ES2343011T3 - CLOTHING CLOTHES AND METHOD DRYER TO CONTROL IT. - Google Patents

Abstract

A condenser-type clothes tumble dryer comprising temperature sensor means (5, 6) to detect a temperature difference value between the drying air entering the condenser (4) and the drying air exiting the condenser (4), humidity sensor means (5) to detect a humidity value of the drying air entering the condenser, control means coupled to said humidity sensor means (5), memory means for storing a threshold temperature-difference value (”T TH ) and a threshold relative-humidity value (RH inTH ), which are representative of a pre-determined dryness degree of the load and depend on the particular drying cycle selected by the user, the control means are further adapted to compare said values for switching off said heating means (3) when at least said temperature difference value (”T) reaches up to said threshold temperature-difference value (”T TH ) or at least said relative humidity value (RH in ) reaches down to said threshold relative-humidity value (RH inTH ).

Description

Clothes dryer by flip and method for control it

The present invention relates to a dryer of clothes by flip and a method to control it.

An important feature of dryers by flipping is the possibility of stopping the drying process so soon as the moisture content of the wash load has been reduced to the desired value. In fact, if the drying process the resulting moisture content is interrupted too soon of the wash load would be too high and that would involve several Obvious disadvantages. On the other hand, interrupting a process of drying too late, in practice means a use unnecessarily high energy while the content of too low humidity resulting from the wash load causes have it undergo a growing wrinkle, have a reduced ironing capacity, and an increased probability of that the garments that form the wash load shrink or suffer other adverse effects such as charging electrostatically

Tumble dryers are known in the art of the type of capacitor comprising a closed circuit for the drying air, intended to make hot drying air circulate through a perforated rotating drum, and a condenser intended to remove moisture from hot, charged, dry air of moisture, which comes out of the drum after having flowed through the drying load in the contents, as well as moisture sensing intended to detect the moisture content of the air leaving the drum. Thus, the drying process stops when it is detected that the moisture content of the drying air leaving the drum is has reduced to a preset value. However, this method has not been able to offer really satisfactory results, since that in practice it has been found that the actual moisture content of the drying load when the drying process is interrupted, you see notably also affected by variables such as quantity of items that constitute the drying load of the drum and the type and nature of the tissues that are being manipulated

Dryers are also known in the art for flip of the type of condenser, in which there are some electrodes arranged in the drum to measure the electrical resistance of the charge, based on the fact that said electrical resistance is a parameter that is directly related to the content of moisture of the garments that form the drying load, that is, It depends on him. Other prior art solutions include the use of a drum constituted in two halves, in which, then, measure the conductivity between these halves to control the drying process. However, this method is not able to ensure a reliable measurement of the moisture content of the garments of the drying load, mainly because the conductivity values are affected by factors such as Water hardness.

US 4,640,022 describes a dryer of clothes of the dehumidifier type in which the exhaust air from a drying space that contains a load that is It is drying, it is subjected to a heat exchange with air outside to remove moisture from the exhaust and, having been reheated by a heater, the exhaust air is returned back to the drying space by a fan with the In order to dry the load with hot air. Clothes dryer includes a first thermosensitive device to measure the exhaust air temperature at an outlet in the drying space, and a second thermosensitive device to measure the temperature of the exhaust air after being subjected to the exchange of heat with outside air or outside air temperature after having been subjected to heat exchange with the air of escape. The difference between the temperatures measured by the first and second heat sensitive devices in an instant default after the start of the drying operation, it stored in a memory as reference value, A, and checked the subsequent relationship between the measured temperature difference and the  reference value A to control the termination of the operation Heat drying

EP 1 420 104 describes a process to dry washed clothes located in an enclosure or drum for laundry of a drying device such as a dryer machine, a washer dryer or drying cabinet, which comprises one or more phases of drying the laundry in an air flow heated by heating means and transported to the enclosure for casting by means of ventilation and a ventilation phase of the laundry in a flow of air at room temperature, transported to the enclosure for laundry by the aforementioned means of ventilation, whose drying process begins with the phase of ventilation, to reduce the maximum, initial, moisture content, of the laundry by means of the air flow at room temperature. A First thermal sensor is located in the air flow, water below the laundry enclosure, in order to detect the air temperature immediately after passing through the laundry A second thermal sensor is located in the section between the heating means and the enclosure for laundry, in order to detect the air temperature before Make it go through the laundry. The data related to temperature readings are transmitted to a control unit, which estimates the moisture content of the laundry based on the difference between upstream air temperature and downstream of the laundry enclosure and determines the duration of the ventilation phase based on the measured values and of the target values for the moisture content reduction of the laundry

EP 0 978 778 describes a dryer of clothing provided with a temperature controller with point double adjustment, modulated by humidity, in which the two points of Temperature settings are regulated based on the measured humidity to control the heating element in order to improve the energy efficiency of the dryer. These set points are regulate based on the RH (relative humidity) detected by a humidity sensor coupled to the temperature controller of double setpoint by means of a voltage signal that is proportional to the level of RH measured in the dryer's exhaust. TO as the RH in the dryer's exhaust decreases, the voltage signal which, in turn, reduces the set points of temperature change.

Therefore, a main object of the present invention is to provide a tumble dryer of the class previously mentioned, in which it can be achieved, automatically, a desired moisture content of the load that is dry, with a high degree of precision when the process is interrupted drying, and this in a way that is very independent of factors such as the amount of drying load, the type of tissues that are handled, of the initial moisture content of the drying load, as well as water hardness.

In accordance with the present invention, this object it is achieved in a tumble dryer that has the characteristics cited and defined in the attached claims 1 to 14

In accordance with the present invention, the object mentioned above is also achieved in a method to control a tumble dryer as defined and exposed in the attached claims 15 to 26.

Either way, the characteristics and advantages of the present invention can be more easily understood by from the description given in the following, by way of non-limiting example, with reference to the attached drawings, in those who:

Figure 1 is a schematic view of a tumble dryer by flip according to the present invention;

Figure 2 is a process chart that describes a method to control a tumble dryer by flipping in accordance with the present invention;

Figure 3 is a diagrammatic view, in function of time, of the course followed by the relative humidity of the drying air entering the condenser during a process of drying, together with the relative humidity threshold values corresponding to a predetermined degree of drying;

Figure 4 is a diagrammatic view, in function of time, of course followed by air temperature drying that enters the condenser and the air temperature of drying out of the condenser during a drying process;

Figure 5 is a diagrammatic view, in function of time, of the temperature difference pattern between the drying air entering the condenser and the drying air leaving the condenser during a drying process, along with the threshold values of such temperature difference corresponding to a predetermined degree of drying;

Figure 6 is a diagrammatic view, in function of time, of the pattern of the dH and dT end coefficients cycle, as well as the magnitude of control D in the case of a "extra dry" drying cycle;

Figure 7 is a diagrammatic view, in function of time, of the pattern of the dH and dT end coefficients cycle, as well as the magnitude of control D in the case of a drying cycle for "drying cotton";

Figure 8 is a diagrammatic view, in function of time, of the pattern of the dH and dT end coefficients cycle, as well as the magnitude of control D in the case of a "slightly wet" drying cycle;

Figure 9 is a diagrammatic view, in function of time, of the pattern of the dH and dT end coefficients cycle, as well as the magnitude of control D in the case of a "dry ironing" drying cycle;

Figure 10 is a diagrammatic view, in function of time, of the pattern of the dH and dT end coefficients cycle, as well as the magnitude of control D in the case of a "dry drained" drying cycle.

The tumble dryer by turning according to the present invention - as generally indicated by the number of reference 1 in the figures - comprises a closed air circuit drying intended to make the hot drying air circulated through a perforated rotating drum 2 that contains the laundry to be dried, heating means 3 intended for heating said drying air, an air cooled condenser 4, intended to remove moisture from hot, charged, dry air of moisture, which leaves the drum after having circulated through from the laundry to dry, an open cooling air circuit, intended to make a stream of cooling air, taken from the outside, circulate through capacitor 4 and over it, to cool it and eventually be evacuated back to the outside atmosphere

The tumble dryer mentioned above it also requires temperature sensing means 5, 6, which must provided in correspondence with an input 7 of the capacitor of drying air, as well as in correspondence with an outlet 8 of the drying air condenser, in order to detect a value ΔT of temperature difference between the drying air that enters the condenser 4 and the drying air leaving it capacitor 4; In addition, it needs 5 moisture sensing means that must be provided in correspondence with input 7 of the capacitor of drying air, in order to detect an RH_ {input} value of relative humidity of the drying air entering the condenser.

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In addition, the tumble dryer The aforementioned comprises control means coupled to the  5 moisture sensing means in order to receive the RH_ {humidity} input and media 5, 6 perceivers of temperature to also receive the ΔT values of temperature difference during dryer operation by flipping.

The tumble dryer is also provided with memory means for storing a threshold value ΔT_ {TH}  of temperature difference between the drying air entering the condenser 4 and the drying air leaving the same condenser 4, and a humidity threshold value RH_ {inputTH} for the air of drying entering the condenser, which are indicative of a level of preset dryness, that is, a degree of drying of the items loaded in the drum according to the drying cycle particular selected by the user, in which said value of temperature difference threshold ΔT_ {TH} and said value of humidity threshold RH_ {inputTH} are initialized in response to said tumble dryer being set up to operate according to the particular drying cycle selected by the user

The control means are intended for compare the actual humidity value RH_ {input} with the value of humidity threshold RH_ {inputTH} and, also, are intended for compare the value ΔT of temperature difference with the threshold value ΔT TH of temperature difference for automatically disconnecting said heating means 3 when at least the value ΔT of temperature difference reaches the threshold value \ DeltaT_ {TH} of temperature difference or what exceed or at least the humidity value RH_ {input} drops up to the threshold value RH_ {inputTH} of humidity or below of the.

Through the closed air circuit of drying, hot and moisture-laden air drying is done exit the perforated rotating drum 2 and is transported to the air-cooled condenser 4; then the drying air dehydrated leaving condenser 4 is sent back to drum 3, after being properly heated again, with the in order to remove additional moisture from the garments that are being turned on the drum 2.

The tumble dryer comprises first means blowers 11 intended to cause the drying air to circulate to the inside and through the closed drying air circuit. A first manifold arrangement 12 is intended to transport the drying air leaving the drum 2 to the air inlet 7 of drying of the condenser, and a second manifold arrangement 13 It is intended to transport the drying air that comes out of the Condenser drying air outlet 8, back to the drum 2.

There are planned 3 water heating means down the outlet 8 of condenser drying air for heating the dehydrated drying air to be sent from new to the drum 2.

The capacitor 4 comprises a plurality of fluid passages, along which air can flow from dried so that moisture condenses and is removed from it, and these fluid passages can be reversed, that is, be exposed to the flow of cooling air flowing through the open circuit cooling air. In particular, the capacitor 4 comprises a first grouping of steps 14 to fluid, separated, for drying air, which are connected in fluid circulation ratio with the first arrangement 12 of collector at the inlet 7 of condenser drying air, as well as connected in relation to fluid circulation with the second manifold arrangement 13 at the outlet 8 of drying air of the condenser.

The capacitor 4 further comprises a second grouping of separate fluid passages 15 for the air of cooling, which are arranged in alternating relationship with said first grouping of fluid passages 14, so that between two of such adjacent fluid passages 14 for the drying air, be provided a fluid passage 15 for the cooling air.

The cooling air that circulates along of the second grouping of fluid passages 15 is intended to sweeping, that is, moving in contact with the fluid passages 14 of the drying air, thus cooling them by convection, in order of making the steam of the hot-drying air loaded of humidity, precipitate by condensation.

The open air cooling circuit comprises second blower means 16 intended to make circulate the cooling air, an intake opening 17 of air and an air exhaust opening 18, connected in relation to fluid circulation with the second grouping of steps 15 of fluid, through which the cooling air is taken from the outside environment, transported to and through the capacitor, to be sent, eventually, back again to the outdoor environment

Inlet 7 condenser drying air substantially represents the area of the condenser in which the drying air that has to be dehydrated, and that circulates from the first collector arrangement, enters the first grouping of fluid passages 14 while the drying air outlet 8 of the condenser represents the area of the condenser in which the air from dehydrated drying leaves the first grouping of steps 14 of fluid to circulate to the second manifold arrangement 13.

In the most obvious way, these areas are not connected in relation to fluid circulation with the steps of cooling air, since both the inlet and outlet of said second grouping of fluid passages 15, are suitably separated from the inlet 7 of condenser drying air and the Condenser drying air outlet 8, respectively.

In fact, in the particular embodiment, the inlet and outlet of the second grouping of fluid passages 15 are provided in a perpendicular arrangement in relation to the condenser drying air inlet 7 and air outlet 8 drying of the condenser, respectively, so that the flows Air drying and cooling air flows They practically cross.

The means 5, 6 temperature sensing and humidity comprise a relative humidity sensor that, also, It is capable of delivering associated temperature measurement values, and which is arranged in the vicinity of the air inlet 7 of drying of the condenser, and a temperature sensor, such as by example a thermocouple, which is located in the vicinity of the outlet 8 condenser drying air. Both perceivers are connected to the control means, which are intended to receive - during dryer operation - the signals that are issued by the recipients in order to monitor the pattern of the temperature T_ {inlet} of the drying air entering the condenser, as well as the temperature pattern T_ {output} of the drying air leaving the same condenser, along with the humidity relative RH_ {inlet} of the drying air entering the condenser.

This process of data acquisition by said control means can occur continuously or at intervals discrete, establishing, in this case, a time interval appropriate to separate successive data acquisition events during which said control means are able to acquire the temperature values T_ {input}, T_ {output}, and values RH_ {relative} humidity input that are detected and emitted by the perceivers.

Extensive experimental trials have put manifest the fact that both the RH_ {input} values of the relative humidity such as T_ {input}, T_ {output} values of drying air temperature detected when garments of clothes are subjected to a gradual drying in the machine, they keep a complete correlation, that is, they can be put in relation mutual with different degrees of final drying of the garments of clothes.

In this way, it has been possible to work with appropriate temperature and relative humidity threshold values of the drying air, corresponding to various degrees of drying end that, usually, are required for the garments treated in said tumble dryers, in such a way as to ensure that the reaching any of these threshold values makes it deactivate the means of heating the air and possibly  the control means stop the operation of the own dryer.

In detail, with a view to judging the degree final drying of the garments, reference has been made - agree with existing standards - to MR residual moisture (gain repeated humidity), calculated in terms of weight difference between a load of clothes subjected to a drying cycle and the same load of clothes in standard conditions, that is, left for 24 hours in a controlled atmosphere at a temperature of 20 ° C and a relative humidity of 60%.

Some of the cycles of most commonly used drying, commonly available in dryers by I turn, namely:

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one

For example, in the case of the extra dry cycle, the drying load - when removed from the drum at the end of the cycle, It has a weight between approximately 6% less than standard load weight specified above to almost the same Weight than standard load. On the contrary, in the case of the cycle dry for ironing, the drying load - when removed from the drum at the end of the cycle - has a weight ranging from 8% to 16% greater than the weight of said standard load.

The tests carried out in this regard have given place to the graph that appears in figure 3, which illustrates the trend, as a function of time, of the RH_ {input} value of the relative humidity of the drying air, detected by means 5 humidity sensors at the inlet 7 of the drying air of the condenser, with heating medium 3 in operation, is say activated. As shown in the graph, the relative humidity RH_ {inlet} tends to decrease as increases the degree of drying of clothing. Also, in the Figure 3 indicates the threshold values for relative humidity RH_ {input TH} [ED, DC, SD, ID, M] of the incoming drying air in the condenser, which have been found in correspondence with the different degrees of drying of the garments in the aforementioned cycles ED, DC, SD, ID, M.

In the description given in the following, the expression "RH_ {value} relative humidity value" is will use to unequivocally refer to the value of the relative humidity of the drying air detected by the means 5 humidity sensors at the inlet 7 of the drying air of the capacitor while the expression "value RH_ {inputTH} [ED, DC, SD, ID, M] of relative humidity "is will use to unequivocally refer to the value of threshold of relative humidity of the drying air which - detected also by means 5 moisture sensing at the entrance 7 of condenser drying air - found to correspond to the different degrees of drying of garments in cycles ED, DC, SD, ID, M, as indicated above.

RH_ {o} is used to indicate the value initial relative humidity of the drying air circulating at capacitor 4, that is, entering it, detected by means 5 moisture perceivers at the start of the selected drying cycle by the user and, therefore, having been connected the means of heating.

Immediately after the activation of the heating means 3, it may be noted that the value of RH_ {o} it becomes extremely variable to eventually stabilize at a relative humidity value of approximately 96 to 97% after a first transitory phase of stabilization. It has been found that the initial value of RH_ {o} is the same for all drying cycles

During this first transitory phase, the machine control means do not acquire any of the readings  RH_ {input} of the relative humidity they receive from the media 5 moisture perceivers, since the related data are not representative of the actual initial condition of relative humidity RH_ {o}.

Thus, the control means are programmed to enter, by themselves, in a kind of observation state, in which they practically determine whether successive readings from the moisture sensing means 5 reveal a substantially constant value. In this regard, it will be readily appreciated that the control means can also be programmed to simply wait for a certain period of time corresponding to the duration of the aforementioned transitional phase, before beginning to acquire the data emitted by the perceiving means. Experimentally it has been found that said transitional phase has a duration of approximately two
minutes

As seen in the clearest way from from the graph in figure 3, the relative humidity RH_ {input} decreases as the clothes of the drum become dry until, eventually, it reaches a respective threshold value corresponding to a certain degree or state of final drying reached by the clothes themselves. For example, when the humidity value relative RH_ {input} drops to at least 68% approximately, it has been found that the degree of drying reached for the garments that are treated corresponds to a degree of drying which is typical of the "extra dry" (ED) cycle.

As a result, this relative humidity value 68% becomes the relative humidity threshold value, RH_ {inputTH} [ED] that can be associated with that cycle "extra dry" ED and - as such - is therefore stored in the Memory media as a reference. When the user selects then an "extra dry" ED cycle through the controls appropriate of the tumble dryer control panel, the control means automatically recover from the means of memory the threshold value of relative humidity, RH_ {inputTH} [ED] associated with said drying cycle and, at at the same time, allow the dryer to start working by activating the heating means 3, connecting the blowing means 11, 16 and allowing the drum 2 to be rotated.

Then, the control means is allowed - while waiting for the phase of transitory observation  initial - start up comparing the humidity value relative, RH_ {input}, with the humidity threshold value relative RH_ {inputTH} [ED] for the "extra dry" cycle [ED]. When it is found that, eventually, the value RH_ {input} of relative humidity has become equal or lower than said threshold value RH_ {inputTH} [ED], the control means will then consider that the drying cycle has concluded and, consequently, will cause the tumble dryer operation by deactivating the heating 3, disconnecting the blower means 11, 16 and stopping drum rotation 2. As at the end of the actual process of drying, it can also be contemplated that a phase of cold air circulation in order to cool clothes before removing them from drum 2, when it is found that the value of relative humidity, RH_ {inlet}, has become equal or lower than the aforementioned threshold value RH_ {inputTH} [ED], the control means, in this case, would simply deactivate the heating means 3, waiting for this phase of cold air circulation before stopping the operation of the tumble dryer.

On the contrary, it has been found that you have a degree of drying of the garments corresponding to which can be considered typical for the "dry cotton" (DC) cycle when the relative humidity value, RH_ {input} drops up to at least about 87%. This value is stored, by both, in memory media and humidity threshold value relative, RH_ {inputTH} [DC] associated with the mentioned "dry cotton" cycle [DC].

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In summary, the following table shows the relative humidity threshold values, RH_ {inputTH} [ED, DC, SD,
ID, M] for the different drying cycles:

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2

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The tests that have been carried out on this effect have also produced the graph represented in the figure 4, which illustrates the trend, as a function of time, of the temperature T_ {inlet} of the drying air detected by the 5 temperature sensing means at the air inlet 7 of drying of the condenser, as well as the trend as a function of time of the temperature T_ {outlet} of the drying air detected by the 6 temperature sensing means at the air outlet 8 of drying of the condenser, during operation of the means of heating 3.

This graph highlights the fact that the drying cycle is actually basically three Different phases A first initial transitory phase, which follows immediately upon activation of the heating means 3 and in which both temperatures rise T_ {input}, T_ {output} and, also, the evaporation rate.

The second phase is a saturation phase, in the that the temperatures T_ {input}, T_ {output} remain almost constants, since the heating thermal energy makes it evaporate the water contained in the garments that are treated, while the capacitor is able to dissipate most of the latent heat of condensation.

Then follows a third phase, final, in the temperature of the drying air at the entrance of the capacitor, T_ {input}, tends to increase, because the clothes are increasingly dry, that is, less and less wet, and the temperature of the drying air at the outlet of the capacitor, T_ {output}, on the contrary, tends to decrease, since that the evaporation rate is reduced and the condenser is capable of dissipating, also, the heat of the drying air, cooling by so much.

It is clearly evident that it is absolutely possible to correlate the temperature difference ΔT between the temperature of the drying air at the condenser inlet, T_ {inlet}, and the temperature of the drying air at the outlet of the condenser, T_ {output}, with the residual moisture content of the garments to be dried, that is, the larger the value of \ DeltaT = T_ {input} - T_ {output}, the greater the degree of drying of the garments.

Even in this case, the temperature values detected by means 5, 6 temperature sensors at continuation of the activation of the heating means 3, are extremely variable and in no way indicative of the real trend of temperatures. Therefore, the control means wait for this transitional or observation phase to end initial before beginning the acquisition of said values.

The graph in Figure 5 illustrates the trend as a function of the time of the temperature difference value
ΔT = T_ {inlet} - T_ {outlet}, as well as the threshold values of this temperature difference ΔT_ {TH} [ED, DC, SD, ID, M] of the drying air between the inlet and outlet of the condenser, which have been found as corresponding to the various degrees of drying that must be achieved by the garments in the respective drying cycle ED, DC, SD, ID, M.

For example, it has been found that when the temperature difference ΔT reaches a value of at least 15 ° C, the degree of drying achieved by the garments in the drum corresponds to the degree of drying that must be achieved in the "extra dry" cycle ED.

A value of 15ºC of the temperature difference becomes, therefore, the threshold value ΔT TH [ED] of the temperature difference associable with the "extra dry" ED cycle and, as such, is stored in memory media.

In the description given in the following, the expression "value ΔT of the temperature difference" it will be used unequivocally to refer to the value of the difference between drying air temperature detected by the means 5 temperature sensors at the air inlet 7 of Condenser drying and drying air temperature detected by the means 6 temperature sensors at the outlet 8 condenser drying air while the expression "threshold value ΔT_ {TH} of the difference of temperature "shall be used to refer unequivocally to the threshold value of the difference between the air temperature of drying detected by the means 5 temperature sensors in the 7 air inlet condenser drying and temperature drying air detected by the means 6 sensors of temperature at the outlet 8 of condenser drying air that is has found that it corresponds to different degrees of drying of the garments in the ED, DC, SD, ID, M cycles of the tests Experimental carried out for this purpose.

When a user selects an "extra dry" ED drying cycle by means of the appropriate control devices on the tumble dryer control panel, the machine control means are started automatically recovering the value from the memory media. of threshold ΔT_ {TH} [ED] of the temperature difference corresponding to that cycle, and start the operation of the dryer by activating the heating elements 3, connecting the blower means 11, 16 and allowing the drum 2 to be operated at rotation. Then, while allowing the initial observation time to elapse, the control means are able to compare the value of the temperature difference ΔT, detected by the means 5, 6 temperature sensors with the threshold value ΔT_ {TH} [ED] of the temperature difference of the "extra dry" ED cycle. As soon as the value ΔT of the temperature difference reaches at least said threshold value ΔT_ {TH} [ED], the control means consider the selected drying cycle to be completed and stop the operation of the dryer by deactivating the heating means 3, disconnecting the means 11, 16 air blowers and stopping the rotation of the drum. In the event that an additional phase of unheated air circulation is expected to be executed after the conclusion of the actual drying process in order to allow the clothes to cool before removing them from the drum, the control means simply makes that the heating means 3 be deactivated when the value ΔT of the temperature difference reaches said threshold value ΔT_ {TH} [ED] of the temperature difference, while waiting for said cold air circulation phase to conclude to turn off the tumble dryer and completely stop its
functioning.

The following table summarizes the values of temperature difference threshold for different cycles drying:

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3

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The threshold values ΔT TH [ED, DC, SD, ID, M] of the temperature difference are independent of the initial amount of water contained in the garments to be dried. In fact, the transition from the intermediate saturation phase to the final phase of the drying cycle occurs at a given value of residual moisture, that is, the moisture that remains in the clothes that dry, the value of which only depends on the parameters of conviction design
sador

In accordance with the present invention, the method to control drying cycles in a tumble dryer they make, first of all, read the drying cycle selected by the user and then set accordingly, that is, about the basis of the selected cycle, the threshold value RH_ {inputTH} of the humidity and the threshold value ΔT_ {TH} of the temperature difference These threshold values are retrieved of memory media, where they are stored properly.

Said cycle reading is selected and said establishment of the corresponding values, are taken carried out by the control means, which are connected to the devices of control of a control panel provided in the dryer by I turn around The selected drying cycle is started then, immediately, by these means of control, starting the operation of the dryer in the manner described in what precedes.

The method according to the present invention asks then that, as the drying cycle progresses, detect the RH_ {input} value of relative humidity and the value T_ {input} of the drying air temperature entering the condenser, as well as the value T_ {output} of the temperature of the drying air leaving the condenser. Control means acquire the data delivered by means 5, 6 recipients of humidity and temperature in order to monitor the trend of relative humidity RH_ {input} and the difference value ΔT of temperature as the drying cycle progresses.

The method causes the RH_ {input} value of the relative humidity thus detected be compared with the threshold value of humidity, RH_ {inputTH} which has been established in accordance with the drying cycle selected by the user and that the value ΔT of temperature difference is compared with the value of threshold ΔT TH of the temperature difference which, Also, it has been established according to the drying cycle selected by the user.

The method then causes the heating means 3 to be disconnected when at least the value ΔT of the temperature difference becomes equal or exceeds the threshold value ΔT_ {TH} of the temperature difference or when at least said value RH_ {humidity} input becomes equal to or less than the threshold value RH_ {inputTH} of the hu-
medad

When one of these values of threshold, in addition to disconnecting the heating means 3, the method can also cause the tumble dryer to stop totally functioning, deactivating the means 11, 16 blowers that circulate air and motor media used to drive the drum to rotation.

The method also preferably makes include a phase of transient observation immediately after that the heating means 3 have been thus connected, during which the control means simply expect that humidity and temperature data from the media recipients stabilize before starting the acquisition of cited data.

The provision of two threshold values different, that is, RH_ {inputTH} and \ DeltaT_ {TH}, for each drying cycle that the user can select, guarantees a greater efficiency and greater accuracy in detecting the actual end-of-cycle condition, particularly in the case of drying cycles such as "slightly damp", "dry for iron "and" dry drained ", which require less drying, that is, a lower degree of dryness of clothing and that They have threshold values that are quite similar.

It has been found, and it has been proven experimentally, that the trend of RH_ {inputTH} and ΔT TH does not depend on the weight of the drying load, it is that is, of the amount of clothing items to be dried.

The method of controlling the drying cycles in a tumble dryer, according to the present invention, is not limited by, that is, it does not necessarily require the use of a condenser manufactured and designed as described in what above by way of example. In the case of a tumble dryer that uses a different type of condenser, or a different condenser design, the trend of temperature difference, ΔT, and relative humidity, RH_ {inlet}, will, in fact, be very similar to the trends that have been found in the course of the experimental tests considered in this document and described above, since the thermodynamics on which these trends are based is always the same, regardless of the capacitor that really
use

The curves that describe the trend as a function of the humidity time RH_ {input} and the difference of temperature ΔT will obviously have a different slope and the threshold values will also be different RH_ {inputTH} and ΔT_ {TH} corresponding to the degrees of drying to be achieved in the various drying cycles that You can select the user.

Also, the drying cycles that are set to user layout, can be established and fixed, naturally, according to principles that differ from those previously described, based on residual moisture in comparison with the same drying load under standard conditions as a control parameter

However, it can be seen, in the most easy, that - even in the presence of a capacitor design different - it is always possible to experimentally derive both the threshold values RH_ {inputTH} of relative air humidity drying that enters the condenser as the threshold values ΔT TH of the temperature difference of the drying air entering and leaving the capacitor, attributable to the various user selectable drying cycles.

Such threshold values will then be at arrangement of the control means through the means of memory as soon as dryer operation starts by turning with the particular drying cycle selected by the Username.

In a preferred embodiment of the present invention, the control means are intended to filter digitally the signals they receive from media 5, 6 humidity and temperature sensors, in order to eliminate all detected values that have been found to deviate significantly from the main trend as a function of time RH_ {relative} relative humidity values and values ΔT of temperature difference being monitored by said control means during the drying cycle, that is, as the clothes of the drum are drying.

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Basically, the control means are intended to discard any deformed, altered or disturbed value that can be detected by the humidity and temperature sensors, so that only the main dynamics of the relative humidity evolution RH_ {inlet are retained } and of the temperature difference ΔT with the
weather.

These disturbances in the detected values include disturbed measurements that do not correspond to the values real humidity and temperature and can occur because these measurements are affected by the dynamics, that is, the conditions of circulation of the drying air.

Another cause of disturbance in the values detected may be due to the fact that, to ensure drying uniform and effective garments that are being flipped in the drum, during the cycle periods of inversion, in which the heating means 3 are disconnected and the drum is rotated in the opposite direction, it is say, it is made to counterbalance in order to allow garments of clothes contained therein are turned in the opposite direction and revolts. These investment periods last only a few seconds and are separated from each other by intervals default of a few minutes each provided between they.

In the most obvious way, the detections made by the perceiving media within these periods of investment, tend to result in the measurement of values of humidity, RH_ {input}, and temperature difference values, ΔT, which depart, to a considerable extent, from the tendency of the corresponding values that, on the contrary, are detected when the heating means 3 are connected. In fact, as can be clearly seen in the graphs that appear in Figures 3, 4 and 5, in correspondence with, that is during, said investment periods, the ΔT difference curve of temperature shows peaks of minimum values, while the curve RH_ {relative} humidity input shows values peaks maximum

The control media filter these values RH_ {humidity} input and these values ΔT of difference of  temperature with the help of a digital filter of low-pass

In particular, the control means associate a first digital low pass filter to values RH_ {humidity} input and a second digital filter of low-pass to difference values of temperature ΔT, while both filters comprise, of preference, a digital low pass filter, of unit gain, of the first order, according to the formulas following:

y_ {n} = a \ cdot y_ {n-1} + (1-a) \ cdot RH_ {entry}

u_ {n} = a \ cdot u_ {n-1} + (1-a) \ cdot \ Delta T

in which the coefficient? represents the filter parameter, the RH_ {input} values relative humidity detected represent the input variables of the first filter in the different moments n, e y_ {n} represents the current value of the first filter in the different instants n, while the difference ΔT values of temperature detected represent the input variables of the second filter at different instants n, and u_ {n} represents the current value of the second filter at different times n.

Experimentally, it has been found that - for the application considered - the? parameter of the filters It can adopt a value between 0.9 and 0.99.

In the particular embodiment that is being describing, the use of the same parameter value was chosen α for all drying cycles selectable by the user, and for both digital filters in order to prevent have a marked intervention in the treatment of load of control means.

However, in order to guarantee an effect of more specific filtering, the value of the parameter α can be varied according to the various drying cycles that can be selected by the user, while within a same cycle selected by the user, the parameter value α may also differ in the two digital filters of low-pass

The values of the parameter α of the filters are stored in memory media and are intended for be recovered by the control means when the cycle starts drying selected by the user.

The control means acquire the values RH_ {input} of relative humidity and ΔT values of temperature difference detected by the corresponding perceiving means and then calculate, that is, make them work related digital filters to get a corresponding filtered value RH_ {input} relative humidity filtering and a corresponding filtered value? filtered of the difference of temperature given by the curves indicated in figures 3 and 5.

The control means are intended for compare each filtered value RH_ {inlet} moisture filtration relative to the respective threshold value RH_ {inputTH} [ED, DC, SD, ID, M] of relative humidity corresponding to the actual drying cycle selected by the user and, in addition, they are intended to compare each of these values filtered ΔTfiltrate the temperature difference with the respective threshold value ΔT_ {TH} [ED, DC, SD, ID, M] of the temperature difference corresponding to the drying cycle actual selected by the user.

In particular, the control means are intended to determine a first dH end-of-cycle coefficient and a second dT end-of-cycle coefficient, representing what similar that the relative humidity filtered value has been made, RH_ {input} filtered, to the respective threshold value, RH_ {inputTH} [ED, DC, SD, ID, M], and the like that has been made the filtered value of the temperature difference, ΔTfiltered, to the respective threshold value ΔT TH [ED, DC, SD, ID, M], respectively. These coefficients are determined by comparing the filtered values with the respective threshold values, according to the formulas following:

4

These end-of-cycle coefficients dH and dT are convert, therefore, into pure numbers that tend to unity to as the filtered values RH_ {input} filtered and ΔTfiltrate approximates the respective threshold values RH_ {inputTH} [ED, DC, SD, ID, M] and ΔT TH [ED, DC, SD, ID, M].

Thus, the control means are intended to compose the dH and dT end-of-cycle coefficients in order to obtain a single magnitude of control D, based on which of they decide, therefore, that the cycle should be stopped drying This magnitude of control D is obtained by calculating the average weighted of the dH and dT end-of-cycle coefficients through a weighting factor δ that determines the contribution specific individual coefficients according to the cycle of drying selected, according to the following formula:

D = \ delta \ cdot dT + (100- \ delta) \ cdot dH,

in which the value of the factor of weighting δ depends on the selected cycle, in order to determine what magnitude, between relative humidity RH_ {input} and temperature difference ΔT, is more significant with in order to identify the end of cycle condition. The factor of weighting δ is variable between 0 and 100 and depends on the cycle selected.

This has a particular value in the case of drying cycles such as "dry for iron" and "dry"  drained ", in which is the value ΔT of the difference of temperature which predominantly determines said condition end-of-cycle, since the RH_ {value} of moisture Relative is less reliable.

The value of the weighting factor δ is has determined experimentally for the different cycles of drying offered for selection in a tumble dryer by flip, and is stored in memory media in order to be available for recovery by control means when Start the selected drying cycle.

The end of cycle condition occurs when the magnitude of control D thus calculated becomes equal to or greater than a stop sD parameter that is variable from 85 to 100, according to the cycle selected by the user.

Even the value of this sd stop parameter has been determined experimentally for the different cycles of drying provided for selection in a tumble dryer by flip, and is stored in memory media in order to remain available for recovery by control means when Start the selected drying cycle.

The following table summarizes the values of threshold RH_ {input TH} [ED, DC, SD, ID, M], ΔTTH [ED, DC, SD, ID, M], the values of the dH and dT end-of-cycle coefficients, the values of the factor of weighting δ and parameter values of for sD for each of several drying cycles:

5

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When the control media find that there is such a cycle end condition, they make them disconnect the heating means 3 and, if provided or necessary, that the blowing means to circulate the air are deactivated together with the motor means used to drive Rotation dryer drum.

According to a preferred embodiment of the present invention, the method of controlling the operation of a tumble dryer by flip includes an initialization phase, in which the control means read the cycle that has been selected by the user and set the threshold values RH_ {inputTH} [ED, DC, SD, ID, M] for relative humidity, the threshold values ΔT_ {TH} [ED, DC, SD, ID, M] for the temperature difference, the value of the parameter α of the filters, values of the weighting factor δ and the value of the stop parameter sD, corresponding to the selected cycle, retrieving related values from memory media.

The control means make the heating means 3 and means 11, 16 being activated air circulation blowers, together with the means of Drum rotation drive.

It should be noted that in another embodiment simplified of the present invention, the dH and dT end coefficients cycle can be determined by comparing the current values, ΔT of the temperature difference and RH_ {inputTH} of the relative humidity, unfiltered, with the respective values of threshold. The dH and dT coefficients of end of cycle, in the manner described above, to obtain the single magnitude D of control on the basis of which the means of control switch off the heating means 3.

The control means are intended for check the heating means 3, regarding the state of connection / disconnection thereof, through a receiver of proper functioning

The method also includes a so-called phase of transitory observation, in which the control means simply expect moisture values to stabilize relative, RH_ {input}, and the difference values of temperature, ΔT.

In a preferred manner, within this phase of transitional observation, at least a period of inversion, in which the heating means 3 are disconnected and drum 2 is actuated to rotate in the opposite direction, that is, It is triggered in counter rotation.

When it is perceived that the detected values of the relative humidity, RH_ {input}, and the detected values of the temperature difference, ΔT, have stabilized, the control means check the on / off status of the heating means 3.

In the event that the heating means 3 are in a disconnected state, that is, the dryer flipping is running an investment period, the means of control do not acquire these relative humidity values, RH_ {input}, nor said temperature difference values, ΔT, and wait for the heating means 3 to pass to their connection status

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In the event that it is found that the means of heating 3 be in its connection state, the method requests that enters into an initialization phase, in which the means of control acquire the relative humidity value, RH_ {input}, and the temperature difference value, ΔT, detected by the perceiving means 5, 6 to initialize the filters digital low-pass related calculating the corresponding initial filtered value of relative humidity, RH_ {input} filtered and the corresponding initial value filtered of the temperature difference, ΔTfiltrate.

As the drying cycle progresses selected, the control means are intended to acquire the relative humidity values, RH_ {input}, and the values of the temperature difference, ΔT, detected by the means perceivers, and to filter these values with the help of filters Low pass digital at time intervals successive, predetermined; In the described embodiment, provides a timeout interval between two occurrences successive acquisition of approximately 5 seconds.

The control means wait for it to pass said timeout interval and, when it has ended, check the heating means 3 to see if they are connected or disconnected.

In the event that it is found that the means of heating 3 are in their disconnected state, that is, the tumble dryer is going through an investment period, the control means - in the form of a closed cycle - await again the timeout interval elapses and when it has finished, check the on / off status again of the heating means 3.

If, on the contrary, it is found that heating means 3 are in their connection state, the means  control acquire the value of relative humidity, RH_ {input}, and the value of the temperature difference, ΔT, detected by the respective sensing means, and calculate the digital low pass filters related to determine the corresponding filtered value of relative humidity, RH_ {input} filtered and the corresponding filtered value of the temperature difference,? Filtered, in the same way as described above.

Then, the control means check if, eventually, the end of cycle condition occurred by calculating the values of the dH and dT end-of-cycle coefficients, the value of the magnitude D and comparing the resulting value of the latter with the value of the stop parameter, sD.

If it turns out that the value of the magnitude of control D is equal to or greater than the value of the stop parameter sD, the control means disconnects the heating means 3 and, if so provided or required, possibly, the cycle, make dryer operation stops.

If it is found that the value of magnitude D is less than the value of the stop parameter sD, the means of control - as a closed cycle - wait again for the timeout interval elapses and, when it has passed, check the state of connection / disconnection of the media of heating 3 with a view to acquiring the values of the relative humidity, RH_ {input} and temperature difference, ΔT, updating the digital filters of related low-pass and checking again if It has reached the end of cycle condition.

Claims (26)

1. Clothes tumble dryer comprising a closed circuit for drying air, intended to circulate heated drying air through a perforated rotating drum (2) containing a charge to dry, a condenser (4) cooled by air, intended to remove moisture from the hot drying air, loaded with moisture, leaving the said drum, heating means (3) provided downstream of the condenser (4) cooled by air to heat the drying air to be sent again to the drum (2), an open circuit for cooling air, intended to circulate on and through the condenser (4) a stream of cooling air taken from the outside environment to cool said condenser, and lead to said stream of cooling air, again, to the outside environment, temperature sensing means (5, 6) arranged in a condenser drying air inlet (7) and in a condenser drying air outlet (8), c on in order to detect a temperature difference value between the drying air entering the condenser (4) and the drying air leaving the condenser (4), characterized in that it also comprises moisture sensing means (5) arranged in said condenser drying air inlet (7) in order to detect a moisture value of the drying air entering the condenser, control means coupled to said humidity sensing means (5) to receive said value of humidity (RH_ {inlet}) and coupled to said temperature sensing means (5, 6) to receive said temperature difference value (ΔT) during operation of said tumble dryer, memory means that store a value of threshold (ΔT_ {TH}) of the temperature difference between the drying air entering the condenser (4) and the drying air leaving the condenser (4), and a threshold value (RH_ {inputTH}) of the relative humidity of the drying air entering in the condenser, which are representative of a predetermined degree of dryness of the load and that depend on the particular drying cycle selected by the user, said control means being intended to recover said threshold values (ΔT TH), RH_ {inputTH}) of the memory means in response to a given drying cycle selected by the user, said control means being further intended to compare said relative humidity value (RH_ {input}) with said threshold value (RH_ {inputTH}) of the relative humidity and said temperature difference value (ΔT) with said threshold value (ΔT TH) of the temperature difference to determine an end-of-cycle condition and to disconnect said heating means (3) when at least said temperature difference value (ΔT) reaches said threshold value (ΔT TH) of the temperature difference or, at least, said value (RH_ {input}) of relative humidity ce said threshold value (RH_ {inputTH}) of humidity
relative. 2. Clothes dryer by flip according to the claim 1, wherein said control means comprise digital filter means to digitally filter said value (RH_ {input}) of relative humidity acquired and said value (ΔT) of acquired temperature difference, in order to remove all detected values that deviate, in one measure significant, of the main trend as a function of the time of the aforementioned values (RH_ {input}) of relative humidity and (ΔT) of temperature difference being monitored by said means of control as the process of progressing drying of clothes. and set a corresponding filtered value (RH_ {input} filtered) of relative humidity and a corresponding filtered value (ΔTfiltrate) of difference of temperature. 3. Clothes dryer by flip according to the claim 2, wherein said digital filter means comprise a first digital low pass filter associated with the relative humidity values (RH_ {input}) and a second digital low pass filter associated with the values (ΔT) of temperature difference. 4. Clothes dryer by flip according to the claim 3, wherein said first digital filter and said second digital filter comprise a filtering parameter (?) that depends on the particular drying cycle selected by the user 5. Clothes dryer by flip according to the claim 4, wherein said memory means are intended to store the values of said filtering parameter (?), said control means being in turn intended, to recover these values when the drying cycle begins selected by the user. 6. Clothes dryer by flip according to the claim 2, wherein said control means are intended to compare said filtered relative humidity value, (RH_ {input} filtered) with said threshold value (RH_ {inputTH}) of the relative humidity corresponding to the cycle of drying selected by the user and, in addition, are intended for compare said filtered temperature difference value (ΔTfiltrate) with said threshold value (ΔT_ {TH}) of the temperature difference corresponding to the drying cycle selected by the user. 7. Clothes dryer by flip according to any of the preceding claims, wherein said control means are intended to determine a first end-of-cycle coefficient (dH) and a second coefficient (dT) of end of cycle that represent, respectively, how similar is the filtered value of relative humidity (RH_ {input} filtered) at respective threshold value (RH_ {inputTH}) and how similar it is the filtered value of temperature difference (ΔTfiltrate) to the respective threshold value (ΔT_ {TH}). 8. Clothes dryer by flip according to any of the preceding claims, wherein said control means are intended to calculate a weighted average of said end-of-cycle coefficients (dH, dT) by a factor of weighting (δ) depending on the drying cycle selected by the user

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9. Clothes dryer by flip according to any of the preceding claims, wherein said weighting factor (δ) depends on the drying cycle selected and said control means are intended to retrieve the value of the mentioned weighting factor (δ) of said memory media when the drying cycle starts selected. 10. Clothes dryer by flip according to any of the preceding claims, wherein said control means are intended to compare the value of said weighted average with a stop parameter (sD) that depends on the particular drying cycle that is selected, in order to disconnect the heating means (3) when the value of said weighted average becomes equal to or greater than the value of said stop parameter (sD), said means of control to recover the value of the mentioned stop parameter (sD) of said memory media when the drying cycle starts selected. 11. Clothes dryer by flip according to any of the preceding claims, wherein inversion cycles during the drying cycle, in which the heating means (3) are disconnected and the drum (2) is actuated to rotate in the opposite direction, said means being intended control means to acquire said values (RH_ {input}) of relative humidity and said values (ΔT) of difference of temperature only when said means of heating (3). 12. Clothes dryer by flip according to any of the preceding claims, wherein said control means are intended to acquire said values (RH_ {input}) of relative humidity and these values (ΔT) of temperature difference in correspondence with events of acquisition separated from each other by a time interval of wait preset. 13. Clothes dryer by flip according to any of the preceding claims, wherein said digital filters comprise a digital filter of low-pass, unit gain, first order. 14. Clothes dryer by flip according to any of the preceding claims, wherein the value of said filtering parameter (?) is comprised between 0.9 and 0.99. 15. Method for controlling a tumble dryer by tumbling which includes a closed circuit for drying air intended to circulate heated drying air through the garments to be dried contained in a perforated rotating drum (2), a air-cooled condenser (4), intended to remove moisture from the hot-drying, moisture-laden air, leaving said drum, heating means (3) provided downstream of the air-cooled condenser (4) to heat the air A drying circuit to be sent back to the drum (2), an open circuit for cooling air, intended to circulate on and through the condenser (4) a stream of cooling air taken from the outside environment to cool said condenser, and then lead to said cooling air stream, again, to the outside environment, characterized in that it comprises the steps of: - recover, in response to a drying cycle given selected by the user, a threshold value (ΔT_ {TH}) stored of the temperature difference between the drying air entering the condenser (4) and the air of drying out of the condenser (4), and a threshold value (RH_ {inputTH}) stored relative air humidity of drying that enters the condenser, both values depending on the drying cycle selected by the user and being representative of a predetermined degree of dryness of the garments that are being treated, - detect a value (RH_ {input}) of the relative humidity of the drying air entering the condenser (4), and - detect a value (ΔT) of the difference of temperature between the drying air entering the condenser (4) and the drying air leaving the condenser (4), - acquire, during the operation of said tumble dryer, said humidity value (RH_ {inlet}) relative and said value (ΔT) of the temperature difference detected by the respective perceiving means, - compare said value (RH_ {input}) of the relative humidity with said threshold value (RH_ {inputTH}) of the relative humidity and said value (ΔT) of the difference of temperature with said threshold value (ΔT TH) of the temperature difference to determine an end condition of cycle and disconnect said heating means (3) when at minus said value of the temperature difference reaches said threshold value of the temperature difference or at least said relative humidity value reaches said threshold value of the RH. 16. Method according to claim 15, which also includes the steps of: - digitally filter these values (RH_ {input}) acquired from relative humidity and these values (ΔT) acquired from the temperature difference, in order to eliminate all detected values that deviate, in a significant measure of the main trend based on time of said relative humidity values (RH_ {input}) and of temperature difference (ΔT) that are monitored by said control means as the drying process of the garments, and establish a corresponding filtered value (Filtered RH_ {input}) of relative humidity and a filtered value corresponding (ΔTfiltrate) of the difference of temperature. 17. Method according to claim 16, wherein said comparison step comprises the operations from: - compare said filtered value (Filtered RH_ {input}) of the relative humidity with said value of threshold (RH_ {inputTH}) of relative humidity corresponding to drying cycle selected by the user, and - compare said filtered value (ΔTfiltrate) of the temperature difference with said value of threshold (ΔT) of the temperature difference corresponding to the drying cycle selected by the user. 18. Method according to any of the preceding claims, further comprising the steps of: - provide investment periods during the drying cycle, in which the means of heating (3) and the drum is operated to rotate in direction contrary, - acquire said value (RH_ {entry}) of the relative humidity and said value (ΔT) of the difference of temperature only if it is found that said means of heating (3) are connected. 19. Method according to claim 16, wherein said digital filtering step comprises the operations from: - digitally filter said acquired value (RH_ {inlet}) of relative humidity through a first digital low pass filter, and - digitally filter said acquired value (ΔT) of the temperature difference over a second digital low pass filter. 20. Method according to claim 16, wherein said digital filtering step further comprises the operations of: - recover, in response to said dryer by flip start working, a digital filtering parameter stored (?) that depends on the drying cycle selected by the user, - filter digitally, differently, said value (RH_ {input}) of relative humidity and said value (ΔT) of the temperature difference based on said digital filtering parameter (?). 21. Method according to any of the preceding claims, wherein said comparison comprises,  In addition, the operations of: - determine a first end coefficient (dH) cycle and a second end-of-cycle coefficient (dT) that are representative, respectively, of how similar it has come to be the filtered value (RH_ {input} filtered) of the humidity relative to the respective threshold value (RH_ {inputTH}), and what similar that the filtered value has become (\ DeltaTfiltered) from the temperature difference to the respective threshold value (ΔT_ {TH}). 22. Method according to any of the preceding claims, wherein said comparison step It also includes the operations of: - calculate a weighted average of End-of-cycle coefficients (dH, dT) through a factor of weighting (δ) depending on the drying cycle selected and that determines the specific contribution of the coefficients individual according to the selected cycle, in order to obtain a single magnitude of control (D), - recover said factor (δ) of Weighting according to the drying cycle selected. 23. Method according to any of the preceding claims, wherein said comparison step It also includes the operations of: - compare the value of said control quantity (D) with a stop parameter (sD) that depends on the drying cycle selected, - retrieve the value of said parameter from stop (sD) according to the selected drying cycle, - disconnect the heating means (3) in case of finding that the value of the magnitude of control (D) as well calculated is equal to or greater than the value of said stop parameter (sD). 24. Method according to any of the preceding claims, wherein said acquisition step It includes the operations of: - acquire said value (RH_ {entry}) of the relative humidity and said value (ΔT) of the difference of temperature in correspondence with separate acquisition events between them for a predetermined time interval. 25. Method according to claim 2, which includes the steps of: - check, after the dryer for flip has started working, that these values (RH_ {input})  of the relative humidity and said values (ΔT) of the temperature difference are stabilizing, - begin the acquisition of these values (RH_ {input}) of relative humidity and these values (ΔT) of the temperature difference if it is found to be They have stabilized. 26. Method according to any of the preceding claims, wherein said filtering step digital includes the operations of: - digitally filter values as well acquired (RH_ {input}) of relative humidity through a first low pass digital gain filter unity, first order, - digitally filter values as well acquired (ΔT) of the temperature difference across a second digital low-pass filter, of unit gain, first order.