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EP1027558B1 - Dispositif a arret de securite - Google Patents

Dispositif a arret de securite Download PDF

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Publication number
EP1027558B1
EP1027558B1 EP97938808A EP97938808A EP1027558B1 EP 1027558 B1 EP1027558 B1 EP 1027558B1 EP 97938808 A EP97938808 A EP 97938808A EP 97938808 A EP97938808 A EP 97938808A EP 1027558 B1 EP1027558 B1 EP 1027558B1
Authority
EP
European Patent Office
Prior art keywords
safety
voltage
cut
thermoelectric
thermocouple
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP97938808A
Other languages
German (de)
English (en)
Other versions
EP1027558A1 (fr
Inventor
Christian Eskildsen
Piero Armanni
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Electrolux AB
Original Assignee
Electrolux AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Electrolux AB filed Critical Electrolux AB
Publication of EP1027558A1 publication Critical patent/EP1027558A1/fr
Application granted granted Critical
Publication of EP1027558B1 publication Critical patent/EP1027558B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
    • F23N5/102—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/46—Details
    • F23D14/72—Safety devices, e.g. operative in case of failure of gas supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
    • F24C3/00—Stoves or ranges for gaseous fuels
    • F24C3/12—Arrangement or mounting of control or safety devices
    • F24C3/126—Arrangement or mounting of control or safety devices on ranges

Definitions

  • the invention relates to a safety cut-off device for a gas-heated hob comprising a thermocouple and a thermoelectric generator as well as a safety solenoid valve.
  • thermocouple which gives off a voltage when it it is heated by the lit flame, and this voltage is sufficient to deliver a holding current for a solenoid safety valve in the gas supply.
  • a system of this kind may have a push-button to perform the initial mechanical actuation of the solenid valve whereby the gas flows and may be lit, possibly by electronic means, and when the thermocouple has been heated, it sustains the open position of the safety valve.
  • EP 0 635 680 it is known to use a series connection of safety valves to increase the security, and one thermocouple functions as above described and a neighbouring thermeoelectric generator (a series connection of several thermojunctions) supplies an activation and holding current for a separate solenoid valve in series with the first mentioned.
  • thermoelectric voltage generators are large which means that they will supply holding currents for many seconds after a flame has disappeared, irrespective of the reason for the disappearance of the flame. This means that unburnt gas escapes for many seconds which will create an explosion hazard when the admixture of air is suitable. Also, first turning-on of the main flame is relatively slow this way.
  • thermoelectric generator provides the supply voltage for a transistor amplifier controlling the holding current for the safety solenoid valve, said transistor amplifier being controlled by the thermoelectric voltage from the thermocouple in order to cut off the holding current at a predetermined thermoelectric voltage.
  • a preferred embodiment is particular in that the transistor amplifier is a DC coupled common emitter amplifier with the collector connected to the thermeoelectric generator, the emitter to the solenoid, and the base to the thermocouple.
  • An advantageous embodiment further comprises a battery source for providing a short-term actuating voltage for the safety valve.
  • a further advantageous embodiment uses the battery source to power a spark ignition electrode at the hob.
  • Fig. 1 shows the voltages generated in a thermoelectric junction and in a generator consisting of a series connection of such junctions. It will be seen that the time constant of the series connection is less than the time constant of the single junction, but that the actual voltage of the single junction has an overshoot before it settles at a stable, temperature dependent voltage.
  • the holding voltage of a magnet used in a safety device is low (although the current may be fairly high), and it is shown in relation to the other voltages present in such appliances.
  • the time constant of the cooling down after a source of heat has disappeared is considerable, and about 6 times as large as the heating-up time constant.
  • a safety cut-out based on the current generated by the voltage of a thermo-junction would let a fair amount of gas escape before the cut-out is effective.
  • Fig. 2 is shown a simple emitter-follower type amplifier in which a thermoelectric generator 1 supplies the drive voltage and the sensing thermojunction 2 provides the input signal to a transistor 3 amplifier.
  • the solenoid 4 of a magnetic safety valve is connected to the emitter of the transistor 3.
  • a silicon transistor will tolerate operating temperatures of ca. 150°C which is ample in practice.
  • the voltages shown graphicaly in Fig. 1 are shown in the schematic, and it will be understood that suitable dimensioning of the base resistor, based on the voltage drops inherent in transistor operation and a knowledge of the resistance of the solenoid for the magnetic valve, will result in a control of the current from the emitter through the solenoid.
  • a cut-off is obtained when the voltage from the thermojunction has fallen only a little with respect to the stable high-temperature condition.
  • Fig. 1 is shown that the gas would continue to flow about 6 times longer, if the safety valve did not release until the voltage had fallen by the thermal time constant alone.
  • Fig. 3 is shown the lay-out "below the top" of a gas hob fitted with electronic ignition of the gas and a safety device according to the invention.
  • a gas burner is generally indicated by the grid at 5, and an ignition electrode 6 is connected to a high-voltage generator 7 supplied by a battery 8 which is remote from the gas burner. Ignition is controlled by the gas valve 9 which is combined with a safety cut-out of the magnetic type. Ordinarily, this valve is actuated by the gas valve during and immediately after ignition, until sufficient holding voltage is available from a thermoelectric source.
  • thermoelectric source Such sources are indicated as a thermojunction 10 and a thermoelectric generator 11. As described above, the thermovoltages generated are fed to an amplifier 12 which is connected to the solenoid in the safety valve 13.
  • thermogenerator and the thermojunction very quickly increase above the holding voltage of the solenoid, and it is not an undue strain on the ignition battery to supply the higher actuation voltage and the solenoid current during the brief period just after ingnition, until the transistor amplifier can take over. This avoids the combination with a mechanical actuation directly from the valve 9.

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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)

Claims (4)

  1. Dispositif à coupure de sécurité pour une plaque chauffée au gaz comprenant un thermocouple et un générateur thermoélectrique ainsi qu'une étectrovalve de sécurité,
    caractérisé en ce que le générateur thermoélectrique (1) fournit la tension d'alimentation pour un amplificateur à transistors (3) commandant le courant de maintien pour l'électrovalve de sécurité, ledit amplificateur à transistors étant commandé par la tension thermoélectrique à partir du thermocouple (2) de façon à couper le courant de maintien à une tension thermoélectrique prédéterminée.
  2. Dispositif à coupure de sécurité selon la revendication 1,
    caractérisé en ce que l'amplificateur à transistors est un amplificateur à émetteur commun couplé au courant continu avec le collecteur relié au générateur thermoélectrique (1), l'émetteur au solénoïde (4) et la base au thermocouple (2).
  3. Dispositif à coupure de sécurité selon la revendication 1,
    caractérisé en ce qu'il comprend une source de batterie (8) pour fournir une tension d'actionnement à court terme pour la valve de sécurité.
  4. Dispositif à coupure de sécurité selon la revendication 3,
    caractérisé en ce qu'il utilise la source de batterie pour alimenter une électrode à allumage par étincelles (6) au niveau de la plaque.
EP97938808A 1997-08-28 1997-08-28 Dispositif a arret de securite Expired - Lifetime EP1027558B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DK1997/000366 WO1999011979A1 (fr) 1997-08-28 1997-08-28 Dispositif a arret de securite

Publications (2)

Publication Number Publication Date
EP1027558A1 EP1027558A1 (fr) 2000-08-16
EP1027558B1 true EP1027558B1 (fr) 2002-01-30

Family

ID=8156223

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97938808A Expired - Lifetime EP1027558B1 (fr) 1997-08-28 1997-08-28 Dispositif a arret de securite

Country Status (6)

Country Link
EP (1) EP1027558B1 (fr)
AU (1) AU4113097A (fr)
DE (1) DE69710229T2 (fr)
DK (1) DK1027558T3 (fr)
ES (1) ES2171990T3 (fr)
WO (1) WO1999011979A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AUPR152400A0 (en) * 2000-11-16 2000-12-14 Garcia, Fernando Teodoro Shut-off safety system and gas applicance including same
AU2002214834B2 (en) * 2000-11-16 2006-11-16 Fernando Teodoro Garcia Shut-off safety system and gas appliance including same
ITMI20010222U1 (it) * 2001-04-19 2002-10-21 Whirlpool Co Dispositivo di sicurezza per apparecchi domestici di cottura a gas
ITTO20120457A1 (it) * 2012-05-25 2013-11-26 Eltek Spa Dispositivo di controllo per rubinetti di gas

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1264955B1 (it) * 1993-07-20 1996-10-17 Sit La Precisa Spa Azionatore per bruciatore a gas con sicurezza di fiamma ed elettrovalvola di regolazione.

Also Published As

Publication number Publication date
WO1999011979A1 (fr) 1999-03-11
DK1027558T3 (da) 2002-05-06
EP1027558A1 (fr) 2000-08-16
AU4113097A (en) 1999-03-22
ES2171990T3 (es) 2002-09-16
DE69710229T2 (de) 2002-10-24
DE69710229D1 (de) 2002-03-14

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