Patent Description:
State of the art domestic laundry dryers are heavy appliances that occupy a large volume of space. Therefore, they are not very suitable for being installed in a small apartment or kitchenette.

<CIT> relates to a laundry washing and/or drying machine comprising a heat pump which is arranged in the rear part of the machine. <CIT> describes a laundry drying appliance with a heat pump arranged in the rear part of the machine. The evaporator can automatically be cleaned in order to remove possible fluff that is not retained by the defluff filter.

The problem to be solved by the present invention is therefore to provide a compact domestic laundry dryer.

This problem is solved by the subject of the independent claim.

Accordingly, the invention relates to a laundry dryer with a cabinet and a drum, wherein the drum is rotatably placed within the cabinet. Advantageously, the drum has an essentially cylindrical shape with the axis of the cylinder extending horizontally within the cabinet.

The drum has an opening at its front side for loading the laundry, and it is closed at its back side, i.e. at the end of the drum facing away from the front side.

The laundry dryer further comprises a heat pump with a condenser and an evaporator. The condenser and the evaporator are arranged on the back side of the drum.

The laundry dryer further comprises an air circulating system connecting the drum to the condenser and the evaporator. The air circulating system comprises a ventilator configured to circulate the air in the system from the drum to the evaporator, the condenser, and back to the drum. Advantageously, the ventilator is located between the condenser and the drum, i.e. the air from the condenser passes the ventilator and then enters the drum.

The laundry drier further comprises a control unit adapted and structured to control the operation of the individual components of the device.

At least part of the condenser and of the evaporator are arranged at the back side of the drum. In other words, when viewing the machine from the front side, i.e. the side of the opening of the drum, at least part of the condenser and the evaporator are arranged behind the drum. This allows to exploit space behind the drum.

The condenser as well as the evaporator comprise plates for exchanging heat between the fluid ducts of the heat pump and the process air. Said plates can be aligned vertically.

The shortest distance between individual plates of the condenser is larger than the shortest distance between individual plates of the evaporator. In particular, the distance between the plates of the condenser can be at least twice the distance between the plates of the evaporator.

In an advantageous embodiment of the invention, the laundry dryer is configured to be a washer-dryer with a tub. The drum is rotatably arranged in the tub. The tub retains the process water while washing the laundry.

In a further embodiment, the laundry dryer can be configured to be a dryer only and to perform only a drying of the laundry. In this embodiment, no tub is required.

In a compact embodiment of the device, the condenser and the evaporator are arranged above each other.

Advantageously, the condenser is positioned vertically above at least a part of the evaporator. In other words, when seen from above, the condenser and evaporator overlap.

Advantageously, at least part of a lower end of the condenser is adjacent to at least part of an upper end of the evaporator. Advantageously, the lower end of the condenser fully aligns with the upper end of the evaporator.

Arranging the evaporator below the condenser provides a compact design. Further, it prevents water from the evaporator from entering the condenser as well as from entering the parts of the air ducts that lead air from the condenser back to the drum.

In an advantageous embodiment of the invention, the condenser and/or the evaporator horizontally extends along at least <NUM>%, in particular at least <NUM>%, of the full width of the cabinet, therefore, exploiting the space within the cabinet. The width of the condenser and/or the evaporator is defined to be the widest extension of the condenser or evaporator in the horizontal direction perpendicular to the rotation axis of the drum.

Advantageously, at least a section of the condenser and/or the evaporator is arranged horizontally behind the drum. In other words, when viewing the drum from its front side along its axis of rotation, at least part of the condenser and/or the evaporator is hidden behind it. This provides a compact machine design.

Using plates that are closer to each other in the evaporator than in the condenser improves the lint-filtering effect that can be achieved by means of the evaporator.

In another advantageous embodiment, the laundry dryer comprises a water trough arranged below the evaporator. It can be configured and positioned to collect water, in particular condensed water and/or rinsing water, from the evaporator and or condenser. Further, a water duct connecting the trough to the tub can be provided.

In another advantageous embodiment, the laundry dryer comprises at least one first rinsing duct. Said first rinsing duct is arranged adjacent to the evaporator and has or is connected to a plurality of nozzles directed towards the evaporator.

A further advantageous embodiment comprises at least one further rinsing duct having or being connected to a plurality of nozzles directed towards the evaporator and/or condenser. The further rinsing duct is advantageously arranged above the first rinsing duct.

In a further advantageous embodiment, the laundry dryer comprises three or four rinsing ducts.

Advantageously, the first rinsing duct and the further rinsing duct are mounted directly onto a housing forming an air duct around the evaporator and/or the condenser.

In an embodiment, said first and further rinsing ducts are adapted to rinse lint from the condenser and/or evaporator.

The rinsing ducts are advantageously fed by either water already processed during the washing cycle or by fresh water.

In an advantageous embodiment of the washer-dryer, the device comprises a lint filter arranged in the air circulation system between the drum and the evaporator, i.e. the air from the drum has first to pass the lint filter before it reaches the evaporator, thus reducing the amount of lint accumulating in the evaporator.

In an advantageous embodiment of the laundry dryer as a washer-dryer, the water duct further comprises a siphon. A siphon is an essentially "U"-shaped duct section that forms a trap for water, such that after flushing, an amount of residual water is retained in the siphon. In this embodiment, the siphon prevents air from passing through the water duct (and thereby circumventing the filter) while drying the laundry.

In a further preferred embodiment, the lowest part of the lint filter is arranged higher than a lower end of the evaporator, in particular higher than all the evaporator. This makes it unlikely that water from the evaporator flows into the lint filter.

A further advantageous embodiment of the invention is free of any lint filter apart from the evaporator and condenser. In other words, the air circulation system does not comprise any dedicated lint filter. In particular, there is no lint filter arranged between the drum and the evaporator. Such a device requires less maintenance. In this case, the water duct can be used to guide the moisture-loaded air from the drum to the evaporator and also as a drain for guiding condensed water and rinsing water from the evaporator to the tub or a drain pipe.

<FIG> and <FIG> show an embodiment of a washer dryer comprising a laundry recipient <NUM> with a drum <NUM> arranged in a tub <NUM>. Drum <NUM> is rotatable about an axis of rotation <NUM> by means of a rotation drive (not shown). Axis of rotation <NUM> is substantially horizontal.

Laundry recipient <NUM> is suspended from a yoke <NUM>, which rests on a base frame <NUM>.

The device comprises a cabinet <NUM>, which is also mounted to frame <NUM>.

Cabinet <NUM> is substantially a cuboid having a width w, a height h, and a depth d (<FIG>).

In an advantageous embodiment of the invention, the cabinet has the maximum dimensions of h = <NUM> in height, w = <NUM> in width, and d = <NUM> in depth. These dimensions allow the cabinet to fit into most of the common kitchen cupboards or niches.

On its front side, drum <NUM> comprises a front opening <NUM>, which mates with a door (not shown) in the front side of cabinet <NUM>.

A heat exchanging device <NUM> is arranged at the back side of laundry recipient <NUM>. It is advantageously mounted to laundry recipient <NUM>, i.e. laundry recipient <NUM> bears the weight of heat exchanging device <NUM>.

<FIG> show views of heat exchanging device <NUM> and laundry container <NUM>. A water duct <NUM> connects heat exchanging device <NUM> to drum <NUM>.

Heat exchanging device <NUM> comprises a condenser <NUM> and an evaporator <NUM> of a heat pump <NUM>.

Heat pump <NUM> is schematically shown in <FIG>. It comprises a compressor <NUM> that feeds a heat pump medium to condenser <NUM>, from where it passes an expansion valve <NUM> and enters evaporator <NUM>. From evaporator <NUM>, the fluid returns to compressor <NUM>.

In operation of heat pump <NUM>, the fluid condenses in condenser <NUM>, thereby heating condenser <NUM> up, and it evaporates in evaporator <NUM>, thereby cooling evaporator <NUM> down.

A motor <NUM> is provided for operating pump <NUM>.

As schematically shown in <FIG>, motor <NUM> and compressor <NUM> can be arranged in a foot section of the device.

In an advantageous embodiment, motor <NUM> and compressor <NUM> are vertically arranged. In a further advantageous embodiment, motor <NUM> can further be arranged horizontally beside the compressor <NUM>. Such arrangement allows to exploit unused volume below heat exchanging device <NUM> and/or laundry recipient <NUM>.

Condenser <NUM> is arranged on top of evaporator <NUM>.

Heat exchanging device <NUM> comprises at least a first rinsing duct <NUM>. In addition, there may be further rinsing ducts <NUM>.

Each rinsing duct <NUM>, <NUM> extends in a substantially horizontal direction. Advantageously, for making it easier to drain all water from the rinsing ducts <NUM>, <NUM>, the rinsing ducts <NUM>, <NUM> are arranged, as shown, under a small angle to the horizontal direction, with said angle being e.g. larger than <NUM>° and/or smaller than <NUM>°.

First rinsing duct <NUM> and, in the shown embodiment, the bottommost of the further rinsing ducts <NUM>, are arranged adjacent to evaporator <NUM>. The remaining further rinsing ducts <NUM> are arranged adjacent to condenser <NUM>.

A trough <NUM> is arranged adjacent to the lower end of the evaporator <NUM>. It is configured to collect water from the heat exchanging device <NUM> and in particular from evaporator <NUM>. The water might result from condensation in the evaporator <NUM> or from water that entered heat exchanging device <NUM> through the rinsing ducts <NUM>, <NUM>.

A water duct <NUM> is connected to trough <NUM> and is configured to guide the collected water from trough <NUM> to laundry recipient <NUM>, in particular to a bottom section of tub <NUM>. Alternatively, water duct <NUM> can be connected to a drain pipe of the device.

In the present embodiment, water duct <NUM> also serves to guide moisture-loaded air from the drum to evaporator <NUM>.

As it is best seen in <FIG>, most of heat exchanging device <NUM> is arranged horizontally behind laundry recipient <NUM> and drum <NUM>.

Condenser <NUM> and evaporator <NUM> both have vertically arranged plates <NUM>, <NUM> in order to increase the heat exchanging surface.

The shortest distance between the individual plates <NUM> of condenser <NUM> is larger than the shortest distance of the individual plates <NUM> of the evaporator <NUM>. Therefore, in the shown embodiment, condenser <NUM> comprises a smaller number of plates <NUM> than evaporator <NUM>.

Heat exchanging device <NUM> forms part of an air circulating system best explained in reference to <FIG> and <FIG>.

The air circulating system comprises, apart from heat exchanging device <NUM>, at least the following components:.

Ventilator <NUM> is advantageously arranged at the bottom of the device, i.e. in the lowest <NUM>% of the device. This allows to exploit room that is available there. Also, this design allows to mount ventilator <NUM> on the bottom parts of the device, in particular on frame <NUM>, which allows to reduce the amount of vibration and noise transmitted to cabinet <NUM>.

In the embodiment shown, ventilator <NUM> is a radial ventilator with a substantially vertical axis of rotation, which allows to better exploit the room available at the bottom of the device.

One of the advantages of mounting condenser <NUM> above evaporator <NUM> lies in the fact that any water in evaporator <NUM> and/or condenser <NUM> will flow downwards and not enter first air duct <NUM>. This is particularly true if first air duct <NUM> is connected to the top end of condenser <NUM> as shown.

First air duct <NUM> has an input end 24a located at a top end of condenser <NUM>. Further, it has an output end 24b located below evaporator <NUM> and connected to ventilator <NUM>.

Second air duct <NUM> is connected, at its input end 25a, to ventilator <NUM> at the bottom of the device. Its output end 25b is located at a level higher than the axis of rotation <NUM>, in particular at a level higher than a maximum water level during washing the laundry. This prevents water from entering second air duct <NUM> from that end.

As mentioned, rinsing ducts <NUM>, <NUM> are arranged on heat exchanging device <NUM>. They are best seen in <FIG>, with <FIG> showing the ducts <NUM>, <NUM> in partially cut-off view. As can be seen, each rinsing duct <NUM>, <NUM> carries a plurality of nozzles <NUM> directed towards evaporator <NUM> or condenser <NUM>.

The ducts <NUM>, <NUM> are mounted directly to a housing 2a forming an air duct around evaporator <NUM> and condenser <NUM>. The nozzles <NUM> are e.g. located at openings in housing 2a.

In the embodiment shown, the nozzles <NUM> are elongate slits or other openings arranged in the wall of each rinsing duct <NUM>, <NUM>. Alternatively, the nozzles may also be formed by separate elements from the rinsing ducts <NUM>, <NUM> and be connected thereto.

<FIG> shows a schematic of a laundry dryer, in particular washer-drier. This may e.g. be the device of <FIG> or any other similar device.

As shown, the device comprises heat exchanging device <NUM> with condenser <NUM> and evaporator <NUM>. Condenser <NUM> and evaporator <NUM> each can comprise the plates <NUM>, <NUM>.

Trough <NUM> is arranged underneath heat exchanging device <NUM> to collect water therefrom.

Heat exchanging device <NUM> is connected to ventilator <NUM>. Ventilator <NUM> is configured to circulate air in the device.

A control unit <NUM> is provided to control the components of the device. It is e.g. a microprocessor equipped with suitable software to carry out all operations of the methods described herein.

For example, control unit <NUM> controls ventilator <NUM> and therefore the transport of air through the air circulating system. It can also control the rotation of drum <NUM>, the operation of heat pump <NUM>, the feeding of water through the water ducts <NUM>, <NUM>, etc..

When laundry is to be dried, e.g. at the end of a washing process or in a stand-alone process, control unit <NUM> activates heat pump <NUM> and ventilator <NUM>. Further, drum <NUM> is rotated.

Due to the operation of ventilator <NUM>, moisture-loaded air is drawn from laundry recipient <NUM> and fed from below into evaporator <NUM>. In <FIG>, this wet air is designated as a2.

In evaporator <NUM>, the air is cooled and loses moisture. Condensed water accumulates on the plates <NUM> and/or other parts of evaporator <NUM> and drops down into trough <NUM>.

Next, the dried air rises into condenser <NUM>, where it is heated up again. It leaves condenser <NUM> through its top end.

Finally, the hot, dry air is conveyed back into laundry recipient <NUM>. In <FIG>, this hot, dry air is designated as a1. Advantageously, the air a1 coming from heat exchanging device <NUM> enters drum <NUM> through front opening <NUM>.

In drum <NUM>, the heated and dry air a1 coming from the condenser <NUM> absorbs the water of the wet laundry, whereupon it is returned to evaporator <NUM>.

During this process, the water falling into trough <NUM> flows through water duct <NUM> into the bottom of tub <NUM> and/or directly to a waste water drain.

Control unit <NUM> can operate a drain pump to convey the water from the device.

In an advantageous embodiment, the lowest part of trough <NUM> is located at a higher level m1 than the lowest part of tub <NUM>, which is at a level m2. This design allows to convey water from trough <NUM> to tub <NUM> by means of gravity.

In the embodiment of <FIG>, the device does not contain a fluff filter separate from heat exchanging device <NUM>. Hence, fluff will accumulate in heat exchanging device <NUM> and in particular in evaporator <NUM>.

To remove such fluff, control unit <NUM> can feed water to one or more of the rinsing ducts <NUM>, <NUM>. When doing so, the water will leave the rinsing ducts <NUM>, <NUM> through the nozzles <NUM> and enter the evaporator <NUM> and/or condenser <NUM> for washing the same.

This rinsing water will enter trough <NUM> and water duct <NUM>, where it is guided to tub <NUM> and/or to the drain pipe.

Such a rinsing process can e.g. take place when required, e.g. before, during, or after drying laundry.

As mentioned, the present device can be designed to not only dry laundry but also to wash it. In that case, process water for washing the laundry has to be fed to laundry recipient <NUM>.

Advantageously, at least part of said process water is fed to laundry recipient <NUM> and therefore drum <NUM> through the rinsing pipes <NUM>, <NUM>. This allows to re-use the rinsing water for rinsing the evaporator <NUM> and/or condenser <NUM> as process water in the washing process, thereby reducing the total water consumption.

In one embodiment, not all of the water used for rinsing evaporator <NUM> and/or condenser <NUM> is used as process water for washing the laundry. Rather, control unit <NUM> is adapted to first feed a first batch of water from the rinsing pipe(s) <NUM>, <NUM> through the condenser <NUM> and/or evaporator <NUM> and to discard this first batch from the machine without it coming into contact with the laundry.

Next, control unit <NUM> can feed a second batch of water from the rinsing pipe(s) <NUM>, <NUM> through the condenser <NUM> and/or evaporator <NUM> and to use this second batch for washing the laundry.

This process is based on the understanding that the first batch of water will be heavily contaminated with lint. Hence, discarding it and not using it for washing reduces the amount of lint that comes into contact with the laundry.

In one embodiment, the user may select, depending on the type of laundry and the desired quality of the washing, if the first batch of rinsing water is to be discarded or not.

Once water has been filled into laundry recipient <NUM>, washing proceeds basically as in a conventional machine.

In one advantageous embodiment, the bottom end of evaporator <NUM> is at a level m3 that is higher than a maximum level m4 of the process water in drum <NUM> while washing the laundry. Control unit <NUM> is adapted to keep the water level in drum <NUM> during washing below said maximum level m4. This design prevents washing water from flooding evaporator <NUM> and/or condenser <NUM>.

<FIG> shows a schematic of another advantageous laundry dryer. In contrast to the one of <FIG>, this embodiment comprises a lint filter <NUM> arranged in the path of the air a2 between laundry recipient <NUM> and evaporator <NUM>.

To avoid lint filter <NUM> from coming into contact with water, it is, in this embodiment, not arranged in water duct <NUM>. Rather, a separate air duct <NUM> is provided between laundry container <NUM> and evaporator <NUM>, with laundry filter <NUM> arranged therein.

In this embodiment, water collected by trough <NUM> still flows through water duct <NUM> into tub <NUM>. However, when drying laundry, the air must be forced through filter <NUM>. To do so, a siphon <NUM> is located in water duct <NUM>. Control unit <NUM> is adapted to make sure that water is present in siphon <NUM> while drying. This water blocks water duct <NUM> for air. Thus, when control unit <NUM> activates ventilator <NUM>, the wet air a2 from drum <NUM> passes through air duct <NUM> and filter <NUM> but not through water duct <NUM>. Thus, it is filtered before entering heat exchanging device <NUM>.

In order to prevent water from entering lint filter <NUM>, the lowest part of lint filter <NUM> is advantageously arranged at a level m5 that is above maximum level m4 of the water in drum <NUM> and/or above the level m3 of the lower end of evaporator <NUM>.

Unless otherwise noted, the following advantageous aspects apply to all embodiments of the machine.

As shown above, the machine may comprise several rinsing ducts <NUM>, <NUM>, and control unit <NUM> can be adapted to individually and selectively feed water to said ducts.

This allows to control the order in which the various parts of heat exchanging device <NUM> can be rinsed.

Control unit <NUM> is advantageously adapted to control the rinsing cycle in a sequence of first rinsing evaporator <NUM> and second rinsing condenser <NUM>. This gives the condenser more time to cool before it is flushed with water, which avoids an excessive calcification of condenser <NUM>.

In one embodiment, control unit <NUM> is adapted to only rinse the condenser <NUM> if it has a temperature below a threshold temperature TP, in particular with TP < <NUM>.

The rinsing water can, as mentioned, be collected by means of trough <NUM>. It can be drained from trough <NUM> to drum <NUM> and be reused for the next washing cycle. Alternatively, part or all of it may be discarded and drained from the machine without using it for washing.

In one embodiment, control unit <NUM> can be adapted to rinse evaporator <NUM> and/or condenser <NUM> with water from the rinsing duct(s) <NUM> and/or <NUM> while turning on and off ventilator <NUM> in cycles. While ventilator <NUM> is running, air is pushed against the top-down-flow of the water into heat exchanging device <NUM> from below. This allows to keep at least part of the water in heat exchanging device <NUM>, to be released once ventilator <NUM> is switched off. At that time, the trapped water will leave heat exchanging device <NUM> in a gush, which increases the cleaning efficiency of the process.

Even though the shown example is a domestic washer-dryer, the design of heat exchanging device <NUM> and of the other components shown here, and the means and methods for operating the machine and in particular for rinsing the heat exchanging device, can also be used in a domestic laundry dryer without laundry washing functionality.

Claim 1:
A laundry dryer, in particular a washer-dryer, comprising
- a cabinet (<NUM>),
- a drum (<NUM>) rotatably placed within the cabinet (<NUM>) having an opening (<NUM>) on a front side for loading laundry,
- a heat pump with a condenser (<NUM>) and an evaporator (<NUM>),
- an air circulating system connecting the drum (<NUM>) to the condenser (<NUM>) and the evaporator (<NUM>), wherein said air circulating system comprises a ventilator (<NUM>) configured to circulate air in the air circulating system (<NUM>) between the drum (<NUM>) and the evaporator (<NUM>) and the condenser (<NUM>),
- a control unit (<NUM>),
- at least part of the condenser (<NUM>) and of the evaporator (<NUM>) are arranged at a back side of the drum (<NUM>), wherein said back side faces away from the opening (<NUM>),
wherein the condenser (<NUM>) and the evaporator (<NUM>) each comprise, in particular vertically aligned, plates (<NUM>, <NUM>) for exchanging heat between fluid ducts of the heat pump and process air of the air circulating system,
characterized in that a shortest distance between the individual plates (<NUM>) of the condenser (<NUM>) is larger than a shortest distance between the individual plates (<NUM>) of the evaporator (<NUM>).