US2332426A - X-ray tube - Google Patents

Description

Oct. 19, 1943. Z. J, ATLEE 2,332,426

i X-RAY TUBE l Filed May 3, 1941 gl l() 65 59 Q7 Q9 i l E@ $29 7 zij '9 53 i? 5 jm 105 01 7j INVENTOR, ZedJHZQe X-rays.

Patented Oct. 19, 1943 i t o -v1;

Y Hx-RAY TUBE Zed 'QI'. tlee, Elmhurst, Ill., assigner to Generalr.

corporation ofNevv York *n Electric 'XRay Corporation, C Clriicago,y Ill., l al.

Application Maye, 1941-, seriaineyaorsv solaires. (o1. '25o-142) My :inventiony relatesin lgeneral to electronics y and has more particular lreference `rto the provision of an improved Xfray generator.

An important object ofthe present invention is to provide an X-ray tube having an envelope structure Which'is substantially immune to deterioration as a yresult of XH-ray action; a'further object being to eliminate X-ray tube failure as a result of envelope deteriorationdue to X-ray action on the envelope.

n. on glass end seals, inturri carried inr rims"sealeolfy tothe opposite endsof the' 'metal sleevefmeniber Another important `object of the inventiorris to provide an envelope construction in X-ray tubes inwhich the absorption of useful X-rays by the envelope is reduced to an inconsequential vminimum.

Another important objectis to form thejenvelope principallyof metal; a further object being to apply preferably metal tubing asan envelope in X-ray generators, so that theenvelope mayr comprise substantially., non-deterioratingmaterial Wherever exposed to the direct action of X-rays. e Y l e Another important object is to provide an X-ray tube having a principally metal envelope,

thereby avoiding rchangezvin envelope voltage gradient characteristics ofthe tube dueto en velope deposits resulting from lament or target evaporation during theservice life of the tube; a furtherobject being to; eliminate the difficulties resulting 'from etching of vglass envelopes in X-ray tubes by Vforming the envelope of metal at' the zones where etching occurs, thereby prevent--V ing the development of cracks and eliminatingv the possibility of developing a gassy tube' in service through localized heating of the envelope as a result of etching.

A further object is 'to providean X-ray tube having an ienvelope comprising a preferably seamless" steel tube Within which all of'theele ments of the X-ray generator, including 'glass y end seals, are enclosed, tothe end that, by

grounding theA steel tube, the entiredevice mayV be rendered absolutely shock-proof; a further object being to arrange the elements of the generator Within tl'letubularenvelope portion in suchV arway 'that the glass end seals vare absolutelyfprotected against metallic deposit thereon through ,electrode evaporation during the service life ofthe tubethe glassfend seals being fur' thermore protected against` 'direct action' "of yAnother important object is to provide an X-ray tube in which the anode and cathode elec-' trodes are supported in place on glass end seals,

the 'structurevbeing arranged so `that "the glass seals carry,extremely!small mechanical loads,

.Answer "important object is to provide an. 1

X-ray'` tube embodying'- a" preferably sleeve-like metal envelope member in' *which is disposed anode and cathode electrodessuprorted in place so that nthe tubeV can "be readily constructed by pre-fabricating the,` electrodes onY the end seals,

assembling the same inthe ltube yand solderingl 'the tube ends on the seal-carrying rings, While ng' and ,evacuating the simultaneously degassi generator.

' Among the numerous other Yimportantr 'objectsV and advantages of theinventionis to'provide Y,an extremely simple and inexpensive X`ray generator Well adapted tomass production practices and embodying a VSubstantially ally-,metal construction having the 'advantage ofmanufac'- turing accuracyiinherent to machine VAnishecl K metal parte;v n, n Y

These'and numerous other important objects, advantages, and inherent functions of the invention will. become apparent as the invention is more fully understood from the A,following description, which, taken in conjunction ,with the in a sealed yenvelope,preferajfily comprisingl a.

- an X-ray generator.

accompanying' drawing.; vdiscloses a preferred embodiment ofthe invention.`

Referring to the drawing:

Figure 1 is a sectional. view villustrating l"an X-ray generatorlembodying the .features of my present invention, the generator being shownin mounted position on supports,vin .accordance with the teachings of the invention; and

FigureZ is asectional View taken substantially along'the lines 2-4-2 irl-Figure 1l i To illustrate the invention, -I have shownon the drawing an X-ray tube II comprisngan anode I3 and an opposed cathode I5 enclosed seamless steel tube I'I.`v L

' The anode I3 comprises ya Vhead `supporting a target I9 in position ropposite Vthe cathodeto 'ref ceive the impingement of electrons emitted by `the lcathode during the operation of the device asv The head of theanode is.V supported on aA stem 2| which formszari 'annular seat 23.'` The cathode I5 also comprises a head in whichmay be mounteda lamentary element 24.Which, whenenergized, forms a source of electrons for impi'ngement upon the `anode target I-9. The head of lthecathode is carried 'on a stem "25 which is formed with ashoulder dening a seat 21. The seats123and 21, respectively,v on the 3' und anode stem 2I and the cathode stem 25 each carry a cup-shaped metallic seal element 29. These elements 29 are formed with openings at one end to snugly receive the seats 23 and 21, the members being hermetically sealed on said seats,

as by soldering. The members 29 extend fromV the seats 23 and 21 and form skirts embracing the stems 2I and 25, respectively, said skirts forming annular edges adapted to make glass-tometal seals 3I with glass end seals 33. Each seal 33 comprises a glass disk having a central neck forming the seal 3I .with the associated member 29, and a marginal flange forming a glass-tometal seal with one end of a rim 31, the other end of which is hermetically sealedon anannular ring member 39. The anode and cathode electrodes I3 and I5 are thus each supported on a ring member 39 and, for manufacturingjconvenience, the anode and cathode may be assembled on the rings 39 as assembly units. outwardly of the rim31 attached thereon, is formed with ,an annular groove 4I configurated tosreceive-anend of the tubeI1, so that merely by` assembling; the anode and` cathode assembly units on the opposite endsy of the: tube I1, the generator may be finished 12o-complete form by silversoldering vthe ends of the tube I1 in place in the grooves 4I, the silver soldered joints being shown at 43.

It should be understood that X-ray generators function-to produce X-rays in response to the activation of the anode by electronic action established by the operation of the cathode I5, said electronic action consisting of the impingement of electronsemitted by thecathode upon the anode target I9. Electronic impingement on the target results in generation. of relatively large quantities of heat at the target, which is dissipated thence through the bodyof the anode, including. the stem 2l, Whichmay carry heat dissipating means, such as nns 45, thereon outwardly of the envelope. Heat generated at the cathode likewise may. be dissipated. thence ,through the stem 25outwardly of the envelope, the stems 2| and 25. extending each. ina chamber 41 opening outwardly of the sealed envelope at the opposite endsthereoi. f

Electrons emittedby the element 24 pass outwardly thereof in straight paths toward the anode, but it will be noted that the body of the anode I3 is formed and arranged in position to shield the anode seal 33V from direct electron impingement., The cathode seal 33 likewise is shaded or shielded bythe structure and arrangement ofthe cathode from direct impingement by X-rays emanating from the target I9. as a, result of activation thereof by electron impingement thereon.'v The glass seals 33 thus'are protected against deterioration as a result of X-ray or electronjbombardment.

It should be understood also that X-ray generators are conditioned for operation by exhausting from the envelope substantially all gaseous and other impurities by evacuating the envelope, as bymeans ci'` a molecular exhaust pump,and nally` sealing the envelope in evacuated condition. 1

` The device of my present invention is particularly suited for the accomplishment of envelope evacuation during and as a part of the final manufacturing step of sealing the electrode support rings 39 to the opposite ends of the tube I1. To this end, the` formation of the silver soldered joints 43 may beaccomplished in vacuum by means of high frequency induction. By introducing the several parts of the generator into a suitable Vacuum chamber, then assembling the parts and finally forming the joints 43 by high frequency inductive action, the generator may be fabricated in completely nished and evacuated condition. Of course, the tube is not necessarily assembled and evacuated in the manner described, but the parts may be assembled and the joints 43 formed under ordinary atmospheric conditions and the tube evacuated by attachment with a molecular'pump through a glass conduit connected in one of the glass seals 33, the connection being sealed off, as at 49, after the tube has been evacuated and otherwise conditioned for service;

Itfwill" be noted that the cathode comprises conductors 5I for supplying energy to the fila- Vmentary element of the cathode, and a conductor 53 which is connected to one end of a gettering wire 55, the other end of which is electrically connected with the stem 25 preferably by connecting the. Wire 55 on the head of the cathode. Byr applying Yelectrical potential between the conductor 53. and thev stem 25 outwardly of the-seal, the gettering; wire 55may be actuated to perform a gettering operation within the envelope ofthe generator. Upon the completion of thegettering operation, the conductor 53 may beelectrically connected to the stem 25, as by tying the parts together as shown. The conductors 5I and53 extend through insulated seals 51 formed in the support member 21 of the cathode structure.

The ltubepof course, may be mounted for operation in any suitable or convenient fashion, and the envelope I1 may be grounded to render tie tube absolutely shock-proof. As shown, a pair of spaced pedestals 59 of insulating material may be provided, said Vpedestals each forming a socket 6I for the reception of high voltage cable terminals E3, the socket of each pedestal being provided with terminal prongreceivers in position to` receive and make electrical contact with connectort prongs 61 on the cable terminals E3 when the same are inserted in the sockets SI. The pedestals59 are formed'with annular seats 69in'position to receive the rings 39 of thetube, which may be secured tothe pedestals in posi.- tion therebetween by fastening bolts 1I extending inopenings-in the rings 39 and threading in sockets formed in the pedestals 59'at` the seats 59. The outer surfaces of the pedestals 59 may be covered with a grounded metal sheath 13 which. 'may be electrically connected with the metalit'ube envelope asa result of the clamping ofl the rings 39 on the'seats 69, thereby rendering the entire assembly shockproof.

The surface of eachpedestal 59 within the annularseatjl is preferably formed with an annular` groovev 'l5 and an annular rib 11 inwardly of the groove 1E, said rib enclosing a seat 19.

' Thepedestal supporting the anode end of thc generator carries a contact prong 8| mounted at one end in the pedestal at the seat 19, said prong 8.I extending outwardly in position to engage in a socket 83 formed in the anode stem 2I.

ductor 85 extending in the insulating material.

of which the pedestal is formed.

The pedestal supporting the cathode end of the generator also carries. means for facilitating electricalconnection oithe stem 25 the conduc tor`s"l Withtheprong lreceii'fer's65.` "I'o this end, the seat 19 is 'fitted'with friction plug vmembers 87, which are electricallyconnected with-the re` ceiversflby conductors BS'eXtending inthe insulating material of thepedestal. The stem 25 withonefof the conductors'5'l. [It will be seen?.

thatthe support frame 9 I1carries the grommets 93 in position to fit upon themernb'ers 8T and'to fornielectrical contact therewith as the ring 39 at the cathode end of the tube is fastened on the seat $9 of the' pedestal. Y

It Ywill be'noted that the chamber 4l defined by the end seals is closed by the pedestals 59- when the generator is in mounted' position therebetween. l Each'pedestal maybe formedwith an inlet conduit 95' and an outlet conduit S1 through whichcooling liquid from a source outwardly of the pedestal maybe circulated into andout of the chamber 41 Ifor the purpose of cooling the anode and cathodestructures. f

Ii desired, the preferably steel envelope'lfl may be formed with a window opening 99 opposite b 3 'The thickness of the beryuiumdisk -mi may vary,'but satisfactory results maybe obtained yby employing a disk having a thickness Within y the range'sle to 1% of an inch." u

I It will be understood, of course, that the'inventi'on is not necessarily lirnitedtothe` use of silver-copperalloy, ralthough it is preferable, for the purpose involved, that the alloy be one hav.- ing va'melting temperature within the rangebetween 700 and 900 centigrade. "Temperatures above 900 centigrade 'are undesirable because of the danger of cracking or checking parts of the generator and also be'causefof the danger of,v dissolving the beryllium during the brazing operation.

In practice, satisfactory ybrazing results' `have been obtained with an alloy comprising 80% copper; 15% nickel,`and 5%v iron, and Ihave also found that aluminum maybe also employed asa`soldering agent for joining `beryllium with other metals.` v `1 vAfter the beryllium window il!!! has been secured in the collar 103, the collar may be sealthe target I9, and a pane of material 'lilLwhich is substantially transparentA to X-rays, may be sealedon the envelope at said opening. I prefer to utilize a beryllium window-pane Illl, V'since Y beryllium has an exceedingly low X-ray absorbing characteristic. applied by soldering it in a ring of cold rolled steel H03 by means of a suitable solder 05. In

. accordance with thisinvention, an allcyof a` vmetalwhich has a tendency to form rapid solution with beryllium and a metal which has fa tendency to form solution with beryllium less rapidly may be employed in order to form a vacuum-tight joint between beryllium and other The beryllium pane "may be metals as, for example, cold rolled'steel.A I prefer, n

therefore, to use a special soldering alloy ccm#l vnrising about %'si1ver and 50% copper to form a vacuum-tight joint between the berylliumwin-I In order that the alloy may ilow evenly upon the beryllium member to form the joint, it should be in a highlymolten state; but the higher the temperature, the faster is the rate at which beryllium will go into solution. Pure copper ln the molten state goes rapidly into solution with berylliumbut silver, on the other hand, dissolves beryllium slowly, while alloys of copper and sil-` ver have yintermediate rates of solution withberyllium. Furthermore, all alloys of copper andsilver have melting temperatures lower than that of pure copper, and all alloys'having less than ,15% of copper have melting points lower than that of pure silver, forwhich reason silver-cona ner alloys have the added advantagethat brazing therewith may be accomplished at low temnerature, which additionally facilitates the con-v trol of the rate of beryllium solution. For the purposes of the presentinvention, it is preferable that the amount of copper in the copper-silver alloy be greater than the copper constituent in the eutectic alloy, which comprises 72% silver and 28% copper.

ingly united with the envelope member l'l in any suitable or` preferred fashion, since the parts I'.' and |03 preferablyboth comprise steel. u

It is thought that the invention and its numerout 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 withoutv departing from the spirit or scope of the invention,` `or sacrificing any of its attendant advantages, the form herein disclosed being a preferred'embodimentfor the purpose of illustrating theinvention. A

The invention is hereby claimed as follows: l. Af'device of the class described comprising a tubular metallic member forming an envelope, re-entrant means extending within theftubular member atY the-oppositeends thereof, said reentrant means forming mounting rims,"an insulated electrode support carried byand annularly sealed to each mounted. rim within said tubular memben andan electrode carried by and Vannularly sealed toeach support within said tubularY member whereby the electrodes', the insulated electrode 'suplciortsand said mounting tallic member. y y

2. A device of the class described comprising a tubular metallic member forming an envelope,

re-entrant means extending within the tubular rims 'are housed entirely within the tubular melated electrode support carried by and annularly sealed to each mounting rim within said tubular member, and an electrode carried by each sup-y portfwithin said tubular member, each electrode comprising an annular mounting skirt annularly sealed to the support on which it is carried.

3. A device of the class described comprising a tubular metallic member forming an envelope, metallic re-entrant means extending within the tubular-.member lat the opposite ends thereof,

lsaid lre-entrant `means forming mounting rims,

lmaking aiglass-to-metal seal with the rim on which it is mountedand an annular electrode mounting edge, and an electrode carried by each l j support Within said tubular member, each electrode comprising amounting skirt providing an annular-edge forming a metal-to-glass seal with the `mounting edge of the electrode support on which it is carried. 1,

4. A device of the class describedrcomprising a tubular metallic member forming an envelope, metallic re-entrant means extending within the tubular member at the opposite ends-thereof; said re-entrant means forming mounting rims, an insulated electrode support carried by andannularly' sealed to each mounting rim within said tubular member, each support comprising a` glass member having an annular anchored edge making a glass-to-metal seal with the rim on which it is mounted and an annular electrode mounting edge, each glass member comprising a disk,- like ring having inner and outer edges projecting oppositely therefrom to form said anchored and electrode mounting'edges, and an electrode carried by each supportrwithin said tubular memberl, each electrode comprising a mounting skirt providing an annular edge forming a metal-toglass seal` with the electrode mounting edgeg'oi the glass member on which it is carried.

5. A device of the class described comprising a tubular metallic member forming an envelope, rfa-entrant means extending Within the tubular member at the opposite ends thereof, said reentrant means forming mounting `rims. Within said tubular member, said tubular member havf, ing inwardly extending liange means at its opposite ends and said mounting rims being carried by and sealed to said flange means,.an insulated electrode support carried by and annularly sealed to each mounting rim Within said tubular member, and an electrode carried by and annularly sealed to each support Within said tubular-membei' whereby the electrodes, the insulated electrode supports, and said mounting n'ins are housed entirely Within the tubular metallic member.

6. A device of the class'described comprising a tubular metallic member forming an envelope, re-entrant means extending Within the tubular member at the opposite ends thereofsaid reven trant means forming mounting rims, an annular flange ring sealed on the tubular member at each end thereof, said ange ring having an outwardly extending mounting portion and an inwardly extending support portion carrying one of4 said mounting rims within the tubular member and annularly sealed thereon, an insulated electrode support carried'by andvannularly sealed to each mounting rim Within said tubular member, and

an electrode carried by and annularly sealed to '5 each support Within said tubular member Whereby the electrodes, the insulated electrode supports, and said mounting-rims are housed entirely within the tubular metallicv member.

7. A device of the class described comprising a tubular metallicmember forming an envelope, metallic re-entrant means extending within the tubular member at the opposite ends thereof, said re-entrant means forming mounting rims, an annular flange ring sealed on the tubular member at each end thereof, said flange ring having an outwardly extending mounting portion and an` inwardly extending support portion carrying one of said mounting rims Within the tubular member and annularly sealed thereon, an insulated electrodeisupport carriedby and annularly sealed to eachv rim Within said tubular member, each support comprising a glass member having an annularv anchored edge making a glass-to-metal seal with the rim on which it is mounted and an annular electrode mounting edge, each glass member comprising a disk-like ring having inner andouter edges projecting oppositely therefrom to form said anchored and electrode mounting edges, and an electrode carried by each sup- 30 port Within said tubular member, each electrode comprising a mounting skirt providing an annular edge forming a `meta1toglass seal with the electrode mounting edge of the glass member on which it is carried.

8. A device of the class `described comprising a` tubular metallic member forming an envelope, re-entrant means extending Within the tubular memberat the opposite ends thereof, said reentrant means forming mounting rims, an insu- 40 lated electrode support carried by and annularly sealed to each mounting rim Within said tubular member, and an electrode carriedby and annularly sealed to'each support Within said tubular member under vacuum conditions whereby the electrodes, theinsulated electrode supportsand said mounting rims are housed entirely within the tubular metallic member under vacuum conditions.

ZED J. ATLEE. 5,@

Images