US3594107A - Electric ignition system using a ptc ignitor as a sensing means - Google Patents

Electric ignition system using a ptc ignitor as a sensing means Download PDF

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Publication number
US3594107A
US3594107A US808840A US3594107DA US3594107A US 3594107 A US3594107 A US 3594107A US 808840 A US808840 A US 808840A US 3594107D A US3594107D A US 3594107DA US 3594107 A US3594107 A US 3594107A
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United States
Prior art keywords
ignitor
electric
burner
coupled
fuel
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Expired - Lifetime
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US808840A
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English (en)
Inventor
James R Willson
Hugh J Tyler
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Robertshaw Controls Co
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Robertshaw Controls Co
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/06—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs structurally associated with fluid-fuel burners
    • F23Q7/10—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs structurally associated with fluid-fuel burners for gaseous fuel, e.g. in welding appliances
    • F23Q7/12—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs structurally associated with fluid-fuel burners for gaseous fuel, e.g. in welding appliances actuated by gas-controlling device

Definitions

  • U-S. ABSTRACT An electric ignition system for a fuel burner in- 317/98 eluding an electrical resistance-type ignitor, wherein the re- Cl. no sistance of the has a positive temperature coeffi ient
  • the present invention relates to electric ignition systems for fuel burners and, more particularly, to an electric ignition system wherein an electric ignitor element having a positive temperature coefficient of resistance is utilized as a fuel ignitor and, at the same time, as a temperature-sensing element for the control of fuel flow to the system burner.
  • Typical of such devices are circuits which employ a heatsensing element to monitor the burner flame.
  • the heat-sensing element is very often either a thermistor to detect heat directly or a photoelectric light detector to sense the light emitted by the burner flame.
  • the electrical control circuitry associated with these elements, as well as the elements themselves, are quite complex and often operate with considerable lag time which, in certain circumstances, can create a dangerously explosive condition in the immediate burner area.
  • Another object of this invention is to provide an electric ignition system with an electric ignitor element acting as both an igniting means and a heat-sensing means.
  • This invention has a further object in the provision of an electric ignition system having increased fail-safe characteristics.
  • An additional object of the present invention is the provision of simplified burner flame-proving circuitry for use with an electricignitor.
  • a still further object of this invention is to construct an electric ignition system having redundant safety characteristics for preventing raw fuel leakage.
  • An advantage of the invention is the provision of a simple and reliable electric ignitor system having few parts and inherent safety characteristics.
  • an electric ignition system for a fuel burner includes an electrical power source coupled to an electric ballast device and an electric ignitor, located adjacent the fuel burner, is coupled to the power source and the ballast device and has a positive temperature coefficient of resistance; an electrically operated fuel valve for the fuel burner is electrically coupled with the electric ignitor to form, an energizing circuit where the electrically operated valve is closed in the absence of electrical energization and opened upon energization by a.
  • the energizing circuit produces a voltage drop which is directly proportional to the temperature of the ignitor and which has a value equal to the above-mentioned particular value when the ignitor is above fuel igniting temperatures.
  • FIG. I shows a schematic circuit diagram of an ignition system embodying the present invention
  • FIG. 2 shows a schematic circuit diagram of a modification of the circuit of FIG. I incorporating flame-proving circuitry
  • FIG. 3 shows a graph illustrating the principles of operation of the circuits of FIGS. 1 and 2.
  • FIG. I which illustrates a preferred embodiment of the invention, shows an electric ignitor 10, having a positive temperature coefficient of resistance, connected in series with the energization winding of an electromagnetic relay 12, a ballast resistor 14, and a switch 16. The entire series circuit is connected to a source of electrical power, illustrated for simplicity by lines I8. Ballast resistor 14 and the winding of relay [2 may be replaced by a relay having a ballast winding, if desired, and are illustrated separately merely for the sake of clarity.
  • ignitor 10 Connected in parallel with ignitor 10 is an additional series circuit comprising an electrically operated fuel valve 20, a switch 22, and a set of normally open relay contacts 24 which are open (as shown) when relay 12 is not energized and are responsive to energization of relay 12 to move to a closed position.
  • the electrically operated fuel valve 20 may be of any well-known type, and may utilize any conventional type actuator, such as a heat motor, an electrom'agnet, etc. Accordingly, the fuel valve 20 is constructed and designed so as to be open only when energized by a voltage having a value which is greater than orequal to V (to be more fully explained with reference to FIG. 3). When fuel valve 20 is open, fuel .will flow via conduit 26 from a fuel source (not shown) through the fuel valve 20 to the fuel burner 28 located within igniting proximity of electric ignitor 10.
  • Hot-wire ballast relay 30 comprises a ballast arm 34 which acts as a series ballast resistor and expends when self-heated by current flowing therethrough to close a set of contacts 36.
  • Contacts 36 are connected in series with switch'22 and the energization winding of electromagnetic relay 38.
  • Relay 38 is magnetically coupled to normally open contacts 24 and a set of normally closed contacts 40 which are connected directly across thermistor 32. Relay 38, when energized, closes contacts 24 while simultaneously opening contacts 40.
  • FIGS. 1 and 2 operate in a similar manner, in accordance with the principles of operation of the invention. Both circuits may be utilized in any of various fuel burner systems, however, their operation will be explained herein in the context of a central heating furnace system.
  • switch 26 might correspond to either the main power switch, if it were desired that the ignitor be constantly energized, or the system thermostat. If switch 16, in a particular installation, corresponds to the system thermostat, switch 22 is not necessary and can be eliminated. It is noted that switches I6-and- 22 can beoperated either manually or automatically in accordance with the particular requirements of the installation.
  • directly operated, or indirectly thermostat where the switching element is responsive to a thermally sensitive device which monitors the temperature of the surrounding area, and are shown as single-pole singlethrow switches for illustrative purposes only.
  • resistor 14 need not be a ballast resistor, but may be of any suitable type such as a conventional fixed resistor; however, the used a ballast resistor, which operates in a conventional manner as a line-voltage-compensating device, is. preferred since the ballast operation of theelectric ignition system of the present invention by preventing power line voltage fluctuations from adversely afi'ectingsystem operation.
  • switch 16 corresponds to a main power-switch
  • switc'h'22 corresponds to a thermostatically operated switch.
  • the system will be at rest, as illustrated.
  • switch 22 will close, preparing the fuel valve 20 for energizatiodAM is point, closure of main power switch 16 will cause curreiit to flow from power source 18 through the series circuit including ignitor 10, relay winding 12 and ballast resistor 14.
  • the relay '12 will therefore be energized causing contacts 24 to close thereby placing the electrically operated valve 20 in parallel with the ignitor. Since the ignitor is cold, its resistance, which increases in direct proportion with its temperature,- will have a relatively low value with the ignitor and the remaining resistance of the series circuit acting as a voltage divider. Thus, the voltage drop across the ignitor initially will besmall. Since the fuel valve 20 is connected in parallel with the ignitor, the voltage drop across the ignitor is directly applied to the valve for energization thereof. As the ignitor increases in-temperature, its resistance will correspondingly increase as will the voltage drop thereacross. Thus, the amplitude of the'voltage drop across igniter [0 acts as a control signal which is responsive to ignitor temperature to preclude raw fuel leakage from the system.
  • FIG. 3 wherein there is shown a curve 42 which illustrates the variation of ignitor temperature with time when the ignitor is initially energized.
  • the curve also illustrates the variation in the voltage drop across the ignitor as its temperature varies.
  • time t in the graph corresponds to the time when the main power switch 16 is turned on.
  • T fuel igniting temperature
  • the voltage drop which is the potential appearing across the fuel valve, will be below V which is the minimum voltage needed to effectuate opening of the valve 20.
  • the fuel valve will only permit fuel to flow to the system bume'rwhen the temperature of the electric ignitor l0 is above thatvalue T which is necessary for ignition.
  • the ignitor 10 therefore, acts as both an igniting element and a heat sensing device to prevent raw fuel leakage.
  • the circuit also provides effective fail-safe characteristics since a failure in any electrical component which produces either a short circuit or an open circuit will rapidly deenergize the fuel valve to shut oh the flow of raw fuel to the burner. More particularly, if the ignitor opens, the current through that the increasing temperature of the ignitor produces an increasing voltage drop across the relay coil 38 which will be sufficiently great to cause its actuation only if the ignitor temperature is above fuel-igniting temperatures.
  • arm 34 of hot-wire relay need not be a ballast arm, but may be of any suitable type such as a conventional heat motor operator which expands when heated to close contacts 36.
  • a ballast device is preferred since the line voltage compensating characteristics thereof serve to enhance the operation of the electric ignition system of the present invention by preventing powerline voltage fluctuations from adversely affecting system operation.
  • an additional safety function is provided.
  • relay 38 When relay 38 is energized, normally closed contacts 40 are opened thereby connecting thermistor 32 in series with ignitor l0.
  • Thermistor 32 has a positive temperature coefficient and will have a sufficiently high value of resistance to reduce the voltage drop across relay coil 38 to a value which is insufficient to maintain its actuation unless a burner flame exists. When the flame is present, it will heat the ignitor causing its temperature, and therefore its resistance, to increase. to the point'where, even with the increased resistance of thermistor 32 in the series circuit, a sufficient voltage drop will be provided to energize the relay 38.
  • relay 12 can be designed to be current sensitive so that it will only operate when sufiicient current is flowing therethrough to assure heating of the ignitor to fuel-igniting temperatures.
  • the resistance of the ignitor will decrease and the potential across the relay coil will be insufficient to maintain fuel flow and therefore raw fuel leakage will be prevented. It is noted that the positive temperature coefficient characteristic of thermistor 32 provides a delay time for the ignitor to come to fuel igniting temperatures and establish a burner flame before the flame-proving feature is enabled.
  • this invention provides a simple, yet reliable, electric ignition system wherein the ignitor acts as a fuel-igniting device as well as a rapid acting heat-sensing element. In this manner, the fail-safe features of such a system are increased while the number of components required'is reduced. This invention therefore makes electric ignition systems available for many diverse applications requiring high-safety and low-production cost.
  • control means coupled to said power source
  • an electric ignitor adapted to be located adjacent the burner and coupled to said power source and said control means, said ignitor having a positive temperature coefficient of resistance
  • valve means adapted to control a flow of fuel to the burner and being electrically coupled with said electric ignitor to form an energizing circuit
  • valve means being closed in the absence of electrical energization and being opened upon energization by a voltage across said energizing circuit having at least a particular value
  • said energizing circuit having a voltage drop which is directly proportional to the temperature of said ignitor and which has a value equal to said particular value when said ignitor is above fuel-igniting temperatures.
  • control means includes current-sensing means for sensing a flow of current to said energizing circuit; and including switch means responsive to said current-sensing means and coupled in series with said valve means for disabling said valve means when said flow of current is below a predetermined level.
  • said currentsensing means includes a hot-wire ballast relay
  • said valve means includes an electrically operated valve and an electromagnetic relay having an energization winding and at least a normally open set of contacts coupled in series with said electrically operated valve across said electrical power source, said contacts closing in response to energization of said electromagnetic relay.
  • said burner flame-proving enabling means includes a thermistor having a positive temperature coefficient coupled in series with said energizing circuit and a normally closed set of contacts coupled in parallel with said thermistor, said contacts opening in response to energization of said electromagnetic relay, and said electric ignitor being maintained above fuel-igniting temperatures in the absence of burner flame outage.
  • An electric ignition system for a fuel burner comprising an electrical power source
  • an electric ignitor coupled to said power source and having a voltage drop thereacross which increases with temperature and has a particular value when said ignitor is at fueligniting temperatures
  • control means coupled in series with said electric ignitor for providing a constant load and for sensing a flow of current through said ignitor, switch means coupled with said electric ignitor by said control means when a flow of current is sensed thereby, and
  • said switch means coupling said electrically operated valve to said power source for energization when the voltage drop across said electric ignitor has a value greater than its said particular value.
  • control means includes a hot-wire ballast relay and wherein said switch means includes an electromagnetic relay having an energization winding and at least a normally open set of contacts coupled in series with said electrically operated valve across said electrical power source, said contacts closing in response to energization of said electromagnetic relay.
  • said burner flame-proving enabling means includes a thermistor having a positive temperature coefficient coupled in series with said electric ignitor and a normally closed set of contacts coupled in parallel with said thermistor, said contacts opening in response to energization of said electromagnetic relay and said electric ignitor being maintainedabove fuel-igniting temperatures in the absence of burner flame outage.
  • an electric ignitor adapted to be located adjacent the burner and coupled to said power means
  • said ignitor having a positive temperature coefficient of resistance
  • an electrically operated valve adapted to control a flow of fuel to the burner and being directly coupled with said electric ignitor to form an energizing circuit
  • valve being closed in the absence of electrical energization and being opened upon energization by a signal having at least a particular amplitude
  • said energizing circuit producing a signal responsive to the temperature of said ignitor having an amplitude equal to said particular amplitude when said ignitor is above fueligniting temperatures.
  • An electric ignition system for a fuel burner comprising input means adapted to be connected with a source of electricity,
  • an electric ignitor coupled with said input means and adapted to be disposed within igniting proximity of the burner, said electric ignitor having a positive temperature coefficient of resistance
  • valve means in direct electrical circuit with said electric ignitor and adapted to control a flow of fuel to the burner, said valve means being operated in accordance with the resistance of said electric ignitor.
  • the invention as recited in claim 14 further including flame proving means coupled to said valve means and said electric ignitor for closing said valve means upon burner flame outage.
  • said flame proving means comprises a thermistor having a positive temperature coefficient.
  • valve means is electrically connected in parallel circuit with said electric ignitor.
  • An electric ignition system for a fuel burner comprising input means adapted to be connected with a source of electricity,
  • an electric ignitor connected with said input means and adapted to be disposed within igniting proximity of the burner, said electric ignitor having a positive temperature coefficient of resistance such that current through said electric ignitor and voltage across said electric ignitor are dependent upon ignitor temperature,
  • valve means adapted to control a flow of fuel to the burner
  • first control means coupled with said voltage sensing means and said valve means to control said valve means in response to the amplitude of the voltage across said electric ignitor
  • second control means coupled with said current-sensing means to control said valve means in response to the amount of current flowing through said electric ignitor.
  • said first control means comprises a switch responsive to said voltagesensing means.
  • An ignition system for a fuel burner comprising input means adapted to be connected to a source of electricity,
  • valve means to control said valve means in response to the amount of current flowing through said electric ignitor whereby said valve means is responsive to the temperature of said electric ignitor. 25.
  • said current-sensing means is in series with said electric ignitor.
  • control means includes a switch connected in series with said valve means and said input means.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Combustion (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)
US808840A 1969-03-20 1969-03-20 Electric ignition system using a ptc ignitor as a sensing means Expired - Lifetime US3594107A (en)

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US80884069A 1969-03-20 1969-03-20

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US (1) US3594107A (es)
BE (1) BE747616A (es)
CA (1) CA918782A (es)
DE (1) DE2012998A1 (es)
ES (1) ES377650A1 (es)
FR (1) FR2039733A5 (es)
GB (1) GB1293202A (es)
NL (1) NL7003910A (es)
SE (1) SE371485B (es)
ZA (1) ZA701873B (es)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3871814A (en) * 1973-09-04 1975-03-18 Raytheon Co Electric ignition system
US4405299A (en) * 1981-07-24 1983-09-20 Honeywell Inc. Burner ignition and flame monitoring system
US5528226A (en) * 1994-06-24 1996-06-18 Advanced Micro Devices Inc. Apparatus and method for controlling the burn-off operation of a gas in a semiconductor wafer fabrication furnace
US5538416A (en) * 1995-02-27 1996-07-23 Honeywell Inc. Gas burner controller with main valve delay after pilot flame lightoff
US20210262661A1 (en) * 2020-02-21 2021-08-26 Hearth Products Controls Co. Ignition system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5035607A (en) * 1990-10-22 1991-07-30 Honeywell Inc. Fuel burner having an intermittent pilot with pre-ignition testing

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE22554E (en) * 1944-10-10 Electrical ignition system for
US2382216A (en) * 1941-09-24 1945-08-14 Robertshaw Thermostat Co Safety control for gaseous fuel burners
US2388909A (en) * 1942-08-25 1945-11-13 American Stove Co Electric ignition system for gaseous fuel burners
US3282324A (en) * 1965-10-11 1966-11-01 Ram Domestic Products Company Automatic fuel ignition and heat detection system
US3454345A (en) * 1966-03-05 1969-07-08 Danfoss As Fuel igniting and flame sensing resistor with fuel feed control

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE22554E (en) * 1944-10-10 Electrical ignition system for
US2382216A (en) * 1941-09-24 1945-08-14 Robertshaw Thermostat Co Safety control for gaseous fuel burners
US2388909A (en) * 1942-08-25 1945-11-13 American Stove Co Electric ignition system for gaseous fuel burners
US3282324A (en) * 1965-10-11 1966-11-01 Ram Domestic Products Company Automatic fuel ignition and heat detection system
US3454345A (en) * 1966-03-05 1969-07-08 Danfoss As Fuel igniting and flame sensing resistor with fuel feed control

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3871814A (en) * 1973-09-04 1975-03-18 Raytheon Co Electric ignition system
US4405299A (en) * 1981-07-24 1983-09-20 Honeywell Inc. Burner ignition and flame monitoring system
US5528226A (en) * 1994-06-24 1996-06-18 Advanced Micro Devices Inc. Apparatus and method for controlling the burn-off operation of a gas in a semiconductor wafer fabrication furnace
US5538416A (en) * 1995-02-27 1996-07-23 Honeywell Inc. Gas burner controller with main valve delay after pilot flame lightoff
US20210262661A1 (en) * 2020-02-21 2021-08-26 Hearth Products Controls Co. Ignition system
US11619385B2 (en) * 2020-02-21 2023-04-04 Hearth Products Controls Co. Ignition system

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FR2039733A5 (es) 1971-01-15
DE2012998A1 (de) 1970-10-08
ES377650A1 (es) 1972-07-16
CA918782A (en) 1973-01-09
BE747616A (fr) 1970-08-31
NL7003910A (es) 1970-09-22
GB1293202A (en) 1972-10-18
SE371485B (es) 1974-11-18
ZA701873B (en) 1971-03-31

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