US2903614A - Envelope structures for electron tubes - Google Patents

Description

Sept. 8, 1959 D. H. PREIST ET AL ENVELOPE STRUCTURES FOR ELECTRON TUBES 2 Sheets-Sheet 1 Filed Feb. 11, 1957 INVENTORS Donald H. Fife/Z57 Pau/ D- Will/urns James L. Hall WM (5 ATTORNEY Sept. 8, 1959 Filed Feb. 11, .1957

D. H. PREIST ET AL FIE-3 ENVELOPE STRUCTURES FOR ELECTRON TUBES 2 Sheets-Sheet 2 INVENTOR. DONALD PRE\ST P D. N\LL\I\N\$ YJAME-b L. H XLL da /ima- ATTORNEY United States Patent ENVELOPE STRUCTURES FOR ELECTRON TUBES Donald H. Preist, Mill Valley, Paul D. Williams, Menlo Park, and James L. Hall, Palo Alto, Calif., assignors to Eitel-McCuliough, Inc., San Bruno, Califi, a corporation of California Application February 11, 1957, Serial No. 639,477

12 Claims. (Cl. 315-552) This invention relates to envelope structures for electron tubes, and more particularly to such structures in which insulating sections are sealed to metal sections to form a vacuum-tight envelope. In more detail, the invention relates to an improved arrangement for sealing a ceramic section of a tube envelope to an adjacent metal section, particularly for use in tubes of the type known as klystrons. This application is a continuation-in-part of our earlier filed application, Serial Number 546,078, filed November 10, 1955, now abandoned.

During the development of klystrons it was found that when glass was used as the insulating material in the resonant cavities it could not withstand the heat and electron bombardment experienced at these cavities, particularly the output cavity. One of the important advances in the klystron field was the substitution of ceramic for glass as the insulating material in the resonant cavities. Since ceramic is able to withstand the effects which proved to be destructive to glass, part of the problem was solved in this manner. However, the problem of making strong vacuum-tight seals between the ceramic and'metal portions of the envelope has continued to limit the production of satisfactory tubes. The difficulty is caused mainly by the fact that the metal portions of the envelope have a much higher coefficient of expansion than the ceramic portions so that as the temperature of the tube changes, the metal portions in effect move relative to the ceramic portions. This action causes cracking of the ceramic which results in weakening of the envelope and admission of air into the tube.

The need for strong vacuum-tight seals is particularly important in klystrons because of the tremendous physical size of these tubes. For example, klystrons now in production reach seven feet in length and weigh as much as one hundred and fifty pounds. Because of their size and weight, klystrons suffer from severe sealing problems to a much greater extent than do small low weight tubes. One problem is that a slight crack partway through the ceramic, which might be tolerated in a small tube, will be fatal in a klystron because, when the klystron is subjected to handling or vibration, its extreme length and weight will cause the crack to be extended completely through the ceramic. In addition, the large size of the metal sections of a klystron envelope aggravates the detrimental effects caused by unequal thermal expansion and contraction of the metal and ceramic envelope sections.

Accordingly, it is among the objects of the invention to provide a klystron having an improved sealing arrangement between the ceramic and metal sections of the tube envelope, particularly between those sections which form the resonant cavities of the tube.

Although the improved sealing arrangement of this invention is particularly necessary in klystrons, it is very beneficial in any type of electron tube which has ceramic envelope sections sealed to metal sections. Therefore, a further object of the invention is to provide an improved sealing arrangement between the ceramic and metal sections of ceramic type electron tubes in general.

Another object of the invention is to provide between the insulating and metal sections of electron tubes an lmproved sealing arrangement which will withstand heat cycling of the tube without cracking the insulating sections.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the invention. It is to be understood that the invention is not limited to the disclosed species, as variant embodiments thereof are contemplated and may be adopted within the scope of the claims.

Referring to the attached two sheets of drawings:

Figure 1 is an axial sectional view of a 3-cavity klystron utilizing a sealing arrangement according to one embodiment of the invention.

Figure 2 is an enlarged sectional view of a portion of Figure l and shows the details of the sealing arrangement; and

Figure 3 is an enlarged sectional view of an electron gun for a klystron and utilizing sealing arrangements according to other embodiments of this invention.

Referring in more detail to the drawings, a klystron which embodies the invention will first be broadly described. The klystron illustrated in Figure 1 comprises an elongated generally cylindrical evacuated envelope having an electron gun assembly 2 at one end and a collector electrode 3 at the other end. The electron beam from the gun to the collector passes through a drift tube formed by sections 4, 6, 7 and 8 of a metal such as copper extending axially of the envelope and having gaps 9' therebetween. The gaps are bridged by resonant cavities generally designated at 11.

Electron gun 2 comprises a cathode 12 housed in a cup-shaped anode 13 preferably made of copper. The anode is fixed to drift tube section 4 at braze 14 and has an aperture 15 forwardly of the cathode and opening into the drift tube. Electrons from the cathode 12 are focused through the anode aperture 15 by a focusing electrode 16. The entire gun structure is mounted on a suitable stem 17 at the end of the envelope, which stem may be of conventional glass and metal construction with suitable terminals for the cathode and focusing electrode.

Collector electrode 3 at the opposite end of the envelope is preferably made of copper and connected to drift tube section 8 at braze 20. The collector electrode can be provided with a metal exhaust tube 21 which is pinched off at 22 after evacuation of the envelope. Normally the collector is cooled by a suitable water jacket or cooling fins (not shown).

The previously described elements of the electron tube like construction, each comprising a pair of metal end: wall disks 25 connected by a cylindrical insulating wall Walls 25, normally made of copper, are apertured 26. to receive the drift tube sections and are fixed to the latter at brazes 27. The resonators are preferably provided with tuning structures externally of the envelope.

These tuning structures, one of which is indicated by the dotted lines 24, may simply comprise split rectangular metal boxes fastened to the resonators l1 and having sliding outer walls for changing the resonant frequency of the resonators.

Patented Sept. 8, 1959 The resonant cavity nearest the col-. lector 3 is the output cavity and the one which is subject awe-ma qthemss x me. wnd f he t nd. r n b01111 bardment.

The cylindrical insulating walls 26 are preferably made of talumina ceramic in order towithstand heat and electron bombardment and toprovide adequate support for the heavy metal portions of the tube. Ceramic sections- 26 are joined to the metal sections 25,- by means of sealing arrangements 28 according to one embodiment of this invention. As is shown best in Figure 2, sealing arrangementsZS accordingto this embodiment ofthe invention essentiallycomprise two elements in addition, to the ceramicandmetalenvelope sections which are to be joined.

The firstlelement, is. a sealing flange structure preferably portions ofthe two ceramic members beingindicated at.

33. Any suitable process can be used to metalize ceramic section 26,. and backing member 31. By way of example, the ceramic areas to be metalized can be coated with an 8.0,%-% mixture of powdered rnolybdenun1.and.man-. ganese in a suitable liquid vehicle and then fired in a reducing atmosphere ata temperature .of about 1500 C. In 'ordercto join the overlapping portion of ring 29 to the metalized areas of ceramic section 26 and backing member 31, these three members are assembled in the position shown in Figure 2 and then brazed together with a brazing material such as copper-silver eutectic at a temperature of about 850 C. The sealing ring .30 is separately brazed to end wall 25, and the final assembly is accomplished by welding together the registering edges of rings 29..an d 30, as indicated at.34. It should be understood that although ring 3! is shown as a separate piece, it could be integrally formed with end wall or alternatively it could be formed integrally with ring 29 and the final assembly could be accomplishedcby weldingor brazing to the end Wall 25.

In accordance with the preceding description, a sealing arrangement 28ris provided in whichthe ceramic section 2 6 is reinforced by a backing member 31which makes a sliding joint with the metal section 25. This sliding joint would, of course, admit air into the tube were it not. for rings 29 and of the sealing flange structure. It will be noted that the sealing flange structure in eifectex-v tends across the joint to seal it from the atmosphere. It

should also be noted that the rings 29 and 30-of the flange structure are made of relatively thin metal so that they will bend easily and not transmit the movement of end wall- 25 to the overlapping portion of ring 29.

Prior to this invention the practice has been to support end'wall 25 by direct contact with the overlapping portion of ring 29 without the use of backing ring 31.. Such prior arrangement was unsatisfactory because of certain actions which will now be explained. Sealing rings 29 and 30 are made of metal, and, as in the case of end wall 25, the metal is normally coppen. However, nickel is,v sometimes used in place of copper for ring29. The.

toficool down to room temperature after being raised to the brazing temperature of about 850 C., the copper ring 22 vwill tend to contract substantially more than the ceramic. I H wardly across the end of cylinder 26 an n doilig ill As a result, the ring 29 will tend to move ine dtqc oek he e m c u h endency to. Qrach he ceramic may be decreased by making the ring 29 thin enough so that it cannot crack the ceramic but is in fact deformed by the ceramic. However, it is desirable that the ring 29 be as heavy as possible in order to enable it to carry the high-frequency, high-voltage electrical currents involved in the operation of the tube with a minimum of loss.

Inaddition, in the prior arrangement the contracting; and-expanding movement of the large copper end Wall25 istransmitted to the ceramic section 26 by virtue ofthe direct contact between wall 25 and the overlappingportion of sealing ring 29. The end wall and the overlapping portion of ring 29 are compressed together by the force of atmospheric pressure so that they are cold welded together. There is probably less welding action when ring 29 is made of nickel than when it is made of copper, but even with nickel the gripping action is sulficientto cause the thin nickel-member, to follow thernove ments ofthe thick end wall 25, Thus, in the prior ar rangement the stressin the ceramic section is caused both by the overlapping portion of ring 29 and by, the end; wall 25.

The use, of a ceramic backing ring 3].: reduces; the; stresses producedin the ceramic as described in-co-nnec; tion with; the prior type of sealingarrangement. Con-. sidering first the stress produced by the sealing ring2 9, by itself, the addition of backing ring 31 has the effect of cutting this-stress approximately in half. Sincethe. backing ring 31 is made of ceramic, it has the samecoefficient of expansion ascylinder26 so that radial movement of 1 the overlapping portion of ring 29 is resisted, about half :by ceramic cylinder 26 and about'hal-f by ceramic backing ring 31, The use of the ceramic backing ring 31 also,substautiallyeliminates theistresses pro; duced by the end wall 25, because there is no cold welding actionbetween wall 25 and the ceramic backing ring 31. The end of backing ring 31 which is in contact with a end'wall 25 is not metalized and permits free sliding; movement between the ring and the end wall. I

' Referring to Figure 3 an electron gun fora klystron is shown which utilizes sealing arrangements accordingsto other embodiments of this invention. In detail, the elec tron gun shown in Figure 3 comprises a thermionic cathode 12 ;in. the form of a concave disk, a metallic anode 15 having a centrally located aperture 15 in axial align; ment with the cathode 12 and into which one end cfthe first drift tube section 4 is brazed. Atubular focus electrode 16 surrounds the cathode 12 focusing the elec trons emitted by the cathode 12 into a beam which-is directed through the aperture 15 in the anode Band down the drift tube. A' filamentary heating element 4t), is supported on siderods 4-2 and a center post 44 in close; spaced relation to the underside of the cathode 12m provide for the heating of the cathode 12 to obtain thermionic emissionof electrons therefrom,v Atubular heat, shieldmember 46 surroundsthe center post 44, fila-. mentary heater 4%,;and side rods 42 to conserve the heat generated bythe, heater 40 and direct such heat to the cathode 12,

he a Q 2 o us le o nd amentaryheater 40 are mounted on a stem structure l which is insulatingly sealed to the anode 13 through a hollow ceramic insulating-cylinder 50.; The insulating cylinder 50 is hermetically sealed to'the anode 13 by a sealing arrangement 52 according to; this invent-ion whichcorn prises a first sealing ring Spmade of thin metal and a, second sealing ring 56 also made of thin metaL The first ring 54 ;is provided with an inwardly extending flange 58 lwhichtis hermetically sealed to a shoulder 69- on the, anode 13, the ring 54 surrounding thetupper endv portion of the ceramic cylinder 51% The second ring 5'6 is dimensioned to fit within the first ring 54 and is pro-- vided with an inwardly extending flange 62 whichis her metically sealed across the end of the ceramic cylinder a u 50. A ceramic backing ring 65 is sealed to the surface of the inwardly extending flange 62 on the second ring 56 opposite from the cylinder 50. The ends of the metal rings 54 and 56 opposite from the flanges 58 and 62 are hermetically sealed to each other as by welding. It will be seen that the sealing arrangement 52 is similar to the sealing arrangement 28 previously described with respect to Figures 1 and 2 except that it is adapted to be used in sealing a tubular metallic member to a tubular ceramic member.

The stem structure 48 is hermetically sealed to the opposite end of the ceramic cylinder 50 from the above described sealing arrangement 52 by means of another sealing arrangement 66 according to this invention. The sealing arrangement 66 comprises a ring 68 made of thin metal, an annular metallic member 70, which serves as a support and terminal for the focus electrode 16 as well as a part of the sealing arrangement 66, and a ceramic backing ring 72. The ring 68 has an inwardly extending flange 74 which is sealed across the end of the ceramic cylinder 50. The metallic member 70 has a downwardly extending flange 76 which is adapted to fit inside and be welded to the ring 68, another portion 78 of the metallic member 78 being sealed across the end of a first ceramic ring 80 of the stern structure 48. The ceramic backing ring 72 is interposed between the flange 74 of the ring 68 and the portion 78 of the metallic member 70 which is sealed to the ceramic ring 80 and is sealed to the opposite surface of the portion 78 of the metallic member from the ceramic ring 80. It will be seen that this sealing arrangement 66 is similar to the sealing arrangements 28 and 52 previously described except that it is used to seal two tubular ceramic members to each other, one of the metallic rings of the sealing arrangement serving as a support and terminal for an electrode within the envelope.

The sealing arrangement 66 is illustrative of a particular advantage of the use of a backing member in accordance with this invention. It will be seen that the annular metal member 70 must be heavy enough to mechanically support the focus electrode 16. However, the heavier the metal member 70 is made the more likely it is to crack the ceramic. The backing ring 72 according to this invention enables the sealing of a considerably heavier metal member 70 to the ceramic ring 80 than would otherwise be possible since the backing ring 72 will take up part of the stress introduced by the metal member as is described above. The sealing ring 68 may be made thin enough to obtain a reliable seal to the ceramic insulating cylinder 58 since the sealing ring 68 does not form part of the mechanical supporting structure of the tube, nor does it conduct high frequency currents into the tube since the focus electrode is maintained at a constant DC. potential. Thus it will be seen that the backing ring 72 performs an essential function in the sealing arrangement 66 even though there is no heavy metal member involved such as the end plate 25 or anode 13 in sealing arrangements 28 and 52.

All three of the sealing arrangements 28, 52 and 66, above described, have a common advantage in that they are adapted to be assembled as a final seal. They are self-centering and the sealing or welding operation is performed outside the envelope of the tube where it may be watched and accurately controlled.

The stem structure 48 comprises a plurality of ceramic rings 80, 82 and 8d. The lower end of the first ceramic ring 80 is hermetically sealed to the upper surface of another annular metallic member 86 which serves both as the terminal for the cathode 12 and as a part of the support for the cathode. The cathode 12 is mounted in the upper end of a tubular metallic member 88, the lower end of which is mounted on the annular metallic member 86. The annular metallic member 86 is provided with a downwardly extending flange 98 at its outer periphery which serves as a terminal surface to which electrical connection may be made.

6 The upper end of the second ceramic ring 82 is hermetically sealed to the lower surface of the metallic member 86 opposite the first ceramic ring. It is preferable that the first and second ceramic rings 88 and 82 be of substan-- tially the same dimension and in axial alignment with each other in order to provide a rigid structure. However, the second ceramic ring 82 may be of slightly smaller diameter than the first ceramic ring 88, as shown, in order to simplify the terminal arrangement by providing for the offset thereof.

The sealing arrangement 91 between the metallic member 86 and the first and second ceramic rings 88 and 82 is well known in the art and is not considered a part of the invention. it will be seen that such sealing arrangement 91 does not have the advantages of the sealing arrangement 66 according to this invention in that the sealing arrangement 91 is not adapted to be assembled as a final seal. Instead the sealing arrangement 91 is normally assembled and the seal made in a jig adapted to hold the various parts thereof in proper alignment. The final seal of the sealing arrangement 66, on the other hand, may be made as a last step in the fabrication of the tube without jigging and in full view where it may be inspected and accurately controlled.

The lower end of the second ceramic ring 82 is hermetically sealed to the outer periphery of another annular metallic member 92. The side rods 42 and heat shield 46 are supported on the metallic member 92 at the inner periphery thereof. The third ceramic ring 84 which is of substantially smaller diameter than the second ceramic ring 82 is positioned within the second ceramic ring 82 and the upper end thereof is hermetically sealed to a portion of the metallic member 92 intermediate its inner and outer peripheries.

The center support post .4 for the filamentary heater 40 is mounted on an inverted cup-shaped metallic member 94 which is in turn supported on an exhaust tubulation member 96. Another annular metallic member 98 completes the vacuum tight envelope, the outer periphery of the metallic member being hermetically sealed to the lower end of the third ceramic ring 8-4 and the inner periphery thereof being hermetically sealed to the outer periphery of the exhaust tubulation member 96. Apertures 108 are provided through the side walls of the cup-shaped member 84 so that gases within the electron gun may be drawn out through the exhaust tubulation 96 which may be provided in addition to the exhaust tubulation 21 previously described with respect to Figure 1. When the evacuation of the envelope is complete, the exhaust tubulation 96 may be pinched off as shown and covered with a cap 182 which is adapted to serve as an electrical terminal for the filamentary heater as, being electrically connected to the heater 48 through the cup-shaped member 94 and center post 44.

According to this invention backing rings 104 and 186 which are not part of the gas tight envelope are sealed to the surfaces of the metailic members 92 and 98 opposite from the ends of the third ceramic ring 84 and the lower end of the second ceramic ring 82 as shown. As shown, rings liid and 106 have the same inner and outer diameters as do the corresponding ceramic rings 82 and 84. it is preferable that backing members according to this invention have at least one diameter (i.e. inner, outer, or intermediate) equal to at least one diameter of the corresponding insulating member. If the metal member has a coefficient of thermal expansion higher than that of the ceramic it is preferable that the backing member have a dimension equal to the outer dimension of the ceramic member and if the metal member has a coefficient of expansion lower than that of the ceramic member it is preferable that the backing member have a dimension equal to the inner dimension of the ceramic member. Howevenit should be understood that embodiments of this invention may utilize backing members which do nothave dimensions equal to any dimension of the corresponding ceramic member.

IlZWiii'bQSfiGIl that-metallic members92 and 98 form structural parts of the tube in that they support the filamentary heater 4%.. heavy as possibleand heavier than could be reliably used in asimilar structure according to the prior art. However, the use of a backing member according to this invention enables the heavy metallic members to hereliably sealed to the ceramic by dividing the stress produced by such members as described above with respect'to sealing arrangement 66.

The backing rings 104 which are sealed opposite the ends of the third ceramic ring 84 are shown as being composed of ceramic which is the ideal situation since they will thenmatch the ring 84 perfectly in coefiicient of expansion and full advantage will be taken of their operation as described hereinabove in protecting the sealbetween the third ceramic ring 84 and the metallic members 92 and 98. However, the backing ring 106 opposite the lower end of the second ceramic ring 82 is shown as metal. This is desirable according to this embodiment of the invention since the metallic member 92 acts as a terminal for the filamentary heater 40, being connected thereto through the side rods 42. If the backing ring 106 is made of metal, electrical connection may be made thereto, thus simplifying the socketing of the gun. It isnccessary that the coefficient of thermal expansion of themetallic backing ring 166 be as near that of'the second ceramic ring 82; as possible for best results with respect toprotection of the seal involved. For example, molybldenurn or Kovar could be used for the backing ring lilfi since they have, coefiicients of expansion hichapproachthat of ceramic. Other materials might be used for the backing member 106 if all characteristics.

siderations in addition to the fact that any metal will tend to seize or cold weld with another metallic member when the two are brought together under pressure, more than. will ceramic and metal under similar conditions.

If a metallic backing ring were used for rings 31, 64

and .72 and assuming that it would not cold weld with the other metallic members of the sealing arrangement, a high resistance interface will be presented to high frequency currents flowing in the seal arrangements. Such high resistance interface will tend to cause arcing and introduce noise and sporadic values of resistance in the operation of thetube at high frequencies and high voltages, Furthermore, the metallic materials which have coefiicients. of thermal expansion approaching that of ceramicare not good electrical conductors and will offer high resistance to both direct current flow and high frequency current flow resulting in excessive heating of the sealing arrangement.

sl Chv acking ring does not form an electrical pathto another part of the tube particularly where high frequency current is involved.

Inview ofthe preceding description, it will now be understoodthat this invention accomplishes an improved sealing arrangement betweenthe insulating and metal,

sections of atube envelope by the use of a backing mem: her to reinforcethe insulating section Although specifi materials have been suggested for the various parts, it should be understood that the invention is somewhat broader innature. One basic teaching, regardless of the materials used, is that where thecoefficient of expansion ofxinsulatinglcylinder -26 is difierent from that, of sealing ring 29, the coefiicient of expansionof, thebackingiring Thus, it is necessary that they be as- Therefore, according to this invention,- a metallic backing ring can only be used when.

must approach the coefficient of; expansion of'the insulating cylinder sothatthe'backingring will assist-the; cylinder in; resisting radial movement of theoverlap: ping portion ofz the sealing ring. Although itiis prefer= able inmost casesfor thebacking' cylinder-to be ofthesame material as the insulating cylinder in-order that thecoefiicientof expansion'of the two-will equal; eachother, it should be understood that a backing member made' of" a material having a coefiicient of expansion whichmatches that of the insulating cylinder-will-ordinarily' accomplishsomeof the advantages of'this'invention; It should beunderstoodthat a material matches another. in coefiicient ofthermal expansion; when-the COBl'fiCiGIItS thereof are close enough-to enable the directsealing of the two materials to; each other, regardless of' size considerations. Furthermore, proper adjustment of thethickness of themetal' member, ceramic member and backing member in accordance, with. the material off which they are composed may enable theuseof agbacking member in accordance with'this invention whichdoes not" have a coefficient of expansion matching that of the-insulating cylinder.

Another basic teaching of the invention isthat it" is beneficial to employ a ceramic backing member in the embodimentofjthis invention shown in Figures 1 and2 even-without regard to differences in thecoeflicientsiof expansion of cylinder 26 andsealing ring 29; Even. if ring Z? could satisfactorily be made of a metal having the samecoefiicient of expansion as cylinder 26, it would still'be very preferable to use a.ceramic'backing member, to prevent directcontact between the large. metalsection 25 and the thin ring 29, sothat there wouldbeno'seiz ing therebetween and the radial movements of metalsec tion 25 'will'notbe transmitted'through the thin overlap ping portion of'ring 29'to cylinder 26; An additional benefit of a ceramic backing ring in the embodiment shown in Figures 1 and 2 is that it will provide insulation. between the end plate 25. and themetal ring 29'thus avoiding arcing problems and excessive heating-of the sealingarrangement whichmwould otherwise resultduring high frequency or high voltage operation.

What is claimedis:

1. An electron tube comprising a gas tight envelope, and abacking member, said gas tight envelope constitutinga hermetically sealed enclosure apart from said 'backingmember andcomprising a tubular ceramic member havinga given transverse dimension, and a metal member having parallel fiat surfaces, one end of said ceramicmember beinghermetically sealed'to one of said surfacescf. said metal member, said ceramic. backing memberbeing sealedto theother of said'surfaces of said metal member in symmetrical alignment with said tubular ceramic .member, said ceramiobacking member. having atransverse dimension, equal to said given transverse di- 1 mension of said ceramic member,

2. An electron tube comprising an envelope having a ceramic section and anothersection adjacent said ceramic. section, a ceramic, backing member positioned'between said envelope sections in sliding abutment with said other section, a metal sealing flange structure ,projecting from said other section acrossthe joint between said other section. and said backing member, the end of said flange structure being sandwichedibetweensaid ceramic section and said'backing member, and a metallic bond joining the sandwiched end of said flangestructure to the adjacent.

surface of said ceramic section.

3, Anelectron tube comprising an, envelope having a. ceramic section, and another section adjacent said. ceramic section, a ceramic backing. member positioned between, said envelope sections in sliding abutment withv said other. section, a metal sealing flange structure projecting from. said other section: acrossthe joint between said other section and said backing member, the end of said flange. structure being sandwichedbetween said ceramic section. and said backing member, and metallicrbonds.joiningthe sandwiched end of said flange structure to the adjacent surfaces of said ceramic section and said ceramic backing member.

4. An electron tube comprising an envelope having a ceramic insulating section and a metal section adjacent said ceramic section, a ceramic backing member positioned between said envelope sections in sliding abutment with said metal section, a metal sealing flange projecting from said metal section, the end of said flange structure being sandwiched between said insulating section and said backing member, said ceramic insulating section and said ceramic backing member being metallized on their surfaces facing the sandwiched end of said sealing flange, and fused metallic bonds joining the sandwiched end of said flange to the metalized surfaces of said insulating section and backing member.

5. An electron tube comprising an envelope having a tubular ceramic insulating section and a metal section adjacent said ceramic section, said ceramic section being metalized on its surface adjacent said metal section, a ceramic backing member positioned between said envelope sections, said backing member being metallized on one surface thereof, said backing member being oriented so that it has a ceramic surface in contact with said metal section and said metallized surface thereof faces said ceramic section, an annular metal sealing flange projecting from said metal section, a portion of said flange being sandwiched between said ceramic section and said backing member, and metallic bonds joining the sandwiched portion of said flange to the metalized surfaces of said ceramic section and of said backing member.

6. An electron tube comprising an envelope having a tubular ceramic section and a metal end wall section adjacent one end of said ceramic section, said ceramic section being metalized on its end adjacent said metal section, a ceramic backing member positioned between said envelope sections, said backing member being metalized on one surface thereof, said backing member being oriented so that it has a ceramic surface in contact with said metal end wall section and said metalized surface thereof faces said ceramic section, an annular metal sealing flange structure projecting from said metal section across the joint between said metal section and said backing member, a portion of said flange structure being sandwiched between said ceramic section and said backing member, and metallic bonds joining the sandwiched portion of said flange structure to the metalized surfaces of said ceramic section and of said backing member.

7. An electron tube having an envelope comprising a ceramic tubular section, another tubular section, and an annular metallic sealing structure, said sealing structure having a first inwardly extending flange sealed across one end of said ceramic tubular section and another inwardly extending flange sealed across one end of said other tubular section, and a ceramic backing ring interposed between said inwardly extending flanges in alignment with said tubular sections.

'8. An electron tube having an envelope comprising a first tubular ceramic section, a second tubular ceramic section, and an annular metallic sealing structure, said sealing structure having a first inwardly extending flange sealed across one end of said first ceramic section and another inwardly extending flange sealed across one end of said second ceramic section, and a ceramic backing ring sandwiched between said inwardly extending flanges in alignment with said tubular sections and sealed to one of said flanges.

9. An electron tube having an envelope containing a plurality of electrodes and comprising a first tubular ceramic section, a second tubular ceramic section, and an annular metallic sealing structure, said sealing structure comprising a first metallic ring having an inwardly extending flange sealed across one end of said first ceramic section and a second metallic ring having an inwardly extending flange sealed across one end of said second ceramic section, said second metallic ring supporting one of said electrodes within said envelope at the inner periphery thereof and serving as an electrical connection to said electrode, a ceramic backing ring being sandwiched between said flanges in alignment with said ceramic sections and being sealed to said second metallic ring, said first and second metallic rings being welded together at their outer peripheries.

10. An electron tube having an envelope comprising a tubular ceramic envelope section, another tubular envelope section, a first metallic sealing ring, and a second metallic sealing ring, said first metallic sealing ring being hermetically sealed to one end of said tubular ceramic section, said second metallic section being hermetically sealed to said other envelope section, the outer peripheries of said sealing rings being hermetically sealed together, and a ceramic backing ring hermetically sealed to said first metallic ring opposite said tubular ceramic section.

11. An electron tube comprising an envelope having a tubular ceramic section and a metal section adjacent said ceramic section, said ceramic section being metalized on its end adjacent said metal section, a first sealing ring surrounding said ceramic section and having an inturned portion overlapping the metalized end of said ceramic section, a ceramic backing ring coaxial with said ceramic section and positioned between said metal section and overlapping portion of said first sealing ring, metallic bonds joining the overlapping portion of said first sealing ring to the adjacent surface of said backing ring and to the metalized end of said ceramic section, a second sealing ring projecting from said metal section into engagement with said first sealing ring, and a metallic bond joining said first and second sealing rings, the coeflicient of expansion of said first sealing ring being greater than the coeflicient of expansion of said ceramic section.

12. A klystron comprising a drift tube having metal sections separated by a gap, a resonator comprising two metal end walls and a ceramic insulating cylinder therebetween, said end walls being fixed to said drift tube sections at opposite sides of the gap, two ceramic backing rings axially in line with said ceramic cylinder, said rings being positioned one at each end of said cylinder in sliding abutment with the adjacent end walls, metal sealing flange structures projecting one from each end wall across the joint between the end wall and the adjacent backing ring, the end of each of said flange structures being sandwiched between said ceramic cylinder and the adjacent backing ring, said ceramic insulating cylinder and said ceramic backing rings being metalized on their surfaces facing the sandwiched ends of said flange structures, and fused metallic bonds joining the sandwiched ends of said flange structures to the metalized surfaces of said ceramic cylinder and backing rings.

References Cited in the file of this patent UNITED STATES PATENTS 2,619,611 Norton et a1. Nov. 25, 1952 2,629,066 Eital et a1. Feb. 17, 1953 2,644,907 Drieschman et al July 7, 1953 2,720,997 Dailey et al. Oct. 18, 1955 2,727,177 Dailey et a1. Dec. 13, 1955 Notice of Adverse Decision in Interference In Interference N 0. 91,200 involving Patent No. 2,903,614, D. H. Preist, P. D. Williams and J. L. Hall, Envelope structures for electron tubes, final judgment adverse to the patent'ees was rendered Nov. 15, 1962, as to claims 1, 5 and 6.

[Ofiioz'al Gazette April 30, 1963.]

Disclaimer 2,9O3,614E.-D0nal0l H. Paeist, Mill Valley, Paul D. Williams, M81119 Park, and

James L. Hall, Palo Alto, Calif. ENVELOPE STRUCTURES FOR ELEC- TRON TUBES. Patent dated Sept. 8, 1959. Disclaimer filed Aug. 19, 1963, by the assignee, Ez'tel-McUullaugh, Inc. Hereby enters this disclaimer to claims 1, 5 and 6 of said patent.

[Ofilcz'al Gazette October 1,1963]

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