FIELD OF THE INVENTION

5 The present invention concerns in general an apparatus to indicate an output level of a pilot flame used in gas appliances provided with manual valves and thermoelectric safety valve devices. In particular, the gas appliances in question can comprise boilers, storage water heaters, stoves, ovens, fireplaces, or similar or comparable appliances, provided with a gas burner.

10 The invention also concerns the connected method to indicate the output level of a pilot flame in a gas appliance.

BACKGROUND OF THE INVENTION

Gas heating appliances are known, for example boilers, or water heaters, generally provided with a main burner and a pilot burner. Normally, also for 15 safety reasons, these gas appliances have sealed combustion chambers, and are provided with a pilot valve, manually drivable by a user, to supply a flow of gas to the pilot burner.

The opening of the pilot valve allows to switch on the pilot flame of the pilot burner by means of an ignition device, for example a piezoelectric element. The 20 pilot flame then powers a thermocouple, which converts the heat into electric energy suitable to power an electro valve that keeps the pilot valve open. The pilot burner therefore remains switched on and bums continuously to keep the pilot flame ignited to supply the ignition source for the main burner.

The gas valves and pilot burners function independently of any connection to 25 the electric power inside the building in which they are installed.

In gas appliances of this type it is normally difficult to control the functioning of the pilot valve and the ignition device since the pilot flame is positioned in places that are not easily accessible to the user and is therefore difficult to see from outside the gas appliance.

30 When the pilot flame is first ignited, or re-ignited following a malfunctioning of the appliance, or a maintenance operation, the user has to manually open the pilot valve, to supply gas to the pilot burner, and subsequently drive the ignition device to ignite the pilot flame, continuing to keep the valve open manually until the thermocouple is able to generate an electric voltage of sufficient value to keep the pilot valve open.

Since the pilot flame is not normally visible to the user, the user cannot understand whether the pilot flame is correctly ignited, or whether it is supplying sufficient energy to keep the pilot valve open, so he does not know if/when he can release the manual drive.

In order to at least partly solve this problem, indication apparatuses are known, associated with the gas appliances, suitable to provide an output level of the pilot flame to indicate to the user when he can release the manual drive of the pilot valve.

For example, from patent US-B-9.080.769 an apparatus is known to indicate an output level of a pilot flame for heating appliances, comprising a voltage measurement circuit which provides an output indicative of a quantity of the voltage generated by the thermocouple, a lighting device and a controller coupled with the thermocouple and with the lighting device. The controller, based on the output provided by the voltage measurement circuit, determines a switching sequence to switch on and switch off the lighting device with a defined frequency, and provides an indication of when the voltage generated by the thermocouple is growing toward a value sufficient to keep the pilot valve open. In the solution described in US-B-9.080.769 the controller and the lighting device are both powered by a battery. This known solution has the disadvantage that the battery, having to power the two components, has a limited duration, so that it is not possible to continuously maintain the flashing of the lighting device.

Another known solution, described for example in patent US-B-4.770.629, describes a control system for a burner provided with a pilot flame which powers a thermoelectric generator, which supplies energy to an oscillator. The oscillator has an output that is increased to a voltage level and converted to a regulated direct current potential, which is in turn used to operate a solid state controller. The controller has a sampling frequency which is visually indicated by a light- emitting diode when a suitable electric voltage is present. This known solution has the disadvantage that it entails an increase in the time required to activate the electro valve due to the fact that part of the energy supplied by the pilot flame is used to power the controller and the emitter diode. Document DE-A-199 17 488 describes an indication device for a gas burner that provides to use the thermocouple as a sensor to signal to a user the actual functioning state of the burner after the initial start-up step.

Further indicator devices are known from JP-U-S56 18984 and JP-A-S63 286619.

There is therefore a need to perfect and provide an apparatus to indicate an output level of a pilot flame which overcomes at least one of the disadvantages of the state of the art.

One purpose of the present invention is to provide an apparatus to indicate an output level of a pilot flame which does not entail an extension of the time required to power the electro valve with a sufficient electric voltage and which, at the same time, can provide the user with a reliable and immediate signal of when the manual drive can be released.

A further purpose of the invention is to provide an apparatus to indicate the output level of the pilot flame that allows to increase the life of a battery without the need to provide downtimes of the apparatus.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

Embodiments described here concern an indication apparatus to indicate the output level of a pilot flame in a gas appliance, which is provided with a thermocouple suitable to convert the energy generated by a pilot flame, which receives gas from a pilot valve, into an electric voltage suitable to power an electro valve of the pilot valve in order to keep the latter open. The indication apparatus comprises:

- a first and a second connector suitable to be coupled with a positive terminal and with a negative terminal of the thermocouple;

- a voltage measurement circuit connected to the first and second connector and configured to calculate the difference in electric voltage at the heads of the terminals so as to determine the electric voltage generated by the thermocouple, and provide an output correlated to the difference in voltage calculated;

- a lighting device configured to provide a light signal;

- a controller device, coupled with the voltage measurement circuit and with the lighting device, and configured to determine the switching on of the lighting device on the basis of the output supplied by the voltage measurement circuit to provide a user with an indication of when the voltage generated by the thermocouple is greater than or equal to a predefined value, sufficient to power the electro valve, that is, such that a user can stop keeping the pilot valve open manually;

- a battery, connected to the controller device, and suitable to power the latter and the voltage measurement circuit, and

- a power circuit, connected between the connectors and the lighting device, and configured to supply the latter with the electric voltage supplied by the thermocouple on the basis of commands received from the controller device, in such a way as to switch on the lighting device in a flashing manner when the voltage generated by the thermocouple is greater than or equal to the predefined value.

When the lighting device is switched on, therefore, the user can release the manual drive of the pilot valve, which is kept open by the electro valve powered by the thermocouple.

In the indication apparatus according to the invention, therefore, a part of the components is powered by a specific battery, in this case the voltage measurement circuit and the controller device, while another part of the components, in this case the lighting device, is powered by the thermocouple.

This particular configuration allows to obtain at least the following advantages:

- the life of the battery is increased, therefore requiring few, or no, interventions to replace it throughout the life span of the indication apparatus;

- it is possible to keep the lighting device switched on in a flashing manner continuously without needing to provide for temporary deactivation intervals of the indication apparatus;

- the level of electric voltage sufficient to keep the electro valve open is reached more quickly, as the controller device is powered only by the battery;

- it is possible to quickly provide the user with an indication of when the electric voltage supplied by the thermocouple is sufficient to keep the electro valve open autonomously.

According to some embodiments, the power circuit comprises a capacitor connected to the lighting device and configured to accumulate a quantity of electric charge supplied by the thermocouple sufficient at least to allow the switching on of the lighting device.

According to further embodiments, the power circuit comprises a second switch connected in series to the lighting device, which can be selectively activated and/or deactivated by the controller device in order to respectively allow and/or prevent the electric charge accumulated in the capacitor being discharged through the lighting device.

At the end of the charge transient of the thermocouple, as long as the pilot flame remains ignited, the lighting device can continue to flash with a frequency correlated to the charging/discharging time of the capacitor, to indicate the correct functioning of the gas appliance, without consuming the battery.

Embodiments described here also concern a gas appliance, provided with a thermocouple suitable to convert the energy generated by a pilot flame, which receives gas from a pilot valve, into electric voltage to power an electric valve of the pilot valve and to keep the latter open in order to allow a pilot flame in a pilot burner to be powered, and with an indication apparatus according to the invention connected with the thermocouple.

A purpose of the present invention is also a method to indicate the output level of a pilot flame in a gas appliance provided with a thermocouple suitable to convert the energy generated by a pilot flame, which receives gas from a pilot valve, into electric voltage to power an electro valve of the pilot valve and to keep the latter open, wherein the method comprises:

- detecting an electric voltage at the terminals of the thermocouple by means of a voltage measurement circuit;

- calculating the difference in electric voltage between the two terminals, and providing a controller device with an output signal correlated to the difference in electric voltage calculated in order to determine the electric voltage generated by the thermocouple;

- comparing the electric voltage generated by the thermocouple with predefined reference values and, when the electric voltage generated by the thermocouple is equal to or greater than a first predefined value, insufficient to power the electro valve, accumulating in a power circuit a quantity of electric charge, supplied by the thermocouple, suitable to switch on a lighting device;

- keeping monitored the electric voltage generated by the thermocouple and the quantity of electric charge accumulated in the power circuit,

wherein the method provides to:

- power the voltage measurement circuit and the controller device by means of a battery;

- command the power circuit, by means of the controller device, in order to supply the lighting device with the quantity of accumulated electric charge so that it flashes when the electric voltage generated by the thermocouple exceeds a second predefined value, sufficient to power the electro valve, and the quantity of electric charge accumulated is sufficient to switch on the lighting device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example, with reference to the attached drawings wherein:

- fig. 1 is a schematic view of a gas appliance provided with an apparatus to indicate the output level of the pilot flame according to embodiments described here;

- fig. 2 is a schematic diagram of an apparatus to indicate the output level of the pilot flame according to embodiments described here;

- fig. 3 is a schematic diagram of an apparatus to indicate the output level of the pilot flame according to variant embodiments described here;

- fig. 4 is a schematic diagram of an apparatus to indicate the output level of the pilot flame according to further variant embodiments described here.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications. DET AILED DESCRIPTION OF SOME EMBODIMENTS

Embodiments described here with reference to the drawings concern an apparatus 10 to indicate the output level of a pilot flame in a gas appliance 11.

Examples of gas appliances 11 of the type in question can comprise boilers, storage water heaters, stoves, ovens, fireplaces or similar or comparable appliances.

With reference to fig. 1, the gas appliance 11 comprises a valve device 12 configured to supply a flow of gas coming from a source of gas respectively to a main burner 13 and to a pilot burner 14.

The valve device 12 comprises a pilot valve 15 which, in an open condition, allows the passage of a gas flow toward the pilot burner 14.

The valve device 12 also comprises a main valve, not shown, which allows the passage of a flow of gas toward the main burner 13.

The pilot valve 15 is provided with a manual drive device 16 by means of which a user can take it into an open condition in which the gas can flow through it, and with an electro valve 17 configured to keep it in the open condition when it is powered with a sufficient voltage. The electro valve 17 can comprise, for example, a magnetic unit, or a solenoid coil which generates a magnetic field suitable to keep the pilot valve 15 open.

The gas appliance 11 also comprises an ignition device 18, for example a piezoelectric device, which can be pressed or activated by the user to ignite a pilot flame in the pilot burner 14 while the pilot valve 15 is kept open by means of the manual drive device 16 driven by the user.

The valve device 12 also comprises a thermocouple 19, configured to convert the heat provided by the pilot flame into electric voltage, which, upon reaching a sufficient value, can be applied to the electro valve 17 to keep the pilot valve 15 open.

The apparatus 10 to indicate the output level of the pilot flame can be connected with, or integrated, in the gas appliance 11. For example, it can be provided that the indication apparatus 10 is made integrated in a gas appliance 11 directly during the step of making the latter, or that it is made as a separate component, connectable to newly made or already existing gas appliances 1 1.

According to some embodiments, the indication apparatus 10 is configured to receive at input information on the value of the voltage generated by the thermocouple 19 and to provide the user with an indication correlated to the voltage value received, in particular to indicate to the user when he can release the manual drive 16.

The indication apparatus 10 (fig. 2) can comprise a first connector 20a and a second connector 20b configured to be connected respectively to a first terminal T1 and a second terminal T2 of the thermocouple 19, for example the positive terminal and the negative terminal respectively.

According to embodiments described with reference to fig. 2, the indication apparatus 10 comprises a voltage measurement circuit 21 configured to measure the electric voltage generated by the thermocouple 19 and supply an output correlated to the value of the electric voltage measured.

The indication apparatus 10 also comprises a lighting device, for example a LED (Light Emitting Diode) 22, and a controller device 23 coupled with the voltage measurement circuit 21 and the LED 22.

The controller device 23 is configured to control the switching on of the LED 22 on the basis of the output supplied by the voltage measurement circuit 21.

According to some embodiments, the indication apparatus 10 also comprises a battery 24 connected to the controller device 23 and configured to power the controller device 23 and the voltage measurement circuit 21 with the electric energy necessary for their functioning.

According to some embodiments, the voltage measuring circuit 21 and the controller device 23 can be made on the same electronic board, not shown, which is connected and powered by the battery 24.

According to some embodiments, the voltage measurement circuit 21 is powered by the electric energy supplied by the battery 24 by means of an output Out3 of the controlling device 23.

The thermocouple 19, therefore, at least in an initial transitional heating step, does not power either the voltage measurement circuit 21 or the controller device 23. These therefore do not risk interrupting or influencing in any way the electric voltage generated by the thermocouple 19.

Furthermore, the battery 24 does not power any component of the valve device 12, which therefore functions independently of the state of charge of the battery 24.

According to one aspect of the present invention, the indication apparatus 10 comprises a power circuit 25 coupled with the thermocouple 19 and the LED 22 and configured to power the latter with the electric voltage supplied by the thermocouple 19.

According to some embodiments, the voltage measurement circuit 21 comprises an operational amplifier 26, which acts as a comparator to calculate the difference between two values of electric voltage. The operational amplifier 26 is connected, by means of the first connector 20a and the second connector 20b, to the positive T1 and negative T2 terminals of the thermocouple 19, and is configured to calculate the difference in electric voltage between the two terminals Tl, T2, and supply an output signal correlated to the difference in electric voltage calculated.

According to possible embodiments, the non-inverting input 27 of the operational amplifier 26, during use, is connected to the positive terminal Tl, while the inverting input 28 is connected, by means of one or more resistances R, to the negative terminal T2, in this example case with a common connection to earth.

According to some embodiments, the operational amplifier 26 is connected, by means of its own output 29, to the controller device 23 to supply the latter with the output signal correlated to the difference in electric voltage calculated.

According to some embodiments, the controller device 23 can be a microcontroller, a microprocessor, or other similar device suitable to receive input signals/data, process them and provide output signals/data correlated to the input signals/data.

According to some embodiments, a program, or a sequence of instructions, can be stored in the controller device 23 to control the power circuit 25 and determine the switching on of the LED 22 based on the input signals/data received.

According to some embodiments, the power circuit 25 comprises a transformer 30 provided with a primary coil 31 and a secondary coil 32, and configured to raise the voltage generated by the thermocouple 19.

According to some embodiments, the ratio between the primary coil 31 and the secondary coil 32 is l :n, where n can be comprised between about 50 and about 150.

The primary coil 31 is connected to the terminals Tl, T2 of the thermocouple 19, while the secondary coil 32 is connected to the clips of the LED 22.

According to some embodiments, the power circuit 25 comprises a capacitor

33 configured to accumulate the electric energy supplied by the thermocouple 19.

In particular, the capacitor 33 is configured to accumulate a quantity of electric charge at least sufficient to allow to switch on the lighting device 22.

According to some embodiments, the capacitor 33 is connected in parallel between the secondary coil 32 and the LED 22, and is configured to accumulate the electric energy supplied by the thermocouple 19 and raised by the transformer 30.

According to some embodiments, the secondary coil 32, the capacitor 33 and the LED 22 can have a common connection to earth.

According to some embodiments, the capacitor 33 is also connected to the controller device 23 by means of an input Ini of its own, so that the latter can monitor the electric voltage at the heads of the capacitor 33 and therefore the quantity of charge accumulated therein.

According to some embodiments, the power circuit 25 comprises a first switch

34 connected in series to the primary coil 31, which can be selectively activated/deactivated by the controller device 23 to respectively allow/prevent the passage of current through it and supply the transformer 30 with an alternate electric current.

In particular, when the first switch 34 is active, it allows the passage of an electric current through the primary coil 31 , while when it is inactive it behaves like an open circuit, preventing the passage of the electric current.

The power circuit 25 can further comprise a second capacitor 35, connected in parallel between the thermocouple 19 and the primary coil 31 and configured to accumulate electric energy when the first switch 34 is inactive.

According to some embodiments, the power circuit 25 further comprises a second switch 36 connected in series with the LED 22, which can be selectively activated/deactivated by the controller device 23 to respectively allow/prevent the electric energy accumulated in the capacitor 33 being discharged through the LED 22.

In particular, when the second switch 36 is active it allows the passage of an electric current through the LED 22, so as to switch on the latter, while when it is inactive it behaves like an open circuit, and prevents the passage of an electric current.

According to some embodiments, the first switch 34 and/or the second switch 36 can be, for example, semiconductor transistor devices, for example of the MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) type, or other similar devices.

According to further embodiments, in the power circuit 25 there is also a diode D connected between the secondary coil 32 and the LED 22 and configured to straighten the electric current at output from the secondary coil 32 toward the capacitor 33 and the LED 22.

The functioning of the indication apparatus 10 at the moment of ignition of the pilot flame is described below.

The controller 23 performs a detection of the electric voltage generated by the thermocouple 19 at intervals with a defined sampling frequency.

According to some embodiments, the sampling frequency can be fixed or vary according to the conditions.

For example, the controller device 23 can be configured to detect the electric voltage with a first frequency when the pilot flame is off or the electric voltage Vt generated by the thermocouple 19 is lower than a first predefined value Voff, insufficient to keep the electro valve 17 open.

The first frequency can be, for example, 0.3Hz.

The controller device 23 can be configured to detect the electric voltage with a second frequency when the pilot flame is on, or when the electric voltage Vt generated by the thermocouple 19 is greater than or equal to a second predefined value Von, sufficient to keep the electro valve 17 open.

The second frequency can be lower than the first frequency, for example 0.1 Hz.

When the controller device 23 detects that the electric voltage Vt generated by the thermocouple 19 is higher than a first threshold value VI, it commands the first switch 34 by means of a first output Outl to activate/deactivate it in a controlled manner.

In this way, the transformer 30 is powered, which raises the voltage generated by the thermocouple 19 which is accumulated in the capacitor 33 disposed downstream.

During the charge transient of the thermocouple 19, the second switch 36 is in an inactive state, therefore no electric current flows through it and all the energy is accumulated in the capacitor 33.

According to some embodiments, the controller device 23 can command the first switch 34 by means of a PWM (Pulse Width Modulation) command with a desired duty cycle.

Furthermore, the controller device 23 keeps the electric voltage at the heads of the capacitor 33 monitored by means of the first input Ini .

When the electric voltage Vt generated by the thermocouple 19 exceeds the second predefined value Von, that is, it is sufficient to keep the electro valve 17 open, and the quantity of electric charge stored in the capacitor 33 is equal to or greater than a predefined threshold value C*, sufficient to allow the switching on of the LED 22, then the controller 23 activates the second switch 36 by means of a second output Out2.

In this way, the circuit branch of the LED 22 is earthed, and the charge stored in the capacitor 33 can be discharged through the LED 22, which switches on with a single flash.

When the LED 22 is switched on, the user can release the manual drive device 16 and the pilot valve 15 is kept in the open state by the electro valve 17.

Once the capacitor 33 is discharged, the second switch 36 is deactivated again to allow a new accumulation of electric charge in the capacitor 33.

Following the transitional step of starting and igniting the pilot flame, the LED 22 can continue to flash with a frequency correlated to the charge/discharge speed of the capacitor 33.

By way of example, the frequency can be about 0.5Hz, that is, one flash approximately every 2 seconds.

In fact, as long as the electric voltage Vt generated by the thermocouple 19 remains higher than the first threshold value VI, the controller device 23 continues to activate/deactivate the first switch 34 to charge the capacitor 33 and, when the accumulated electric charge reaches the predefined threshold value C*, it commands the activation of the second switch 36.

According to further embodiments, described with reference to fig. 3, the power circuit 25 can be connected to the battery 24.

According to these solutions, the power circuit 25 can comprise a resistor 37 connected between the battery 24 and the capacitor 33.

In this case, the capacitor 33 can be pre-charged directly by the battery 24 when it is installed, therefore the execution of the first flash of the LED can occur as soon as the controller device verifies that the electric voltage Vt is equal to or greater than the second predefined value Von, without needing to wait for a charge transient of the capacitor 33 with the electric energy supplied by the thermocouple 19.

According to some embodiments, the resistance value of the resistor 37 can be defined in the design step so as to satisfy the following requirements:

- it must be high enough to prevent the LED 22 from switching on by means of the battery 24;

- it must be low enough to allow the capacitor 33 to charge in a limited period of time after the battery 24 has been installed.

By way of example, this period of time can be comprised between a few seconds and a few minutes, for example less than five minutes.

According to this variant embodiment, therefore, the energy required for the first switching on of the LED 22 at the end of the charge transient of the thermocouple 19 is supplied to the power circuit 25 by the battery 24.

Subsequently, once normal working conditions have been reached, as long as the pilot flame remains on, the energy required to switch on the LED 22 is supplied almost completely by the thermocouple 19 by means of the transformer 30 and the capacitor 33, since the energy transfer from the battery 24 is limited by the resistor 37.

Furthermore, when the pilot flame is switched off, the lighting device stops flashing, and the power circuit 25 only takes from the battery 24 the energy necessary for the charge transient of the capacitor 33, since the diode D on one side and the second switch 36 on the other prevent the passage of the electric current to the earth. It is clear that modifications and/or additions of parts may be made to the apparatus 10 and method to indicate the output level of a pilot flame as described heretofore, without departing from the field and scope of the present invention.

For example, according to a further embodiment described with reference to fig. 4, it can be provided that the controller device 23 is also connected, in addition to the battery 24, to the power circuit 25.

According to these embodiments, the controller device 23 can be provided with two distinct power branches, of which a first branch 38 is connected to the battery 24, and a second branch 39 is connected to the power circuit 25, and in particular to the secondary coil 32.

According to some embodiments, the two branches 38, 39 are connected in a common node 45, so that the controller device 23 is powered by the branch 38, 39 which on each occasion has the greatest electric voltage.

According to some embodiments, a capacitor 42 can be present between the common node 45 and the earth, having the function of a filter and configured to stabilize the electric voltage supplied to the controller 23.

During the initial transitional step of heating the thermocouple 19, the electric voltage supplied by the power circuit 25 is lower than the electric voltage supplied by the battery 24, therefore the controller device 23 is powered by the latter by means of the first branch 38.

During the functioning under normal working conditions, when the thermocouple 19 has heated up, the electric voltage at the heads of the secondary coil 32 of the power circuit 25 is generally greater than that supplied by the battery 24, therefore the controller device 23 is powered by the power circuit 25 by means of the second branch 39.

This embodiment allows to further increase the duration of the battery 24, since, under normal working conditions, when the pilot flame is ignited, the entire apparatus 10 is powered only by the thermocouple 19.

In the event that the pilot flame goes out, and/or the electric voltage of the second branch 39 in the common node 45 falls below the electric voltage of the battery 24, the functioning of the controlling device 23 is in any case guaranteed by the battery 24.

According to some embodiments, the first branch 38 and the second branch 39 comprise respective diodes 40, 41 which perform a protective function. In particular, the diode 40 in the first branch 38 prevents the electric voltage supplied by the power circuit 25 from damaging the battery 24, while the diode 41 in the second branch 39 prevents the electric energy supplied by the battery 24 from flowing in the form of electric current toward the power circuit 25 and toward the LED.

According to some embodiments, the apparatus 10 comprises a voltage limiting circuit 46 connected between the controller device 23 and the common node 45 and configured to limit the voltage at input to the controller device 23 so as to prevent possible damage to the latter.

According to possible embodiments, the voltage limiting circuit 46 can comprise a resistor 43 and a third switch 44, which can be selectively activated by the controller device 23, disposed in series one after the other.

According to some embodiments, the third switch 44 can be activated by the controller device 23 by means of an output Out4 of its own, when it detects that the electric voltage at the input Vcc exceeds a predetermined voltage value, so as to allow the passage of an electric current through the resistor 43 to the earth, thus reducing the electric voltage at input to the controller device 23.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of apparatus 10 and method to indicate the output level of a pilot flame, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.