EP1279760B1 - Method for drying laundry - Google Patents

Abstract

The method involves subjecting the moist wash to hot air, measuring at least the temperature of the washing and finally cooling the washing if appropriate. Several temperatures of the washing are measured at least during a defined period of the drying process and a time point at which to terminate the drying process is derived from the temperature measurement values.

Description

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

The drying of laundry, including both flat linen (bed linen, table linen) and clothing (underwear and outerwear) is expected to be done both for commercial and private purposes by dryers. In the dryers, the laundry is dried by warm air. Optionally, the after-treatment by cooling can be followed by the hot air treatment of the laundry, using cold air or air at ambient temperature. The drying process is then composed of a warm air drying phase and a cooling phase.

For reasons of economy, it is endeavored to keep the phase of the warm air of the laundry during the drying process as short as possible. But also for the purpose of the greatest possible protection, especially temperature-sensitive laundry, it is endeavored to apply the laundry only a shortest possible time with hot air, so that the laundry is not overheated. The termination of the drying process, in particular the shutdown of the hot air supply to the laundry, is particularly important for the reasons mentioned. Various methods for controlling the drying process are already known. However, these have the disadvantage that they are either too expensive or require the input of various data in the control of the dryer, which is user-consuming and can lead to incorrect entries to damage the laundry.

Methods for drying laundry according to the preamble of claim 1 are known, for example US 5,651,192 ,

On this basis, the present invention seeks to provide methods for drying laundry, which allow a reliable automatic termination of at least the drying process in a simple manner.

A method for achieving this object comprises the measures of claim 1. By determining several temperatures of the laundry during a certain period of the drying process, one obtains statements about how fast the concrete drying process takes place. As a result, reliable predictions regarding the end of the drying process can be made, so that the drying process can be finely controlled on the basis of the temperature measured values, without the risk of overheating of the laundry and no unnecessary heat supply being necessary.

To compare the measured temperature values determined during the hot air application with ideal specifications and thereby determine the appropriate time to complete the drying process. The comparison is made with reference curves. A suitable reference curve or reference curve is selected which is closest to the temperature readings. The selected reference curve contains the previously determined, most favorable time for the completion of the drying process, in particular for switching off the hot air supply to the laundry. The most favorable time of shutdown of the hot air supply can be so simple, but still be predicted with relatively high accuracy. It is also possible to use the reference curve to determine the duration of the cooling phase and to control it accordingly. It is also possible, on the basis of the initial slope of the selected reference curve or of the initial slope of the measured temperature curve determined from the first measured temperature values, to determine the degree of loading of the drum or the weight of the laundry item.

Preferably, several temperatures are determined in that phase of the drying process in which the laundry hot air is supplied. These temperature measurements make it possible to predetermine the preferred time of switching off the hot air supply according to the invention. As a result, an impairment, namely overheating, the laundry items is reliably avoided and it is the energy for hot air generation is limited to a minimum.

The reference curves are formed from reference temperature readings, which have preferably been previously determined separately during a complete exemplary drying process, at least the phase of the hot air supply to the laundry. The reference curves are determined at least as a function of the particular type of laundry, in particular the material of the laundry. But it is also conceivable to create the reference curves in addition to the type or the material of the laundry still depending on the loading condition or loading level of the dryer. There then exist for the same type of laundry or laundry of the same material several reference curves for different loading conditions or load levels of the dryer.

The temperature of the laundry is determined several times during a certain time interval. At least two temperature values are determined, which are at the beginning and at the end of the respective time interval. From these values, the time-related increase in temperature during the drying of the laundry can be determined. In particular, a first derivative of the temperature profile can be formed according to time and from this the slope of the temperature curve in the time interval can be determined. If more than two temperature values are determined, it is also possible to determine different gradients of the temperature profile curve in the time interval. Reliable statements about the remaining drying time, in particular the time at which the exhaust air supply to the laundry is switched off, can be determined from the determined time-related temperature increases or gradients or changes in the slope of the temperature curve in the time interval. Also in this way relatively simple predictions can be made by simple means taking into account, in particular, the material of the laundry and / or the degree of loading of the dryer over the time of completion of the drying process, in particular the termination of the hot air supply.

According to a preferred embodiment of the method, it is provided to let the time interval begin only after a certain start time (dead time) of the drying process. Thus, initial inaccuracies that do not allow prediction of the end of drying are eliminated. Instead, reliable assumptions about the expected end of the drying process, in particular the phase of the hot air supply to the laundry, depending on such a time interval can be made by the temperature increase has sufficient explanatory power. The method described above is particularly suitable for terry towels.

Another method for developing the method described above comprises the measures of claim 10. Accordingly, the temperature of the laundry is determined during the drying process and compared with the temperature of the supplied hot air (supply air) and / or the discharged air (exhaust air), preferably the measured temperature of the laundry of at least one of the latter temperatures subtracted. It has surprisingly been found that the resulting temperature difference is in a certain relation or in connection with the residual drying time. With decreasing temperature difference of the drying process is progressing progressively. At a certain temperature difference can then be reliably shut off the drying process, in particular a break in the hot air supply to the laundry done.

Preferably, the temperatures of both the laundry and the supply air and / or exhaust air are determined and compared continuously or at certain successive time intervals or steps. On the basis of preceding drying tests or empirical values, the temperature difference can be ascertained, at which a termination of the drying process, in particular a deactivation of the hot air supply to the laundry, is advantageous. This temperature difference used for switching off as a function of the type and / or the material of the laundry can optionally be determined in addition to the degree of loading of the dryer. Preferably At the same time determined temperatures of the laundry and the supply air and / or exhaust air compared. This increases the reliability of the method according to the invention. This method is particularly suitable for sensitive materials, especially microfibers.

Another method for developing one or both of the previously described methods comprises the measures of claim 12. Accordingly, the drying process is terminated when the measured temperature of the laundry has reached a predetermined temperature limit. This temperature limit can be previously determined by experiment, depending on the type, in particular of the material, the laundry. In addition, the temperature limit value can also be determined as a function of the loading level of the dryer. For this purpose, it is possible to previously determine comparison curves and evaluate them. By storing the comparison curves in a programmable controller of the dryer, the temperature values can be called up at any time, in particular temperature limit values. Then then a targeted shutdown of the drying process, in particular the hot air supply to the laundry done.

In all the methods described above, it is advantageous if the temperature of the surface of the laundry is measured, preferably a non-contact measurement of the surface temperature of the laundry is made. In this way, temperature measurements can be determined particularly reliably without affecting the laundry, even within a relatively short time sequence, so that a temperature curve or a region thereof can be determined almost completely.

All of the above-described methods according to the invention are characterized by a simple operation of the dryer. It only needs the type of laundry, in particular the material of the laundry to be dried, to be entered into the controller or to be selected from the programmed in a controller types of laundry the appropriate type of laundry. Thereafter, upon reaching the intended degree of drying of the laundry, the drying process, in particular the hot air supply, is automatically and reliably terminated. If also the loading condition or degree of loading of the dryer in the determination of the shutdown of drying In the simplest case, enter a corresponding value in addition to the material type. In a preferred embodiment of the method, this value does not need to be entered. The degree of loading of the drum can be derived, for example, from reference curves, namely from the slope of the same at the beginning of the curve, ie at the beginning of the drying process. But it is also possible to determine the weight of the laundry in the dryer by appropriate transducers. Under deduction of the known, constant weight of the drum is then given the weight of currently located in the same laundry and thus the degree of loading of the dryer.

According to one embodiment of the invention is provided for different types of laundry different programs in a control of the dryer. These programs can work according to the methods described above. In this case, the method preferably used for the respective type of laundry is used for the respective type of laundry. Then practically all the previously described methods or at least some of the previously described methods are used alternatively in the control of the same dryer, namely as a function of the material or fabric of the respective laundry to be dried. The drying process is then monitored and terminated according to the most favorable process specific to the product.

Fig. 1

ein Prinzipschema eines Trockners mit Teilen einer Steuerung, und

Fig. 2

ein alternatives Prinzipschema gemäß Fig. 1.

Preferred methods according to the invention are explained in more detail below with reference to the drawing. In this show:

Fig. 1

a schematic diagram of a dryer with parts of a controller, and

Fig. 2

an alternative schematic diagram of FIG. 1.

The dryer 10 shown diagrammatically in FIGS. 1 and 2 has a stationary outer housing 11 and a drum 12 which can be driven in rotation about a horizontal axis of rotation. A loading door 13 in one end face of the housing 11 loads the drum 12 of the dryer 10 with the laundry 14 to be dried, which is hinted at in the figures. Likewise, the closing during the drying process loading door 13 for removing dried laundry 14 from the drum 12 of the dryer 10 is used.

The housing 11 is associated with a heater 15 from the outside. In this warm air is generated, which is passed through openings or channels not shown in the perforated drum 12. Symbolically, the hot air flow 16 is shown in the figures by arrows. The warm air at the same time forms the supply air to the dryer 10. Cooled and moisture-enriched air is led out of the housing 11 as exhaust air. By arrows, the exhaust air flow 16 is hinted and symbolically represented.

Heating energy is supplied in the form of steam, gas or electricity via a power supply line 18 of the heater 15. By a heating valve 19 (or in the case of heating with electricity another suitable means), the energy flow through the power supply line 18 is changeable and at the end of the heating or drying process completely interruptible. The heating valve 19 is an actuator 20, for example, an electric servomotor assigned. The actuator 20 closes and opens the heating valve 19 or changes the energy flow through the heating valve 19 and the power supply line 18. The actuator 20 is controlled or regulated by a suitable means, which in the exemplary embodiment shown is a programmable logic controller (SPS 21). is. In the example of FIG. 1, a temperature-proportional measuring signal of a sensor, for example a non-contact infrared sensor 22, is fed to the PLC 21. In the SPS 21, specific drying parameters, in particular temperatures, and / or several different materials or fabrics of the laundry are preferred. or programs deposited. The infrared sensor 22 is associated with the dryer 10 such that it measures the temperature of the laundry 14 in the drum 12 without contact, preferably the surface temperature of the laundry 14th

The dryer of Fig. 2 substantially corresponds to the dryer 10 of Fig. 1. For identical parts, therefore, like reference numerals are used. In addition, the dryer 10 of FIG. 2 has two temperature sensors, preferably of the BT 100 type. A temperature sensor 23 serves to measure the temperature of the warm air flow 16. The other temperature sensor 24 measures the temperature of the exhaust air flow 17. Temperature-proportional values of both temperature sensors 23 and 24 are also routed to SPS 21. Optionally, a single temperature sensor 23 or 24 is sufficient.

A first method according to the invention is explained with reference to FIG. 1:

In this case, the temperature of the laundry 14 is measured by the infrared sensor 22 during at least part of a first phase of the drying process, namely during the loading of the laundry 14 with the hot air flow 16. This measures contactless the surface temperature of the laundry 14 during drying with hot air. The surface temperature of the laundry 14 is determined several times at least during a representative part of the hot air application of the laundry 14, preferably by determining the surface temperature of the laundry 14 at regular intervals or in short successive times or else continuously. The measured values obtained in this way, which are proportional to the surface temperature of the laundry 14 at the respective time of the measurement, result in temperature measured values which are stored in the SPS 21. It is sufficient if several temperature measured values are determined within a time of a few minutes, for example 1 to 5 minutes, so that temperature measurements do not have to be determined during the entire drying period, which is basically possible.

In the PLC 21 reference curves are stored, which also contain temperature values or with the surface temperature of the laundry 14 proportional values. The values together give the respective reference curve. There are more several reference curves stored in the PLC 21, and those for different materials or fabric of the laundry 14. In addition, even reference curves for different load levels of the drum 12 of the dryer 10 with laundry 14 in the PLC 21 are stored. Then the PLC 21 receives for each type of material of the laundry 14 several reference curves, for example, for a full, half or only one-third loaded drum 12th

In the method described, the degree of loading of the drum 12 can be determined from the initial slope of the temperature curve at the beginning of the drying process. The slope of the temperature curve at the beginning of the drying process provides a reliable indication of the degree of loading of the drum 12. The degree of loading of the drum 12 can also be determined if in the PLC 21 only a single reference curve for an exemplary, but known loading level is stored. Due to deviating slope of the temperature curve at the beginning of Drying process can then calculate the actual load level, without this must be entered into the PLC 21.

The temperature measured values (or temperature-proportional values) recorded by the infrared sensor 22 during the respective drying operation are then compared with the at least one reference curve in the SPS 21. Expediently, identical time segments are compared with one another. If temperature readings of the surface of the laundry 14 are determined during a certain period of time or only after the beginning of the drying process only during the current drying process, a comparison of the temperature measurements obtained with a temperature curve of the reference curve takes place within the associated time spectrum of the reference curves. In the described comparison, either a same reference curve is determined, for which then no further reference curves would have to be compared with the recorded temperature values, or all reference curves are compared with the recorded temperature values and that reference curve is selected which is closest to the measured region or section of interest Temperature values of the current drying process approaches.

All reference curves have a switch-off time for the hot air supply to the laundry 14 in the drum 12. Based on the selected reference curve, the resulting shutdown of the hot air supply is used to interrupt the hot air supply in the current drying process, in particular to end, by the PLC 21 to the actuator 21, a signal to close the heating valve 19 and thus to interrupt the by the power supply line 18 to the heater 15 passing energy there.

If the phase of the drying process in which hot air is supplied to the laundry 14 is followed by a cooling phase without a supply of hot air to the laundry 14, this cooling phase can take place over a constant period of time, this constant period starting with the end of the hot air supply. This constant time period is preferably dependent on the particular material of the laundry, so that a constant time duration is entered in the SPS 21 for each material. However, it is also conceivable to control the duration of the cooling phase as a function of the material of the laundry 14 or the degree of loading of the drum 12, preferably again on the basis of the respectively selected reference curve. But it is also It is conceivable to control the cooling duration representing a final phase of the drying process as a function of temperature measured values or temperature-proportional measured values which are recorded by the infrared sensor 22 during the cooling phase. It is then entered a cooling temperature for the respective material of the laundry in the PLC 21 and when it reaches the end of the cooling phase. In this case, preferably, the PLC 21 would also control the motor for rotating the drum 12.

Another inventive method is also explained with reference to FIG. 1. Basically, the dryer 10 is operated as in the method described above. The infrared sensor 22 also measures temperatures of the surface of the laundry 14 without contact during at least the first phase of the drying process in which hot air flow 16 is conducted to the laundry 14 into the drum 12. The temperature measured values or temperature-proportional measured values determined in this way are in turn passed to the PLC 21 where they are stored and / or processed.

In the method described here, the temperature measurement of the surface of the laundry 14 takes place during drying with the hot air flow 16 only within a specific, selected time interval (time window). This time window may be, for example, one to five minutes, preferably one and a half minutes of hot air drying. The time interval or the time window begins only a certain time after the beginning of the drying process, in particular from the time of the beginning of the supply of hot air flow 16 to the laundry 14, for example, five to ten minutes later. This eliminates a dead time at the beginning of drying with hot air.

Within the time interval or time window, at least two measurements of the surface temperature of the laundry 14 are made by the infrared sensor 22. Preferably, more than two temperature measurements within the predetermined time interval take place at regular short time intervals. From the temperature measured values, the PLC 21 determines a slope of the temperature profile or a temporal temperature rise. This corresponds to the first derivative of the temperature difference between two consecutive temperature measurements over time. From this, the degree of loading of the drum 12 can be derived.

On the basis of the measured or calculated slope of the temperature profile or possibly also changes in the slope, the remaining duration of the drying process with hot air is determined on the basis of differential values or empirical values stored in the SPS 21. After the time thus determined, the further energy supply to the heater 15 is interrupted by closing the heating valve 19 and the first portion of the drying of the laundry 14 which ends with hot air is ended. It may then be followed by a cooling phase, which extends over a constant period or as described in more detail above is controlled. It is also conceivable, however, to complete the drying process immediately after completion of the hot air supply to the laundry 14 in the drum 12 when the drying process has only one working with hot air drying area.

Another inventive method will be explained with reference to FIG. 2. Here, not only the temperature of the surface of the laundry 14 is determined by the infrared sensor 22 during drying with hot air, but the temperature of the warm supply air, ie the warm air flow 16, and determined by the temperature sensor 24, the temperature in the exhaust air through the temperature sensor 23 , So the exhaust air flow 17, found. Alternatively, it may be sufficient to determine only the temperature of the hot air flow 16 or the temperature of the exhaust air flow 17. The measured temperature values are collected and stored in the PLC 21. Furthermore, a constant comparison of the temperature values of the infrared sensor 22 with the temperature value of the hot air flow 16 and / or the exhaust air flow 17 takes place. From this comparison, the drum 14 is supplied to the drum 12 during the drying process, namely in the drying phase, in the hot air. constantly calculated a temperature difference from the PLC 21.

The method described is based on the knowledge that the temperature difference between the temperature of the hot air flow 16 and / or the exhaust air flow 17 and the temperature at the surface of the laundry 14 decreases towards the end of the drying. If a predetermined temperature difference is reached, either the working with hot air drying process is terminated immediately, that is, the heater 15 is turned off, or even dried over a predetermined period of time. This period is preferably dependent on the material of the laundry 14 and / or the degree of loading of the drum 12.

While the degree of loading of the drum 12 can be determined mathematically from the measured temperatures or by weighing the drum after loading the same with the dry laundry 14 can be determined, so no input to the control panel of the dryer 10 requires the type of material of the laundry 14 is entered beforehand , This also applies to the previously described procedures of the invention.

Finally, according to a further method of the invention, it is provided to switch off at least the phase of the drying process which operates with hot air when the temperature of the surface of the laundry 14 measured by the infrared sensor 22 has reached a specific value. For this purpose, it is sufficient if, according to FIG. 1, only the infrared sensor 22 is provided. The temperature sensors 23 and 24 of Fig. 2 can be omitted in these methods.

The temperature of the surface of the laundry 14 is kept constant throughout the hot air drying process, i. continuously or at regular (even) intervals. The temperature measured values obtained are compared in SPS 21 with preset limit values. These limit values are determined by previous tests or sample drying with laundry 14 of different materials and / or different loading grades of the drum 12. It is entered manually only at the beginning of the drying process in the control panel of the dryer 10, which material consists of the laundry 14 to be dried. If you work with the degree of loading of the drum 10, this is determined automatically, as has already been described above.

The PLC 21 now selects depending on the material of the laundry to be dried 14 and possibly the degree of loading of the drum 12 from the appropriate limit. The SPS 21 now compares the surface temperatures of the laundry 14, measured without contact during drying with hot air by the infrared sensor 22, with the selected limit value. Once a match is achieved, the PLC 21 shuts off the hot air drying operation by interrupting the power to the heater 15. Subsequently, a cooling phase can still be run through. This is also done in this method preferably over a predetermined period of time, which may be dependent on the material of the laundry 14 and / or the degree of loading of the drum 12, if necessary.

The dryer 10 may operate according to one of the methods described above. Then in the dryer 10 all types of laundry, especially laundry of different materials, dried by the same process, in particular the completion of the drying process controlled by the same method.

However, it is preferably provided according to the invention that the dryer 10 works according to several, preferably all methods described above. The PLC 21 is then programmed to control the dryer 10 by several or all methods. It is then worked alternatively by a suitable method. The selection of the method preferably takes place according to the type of material or type of fabric of the laundry to be dried in each case. For example, in microfiber, a method is used in which the temperature difference of the temperature of the surface of the laundry 14 and the temperature of the exhaust air and / or the supply air is used to terminate the drying process. For terryclothes, on the other hand, a process is used in which the temperature rise in a time window is used to determine the most favorable end of the drying phase. Other methods are preferred for other types of laundry.

The eligible types of laundry are programmed into the PLC 21. It is then before starting the drying only in the controller, that is, the PLC 21, each to be dried laundry type that corresponds to an entered type of laundry to select. Thereafter, the drying process is automatically controlled by the PLC 21 performs the drying of a suitable method for the type of laundry or the material of the laundry, which has been assigned in the programming of the SPS 21 of each stored therein type of goods (type of material and / or type of fabric) is. According to the applicable method described above, the drying operation is then controlled, in particular, the end of the drying process precalculated and the drying process finished at the calculated time. The prediction of the end of the drying process is thus carried out according to the invention always according to such a method that is particularly suitable for the particular laundry to be dried or has been found to be particularly suitable. In an analogous manner to what has been described above, the cooling phase is controlled by the PLC 21 as a function of the material or fabric of the respectively dried item of the laundry. Due to the selected type of laundry follows as needed, so if it is for the respective Goods is provided on the dry phase, a cooling phase, in a manner provided for the respective type of goods, in particular Zeidauer.

The methods described above are suitable for both dryers 10 used in commercial laundries and dryers in the home (household dryers). The invention is not limited to the initially described by way of example dryer 10; is more suitable for any dryer.

LIST OF REFERENCE NUMBERS

10

dryer

11

casing

12

drum

13

loading door

14

Laundry

15

heater

16

Warm air flow

17

exhaust air flow

18

Power line

19

heating valve

20

actuator

21

SPS

22

infrared sensor

23

temperature sensor

24

temperature sensor

Claims (15)

1. Method for drying laundry (14), with the damp laundry (14) being subjected to the action of warm air, in the process a plurality of temperatures of the laundry (14) being measured at least during a specific time period of the drying process, a time for ending the drying process being determined from these measured temperature values, and the laundry then optionally being cooled, characterized in that the measured temperature values obtained from the measured temperatures of the laundry (14) are compared with reference curves and the time for ending the drying process is taken from the matching or closest reference curve.
2. Method according to Claim 1, characterized in that the temperature is preferably determined at the surface of the laundry (14) in that phase of the drying process in which warm air (warm air flow 16) is supplied to the laundry (14).
3. Method according to Claim 1 or 2, characterized in that the time for interrupting the supply of warm air (warm air flow 16) is determined on the basis of prespecified temperature values using the determined temperature of the laundry (14).
4. Method according to one of the preceding claims, characterized in that the time for ending the drying process with warm air (warm air flow 16) is taken from the selected reference curve.
5. Method according to one of the preceding claims, characterized in that a curve line is determined or formed from the measured temperature values of the laundry (14) and this curve line is compared with the reference curves, with that reference curve preferably being selected which has the respective curve line or at least comes closest to it.
6. Method according to one of the preceding claims, characterized in that the reference curves are determined from reference measured temperature values during the drying process, preferably the entire drying process with at least warm air (warm air flow 16), as a function of the type, in particular the material, of the laundry (14) and/or the loading of the dryer (10), preferably of the drum (12).
7. Method according to one of the preceding claims, characterized in that the temperature of the laundry (14) is measured several times, at least twice, during a specific time interval and the time-related rise in temperature, in particular the gradient of the temperature profile, is determined from these measured temperature values, and the time for ending the drying process, in particular switching off the warm air supply (warm air flow 16), is determined from the time-related rise in temperature, with the time interval preferably beginning only after a specific start time of the drying process.
8. Method according to one of the preceding claims, characterized in that the time for ending the drying process, in particular for switching off the warm air supply (warm air flow 16), is determined as a function of the rise in temperature over time, taking into account the type of laundry, preferably the material of the laundry (14), and/or the degree of loading of the dryer (10).
9. Method according to one of the preceding claims, characterized in that the time for ending the warm air supply to the laundry (14) is determined, in particular predetermined, as a function of the rise in temperature over time within the specific time interval.
10. Method according to one of the preceding claims, characterized in that the temperature of the laundry (14) which is measured during the drying process is compared with the temperature of the supplied warm air (warm air flow 16) and/or the discharged air (discharge air flow 17), and the drying process is ended when there is a specific temperature difference.
11. Method according to one of the preceding claims, characterized in that the temperatures are determined and compared continuously or in successive, preferably uniform, time intervals, with simultaneously determined temperatures being compared in particular, and the drying process, in particular the warm air supply (warm air flow 16), being ended preferably when a specific temperature difference is reached.
12. Method according to one of the preceding claims, characterized in that the drying process is ended as soon as the measured temperature of the laundry (14) has reached a prespecified temperature limit value.
13. Method according to Claim 12, characterized in that the temperature limit value is determined as a function of the type, in particular the material, of the laundry (14).
14. Method according to one of the preceding claims, characterized in that the temperature limit value is determined on the basis of experimental curves of the respective type, in particular of the respective material, of the laundry (14) and/or the degree of loading of the dryer (10).
15. Method according to one of the preceding claims, characterized in that the temperature of the laundry (14) is determined at the surface of the said laundry in a contactless fashion, preferably by at least one infrared sensor (22).

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