EP0424781B1 - Household laundry drier - Google Patents

Abstract

To increase the effectiveness of and shorten the entire drying process, in laundry dryers the invention provides for driving their laundry drum and air-circulating blower from a single motor in a reversing manner and for giving the duration of the preferred direction of rotation of the blower in comparison with the duration of its opposite direction a design ratio of approximately 1:10 to approximately 1:50 during the heating phase. <IMAGE>

Description

The invention relates to a household tumble dryer with a horizontally rotatably mounted laundry drum and a drive motor, which at the same time drives the laundry drum and a fan, which is used to transport air flowing past a radiator through the laundry drum, and with a program sequence in at least 4 phases, namely a heating phase, a moisture expulsion phase, a post-drying phase and a cooling phase, whereby during the post-drying phase the respective duration of the drive phases in which the fan runs with the intended direction of rotation (preferred direction) is longer than the respective duration of the drive phases with the opposite direction of fan rotation (Opposite direction).

Such a tumble dryer is known from European patent application 328 250. In order to avoid that in such a known tumble dryer the drying air heated much higher in the opposite direction can damage the laundry, it is specified that the ratio of the drive times in the preferred direction and in the opposite direction is greater than 2: 1, 4: 1 or 8: 1 should be. Such a way of working contributes to protecting the laundry, but is only necessary as soon as the laundry is almost or completely dry. However, such an operating mode can lead to an acceleration of the drying program even when the heating is switched off in the cooling phase.

The object of the invention is to further reduce the amount of heating energy required in a household tumble dryer mentioned at the outset compared to the prior art and to further shorten the time required for drying.

According to the invention, this object is achieved in that during the heating phase the duration of the preferred direction has a ratio of approximately 1:10 to approximately 1:50 compared to the duration of the opposite direction. Due to the substantial increase in the on-time of the opposite direction compared to the on-time of the preferred direction, the temperature level of the drying air can be kept very high during the heating phase without the laundry, which is contaminated with a considerable amount of water, being damaged. On the one hand, the water remaining in the laundry cannot assume a temperature higher than 100 ° C and, furthermore, the temperature at the laundry is kept considerably below 100 ° C due to the evaporation heat extraction already beginning at far lower temperatures. However, the higher temperature level during the heating phase allows the washing and drying system to reach the temperature level required for the moisture expulsion phase in a considerably shorter time, so that this heating phase becomes significantly shorter than in the prior art. This can significantly shorten the entire drying program.

A further shortening of the drying program results from an advantageous further development of the invention, in which during the cooling phase the duration of the preferred direction has a ratio of approximately 10: 1 to approximately 50: 1 compared to the duration of the opposite direction. The heating is not switched on during the cooling phase; only cool air is blown through the laundry. In order to maintain the drum reversing on the one hand so that the laundry does not become tangled up but on the other hand to accelerate the cooling phase, it is particularly advantageous to let the fan run longer in the preferred direction than in the opposite direction.

Likewise, such an operation, as is known per se from the prior art, is advantageous during the post-drying phase. A ratio of approximately 5: 1 to approximately 50: 1 for the duration of the preferred direction compared to the duration of the opposite direction has proven to be particularly advantageous for this.

In contrast, the drying process can be adapted even more optimally to the residual moisture in the laundry which gradually decreases during the drying in the moisture expulsion phase. For this purpose, according to a further embodiment of the invention, a ratio of approximately 1: 5 to approximately 5: 1 can be set for the duration of the preferred direction compared to the duration of the opposite direction. The selection of a ratio between the specified ratio limits can be determined, for example, by the type of laundry to be dried. This information is given by the operator when setting a drying program by actuating the handles provided for this purpose. For example, a ratio of about 1: 5 can be selected when drying cotton laundry, which can be subjected to significantly higher temperatures, while a ratio of about 5: 1 can be selected for drying laundry that is not as highly temperature-resistant (e.g. synthetics) Duty cycle of the preferred direction compared to the opposite direction the general temperature level is lower. In the same way, ratio choices can be made depending on the amount of initial residual moisture in the laundry, i.e. the speed at which the laundry was previously spun.

In a particularly advantageous manner, the invention can be further developed in that the ratio can be changed smoothly or in stages from about 1: 5 to about 5: 1 in the course of the moisture expulsion phase. Since the residual moisture in the item of laundry decreases in the course of the moisture expulsion phase, the duty cycle ratio can be changed from initially, for example, 1: 5 to approximately 5: 1 towards the end of the moisture expulsion phase in order to make the temperature level in the laundry more uniform.

Fig. 1

eine schematische Innenansicht eines Wäschetrockners und

Fig. 2

eine schematische Ansicht eines Gebläses mit spiralförmigem Gehäuse.

The invention is explained below using the exemplary embodiment shown in the drawing. Show it:

Fig. 1

a schematic interior view of a clothes dryer and

Fig. 2

a schematic view of a fan with a spiral housing.

The tumble dryer shown in Fig. 1 has a laundry drum 1 which is rotatably mounted about a horizontal axis. Its front drum opening opens into a fixed porthole 2, which on its underside has an opening covered with a sieve to an exhaust air duct 3, which opens axially to an impeller 4 in the spiral housing 5. The fan wheel is driven by an electric motor 6, on the armature shaft of which, in addition to the fan wheel 4, there is also a drive pinion which is partially wrapped around by a belt 7 which is stretched over the jacket of the laundry drum 1. The drying air sucked out of the laundry drum is fed to a duct system 8, which can contain, for example, a condenser (not shown) in order to condense the moisture out of the exhaust air. In the case of an exhaust air dryer, this duct system 8 can contain openings (not shown) for blowing off the exhaust air and drawing in the fresh air. In the supply air duct 9, a heating device 10 is arranged, around which the supply air flows. The heated supply air finally passes through the rear drum bottom sieve 11 into the laundry drum 1.

The reversing operating mode of the laundry drum has proven to be advantageous so that the laundry item lying in the laundry drum and to be dried is not wound into a ball during the drying process. In general, the reversing ratio, that is the duty cycle of the drive motor 6 in the clockwise direction of the drum to the duty cycle in the counterclockwise direction, is set to 1: 1.

The drum is moved in this way during all phases of the drying process. The first operating phase is the so-called heating phase and serves to set the so-called static state with a temperature level at which the amount of heating heat supplied is balanced by the amount of evaporation heat absorbed when the laundry moisture evaporates. This static state is maintained in the subsequent moisture expansion phase. From a certain amount of the sinking residual moisture, this absorbed amount of evaporation heat becomes so small that the temperature level in the laundry very quickly increases. At this point the post-drying phase begins, which is essentially characterized in that the temperature level maintained in the moisture expulsion phase is essentially maintained by reducing the amount of heat supplied. In this post-drying phase, which is generally time-controlled, the residual moisture in the laundry can be reduced to a desired value depending on its duration. At the end of this post-drying phase, the cooling phase follows, in which the drying air continues to be blown through the laundry without heating. As a result, the constantly moving laundry cools down without creasing. On the other hand, this also avoids unpleasant touches of the operator's hands with the hot laundry.

A blower for the drying air is generally a so-called radial blower, as shown in Fig. 2. In it, the impeller 4 has a series of at least approximately radially standing air blades, which centrifugally centrifugally throws off the air hitting the impeller. The pressure that builds up on the circumference of the impeller 4 flows off in the direction of the arrow VS via the fan housing 5, which gradually widens in the direction of rotation of the impeller (preferred direction VR). If the impeller 4 rotates in the opposite direction GR, there is also an air flow GS, which, however, is considerably smaller than the preferred direction flow VS because of the unfavorable shape of the fan housing 5 in this direction of rotation. This is made clear by the arrows VS and GS of different lengths.

According to the invention, the ratio of the on-time of the preferred direction VR compared to the on-time of the opposite direction GR is set to about 1:10 to about 1:50 during the heating phase. As already explained above, this results in a higher temperature level of the incoming drying air during the heating phase, which means that both the moisture-laden laundry and the entire drying system heat up considerably faster than with a reversing ratio of about 1: 1 in accordance with the previously customary procedure. If the process sequence described in EP-A-328 250 is used, in which the duration of the preferred direction compared to the duration of the opposite direction has a ratio of at least 2: 1, the heating-up phase is even extended compared to previous practice.

In addition, a ratio of the duty cycle of the preferred direction compared to the opposite direction of approximately 10: 1 to approximately 50: 1 during the cooling phase is particularly advantageous with regard to the shortening of the overall process time. As a result, the cooling air throughput through the laundry drum can be increased considerably compared to the tumble dryer known from EP-A-328 250, without the laundry thereby being damaged or even becoming entangled when shortened reversing.

During the post-drying phase, a reversing ratio of 5: 1 to about 50: 1 has proven to be favorable, the setting of the ratio again being dependent on the type of laundry item; for cotton laundry closer to 5: 1, for synthetic laundry closer to 50: 1.

It is particularly advantageous to adapt the reversing ratio to the progress of the drying process during the moisture expulsion phase. With initially high residual moisture, the temperature level of the incoming drying air can be relatively high, so that a reversing ratio of about 1: 5 can prove to be favorable. In the course of the drying progress, this ratio can be changed slowly towards 1: 1 or beyond 1: 1 after about 5: 1 towards the end of the moisture expulsion phase, at which the residual moisture reached is only comparatively low (e.g. 20%) .

The setting of the reversing ratio between approximately 1: 5 and approximately 5: 1 can be made dependent on the laundry item to be processed, either alone or in addition. This affects both the amount of laundry to be dried and the type of fabric. With a large amount with a correspondingly large amount of moisture, the reversing ratio can be closer to 1: 5 than with a smaller amount of laundry with a smaller amount of moisture. Accordingly, the reversing ratio can be 1: 5 if the laundry item to be processed consists of a temperature-resistant natural fiber, e.g. Cotton or linen. In contrast, a reversing ratio towards 5: 1 should be set if the item of laundry to be processed is composed of temperature-sensitive laundry, e.g. certain synthetic fibers.

Claims (5)

1. Domestic laundry drier with a washing drum (1), which is borne to be horizontally rotatable, and a drive motor (6), which reversingly and simultaneously drives the washing drum and a fan (4), which serves for the transport of air flowing past a heating element (10) and through the washing drum, and with a program sequence in at least four phases, namely a heating phase, a moisture expulsion phase, a further drying phase and a cooling phase, wherein the respective duration of the drive phases, in which the fan runs with intended direction of rotation (preferred direction), is longer during the further drying phase than the respective duration of the drive phases with opposite direction of fan rotation (opposite direction), characterised thereby, that the duration of the preferred direction (VR) has a ratio of about 1:10 to about 1:50 by comparison with the duration of the opposite direction (GR) during the heating phase.
2. Domestic laundry drier according to claim 1, characterised thereby, that the duration of the preferred direction (VR) has a ratio of about 10:1 to about 50:1 by comparison with the duration of the opposite direction (GR) during the cooling phase.
3. Domestic laundry drier according to claim 1 or 2, characterised thereby, that the duration of the preferred direction (VR) has a ratio of about 5:1 to about 50:1 by comparison with the duration of the opposite direction (GR) during the further drying phase.
4. Domestic laundry drier according to one of the preceding claims, characterised thereby, that the duration of the preferred direction (VR) has a ratio of about 1:5 to about 5:1 by comparison with the duration of the opposite direction (GR) during the moisture expulsion stage.
5. Domestic laundry drier according to claim 4, characterised thereby, that the ratio is variable continuously or in steps from about 1:5 to about 5:1 in the course of the moisture expulsion stage.

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