, one lead-in in the next adjacent circle for the cathode, and a lead-in in each of the two next adjacent circlesfor a grid and an anode. i i

In addition to the lead-ins referred to, for the cathode, grid, and anode, additional red-like conductors or wires serving exclusively as supports, may partly extend through openings in the stem wafer, for contributing to the support of each of a cathode sleeve, grid and anode. The additional wires in each circle are spaced 120 from each other and from the lead-in Wire positioned in this circle. A pair of each of the support wires aforementioned extends inwardly of the tube for engagement with the collars for each of the cathode sleeve, grid and anode. In this way the lead-in for each of these electrode elements cooperates with two support wires to provide a tripod type of support for each electrode element.

i This tripod type of support is advantageous in that the :inner ends of the wires or red-like members constituting each tripod system, terminates in and defines a plane normal to the electrode axes. This eifectively restrains tilting of the electrodes so that the cathode and grid may be relatively closely spaced without danger of electrical shorts therebetween.

The cathode sleeve aforementioned serves to carry a later applied cathode member in the form of a metallic cup that bears an active emitting coating.

It will be noted that the parts referred to are relatively simple in structure and therefore not only contribute to ruggedness of the tube, but also facilitate appreciably the assembling of the parts to thereby allow an assembling technique to be practiced that assures freedom from harmful strains in the completed tube. The novel assembling procedure permitted by the structure of the parts referred to provides an essentially complete tube structure. T0 this end the method involves the use of a jg adapted to receive and support individual tube parts in strain-free relation. The jig has means for receiving successively in vertical position a tubular cathode sleeve, a cylindrical grid and a cylindrical anode in concentric and suitably spaced relation. Thereafter the collars or flanges are loaded to engage and rest on the upper ends of the electrode elements when the same are in the aforementioned position. The cathode heater may be positioned in the cathode sleeve `at any stage of the foregoing procedure after the cathode sleeve has been loaded. Thereafter the wafer or disc is positioned on a portion of the jig which disposes the wafer above the electrodes and in coaxial relation therewith and with the heater legs extending partly through openings in the wafer. Then the wire lead-ins and supports are threadedl through appropriate openings in the'wafe'r to provide a tripod engagement with each of the collars |and with the free ends of the heater legs.

The jig may be made of a suitable metal or ceramic material adapted to withstand elevated temperatures. This permits the jig with the parts loaded thereon as aforementioned, to be placed in an oven having a sufliciently high temperature for sealng the wire lead-ins and supports to the metalized coatings in the stem openings through which they extend, and for brazing end portions of the lead-ins to the collar supports. This serves to fix the parts referred to, thereby simultaneously providing a unitary structure comprising essentially a completed tube. It will be noted that no stresses are applied to the parts during 'the fixing operation, andaccordingly no strains are set up in the resultant tube structure.

To provide an emitting surface on the cathode sleeve, a metal cup carrying an emitting coating, is telescoped over the cathode sleeve. A Shell, such as'of metal or Ceramic, is telescoped over the tube structure aforementioned with the rim of the shell slightly spaced from the periphery of the wafer. This periphery is provided with a metallic coating,l so that on dispostion of the tube structure and the shell in an evacuating ,oven such as a bell jar, evacuation of the bell jar will cause evacuation of the shell through the space between the Shell and the wafer. Thereafter suitable means may be used to heat the rim of the Shell to seal it to the metallic coating on the periphery of the wafer and to sinter the cathode cup to the cathode sleeve. Here again it Will be noted that no stresses are applied to the tube structure during the exhaust and sealng operations. p

One important advantage accruing from the rela-tively simple constructions of the tube parts according to the invention is that 'the assembly may be efected with substantially equal facility no matter how small or large the parts are. ATherefore, it is feasible according to the invention lto make an electron tube of extremely small size.

The foregoing brief description of an embodiment of the invention is presented for i-llustrative purposes only. It will be apparent to persons skilled in the art that the invention may be embodied in constructions difiering from those described heretofore. V

Further features and objects of the invention will become apparent as the description continues.

Reference to the drawing for a more detailed conspo-1,185

sideration of the embodiment of the invention briefly described in the foregoing, will reveal that- FIG. 1 is 'an exploded view of the parts constituting an electron tube according to one embodiment of the invention;

FIG. 2 shows a sectional elevation of a jig with certain parts shown in FIG. 1, mounted thereon;

FIG. 3 is a view taken along the line 3-3 of FIG. 1;

FIG. 4 is a view taken along the line 41-4 of FIG. 3;

FIG. 5 is an elevational view partly in section of a tube structure assenrbled `as in FlG. 2 and after fixing of the parts and the addition of an active cathode surface, to provide a self-supporting structure;

FIG. 6 shows a sectional elevation of a beil jar type oven adapted to receive the mount and bulb in telescoped relation, for de-gassing the tube components, breaking down the active cathode coating, exhausting the envelope formed by the telescop'ed shell and tube structure, and sealing the shell to the wafer of the aforementioned structure; and

FIG. 7 shows a side elevation partly in section of a completed tube.

One embodiment of the invention selected for illustrative purposes comprises an electron tube having the parts shown in FIG. 1. When these parts are assernbled in accordance with the method of the invention there results an electr'on tube depicted in FIG. 7.

A brief description of the parts employed in the aforementioned embodiment, and their functions, will be of aid in the later consideratio-n of a method used in assembling the parts to form a tube structure. The parts referred to, as shown in. FIG. 1, comprise a shell 12 which is shown as being made of metal such as steel, but which may be made of other materials such as ceramic. A wafer or disc 14 made of a Ceramic such as Forsterite, for example, is provided with a metallic coating 16 on its periphery and has a diameter for snugly entering the open end of shell 12. The metallic coating 116 may be molybdenum. The wafer 14 also is provided with a plurality of openings extending therethrough. The walls defining the openings are provided with a metallic coating 18 such as molybdenum and are arrayed in a predetcrmined fashion to be described. A plurality of leadin wires 20, 22, 24, 216, 28 and support wires 30, 32, 34, 36, 318, 40, made of a refractory metal such as molybdenum, have a diameter for snugly but freely entering the openings in wafer 14. Electrodeelements comprise a tubular cathode sleeve 42 which may be made of a,

metal such 'as is commercially known as Nichrome, a tubular grid 44, and a tubular anode 46 made of a metal such as nickel. The electrode elements referred to are adapted to be fixed to collars or flanges 48, 50, 52, respectively, vmade of Steel, for example, and have diameters for snug entrance into the tubular - portions 54, 56, 58 of the flanges referred to, and against the inwardly turned stops 60, 62, 64 thereof. The flanges 48, 50, 52 are adapted to engage wire lead-ins '20 to 28 and supports 30 to 40 at recessed annular portions thereof provided with coatings 68, 70 and 72 of a suitable brazing material. The tubular cup or 'member 74 having an emitting coating 76 and closed at one end, has a diameter for snug telescoped receipt by the cathode sleeve 42, and in combination with the sleeve 42, forms the cathode element of the tube. A heater 77, which may be of the double helical type, is adapted to be positioned into the cathode element consisting of member 74 and sleeve 42, for heating the same to desired emitting temperature.V

As shown in FIG. 3, the openings through wafer 14 for accommodatingra triode type tube, are arrayed in four concentric circles 78, 80, 82 and 84, shown in phantom. Three openings are disposed in equi-distant relation in each of the circles. The openings in adjacent circles are angularly displaced 60 from each other to provide maximum sp'acing therebetween.

In conformity with this arrangement, the nnermos't circle 84 includes three openings 86, 88, 90 angularly space'd 120. The next adjacent circle 82 includes three openings 912, 94, 96 angularly spaced, not only 120 from each other but also 60i from openings 86, 90'. The third circle includes openings 98, 100, 102 also angularly spaced 120d from each other and 60 from openings 92, 94, 96. Openings 104, 106, 108 in the outer'most circle 78 are likewise mutually angularly spaced 120 and spaced from the openings 98, 100, 102 by' 60. Lead-in and support wires extending through the several openings referred to, are therefore adapted to provide a plurality of tripod supporting systems characteriz'ed by increased ruggedness, an'd reduced capacitance.

Flang'es' 48, 50 land 52, as aforernentioned ar'e provided with metallic coatings, such as coatings 68, 70, and 72, which may be copper or other suitable bra'zing material. The lead-in and support 'wires are likewise provided with metallic coatings, such as copper, for brazing purposes. These coat'ings in the current embodiment, iare applied by electroplating'.

The metallic coating on the cerarnic wafer can be applied by any of the well known metallizing processes. In this embodiment, howeve'r, the solution metalli'zing process based on soluble salts of molybdenumV is utilized to apply a ni'etallic coating on all exposed surfaces of the wafer. After reduction of the salt to molybdenum, a grinding process is employed to remove the metal coating from the flat surfaces of the wafer. After such grinding operation the wafer 14 has metal coatings 18, 16, only on desired portions thereof consisting of the Walls defining the openings therethrough as aforernentioned, and the periphery of the wafer.

In the embodi'rnent described, only certain of the wire structures shown in FIG. 1, i.e., wires 20, 22, 24, 26 and 28, are employed for 'lead-in purposes. These wires therefore have a suflicient length for engaging their associated elements within the completed tube, and for extending outwardly from the wafer 14 for service as contact prongs. Thus, as shown in FIG. 2, lead-in wires 20, 22, 24, 26 and 28 extend through wafer openings 106, 98, 94, S6 and 88 respectively. Lead-in wires 20, 22 and 24 engage collars 52, 50 and 48 respectively, connected to the three electrodes of the tube, and lead-in wires 26 and 28 exten'd partly through the wafer 14 for engaging the free en-tls of heater legs 110 and 111. The inner ends of the lead-in wires 26, 28 may have a metallic coating, such as copper, for fixing the heater legs thereto.

The other wire structures shown in FIG. l, i.e., wires 30, 32, 34, '3-6, 38 and 40, have -a length for engaging the collars 43, 50 and 52, and for only partly extending through the wafer 14,,as shown in FIG. 4 in relation to one of the support wires, i.e., wire 34. The resultant cavities defined by the openings 92, 96, 100, 102, 104 and 108 (FIG. 3) one of which cavities is shown in FG. 4, may be filled with a body of metal 113, such as copper. The opening of the innermost circle, into which no lead-in wire extends, rnay also be filled with a stud or body of metal, such as copper for herrnetically closing this opening. While the opening 90 has no utility once a selection has been made of the appropriate openings in the innermost circle for receipt of heater Iegs 110 and 111, it posesses advantage in facilitating orientation of the wafer in relation to the heater legs referred to, which is of particular value in mechanized assemblng techniques. The lead-in and support wires in an alternative "arrangement, are of the same length and cut to desired length after the tube has been completed.

As has been previously described, the collar portions 54, 56, '518 of the flanges aforementioned have been provided with metallic coatings including internal metallic coatings 115, 117 and 119 (FIG. l), for brazing the flanges referred to, to the cathcde sleeve 412, grid 44. and anode 46 in a manner to be described.

The metal shell 1-2 (FIGS. l and 7) is provided with an outw'ardly stepped portion '116, resulting in the formation of an annular Stop 1118 against which the wafer 14 may abut to determine the magnitude of the entrance of the wafer into the bulb. For hermetically joining Shell 12 to the metallic coating on the periphery of the wafer, a ring of brazing material 120 (FIG. 6) is utilized.

'The foregoing structural and the functional description of the parts constituting an electron tube embodiment of the invention, will facilitate an appreciation of the following description of a method or technique for assembling and processing the parts aforementioned to form an improved electron tube.

A method according to the invention includes three groups of Steps. The first group of Steps comprises assemblng certain parts shown in FIG. l on a suitable jig as shown in FIG. 2.

The second group of steps comprises heating the jig and the assembled parts to fix the parts in a strain-free Self-Supporting structure, and thereafter adding to the structure a further part deliberately omitted for preserving the last-named part from the heat employed during the fixing step of the second group.

The third group of Steps involves adding to the fixed structure a still further part and heating the resultant structure to a lower temperature than the temperature of the first-named heating step, for fixing the further and still further parts to the fixed structure. At the same time, the metal components become suficiently heatcd to drive ofi gasses occluded therein and the envelope formed by certain of the assembled parts is evacuated. A more detailed consideration of each group of Steps follows.

In carrying out the first group of Steps, a jig 121 made of a metal such as Nichrome, or of a Ceramic such as zircon or alumina, is employed. As shown in F'IGS. 2 and 3, the jig includes a cylindrical outer wall 1122 closed at one end by a bottom portion 124. To facilitate heat transfer, portions of the wall may be cut away. The wall =122 is relatively thin adjacent to its free end to provide an annular shoulder 125. Projecting upwardly from the bottom portion 124 are two concentric and relatively thin cylinders 126, 128 spaced for receipt therebetween of the cylindrical grid 44 and the cylindrical anode 46, in spaced relation, as shown in FIG. 2. The outer cylinder 126 has a length slightly less than that of the cylindrical anode 46, and an inside diameter for snugly receiving the anode. The inner cylinder 128 has a length substantially equal to the length of the outer cylinder 126 and has an outside diameter for snugly receiving the grid and an inner diameter for snugly receiving therein the cylindrical -cathode sleeve 42. The bottom portion !124 of the jig has an annular groove 129 adjacent to the outer surface of inner cylinder 128, to allow the grid 44 to extend downwardly, as shown in FIG. 2, farther than the anode 46 and cathode sleeve 42, for a purpose that will become apparent. The reduced thickness wall portion 130 of the outer wall 122 of the jig has an inner diameter for snugly receiving the wafer 14.

In assembling parts on the jig aforedescribed, the anode 46, grid 44 and cathode sleeve 42 are mounted in telescoped relation with respect to the jig cylinders 126 and 128 as shown in FIG. 2. No particular order in mounting these elements on the jig need be observed, since none of these parts when mounted obstructs the mounting of the other two parts.

Thereafter, the flanges, 48, 50 and 52 are mounted on the three previously mounted parts as aforementioned and held in the desired orientation by an abutment of the free ends of these parts with stops 60, 62 and 64 on the |flange structures. Due to the sizes of the flanges referred to, a predetermined mounting order thereof is required. Thus fiange 52 must be mounted first on anode 46. Then fiange 50 must be mounted on the grid 44, and thereafter the flange 48 may be mounted 8 V on cathode sleeve 42. This order is required since the lateral extents of the anges preclude a mounting of flange 50 Subsequent to flange 48, or a mounting of flange 52 after either fianges 48 or 50 have been mounted. When the fianges are mounted as indicated, the annular troughs thereof having metallic coatings 68, 70 and 72, face upwardly.

The heater 77 may then be extended into the cathode support 42 and permitted to abut against the lower wall portion 124 of the jig. No critical order need be followed in mounting the heater 77 other than that its mounting should preferably be preceded by the mounting of cathode sleeve 42 to avoid entanglement of the sleeve with heater legs 1'10, 111.

After the tube elements have been loaded as aforementioned, the wafer 14 is telescoped into the end portion of the jig defined by the relatively thin wall portion 130, until the wafer comes to rest on the annular shoulder 125, as shown in FIG. 2. During the mounting of wafer 14 on the jig, the upwardly extending heater legs are inserted into two openings in the inner circle of openings through the wafer. For example, the heater legs may be extended partly into openings 86, 88 shown in FIG. 3.

The final elements to be loaded on jig '121 are the lead-in and support wires shown in FIG. 1. For convenience, the wires intended for service as supports are loaded prior to the loading of the wires intended for leadin purposes. This permits the support wires to be loaded with freedom from obstruction by upwardly extending lead-in wires. Since the support wires do not extend upwardly from the wafer when loaded, the loading of the lead-in wires is also free from obstruction and the lead-in wires accordingly, may be suitably angularly and rectilinearly spaced to insure reduced capacitance effects therebetween. Due to a predetermined structural correlation between the stem 14 and the flanges 48, 50 and 52, the three outermost circular arrays of openings through the stem are in axial register with the annular fiange troughs having the metallic coatings 68, 70 and 72. As a consequence, any random angular orientation of the wafer 14 with respect to the fianges aforementioned, while preserving a coaxial relation therebetween, disposes a predetermined circular opening array in the wafer, in axial register with a portion of the annular trough in a predetermined flange. This freedom from dependence on a particular angular orientation of the wafer 14 and the fianges 48, 50 and 52, contributes to facility in assembly, whether of the manual or mechanized kind.

The aforementioned loading of the lead-in and support wires, causes them to engage appropriate flanges 48, 50 and 52 and heater legs 110, 111. For exam` ple, support wires 30, 3'2 (FIG. 1)'engage flange 52, the support wires 34, 36 are positioned to contact fiange 50, and support wires 38, 40 are mounted to rest on flange 48. lt will be noted that the wires comprisng group 30, 32 are longer than the wires comprising group 34, 36 and that the latter wires are longer than the wires comprising group 38, 40. This difference in length in the support wires is due to the axial spacing between the fianges 48, 50, 52. Likewise, lead-in wires 20, 22 and 24 engage fia'nges 52, 50 and 48 respectively. Lead- ins 26, 28 engage heater legs 111, and 110, respectively.

Finally balls of copper (not shown) may be placed in the cavities representing portions of openings 92, 96, 100, 102, f104 and 108 not occupied by Wire supports, to form a copper mass 1:13 (FIG. 4) for filling the cavities and contributing to an hermetic sealing of the cavities. A Stud 131 made of or coated with copper may be snugly inserted in vacant opening (FIG. 3) and may have a length substantially equal to the thickness of wafer 14.

The resultant loose assemb'ly of parts involves a flange pattern, wherein the lflanges are stepped transversely and longitudinally of the jig 121. This is of advantage not only in facilitating the mounting operations just described, but alsolin that it results in a structure wherein capacitance effects between the leads are reduced. Furthermore, each of the elements mounted engages another through a metallic coating adapted to bond the elements together in a fixed structure, after the second group of steps to be described have been completed. Also, it will be observed that the loosely assembled parts are free from stresses and therefore strain-free.

'The second group of steps comprises heating the jig 121, and the parts assembled thereon as indicated in FIG. Z, in a reducing atmosphere, such as hydrogen. 'The first step comprises heating the jig and parts in a hydrogen oven having a temperature of about 1l30 C. During the first minute of such heating, in one example, the parts were raised to the temperature of the oven. After acquiring this temperature, the parts were permitted to remain in the oven for several minutes. The next step comprises cooling the parts and the jig to a temperature of about 250 C. This coo-ling step requires about two minutes. The parts mounted on the jig 12,1, are now fixed in brazed engagements by the several metallic coatings aforementioned. On removal from the oven the jig and the parts thereon are allowed to cool naturaily to room temperature. It will be noted that no strains are applied to the parts during the aforementioned second step.

The resultant brazed structure is then removed from jig 121 and cathode member 74 is telescoped snugly over the free end of'cathode sleeve 42, as shown in FIG. 5. The inner surface of the member 74 and the outer surface of cathode sleeve 42 are sufiiciently rough to provide a plurality of point engagements which are adapted to be joined together as by sintering during the Operations involved in the third group of steps to be descnibed.

The third group of steps involves use of a heating and exhaust system shown in FIG. 6. This system includes an evacuated chamber, such as a bell jar 140' made of a Ceramic material or a high temperature glass sealed to a vacuu-m source (not shown) by engagng a heat resistant gasket 142 mounted on flanged metallic conduit 144 communicating with the vacuum source. Within the bell jar 1140 is disposed a metallic Vtubular mufile 146 having heat bafiies 148 and 150 adjacent to its ends. A support 152 within the muffle is adapted to support a tube assembly comprising bulb 12 and -wafer 14 which includes the mount structure shown in FIG. 5, between the heat baffles l148 and 150. A high frequency induction coil 154, connected to a suitable adjustable power source, not shown, is adapted to heat the muffie 146. The mufie in turn radiates heat to the tube assembly referred to.

In carrying out the third group of tsteps, the shell 12 is telescoped over the wafer 14 until the shoulder or stop 1'18 on the shell rests on the wafer, a ring 120 of brazing material having been positioned to engage the periphery of the wafer and to rest on the r'im edge of the Shell, as shown in FIG. 6. The resultant tube structure is then placed on support 152 and the coil 154 is electnically energized to heat muffle 146 to' a temperature sufiiciently high to cause the heat radiation therefrom to the tube structure to raise vthe parts thereof to a temperature of about 800 C. The structure is per-mitted to remain at this temperature for several rninutes for de-gassing the metal components of the assembly. During this heating step, the vacuum source referred to ontinues to' remove gas from the bell jar and from the interior of the tube envelope defined by shell 12 and wafer 14. Removal of gasses from the envelope referred to occurs through an annular space between the loosely mounted shell and the initially formed tube structure. The temperature aforementioned is insuflicient to melt the brazing ring 120 or to completely sinter the cathode member 7,4 to its sleeve 42. Tests have revealed that a peniod of several reduced shrinkage.

10 minutes for out-gassing and exhaust produce satisfactory' tubes. Longer periods up to 60 minutes, of course, provide increased assurance that the out-gassing and evacuation have proceeded as far as possible.

Thereafter and while the bell jar 140 is kept evacuated, the energy to the coil 1594 is increased, to cause the tube parts to be raised to temperature of about 950 C. At this temperature the member 74 becomes further sintered to its support sleeve 42, and the brazing ring i melts to braze the shell 12 to wafer 14 in a vacuum tight seal.

During the out-gassing operation electric power may be applied to the heater 77 for supplementing the heat applied by mufile 146, for improved out-gassing. I-Io'wever, tests have revealed that satisfactory tubes are obtainable without energizing the heater during the outgassing step.

It will be noted that the out-gassing and sea-ling temperatures above referred to are appreciably below the temperature of 1130 C. to which the initial tube structure was subjected during the second group of steps, thereby precluding a re-melting of the copper brazing material. The lower temperature, i.e., 950 C., does not adversely aifect the conditions previously established. To respond in brazing to this lower temperature, the brazing ring can be made of a suitable alloy such as nickel-tin, or one known as NIORO solder which includes nickel and gold.

A tube produced by the foregoing three groups of Steps is shown in FIG. 7. It includes a tube structure wherein the cathode member 74, grid 44 and anode 46 are ruggedly supported on flanges 48, 50 and 52. respectively. The flanges referred to have an appreciable lateral extent and each is supported adjacent its periphery by a tripod array of lead-in and support wires firrnly fixed to wafer 14. This eiectively restrains relative movements between the electrodes, in both angullar and rectilinear directions, and permits extremely close spacing between the cathode and grid without danger of Shorts therebetween. I

The relatively sirnple construction of the tube parts and the advantageous method for their assembly, as pointed out in the foregoing, make it feasible to fabnicate the tube to very small dimensions.

In one example, the overall diameter of the tube was three-eights of an inch and the length of the tube was approximately one-half inch. While the she'll 12shown in FIG. 7 is 'longer than necessary to provide space accommodation for the electrodes therein, its extra length results in an increased shell area desirable for `heat dissipation. Shorter shells, of course, may be used and a desired heat dissipation therefrom may be efiected by supplemental heat exchange means, not shown. This is particularly feasible since the shell 12 is free from connection to any electrode element.

While the relatively small size referred to above is presented as an example, it is not to be inferred that this constitutes a limit to which miniatur'ization is feasible according to the invention. While the advantage of lending itself to small tube size has been pointed out, it should be noted that the structure and method of the invention have utility in tubes of any size, including relatively large power tubes.

It will be appreciated from the foregoing that an electron tube according to the invention is characterized by simplioity in structure which contributes to improved performance eflioiency, thus appreciably reducing the normal power needs in operation. Furtherrnore, the simplicity of the parts constituting the tube structure renders tolerable a relatively low order of skill in the assembling operation, and permits a progressive type of assembly operation to be practiced in which the final tube structure is made by successively adding the parts individually for Such progressive type vofl assembly is more advantageous than a type requiring the fabricat'ion of subassemb'lies, both in respect of the simplicity of 11 the assembling operation as well as the ease with which it lends itself to mechanization.

I clairn:

l. An electron tube having a structure comprising an insulating wafer having a plurality of openings therethrough, a plurality of wires fixed to the walls of said openings and having ends defining a plane spaced from and parallel to said wafer, a support having a flange fixed ladjacent its periphery to said ends of said wires and including a central tubular portion, and an elongated electrode fixedly mounted at one end thereof in said tubular` portion.

2. An electron tube having a structure comprising a ceramic wafer having a plurality of openings therethrough, a plurality of parallel red-like members extending into said openings and fixed to the walls thereof and disposed in a plurality of concentric arrays, said red-like members extending from one face of said wafer and having ends terminating in spaced planes parallel to said wafer, a plurality of concentric electrodes in coaxial relation with said arrays, and support means conneoting each of said electrodes to a different one of said arrays, each of said arrays having a larger diameter than its associated electrode, for reduced capacitance between two adjacent arrays of said wires.

3. An electron tube having a structure comprising an insulating wafer having a plurality of openings therethrough, a plurality of parallel rod-like members extending into said openings and fixed to the Walls thereof, one group of said rod-like members extending from one face of said wafer in a circular array and having ends terminating in a plane parallel to said wafer, a flanged support fixed to said ends, and an elongated electrode fixedly mounted at one end thereof on said support, said flanged suppont being circular and having a diameter larger than the diameter of said array, and including a centrally disposed 'tubular portion having a diameter smaller than the diameter of said array, one end portion of said electrode extending snugly into said tubular portion and fixed thereto in coaxial relation therewith.

4. An electron tube having a structure comprising an insulating wafer having a plurality of openings therethrough, a plurality of parallel red-like members extending into said openings and fixed to the walls thereof, said rod-like members extending from one face of said wafer in a circular array and having ends terminating in a plane parallel to said wafer, a flauged support fixed to said ends, and an elongated electrode fixedly mounted at one end thereof on said support, said -anged support comprising an annular flange engaging said ends, |and a tubular portion coaxia'l with said flange and having a smaller transverse extent than said fiange, said tubular portion extending in one direotion from said flange, said electrode having an end portion engaged by said tubular portion andextending from said flange in a direction opposite to said one direction, whereby said electrode is ruggedly supported by said wires and said support.

5. An electron tube structure oomprising an insulating wafer, a plurality of flange-like eleotrode supports progressively -spaced from one face of said wafer, a plurality of concentric elongated electrodes fixed at end portions to said supports, and a tripod array of rod-like elements fixed to each of said flange-like electrode supports adjacent the periphery thereof and extending fixedly into said wafer, for restraining said electrodes from relative movement.

6. An electron tube structure comprising an insulating wafer, two electrode supports progressively spaced from one face of said wafer, said supports being coaxial and of progressively larger transverse extents parallel to said wafer with said progressive spacing, and first and second groups of an equal number of parallel rod-like members fixed to said wafer, said first group of said rod-like membersbeing. fixed to one of said supports adjacent to the periphery thereof, said second group of said red-like members being fixed to the other of said supports adjacent to the periphery thereof, whereby one of said groups of rod-like members has a longer length than the other group and the rod-like members therein are more wdely spaced than the red-like members in said other group, and tubular electrodes mounted on said supports, whereby said electrodes are equally ruggedly supported on said wafer.

7. An electron tube structure comprising a wafer made of insulating material, a first electrode support having a predetermined transverse dimension, a first group of parallel rod-like members fixedly extending into said wafer and having ends terminating in a first plane parallel to said wafer,'said ends being fixed to said first electrode support adjacent to the periphery thereof, a second electrode support having a larger transverse dimension than said predeterrnined dimension, and a second group of rod-like members parallel to the first group of rod-like members and fixedly extending into said wafer and having free ends terminating in a second plane more remote from said wafer than said first plane, whereby said second group of rod-like members is longer than said first group, said last named ends being fixed to said second support adjacent to the periphery thereof, whereby said second group of rod-like members engage said second support at regions thereof spaced farther than the regions of said first support engaged by said first group of rod-like members, whereby said supports are supported by said rodlike members to a substantially equal degree of ruggedness, and an elo-ngated electrode supported at one end on each of said supports.

8. An electron tube structure comprising an insulating wafer having openings extending therethrough, 'a first tubular electrode support having an annular fiange, a second tubular electrode support extending into and fixed to said first support and extending parallel to the axis of said flange, said fixed support having an end portion remote from said fiange, a tubular electrode fixed to said end portion in telescoped relation therewith, and a tripod array of parallel wires fixed in said openings and fixedly engaging said flange, whereby said electrode is supported ruggedly on said wafer.

9. An electron tube structure comprising a tubular cathode member having an emiftting coating thereon, a sleeve extending fully into said member and including an end portion extending outside of said member, said sleeve having an outer surface engaging the inner surface of said member in a plurality of contacts adapted to be sintered together at a relatively low temperature, and a support engaging said end portion and adapted to be fixed thereto at a relatively high temperature, whereby said end portion may be fixed to said support prior to the fixing of said member to said sleeve, for preserving said coating from harm by said relatively high temperature.

10. An electron tube having a structure comprising a. ceramic wafer having a plurality of openings therethrough, a plurality of parallel rod-like members extending into said openings and fixed to the walls thereof and disposed in a plurality of concentric arrays, said rod-like members extending from one face of said wafer, a plurality of concentric elongated electrodes in coaxial relation with said arrays, and support means connecting the end of each of said electrodes to a different one of said arrays, each of said arrays having a larger diameter than its associated electrode, whereby reduced capacitance between two adjacent arrays of said wires is obtained.

11. An electron tube having a structure comprising an insulating wafer having a plurality of openings therethrough, a plurality of parallel red-like members extending into said openings and fixed to the walls thereof, one group of said rod-like members extending from one face of said wafer in a circular array and having ends spacedV from said wafer, a 'fianged support fixed to said ends, and an elongated electrode fixedly mounted at one end thereof on said support, said flanged support being circular and having a diameter larger than the diameter of said array, and including a centrally disposed tubular portion having a dameter smaller than the diameter of said array, one end portion of said electrode extending snugly into said tubular portion and fixed thereto in coaxial relation therewith.

12. An electron tube having a structure comprising an insulating -wafer having a plurality of openings therethrough, a plurality of parallel rod-like members extending into said openings and fixed to the walls thereof, said rod-like members extending from one face of said wafer and having ends spaced from said wafer, a fianged support fixed to said ends, and an elongated electrode fixedly mounted at one end thereof on said support, said fianged support including a tubular portion extending towards said wafer, said electrode having an end portion and extending into said tubular portion in a direction away from said wafer.

13. An electron tube having a structure comprising an insulating wafer having a plurality of openings therethrough, a plurality of parallel 'rod-like members extending into said openings and fixed to the walls thereof, said rod-like members extending from one face of said wafer in a circular array -and having ends spaced from said wafer, a fianged support fixed to said ends, and an elongated electrode fixedly mounted lat one end thereof on said support, said fianged support comprising an annular flange engaging said ends, and a tubular portion coaxial with said flange and having 'a smaller transverse extent than said flange, said tubular portion extending in one direction from said flange, said electrode having an end portion engaged by said tubular portion and extending from said flange in a direction opposite to said one direction, said electrode being ruggedly supported by said rod-like members and said support.

14. An electron tube compn'sing a Wafer made of insulating material, a first tubular electrode having a first end rel'a-tively close to said wafer, va first fiange having a predetermined transverse extent and fixed to said wafer adjacent its periphery and engaging said first end for ruggedly supporting said first electrode in normal relation to said Wafer, a seoond tubular electrode in concentric relation to said first electrode and having a second end adjacent to said first end and 'father spaced from said wafer than said first end, a second fiange having a larger transverse extent than said first fiange, said second flange being fixed to said 'wafer at a pen'pheral region of said second fiange and to said second end, for supporting said seco-nd electrode at least as ruggedly as said first electrode is supported, and a bulb enclosing said first and second electrodes and fixed to said wafer.

15. An insulating disc for an electron tube, said disc having a dia'meter of substantially one-half inch, three circular arrays of openings through said disc, said arrays being concentric with said disc and having different diameters, the innermost and outermost of said arrays having their openings disposed along three radii of said disc spaced 120 from each other, the intermediate of said arrays having its openings disposed intermediate said three radii, whereby support wires are adapted to be received in said openings in suitable spaced relation for reduced capacity effects therebetween.

16. An electrode mount comprising a support, said support having an annual channel and a coating of brazing material on the inner surface of said channel, the annulus of said channel having a predetermined diameter, an insulating Wafer having 'a plurality of passage- Ways therethrough extending in parallel relation to the Wafer axis and disposed in a circular array having said predetermined diameter, a plurality of rectilinear parallel wires extending into and fixed to the said passageways and having an adjacent group of end surfaces, said end surfaces only, engaging said br-azing material in fixed relation, and an electrode fixed to a portion of said support surrounded by said channel.

17. An electron discharge device including a ceramic wafer, a plurality of parallel conductors sealed in said wafer and extending from one surface thereof, said conductors being arranged in groups and in concentric circular array, the conductors in each group proceeding radially outward from the center of said wafer being progressively longer, a plurality of centrally apertured flange-like elements of progressively increasing diameter spaced from said wafer and from each other, each flange-like element being fixed adjacent its periphery to the ends of a different array of said conductors, each of said flange-like elements having 'an elongated tubular electrode rigidly fastened thereto at one end of said electrode, the tubular electrodes being concentric with each other and coaxial with the apertures of said flange-like elements, and an envelope sealed to the periphery of said Ceramic wafer to enclose the members supported thereon.

18. -An electron discharge device including a ceramic w-afer, a plurality of parallel conductors sealed in said wafer and extending from one surface thereof, said conductors being arranged in groups and in circular array, the conductors in each group proceeding radially out- Ward from the center of said wafer being progressively longer, a plurality of flange-like elements spaced from said Wafer and from each other and having tubular portions centrally thereof, said fiange-like elements being of progressively increasing diameter away from said Wafer, each of said flange-like elements being fixed adjacent its periphery to the ends of a different array of said conductors and in coaxial relationship, an elongated tubular electrode received within the tubular portion of each flange-like element and fixed thereto at one end thereof, the tubular electrodes being concentric and coaxial with each other, and an envelope sealed to said wafer and enclosimT all of the members supported thereon.

19. An electron discharge device including a ceramic wafer, a plurality of parallel conductors sealed in s-aid wafer and extending from one surface thereof, a platelike member having a tubular central portion extending toward said wafer and provided with an inwardly extending shoulder at the end of said tubular portion nearest said wafer, said plate-like member being fixed adjacent its periphery to the ends of said conductors, and an elongated electrode having one end received within said tubular portion and abutting said shoulder and fixed to said plate at said one end.

20. An electron discharge device including a Ceramic Wafer, a plurality of parallel conductors sealed in said -Wafer and extending from one surface thereof, a dishshaped flange-like member having a central portion extending away from said w'afer, said fiange-like member having a central tubular portion extending toward said wafer, said central tubular portion being provided with an inwardly extending shoulder at the end nearest said Wafer, said fi-angcflike member being fixed adjacent its periphery to the ends of said conductors, and an elongated electrode having one end received Within said central tubular portion and abutting said shoulder and fixed to said -fiange-like member at said one end.

21. An electron tube including a flat baseand an envelope, a plurality of elongated electrodes arranged within said envelope with their longitudinal axes sub'- stantially perpendicular to the plane of said base, a plurality of sets of rod-like members secured to said base and extending therefrom within said envelope, and a respective single positioning and supporting member for each of said electrodes, each of said positioning and supporting members extending between the end of the elongated electrode located near said base and a set of said red-like members to provide with said set of rod-like members the sole positioning and supporting means for that electrode, said positioning and supporting members being annular in shape, the inner part of the annulus being secured to one end of an elongated electrode -and the outer part of the annulus being seeured to one end of each of the red-like members'forming the set.

References Cited in the file of this patent UNITED STATES PATENTS McCall Jan. 26, 1926 Shaw Dec. 29, 1942 Miller Dec. 21, 1943 Wagner July 16, 1946 Binneweg Nov. 18, 1947 FOREIGN PATENTS 3 Switzerland Nov. 30, 1941 ww... Wy

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