Note: Descriptions are shown in the official language in which they were submitted.
PH~. 60.002
The invention relates to a method of fabricating a cathode-
ray tube comprising in an evacuated envelope an electron g~m to
generate an electron beam and a target for receiving said electron
beam, the electron glm including a cathcde and at least two grid elec-
trodes, a discretely configurated beam shaping region being fabricatedin at least one of the grid electrodes, said region having a one-piece
effectual portion evidencing upper and lower surfaces defining a
material thickness therebetween.
Such cathode-ray tubes are used to display, for example, tele-
vision pictures or are used in an oscilloscope. In such cases the tar-
get is a display screen having a phosphor layer, for example, in a
black-and-white ~isplay tube or in an oscilloscoFe tube, or having a
pattern of phosphor elements luminescing in different colours in a
colou~ display tuke.
Such a tube may also be used as a camera tube. In that case
the target is a photosensitive layer, for example, a photoconductive
layer.
In all applications the spot formed when the electron beam
impinges on the target must have predeterrnined, generally small, dimen-
sions and the haze surrounding the target should be minimum.
Such a method is disclosed in the publi.shed Canadian Patent1,112,284 - Bijma et al issued November 10, 1981 (PHN 8960). In the
first grid electrode of the electron gun of the cathode ray tube des-
cribed in said specification an aperture and a V-shaped or U-shaped
groove is provided. This first ele.ctrode with groove consti-tu-tes, in
cooperation with the second grid, a non-rotationally symmetrical elec-
tron lens, this asymmetry becaming manifest mainly as a quadrupole lens
action focusing the electron beam in tw~ focal lines instead of one con-
centrated stigmatic cross-over (waist). To permit such grooves to be
made, a comparatively thick plate material has to be used.
Some beam shaping electrodes have been manufactured as tw~~
piece structures in an effort to achieve the desired beam fo7~ning
characteristics. For example, the article "30AX Self-aligning 110
~`
FHA. 60.002 2
in-line color TV display" in lLL~ Transactions on Consume~s Electronics,
Vol. CE-24 Mo. 3, August 1978, pp. 481-487 discloses beam shaping elec
trodes constructed of two superimposed rectanguk~rly slotted elements
affixed in orthogonal relationship to provide a substantially square
aperture there-through. mrough these slo-ts the first gcid electrode,
in cooperation with the cathode, forms a first elec-trostatic quadrupole
lens field and, in cooperation with the second grid electrode, forms a
second electrostatic quadrupole lens field rotated 90 with LespeCt to
the first electrostatic quadrupole lens field. The electron beam is
focused in two focal lines by said lens fields so that the mutual
repelling of the electrons (space charge repelling) becomes less than
in the case of one concentrated stigmatic cross-over. In fabrication,
it is difficult to keep proper alignment between the two slots, and
the affimral welding can produce surface imperfections which are dele-
terious to the forming of the desired beam shapulg lensing.
Generaliy speaking, the use of beam shaping electrodes inelectron guns to beneficially modify the lensing of the beams is kncwn
in the art. Discrete beam shapingsmin~ize deflected spot distortion,
such being especially true when self converging yokes are employed with
in-line gun tubes. Electrodes with beam shaping properties provide a
lensing field of equipotential lines of force to form the bundle of
moving electrons into a beam of desired cross-sectional shaping .
Exemplary art is also evidenced in U.S. Patent Nos. 3,852~608 - Johannes
et al issued December 3, 1974~ 3,866,081 - Hasker et al issued
25 February 11, 1975 and 4,143,293 - Hasokoshi et al - issued March 6, 1979.
It is therefore an object of this invention to reduce and
obviate the aforementioned disadvantages and to provide a rnethod of
facilely fabricating a cathode ray tube comprising an improved dis-
cretely configurated beam shaping region in a grid electrode.
Another object of the invention is to provide a method of
fabricating a one-piece beam sha~ing electron gun electrode tha-t
e~idences improved be~m forming properties.
PE~ 60.002 3 14.07.1981
.~ccording to the invention such a ~etho~ is chclracterized
m that sald method comprises the steps of coinina an elongated recess
inward fron~ said upper surface; coinlng a depression lnward from said
lower surface in opposed orientation to said recess coining to e~pedite
a EIow of electrocle material to rhe upper coinina reaion, thereby promo-
ting the formation oE a substantially sharp periilletrical edge
in at leas-t the central reaion of said recess shapir.a; and forming
an aperture thrcucrh the residual electrode material interme~iate ~he
bottoms of said coined recess and said coined depression to co3rplete
In said bea3n shap mg configuration.
The electrode fabrica-tion procedure utilizing the afore-
mentioned opposed coining makes -the electrode material flow in a manner
-to assure the fonnation of a beneficially sharp per~n~etrical edge at
least partially a~out the upper surface rela-ted recess. This sharp
edge perime-ter, in the region of the apert~re, markedly augmellts -the
beam-shaping properties of the configuration, thereby promoting an umr
proved lensing effect which beneficially modifies the cross-sectional
shaping of the beam in the desired manner.
~qoreover, the electrode is also comparatively thin in the re-
gion of the aperture.
Fig. 1 is a cross-sectional view of a catho~e-ray -tube fabri-
cated according to the invention;
Fig. 2 is an enlarged sectional view of a portion of an
electron gun showing the initial beam shaplng region thereof;
Fig 3 is a sectional perspective view of the improved beam
shaping electrode;
Fig. 4 is a plan view of -the same, taken along the line
4-4 of Fig. 3;
Fig. 5 is a sectional view of the electrode blank prior to
imparting hea~n shapir.g proper-ties thereto; and
Fia,. 6 is a sectional perspective view illustrating fabrication
of the electroce.
For a better ~Iderstandinq of the presen-t invention together
with other and further objects, advantages and capabilities thereof,
reference is made to the following disclosure and appended claims -taken
in conjunction with the aforedescrih~ed drawings.
For pur?oses of illustration, a color catnode ray tube emplo-
ying an apertured mask and an in-line plural gun electron generating
PHA 60.002 4 ~ 14.07.19d1
assernbly ~7ill be :initially desccibed m this specifica-tiorl as an
e~emplary sett~r.c~ for the invention. It is understood that such is not
to ~e consldere~ 'uni~ing to the concept of the inven-tion.
With particular reference -to Fig. 1, -the essentials of a
plural in-line beam color cathode ray tube construction 11 are showrl.
The encompassing envelope is colnprised of an integra-tion of neck 13,
furnel 15 and face panel 17 portions. A pa-t-terned catho~olum:Lnescent
screen 19 of color-emi-tting phosphor areas lS disposed on the in-terior
-surface of the viewing panel 17 as an array of definitive stripes or
O dots, in !ceeping with -the state of the art. ~ multlple apertured struc-
ture 21, in thls instance a shadowrnask, is spatially related -to the
patterned screen; such being located wlthin the panel by conventional
means, no-t shown.
Positioned wi-thin tlle lleC~ portion l3 of the envelope is an
lS elec-tron gun assembly 23 cornprlsed of several rela-ted electron guns,
each of which procluces a respective electron beam 25, 27 and 29. While
not shown, each of these individual guns includes a ca-thode and a
plurality of sequentially arranged cooperating electrc~le elements which
are formed and spaced to provide the source~ forrnation, acceleration
and fccusing of the respective electron beam in a ma~uler -to properly
impinge the screen 19.
Positioned externally of the tube 11 is a deflection yoke 31
which deflects the beams in a c'etermined manner -to provide an image
display raster upon the screen. Wi-th the accep-tance in the art of self-
converging deflection yokes, a need has arisen for improve~ edge-of-
screen focus 33. Thus, an irnprovernent in the beam forming region of each
electron g~m is of importan-t significance.
In referring to Figs. 2, 3 and 4, there is shown an e.~emplary
enlarged sectional view of the rear beam forming region of one of the
electron guns of the gun assembly 23. This shown por-tion of the ~un
stnlcture includes a thermionic cathode s-tructure 35 having e~ternal
electron emissive ma-terial 37 terrl~inally disposed thereon, such being
aetivated by an internally positioned heating element 39. Positioned
adjacent thereto is a first or control grid electrode (G1) 41 having a
one-piece effectual por-tion 43 transversely oriented to the path of the
beam bundle of electrons 45. This effectual portion evidences an upper
surface 47 and a lower surface 49, such defining a ma-terial thickness
"T" therebetween. The shcwn effectual portion 43 of the control electrode
Pl~ 60.002 5
41 may be an ele~ent of several electrode constructions. For example,
it can be the bottom part of an individual cup-shaped (G1) mem~er, or
a subst.~ntially planar dish-shaped portion of an ln-t~ra-tecl (G1)
ascembly u-tilizina a common grid pLane for a plurali-ty of guns. The in-
5 vention relates -to the improved beam shaping region regardless of the
over-all construction of ~he electrode.
Formeci in the electrode effectlal portion 41 of the contrcl
electrode is the i~proved beam shaping region 5l, which, in conjunction
with the spatially related apertured second or screen grid electrode
(G2) 53 in c~ operating gun, provides c~ initial beam lensing influence
in -the inter-electrode spacing 5~ therebetween. The contoured confiau-
ration of the (G1) beam shaping region 51, adjacent the aperture 55
therethrough, and the related apertured effectual portion 57 of the
second (G2) electrode, toaether influence shaping of the array of
equipotential lines of force constituting the lensing in a manner
to beneficially modify the shaping of the beam bundle of electrons 45
passing therethrough.
In greater detail, the improved configurc~ted beam shaping
region in the control electrode 41 has an elongated recess 59 for~ed,
as by coining, inward from the upper surface 47 thereof. The term
"coining" as used herein refers to the deforma-tion of material by
applied pressure, whether or not the deformed material is con-tained in
a die cavity. This recess, which is free of surface imperfections,
has a definecl width "W", length "L" and depth "D", and as exemplarily
shown, is suhstantially rec-tangular in shape. There may be occasions
when -the desired lensing effec-ts may re~uire a more ovate modified
shaping. It is an important lens forming consideratlon that this recess
evidences a substantially sharp perime-trical edge 61 at least partially
thereabout. This is usually difficult to achieve in a stamping or
coining operation per se since such pressure techniques tend to form a
slightly rolled or radiused edge.
To achieve the desired sharp edge 61 about at least the
central region of the recess 59, a depression 63 is fom~ed, as ~y
coining, inward from the lower surface ~9 of the control electrode 41
3s in opposed orientation to the upper surface-related recess 59. These
upper and lower related coining operations produce a beneficial flow of
electrode material. This lower surface depression is exemplarily shown
as being circular in shape, but it too, may be of a modified cvate
Pl~ 60.OG2 6
sha ing. Its di~ ter ^- longest lateral dir~ension "B" shoulcl b~? suffi-
clent to prcvide a flow of materlal -to at least the central periTr~rical
region of tl~e related re~ess ~9. The resiclual electrode material 6l inter-
m~iiate the kotton b5 of the recess and the kottom 67 o--' the depression
evldencc?s a t~lickness "t". In one ~Yarnple of s-~nlctural relationships,
the depth "D" of the recess 59 does not e~Yceed the -thickness "t" of the
residual material, and the depth "d" of the depression 63 is less tha
the thickneàs "t" of the residual materlal. r~S shown in ~ig. 2, the
depression b3 is dimensioned to accommodate positioniny of he catnoe
35 in close spatial relationship with the kottom surface of the cor,trol
(G1) electrode. Such accom~odation tends to effect a degree of shieidinq
for the emlssive surface of the cathode.
~ n aperture 55 is formeà throuql1 the residual materlal 64
in symmetrical relationship with the recess 59 and the depression 63
~5 to comple-te the urproved configurated beam shaping region 51.
This aperture is eYemplarily sho~n as being circular in shaping, ~lt
such is not to be considered limiting. Regardless of :its shaping, its
width cr diametrical dinension "A", is slightly less than the width
dimension ll~,~TII of -the recess. Suci1 dimensional relationship, as shown
in Figs. 3 and 4~ allows a clean aperture to be formed through the
residual material 64 without damaging the sharp periunetrical edge ~1
of the recess or scarring the sidewalls thereof.
Regarding fabrLcation of the beam shaping config~ra-tion of
the electrode, reference is directecl to Fig. 5 wherein there is sho~n
a grid blank for the conl-rol (G1) electrode 41. The effectual portion
is defined by the perireter 69, in this ins-tance circular, with the
upper surface 47 and the lower surface 49 thereof clefining a given
thickness thereL^e-tween. This blank is positioned in a tooling arrangement
71 as sho~n in F`ig. 6. With the blank resting on a bottom anvil m~mber,
72 a top forming die 73, having a defined projection 75, is pressured
against an appropriate part of the upper surface of the electrode
blar~ 41 in a manner to coin the substantially rectangular recess 59
therein. Preferably simultaneously, a movable coining die 77, contained
for sliding operation within anvil member 72, is pressurecl against -the
lower surface 49 of the blank to coin the substantially circular de-
pression ~3 in the lo~er surface thereof. The resultant flow of material
effectecl by the colning of the depression, forces some of the flcw
material to the top forrning die to fill in t~e inherently round eclge
P~ 60.00~ 7
~i~out the recess 59, thereby prornoting the formation or the sllbstan-tiallv
sharp perirrRtrical edae ~1 a~out a-t least the central portion thereof.
This is an ir~ortant tabrica-tion consideration, since the sharp edae
of the recess, par-tlcularly in the region of the aperture, subsequen-tlv
efEects a Leneficlal improvement ul the beam shaping lensing.
The beam aperture 55 is thence provided in -the coined
realon, being orlented as heretofore c~escribed. Thus, the forming of the
confic~lrated beam shaping region is completed.
Utilization of -the aforedescribed double-coining fabrication
pxocedure and -the resultant ~mproved electrc~e st~uchire form~xl thereby
obviate many of the disadvantages evidences in the prior art.
The e]ectron g m electrode structure of cathocle ray tu~e
Eabricated by the method according -to -the invention incorporates the
forming of a d:iscretely confic~lrated beam shaping region which con-
tributes to unproved lensing influencing the initial shaping of thebeam. The economical and expeditious double coined fabrica-tion proce-
dure assures -the achievement of the beneficially sharp perimetrical edge
in at least the critical region of the recess portion of the configura-
tion. The one-piece electrode structure reduces mc~nufacturing costs,
and overcomes further disadvantages of tne two-piece structures of -the
prior art by eliminating the inaccuracies of multiple piece assembly and
the possible presence of weld ~rrs on critical surfaces.
3~
