WO2013090155A1

WO2013090155A1 - Commercial dishwasher with a fresh-air drying system, and method for operating a dishwasher of this kind

Info

Publication number: WO2013090155A1
Application number: PCT/US2012/068658
Authority: WO
Inventors: Harald Disch; Bjorn Brodowski; Matthias LILIENTHAL
Original assignee: Premark Feg L.L.C.
Priority date: 2011-12-15
Filing date: 2012-12-10
Publication date: 2013-06-20
Also published as: EP2790563B1; DE102011088754A1; EP2790563A1

Abstract

A commercial dishwasher (1) in the form of a box-type dishwasher has a treatment chamber (10) for accommodating washware (50), and also has a wash system for spraying wash liquid in the treatment chamber (10) and a final-rinse system for spraying heated final-rinse liquid in the treatment chamber (10). For optimum drying results, particularly for washware (50) which is formed from plastic or glass, without subsequent manual drying or polishing being required, a fresh-air drying system having at least one fan (19, 20) is provided for generating an air stream (24) along an air path (25), which extends from an air inlet (21) into the treatment chamber (10), through the treatment chamber (10), to an air outlet (22) out of the treatment chamber (10), wherein the fresh-air drying system has a heating device (30) for supplying thermal energy to the treatment chamber (10) as required during drying.

Description

COMMERCIAL DISHWASHER WITH A FRESH-AIR DRYING SYSTEM, AND METHOD FOR OPERATING A DISHWASHER OF THIS KIND

Technical Field

The invention relates to a commercial dishwasher and, more particularly, to a box-type dishwasher with an associated drying system and to a method for operating a dishwasher of this kind.

Background

Box-type dishwashers, also known as batch dishwashers, are dishwashers which can be loaded and unloaded manually. These include hood-type dishwashers or front-loader dishwashers. Front-loader dishwashers may be in the form of under-counter machines, counter-top machines or free-standing front- loader dishwashers.

A dishwasher designed in the form of a box-type dishwasher usually has a treatment chamber for cleaning washware. The treatment chamber usually has arranged beneath it a wash tank, in which liquid can flow back out of the treatment chamber under gravitational force. The wash tank contains wash liquid, which is usually water, to which, if appropriate, detergent can be supplied.

A dishwasher designed in the form of a box-type dishwasher also usually has a wash system having a wash pump, having a line system connected to the wash pump and having a multiplicity of spray nozzles formed in at least one wash arm. The wash liquid located in the wash tank can be delivered by the wash pump, via the line system, to the wash nozzles and sprayed in the treatment chamber, by the wash nozzles, on to the washware which is to be washed. The sprayed wash liquid then flows back into the wash tank.

Such a dishwasher designed in the form of a box-type dishwasher is known, for example, from DE 10 2005 023 429 Al .

The term "washware" used here is to be understood, in particular, as being crockery, glassware, silverware, cooking utensils, baking utensils and serving trays. A commercial dishwasher designed in the form of a box-type dishwasher differs from a domestic dishwasher, in particular, in that a commercial dishwasher has to be designed such that - depending on the washing program selected - it is possible to realize program running times between one and five minutes, whereas domestic dishwashers usually have running times of up to 2.5 hours or more. The short program duration required for commercial dishwashers means that technology used in domestic dishwashers usually cannot readily be transferred to commercial dishwashers.

Commercial dishwashers which are designed in the form of box-type dishwashers usually operate in two main process steps: a first step, which contains washing with a wash liquid, and a second step, which contains final rinsing with heated fresh water and metered rinse aid.

In order for it to be possible to carry out these process steps, a commercial dishwasher designed in the form of a box-type dishwasher is usually provided with two independent liquid systems, which are completely separate from one another. The one liquid system is a wash-washer circuit, which is responsible for washing the washware, wherein washing is carried out using recirculated water from the wash tank of the dishwasher. The other liquid system is a fresh-water system, which is responsible for final rinsing. The final rinsing is carried out using fresh water, preferably using fresh water from a boiler. The fresh water, once sprayed, is likewise taken up by the wash tank of the dishwasher.

The main task of final rinsing is that of removing detergent solution located on the washware. In addition, the final-rinse water which flows into the wash tank during the final-rinse step serves for regenerating the wash water present in the wash tank.

Before fresh water is sprayed, by the final-rinse operation, as final-rinse liquid and is thus directed into the wash tank of the dishwasher, a quantity of wash liquid which is equal to the quantity of fresh water is pumped out of the wash tank.

It is usually the case that commercial dishwashers which were designed in the form of box- type dishwashers are provided with a number of programs. These programs differ mainly by program running times of different lengths for the washing process. It is possible for the operator to select a short wash program if the washware is lightly soiled or, if the washware is heavily soiled, to select a correspondingly longer wash program. Commercial dishwashers which are designed in the form of box-type dishwashers and for loading batches of washware into, and unloading the same from, the treatment chamber are available, in particular, in the form of front-loader dishwashers or hood-type dishwashers. In the case of front-loader dishwashers, the washware is placed in a rack and the rack loaded with washware is positioned in the treatment chamber of the dishwasher through a front door and, following washing, removed through the front door again. In the case of hood-type dishwashers, the racks loaded with washware are pushed manually into the treatment chamber from an entry side and, following completion of a dishwashing program, removed manually from the treatment chamber from an exit side. Front-loader dishwashers and hood-type dishwashers contain just a single treatment chamber for treating the washware. The front- loader dishwashers may be under-counter dishwashers or counter- top dishwashers.

Mainly two drying methods are used in commercial dishwashers which are in the form of box-type dishwashers. In the first method, the washware, still hot following the final-rinse process, is removed from the machine, where it then dries in the ambient air within four to ten minutes. In order for the washware to dry, in the method described above, it is usually left in the racks in which it has been arranged for washing purposes in the dishwasher.

In the second method, air drying takes place within the treatment chamber of the dishwasher. Use is made here of fresh-air drying systems. Such fresh-air drying systems for commercial front-loader or under-counter dishwashers always operate with a high volume flow of air in the region of 25 to 100 m³ per hour, in order for it to be possible for the washware remaining in the treatment chamber to be dried in a very short period of time. The high volume flows of air are necessitated by the brevity of the drying operation in the commercial sector. In comparison with conventional drying in a domestic dishwasher, the active drying time of a commercial dishwasher is many times shorter. Whereas the drying- program time in a domestic dishwasher is approximately 30 minutes to 2.5 hours, the drying-program time in the commercial sector is between 1.5 and 5 minutes.

In the case of air drying in a commercial dishwasher which is in the form of a box-type dishwasher, fresh air is taken in from the outside and directed through the treatment chamber of the dishwasher, in order to take up moisture from the washware which is to be dried. The moisture-laden drying air is usually then blown out as exhaust air into the area where the dishwasher is set up.

The fresh-air drying systems used for conventional commercial dishwashers are based on a drying operation which, from a physical point of view, is an evaporation process in which the residual moisture which remains on the washware following the final-rinse phase evaporates at least in part. The evaporation enthalpy dh which is necessary for evaporating the residual moisture m_w here stems exclusively from the heat energy which is stored in the washware and has been introduced into the washware beforehand by virtue of the washware being wetted with hot wash and/or final-rinse liquid. For this purpose, it is conventional, during the wash and/or final-rinse phase in the treatment chamber of the dishwasher, for the wash and/or final-rinse liquid to be sprayed at temperatures higher than 60°C.

In accordance with the heat-energy equation Q = mo * cp * dT, the heat energy introduced into the washware during the wash and/or final-rinse phase is dependent on the mass mo of the respective item of washware, on the specific coefficient of heat cp of the respective item of washware, wherein the specific coefficient of heat cp, in turn, depends on the material of the corresponding item of washware, and on the temperature difference dT between the item of washware and the ambient temperature.

The problem with the conventional approaches is that the heat energy introduced into the washware in the wash and/or final-rinse phase, in accordance with the aforementioned heat-energy equation, depends not just on the temperature difference dT between the washware and the wash/final-rinse liquid, but also on the specific coefficient of heat cp of the material of the corresponding item of washware and on the mass mo of the item of washware.

In other words, an item of washware produced, for example, from plastic, such as a tray, has an inherent drying behavior which is different from that of an item of washware of the same mass, but nevertheless produced from a different material, for example glass, porcelain or metal. Different inherent drying behaviors are also manifested by items of washware which are made of the same material (and thus have the same specific coefficient of heat cp), but are of different masses mo- For example, wine glasses have an inherent drying behavior different to that of beer glasses, since beer glasses usually have a higher mass mo than wine glasses.

It is therefore the case that conventional fresh-air drying systems are often not suitable always to give an optimum drying result for different types of washware and/or for washware made of different materials, i.e. for items of washware with different inherent drying behaviors. In particular in the case of all types of items of washware produced from plastic, but often also in the case of drinking glasses or wine glasses made of a glass material, it is usually necessary, using the conventional approach, for the relevant items of washware to be subjected to subsequent manual drying or polishing, following completion of the drying phase, since it has not been possible, during the drying phase of the dishwasher, for the residual moisture on the relevant items of washware to be completely removed. Account should be taken here of the fact that an additional processing time of five to ten minutes is required for the subsequent manual treatment of the contents of a rack of glassware.

Proceeding from this problem, it is an object of the invention to develop a commercial dishwasher of the type mentioned in the introduction to the extent that an optimum drying result can always be achieved, particularly also for items of washware produced from plastic and/or drinking glasses made of a glass material, without the efficiency of the dishwasher being adversely affected and, in particular, without subsequent manual drying or polishing of the relevant items of washware being required. It is a further object of the invention to specify a method for operating a dishwasher which is the form of a box-type dishwasher and is designed to avoid the abovedescribed problems with dishwashers which are known from the prior art.

Summary

The invention thus specifies a dishwasher which, for the purpose of drying the washware during a drying phase of the dishwasher, has a fresh-air drying system having at least one fan, in order to generate an air stream extending along an air path, which extends from an air inlet into the treatment chamber, through the treatment chamber, to an air outlet out of the treatment chamber. The fresh-air drying system also has a heating device for preferably supplying thermal energy to the treatment chamber as required during the drying phase. The advantages which can be achieved by the solution according to the invention include: providing a heating device, by means of which thermal energy (heat energy) is preferably supplied to the treatment chamber as required, makes it possible for the treatment chamber to be supplied with additional heat energy as required, in particular if the heat energy which is introduced into the washware during the wash and/or final-rinse phase should be insufficient in order for the residual moisture which remains on the washware following the final-rinse phase to be removed by evaporation to a sufficient extent during the drying phase. This means that, even in the case of items of washware which have a relatively poor inherent drying behavior, for example wine glasses or drinking glasses of low mass or trays produced from plastic, it is possible to achieve an optimum drying result, without subsequent manual drying or polishing having to be used for this purpose. This can be attributed, in particular, to the fact that, according to the invention, the heating device can be used to introduce additional heat energy into the treatment chamber, as required, during the drying phase. This is the case, in particular, when the thermal energy which is introduced into the washware during the wash and/or final-rinse phase has already been used up, during the drying phase, for evaporating the residual moisture present on the washware, before it has been possible for the residual moisture to be completely removed from the washware.

As far as the method is concerned, the object of the invention is achieved, according to the invention, by the following method steps: i) heated wash or final-rinse liquid is sprayed onto the washware in the treatment chamber of the dishwasher during a wash phase and/or during a final-rinse phase; and

ii) an air stream is generated along an air path, which extends from an air inlet into the treatment chamber, through the treatment chamber, to an air outlet out of the treatment chamber, for the purpose of drying the washware during a drying phase with the aid of at least one fan, wherein thermal energy is preferably supplied to the treatment chamber as required during the drying phase with the aid of a heating device. Advantageous developments of the dishwasher according to the invention are specified in the dependent claims and advantageous developments of the method according to the invention are specified in the dependent claims.

The solution according to the invention ensures in particular, without exception, a good and uniform drying result in short cycle times, as are necessary for commercial dishwashers.

In a preferred realization of the solution according to the invention, the dishwasher has, in addition, a device for detecting the temperature of the air stream in the treatment chamber and preferably for detecting the temperature of the air stream at the air outlet out of the treatment chamber, in order to detect the temperature of the air flowing through the treatment chamber, in particular, in the drying phase of the dishwasher. The detected air temperature serves to ascertain whether the washware which is to be dried in the treatment chamber has already given off the heat energy introduced, in particular, during the wash and/or final-rinse phase, or whether the washware is still heated, in relation to the ambient air, to the extent where the residual moisture which remains on the washware can evaporate.

If the temperature of the air stream falls below a lower critical value, in the case of a preferred embodiment of the dishwasher according to the invention, the heating device is activated correspondingly in order to introduce additional thermal energy into the treatment chamber and thus to assist the drying process.

In a preferred development of the last-mentioned embodiment, the detected temperature value is compared with at least one predefined or predefmable setpoint value, wherein the heating device is activated when the temperature falls below the at least one setpoint value and the heating device is deactivated when the temperature exceeds the at least one setpoint value. It is conceivable here to provide a lower setpoint value and another, upper setpoint value.

An optimum drying result can be achieved, in particular, when the at least one fan is operated intermittently. In a preferred embodiment of the solution according to the invention, it is provided that the fan is operated at a first rotation speed at the beginning of the drying phase up until a first time, wherein, subsequently, the fan is switched off, or is operated at a reduced rotation speed in relation to the first rotation speed, for a predefined or a predefinable period of time up to a second time, and wherein, subsequently, the rotation speed of the fan or the power of the fan is correspondingly increased again up until the end of the drying phase. It should be the case here that the heating device is activated at least between the first and the second time.

Brief Description of the Drawings

The invention is described hereinbelow using exemplary embodiments and with reference to the drawings, in which: figure 1 shows a lateral sectional view of a first embodiment of the invention of a commercial dishwasher; figure 2 shows a perspective view of the dishwasher according to figure 1 ; figure 3 shows a lateral sectional view of a further embodiment of a dishwasher according to the invention; figure 4 shows, schematically, a sectional view of yet another embodiment of the dishwasher according to the invention; and figure 5 shows alternative program sequences during the drying phase of the

dishwasher according to the invention.

Figures 1 , 3 and 4 each show a longitudinal section through a commercial dishwasher 1 having a treatment chamber 10 for accommodating washware 50 and having a door 2 for closing a loading and unloading opening 5. The dishwasher 1 is designed for loading batches of the washware 50 into, and unloading the same from, a washware region 11 in the treatment chamber 10.

An air inlet 21 into the treatment chamber 10 is arranged beneath the door 2 at a lower level than the washware region 11. An air outlet 22 out of the treatment chamber 10 is arranged at a higher level than the air inlet 21 and the washware region 11.

The dishwasher 1 has a fan 20 for generating an air stream 24 along an air path 25, wherein the air path 25 extends from the air inlet 21, through the treatment chamber 10, to the air outlet 22. The air stream 24 in the treatment chamber 10 is channeled through the washware region 11 in order to dry the washware 50 during a drying phase of the dishwasher 1.

A deflector device 12 with at least one deflector is provided and designed for the purpose of acting on the air stream 24 passing into the treatment chamber 10 through the air inlet 21, this causing the air stream 24 to pass into the washware region 11 from beneath in a uniformly distributed manner.

The treatment chamber 10 has, for example, a volume of between 60 1 and 280 1.

The term "washware" used here covers, in particular, crockery, glassware, silverware, pots and pans, containers, boxes, trays, etc.

The washware region 11 is a region in the treatment chamber 10 in which the washware 50 is positioned in order to be washed. The washware 50 here is preferably arranged in a rack 6. The treatment chamber 10 may have one or more rack mounts, for example, as illustrated, a single rack mount 7, on which a respective rack 6 can be, or has been, positioned. As an alternative, it is possible to arrange, for example, two rack mounts one above the other.

The treatment chamber 10 contains a multiplicity of spray nozzles 13 to spray wash liquid or final-rinse liquid on to the washware 50. Separate spray nozzles 13 may be provided in each case for spraying wash liquid and final-rinse liquid. The spray nozzles 13 may be formed in particular, as illustrated, on rotatable spray tubes, on stationary spray tubes or in a treatment-chamber wall. In the embodiments illustrated, the loading and unloading opening 5 is formed in a front treatment-chamber wall.

A treatment-chamber base 15 has a through-opening 16 into a tank 17 or into a reservoir, which is provided for accommodating wash liquid and/or final-rinse liquid. The through- opening 16 in the treatment-chamber base 15 is preferably covered by a tank screen. The dishwasher 1 is set up preferably for at least partially reusing the wash liquid in the tank 17 for a further dishwashing program, i.e. for a new batch of washware 50. In particular, the dishwasher 1 may be designed for regenerating final-rinse liquid.

The operating temperature of the wash liquid in the tank 17 is preferably between 55°C and 65°C and is kept at the operating temperature by a suitable temperature-control device. It is possible to provide a temperature-control device for a final-rinse liquid (not illustrated), for example outside the treatment chamber 10, which keeps the temperature of the final-rinse liquid preferably between 63°C and 85°C.

According to the embodiments which are illustrated in figures 1 and 3, the air inlet 21 is formed between directing elements 44, 45 which are connected to a machine housing or are formed by the same. An upper directing element 44 and a lower directing element 45 here form at least one gap or slot. The lower directing element 45 is preferably inclined downward in the direction of the treatment chamber 10. The upper directing element 44 is preferably inclined away from the treatment chamber 10.

Instead of a slot or a gap, a nozzle may be provided (not illustrated). One of the directing elements 44, 45, in particular the upper directing element 44, may be formed by the door 2 or connected to the door 2.

The air inlet 21 is preferably designed to generate an air stream 24 which covers the entire width of the washware region 11.

In the case of those embodiments of the dishwasher 1 according to the invention which are illustrated in figures 1 and 3, the deflector device 12 is spaced apart from the air inlet 21. In particular, the deflector device 12 may be arranged on the treatment-chamber base 15, as illustrated in figures 1 and 3. As an alternative, the deflector device 12, or at least one deflector thereof, may be arranged on the tank screen. It is also conceivable for the deflector device 12 to be arranged adjacent to the air inlet 21, for example on a treatment- chamber wall.

The air outlet 22 out of the treatment chamber 10 is arranged in an upper rear region of the treatment chamber 10. The air path 25, and the air stream 24, thus extend diagonally through the treatment chamber 10, a good drying result thus being achieved. As an alternative, the air outlet 22 may be arranged at some other location above the washware region 11.

Downstream of the air outlet 22, as seen in the flow direction, an outlet channel 26 extends from the air outlet 22 to a machine outlet 23, which is preferably arranged on the front side of the machine, as is shown in figures 1 to 4. The outlet channel 26 preferably extends above the treatment chamber 10, as is illustrated in figures 1, 3 and 4. An outlet cover may be provided in order to conceal the machine outlet 23 in accordance with the desired design of the dishwasher 1.

The machine outlet 23 may have formed beneath it a sloping drainage surface, by means of which droplets which form on the machine outlet 23 are directed behind the door 2. In the case of the embodiment illustrated, the sloping drainage surface is formed in one piece with the outlet cover. As an alternative, the sloping drainage surface may be formed by a separate part, for example a housing part. In the embodiment illustrated, the droplets which drain off collect in a region above the door seal and, when the door 2 is opened, run down the door 2 into the treatment chamber 10.

In the embodiments illustrated, the fan 20 is arranged in a region between the air outlet 22 out of the treatment chamber 10 and the machine outlet 23 and serves to take in air out of the treatment chamber 10. The fan 20 is preferably arranged at the air outlet 22.

As an alternative to the embodiments illustrated, however, it is also possible for the fan 20 to be arranged so as to blow the air into the treatment chamber 10.

A condensate drain 27 extends from the outlet channel 26 into the treatment chamber 10, and therefore condensate or wash and/or final-rinse liquid sprayed into the outlet channel 26 can drain off into the treatment chamber 10. It is preferable for a base region of the outlet channel 26 to be inclined in the direction of the condensate drain 27, and therefore condensate which collects at the base region drains off in the direction of the condensate drain 27. In particular it may be provided, as is illustrated in figures 1 and 3, that an axis of rotation of a rotor of the fan 20 is inclined in the direction of the condensate drain 27, and therefore liquid in the fan 20 drains off in the direction of the condensate drain 27.

The outlet channel 26 contains a condenser device 3 (illustrated by dashed lines in figures 1 and 3) for condensing moisture from outflowing air and thus for dehumidifying the outflowing air. The condenser device 3 is arranged downstream of the air outlet 22. In particular the condenser device 3 may be arranged downstream of the fan 20, as is illustrated in figures 1 and 3. The condenser device 3 may be formed, for example, by a heat exchanger, by means of which the heat of condensation which is released during condensation is made available to the dishwasher 1 again. As an alternative, the condenser device 3 may be cooled by cooling liquid, for example cooling water, or by cooling air, in order to channel away the heat of condensation.

In the embodiment illustrated, the fan 20 is designed for generating an air stream 24 at a rate corresponding to 6 times to 12 times the treatment-chamber volume per minute.

As is illustrated in the drawings, the fan 20 is preferably provided for sucking air out of the treatment chamber 10.

According to an embodiment of the dishwasher 1 according to the invention which is illustrated in figure 4, a further fan in the form of a distributor fan 19 is provided for recirculating air in the treatment chamber 10 and thus for achieving a more uniform drying result. In the embodiment which is illustrated in figure 4, a rotor of the distributor fan 19 is arranged in the treatment chamber 10. However, it is also possible for the rotor of the distributor fan 19 to be arranged outside the treatment chamber 10 (not illustrated).

In addition, it is conceivable, in principle, to provide at least one auxiliary fan in order to supply ambient air to the air stream 24 downstream of the fan 20, and downstream of the air outlet 22, as seen in the flow direction of the air stream 24. It is conceivable here for the auxiliary fan to be designed to deliver ambient air into the outlet channel 26 through an auxiliary-air channel.

The exemplary embodiments of the dishwasher 1 according to the invention each have a heating device 30 assigned to the fresh-air drying system, for preferably supplying thermal energy (heat energy) to the treatment chamber 10 as required during a drying phase. The structural conditions favor installation of the heating device 30 on the rear side of the machine, opposite the door side. It is thus conceivable, for example, for the heating device 30 to be arranged inside the treatment chamber 10, on the rear wall 4 of the dishwasher 1. As an alternative to this, however, it is also conceivable for the heating device 30 to be provided outside the treatment chamber 10, for example at the air inlet 21. The heating device 30 can be used to supply additional thermal energy to the treatment chamber 10 when this additional energy is required for the drying process. The heating device 30 may be configured as a tubular heater, radiant panel heater, foil heater, heating mat, cartridge heater, etc. In order for the drying process to be carried out quickly, a heating power of 1 to 4 kW and preferably 1.5 to 3 kW is expedient.

According to a preferred embodiment of the dishwasher 1 according to the invention, the heating device 30 is provided with a cover or with a contact-prevention means (not illustrated).

The dishwasher 1 according to the present invention is particularly preferably provided with a device 29 for detecting the temperature of the air stream 24. The device 29 preferably has at least one temperature sensor, which is arranged at a suitable point in the treatment chamber 10, and preferably at the air outlet 22 out of the treatment chamber 10.

In order for it to be possible for the heating device 30 and the at least one fan 20 to be actuated in a suitable manner during the drying phase, a control device 100 is also provided. It is conceivable here for the control device 100 to be programmed or otherwise configured or designed to actuate the heating device 30 as a function of the temperature detected by the device 29.

In this context, it is recommended for the temperature of the air stream 24 to be detected preferably continuously or at predefined or predefmable times or with the occurrence of predefined or predefmable events in the treatment chamber 10 and in particular at the air outlet 22 out of the treatment chamber 10, wherein the control device 100 is designed to control the power of the heating device 30 as a function of the detected temperature of the air stream 24. It is preferred here if the power of the heating device 30 is adjusted with the aid of the control device 100 in such a way that the temperature of the air stream 24 in the treatment chamber 10 does not fall below a lower setpoint value.

In a preferred realization of the dishwasher 1 according to the invention, the control device 100 has a comparator 101, by means of which the temperature value detected with the aid of the device 29 is compared with at least one predefined or predefmable setpoint value. The control device 100 here is designed to activate the heating device 30 when the temperature falls below the at least one setpoint value and to deactivate the heating device 30 when the temperature exceeds the at least one setpoint value.

Those embodiments of the dishwasher 1 according to the invention which are illustrated in the drawings also have a device 28 for preferably automatically and, in particular, selectively detecting the type and/or the material of the washware 50 which is

accommodated or is to be accommodated in the treatment chamber 10. This device 28 may have, for example, an inductive or capacitive sensor for detecting the material of the washware 50 which is accommodated or is to be accommodated in the treatment chamber 10. It is also conceivable for the device 28 to be designed to read out a marking 8 provided on the rack 6, wherein this marking 8 supplies information regarding the type and/or the material of the washware 50 which is accommodated in the rack 6.

In a preferred embodiment of the device 28, the latter is designed to distinguish between washware made of metal (for example silverware or pots and pans), washware made of porcelain (for example plates or cups) and washware made of glass (for example drinking glasses). As an alternative, or in addition to this, it is conceivable for the washware 50 which is accommodated or is to be accommodated in the treatment chamber 10 to be classified by the device 28 into one of the following types of washware:

- trays produced from plastic;

drinking glasses produced from glass;

items of crockery produced from porcelain;

cooking utensils produced from metal; and

items of silverware.

The control device, which is connected to the device 28, is designed to adjust the power and, in particular, the rotation speed of the at least one fan 20 and the power of the heating device 30 as a function of the type of washware detected by the device 28, and/or as a function of the material of the washware 50, in such a manner that it is always possible to achieve an optimum drying result.

During the drying phase, the heating device 30 is particularly effective if it has not already been activated at the beginning of the drying phase. In particular tests have shown that the effectiveness of the heating device 30 can be optimized if the at least one fan 20 is switched off, at least at certain times, during operation of the heating device 30.

Accordingly, in the case of the illustrated exemplary embodiments of the dishwasher 1 according to the invention, the control device 100 is designed to adjust the power and, in particular, the rotation speed of the fan 20 in such a way that the fan 20 is operated at a relatively high power at the beginning of the drying phase (at time to) up until a first time ti, wherein the fan 20 is then not operated or is operated only at a reduced rotation speed for a predefined or predefmable period of time up to a second time t₂, and wherein, subsequently, the fan 30 is again operated at a relatively high power up until the end of the drying phase (time t₃). At the same time, the control device 100 is designed to activate the heating device 30 at least between the first and the second time t_ls t₂.

In a preferred embodiment, the fan 20 is switched on at the beginning of the drying phase in order for the heated and moisture-enriched air to be blown out of the treatment chamber 10 and replaced by fresh air. Once the predefined time has elapsed, the fan 20 is switched off for a period of time. In this period of time, the heating device 30 is switched on, in order to heat up the air which has previously been exchanged in the treatment chamber 10, and therefore this air can take up moisture again and energy is delivered for evaporation drying. It is conceivable here for the heating device 30 to be activated with the fan 20 still switched on, as a result of which, in particular, it is ensured that the maximum heating power of the heating device 30 already prevails at the time when the fan 20 is switched off.

Once the air which is present in the treatment chamber 10 has been heated to a sufficient extent with the aid of the heating device 30, the fan 20 is switched on again in order for the heated and moisture-laden air to be blown out of the treatment chamber 10 and replaced again by fresh air. In this phase, it is possible for the heating device 30 to be switched off or else also switched on.

As can be gathered from the program sequences which are illustrated in figure 5, different variations are conceivable for actuation of the fan 20 and of the heating device 30 during the drying phase of the dishwasher 1. The invention, rather than being limited to those embodiments of the dishwasher 1 according to the invention which are illustrated in the drawings, is a combination of all the features disclosed therein.

Claims

Patent claims

1. Commercial dishwasher (1) which is in the form of a box-type dishwasher and has a treatment chamber (10) for accommodating washware (50), wherein the dishwasher (1) also has a wash system for spraying wash liquid in the treatment chamber (10) and a final- rinse system for spraying heated final-rinse liquid in the treatment chamber (10), characterized in that

a fresh-air drying system having at least one fan (19, 20) is also provided for the purpose of generating an air stream (24) along an air path (25), which extends from an air inlet (21) into the treatment chamber (10), through the treatment chamber (10), to an air outlet (22) out of the treatment chamber (10), for the purpose of drying the washware (50) during a drying phase of the dishwasher (1), wherein the fresh-air drying system has a heating device (30) for preferably supplying thermal energy to the treatment chamber (10) as required during the drying phase.

2. Dishwasher (1) according to Claim 1,

wherein the dishwasher (1) has a door (2) for closing a loading and unloading opening (5) of the dishwasher (1) and is designed to load and unload washware (50) in batches into a washware region (11) in the treatment chamber (10), and wherein the air inlet (21) is preferably arranged beneath the door (2) at a point lower than the washware region (11) and the air outlet (22) is preferably arranged above the door (2) at a point higher than the washware region (11).

3. Dishwasher (1) according to Claim 1 or 2,

wherein the dishwasher (1) also has a condenser device (3) for condensing moisture from outflowing air downstream of the air outlet (22) out of the treatment chamber (10) and upstream of an air outlet (23) out of the dishwasher (1).

4. Dishwasher (1) according to one of Claims 1 to 3,

wherein the heating device (30) is arranged inside the treatment chamber (10), preferably on a rear wall (4) of the dishwasher (1).

5. Dishwasher (1) according to one of Claims 1 to 4, wherein the heating device (30) is provided with a cover or with a contact-prevention means.

6. Dishwasher (1) according to one of Claims 1 to 5,

wherein a device (29) for detecting the temperature of the air stream (24) in the treatment chamber (10) and preferably at the air outlet (22) out of the treatment chamber (10) is also provided, and wherein a control device (100) is provided, said control device being designed to actuate the heating device (30) as a function of the detected temperature.

7. Dishwasher (1) according to Claim 6,

wherein the control device (100) is designed to adjust the power of the heating device (30) in such a way that the temperature of the air stream (24) in the treatment chamber (10) does not fall below a lower setpoint value, preferably as a function of the temperature of the air stream (24) which is detected preferably continuously or at predefined or predefmable times or with the occurrence of predefined or predefmable events in the treatment chamber (10) and in particular at the air outlet (22) out of the treatment chamber (10).

8. Dishwasher (1) according to Claim 6 or 7,

wherein the control device (100) has a comparator (101) for comparing the detected temperature value with at least one predefined or predefmable setpoint value, and wherein the control device (100) is designed to activate the heating device (30) when the temperature falls below the at least one setpoint value and to deactivate the heating device (30) when the temperature exceeds the at least one setpoint value.

9. Dishwasher (1) according to one of Claims 1 to 8,

wherein a control device (100) is provided, said control device being designed to adjust the power and, in particular, the rotation speed of the at least one fan (19, 20) in such a way that the fan (19, 20) is operated at a relatively high power at the beginning of the drying phase (t₀) up until a first time (ti), then is not operated or is operated at a reduced rotation speed for a predefined or predefmable period of time up to a second time (t₂), and subsequently again operated at a relatively high power up until the end of the drying phase (t₃), and wherein the control device (100) is also designed to activate the heating device (30) at least between the first and the second time (t_ls t₂).

10. Dishwasher (1) according to one of Claims 6 to 9, wherein the dishwasher (1) also has a device (28) for preferably automatically and, in particular, selectively detecting the type and/or the material of the washware (50) which is accommodated or is to be accommodated in the treatment chamber (10), wherein the control device (100) is designed to adjust the power and, in particular, the rotation speed of the at least one fan (19, 20) and the power of the heating device (30) as a function of the type of washware (50) and/or the material of the washware (50).

11. Method for operating a commercial dishwasher (1) which is in the form of a box- type dishwasher and has a treatment chamber (10) for accommodating washware (50), in particular for operating a commercial dishwasher (1) according to one of Claims 1 to 10, wherein the method comprises the following method steps:

i) heated wash or final-rinse liquid is sprayed onto the washware (50) in the treatment chamber (10) during a wash phase and/or during a final-rinse phase; and

ii) an air stream (24) is generated along an air path (25), which extends from an air inlet (21) into the treatment chamber (10), through the treatment chamber (10), to an air outlet (22) out of the treatment chamber (10), for the purpose of drying the washware (50) during a drying phase with the aid of at least one fan (19, 20), wherein thermal energy is preferably supplied to the treatment chamber (10) as required during the drying phase with the aid of a heating device (30).

12. Method according to Claim 11,

wherein, in method step ii), the at least one fan (19, 20) is operated intermittently during the drying phase, specifically in such a way that the fan (19, 20) is operated at a relatively high power at the beginning of the drying phase (to) up until a first time (ti), then is not operated or is operated at a reduced rotation speed for a predefined or predefmable period of time up until a second time (t₂), and subsequently again operated at a relatively high power up until the end of the drying phase (t₃), and wherein the heating device (30) is operated at least between the first and the second time (t_ls t₂).

13. Method according to Claim 12,

wherein thermal energy is already supplied to the treatment chamber (10) by the heating device (30) before the first time (ti); and/or wherein the heating device (30) is operated up until the end of the drying phase (t₃).

14. Method according to Claim 12 or 13,

wherein the first time (ti), up until which the at least one fan (19, 20) is operated, is selected as a function of the type and, in particular, the material of the washware (50) which is accommodated or is to be accommodated in the treatment chamber (10); and/or wherein the first time (ti) up until which the at least one fan (19, 20) is operated is selected as a function of the temperature of the air stream (24) in the treatment chamber (10) and preferably at the air outlet (22) out of the treatment chamber (10).

15. Method according to one of Claims 12 to 14,

wherein the second time (t₂), starting from which the at least one fan (19, 20) is operated again, is selected as a function of the type and, in particular, the material of the washware (50) which is accommodated or is to be accommodated in the treatment chamber (10); and/or wherein the second time (t₂), starting from which the at least one fan (19, 20) is operated again, is selected as a function of the temperature of the air stream (24) in the treatment chamber (10) and preferably at the air outlet (22) out of the treatment chamber (10).

16. Method according to Claim 14 or 15,

wherein the type of washware (50) and/or the material of the washware (50) is preferably detected automatically, in particular selectively automatically.

17. Method according to one of Claims 11 to 16,

wherein the power of the heating device (30) during the drying phase is adjusted as a function of the type of washware (50) and/or the material of the washware (50) in method step ii).

18. Method according to one of Claims 11 to 17,

wherein, in method step ii), the temperature of the air stream (24) in the treatment chamber (10) and preferably at the air outlet (22) out of the treatment chamber (10) is detected preferably continuously or at predefined or predefinable times or with the occurrence of predefined or predefinable events during the drying phase, and wherein thermal energy is supplied to the treatment chamber (10) as a function of the detected temperature with the aid of the heating device (30).

Method according to Claim 18, wherein the detected temperature value is compared with at least one predefined or predefmable setpoint value, and wherein thermal energy is supplied to the treatment chamber (10) with the aid of the heating device (30) when the temperature falls below the at least one setpoint value, and wherein the heating device (30) is deactivated when the temperature exceeds the at least one setpoint value.

20. Method according to Claim 18 or 19,

wherein the power of the heating device (30) can be adjusted in such a way that the value of the detected air temperature does not fall below a lower setpoint value, preferably as a function of an air temperature which is detected in the treatment chamber (10) preferably continuously or at predefined or predefmable times or with the occurrence of predefined or predefmable events.