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Патент USA US2128597

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Aug. 3o, 1938,
E. ' RUSKA
BRAUN TUBE
Filed Aug. 5, 1936
2,128,597
Patented Aug. 30, 1938
UNITED STATES
Arr orties
2,1 28,597
BRAUN TUBE
Ernst Ruska, Berlin-Zehlendorf, Germany, as
signer to the firm Fernseh Aktiengesellschaft,
Zehlendorf, near Berlin, Germany
Application August 5, 1936, Serial No. 94,433
In Germany August 7, 1935
6 Claims.
(Cl. Z50-27.5)
In order to attain ample energy for the de
flected ray and for example an attendant great
luminosity on the luminous screen in electron’
ray tubes of the type wherein the ray is cross de
5 iiected, e. g. as in oscillograph tubes, picture
transmitting tubes and receiving tubes, accom
panied at the same time by small expenditure
for the magnetic. or electrical cross-control fiel-ds,
the proposal has been made to supply energy by
liecting system.
At that point a ñeld is always
formed which subsequently tends to decrease the .
angular deflection of the ray already produced
by the cross-control system;v The result is a
sagging of the accelerated level surface from the
luminous screen, that is, in a direction convexly
towards the cathode, and exactly ,the reverse
of what is required for satisfactory retarded ac-y
celeration. Although the voltage within the thus
10 means of a so-called retarded accelerating ñeld
deviated level surface and traversed by the elec- .
("Nachbeschleunigungsfeld”) to the already low
velocity controlled ray and to effect said object
without deleteriously affecting the degree of its
existing deñection.
15
In the embodiments of such arrangements
hitherto used, it has however appeared that the
trons is relatively small comp-aredwith the total
voltage of the retarded accelerating ñeld, never
theless the corresponding decrease in` original
ray deñection becomes quite noticeable` on the
screen since, ñrst, the electron ray hasa rela- -
tively low velocity in the critical domain and
retarded acceleration was always associated with
a decrease in the deflectional angle and hence
suli‘ers a relativelyvpowerful angular deflection
in the deflection on the luminous screen.
to the screen is greatest at this point and makes
itself noticeable through a definiteangular de,
crease `and hence in a great reduction in the spot
In
order to attain the original degree of deflection
the ray therefore had to be deflected in the cross
and, because, secondly, the leverage with respect
control ñeld to a greater angular degree. This, deflection on the screen.
.
.
in addition to the occasional very appreciable
In order to obviate these drawbacks the inven
expenditure involved in the stronger cross-con
tion, when applied to magnetically cross-deflected
trol fields required, also had the very inconven
and magnetically or electrically concentrated
.ient drawback that the distortions in the rayy electron ray bundles, proposes' to permit the
cross-section (image element on the luminous
screen) which rapidly increase as the deflec
tional field increases, occur o-ven in portions of
electron ray to pass through a tube having the
same or nearly the same potential as the negative
y30 the screen which are relatively near to the center.
tending into said field and thus to place the end
It is the object of the present invention more
or less appreciably to obviate this decrease in
sensitivity hitherto associated with retarded ac
of the anode tube facing the luminous screen
at a lower potential difference relative to the
screen than is the beginning of the accelerating
celeration and even to attain an increase in
field, that is, to place the end of the anode tube
somewhat in the interior of the accelerating field. :
A plane passing through the end of the anode
tube and perpendicular to the tube axis will
therefore strike the periphery of the tube at
level surfaces which are already _more or less
positive with respect to the potential of the anode
tube. These potentials should therefore under
no conditions lie in the vicinity of the positive
end of the retarded accelerating field since other
wise the rays within the cross-control field will
attain appreciably -diiïerent speed depending on
5 sensitivity by means of the retarded accelerat
ing iield.
The known types of retarded accelerated fields
which have been fundamentally tested as to
serviceability and which have an approximately
40 plane extent of level surface are produced, for
example, by a current-traversed resistance layer
disposed on the inner Wall of the tubes and which
extends either vin the form of a conical convolu
tion along the bulb or else is formed as a homo
end of the retarded accelerating iield and ex
45 geneous layer. 'I'he retarded accelerating> ñelds
may also be produced by a number of annular - the degree of cross-deflection involved and thus>
electrodes separated from each other and which produce a deñection which is insensitive asr a
are gradually brought to increasingly higher po
tentials the nearer the individual rings approach
whole and of non-linear extent.
In order to give the level surfaces of the re
50 the screen.
tarded acceleration system (which are at anode
The lines of force of the retarded accelerating l potential), a` slightly convex shape facing the
`i’ields should extend as much as possible towards
the ray-.deflecting pivot point in the entire field
domain. The fulfillment of this condition is
55 4difficult however in the neighborhood `of the de
screen the anode tube is provided at one end
with a cap- of approximately hemispherical shape
which is >provide-d with a diaphragm opening for
permitting passage and also limitation of the ray.
2.
2,128,597
Two embodiments of the invention subject
and hence favorable to cross deflection. In this
matter are illustrated in the drawing.
arrangement in contrast to the system using
Fig. 1 showsr a longitudinal section of a Braun
tube.
Fig. 2 is a section through the deflecting cham
magnetic ray concentration there occurs no un
ber of the tube.
The tube, at the end of the tube neck I, is pro
vided with a. ray producing system 2 to which the
desired deformation of the accelerated potential
surfaces since all of these are curved convexly
towards the screen. In the case of magnetic ray
concentration some few level surfaces are located
directly adjacent the anode potential which are
drawn into the opening of the anode tube dia
phragm. These however exert a slight ray con 10
centrating refracting power which therefore is
The interior wall of the tube neck is provided “ insufficient to focus the ray. This function is
rather assumed by the magnet coil,
with a conducting coating 6 or an annular elec
The anode tube 3 of the invention is preferably
trode which is at anode potential or, if desired,
anode tube 3 is attached. The anode tube is pro
vided with a cap 4 at its front end, said cap hav-,k
ing a ray limiting opening 5.
even at a more negative potential than` can be
adapted to be positively centered, together with
assigned to the anode potential. The edge of the
short circuiting ring 6 (annular electrode) which
the accelerating system, on a cross yoke I3 which
is fastened as by spot welding to the center of a
faces the luminous screen and which is- at anode
potential and which cuts off the retarded accel
20 erating ñeld lies further removed from screen 'I
than the end of anode tube 3 having the ray
limiting diaphragm 5. A free annular space be
tween anode tube 3 and the tube wall draws the
level surfaces into itself, these lying against the
25 anode tube andv being indicated by dash lines,
and thereby improves >the spread of the level
surfaces in the `space in front of the anode tube.
The term “level surfaces”, is used to denote iso
potential ñeld strength planes.
30
'
The magnetic cross-control which must ob
viously lie behind the ray limiting diaphragm 5
occurs, when the accelerating ñeld is designed
in accordance with the invention, in a space
occupied by the accelerating field, nevertheless
35 the average electron velocity in the cross-con
trol field is only inappreciably increased com
pared to the inlet velocity. Since the dis-tributed
shape of the ñeld is favorable for cross-control
purposes, the advantages incident to retarded
40 acceleration may be utilized without the there
with associated drawback of loss of sensitivity.
Inasmuch as a slight increase in deflectional field
strength .is frequently accompanied by a no
longer industrially permissible expense, the in
troductionofthe.retarded accelerating field ac~
cording to the invention means that ñrst the
degree of retarded acceleration (retarded accel
eration voltage/preliminary or anode voltage)
can be chosen so high that the great advantages
inherent in the use of retarded accelerati-on can
50
be especially well utilized.
Concentration of the ray in systems according
to the invention may be effected electrically or
magnetically. A magnet coil 8 may, according
to
Fig. 1, be forced either outwardly over the
55
tube neck I or else wound in the inside of the
tube around'the end of the anode tube 3 as
45
shown'in the dotted lines, two disks 9, _Iü being
first fastened to this tube by spot welding at dis
60 tances corresponding to the desired length of
coil. Electrical concentration of the ray is ef
fected according to Fig. 2 preferably by means
of -an annular electrode II negatively charged
with respect to the tube and located shortly in
65 front of the opening 5 of the anode tube 3 and
within the interior thereof, the field of said elec
trode facing the cathode being screened by means
of a perforated disk I2 which is at anode poten
tial. The potential increases between the nega
70 tive annular electrode I I and the apertured dia
phragm 5 in the anode tube, and likewise also
after the ray has passed the apertured dia
phragm. The shape of all positive level sur
Spread ring band I 4. The spread ring permits
the entire system to be anchored rigidly in the
tube neck I without requiring any special ar
spect to a hole in the cross yoke by means of
about three bent-overlugs through which an
anode cap I5 >provided with external threads and 25
collar is inserted from the screen side.
An in
ternally threaded insulating screw ring I8 locks
both the anode cap andanode tube together with
the cross yoke which is fastened to the-spread
ring. The control electrode fastened to the press 30'
foot and the cathodeare screwed intothe insu-`
lating screw mount I8 and thereby centered with
respect to the anode system whereupon the press
foot is fused together with the tube neck. 'I'he
inside thread of the insulating ring I8 is re
cessed in the center so as to obtain as high a
strike-over voltage of the accelerating system as
possible.; The tube according to the invention
may therefore as a whole (inclusive of anode
voltage andacceleration voltage) beV operated at 40
very high operating voltages (2O kv. and greater)
without excessively increasing the ampere turns
necessary for magnetic cross control.
The resistance `layer I6 used for producing the ‘
homogeneous acceleration ñeld extends from the
short circuiting ring I'I near screen l over the
conical or bowed bulb'to far- within the bulb
neck I `at the point on which subsequently the
spread ring I4 acts as lead-in electrode for con
veying the anode voltage.~ Obviously this point
of the neck i may also be preliminarily metal
lized in order to insure positive contact with the
high ohmic layer -IE on> the one hand and the
spread ring It »(ancde system) on the other hand.
The short> circuiting ring I‘I near the screen
is preferably made broad in order to impart a
good convex shape to the level surfaces near and
facing the screen.
I claim:
1_.A Braun tube having therein an electron
gun comprising a cathode, a control electrode,
and an anode, said control electrode having an
exteriorly threaded portion directed toward said
anode, said anode having an exteriorly threaded
portion directed toward said control electrode,
an insulating ring having an interiorly threaded
portion adapted to engage said controlv electrode
and a second interiorly threaded portion adapted
to engage said anode, said insulating ring having
its inner surfacebetween said interiorly threaded 70..
portions recessed to a diameter substantially
greater than said threaded portions.
l 2. In combination with a cathode ray tube
having a tubular neck portion enclosing electron
75 spect tothe anode, is convex towards the screen ~ gun elements substantially as described in claim
faces,- considering their potential values with re
20
rangement. In constructing .the anode system
of Fig. 2 the anode tubeV 3 is centered with re
3
2,128,597
1, an annular conducting shield positioned with-_
in said neck, a cylindrical metal element, having
one closed end, positioned within said shield and
having a central aperture disposed through said
closed end adapted to ?it around said threaded
anode portion and be held thereby between’said
anode and said insulating ring.
3. In combination with a cathode ray tube
having a tubular neck portion surrounding elec
10 tron gun elements substantially as described in
claim 1, a cylindrical metallic shield disposed
within said neck portion, an annular support
ing diaphragm disposed in Contact with said
shield centrally arranged to `lit around said
15 threaded anode portion, and a cylindrical anode
tube having one end terminated by an apertured
diaphragm portion similarly arranged to ñt over
said threaded anode portion, whereby said in
sulating ring, said supporting diaphragm, said
anode tube, and said anode may be held together
by the threadable cooperation of said anode and
said insulating ring.
4. In combination with a cathode ray tube
havingfa tubular neck portion surrounding elec
25 tron gun elements substantially as described in
claim 1, a cylindrical metallic shield disposed
within said neck portion, an annular supporting
diaphragm disposed in contact with said shield
centrally arranged to fit around said threaded
30 anode portion, and a cylindrical anode tube hav
ing one end terminated by an apertured dia
5. In combination with a cathode ray tube
having a tubular neck portion surrounding eleo
tI‘On gun elements substantially as described in
claim 1, a cylindrical metallicA shield disposed
within said neck portion, an annular supporting
diaphragm disposed in contact with said shield
centrally arranged to lit around said threaded
anode portion, and a cylindrical anode tube hav
ing one end terminated by an apertured dia
phragm portion similarly arranged to ñt over said
threaded anode portion, whereby said insulating
ring, said supporting diaphragm, said anode tube,
and said anode may be held together by the
threadable cooperation of said anode and said
insulating ring, the other end of said cylindrical
anode tube having a centrally apertured dia
phragm and a centrally apertured hemispherical
cap, and an annular electrode disposed in axial
alinement with said anode tube within said hemi
spherical cap.
20
6. In combination with a Braun tube having
an envelope enclosing an electron gun, having
a cathode, an anode, and a control electrode,
positioned at one end thereof and an oppositely
disposed fluorescent screen, a cylindrical shield 25
disposed Within said tube knear said gun, a sup
porting diaphragm connecting said shield and
said anode, a cylindrical anode tube, ñxedly as
sociated with said anode, having at the end
opposite thereto an apertured diaphragm, a cen
trally apertured hemispherical cap, and an an
phragm portion similarly arrangedv to ñt over
nular electrode disposed Concentrically within
said threaded anode portion, whereby said insu
said cap; a high resistance layer fixed upon the
inner surface of said envelope connected to said
cylindrical shield and extended therefrom toward
said fluorescent screen, and an annular unipo
lating ring, said supporting diaphragm, said
35 anode tube, and said anode may be held together
by the threadable cooperation of said anode and
said insulating ring, the other end of said cylin
drical anode tube having a centrally apertured
diaphragm and a centrally apertured hem
ispherical cap.
tential electrode disposed in contact with said
high resistance layer near but not in contact
with said fluorescent screen.
'
ERNST RUSKA.
30
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