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Патент USA US2413020

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Dec. 24, 1946.
_ w. FSWOLFNER, 2D
2,413,020
ELECTRONIC RELAY
Filed May 19, 1945
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Patented Dec. 24,1946 »
2,413,020
UNITED STATES PATENT OFFICE
2,413,020
ELECTRONIC RELAY
William F. Wolfner, II, Asbury Park, N. J ., assign
or to Photoswitch Incorporated, Cambridge,
Mass., a corporation of Massachusetts
Application May 19, 1943, Serial No. 487,671
5Claims. .(Cl. 250-27)
~
1
2
The present invention relates to electronic de
ad ‘form a conventional diode. It will be under
vices and especially to relays which respond to
stood that two separate tubes, a controlled elec
changes of the value of a detecting impedance.
tron discharge means and an uncontrolled elec
Some of the principal objects of the invention
tron discharge means each in its individual Vessel,
are to provide a relay of the above-mentioned
may be used and that the tube or tubes may
general type which is very sensitive and detects
include conventional supplementary electrodes
comparatively slight changes, such as of the order
such as suppressors and screens.
of less than 5% of the value of the detecting im
A bridge net-work Nl comprises a probe con
pedance in the input circuit, but which is suffi
denser Cl, a bridge condenser C2 and two re
ciently rugged to permit use in industrial in 10 sistors RI and R2, one of which may be con
stallations as for example as level detector, to
tinuously adjustable and the other of the ex
provide an electronic device containing a detect
changeable plug-in type. The probe condenser
ing bridge circuit coupled to an ampli?er through
Cl may consist of two plates l and 2 forming a
a separate sensitive unbalance detector, to pro
gap 3. If the device according to the invention
vide a voltage detecting circuit which reacts only
is used as a level detector, plates I and 2 will be
to change of a controlling voltage in one direc
vertically arranged so that gap 3 will contain
tion, and to provide an electronic detecting cir
liquid or another agent 4 con?ned in tank 5, when
cuit which can be regulated to react to an event
the level of that agent reaches the probes.
to be detected with an appreciable time delay so
Cathode kl of tube Tl is connected to a point 0
that premature or accidental operation is fore 20 between condenser C2 and resistor El, and grid
stalled.
gl is through a limiting resistor connected to a
One important feature of the invention, the
point 112 between condenser Cl and resistor R2.
above-mentioned unidirectional unbalance de
The outer terminals of condensers Cl and C2 are
tector, includes potential apportioning triode and
connected to line B, and the outer terminals of
diode circuits on either side of a condenser whose 25 resistors El and R2 are connected to adjustable
charge changes with the changing controlled con
tap S of potentiometer R6. Plate at is connected
ductivity of the triode and affects a control poten
to line termbinal A in series with a load re
tial derived'from the rectifying diode. In an
sistor R3.
other aspect, the invention involves conversion
The anode ad of the diode portion of tube Tl
of a controlling alternating voltage, derived from 30 is connected to a voltage combining and rectify
and in phase with the voltage of a conventional
ing load network N2 comprising a capacitance
supply line, into an alternating voltage of a phase
means such as condenser C3 which is connected
in opposition to the supply phase and hence
at x, y respectively, between the two anodes at
adapted to provide a blocking potential to a tube
and ad, resistors RA and R5 connected in series
in the supply circuit.
between condensers C3 and tap S and a con
These and other objects, features and aspects
denser Cll connected at a point 2 between resistors
will be apparent from the following description
R4 and R5.
of a practical embodiment illustrating the char
An ampli?er tube T2 has a cathode k2 con
acter of the invention; this description refers to
nected to line terminal B, a grid g2 connected to
a drawing in which
40 point z of network N2 and an anode a2 connected
Fig. 1 is the circuit diagram of a level control
to a coupling network N3.
installation incorporating the present invention;
Network N3 comprises a load resistor R8 in
and
parallel to a condenser C5 and connecting anode
Figs. 2 and 3 are diagrams illustrating the
a2 to line terminal A.
operation of the circuit according to Fig. 1.
45
A third ampli?er tube T3 has a cathode 703
Fig. 1 shows two line terminals A, B which may
connected to line wire A, a grid 93 connected to
for example supply 60 cycle alternating current.
the tube side of network N3, and a plate a3 con
A potentiometer R6 is connected between line
nected to line terminal B through relay magnet
terminals A and B and may be in series with the
M in parallel to a sustaining condenser C6. Mag
heater elements hl, h2, 723 of the tubes used in
net M may operate a switch Sm which in con
the circuit.
ventional manner controls for example a signal
A double duty electron discharge tube Tl com
device ll or a motor that drives apparatus for
prises a cathode kl, two anodes at and ad re
?lling tank 5.
spectively, and a grid gl which constitutes, with
It should be noted that tubes T2 and T3 con
kl and at, a conventional triode, whereas kl and 55 duct in different directions and are related to
2,418,020
networks N2 and N3 as follows. The conductivity
of T2 depends during the half cycles when line
wire A is positive, on the grid-cathode voltage
of T2 which again depends on the condition of
4
B is positive, so that magnet M remains deene'r
gized.
Recapitulating the condition of the circuit
while bridge NI is balanced, the triode portion
of Tl is then conducting together 'with the diode
portion, the grid-cathode voltage of tube T2 is
more positive when line terminal A becomes posi
certain amount of current, charges during these
tive, T2 is conducting, and T3 is non-conducting
conducting periods condenser C5 to such a degree
with M deenergized.
that the charge of C5 will, during the half cycles
If now the material 4 in tank 5 rises until
when line terminal B is positive, render grid 93 10
probe plates l and 2 become immersed into that
su?iciently negative to make T3 non-conductive
or at least incapable of energizing magnet M to
material the dielectric properties of which differ
from those of air, the capacity of condenser Cl
operate switch Sm. If now network N2 causes
grid g2 to become more negative and hence tube
will increase, and ‘bridge NI becomes unbalanced
with a voltage appearing between cathode kl and
T2 less conductive, condenser C5 will be charged
to a lesser degree during the half cycle series
grid gl, which renders gl negative when line ter
when A is positive, and correspondingly 93 will
minal A is positive, so that tube TI is now less
be more positive, and T3 more conductive during
conductive during these half cycles.
the other half cycle series when B is positive,
The alternating component passed by condenser
with the result that M will be energized when 20 03 becomes under these conditions considerably
the cathode-grid potential of tube T2 is com
greater than before, since there exists now a
paratively more negative.
considerable plate voltage change across the tri
This arrangement operates as follows:
ode portion of Tl during both half cycles where
It is assumed that, under normal conditions,
as, as pointed out above, appreciable voltage
the plate gap 3 of detecting condenser Cl is free 25 change occurred previously only during those half
from any agent other than the air therebetween,
cycles when tube TI is non-conductive. This
and that the bridge network Nl has been so bal
considerable voltage change or gradient during
anced, by means of adjustable resistor Rl, that
the conducting half cycles, together with that
there exists no potential di?erence between points
during the half cycles with line terminal A neg
0 and p or cathode kl and grid gl. Tube Tl
ative, provides a greater voltage across condenser
will then carry current in its triode portion with
C3. As indicated at V0’ and Vr’ of Fig. 3, this
anode at positive, during the half cycles of the
higher voltage across C3 which counteracts the
supply alternating current when A is positive, as
drop in resistor R5 makes more negative the volt
indicated in Fig. 2, where V5 is the supply voltage.
age Vb’ between tap S and grid g2, decreases the
network N2. The plate current of T2 and net
work N3 is so selected that tube T2 carrying a
The plate potential of the diode portion of tube 35 conductivity of tube T2, and renders grid g3 of
tube T3 more positive since condenser C5 fur
TI with respect to cathode kl is composed of the
nishes now less counterpotential against the drop
alternating component of the potential at triode
in resistor R8 during the half cycles when line
anode at with respect to cathode lcl, as passed
terminal B is positive and tube T3 is in condition
by condenser C3, and of potential components in
troduced into the diode circuit by network l<:l— 40 to conduct. With grid 93 more positive, tube T3
o—Rl—S—-R5-—R4-—ad. During the half cycles
becomes more conductive, and magnet M is ener
gized, operating whatever device is controlled by
when line terminal A is positive and tube Tl
switch Sm.
conducts, the potential at .r is not subject to
By properly dimensioning condenser C5 the
much variation. During the other half cycles,
when tube TI is non-conductive, the potential at 45 time interval between response of tube T3 and
a: and therefore at 1/ changes in accordance with
decrease in conductivity of tube T2 can be con
the line voltage. The potential at a: with respect
to kl is indicated at V0 Of Fig. 2. The poten
tial at y is also in?uenced by the voltage drop
across Rl, of the general shape of Vs, as ap
plied in series with resistors R4 and R5.v The
capacity of condenser C3 is preferably chosen to
be comparatively large so that no appreciable
trolled according to well known principles; hence,
by making condenser C5 comparatively large it
is easily possible to avoid premature or acciden
tal response of relay M, for example due to mo
mentary immersion of probe plates l and 2
caused by splashing of liquid.
'
It will be noted that the present circuit re‘
voltage drop appears across it; it acts as. a cou
sponds only to unidirectional change of the de
pling or boosting element and at the same time
tecting value, that is tube Tl Will react only to
as a blocking element passing to point y voltage
change of the bridge voltage, from balance, in
variations appearing at point a: but blocking the
one direction, namely a change rendering grid gl
more negative. In the particular bridge circuit
flow of a direct current component between these
shown in Fig. 1, this corresponds to an increase
points.
The resultant of these voltages is recti?ed in 60 in capacity of condenser Cl. If response of the
circuit to decreasing capacity is desired, the
the diode portion of TI and smoothened into a
bridge may be adjusted to be normally unbal
steady direct voltage by resistor R4 and con
anced, so that decreasing capacity of the de
denser CG, as indicated at Vr of Fig. 2. This
tecting condenser will balance the bridge. A sim
recti?ed voltage between y and S is added to the
ilar result can be obtained by interchanging con
voltage drop across R5 which is‘ positive when
line terminal A is positive and tubes TI and T2
denser Cl and resistor Rl, in which case, how
the detecting condenser can not be
are conducting, the sum of these voltages con
' ever,
stituting the cathode-grid potential of tube T2.
It should be understood that the present dis
As indicated at Vb of Fig. 2, the bias of grid g2
of that tube is so adjusted by means of slider P closure is for the purpose of illustration only and
that this invention includes all modi?cations and
S that, with bridge Nl balanced, tube T2 passes
equivalents which fall within the scope of the
enough current to effect a voltage drop in R8
appended claims.
’ '
'
which, as above described, renders grid g3 of tube
T3 sufficiently negative to prevent that tube from
becoming conductive during the half cycles when
1. In an electronic control device wherein a
grounded.
'
.
.
5
2,413,020
6
probe impedance of an alternating current bridge
network affects the voltage between the control
electrode and the cathode of a controlled electron
discharge means having at least three electrodes,
an uncontrolled rectifying electron discharge
connected between said anodes, and a load net
work in the anode circuit of said rectifying dis
charge means, the voltage across said capacitance
and hence across said load network varying with
Ll
varying conductivity and hence alternating volt
means having an anode and a cathode which is
age variation in the anode circuit of said con
connected to said cathode of said three electrode
means, a capacitance connected between said
anode and the anode circuit of said three elec—
trode means, and a load impedance in the anode
circuit of said rectifying discharge means, the
trolled discharge means upon unbalance of said
bridge network due to change of dielectric mate
rial between said probe plates, as compared with
the substantially constant voltage variation in
the anode circuit of said rectifying discharge
voltage across said capacitance and hence across
said load impedance varying with varying con
ductivity and hence voltage variation in said
means.
anode circuit of said three electrode discharge
means upon unbalance of said network, as com
pared with the substantially constant voltage
4. In an electronic control device wherein a
detecting impedance of an alternating current
bridge network aiiects the voltage between the
control electrode and the cathode of an electron
discharge means having at least three electrodes,
an electron discharge device having two anodes,
variation in said anode circuit of said rectifying
discharge means.
a control grid associated with the ?rst one of said
2. An electronic control device comprising an 2-0 anodes and a cathode common to both anodes,
alternating current bridge network including a
means associated with said network and said
detecting impedance, a controlled electron dis
cathode and control element for varying the con
charge means having anode, cathode and control
ductivity between said cathode and said ?rst
electrode, means associated with said network
anodeupon variation of said detecting impedance,
and said cathode and control element for vary
a capacitance connected between the circuits of
ing the conductivity of said discharge means
said anodes, and a load impedance in the circuit
upon variation of said detecting impedance, an
of said second anode, the voltage across said
uncontrolled rectifying electron discharge means
capacitance and hence across said load imped
having an anode and a cathode connected to the
ance varying with varying conductivity and hence
cathode of said controlled discharge means, a '
alternating voltage variation in the circuit of
condenser connected between said anodes, and a
said ?rst anode upon unbalance of said network,
load impedance in the anode circuit of said recti
as compared with the substantially constant volt
fying discharge means, the volt-age across said
age variation in the circuit of said second anode.
condenser and hence across said load impedance
5. An electronic control device comprising a
varying with varying conductivity and hence al
source of alternating current; a controlled circuit
ternating voltage variation in the anode circuit
including potential apportioning means; a con
of said controlled discharge means upon varia
trolling circuit including a ?rst electron discharge
tion of said detecting impedance, as compared
means having anode and cathode connected .to
with the substantially constant voltage variation
said source and having conductivity control
in the anode circuit of said rectifying discharge 40 means, and detecting means associated with said
means.
control means for varying the conductivity of
3. An electronic level control device comprising
an alternating current bridge network having in
said discharge means; a second, recti?er, electron
one of its arms condenser means including two
?xed plates constituting probes with a gap there
between adapted to be penetrated by material
whose level is to be detected, a controlled elec
tron discharge means having anode, cathode and
control electrode, means for applying the output
voltage of said bridge between said cathode and
said control element, an uncontrolled rectifying
electron discharge means having an anode
and a cathode connected to the cathode of
said controlled discharge means, a capacitance
discharge means having a cathode connected to
the cathode of said ?rst discharge means and an
anode associated with said potential apportioning
means of said controlled circuit; and condenser
means connected between said two anodes; the
charge of said condenser means and hence the
potential of said apportioning means of said con
trolled circuit varying with the current variation
in said controlling circuit and hence with the
e?‘ect of said detecting means.
WILLIAM F. WOLF'NER, II.
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