US3741709A - Solid state safety control for fuel burning apparatus - Google Patents

Solid state safety control for fuel burning apparatus Download PDF

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Publication number
US3741709A
US3741709A US00217003A US3741709DA US3741709A US 3741709 A US3741709 A US 3741709A US 00217003 A US00217003 A US 00217003A US 3741709D A US3741709D A US 3741709DA US 3741709 A US3741709 A US 3741709A
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United States
Prior art keywords
flame
thyrister
lead
variable resistance
set forth
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Expired - Lifetime
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US00217003A
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English (en)
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L Clark
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Desa International LLC
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Koehring Co
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Assigned to KOEHRING COMPANY, A CORP. OF DE reassignment KOEHRING COMPANY, A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KOEHRING COMPANY A WI CORP.
Assigned to DESA INTERNATIONAL, INC., 2701 INDUSTRIAL DRIVE, BOWLING GREEN, KENTUCY, A CORP. OF DE. reassignment DESA INTERNATIONAL, INC., 2701 INDUSTRIAL DRIVE, BOWLING GREEN, KENTUCY, A CORP. OF DE. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KOEHRING COMPANY, 200 EXECUTIVE DRIVE, BROOKFIELD, WI., A CORP. OF DE.
Assigned to GENERAL ELECTRIC CREDIT CORPORATION reassignment GENERAL ELECTRIC CREDIT CORPORATION SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DESA INTERNATIONAL, INC.
Assigned to CONFEDERATION LIFE INSURANCE COMPANY reassignment CONFEDERATION LIFE INSURANCE COMPANY SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DESA INTERNATIONAL, INC., A DE CORP
Assigned to CONFEDERATION LIFE INSURANCE COMPANY reassignment CONFEDERATION LIFE INSURANCE COMPANY SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DESA INTERNATIONAL, INC.
Assigned to GENERAL ELECTRIC CREDIT CORPORATION reassignment GENERAL ELECTRIC CREDIT CORPORATION ADDENDUM TO SECURITY AGREEMENT Assignors: DESA INTERNATIONAL INC.
Assigned to COPENHAGEN HANDELSBANK A/S (AKTIESELSKABET KJOEBENHAVNS HANDELSBANK) CAYMAN BRANCH reassignment COPENHAGEN HANDELSBANK A/S (AKTIESELSKABET KJOEBENHAVNS HANDELSBANK) CAYMAN BRANCH SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DESA INTERNATIONAL, INC.
Anticipated expiration legal-status Critical
Assigned to DESA INTERNATIONAL, INC. reassignment DESA INTERNATIONAL, INC. TERMINATION AND RELEASE Assignors: COPENHAGEN HANDELSBANK A/S (NOW KNOW AS DEN DANSKE BANK)
Assigned to DESA INTERNATIONAL, INC. reassignment DESA INTERNATIONAL, INC. RELEASE AND TERMINATION Assignors: GENERAL ELECTRIC CAPITAL CORPORATION
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/08—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements
    • F23N5/082—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/20—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays
    • F23N5/203—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays using electronic means

Definitions

  • ABSTRACT A solid state flame sensing control circuit for a fuel burning device incorporates a thermal sensitive circuit breaker, a heating coil to energize the circuit breaker, a variable resistance device arranged to monitor and respond to a given physical condition or absence of the I flame of the fuel burning device and a thyrister type unit which when energized permits sufficient current to pass through the heating coil to trip the circuit breaker.
  • variable resistance device senses a proper flame condition the thyrister will be non-conductive; the thyrister becoming conductive when the variable resistance device, dependent on its nature, senses an absence of flame or a flame shift, or a temperature condition of such flame within the combustion chamber of the fuel burning device indicative of an absence of orimproper burning.
  • means are also provided to render the circuit insensitive to normal flame flicker.
  • the invention relates to a safety control for afuel burning device, and more particularly to a solid state flame sensing control circuit capable of constantly monitoring the operation of the fuel burning device and of shutting down the fuel burning device upon the occurrence of faulty ignition, flame loss or improper burning, irrespective of the cause.
  • control circuit of the present invention is generally applicable to fuel burning systems, for purposes of an exemplary illustration it will be described in connection with portable space heaters of conventional and well known types frequently used, for example, by contractors for heating and drying purposes.
  • such a space heater typically comprises an outer housing surrounding a combustion chamber. Means are provided to introduce air into the combustion chamber. A burneris located at one end of the combustion-chamber; The burner normally has a fuel nozzle, frequently incorporating eductor means providing jets of air to draw, mix and atomize the fuel delivered by the nozzle. The nozzle, together with the eductors, discharge a'combustible fuel-air mixture into the combustion chamber. Means are provided to ignite the mixture, and after initial ignition continuous burning occurs. Typically, during the continuous combustion, convection heat currents issue from the end of the heater opposite the burner and additional heat radiates from the surface of the heater housing.
  • Portable space heaters of the general type described are frequently provided with an ignition transfonner and a motor.
  • the motor normally runs a fan supplying airto the combustion chamber and the eductors and operates a fuel pump.
  • Inadequate and possibly dangerous conditions may also be indicated by a lower than normal temperature of the burner flame, representing improper combustion conditions.
  • thermosensitive circuit breaker and heating coil were again used, to-
  • a relay was provided having normally closed contact points in series with the heating coil.
  • the armature of the relay would react so the normally closed contact points would open removing sufficient power from the heating coil to prevent tripping of the circuit breaker.
  • Such a circuit has proven expensive to manufacture, requiring a relay (a relatively large component) and was subject to mechanical failure of the relay.
  • the safety control circuit of the present invention is a solid state circuit which is very small in size as compared to those of the prior art making it easy to apply in the most convenient manner and is very inexpensive to manufacture.
  • the circuit is reactive, and more effec tively in any case, both to improper burning and loss of flame, irrespective of the cause. Nevertheless, the circuit is so designed that in preferred embodiment it is not reactive to ordinary flame flicker so that unnecsary and sometimes highly damaging shut down of the fuel burning device will not occur.
  • the circuit contains no relays or similar devices of prior art apparatus which have been often subject to mechanical failure.
  • the device providing the solid state flame sensing control circuit of the present invention comprises first and second leads capable of providing its connection to a power source.
  • the electrical power means of the fuel burning device is connected across the first and second leads in parallel.
  • Such electrical power means may comprise, for example, a motor and an ignition transformer.
  • a thermal sensitive circuit breaker has the contacts thereof connected .in the first lead and across the first and second leads is connected an additional lead incorporating, in series,ia heating coil for actuating the circuit breaker, a first resistor and a silicon controlled rectifier. Yet another lead is provided incorporating a second resistor and a cadmium sulfide cell.
  • This last mentioned lead is connected at one end to that lead containing the heating coil, first resistor and silicon-controlled rectifier at a position between the heating coil and the first resistor.
  • the other end of the lead containing the second resistor and the cadmium sulfide cell is connected to the second lead.
  • the gate of the silicon controlled rectifier is connected by a lead to that lead containing the second resistor and the cadmium sulfide cell, at a position between the last two mentioned elements.
  • the silicon controlled rectifier gate lead contains a break-over device.
  • the circuit is such that when the cadmium sulfide cell senses a proper flame, sufficient voltage for firing the break-over device does not exist and the gate of the silicon controlled rectifier is not energized. Therefore, the silicon controlled rectifier will, under such conditions, be rendered non-conductive and the heating coil will then carry an insufficient amount of current to trip the thermal sensitive circuit breaker. Upon the occurrence of a flame failure or improper burning, the resistance of the cadmium sulfide cell will responsively increase to produce the firing voltage of the break-over device. Once this occurs, the gate of the silicion controlled rectifier will be energized and the silicon controlled rectifier will be rendered conductive, thereby permitting a flow of current through the heating coil sufficient to cause it to trip the thermal sensitive circuit breaker. As provided, the break-over device insures that the circuit will not react to normal flame flicker.
  • leads 1 and 2 are connectable to a suitable source of power (not shown). This connection may be made through the use of a simple plug. In addition, one of leads 1 and 2 may be provided with a conventional start switch.
  • the fuel burning apparatus is not shown, but exemplary electrical power means for the fuel burning apparatus are represented by the motor 3 and the ignition transformer 4.
  • the motor 3 and transformer 4 are connected in parallel across the leads 1 and 2 by leads 5 and 6, respectively.
  • the transformer 4 will serve in the ignition of the air-fuel mixture.
  • the motor 3 will operate a fan providing air for the combustion chamber and the eductors.
  • the motor may also drive a fuel pump, as the fuel burning device is provided with one.
  • a thermal sensitive circuit breaker and heating coil unit are generally indicated at 7.
  • the thermal sensitive circuit breaker 8 thereof is located in lead 1 while the heating coil 9 is located in a lead 10 connected across leads 1 and 2.
  • Lead 10 also incorporates, in series following relation, a first resistor 11 and a silicon controlled rectifier 12.
  • An additional lead is indicated at 13, connected at one end to the lead 10 between the heating coil 9 and the first resistor 11.
  • the other end of lead 13 is connected to lead 2.
  • the lead 13 incorporates, in series relation, a second resistor 14 and a cadmium sulfide photo conductive cell 15.
  • the gate of the silicon controlled rectifier 12 is connected by a lead 16 to lead 13 at a point 17 between the resistor ]4 and the cell 15.
  • the lead 16 incorporates a break-over device such as a neon tube 18.
  • Leads 1 and 2 are connected to a source of electrical current. This, in turn, will normally cause energization of the motor 3 and the ignition transformer 4. Since at the very outset there is no flame for the cadmium sulfide cell 15 to sense, the cell will have a very high resistance. Therefore, a voltage will appear at point 17 sufficient to fire the neon tube 18. This, in turn, will energize the gate of the silicon controlled rectifier 12, rendering the silicon controlled rectifier conductive. Since the silicon controlled rectifier 12 is in a conductive state, current sufficient in a very short period to heat the coil 9 to the point of tripping the circuit breaker 8 will begin to flow.
  • the cadmium sulfide cell will be energized by the light of the flame and its resistance will drop substantially. Consequently, the voltage at 17 will drop below the break-over voltage of the neon tube 18 and the gate of the silicon controlled rectifier will be deenergized. Therefore, if proper ignition occurs quickly, the silicon controlled rectifier 12 will be rendered non-conductive before the heating coil 9 will have attained a temperature sufficient to trip the circuit breaker.
  • the cadmium sulfide cell 15 will remain energized by exposure to the light of the flames, the silicion controlled rectifier 12 will remain in a non-conductive state and the circuit breaker 8 will remain closed. However, should the flames shift due to improper burning or extinguish for any reason, the cadmium sulfide cell will no longer be properly energized by exposure to the light of the flames, its normally high resistance will be reinstated causing the break over voltage of the neon tube 18 to be reached. In this manner the silicon controlled rectifier is rendered conductive once more. If the apparent malfunction does not immediately self correct, this, in turn, will cause the coil 9 to almost immediately heat to a sufficiently high temperature level to trip the thermal sensitive circuit breaker 8, and the motor 3 and ignition transformer 4 will be deenergized.
  • the neon tube 18 adds a safety element of important significance. Since it has a definite firing voltage, the variation in resistance of the cadmium sulfide cell 15 due to a normal type of flame flicker will have no effect on the gate of the silicon controlled rectifier 12. This is true for two reasons, the inherent slight delay in the response of the cadmium sulfide cell and the fact that the firing voltage of the neon tube will not be reached at point 17 when the position of a displaced flame is quickly reestablished. It will be understood by those skilled in the art that the neon tube 18 could be any appropriate break-over device such as a diac or the like.
  • the cadmium sulfide cell 15 must be located in a position to properly sense the flames so as to receive the proper amount of illumination from them.
  • the cell 15 may be mounted on the casing of the portable space heater adjacent a port in the combustion chamber.
  • the port in the combustion chamber should be located at a position adjacent the position the flames would normally assume in the combustion chamber when proper combustion is taking place.
  • the resistor 14 should be chosen in conjunction with the cadmium cell and the break-over device 18, based on their respective characteristics.
  • any perceptible current should flow through the heating coil 9 during normal operation of the space heater, it will be in an extremely small amount.
  • the rectifier as above described and here employed in conjunction with the heater coil 9 and resistor 111 is an element of such a nature that it will bring a cold coil 9 to a tripping condition in about 15 seconds.
  • the resistor 11 should have a rating such as to assure the presence of a gate voltage when the silicon controlled rectifier 12 is in the conductive state.
  • the silicon controlled rectifier 12 must be capable of carrying sufficient current to enable the proper heating of coil 9. It should also beof such sensitivity as to properly respond when combined with the other components of the circuit.
  • the resistor 11 was chosen to have a rating of 400 ohms
  • the resistor 14 was chosen with a rating of 100,000 ohms
  • the breakover device 18 was a readily available neon tube of the designation NEZA.
  • circuit of the Figure may incorporate a thermal sensitive switch which will open the circuit should too high a temperature be achieved in the combustion chamber.
  • the neon tube 18 may be eliminated from the circuit which will then function in an obvious manner with highly desirable results which have the aforementioned advantages.
  • variable resistance device and the thyrister in the form of the rectifier described contributes a significant advance to the art of safety controls of the type described.
  • the foregoing description of a preferred embodiment and application of the invention concept highlights its advantages and distinct features of novelty.
  • the invention embodiments be thereby limited to the elements as comprised in the described circuit nor to a control circuit wherein only a photo-sensitive control cell is employed as a sensing element.
  • the sensing device exposed to the heater flame has been described as a cadmium sulfide cell, it may be an equivalent device having the criteria to meet the requirements of a variable resistance of the nature characteristic of the cadmium sulfide cell.
  • the flame sensing device may be another type of light sensitive unit.
  • the invention contemplates a flame sensing unit which on the one hand may respond to light or absence of light or on the other hand to a given temperature level or its absence to vary its resistance in the circuit provided and thereby react similarly to the cadmium sulfide cell above described. In either event, the presence or ab sence of flame light or the inadequacy of or the nonexistence of a predetermined flame temperature level will be a criteria indicative of faulty heater operation and possible dangerous conditions.
  • the silicon controlled rectifier is .a unit in the thyrister category. On this basis, one can substitute a Triac which will function similarly.
  • the physical embodiment of the invention will be highly economical and the resulting package so small in size as to facilitate its application.
  • thecost of the invention embodiment is in many cases as little as about one third that of prior art packages of similar usage.
  • the response of the unit is such as to make it substantially fail safe and to ignore false signals. It obviates the chance of disaster due to incomplete fuel burning or flame failure.
  • a safety control circuit for a fuel burning device of the type producing a flame in normal operation and having electrical power means comprising first and second leads connected to said electrical power means and connectible to a power source for energizing.
  • said electrical power means a thermal sensitive circuit breaker connected to one said lead having in connection therewith means for tripping breaker contacts included therein, a device of the thyrister category connected to said tripping means, a variable resistance device 'operatively related to said thyrister device and arranged to monitor and sense a flame condi tion in the fuel burning device to which it is applied, means including a device having a defined firing voltage included to render said thyrister device nonresponsive'to said variable resistance device when the latter is energized by'a predetermined flame condition during proper combustion conditions in the related fuel burning device and responsive to a deenergizing of said variable resistance device in instances of improper flame, flame absence or failure, faulty ignition or improper combustion in said fuel burning device to trip said tripping means and open said
  • Apparatus as set forth in claim 4 characterized by said thyrister being a silicon controlled rectifier and said variable resistance device being a photo-sensitive device.
  • Apparatus as set forth in claim 1 characterized by said device having a defined firing voltage including means rendering the circuit insensitive to momentary change in flame condition connected between a gate of said thyrister device and said variable resistance device.
  • Apparatus as set forth in claim 6 including complementary resistor means in said circuit, connected between said tripping means and said variable resistance device and said tripping means and said thyrister device.
  • Apparatus as set forth in claim 4 characterized by said thyrister device bieng inserted in a third lead across said first and second leads in series with said tripping means and said variable resistance device being connected between said third lead and the other of said first and second leads.
  • thyrister device is a silicon controlled rectifier and said variable resistance device is a photo-sensitive device sensing flame condition.
  • a structure as set forth in claim 9 including a resistor interposed between and in series with said heating coil and said rectifier, a fourth lead containing a second resistor and said photo-sensitive device in series, one end of said fourth lead being connected to said third lead between said heating coil and the said first resistor, the other end of the said fourth lead being connected to said second lead and the gate of said rectifier being connected to said fourth lead between said second resistor and said photosensitive device.
  • a structure as set forth in claim 10 characterized by said device having a defined firing voltage including a break-over device in afith lead connecting between said gate and said fourth lead and providing means operable to render said circuit insensitive to ordinary flame flicker or momentary flame displacement.
  • a structure as set forth in claim 11 wherein said break-over device comprises a neon tube or the like having a defined firing voltage.

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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)
US00217003A 1972-01-11 1972-01-11 Solid state safety control for fuel burning apparatus Expired - Lifetime US3741709A (en)

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US21700372A 1972-01-11 1972-01-11

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US3741709A true US3741709A (en) 1973-06-26

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US00217003A Expired - Lifetime US3741709A (en) 1972-01-11 1972-01-11 Solid state safety control for fuel burning apparatus

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US (1) US3741709A (enrdf_load_stackoverflow)
JP (1) JPS4878528A (enrdf_load_stackoverflow)
CA (1) CA982677A (enrdf_load_stackoverflow)
DE (1) DE2301283A1 (enrdf_load_stackoverflow)
FR (1) FR2174528A5 (enrdf_load_stackoverflow)
GB (1) GB1415041A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959697A (en) * 1974-11-29 1976-05-25 Robertshaw Controls Company Oil burner safety control system with integral ignition
US3975137A (en) * 1970-06-25 1976-08-17 Raytheon Company Burner control system
US5470223A (en) * 1994-11-30 1995-11-28 Desa International, Inc. Microprocessor controlled fuel and ignition control for a fuel burning device
US5567144A (en) * 1995-10-05 1996-10-22 Desa International Inc. Hot surface ignition controller for fuel oil burner
US5899684A (en) * 1997-07-11 1999-05-04 Desa International, Inc. Power phase regulator circuit improvement, motor start switch, self-adjusting preheat and ignition trial improvement, and series-type voltage regulator improvement to hot surface ignition control for fuel oil burner
EP1033535A2 (en) 1999-03-03 2000-09-06 Desa International, Inc. Hot surface ignition controller for fuel oil burner
US20040209209A1 (en) * 2002-11-04 2004-10-21 Chodacki Thomas A. System, apparatus and method for controlling ignition including re-ignition of gas and gas fired appliances using same
US20100108658A1 (en) * 2008-10-20 2010-05-06 Saint-Gobain Corporation Dual voltage regulating system for electrical resistance hot surface igniters and methods related thereto
US20100141231A1 (en) * 2008-11-30 2010-06-10 Saint-Gobain Ceramics & Plastics, Inc. Igniter voltage compensation circuit
US20110086319A1 (en) * 2009-07-15 2011-04-14 Saint-Gobain Ceramics & Plastics, Inc. Fuel gas ignition system for gas burners including devices and methods related thereto
US10215809B2 (en) 2015-11-24 2019-02-26 Carrier Corporation Method and system for verification of contact operation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3537804A (en) * 1968-03-01 1970-11-03 Fenwal Inc Fuel ignition and flame detection system
US3672811A (en) * 1971-03-15 1972-06-27 Honeywell Inc Burner control system using a radiation operated relay means

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3537804A (en) * 1968-03-01 1970-11-03 Fenwal Inc Fuel ignition and flame detection system
US3672811A (en) * 1971-03-15 1972-06-27 Honeywell Inc Burner control system using a radiation operated relay means

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975137A (en) * 1970-06-25 1976-08-17 Raytheon Company Burner control system
US3959697A (en) * 1974-11-29 1976-05-25 Robertshaw Controls Company Oil burner safety control system with integral ignition
US5470223A (en) * 1994-11-30 1995-11-28 Desa International, Inc. Microprocessor controlled fuel and ignition control for a fuel burning device
EP0767344B1 (en) * 1995-10-05 2002-02-27 Desa International, Inc. Hot surface ignition controller for fuel oil burner
US5567144A (en) * 1995-10-05 1996-10-22 Desa International Inc. Hot surface ignition controller for fuel oil burner
US5899684A (en) * 1997-07-11 1999-05-04 Desa International, Inc. Power phase regulator circuit improvement, motor start switch, self-adjusting preheat and ignition trial improvement, and series-type voltage regulator improvement to hot surface ignition control for fuel oil burner
US6099295A (en) * 1997-07-11 2000-08-08 Desa International, Inc. Power phase regulator circuit improvement motor start switch self-adjusting preheat and ignition trial improvement and series-type voltage regulator improvement to hot surface ignition controller for fuel oil burner
EP1033535A2 (en) 1999-03-03 2000-09-06 Desa International, Inc. Hot surface ignition controller for fuel oil burner
US20040209209A1 (en) * 2002-11-04 2004-10-21 Chodacki Thomas A. System, apparatus and method for controlling ignition including re-ignition of gas and gas fired appliances using same
US20100108658A1 (en) * 2008-10-20 2010-05-06 Saint-Gobain Corporation Dual voltage regulating system for electrical resistance hot surface igniters and methods related thereto
US20100141231A1 (en) * 2008-11-30 2010-06-10 Saint-Gobain Ceramics & Plastics, Inc. Igniter voltage compensation circuit
US20110086319A1 (en) * 2009-07-15 2011-04-14 Saint-Gobain Ceramics & Plastics, Inc. Fuel gas ignition system for gas burners including devices and methods related thereto
US10215809B2 (en) 2015-11-24 2019-02-26 Carrier Corporation Method and system for verification of contact operation

Also Published As

Publication number Publication date
DE2301283A1 (de) 1973-07-19
GB1415041A (en) 1975-11-26
CA982677A (en) 1976-01-27
JPS4878528A (enrdf_load_stackoverflow) 1973-10-22
FR2174528A5 (enrdf_load_stackoverflow) 1973-10-12

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