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Патент USA US2121631

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June 21, 19380
Filed May 11, 1956
— -
.Malver'n J. Gross;
Zed J. Atlee ,
b5. fr/wajwéw
Their‘ Attorney.
Patented June 21, 1938
V 'Malvernl J .- Gross
and Zed J; Atlee,-: Chicago, 111;,
, assignors to General ElectridlXaRziy corpora-c.
tion, a corporation of-New..-Yorkr,-‘
ApplicationMay 11; 193mmtime.
4 Claims.
(01.“ '250-:.-;35)1
The . present. inventiongrelates tax-ray ‘tubes,
staton. lllqprovided with energizing windings l5,
and,re . ‘particularly . to. any improved. cathode
structure. suitable. for-.use inan X-ray. tube. of. a turning force in the rotor ‘I.
the .type in.,which.the anodeis rotatable topro- .
5 vide. relative . motionnbetweengthe. electron. beam »
andthetar-get surface._
. a. primary object ‘of. the invention to. pro
vide, acathode capableof .producing two or more
independently , usable» electron. beams of. sub
stantially different. cross-sectional area. which
The details .of,,;
construction. of ,theanode driving means. aredis
closediandrlaimed. inv our.copendineapplicatiom.
SerialNo. 78,9,96; ?led May .,11, 1936,, and assigned,
tothe same assignee as theypresent invention.
The nature; of _ the cathode , and anode andlxof‘ _
the co-_.operative‘ relationship’ between. ‘Jib-6H1:is‘v
well illustrated in Fig._ 2.‘ It will be.noted,_that, 10-,
maybe. projected as substantially parallel elon- . theirotatalble anode (Us providedwith a beveled,
gated: focal. spots‘. on‘ closely. adjacent (peripheral . targetaface l8,-.,suitably.consisting-of. a refraQa.
torylmetalsuchya's tungsten, inclinedat ananglev
elements _of__.a. rotating ‘target; o
The. noveLfeatures which we consider to be‘
15 characteristicof. our inventionwill be ‘pointed out
with ,particularily in. the-appended._ claims. The
inventiontitself, however; together- with further
objects ,and. advantages thereof, will best be un.-,
ders‘tood. by, reference »to- the. following speci?caf
20 tiomtakenin. connection with the. drawing; in
which, ,Eig. 11,shows; in ‘elevation. an X-ray tube
suitably embodying thegi‘nventionp- Fig. 2>is an
to theaxis
may be supported. by-ineans of. a glass-to-metal
sealx 2.0 ‘from, aireentrant. envelope stem.- 2] ,_ corn- ..
prisesalaterally-projectingsleeve 23 and anelec
trostaticxfocusing,cup,25supported at the extreme
ity; of thee-sleeve, Agskirt-like. shield 21, mounted ,
at, ther'base. of, the cathode, serves, tov intercept
r'andoinH XEr'ay > emanations. and. electrically
enlarged view. showing. the - cathode in'section, and
chargedmparticlesrcorningz from . the direction‘. of
illustrating the relationship betweenv the cath-.
node and. the anti-cathode oritarget; Fig. 3 com-.
the anode... The-:focusingz-cuplis provided.-in-_,.its.
prisesv aseries of. schematic views illustrating a»
sion‘s?of whichionl‘y one, designated as,26,.is,-.1ap.‘—...
ersefacewith apair. ofrecesses or depres- ~
particular aspectof the. invention, and Fig. 4.1 parentiin Fig 2,“. 1 Theserecesseseare,spaced from .
comprisesa similar group of ‘views illustrating. a
onesanother ‘transverselyythat. is, in a" direction
preferred modi?cation thereof.
transversev to‘ their .maj or- axes.~~ At the bottom of
.Gne application- of~_the..invention:is illustrated
each‘ arranged ‘at substantially. lin-p. 301
in Fig. 1, in whichewe haveshown a rotatable? early} disp'psed' incandescible. ?lament, suitably- of 3
anode X-raytubesuitable for'uselin apparatus of turigstemj one .of . such _ ?laments» being shown» at Yr
the type disclosedand claimed in our copending.
2§rinconnection with-the. recess 26.. ~ As_>~previous
application, Serial No; 78,994, ?led May-11, 1936, lysindicated, theseare supplied with heating-cur
35 and assigned to. the same assignee as the present.
invention. The tube comprises an evacuated en-.
velope: l>v enclosing an anode3orrtargetv3, and a
cathode ll.v The cathodeisaxially- spaced and is
offset with respect to the center of the anode and
is supplied with heating current and with poten
rent. by means of .the in—.1ea_d conductors“, l2;
IQianciJA,sealediinto theglass press 29; Inor
deri to. permit ;the . cathode-structure to; be- placed»
as_,.,far as pl_)ssib1e.=f1_~om.tlflewallv of-»-the envelope’
and-.therebygto. decrease the- danger of’ electrical ‘
breakdpwn, ‘the. axis. ‘of. each . ?lament and » of its
tial from an external-high voltage source (not
associated focusing recess. is somewhat inclined
shown) by means of the leadg-in wires ll, l2, l3.
withrespecttothefplanelof rotation of the:anode
so? as ;to vfacectowarcll.theiouter periphery-of the
The anode is mechanically connected to a ro
4:5 xtata-ble structure 6 comprising an electromagnet-r
When ahigh potential is impressed vbetween thev
ic rotor l, for example, of these-called “squirrel
cage” induction type. Thispreferably consists
from the heated._?lament..28 istdirectedi primarily -
ofxa laminated magnetic core having longitudinal '
by. theielectrostatic .elfect . of. the .walls of. the ‘re-
slots therein ?lled with a highly conductive metal
50 as, for example, vacuum-cast'copper, The rotat
ablestruct-ure asa wholemay be supportedonan
inwiardly projecting portion of, a shaft 9.v by
means of‘ suitable antifriction bearings (not
for“ supplying a.,,rotati_ng, ?eld effective tolinduce.
anodeand cathode, the. electron beamemanating;
cessj-i ,2§.,so_§as. toforrn- an elongated .‘~‘focal spot’"
on theibeveledfacef l8.of the... anode 3,. the. ex
tremitics of‘ this; spot. being represented;- by. ‘the.
dottegdiprojectionilinesa, 1).. Due to the extremev
angle of’ inclination of the target ‘facepthe .corree.
spQndingi‘X-ray ‘pattern. formed on an external
shown). Outside theenvelope and'in theregion
5.5 of: the rotor 1, is arranged \an_ electromagnetic object. 39; will represent a fore-Shortened proisc- <
tion of the focal spot as indicated at .r.
mode of concentrating the X-rays emanating
from an elongated focal spot obtains the effect
of a small X-ray source of high energy content
and is very desirable from the standpoint of pro
, ducing a sharply de?ned radio-graphic image.
radiographic objective, so as to produce the max
imum concentration of X-ray energy, as pre
viously explained, the other focal spot will neces
sarily be somewhat out of alinement and will
constitute a more diffused source of X-rays than
is desirable.
Consequently, in changing from
In the practical application of X-ray tubes,
one ?lament to another in the operation of the
and more especially of rotatable anode tubes, it
is of great importance that each tube have a
10 wide range of operation in order to avoid the
need for frequent substitution of units. While
it is possible to vary the intensity of radiation
of the X-rays and thereby the depth of their
tube, the best possible radiographic results will
penetration by changing the heating current of
15 a particular ?lament, the ?exibility of an X-ray
tube of given size may be still further increased
by providing it with a plurality of independ
ently usable ?laments having different dimen
sions or which produce electron beams of dif
ferent cross sectional dimensions. In Fig. 3 we
have shown one example of a cathode construc
tion which takes advantage of this latter possi
Here, the lowest view shows the frontal ap
25 pearance of the cathode structure while the two
center views show the cooperative relationship
between the cathode and the target face I8 as
seen from below. In the center views the cathode
is shown as a section taken along the line A-A
of the frontal view previously mentioned. As
hereinbefore explained, the cathode structure
comprises a focusing cup 25 having a pair of
elongated recesses 26 and 32 formed in the mu-'
tually inclined faces thereof. These recesses
may be described as being “approximately ra
dially directed” with respect to the axis of ro
tation of the anode 3. However, when this mode
of description is used herein and in the appended
claims, it is to be understood as comprising an
arrangement such as that shown in Fig. 3 in
which either or both of the recesses may depart
somewhat from a precisely radial orientation.
Within the recesses there are provided sub
stantially linear incandescible ?laments 28 and
45 33 which are also approximately radially direct
ed with respect to the axis of rotation of the
anode. The position of each ?lament with re
spect to its corresponding recess. is such that
electrons emitted from it'during the operation
50 of the tube will be projected toward the target
not be attainable under all conditions of use.
This di?iculty may be overcome and parallel
ism' of the focal spots assured by arranging the‘
individual ?laments as shown in Fig. 4, in which
the various views correspond to those already
described in connection with Fig. 3. By inspec
tion of these views, it will be seen that if the fo—
cusing recess 26' (corresponding to the similarly"
numbered recess of Fig. 2) is arranged so that?
the axis of the focal spot produced by an elec
tron beam emanating from the ?lament 28'
assumes the position indicated by the line a, b,
then the complementary ?lament 33’ can be
made to produce an electron beam whose focal
spot has a parallel axis by disposing the ?lament
itself in a non-parallel position as shown. Func
tionally expressed, the central planes of the two 25
electron beams should intersect the target face
in lines which are essentially parallel and which
are substantially closer together than are the
?laments themselves. Referred to the cathode
structure this means that projections of the ?la
ments 28' and 33’ on a plane which is precisely
normal to the path of the electron beams should
be non-parallel and slightly convergent toward
the axis of rotation of the anode or toward the
portion of the cathode most nearly approached
by the anode surface. The amount of this latter
convergence will depend on the relative dimen
sions and spacing of the electrode parts and on
the electrostatic e?ect of the envelope and may
be determined experimentally or by calculation 1
for a particular case so that the focal spots are
actually parallel as indicated.
While we have shown particular embodiments
of our invention, it will be understood by those
skilled in the art that'modi?cations in the struc 45
ture may be made without departing from our
invention, and we aim in the appended claims to‘
cover all such modi?cations as fall within the
true spirit and scope of our invention.
What we claim as new and desire to secure‘ by 50
face IS in the form of an elongated beam. Due
to the fact that the two faces of the cathode cup
Letters Patent of the United States is:
25 are mutually inwardly inclined to face a com
a peripherally extending target surface thereon
mon region of the target l8, the two beams cor
responding to the separate ?laments will strike
and a cathode structure axially spaced from the
the target at adjacent focal spots which are sub
rality of transversely spaced linear ?laments each
stantially closer together than the ?laments’
themselves. This is desirable in order to- have
the central beams of X-rays from each of the
60 two focal spots in approximately the same rela
tion with respect to an external objective.
It will be noted, however, that with the par- _
allel arrangement of ?laments shown in Fig. 3,
the individual focal spots will not be precisely
parallel but will have central axes which if pro
jected will intersect as‘ shown in the‘ two upper
views of the?gure, which ‘views, will be rec
ognized as different aspects of the same target
face. This intersection, which may be readily
70 veri?ed as a matter of projective geometry is
due to the fact that the cathode ?laments and
the target surface are relatively inclined with re
spect to one another.
This means that if the axis of one focalspot
'7 is perfectly alined with respect to an external
'_ 1. In an X-ray tube, a rotatable anode having
anode,_said cathode structure including a plu- -'
relatively inclined with respect to the target sur
face and adapted during the operation of said
tube to project an electron beam toward a com
mon focal region on said surface, said ?laments
being arranged approximately radially with‘ re
spect to‘ the axis of rotation of said anode and
being slightly convergent in the direction of said
axis thereby to cause said'electron beams to form
parallel elongated focal spots on said focal region
of said target‘ surface.
2. In an X-ray tube, a rotatable anode, a cath-.
ode structure axially vspaced therefrom, a periph
erally extending target surface on said anode
angularly inclined away from said cathode struc 70
ture, said cathode structure including a focusing
body having a pair of mutually inwardly inclined
surfaces thereon facing toward a common focal
region on said target surface, each of said sur
faces being provided with an elongated recess
therein approximately radially directed with re
spect to the axis of rotation of said anode, and
linear ?laments respectively arranged in each of
said recesses, said ?laments being slightly con
vergent toward the axis of rotation of said anode.
3. In an X-ray tube, a rotatable anode having
a peripherally extending target surface thereon,
a cathode structure including a pair of trans
versely spaced linear ?laments each arranged ap
10 proximately radially with respect to the axis of
rotation of said anode, means for connecting said
?laments to an energy source, and electrostatic
4. In an X-ray tube, a rotatable anode having
a peripherally extending target surface thereon
and a cathode structure axially spaced from the
anode, said cathode structure including a focus
ing body having a pair of spaced elongated re
cesses therein approximately radially directed
with respect to the axis of rotation of the anode,
and independently operable linear ?laments re
spectively arranged in each of said recesses, said
recesses being located in surfaces of said focus
ing body which are mutually inwardly inclined to
face toward a common focal region on said target
means for focusing the electrons emitted bysaid
?laments into elongated beams the central planes
surface, whereby electron beams projected from
the respective ?laments during the operation of
of which intersect a common focal region of said
said X-ray tube produce on said common focal 15
target surface in approximately radially extend
ing lines substantially closer together than said
?laments, said ?laments being usable independ
ently and being adapted to produce electron
20 beams of substantially different cross-sectional
region of the target surface elongated focal spots
which are substantially closer together than said
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