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Патент USA US2403412

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July 2, 1946
c. K. sT|§oBEL EI‘AL '
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2,403,412‘
IGNITION AND SAFETY CONTROL SYSTEM FOR FUEL BURNERS
Filed Aug. 8, 1945
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' Patented July 2, 1946,
2,403,412 '
ITED STATES PATENT-OFFICE
2,403,412
IGNITION AND SAFETY CONTROL SYSTEM ‘ ._
FOR FUEL BURNERS
Charles K. Strobel, Pittsburgh, Pa., and Samuel
G. Eskin, Los Angeles, Calif., assignors to
Robertshaw Thermostat Company, Youngwood,
Pa, a corporation of Pennsylvania
Application August 8,- 1945, Serial No. 609,626
6 Claims. (Cl. 158-4171)
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1 i
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ticularly,
to; electrically
therefor.
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operated
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may form part of a. thermostatic fuel ‘control de
vice of well-known form. The cock and switch- .
systems
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_2
main fuel cock and switching ‘means “which
This invention relates to ignition and safety
control systems for fuel burners and, more'par-v
_
Systems of the type indicated may be arranged
so that an electromagnetic safety valve may be
opened when a main switch is closed and the
fuel supply. turned on. The fuel is then ignited
by an electric igniter controlled by the main
switch and after the expiration of a starting 10
ing means It is arranged for manual operation
by a handle l5 carrying temperature indicia- It.
It will be apparent that the main fuel cock and
switching means it could be arranged for sepa
rate operation if desired and that the thermo
static device could be dispensed with.
‘ Interposed in the fuel supply pipe it between
the main fuel cock l4 and the burner it is an
period the .igniter is disconnected by operation
electromagnetic fuel valve_l6 of any known type
which may be arranged, as in this instance, to be
opened when current of su?lcient energizing
supply thereto according to variations in the re- .
sistance of a thermal resistor exposed to the 15 value is supplied to the solenoid ill thereof and
closed by gravity, spring. or other means upon a
heat of the burning fuel.
reduction of the current value thereto below
Where an electromagnetic relay is employed
holding value. A pilot burner it is provided for
I in conjunction with the timing device it is ap
of a timing device. The valve then either re
mains open or is closed by varying the current
igniting the main burner, ill and is supplied with
parent that power consumption and operating
noise would be'reduced if the power consuming 20 fuel from a conduit 28 connected to the main
fuel pipe it between the main burner it and the
element of the relay were disconnected after the
electrometlc valve it. .It will be observed,
starting period. It is, therefore, an object of
therefore that the electromagnetic valve 86 con
this invention to render the system substantially
trols the flow of fuel to both the main burner til ‘
noiseless during the running period.
Another object of the invention is to effect a 25. and the pilot burner 58. It will be apparent,
however, that where the pilot burner it is not
saving in, power consumption in the operation of
desired it could be. dispensed with without a?ect
safety and ignition systems.
ing the operation of the system in its essential
Another object of the invention is to insure
‘
reliable operation of the ‘system in performing . aspects.
The fuel issuing from the pilot burner ‘it is
its functions during the starting and. running
adapted to he ignited by an electric resistance
periods when normally operated.
ignite:
The heat of the ?ame of the burning
Another object of the invention is to render
the system suf?ciently ?exible as to length of
the‘ starting period to provide a wide range of
operation.
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Another object of the invention is to ‘place the
' .fnei
35 resistance eieinent 255 is preferably in the form
of soil
wire of material having normally a
timing device in condition for another starting '
period immediately upon inception of the prior
running period.
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other objects and advantages will become ap- ‘
parent from the following description taken in
connection with the accompanying drawing,
wherein:
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Fig. 1 is a schematic view of part of'a safety
control apparatus‘ for a gaseous fuei tanner
embodying this invention;
2 is a circuit diagram showing the elec
trical connections: and
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adapted to cause variation in resistance
of a thermos resistance element 2%. The thermal
W
reiatively low resistance and a positive tempera
ture eoefdcient of resistance and is adapted to
increase appreciably in resistance when heated
by the Same. While this resistance element 2!;
is also heated by passage of current therethrough
and other types of ballast resistors or ?ame sensi
tive elements could he substituted, it wili he tin
derstocd to he primarily responsive to the heat
of the
The igniter 22 and thermal resist
ance element
both located in proximity to
the piiot banner
where this burner is dis
-e’nsed
these elements wonid be positioned
in proximity to the main turner id.
‘
Figs. 3 and e are detailed views of the main
switching means in di?erent positions of 50 a. second thermai resistance era-sent at is m- '
cluded in the eiretnt and is also formed from a
operation.
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coil oi‘ wire . sting normally a relatively'low
Referring more particularly to the drawing, a
resistance
e
m “emperatlire cce?cient
gaseous fuel burner la is shown in Fig. l as be
ing supplied with fuel by a main fuel pipe E2.
The fuel supply is under control of aicombmed 55
esistance element it
a the demo of any
2,403,412
4
3
burner and is adapted to vary its resistance only
due to the passage of current therethrough. As
will be apparent hereinafter, the thermal re
sistance characteristics of the element 26 could
- be dispensed with and a ?xed or constant re
be traced as follows: From a source of electrical
7 energy by line wires 54, primary of transformer
56, wire 58 connected to one terminal of the sec
ondary of transformer 56, movable switch arm 50,
sistor employed if desired.
A cut-out 28 is provided for opening the circuit
of the solenoid ill in the event of an open circuit
occurring in the thermal resistance element 24.
The cut-out 28 is preferably of the thermal type 10
having time-lag operation. Such devices are con
structed with predetermined time current char-.
acterlstics and usually contain a heater element
in addition to and affecting a fusible member
which opens the circuit by passage of overcur 15
rent.‘
A control relay, designated generally by the
reference numeral 30, is provided for establish
ing desired circuit conditions during the starting
and running periods of the burner. The control 20
relay 36 is preferably of the electromagnetic type
having a winding 32 and a pivotally mounted
armature '34 which is rendered responsive vto en
ergization of the winding 32 by means of a core
terminal 52, wire 60, winding 32, wire 62 and
wire 64 to the other terminal of the secondary
of transformer 56.
The winding 32 being now energized from the
source of current supply, the armature 34 will be
operated to close the contact pairs 38, 40, pro
vided that the contacts are not already closed, as
will'be hereinafter explained. As the heater coil
55 is notenergized at this time the bimetal ele
ment 45 is cold and occupies the full line posi
tion shown in Fig. 2 of the drawing. In this po
sition the bias of the spring 44 is overcome and
the arm 42 is enabled to latch the armature in
its contact, closed position.
The normal rotation of the handle l5 of the
main fuel cock l4 from “off” to “on” position will
next cause disengagement of the switch arm 50
from the terminal 52 and positioning of the
parts in full “on” position as shown in Fig. 4.
It is apparent that the circuit for the winding
36 to which the armature is hinged at one end. ' 25 32 is opened but the contact pairs 38 and 40
A plurality of pairs of switch contacts, in this
remain engaged due to the latching arrange
ment. In this full “on” position the fuel cock
I4 is fully opened and the fuel may flow in the
main fuel pipe [2 at least as far as the electro
the arrangement shown both contact pairs 38
and 46 are closed and opened substantially si 30 magnetic valve IB which is normally closed. The
instance two, 36 and 4|], are adapted to be opened 5
and closed by operation of the armature 34. In
multaneously by appropriate movements of the
I arcuate switch arm 66 is now engaged with the
terminal 68 of the main switching means of fuel
armature, 34.
‘ cock l4 and establishes a starting circuit for the
'Means are provided for latching the armature
safety control and ignition apparatus.
34 in the closed position for a predetermined
This starting circuit is in the form of an elec
period during which the winding 32 may be de 35
trical bridge and may be traced from the source,
energized. The latching means comprises a piv
line wires 54, primary and secondary of trans
oted arm 42 adapted to engage and latch the
former 56, wire 58, switch arm 66, terminal 68,
armature 34 but being normally biased to free
and wire 10 to junction 12 of the bridge. The
position by a spring 44. A thermal timer of any
first arm of the bridge may be traced from junc
known type comprising a bimetal element 46 and
heater coil 48 therefor is adapted to overcome
tion 12, wire ‘I4, contact pairs 38 and 40, wire ‘I6,
igniter 22 and wire 18 to junction 86 of the bridge.
the bias of the spring 44 to enable the arm 42
to move into latching engagement with the arma
ture 34 when the bimetal element 46 is cold as
The second arm of the bridge may be traced from
junction 80, wire 82, solenoid coil H and wire
84 connected to junction 86 of the bridge. The
third arm of the bridge may be traced from
shown in Fig. 2. The thermal timer preferably
includes the so-called instantaneous reset device
(not shown) generally consisting of a cold con
junction 86, wire 88, thermal‘ resistance element
ducting surface for the bimetal element 4-8 which
24 and wire 90 connected to junction 32 of
causes return of the latter to its cold position
the bridge. The fourth arm of the bridge may
after warping therefrom.
be traced from junction 92, wire 94, second ther
The switching means of the main fuel cock l4
mal resistance element 26 and wire 96 connected
includes two movable switch arms 50 and 66 and
to junction 12.
two spaced terminals 52 and 68. The movable
The cut-out 28 is connected as the detector arm
switch arm 50 is adapted for operative engage
in the bridge circuit by a wire 3!! connecting one
ment with terminal 52 when the handle I5 is
terminal thereof to junction 92, the opposite ter
rotated to an intermediate position between “off”
minal
of the cut-out 28 being connected directly
and “on” (Fig, 3). The switch arm 66 is of
to the junction 80. The circuit for the bridge
arcuate form and is adapted to maintain opera
is completed by a wire Hi6 connected [at one end
tive engagement with terminal 58 from the “on”
to the junction 86 and at the opposite end to
60
position (Fig. 4) throughout a range of move
wire 64 which is connected to the secondary of
ment of the handle 55 so that various tempera
the transformer 56. If the cut-out 28 is consid
‘ ture settings may be selected at which the ther
ered of negligible impedance it is apparent that
mostat will operate. The arcuate switch arm 66
does not, however, engage the terminal 52 at any 65 the bridge circuit is, in eiiect, two parallel meshes
connected in series with the secondary of the
transformer 58. The impedance of this circuit is
The operation of the system is as follows: The
relatively low and sumcient current ?ows to the
main fuel cock i4 is shown in Fig. 2 in the “off”
solenoid ll of the electromagnetic valve it to
position and no fuel is being supplied to the main
time.
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open this valve regardless of whether or not the
burner it) or the pilot burner It. When the
main fuel cook it is turned toward the “on” posia 70 .thermal resistance element 24 is heated by the
burning fuel. Moreover, it will be apparent that
tion engagement occurs in an intermediate “on”
' the cut-out 23 which is connected in the detector
position between the movable switch arm 56 and
arm of the bridge circuit receives current which
-‘ the terminal 52 of the switching means as shown
is maintained below its steady state operating
in Fig. 3. A‘ circuit is then established for the
value at all times during the starting period due
winding 32 of the control relay 3!! which may ~
2,403,412 ‘
to the various arms of the bridge being in sub
stantial balance.
,
As the foregoing described bridge circuit causes
energization of the igniter 22, the fuel which is
"01?’ position will cause the movable switch arm
50 to become engaged with terminal 52. The
winding 32 of the control relay is thereupon
energized and the contact pairs 38', 40 will be
admitted to both the main burner l0 and the pilot -
closed.
burner is is vignited substantially simultaneously
with the opening of the electromagnetic valve It.
As the bimetal element 46 preferably is ar
ranged to engage a cold conducting surface as
The heat of the burning fuelwill cause the thermal _
described, when in the broken line position, it
will return quickly to its initial position, shown
resistance element 24 to become eil’ectively heated
after a predetermined period which may be a few
seconds.
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in full lines, causing the arm 42 to be moved tov
latching position as soon as the contact pairs 28
and 40 are opened. Thus, when the “off” posi
tion shown in Fig. 2 of the drawing is ?nally
reached and the winding 22 is again deenergized,
'
During this starting period, the heater coil 48
. 'of thethermal timer is also energized through a
vcircuit which may be traced from the source, line
wires l4, primary and secondary of transformer 15 the contact pairs 38 and 40 may be held in closed
56, wire 58, switch arm 88, terminal 68, wire 10,
position by the latching means due to the opera
wire 14. contact pair 28, wire I02, heater coil 48,
tion of the thermal timer described.
v wire I04, wire 82 and wire 84 to the secondary of
The winding 32 forming the electromagnetic
' component of the control relay is thus energized
the transformer 58. The bimetal element 46
becomes heated by the heater coil 48 ‘and warps '20 momentarily and then deenergiaed by the normal
to the broken line position shown in Fig. 2 of the
drawing.
‘ operation of the main fuel cock“ during the start
Thus, the I‘ bimetal element 46 is
ing operation. Thus, the circuit timing function
rendered incapable of overcoming the. bias of- the
‘ is performed while the power consuming element
spring 44 and the arm 42 istripped to cause open
is disconnected. The usual source of noise is thus
ing of the contact pairs 38 and 40. The thermal 25 not present during normal running of the burner
timer may conveniently operate after an eighteen
and the current consumption is correspondingly
second starting period which is sufficient to allow
the thermal resistance element 24 to become
heated bythe burning fuel. This period maybe
reduced.
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It will be understood that various changes can
be made in the arrangement and combination of
varied as desired by adjustment of the timer as 30 parts and in the form of the elements herein dis
will be apparent. 4
closed within the scope ofv the appended claims
without departing from the spirit of the inven~
'
This operation of the contact pairs Stand 40
terminates the starting period and marks the
tion.
inception of the normal running period of the
We claim:
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burner. The operation of contact pair 40 serves 35
1. An ignition and safety control system for fuel
to open the ?rst [arm of the bridge circuit and
. burners having a source of electrical energy, com
deenergize the igniter 22. _ The bridge circuit is
now converted to a circuit including the thermal
resistor 24 in parallel with the solenoid i1 and
cut-out 28 all in series with thermal resistor 26.
The total circuit impedance'is thus increased and
causes a'reduction in the value of the current
through the solenoid H. The current value is not
reduced below that required‘ to hold the electro
magnetic valve is in open position if the thermal is El
resistance-element 24 has now become 'su?lciently
prising electrically operable fuel controlling means
movable between fuel. flow permitting and pre
venting. positions, switching means for control
ling energization of said fuel controlling means
from the source and operative to cause said move-V
ment thereof, means responsive we condition
caused by combustion of the fuel and electrically
connected to said fuel controlling means for re
ducing the energy value supplied thereto su?i
ciently to cause movement thereof to flow pre
heated by the burning fuel and has increased
venting position in the absence of combustion, an
in resistance.. However, if at the end of the start
electric resistance igniter for the. fuel, control "
ing. period or at anytime during operation of the
means responsive to operation of said switching
system the ?ame of the pilot burner it should 50 means for rendering said condition responsive
cease. then the "resistance of the thermal re
means ineifective to cause said movement for a
sistance element 24 will be reduced by cooling
predetermined period during which said condi
thereof and the current to the coil II will be
‘ tion responsive means has time to become respon
rendered insumcient to maintain the electromag-,
siVe. said control means comprising a winding
netic valve iBin open position. Flow of fuel to
and switch contacts adapted to be closed for es
'both burners will then cease. This action is
tablishing a circuit from the source including
accelerated by making the resistance element 28
said fuel controlling means, said igniter and said ,
‘of the thermally responsive type.
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_
condition responsive means of su?lcient enersiz- ‘
It will be apparent that if the thermostatic con
trol deyice previously mentioned is included as
part/of the main fuel cock and switching means N
that the fuel supply to the main burner may be
60
ing value to cause said movement to vfuel ?ow
permitting position, said winding being connected
ina separate circuit with the source and adapted
to be deenergized by operation‘ of said switching
turned off and on thereby while the arcuate
switch arm 86 which is in operative'engagement
means to cause opening of'said switch contacts
ditions at the temperature setting inwhich the
handle I! is positioned. When the operation of
the main burner i0 is no longer desired. then the
handle ii of the main fuel cock 64 may be rotated
not exist.
2. An ignition and safety control system for fuel
burners having a source of electrical energy,
todisconnect said igniter and render said condi
‘with the terminal 88 maintains closed circuit con- _ 65 tion responsive means effective if combustion does
’ v in reverse direction from "on" to, "01!” position. 70
Such operation will serve to disengage the arcu
ate switch arm 68 from terminal 88 and cause
deenergization of the coil ll of the electromag
netic valve i8 whereupon the valve willclose.
Further reverse rotation- of the handle it toward I
comprising‘electrically‘ operable fuel controlling
means movable between fuel ?ow permitting and
preventing positions, switching meansv for con
trolling energization of said fuel controlling means
from the source and having a plurality of oper
ative positionsjmeans responsive to a conditionv
75 caused
by combustion of the fuel and electrically
2,403,412
7
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connected to said fuel controlling means for re' ,
ment effective if‘ the pilot burner does not pro
ducing the energy value supplied thereto sum
ciently to cause movement thereof to flow pre
venting position in the absence of combustion, an
electric resistance iguiter for the fuel, control
duce a flame.
_fuel burners energizalole from a source oi’ current
means e?ective in one said position of said switch
ing means for rendering said condition respon
bridge circuit, an electrically operable fuel con
sive means ineffective to cause said movement
trol device in a second arm of said bridge and
operable to supply fuel when current of sumcient
4. An ignition, and safety control system for
supply and comprising an electric igniter for the
fuel connected in a ?rst arm.‘ of an electrical
for a predetermined period during which said
condition responsive means has time to become
responsive, said control means comprising a
value is supplied‘ thereto, a pair of resistors in
third and fourth arms respectively of said bridge.
winding and switch contacts adapted to be closed
one of said resistors being exposed to the heat
of the burning fuel for varying in resistance and
for establishing a circuit from the source in
causing variation in said current value, control
cluding said fuel controlling means, said igniter
and said condition responsive means or‘ su?icient 15 means for rendering said igniter inoperable and
said current value ihsu?icient after a predetera
energizing value to cause said movement to fuel
?ow permitting position, said winding being con ‘_ mined period unless said one resistor is heated,
said, control means comprising switch contacts
nected in a separate circuit with said source and
operative for opening and closing said ?rst arm
adapted to be deenergized in said one position
of said switching means and energized in another 20 and a winding for operating said contacts,
switching means for connecting the source across
said position thereof, means responsive to clos
opposite junctions of said bridge with said ?rst
ing of said switch contacts for holding the same
and second'arms and said third and fourth arm
closed when said switching means is operated
in series circuit resmctively and in multiple
from said other position to said one positionv
thereof, and means for rendering said holding 25 across said junctions, said winding being con
nected in a separate circuit with the source and
means inoperative upon expiration of said period
adapted to be deenergized by operation of said
to cause opening of said switch contacts to dis
switching means to cause operation of said switch
connect said lgriter and render said condition re
contacts ‘for opening said iirst arm.
sponsive means eilective if combustion does not
exist.
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30
5. An, ignition and safety control system for
3.‘ An ignition and safety control system for fuel
burners having main and pilot burners and a
fuel burners energizalole from a source or current
source of electrical energy. comprising electro
fuel connected in a ?rst arm of an electrical
supply and comprising an'electric igniter for the
bridge circuit, an electrically operable fuel con
magnetic valve meansimovable between- closed
and open positions for controlling the fuel supply 35 trol device in a second arm of said bridge and
operable to supply fuel when current of sumcient
to the main burner, manually operable switch
ing means [for controlling energization of said
value is supplied thereto, a pair of resistors in
the third and fourth arms respectively of said
electromagnetic valve means and having a plu
bridge, one of said resistors being exposed to'the
rality of operative positions, a thermal resistance
element having a preselected temperature co 40 heat of the burning iuel for varying in resistance
and causing variation in said current value, con
emcient of resistance located in proximity of, the '
pilot burner and electrically connected to said
trol means for rendering said igniter inoperable
and said current value insumcient after a pre
electromagnetic valve means for reducing the en
ergy value supplied thereto upon variations in the 45 determined period unless said one resistor is
heated, said control means comprising switch
resistance of ‘said element due to the absence of
contacts operative for opening and closing said
a ?ame at the pilot burner, an electric resistance
first arm and a winding for operating said con
igniter for the pilot burner; a control relay effecr
tacts, switching means having a plurality of oper—
tive in one position of said switching means for menderingxsaid thermal resistance element ineffective 50 ative positions in one of which the sourceis con
to reduce said energy value su?iciently to cause
nected across opposite Junctions of said bridge
closing." of said electromagnetic valve means for
with said ?rst and second arms and said third
a predetermined period during which. said thermal
resistance element has time to become heated,
and fourth arms in series circuit respectively and
in multiple across said junctions, said winding
being connected in a separate circuit with the
said control relay comprising a winding'and a
plurality of switch contacts adapted to be closed i
source in said one position of said switching
source and adapted to be deenergized in said one
position of said switching means and energized
in another of said position thereoi’, means re
means, said ?rst circuit including said electro
magnetic valve means, said thermal resistance ele
>ment and said i'gniter and causing ‘movement’ of
when said switching means is operated from said
- for establishing first and second circuits from the
sponsive to operation of said switch contacts to
close said ?rst arm‘for holding the same closed
other position to said one position thereof, and
means for. rendering-said holding means inoper
'tion, said winding being connected in a third ative upon expiration of said period to cause
circuit with the source and adapted to be ener
' sized in another position of said switching means 65 operation of said switch contacts to open said
and immediately deenergized upon operation
6. An‘ ignition and safety control system for
thereof to said one position, means responsive
fuel ‘burners energi'zable from a source of cur
to closing of said switch contacts for holding the
rent supply and comprising an electric igniter
same closed when said switching means is- oper
for thefuel connected in a ?rst arm of an elec
ated to said one position thereof, and a thermal
trical bridge circuit having arms arranged in
,t'imcrhavinga heater coil in saidsecond circuit
'a
sequence, an electrically operable fuel control
adaptedfor rendering said holding means inop
erative upon expiration of- said period to cause. - _ device in a second arm of said bridge and oper
able to supply fuel when current of sufficient
opening of said switch contacts to disconnect said
said electromagnetic valve means to open posiy
?rst
isnlter and ‘ render said thermal resistance ele
arm.
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value is supplied thereto‘: pair of resistors in
2,403,412 '
10'
position of said switching means and
the third and fourth arms respectively of said
bridge, one of said resistors being exposed to the
heat oi the burning fuel for varying in resistance
and causing variation in said current value, con
energized '
I in another said position thereof, latching means
tor said armature normally biased to free posi
tion and adapted to hold said ?rst arm closed
when said switching means is operated from said
other position to said one position thereof, and I
trol means for rendering said igniter inoperable
, and said current value insu?icient after a prede
a thermal timer adapted to overcome the bias
termined period unless said one resistor is heated,
of said latching means to enable the same to-hold
said control means comprising a plurality 01' pairs
said ?rst arm closed, said timer having a heater
of switch contacts, a winding and an armature,_
one said contact pair being adapted for opening 10 coil controlled by another said contact pair and
connected to the source when said switching
and closing said ?rst arm, switching means hav
means is in said one position for rendering said
in: a plurality oi‘ operative positions in one of
timer incapable of overcoming said bias upon
which the source is connected to opposite junc
_ tions' oi’?'said ?rst and fourth arms and said sec-
-
0nd and third arms respectivel7,- said’ winding 15
being connected in a separate circuit with the
source and adapted to 'be deenergized in said one
expiration of said period.
;
crmnms K. s'moBEL
smear. a. serum.
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