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Патент USA US2099749

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Nov. 23, 1937.
'
R. T. ORTH
ELECTRON TUBE
2,099,749
‘
Filed May so, 1935
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INVENTOR
7-“ RICHARD T. ORTH
12
BY
ATTORNEY
'
Nov. 23, 1937. Y
R. 'r. ORTH
’
2,099,749
ELECTRON TUBE
Filed May 30, 1933
> 2 Sheets-Sheet 2
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INVENTOR
RlCHARD
'
BY?
-
,
ORTH
M44,
A‘TTORNEY
Patented Nov. 23, 1937
2,099,749
UNITED STATES PATENT OFFICE
2,099,749
ELECTRON TUBE
Richard T. Orth, Orange, N. J., assignor to Radio
Corporation of America, a. corporation of
Delaware
Application May 30, 1933, Serial No. 673,572
3 Claims.
(Cl. 250-275)
This invention relates to electro-optical de
vices and systems and more particularly to the
use of a cathode ray tube frequently referred to
as a Braun tube in connection with such systems.
In the prior art the cathode ray tube used for
television and oscilloscope purposes usually em
ploys a translucent screen which has the prop
erty of ?uorescing when subjected to the bom
bardment of an electronic beam.
In cases where
10 it is desired to producevariations in intensities
of the resulting ?uorescent effects, which varia
tions might be in accordance with variations in
photoelectric currents resulting at a point of
transmission in accordance with the scanning of
15 a subject of which the electrc-optical image was
One of the more important reasons is '
time, been practically universally adapted, it
nevertheless has the inherent disadvantage that
upon impressing various voltages or biasing po
tentials to produce the control action the effect 10
is that of changing the cross-sectional area of
the electron beam, as will become more apparent
from what follows.
Cathode ray tubes, as designed for television
work, reference being made herein to the subject 15
desired, the beam may be modulated by means
of television merely in ‘order to illustrate one
of an electrostatic control electrode or grid which
suitable use for a type of cathode ray tube and
control therefor, as herein disclosed, are usually
characterized by a long tubular neck one end of
which carries the base of the tube and the other a N,
conical portion terminating in a section whose 0
normal projection is perpendicular to the axis of
the tube. This section is usually concave on the
inside, although for small tubes especially it may
is disposed in the path of the electronic beam di—
rected toward the ?uorescent viewing plane. The
control electrode or grid is biased under the in
2 O ?uence of the photoelectrically controlled signal
eifects to vary the degree of ?uorescence.
According to still other arrangements of the
prior art, it has been proposed to control the in
25
another.
that the intensity controls of the types above
outlined frequently cause the effects of streaking
or the like in the view-ed electro-optical effects
produced from screen ?uorescence.
5
While the grid control has, up to the present
tensities of the observable effects upon the
?uorescent end wall of the cathode ray tube by
de?ecting the cathode ray pencil with respect to
an aperture or opening in a screen plate or with
respect to a limiting or beam de?ning edge of a
screen plate which is opaque to the passage of
30 the electrons. This type of prior art arrange
ment functions so as to control variably the num
ber of electrons which pass through the opening ’
or past the beam de?ning edge of the shield.
Still other arrangements of the prior art have
35
provided for intensity control of the fluorescent
e?ects by a variation in the velocity of impact of
the electron stream upon the ?uorescent screen.
Other arrangements operate to control the ob
servable intensity of the ?uorescent spot by
varying the velocity of traversal of the cathode
ray stream projected at constant instantaneous
impact. velocity upon the ?uorescent viewing
plane so that the variations produced in the pc
45 riods of actual impact of the cathode ray beam
4
at any diilerential area upon the screen produce
the e?ects of varying lights and shadows from the
resulting light spot, the intensity of ?uorescence
being a function of both velocity of impact and
50 time of impact.
All such arrangements of the prior art while,
in general, satisfactory, particular reference be
ing made to the grid control effect so universally
used, nevertheless are somewhat unsatisfactory
55 for extremely accurate control for one reason or
be ?at or even convex, and is provided with screen
structure of a ?uorescent character upon which
the cathode ray stream or pencil impinges. The
pencil or beam of rapidly moving electrons has
its origin in a heated cathode or, where desired,
even a cold cathode located at the base end'oi' 0
the tube. From the point of origin of the oath
ode ray beam or pencil to the point where it
strikes the ?uorescent screen the beam is con
trolled by either electrostatic or electromagnetic
?elds or both so arranged as to accelerate, focus 35
and de?ect the cathode ray pencil in the direc
tion or directions desired.
One suitable means for de?ecting the cathode
ray beam is by the use of electrostatic de?ecting
plates conveniently located in the neck of the
tube, or, where desired, externally of the tube.
An electrostatic ?eld produced between these
plates upon the application of voltages of suit
able frequency thereto produces an acceleration
of the beam in line with the ?eld between the
plates. For television work two sets of de?ect
ing plates may be used and, if so, the surfaces of
each set are at right angles to each other. Such
an arrangement permits de?ection of the cathode
ray pencil in two planes perpendicular to each
other but both normal to the axis of the tube.
Where desired, of course, it is possible to substi
tute electromagnetic de?ection for the electro
static de?ection hereinabove suggested and it has
been found in many instances desirable to com-
40
45
50
55
2
2,099,749
nal sections of the electrode structures shown by '
bine electromagnetic and electrostatic de?ection
systems;
Figs. 3a and 3b;
Fig. 4 illustrates a modi?cation of the invention
in which a double helical heater and unipotential
type cathode is provided with a hollow core and
an electrode in positiontwithin the cathode mem
7
To controlthe intensity of the cathode ray
thus de?ected and positioned upon the tube
screen, according to the prior art, the electro
static or grid control consisted in an electrode
member substantially surrounding the electron
ber;
Fig. 5 illustrates a mandrel suitable for form- '
' emitting area. in such manner that the issuing
ing a unipotential cathode heater shown by Fig. 4;
electrons were drawn through an aperture of
Fig. 6 illustrates conventionally a cathode ray
10 predetermined size.
Modulation of the cathode
ray beam to vary the intensity of the resulting
?uorescent effects was accomplished by varying
the negative bias. With zero bias on the grid
electrode the effective aperture has been found
tube assembly omitting the enclosing envelope
and comprising the cathode‘ of Fig. 4 and the
helical heater assembly together with related
electrodes adjacent thereto; and
Fig. 6a illustrates the cross section of the elec
tron beam at the line B—-B of Fig. 6.
15 to be the same as the actual aperture. However,
as the negative bias is increased the effective di
ameter of the aperture in the control grid mem
The general type of cathode ray tube used for
ber decreases with the result: that the size of the television purposes is similar to that shown by
Fig. 1. vThis tube, as has been above stated, is
spot on the screen decreases in diameter. In tele
20
20 vision seanning this will result in a variation in characterized by a long tubular neck portion I
the light spot diameter with each change in, upon one end of which is supported the base 2
' modulation.
and the other a'conical portion 3 terminating in '
a ?uorescent screen 4. The cathode rays are
This effect then becomes observable
in the form of dark lines on the ?uorescent screen
generated within an electron gun structure des
because the line de?nition at all times throughout
25 the scanning period remains constant. I
ignated as 5 and the rays or electron stream thus
It is',._ therefore; one of the primary objects of . developed and projected toward the ?uorescent
this invention to overcome this changing spot size screen member 4 may be suitably de?ected by
applying suitable controllingv voltages in'the elec
trostatic de?ecting plates 5 and to a secondv set
of plates (not shown) arranged transverse to the 30
set of plates 6. Of course, magnetic de?ection or
a combination of electrostatic and‘ electromag
defect and to producea scanned area on the ?u
crescent viewing screen which is devoid of all
so
streaked veifects.
.
.
Still other objects of the invention are to pro—
vide more suitable means for controlling the den
sity of a beamrof electrons.
~
I
Another object of the invention is to provide
means by which a beam of electrons may be mod
ulated and controlled by suitable controlling elec
trodes without in any way‘a?ecting the operation
:35
V netic, provided the electrostatic de?ecting mem
bers are formed from non-magnetic material so
as not to be subjected to the in?uence of the
magnetic de?ecting materials; might be used. .
According to the conventional type of cathode
or changing the actual diameter of the resulting ' ray tube design a control grid member, such as
area of ?uorescence upon the viewingscreen.
Other objects of the invention areto provide
40
the structure Ill shown by'Figs. 3a and 3c, is
usually arranged to surround substantially the
40
modulation or control arrangements for varying
the intensity of a cathode ray pencil of electrons
in whichthe control is more sensitive than that
found in‘ arrangements heretofore used in the
45 prior art; to provide a control system which is
extremely simple in its arrangement; to provide a
control system which readily adapts itself to
ture as is used in the cathode ray tubes ,now .
use in connection'w'ith cathode ray tubes of the
present type so that it will be unnecessary to re-'
conditions of zero bias on this controlielement '
design the general structure of the tube; and to
provide a control system that is extremely e?i
cathode ray stream I5 is adapted to pass is the
50
cient in its operation.
cathode emitting surface and the» developed elec
trons are projected toward the ?uorescent screen
structure 4 through the aperture l I. Such struc
usually known varies the modulation of the beam
or electron stream by varying the negative bias
applied to the grid or control electrode 10. For
4.5
Ill the’ e?ective aperture through which the »
same as the actual aperture ll so that the oath-1
ode ray pencil emerging from the grid structure
I V
' 'Still other and further objects of the invention
' will become apparent and suggest themselves to
55 those skilled in the art to which the invention
will have an actual electronic diameter equal to '
the diameter of the aperture H.’ However,, as
relates from reading the following speci?cation
the negative bias is increased to vary the intensity
of the resulting electronic light spot on the
and claims in connection with the accompanying
?uorescent screen structure the effective diam- t
drawings, wherein:
m
'
'
"
V
Fig. 1 illustrates one type of cathode ray tube
60 to which this invention is applicable}.
> Fig. 2 illustrates. one form of electrode struc
V ture which may be enclosed within the tube
shown by‘ Fig. 1;
'
,
I
Fig. 2a represents a transversesection through
65 the electron stream on the line‘ A-—A;
Fig. 3 shows various forms of modulating elec
trode which’may be'incorporated as apart of the
electrode structure within the ‘tube of Fig. 1;'
eter of the aperture 1 I decreases due, for example,
to repulsion of theemerging electrons from the
edges of the diaphragm member, so that the spot;
size also decreases. This e?ect produces, as has‘
been above de?ned in the statement of invention,
dark lines on the ?uorescent screen because the
line de?nition remains, always constant.
'
'
According to the present invention these above 6-5.
mentioned difficulties have been substantially
overcome by changing the control electrode struc
ture to some extent from the form now used inv '
-~ Fig.'3a designates an electrode structure having '
7 tubes known in the art. In the new form of the
a circular aperture across which the control ele- '
ment is provided;
'
.
Fig.f3b indicates an'electrode structure with a
75
control electrode herein disclosed the control
electrode structure includes the disk or plate
square aperture controlled similarly to the ar
member in formed with the shielding structure 7
rangement of Fig. 3a;
l2 attached theretoso that it resembles closely
the usual grid structure 10 above discussed but’
‘
'
'
Figs. 3c and 3d respectively vindicate longitudi
is
2,099,749
is distinguishable therefrom both in formation
and operation as will herein be pointed out. As
‘shown by all of Figs. 3a through 301 inclusive,
the aperture of the control electrode 10 may be
round, as shown by the apertures ll of Figs. 3a
and 30, or square, as shown by the apertures l3
of Figs. 3b and 3d, or may be of any other suit
able formation. In addition, the aperture should
be formed slightly larger than the aperture in the
10 regularly used control elements wherein the light
spot diameter depended upon the aperture diam
eteri Across the aperture H or l3 in such man
ner as to divide the area of the aperture into two
substantially equal parts there is attached to
15 either side thereof, by welding or by other suitable
means, a wire M which is stretched and forms
electrical contact with the disk surface 10.
The effect of this design, as can be seen more
particularly from Fig. 2 of the drawings and
20 also from Fig. 2a thereof, is to control the cen
ter of the electron pencil or beam l5, which is
developed by drawing the electrons issuing from
the electron emitting surface I‘! of the heated
cathode member l8 by means of the application
25 of suitable positive voltages upon an anode elec
trode [9 for example, rather than to change the
beam diameter as is the case when modulation is
produced by the usual type of control electrode.
The apertures I! and I3, depending upon the
30 shaping of the disk member as in Figs. 3a and 3c,
are so large that little or no current will be cut
off from the outside of the electron beam and the
wire l4 stretched across the aperture will cut a
diametric swath from the beam 15. As the bias
35 on the control electrode comprising the disk mem
ber l0 and. the shielding portion I2 is increased
negatively the apparent size of the wire l4 as re
gards the control of the electron beam will in
crease. This effective or apparent increase in
the size of the wire l4 causes a reduction in the
number of electrons forming the central portion
of the electron beam or pencil l5 which passes
through the aperture 20 of the disk member 2|
forming a part of the anode structure I9. This
45 effect, in turn, results in an electron stream which
takes the general form of the aperture 20 of the
3
hollow along its axis A-A. The electrode mem
ber 40 is so formed as to extend beyond the
continuous end of the ?lament 34. To the end of
the electrode 40 nearest to the terminal mem
bers 35 and 36 of the ?lament 34 there is at
tached a suitable tab or contact member 39 to
which electrical connections may be established.
In manufacturing a ?lament of this general
type the ?lament is wound upon a mandrel such
as that shown by 42 in Fig. 5. This mandrel is 10
formed preferably of molybdenum and provided
with a double helical groove 43. A tip portion 44
is machined on the end of the mandrel to. pre
vent the wire which is wound thereon crossing
the -axis of the coil. This suggested method of 15
winding is merely illustrative since there are
various suitable methods for performing this op
eration.
'
Following the winding of the ?lament it is
covered with a layer of insulating material which 20
is baked by suitable heat treatment. The elec
trode 40 which will constitute the control elec
trode and which can be seen in its assembled
form from the showing in Fig. 6 is also coated
with insulating material and baked whereupon 25
it is inserted into the coil so that the contactor
tab portion 39 lies at the same end as the lead
wires of the ?lament 34. This assembly is suit
ably inserted into the cathode sleeve portion 31
which is provided with a conducting tab portion 30
4i electrically connected thereto by welding or
other suitable means. The cathode sleeve portion
31 is provided with an aperture 38 of suitable
diameter through which the electrode member
45 protrudes. The annular face 45 of the cath 35
ode sleeve 31 is coated with a thermionically ac
tive substance prior to the assembly operation so
that upon heating the cathode member by the
application of current to the terminals 35 and
36 of the ?lament 34 electrons are emitted from 40
the activated surface of the annular face 45 to
form an electron beam 46. This electron beam
46 is suitably controlled, limited and focused by
the electrodes 49, 411, 48 and 33.
The function of the electrode 40 is similar 45
to that of the wire I 4 of Fig. 2, in that, its pur
electrode l9 except that the fluorescent spot pro
pose is to modulate the cathode beam or pencil
duced upon the ?uorescent screen structure 4 is
46. However, with the arrangement shown by
Figs. 4 through 6, and more particularly by Fig.
divided by the wire member 14 into two parts as
50 can be readily appreciated from an observation
of Fig. 2a which represents a cross-section
through the electron stream on the line A-A
intermediate the aperture 20 and the screen struc
ture 4. From what has been above stated, it
55 will be appreciated that the wire l4 effectively
casts its shadow upon the screen structure 4 but
this shadow is not in any way detrimental to
any detail of the area scanned provided that the
electron beam is swept back and forth across the
60 ?uorescent screen structure in such manner that
the resulting shadow or dark line produced is
perpendicular to the direction of beam motion.
It is also possible in accordance with the teach
ings of this invention, disclosed especially by Figs.
65 2 and 3, to modulate the electrons emanating
from the heated cathode in still another manner
in accordance with this invention. In such form
use is made of a double helically wound ?lament
which is hollow along its axis. With such a con
70 struction a rod-like electrode is then supported
within the hollow portion of the ?lament mem
ber. Such a construction is shown more partic
ularly by Fig. 4 which represents the various
companion parts of a ?lament assembly.
75
In Fig. 4 the filament 34 is formed so as to be
6, it will be seen that the cathode ray beam or 50
pencil 46 is similar to a hollow cylinder as shown
by the section through the beam taken on the
line B—B, whereas the cathode ray pencil l5
of Fig. 2 has a cross—section which consists sub
stantially of two areas bounded by semi-circles. 55
In the operation of the arrangement shown by
Fig. 6 the electrode member 40 tends to spread the
cathode ray beam 46 with any increase in negative
potential. If the anode element 33 has a ?xed
aperture 3| provided at one end thereof and has a 60
constant positive potential impressed thereupon
the beam passing through this aperture will at
all times be constant in cross-section regardless of
the potential impressed upon the modulating elec
trode 4B. The electrode 33 will collect any of the 65
electrons which may have been spread out to cover
a larger area than that of the aperture 3|. Thus,
modulation of the cathode ray beam may be ac
complished without changing its diameter or
boundaries. The luminescent spot produced upon 70
the ?uorescent screen structiu'e 4 will then be of
uniform size, that is, the boundaries will at all
times remain constant, regardless of the modulat
ing voltages impressed thereon.
The cathode ray spot thus produced and con
75
wad-14.0 '
trolled or modulated may be, focused 31)“! the
screen structure in such a way as to eliminate the
dark spot which would naturally be expected from
‘ the hollow nature of the beam.
This focusing
C21 action may be accomplished. by impressing suit
able potentials upon the first and second anode
members .33 and 33a, respectively. As shown by
' Fig. 1', for example, the conical portion 33 of the
tube member is formed of conducting material
10.
and suitable voltages may be applied thereto by
' Way of the metal cap 50 formingcontact there
thereon, means forv maintaining . constant the. _
bounding area of instantaneous impact of
electron stream upon the screen to maintain a
constant outer boundary of the resultant luminous
effect, and a control electrodelocated within the
outer boundary of the electron source electrode for
reducing the electron density of, the projected‘
electron stream withina central portion of the
boundary limits to produce an annular shaped
electron stream with a constant outer diameter
.10
and a variable inner'diamet'er so as to vary there
with in any suitable manner, such as shown for ‘by’ the observable intensity of the luminous effect f
example by my copending application, Serial No. produced.
2. An electron tube which comprises an emissive
643,955, ?led November 23, 1932. Other voltages
surface electrode serving as, a source of electrons, .115,
for operating the tube are-applied to the tip mem
bers or contact points 5i formed as a part of the
base member 2, except that it isusually preferable
a ?uorescent screen coating on the inner surface
of the tube end wall opposite the electron emissive '
to make electrical contact to the de?ecting memV-V , surface, means for causing the electrons generated >
at the’ source to pass toward the ?uorescent end ‘
bers such as the de?ecting plates 6 at points sub
20 stantially
adjacent these members byway of lead
wall of the tube as a pencil of electrons, means for
2,0
maintaining the bounding area of‘ the electron
passing through the tube wall at points closely’ pencil ‘developed constant, means for causing the
electron pencil to traverse the ?uorescent screen
adjacent to the'de?ecting members.
' Without departing from the spirit and scope of 7 according to a predetermined pattern of traversal,
and a control element protruding beyond the cen- :
25 this invention it will be apparent that otherrand
tral portion of the electron sourceandlocated
various waysand means may be provided for con
within the outerboundaries of the emissive sur
trolling the intensity of the ?uorescent spot re
wires connected to the de?ecting elements and
sulting upon the, ?uorescent screen of a cathode
face electrode, said element adapted to have yary- . 7
ray tube or other type of electronic device where? ing voltage applied thereto tovary the electron
density within, a central portion‘of the electron
30 in the effect of variation in the size or diameter of
the resulting ?uorescent spot is avoided, and vI beam to vary the intensity of luminescence pro
there-fore believe myself, in accordance with the :duced over a substantially constant area of the
?uorescent screen. .
.
1
modi?cations of this general scheme herein sug
v3. A cathode ray tube comprising a surface for '
gested, to be entitled tomake and use any and
. emitting a stream of electrons, a target positioned 35
35 all of these modi?cations which fall fairly with
in the spirit and scope of the invention asset in the stream and adapted to luminesce under im
' pactof the electrons, means to focus the emitted
forth by theappended claims.
I
Having thus described the invention, what I electron stream on the target_,‘means to limit and
claim and desire to secure by Letters Patent is the ?x the boundary area of the instantaneouslyim
following:
.
1. An electron ‘device including an electrode
serving as an electron source, means to cause the
electrons emitted to be projected along a prede
pinging electrons and electrode means acting only (
within the ‘emitted electron'stream to variably re- '
move under the control of signals the electrons
from the inner portion of the boundary area of:v '
termined path, an observation screen in the path . impact to vary the intensity of the luminescent
of the projected electrons adapted to become
luminescent when the projected electrons impinge
effects
produced.
'
.
I
RICHARD T. ORTH. '
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