US2497479A - Rotating vacuum seal - Google Patents

Description

Feb. 14, 1950 J. J. vLAcH ROTATING VACUUM SEAL Filed June 7, 1946 2 Sheets-Sheet 1 A @Ue/dior gy M /baya/jm @2v/Q 5 Feb. 14, 195o Filed June 7, 194e 2 Sheets-Sheet 2 I a@ Q5 /A} 159 A 1 L a; Illll M60/k 27 J2 242 JQ .52

:i "59 @a @y 'L Patentedv Feb. 14,1950

ROTATING VACUUM SEAL Jfohn J osephI Vlach, i Chicago, Ill., assignor f to vGeneral 'Electric :X-Ray ,Corporatiom Chicago, Ill., a corporation of New York v @marianne i., ma serial no, 615,048

Ther present invention vrelates in Ageneral to seals and sealing, and has more particular referencel to the provision of means for sealing rotating, shaft-like members to prevent fluid leakage along the member through a wall or journal in which the shaftextends; the invention especially relating to the sealing of low pressure vessels, such as vthe envelopes of X-ray generators, particularly X-ray generators having rotating anodes driven by motive means disposed'outward- 1y of the envelope, 'wherein the anode and motive means are drivinglyconnected' by a shaft-like member extendingthrough'a wall portion of the envelope. n

Y X-ray generators commonly comprise an electron emitting cathode, and a cooperative anode forming a target for receiving impingement .of electrons emitted from the cathode, X-rays being generated by such'electro'n impingeme'nt on the anode target. kThe anode and cathode are commonly enclosed withina sealed 'and exhausted envelope, whereby the anode aridcathodeelel ments may operate substantially in vacuo.' -In certain circumstances, particularly in heavy duty generators, it is desirable to utilize a rotating anode'positioned to receive electrons,at any instant, upon a portion onlyvof vthe anode target, said target being `of annular configuration, whereby, when rotated,l the target may be continuously moved to progressively shift the portions thereof under electronA bombardment, and, thus, prevent any target varea from becoming overheated, it being understood Ythat electron bombardment results in the, generation of excessive heat in the target element. -l

An important object of the present invention is to provide an improved X-rayvgenerator having a rotating anode mounted within a sealed and evacuated envelope, together with facilities for driving the anode'frorn 'outwardly of the envelope, by shaft-like means driving-ly connected with the anodean'd 'extending loutwardly of the envelope through a novel and'A eff'ective'shaftv seal formingA agportionof the'envelope.

Claims. (CL Z50- 148) v2 v Another important object lsv-to provide arfshaft seal embodying Aan expansible'bellows element, carrying a 'seal fing adapted toforrn-a ground joint with a cooperating seal seat, wherebyisaid ringand seat may provide a vacuum sealwhen in relative rotation;'a furtherfobject beingto provide for the retention of a liquid sealing medium at, and on onel side of, said ground joint; a further object beingto utilize the expansible bellows as a means for-retaining the-liquid-v sealing medium at said'ground joint. i f.

Another important-object i to-provide vreservoir means for insuring the maintenance of liquid sealing medium at, and on one side of, the ground joint;- a further object being vto Vregulate the. sup ply of liquid sealing medium toprevent leakage 'thereof through,theV grqundjoint and into Athe evacuated vessel; 4 Another important object is to providev a shaft sealutilizing a liquidseal medium in comunetion With a seal ring and cooperating seat forming a running groundjoint'including the novel arrangement of'partsv whereby-the seal may be Y formed as a separate assembly unit, adapted for application upon -an envelope-or housing at a shaft opening therein, in position to sealingly cooperate With-a` shaft-like member extending in said opening, the particular arrangement of the seal 'making it` adaptable for use as avreplacement unit-,said unit, when` mounted, forming a partof the envelope or housing on vWhich, itis-assembled. ..Another important objecty is to provide ar shaft seal for the rotatingeanode of an X-ray generator, including sealed-meansfor circulating a cooling medium through the shaft to and from the anode of the generator, for thepurpose'of conf "tinuously cooling the .same while: the Vgenerator islin operation. i q f Y, p v f The foregoing and numerous other important objects, advantages, and inherent functions of the inventionr Willbecome apparent as the'same is more fully understood from the followingl description, which, .taken in connectionl with the accompanying drawings, discloses a preferred embodiment of` the invention. y

'Referringto `the-drawings: f.; ,t Fig. 1 isa sectional view through arr'X-ray generator embodying the present invention o Fig. 2 is an enlarged sectionalview ofa seal structure formlngfa part .of the device shown in Fig. l; and f Y iff f '.aFig. 3 is a modified seal arrangement embodying the invention. 'i1 i To, illustrate the invention, fthe. drawings show anzielcctronic device :comprising .ari X-ray igenerator II, although it will be understood that the invention is not necessarily limited, in all of its aspects, to X-ray generators, some of the features of the present invention having general application wherever effective shaft sealing functions are required. As shown on the drawings, however, the generator I| may comprise sealed envelope means I2 containing an anode I3 and a cooperating cathode I4 of any suitable or preferred construction The envelope I2 may be formed in any convenient or preferred manner, and may comprise any suitable envelope material. As shown, the envelope may comprise a tubular glass sleeve I5, having a re-entrant neck I3, at one end, upon which neck the cathode structure I4 may be supported and sealed in any suitable fashion, as by means of the seal ring I'I, making an annular glass-to-metal seal with the re-entrant neck IS. The opposite end of the envelope sleeve I5 may, likewise, be sealed upon the upstanding neck portion I3 of an annular flanged structure I9, the end of the sleeves I5 being sealed to the neck portion I8, as by means of a ring 20, similar to the ring I'I, and forming a glass-to-metal seal with the end of the sleeve I5.

The envelope I2 may, also, include closure means 2|, adapted for application to the flanged member I9 for sealing the opening therethrough into the sleeve I5, said closure means 2| being e preferably formed to turnably support the anode I3. To this end, the closure means 2| may include a preferably annular structure, comprising a plate portion 22 formed with a central opening and adapted to be clamped sealingly with the flange structure I9, and a housing portion 23 of preferably sleeve-like conguration adapted to form, with the plate 22 and the flanged structure I9, a bearing cavity 24 extending axially of, and forming a continuation of, the space enclosed by the envelope sleeve I5.

The closure means 2| carries a bearing structure 25 within the chamber 24, said structure being preferably mounted on a support spider 26 disposed within the central opening of the plate portion 22. This spider may conveniently be formed as an integral part of the plate portion 22. The housing portion 23 may extend outwardly of the plate portie-n 22, and may be formed with a seal seat 21 at the end thereof remote from the plate portion 22. This seal seat preferably dei'lnes `a central opening 28 through which the shaft member 3|) extends. The flanged structure It and, also, the closure means 2| may be made of any suitable, preferably metallic material, and may comprise tubular and plate-like sections welded, brazed, or otherwise sealingly secured together, as shown, to provide the required envelope parts.

The anode I3, which may be of any suitable or preferred structure, is supported within the envelope sleeve I5 on a shaft-like element 30, said element preferably comprising a tube which extends from the ano-de through the chamber 24 and outwardly thereof through the opening 28, said tubular shaft member being journaled for rotation in the bearing means 25.

The entire structure may conveniently be supported in operating position on pedestals 3 I, comprising rods mounted on, and extending upwardly of, a suitable supporting base 32, the rods 3| carrying the flange structure I9 with closure means 2| sealingly clamped thereto.

The end of the shaft sleeve 3D, which projects outwardly of the closure means 2|, may be drivl is also preferably formed with a packing gland for turnably receiving the terminal end of the member 30, the gland 35 providing a liquid seal for connecting the open end of the member 30 with conduit means 36. The base 32 may, also, be formed with a liquid conduit 3T connected with one end of a tube 38, `which extends concentrically within the tubular member 30, the

tube 33 opening, at its remote end, into a cavity 39 formed within the body of the anode I3, said cavity communicating, also, with the anode connected end of the member 3|). By circulating a cooling medium, such as water, through the cavity 39 by way of the conduits 36 and 3l and the concentric tubes 30 and 38, the operating tempera-ture of the anode may .be held within safe limits.

In order to maintain desired low pressure, substantially vacuum conditions within the envelope, during operation of the generator, the closure means 2| may be provided with a conduit 40 adapted for connection with suitable exhaust that is to say, through the opening 28. To this end, the present invention contemplates the provision of novel vacuum seal means 4I, preferably arranged as a replaceable unit adapted to be mounted on, and to form a part of, the envelope structure. As shown, the seal means 4| comprises a housing 42 of preferably cup-shaped configuration, having flange means 43 at the lip of the cup member, said flange being adapted to sealingly engage in the seat 21 formed on the closure means 2|. To this end, the flange 43 may be secured on the seat 21, as by means of clamping studs 44, a suitable sealing gasket 45 being applied and clampingly received between the flange 43 and the seat 2l. The bottom of the cup-like housing 42 is formed with a central opening 46, sized to snugly, yet turnably, receive the shaft member 33, said opening being preferably tted with a packing gland 41 around the shaft. The housing member 42 is preferably made of metal.

The cup-shaped housing 42 is, thus, adapted to define a chamber 48 around the shaft member 30 at, and communicating with, the opening 28, and, thus, when mounted, comprises a part of -the envelope itself. The seal comprises a pair of cooperating, preferably metal rings 49 and 50, one of which is mounted, or formed, on the shaft member 30 in iposition providing an annular sealing surface facing into the chamber 48, and the other of which is moimted on the cup-shaped housing 42 in position providing an annular sealing surface adapted to engage and form a running seal with the sealing surface of the cooperating ring. One of the ring elements preferably comp-rises relatively hard material, such as steel, while the other may comprise a relatively softer metal, such as bronze. The more readily replaceable ring 49 is preferably made of the softer material to take the wear. One of the ring elements, also, is yieldingly supported, as on a metal bellows 5l, whereby the resilience of said bellows may serve to hold the ring element in yielding engagement with the cooperating ring element."v If desired, spring means 52 may be employed to aid in holding the ring elements yieldingly in mutual sealing engagement.

If desired, the shaft mounted ring 50 may be, thus, yieldinglysupported on the shaft in the manner shown in Fig. 3, wherein the shaft mounted ring comprises an element 50' supported on the shaft by means of the bellows 5l and urged by the spring 52 into engagement with the seat element 49 on the housing 42. It is preferable, however, as a matter of manufacturing convenience, to mount the ring 50 rigidly, and sealingly on the shaft member 30, as shown in Fig. 2, as by welding, or brazing, or otherwise integrally fastening the ring 50 upon the shaft, preferably in position extending in the opening 28, If desired, the shaft 3|) may be integrally formed with a shoulder in the opening 28, in position to cooperatively engage the seal ring 49. In either case, the cooperating annular surfaces of the ring or shoulder 50 and the seal ring 49 `are finished accurately, to provide smooth, highly polished annular sealing surfaces. The ring 49, also, is sealed, as by brazing the same in a central opening formed in a metal plate 53, the plate, in turn, being sealed, outwardly of the ring 49, to one end of the bellows element 5|. The other end of the bellows is sealed on a metal mounting ring 54, adapted to sealingly engage vin an annular seat 55 formed in the cup-shaped housing 42, the mounting ring being retained in its seat as by means of clamping rings 55, which may be threadingly secured in the housing. The spring means 52 may comprise a helical spring element ,encircling the shaft, and, as shown in Fig. 2, bearing at one end on the seal ring 49,

the other end of the spring seating upon the bottom of the cup-shaped housing around the opening 46. As shown in Fig. 3, however, the spring 52 may bear at one end on the shaft mounted seal ring 50, the other end of the spring engaging a shoulder formedA on the shaft. .In this connection, the arrangement, as shown in Fig. 3, embodies a removable mounting nut 54' adapted for threaded, sealing engagement on the shaft, said nut providing an armular spring seat and a concentric annular rib, to which one end of the bellows element is sealingly secured,

the other end of the bellows element carrying the disk 53' on which the shaft supported seal ring 5U is sealingly mounted. In the Fig. 3 embodiment, the cooperating seal ring 49' is sealed directly on the mounting ring 54.

When the shaft 30 is rotating, the rings 49 and 59 will turn, one with respect to the other, to form a running ground joint between the cooiperating seal faces of the rings, the rings being, at all times, maintained in tight sealing engagement by the action of the spring 52. The envelope will, thus, fbe sealed against fluid leakage around the shaft at the opening 28, since the ring 50 is sealed around the shaft, the ring 49 is sealed to the bellows, which, in turn, is sealed to the housing 42, the housing 42, in turn, being sealed to t'he envelope closure member 2l, and the running ground joint sealing against leakage between the rings 49- and 50, as shown in Fig. 2. In theFig. 3 embodiment, the envelope is sealed againstffiuid leakage since the ring v50 is sealed 6 to the bellows, which in turn is sealed to the shaft, while the ring 49' is sealed to the housing 42, the running ground joint sealing against leakage between the members 49' and 50'.

In order to enhance the efficacy of the seal, means is provided for maintaining a supply of a liquid sealing medium, such as oil, around the shaft 30 at, and outwardly of, the seal ring 49, said supply of liquid preferably being contained within the space 51 defined around the shaft between the bottom of the housing 42 and the ring supporting means, comprising the disk 54,- bellows 5I, and disk 53. To this end, the housing 42 is provided with conduit means 58 connect ing with an oil reservoir 59, whereby oil may be supplied to,` and held in, the space 51 to completely ll the same up to the ring 49. In this connection, it is desirable, also, though not absolutely essential, to connect the reservoir 59 with suitable exhausting means, so that the seal-- ing liquid in the reservoir 59 and the space 51 may be held under reduced pressure, to thus minimize any tendency for the liquid sealing medium to leak through the ground joint into the evacuated envelope.

It is thought that the invention and its numer` ous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the forms herein disclosed being preferred embodiments for the purpose of illustrating the invention.

The invention is hereby claimed as follows;

l. An X-ray generator comprising means forming a sealed envelope providing a main chamber and a sleevelike extension, a cathode and a c0- operating rotatable anode mounted within the main chamber, a shaft member drivingly connected with said anode and extending in said sleevelike extension and outwardly thereof through a shaft opening in said extension, means for sealing said opening against fluid leakage therethrough along said shaft member, comprising a running seal and flexible partition means supporting the same in position forming a liquid chamber in said sleevelike extension, at the end thereof remote from said main chamber, and around said shaft at said opening, means for maintaining Aa supply of liquid sealing medium in said liquid chamber, and exhaust conduit means yconnected to said sleevelike extension between said main and liquid chambers.

2. An X-ray generator comprising means forming a sealed envelope providing a main chamber and a sleevelike extension, a cathode and a cooperating rotatable anode mounted within the main chamber, a shaft member drivingly connected with said anode and extending in said sleevelike extension and outwardly thereof through a shaft opening in said extension, means for sealing said opening against fluid leakage therethrough along said shaft member, comprising means defining a liquid chamber in said sleevelike extension, at the end thereof remote from said main chamber, and around said shaft at said opening, means for maintaining a supply of liquid sealing medium in said liquid chamber under substantial pressure of the order of atmospheric pressure, and exhaust conduit means connected to said sleevelike extension between said main and liquid chambers to maintain low pres 7 sure conditions :therein .of the: orderapproaching am absolute: vacuum..

3.' An Xfray generaton comprisingmeansforming a sealed: envelope providingza mainzchamber and.sleevelike-extensicn, aV cathode'and a cooperating rotatable anodei mounted'. within the main. chamber, a shaft memberdrivingly.l connected" with said anode andv extending in said sleevelike extension and outwardlyv thereof throughza shaft opening in saidextension, means for sealing said opening'v against uid leakage therethrough along said shaft member, compris'- ing:l means forminguannular abutments on said shaft and on. said. envelope extension. adjacent said'v opening, onev off said. abutments providing anxannular runningrseal seat, an. extensible bellows sealedatone endonfche other-of saidzabut. ments, a seali ring sealingly secured on said bellows at the opposite. end` thereof lin position toV form: runningv engagement with said: seat, whereby to denne a liquid. chamberiin saidsleevelike extension around saidshaft'at said opening, means for maintaining asupply of liquidzsealing medium in saidi chamber, and. exhaust conduit means connected to said sleevelike extension between said main and'liquid chambers.

4. Arr X-ray generator comprising means'forminga.y sealed envelopeproviding aY main chamber and a sleevelike extension, ay cathode anda cooperating rotatable anode mounted within the mainl chamber, a shaft member drivingly connected with. said anode and extending in said sleevelikev extension and: outwardly thereof througha shaft openingj in said extension, means for sealing said opening against fluidA leakage therethroughalong; said shaft member, comprising meansTOrming` an annular running seal seat on saidshaft and an annular mounting abutment onsaid envelopey extension adjacent said opening, an extensible-bellows sealed at oneend on the mounting abutment, a seal ring sealingly secured on. said bellows at the oppositeiend thereof in position toformI running engagement with said seal seat, whereby to dene a liquid chamber in saidisleevelike extension around said shaft at said opening, means for maintaining a supply of liquid sealing medium in said chamber, and exhaust conduit means connected to said sleevelikev extension between said main and liquid. chambers.

5. An -X-ray generator comprising' means forming a sealed envelope providing a main chamber anda sleevelike extension, a cathode'and a cooperating rotatable anode` mounted within the main chamber, a shaft member drivingly connected with. said anode` and extending in said sleevelilse extension and outwardly thereof through a shaft opening in said extension, means for sealing said opening against fluid leakage therethrough along said shaft member, comprisingmeans forming an annular mounting abutment on said shaft and an annular running seal seat on said envelope extension adjacent said opening, an extensible bellows sealed at one end onthe mounting,.a seal ring sealing secured on said bellows at the opposite endthereof in position to form running engagement" with' said seat, whereby to denne a liquid chamber in said sleevelike extension around saidv shaft at'said opening, means for maintaining a supply of liquid sealing medium in said chamber, and exhaustY conduit I chamber; anda sleevelike; a. rotatable element incsaimmain chamheraa shaftimember' drivingly connected withsaidgelementiand exe tendingin said sleevelik'e extensionandputwardly thereof through: a.. shaft openingv extene sion, .means for sealingfsaid opening againstfluid leakage. therethrough. along said shaft member, comprising a running'seal andexible partition meanssupporting. the same inpositionfomningra liquid chamberv int said sleevelike" extensiong. at the end thereof remote from said main; chamber, and aroundfsaid shaft: at :said opening; ,means for:maintainingal supplyA of liquid sealing medium inf. said. liquid chamben. and exhaust conduit meansconnectedi to said sleevelike extension betweensaidmain. and liquid chambers;`

A.. low pressure'. deviceA comprising means forming a sealedA envelope providing. a main chamber'` and a sleevelikelv extensioma` rotatable elementi inv said maiirY chamber, a shaft member drivingly. connected; with said element and extendingl in said-:sleevelike extension and outwardly thereof. through a. shaft opening in said exten? sioruineans for 'sealing said opening against fluid.

leakage" therethrough alongl said shaft. member; comprising` means' defining; a: liquid chamber:v in said sleevelike extension, at: the' end thereof remote.- from said. main chamber, andv around said shaft at said.y opening; means `for maintaining: a supply of liquid sealing mediumv inv said liquid chamber 'under substantial. pressureY of the. order ofi atmospheric pressure, and exhaust conduit means connected tov saidsleevelikeextension be.- tweensaid main and liquidcharnbers toV maintain low pressure conditions therein of the order appreaching. an. absolute vacuum.

8. A low pressure device comprising means forming a sealed:envelope-providinga main chamber: and a sleevelike extension, a rotatableelement said main chambera shaft membery drv; ingly connected with said element and extending in said sleevelike extension andzoutwardlythereof through a shaftopeningin.saidextension, means for sealing said opening against fluid leakage therethrough along'said shaftmemb'er; comprising means; forming annular abutments on said shaft and on said envelope. extension adjacent said. opening, one of said abutmentsv providing an annular running seal seat,' an extensible bellows sealed at one endonthe. other of .said abutments,'.a.seal ring sealingly secured on said bellows at. the. opposite. end. thereof in: position to formI running engagement withsaid seat; whereby .tozdene a liquid chambertinsaid: sleevelike'fex'- tension around saidv shaftw at. saidA opening, means for maintaining a. supply of( liquid sealing me'.- diuini inl said chamber, and exhaust conduit means connected to said sleevelike extension be.- tween said main and liquid chambers.4

9. A low pressure device comprising means forming aisealed envelope' providing a main chamberxand. a sleevelike extension, a rotatable. ele.- Inent in said main' chamber, ashaft'member drivingly/connected'with said elementv and extend.- ing insaid sleevelilie extension. and outwardly thereofthrough a shaftk opening insaid." extension; means. for sealing said. opening against uid leakage therethrough along said. sha-:ftLmembei-, comprisingv means formingr an .annular ruiming seal` seat onsaid shaft'andiant annular: mount;

abutment on said' envelopeY extensiona'dja'- cent said opening, an extensible bellows sealed atone endronthe: mounting abutment, a seal ring sealingly secured.onsaidbellows'at the opposite end therenfgin'. positonito: form running e engagesment: withgsaidseal seat;v whereby'to; deneia' liquid chamber in said sleevelike extension around said shalt at said opening, means for maintaining a supply of liquid sealing medium in said chamber, and exhaust conduit meansnconnected to said sleevelike extension between said main and liquid chambers.

10. A low pressure device comprising means forming a sealed envelope providing a@ main chamber and a sleevelike extension, a rotatable element in said main chamber, a shaft member drivingly connected with said element and extending in said sleevelike extension and outwardly thereof through a shaft opening in said extension, means for sealing said opening against fluid leakage therethrough along said shaft member, comprising means forming an annulfar mounting abutment on said shaft and an annular running seal seat on said envelope extension adjacent said opening, an extensible bellows sealed at one end on the mounting," a seal ring sealingly secured on said bellows at the opposite end thereof in position to form running engagement with said seat, whereby to dene a liquid chamber in said sleevelike extension around said shaft at said opening, means for file of this patent:

maintaining a supply of liquid sealing medium in said chamber, and exhaust conduit means connected to saidsleevelike extension between said main and liquid chambers.

JOHN JOSEPH VLACH.

REFERENCES CITED The following references are of record in the 'l OTHER REFERENCES Lubrication in Vacuum by Vaporzed Thin Metallic Films, by Z. J. Atlee, J." T. Wilson, and J. C. Filmer, Vacuum Tube Engineering Dept., General Elec. X-Ray Corp., Chicago, Illinois (Rec. Apr. 15, 1940). Reprinted from Journal of Applied Physics, Vol. 11, No. 9, 611-615, Sept. 1940.

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