Technical Field

The invention relates to a dryer, in particu lar a laundry dryer or a washer-dryer, with a self-clean ing program. Self-cleaning particularly comprises at least one of decalcifying and disinfecting.

Background Art

Conventional laundry dryers or washer-dryers are often polluted in use, e.g. due to depositing lint, scale and/or microorganisms. This is particularly true for a heat pump in such devices comprising an evaporator and a condenser for drying laundry. The deposits may have various undesired effects: polluted laundry, unhygienic laundry and/or a reduced heat transfer at the heat pump and hence a higher energy consumption or less dry laun dry. Furthermore, the deposits may lead to failures in other elements of the device, e.g. by clogging of a fil ter or pipe. For these reasons, conventional laundry dry ers and washer-dryers require maintenance in regular time intervals, often by trained maintenance personnel, which is time consuming and expensive.

In order to reduce deposits, filters are built into the systems for air circulation and water cir culation. However, also these filters are prone to failures and require maintenance.

WO 2019214807 A1 describes a method for oper ating a washer-dryer with a heat pump, wherein rinsing water is fed to at least one of the condenser and the evaporator for removing lint, and at least a part of the rinsing water is guided to the drum and used as process water for washing laundry. Disclosure of the Invention

The problem to be solved by the present invention is to provide a dryer which requires less mainte nance .

This problem is solved by a dryer with a self-cleaning program. The dryer may e.g. be a washer- dryer, i.e. a combination device for washing and drying laundry, or a laundry dryer, i.e. a device with drying but no washing functionality. Specific features of the washer-dryer and the laundry dryer, respectively, are described later.

Dryer in general

The dryer in general comprises

- a rotatable drum: In regular operation, the drum receives the laundry to be dried.

- a heat pump: The heat pump has an evapora tor and a condenser for drying and heating process air during laundry drying.

- an air circulating system: The system con nects the drum to the evaporator and the condenser. The system comprises a ventilator configured to circulate air between the drum, the evaporator and the condenser.

- a cleaner circulating system: This system is connected to at least one of the evaporator and the condenser. It comprises a pump configured to circulate a liquid cleaner along at least one of the evaporator and the condenser.

- a control unit: The control unit is config ured to carry out the self-cleaning program. This program comprises circulating the cleaner along at least one of the evaporator and the condenser.

In particular, the cleaner comprises water.

In an embodiment, the cleaner comprises at least one of a decalcifier and a disinfectant. The decalcifier typically comprises an acidic compound, e.g. acetic acid, citric acid, glycolic acid, formic acid, phosphoric acid, sulfamic acid and/or hydrochloric acid. The disinfectant may comprise one or more of the group of alcohols, aldehydes, oxidizing agents, peroxy and peroxo acids, phenolics, quaternary ammonium compounds, chlorine, iodine and ter- penes .

The effect of circulating the cleaner along at least one of the elements evaporator and condenser is that the at least one element is cleaned and in particular decalcified, i.e. descaled, and/or disinfected. This in turn improves a heat transfer between the at least one element and the process air, which is dried, in particular by cooling, and heated during laundry drying. Moreo ver, the cleaning of the at least one element leads to clean laundry, in particular with less deposition of lint on the laundry. Also, the cleaning of the at least one element may lead to a hygienic laundry, in particular with less bacteria on the laundry.

In an embodiment, the air circulating system may hence be free of any lint filter. This leads to a simpler operation of the dryer by a user since no lint filter must be cleaned or exchanged.

In general, the dryer with self-cleaning pro gram has the advantage that it is reliable, i.e. less prone to failure, and in particular has a longer lifetime than a conventional dryer. Besides, it requires less maintenance and is thus more user-friendly and cheaper in operation.

In an embodiment of the dryer, the condenser is located above the evaporator, wherein "above" or "higher" is defined as opposite direction to the gravita tional force when the dryer is oriented in its intended orientation for drying laundry. The arrangement of the condenser above the evaporator simplifies the path of the process air when circulating along evaporator and conden ser since the heating of the process air at the condenser supports the circulation imposed by the ventilator. For a similar reason, namely improving the cleaning effect, it is advantageous that circulating the cleaner along at least one of the evaporator and the condenser is performed in a top-down direction. In that way, lint, scale and other deposits are swept away supported by the gravi tational force.

In an advantageous embodiment, the self cleaning program comprises circulating the cleaner to at least one of the elements to-be-cleaned, for at least 1 min, in particular for at least 5 min, more particu larly for at least 10 min. This leads to a thorough cleaning of the element and is particularly important in case the element is polluted with persistent scale and/or bacteria .

Further, it is advantageous that the control unit is configured to carry out the self-cleaning program dependent on at least one of several criteria:

- A regular time interval has passed. In par ticular, it may be desired to clean the at least one element once per month.

- The dryer has been used a certain number of times since the self-cleaning program was last carried out. In particular, the at least one element may be cleaned once every 20 uses.

- A pollution of at least one of the evapora tor and the condenser exceeds a pollution threshold as sensed by a pollution sensor. Such sensor may sense a pressure drop or a temperature difference over the evapo rator and/or the condenser, or a weight or thickness of deposits on the evaporator and/or condenser. Alterna tively, it may sense a quality or a pollution of the process air after passing the heat pump.

Also, there may be conditions that prohibit carrying out the self-cleaning program. In particular, the control unit may be configured to carry out the self cleaning program only if a temperature of the condenser is below a threshold temperature, in particular below 50°C. In this way, an immediate re-deposition of particularly scale on the condenser due to evaporation of water is reduced. Alternatively or additionally, the control unit may be configured to carry out the self-cleaning program only if no laundry is present in the tub. In order to sense the presence of laundry in the tub, the dryer may comprise a dedicated sensor, e.g. a scale.

Washer-dryer

In an embodiment, the dryer is a washer- dryer. Advantageously, the washer-dryer additionally comprises a tub: The drum is rotatably placed in the tub. By rotating the drum in a bath with detergent in the tub, laundry placed in the drum may be washed. Further, the cleaner circulating system is additionally connected to the tub and configured to circulate cleaner between the tub and at least one of the evaporator and the condenser. Advantageously, the pump is located below a defined cleaner level in the tub. In particular, the self-clean ing program comprises receiving cleaner in the tub up to the defined cleaner level, and circulating cleaner be tween the tub and at least one of the evaporator and the condenser. The location of the pump below the defined cleaner level in the tub facilitates the functioning of the cleaner circulating system since the cleaner will always reach the pump when filled up to the defined cleaner level.

Advantageously, the self-cleaning program further comprises prompting a user to feed at least one of a decalcifier and a disinfectant to the drum, in par ticular up to the defined cleaner level. Such prompt may be output via a display of the washer-dryer. Further, the self-cleaning program may comprise checking if the tub is filled with the cleaner up to the defined cleaner level. In particular, the pump is only operated when this check is positive.

In an embodiment, the evaporator and the condenser are located above a regular water level in the tub for washing. This ensures that in normal operation, i.e. for washing laundry, the water or detergent from the tub does not reach the evaporator and the condenser. Further, the evaporator and the condenser may in particular be lo cated above the defined cleaner level, which in particu lar is higher than the regular water level. Thus the cleaner only reaches the evaporator and the condenser if the pump is operated.

In an embodiment, the pump additionally ful fils another purpose: The pump is further configured to convey rinsing water from an external water supply to at least one of the evaporator and the condenser for removing lint. The control unit is further configured to carry out a washing program which comprises conveying rinsing water to at least one of the evaporator and the condenser. In particular, a majority, more particularly at least 90%, of the water from the external water supply is used as rinsing water. Further, the washing program com prises guiding at least part of the rinsing water to the drum and using it as process water for washing laundry.

In this way, water that is anyways required as process water is additionally used as rinsing water, which makes the washer-dryer more water-efficient. Besides, this amounts to a removal of lint during every washing process which makes the heat transfer at the evaporator and/or condenser more efficient and hence saves energy.

Advantageously, the washer-dryer additionally comprises another pump located below the tub and config ured to circulate water between the tub and an upper part of the drum for washing laundry. For this purpose, the water in particular comprises a detergent. The other pump is regularly operated during the washing program. It re distributes the water over the laundry in the drum and leads to a homogeneously good washing result.

In an embodiment, the drum of the washer- dryer comprises at least one chamber that is fillable with water for reducing an unbalance of the drum. In that case the washer-dryer advantageously also comprises a compensation water circulating system connecting the tub to the at least one chamber. The compensation water circulating system comprises a compensation pump located below the defined cleaner level and configured to circulate cleaner between the tub and the at least one chamber. In particular, the compensation pump may coincide with the pump of the cleaner circulating system. In this case, the self-cleaning program further comprises circulating cleaner between the tub and the at least one chamber.

This has the advantage that the at least one chamber may regularly be cleaned and a clogging prevented.

In a further embodiment, the washer-dryer ad ditionally comprises a detergent tank connected to the drum: The detergent tank may receive detergent that is to be used for washing laundry. In particular, the detergent tank may be implemented as a detergent drawer. Advanta geously, the washer-dryer further comprises a tank cleaner circulating system connecting the tub to the detergent tank: The tank cleaner circulating system com prises a pump located below the defined cleaner level and configured to circulate cleaner between the tub and the detergent tank. Again, this may in particular be the pump of the cleaner circulating system. In this case, the self-cleaning program further comprises circulating cleaner between the tub and the detergent tank. Thus, also the detergent tank may be cleaned, in particular decalcified and/or disinfected.

With respect to the different described cir culation systems, it is advantageous that at least one of the cleaner circulating system, the compensation water circulating system and the tank cleaner circulating system comprise a valve controllable by the control unit. In particular, the self-cleaning program further comprises switching between circulating cleaner to the evaporator and at least one of the condenser, the at least one chamber and the detergent tank. Further, it is advantageous that the self-cleaning program further comprises circulating more cleaner to the evaporator and/or the conden ser than to the at least one chamber and/or the detergent tank. Such focus on the evaporator and/or the condenser helps cleaning the elements where most deposits occur and/or where the removal of the deposits is most important, in particular for a maintenance-free and energy- efficient operation of the washer-dryer.

Laundry dryer

In a different embodiment, the dryer is a laundry dryer, i.e. does not have washing functionality. As a laundry dryer conventionally is not connected to an external water supply, the cleaner circulating system may be configured differently than in a washer-dryer. Advan tageously, the laundry dryer comprises a cleaner tank with an inlet, in particular for receiving cleaner from a user. The cleaner circulating system is additionally connected to the cleaner tank and configured to circulate cleaner between the cleaner tank and at least one of the evaporator and the condenser. In this case, the self cleaning program comprises receiving cleaner in the cleaner tank via the inlet, and circulating cleaner be tween the cleaner tank and at least one of the evaporator and the condenser. The inlet may be located on a front side or a top side of the laundry dryer, in particular on the side where laundry is put into the drum.

Advantageously, the self-cleaning program of a laundry dryer comprises prompting a user to feed at least one of a decalcifier and a disinfectant to the in- let. Such prompt may be output on a display of the laundry dryer. For cleaning the evaporator and/or condenser, a small amount of cleaner may be sufficient, particularly less than 0.51, more particularly less than 0.21.

Other advantageous embodiments are listed in the dependent claims as well as in the description below.

Brief Description of the Drawings

The invention will be better understood and objects other than those set forth above will become apparent from the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

Fig. 1 shows a schematic view of a washer- dryer with a cleaner circulation system according to a first embodiment of the invention;

Fig. 2 shows a schematic view of a washer- dryer with a tank cleaner circulation system according to a second embodiment of the invention;

Fig. 3 shows a schematic view of a washer- dryer with a compensation water circulation system ac cording to a third embodiment of the invention;

Fig. 4 shows a schematic view of a laundry dryer with a cleaner circulation system according to a fourth embodiment of the invention.

Modes for Carrying Out the Invention

The first, second and third embodiment below relate to a washer-dryer, the fourth embodiment to a laundry dryer. All embodiments share the common features of a drum 10, wherein the laundry is placed for regular operation, i.e. for drying and, if applicable, washing. In regular operation, the drum 10 is rotated, e.g. intermittently. During drying, air that is in contact with the wet laundry takes up humidity. The humid air a2 is then transported to a heat pump 20, e.g. by a duct. The heat pump 20 comprises an evaporator 22 and a condenser 21.

The humid air a2 is first cooled at the evaporator 22, in particular below its dew point. Thus, a part of the hu midity condenses as water and is led away or re-used, e.g. for cleaning purposes. Then the air is heated at the condenser 21, thus lowering its relative humidity. Such dry air al is finally recirculated to the drum 10 with the help of a ventilator VI. Such air circulation system between drum 10 and heat pump 20 may be combined with further features such as a recirculation of the condensed water through the heat pump 20 for cleaning the evapora tor 22 and/or the condenser 21, e.g. from lint.

First embodiment

Fig. 1 shows a washer-dryer according to a first embodiment. It comprises a cleaner circulating sys tem with a pump PI. The pump PI is connected to the tub 11, in which the drum 10 is rotatably placed, e.g. by a duct. Further, the pump PI is connected to at least one of the evaporator 22 and the condenser 21. The cleaner circulation is closed by a connection between the evapo rator 22 and/or the condenser 21 and the tub 11.

While the tub 11 is shown as a cylinder, it may in general be implemented in various shapes, e.g. in the shape of a cuboid. The cleaner may e.g. be water, but it may also further comprise a decalcifier and/or a disinfectant. For executing the self-cleaning program, the tub 11 is filled with the cleaner up to a defined cleaner level ml. The pump Pi is located below the defined cleaner level ml in order to receive the cleaner. The de fined cleaner level ml may be higher or lower than the water level m2 during a regular washing program. For the heat pump 20, it is advantageous to be arranged above the defined cleaner level ml as well as the water level m2.

Advantageously, no laundry is present inside the drum 10 during the self-cleaning program. Otherwise, the cleaner may damage the laundry. During the self cleaning program, the pump Pi pumps cleaner cl from the tub 11 to at least one of the elements of the heat pump

20, in particular the evaporator 22 and/or the condenser

21. The element is cleaned mechanically and/or chemically by the cleaner c2. In particular, deposits like lint or scale are removed and/or the element is disinfected. Then the cleaner c3 together with any removed deposits or the like is re-directed to the tub 11. The cleaner circulation is iterated and performed for a defined time, e.g. at least 10 min, for a sufficient cleaning result.

The pump PI may be used for a further pur pose, namely circulating water wl from an external water supply 30 to at least one of the elements of the heat pump 20. Such circulation may be performed outside the self-cleaning program, e.g. during the regular washing program. Advantageously, all of the water from the external water supply 30 or at least a majority of it is directed to the evaporator 22 and/or the condenser 21. There, the water w2 removes lint and further deposits. Then the water w3 together with lint and deposits is directed to the tub 11 and used as process water for washing laundry.

Fig. 1 also shows a control unit 40 which is configured to control the operation of the washer-dryer. In particular, the control unit 40 is configured to carry out regular washing and drying programs as well as the self-cleaning program. The control unit 40 may be con nected to input buttons for receiving a user input, e.g. a choice of program by the user. Further, the control unit 40 may be connected to a display as output unit, which may inform the user of a current status of the washer-dryer or any running program. Additionally, the display may prompt a user action such as a recommended operation of the self-cleaning program of filling cleaner in to the tub 11.

Due to the self-cleaning program cleaning the evaporator 22 and/or the condenser 21, the washer-dryer reliably works for a long time, e.g. for more than 5 years, without a lint filter in the air circulation system and without the necessity of a maintenance.

Second embodiment

Fig. 2 shows a second embodiment of the washer-dryer. Here, the cleaner circulation system is ex tended compared to the first embodiment.

Such washer-dryer additionally comprises a detergent tank 50 for feeding detergent dl to the drum 10 with the laundry to-be-washed. For that purpose, the detergent tank 50 is connected to the external water supply 30, from where it receives water w4 flushing the deter gent to the drum 10. This connection is advantageously controlled by a valve 51 that controls the amount of wa ter w4 to the detergent tank 50 relative to the amount of water wl to the pump PI. Advantageously, the ratio w4/wl is at most 1/9.

Fig. 2 further shows another pump P2 connected to and located below the tub 11. Pump P2 is configured to circulate the process water, in particular containing detergent, inside the tub 11 and the drum 10. Pump P2 is advantageously separate from the cleaner circulating pump PI since the process water in contact with pump P2 contains a lot of lint, which may be counterproductive for the cleaning purpose of pump PI.

The detergent dl from the detergent tank 50 may be fed into this circulation of process water as shown. An advantageous feature of the second embodiment is the circulation of cleaner c4 to the detergent tank 50, which may be controlled by valve 52. In this way, the pump PI may also be used to clean, in particular decalcify and/or disinfect, the detergent tank 50 during the self-cleaning program. After cleaning the detergent tank 50, the cleaner is directed to the drum 10 or the tub 11, respectively, as the detergent dl during a regular washing program.

Third embodiment

Fig. 3 shows a third embodiment of the washer-dryer. Again, the cleaner circulation system is extended compared to the first embodiment. The third embodiment may also be combined with the second embodiment.

In the third embodiment, the drum 10 comprises compensation chambers 12, which may receive water from the external water supply 30 via valve 54. The com pensation chambers 12 may be filled with water entirely or partially as counter-weight to the laundry during washing, in particular during the spin cycle centrifuging water out of the laundry. Thus, the compensation chambers 12 reduce an unbalance of the drum 10 when rotating.

However, also such compensation chambers 12 may suffer from deposits such as scale or from pollution. According to the third embodiment of the invention, the compensation chambers 12 are hence connected to the cleaner circulation system. The pump PI and the valve 53 may hence be controlled to circulate the cleaner additionally through the compensation chambers 12 during the self-cleaning program.

As in the previous embodiments, the cleaner circulation system thus enables a reliable operation of the washer-dryer which in particular is maintenance-free.

Fourth embodiment Fig. 4 shows a laundry dryer according to a fourth embodiment of the invention. As in the previous embodiments, also the heat pump 20 of a laundry dryer may suffer from deposits and/or pollution on the evaporator 22 and or the condenser 21. This may lead to dirty laundry after drying and in the worst case to a spreading of pathogens, in particular due to the hot and humid condi tions .

As a remedy, the laundry dryer of Fig. 4 com prises a cleaner tank 60, which may be filled by the user. The cleaner tank 60 is again connected to a cleaner circulation system comprising a pump Pi. During the self cleaning program, the pump PI circulates cleaner cl from the cleaner tank 60 to the evaporator 22 and/or the con denser 21. There, the cleaner c2 removes deposits such as lint and in particular scale and other pollutions. Since the cleaner c3 may be recirculated directly to the evapo rator 22 and/or the condenser 21, only a small amount of cleaner is needed for the self-cleaning program; an amount of 0.3 to 0.61 of cleaner may be sufficient.

Additionally, the cleaner circulation system may be used to circulate water condensed at the evapora tor 22 during a regular drying program. Such condensed water may be collected in a water tank, in particular in the cleaner tank 60, and used to rinse the heat pump 20 before and/or after the regular drying program.

The cleaner tank 60 may have a larger volume than required for one operation of the self-cleaning program. In that case, the control unit 40 may be configured to perform the self-cleaning program automatically, i.e. without a user interaction, if one or more of the crite ria discussed before are fulfilled.

Such laundry dryer is reliable, hygienic and requires minimum maintenance by the user or by technical personnel.