JOHN F. DE ANO

Nov. 3, 1953
J. F. DE ANO
IMAGE-REPRODUCIN‘G DEVICE
2,658,161
Filed Jan. 9, 1952
Bnrnetnl ho
6
29
29
"
Grid 1
INVENTOR.‘
JOHN F. DE ANO
BY
HIS
ATTORNEY.
Patented Nov. 3, 1953
2,658,161
UNITED STATES PATENT OFFICE
2,658,161
IMAGE-REPRODUCING DEVICE
John F. De Ano, Melrose Park, Ill., assignor to
The Rauland Corporation, a corporation of
Illinois
Application January 9, 1952, Serial No. 265,627
2 Claims. (Cl. 313—82)
1
’ This invention relates to image-reproducing
devices and more particularly to cathode-‘ray
tubes for use as picture-reproducing devices in
television receivers and the like.
One of the problems often encountered in the
production of television receivers stems from the
susceptibility of commonly employed cathode-ray
tube constructions to exhibit extraneous cold
emission and spark discharge in the electrode
system. Whenever two closely spaced electrodes -
are maintained at large potential differences,
these undesirable phenomena are apt to be en
countered. For example, most electron guns
comprise a cathode, a control grid, a so-called
second grid which is maintained at a low con—
stant positive potential with respect to the oath
ode, and a tubular anode closely spaced from the
2
bear outwardly against the auxiliary conductive
coating. In practice, considerable difficulty has
been encountered in a construction of this type,
for the reason that during the sealing-in process
when the gun assembly is fused to the neck por
tion of the envelope, the metal contact springs
are heated appreciablyabove ambient or room
temperature while the glass envelope, being a
much better insulator, remains at a much lower
temperature. This has been found to result in a
troublesome tendency toward breakage of the
envelope in the region where the contact springs
bear on the auxiliary coating.
Difficulties of a practical nature have also been
encountered during the outgassing operation
when the gun is subjected to a radio-frequency
induction heating field as the envelope is being
evacuated. Localized stresses are also produced
positive potential. Due to the large potential
during this operation, with a, further tendency
510
difference and the close spacing between the
toward breakage of the envelope. Moreover, it
tubular anode and the second grid, cold emission‘
has been found that with a construction of the
and spark discharge may lead to a condition com
typedescribed in the above-identi?ed Peterman
monly referred to as “popover” which is mani~
application, successful outgassing of the gun
fested by a momentary loss of brightness or a
electrodes has been exceedingly di?icult to ac
“tearing out” of minor portions of the reproduced
complish when more than one contact spring is
image. The problem is further aggravated in the
employed to establish the electrical connection
case of electrostatically focused cathode-ray
between
the second grid and the auxiliary coat
tubes employing unipotential focusing lens sys
mg. While a single contact spring is adequate
tems, particularly in the case of such systems
establish the desired electrical connection, the
wherein the focusing electrode is maintained at I. to
use of plural springs is desirable for reasons
or near cathode potential, due to the extremely
which are well known in the art.
high voltage gradients between the focusing elec
. It is an important object of the present inven
trode and the other two elements of the focusing
t1on_ to provide a new and improved image-repro
lens.
second grid and maintained at a much higher
In the copending application of Russel S. .‘
Peterman, Serial No. 257,692, ?led November 23,
1951, for “Image-Reproducing Device” and as
signed to the present assignee, there is disclosed
ducing device of the type disclosed and claimed
in the above-identi?ed Peterman application in
which breakage of the envelopes during the seal
mg-ln process is effectively avoided.
Another object of the invention is to provide
and claimed an image-reproducing device in
new. and improved image-reproducing device,
which the problem of cold emission and spark 40 acomprising
an auxiliary conductive coating on
discharge in the electrode system is effectively
the
inner
wall
of the neck as disclosed and
overcome by providing a conductive coating, sep
claimed in the above-identi?ed Peterman appli
arate from the ?nal anode coating, on the inner
cation, in which plural contact springs may be
wall of the neck portion of the envelope at least
partially encompassing the electron gun. To in 45 employed to establish the desired electrical con
nection. with the auxiliary coating while at the
hibit cold emission and spark discharge, this’
same time permitting successful outgassing of
auxiliary conductive coating is preferably main
the gun electrodes with conventional radio-fre
tained at a low positive operating potential with
quency induction heating methods.
respect to the cathode, as by direct connection
to the ?rst accelerating electrode known as the 50 _It is a further object of the invention to pro
vide a new and improved device for establishing
second grid. To minimize the number of external
connections to be brought through the tube base,
it is preferred that this connection be made in
wall of the tube envelope.
ternally of the envelope by ;means of contact
_
the present invention, a
springs ?xed to the second grid and adapted to 55
new and improved electron-discharge device such
52,668,161
3
as a cathode-ray tube or the like comprises an
evacuated envelope, an electrode within the en
velope, and a conductive coating on the inner
wall of the envelope. An electrically conductive
bimetallic contact member is ?xed to the elec
trode and adapted to make electrical contact with
the conductive coating under predetermined am
bient temperature conditions such asthose ena
fcountered in normal operation of the device.
Withan arrangement of this type, a predetere
mined change in the ambient temperature con
ditions, such as that which may be effected dur
ing the sealing-in process, results in a withdrawal
of the contact member from mechanical and
electrical contact with the conductive coating, so
that breakage of the envelope is effectively
4!
those skilled in the art. Separate leads for grids
I, 2 and 4 extend through the base 25 of the
tube, as do the supply leads for the cathode l3
and its associated heater element (not shown).
Lead 26 from grid 4 through the base of the tube
may be provided with an insulating glass bead
(not shown) to inhibit spark discharge to elec
trode I 6. Conductive disc 2| is mechanically sup
ported from and electrically connected to grids
3 and 5 by means of metal connecting strips 21.
'Operating potential for the conductive coating
22, and therefore for the third and ?fth grids,
may be supplied by means of a conventional con
tact button if the envelope is of the all glass type,
or directly to the metal cone member if the tube
is of the glass=metal variety.
An external permanent magnet 28, supported
in a spring clamp 29 which ?ts snugly around the
neck of the tube and is movable both axially and
are believed to be novel are set forth with par
rotationally, is provided to develop a magnetic
ticularity in the appended claims. The inven 20 ?eld within the tube to provide separation of the
tion, together with further objects and advan=
negative ions from the electron beam._ _
tages thereof, may best be understood, however,
The tube is evacuated, sealed and based in- ace
by reference to the following description taken in
cordance with well known procedures which re‘
connection with the accompanying drawing, in
quire no further explanation, and suitable gettcrs
which the single ?gure is a fragmentary side ele
3| are supported from the surface of conductive
vation, partly in cross-section and partly cut
disc 2| facing ?uorescent screen it to absorb
avoided.
_
~
‘
‘_
The features of the present invention which
away, of an image-reproducing device con
structed in accordance with the present inven
residual gases after evacuation.
.
In operation, a mixed beam of electrons and
tion.
negative ions originating at cathode I3 is pro
30
The imageireproducing device of the ?gure
jected through the aperture in second grid l5.
comprises a ?uorescent screen 10 affixed to the
When the mixed beam emerges from grid 2, it
glass target portion ll of a cathode-ray tube
encounters an electrostatic field having a trans
envelope which also comprises a glass neck por
verse component due to the lateral offset of grid
tion 12 enclosing an electron gun and an electro
3 with respect to grid 2. Consequently, electrons
static focusing system. The electron gun com
and ions are both de?ected to the left in the view
prises a cathode 13, a control electrode 1 4, and
of the ?gure, The magnetic ?eld imposed by
?rst and second tubular accelerating electrodes
beam-bender magnet 28 serves to deflect the elec‘
I5 and I6 respectively. A diaphragm i'l having
trons to the right as viewed in the ?gure with
a central aperture I8 is disposed across the cute
out substantially affecting the path taken by the
let end of second accelerating electrode l6, and 40 negative ions. ’ Thus, when beam-bender magnet
aperture [8 is symmetrically centered with re
28 is accurately adjusted, the beam of electrons
spect to the tube axis A-—A perpendicular to the
is projected centrally through aperture l8 of dia
center of the fluorescent screen It). Second ac
phragm H in a direction along the tube axis
celerating electrode I6 is laterally offset. from
AQA, while the negative ions are intercepted by
?rst accelerating electrode IE to provide a steady 45 the metallic portions of grid 3 and diaphragm
transverse electrostatic-de?ection ?eld compo‘
H’. The ion-trap mechanism is- disclosed and
nent in the region between these two electrodes,
claimed in the copending application of Willis E.
and the entire electron gun structure is tilted
Phillips et 2.1., Serial No. 156,746, ?led April 19-,
with respect to the tube axis Ae-A by the angle 6-.
1950, now Patent No. 2,596,508, issued May 13,
50
An electrostatic focusing system of the unipoa
1952, for “Electron Gun for Cathode-‘Ray Tubes,"
tential lens type is. disposed between the electron
and assigned to the present assignee.
gun and the ?uorescent screen. The focusing
Thev axially directed electron beam is subjected
system comprises the outlet end of second accele
to the focusing action of the electrostatic ?elds
crating electrode it including diaphragm H‘, a
produced by diaphragm H, lens electrode l9 and
lens electrode is, and an additional electrode 20 55 the ?fth grid 20 which together constitute a uni
which are all coaxially' mounted with respect
potential electrostatic focusing lens system. The
to the tube axis A-A. A centrally apertured
general construction and operation of lenses" of
conductive disc 21' is disposed in the neck por
this type are well understood by those skilled in
tion of the» envelope between the focusing‘ system
art as indicated by an article entitled “Mensa
and target portion H. A conductive coating 22, 60 the
ur'ed properties of strong ‘unipotential’ elec
of colloidal graphite such as aquadag or the like
tron lenses” by G.- Liebmann, Proceedings ot the
extends from the direction of target portion H
Physical Society, Section B, volume‘ 62, Part 4:,
into the neck portion of the envelope, and com
pages 213-228 (April 1, 1949').
ductive disc 2| is maintained at a common po
The required operating potential. difference
65
tcntial with conductive coating 22 by means of~
between the lens electrode (grid #1)‘ and the other
metal contact springs 23.
electrode's'of the focusing system (grids 3 and U
For convenience, electrodes M, ii, I6, is and
is determined by the dimensions of and the spac
20 may be termed “grids” and may be designated
ing' between the electrodes constituting the uni‘
by number starting with control electrode 14 as
potential lens. Although the relationships are
the ?rst grid and progressing in the direction of 70 not necessarily linear, the required focusing pod
beam travel to additional electrode 20 which is
tential difference varies directly with the length
the fifth grid. All ?ve grids are supported in. pre~
and inversely with the diameter or grid 4, and
determined mutually spaced relation by means
inversely
with the separation between grid | and
of a pair of glass pillars 24, of which only one is
75
grids
3
and
5. certain limitations on thésc
shown, in a. manner which will be apparent to
2,658,161
-7
5
.parameters are imposed by practical considera
tions; if the diameter of grid 4 is made too small,
.excessive spherical aberration is encountered, and
if the separation between grids 3 and 4 is made
disc 2|, high potential gradients and undesirable
spark discharge between the low-potential lens
electrode l9 and the high-potential conductive
coating 22 are substantially avoided. Moreover,
too great, the de?ecting in?uence exerted by the
even though this construction results in a space
asymmetrical electrostatic ?eld established be
between grid 5 and conductive disc 2| in which
tween lead wire 26 and grid 3 becomes objection
the boundary potentials are not de?nitely estab
able. The focusing system is preferably con
lished, no observable distortion or defocusing of
structed and arranged to obtain focusing with
the beam is encountered. The size of the aper
grid 4 operated at or near cathode potential, 10 ture in conductive disc 2| is not critical but
in order to avoid the necessity of providing a
should be large with respect to the apertures in
source of operating potential intermediate the
grids 3 and 5.
Y
B-supply voltage and the ?nal anode voltage.
Moreover, conductive disc 2| serves as an ef
In order to obtain satisfactory focusing with
fective getter shield to avoid conductive deposits
grid 4 operated at a potential between cathode
on glass support pillars 24 when the getter 3| is
potential and the B-supply voltage, it is necessary
?ashed during the processing of the tube. In this
to maintain rather stringent manufacturing
manner, excessively high potential gradients along
tolerances with respect to the dimensions and
the insulating pillars and possible insulator
spacings of the several electrodes constituting
breakdown are substantially avoided.
the focusing system. In addition, when grid 4 20 Due to the close spacings and the high po
is operated at a potential substantially equal to
tential differences between grids 2 and 3 and
that of the cathode, extremely high voltage
between grid 4 and grids 3 and 5, undesirable
gradients are produced between grid 4 and grids
cold emission and spark discharge between these
3 and 5. In order to suppress undesirable corona
electrodes may be encountered. This undesir
effects and ?eld emission, grids 3 and 5 are each 25 able situation may be avoided by observing every
provided with corona rings 32 and 33 in the form
precaution to insure that the glass envelope and
of rolled ?anges of stainless steel or the like which
are welded or otherwise secured to the respective
all of the electrodes are kept clean and free from
grease or other organic matter, and by avoiding
sharp edges on the closely spaced opposing por
the two ends of a metal cylinder 34 over the edge 30 tions of the several electrodes. -Moreover, it has
of a large aperture in a metal disc 35.
been found in practice, particularly in the pro
Corona rings 32 and 33 also perform an ad
duction of electrostatically focused picture tubes
ditional function in facilitating the maintenance
embodying unipotential focusing lens systems,
of the required close manufacturing tolerances
that the requisite degree of cleanliness cannot be
by mechanically reinforcing the circular ?anges . effectively maintained by the use of commercially
to which they are attached against warping or
feasible production methods.
.
bending during the assembly of the electrode
As disclosed and claimed in the above-iden
system. The electrodes are assembled by means
ti?ed Peterman application, undesirable cold
of accurately constructed jigs and are all rigidly
emission and spark discharge in the electrode sys
supported by means of opposed common glass
tem are effectively inhibited by providing a second
pillars 24, the gun assembly being properly orient
conductive coating 40, separate from the conduc
ed in the tube neck by means of other jigs in
tive coating 22 which is connected to grids 3 and
the usual manner. It has been found that these
5 and maintained at high potential,- within the
precautions suffice to insure satisfactory opera
glass neck portion of the envelope in a position
tion of the completed'structure, any small devia 45 at least partially encompassing the tubular elec
tions in dimensions and spacings being readily
trodes I5 and Hi of the electron gun. , Conductive
compensated by adjustment of the ion-trap
coating 40 is maintained at a constant low posi
magnet 28.
tive potential with respect to cathode l3, prefer
For best results, it has been found that the
ably by means of contact springs 4| connected
apertures in grids |, 2, 3 and 5 should be in
to the second grid l5. It has been found that a
marginally overlapping alignment in a direction
cathode-ray tube constructed in this manner may
parallel to the tube axis A—-A. In other words,
be operated with ?nal anode voltages consider
all of these apertures should intercept an imagi
ably in excess of those required in actual use of
nary straight line parallel to reference axis A—A,
the tube in a television receiver or the like with
and the apertures in grids | and 2 should inter 55 out encountering spark discharge or “popover”-in
cept that line asymmetrically. Ful?llment of
the electrode system.
this condition is dependent upon the angle 0 by
The technical reasons underlying the success of
which the entire electron gun is tilted with re
the illustrated construction are not fully-under
spect to the tube axis, and also upon the length
stood. One theory which seems in agreement
of the electron gun from the cathode to aperture 60 with numerous observations is predicated on the‘
I8 in diaphragm |‘|. If the angle 0 and/or the
hypothesis that cold emission and spark discharge
length of the gun is increased to such an extent
are only encountered, at normal operating volt
that the apertures in grids |, 2, 3 and 5 are no
ages, in the presence of extraneous gas molecules.
longer in marginally overlapping alignment in a
In a conventional image-reproducing device not
direction parallel to the tube axis, increased 65 provided
with the conductive coating 40 of the
multiplicity of focus is encountered, and the
present invention, primary or secondary electron
performance of the focusing system is inferior.
bombardment of the glass neck portion of the
On the other hand, if the angle 0 is decreased so
envelope is thought to result in the liberation of
that the apertures are in complete coaxial align
ment, ion trapping may no longer be conveni 70 occluded gases from grease, dirt, or other extrane
ous organic matter which may be present. These
ently accomplished.
gas molecules then become ionized and are caused
By employing a separate conductive disc 2| for
to bombard the gun electrodes, leading to cold
establishing electrical contact to conductive coat
emission which ultimately results in spark dis
electrodes, and grid 4 is constructed by rolling
ing 22, and by terminating conductive coating
charge. This theory is supported by the observa
22 at substantially the plane of the conductive 75 tion that troublesome spark discharge generally
9,658,161
takes‘ place along the. glass wall of the envelope
Ilnthe ?rst instance. and only later across the
shorter intervening space between the gun elec
trodes. By-providing internal conductive coating
~40, andby maintaining that. coating. at a low
constant positive potential by means of contact
springs“ connected to second. grid 15, gas libera
tion :is avoided for two reasons. In the. first
place,coating 40 acts as a physical barrier be
tween the offending primary and/or secondary
electrons and the glass .wall of. the envelope, thus
rendering extraneous grease or dirt onthe glass
wall- inaccessible. In the second place, such stray
electrons as reach the wall of the tube arecol
lectcd by coating 40 and conducted of: through
the external circuit associated with the second
grid;
»
.
.
Coating Ml may beiormed of silver. paint. or
any other conductive material which is amenable
to‘ application in the form of an internal coating.
The length of coating 60 is not critical, although
it is, essential that. the tubular gun electrodes be
at least partially encompassed by the coating,
and. that coating All-be maintained physically and
‘electrically separate from the ?nal anode coat~
ing 12.
8
process. Moreover, when a plurality of contact
springs are employed, the contact members and
the conductive coating form one or more closed
conductive loops or short-circuited turns which
have the eilect of suppressing the induction heat
ing ?eld.
On withdrawal of the bimetallic con
tact members from contact with the auxiliary
coating, which is accomplished automatically
during the induction heating process, these closed
loops are interrupted or opened, and the entire
applied induction heating ?eld is utilized in the
subsequent outgassing of the v‘gun electrodes.
Consequently, any number of bimetallic contact
springs may be employed, as dictated by- consid
erations of a practical nature.
Thus the present invention provides a new and
. improved arrangement for establishing electrical
contact between an electrode and a conductive
coating on the inner wall of a glass envelope while
avoiding glass breakage caused by unequal
stresses induced during sealing-in or other proc
esses involving the application of localized heat
during the manufacture of an electron-discharge
device. The arrangement is simple and inexpen
sive, and the desired purpose is achieved auto
matically without the attention of the processor.
While the invention has been described in con
In practice, considerable difliculty has been en
nection with a particular type of conductive coat
countered during the process of sealing the elec
ing employed in an e1ectron—discharge devices of
tron gun into the neck portion of the envelope,
cathode-ray type, it is apparent that the in
due to stresses caused by unequal heating of the 30 the
vention may be employed to advantage in other
glass neckand the metal contact members M.
types of electron-discharge device where ana
In accordance. with the. present invention, this
logous
problems may be presented.
difficulty is effectively avoided by constructing
Certain features of the construction illustrated
'contact'members H of bimetallic strip material.
and described in the present application are dis
To this end, contact springs M are of bilaminar 35 closed
and claimedin the copending applications
construction each comprising an outer strip 42 of
of Constantin S. Szegho, Serial No. 229,013, ?led
material having a predetermined temperature
May 31, 1951, for “Image-Reproducing Device,”
coe?icient of expansion and an inner strip 43 of
Jerome J. O’Callaghan,' Serial No. 235,045, ?led
different material having a predetermined, lower,
temperature coe?icient of expansion. With this 40 July 3, 1951, for “Image-Reproducing Device,”
now U. S. Patent No. 2,627,043, issued January
construction, during the sealing-in process when
27, 1953, and Robert W. Shawfrank, Serial No.
the gun assembly is fused to the neck portion of
234,920, ?led July 3, 1951, for “Cathode-Ray Tube
the envelope, contact springs 46 are heated con
Electrode," now U. S. Patent'No. 2,627,049, issued
siderably above normal room. temperature- Both
the inner and outer strips 42 and 43. are thereby 45 January 27, 1953, all of which are assigned to the
present assignees.
caused to expand, but the inner strips 43, having
While a particular embodiment of the present
a lower temperaturecoe?icientor expansion than
invention has been shown and described,'it'is
the outer strips 42, expand to a lesser extent. As
apparent that various changes and modi?cations
a result, contact springs 4! are retracted inwardly
may be made, and it is therefore contemplated
50
toward the gun assembly and are withdrawn from
in the appended claims to cover all such changes
‘contact with conductive coating 40. On cooling,
and modi?cations as fall; within the true spirit
after the sealing-in process has been completed,
and in subsequent operation, contact springs 4|
and scope oi! the invention.
"'
I claim:
resume their original shape and are caused by
1. A cathode-ray tube comprising: an evacuat
virtue ol'. their natural resiliency to bear against 55
ed envelope; a ?uorescent screen supported with
conductive coating 40 to maintain the desired
in said envelope; an electrode system within said
electrical contact.
envelope including a cathode, a plurality of tubu
‘ ‘In order tov achieve'this type of operation, the
lar electrodes, and a conductive coating on the
outer strips ‘2 may be constructed of an alloy
inner wall of said envelope between said tubular
of 22% nickel, 3% chromium, andv the balance
electrodes and said fluorescent screen; means for
iron, or an alloy of 72% manganese, 18% copper,
electrically connecting said conductive coating to
and 10% nickel, while the inner strips 43 may be
one of said tubular electrodes; another conduc-.
constructed of an alloy of 36% nickel, and 64%
iron. These alloys are specified merely by way of
tive coating on the. inner wall of said envelope,
example, as other bimetallic strip materials suit 65 separate from said first mentioned coating and at
able for use in high vacuum are known in the art.
least partially encompassing said tubular elec
The use of bimetallic contact springs Al is, also
trodes, for inhibiting cold emission and spark
advantageous with respect to the outgassing op
discharge in said electrode system; and at least
eration during exhaust of the envelope when the
one
bimetallic contact spring ?xed to another of
gun electrodes are subjected to a radio~frequency 70
said tubular electrodes and adapted tomake elec
induction heating ?eld. In the first place, con
trical contact with said other conductive coating
tact springs 4| are automatically withdrawn from
under normal ambient temperature conditions,
contact with the auxiliary coating 40 during this
whereby said contact spring is withdrawn from
operation, thus avoiding breakage of the envelope
as explained in connection with the sealing-in 75 contact with said other‘ conductive coating in re-;
2,668,161
sponse to a predetermined change in said ambient
temperature conditions.
2. A cathode-ray tube comprising: an evacuat
ed envelope; a ?uorescent screen supported with
in said envelope; an electrode system Within said
10
?xed to said second grid and adapted to make
electrical contact with said other conductive coat
ing under normal ambient temperature condi
tions, whereby said contact spring is withdrawn
from contact with said other conductive coating
envelope including a cathode, ?rst and second
in response to a predetermined change in said
grids, a tubular electrode, and a conductive coat—
ambient temperature conditions.
ing on the inner wall of said envelopebetween
JOHN F. DE ANO.
said tubular electrode and said ?uorescent screen;
means including a plurality of contact springs 10
References Cited in the ?le of this patent
for electrically connecting said conductive coat
UNITED STATES PATENTS
ing to said tubular electrode; another conductive
Number
Name
Date
coating on the inner wall of said envelope, sep
2,139,678
Glass ___________ __ Dec. 13, 1938
arate from said first-mentioned coating and at
least partially encompassing said second grid and 15 2,323,140
Lane ____________ __ June 29, 1943
2,432,037
O’Larte et a1. _____ __ Dec. 2, 1947
said tubular electrode, for inhibiting cold emis
2,596,508
Phillips et a1 ______ __ May 13, 1952
sion and spark discharge in said electrode sys
2,598,241
Elenbaas _________ __ May 27, 1952
tem; and a plurality of bimetallic contact springs

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