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Патент USA US2132216

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@Cito 4, 1938.
Filed July 51, 195e
Patented Cet. 4, 1938
l 2,132,216
Herbert Nelson,'BloomIield, N. J., assigner, by
mesne assignments, to Radio Corporation of
America, a corporation of Delaware
Application July 31, 1936, Serial No. 93,539
2 Claims. ' (Cl. Z50-27.5)
My invention relates to 4electron discharge de
vices, more particularly> to such devices useful
as visual indicators of voltage and having an
electrode which is rendered luminous, and has
the appearance of afilament of light which may
be of constant height-~ and varying intensity oi
incandescence and'which changes in response to
the change in the magnitude of the applied volt
age, a device of this character being particularly
useful as a tuning indicator in radio receiving
It is an object of my invention to provide an
electron discharge device of the kind described,
which is particularly suitable for use as a visual
tuning indicator in a radio receiving set Vand in
which resonance is indicated by a brilliant lumi.
nous glow of an electrode.
VIn general _my invention comprises an envelope
having within it a straight ñlamentary anode and
a pair of straight thermionic cathodes positioned
on opposite sides of and parallel to said anode.
Around each cathodeis mounted a straight tubu
lar control electrode‘parallel to the cathode and
>having a longitudinal slit opposite and parallel
to the ñlamentary anode and through which elec
trons from the cathode are projected toward the
anode to l'make it incandescent in response to
electron bombardment. In operation the elec
The electron discharge device or tuning indi
cator tube shown in Figure 1 comprises van
evacuated envelopel I 0 provided with the usual v"5
stem and press II, and base I2.
`In accordance with my invention I mount ver
tically Within the`> envelope a pair of parallel
straight preferably oxide coated ñlamentary type
thermionic cathodes I3 and support them at the i10
lower ends by means of lead and support wires
I4 mounted in the press II, their upper ends by
means of springs I5 electrically connected in
series through the back support I6 mounted in
the glass bead I‘I, which is in turn supported by
the back support I8 mounted on the press II.
Positioned between these cathodes and coexten
sive with and parallel tov the cathodes is the
filamentary type anode I9 which receives elec
trons from the cathodes I3 during operation of *N
the tube. The filamentary anode preferably a
une tungsten wire is supported at its lower end
jfrom a lead-in and support wire 20 and at its
upper end by' a spring 2IA attached to the back
support I8. Although I specifically show a ñla- ‘2
mentary type anode a strip of small mass could
serve equally as well since it could be heated to
incandescence by electron bombardment.
trons» ñowvfrom thev cathodes to the anode with
control the ilow of electrons from the ñlamentary l
suñicient velocity to bombard the anode and ren
der it incandescent. The control electrodes are
so connected in a radio receiving circuit that
when the circuit is tuned to resonance with an
each cathode a tubular control member 22 prefer
ably of sheet metal provided with a slot or open
incoming signal the ñlamentary anode becomes
incandescent while when the set is not tuned to
resonance the anode is dark. The tube is sensi
tive to small changes in control voltage and in
a properly designed circuit the anode can be
changed from a dark color to bright incandes
40 cence with only a 2 volt change on the control
'I'he novel features which I believe to be char
acteristic of my invention are set forth with par
45 ticularity in the appended claims, but the inven
tion itself will best be understood by reference
to the following description taken in connection
with the accompanying drawing in which Figure
1 is a perspective View of an electron discharge
ing a tube made in accordance ’with my inven
device embodying my invention with parts broken
away to show details of construction; Figure 2
is an enlarged transverse section taken along line
2--2 of the tube shown in Figure 1; Figure 3 is
a transverse section of a modification of Figurel
55 2; and Figure 4 shows a circuit arrangement us
cathodes I3 to the anode. I9 I provide around 30
ings 23 parallel to and opposite the anode I9.
The electrons from the cathodes I3 pass through
05 5
the slots 23 to the anode I9. These control elec
trodes are supported at their lower end by means
of a metal collar 24 supported in turn by the
support rods 25 mounted in the press I I. While
I show a pair of cathodes and control electrodes, 0
a single cathode and control electrode can be
used. The upper end of the electrode assembly
may be properly spaced by means of the mica
spacer 26.
In operation the voltage applied to the control
electrodes 22, determines the intensity of incan
descence of the anode I9. The less negative this
control electrode 22 is biased with respect'to the
cathodes I3, the brighter will be the incandescent
portion of the anode I9, inasmuch as more elec 50
trons from the cathodes reach the anode than
when the negative bias on the control electrode
is large the electrons reaching the anode are fewer
and the anode is dull red or dark.
In this em
bodiment of my invention the incandescent por
tion ofthe voltage or tuning indicator may be
viewed from the side of the tube With ease.
Referring to Figure 2, which shows a transverse
section of the tuning indicator shown in Figure l,
the control electrodes 22, are so biased that when
no signal is being received the voltage difference
between the control electrodes 22, and the cath
odes |3,vis such that the anode is dark, that> is
the relatively high negative potential ion. the con
indrical members surrounding the cathodes I3
and joined at the back to provide a background
against which anode I9 can be viewed. The con
trol electrode is in eiîect a tubular member hav
ing separate chambers around each cathode,
each chamber having a longitudinal opening
parallel and opposite to the anode for permitting
electrons to reach the anodes, and a longitudinal
j’o'pening in the side Wall through which the anode
can be viewed.
10 trol electrodes or cylinders permits ‘few if‘ any
While I have indicated the preferred embodi
electrons to get through the slots 23 to the anode“
I9. As the set is tuned to resonance the voltage ment of my invention of which I am now aware
and have also indicated only one specific appli
difference between the cathodes and the >elec
trodes becomes less, so that the control leffect ofl cation for which my invention may be employed,
15 theY electrodes 22 on the electrons leaving the> ."itiwillbe apparent that my invention is by no 15
cathodes |3 is less, permitting more electrons ' meansv limited to the exact forms illustrated or
from the cathodes I3 to reach the anode I9, so> the use indicated, but that many variations may
that When the set is tuned to resonance the anode
be made in the particular structure used and the
is incandescent and easily seen. Y
purpose for which it is employed without depart
The application of an electron discharge de-" ing from the scope of my invention as set forth 20
Vice made in accordance with: my invention toa
in the
radio circuit is shown in Figure 4. Normally
Y «What I claim as new is:
the cathodes I3, heated byrbattery 29, _are‘elec
trically connected through a biasing battery. 3D,
25 to one side of a loadresistor 3|, the voltage across
which is to be measured and which may for ex
ample be in the> a.--V.-c. portion ofthe circuit.
«The control electrodes 22 are connected tothe
other side of the resistor 3 l;
The anode voltage is
supplied by battery 32. With no Voltage. onvthe
controlelectrodes 22, veryA few electronsI and
hence very little current flows through the tube
between thev cathodes and anodes `due tothe
biasing voltage on the control >electrodes 22 and
35 the anode is dark. Any-voltage dropacross re~
sistor 3| is >in, opposition to the biasing battery
1. An electron discharge device having an en
velope, a pair of straight parallel thermionic
cathodes` within the envelope for emitting elec 25
Vtrons, a straight ñlamentary anode positioned
between and parallel to said cathodes for receiv
ing electrons from said cathodes, and a control
electrode for each cathode vand comprising a
tubular conductor partially surrounding ~ .the Y30
cathode and having parallel to the cathode and '
Opposite the anodean opening through‘which
electrons reach the anode.r
2.- An electron discharge device having an en
velope, a pair. of rparallel straight thermionic f
3e. As the voltage _drop across resistor 3| ín
creases when the set is tuned to resonance `the
cathodes within said envelope for emitting elec
trons, a straight ñlamentary anode ybetween and
parallel to the'cathodes, and coextensive there
effective biasing voltage on. the controlïelecf
trodes.22 decreases. Under these circumstances
with, and a control electrode for said cathodes
comprising a tubular electrode of sheet metal (.40
the control electrodes 22 become~less negative
With respect to the cathodes I'3`,„and more elec
trons go through the slots 23 to the anode. ` Thus Y
the anode becomes incandescent as the negative
45 bias
on the control
of .the
tuning 22indicator
decreases._tube is
made use of When'connected for example to a
coni'fentional` automatic volume control circuit
in which resistor 3| maybe placed. `
appended claims.
In the modiñcation shown in Figure 3 the'con
trol electrode 2'I comprises two conductingkcyl
partially surroundingsaid cathodes and anode,
and>` providing a separate chamber around each
cathode, eachf chamber vhaving> parallel and
opposite saidranode an. openingthrough _which
electrons can pass from each cathodeto said
anode, said control electrode having alongi
tudinal opening in the >wall parallel to said anode
through which the ñlamentary anode _can be
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