EP0821199B1 - Positive safety device for the gas supply in a burner - Google Patents

Abstract

The burner admission valve (25) is initially opened by a boost-type control circuit (27), having 1W output, via a self-resetting bi-metal (SRC), guarding against flue obstruction. A second boost circuit (24), with 30 mW output, keeps the valve open. Both circuits give higher output voltages than the battery which provides power supplies, and the latter is insufficient to operate the valve. The burner is lit by a spark generator (20), based on an oscillator (21) and a discharge circuit (22) giving a 15 kV output for 5 microseconds; this is associated with a flame detector (11) using the diode effect of ionisation. These devices are directed at an igniter gas nozzle near the burner. The equipment is further described in European Patent 0 821 198 (q.v.).

Description

The present invention relates to a device for positive securing intended to control functions of safety around a burner, for example in a boiler or water heater.

Burners require safety devices to avoid on the one hand that the flame remains absent from the burner, this which prohibits the functioning of the thermal system and, on the other hand, that if the flame goes out, the gas continues to be diffused by the burner.

Many devices, all intended to be connected to the 220 Volts sector, are known to those skilled in the art job. Indeed, the known devices have a high consumption of electrical energy due to two functions, that of lighting the flame and that of gas inlet control, which is usually consisting of a relay which controls a solenoid valve. The electrical power required for such devices prohibits their use on devices powered by Battery.

The present invention intends to remedy these disadvantages of presenting an electronic device flame ignition on a burner, detection of said flame and gas intake control in the burner, whose consumption is so low that it can be supplied by electric batteries.

To this end, the device which is the subject of the invention includes a positive safety electronic assembly, for lighting and controlling the flame of a burner. The device allows the ignition of a burner main using an ignition burner. He commands ignition of the main burner only when the flame is present at the ignition burner. Electronic assembly, powered by batteries, sparks, checks presence of flame and positively feeds a solenoid valve which allows the admission of gas to the burner main. This assembly applies to the burner ignition with non-permanent ignition burner.

Remember that positive security consists of that no failure of a component can induce dangerous situation for the user.

An example of a device ensuring positive security is given in US Patent 3,890,579 (A). This document describes a device intended for flame ignition, flame detection and admission control of gas from a burner comprising a supply circuit of a solenoid valve controlling the admission of gas to the burner, this circuit being composed of a transformer supplied by an oscillator, so that a possible Oscillator malfunction prevents activation of the solenoid valve.

The invention firstly relates to a device for positive burner safety for flame ignition, flame detection and gas inlet control characterized in that it comprises a means of admission of gas which lets gas pass to a burner only when a voltage difference between its terminals is higher than the supply voltage, and in that it has a power supply circuit suitable for apply between the terminals of the gas inlet means a higher voltage the output voltage of the source power supply, so that a possible malfunction of said supply circuit prevents the gas passage through the gas inlet means.

Thanks to these features, any circuit failure supply causes the voltage across the terminals to drop the means of gas admission below the voltage power supply and therefore the voltage which is suitable for its opening. The gas inlet is therefore protected against failure or short circuit in the supply circuit.

According to preferential characteristics, the device according to the present invention comprises means chimney backflow detection device suitable for opening the supply circuit of the gas inlet means during detection of a backflow, the difference in voltages between the terminals of the gas inlet means being, when of the closure of the detection means, less than the opening voltage of the gas inlet means.

Thanks to these provisions, the voltage across the terminals of the gas inlet means when closing the anti-backflow safety is insufficient to reopen the gas intake means, safety against chimney discharge is directly ensured by opening of the supply of the gas intake means.

• un oscillateur produisant un signal alternatif entre deux électrodes placées à proximité du brûleur, des étincelles entre ces deux électrodes étant adaptées à allumer une flamme sur le brûleur, ladite flamme ionisant l'intervalle entre les deux électrodes ;
• un comparateur qui reçoit un signal représentatif de la tension entre lesdites deux électrodes et qui le compare à une tension de consigne ; et
• un moyen de commande de l'oscillateur prenant en compte le signal sortant du comparateur.

According to preferential characteristics, the device according to the invention comprises:

• an oscillator producing an alternating signal between two electrodes placed near the burner, sparks between these two electrodes being adapted to ignite a flame on the burner, said flame ionizing the interval between the two electrodes;
• a comparator which receives a signal representative of the voltage between said two electrodes and which compares it with a reference voltage; and
• means for controlling the oscillator taking into account the signal leaving the comparator.

Thanks to these provisions, the tension between the electrodes are used both to light a flame, producing a spark, and detecting the presence of flame. Indeed, it is well known that a flame ionizes the material between the electrodes and that this material ionized behaves electrically like a diode, i.e. that it allows the passage of electrons only in a direction.

According to a first aspect of the invention, the signal leaving the control means is adapted to reduce the frequency of the oscillator when the signal coming out of the comparator is representative of the presence of a flame between said two electrodes.

According to a second aspect of the present invention, the outgoing signal from the control means is adapted to reduce the output voltage of the oscillator when the signal leaving the comparator is representative of the presence of a flame between said two electrodes.

Through each of these provisions, and preferentially to both, the electricity consumption of the device is very reduced since the ignition phase, which is the largest consumer of energy, is very short and then the operation of the device serves to test the operation of a heating system.

According to particular characteristics, the circuit power supply includes a switching power supply current regulation, which provides an opening current a gas intake means. Thanks to these provisions, the energy required to control the intake means of gas is low enough that a battery can power it for several months, in operation normal.

According to other particular characteristics, a power source of electronic circuits is made up of electric batteries.

Thanks to these characteristics, no connection to the sector is not necessary and the installation is greatly simplified since there is no more installation electric to provide.

The invention also relates to a heating means, water heater or boiler, for example, characterized in that it includes a device as briefly described above.

• la figure 1 représente un premier type d'installation thermique incorporant un dispositif selon la présente l'invention ;
• la figure 2 représente un premier mode de réalisation d'un circuit électronique mettant en oeuvre la présente invention et incorporé dans le dispositif présenté en regard de la figure 1 ;
• la figure 3 représente un deuxième mode de réalisation d'un circuit électronique mettant en oeuvre la présente invention ;
• la figure 4 représente un deuxième type d'installation thermique incorporant un dispositif selon la présente invention, incorporant le deuxième mode de réalisation du circuit présenté en regard de la figure 3 ;
• la figure 5 représente un troisième mode de réalisation d'un circuit électronique mettant en oeuvre la présente invention ; et
• la figure 6 représente un troisième type d'installation thermique incorporant un dispositif selon la présente invention, incorporant le troisième mode de réalisation du circuit présenté en regard de la figure 5.

Other advantages, aims and characteristics will emerge from the description which follows, given with reference to the accompanying drawings for explanatory purposes in which:

• FIG. 1 represents a first type of thermal installation incorporating a device according to the present invention;
• FIG. 2 represents a first embodiment of an electronic circuit implementing the present invention and incorporated in the device presented opposite FIG. 1;
• FIG. 3 represents a second embodiment of an electronic circuit implementing the present invention;
• FIG. 4 represents a second type of thermal installation incorporating a device according to the present invention, incorporating the second embodiment of the circuit presented opposite FIG. 3;
• FIG. 5 represents a third embodiment of an electronic circuit implementing the present invention; and
• FIG. 6 represents a third type of thermal installation incorporating a device according to the present invention, incorporating the third embodiment of the circuit presented opposite FIG. 5.

Examples of implementation of the invention which will follow are applied to a thermal installation using gaseous fuel. However, the invention easily applied to thermal installations using other forms of fuel, for example liquids, solids or powdery, by the simple setting work of normal knowledge of the skilled person.

FIG. 1 shows a thermal installation 1, comprising a gas inlet 2, a fluid inlet 3, a fluid outlet 4 and a burner 5 connected to the inlet of gas 2 and thermally connected to a fluid circuit 6 from the fluid inlet 3 to the fluid outlet 4.

An electronic circuit 7 is supplied by a power supply 8, is connected to a means of flame presence detection 11 placed near the output of an ignition burner 14, to an ignition means of flame 9 placed at the outlet of the ignition burner 14, at a gas inlet means 25 placed between the gas inlet 2 and the burner 5 and to a draw-off switch 13.

We note that, according to an advantageous characteristic of the invention, it is the same electrode which ensures here the production of sparks for igniting the flame and which detects the presence of the flame. This electrode therefore corresponds both to the flame ignition means 9 and to a flame detection means 11.

The thermal installation 1 is, for example, consisting of a water heater or boiler, of types known. The burner 5 is suitable for mixing air with gas from gas inlet 2, via gas intake means 25, to ensure good combustion of the mixture thus formed and to evacuate the gases burned by a chimney 12. The burner 5 is of the type known.

Main burner 5 is lit by a burner ignition 14 whose flame is lit by the means flame ignition 9 and on which the presence of a flame is detected by the flame detection means 11.

The fluid, for example water, which circulates between the fluid inlet 3, where it is at a given temperature, and the fluid outlet 4, where it was heated by the flame of the burner 5, then runs through a circuit which depends on thermal installation 1.

The gas inlet 2 is either connected to a tank of gas, or connected to a gas distribution network.

The electronic circuit 7 is presented, according to several embodiments in FIGS. 2, 3 and 5. The power supply 8 preferably comprises an electric battery or an electric accumulator. However, it can possibly be supplemented by the electrical sector.

The flame presence detection means 11 placed near the outlet of the ignition burner 14 is adapted to emit a signal representative of the presence or the absence of a flame at the burner outlet 5. The flame ignition means 9 placed at the burner outlet ignition 14 is suitable for lighting a flame at the outlet of the burner 5. The gas inlet means 25 placed between the gas inlet and the burner 5 is suitable either to leave pass gas from gas inlet 2 to the burner 5, when open, or to prohibit this traffic, when closed.

The drawing switch 13 is controlled by the water flow in circuit 6, according to techniques known which are not detailed here.

The electronic circuit 7, which will now be described with reference to Figures 2, 3 and 5, controls the means flame ignition 9 and a gas inlet means 10 as a function of the signal leaving the detection means of flame 11.

• le moyen de détection de flamme 11 qui fonctionne par détection de l'ionisation de la flamme (cette ionisation de la flamme est électriquement similaire à une diode), et est constitué d'un amplificateur opérationnel IC1, d'un transistor TR2 et de composants associés dont notamment une résistance R9 18 de polarisation du transistor TR2, émet un signal lorsque la flamme est présente au brûleur ;
• un générateur d'étincelles 20 constitué d'une part d'un oscillateur blocking 21 comportant un transistor TR1, un transformateur T1 et une résistance R1, qui reçoit le signal sortant du moyen de détection de flamme 11 et d'autre part d'un allumeur à décharge de condensateur 22 comportant une diode D1, un condensateur C2, un éclateur au silicium sidl, constitué d'un thyristor auto-déclenché qui ne possède que deux électrodes, et un transformateur T2 qui fournit un signal de 15 kV pour générer des étincelles d'une durée de 5 microsecondes, qui reçoit le signal sortant de l'oscillateur blocking 21. Enfin, un éclateur El permet d'isoler la masse de l'installation thermique 1, d'une part, du circuit électronique 7, d'autre part, pendant la détection de flamme. L'oscillateur blocking ainsi constitué produit un signal alternatif qui est redressé par la diode constituée de l'ionisation de la flamme. Le signal redressé sortant de cette diode est intégré par des résistances R4 et R5 ainsi que par un condensateur C3 du détecteur de flamme puis comparé, par l'amplificateur opérationnel IC1, à une consigne fixe donnée par les résistances R7 et R8. De cette manière, en présence de la flamme les tests de sa présence s'effectuent avec une période réduite, ce qui économise l'énergie de la pile ;
• un comparateur, oscillateur à fenêtre 23, constitué d'amplificateurs opérationnels IC2-a et IC2-b et de composants périphériques, reçoit un signal prélevé entre la résistance 18 et le transistor TR2. Ce comparateur oscillateur a donc deux consignes qui sont données par des résistances de polarisation R27 et R28, et détecte les transitions du signal prélevé ;
• un moyen de commande de l'oscillateur prenant en compte le signal sortant du comparateur et comportant dans l'exemple décrit et représenté une simple résistance R2 ;
• une alimentation à découpage 24 de type connu sous le nom de boost alimente le moyen d'admission de gaz 10, ici constitué de l'électrovanne 25, de façon positive. Cette alimentation est composée d'un transistor TR60 d'une inductance L60, d'une diode D60 et d'un condensateur C60. Elle fournit 30 mW, ce qui suffit au maintien de l'électrovanne 25 ;
• un moyen de temporisation 26, composé d'un amplificateur opérationnel IC2-c, d'un transistor TR41 et des résistances et capacités associées, permet de donner un courant d'ouverture d'électrovanne pendant une durée limitée, pour économiser les piles ;
• une alimentation à découpage 27 à régulation de courant, elle aussi de type connu sous le nom de boost, constituée d'amplificateurs opérationnels IC2-d et IC3-A, de transistors TR50, TR51 et TR61, d'une diode D61, d'une inductance L61 et d'une tension de référence VRef1, fournit le courant d'ouverture de l'électrovanne 25, de façon positive. Cette alimentation à découpage 27 fournit 1 watt.
• un moyen de sécurité contre le refoulement de la cheminée, référencé SRC, est constitué d'un bilame à réarmement automatique, monté en série avec l'électrovanne, qui coupe le circuit lorsqu'un refoulement est détecté de manière connue, le réallumage étant interdit par la faible puissance de maintien de l'électrovanne qui est insuffisante pour la rouvrir lorsque la sécurité contre le refoulement se referme.

FIG. 2 shows a first embodiment of the electronic circuit 7. The circuit comprises, in the first embodiment presented in FIG. 1:

• the flame detection means 11 which operates by detecting the ionization of the flame (this ionization of the flame is electrically similar to a diode), and consists of an operational amplifier IC1, a transistor TR2 and components associates including a resistor R9 18 for biasing the transistor TR2, emits a signal when the flame is present at the burner;
• a spark generator 20 consisting on the one hand of a blocking oscillator 21 comprising a transistor TR1, a transformer T1 and a resistor R1, which receives the signal leaving the flame detection means 11 and on the other hand of a capacitor discharge igniter 22 comprising a diode D1, a capacitor C2, a silicon spark gap sidl, consisting of a self-triggered thyristor which has only two electrodes, and a transformer T2 which supplies a signal of 15 kV to generate sparks with a duration of 5 microseconds, which receives the signal leaving the blocking oscillator 21. Finally, a spark gap El makes it possible to isolate the mass of the thermal installation 1, on the one hand, from the electronic circuit 7, d on the other hand, during flame detection. The blocking oscillator thus formed produces an alternating signal which is rectified by the diode consisting of the ionization of the flame. The rectified signal leaving this diode is integrated by resistors R4 and R5 as well as by a capacitor C3 of the flame detector and then compared, by the operational amplifier IC1, to a fixed reference given by the resistors R7 and R8. In this way, in the presence of the flame, the tests of its presence are carried out with a reduced period, which saves the energy of the battery;
• a comparator, window oscillator 23, consisting of operational amplifiers IC2-a and IC2-b and peripheral components, receives a signal taken between the resistor 18 and the transistor TR2. This oscillator comparator therefore has two setpoints which are given by polarization resistors R27 and R28, and detects the transitions of the sampled signal;
• means for controlling the oscillator taking into account the signal leaving the comparator and comprising, in the example described and shown, a simple resistor R2;
• a switching power supply 24 of a type known as a boost supplies the gas inlet means 10, here consisting of the solenoid valve 25, in a positive manner. This power supply is composed of a transistor TR60 with an inductance L60, a diode D60 and a capacitor C60. It provides 30 mW, which is sufficient to maintain the solenoid valve 25;
• a timer means 26, composed of an operational amplifier IC2-c, a transistor TR41 and the resistors and associated capacitors, makes it possible to give a solenoid valve opening current for a limited period, to save the batteries;
• a switching power supply 27 with current regulation, also of the type known as a boost, consisting of operational amplifiers IC2-d and IC3-A, transistors TR50, TR51 and TR61, a diode D61, d ' an inductor L61 and a reference voltage VRef1, supplies the opening current of the solenoid valve 25, in a positive manner. This switching power supply 27 provides 1 watt.
• a safety means against the backflow of the chimney, referenced SRC, consists of a bimetal with automatic reset, mounted in series with the solenoid valve, which cuts the circuit when a backflow is detected in a known manner, re-ignition being prohibited by the low holding power of the solenoid valve, which is insufficient to reopen it when the backflow protection closes.

It is noted that, to ensure positive security, the switching power supplies 24 and 27, provide voltages higher than the voltage of the voltage source. In the event of a fault, the solenoid valve 25 cannot therefore be accidentally ordered.

The circuit marked "drawing switch, at the top of the figure 2, represents a means of energizing the circuit Figure 2. It controls a drawing switch 13 (figure 1) which makes the ignition request.

Figures 3 and 4 relate to an installation thermal where the main burner 5 is directly lit by the ignition means 9 and the flame on this burner is controlled by the flame detection means 11.

In the second embodiment, presented in Figure 3, we see that a circuit breaker 30, comprising two TR3 and TR4 transistors, associated resistors and a fuse F1, is connected to an input of the power supply 24.

The circuit breaker 30 provides, together with a capacity C20 of the window oscillator comparator 23, the locking the device when the burner is not on before C20 capacity is charged up to the first predetermined value of the comparator oscillator 23, the system can only be unlocked by stopping the drawing.

In addition, the timer means 26 does not part of this embodiment of the electronic circuit 7. On the other hand, a power authorization circuit maximum 31, consisting of an operational amplifier IC2-e, receives the same signal as the comparator oscillator 23 and outputs a signal to the power supply to current regulated switching 27 whose diagram is simplified in Figure 3.

The simplification of the switching power supply 27, shown in Figure 3 corresponds to a variant of electronic diagram of the power presented in figure 2. This variant has the advantage of being able to be connected to the mains.

The electronic circuit 7 presented opposite the figure 5 is specifically adapted to the installation thermal 1 presented with reference to FIG. 6.

Figure 6 shows a third type thermal installation incorporating a device according to the present invention, in which, in comparison with Figure 1, two solenoid valves 42 and 43 (presented in FIG. 5) replace the solenoid valve 25, and in which an electronic circuit 7, as presented in FIG. 5, controls said solenoid valves 42 and 43, depending on the electrical signals and switch positions corresponding to backflow protection, on request ignition or draw, and the ignition electrode.

• le moyen de détection de flamme 11 ;
• le générateur d'étincelles 20 constitué d'une part d'un oscillateur blocking 21 et d'autre part d'un allumeur à décharge de condensateur 22 ;
• le comparateur, oscillateur à fenêtre 23, identique à celui présenté en figure 1 à l'exception d'une diode ajoutée en parallèle de la résistance R21, en entrée du circuit comparateur 23 ;
• l'alimentation à découpage 24 qui alimente une électrovanne primaire 43 ;
• un moyen de sécurité contre le refoulement de la cheminée, référencé SRC, placé en série avec l'électrovanne primaire 43 ; et
• l'alimentation à découpage 27 qui alimente une électrovanne secondaire 42.

In Figure 5, we find:

• the flame detection means 11;
• the spark generator 20 consisting on the one hand of a blocking oscillator 21 and on the other hand of a capacitor discharge igniter 22;
• the comparator, window oscillator 23, identical to that presented in FIG. 1 with the exception of a diode added in parallel with the resistor R21, at the input of the comparator circuit 23;
• the switching power supply 24 which supplies a primary solenoid valve 43;
• safety means against the backflow of the chimney, referenced SRC, placed in series with the primary solenoid valve 43; and
• the switching power supply 27 which supplies a secondary solenoid valve 42.

• un circuit d'autorisation de puissance maximale 31 qui comporte un amplificateur opérationnel dont l'entrée inverseuse reçoit une tension prédéterminée constante et dont l'entrée non inverseuse reçoit le signal entrant dans le comparateur oscillateur à fenêtre 23. Le signal de sortie du circuit d'autorisation 31 rentre dans le circuit d'alimentation 27 ;
• un circuit de régulation 40 comportant un amplificateur opérationnel 41 dont l'entrée inverseuse reçoit un signal prelevé entre l'électrovanne secondaire 42 et un résistance R13 relié à la masse électrique. L'entrée non inverseuse de l'amplificateur opérationnel 41 reçoit une tension prédéterminée fixe correspondant à une consigne de régulation. Le signal de sortie du circuit de régulation 40 rentre dans le circuit d'alimentation 27, conjointement au signal sortant du circuit d'autorisation 31.

In addition to these elements presented with reference to Figures 2 and 3:

• a maximum power authorization circuit 31 which includes an operational amplifier whose inverting input receives a constant predetermined voltage and whose non-inverting input receives the signal entering the window oscillator comparator 23. The output signal of the circuit d authorization 31 enters the supply circuit 27;
• a regulation circuit 40 comprising an operational amplifier 41 whose inverting input receives a signal taken between the secondary solenoid valve 42 and a resistor R13 connected to the electrical ground. The non-inverting input of the operational amplifier 41 receives a fixed predetermined voltage corresponding to a regulation setpoint. The output signal from the regulation circuit 40 enters the supply circuit 27, together with the signal from the authorization circuit 31.

OPERATION OF THE DEVICE:

• le signal de détection flamme est prélevé dans la boucle du contrôle de ionisation de flamme. Le comparateur IC1-a fixe une valeur de consigne du signal de flamme, interrompt l'oscillateur comportant le transformateur T1 et le transistor TR1 si le signal est supérieur à la consigne et le libère si le signal est inférieur à la consigne. Il commande ainsi la génération d'étincelles au brûleur 5.
• la validation du signal de flamme est effectuée par l'oscillateur comparateur à fenêtre : les amplificateurs opérationnels IC2-a et IC2-b forment conjointement un oscillateur qui ne peut démarrer que si le signal sur l'entrée de IC2-a est compris dans une fourchette définie par les résistances de polarisation R27 et R28. Cet oscillateur est positif : aucun défaut de composant ne peut le faire osciller si le signal d'entrée n'est pas dans la fourchette définie. On note que, dans le mode de réalisation décrit et représenté, le signal sortant du moyen de commande est adapté à réduire la fréquence et la tension de sortie de l'oscillateur lorsque le signal sortant du comparateur est représentatif de la présence d'une flamme entre lesdites deux électrodes.
• l'alimentation à découpage 24, de type boost, produit une tension supérieure à la tension d'alimentation nécessaire pour commander l'électrovanne 25. L'énergie emmagasinée dans l'inductance L60 lorsque le transistor TR60 est saturé se décharge par l'intermédiaire de la diode D60 dans le condensateur C60 lorsque le transistor TR60 est bloqué. Ce système ne peut fonctionner que si tous les composants sont actifs et, par conséquent, aucun défaut de composant ne peut provoquer l'alimentation de l'électrovanne 25 si un signal dynamique n'est pas présent sur la base du transisor TR60.
• le moyen de temporisation 26 n'autorise l'ouverture de l'électrovanne à pleine puissance, de façon positive que pendant une durée limitée. Ceci permet d'économiser les piles et d'assurer la sécurité d'un moyen antirefoulement.
• le moyen anti-refoulement est constitué d'un bilame qui s'ouvre lorsque les gaz brûlés sont refoulés dans la pièce.
• la temporisation, initialisé par l'entrée en oscillation de l'amplificateur opérationnel IC2-a autorise le fonctionnement de l'alimentation à découpage 27 pendant une fraction de seconde. Cette alimentation 27 est excitée par l'amplificateur opérationnel IC2-d qui utilise la tension de charge et décharge du condensateur C22 de l'oscillateur comparateur à fenêtre. Le courant dans l'électrovanne 25 est régulé par la résistance R64 en coopération avec la tension de référence Vréf, avec l'amplificateur opérationnel IC3-A et les autres résistances associées. Il agit sur la rapport cyclique du signal carré produit par l'amplificateur opérationnel IC2-d.
• une sécurité contre le refoulement de la cheminée est assurée par un bilame (non représenté) monté dans un boítier coupe-tirage (non représenté). Il interrompt le courant dans l'électrovanne 25 lors d'un refoulement dans la cheminée, ce qui provoque la fermeture de l'électrovanne 25. La réouverture de l'électrovanne 25 est interdite lors de la fermeture du bilame, par le faible courant de maintien délivré par l'alimentation 24. Pour autoriser la réouverture de l'électrovanne 25, il faut faire cesser le puisage et refaire une demande puisage, selon le fonctionnement présenté ci-dessus.
• pour un allumage direct du brûleur 5, figure 4, il faut utiliser une temporisation qui limite le temps d'ouverture de l'électrovanne 25 à moins de 5 s (durée connue sous le nom de "temps de sécurité en allumage"), de façon sûre ; ceci est obtenu par la capacité C20 qui est chargée progressivement par la résistance R21 lors d'une demande d'allumage et maintenue à la valeur de consigne lors d'une détection de flamme. Tant que la tension appliquée au condensateur C1 est comprise dans la fourchette de fonctionnement de l'oscillateur, celui-ci fonctionne. Par contre, si une détection flamme n'apparaít pas avant la charge complète du condensateur C20, la tension de celui-ci sort de la fourchette de l'oscillateur et celui-ci s'arrête.
• l'électrovanne 25 est alimentée dès le début de la demande puisage lorsque la tension de charge du condensateur C20 a dépassé la limite inférieure de la fourchette de l'oscillateur.
• dans la variante présentée en regard de la figure 3, pour verrouiller le dispositif, en cas de non présence de flamme avant la fin du temps de sécurité défini par le moyen de temporisation, on utilise le fait que l'oscillateur se bloque en position haute en cas de charge complète du condensateur C20, ce qui provoque une saturation permanente du transistor TR60 puis du transistor TR3, celui-ci bloquant à son tour le transistor TR4. Ce verrouillage est maintenu par la résistance R10 tant que l'alimentation du système est maintenue, même si l'oscillateur bascule à nouveau. Un fusible garantit le verrouillage en cas de court circuit d'un transistor, le courant au moment du défaut devenant très important dans le transistor TR60, l'inductance L60 et le transistor TR4.

To ensure the safety of flame detection at the solenoid valve, the following principles are used:

• the flame detection signal is taken from the flame ionization control loop. The comparator IC1-a fixes a set point value of the flame signal, interrupts the oscillator comprising the transformer T1 and the transistor TR1 if the signal is higher than the set point and releases it if the signal is lower than the set point. It thus controls the generation of sparks at burner 5.
• validation of the flame signal is carried out by the window comparator oscillator: the operational amplifiers IC2-a and IC2-b jointly form an oscillator which can only start if the signal on the input of IC2-a is included in a range defined by the polarization resistors R27 and R28. This oscillator is positive: no component fault can cause it to oscillate if the input signal is not within the defined range. It is noted that, in the embodiment described and shown, the signal leaving the control means is adapted to reduce the frequency and the output voltage of the oscillator when the signal leaving the comparator is representative of the presence of a flame between said two electrodes.
• the switching power supply 24, of the boost type, produces a voltage greater than the supply voltage necessary to control the solenoid valve 25. The energy stored in the inductor L60 when the transistor TR60 is saturated discharges via diode D60 in capacitor C60 when transistor TR60 is blocked. This system can only work if all the components are active and, therefore, no component fault can cause power to the solenoid valve 25 if a dynamic signal is not present on the base of the TR60 transisor.
• the delay means 26 authorizes the opening of the solenoid valve at full power, positively only for a limited period. This saves the batteries and ensures the safety of a backflow preventer.
• the anti-backflow means consists of a bimetallic strip which opens when the burnt gases are pushed back into the room.
• the time delay, initialized by the oscillation of the operational amplifier IC2-a authorizes the operation of the switching power supply 27 for a fraction of a second. This power supply 27 is excited by the operational amplifier IC2-d which uses the charge and discharge voltage of the capacitor C22 of the window comparator oscillator. The current in the solenoid valve 25 is regulated by the resistor R64 in cooperation with the reference voltage Vref, with the operational amplifier IC3-A and the other associated resistors. It acts on the duty cycle of the square signal produced by the operational amplifier IC2-d.
• security against the backflow of the chimney is ensured by a bimetallic strip (not shown) mounted in a draft-reducing box (not shown). It interrupts the current in the solenoid valve 25 during a discharge into the chimney, which causes the solenoid valve 25 to close. The reopening of the solenoid valve 25 is prohibited during the closing of the bimetallic strip, by the low current of maintenance delivered by the power supply 24. To authorize the reopening of the solenoid valve 25, it is necessary to stop the drawing and repeat a drawing request, according to the operation presented above.
• for direct ignition of the burner 5, FIG. 4, a time delay must be used which limits the opening time of the solenoid valve 25 to less than 5 s (duration known as the "ignition safety time"), safe way; this is obtained by the capacitor C20 which is gradually charged by the resistor R21 during an ignition request and maintained at the set value during a flame detection. As long as the voltage applied to the capacitor C1 is within the operating range of the oscillator, the latter operates. On the other hand, if a flame detection does not appear before the full charge of the capacitor C20, the voltage of the latter leaves the range of the oscillator and the latter stops.
• the solenoid valve 25 is supplied from the start of the drawing request when the charging voltage of the capacitor C20 has exceeded the lower limit of the range of the oscillator.
• in the variant presented with reference to FIG. 3, in order to lock the device, in the event of the absence of a flame before the end of the safety time defined by the timing means, the fact is used that the oscillator locks in the high position in the event of full charge of the capacitor C20, which causes permanent saturation of the transistor TR60 and then of the transistor TR3, the latter in turn blocking the transistor TR4. This locking is maintained by the resistor R10 as long as the power supply to the system is maintained, even if the oscillator switches again. A fuse guarantees locking in the event of a short circuit of a transistor, the current at the time of the fault becoming very large in transistor TR60, inductance L60 and transistor TR4.

• une deuxième électrovanne qui autorise la grande puissance dès que la flamme est présente,
• une électrovanne à clapet double.

Alternatively, shown in Figure 4, the device of the invention can be applied to the ignition control of a burner in 2 times which allows a safety time of 10 seconds. We use for this purpose:

• a second solenoid valve which allows great power as soon as the flame is present,
• a double valve solenoid valve.

For this purpose, the circuit IC2-c TR50 is used, 51, 61, D61, or another similar circuit for order the second solenoid valve or supply the current for the large valve.)

High flow detection is ensured by a comparator IC2-c which detects the passage of the signal flame at the voltage characteristic of a presence of flame and authorizes the operation of the second booster.

The second booster (simplified in diagram 2) can be set to a fixed current or be controlled by a regulation system (see Vréfl order on diagram 1).

So the power supply circuit, comprising the two switching power supplies 24 and 27 is suitable for applying between the terminals of the intake means of gas consisting of the solenoid valve 25, a voltage higher than the output voltage of the source power supply, so that a possible malfunction of said supply circuit prevents the gas passage through the gas inlet means.

We note that these systems meet the standards European control and safety systems for appliances using gaseous fuels: EN 298 and EN 26.

Claims (8)

1. Positive safety device for a burner (5) for flame ignition, flame detection and gas admission control comprising a means (25, 42, 43) for admitting gas to the burner (5), fed by an electric supply circuit (7, 24, 27), characterised in that:

   said gas admission means (25, 42, 43) allows gas to flow to the burner only when a voltage difference across its terminals is greater than the supply voltage;

   said electric supply circuit (7, 24, 27) is adapted to apply across the terminals of the gas admission means (25, 42, 43) a voltage greater than the output voltage of the power supply (8), in such a way that any malfunctioning of said supply circuit (7) prevents the gas from flowing through the gas admission means.
2. Device according to claim 1, characterised in that it comprises a flue back-flow detection mean (SRC) adapted to open the supply circuit for the gas admission means (25, 42, 43) upon detection of a back-flow, the voltage difference across the terminals of the gas admission means being, at the time of closing of the detection means (SRC), less than the opening voltage for the gas admission means (25, 42, 43).
3. Device according to either of claims 1 or 2, characterised in that it comprises:

   an oscillator (20, 21) producing an alternating signal between two electrodes (11, 5, 14) placed in the vicinity of a burner (5, 14), with sparks between these two electrodes being adapted to ignite a flame on the burner, said flame ionising the interval between the two electrodes;

   a comparator (23) adapted to receive a signal representative of the voltage between said two electrodes and to compare it with a reference voltage; and

   a means (11) for controlling the oscillator taking into account the signal from the comparator.
4. Device according to claim 3, characterised in that the control means is adapted to reduce the frequency of the oscillator when the signal from the comparator is representative of the presence of a flame between said two electrodes.
5. Device according to either of claims 3 or 4, characterised in that the control means is adapted to reduce the voltage at the output from the oscillator when the signal from the comparator is representative of the presence of a flame between said two electrodes.
6. Device according to any one of claims 1 to 5, characterised in that the supply circuit comprises a current regulating, chopping type power supply (IC2-d, TR50, TR51, TR61, D61, L61, IC3, Vref1), which supplies an opening current for a gas admission means (25, 42, 43).
7. Device according to any one of claims 1 to 6, characterised in that the power supply source (8) of the electronic circuits is constituted by electric batteries.
8. Heating means, characterised in that it comprises a device according to any one of claims 1 to 7.

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