FR2751730A1 - POSITIVE SECURING DEVICE FOR ADMISSION OF GAS INTO 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 positive security device

  intended to control safety functions around a burner, for example in a

boiler or water heater.

  The burners require safeguards to prevent on the one hand that the flame remains absent from the burner, which prohibits the operation of the thermal system and, on the other hand, that, if the flame were extinguished, the

  gas continues to be diffused through the burner.

  Many devices, all intended to be connected to the 220 Volts sector, are known to those skilled in the art. Indeed, the known devices have a high consumption of electrical energy because of two functions, that of ignition of the flame and that of the gas inlet control, which is generally constituted by a relay which controls a solenoid valve. The electrical power required for such devices prohibits their use on battery-powered devices. The present invention intends to remedy these drawbacks by having an electronic device for igniting a flame on a burner, for detecting said flame and for controlling the admission of gas into the burner, the consumption of which is so small that it can

  be provided by batteries.

  For this purpose, the device which is the subject of the invention comprises a positive-security electronic circuit which makes it possible to switch on and control the flame of a burner. The device allows the ignition of a main burner with the aid of an ignition burner. It controls the ignition of the main burner only when the flame is present at the ignition burner. The battery-powered electronic assembly produces sparks, checks for flame, and positively supplies a solenoid valve that allows gas to be fed to the main burner. This assembly applies to burner ignition

  with non-permanent ignition burner.

  It is recalled that positive security consists in that no breakdown of a constituent can induce

  dangerous situation for the user.

  The invention firstly relates to a device for positively securing a burner for flame ignition, flame detection and gas admission control characterized in that it comprises a gas inlet means that does not allow gas to pass through. to a burner only when a voltage difference between its terminals is greater than the supply voltage, and in that it has a suitable power supply circuit to be applied between the terminals of the gas inlet means a voltage the output voltage of the power source, so that a possible malfunction of the power supply circuit prevents the

  passing gas through the gas inlet means.

  Thanks to these characteristics, any failure of the supply circuit causes the voltage across the terminals of the gas intake means to fall below the supply voltage and therefore the voltage that is suitable for its opening. The admission of gas is therefore protected against

  failure or short circuit in the supply circuit.

  According to preferred features, the device according to the present invention comprises a chimney return detection means adapted to open the supply circuit of the gas admission means during the detection of a backflow, the difference in voltages between the terminals of the gas inlet means being, when closing the detection means, less than the

  opening voltage of the gas inlet means.

  Thanks to these arrangements, the voltage across the gas intake means when closing the backflow prevention is insufficient to reopen the gas inlet means, the safety against the discharge of the chimney is directly provided by

  opening of the supply of the gas intake means.

  According to preferred features, 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 ionizing flame gap 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 oscillator control means taking into account

the signal coming out of the comparator.

  Thanks to these arrangements, the voltage between the electrodes serves both to supply a flame, to produce a spark, and to detect 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, that is,

  to say that it allows the passage of electrons only in

a direction.

  According to a first aspect of the invention, the signal coming out of 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 signal output from the control means is adapted to reduce the output voltage of the oscillator when the output signal of the comparator is representative of the presence

  a flame between said two electrodes.

  Thanks to each of these provisions, and preferably to both, the power consumption of the device is very small since the ignition phase, which is the largest energy consumer, is very short and then the operation of the device serves

  to test the operation of a heating system.

  According to particular features, the supply circuit comprises a current-regulated switching power supply, which supplies an opening current of a gas intake means. Thanks to these provisions, the energy required for the control of the gas intake means is low enough for a battery to power for several months in normal operation. According to other particular characteristics, a power source of the electronic circuits is constituted

electric batteries.

  Thanks to these features, no connection to the mains is necessary and the installation is greatly simplified since there is no more installation.

electric to predict.

  The invention also relates to a heating means, water heater or boiler, for example, characterized in that it comprises a device as briefly described above. Other benefits, goals and features

  will emerge from the description which will follow, made in

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

  realization of the circuit presented with reference to FIG.

  The following examples of embodiments of the invention are applied to a thermal installation using a gaseous fuel. However, the invention is easily applicable to thermal installations using other forms of fuels, for example liquid, solid or powdery, by the simple implementation of

  normal knowledge of the person skilled in the art.

  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 gas inlet 2 and thermally connected to a fluid circuit 6

  ranging 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 flame presence detection means 11 placed near the exit of an ignition burner 14, to a flame ignition means 9 placed at the output of the ignition burner 14, to a gas inlet means 25 placed between the gas inlet

  2 and the burner 5 and a draw switch 13.

  It should be noted that, according to an advantageous characteristic of the invention, it is the same electrode which here ensures the production of sparks for ignition of the flame and which detects the presence of the flame. This electrode therefore corresponds to both the flame ignition means 9

  and flame detection means 11.

  The thermal installation 1 is, for example, consisting of a water heater or a boiler of known types. The burner 5 is adapted to mix air with the gas coming from the gas inlet 2, via the gas admission means 25, to ensure the good combustion of the mixture thus formed and to evacuate the gases. burned by a chimney 12. The burner 5 is of known type. The main burner 5 is ignited by an ignition burner 14 whose flame is ignited by the flame ignition means 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 has been heated by the flame of the burner 5, then goes through a circuit which

  depends on the thermal installation 1.

  The gas inlet 2 is 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 may possibly be supplemented by the

electrical sector.

  The presence of flame detection means 11 placed near the exit of the ignition burner 14 is adapted to emit a signal representative of the presence or absence of a flame at the burner output 5. The means flame ignition 9 placed at the exit of the ignition burner 14 is adapted to ignite a flame at the outlet of the burner 5. The gas admission means 25 placed between the gas inlet and the burner 5 is adapted either to let the gas coming from the gas inlet 2 to the burner 5, when it is open, either to prohibit this

circulation, when closed.

  The tapping switch 13 is controlled by the flow of water in the circuit 6, according to techniques

  known that are not detailed here.

  The electronic circuit 7, which will now be described with reference to FIGS. 2, 3 and 5, controls the flame ignition means 9 and a gas admission means 10 as a function of the signal coming out of the detection means of FIG.

flame 11.

  FIG. 2 shows a first embodiment of the electronic circuit 7. The circuit comprises, in the first embodiment shown 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 associated components including a resistor R9 18 polarization 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 coming out of the flame detection means 11 and on the other hand a capacitor discharge igniter 22 having a diode D1, a capacitor C2, a silicon spark gap sid1, consisting of a self-triggered thyristor which has only two electrodes, and a transformer T2 which provides a signal of 15 kV to generate sparks with a duration of 5 microseconds, which receives the signal coming out of 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,

  on the other hand, during flame detection.

  The blocking oscillator thus constituted produces an alternating signal which is rectified by the diode constituted by 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 setpoint given by the resistors R7 and R8. In this way, in the presence of the flame the tests of its presence take place 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; a means for controlling the oscillator taking into account the signal output from the comparator and comprising in the example described and shown a simple resistor R2; - A switching power supply 24 of a type known as boost supplies the gas inlet means 10, here consisting of the solenoid valve 25, positively. This power supply is composed of a transistor TR60 of a

  inductor L60, a diode D60 and a capacitor C60.

  It provides 30 mW, which is sufficient to maintain the solenoid valve 25; - Delay means 26, consisting of an operational amplifier IC2- c, a transisor TR41 and resistors and associated capacitors, allows to give a solenoid opening current for a limited time, to save 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, of transistors TR50, TR51 and TR61, of a diode D61, an inductance L61 and a reference voltage VRefl, provides the opening current of the solenoid valve 25, positively. This switching power supply 27 provides

1 watt.

  - A safety means against the discharge of the chimney, referenced SRC, consists of a bimetallic automatic reset, mounted in series with the solenoid valve, which cuts the circuit when a discharge is detected in a known manner, the re-ignition being forbidden by the low holding power of the solenoid valve which is insufficient to reopen it

  when security against refoulement closes.

  It is noted that, to ensure a positive security, switching power supplies 24 and 27 provide

  voltages higher than the voltage of the voltage source.

  In case of failure, the solenoid valve 25 can not be

accidentally ordered.

  The circuit noted "switch tap, at the top of Figure 2, represents a means for energizing the circuit of Figure 2. It controls a tapping switch 13

  (Figure 1) which makes the ignition request.

  FIGS. 3 and 4 relate to a thermal installation where the main burner 5 is directly ignited by the ignition means 9 and the flame on this burner is

  controlled by the flame detection means 11.

  In the second embodiment, shown in FIG. 3, it is observed that a circuit breaker 30, comprising two transistors TR3 and TR4, associated resistors and a

  fuse F1, is connected to an input of the power supply 24.

  The circuit breaker 30, together with a capacitor C20 of the window oscillator comparator 23, locks the device when the burner is not lit before the capacitor C20 is charged to the first predetermined value of the oscillator comparator 23, the system that can only be unlocked

by stopping the drawing.

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

simplified in Figure 3.

  The simplification of the switched-mode power supply 27, represented in FIG. 3, corresponds to a variant of the electronic circuit diagram of the power supply shown in FIG. 2. This variant has the advantage of being able to be

connected to the mains.

  The electronic circuit 7 presented with reference to FIG. 5 is specifically adapted to the installation

  thermal 1 presented with reference to FIG.

  FIG. 6 represents a third type of thermal installation incorporating a device according to the present invention, in which, in comparison with FIG. 1, two solenoid valves 42 and 43 (shown in FIG. 5) replace the solenoid valve 25, and in which a electronic circuit 7, as shown in Figure 5, controls said solenoid valves 42 and 43, according to the electrical signals and switch positions corresponding to the backflow prevention, on demand

  ignition or draw-off, and the ignition electrode.

  In FIG. 5, there are: 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 shown in Figure 1 except for a diode added in parallel with the resistor R21, at the input of the comparator circuit 23; switching power supply 24 which supplies a primary solenoid valve 43; - Safety means against the discharge of the chimney, referenced SRC, placed in series with the primary solenoid valve 43; and the switching power supply 27 which supplies power to a

secondary solenoid valve 42.

  To these elements presented with reference to FIGS. 2 and 3 are added: a maximum power authorization circuit 31 which includes an operation 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 authorization circuit 31 enters the supply circuit 27; a control 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 earth. The non-inverting input of the operational amplifier 41 receives a fixed predetermined voltage corresponding to a regulation setpoint. The output signal of the regulation circuit enters the supply circuit 27, jointly

  the signal leaving the authorization circuit 31.

OPERATION OF THE DEVICE

  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 value of the flame signal, interrupts the oscillator comprising the transformer T1 and the transistor TR1 if the signal is greater than the setpoint and releases it if the signal is lower than the setpoint. It thus commands the generation of sparks at

burner 5.

  the validation of the flame signal is carried out by the window comparator oscillator: the operational amplifiers IC2-a and IC2-b together 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. Note that, in the embodiment described and shown, the signal output from the control means is adapted to reduce the frequency and the output voltage of the oscillator when the output signal of the comparator is representative of the presence

  a flame between said two electrodes.

  the switching power supply 24, of the boost type, produces a voltage greater than the supply voltage required to control the solenoid valve 25. The energy stored in the inductor L60 when the transistor TR60 is saturated is discharged by the intermediate of the diode D60 in the capacitor C60 when the transistor TR60 is off. This system can only work if all the components are active and, therefore, no component faults can cause the solenoid 25 to supply power if a dynamic signal is not present.

based on TR60 transisor.

  - The delay means 26 allows the opening of the solenoid valve at full power, positively for a limited time. This saves

  batteries and to ensure the safety of a means of antirefoulement.

  - The backflow prevention means consists of a bimetallic which opens when the burnt gases are discharged into the room. the delay, initialized by the oscillation input of the operational amplifier IC2-a, enables the switching power supply 27 to operate for a fraction of a second. This power supply 27 is excited by the operational amplifier IC2-d which uses the charging and discharging 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 cyclical report of the

  square signal produced by the operational amplifier IC2-

  d. - A safety against the discharge of the chimney is provided by a bimetallic strip (not shown) mounted in a draft hood housing (not shown). It interrupts the current in the solenoid valve 25 during a discharge in the chimney, which causes the closure of the solenoid valve 25. The reopening of the solenoid valve 25 is prohibited during the closing of the bimetal, by the weak current of maintenance delivered by the power supply 24. To allow the reopening of the solenoid valve 25, it is necessary to stop the drawing and redo a drawing application,

  according to the operation presented above.

  for a direct ignition of the burner 5, FIG. 4, it is necessary to use a delay which limits the opening time of the solenoid valve 25 to less than 5 s (duration known as the "ignition safety time"), in a safe way; this is obtained by the capacitance C20 which is progressively charged by the resistor R21 during an ignition request and kept at the setpoint value during a flame detection. As long as the voltage applied to the capacitor C1 is within the operating range of the oscillator, it operates. On the other hand, if a flame detection does not appear before

  full charge of capacitor C20, the voltage of this

  it comes out of the range of the oscillator and it stops. the solenoid valve 25 is supplied from the beginning of the drawdown 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 security time defined by the delaying means, the fact is used that the oscillator locks in position high in case of complete charge of the capacitor C20, which causes a permanent saturation of the transistor TR60 and the transistor TR3, the latter in turn blocking the transistor TR4. This lock is maintained by the resistor R10 as long as the power to the system is maintained, even if the oscillator switches over again. A fuse guarantees the lock in case of short circuit of a transistor, the current at the moment of the defect becoming very important in

  transistor TR60, inductance L60 and transistor TR4.

  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 seconds. For this purpose: - a second solenoid valve which allows the high power as soon as the flame is present,

  - a double valve solenoid valve.

  For this purpose, the circuit IC2-c TR50, 51, 61, D61 is used, or another similar circuit for controlling the second solenoid valve or supplying the current for the large valve.) The detection of the large flow is ensured by a comparator IC2-c which detects the passage of the flame signal at the characteristic voltage of a presence of

  flame and allows the operation of the second booster.

  The second booster (simplified in figure 2) can be set to a fixed current or controlled by a control system (see Vrefl 1 command in diagram 1). Thus, the power supply circuit comprising the two switching power supplies 24 and 27 is adapted to apply between the terminals of the gas intake means constituted by the solenoid valve 25, a voltage greater than the output voltage of the source. in such a way that a possible malfunction of said supply circuit prevents the

  passing gas through the gas inlet means.

  It is noted that these systems comply with European standards for control and safety systems for appliances using gaseous fuels: EN 298 and EN 26. The present invention is not limited to the examples described and shown but extends, on the contrary, variants, improvements and modifications to the

scope of the skilled person.

Claims (8)

  1. Positive burner securing device (5) for flame ignition, flame detection and gas admission control characterized in that it comprises a gas admission means (25,42,43) which does not leave passing gas to the burner (5) only when a voltage difference between its terminals is greater than the supply voltage, and in that it has a power supply circuit (7,24,27) adapted to applying between the terminals of the gas intake means (25,42,43) a voltage greater than the output voltage of the supply source (8), so that a possible malfunction of said supply circuit ( 7) prevents   passing the gas through the gas inlet means.   2. Device according to claim 1 characterized in that it comprises a chimney backflow detection means (SRC) adapted to open the supply circuit of the gas inlet means (25,42, 43) during the detecting a discharge, the difference in voltages between the terminals of the gas admission means being, when closing the detection means (SRC), lower than the opening voltage of the gas admission means (25,42,43).   3. Device according to any one of claims 1   or 2 characterized in that it comprises: - an oscillator (20,21) producing an alternating signal between two electrodes (11,5,14) placed near a burner (5,14), sparks between these two electrodes being adapted to ignite a flame on the burner, said flame ionizing the gap between the two electrodes; a comparator (23) which receives a signal representative of the voltage between said two electrodes and compares it with a set voltage; and - control means (11) for the oscillator taking   the output signal of the comparator.   4. Device according to claim 3 characterized in that the control means is adapted to reduce the frequency of the oscillator when the signal output of the comparator is representative of the presence of a flame between said two electrodes.   5. Device according to any one of claims 3   or 4 characterized in that the control means is adapted to reduce the output voltage of the oscillator when the output signal of 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 characterized in that the supply circuit comprises a current-regulated switching power supply (IC2-d, TR50, TR51, TR61, D61, L61, IC3, VRefl), which provides an opening current of a admission method of gas (25,42,43).   7. Device according to any one of claims 1   characterized in that a source of energy (8)   electronic circuits consists of electric batteries.   8. Heating means characterized in that it comprises a   device according to one of claims 1 to 7.