U.S. patent number 3,668,466 [Application Number 05/027,713] was granted by the patent office on 1972-06-06 for electron type fluorescent display device with planar adjacent control electrode.
This patent grant is currently assigned to Sony Corporation. Invention is credited to Satoshi Shimada.
United States Patent |
3,668,466 |
Shimada |
June 6, 1972 |
ELECTRON TYPE FLUORESCENT DISPLAY DEVICE WITH PLANAR ADJACENT
CONTROL ELECTRODE
Abstract
An electron tube having at least two electrodes and a cathode
disposed within an evacuated envelope. One of the electrodes is
spaced generally transversely with respect to the electro beam path
from the cathode to the other electrode. The electrode which is
spaced from the electron beam path is used to control the cathode
current. Means are provided to couple various voltages to the
respective electrodes to accomplish the desired control. The anode
electrode may have a phosphor coating thereon so as to glow when
bombarded by an electron beam from the cathode. Accordingly, an
electron tube of this type is adaptable to display units for the
display of letters, symbols, numerals and the like. In one form of
the invention, the anode electrode and the control electrodes are
arranged in a predetermined pattern to cause elemental areas of the
anode electrode to glow and produce a display.
Inventors: |
Shimada; Satoshi (Tokyo,
JA) |
Assignee: |
Sony Corporation (Tokyo,
JA)
|
Family
ID: |
26368117 |
Appl.
No.: |
05/027,713 |
Filed: |
April 13, 1970 |
Foreign Application Priority Data
|
|
|
|
|
Apr 17, 1969 [JA] |
|
|
44/29863 |
Apr 12, 1969 [JA] |
|
|
44/29865 |
|
Current U.S.
Class: |
345/47; 313/497;
313/517 |
Current CPC
Class: |
H01J
31/15 (20130101) |
Current International
Class: |
H01J
31/15 (20060101); H05b 037/02 () |
Field of
Search: |
;313/109.5,108
;315/169TV |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lake; Roy
Assistant Examiner: Demeo; Palmer C.
Claims
1. An electron tube comprising:
an evacuated envelope with at least one side transparent;
an insulating base mounted in said envelope such that at least part
of a first side is visible through the transparent side of said
envelope;
a first plurality of indicator electrodes mounted on the first side
of the base and arranged in the form of a figure 8;
a second electrode of planar form mounted on said first side of
said base and surrounding said first plurality of indicator
electrodes and lying substantially in the same plane as said first
plurality of indicator electrodes;
a cathode electrode mounted in said envelope adjacent said
indicator electrodes and said second electrode;
a plurality of selector leads mounted on said base and respectively
connected to said first plurality of indicator electrodes;
control means connected to said plurality of selector leads and
adapted to selectively apply a voltage to said indicator electrodes
which is positive relative to said cathode;
a second electrode lead mounted on said base and electrically
connected to said second electrode, and said control means
connected to said second electrode lead to selectively apply a
voltage to said second electrode which can be switched between two
values such that when at one value sufficient current passes
between said cathode and indicator electrodes to render said
indicator electrodes visible and when at the other value
insufficient current passes between said cathode and said indicator
electrodes to render said indicator electrodes visible and wherein
a layer of phosphor material covers said first plurality of
indicator electrodes.
2. An electron tube according to claim 1 wherein opaque material
covers
3. An electron tube according to claim 1 wherein a layer of
phosphor material covers said second electrode in areas adjacent
said first
4. An electron tube according to claim 1 comprising an auxiliary
indicator electrode mounted on said base adjacent said first
plurality of indicator electrodes, and an auxiliary indicator lead
connected to said auxiliary
5. An electron tube according to claim 1 comprising a second
plurality of indicator electrodes mounted on the first side of the
base adjacent the first plurality of indicator electrodes and
arranged in the form of a figure 8, a third electrode of planar
form on said first side of said base adjacent said cathode
electrode and surrounding said second plurality of indicator
electrodes and lying substantially in the same plane as said second
plurality of indicator electrodes, said first plurality of selector
leads respectively connected to said second plurality of indicator
electrodes, and a third electrode lead mounted on said base and
6. An electron tube according to claim 5 wherein a layer of
phosphor material covers said second plurality of indicator
electrodes.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The field art to which this invention pertains is electron tubes
and in particular to electron tubes which are useful for the
purpose of presenting a display of a letter, numeral, or other
symbol.
SUMMARY OF THE INVENTION
It is an important feature of the present invention to provide an
improved electron tube.
It is another feature of the present invention to provide an
electron tube having at least two electrodes and a cathode sealed
in an evacuated envelope.
It is a principal object of the present invention to provide an
electron tube having a control electrode which is spaced generally
transversely of the electron beam path between the cathode and
another electrode.
It is also an object of the present invention to provide an
electron tube having at least two electrodes disposed generally in
a plane wherein one of the electrodes is used to control the
current received by the other electrode.
It is the further object of the present invention to provide an
electron tube as described above wherein the anode electrode is
coated with a luminescent material and is caused to glow when
bombarded with an electron beam from the cathode.
It is an additional object of the present invention to provide an
electron tube which is capable of being used as a display unit to
produce a display of letters, numerals, symbols or the like.
It is another object of the present invention to provide an
electron display tube as described above wherein the control
electrodes are spaced transversely relative to the electron beam
and are used to control the electron beam delivered to elemental
portions of the phosphor coated electrodes.
It is also an object of the present invention to provide an
electron display tube as described generally above wherein the
phosphor coated electrodes thereof are arranged generally in a
figure "8" pattern.
These and other objects, features and advantages of the present
invention will be understood in greater detail from the following
description and the associated drawing wherein reference numerals
are utilized to designate a preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing the principle of an electron
tube of this invention;
FIGS. 2A and 3A are plan views respectively showing fundamental
constructions of the electron tube of this invention;
FIGS. 2B and 3B are cross-sectional views respectively taken along
the lines II--II and III--III in FIGS. 2A and 3A;
FIG. 4 is a plan view schematically showing one example of this
invention as being applied to an amplifier;
FIG. 5 is a circuit connection diagram of the amplifier depicted in
FIG. 4;
FIG. 6 is a diagrammatic plan view illustrating another example of
this invention as being applied to a flip-flop circuit;
FIG. 7 is a circuit connection diagram of the flip-flop circuit
shown in FIG. 6;
FIGS. 8 and 9 are respectively a top plan and a perspective view
schematically illustrating other examples of this invention when
employed as active elements;
FIGS. 10 and 11 are respectively a perspective and a
cross-sectional view schematically showing modified forms of this
invention;
FIG. 12 is a plan view diagrammatically illustrating one example of
an indicator tube made up of the electron tube of this
invention;
FIGS. 13A, 13B, 13C are waveform diagrams showing signals to be
applied to the indicator tube of FIG. 12;
FIGS. 14 and 15 diagrammatically illustrate in cross section
modified forms of the indicator tube produced according to this
invention;
FIG. 16 is a plan view schematically showing the principal part of
the indicator tube of FIG. 15;
FIG. 17 is a schematic diagram showing another modification of the
indicator tube made up of the electron tube of this invention;
FIG. 18 is a plan view for explaining one example of a method for
the manufacture of the indicator tube;
FIG. 19 is a cross-sectional view taken along the line XIX--XIX in
FIG. 18;
FIGS. 20 and 21 are respectively a plan and a side view
illustrating the manner in which an indicator electrode unti
assembly is sealed up in an envelope; and
FIGS. 22 to 32, inclusive, respectively illustrate in cross section
other examples of the electron tube of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
This invention relates to an electron tube which has many
applications as an active element such as in an amplifier, a
switching circuit, a digital logic circuit or the like and also to
an indicator tube for providing a display of numerals, letters,
symbols or the like and, further, to a picture display device. The
electron tube of this invention is simple in construction, small in
size and easy to manufacture.
The electron tube of this invention comprises at least two
electrodes arranged in substantially the same plane and a cathode.
These electrodes and cathode are placed in a vacuum envelope and
arranged so that current from the cathode is controlled by a
voltage applied to at least one of the electrodes.
Referring to the drawings in further detail, a first electrode A
(FIG. 1) is provided and elements G.sub.A and G.sub.B are insulated
from the electrode A and arranged in substantially the same plane.
The elements G.sub.A and G.sub.B are interconnected by a lead to
form a second electrode G. A cathode K is placed oppositely of the
electrodes A and G.
The electrode A is used as an anode, which is supplied with a
predetermined positive voltage, and the cathode K is grounded. The
electrode G is used as a control electrode which is supplied with a
predetermined voltage. With this voltage, a composite electric
field established between the anode A and the cathode K is
controlled, thereby to control the current emitted from the
cathode.
When a small negative voltage is applied to the control grid and
assuming that the composite electric field formed by the negative
voltage and the voltage impressed on the anode A is positive,
electrons generated by the cathode K are derived therefrom and
directed to the anode A. The resulting current varies with the
magnitude of the voltage applied to the control electrode G. Where
the absolute value of the negative voltage impressed on the control
electrode G is relatively great and the composite electric field
established by the above voltage and the voltage fed to the anode A
is negative, there is no anode current.
Consequently, a switching operation can be achieved by the voltage
applied to the control electrode G and, in addition, an input
signal voltage fed to the control electrode G can be amplified.
In the electron tube of this invention the cathode current is
controlled by the composite electric field which is established by
the voltages impressed on a plurality of electrodes. The functions
of the electrodes A and G can be interchanged. Namely, it is
possible to use the electrode G as the anode to be supplied with
the positive voltage and cause the current between the anode G and
the cathode K to vary with the voltage impressed on the electrode A
which is then used as the control electrode.
Further, the cathode K may be pinhead shaped, strip-like or
plate-like and any number of cathodes may be used.
If the surface of the anode A facing the cathode K is coated with a
phosphor material such as ZnO, ZnS or the like, the phosphor
material can be made luminescent by selecting the voltage applied
to the control electrode G. According to my experiments, in a case
where the anode A and the elements G.sub.A and G.sub.B were each
0.3 mm wide; the distances between the anode A and the elements
G.sub.A and G.sub.B were 0.4 mm; the distance between the anode A
and the cathode K was 5 mm; and a voltage of +70 to 80 volts was
impressed on the anode A with a positive voltage applied to the
electrodes G.sub.A and G.sub.B, the phosphor material glowed
completely. When a voltage of -50 or less was impressed on the
elements G.sub.A and G.sub.B, the phosphor material did not
glow.
Accordingly, an indicator tube for providing a display of a number,
character, symbol or the like and a picture display device can be
produced by the use of the electron tube of this invention. By
supplying the anode A with a high positive voltage and the control
electrode G with a lower voltage, only the anode A is lighted even
if the control electrode G has been coated with the phosphor
material.
In the making of such an electron tube the anode A and the control
electrode G are deposited on an insulating base plate S (FIG. 2A)
such as alumina, forsterite, ceramic, glass or the like, and the
resulting assembly is placed in a vacuum envelope.
In FIG. 2A rectangular electrodes G.sub.A and G.sub.B are shown to
be interconnected by a lead L.sub.G. A rod-like cathode K is
disposed above the anode A in parallel relation thereto.
In FIGS. 3A and 3B an annular control electrode G is disposed on
the outside of a circular anode A, and a cathode K is disposed
above the center of the anode A. In this case the cathode K is
secured to the base plate S by suitable means.
FIG. 4 schematically shows a multistage amplifier employing the
electron tube of this invention as an amplifier element in each
stage, and FIG. 5 is a circuit connection diagram of the amplifier.
In this case the amplifier elements of the respective stages are
formed on a common insulating base.
An amplifier element X.sub.1 of a first stage comprises an anode
A.sub.1 and a control electrode G.sub.1 formed by interconnected
elements G.sub.1A and G.sub.1B disposed on both sides of the anode
A.sub.1. An amplifier element of the next stage is similarly
comprised of an anode A.sub.2 and a control electrode G.sub.2
consisting of interconnected elements G.sub.2A and G.sub.2B
arranged on both sides of the anode A.sub.2. An amplifier element
of the output stage comprises an anode A.sub.3 consisting of three
interconnected electrodes A.sub.31 to A.sub.33 and a control
electrode G.sub.3 consisting of four interconnected elements
G.sub.3A to G.sub.3D disposed on both sides of each of the
electrodes A.sub.31 to A.sub.33. Further, resistors R.sub.1A,
R.sub.2A, R.sub.1G, R.sub.2G, and R.sub.3G are used on the same
base and an electrode T.sub.1 is formed on the underside of the
element G.sub.1A through a suitable dielectric to provide a
coupling capacitor C.sub.1. An electrode T.sub.2 is similarly
formed on the underside of the element G.sub.2A to provide another
coupling capacitor C.sub.2, and electrodes T.sub.3A to T.sub.3D are
respectively formed on the undersides of the elements G.sub.3A to
G.sub.3D and are interconnected to provide a coupling capacitor
C.sub.3. An input terminal I, an output terminal O and terminals B,
K' and C are to be connected to the plus and minus sides of a power
source. A strip-like cathode K is disposed above the electrodes and
extends as shown. The resulting assembly is sealed in a vacuum
envelope.
With an input signal being applied to the input terminal I and a
load connected between the terminals B and O, the amplifier of the
above arrangement can be caused to perform exactly the same
amplifying operation as a usual amplifier using vacuum tubes or
transistors. The functions of the electrodes A.sub.1 to A.sub.3 and
those of the electrodes G.sub.1 to G.sub.3 in the amplifier
elements X.sub.1 to X.sub.3 can be interchanged as indicated
above.
FIG. 6 illustrates a flip-flop circuit employing the electron tube
of this invention as an active element and FIG. 7 is its circuit
connection diagram. Active elements, of the same construction as
those X.sub.1 and X.sub.2 in FIG. 4 are formed on a common base,
and electrodes T.sub.1, T.sub.2 and T.sub.3 are respectively
deposited on the undersides of elements G.sub.2A, G.sub.1B and
G.sub.1A through dielectric members to form capacitors C.sub.1,
C.sub.2 and C.sub.3. Resistors R.sub.1A, R.sub.1G, R.sub.2A and
R.sub.2G, a trigger input terminal T, a terminal B connected to the
plus side of a power source, a ground terminal E and an output
terminal P are provided as shown. A strip-like cathode is disposed
opposite the electrodes, and the resulting assembly is sealed in a
vacuum envelope. In this case, if a luminescent material is coated
on anodes A.sub.1 and A.sub.2 of both active elements X.sub.1 and
X.sub.2, the anodes of the elements glow when switched "on," so
that it can be detected visually which element is in the on
state.
When the electron tube of this invention is used as an active
element, especially in cases where many circuits are required, such
constructions as shown in FIGS. 8 and 9 can be employed. In FIG. 8
elements and circuits are formed on both sides of a base plate S
shaped in the manner of a folding screen and cathodes K are each
provided in common to the elements formed on opposing surfaces of
adjacent plate portions. In FIG. 9 a plurality of base plates, each
having elements and circuits formed on both sides thereof, are
disposed side by side in parallel relation to one another, and
common rod-like cathodes K are each disposed between adjacent
bases.
The so-called hybrid integrated circuit device can also be produced
by mounting a semi-conductor device on the base.
The electron tube of this invention may be of a construction shown
in FIG. 10 in which an anode A and electrodes G.sub.A and G.sub.B
of an annular configuration are formed on the inner wall of a
cylindrical base S, and a rod-like cathode K is disposed at the
axis of the cylinder. It is also possible to adopt a construction
depicted in FIG. 11 in which the anode A and electrodes G.sub.A and
G.sub.B are formed on the inner wall of a ring-shaped base plate S,
and a pinhead-like or strip-like cathode K is placed at the axis
thereof.
In short, the electrodes need not always be placed in exactly the
same plane, but may lie in slightly offset planes.
In FIG. 12 there is illustrated an example of the electron tube of
this invention as applied to an indicator tube of a matrix-like
construction. Namely, one indicator electrode unit or a display
unit 1 is made up of a first electrode group consisting of a
plurality of first electrodes A.sub.1 to A.sub.7 which extend
parallel to one another, and are arranged in substantially the same
plane. A second electrode group consisting of a plurality of second
electrodes G.sub.A1 to G.sub.A6 which extend, for example,
vertically parallel to one another and which are arranged in
substantially the same plane above the first electrode group while
being insulated therefrom. A third electrode group consisting of a
plurality of third electrodes G.sub.B1 to G.sub.B5 which extend
vertically intermediate between adjacent second electrodes G.sub.A1
to G.sub.A6 and are insulated from the first and second electrode
groups. In this indicator tube the first electrodes A.sub.1 to
A.sub.7 are sequentially arranged in common with the respective
display units. The second electrodes G.sub.A1 to G.sub.A6 of each
unit are interconnected by a common lead L.sub.GA, and the third
electrodes G.sub.B1 and G.sub.B5 are respectively connected to
selector leads L.sub.GB1 to L.sub.GB5. The first electrodes A.sub.1
to A.sub.7 are coated with a phosphor material, and a common
cathode K (not shown) is disposed above the respective display
units.
In this case the minimum unit area caused to glow is a portion of
each of the first electrodes defined by the space between adjacent
electrodes of the second electrode group and respective electrodes
of the third electrode group. Accordingly, each display unit has 35
luminescent units, and these luminescent units are selectively
caused to glow to provide a display of a predetermined numeral,
letter or the like.
The luminescent units are lighted by impressing a positive
predetermined voltage to the second electrodes and applying a
positive predetermined voltage to those electrodes of the first and
third electrode groups which correspond to one another.
The second electrodes G.sub.A1 to G.sub.A6 are supplied with a
voltage E.sub.GA through the lead L.sub.GA for a time T as shown in
FIG. 13A. In a first period T.sub.1 (FIG. 13C), which is one-fifth
of the time T, the electrode G.sub.B1 is supplied with a voltage
E.sub.GB, and the electrodes A.sub.2 and A.sub.7 are respectively
supplied with a voltage E.sub.A as depicted in FIGS. 13B and 13C.
In a second one-fifth period T.sub.2, (FIG. 13C), the electrode
G.sub.B2 is supplied with the voltage E.sub.GB, and the electrodes
A.sub.1, A.sub.6 and A.sub.7 are supplied with the voltage E.sub.A.
In a third one-fifth period T.sub.3, the electrode G.sub.B3 is
supplied with the voltage E.sub.GB, and the electrodes A.sub.1,
A.sub.5 and A.sub.7 are supplied with the voltage E.sub.A. In a
fourth one-fifth period T.sub.4, the electrode G.sub.B4 is supplied
with the voltage E.sub.GB and the electrodes A.sub.1, A.sub.4 and
A.sub.7 are supplied with the voltage E.sub.A. In the last
one-fifth period, T.sub.5, the electrode G.sub.B5 is supplied with
the voltage E.sub.GB and the electrodes A.sub.2, A.sub.3 and
A.sub.7 are supplied with the voltage E.sub.A. Thus causing
predetermined luminescent units on the electrodes A.sub.1 to
A.sub.7 to glow from left to right sequentially in a time
divisional manner to provide a display of a numeral "2" in the
entirety of the display unit. In this manner, desired numerals,
letters, or symbols can be sequentially indicated by the respective
display units. In this case, if the leads L.sub.GA, L.sub.GB1 to
L.sub.GB5 are provided on the back of the base, the indicator tube
can be made correspondingly smaller in size.
In the illustrated example the second and third electrode groups
are arranged perpendicular to the first electrode group but they
need not always cross the latter at right angles thereto and may
cross obliquely. Further, as will be apparent from the description
in connection with FIGS. 1 to 3, the indicator tube need not always
be comprised of three electrode groups but may be formed with two
electrode groups.
The electrode A which is coated with a luminescent material may be
in the form of a sheet metal as shown in FIG. 14. In this case
parallel electrodes G.sub.1, G.sub.2, G.sub.3, . . . are formed
substantially flush with one another on one surface of the sheet
electrode A through insulating layers I.sub.1, I.sub.2, I.sub.3, .
. . as of mica, glass or the like and a phosphor material is laid
down on those areas of the electrode A which are defined between
adjacent electrodes G.sub.1, G.sub.2, . . . as indicated by
4.sub.1, 4.sub.2, . . . A cathode K is located opposite the
electrodes, and the resulting assembly is sealed in a vacuum glass
envelope 3.
A phosphor area may be formed separately as exemplified in FIGS. 15
and 16. The figures illustrate an indicator device of the same
construction as that of a shadow mask color picture tube. Reference
character A indicates a sheet metal having bored therein apertures
H.sub.11, H.sub.12, H.sub.13, . . . H.sub.21, H.sub.22, H.sub.23, .
. . H.sub.31, H.sub.32, H.sub.33, . . . sequentially arranged in a
lateral and a vertical direction. On one surface of the apertured
sheet metal A a plurality of parallel electrodes G.sub.A1,
G.sub.A2, G.sub.A3, . . . are provided adjacent to insulating
layers I.sub.A1, I.sub.A2, I.sub.A3, . . . , thus constituting a
first electrode group. On the other surface of the sheet metal a
plurality of parallel electrodes G.sub.B1, G.sub.B2, G.sub.B3, . .
. are provided adjacent to insulating layers I.sub.B1, I.sub.B2,
I.sub.B3, thus constituting a second electrode group. The resulting
assembly is sealed in a vacuum glass envelope 3, and a suitable
number of cathodes K.sub.1, K.sub.2, K.sub.3, . . . are disposed in
the envelope 3 at suitable locations.
A phosphor material is coated on the inner wall of the envelope 3
on the opposite side from the cathodes, providing a phosphor area
4. The phosphor area 4 is caused to glow at desired locations by
selectively applying a positive voltage to the electrodes G.sub.A1,
G.sub.A2, . . . G.sub.B1, G.sub.B2, . . . under such conditions
that the sheet metal A is supplied with zero or positive voltage,
and the phosphor area 4 is supplied with a high voltage. When a
predetermined positive voltage is applied to the electrodes, for
example, G.sub.A1 and G.sub.A2, G.sub.B1 and G.sub.B2, the cathode
current passes through the aperture H.sub.11 surrounded by these
electrodes and impinges upon the phosphor area 4 to cause it to
glow at a location under the aperture 11. Applying a predetermined
positive voltage to the electrodes, for example, G.sub.A2 and
G.sub.B2, the currents from the cathodes K.sub.1 and K.sub.2 pass
through the four apertures H.sub.11, H.sub.12, H.sub.21, and
H.sub.22 near the electrodes and strike the phosphor area 4 to
light it at positions just under the apertures. Consequently, not
only numerals, letters, symbols or the like but also pictures can
be displayed by sequential radiation of the phosphor area at
predetermined positions and, further, the display can be provided
in color.
In the above example the apertures are aligned in rows and in
columns and the electrodes G.sub.A1, G.sub.A2, . . . and G.sub.B1,
G.sub.B2, . . . are arranged to extend perpendicular to each other,
but these electrodes may be oblique to each other as well.
In FIG. 17 the indicator electrode unit is made up of a plurality
of indicator electrodes arranged in the form of a number "8" and is
designed to indicate any number "0" to "9" by selective radiation
of the indicator electrodes. Seven strip-like indicator electrodes
A.sub.1 to A.sub.7 are arranged on an insulating base in the form
of the number "8", and a dot-like electrode A.sub.8 for decimal
indication is located in the vicinity of the foot of the assembly.
Another electrode G (FIG. 18) surrounds the electrodes A.sub.1 to
A.sub.7. Such display units are sequentially aligned along the
length of the base. The electrodes A.sub.1 to A.sub.7 may be formed
by means of printing and baking of a conductive paint containing
silver powder or the like, and by etching or punching of sheet
metal or the like. The electrodes A.sub.1 to A.sub.8 are
respectively connected through leads 6.sub.1 to 6.sub.8 to selector
leads 10.sub.1 to 10.sub.8 extending in the direction of array of
the display units, and the electrode G is connected to a lead
6.sub.9. Then, a phosphor material is coated on the surfaces of the
electrodes A.sub.1 to A.sub.8, and a common cathode K is disposed
opposite the indicator electrode units.
By applying a positive voltage of, for example, 20 volts to
predetermined ones of the electrodes A.sub.1 to A.sub.8, under such
conditions that the electrode G is supplied with a voltage of -20
to -100 volts, composite electric fields established near the
electrodes supplied with the positive voltage are made positive.
Therefore, these electrodes glow to display a desired number.
Application of a positive voltage to the electrodes, for example,
A.sub.1, A.sub.3, A.sub.4, A.sub.6 and A.sub.7 leads to a display
of a number "3" and application of a positive voltage to the
electrodes A.sub.1, A.sub.2, A.sub.3 and A.sub.6 results in the
display of a number "7".
In this case it is also possible to coat the phosphor material on
the electrode G for lighting the surrounding area of a number being
displayed in such a manner that a number, for example, "8" is
displayed by lighting only the electrode G and "0" is indicated by
lighting the electrodes G and A.sub.4.
By providing the selector leads 10.sub.1 to 10.sub.8 on the
opposite surface of the base plate on which are formed the
electrodes A.sub.1 to A.sub.8 and G, the base plate can be narrowed
correspondingly.
In the construction of such an indicator device it is preferred
that a driving device for actuating the indicator device be also
enclosed in the glass envelope together with the indicator
assembly.
Referring now to FIGS. 18 and 19, a description will be made of one
example of the way of making such indicator tubes. The manufacture
begins with the preparation of an insulating base 5 formed of, for
example, alumina, ceramic, forsterite, glass or the like. On one
surface of the insulating base 5 seven strip-like electrodes
A.sub.1 to A.sub.7 are arranged in the form of a number "8," and a
dot-like electrode for decimal indication is disposed in close
proximity to the foot of the assembly. Further, leads 6.sub.1 to
6.sub.8 for connecting the electrodes A.sub.1 to A.sub.8 to
selector leads are extended to the marginal portions of the base
plate 5, and a lead 6.sub.9 is formed for leading out another
electrode which surrounds the electrodes A.sub.1 to A.sub.8.
Display units, each having the electrodes A.sub.1 to A.sub.8 and
the leads 6.sub.1 to 6.sub.9, are sequentially located along the
length of the base plate 5. In addition, terminals 7.sub.1 to
7.sub.8 are provided for external connection of the selector leads.
Electrodes A.sub.1 to A.sub.8 and the leads 6.sub.1 to 6.sub.9 and
terminal 7.sub.1 to 7.sub.8 may be formed by means of printing and
baking or, for example, silver paint, a molybdenum-manganese alloy
or the like. The molybdenum-manganese alloy is readily oxidized, so
that when the electrodes and the leads are formed of this alloy,
they are plated with nickel so as to prevent oxidation. Then, the
surfaces of the electrodes A.sub.1 to A.sub.8 are coated with the
phosphor material.
Next, glass frit, for example, is coated by printing on the base
plate 5 except on those areas where the electrodes A.sub.1 to
A.sub.8 have been formed and except on the end portion of the base
5 where the terminals 7.sub.1 to 7.sub.8 have been formed. Then the
insulating base 5 is baked to form thereon an insulating layer 8.
The insulating layer 8 is not formed on the electrodes A.sub.1 to
A.sub.8 but, in practice, the insulating layer 8 is formed across
the electrodes A.sub.1 to A.sub.7 so as to join electrodes G which
will be subsequently deposited on the insulating layer 8 inside and
outside of the electrodes A.sub.1 to A.sub.7.
In the insulating layer 8 small windows 9.sub.1 to 9.sub.9 are
bored each just on one end of each of the aforementioned leads
6.sub.1 to 6.sub.9 in such a manner that the ends of the leads are
exposed through the windows 9.sub.1 to 9.sub.9. Then, the electrode
G is formed on the insulating layer 8 surrounding the electrodes
A.sub.1 to A.sub.8 and selector leads 10.sub.1 to 10.sub.8 are
formed on the marginal portions of the base plate 5 which extend in
the direction of array of the display units. In this case these
leads 10.sub.1 to 10.sub.8 are respectively connected at one end to
the terminals 7.sub.1 to 7.sub.8. Thus, the electrodes A.sub.1 to
A.sub.8 are respectively connected to the terminals 7.sub.1 to
7.sub.8 through the leads 6.sub.1 to 6.sub.8 and selector leads
10.sub.1 to 10.sub.8. Further, the electrode G is formed over the
window 9.sub.9, too, and hence is connected to the lead 6.sub.9. On
the back of the base 5 a lead and its terminal are previously
formed, so that the lead 6.sub.9 of the electrode G in each display
unit is connected to the lead and terminal on the back of the base
5.
Thereafter, the electrodes G, the leads 10.sub.1 to 10.sub.8 and
the terminals 7.sub.1 to 7.sub.8 are coated with an opaque material
to prevent their radiation. A common strip-like cathode is mounted
by suitable means on the base 5 in opposing relation to the display
units, though not shown, thus providing the plurality of display
units, and the base 5 is sealed in a glass envelope.
It is preferred to seal the base 5 in a glass envelope 3 in a
manner to project out therefrom the end portion of the base 5 on
which are formed the terminals 7.sub.1 to 7.sub.8 for leading out
the electrodes A.sub.1 to A.sub.8, and the lead on the back of the
base plate 5 for leading out the electrode G, though not shown, as
illustrated in FIGS. 20 and 21. In the event that the base 5 is
formed of ceramic, glass or the like, the open end portion of the
envelope 3 can be readily closed by applying to the open end
Pyroceram cement (Trademark) made by Corning Glass Works, as
indicated by 17' in FIG. 21. When the base plate 5 is thus sealed
up in the glass plate 3 with the end portion 5a of the base plate 5
projecting out therefrom, the terminals 7.sub.1 to 7.sub.8 formed
on the end portion 5a can be used as external leads. This
eliminates a process for attaching external leads to the base and
simplifies the placement of the base in the glass envelope, which
allows ease in the manufacture of the indicator tube, reduces the
manufacturing cost and provides for enhanced mechanical strength,
as compared with a method wherein external leads are connected to
the terminals 7.sub.1 to 7.sub.8 on the base 5 and the base 5 is
entirely sealed in the glass envelope with the external leads
partially projecting out therefrom.
A description will be given of examples of the method by which the
electron tube of this invention used as an active element or
indicator tube as above described is sealed in and attached to a
vacuum container such as a glass envelope. In the drawings the
active element or indicator tube is symbolically indicated by a
base S and electrodes A and G formed thereon.
The base having formed thereon the device may be entirely sealed in
the vacuum envelope, but it is also possible that the base plate
itself forms one portion of the envelope as shown in FIG. 22, in
which a dish-like glass vessel 12 is mounted on the base plate S in
a manner to cover the electrodes A and G. In this case the vessel
12 is secured at marginal portion to the base S by the use of, for
example, fused glass frit, cement or the like.
In FIG. 23 one end portion of the base S projects out from an
envelope 13, namely, the envelope 13 is sealed up at the projecting
end portion of the base S, and a multi-connector socket 14 is
engaged with the projecting end portion. Reference numeral 22
designates a support for mounting a cathode K on the base S. This
method is possible in the case where the base is not an insulating
plate but a metal plate as in FIGS. 14 to 16.
Where the base plate projects out from the glass envelope, the base
plate and the glass envelope equally receive external heat, so that
they are equally expanded and electrode leads L formed on the base
plate can be used as external leads. Accordingly, this method
lessons the number of steps in the manufacturing process, as
compared with the case where external leads are connected to the
terminals formed on the base and the external leads partially
project out from the glass envelope.
The cathode need not always be located opposite the electrodes A
and G but may be disposed, for example, substantially flush with
the electrodes A and G as depicted in FIG. 24. In this case,
although a dish-like glass vessel 12 is mounted on the base plate S
by glass frit as in the case of FIG. 22, annular electrodes A and G
are concentrically formed, with the electrode G being inside of A
and a cathode K being disposed substantially flush with the
electrodes A and G at their center.
In the case where the device is sealed in the vacuum envelope, the
operation of the device is sometimes affected by a change in the
internal electric field due to charge produced on the envelope
wall, for example, by touching on the envelope by hand or due to an
external electrostatic field. To avoid this, a transparent
conductive coating, a mesh, netting or wire-like conductor as of
graphite, aluminum or the like is deposited on the inner wall of an
envelope 14 and is connected, for example, through a contact piece
16 to a lead formed on the base S and led out from the envelope,
through which lead the conductor 15 is always held at a suitable
potential.
FIG. 26 illustrates another modification in which a grid electrode
is provided as indicated at 17 or 18 between the electrodes A and B
in the vicinity of the cathode K, and the grid electrode is
supplied with a predetermined voltage so as to promote emission of
thermoelectrons. The grid electrode may be in a spiral form.
It is also possible to provide a plurality of cathodes and maintain
them at different DC potentials, as depicted in FIG. 27 in which
two cathodes K.sub.1 and K.sub.2 are provided opposite the
electrodes A and G. In this case, the cathode, for example K.sub.1,
is held at ground potential; the cathode K.sub.2 is supplied with a
voltage of 20 volts; the electrode, for example, G is held at
ground potential; and the electrode A is supplied with a voltage of
50 to 100 volts. With such potential distribution, electron
currents from the cathodes K.sub.1 and K.sub.2 are controlled by
the composite potential on the electrodes A and G in such a manner
that electrons are derived from the cathode K.sub.1 at all times
and that electrons are derived from the cathode K.sub.2 when the
voltage applied to the electrode A exceeds a certain value. In this
case it is also possible to vary the voltage fed to the electrode G
or to vary the potential applied to the cathode, for example,
K.sub.2 while holding constant the voltages applied to the
electrodes A and G. FIG. 28 shows the case in which electrodes
A.sub.1, A.sub.2 and G.sub.1, G.sub.2 are provided on both sides of
the base S while being respectively interconnected through
apertures bored in the base S, and cathodes K.sub.1 and K.sub.2 are
located on both sides of the base plate S. The operation of this
device may be achieved in the same manner as in the case of FIG.
27. The constructions such as exemplified in FIGS. 27 and 28 are of
particular utility when employed in amplifiers or the like.
The cathode may be a source of free electrons which are secondarily
generated by heat, irradiation by light rays, electron rays,
radioactive rays, X-rays, cesium or the like or high-frequency
heating from the inside or outside of the envelope. In FIG. 29, a
heater 19 is disposed near the cathode K and in FIG. 30 the cathode
K is irradiated by the sun's rays through a lens 20. In short, the
cathode may be of any type utilizing irradiation by light.
In the making of the indicator tube it is also possible to form the
base S of semitransparent or transparent glass or like material and
the electrodes A and G of a transparent conductive coating so that
a number being displayed may be seen from the back of the base
plate S, that is, from the opposite side from that where the
electrodes A and G are formed, as indicated by the arrow. In such a
case, the cathode K may be formed relatively large.
In FIG. 32 a conductor 21 for preventing the influence of charge on
the envelope wall or external electrostatic field previously
described with FIG. 25 is provided on the side of the base plate S
where the electrodes A and G are formed so that the conductor 21
may not be noticeable when viewed from the back of the base plate
S.
As will be understood from the foregoing, the electron tube of this
invention has a wide range of applications as an active element in
such circuits as amplifiers, switching circuits, digital logic
circuits, and indicator tubes for displaying a number, letter,
symbol or picture. Further, the electron tube of this invention is
made up of at least two electrodes disposed in substantially the
same plane and a cathode, and hence is very simple in construction,
small and flat and easy to make.
* * * * *