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Патент USA US2406752

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Sept. 3, 1946.
s, G. E$K|N ET AL
v
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SAFETY CONTROL .FOR GASEOUS FUEL BURNERS
‘ Filed April l0, 1943
-2,406,752
2,406,752
Patented Sept. 3, 1.946
UNITED'STATES PATENT OFFICE
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v 2,406,752
SAFETY CONTROL FOR GASEOUS FUEL
.
BURNERS
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Samuel G. Eskin and Charles K. Strobel, Pitts
burgh, Pa., assignors to Robertshaw Thermostat
Company, 'Youngwood Pa., a corporationof
Pennsylvania
‘ f' Application April 1o, 1943, serial No. 482,592
15 claims. `(c1. 15s-117.1)
more particularly, tocombined safety and condi
when such current is reduced below a certain
Operation of the main con
. trol-valve I6 from'closed to open position will
tion controlling means for fuel burners and the
like»
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2
sufficient energizing current is supplied to the
solenoid of valve I8 and to be closed by gravity
Thisiinvention relates to control systems and,
Lminimum value.
"
In application S. N. 439,148 filed April 15, 1942,- "Si
permit ñow of fuel from the pipe I4 to the pilot
now Patent No. 2,366,774, granted January 9,
1945, there is disclosed aV safetyfsystem for fuel
burners employing both av flame or heat sensitive
- burner I2, but fuel is not supplied to theV main
burner IIl'unless the solenoid Valve IS is also in
open position.
y. device anda current sensitive device for con
trolling operation l of Van' electromagnetic fuel
valve. The valve in this systemV was used solely
for safety purposes and would function to ter
minate the supply of fuel to the main burner
upon extinguishment offthe flame to which the
flame sensitive device was exposed. In this
present invention it is proposed to employ the
electromagnetic valve„as disclosed in‘the former
application, both to regulate the ñow of fuel to
the main burner for temperature regulation and
also terminate suchflow in the event of. ñame _
failure. It will readily be apparent> that in its
broad aspects the present invention may be
utilized both for condition and safety control as
previously indicated.
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An object of this invention is to permit utiliza- v
tion of the condition regulating means for safety
control also.
.
K,
, Electric current for the operation of the ap
pa'ratus is supplied by the line wires 20 connected
to the primary of a transformer 22 which, in this
instance, receives commercial current at the
primary where a voltage variation from 105~to
125 volts -can occur.l In this> embodiment the
main valve I6 has a main switch combined there
with which is connected to one line wire 2Uv by
wires 24 an'd- 26. Any suitable means may be in
corporated in the combinedY valve and switch
structure to close the switch when the main valve
Itis-actuated to open position. The secondary
of the transformer 22 delivers the current from
line wires 20 at voltages varying in accordance
with the primary Yvoltage variation above and
below an averager of six volts. Connected to one
terminal of thetransformer secondary by a wire
28 is one junction A of a parallel mesh of which
a name sensitive element 30 forms one branch
.Another object of the invention is to insure a
and is connected at'oneend by wire 29 to wire 28
minimum -time lag in the response of the control
when operation of the burner should be termi 30 and at the other end by wire 3| to wire 32 at the
nated.
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Another object of the invention is to render the
device substantially uniform as to operating time
opposite junction B of the mesh. .The element 30
is positioned adjacent the pilot burner I2 exposed
to the heat of the flame thereof and may be in 1
the form of a coil of wire formed from material
over a range of operating conditions.
Other objects and advantages will become ap
35 having normally a relatively low resistance and a
positive temperature coeflicient of resistance
forming a ballast resistor. It will be apparent
that other types of flame sensitive, heat respon
wherein:
sive or thermal resistance elements havingV the
Fig. 1 is a schematic view of a combined safety
and condition controlling apparatus for a fuel f required characteristics may be substituted and
that it is not essential that the flame of the pilot
burner embodying the invention;
burner I2 actually impinge on the coil.
Fig. 2 is a schematic View of a detail in one op
Therother terminal of the flame sensitive ele
erating position; and
l
ment 30 is connected by wires 3l and 32 with one
Fig. 3 is a schematic View of the same detail in
45 end of another parallel mesh included in the
another operating position.
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secondary. circuit, the other end of this parallel
Referring more particularly to the drawing, a
mesh being connected by a wire 34 to the other
gaseous fuel burner I0 and an associated pilot
terminal of the secondary of the transformer 22.
burner I2 are shown as being supplied with fuel
One branch of this parallel mesh comprises a re
by a main fuel pipe I4. The fuel supply- to both
burners is controlled by. a main valve I6 which 50 sistance` element 36 whichy will be hereinafter
parent from the following description taken in
connection with theA Y accompanying
drawing,
may be manually‘operated. Interposed in the
fuel supply line I4 between the main valve I6 and
the burner I0 is an electromagnetic or solenoid
designated as a valve control resistor. This re
sistor 36 is preferably in the form of a coil of wire
of material having normally a ‘relatively low re
sistance and a positive temperature coefficient of
gas valve VYI8 of any known type which maybe
arranged, asin this instance, to be opened when 55 resistance >forming a ballast resistor, althougnas
$2,406,759
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4
will appear hereinafter, a constant resistor could
be employed. The resistor 35 is not, however, eX
posed to the heat of any flame but is adapted to
to the coil of the solenoid valve i8 to actuate this
become heated upon passage of electric current
valve to open position.
The fuel issuing from the pilot burner l2 may
be ignited by a match and the relatively small
therethrough and will change its resistance in Cl
heating effect of the current on the flame sensi
accordance with changes of temperature caused
tive element 3i? is amplified by themuch greater
by changes in the value of current fiowing through
heating effect of the pilot burner which will then
it.
occur. Assuming that the control thermostat is
The other branch of the parallel mesh com
prises a constant resistance elementA 53 forming
a pick-up resistor for the solenoid valve, and' a
control switch connected in series circuit there
in the cold contact position with the contact 46
with. The control switch may take the form of
a thermostat composed of a bimetal arm lll! carry
ing on one end thereof a pair of contacts HI, 43
disposed one on each side and which upon warp
ing of the arm will engage alternately with con
tacts ¿l2 and (it, designated hot contact and cold
Contact respectively, and spaced one from the
other. The control switch may be placed in the
space tobe heated by the main burner It and the
arm t3 be subjected tothe temperature variations
therein forming a space thermostat of special
form. To this end, the cold contact ‘t3 is prefer
engaged by related contact on arm All), then the
circuit Will be as previously described, that is, the
parallel mesh of pick-up resistor 35i and valve
control resistor 36, the parallel mesh of solenoid
valve I3 with its cut-out 58 and name sensitive
element 3l), all in series with the transformer
secondary. Upon heating of the flame sensitive
resistor 30 by the pilot flame in this starting or
cold Contact position, the shunting of the valve
control resistor 36 by the pick-up resistor 38 and
cold contact 423 causes sufficient currentV to ñow
through the solenoid valve I8 to actuate this valve
to open position. As in the case of application Se
rial No. 439,148 previously referred to, this effect
is produced by a relatively large increase of' re
ably carried upon a second bimetal arm M which 25 sistance with increase of temperature of the llame
is adapted to warp upon passage of electric cur
sensitive resistor St. However, if the flame sensi
rent therethrough so that only the hot contact ft2
tive resistor 33 is not heatedV by the pilot flame
can be considered as a relatively iixed contact for
there is insufñcient current impressed upon the
the thermostatic switch. A limit stop 48' is inter
coil of the solenoid valve I8 to effect actuation of
posed between the bimetal arms 46 and 44 in posi 30 the valve to open position as previously described
tion to be engaged by thearm dû to restrain move
therein.
ment thereof toward the arm ¿i4 for a purpose
Operation of the main burner I3 Will serve to
which will be> apparent hereinafter.
increase the temperaturev ambientto the thermo
The hot contact 42 is connected by a ’wire 53
stat causing movement of the bimetal arm til
to one end of a constant resistance element 52, 35 toward the hot contact 42. It may be assumed for
the other end of which is connected by a wire 5I
the purpose of this description that the bimetal
to wire 23 at junction A' of the parallel mesh.
arm 150 now movesito a neutral position engaging
Another branch of this mesh includes a cut-out
neither the cold contact 48 nor the hot contact
58 which is thermally sensitive and may be of the
ä2. A circuit is then established from the valve
slow acting bimetallic snap switch type. One ter 40 control resistor 36, the parallel mesh of solenoid
minal of the cut-out 58'is connected‘by a wire 53
valve It with its cut-out 58 and flame sensitive
to‘ the wire 23 at junction A and the other termi
element 33 all in series with the transformer
nal is connected by'wire 54 to one terminal of the
secondary. In this circuit the resistor 33 and
solenoid valve I8. The other vterminal of the
resistor 52 are disconnected as will be apparent
solenoid valve I3 is connected by a wire 56 to the ‘ and the current through the solenoid valve I8 is
wire 32 at the junction B, thus placing the' name
consequently reduced by removal of resistor 3S
sensitive element' 33’ in parallel circuit with the
from parallel relation with the valve control re
cut-out 58 and solenoid valve i3.
sistor 33. However, when the thermostat moves
InV the operation of the’ apparatus the closing
as describedfrom the cold contact to neutral posi
of the main switch of' valveV I6 is effective upon 50 tion the current value impressed on solenoid
manual opening of this valve, as described, and
valve I8 is not reduced below the minimum value
permits fuel to flow to the pilot burner I2.` As
required to hold the valve in its open or operat
the solenoid valve I8 remains closed, no fuel can
ing position, but the circuit constants are ad
flow to the main burner Iû at this time. The cir
justed at the lowest line- voltage which may be
cuit thus-established may be traced from the line Ul Ul 105 volts at the primary so that the normal,
steady operating current is slightly above the
wire 23 to wire 23, electric switch of main valve
I6 and wire 26 to the primary of the transformer
minimum Value. The resistance of the parallel
circuit in> operating condition is increased sulîi
22, from the secondary of the transformer by wire
ciently by the higher resistance value of the dame
28 to wire 53, cut-out 58, wire 54, to one terminal
of solenoid valve I8, wire 56 to wire 32, valve 60 sensitive element 30 when heated to permit sufii
cient current to the solenoid valve t0 maintain it
control resistor 33 and wire 34 to the other side of
in the open position.
the transformer secondary. Current also flows
After the main burner I3 has been operating
in the shunt established by the flame sensitive ele
ment 3l! which is connected by wires 29 and 3I 65 for some time the bimetal arm 4i) may move to
the hot contact position due to the thermostat
around the coil of the solenoid valve I3» causing
becoming satisfied, whereupon a circuit arrange
the element 30 to become heated to some extent.
ment is established from the transformer second
During this starting operation the control ther
ary and the valve control resistor 36 in series
mostat is usually in cold-contact position so that
pick-up resistor 38 is connected in parallel cir 70 with the three-branch parallel mesh of flame sen
sitive resistor 33, solenoid valve IS and cut-out 58,
cuit with the valve control resistor 33. The cur
and constant resistor 52 with the hot contact d2.
rent values in the circuit are adjusted so that
The constant resistor 52 which acts as an adjust
when these circuit conditions exist and the flame
ing resistor for the solenoid valve I8 is of such a
sensitive element 3i! remains unheated by the pilot
burner flame, there is insuflicient current flowing 75 Value as to shunt sufficient current from the sole
2,406,752
5
noid valve I8 tocause this valve to move to closed
position.
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» When the thermostat moves fromV the hot con
tact 42 tothe neutral position the solenoid vvalve
I8 remains closed until the bimetal arm warpsl to
close the cold contact 46. In' such event the
6
viewed in Fig. 3, and a separation of the cold
contact 46 from arm 40 can occur as soon as the
arm 44 becomes heated by passage of current
therethrough. The separation of the cold con
tact thus has the same effect as movement of the
arm 40 to neutral position` and the valve closing
cycleis repeated due to the flame sensitive ele
ment Vill) being heated by the pilot burner. In
timeisgenerally short. Y It will be apparent that
a heater coil could be used in place of conducting
case the llame sensitive element 30 becomes open
' current directly to the arm 44 and such variation
circuited, sufficient current flows through the cut 10 is Within the scope of this invention.
It will be understood that aconstant resistor
out .58;to cause it to operate to close the valve,
could beused in place ofA the current sensitive
providing the thermostat is inl either the cold
resistor asthe valve control. The system would
contact position or neutral position. If, however,
then
operate over a narrower range of voltages
the thermostat is in the hot contact position, the
solenoid valve I8 is closed due to the shunting 15 and the valve closing times would be increased.
However, the system would not in such case be
action of the resistor 52.
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quite as sensitive as the preferred form to rapid
The foregoing sequence of operation continues
voltage variations, and the advantages of reduced
during the normal running condition of the
valve closing times and an extension of the' pri
burner to control a condition caused by operation
mary voltage range over which the system will
of the burner. The operation of the safety device
operate are believed superior. Considerable flexi
will now be described.
o
If the Aflame of the pilot burner I2 becomes ex
'
bility of circuit arrangement results as the value
of the respective resistances canbe varied to suit
diiierent operating conditions. The single sole~
40 is in the het contact position, vor in the neutral
noid valve functions as condition and safety con
position upon warping from the hot contact posi
trol in the arrangement described and it will be
tion, then the solenoid valve I8 is already closed
apparent that various changes may be made in
at the time of the flame failure. If, however, the
the form .and arrangement of parts within the
bimetal arm 40 is in theneutral position upon
scope of the appended claims.
warping from the cold'contact position, the sole- y
We claim:
noidzvalve I8 is open. IThe flame sensitive ele
y l. A control system for fuel burners having `
ment 3l)Y will cool in the `absence of pilot burner
main and pilot burners comprising in combina
name and its resistancewill decrease causinga
tion, electrically operable control means movable
corresponding decrease in current value to the
between positions for controlling the main burner,
solenoid valve I8 which then closes. Such clos
ing of the solenoid valve occurs in a relatively 35 a controller in circuit with said means and re
sponsive to changes in a condition caused by op
short time Vdue to the combined action- of the
eration of the main burner, a ballast resistor ex
flamesensitive resistor 30 and the valve rcontrol
posed to the heat of the pilot burner iiame and
resistor 36. As previously described, the current
electrically connected to said control means for
impressed upon the solenoid valve I8 in the neu
varying theV current value supplied thereto upon
tral position of the thermostat is only slightly
variations in the resistivity of said resistor due to
above the minimum value required to hold the
the presence or absence of said flame, and a
valve in its `open or operating position. Thus,
plurality of resistance circuits adapted to be
by making the valve control resistor 36 sensitive
establishedalternately'by operation of said con
to Vcurrent changes the decrease in voltage drop
troller and including said control means and said
across the coil'of the solenoid valve will be accel
ballast resistor, said resistance circuits having
erated` whenever an increase of resistance of the
different resistance values for varying the cur
valve control resistor occurs upon cooling of the
rent values to said control means, said means
flame sensitive resistor 36 and consequent in
being movable to one position upon establishment
crease in current through the valve control re
sistor. The resulting temperature increase in 50 of one said_ resistance circuit for impressing a
predetermined current value thereon and main
valve control resistor 36 causes increase in voltage
tained in said position upon establishment of an
drop across this resistor and the rapid decrease
other said circuit for impressing a different cur
in voltage drop across solenoid valve I8,
rent value thereon, said resistor being adapted by
ln order to make the adjustment of the circuit
constants less critical and the shut-01T times of ' said variations in resistivity thereof for cooperat
ing with said resistance circuits to determine
the solenoid valve comparatively short, the cold
whether said control means is moved and main
contact 46 of the thermostat is mounted on the
tained in said position.
,
bimetal arm 44. Thus, uponclosure of the cold
2. A control system for fuel burners having
contact the bimetal arm 44 will warp, after the
circuit has been established, from the position 60 main and pilot burners comprising in combina
tion, electricallyoperable control means movable
shown in Fig. 2 to that shown in Fig. 3. Even if
between Ypositions for controlling the main burn
the thermostat arm 40 remains in cold contact
er, alcontrol switch having a pair of contacts
position, the contacts separate and rejoin several
adapted to be opened and closed for controlling
times as the arm 44 heats and cools upon auto
current supplytosaid means in response to
matic making and breaking of the circuit. Thus,
changes in a condition caused by operation ofv
the bimetal arm 44 serves to open the cold con
tinguished for anyreason when the bimetal arm ,
tact 46 independently of the controlled tempera
ture. when the cold Contact remains closed for a
givenlength of time.` VThe normaloperation of
the system is not affected by this action o_f the
arm 44 as once the solenoid valve is actuated to '
open position it remains open until the hot con
tact Yis made; Due to the provision` of the stop
the main burner, a ballast resistor exposed to
heat `of the pilot burner flame and electrically
connected to said control means for varying the
current value supplied thereto upon variations
in the resistivity of said yresistor due to the
presence’or absence of said flame, a resistance
circuit adapted to be established upon closure
of said contacts and including saidcontrol means
4B, the thermostat"armv 40 is restrained from fol
lowing movement ofthe arm _44_to the left as .7.5 andsaid ballast _resistor for adjusting thev cur
2,406,752
rent value to said control means and causing
main and. pilot burnersI comprising in combina
movement thereof to> one position, and> a second
tion, electrically operable control means movable
between‘positions'fcr controlling the main burn
er,a control switchf> having hot and cold contacts
for controlling current supply to’ said means in
response toz‘chaniges in ar condition caused by
operation of the- main burner, said switch Ibeing
movable to a neutral position for establishing
circuit conditions differentfrom those established
in said hot. and cold> contact positions, a ballast
resistor exposed to heat ofY the pilot burner flame
and electrically> connected to said control means
for varying the current value supplied thereto
upon variations.V in` the'. resistivityY of said resistor
resistance circuit established upon opening of
said contacts and. includingr said control means
and said ballast resistor, said second resistance
circuit having a resistance value difierentifrom
the first said resistance circuit for changing the
current value to said control means, the last said
current value being insufilcient to. cause said
movement but suiìcient to maintain said posi 10
tion, said resistor being adapted by said varia
tions in resistivity thereof for cooperating with
both said resistance circuits to determine whether
saidl control means is moved' and maintained
in said position.
15 due to the presence or absence of said flame, a
S. A control system for fuel burners having
resistance circuit adapted to be" established upon
main and pilot burners comprising in combina
closure of said cold contacts and including said
tion, electrically operable control means movable
control means and said ballast resistor for ad
between positions for controlling themain burn
justing the current value to said control means
er, a control switch having a pair of contacts 20 and causing movement thereof to one position
adapted to be opened and closed for controlling
if the resistivity of said resistor has varied
current supply to said control means in response
as aforesaid due to the presence 0f a flame,
to changes in a condition caused by operation of
meansio-r rendering said cold contacts responsive
the main burner, means for rendering one of said
to current i‘low in said circuit to cause move
contacts responsive to current flow acting to’ open 25 ment thereof to said neutralr position, a second
said contacts when closed, a ballast resistor ex
resistance circuit including> said control means
posed to heat of the pilot burnerv llame and
and said ballast resistor having a greater resist
electrically connected to said control means for
ancel value than the first said circuit and estab
varying the current value supplied thereto upon
lished in said vneutral position for causing a re
variations in the resistivity of said resistor due
duction in the current Value to said control means
to the presence or absence of said flame, a pair
to an amount suñicient to maintain'said one posi
of resistance circuits adapted to be established
tion thereof' but insuñlcient to cause said move
alternately by closure and opening of said con
»ment of said control means, said ballast> resistor
tacts and including said control means and said
being effective by said variations in resistivity
ballast resistor, said resistance circuits having 35 thereof under both said circuit conditions to de
different resistance values for adjusting the cur
termine whether said control means is moved and
maintained in said position, and means estab
rent value to said control means, said control
means having suiiicient current value impressed
lishing a- third> resistance circuit upon closure of
thereon when said contacts are closed. to cause
said hot contacts and including said control
movement thereof to one position and having
means, said ballast resistor and said second re
only suliicient current value impressed thereon
sistance circuit, said third resistance circuit hav
when said contacts are open to maintain said
ing a greater resistance value than said second
one position, said resistor being adapted by said
resistance circuit for reducing the current value
variations
resistivity thereof for cooperating
to saidl control means and causing: movement
with both said resistance circuits to determine
thereof from said one position to initial position
whether said control means is moved and main..
irrespective of the heated or unheated condition
tained in said position.
of said Iballast resistor.
4. A control system for fuel burners having
6. A control system for fuel burners having
main and pilot burners comprising in combina
main and pilot burners comprising in combina
tion, electrically operable control means movable 50 tion; electricallycperable control means movable
between` positions for controlling the main burn
between positions for controlling the main burn
er, a control switch having a pair of contacts
er, a control switch having hot and cold contacts
adapted to be opened and closed for controlling
for controlling current supply to said means in
current supply to said means in response to
response to changes in a conditionA caused by
changes in a condition caused by operation of the 55 operation of the main burner,_said switch being
main burner, means for rendering one of said
movable to a neutral position for establishing
contacts responsive'to current flow acting to open
circuit conditions different from those established
said contacts when closedfa ballast resistor con
in said hot and cold contact positions, a ballast
nected in parallel circuit with said control means
resistor connected in parallel circuit with said
and exposed to heat of the pilot burner flame 60 control means and exposedV to heat of the pilot
for varying the current value supplied thereto
burner flame and electrically connected to said
upon variations in the resistivity of said resistor
control means for varying the' current value sup
due to the presence or absence of said llame,
plied thereto upon variations in the resistivity
and a pair of resistances in mutual parallel rela
of said resistor due to the presence or absence of
tion and jointly connected in series circuit with 65 said name, a pair of resistances in mutual parallel
said control means and said ballast resistor, one
relation and adapted to be jointly connected in
of said resistances being connected in said series
series circuit with said control means and said
circuit by operation of said contacts and being
ballast resistor, one of said resistances being con
cooperable with the other said resistance for
nected in said series circuit «by closure of said
adjusting the current value to said control means 70 cold contacts and’ being thereby cooperable with
when said contacts are closed whereby said con
the other said resistance for adjusting the cur
trol' means is caused to move to one of said posi
tions upon the variation in resistivity of said
ballast resistor due to the presence of said iiame.
rent value to said control means to cause move
ment thereof‘to one of said positions upon the
variationY in` resistivity oi said ballast resistor due
5. A control system for fuel vburnersA having 75 tol the presence of said flameV as aforesaid, and a
2,406,752
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thirdv _resistance >adapted to' be connected in
of said resistor due to the presence or absence
parallel circuit with saidfcontrol means and said
ballast resistor and in series circuit with said
other resistance upon closure of said hot con
tacts for adjusting the current value to said
control means and causing movement thereof
of said flame, a pair of resistorsone of which
changes its resistivity upon a change in tempera
from said one position toinitial position irre
spective of the heatedor unheatedV condition of
said ballast resistor.
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7. In a combined temperature and safety con
ture of said one resistor due to the flow of current
in said'circuit, a bimetal switch arm in said con
troller movable in one direction when said main
burner is not operating for connecting said pair
of resistors in said circuit in mutual'parallel rela
tion and in series circuit with said control means
and first resistor in mutual parallel relation
trol for fuel burners, the combination with elec
thereby causing sufficient current to be impressed
trically operated _fuel ‘control means and a plu
rality of electrical circuits for said means having
different resistance values, of a control switch
on said control means to actuate it to a position
operable for alternatively establishing said cir
cuits and thereby varying the currentvalue to
said means, said switch comprising a thermally
responsive element movable in response to
changes in ambient temperature caused by op
eration of Va burner, a second thermally respon
sive element movable in response to passage of
electric current therethrough, switching means
.for supplying fuel to said main burner when
saidv first resistor is heated', a second bimetal
switch -arm in said controller movable in one di
rection in response to current ñow in said circuit
for electrically disconnecting the other one of
said pair of resistors from said circuit, said first
resistor and said one resistor having a combined
resistance value such as to cause a reduction in
the current value impressed upon said control
means to an amount Sufficient only to maintain
operable by movement of said ñrst element upon
said position but insufficient to effect actuation
one ambient temperature condition to establish
thereof, and means cooperable with said first bi
`one of said circuits and cause variation in the 25 metal arm upon'movement thereof in another
direction'forintroducing additional resistance in
current value to said control means, said second
parallel circuit withY said control means While the
element being moved upon said operation of said
switching means to discontinue said passage of
current value thereto is so reduced to render said
current therethrough and cause return Vof said
current insufficient to maintain said position and
second element to initial position to -establish a 30 cause discontinuance of fuelfsupply to the main
second one of said circuits and another variation
10. A control> system for fuel burners having
in the current value to .said control means; and
main and pilotburners, comprising an electrically
second switching means operable by movement
operable device for controlling supply of fuel to
of said first element upon another ambient tem
the main burner, said fuel supply being contingent
perature condition to establish a third one of said
upon current of a predetermined minimum value
circuits and cause a'further _variation in the cur
being supplied- to said device, a source of current
rent value to said control means.
i
supply for said device and being of at least said
8. The combination with a fuel burner Asystem
minimum value, a ballast resistor electrically con
comprising a main fuel burner, a, pilotfburner,
electrically operable control means, a controller, 40 nectedfto said device and exposed to the heat of
a ñame at the pilot burner for varying the cur
and an electrical circuit including said'vcontroller
and control means for controlling said main burn
rent value to said device according to variations
er, of a first resistor exposed to the heat of the
in the resistance of said ballast resistor dueto
the presence or absence of said flame, a resistance
pilot burner llame for varying the current value
supplied thereto upon variations in the resistivity 45 element in circuit with said device and ballast
resistor and cooperable with said ballast resistor
of said resistor due to thepresence or absence
to cause said current value to fall below said
of said flame, a pair of resistors one of which
minimum upon the variation in resistance of said
changes its resistivity upon a change in tem
ballast resistor due to the extinguishment of the
perature of said one resistor due to the, ñow of
current in said circuit, means associated with said 50 f flame at the pilot burner, a controller responsive
to changes in a condition caused by operation of
controllerY for connecting said pair of resistors
in said circuit in mutual parallel -relation and in
the main burner and means _controlled by said
controller fory introducing additional resistance
series circuit with said control means and ñrst
into rsaid circuit and being cooperablev with said
resistorin mutual parallel relation thereby caus
ing sufhcient current to be impressed on said con 55 resistance element to cause said current value to
fall below said minimum irrespective of the heated
trolY means to actuate itto one controlling posi
condition of said ball-ast resistor.
»
tion when said ñrst resistor is heated, and means
K l1. A control system for >fuel burners having
Y'associated withsaid controller and responsive to
main andpilot burners, comprising an electrically
current flow in said circuit for electrically dis
connecting the other one of said pair of resistors 60 operable device for controlling supply of fuel to
the main burner, said fuel supply being contin
from said circuit when said control means is in
gent upon current of a predetermined minimum
said one controlling position, said first resistor
l value being supplied to said device, a source of
and said one >resistor having a combined resist
current supplyV for said device and being of at
ance value such as to cause only suñicient current
least said minimum value, a ballast resistor elec
to be impressed upon said control means to main-`
burner.
s
l
e
'f
tain it in said position but insufficient to effect ,
trically connected to Ysaid-source in shunt with
actuation thereof.
said device and exposed to the heat of a flame
Y
at the pilot burner _for varying the current value
9. The combination with a fuel burner system
to said device according to variations in the
comprising` a main fuel burner, a pilot burner,
electrically operable control means, a controller, 70 resistance of said ballast resistor due to the pres
and an electrical circuit including said controller
ence or absence of said flame, a resistance ele
ment cooperable with said ballast resistor and
and control means for controlling said main burn
connected in series circuit with said resistor and
er, of a first resistor exposed to the heat of the
pilot burner flame for varying the current value
device to cause said current value to fall below
supplied thereto upon variations in the resistivity 75 said minimum upon the variation in resistance
2,406,752
12
111
contactpairs on a A`further rise in said' tempera
of said ballast resistor due to the cxtinguishrnent
of the fiame'at the .pilot burner, a-controll'er re
sponsive to changes in a condition causedby
ture yand having sufficiently greater resistance
cause _said Vcurrent', value to fall 'below ,saidmini
than »said second circuit to render the current
value to `said means insufficient to maintain said
means in fuel supply position in the heated vcon
dition of said >ballast resistor, and thermally re
sponsive means operable to cause opening of said
one contact pair to establish said second circuit
acircuit for -said lmeans established linltl'ie `open
value suchîthatsa'id control means is’maintained
operation of the vmain bur-ner, and means con
trolled iby ysaid controller for introducing ¿addi
tional resistance in »shunt >with said `device :and
being cooperable withfs'ai-d resistance element to
irrespective of said temperature condition.
mum irrespective of theheated -conditicn'of said
10
14. YIna control îsystem for fuel burners, elec
ballast resistor.
trically operable'fuelfcontrol-means arranged for
l2. A control system lfor fuel 4burnersxhaving
fuel supply to -a burner when said means is vplaced
'main and pilot burners, comprising electrically
in energized condition and for preventing .said
operable means ,movable .between positions for
fuel :supply when -placed in effectively deener
controlling the fuel <supplyto ,the `main burner, '
gized condition, a control switch ,for said means
a ballast resistor having -a preselected tempera- i
including a'plurality of contact ¿pairs 'adapted to
ture coefficient of yresistance :located‘to be heated
be nalternatively closed 1in response to lchanges-in
by the pilot burner `and electrically connected'to
a condition caused 'by'operation :of the burner,
said means, a control switch‘for said >means `in
said `svi/“itch .having an :open position vof all of -said
cluding a plurality >of pairs .of contacts adapted
to be alternatively closed ‘inresponse 'to :changes 20 contact pairsyacircuit for said fuel controlineans
initially yestablished in the -zopen `position fof said
ina condition caused by operation of the ymain
switch, meanslresponsiveto closure of ‘oneîofzsaid
burner, .separate circuits for .said means estab
Contact ‘pairs .for reducing >the :total 'resistance
lished respectively by closure of said contact pairs
Value of lsaid circuit sufliciently to cause said
and having different resistance values, one-ofsaid
circuits having a resistance value iin the heated 25 fuel >control‘rnea‘nsto be'placed in said energized
condition, Iand means responsive to closure .of
condition `of said -ballas't resistor such »that Athe
another .one >of said Contact pairs for increasing
current vvalue to said means is »Isu'flicient lto «cause
vthe;tota`l resistance Vvalue o‘fzsaid circuit sufficient
movement thereof to l-fuel supply position and
ly ‘to .cause ‘said -fuel control 'means lto Ibe rplaced
another said circuit »having a `resistance value
such that the ycurrent-value is insufficient to main 30 in said effectively deenergized condition, said cir
cuit as Ainitially established having a vresistance
tain said means in said fuel supply position, and
in the condition in :Whichit has 'been placed 'by
position of all .of said ‘Contact pairs Yand having
a resistance value `intermediate those of said‘sep
arate circuits for rendering the current value in
effective‘to ycause said means -to change Athe'po
sition to which it has Vbeen‘n'loved Iby establish
ment of said one or another‘of said'separate-cir
a preceding.closure‘of‘either said one or the other
35 ofY said contact pairs.
cuits, `said `ballast resistor being eifective `upon
Y extinguishment of >said flame for increasing'the
resistance value Vof the last-saidvcircuit and there
by reducing the current value 'to saidmeans suffi
ciently to cause movement thereof from “said’fuel
supply position.
l5. In a control system for fuel ~burners,-electrically operable fuel control means arranged ‘for
fuel supply -to a'burner whensaidmeans is placed
in energized condition and for preventing said
fuel 'supply when placed in effectively ydeener
gized condition, a con‘trol switch vfor said Ameans
including a plurality of contact pairs adapted
to be alternatively closed in response yto changes
in-a condition caused by‘operation ofthe burner,
said switch having -an open position of all of Vsaid
contactpairs, acircuit for said fuel control means
initially established in the open position of «said
operable means movable 'between Apositions for
switch and ‘including ya resistor, means responsive
controlling the supply of fuel to the main burner,
to Vclosure of one of «saidcontact pairs for >introa ballast‘resistor electrically `connected to said
means and >responsive to the presence or absence 50 ducing resistance means ‘in parallel circuit with
said resistor for reducing lthe total resistance
of a flame .at ‘the `pilot burner for varying the
value of said circuit sufficiently to cause said fuel
current value supplied to said means, a thermo
control means to beplaced in saidenergized con
static control'svvitch for said.m'eans including'two
dition, and means responsive to closure of another
pairs of contacts adapted to be alternatively
oneof said contact pairs for introducing another
closed- in response to changes in a temperature
resistance means in parallel circuit with‘said fuel
condition causedby operationofthe mainburner,
control means for increasing the Atotal resistance
a circuit for said means established upon closure
value of >said circuit sufñciently to cause 'said
of one of said contact pairs on Ya >drop in .said
fuel control :means to be placed in said 'eifec
temperature and’havinga resistance value „such
tively deenergized condition, _said circuit as
that the current value to said meansis sufficient
initially established having a resistance value
to cause movement ïthereof to fuel supply position,
13. A control system for .fuel burners having "
main “and 'pilot burners, -comprising electrically
a second circuit for said means „established in
without either of said resistance means such that
the open ,position of said two `contact `pairs on
a rise insaid temperature and having aresistance
value :greater than that Vof the Afirst >said ,circuit
to reduce the current value .to said means ïbut
insuiiiciently 'to `.cause movement from Asaid ~fuel
supply position, a'third circuit for said Ymeans
established `upon closure of `the other of said
said control ‘means_is maintained in the condition
in which it has‘been placed by apreceding closure
of either saidone or the other ofsaid-contact
pairs.
'
SAMUEL G._ ESKIN.
`CI-llAlÈtLES 4K. STROBEL.
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