WO2024062510A1

WO2024062510A1 - Control method for a boiler and corresponding boiler

Info

Publication number: WO2024062510A1
Application number: PCT/IT2023/050215
Authority: WO
Inventors: Simone BALDISSIN
Original assignee: De Longhi Appliances SRL
Current assignee: De Longhi Appliances SRL
Priority date: 2022-09-23
Filing date: 2023-09-21
Publication date: 2024-03-28
Anticipated expiration: 2025-03-23
Also published as: EP4591009A1; IT202200019563A1

Abstract

Control method for a boiler (10) comprising a verification step (S2) which provides to detect at least one first parameter (Pl) correlated to the heating efficiency of the container (11) of boiler (10) and to compare said at least one first parameter (Pl) with at least one second parameter (P2) in order to verify whether said container (11) has been cleaned.

Description

“CONTROL METHOD FOR A BOILER AND CORRESPONDING BOILER”

FIELD OF THE INVENTION

The present invention concerns a control method for a boiler and the corresponding boiler, which can find application, for example but without any limitations to generality, in the field of household appliances or professional machines, such as, for example, apparatuses for ironing or cleaning, apparatuses for preparing beverages, steamers for cooking food, steam ovens, or similar and comparable apparatuses. BACKGROUND OF THE INVENTION

Household appliances or professional machines which comprise a boiler for producing hot water or steam are known. For example, such household appliances or professional machines are apparatuses for ironing or cleaning, apparatuses for preparing beverages, steamers for cooking food, steam ovens, or similar and comparable apparatuses.

Normally, a boiler comprises an airtight container for the water, a heat source attached to the container to heat the water, and a delivery aperture through which the heated water or steam can escape.

It is also known that, after a period of use of the boiler, the container must be cleaned to ensure the correct operation of the boiler and not reduce its reliability and efficiency.

The cleaning is normally carried out by hand by a user, and provides to empty and possibly also rinse the container a few times until it is completely emptied.

It is also known that the most modern boilers comprise signaling devices to signal to the user when to clean the container.

As a rule, the signaling devices are configured to measure the amount of water processed over time by the boiler and generate a warning signal, luminous, audible or suchlike, when the amount of water processed reaches a maximum value.

A disadvantage of known boilers is that the warning signal can be deactivated by the user even without having actually cleaned the container.

For example, there are known boilers which have a reset button to deactivate the warning signal, or boilers for which the warning signal can be permanently deactivated by simply turning off the power supply to the boiler. This encourages negligent behavior by the user who, instead of cleaning the container, deactivates the warning signal without having actually cleaned the container.

This behavior significantly shortens the useful life of the boiler and substantially decreases its energy efficiency.

There are known documents that provide different ways to assess whether or not limescale cleaning is necessary.

Document W02020/003333A1 describes a method for controlling and cleaning a boiler which provides to set a desired programmed frequency of cleaning cycles, which can be automated or signaled to be started manually by a user, and to assess whether or not to vary this frequency according to whether the boiler is operating effectively.

Document US6236321B1 describes an apparatus and a method for determining when it is necessary to clean a boiler based on limescale deposits which accumulate therein and signaling it to the user.

Document US7167813B2 describes a system for monitoring a boiler which provides to determine the amount of time it takes to heat the water to a required temperature and, as a function of the time determined, signal the need to clean the boiler. None of the known documents disclosed, however, addresses the problem of preventing negligent user behavior by preventing the user from being able to deactivate maintenance request signals without carrying out the maintenance and cleaning interventions duly reported, which lead to inefficiency of the boiler and a reduction in its useful life. There is therefore the need to perfect a boiler that can overcome at least one of the disadvantages of the state of the art.

To do this, it is necessary to solve the technical problem of verifying that the user has actually cleaned the container.

In particular, one purpose of the present invention is to provide a control method for a boiler that allows to detect if the boiler has been cleaned.

Another purpose of the present invention is to provide a control method for a boiler that allows to keep the thermal efficiency of the boiler constant over time.

Another purpose of the present invention is to provide a control method for a boiler that allows to keep the reliability of the boiler constant over time.

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. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes and to resolve the technical problem disclosed above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a control method is provided according to the present invention for a boiler which comprises a container for containing water, heating means associated with the container and signaling means for signaling to a user the need to clean the container. In accordance with one aspect of the invention, the method comprises a signaling step in which the signaling means are activated.

According to some embodiments, the signaling means can be activated after a certain time of use of the boiler, after the passage of a certain amount of water and/or or when operating inefficiencies or anomalies of the boiler are identified, which could be caused by the presence of limescale.

In accordance with one aspect of the invention, the method also comprises a verification step which provides to detect at least one first parameter correlated to the heating efficiency of the container, and to compare the at least one first parameter with at least one second parameter in order to verify whether the container has been cleaned and then, consequently, allow to deactivate the signaling means.

According to some embodiments, the method provides to allow the deactivation of the signaling means only when the verification step gives a positive outcome, that is, when it has been verified that a cleaning of the container has been carried out.

According to other embodiments, the method provides to prevent the deactivation of the signaling means when the verification step gives a negative outcome. In other words, the user is not allowed to deactivate the signaling means until it has been verified that the water container has been suitably cleaned.

According to some embodiments, it can be provided that the verification step is carried out following the receipt of a command to carry out a cleaning of the boiler, and the method can provide to automatically deactivate the signaling means when the verification step gives a positive outcome while, in the opposite case, it provides to keep the signaling means active.

According to other embodiments, it can be provided that the verification step is carried out downstream of the receipt of a command to deactivate the signaling means, and the method can provide to keep the signaling means deactivated when the verification step gives a positive outcome and activate them again immediately after the verification step in the event of a possible negative outcome.

This effectively guarantees that the user has to clean the boiler when suggested in order to allow an effective deactivation of the signaling means.

In accordance with another aspect of the present invention, the at least one first parameter comprises an effective heating rate of the container and the at least one second parameter comprises a minimum heating rate of the container.

In accordance with another aspect of the present invention, the verification step provides to:

- activate the heating means to heat the container; - detect the temperature of the container in at least two time instants between which a control time elapses;

- determine the effective heating rate, calculated as the ratio between the difference between the temperatures in the two instants and the control time; and

- compare the effective heating rate with the minimum heating rate. In accordance with another aspect of the present invention, the minimum heating rate can be a value defined in the design phase and stored in a storage module.

In accordance with one aspect of the invention, the minimum heating rate is comprised between about 0.5 and 8 °C/s, preferably between 1 and 2.5 °C/s. In accordance with one aspect of the present invention, the at least one first parameter comprises an effective heating time of the container and the at least one second parameter comprises a maximum heating time of the container.

- detect the temperature of the container until it reaches a predetermined comparison temperature;

- determine the effective heating time as the time elapsed from the activation of the heating means to the comparison temperature being reached;

- compare the effective heating time with the maximum heating time.

In accordance with another aspect of the present invention, the comparison temperature and the maximum heating time can be values defined in the design phase and stored in a storage module. In accordance with another aspect of the present invention, the comparison temperature is comprised between 25 and 150 °C, preferably between about 40-60 °C, and the maximum heating time is comprised between 5 and 120 seconds, preferably between about 30-50 seconds.

In accordance with another aspect of the present invention, if the effective heating rate is greater than or equal to the minimum heating rate, the method provides to deactivate the signaling means and/or to keep them deactivated.

In accordance with another aspect of the present invention, if the effective heating time is less than or equal to the maximum heating time, the method provides to deactivate the signaling means and/or to keep them deactivated.

In accordance with another aspect of the present invention, if the effective heating time is less than or equal to the maximum heating time, and if the effective heating rate is greater than or equal to the minimum heating rate, the method provides to deactivate the signaling means and/or to keep them deactivated.

The present invention also concerns a boiler comprising a container for containing water, heating means associated with the container and signaling means configured to signal to a user the need to clean the container.

In accordance with another aspect of the present invention, the boiler comprises at least one temperature sensor associated with the container and a control unit connected to the temperature sensor, to the signaling means and to the heating means, and configured to carry out a control method in accordance with the present invention.

In accordance with another aspect of the invention, the boiler comprises a storage module in which reference values are stored for one or more parameters chosen from a minimum heating rate, a comparison temperature and a heating time of the boiler.

DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages 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 representation of a boiler in accordance with an embodiment of the present invention;

- figs, from 2 to 4 are flow diagrams of the control method in accordance with respective embodiments of the present invention. We must clarify that in the present description the phraseology and terminology used, as well as the figures in the attached drawings also as described, have the sole function of better illustrating and explaining the present invention, their function being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims. 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 be conveniently combined or incorporated into other embodiments without further clarifications. DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION With reference to fig. 1, a boiler 10 according to the present invention is configured to be connected to a user device in order to supply the latter with heated water or steam.

The user device to which the boiler 10 can be connected can be any user device whatsoever that requires a feed of heated water or steam to operate, such as, for example, an iron, a beverage machine, steamers for cooking food, steam ovens, or similar and comparable devices.

The boiler 10 comprises a container 11 for containing the water to be heated, formed by one or a plurality of walls 12 attached together in a hermetic manner and defining an internal containing volume 13. In the example given here, on the walls 12 of the container 11 there are created a feed aperture 15 that allows the insertion of the water into the container 11 , a discharge aperture 16 that allows the discharge of the water from the container 11 and a delivery aperture 17 configured to be connected to the user device (not shown) and from which, during use, the heated water or water vapor is delivered.

We must clarify that, during use, the feed aperture 15 and the discharge aperture 16 are both closed by a respective cap configured to keep the container 11 hermetically closed. In addition, the boiler 10 comprises heating means 21 associated with the container 11 and configured to heat the water contained therein to a desired temperature.

In the embodiment shown here, the heating means 21 are attached to the external surface of a wall 12 of the container 11 . However, in other embodiments, the disposition of the heating means 21 may be different from what is shown in the attached drawings. For example, the heating means 21 can be disposed inside the container 11, or the heating means 21 can constitute a wall 12 of the container 11.

By way of example only, the heating means 21 can be of the electric type and comprise one or more electrical resistances 22 suitable to heat, directly or indirectly, the water inside the container 11 by means of the Joule effect.

The heating means 21 are commanded by a control unit 23 configured to manage their operation.

The boiler 10 also comprises a temperature sensor 25 associated with the container 11 and configured to transmit an electric signal to the control unit 23 correlated to the temperature of the container 11 and/or of the water therein.

In the example given here, the temperature sensor 25 is attached to the external surface of a wall 12 of the container 11.

However, in another embodiment, the disposition of the temperature sensor 25 can be different from what is shown in the attached drawings. For example, the temperature sensor 25 can be attached to the internal surface of a wall 12 of the container 11 , or it can be disposed directly inside the container 11 , or it can even be associated with the heating means 21.

The boiler 10 also comprises signaling means 26 configured to signal the need to perform a cleaning of the container 11. The signaling means 26 are connected to the control unit 23 which manages their operation.

By way of example, the signaling means 26 comprise at least one signaling element 27 which can be of any known type whatsoever. For example, the signaling element 27 can be of the luminous type, such as an LED or a bulb, or of the acoustic type, such as a speaker, or of the vibration type, or a combination thereof.

Alternatively, or in addition, the signaling means 26 can comprise a communication module (not shown), for example of the Wi-Fi, Bluetooth, NFC or other type, configured to communicate with an external device, for example a smartphone, a tablet or suchlike on which a special software application is installed, in order to transmit to the latter a message indicating the need to wash the container 11. The control unit 23 also comprises a processing module 29 and a storage module 30, and it is also configured to carry out a control method of the boiler 10 according to the present invention, which will be described below.

In particular, the control method of the present invention comprises a signaling step S 1 in which the control unit 23 activates the signaling means 26 to signal to a user the need to clean the container 11.

Purely by way of example, the activation of the signaling means 23 takes place, for example, after a predetermined time of use of the boiler 10, or after the passage of a certain amount of water inside the boiler 10 and/or of water or steam through the delivery aperture 17. The time of use and/or the amount of water can be monitored by means of suitable sensors or detection devices.

According to some embodiments, in addition or as an alternative to the above, the signaling means 26 can be activated by the control unit 23 when operating inefficiencies and/or anomalies of the boiler 10 are identified, which could be due to an accumulation of limescale in the container 11 of boiler 10.

Such inefficiencies and anomalies can be identified by means of a process of monitoring the operation of the boiler 10, for example on the basis of a comparison between the actual operation of the boiler and a predefined operation thereof.

For example, a monitoring process could provide to compare a detected value of a heating time used to heat the water to a desired temperature with a predefined reference value, or compare the current temperature growth ramp with an ideal growth ramp and verify the extent of the deviation with respect to the respective reference value, although other methods may be used to determine a drop in efficiency of the boiler 10.

The method also comprises a verification step S2 aimed at verifying whether the container 11 has been cleaned and allowing the signaling means 26 to be deactivated accordingly. According to some embodiments, the method provides to allow the deactivation of the signaling means 26 only when the verification step gives a positive outcome, that is, when it has been verified that a cleaning of the container 11 has been carried out.

According to other embodiments, the method provides to prevent the deactivation of the signaling means 26 when the verification step gives a negative outcome. In other words, the user is not allowed to deactivate the signaling means 26 until it has been verified that the water container 11 has been suitably cleaned.

The verification step S2 can be performed following receipt of a command to perform a cleaning of the boiler 10, and the method can provide to automatically deactivate the signaling means 26 when the verification step S2 gives a positive outcome, while in the opposite case it provides to keep the signaling means 26 active.

According to other embodiments, it can be provided that the verification step S2 is performed downstream of the receipt of a command to deactivate the signaling means 26, which can therefore be momentarily deactivated. In this case, the method can provide to keep the signaling means 26 deactivated when the verification step S2 gives a positive outcome and to activate them again, immediately after the verification step S2, in the event of a possible negative outcome. That is to say that the signaling means 26 are reactivated without waiting for a predetermined time of use, or for the passage of a predetermined amount of water.

The verification step S2 provides to detect at least one first parameter Pl correlated to the heating efficiency of the container 11 and to compare the first parameter Pl with at least one predetermined second parameter P2 stored in the control unit 23, in particular in the storage module 30.

If the comparison between the two parameters Pl, P2 gives a positive outcome, then the heating efficiency of the container 11 is sufficient and the container 11 is therefore clean, or at least does not need to be cleaned. Instead, if the comparison between the two parameters Pl, P2 gives a negative outcome, then the heating efficiency of the container 11 is not sufficient and the container 11 needs to be cleaned, therefore the signaling means 26 remain active or are promptly reactivated.

With reference to fig. 2, in a first embodiment of the method, the first parameter Pl detected in the verification step S2 is an effective heating rate V 1 and the second parameter P2 is a minimum heating rate V2, in particular defined in the design phase.

Preferably, in order to calculate the effective heating rate V 1 the verification step S2 provides a heating sub-step S2.1 in which the control unit 23 activates the heating means 21 and a sampling sub-step S2.2, parallel to the heating sub-step S2.1, in which the control unit 23 records data pairs in the storage module 30, each of which comprises a temperature T detected by the temperature sensor 25 and the time instant H in which the temperature T was detected.

The verification step S2 comprises a further processing sub-step S2.31 performed after a certain control time C from the start of the heating S2.1 and the sampling S2.2 sub-steps, in which the processing module 29 processes the recorded data pairs and calculates the effective heating rate V 1.

Preferably, the control time C is comprised between 0.5 and 60 seconds, preferably about 5-10 seconds. For example, the control time C may be about 8 seconds.

Purely by way of a non-limiting example, the effective heating rate can be calculated as:

The verification step S2 also provides a comparison step S2.41 in which the control unit 23 compares the effective heating rate V 1 with the minimum heating rate V2.

Preferably, but not necessarily, the minimum heating rate V2 is comprised between 0.5 and 8 °C/s, preferably between 1 and 2.5 °C/s. For example, the minimum heating rate can be 1.5 °C/s.

In this embodiment, the verification step S2 gives a positive outcome if the effective heating rate VI is greater than the minimum heating rate V2, and it gives a negative outcome if the effective heating rate VI is less than the minimum heating rate V2.

If the comparison gives a positive outcome, the method also provides a deactivation step S3 in which the control unit 23 deactivates the signaling means 26, or keeps them deactivated.

The deactivation step S3 can also provide to reset and restart the monitoring of a predetermined time of use, or of the passage of a predetermined amount of water in order to correctly reactivate the signaling means 26.

On the other hand, if the comparison gives a negative outcome, the method provides to return to the signaling step S 1 and iterate the verification step S2 until the comparison step S2.41 gives a positive outcome.

Below is an example of the calculation of the effective heating rate V 1 based on a set of examp e data pairs, shown in the following table:

In this case, the effective heating rate VI is:

With reference to fig. 3, in a second embodiment of the method, the first parameter Pl detected in the verification step S2 is an effective heating time Hl and the second parameter P2 is a maximum heating time H2.

Preferably, the verification step S2 provides a heating sub-step S2.1 in which the control unit 23 activates the heating means 21 and a sampling sub-step S2.2, parallel to the heating sub-step S2.1, in which the control unit 23 records data pairs in the storage module 30, each of which comprises a temperature T detected by the temperature sensor 25 and the time instant H in which the temperature T was detected.

The heating sub-step S2.1 and the sampling sub-step S2.2 as above continue until the temperature T detected by the sensor 25 reaches a predetermined comparison temperature E. Preferably, the comparison temperature is comprised between 25 and 150 °C, preferably between 40-60 °C. For example, the comparison temperature E is about 50 °C.

The verification step S2 also provides a reading sub-step S2.32 of the effective heating time Ell, which corresponds to the time elapsed from the activation of the heating means 21 to the comparison temperature E being reached.

The verification step S2 also provides a comparison sub-step S2.42 in which the control unit 23 compares the effective heating time Hl with the maximum heating time H2. Preferably, but not necessarily, the maximum heating time H2 is comprised between 5 and 120 seconds, preferably between 30-50 seconds. For example, the maximum heating time H2 is 40 seconds.

In this second embodiment, the verification step S2 gives a positive outcome if the effective heating time Hl is less than the maximum heating time H2, and gives a negative outcome if the effective heating time Hl is greater than the maximum heating time H2. If the comparison gives a positive outcome, the method also provides a deactivation step S3 in which the control unit 23 deactivates the signaling means 26, or keeps them deactivated, possibly causing the monitoring of a predetermined time of use, or of the passage of a predetermined amount of water to be reset and restarted. On the other hand, if the comparison gives a negative outcome, the method provides to return to the signaling step S 1 and iterate the verification step S2 until the comparison step S2.41 gives a positive outcome.

Below is an example of the verification of the heating time based on a set of example data pairs, shown in the following table:

In this example, the effective heating time Hl is 39 s.

With reference to fig. 4, in a third embodiment, the method provides to carry out both a verification step S2 as in the first embodiment, and also a verification step S2 as in the second embodiment. In this case, the verification step provides a processing step S2.33 in which the time instant H is read and the effective heating rate V 1 in correspondence with this time instant H is calculated.

The verification step S2 also provides a comparison sub-step S2.43 in which the control unit 23 compares the time instant H in which the effective heating rate VI has been calculated, and which corresponds to the effective heating time Hl to reach a given temperature, with the maximum heating time H2, and in which the control unit 23 compares the effective heating rate V 1 with the minimum heating rate V2.

In this case, the verification step S2 gives a positive outcome if the effective heating rate VI is greater than the minimum heating rate V2 and the time instant H in which the effective heating rate V 1 was calculated is less than the maximum heating time H2.

If the verification step S2 gives a positive outcome, the method also provides a deactivation step S3 in which the control unit 23 deactivates the signaling means 26.

On the other hand, if the verification step S2 gives a negative outcome, the method provides to return to the signaling step S 1 and iterate the verification step S2 until the comparison step S2.44 gives a positive outcome.

It is clear that modifications and/or additions of parts may be made to the control method for a boiler and to the boiler 10 as described heretofore, without departing from the field and scope of the present invention, as defined by the claims.

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 will be able to achieve other equivalent forms of control method for a boiler and boiler 10, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby. In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

1. Control method for a boiler (10) which comprises a water container (11) with which heating means (21) and signaling means (26) are associated which, in a signaling step (SI), are activated to signal to a user the need to clean said container (11), characterized in that it also comprises a verification step (S2) which provides to detect at least one first parameter (Pl) correlated to the heating efficiency of said container (11) and to compare said at least one first parameter (Pl) with at least one second parameter (P2) in order to verify whether said container (11) has been cleaned and consequently allow to deactivate said signaling means (26).

2. Method as in claim 1 , characterized in that it provides to allow the deactivation of said signaling means (26) only when said verification step gives a positive outcome.

3. Method as in claim 1 or 2, characterized in that it provides to prevent the deactivation of said signaling means (26) when said verification step gives a negative outcome.

4. Method as in one or the other of claims from 1 to 3, characterized in that said at least one first parameter (Pl) comprises an effective heating rate (VI) of said container (11) and said at least one second parameter (P2) comprises a minimum heating rate (V2) of said container (11).

5. Method as in claim 4, characterized in that said verification step (S2) provides to:

- activate said heating means (21) to heat said container (11);

- detect the temperature (T) of said container (11) in at least two time instants (H) between which a control time (C) elapses;

- determine said effective heating rate (VI) of said container (11), calculated as the ratio between the difference between said temperatures (T) in said two instants (H) and said control time (C); and

- compare said effective heating rate (VI) with said minimum heating rate (V2).

6. Control method as in claim 5, characterized in that said minimum heating rate

(V2) is comprised between 0.5 and 8 °C/s, preferably between 1 and 2.5 °C/s.

7. Control method as in any claim from 4 to 6, characterized in that if said effective heating rate (VI) is greater than or equal to said minimum heating rate (V2), the method provides to allow to deactivate said signaling means (26).

8. Control method as in any claim hereinbefore, characterized in that said at least one first parameter (Pl) comprises an effective heating time (Hl) of said container (11) and said at least one second parameter (P2) comprises a maximum heating time (H2) of said container (11).

9. Method as in claim 8, characterized in that said verification step (S2) provides to:

- detect the temperature of said container (11) until it reaches a predetermined comparison temperature (E); - determine said effective heating time (H 1 ) as the time elapsed from the activation of said heating means (21) to said comparison temperature (E) being reached;

- compare said effective heating time (Hl) with said maximum heating time (H2).

10. Method as in claim 9, characterized in that said comparison temperature (E) is comprised between 25 and 150 °C, preferably between 40-60 °C, and said maximum heating time (H2) is comprised between 5 and 120 seconds, preferably between 30-50 seconds.

11. Control method as in any claim from 6 to 8, characterized in that if said effective heating time (Hl) is less than or equal to said maximum heating time (H2), it provides to allow to deactivate said signaling means (26).

12. Control method as in any claim from 8 to 10 when they depend on any claim from 2 to 4, characterized in that if a time instant (H) in which the effective heating rate (VI) is calculated is less than or equal to said maximum heating time (H2), and if said effective heating rate (VI) is greater than or equal to said minimum heating rate (V2), it provides to allow to deactivate said signaling means (26).

13. Control method as in any claim hereinbefore, characterized in that it provides to activate said signaling means (26) after a certain time of use of the boiler (10), after the passage of a certain amount of water and/or or when operating inefficiencies or anomalies of said boiler (10) are identified.

14. Control method as in any claim hereinbefore, characterized in that upstream of said signaling step it provides to carry out a monitoring process of the operation of said boiler (10) in order to identify any operating inefficiencies or anomalies of said boiler (10), and to activate said signaling means (26) when an inefficiency or anomaly is identified.

15. Boiler (10) comprising a container (11) for containing water, heating means (21) associated with said container (11) and signaling means (26) configured to signal to a user the need to clean said container (11), characterized in that it comprises at least one temperature sensor (25) associated with said container (11) and a control unit (23) connected to said temperature sensor (25), to said signaling means (26) and to said heating means (21) and configured to carry out a method as in any claim hereinbefore.