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Title:
METHOD TO CONTROL AND CLEAN A BOILER
Document Type and Number:
WIPO Patent Application WO/2020/003333
Kind Code:
A1
Abstract:
Method to control and clean a boiler provided at least with a watertight container (11) and a discharge aperture (23).

Inventors:
LORENZON ANTONIO (IT)
GIROTTO RICCARDO (IT)
Application Number:
IT2019/050152
Publication Date:
January 02, 2020
Filing Date:
June 25, 2019
Export Citation:
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Assignee:
DE LONGHI APPLIANCES SRL (IT)
International Classes:
F24H1/00; F22B37/48; F24H9/00; F24H9/20
Domestic Patent References:
WO2017182664A12017-10-26
Foreign References:
US6236321B12001-05-22
DE102006042902A12008-03-27
DE19912444A12000-09-28
DE102015016247B32017-04-13
Attorney, Agent or Firm:
PETRAZ, Davide Luigi et al. (IT)
Download PDF:
Claims:
CLAIMS

1. Method to control and clean a boiler provided at least with a watertight container (11) and a discharge aperture (23), said method being characterized in that it comprises:

- setting a programmed frequency of cleaning cycles for a first predefined quantity (L) of liters of water;

- starting from said predefined quantity (L), the detection, by a control and command unit (25), of a heating time (T) to take the water contained in the watertight container (11) from ambient temperature to the desired temperature, and the comparison of said heating time (T) with a preset reference heating time (TR);

- if said heating time (T) corresponds to the reference heating time (TR) plus or minus a desired tolerance threshold (K), the frequency of the cleaning cycles is not modified with respect to the frequency corresponding to the first predefined quantity (L) of liters of water;

- if said heating time (T) exceeds the desired tolerance threshold (K) with respect to reference heating time (TR), the frequency of the cleaning cycles is increased with respect to the frequency corresponding to the first predefined quantity (L) of liters of water.

2. Control and cleaning method as in claim 1, characterized in that the desired tolerance threshold (K) is a percentage value comprised between 30% and 40%.

3. Control and cleaning method as in any claim hereinbefore, characterized in that the predefined quantity (L) of liters of water used by the boiler (10) is set to 100 liters.

4. Control and cleaning method as in any claim hereinbefore, characterized in that the programmed frequency of the cleaning cycles, for the first predefined quantity (L) of liters of water, is such that a cleaning cycle begins, in a periodic manner, after each quantity of water, used by the boiler (10), comprised between 10 liters and 25 liters.

5. Control and cleaning method as in any claim hereinbefore, characterized in that if the heating time (T) exceeds the desired tolerance threshold (K) with respect to reference heating time (TR), the frequency of the cleaning cycles is increased by 30% - 50% compared to the frequency corresponding to the first predefined quantity (L) of liters of water.

6. Control and cleaning method as in claim 5, characterized in that if the difference between the heating time (T) and the reference heating time (TR) is over 70%, the frequency of the cleaning cycles is increased in proportion to the value of the difference between the heating time (T) and the reference heating time (TR).

7. Control and cleaning method as in any claim hereinbefore, characterized in that it first comprises a control and correction step which provides that, when the boiler (10) is first switched on, the control and command unit (25) detects a first value of heating time (Tt) and then compares the preset reference heating time (TR) with the first value of heating time (T in order to establish whether the reference heating time (TR) preset by the manufacturer is actually a correct time in the real functioning conditions of the boiler (10).

8. Control and cleaning method as in claim 7, characterized in that the comparison of the first value of heating time (Tt) with the preset reference heating time (TR) comprises the following steps:

- if the difference between the first value of heating time (TO and the reference heating time (TR) is less than 20% in absolute value, the control and command unit (25) maintains, as a reference, the preset reference heating time (TR);

- if the difference between the first value of heating time (T[) and the reference heating time (TR) is between 20% and 50% in absolute value, the control and command unit (25) takes, as a reference, the mean value of heating time detected;

- if the difference between the first value of heating time (TO and the reference heating time (TR) does not figure among the previous cases, the control and command unit (25) indicates a malfunctioning state of the boiler (10).

9. Control and cleaning method as in any claim hereinbefore, characterized in that it comprises informing the user, by means of luminous and/or acoustic signals, of the state of progress of the cleaning cycles by a user interface (29).

Description:
“METHOD TO CONTROL AND CLEAN A BOILER”

* * * * *

FIELD OF THE INVENTION

The present invention concerns a method to control and clean a boiler. By boiler, here and in the following description and claims, we mean any device suitable to generate steam and/or heat water, which can be used in household appliances or professional machines, such as, for example, apparatuses for ironing, cleaning, coffee machines, steamers to cook food, steam ovens, or suchlike.

BACKGROUND OF THE INVENTION

Boilers used to selectively generate steam and/or to heat water in household appliances and professional machines normally comprise a hermetically sealed metal container, provided with at least an aperture to feed water inside it, an outlet to deliver steam and possibly a discharge aperture which can be selectively opened/closed to discharge the water from the container.

A heating element is normally associated with the metal container, generally a resistance or an electric plate, which acts as a source of heat, which can be selectively activated to generate the desired quantity and/or quality of steam and/or heat the water to the desired temperature.

It is known that, while the boiler is in use, limescale formations are generated inside the watertight container, facilitated by the heating of the water. The limescale formations mainly consist of calcium carbonate and/or other minerals such as magnesium, potassium, silicon, etc., which are normally dissolved in water.

The limescale formations can remain suspended or can deposit and attach to the internal surfaces of the watertight container to form incrustations of increasing thickness. In particular, the incrustations are more prone to form in correspondence with the hotter portions of the container, for example in proximity to or in correspondence with the heating element.

The formation of limescale layers in correspondence with the portion of wall in which the heating element is associated with the watertight container reduces the efficiency of the water heating, thus slowing down the transmission of heat, with a consequent need for a longer time to reach the desired temperatures and a consequent waste of energy.

To remove the limescale, known solutions propose the use of an elongated extractable collector element, also gutter shaped, configured to be inserted inside the watertight container in order to collect the limescale and remove it from the inside of the container.

However, this solution is not optimal for the removal of limescale, nor does it appear to be, at least in part, automatic or automatable. In fact, it entails a high involvement of the user who must first unscrew at least a closing cap of the exit aperture (an operation that can be particularly tiring and risky), move the entire boiler to a sink, possibly shake the boiler to effectively perform a rinsing and, finally, firmly close the closing cap.

These operations, which make the cleaning of the boiler complicated, discourage the user who often does not perform this cleaning with the required frequency, reducing the effectiveness of limescale removal and, therefore, the very duration of the boiler.

Furthermore, during the cleaning of the boiler there is the risk that the user suffers electric shocks as the boiler has not been disconnected from the power supply. Furthermore, possible splashes of still hot water can reach the user, which can cause bums.

There is therefore the need to identify a control and cleaning method that facilitates the user in the cyclical discharge and cleaning operations of a boiler to generate steam.

One purpose of the present invention is to define a method to control and clean a boiler that guarantees an effective, quick and easy cleaning of the boiler, guaranteeing safety conditions for a user.

A further purpose of the present invention is to define a method to control and clean a boiler which allows an easy removal of the limescale from inside the boiler without requiring particular skills, efforts or risks for the user.

A further purpose of the present invention is to define a method to control and clean a boiler which is at least partly automatic or automatable, which allows to monitor the efficiency of the boiler and which warns the user of a possible malfunction and/or the need for a cleaning intervention.

Another purpose of the present invention is to define a method to control and clean a boiler that makes the latter economical, reliable and durable.

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 claim, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, the present invention concerns a method to control and clean a boiler which allows to program suitable cleaning cycles, which are substantially or partly automated, in order to guarantee a correct and continuous efficiency of the boiler itself.

The cleaning cycles facilitate the detachment of the limescale deposits which can form in correspondence with the lateral walls and the bottom and/or the lid of the boiler.

The method according to the invention is applied to a boiler which normally comprises a watertight metal container provided with at least one feed aperture to feed water inside it, at least one heating element associated with the container, a discharge aperture and an aperture to deliver steam.

The method to control and clean a boiler comprises:

- setting a programmed frequency of cleaning cycles for a first predefined quantity of liters of water;

- starting from said predefined quantity, the detection, by a control and command unit, of a heating time to take the water contained in the container from ambient temperature to the desired temperature, and the comparison of the heating time with a preset reference heating time;

- if said detected heating time corresponds to the reference heating time plus or minus a desired tolerance threshold, the frequency of the cleaning cycles is not modified with respect to the frequency corresponding to the first predefined quantity of liters of water;

- if said heating time exceeds the desired tolerance threshold with respect to the reference heating time, the frequency of the cleaning cycles is increased with respect to the frequency corresponding to the first predefined quantity of liters of water.

The control and cleaning method can be applied to any type of steam generating boiler, such as for example the boiler of an iron.

According to one embodiment, the choice of the particular type of cleaning cycle and/or the frequency of cleaning cycles can be set by the user by means of knobs or buttons, or by means of suitable interactive communication interfaces, for example a touch screen or suchlike.

Alternatively, the choice of the cleaning cycle and the frequency of cleaning cycles can be selected automatically by the control and command unit following determinate changes detected, through suitable sensors, in the performances of the boiler.

In this way, the entire discharge and cleaning cycle of the boiler is automated, minimizing the activities required by the user.

Furthermore, the frequency of the cleaning cycles can be determined taking into account the functioning time and/or physical quantities, such as the temperature and/or pressure, which are measured on the boiler.

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 representation of a boiler in which a control and cleaning method according to the present invention can be used;

- Fig. 2 is a block diagram of the control and cleaning method according to the present invention.

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.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

We will now refer in detail to the various embodiments of the present invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

With reference to fig. 1, a boiler 10 comprises a metal watertight container 11 suitable to contain water and possibly also to transform it into steam.

The watertight container 11 has a bottom wall 12, an upper wall 13 opposite the bottom wall 12, and at least one lateral wall 14 connected to the bottom wall 12 and to the upper wall 13.

The watertight container 11 is provided with at least one feed aperture 15 to feed water inside the watertight container 11.

The boiler 10 also comprises an automatic feed device 16 hydraulically connected to the feed aperture 15 and configured to introduce the water into the watertight container 1 1.

According to possible solutions, the feed device 16 can comprise a tank 17 to contain the water and a feed pump 18 provided to remove the water from the containment tank 17 and transfer it to the watertight container 11.

The watertight container 11 can also be provided with an aperture 19 to deliver the steam generated inside the watertight container 11.

The steam delivery aperture 19 can be connected to devices for using, and possibly adjusting, the steam, for example an electromechanical valve 20, or suchlike.

The boiler 10 comprises at least a heating element 21 associated with the watertight container 1 1 and configured to heat the water inside it to the desired temperature.

According to a preferred solution, the heating element 21 can be positioned externally to the watertight container 11. In this way, the formation of limescale does not affect the heating element 21.

The watertight container 1 1 can be provided with a detector 22 to detect physical quantities. The physical quantities detector can be suitable to measure the temperature and pressure inside the watertight container 11 of the boiler 10.

Furthermore, the physical quantities detector 22 can be correlated to a timer or chronometer to measure the time taken by the heating element 21 to heat the water in the watertight container 11 from the ambient temperature to the desired temperature.

Alternatively, the timer or chronometer can be present but not associated with any detector of physical quantities.

The watertight container 11 is provided with a discharge aperture 23 to discharge water and possible particles, for example the limescale formed in the watertight container 11.

The discharge aperture 23 can be made on the lateral wall 14 of the watertight container 11 although a different positioning is not excluded, for example in correspondence with the bottom wall 12 of the watertight container 11.

According to a preferred solution, the discharge aperture 23 can be disposed on a lower portion of the lateral wall 14 in proximity to the bottom wall 12 of the watertight container 11.

In this way, advantageously, it is possible to use the force of gravity to facilitate the discharge of water and possible solid and/or aggregate particles from the watertight container 11 and, furthermore, to guarantee a substantially complete emptying of the watertight container 11 , as the discharge aperture 23 is disposed below the mean water level. Furthermore, the user does not need to intervene to shake and/or incline the boiler 10 in order to facilitate the emptying of the watertight container 11.

The boiler 10 comprises a valve device 24 associated with the discharge aperture 23 and configured to selectively open/close the discharge aperture 23 and selectively put it in communication with the outside environment.

In this way, advantageously, the water and possible solid and/or aggregate particles contained inside the watertight container 11 can be discharged, when the need arises to perform this operation, thanks to the controlled drive of said valve device 24.

The valve device 24 thus configured ensures a greater seal of the watertight container 1 1 , avoiding accidental leakages of water from the discharge aperture 23.

The presence of the valve device 24, which can be selectively driven, replacing a conventional cap, allows to reduce the risk of a user coming into direct contact with the water and with the possible particles exiting the container, thus avoiding the risk of scalding due to the high temperatures.

The valve device 24 thus made is less subject to wear, considerably reducing maintenance interventions. This also reduces the management and maintenance costs of the boiler and increases the life-span of the boiler itself.

According to one embodiment, the part of the valve device 24 in contact with the water can be made of metal or heat-resistant material, or of any metal resistant to high temperatures and pressures.

According to a further embodiment, the boiler 10 can comprise a container 26 to collect the water and possible particles or residues exiting the watertight container 11 through the discharge aperture 23.

In one embodiment, the collection container 26 can be connected watertight to the discharge aperture 23.

In this way, advantageously, the operation of discharging the water and possible limescale particles can occur safely for the user without the risk of accidental splashes with consequent electric shocks, or bums.

According to one embodiment, the collection container 26 can comprise a sensor or detector 28, for example a capacitive sensor, configured to detect the level of water and possible particles inside the collection container 26.

According to one embodiment of the present invention, the detector 28 can be an optical sensor to detect the water level and the corresponding impurities thereof inside the collector container 26.

According to a variant embodiment, the collection container 26 can be transparent so as to make its contents visible to a user. In this way, it is possible to visually see the water level inside the collection container 26 and, therefore, the detector 28 can possibly not be installed.

According to a further variant embodiment, the collection container 26 can be removed by the user at the end of the cleaning cycle in order to be emptied and/or cleaned.

According to one embodiment, the collection container 26 can comprise, in addition to the detector 28, a detector 27 configured to detect the temperature of the water inside the collection container 26.

According to a further embodiment, the collection container 26 can be equipped with a safety device (not shown) which does not allow the extraction of the collection container 26 until the temperature of the discharge liquid, measured by the detector 27, has fallen to a safe level for the user.

The valve device 24 can be driven by an actuator device (not shown), for example an electric gearmotor.

The actuator device can be activated manually by a user by means of a switch or a lever, or it can be conditioned by an automatic device, or control and command unit 25 which drives the actuator device after a determinate time interval has elapsed, or on the basis of the volume of water entering the watertight container 11. In this way, driving the valve device 24 is easy and safe for a user.

In other embodiments, the valve device 24 has release means which can be activated selectively, which allow its subsequent manual drive only when safety conditions for the user have been met.

According to some embodiments, the control and command unit 25 can be equipped with a user interface 29, which by means of luminous and/or acoustic signals, indicates to the user when the cleaning of the boiler 10 is required and/or the state of progress of the cleaning cycle.

If the valve device 24 is driven automatically by an electric gearmotor, the user interface 29 can indicate the status of the cleaning operations, informing the user if the container 26 collecting the discharged liquid needs to be emptied.

According to embodiments of the present invention, the valve device 24, the possible user interface 29, the heating element 21, the feed pump 18, the electromechanical valve 20, the detectors 22, 27 and 28 are connected to, and commanded by, the control and command unit 25.

In particular, the control and command unit 25 defines whether or not it is possible to drive the valve device 24 in order to open the discharge aperture 23 according to the water level measured by the detector 28, so as to avoid leakages of liquid from the collection container 26.

Furthermore, the temperature detector 27 can signal to the control and command unit 25 when it is possible to unload the collection container 26, that is, when the water is no longer hot.

The control and command unit 25 guarantees a continuous and constant control of the boiler 10 regardless of the external intervention of the user and almost automatically manages the cleaning cycles according to the parameters detected by the detectors 22, 27, 28.

According to some embodiments, the control and command unit 25 can automatically start the cleaning cycles.

According to possible variants, it can provide that the control and command unit 25 signals to a user, for example by means of the user interface 29, when and whether to start a cleaning cycle. In this case, the cleaning cycles can be activated and terminated manually by the user.

A cleaning cycle can consist of discharging the water, with the solid particles in suspension, by driving the discharge aperture 23 of the watertight container 11 of the boiler 10. The discharge aperture 23 is selectively opened by driving the valve device 24.

The cleaning cycle can provide that said drive of the valve device 24 occurs simultaneously or alternatively to at least one of the following steps:

- driving the feed pump 18 to alternate emptying steps and filling steps in order to generate one or more rinses.

- selectively driving, within predetermined temperature values, the heating element 21, in order to increase the effectiveness of its cleaning, by means of thermal shocks.

According to the present invention, the control and cleaning method with which the activation of programmed and automated or automatable cleaning cycles is managed, provides a sequence of steps based on suitable detections of functioning parameters of the boiler.

In the preferred embodiment, the control and cleaning method substantially provides two different procedures between a first predefined quantity L of liters used by the boiler starting from the first functioning of the boiler itself, and the subsequent steady-state functioning.

In particular, the control and cleaning method comprises:

- setting a programmed frequency of cleaning cycles for said predefined quantity L of liters of water;

- starting from said predefined quantity L, the detection, by a control and command unit 25, of a heating time T to take the water contained in the watertight container 11 from the ambient temperature to the desired temperature, and the comparison of the heating time T measured with a preset reference heating time T R ;

- if the heating time T corresponds to the reference heating time T R plus or minus a desired tolerance threshold K, the frequency of the cleaning cycles is not modified with respect to the frequency corresponding to the first predefined quantity L of liters of water;

- if said heating time T exceeds the desired tolerance threshold K with respect to the reference heating time T R , the frequency of the cleaning cycles is increased with respect to the frequency corresponding to the first predefined quantity L of liters of water.

According to one embodiment of the present invention, L is advantageously set to 100 liters. In fact, for the first 100 liters used by the boiler 10, we believe that the limescale formations do not determine an increase in the heating time T which is significant and/or can be correctly detected by the control and command unit 25; however, as inside the boiler 10, even before its first use, mineral deposits or first limescale formations could be present, cleaning cycles can be provided with a fixed preset frequency, generally low.

According to one embodiment of the present invention, the programmed frequency of cleaning cycles for the first predefined quantity L of liters of water is such that a cleaning cycle starts, periodically, after each quantity of water used by the boiler 10 comprised between 10 liters and 25 liters.

According to a further embodiment, the desired tolerance threshold K between the heating time T detected and the reference heating time T R is a percentage value comprised between 20% and 50%, preferably between 30% and 40%.

The reference heating time T R and the predefined quantity L can be preset by the manufacturer in the control and command unit 25. In a possible solution, one or more of these values can be modified by the user.

Advantageously, the control and command unit 25 detects, by means of the timer associated with the temperature detector 22, the heating time T after each switching on following a cleaning cycle. In fact, only after one cleaning cycle is the quantity of water actually present in the boiler known and, therefore, the measured value of heating time T can be compared with that of the reference heating time T R in the same operating conditions. Furthermore, the control and cleaning method can comprise informing the user, by means of light and/or acoustic signals, of the state of progress of the cleaning cycles by the user interface 29.

According to one embodiment, first of all, a step of controlling and correcting the preset value of the reference heating time T R can be provided.

The control and correction step can provide that, when the boiler 10 is first switched on, the control and command unit 25 detects, by means of the timer associated with the detector 22, a first value of heating time T [ and then compares the preset reference heating time T R with the first value of heating time Ti in order to establish whether the reference heating time T R preset by the manufacturer is actually a correct time in the real functioning conditions of the boiler 10.

For example, if the difference between the first value of heating time T t and the reference heating time T R is less than 20% in absolute value, the control and command unit 25 maintains the preset reference heating time T R as a reference. If said difference is comprised between 20% and 50% in absolute value, the control and command unit 25 takes, as a reference, the mean value of heating time detected. If the difference between the first value of heating time Ti and the reference heating time T R does not figure among the previous cases, the control and command unit 25 indicates a malfunctioning state of the boiler 10.

With reference to fig. 2, which shows by way of example the control and cleaning method 100, the initial step 101 provides to switch on the boiler, after it has been suitably connected to a power socket or to another power source.

The procedure identified by step 102 is performed for a predefined quantity L of liters, while starting from the predefined quantity L of liters the procedure identified by step 103 is performed.

The procedure identified by step 102 provides to set cleaning cycles with a determinate preset frequency, that is, a cleaning cycle for each determinate quantity of liters of water used by the boiler 10. In particular, the control and command unit 25 programs the start of a cleaning cycle in a periodic manner defined by said preset frequency.

In a variant, the control and cleaning method according to the invention can also comprise the setting, or the detection by the control and command unit 25, of a level of the water hardness D, correlated to the quantity of limescale contained in the water, and the programming of a determinate frequency of cleaning cycles that varies according to the level of the water hardness D.

According to one embodiment, the level of the water hardness D can be set externally by the user by means of suitable commands present on the interface 29.

According to a further embodiment, the level of the water hardness D can be detected by the command and control unit 25, automatically, by means of a sensor suitable to detect the level of the water hardness D.

There can be at least two levels of the water hardness D, for example low and high.

For example, if the level of the water hardness D is low the cleaning cycle can be set with a frequency equal to one activation every 20 liters, while for a high level D the frequency can be equal to one activation every 10 liters.

In step 103, starting from the predefined quantity L, the control and command unit 25 measures the actual heating time T taken by the heating element 21 to heat the water of the boiler 10 from the ambient temperature to the desired temperature.

The heating time T is compared with the reference heating time T R set in the control and command unit 25.

If the heating time T measured is substantially equal, within a desired tolerance threshold K, to the set reference heating time T R , as expressed in step 104, the cleaning cycle is performed according to the frequency programmed in step 102, that is, up to the predefined quantity L of liters.

If the hardness level D is also present in the initial settings, in step 104 a corresponding, and different, frequency of cleaning cycles will correspond to each level of hardness D as in step 102.

If the heating time T measured exceeds the reference heating time T R beyond the tolerance threshold K, as expressed in step 105, the frequency of the cleaning cycles is increased (step 106) compared to the frequency of the step 102.

In particular, the increase in the frequency of the cleaning cycles of the boiler 10, set by the control and command unit 25, can even be by 30% - 50% compared to the preset frequency, and, therefore, the cleaning cycles can be more frequent until a cleaning cycle for each quantity of water comprised between 5 liters and 18 liters is reached.

For example, if in step 102 (first 100 liters) a cleaning cycle is set every 15 liters, in step 106 a cleaning cycle can occur every quantity of water comprised between 8 liters and 12 liters, preferably about 10 liters.

If the hardness level D is also present in the initial settings, in step 106 the frequencies of the cleaning cycles relating to each level D will also increase proportionally, that is, the quantity of water between one cleaning cycle and the next is reduced for each hardness level D.

For example, if in step 102 a cleaning cycle every 20 liters corresponded to a low hardness level D, in step 106 this quantity of water is reduced, for example, to 15 liters.

According to some embodiments of the present invention, there can be further settings of threshold values of the heating time T for step 105.

The threshold values are greater than the desired tolerance threshold K and are indicators of high difference between the heating time T and the reference heating time T R . If the difference between the heating time T and the reference heating time T R is high, the cleaning cycles are performed more and more closely, increasing their frequency.

If the difference between the heating time T and the reference heating time T R greatly exceeds the desired tolerance threshold, for example by over 70%, the frequency of the cleaning cycles is increased in proportion to the value of the difference between the heating time T and the reference heating time T R .

For example, if the heating time T is greater, in percentage terms, than the reference heating time T R by between 70% and 100%, then the frequency of the cleaning cycles increases, going for example from a cleaning cycle every 10 liters to one every 5 liters.

Furthermore, if the heating time T is greater than the reference heating time T R by over 100%, then the frequency of cleaning cycles can increase further.

It is clear that modifications and/or additions of parts and/or steps may be made to the control and cleaning method as described heretofore, without departing from the field and scope of the present invention.

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 control and cleaning method, 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 reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.