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Патент USA US2125073

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July 26, 1938.
o. D. KNOWLES
2,125,073
LIGHT SENSITIVE SYSTEM
Filed April 25. 1930
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Patented July 26, 1938
2,125,073
UNITED STATES PATENT OFFICE
2,125,073
LIGHT- SENSITIVE SYSTEM
Dewey D. Knowles, Wilkinsburg, Pa., assignor to‘
Westinghouse Electric & Manufacturing Com
pany, a corporation of Pennsylvania
Application April 23, 1930, Serial No. 446,482
9 Claims.
(Cl. 250-415)
My present application is a continuation, in
part, of my pending application, Serial No.
149,290, filed Nov. 19, 1926, and assigned to West
inghouse Electric 8: Manufacturing Company,
5 that deals, in particular, with electronic relays.
The present invention relates to improvements
in light-sensitive apparatus of which an elec
tronic relay forms an essential element, and it
has particular relation to devices of this type
10 wherein means is provided for varying the sensi
According to one modi?cation of my inven
tion, I provide a light-sensitive system compris
ing an electronic relay, a plurality of photo-cells
and a variable impedance. The principal elec
trodes of the relay are connected to the terminals 5
of a power source, the photo-cells provide a po
tential conductive path between one principal
electrode and the control electrode of the relay,
and the impedance is connected between the re
maining principal electrode and the control elec- 10
tivity.
trode. The impedance is, furthermore, respon
Light-sensitive apparatus, of this nature, con
structed according to the teachings of the prior
art, with which I am familiar, comprises, chie?y,
varies therewith, thus varying the illumination
15 an electronic relay actuated from a source of
power and controlled by a plurality of light
sensitive cells. ‘
It often happens that apparatus is used in
localities where the power supply is not constant
20 but has comparatively large periodic and random
?uctuations.
These variations seriously impair
_ the utility of the apparatus, since account of
them must be taken in designing the apparatus,
and, as a result, a comparatively large margin
25 must be provided over which the system does
not operate. In the present tra?ic-control sys
tems, wherein equipment of this nature is pro
vided as the operating element, a variation of
i
48% in the light ?ux eii'ecting the photo-cells
30 is required.
It is, accordingly, an object ‘of my invention
to provide light-sensitive apparatus the vsensi
tivity of which is adjustable.
Another object of my invention is to provide,‘
35 in light-sensitive apparatus, means for compen
sive to ?uctuations in the power source and
required to actuate the relay.
'
In a more speci?c application of my inven- 15
tion, the variable impedance comprises a photo
cell energized by a source of light heated from
the same power supply that yields the voltage
for the electronic relay.
The novel features that I consider character'- 20
istic of my invention are set forth with particu
larity in the appended claims. The invention
itself, however, both as to its organization and
its method of operation, together with additional
objects and advantages thereof, will best be un- 25
derstood from the following description of spe
ci?c embodiments, when read in connection with
the accompanying drawing in which;
Figure 1 is a view, partly in elevation and
partly in section, of the discharge tube described 30
in my copending application to which reference
was hereinabove made.
Fig. 2 is a schematic drawing showing a cir
cuit from which my invention has been devel
sating for variations in the operating potential.
Oped.
Fig. 3 is a schematic drawing showing the gen
An additional object of my invention is to pro
vide a gaseous relay, the response of which is,
eral form that a circuit comprising my invention
within predetermined limits, independent of the
Fig. 4 is a schematic drawing showing a gen
eral form of my improved apparatus,
Fig. 5 is a graph that will be utilized in de
40‘ value of the difference of potential supplied be
tween the electrodes thereof.
It is still another object of my invention to
provide an electronic relay wherein the value of
the potential difference required to cause a dis
45 charge between the cathode and the anode in
creases as the potential dl?erence between these
two electrodes is increased.
More speci?cally stated, it is an object of my
invention to provide, in light-sensitive apparatus
50 of the type incorporating an electronic relay,
an impedance disposed between the control elec
trode and one principal electrode of the relay,
and responsive to variations in the electromotive
force applied to the principal electrodes of the
55 relay.
35
takes,
40
scribing the theoretical basis of my improvement,
and
Fig. 6 is aschematic drawing showing a spe
cific form of my improved apparatus.
45
The apparatus shown in Fig. 1 comprises a
glass envelope l having a press 2 mounted there
in from which are supported a cylindrical cath
ode 3 and a central anode 4. The anode 4 is
surrounded by a glass tube 5 which is either 50
continuous with, or is welded to, the material
of the press 2. A metallic screen element 6
surrounds the glass tube 5 and fits closely over
the upper end of the anode 4.
The tube contains an inert gas, such as argon 55
2.
2,125,074;~
or neon, at a pressure oi’ approximately 2 milli
meters of Hg, and the screen element 6 is sepa
rated from the anode by a distance preferably
less than the mean-free-path of an electron in
the gas, at this pressure.
_
Suitable conducting leads ‘I, 8 and 9 extend
from the various electrodes to the exterior of
6 and the anode 4 is less than the mean-free
path of the electrons in the gas, and, consequent
ly, the collisions that take place in the gas be
tween these two electrodes is not su?lcient to
cause a disruptive discharge between these elec-.
trodes. The tube is then virtually non-conduc
tive.
‘
‘
-
the tube and are connected to a plurality of
If, however, Zc'iS large and Z9. is small, the drop
contact posts l0, H, I! carried by a base ele
in potential between the cathods 3 and the grid 6
is large, and the drop in potential between the
10 ment 13 into which the tube is cemented.
The cathode 3 and the anode 4 are customarily . anode 4 and the grid 6 is small. It Zc is large
designated as the principal electrodes of the dis
chargetube, while the screen element 6 is termed
the control electrode or grid.
It is well to mention here that the separation
15
between the screen element 6 and the anode 4
is more than an academic matter related to the
kinetic theory of gases, in this connection, and
has distinct physical signi?cance. It is a well
enough, su?icient drop in potential may exist be—
tween the cathode 3 and the control electrode 6
to cause a discharge therebetween.
25 minimum value for a certain distance between
the control electrode 6, necessary to cause a
The gas column through which the discharge 15
takes place is now in a highly ionized state and,
consequently, theimpedance between the oath
ode 3 and the grid, 6 is relatively small. Virtually,
the total electromotive force E is, therefore, now
20 established experimental fact that the electro- ‘ applied between the grid 6 and the anode 4 and,
motive force required to cause a disruptive dis
as a result, the insulating gas between the grid
charge between two electrodes of a gaseous dis
and the anode breaks down, and a heavy current
charge is not a permanently decreasing function flows through the tube.
'
of the distance between the electrodes but has a
The impedance Zc between the cathode 3 and
the electrodes and rapidly increases, thereafter,
as the distance between the electrodes is de
creased. Quantitative comparisons between the
electrode spacing at which the break-down volt
30 age begins to increase, and values of the mean
free path of an electron in the gas between the
electrodes, determined from independent physical
considerations, have established the prediction
35
trons. By decreasing the probability of collision,
the contribution of molecular ionization toward
e?‘ecting a break-down of the tube is decreased
collect on the control electrode 6 and establish
that the two values are approximately equivalent.
The explanation of the phenomenon from the
and, consequently, the difference in potential that
must be applied between the principal electrodes
to cause a discharge is correspondingly increased.
In view of the above explanation, it is seen that,
in a discharge tube of the type described herein
} above, the drop in potential, between the cathode
and- the grid 6, that is required to cause a disrup
tive discharge, may be considerably smaller than
the corresponding drop in potential between the
.
55 grid 6 and anode 4.
In operation, impedances l5 and I6 are con
nected between each principal electrode and the
85
70
75
cause a discharge in the tube decreases.
It should be noted that, if the control elec
trode 6 is entirely insulated from the anode 4
and the cathode 3, the ?rst ?ow of electron cur
rent from the cathode results in an accumulation 35
of electrons on the control electrode and causes it
to block the ?ow of further electron current.
In Fig. 2, an arrangement of the apparatus is
shown whereby a discharge tube I may be op
erated. In this case, the control electrode is, 40
under normal circumstances, insulated from both
the anode and- the cathode. That is to say, the
impedances between the electrodes are very large.
standpoint of the kinetic theory of gases is simple.
Physically, the mean-free path is simply some
form of the mean distance between two successive
collisions of a random electron in the gas. One
40 of the principal active elements in producing a
disruptive discharge is the ionization eiTected by
the collisions between the molecules and the elec
60
discharge in the tube, depends on the drop in
potential between the principal electrodes 3 and
4 and on impedance Zc. As the drop in poten
tial between the principal electrodes increases,
the value of impedance Zc that is necessary to 30
control electrode of the tube, and a di?erence of
potential is applied by a generator ll between the
principal electrodes of the tube.
Let Za be the impedance l5 between the anode
4 and the control electrode 6, and Zc be the im
pedance l6 between the cathode 3 and the con
trol electrode 6. The drop in potential between
each of the principal electrodes 3 and 4 and the
control electrode 6 is dependent on Za and Zn.
If Z3 is large and Zn is small, the drop in poten
tial between the anode 4 and the control electrode
6 is large, while the drop in potential between
the cathode 3 and the control electrode 6 is small.
As a result, the electron current drawn from the
cathode 3 to the control electrode 6 is small, and
a disruptive discharge does not take place be
tween the two electrodes 3 and 4. 0n the other
hand, the distance between the control electrode
Electrons ?owing from the cathode 3, therefore,
a negative potential blocking the ?ow of further
electrons therefrom.
To provide for the leakage of the electrons from
the control electrode 6, a photo-electric cell I9
is connected between the electrode 3 and the 50
ground 20. The anode 2| of the cell I9 is con
nected to ground 20 and the cathode 22 to the
grid 6 of the tube. The grid circuit is completed
through the distributed-capacity-to-ground 23 of
‘the secondary 24 of the transformer 25, which
supplies the voltage between the principal elec
trodes 3 and 4.
When the photo-electric cell I9 is energized,
the blocking charge continually leaks away from
the grid 6, and a permanent difference of poten 60
tial is established between the grid and the‘
cathode 3 which results in a break-down of the
tube I. As shown in Fig. 2, the discharge cur
rent excites a relay 21 which, as a matter of fact,
may symbolize any signalling device.
In the apparatus shown in Fig. 3 and other
apparatus constructed according to the teach
ings of the prior art, of which I am aware, pro
vision is not made for taking care of variations
in the impressed voltage. As a result, when the
tube I is not operating, the photo-cell 28 must
be under the in?uence of a light flux determined
by the maximum value of the voltage and not
by its average value. The di?e-rence between
the light ?ux necessary to operate the tube and
2,125,073 \
the light ?ux under which it does not operate is.
therefore, materially increased.
In Fig. 4, the apparatus that I provide to
remedy the situation is shown in detail. The
apparatus shown in the drawing comprises, in
addition to the electronic relay I and the source
of potential I'l connected to its electrodes 3 and 4,
3
source rather than to the principal electrodes 3
and 4 of the tube.
In Fig. 6 a speci?c form of my improved system
is shown thabhas particular application in tra?lc
control apparatus. In the system shown in the
drawing, the photo-electric cell or cells 28 that
operate the tube I is under the action of a source
a photo-electric cell 28 connected between the of illumination 31 that is operated from the same
grid 8 and the anode 4, a variable impedance 28 transformer 48 that supplies the voltage for the
10 connected between the grid 6 and the cathode 3,
tube. A second photo-cell 32 is disposed be
and an impedance 30 connected in series with the .tween the control electrode 8 and the cathode 3
source of. potential II.
and is under the in?uence of a second source of
The function of the impedance 38 in the power light 38, also operated from the transformer 48.
line I1 is simply to limit the current that ?ows
It is to be noted that, in apparatus of this na
15 through the tube I. The variable impedance 28, ture designed according to the teachings of the
on the other hand, is responsive to variations in prior art, the second photo-cell 32 and the lamp
the impressed potential, and decreases as the 38 are replaced by a constant impedance. In this
electromotive force of the source I‘I increases.
case, an increase in the voltage in the primary 4|
It is representative of a ballast tube or a photo
of the transformer 48 results not only in an in
20 cell 32 connected as shown in Fig. 6 that will
crease in the voltage between ‘the principal elec
presently be explained.
trodes 3 and 4 of. the tube I, but also in a large
In ‘Fig. 5, the relation between the illumina
increase in the light intensity of the operating
tion on the photo-cell and the impressed voltage,’ lamp 31. As a result, the margin between the
necessary to cause a discharge in the tube relay, illumination required to operate the tube and the
25 is shown graphically. The curve on the left 34 illumination at which it does not operate must
is plotted for a certain value of impedance 28 be
be rather large.
tween the cathode 3 and the control electrode 8,
The secondlamp 38 and the second photo-cell
and the curve» on the right 35 _is plotted for a 32 may be of such structure that they are more
smaller value of the impedance 29. It is seen sensitive to variations in the voltage than the
30 that the voltage E1, necessary to cause a discharge ?rst lamp 31 and the ?rst photo-cell 28. Con
in the tube, at a given intensity of illumination sequently, an increase in the voltage supplied to
Io, increases as the impedance decreases. A the primary 4| of the transformer 48 causes a
potential difference E2 greater than E1 must be decrease in the impedance between the electrodes
applied between the principal electrodes of the 2| and 22 of the second photo-cell 32 that is rela
" tube to operate it with the smaller impedance tively larger than the decrease between the elec
29 between the grid 8 and the cathode 3.
trodes 2| and 22 of the ?rst photo-cell 28.
It is seen then that, if. the impedance 28 is Hence, the voltage required to cause a discharge
responsive to the voltage ?uctuations between in the discharge tube I is increased, and thus
the principal electrodes 3 and 4, the character
the ?uctuations in the power supply are at least
40 istic of the tube I itself becomes responsive to partially compensated.
the variations in the voltage, and compensation
I have found that while, in the earlier tra?ic
of the irregularity of the source I1 is effected. control systems, the decrease in illumination of
It is thus possible to operate my improved light
the operating light 31, necessary to actuate the
sensitive apparatus between considerably smaller system, is 48%, my-improved system operates sat
45 limits of intensity of the illumination e?ecting isfactorily for a decrease in illumination of only
the photo-cell 28 than is possible with the earlier 24%.
apparatus.
In addition to the‘ above discussed advantages,
It is to be noted that, in the apparatus shown the apparatus shown in Figs. 3 and 4, and, to an
in Fig. 4, the tube I is active when the photo
even greater degree, the apparatus shown in
50 electric cell 28 is in an energized state.
If the
anode 2| of the photo-cell is connected to the
grid 8, instead of the anode 4 of the tube, and
the cathode 22 is connected to the cathode 3 of
the tube, a system is obtained wherein the dis
charge I is inactive when the photo-cell 28 is
energized. In this case, the impedance 29 is
connected between the grid 8 and the anode 4
and responds to the voltage E by increasing
therewith. A system of this type is within the
60 scope of. my invention.
Also within the scope of my invention, is a
system wherein a plurality of cells 28 are used
instead of a single cell 28. These cells may, of
course, have any predetermined arrangement in
the circuit.
Furthermore, I may point out that my system
is operable with direct current as well as with
alternating current. The condenser 28 in the
drawing, which represents the impedance is,
therefore, to be regarded as only symbolical.
Finally, it should be noted that it is within the
province of my invention to connect the anode 2|
of the photo-cell 28 and the lower terminal of
75 the impedance 28 to the terminals of the power
Fig. 6, involve certain features which are of con
siderable importance. This aspect of the situa
tion may be discussed with reference to the modi
20
25
30
35
40
50
?cation shown in Fig. 6.
In the apparatus shown in this view, the anode
of the photo-cell 28 is connected to the junction
point of the anode 4 of the discharge device I
and the resistor 30. When the discharge device
I is deenergized, the total potential of the source
48 is impressed between the cathode 22 of the
cell 32 and the anode 2| of the cell 28. How 60
ever, when the discharge device I is energized
current flows through the resistor 30 and the
potential drop across the photo-cells 28 and 32 is
decreased by the drop across the resistor. The
latter potential drop is in general of considerable
magnitude and the decrease is therefore com
paratively large. By reason of the decrease, the
photo-cells are protected against disruptive dis
charge and the injuries resulting therefrom at
the very instant that such protection is necessary,
namely, when the discharge device I is energized,
It is to be noted that the resistor 30 is an im
portant element in producing the advantage dis
cussed above. Where the current source is of the
usual constant-voltage type, the desired result 75
4
9,125,073
.
is produced by reason of the voltage absorbed by
the resistor as current is transmitted through the
discharge device I. Hereinafter, I shall refer to
a '_‘voltage absorbing device" when discussing or
' claiming the feature. This expression is used
with the understanding that it may apply to any
,
4. Translating apparatus comprising an elec
tric-discharge device having a control electrode
and a plurality of principal electrodes immersed
in a gaseous medium, said device having an ener
it may be taken as calling for an element such
gized condition and a deenergized condition and
being capable only of abrupt transition from one
as the resistor 30 or the load 21.
condition to the other, a source of electrical ener
Although I have shown and described certain
speci?c embodiments of my invention, I am
gy for impressing potentials between the elec 10
trodes of said device to maintain said device in
fully aware that many modi?cations thereof are
one or the other of said conditions, a ?rst photo
possible. My invention, therefore, is not to be
1. Translating apparatus comprising an elec
tric discharge device having a control electrode
and a plurality of principal electrodes immersed
sensitive device coupled between the control elec
trode and a principal electrode of said discharge
device, means energized from said source for sub 15
jecting said ?rst photo-sensitive device to radia
tion, a second photo-sensitive device coupled be
tween the control electrode and another principal
electrode of said discharge device and a second
in a gaseous medium, said device having an ener
means energized from said source and having a 20
general element which absorbs voltage. Thus,
10
trical condition of said discharge device are neu
tralized.
restricted except insofar as is necessitated by the
prior art and by the spirit of the appended claims.
I claim as my invention:
gized condition and a deenergized condition and di?erent radiation characteristic from said means
being capable only of abrupt transition from one. last named for subjecting said second photo-elec
condition to the other, a source of electrical
tric device to radiation.
energy for impressing potentials between the
electrodes of said device to maintain said device
5. An electric discharge device having a control
electrode, an anode and a cathode, means for im
pressing a potential di?erence between said anode
in one or the other of said conditions, a photo
_
and cathode, impedances connected between said
sensitive device coupled between the control elec
trode and a principal electrode of said device,
means for energizing said photo-sensitive device
to vary the condition of said electric discharge
device, another photo-sensitive device coupled be
tween the control electrode and another principal
electrode of said electric discharge device and
control electrode and each of the other said
electrodes and means, responsive to a variation in
the terminal potential di?erence of the ?rst said 30
means to decrease the ratio of the impedance
connected to the cathode to the impedance con~
’ means, to be energized from said source, for
nected to the anode when said potential di?er
energizing said last named photo-sensitive device
ence rises.
6. An electric discharge device having a con- , ,
to suppress variations in the condition of said
electric discharge device that tend to arise by
trol ‘electrode and a. plurality of principal elec
trodes, said principal electrodes being immersed in
reason of variations in said source.
a gaseous medium, means for impressing a poten
2. Translating apparatus comprising an elec
40 tric discharge device having a control electrode
and a plurality of principal electrodes immersed
in a gaseous medium, said device having an ener
gized condition and a deenergized condition and
being capable only of abrupt transition from one
condition to the other, a source of electrical
energy for impressing potentials between the elec
' trodes of said device to maintain said device in
one or the other of said conditions, a ?rst photo
sensitive device energized from said source
coupled between the control electrode and a
principal electrode of ,said discharge device, a
second photo-sensitive device energized from said
source coupled between the control electrode
and another principal electrode of said discharge
55 device, said photo-sensitive devices having differ
ent voltage-sensitivity characteristics.
'
3. Translating apparatus comprising an elec
tric discharge device having a control electrode
and a plurality of principal electrodes immersed
60 in a gaseous medium, said device having an ener
gized condition and a deenergized condition and
being capable only of abrupt transition from one
condition to the other, a source of electrical en
ergy for impressing potentials between the elec
trodes of said device to maintain said device in one
or the other of said conditions, a ?rst photo
sensitive device energized from said source cou
pled between the control electrode and a principal
electrode of said discharge device, a second
photo-sensitive device energized from said source
coupled between the control electrode and
another principal electrode of said discharge de
vice, said photo-sensitive devices having diilerent
voltage-sensitivity characteristics, whereby the
75 e?ects of variations in said voltage on the elec
tial diiierence between said principal electrodes
and also between said control electrode and one 40
of said principal electrodes and light responsive
means to be energized in response to variations
in the terminal potential difference of the ?rst
said means to compensate for the eiiect of said
variations‘in producing variations in the poten-'
tial di?erences impressed between said principal
electrodes and in the potential di?erence im
pressed between said principal electrodes and said
control electrode.
'1. An electrical circuit comprising a source
of electrical energy, a tube connected to receive
current from said source and equipped with a con
trol electrode, an anode and a cathode, and a plu
rality of photo-cells provided each with a cathode
and an anode, the cathode of one of said photo
cells being connected to the cathode of said tube,
the anode of said photo-cell being connected to
said control electrode and the cathode of another
of said photo-cells being connected to said con
trol electrode and the anode of said cell being 60
connected to the anode of said tube, and means
to decrease the ratio of the-resistance of the ?rst
mentioned photo-cell to that of the last-men
tioned photo-cell as the voltage of said source
rises.
8. An electrical circuit comprising a source of
electrical energy, a device of the glow discharge
type connected to receive current from said source
and equipped with a control electrode, an anode
and a cathode, a plurality of impedances one of
which is a photo-cell provided with a cathode and
an anode, one of said impedances being connected
between the anode of said device and said con
trol electrode, and the other said impedance be
ing connected between the control electrode and 76
2,125,073
the cathode of said device, and‘means to cause
the ratio of the last-mentioned impedance to the
?rst-mentioned impedance to decrease when the
voltage of said source rises.
9. An electric discharge device having a con
trol electrode, an anode and a cathode, means
for impressing a potential di?erence between said
anode and cathode, impedances connected be
5
tween said'control electrode and each of the other
said electrodes and means, responsive to a varia
tion in the terminal potential difference of the
?rst said means to decrease the ratio of the im
pedance connected to the cathode to the imped
ance connected to the anode when said potential
difference rises.
DEWEY D. KNOWLES.
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