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Патент USA US2124224

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Juuly 19, 1938-
Filed Feb. 1, 1935
s - Sheets-‘Sheet 1
1111/, 71/170,711”(7/10/71!
-. July 19, 1938.
2,124,224 _
Filed Feb. 1, 1935 ' \
:5 Sheets-Sheet 2'
July 19., 1938.
2,124,224 I
Filed Feb. 1, 1955
s Sheets-Sheet 5
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2,124,224 ’
Patented July 19, 1938
John C. Batchelor, New York, N. Y.
Application February 1, 1935, Serial No. 4,494
4 Claims. ‘ (Cl. 250-275)
provide a cathode ray tube having a v?uorescent
My invention relates to ?uorescent screens, screen so prepared‘ and mounted that the heat
and, more particularly, to such screens for use in generated therein may be dissipated easily, there
cathode ray tubes designed to produce high in
by making possible greater intensity of illumlnal
tensity illumination suitable for the production
5 of television images which may be enlarged by
tion and reducing the possibilty of destroying, by
overheating, the ability of the ?uorescent screen
to produce light under the in?uence of electronic
It is customary in the art to produce cathode
ray tubes having a light producing member com ' bombardment.‘
In accordance with my invention, I prefer to
prising a ?lm of ?uorescent material, such as ' use as a ?uorescent member in a cathode ray tube, 10
willemite, zinc sulphide or the like, deposited upon a wire gauze or perforated metal plate, in the in
tube »
an inner surface of ‘the glass envelope-ofthe
terstices of which has been placed material capa
or on a mica or other light transmitting ‘plate
within the envelope of the tube, such that the
?uorescent film may be scanned rhythmically by,
15 a modulated electron beam; to produce ;upon. the
?uorescent screen .a visible image of a remotely
ble of producing ?uorescent light when struck by
rapidly moving electrons. In such a member the
metal of the gauze or plate serves effectively to
transfer the heat generated by the electron im
pact away from the point of impact and distribute
it over the entire area ofv the screen. Further, in
.accordance with my invention, I have provided
‘netic energy of the moving electrons of the elec
such a ?uorescent member with heat radiating
20 tron beam into visible radiation through the proc- . members attached for the purpose .of radiating
ess of ?uorescence is relatively low, and the the heat generated in the ?uorescent member.
area of impact of the ele tron beam is relatively Still further, I have, in cases where the energy to
small, so that each elemental area of a ?uorescent be dissipated is greater than can be radiated
screen is required to dissipate the heat energy through the vacuum of the tube, provided means 25
25 which arises from the ine?icfent energy trans ‘for heat conductive communication between the
. formation in the ?uorescent screen. Because of metal of the ?uorescent member and heat radi
the relatively low thermal conductivity of the flu- ating members disposed externally to the tube so
orescent material, of the glass or other material that the heat may be transferred conductively to
upon which the ?uorescent material, is deposited the air about the tube. For-use in cases where‘ 30
analyzed object. "
,. '
The e?iciency of the transformation of the ki
and of the'vacuum in the space within the tube
adjacent the screen, there is ‘but little removal of
heat by conduction, ‘and,
my ?uorescent member, I have provided liquid
consequently, the tem- - cooling means external to the tube and in heat,
perature of the ?uorescent screen itself will rise
to such a value that the heat will be dissipated by
extreme amounts of heat are to be removed from
It is known that the efficiency of cathodo-lumi
nescence decreases quite rapidly when the tem
perature of the luminescent material is increased,
and for this reason there is a maximum intensity
40 vof electron bombardment beyond which no fur
conductive communication with the ?uorescent
In order to explain my invention more fully, I
shall refer to the appended drawings, of which
Figure 1 is a se‘ctional'view of one embodiment of
my ‘invention; Figure 2 is a sectional view of the
?uorescent screen portion of [a modi?ed embodi 40
ment, the section being taken on the line 2-2 in
ther increase in luminosity occurs with increase 'Figure 3; Figure 3_is an end view of the'embodi
in bombarding intensity. Furthermore, even in merit shown in Figure 2; Figure 4 is a sectional‘
the absence of such a decrease in e?iciency with view of the ?uorescent screen portion of a fur
temperature, there is another temperature I at ther modi?ed embodiment; Figure 5 is a sectional
which the chemical and/or crystalline structure view of the ?uorescent screen portion of a still
of the ?uorescent material is so altered that its further modi?ed embodiment; Figure 6 _repre—
ability to ?uoresce is permanently eliminated, and sents an enlarged sectional view of a ?uorescent‘
' this temperature must never be reached by a ?u
orescent-screen in a cathode ray tube.
With the foregoing in mind, it is an object of
my invention to provide a cathode ray tube capa
ble of producing a small television image of such,»
luminous intensity that it may be projected to a
large size with sufficient brilliancy for. convenient
55 viewing. A further object of vmy invention is to
screen; Figure '7 is a full view of a portion of an
other embodiment of my invention; Figure 8 is an
end view of the embodiment shown in Figure 'I.
In the cathode ray tube shown in Figure 15a _ ‘
disc I of woven wire mesh is mounted on the
metal support ring 2 which is in turn carried
by the lead-in wires 3 in the stem 4 which is in 5,5
turn sealed into the glass envelope Sin a manner
such that thefdisc I will lie adjacent the window‘
8 in the end of the envelope 5.
Prior to the insertion of‘ the disc I into the
tube 5 the interstices of the disc I are ?lled with
a ?lm ‘I of ?uorescent material, as shown in
Figure 6. The ?lm ‘I may be introduced into
the interstices of the disc I by any of a number
of methods. For example,‘ the disc I may be
10 dipped into a suspension of ?uorescent powder
in a liquid in which the material is insoluble, then
withdrawing the mesh disc allowing the interstices to remain ?lled with the suspension which,
upon drying of the suspending liquid, will leave
v15 a film of ?uorescent material within the inter
stices of the gauze. As an alternate method, a
suspension of the ?uorescent material may be
painted or sprayed onto the. screen in such a
conducting material‘ such as copper, and are
preferably blackened by any suitable process such
as carbonization.
In the case of tubes in which the energy to be
dissipated from the screen is very large, my tube
is built as shown in Figure 4. A section of cop
per cylinder I5 is inserted at the end of the
glass tube at I 6 by a glass to copper seal, and
said copper cylinder carries at its opposite end
the plate glass window I‘I. Mounted by means 10
of the metal ring' I8 on the cylinder I5 is the
screen I carrying the ?uorescent material ‘I.
This type of construction provides the periphi
eral cooling surface I9 exposed to the air, and,
when larger amounts of heat are to be dissipated, 15
I have provided radial fins 20 to cause additional
cooling. In some extreme cases I have provided
manner that the interstices will be ?lled with _ a water or liquid coolant jacket 2| in Figure 5
having a liquid inlet 22 and outlet 23. In this
rate. Another method comprises rolling the case I have found it convenient to provide a local 20
radiator 24 as shown in Figures 7 and 8, for cool
?uorescent material, either dry or in a suspend
ing the liquid. It should be noted' that in the
ing liquor, into the mesh by means of a suit
able roller. Although the ?uorescent material embodiment shown, the radiator 24 is disposed
will in general remain in position without the for free circulation of air when the tube is mount
aid of any binding material, it is possible'in cases ed in a vertical position; the radiator may, how 25
when still greater tenacity is required to intro~ ever, be built to provide suitable cooling for any
duce a small quantity ofany suitable binder such desired angle of mounting. This radiator may,
further, be provided with a fan for cooling it,
as sodium silicate in water. As a result of the
or it may depend entirely upon normal air cir
30 presence of the metal mesh within the screen any
heat which is generated locally is very rapidly culation; a pump for circulating the liquid may 30
conducted to the remaining area of the screen, be provided if desired. Obviously the cooling
liquid need not be water, but may be any liquid
and the ?uorescence of the spot being bom
barded is not, therefore, impaired by excessive of suitable thermal capacity, viscosity and chem
ical inertness. For example, ,a liquid may be
35 temperature.
20 the suspension, and the liquor allowed to evapo
When consideration is given to the facts that
the thermal conductivity of metals is of the order
of 0.1 to 1.0 calory per second per centimeter
cube per degree centigrade whereas that of glass
chosen having su?iciently low freezing tempera
ture that danger of freezing'will be eliminated
when the instrument is in storage. The cooling
system may be hermetically sealed in order to
prevent loss of coolant by evaporation or spilling.
40 is of the order of 0.002 calory ‘per second per
From the foregoing it will be seen that in Fig 40
centimeter cube per degree centigrade, it may be
2, 3, 4, 5, 7 and 8, associated with the mosaic
seen that the insertion of mycooling members '
in screens is advantageous when the greatest ?uorescent screen structure comprising wire
distance from the ?uorescent material to metal gauze or a perforated metal plate and ?uore'sQ
is 0.1 inch and the thermal conductivity of the cent material disposed in and closing the rela
metal is 0.1 calory per second per centimeter cube tively minute openings as described, there are 45
means in direct, heat conductive relation with
per degree centigrade. In this casethe dissi
pation of heat from the ?uoresoentscreen is in respect to the screen structure only at the outer
excess of that from a screen deposited directly" edge portion thereof, and that such means op
upon a glass wall of a cathode ray‘ tube 0.1 inch erate to induce heat removal from each of the
thick and the outer surface of said wall exposed individual elemental sections of the mosaic in 50
directions substantially radially outwardly from
directly to air.
center of the screen structure.
The interior of thetube 5 is coated with a film
It is apparent that any suitable metal may be
8 of metal preferably darkened on the inside to
prevent internal re?ection of light from the used as the material for the wire gauze carrying
screen. Contact is made to the metallic vcoating the ?uorescent material; I prefer copper or silver 55
8 by the wire 9 sealed into‘ the bulb, and the because of their relatively high thermal con
coating serves as an accelerating and focusing ductivity and their stability at elevated tempera
tures in vacuum. Further, the gauze may be re
electrode for the electrons coming ‘from the elec
placed by a perforated metal plate.
60 tron gun III. The number of electrons in the
A compromise must obviously be effected in .60
beam is controlled by the control electrode II.
The electron beam may be caused to scan the
screen I by electromagnetic fields applied adja
cent the neck of the tube in the region I2, or
as an alternate method, de?ecting plates, (not
shown) may be inserted in the neck of the tube
in the region'IZ.
In the event the electron beam is of consider
able intensity or the voltage is su?lciently high
70 that the total heat reduces the quantity of ?uo
rescent light, heat radiating ?ns I3, Figures 2
and 3, have been attached to the screen sup
porting ring 2 for the purpose of dissipating the
heat transmitted to the ring'2 from the wires
II in the screen I. These ‘fins are of any heat
choosing the correct ratio of wire area ‘to open
ing area inv the gauze used. When the'ratio
becomes too large the electrooptical translation
efficiency becomes quite low because of the ab
sorption of electrons by the wires of the gauze; 65
when the ratio is too small the ruggedness of the '
screensuffers because of the relatively large ex~
panse of unsupported ?uorescent material, and
also the cooling effect of the wires is not as great
as is desirable because of the reduced cross sec
tional area of the wires. I have found a region
from unity to- one-tenth to be suitable values
for this ratio of wire area to opening area, but
the range may be extended under favorable
conditions. It is apparent that as this ratio
2, 124,224
cent material. Almost all ?uorescent materials
grows smaller the cooling e?iciency of the sys
lose ‘some emciency above certain temperatures,
tem becomes smaller because oi the relatively
low heat conductivity of the ?uorescent mate
and it is therefore advisable not to exceed those‘ .
rial itself. Heat generated by the center of any . temperatures in operation. For this reason my
span ‘I, Figure 6, of the ?uorescent material in
a single interstice must traverse more of itself
to reach the wires H as the ratio becomes small
er, and consequently the size of the. openings
invention should be considered to be applicable
to any ?uorescent material exhibiting this char- >
acteristic, and to any cathode raytube'using one
or more of these materials.
I claim:
In a cathode ray tube, a ?uorescent screen, 10
rescent material at the center of any interstice an1.electron
gun whereby an electron beam may
will not become too hot. I have found it con ; be caused to impinge said screen, said screen com
venient to use a woven wire mesh having sev
prising a member formed of heat conductive ma
eral interstices in the area of one element of the
' must be made su?icientiy small that the 11110
image being reproduced; ‘Thus, if, for example,
a four hundred line picture were to be reproduced
in a screenarea two inches square, there would
be 200 lines per lineal inch of mesh, and it it
were desired that each picture element should
- cover four interstices of the mesh, there would
be required two interstices in each direction per
image element so that the mesh would have 400
interstices per lineal inch.
Tubes in use prior to my invention have shown
marked decrease in the electrooptical eiilciency
of ?uorescence when the energy of bombardment
is greater than one watt per square inch of area
terial and having openings therein and ?uores
cent material in said openings, a portion of the 15
surface of said member being exposed to elec- I
tronic bombardment from said electron beam‘
whereby secondary electrons may be drawn from
said ?uorescent material.
2. In a cathode ray tube, a ?uorescent screen 20
comprising a member iormed'ot heat conductive
material having a thermal conductivity of the
order oi.’ 1.0 calory per second per centimeter cube
per degree centigrade and said member having
openings therein,v a ?uorescent material sup 26
ported by said member in said openings and in
intimate contact with said member. I
in the ?uorescent screen, whereas, with the em
3. In a cathode ray tube, a ?uorescent screen
‘ bodiment of my invention in an otherwise similar - comprising a member formed of heat-conductive
tube, substantially constant electrooptical er material having'openings therethrough and ?u
?ciency is maintained with intensities of bom orescent material supported by said member in
bardment in excess of 25 watts per‘ square inch, said openings, the ratio of the total projected
' and thus, the factor limiting the intensity of "area of said heat conductive material in the plane
bombardment in such tubes is no longer the abil
of the member to the total area of the openings
ity of the ?uorescent screen to dissipate heat, in
said plane being in the region from unity to
but is the design of an electron gun capable of
concentrating su?lcient current in a sufficiently
4. In a cathode ray tube, mosaic ?uorescent
small area.
structure comprising a member formed of
A further advantage oi the presence of the screen
material and provided with rel
gauze is the improvement in the collection of the atively minute openings
therethrough, ?uores 40'
secondary emission from the screen and the resul
cent material disposed ‘in and closing said open
tant more e?icient utilization of the beam. In ings, the ?uorescent material in the individual
‘general, a tube of this nature depends upon openings being exposed on both sides of said
secondary emission to remove the charge vwhich
structure, and means associated with said
would otherwise accumulate'on the. screen, and screen
screen structure and in direct heat conductive 45
it is apparent that the gauze will collect the sec
relation with respect thereto only at the outer
ondary electrons with less space charge imped
ance than would the metallic coating 8 whose edge portion thereof and operating to induce
function that collection would be in the absence heat removal from each individual elemental
of the gauze.- The e?iciency oi’ this collection section of the mosaic in directions substantially,
.may be still i'urther increased by the removal of radially outwardly from the center of said screen
the ?uorescent material ,irom the wires ll onthe structure.
back or bombarded side of the screen‘ I.
My inventimi is in no way limited in ?uores
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