EP2657395A1 - Method for drying laundry items - Google Patents

Abstract

The method involves subjecting the laundry articles to the action of hot air (21) in a drying drum (14), so as to dry the laundry article. The drying process is terminated when the laundry articles reach a specified degree of drying. The drying process is controlled based on the factor determined from drying parameters. The drying process is terminated when the factor is reached.

Description

The invention relates to a method for drying laundry items according to the preamble of claim 1.

In commercial laundries, laundry of all kinds, in particular flat linen, clothing, dirt mats or the like, dried in dryers with at least one rotating drivable drying drum. For drying, for example, at least one burner uses heated air, which is passed as hot air through the drying drum with the items to be dried. The drying is initially only with hot air heated by the burner. As the drying process progresses, drying takes place both with circulating air and with hot air, the proportion of circulating air increasing at the end of the drying process. By at least one recirculation damper of the dryer, the ratio of hot fresh air and circulating air is set.

The garments must not be dried to such an extent that the moisture content is 0 or almost 0, otherwise there is a risk of the laundry over-drying, which could result in scorching of the laundry items. The drying process is therefore terminated when the laundry items still have a certain residual moisture, but which must not be too high, because otherwise the laundry items can be affected, for example, by mold formation, especially in a longer storage. So far, the drying process is terminated either by empirically determined empirical values or by measuring various drying parameters. This procedure is either too inaccurate or it requires a complex measurement technique. In addition, it is endeavored to control the drying parameters or to regulate that the energy consumption during drying is as low as possible. This is emphasized due to rising energy costs. Economically optimal drying requires complex control. This requires a high metrological and control or control engineering effort.

The invention has for its object to optimize the drying, in particular the control or regulation of the drying process, preferably to simplify.

A method for achieving this object comprises the measures of claim 1. Accordingly, it is provided to form at least one factor from a plurality of drying parameters and to terminate the drying process on the basis of this factor and / or to control or regulate the drying process. The respective factor can be easily formed, especially from a larger number of drying parameters. The factor then represents a concrete value, according to which the drying process is purposefully and accurately terminated and, alternatively or preferably, in addition a simple, but nevertheless precise control or regulation of the drying process is possible. It is thus possible in a simple manner, taking into account certain drying parameters with simple means a targeted and reliable control or regulation of the drying process and it can additionally or alternatively be determined exactly when the drying process is completed.

During drying, it is preferably intended to determine the factor several times in succession, preferably continuously, on the basis of a plurality of drying parameters, in particular mathematically. As a result, factors are constantly being determined or formed during the entire drying process, so that it is possible to draw conclusions about the course of drying, in particular the progress of drying, on the basis of the successively determined factors. Accordingly, the drying operation can be easily controlled or regulated in a simple manner. Above all, the drying end can be reliably determined by the factors.

According to a preferred embodiment of the method, when a particular factor is reached, the drying process is ended. It becomes so effective Overdrying avoided, which could lead to damage of the laundry to be dried and unnecessary energy costs avoided.

It is preferably provided that the factor is compared with a predetermined switch-off value. The drying process is then stopped as soon as the factor determined gradually during the drying process corresponds to the cut-off value. It can thus be done in a simple manner, the termination of the drying process, wherein the continuously during the drying process, in particular continuously determined factor provides a reliable reference value. The end of drying can be determined very easily by a constant comparison of the respectively determined factor with the predetermined cut-off value.

It is provided in an advantageous embodiment of the method to set the cut-off individually as a function of the laundry to be dried. In particular, the shutdown value is determined according to the type of laundry items to be dried. Alternatively or additionally, the switch-off value can also be determined as a function of the laundry thickness or the thickness of the fabric. For example, a distinction can be made between terrycloth and thin laminate. The cut-off value is greater with thicker fabrics than with thinner fabrics. Also, the shutdown value is greater for insensitive fabrics.

The successive, in particular continuously determined during the drying process factor can be used not only to determine the completion of the drying process, but alternatively or additionally, to control the drying process. Since new factors are constantly being determined during the drying process, the drying stage can be derived from this course and / or the current factor. The respective factor provides concrete clues for a specific control or regulation of the drying process.

It is preferably provided that the drying operation is controlled by a change in the angular position of a recirculating air flap of the dryer depending on the factor and / or by an adaptation of the falling curve of the laundry items in the drying drum, preferably by a corresponding change or adaptation of the rotational speed of the drying drum or regulated. Influencing the angular position of the recirculation flap and the falling curve is essential for optimal drying. Above all, the position of the recirculating-air flap and the falling curve are decisive for the efficiency of the drying. On the basis of several times, in particular continuously, during the drying process determined factors, the position of the recirculation flap or the falling curve in very short time intervals, namely ideally after each determination of a new factor, adjusted or adjusted for accurate and high resolution adaptation to the current drying stage and the associated drying state of the laundry.

According to a preferred embodiment of the method, it is provided to set time-related setpoint values of the factor distributed over the drying time and to carry out the control or regulation of the drying process in such a way that the factors correspond or come as close as possible to the setpoint values. In particular, it is provided that the respectively determined factor is compared with the desired value with regard to time, that is to say it is checked whether the factor determined after a certain drying time coincides with the setpoint associated with this drying time or not. In case of deviations, at least one drying parameter is automatically changed, preferably the recirculating-air flap position and / or the falling curve. It is thus preferably continuously monitored the drying process and / or the degree of drying of the laundry and controlled or regulated accordingly.

The invention preferably provides that the respective factor from the drying parameters is determined on the basis of a Mollier diagram (h-x diagram). It has surprisingly been found that in this way the factor can be determined from a few drying parameters in a manner which is particularly advantageous for the method according to the invention.

Another advantageous embodiment of the method provides, as a drying parameter for determining the at least one factor to use the supply air temperature, the exhaust air temperature, the surface temperature of the items to be dried and / or the angle of the position of a recirculating air flap of the dryer. The mentioned drying parameters are easily ascertainable. In part, they must be determined anyway. Therefore, no additional metrological effort is required. Only the measured values obtained in accordance with the invention are linked or converted in such a way that it is possible to derive information about the progress of the drying process and the degree of drying of the laundry items.

A preferred embodiment of the invention will be explained in more detail with reference to the drawing. The sole figure of the drawing shows a schematic Cross section through a dryer, which among other things, the inventive method is feasible.

The dryer 10 shown in the figure is used for highly effective and energy-efficient drying of laundry. Such a dryer 10 is used primarily in commercial laundries.

In the dryer 10 shown, air for drying the laundry is heated by a single burner 11. However, the dryer 10 may also have a plurality of burners 11 arranged in parallel or in series. The burner 11 may be any burner 11, preferably a gas burner or an oil burner.

The dryer 10 has an outer housing 12, preferably a closed, box-like housing 12, in which a about a horizontal axis of rotation 13 rotatably drivable drying drum 14, said burner 11, a circulating air fan 15 and corresponding air ducts are arranged.

The rotationally drivable drying drum 14 serves to receive the laundry items to be dried. The laundry items are not shown in the figure. The drying drum 14 also has a loading and unloading also not shown. In particular, the jacket of the cylindrical drying drum 14 is designed permeable to air so that air serving for drying can flow through the drying drum 14 and the laundry to be dried therein. The drying drum 14 is partially surrounded by a small distance from the cylindrical shell of air-impermeable, arcuate walls. The walls are located on a concentric about the axis of rotation 13 extending circular path. The walls are preferably diametrically opposed openings, namely an upper air inlet opening 16 and a lower air outlet opening 17, free.

Above the drying drum 14 is located in the housing 12 of the recirculation fan 15, which may also be another air flow generator, such as a fan, act. In addition to the circulating air fan 15, the burner 11 is arranged approximately centrally in the upper region of the housing 12, in such a way that the axes of the flames extend approximately horizontally transversely to the axis of rotation 13.

In a chamfered upper right corner region of the housing 12 is an exhaust port 18. The exhaust port 18 is associated with a not shown temperature sensor, whereby the exhaust air temperature can be determined.

Under the exhaust port 18, a recirculating air flap 19 is provided in the interior of the housing 12. The recirculation flap 19 is pivotable about a preferably horizontal pivot axis 20 by a drive, not shown. The recirculation damper 19 is pivotable so far that it completely closes the exhaust port 18 in an open position on the one hand and the exhaust port 18 completely releases in a closed position and completely interrupts or prevents a circulating air flow to the air inlet opening 16 in the drying drum 14. Any intermediate positions of the recirculating air flap 19 are possible between said extreme positions. By an angle sensor, not shown, the angular position of the recirculating air flap 19 can be determined.

The drying process takes place in the described dryer 10 as follows:

At the beginning of the drying process, heated air 21 is passed from the burner 11 via the air inlet opening 16 of the rotationally driven drying drum 14 with the laundry to be dried therein. When flowing along the wet laundry, the heated air 21 absorbs moisture. As a result, moist air 22 is discharged through the air outlet opening 17 from the drying drum 14. The moist air 22 is removed by the circulating air fan 15. When the recirculating-air flap 19 is completely closed, the moist air 22 is led completely through the exhaust air outlet 18 into the open air. The discharged moist air 22 is replaced by heated from the burner 11 fresh air, which passes as heated air 21 without circulating air through the air inlet opening 16 to the drying drum 14.

As the drying process progresses, moisture in the moist air 22 decreases. Then a portion of the moist air 22 is supplied as circulating air to the burner 11 over the drying drum 14 with the laundry to be dried again. For this purpose, the recirculation damper 19 is partially opened by pivoting clockwise (relative to the figure) to the pivoting pocket 20. The recirculation damper 19 is opened so far that sets the desired circulating air flow, so a targeted proportion of moist air 22 as recirculation 24th the drying drum 14 is supplied again and a remaining portion of the moist air 22 is passed through the exhaust port 18 as exhaust air 23 into the open. The proportion of the exhaust air 23 conducted to the outside is replaced by fresh air heated by the burner 11 and heated air 21 together with the circulating air or drying drum 14 through the air inlet opening 16 is supplied. It is then only that part of the moist air 22 is replaced, which is passed as exhaust air 23 to the outside. With increasing drying time, the proportion of circulating air 24 is gradually increased. For this purpose, the recirculation flap 19 is gradually opened further, so that it closes the exhaust port 18 more and more and less still considerable residual heat having moist air 22 escapes through the exhaust port 18 into the open.

The method according to the invention is explained in more detail below with reference to the dryer 10 described above:

According to the invention, actual factors are formed from several drying parameters during the drying process. The factors are used on the one hand to control the drying process and on the other hand to end the drying process. The invention is, however, not limited thereto. The method according to the invention can also relate to ending the drying process on the basis of the factor or to controlling or regulating the drying process on the basis of continuously determined factors.

In the present embodiment, to form the factors as drying parameters, the angular position of the recirculating air flap 19 determined by an angle sensor, the supply air temperature determined by a temperature sensor, ie the temperature of the fresh air to be heated by the burner 11, is also the exhaust air temperature determined by a temperature sensor, ie the temperature the exhaust air outlet 18 leaving moist air 22, and the surface temperature of the dried laundry used. The surface temperature of the dried laundry is determined without contact by a sensor associated with the drying drum 14, for example an infrared sensor.

The said drying parameters are continuously determined during the entire drying process, continuously or at regular intervals, that is to say, with regard to duration pauses between successive determinations of the factors. It thus creates current factors related to the current drying phases. The respective drying time can be assigned to the factors so that time-related or time-normalized factors are formed. The factors are calculated by, for example, a microprocessor using the Mollier diagram (hx diagram).

In order to determine the end of the drying process, based on the particular laundry to be dried, according to the type of laundry, in particular the type of fabric and / or the laundry thickness, set a shutdown. When the determined factor reaches this value, the drying process is automatically ended. The cut-off value is set to be between 0 and 100, where 0 is wet laundry, 100 is a strongly overdried laundry that has almost no residual moisture, while a shutdown value below 100 corresponds to the optimum drying point. This switch-off value is determined according to the type of laundry. The shutdown value is the setpoint of the factor. If the factor reaches the cut-off value, this means that the optimum drying point of the laundry has been reached. The drying process is then stopped.

In order to be able to determine when the shutdown value representing the optimum drying point for the respective laundry is reached, a determination of the factor is preferably carried out continuously during the entire drying process. If, on the basis of the factor, only the automatic termination of the drying process is to take place, it may be sufficient to start the formation of the factor only after a certain initial drying time has elapsed. The determination of the factor is started when, as experience shows, the drying process is largely completed, but certainly the cut-off value specified for the particular laundry has not yet been reached.

To control or regulate the drying process, preferably drying-time-related factors are determined successively over the entire drying process, either at regular time intervals or continuously in succession. This creates a series of factors for the respective drying time. Preferably, the factors related to the associated drying time, ie at the time from the beginning of the drying, when it has been determined, recorded, in particular stored.

The determined time-related factors are compared with target values that are assigned to the respective drying period. The setpoint of a certain drying time is used to compare the factor determined during this drying period. In case of deviation, the drying process is controlled or regulated accordingly.

For the control or regulation of the drying process, deviations of each factor relating to a certain drying time to the setpoint value relating to the same drying time can be determined and, accordingly, the drying process controlled or regulated by reference to corresponding drying parameters.

It is also conceivable to form a trend or forecasts from several successive factors. Accordingly, the drying parameters are influenced. It is also conceivable that certain drying parameters are influenced by the current comparison of the factor with the setpoint, while other drying parameters remain unchanged based on the course or the trend of several factors and their comparison with the timed setpoints.

The position of the recirculating-air flap 19 is preferably controlled on the basis of the factors, in particular its comparison with the associated desired values, ie a corresponding value of the angular position of the recirculating-air flap 19 is set and / or the fall curve of the laundry in the drying drum 14 is changed. This is done in such a way that a fall curve that changes as the drying of the laundry increases is adjusted by a corresponding change in the rotational speed of the drying drum 14. The fall curve of the laundry can be adjusted in the drying drum 14 so the current degree of drying of the laundry, so that in the rotating driven drying drum 14 always results for the laundry to be dried optimum fall curve.

By controlling or regulating the circulating-air flap position on the basis of the measured angular position of the same, the circulating-air proportion can be optimally increased, preferably continuously, as a function of the factor permanently determined via the drying process and preferably by comparison of the respective determined factor with the associated setpoint , In this way, as much hot circulating air as possible can be reused for drying the laundry by returning it to the drying drum 14. This leads to a particularly energy-efficient drying.

It is also conceivable to change, in particular to control or regulate other drying parameters by using the factors determined during drying. This can be, for example, the rotational speeds of the drying drum 14 and / or the circulating air fan 15, but also the temperature at which the burner 11 heats the air 21.

The inventive method is not only suitable for the dryer 10 described above, but also for differently constructed dryer, in particular those for commercial laundries. <B> LIST OF REFERENCES: </ b> 10 dryer 11 burner 12 casing 13 axis of rotation 14 dry drum 15 circulation fan 16 Air inlet opening 17 Air outlet opening 18 air vent 19 recirculation damper 20 swivel axis 21 heated air 22 moist air 23 exhaust 24 circulating air

Claims (11)

Method for drying items of laundry, wherein the items of laundry preferably in a rotationally driven drying drum (14) with hot air (21) acted upon and dried and the drying process is terminated upon reaching a predetermined degree of drying of the laundry, characterized in that from several drying parameters at least a factor is formed and on the basis of this factor the drying process is ended and / or the drying process is controlled or regulated. A method according to claim 1, characterized in that several factors during drying successively, preferably continuously, based on the drying parameters are determined in particular by calculation. A method according to claim 1 or 2, characterized in that the drying process is terminated when the factor is reached. Method according to one of the preceding claims, characterized in that the factor is compared with a predetermined cut-off value, wherein the drying process is terminated as soon as the preferably continuously determined during the drying process factor corresponds to the cut-off value. Method according to one of the preceding claims, characterized in that the cut-off value is set individually as a function of the type of laundry items to be dried, preferably their type of fabric and / or thickness. Method according to one of the preceding claims, characterized in that the cut-off value for items of laundry made of thicker materials is greater than for items of laundry made of thinner materials. Method according to one of the preceding claims, characterized in that on the basis of successive, preferably continuously determined during the drying process factors of the drying process is controlled or regulated. A method according to claim 7, characterized in that the drying process by depending on the factors resulting change in the angular position of a recirculating air flap (19) of the dryer (10) and / or a falling curve of the laundry items in the drying drum (14), preferably by changing the speed the drying drum (14) is controlled or regulated. A method according to claim 7 or 8, characterized in that distributed over the drying time time-related setpoint values of the factor are determined and the control or regulation of the drying process takes place such that the factors correspond to the set values or come as close as possible, in particular the determined at the respective time of the drying process Factor corresponds to the value assigned to this time or at least comes as close as possible. Method according to one of the preceding claims, characterized in that the at least one factor from the drying parameters is determined according to a Mollier diagram. Method according to one of the preceding claims, characterized in that the supply air temperature, the exhaust air temperature, the surface temperature of the items to be dried and / or the angle of the position of a recirculating air flap (19) of the dryer (10) are used as the drying parameter for determining the at least one factor ,

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