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Патент USA US2407082

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v‘Swift. 3; 1946.
Filed Jan. 27, .1943
t.TuR “PT-.samm,
,by RWW
nol.4.: J06.0
Thei Attorney.
Patented Sept. 3, 1946
RalphP. Johnson and WilliamR. Grams, Sche-~
nectady, N. Y.z assignors: to General Electric
Company, a corporation ofv New York .
Application January 27, 1943‘, Serial No. 473,706
4, Claims. (Cl. 250-164)
~ I
The present invention relates to cathode ray
and associated. means for focusing and de?ect.
devices of’ the. type. known as. dark‘ trace tubes:
ing the electron beam are. well known to those
(for skiatrons) wherein a dark pattern is. produced
skilled; in. the art.v The chamber 5 is closed at.
one endv by a relatively thick. screen-carrying; wall
on a screen, of suitable material by the impinge
ment. thereon of a. beam of electrons. It. is. the
1;- which may be flat,_ or: may have... a. moderate
aim of our invention to improve; the optical eili
' convex curvature toincrease its resistance to cit-e
ciency of. such devices.
ternal air- pressure.
The pattern on thescreen of. a dark tracetube.
Before. the parts“ of- the device are assembled,
may be viewed by light which falls. on the screen.
the‘ interior surface of the tubular part. 6 of. the
from an external source :andis diffusely re?ected. 10 envelope- is coated with a layer‘ 9} of graphite, or
other‘ suitable conducting, medium. ‘ This layer‘
therefrom to the eye of the observer- The pat
or: coating 9‘ may. be applied upon the interior
tern on a dark trace screen also may be projected
by optical means, including a mirror or lens ar
surface; of the tubular part of the envelope be.
ranged to form an enlarged image, the light. em
fore the end closures are. applied. The method
ployed for such projection being incident on the
described in United StatesLetters Patent. 21,264,-‘
358", issued. to
Record, utilizing an: aque
screen. from an external. source. In the past it
ous suspension of: graphite admixed withya dis.
has. been customary to provide on the interior
persi'ng: agent, such. as, bentonite, is; suitable for
surface of the. envelope of cathode ray tubes. an
this purpose. The coating; preferably; is baked
electrically conducting layer,’ for example, a
graphite layer. Such layers alsov were light-ab
in contact with the».
In consequence. of our invention the e?ective
ness; of darktrace cathode ray deviceshas been
The cathode I4 of the electron. gun 8 is con
nected. to. a. negative, terminal. of. a high voltage
source 153 byagroundedconducton IS. The cath
ode is provided with a. ?lamentary heater and
improved by providing, on the interior or exterior
ordinarily, is coatedexternally with. alkaline, earth
surface of a. portion of. theenvelope a. matte
oxideto promote; electron emissivity.
white surface. A large. fraction of the impingElectrically in contact with the conducting:
ing light penetrating through the screen. is. dif
coating-llv and extending; to- the. sealed-in terminal
fusely reflected. from this matte white surface
and is returned. through the screen to the optical
I illiiszaninternal. coating; l I of aluminum, or‘other
system employed for. projecting the image,’ or 30 suitable re?ecting. metal. This coating consti
tutesa the ‘so-called ?nal anode in the device. It is
reaches the observer direct with accompanyingv
advantages as will be explained. In a. preferred
embodiment. of our invention a metallic. re?ect
ing; foundation coating. ?rst is produced on. the
interior glass: surfaceof the envelope; Upon this
reflecting foundation. a layer of matte white. ma
terial is deposited.
Fig. L of the accompanying drawing is a. side.
view of a cathode ray device, shown partly broken
away, and. embodying a preferred form of. our
invention; Fig. 2 is a front view; Fig. 3 illustrates
a. modi?cation; and Fig. 4 is a diagrammatic view
of one form of an optical projection system ems
bodying a dark trace cathode ray device.
connected. through the sealed-in lead l0‘ and a.
conductor l2 to, thepositive terminal of the high.
voltagesource l3. Superimposed onthere?ect
ing layer M is a layer of matte white material
It; which. extends almost to the front wall. ‘I of
the. envelope...
In the fabrication. of‘ the device. before. the
front wall. 1 is applied, aluminum or‘ other; re.
flectingi metal chosen to form the layer IL, is
vaporized in any suitable way, as by high fre
quency induction heating or by passage of cur
rent. through a wire of. refractory metal (not.
shown) on which a. pellet of. the metal to be
Theenvelope of the‘ cathode ray tube of Fig. 1, 45 vaporized has been placed.
which may consist of glass or other transparent
material, is elongated and includes an end cham
her 5 which is of greater diameter than the ad
A suitable gas-free, heat-resisting white. ma
terial, for example magnesium oxide, next is de
on the interior surface of the window 1. The
also occur from a suspension of ?nely divided
posited on the inner surface of the side wall of
joining elongated tubular portion 6. Within the
the cathode ray tube as the indicated layer l6,
tubular portion 6 adjacent the opposite end 50 Fig. 1. In accordance with one method, metal
lic magnesium may be burned in air and the
(broken away in the drawing) is located a so
resulting fumes or smoke conducted into contact
called electron gun 8, whereby a beam of electrons
with the surface to be coated. Deposition may
is projected upon a screen which is deposited
construction and operation of such electron guns 55 magnesium oxide in water. The suspension or
slip is suitably applied and the resulting adherent
distant surface, diagrammatically indicated at
layer is baked at about 400° C. in air. A getter
material, for example barium or magnesium, may
be introduced for the absorption of residual dele
ten'ous gas in the tube. A spring-supported get
ter metal, which can be vaporized by high fre
33 through a correcting lens 34 gripped on its
periphery by a holder 35. If the cathode my
device 30 is one which employs our invention, a
large fraction of the light which proceeds through
the screen of the device and strikes the wall of
quency heating and deposited on the inner sur
the envelope is returned in a forward direction,
face of the neck, 6, is illustrated at IT.
Small‘ masses of suitable screen material, for
that is, through the screen into the concave mir
ror and thence to the ?nal image, increasing its
example potassium chloride, bromide, sodium
chloride 01' other suitable halide of an alkali
brightness and visibility.
We do not wish to limit ourselves to the par
metal, are introduced in such Way that they are I
ticular optical projection system shown in Fig. 4,
deposited on the inner surface of the end wall
‘I. For example, masses of the screen material
nor to the details of construction of the described
cathode ray devices. We have described some
may be held in the shallow metal ‘holders l8 15 of these details, which are not a part of the pres
which are attached to a spring l9 engaging with
ent invention, in order to make clear the nature
wall protuberances 20 (Fig. 2). Heat is applied 7 of our invention and how it is to be performed.
(as by high frequency induction) until the halide
It will be evident to those skilled in the art that
is vaporized.
other details of construction of the cathode ray
The face plate ‘I is fusion-sealed to the rim of 20 device can be chosen, and other forms of optical
the main envelope 5 in any suitable way, for ex
apparatus can be used for viewing the screen or
ample by the combined effect of combustion heat
ing and electrical high frequency heating, as de
scribed in United States Letters Patent 2,306,054
for projecting the pattern appearing thereon,
without departing from the spirit and scope of
the present invention.
issued to Guyer. The electron gun 8 is sealed 25
What we claim as new and desire to secure by
into place and the envelope is exhausted and
Letters Patent of the United States is:
baked to free the walls and enclosed metal parts
1, A cathode ray devicelcomprising a tubular
of deleterious gases, all by well-known technique.
envelope, a dark trace screen therein, means for
The screen material next is deposited on the glass
producing a pattern on said screen and a matte
foundation‘, for example by high frequency heat 30 white re?ector adjacent said screen in such posi
ing of the cups [8 which contain the massive
tion that said reflector will constitute a light
material. It is sublimed and deposits as a thin
diifusing background for a pattern on said said
layer on the inner wall of the face plate 1. The
cathode is activated and the other well-known
2. An electron discharge device comprising an
fabrication steps are taken as usual. The per
elongated envelope, a dark trace screen located
forated electrode or control grid 2| of the electron
at one end of said device, cooperating electrodes
gun is connected by the conductor 22 to a point
in said device remote from said screen whereby
of potential on the source ‘I3 which is negative
electrons may be projected on said screen, and
with respect to the cathode l4. The electrode
a coating of white material on a side wall sur
23 also is connected to the source l3 by a con
face of said envelope adjacent said screen, to
ductor 24, as shown.
increase the visibility of a dark screen pattern
In another form of our invention, as shown
when illuminated by light projected thereon.
in Fig. 3, the inner wall of the envelope 5 is left
3. A cathode ray device comprising an elon
bare except for a narrow strip 25-of a suitable
gated envelope having alcathode-ray-responsive
conducting material, such as graphite, which con
screen at one end thereof, means longitudinally
nects the coating 9 to the sealed-in lead l0. After
displaced in said envelope for projecting a beam
fabrication of the device according to the method
of electrons on said screen, means for de?ecting
outlined above herein, a coat 26 of suitable white
said beam in response to external impulses, a
material, such as an enamel or paint, is applied
coating of light-re?ecting material on the inner
upon the exterior of the side wall of the envelope 50 surface of said envelope adjacent said screen, and
5. To-increase the diffuseness of reflection from
a coating of light-diffusing material superim
the wall of the vcathode ray tube, its inner sur
posed on said re?ecting material.
face may be roughened in any suitable fashion,
4. An electron discharge device comprising an
such as by sandblasting, before the device is as
elongated envelope, ascreen of alkali halide lo_
The advantages of our invention in increasing
the brightness and visibility of a pattern formed
55 cated at one end of said device, an electrode con
on the screen by electron impact appear when our
improved'devices are viewed directly or are em
stituted of an electrically conductive coating on
the inner surface of said envelopeadjacent said
screen, cooperating electrodes in said device re
mote from said screen whereby electrons may be
ployed in' an optical projection system such as 60 projected on said screen, and a coating of mag
the Schmidt projector shown in Fig. 4. As shown
nesium oxide on said conductive coating on an
here, the pattern on the screen of the cathode
interior surface of said envelope adjacent said
ray device 30 is illuminated by a projection lamp
which is diagrammatically indicated at 3|. Light
from the screen thus illuminated falls on the con 65
cave mirror 32 from which it. is projected on a
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