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Патент USA US2403411

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Juli’ 2, 1946- I
‘
’
.
v
'
c. K. STROBEL
_
2,403,411
COIiTROL SYSTEM FOR FUEL BURNERS
Filed ‘Aug. 23, 1944
IN VEN TOR
2'
'BY
HIS
ATTORNEY
2,403,411
Patented July 2, 1946
UNITED STATES ‘PATENT OFFICE "
CONTROL SYSTEM FOR FUEL BURNERS‘
Charles K. Strobel, Pittsburgh, Pa., assignor to -
Robertshaw Thermostat Company, Youngwood,
Pa... a corporation of Pennsylvania
'
Application August 23, 1944, Serial No. 550,755 '
10 Claims.
- (01. 158-1171)
This invention relates to control and ignition
systems for fuel burners and, more particularly,
and a series resistor 34 is associated therewith to
facilitate adjustment of the current values in the
to systems for domestic gas water heaters em
secondary circuit. A ballast resistor. 36 having
bodying water temperature andsafety controls.
normally a relatively low resistance and a. posi
An object of this invention is to control ig
nition and fuel flow in conjunction with a bum
tive temperature coe?icient of resistance is posi
tioned to be exposed to the ?ame of the burner
It! for causing, either directly or in cooperation
with other devices to be described, operation of
the solenoid valve l8 under certain conditions.
It will be understood that although the ballast
resistor 36 is thermally responsive to the passage
er under a number of di?erent conditions includ
ing ?ame failure and water temperature.
Another object of the invention is to achieve
economy in operation by eliminating a constant
burning gas pilot.
.
Another object of the invention is to prolong
the life of the electrical ignition device by deen
ergizing it as soon as the burner is ignited.
Another object of the invention is to utilize an 15
of current therethrough, it isprimarily the heat
ing thereof by the burner ?ame which causes
the variation in resistance relied upon in this
embodiment.
'
-
electrical bridge type of control circuit in which
very little power is consumed during off periods
As indicated hereinbefore, a control resistor
38 is provided for cooperation with the ballast
of the burner.
'
resistor 35 to control operation of the solenoid
Other objects and advantages will become ap
valve 56 and serves to render the adjustment of
parent from the following description taken in 20 the circuit constants less critical. In order to
connection with the accompanying drawing,
accelerate the operation of the solenoid valve it
upon a change in the value of the current sup
wherein
_
I
Fig. 1 is a schematic view of a safety control
plied thereto, the control resistor 38 may also _
apparatus and ignition system for a gaseous fuel
vary appreciably in resistance value upon ther- -_
mal changes and have normally a relatively low
burner embodying the temperature control fea
resistance and a positive temperature coezmcient
tures of this invention; and
Fig. 2 is a circuit diagram showing the elec
of resistance, asin the case of the ballast resis
trical connections.
tor 36. The resistor 381s not, however, exposed
Referring more particularly to the drawing, a
to the heat of any ?ame but is adapted to become
gaseous fuel burner i0 is supplied with fuel by a 3.0 heated upon passage of electric current there
through and will vary in resistance value in ac—
main fuel pipe l2‘. The fuel supply is controlled
-cordance with changes of temperature caused by '
by a main valve it! which, in this instance, is ar
changes in the value of the current ?owing
ranged for manual operation by a suitable knob
through'it. A cut-out 40 is also included in the _
or handle it but which may be arranged for
thermostatic operation if desired. Interposed in 35 secondary circuit and is preferably of the ther
the fuel supply pipe I? between the main valve
M and the burner I0 is an electromagnetic or
mal type having time-delayed operation for a‘
purpose which will be apparent hereinafter.
Such devices are constructed with predetermined
time-current characteristics and usually contain
solenoid gas valve iii of any known type which
is arranged to be opened by energization of the
solenoid and closed by gravity, spring or other 40 a heater element in addition to and a?‘ecting a
fusible member which opens the circuit by pas
bias upon deenergization or reduction of the cur
rent value thereto below holding value.
sage of ovcrcurrent.
_
,
The operating coil of the solenoid valve to is
Electric current for the operation of the ap- ‘
paratus is'supplied by the line wires .20 which.
arranged to be short-circuited by switching
may carry commercial current'at a voltage vari 45 means ,of any suitable type for a predetermined
period of time following operation of the main
ation from 105 to 125 volts. In this embodiment,
switch of valve I 4. Moreover, after the expira
the main valve M has a main switch (not shown)
tion of a second and longer predetermined pe
combined therewith which is of the double-pole
riod of time. the igniter 82 is deenergizedand re
type having two terminalsconnected in series
circuit with the line Wires 20 by wires 24 and 26. 50 mains inoperative during the remainder of the '
running period of the burner M. A thermal tim
The other two terminals ' of ‘the double-pole
ing switch generally designated 4! is provided
switch are connected by wires 28—30 in series
for these purposes and includes abimetal switch
An electrical igniter 32, preferably of the re
arm 42 having a heater coil 44 and resistor 45 as
sistance coil type, is provided for the burner-10 55 sociated therewith; a long time-delay- switch arm .
circuit with the primary of a transformer 22. '
2,403,411
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4
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48 and a short time-delay switch arm 48 both
' facilitate illustration of the circuit connections‘
of which are resilient and movable in response
but without otherwise altering the essential char
to warping of switch arm 42. The long delay arm
48 carries contacts 58-—5i on opposite sides
it is connected.
acter of this timing device or the circuit wherein
8
_ thereof which are movable into and out of op
The thermostatic or manual opening of the
. erative engagement with contacts 48 and 52 car
main valve l4 by its handle l8 permits fuel to
ried on bimetal arm 42 and switch arm 48, re
?ow in the main fuel pipe [2 as far as the electro-.
magnetic or solenoid valve [8 which is initially
closed. As the main switch combined with the
spectively.
Both switch arms 48 and 48 are initially po
sitioned with their contacts 5| and 52 engaged 10 main fuel valve I4 is also operated to closed po
sition when the main fuel valve is opened the
and with contacts 58 and '48 also engaged, and
electrical bridge circuit is established as follows
are adapted to open their contacts upon warping
with reference to Fig. 1 of the drawing: From the
, of the bimetal arm 42 due to the heat of the coil
lower terminal of the secondary of the trans
44. Suitable stops may be provided to limit
movement of switch arms 48-48 during the 15 former 22, wire 12 to junction A, wire 18, solenoid
valve l8, wire 14 to junction B, wire 18, switch
opening movement. 'In this embodiment of the
arm 48, contacts 58-48, wire 18, resistor 84, wire
invention the switch arm 48 has the longer time
88, igniter 32, wire 82, contacts 88-18, wire 8|
delay before opening ‘of the contacts 48-58 and
to junction C, wire 84, resistor 38, wire 88 to
this delay period may be eighteen seconds after
the main switch of valve i4 is closed. The switch 20 junction D, and wire 81, resistor 88, wire 88 to
. junction A. Wire 88 connects jun'ction- C to the
arm 48 has the shorter time delay before open
upper terminal of the secondary of transformer
ing of the contacts 5I—'52 following the closing
22.
i
of the main switch of valve l4 and this period
may be ?ve seconds.
Means responsive to a condition caused by op
eration of the burner l8 are provided for con
The cut-out 48 is connected as the detector arm
25 of the bridge in this initial or starting period
circuit by a wire 88 connecting one terminal
thereof to junction B and a wire 82 connecting
the other terminal thereof to junction D. The
temporary short-circuiting of the solenoid valve
30 I8 is established by a shunt path across junctions
A and B by a wire 88 from junction A, wire 84,
the drawing, the knob or handle i8 for operating
switch arm 48. contacts 52-5 l , switch arm 48 and
the combined valve and switch i4 could be uti
wire 18 to junction B. The heater coil 44 for
lized for setting the temperature regulator 54 to
the bimetal switch is connected at one end by a
operate at a desired temperature. As indicated
schematically in this ?gure, the temperature reg 35 wire 88 to the wire 88 and the opposite end thereof
is connected by a wire 88 to one end of resistor 45
ulator 54 may comprise a pair of levers 58-58
the opposite end of which is connected by a wire
connected by an overcenter spring 88 and sup
I80 to contact 88.
ported at opposite ends for snap-action in knife
By referring to Fig. 2 of the drawing it will be
edgc bearings carried on a pivoted frame 82. The
apparent that the bridge consists of the valve coil
lever 58 is adapted to be engaged by the actuat
iii in one arm in series with the adjacent arm
ing portion of a thermally sensitive element 84,
formed of the long time-delay switch“, resistor
the other portions of the thermal element com
84, igniter 32 and the thermostatic switch 54.
prising‘ the usual capillary tube .88 and bulb 88
The other two arms in parallel with‘the fore
which is located in the space to be heated by the
going consist individually of resistor 88 and re
main burner l8. As previously indicated herein
sistor 88 'in series. Thus, the current‘from ‘the
this space could well be the water tank of a
secondary of transformer 22 enters the bridge at
domestic water heater and the temperature could
junctions A and C while the cut-out 48 is con
be regulated by operation. of the thermostat 54
nected as the detector arm at junctions B and
in accordance with the setting of the handle £8.
The lever 58 carries, at the end opposite the knife 50 D. The short-circuiting of the valve coil is
shown as being established by switch arm 48
edge bearing therefor, a contact 88 adapted for
connected at junctions A and B. The heater coil
movement into and out of engagement with a sta
44 and resistor 45 are shown as connected in par- '
tionary contact 18 to open and close the circuit
allel with all the elements of the ?rst two bridge as hereinafter described. It will be apparent
that the snap-acting thermostatic regulator 54 55 arms except the thermostatic switch 54 which is
in series. circuit therewith.
‘disclosed herein is in schematic form only and
In Figs, 1 and 2 the parts are shown in the
various modi?cations could be made in the de
trolling operation of the thermal timing switch
4| through its heater coil 44 and may comprise
a temperature regulator 54 of the snap-acting
type. As indicated in broken lines in Fig. 1 of
running position with the thermostat calling for
heat. Upon initial closing of the main switch of
The description of the operation of the device, 60 valve M the elements comprising the bridge cir
which now proceeds, includes a description of '
cuit are unheated and the coil of the solenoid
the electrical connection for the various parts 01'
valve 18 is short-circuited by the short time-delay
the apparatus and-reference may be had to Fig. 2
switch comprising switch arm 48 and contacts
of the drawing for a clearer understanding of the
8I—52. It will be apparent, therefore, that at
65
precise form of electrical circuit. It will be ap
this time the bridge ‘network is considerably un
parent from the diagram showri‘in Fig. 2 of the
balanced so that the current through the wires
drawing that upon initial closure of the main
88—82 to the cut-out 48 is large until the circuit
switch of valve l_4 the various elements are con
elements
heat up and the bridge balance is im
nected in abridge type of circuit, except insofar
proved. However, due to the time lag of the cut
as the heater coil 44 and the short time-delay
out 48 the large inrush current upon initial clos
switch arm 48 and associated contacts are con- ing of the main switch of valve I4 is ineffective
cerned. It will further be observed that the ther
to cause operation of the cut-out. Upon expira
mal timing element 4| vwhich is shown as a unit
tion of the specified ?ve seconds time-delay the
in Fig. 1 of the drawing has been separated into
two switching devices in Fig. 2 of the drawing to 75 short time-delay switch opens and causes re
tails of construction and operation for commer- ,
cial use.
,
solenoid valve I8 at the end of the starting pe
riod if the ballast resistor 36 has not become
heated, a similar provision is made for such valve
moval of the short-circuit from the coil I8 01’
the solenoid valve.
.
-
During this preliminary period the igniterv 32
is preheated before any fuel flows from the burn
er ‘In and reaches igniting temperature. The
solenoid valve I8 is now actuated to open posi
closureduring the running period. Thus, if at
any time during the operation of the apparatus
the flame of the burner I8 ceases, then the ballast
tion through the circuit previously traced and
the fuel ?owing from the burner III is ignited
to produce a ?ame. It will be understood that
the current supplied to the coil of the solenoid
resistor 38 will cool and its resistance be lowered
in consequence so that the current through the
valve I8 to cause the pick-up from closed posi
tion may be of greater value than that required
to maintain this valve in open position. As the
igniter 32 is still connected in the circuit when
the pick-up occurs and is establishing a rela 15
whereupon closure will occur.
tively low impedance therein, it is apparent that
coil of the solenoid valve I8 is rendered insu?l- -
cient to maintain the valve in open position
The heater coil 44 of thebimetallic time-de
lay switch, together with the coil of the solenoid
valve I8, remains energized until the contacts
88—‘I0 of the thermostat are opened due to the
thermostat becoming satisfied. When this oc
curs, the heater coil 44 in series circuit with
the required value of the current is available
these contacts becomes deenergized causing bi
even if the ballast resistor 36 is unheated by the“
metal arm 42 to return toward its initial posi
burner ?ame and is of relatively low resistance.
~It may be assumed that the ballast resistor 38 20 tion closing ?rst the long delay switch contacts
and the control resistor 38 have now become
49-50 and then the short delay switch contacts
heated, the former due to the ?ame from the
burner I8 and the passage of current'there
through and the latter due to the passageoi cur
5I-—5.2.
The coil I8 of the solenoid valve con
tinues to receive current above release vvalue
during this switch closing action and the fuel
rent therethrough only. Consequently, the 25 continues to ?ow from the burner I0 until the
contacts 5I--52 of the short time-delay switch
bridge‘ balanceis improved to such an extent
close and cause the coil to be short-circuited.
When the temperature of the water in the tank
falls below that for which the thermostat has
of regardless of whether the main switch of valve
I4 is manipulated in on-off-on cycles at this 30 been set then the contacts 83-18 again close
‘ that current through the cut-out 40 is reduced
to a value insufficient to cause operation there
period of starting operation. The cut-out will
. and the sequence of operations previously de
now operate only on passage of overcurrent and
scribed will commence.
thus protects the circuit against failure of the
ballast resistor 38 during the running operation.
At the expiration or the eighteen-second
It will be apparent that the introduction of
the high resistance branch circuit in parallel
with the coil of the solenoid valve I8 upon, en
gagement of the contacts 49-50 of the long
_ time-delay of the long time-delay switch com
prising switch arm 48 and contacts 50 and 48,
- the igniter 32 and series resistor 34 become de
energized by operation of the long delay switch
to open position. The bridge nature of the cir
, cuit is thus eliminated unless the network is
considered a bridge with‘ in?nite impedance in
one arm. This operation of the switch having
the longer‘time-delayed action to open position
is entirely automatic and occurs regardless of
whether the ballast resistor 38 is heated by the
burner ?ame or even whether the burner has be
come ignited. As previously indicated, the cur
rent to the coil of‘the solenoid valve I8 is now
_ time-delay ‘switch during the shutting-off pe
riod of the burner does not affect the operation
of any part of the system as this branch only
40 carries a fraction of an ampere of current. How?
ever, this small current can be eliminated if de
sired by substituting a double-pole thermostat
for the single-pole type disclosed herein. Such
substitution would also eliminate the small
amount ' of current which ?ows through the
igniter 32' during part of the time the thermo
stat contacts 68—'I8 are open.
It will be ap
parent that‘the substitution of the double-pole
thermostat would merely involve the introduc
at the predetermined minimum value su?lcient
tion of an extra pair of contacts in the circuit of
the heater coil 44 as indicated in the broken lines,
to retain the valve in open‘ position.
Fig. 1 of the drawing.
reduced below pick-up value and need be only
'
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It will be seen that a complete condition and
safety control system has been provided in con
sistor 38 should have become heated by the burn- 55
I junction with ignition means for the main burn
er of a water heater or like appliance. While
er ?ame and its resistance have increased su?i
a preferred embodiment has been disclosed here
ciently to cooperate with resistor 38 and raise.
in, it will be apparent that many changes can
the resistance of the shunt established thereby
be made in the arrangement and combination
around the coil ‘of the solenoid valve I8 and cut
out 48 to compensate for the increase in' total 60 of parts and in the details of construction herein
disclosed within the ‘ scope of the appended
circuit resistance. Unless this increase in re
claims without departing from the spirit of the
sistance has occurred'then the current to the
solenoid valve coil will decrease below the pre—
I claim:
determined minimum value for holding purposes
1. In a control system ‘for fuel burners, an elec
and the valve I8 will be released to closed posi 65
trical igniter, an energizing circuit for said igniter,
tion. It will be understood that the predeter
a thermal switch having contacts operable for
mined minimum current value referred to herein
opening and closing said circuit, a heater for said~
is established by adjustment of the-circuit con
switch, and a control switch having contacts oper
stants and takes into account the ?uctuations in
able ior'controlling said heater and being coop~
the line voltage. Such action of the resistors
era-ble with said thermal switch contacts for con
38 and 38 is accelerated by providing that re
trolling said circuit.
sistor 38 be subject to the heating effects of the
When the contacts 49-58 of the long time-de
lay switch become disengaged the ballast re
invention.‘
. current passing therethrough and the valve clos
ing time is generally short.
,
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In addition to the provision for closing oi the
_
.
2..In a control system for a fuel burner, an
electrical igniter, an energizing circuit for said
igniter, a thermal switch having contacts oper
2,403,411
I7
8 .
adapted in one position to short-circuit said con
able for opening and closing said circuit, a heater
trol device, a heater for said thermal switch con
connected in parallel circuit with said igniter and '
_ thermal switch and causing operation» of said
-
thermal switch contacts for supplying heat‘ to
said thermal switch, a control switch having con
trolled by thelcontact iposition of said control
switch, and means responsive to the demand for
heat from the burner for actuating said control
tacts operable for opening and closing said heater
switch.
8. A safety control system for fuel, burners,
circuit and being cooperable with said thermal
comprising in combination, an electrical bridge
switch contacts for controlling said energizing
circuit having a plurality of resistors in two arms
circuit, and- means responsive to the demand for
heat from the burner for actuating said control 10 thereof, one ‘of saidresistors being exposed to '
the burner flame and adapted to vary in resistance
switch.
»
3. A safety control and ignition system for fuel
value when heated thereby; an electrically oper
burners comprising in combination an electrical
able fuel control device and a control switch in the
other two arms ‘respectively, said other two arms
bridge circuit having a plurality of resistors in
two arms thereof; a pair of bridge arms in par 15 being in parallel circuit with said resistor arms,
the current value to said control device being
allel circuit with said resistor arms and includ
ing an electrically operable fuel control device in
varied according to said resistance value to control
one of said pair of bridge arms, an igniter in an
operation of said device; means affording a cur
rent path across intermediate points of said bridge
other of' said pair of bridge arms, and a pair of
switches having contacts in said other pair of 20 circuit to maintain said device energized irrespec
tive of said switch position; a thermal switch
bridge arms and in series circuit with said device
and igniter; vand means operable in one contact
adapted in one position to short-circuit saidcon- .
position of one of said switches for operating the
trol device; and a heater for said thermal switch
other to open its contacts and thereby deenergize ,
controlled by said control ‘switch.
_
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>
9. A safety control and ignition system for a
25
said igniter.
'. .4. A safety control and ignition system for fuel
burners comprising in combination an electrical
bridge circuit having‘a plurality of resistors in
fuel burnerLcornprising in combination, an-elec- ‘
trical bridge circuit having a plurality of resistors
in two arms thereof, one of said resistors being
two armsthereofwa pair of bridge arms in par- 1. exposed to the burner ?ame and adapted to vary
allel circuit with said resistor arms and includ 30 in resistance value when heated thereby; a pair
ing an' electrically operable fuel control device in
of bridge arms in parallel circuit with said resistor
one of said pairrof bridge arms, an igniter in
a'rmsand including an electrically operable fuel
another of said pair of bridge arms, and a pair
control device in one of said pair of bridge arms,
of switches having contacts insaid other pair of
an igniter in another one of said pair of bridge
bridge arms and in series circuit with said device
arms, and a pair of switches having contacts in.
and igniter, one of said switches being thermally‘
said other one of said pair of bridge arms‘and in
operable vwith time delayed action; and heating
series circuit with said device and igniter, the
means controlled by the contact position of the
current value to said control device being varied
other said switch for operating said thermal
according to said resistance value to control oper
switch to open its contacts and thereby deener 40 ation of said device; means affording a current
gize said igniter. '
path across intermediate points of said bridge
5. Asafety control and ‘ignition system for a
circuit to maintain said device energized irre
fuel burner comprising in combination an elec
spective of said switch contact position; a third -,
trical bridge circuit having a plurality of resis
switch having contacts adapted in one position ‘
tons in two arms thereof; a pair of bridge arms in
' to short-circuit said control device; means con
parallel circuit with said resistor arms and includ
trolled by one of said ,pair of switches for causing
ing an electrically operable fuel control device
operation of the other one of said pair and said
in one of said pair of bridge arms, an igniter in
third switch;_and means responsive to the demand
another of'said pair of bridge arms, and a pair
for heat from the burner for actuating said one
of switches having contacts in said other pair of 50 switch.v
.
bridge arms and in series circuit with said de
10. A safety control and ignition system for a
vice and igniter, one of said switches being ther-'
fuel‘burner', comprising in combination, an elec
mally operable with time delayed action, heating
trical bridge circuit having a plurality of resistors
means controlled 'by the ‘contact position of the
in two arms thereof, one of said'resistors being
other said switch for operating said thermal 55 exposed to the burner ?ame and adapted to vary
switch to open its contacts and thereby deener
in resistance value when heated thereby; a third
gize said igniter, and means responsive to the
arm of said bridge including an electrically oper
demand for heat from the burner for actuating
able fuel control.device;a fourth arm of said
said other switch to change said contact position.
bridge including an igniter, a control switch and a
6. In a safety control system for fuel burners 60 thermal switch, said ‘switches having contacts
havinga source of electrical energy, an electri-v
in series circuit with said device and igniter, the
cally operable fuel controldevic'e in circuit with
current value to said device being varied accord
the source,‘ a control switch having contacts oper
ing to said resistance value to control operation '
able for opening and closing a second circuit from
of said device; means “affording a current path
the source, a thermal switch. having contacts 65 , across intermediate points of said bridge to main
adapted in one position to short-circuit said con
tain said device energized irrespective of said
trol-device, and a heater for saidthermal switch
controlled by the contact position of, said control
switch.
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_
switch'contact position; a second thermal switch
having contacts adapted in one position to short
circuit said control device; heating means for i
7.‘ In a safety control system for a fuel burner 70 said thermal switchescontrolled by~ the'contact
having a source of electrical energy, an electrically
position of said control switch; and means re
operable fuel control device in circuit with the
source, a control switch having contacts oper-'
. able for opening and closing a secondv circuit from
the source, athermal‘switch having contacts 75
sponsive to the demand for heat from the burner -
for actuating said control switch to change ‘said
contactiposition.
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QHARLIS K. STROBEL.
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