US1986466A - X-ray tube and cathode structure therefor - Google Patents

Description

Jan. 1, 1935. F. EHRKE X-RAY TUBE AND CATHODE STRUCTURE THEREFOR Filed Dec. 1, 1955 m H5} ME 4% /7E ATTORNEY g I M Patented Jan. 1,1935

.UNITEDI STATES ir Rey TUBE AND- CATHODE sTnUorURE if .r v byP R FQ 'y1 zll y i er k E k l News s' horl to WestinghouseLamp Qompanyya corporation j of ennsy v n a Application December 1, 1

f invention relates to electric discharge de"- vices and more particularly to oathode'structures therefor. In its more specific aspect the inven- 9 2 5 v ture fOr-X-raytubesfi X-ray tubes are employed anurnber of ferent fields. They find special application inthe radiographic and therapeuticfields'ij Because of" p, the difierent quantities'and charaoterf of X-rays and theshape of jtheX ray beam, ithas sometimesbeenfnecessary to employ difierent tubes for different purposes. In the dental fiel'djonly lowvoltage X-rays are requiredv whereas in the r m deep therapy fieldQreIatiVeIy high voltage X-rays bytwo considerations, first the energyQwhich the tube may safelypassand second the degree of detail or definition required in the X-ray film. The energy'requirements make. a large spot deg, sirable but the .necessityof fine defiriitionjin 2 radiographie' work makes a spot of ;,very"small area'desirable. Therefore, the sizeof focal spots in X-ray tubes employed for radiographie purposes is one that is small butof such anarea that it will successfully accommodate the energy input during operation ithout deleterious'pit ting of thetarget. Obviously," focal, spots of different sizes are desirable in various classes of radiography. Some exposures such as chest y, w intestine and the likeiexpdsurs in radiography require high energy inputs in the tube especially" r "endLofthe c'athodeis'tructure.

when the tube during operation is lofeated {a Considerable distance from the body be X rayed.

Other] exposures} such as body ezitremitiegl sinuses and the'like require smaller powerlinputs. In the ther'apeuticalfield and especially,

that field generally. known as deep therapy the energy inputfin an X-ray"tube,is commonly much greater than that required in the radio urposes and still another for deep therapy pur-i 5 posesso that'the best results'could be obtained my u cases; The uselko'f different tubesfor different. purposes has necessitated either the em-.

ployment of three circuits containing the differntftubesbr the time eonsumingtask" of tube replacements accordance with particular deed to; an improved cathode struce v Fig. 4 represen of the X-ray tube when only afportion of oneuof 933, Serial No. 700,415 q 1 mands. These disadvantages have ebeenfflapparentflin all tubes/of the line'focus type Where simple and rugged, cathode structures having but a single slot were employed. v I

' Inorder to obviate the above difiieulties and 5 y to provide "a simple 'catho de'fstrueture,which ma be readily manufactured andjassembled, I have; made the following inventioniBriefly, the invention comprises acathode structure for. X faytubes'andfcomprises afoeusing'cun hav]? 10 ingajslot in which are located a pluralitybfin-g dependent filaments so "arranged that the tube? may be employed for light duty radiographic; heavyduty radiographic and deep therapy'pur poses. 'j .f r n y Y I t Anfobject of my invention is jtof'provideanj improved cathodestructurejfpr anf X-rayTtube;

Another object of myinventien isfto provide an improved cathode structure for an" X-ray tube .so that; the; tubeisadaptedflto: be operated in a number of differentfields) Anothe'r object of my invention is to; provide a n Xnray tube of the line focus type andada'pted to be"efiic iently operated for light and heavy w dutyradiography as" vvell ias forfdeep therapy.

r ose heseandother objectsj ofmy invention will be readily apparent 'fromflthe followin l Qr l -r 1 h i i r i I, i

longitudinal cross jseothe partstifi eleya njof' a .-;2" 'representsa top pIanvieWfof'mY'imQ Proved cathode; structure and yl'support therefor, to

Fig. 3 is an' endlviewlooliingtoward'st open ts the, focal: spot on. the target o'ffz the X-raytube whenronejfllanient of "the fcathode 'stifiucture'is'incandesoedif'flj Fig. 5repr esents the focal spotonthe target of thefX-ray tubejwhenall of the filaments" of the cathodestructure are incandesced.

Figqfirepresentsthef cal spot on the candesced. a j Fig. represents thefoealspotonthetargetof an X -ray tube whenanotherZ-portionfof lthe filament thanf'that referred to inil5ig. G' is' in candesced. r

Fig. 8 represents the focal spot on the target of an X-ray tubejwhere both portions (of the filamentreferredfto in Figs 6 and 7 fateinoandescedm' s shownin Fa l-"sexist ate comprises" the filaments: ,of V the cathode a dielectric vitreous envelope 10 having a re- 7 extending. from, one end' thereof entrant stem (not shown) at one end and a reentrant stem 11 at its other end. Secured to said reentrant stem which is not shown is an anode 12 having a target 13 in the free end thereof. The targetmay'be composed of tungsten or other refractory material adapted to generate Xgrays 'whenit .is subjected to' electronic bombardment.- Another reentrant tube 14 surrounds the anode 12. A plurality of resilient plates 15 are located between the anode 12 and'= sleeve 14 for supporting theanode According to my invention thestem ll ter,

minates in a cruciform pinch or press 16 having a plurality of rods hermetically sealed thereinw In one of said'cross arms -=of-"-' said press andspaced from each other are sealed rods 19, 20 and 21.

' sectionbeing-inthe form: of arcs. of a circle.

Thebottompo rtion 30 of ,the blockhas a slot '31 to a point adjacenttheother .end thereof- The slot 31 is rectangular incross section and has its-upperend coincident with the lower end of .thejgro'ove. 29 and its lower. end coincident with jthejlower .face'v of the bottom 30; The groove 29'andthe slot31 form a slot extending toboth the-upper and lower faces of theblock,

a portion of thes'lot extendsto two sidev limiting faces. thereof and another portion to only one s'ideli 'ting 'face' thereof- .Tii. thrmionically active filaments 26, .27. and. cated in the b c zi- 11561; of. these.

' filaments "consists of an ap ropriately coiled tungsten .or .tantalum. wire ,of predetermined of each coil being substantiallyfthesame asthat.

thickness and" coil diameter, with the diameter o f the,, adj acent. coil throughout .'the' length of saidiem'm ents. The, filament 26 "extends along the length o fJslot ifithelblock...withthe. central longitudinal ,'.axis' of ,.the filament being sub stantially "parallel to the sides" of the block 24.1

defining-the slot "31 and. located close to .oneof said'fsides, but not contactingQthe ,s'ame. The

' ends of,.the fi1amen't are short straight portions" depending i'n thedirectionjof the depth of the slot. Th'eendslof said filament are respectivelywelded or otherwisesecured to the upper por-' tion, of the-rod 1'7 whose end is. close to" said block 24'an,d to a metallicstrap 32 welded toi the bottom of'said block 24. The filament 2'7 is spaced from said filament 26 r and is.also mpl nted fin said (slot. The central longitudinal axes of the filaments 26 and 27 and theuppe'r.

edge of the. slot 31 are, all in substantiallythe same plane... The dependingends ofthe filament.

27 are' respectively. welded to the rod18 and .to a metallic strap33 welded to the bottomof the b ockza...

The fil ament28, is located in ,s'aid slot 31. and.

betweenfthe "upper and lowerglimits thereof.

The filament 28"is so disposed in said slot thatit.

islqc bel w th m ts,26..a d..2 7 nd Sealed in said gothen ross arm and. spaced from each other are rods 17, 18, 22 and 23. My improved cathode structure is mounted" withjhe envelope lflvandsupported by said rods. The, .1 improved, fcathode structure. comprises a between the sides of the slot 31. The ends of the filament 28 depend downwardly and are respectively connected to the rods 19 and 20. Secured by welding to the coil at about one third length thereof from the open end of the slot 31 is a metallic strap 34 also welded to the bottom of the block 24. v n I The rod 211s located in arecess andgwelded to the cross portion of the block which "limits the length of the slot 31. The other two rods 22 and 23 are respectively located in recesses in and welded. to;the sides of said block near the other endthereof. These three rods 21, 22 and 23 support said focusing block 24. The rod 21 further functions as :a: current carrying means. The

cathode;structure-thus mounted has the mouth of the block 24 facing the anode.

A. 03111.405'. carrying .five conducting pins 41 is secured to the cathode end of the envelope. Th'e'pins or contacts are appropriately connected,to,the.rods-- connected to. the cathode and focusin'gLcu'p. Surrounding the pinch or press'f16, andsecured toonly-therod 21 is an inverted. cup 42 for v shielcling th e pinch. from, electron bombardment; In order that the ends of theiocalspots may be well defined andfree from fanning, ,.I employ the invention. as described by Norman C. Beese. in his. pending ap-- plication Serial.'No. 680,013, filedJuly 12,: 1933, and entitled X-.ray tube and cathode-structure therefor. For this purpose. pins 43' and fl lare secured to the focusingblock and located above and near. the endsof. the filaments.

v In operation, if I desire-a focal spot measureing about. 4 mm in widthso that body extremities may beradiographed, I energize only fi1a. ment 26 or. 27. When eitherone'of these two. filaments is energized; the. sides of the focusing block and. the other filaments in{.said block focus the electrons emanating from said. energized. filament. If a: focal spot of lesser width is desired, I energize a portionbf. or all-of. the

filament 28 .depending .upon the, quantityof X rays desired. If a great deal of energy isfto. be, put inthe tube all of-the filaments mayabej energized sothat' thefocal spot may be long and broad sothat the anode will accommodate the energy input-without target pitting and fusion. P

7 Although I haveides cribed my invention withbe limited only by.

someparticularity, it is to the prior art..

What is claimed:

anruciform, pr'ess,..a pluralityof rods sealedin the cross arms of said press and supporting, said cathode structure, said cathode structure includinga focusing-means having. aslot therein, the

mouth of said slotfacingsaidl'anode, three coiled.

filaments disposed .in said focusing means, all of said filaments having their central longitudinal axes'disposedalong the.- length ofone of the walls of said focusing means defining-said.

slot, oneof said filaments being. locatedbelow theoth'ertwo filaments.

2.; An electric device, thecombination of. an envelope. and an anode, ,with a cathode struce ture, said cathode structure including a focusingv block having a.s1ot,.therein, three coiled 'filae- 1; Anj. electric device comprising an envelope,- an anode and'a cathodestructure therein, said, envelope having a .reentrant stem terminating. in.

mentsf mounted insaid, block,,with.their .cene' tral. longitudinal, axes substantially parallel to. each other and along the length .of said .slot,.one. of said filaments .being located .below. theotherf.

two, said other two filaments being spaced from each other for the passage of electrons from said first mentioned filament when the same is energized and to aid in focusing the electrons from said first mentioned filament.

3. An X-ray tube comprising anenvelope, an anode and a cathode structure therein, said cathode including a focusing block having a groove extending along the-length thereof, with the sides of the groove in cross section being of curvilinear form, a slotin the lower portion of the block and having its upper edge coinciding with the lower edge of said groove, 9. pair of longitudinal filaments extending along the length of said block, with a portion of each of said filaments being located in said slot, said filaments being spaced from each other, athird filament located below said first two filaments andopposite the space between said first two filaments, said third filament being located entirely within said slot.

LOUIS FREDERICK EI-IRKE.

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