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Патент USA US2127977

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Aug. 23, 1938.
Filed sept. f1, 1955
Patented Aug. 23, 1938
" 2,121,911
Anthony H. Lamb, Elizabeth, N. J., assignor to
Weston Electrical Instrument Corporation,
Newark, N. 1., a corporation of New Jersey
Application September "I, 1935, Serial No. 39,654
' 11 Claims.
(Cl. 175-320)
This invention relates to thermionic relay cir
cuits and more particularly to circuits in which
the space current path of the relay circuit lies
in a ?ame stream.
It has been proposed to control the operation
of electronic tubes, such as grid glow tubes and
ampli?ers, by changes in the conductivity of a
?ame. The grid bias circuits of the electronic
tubes included a source of polarizing potential
and a portion of the ?ame path and, in general,
the action was exactly the same as that which
would take place if a mechanical resistor of
variable magnitude were substituted for the re
sistance of the ?ame path. In these prior con
15 trol systems, the initial or primary control cir
cuit is of the “voltage-change” type, and the
voltage change resulting from a variation in the
resistance of the ?ame path is employed to con
trol the electronic tube. The ultimate control
20 is obtained by the action of a “current-change”
device or relay in the output circuit of the tube.
An object of the present invention is to pro
vide a relay circuit including, in series, the ther
mionic or space current path of an open ?ame
25 and a current-responsive control device. An ob
ject is to provide a ?ame-controlled relay cir
cuit of simple electrical and physical design that
may be energized from the usual house lighting
circuits of either the alternating or direct cur
rent type. More particularly, an object is (to
provide a relay circuit including a current-re~
sponsive control device and a source of voltage
in series with two electrodes, the electrodes be
ing spaced apart in a ?ame stream and only one
35 of theelectrodes being an electron-emitting body
energized by the heat of the ?ame.
These and other objects and advantages of the
invention will be apparent from the following
speci?cation when taken with the accompanying
40 drawing in which:
Fig. 1 is a schematic diagram of an embodi
ment of the invention;
Fig. 2 is a fragmentary diagram illustrating
another arrangement of the electrodes with re
' spect to the ?ame path;
Fig. 3 is a circuit diagram of an embodiment
of the invention as applied to a safety control
for a fuel burner; and
positioned. As shown in Fig. 1, the nozzle l acts
as the cooperating electron-receiving electrode
or anode when maintained at a positive poten
tial with respect to electrode 3 by a current source
4. The moving coil 5 of a sensitive current-re
sponsive relay is included in the circuit between
the electrodes, the relay being preferably of the
type including a movable arm 6 carrying a mag
netic rider 1 for cooperating with a relatively
stationary contact 8 in the form of a small per 10
manent magnet. Magnetic attraction at the
contacts assures good contact engagements, and
a pusher arm 9 is provided for separating the con
tacts. The pusher arm maybe operated manu
ally by a knob 9'.
The exact design of the sensitive instrument
type relay is not an essential feature of this in
vention, and appropriate constructions of the
magnetic contact type are illustrated and. claimed
in my prior patents numbered 2,014,385 to N) 0
2,014,388, inclusive, granted Sept. 17, 1935.
While this is the preferred construction, it is
possible to use sensitive relays of the presser bar
type in some instances.
The circuit controlled by the sensitive relay N) 5
includes a source of current [0 and an alarm or
control unit ll serially connected between the
contact arm 6 and the magnetic contact 8. So
long as the thermionic current established by
source 4 between the electrodes I and 3 remains
above some predetermined value, the current
?ow in the moving coil 5 prevents an engage
ment of the relay contacts ‘I, 8. The thermionic
current ceases when the ?ame is extinguished,
and the contacts 1, 8 engage to energize the sig
nal or control device II.
It is particularly to be noted that the ohmic
resistance between electrodes l and 3 has a neg
ligible effect upon the operation of this thermi
onic relay system. The resistance between the 40
electrodes is reduced when the ?ame is present,
but the current ?ow which determines the oper
ation of the relay is a thermionic current be
tween the electron-emitting electrode or cathode
3 and the “cold” electrode or anode I. The fact 4
that the purely conductive current flow between
the electrodes is of an order substantially lower
than that of the thermionic current, and not
Fig. 4 is a chart showing the relation between
voltage and current when operating the inven
su?icient to operate the relay system, may be
demonstrated by reversing the polarity of the 0
tion from an alternating current source.
current source 4.
In the drawing, the reference numeral l iden
ti?es a nozzle for projecting a ?ame stream 2
in which an electron-emitting electrode 3, such as
55 a wire of tungsten or a nickel-chromium alloy, is
A further indication of the fact that the opera
tion is due essentially to thermionic emission is
afforded by the operative construction illustrated
in Fig. 2. In this embodiment of the inven
tion, the cold electrode or anode I2 is not located
in, but adjacent to, the ?ame stream 2. The
gap between the flame stream and the anode I!
may be of the order of 1/8 inch when the poten
tial of the current source 4 is as low as about
110 volts.
Relays such as contemplated by this inven
tion may be used for various purposes where a
control or an alarm device is to be actuated upon
10 the presence, or the absence, of a ?ame stream.
The invention is well adapted for use as a safety
control for, oil burners and/or in other heaters
employing a pilot ?ame.
A typical form of safety control for an oil
burner is illustrated in Fig. 3. The nozzle l di
rects the pilot ?ame 2 into the path of the fuel
projected from the burner nozzle IS. The con
trol system for the main burner may be of any
appropriate or desired design, as is indicated by
20 the block element II which is energized from
an appropriate power source i5 which, in most
instances, is the usual 110 volt power line. Leads
I 6, l6’ extending from the block element I! to
the contact arm 6 and magnetic contact 8, re
25 spectively, of the sensitive relay indicate the op
eration of the burner control is dependent upon
an open circuit between the relay contacts.
It is not essential that a direct current source
of potential be included in the relay system and,
30 as shown in Fig. 3, an alternating current source
case of oil burners which may roar and burn
unevenly, it may be desirable to increase the
damping to prevent the relay from responding
to current ?uctuations of one cycle per second.
thus preventing the relay from closing in re
sponse to momentary current drops due to the
uneven ?ame or combustion.
It will be apparent that the invention is not
limited to the particular embodiments herein il
lustrated and described. The design of the con~
trolled circuit may be varied in accordance with
the particular control which is required in any
given installation. The relay may be, for exam
ple, of the type described in my prior Patent No.
2,014,386 and include means for operating a con
trol switch only upon a predetermined number of
closures of the relay contacts. Such a relay is
especially suited for use in an oil burner con
trol in which the oil burner is to be tie-energized
only upon a failure to establish a ?ame by a pre
ceiving electrons emitted by the first electrode,
said second electrode being heated by the ?ame
stream to a substantially lesser degree of electron
apparent from a consideration of the curves oi.‘
Fig. 4. The voltage on the cold electrode or an
emission than the ?rst electrode and a source of
potential and a current-responsive control de
to 110 volts negative, as indicated by the curve
IT. The current ?ow between electrodes l and
3 includes an alternating current component,
shown by curve II, which is relatively small, for
example of the order of a fraction of a micro
It is to be noted that the prior volt
age-change control systems, as noted above, em
ployed this conductive current component to ob
tain a control action and transformers were used
to produce high bias voltages, of the order 01'
400 to 600 volts, to produce the required grid
establishing a ?ame stream, an electrode nor
mally heated to electron-emitting temperature
by the ?ame stream, a second electrode for re
vice serially connected between said electrodes 40
to complete a circuit in which a thermionic cur
rent is produced by the attraction of electrons
to said second electrode when that electrode has
a positive potential with respect to the first elec
trode, said control device including a pair of con 45
tacts and movable means actuated by thermionic
current ?ow in said circuit for controlling said
2. A thermionic relay circuit as claimed in
rent of much greater value is established at a
claim 1, wherein said source of potential is an
alternating current source.
3. A thermionic relay circuit as claimed in
claim 1, wherein said source of potential is an
alternating current source, and said means of
the control device is damped to render the same
non-responsive to current impulses of the fre
quency of the alternating current source of
‘lower potential difference and ?ows through a
bias variation by the relatively high conductivity
of a ?ame stream. According to this invention,
the conductive current is not employed to pro
duce a change in the biasing potential applied
to a thermionic tube but a thermionic cur
current responsive device to actuate the same.
The thermionic current is extinguished during
half-cycles when the cold electrode I is negative,
but rises to values of the order of 20 micro
amperes when the cold electrode is at a positive
potential with respect to the electron-emitting
electrode 3. The recti?er action thus results in
periodic current impulses, indicated by curves
IQ, of a magnitude adequate for the actuation of
a relay instrument oi.’ high sensitivity. As noted
above, the damping of the moving coil system
70 must be such that it does not respond to the fre
quencyv oi.’ the alternatingcurrent source but
to the average value of the pulsating current. In
general, the damping is preferably such that
the moving system will not respond to frequen
75 cies about 2 or 3 cycles per second and, in the
determined number of trials. The invention is
not restricted in its applications to a safety
control for oil furnaces, but may be used in ?re
alarms or for indicating or controlling abnormal
conditions in a furnace or other heating systems. 25
The invention is therefore open to substantial
variation in the design and relation of the sev
eral components of a thermionic control or sig
nal system.
I claim:
1. In a thermionic relay circuit, means for
4' is employed. This current source may be, and
preferably is, the usual 110 volt system for house
lighting. Commercial power systems are either
25 or 60 cycle and the damping of the moving
35 system of the relay must be such that it will not
respond to frequencies of this order.
The operation of the burner control will be
-10 ode l varies periodically from 110 volts positive
4. In a relay circuit, the combination with
means for establishing a ?ame stream, of an
electrode positioned to be heated to electron
emitting condition by said ?ame stream, a coop
erating relatively cold electrode, a sensitive relay
instrument comprising a moving coil carrying a
contact cooperating with a relatively stationary 65
contact, a source oi.’ potential, and means con
necting the moving coil and the source of poten
tial in series between said electrodes.
5. A relay circuit as claimed in claim 4,
wherein said means for establishing a ?ame 70
stream constitutes said cooperating electrode.
6. A relay circuit as claimed in claim 4,
wherein said source of potential is an alternating
current source.
7. A relay circuit as claimed in claim 4, 78
wherein the contacts oi’ said sensitive relay in
strument are magnetic contacts, and said relay
instrument includes means operable to separate
10. In a relay device, the combination with a
circuit to be controlled and including a par of
said contacts after a closure thereof.
8. A thermionic relay of the type including a
trodes spaced apart in open air, one electrode
being adapted to emit electrons when heated, a
' relay having a moving system actuating one of a
pair of contacts in a controlled circuit, an elec
tron-emitting electrode, an anode, and a source
of polarizing potential connected in series with
said moving system between said electrode and
anode, characterized by the fact that said elec
trode is positioned to be heated to electron
emitting temperature ‘by a ?ame stream and
said anode is heated by the ?ame stream to less
15 than electron-emitting temperature. >
relatively movable contacts, of a pair of elec
source of potential for establishing a thermionic
current between said electrodes when said elec
tron-emitting electrode is heated, and means
responsive to the thermionic current for effecting
relative movement of said contacts, said means 10
being connected in series with said potential
source and said electrodes.
'11. Apparatus controlled by a combustion
?ame, including: an electrode having an appre
ciable portion located in the ?ame and heated 15
thereby to emit electrons, a second electrode ad
9. A thermionic relay of the type including a
source of polarizing potential and a relay device jacent said ?ame but su?iciently spaced there
serially connected between a cathode and an -' from to remain at a temperature below that at
anode, said relay device including‘ relatively which it emits electrons; means for maintaining
20 movable~ contacts adapted to be included in a
between said electrodes a voltage diii’erential of 20
controlled circuit, characterized by the fact that a magnitude to establish a thermionic current
said cathode and anode are positioned at spaced ?ow between said electrodes while said portion in
points in open air to be heated by a ?ame, and said ?ame is heated thereby; and'current re
said cathode is heated to electron-emitting tem
sponsive means in series with said electrodes.
25 perature by the ?ame.
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