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United States Patent Application 20180140163
Kind Code A1
Heidt; Markus ;   et al. May 24, 2018

COMMERCIAL DISHWASHER CONFIGURED IN THE FORM OF A BOX-TYPE DISHWASHER AND METHOD OF OPERATING SUCH A DISHWASHER

Abstract

A box-type dishwasher (1) has a treatment chamber (2), a wash system and a drying device (50). The drying device (50) has a sorption unit (51), having a reversibly dehydratable drying material (52), and at least one fan (53) for forming an air circuit, such that an air stream is directed through the sorption unit (51) and then supplied to the treatment chamber (2) again. The sorption unit (51) has a housing (54), which encloses at least some of the drying material (52) and has at least one outer wall (55). A device (56) is designed so that the air stream is divided up into a first air sub-stream (57a), at least some of which is directed through the drying material (52), and a second air sub-stream (57b), which is not directed through the drying material (52) and is used for thermally insulating or cooling the sorption unit (51).


Inventors: Heidt; Markus; (Kehl, DE) ; Schemel; Jurgen; (Achern, DE)
Applicant:
Name City State Country Type

ILLINOIS TOOL WORKS INC.

Glenview

IL

US
Family ID: 1000003174525
Appl. No.: 15/564011
Filed: April 7, 2016
PCT Filed: April 7, 2016
PCT NO: PCT/US2016/026329
371 Date: October 3, 2017


Current U.S. Class: 1/1
Current CPC Class: A47L 15/481 20130101; A47L 15/0076 20130101
International Class: A47L 15/48 20060101 A47L015/48; A47L 15/00 20060101 A47L015/00

Foreign Application Data

DateCodeApplication Number
Apr 9, 2015DE10 2015 206 331.3

Claims



1. Commercial dishwasher (1) which is configured in the form of a box-type dishwasher, wherein the dishwasher (1) has the following: a treatment chamber (2), into which, and from which, washware can be inserted, and removed, preferably manually; and a wash system having a wash pump (13) and a wash-line system (16) for delivering wash liquid, during a wash phase, from a wash tank (12) of the dishwasher (1) and for spraying the wash liquid through wash nozzles (15a, 15b) in the treatment chamber, characterized by a drying device (50) for withdrawing moisture continuously, or as and when required, from drying air which circulates in the treatment chamber (2), in particular during a drying phase, wherein the drying device (50) has at least one sorption unit (51), having a reversibly dehydratable drying material (52), and at least one fan (53) for forming an air circuit, as and when required, such that an air stream is directed through the sorption unit (51) and then supplied to the treatment chamber (2) again, wherein the sorption unit (51) has a housing (54), which encloses at least some of the drying material (52) and has at least one outer wall (55), and wherein a device (56) is provided for dividing up the air stream which is to be directed through the sorption unit (51), wherein the device (56) is designed so that the air stream which is to be directed through the sorption unit (51) is divided up into a first air sub-stream (57a), at least some of which is directed through the drying material (52), and a second air sub-stream (57b), which is not directed through the drying material (52) and is used for thermally insulating or cooling the sorption unit (51).

2. Dishwasher (1) according to claim 1, wherein the device (56) for dividing up the air stream which is to be directed through the sorption unit (51) is designed so that the air stream generated by the fan (53) is divided up into the first and the second air sub-streams (57a, 57b) such that at least some of the second air sub-stream (57b) is directed, at least in certain regions, along the outer wall (55) of the housing (54).

3. Dishwasher (1) according to claim 1, wherein the device (56) for dividing up the air stream which is to be directed through the sorption unit (51) is designed so that the air stream generated by the fan (53) is divided up into the first and the second air sub-streams (57a, 57b) such that the air of the first air sub-stream (57a), prior to being mixed with the air of the second air sub-stream (57b), is at a temperature between 150.degree. C. and 300.degree. C., preferably between 200.degree. C. and 250.degree. C. and even more preferably between 220.degree. C. and 230.degree. C., and that the air of the second air sub-stream (57b), prior to being mixed with the air of the first air sub-stream (57a), is at a temperature between 70.degree. C. and 120.degree. C. and preferably between 80.degree. C. and 100.degree. C.

4. Dishwasher (1) according to claim 1, wherein the device (56) for dividing up the air stream which is to be directed through the sorption unit (51) is designed so that at least 50%, and preferably at least 70%, of the air stream generated by the fan (53) is directed as first air sub-stream (57a) through the drying material (52).

5. Dishwasher (1) according to claim 1, wherein the housing (54) of the sorption unit (51) contains a mixing region (58) for mixing the first air sub-stream (57a) with the second air sub-stream (57b) once the first air sub-stream (57a) has passed by the drying material (52).

6. Dishwasher (1) according to claim 1, wherein the device (56) for dividing up the air stream which is to be directed through the sorption unit (51) is designed so that at least some of the second air sub-stream (57b) is directed along the outer wall (55) of the housing (54) at least in certain regions in the interior of the housing (54).

7. Dishwasher (1) according to claim 1, wherein the device (56) for dividing up the air stream which is to be directed through the sorption unit (51) is designed so that at least some of the first air sub-stream (57a) is directed through the drying material (52) such that the first air sub-stream (57a), once it has passed by the drying material (52), runs, at least in certain regions, parallel to the second air sub-stream (57b).

8. Dishwasher (1) according to claim 1, wherein an air-directing element (63), in particular an air-directing plate, is provided, at least in certain regions, in the housing (54) of the sorption unit (51) in order to guide the first and/or second air sub stream (57a, 57b) through the sorption unit (51).

9. Dishwasher (1) according to claim 8, wherein the air-directing element (63), which is configured in particular in the form of an air-directing plate, is designed, and arranged, at least in certain regions, in the housing (54) of the sorption unit (51), such that the first air sub-stream is separated from the second air sub-stream (57b) at least in certain regions.

10. Dishwasher (1) according to claim 9, wherein the air-directing element (63), which is configured in particular in the form of an air-directing plate, is designed to transfer thermal energy from the first air sub-stream (57a) to the second air sub-stream (57b).

11. Dishwasher (1) according to claim 8, wherein the air-directing element (63), which is configured in particular in the form of an air-directing plate, is arranged in the housing (54) of the sorption unit (51) such that a flow channel (64) is formed between the air-directing element (63) and the drying material (52), the first air sub-stream (57a) flowing through the flow channel at least in certain regions.

12. Dishwasher (1) according to claim 11, wherein the device (56) for dividing up the air stream which is to be directed through the sorption unit (51) has an air separator (61) with an inlet and a first and second outlet, wherein the inlet of the air separator (61) is flow-connected to the pressure side of the fan (53), and wherein the first air sub-stream (57a) is supplied to the sorption unit (51) via the first outlet of the air separator (61) and the second air sub-stream (57b) is supplied to the sorption unit (51) via the second outlet of the air separator (61).

13. Dishwasher (1) according to claim 12, wherein the second outlet of the air separator (61) is flow-connected to a flow channel (62) designed in the form of an air bypass, wherein the flow channel (62), which is designed in the form of an air bypass, is bounded, at least in certain regions, by the outer wall (55) of the housing (54) of the sorption unit (51).

14. Dishwasher (1) according to claim 13, wherein the flow channel (62), which is designed in the form of an air bypass, extends preferably over the width of the housing (54) of the sorption unit (51), and wherein the flow channel (62), which is designed in the form of an air bypass, has a height of 3 to 10 mm and preferably 4 to 6 mm.

15. Dishwasher (1) according to claim 13, wherein the air-directing element (63), which is configured in particular in the form of an air-directing plate, bounds, at least in certain regions, the flow channel (62), which is designed in the form of an air bypass.

16. Dishwasher (1) according to claim 12, wherein the first outlet of the air separator (61) is flow-connected to a flow channel (65) bounded, at least in certain regions, by the drying material (52).

17. Dishwasher (1) according to claim 16, wherein the effective flow cross section of the flow channel (65), which is bounded, at least in certain regions, by the drying material (52), decreases in the flow direction of the first air sub-stream (57a).

18. Dishwasher (1) according to claim 16, wherein an air-directing element (66) is provided, this being assigned to the first air sub-stream (57a) and additionally bounding the flow channel (65), which is bounded, at least in certain regions, by the drying material (52).

19. Dishwasher (1) according to claim 12, wherein the first and second outlets of the air separator (61) and the air-directing element (63), which is configured, in particular, in the form of an air-directing plate, are designed such that it is only once it has passed by the drying material (52) that the first air sub-stream (57a) flows through the flow channel (64), which is formed between the air-directing element (63) and the drying material (52).

20. Dishwasher (1) according to claim 1, wherein the quantity of air circulated by the at least one fan (53) per unit of time is around 20 to 120 m.sup.3/h, preferably around 40 to 100 m.sup.3/h, and even more preferably around 80 to 100 m.sup.3/h.

21. Dishwasher (1) according to claim 1, wherein the treatment chamber (2) has at least one intake opening (60), which is flow-connected to the suction side of the fan (53) in order to take in air from the treatment chamber (2), and wherein the treatment chamber (2) has at least one exhaust opening (59), via which the first and second air sub-streams (57a, 57b) are supplied, preferably jointly, to the treatment chamber (2) again once they have passed by the sorption unit (51).

22. Dishwasher (1) according to claim 21, wherein the at least one intake opening (60) and the at least one exhaust opening (59) are spaced apart from one another and open out into the treatment chamber (2) preferably in an upper region of the treatment chamber (2).

23. Dishwasher (1) according to claim 1, wherein the reversibly dehydratable drying material (52) has 0.3 to 3.0 kg, and preferably 1.0 to 1.5 kg, of zeolite-containing material preferably in the form of granules with a particle diameter of 0.5 to 10.0 mm.

24. Dishwasher (1) according to claim 1, wherein the drying device (50) also has a heating unit for heating the reversibly dehydratable drying material (52) as and when required, wherein the heating unit has a multiplicity of heating elements, which are arranged preferably at uniform intervals within the reversibly dehydratable drying material (52).

25. Method of operating a dishwasher (1) which is designed in the form of a box-type dishwasher and has a treatment chamber (2) for accommodating washware which is to be cleaned, wherein the method has the following steps: i) during an absorption phase, air is directed out of the treatment chamber (2) through a sorption unit (51), having a reversibly dehydratable drying material (52), such that the drying material (52) absorbs moisture from the air stream, wherein the air is then supplied to the treatment chamber (2) again; and ii) during a desorption phase, the drying material (52) of the sorption unit (51) is heated and, at the same time, air is directed out of the treatment chamber (2) through the sorption unit (51) such that moisture is desorbed from the drying material (52) and at least some of the thermal energy introduced into the drying material (52), and at least some of the moisture desorbed from the drying material (52), is discharged as water vapour from the sorption unit (51) with the aid of the air stream directed through the sorption unit (51), wherein the air which is to be directed through the sorption unit (51) is divided up into a first air sub-stream, at least some of which is directed through the drying material (52), and into a second air sub-stream (57b), at least some of which is directed, at least in certain regions, along an outer wall (55) of the housing (54) of the sorption unit (51).

26. (canceled)
Description



TECHNICAL FIELD

[0001] The invention relates to a commercial dishwasher which is designed in the form of a box-type dishwasher, and a treatment chamber for receiving washware which is to be cleaned, as well as to a method of operating such a dishwasher.

BACKGROUND

[0002] Box-type dishwashers are manually loadable and unloadable dishwashers. The box-type dishwashers (also referred to as "box-type warewashers" or as "batch dishwashers") can be crockery rack pass-through dishwashers, also termed "hood-type warewashers" or "front loader warewashers". Front loaders can be "undercounter machines", "top counter machines" or "freestanding front loaders".

[0003] A dishwasher designed in the form of a box-type dishwasher usually has a treatment chamber for the cleaning of washware. Under the treatment chamber is generally arranged a wash tank, in which liquid can flow back out of the treatment chamber by gravitational force. In the wash tank is found wash liquid, which is usually water, to which, if need be, detergent can be supplied.

[0004] A dishwasher designed in the form of a box-type dishwasher usually also has a wash system comprising a wash pump, a line system connected to the wash pump, and comprising a multiplicity of spray nozzles designed in at least one wash arm. The wash liquid present in the wash tank can be delivered by the wash pump via the line system to the wash nozzles and sprayed through the wash nozzles in the treatment chamber onto the washware which is to be cleaned. The sprayed wash liquid then flows back into the wash tank.

[0005] Such a washing machine designed in the form of a box-type dishwasher is known, for instance, from printed publication DE 10 2005 023 429 A1.

[0006] The term "washware" which is used herein should be understood as, in particular, crockery, glasses, cutlery, cooking utensils, baking utensils and serving trays.

[0007] A commercial dishwasher designed in the form of a box-type dishwasher differs from a domestic dishwasher in particular in that a commercial dishwasher must be designed such that--depending on the chosen cleaning program--program run times between one and five minutes can be realized, while domestic dishwashers generally have run times of up to 2.5 hours or above. Due to the short program length which is demanded in commercial dishwashers, techniques which are used in domestic dishwashers are generally not readily transferrable to commercial dishwashers.

[0008] Commercial dishwashers which are designed in the form of a box-type dishwasher usually operate in two main process steps: a first step, which involves washing with a wash liquid, and a second step, which involves rinsing with warmed fresh water and metered rinse aid.

[0009] In order to be able to perform these process steps, a dishwasher designed in the form of a box-type dishwasher is generally equipped with two independent liquid systems, which are completely separate from each other. One liquid system is a wash water circuit, which is responsible for washing the washware, wherein the washing is performed with recirculated water from the wash tank of the dishwasher. The other liquid system is a fresh water system, which is responsible for the rinsing. The rinsing is performed with fresh water, preferably with fresh water from a boiler. Following the spraying, the fresh water is likewise received by the wash tank of the dishwasher.

[0010] The main object of the rinsing is to remove lye present on the washware. In addition, the rinse water which flows into the wash tank during the rinsing step serves to regenerate the wash water present in the wash tank.

[0011] Before, through the rinsing, fresh water is sprayed as the rinsing liquid and is thereby directed into the wash tank of the dishwasher, a quantity of wash liquid which is equal to the fresh water quantity is pumped off from the wash tank.

[0012] Usually, commercial dishwashers which are designed in the form of a box-type dishwasher are equipped with several programs. These programs differ mainly by different lengths of program run times of the wash process. The operator has the option of choosing a short wash program in the case of lightly soiled washware, or of choosing a correspondingly longer wash program in the case of heavily soiled washware.

[0013] Commercial dishwashers which are designed in the form of a box-type dishwasher and for the batchwise loading and unloading of the treatment chamber with washware are, in particular, front door machines or rack pass-through machines. In front door machines, the washware is placed into a rack and the rack laden with washware is placed through a front door into the treatment chamber of the dishwasher and, following the cleaning, removed again through the front door. In rack pass-through machines, the crockery racks laden with washware are pushed from an inlet side manually into the treatment chamber and, following completion of a rinse program, removed from an outlet side manually from the treatment chamber. Front door machines and rack pass-through machines contain just a single treatment chamber for treating the washware. The front door machines can be undercounter machines or top counter machines.

[0014] In commercial dishwashers which are designed in the form of a box-type dishwasher, mainly two drying processes are used. In the first process, the, after the rinsing process, still hot washware is removed from the machine, where it then dries in four to ten minutes in the ambient air. For the drying of the washware, in the above-described process it is usually left in the racks in which it was arranged for cleaning in the dishwasher.

[0015] According to the second process, an air drying takes place within the treatment chamber of the dishwasher. In this case, fresh air drying systems are used. Fresh air drying systems of this type for commercial front door or undercounter dishwashers always operate with a high air volume stream in the region of 25 to 100 m.sup.3 per hour, in order to be able to dry in a very short time the washware remaining in the treatment chamber. The high air volume streams are dictated by the shortness of the drying operation in the commercial sector. In comparison to a conventional drying of a domestic crockery dishwasher, the active drying time of a commercial crockery dishwasher is many times shorter. While the program run time in a domestic dishwasher is about 30 minutes to 2.5 hours, the program run time drying in commercial usage is between 1.5 and 5 minutes.

[0016] In the case of air drying in a commercial dishwasher designed in the form of a box-type dishwasher, fresh air is sucked up from outside and directed through the treatment chamber of the dishwasher in order to absorb moisture from the washware which is to be dried. Generally, the drying air laden with moisture is then blown out as waste air into the installation room of the dishwasher.

[0017] The fresh air drying systems which are used in conventional commercial dishwashers are based on a drying operation which, in physical terms, is an evaporation process in which the residual moisture which remains on the washware after the rinsing phase at least partially evaporates. That is to say, the enthalpy of vaporization which is necessary for the evaporation of the residual moisture m.sub.w comes exclusively from the thermal energy which is stored in the dishware and which has previously been introduced into the washware by the wetting of the washware with warm wash liquid and/or rinse liquid. For this purpose, it is customary, during the washing and/or rinsing phase in the treatment chamber of the dishwasher, to spray the wash or rinse liquid at temperatures higher than 60.degree. C.

[0018] The thermal energy which has been introduced into the washware during the washing and/or rinsing phase is, in accordance with the thermal energy equation Q=m.sub.G*cp*dT, dependent on the mass m.sub.G of the respective washware part, the specific thermal coefficient cp of the respective washware part, the specific thermal coefficient cp being in turn dependent on the material of the corresponding washware part, and the temperature difference dT between the washware part and the temperature of the environment.

[0019] In the traditional approaches, it is problematic that the thermal energy which has been introduced into the washware in the washing and/or rinsing phase, in accordance with said thermal energy equation, depends not merely on the temperature difference dT between the washware and the washing/rinsing liquid, but also on the specific thermal coefficient cp of the material of the corresponding washware part and the mass m.sub.G of the washware part.

[0020] In other words, a washware part produced, for instance, from plastic, e.g. a tray, has different self drying characteristics than a washware part of equal mass which is produced, however, from a different material, e.g. glass, porcelain or metal. Different self drying characteristics are also manifested in washware parts made of the same material (and thus with the same specific thermal coefficient cp) but of different mass m.sub.G. For instance, wine glasses have different self drying characteristics compared to beer glasses, since beer glasses usually have a higher mass m.sub.G compared to wine glasses.

[0021] Traditional fresh air drying system are therefore frequently not suitable for always delivering an optimal drying result for different washware types and/or for washware made of different materials, i.e. for washware parts having self drying characteristics. In particular in all types of washware parts produced from plastic, but also frequently in drinking glasses or wine glasses made of a glass material, with the traditional approach it is generally necessary for the particular washware parts to have to be manually redried or repolished following the conclusion of the drying phase, since during the drying phase of the dishwasher the residual moisture on the particular washware parts could not be completely removed. In this context, it should be borne in mind that, for the manual after-treatment of the content of a glasses rack, an additional handling time of five to ten minutes accrues.

[0022] Starting from this problem definition, the object of the invention is to refine a commercial dishwasher of the type stated in the introduction such that, in particular also for washware parts produced from plastic and/or drinking glasses made of a glass material, optimal drying characteristics are always obtainable without the efficiency of the dishwasher being adversely affected, and in particular without the need for manual redrying or repolishing of the particular washware parts.

[0023] In addition, the object of the invention is to define a method of operating a dishwasher designed in the form of a box-type dishwasher, which method is designed to avoid the previously described problems in respect of dishwashers known from the prior art.

SUMMARY

[0024] There is hence in particular proposed a commercial dishwasher which is configured in the form of a box-type dishwasher and has a treatment chamber and a wash system. Washware can be inserted into the treatment chamber, and removed therefrom, preferably manually.

[0025] The wash system has a wash pump and a wash-line system for delivering wash liquid, during a wash phase, from a wash tank of the dishwasher, and for spraying this wash liquid through wash nozzles in the treatment chamber.

[0026] According to the invention, it is provided that the dishwasher has a drying device for withdrawing moisture continuously, or as and when required, from drying air which circulates in the treatment chamber, in particular during a drying phase. The drying device has at least one sorption unit, having a reversibly dehydratable drying material, and at least one fan for forming an air circuit, as and when required, such that an air stream is directed through the sorption unit and then supplied to the treatment chamber again. It is here provided that the sorption unit has a housing, which encloses at least some of the drying material and has at least one outer wall. In addition, a device is provided for dividing up the air stream which is to be directed through the sorption unit. This device is designed so that the air stream which is to be directed through the sorption unit is divided up into a first air sub-stream and a second air sub-stream. At least some of the first air sub-stream is directed through the drying material, while at least some of the second air sub-stream is directed, at least in certain regions, along the outer wall of the housing.

[0027] The sorption unit is operated alternately in an absorption phase and in a desorption phase. During the absorption phase, with the first air sub-stream air is directed out of the treatment chamber of the dishwasher through the reversibly dehydratable drying material of the sorption unit such that the drying material absorbs moisture from the air stream, whereafter the air (together with the air of the second air sub-stream) is fed back to the treatment chamber of the dishwasher.

[0028] During the desorption phase, the drying material of the sorption unit is heated and, simultaneously with the first air sub-stream, air is directed, in particularly forcibly glides, out of the treatment chamber through the sorption unit such that moisture is desorbed from the drying material, and at least some of the thermal energy introduced into the drying material, as well as at least some of the moisture desorbed from the drying material, is discharged as water vapor from the sorption unit with the aid of the first air sub-stream forcibly guided through the sorption unit.

[0029] During the absorption phase, the air of the first air sub-stream, as it flows through the drying material, is dehumidified and, at the same time, warmed, since the absorption of water through the drying material constitutes an exothermic reaction. The air of the first air sub-stream can thus be used during the absorption phase, in the treatment chamber of the dishwasher, to dry the washware.

[0030] The drying material is suitable for the (exothermic) absorption of the moisture contained in the first air sub-stream, up to the point where the drying material is saturated with water. Since the material in question is a reversibly dehydratable drying material, in the following sub-process of the desorption by heat supply, the water previously stored in the drying material can be expelled (desorbed) in the form of steam. Since, during the desorption phase, the first air sub-stream guided through the drying material discharges not only the desorbed water vapor, but also some of the thermal energy introduced into the drying material for the purpose of the desorption, the first air sub-stream for warming, as and when required, the washware received in the treatment chamber of the dishwasher can be used also during the desorption phase.

[0031] Since, in the solution according to the invention, the air stream directed through the sorption unit is divided up into a first and a second air sub-stream, wherein only the first air sub-stream is directed through the drying material, while the second air sub-stream is not directed through the drying material and is used for thermally insulating or cooling the sorption unit, a cooling of the thermally highly stressed regions of the drying device with a part-quantity of the air circulated by the fan of the drying device is advantageously realized. This second air sub-stream which is used for cooling is preferably directed along an outer wall of the housing of the sorption unit in order to appropriately cool those regions of the housing which face outward, i.e. away from the drying material. In addition, the second air sub-stream serves to supply again to the treatment chamber at least some of the thermal energy which is otherwise lost through convection, since the second air sub-stream, as the outer wall of the housing is cooled, is simultaneously warmed, and this thermal energy is returned into the treatment chamber of the dishwasher.

[0032] In an advantageous realization of the solution according to the invention, it is provided that the device for dividing up the air stream which is to be directed through the sorption unit is, in particular, designed so that the air stream generated by the fan is divided up into the first and the second air sub-streams such that the air of the first air sub-stream, prior to being mixed with the air of the second air sub-stream, is at a temperature between 150.degree. C. and 300.degree. C., preferably between 200.degree. C. and 250.degree. C., and even more preferably between 220.degree. C. and 230.degree. C. It is herein ensured that, per unit of time, a sufficient quantity of air is directed through the drying material of the sorption unit to avoid overheating, or at least local overheating, of the drying material, in particular during the desorption phase. Of course, other temperatures too can be chosen, in particular depending on the specific drying material which is used.

[0033] In this context, it is also of advantage if the device for dividing up the air stream which is to be directed through the sorption unit is designed so that the air stream generated by the fan is divided up into the first and the second air sub-streams such that the air of the second air sub-stream, prior to being mixed with the air of the first air sub-stream, is at a temperature between 70.degree. C. and 120.degree. C. and preferably between 80.degree. C. and 100.degree. C.

[0034] With the solution according to the invention, it is not only possible that highly stressed regions of the drying unit is cooled with a part-quantity of the air circulated by the fan, but, in particular, also that the quantity of air which is circulated in absolute terms per unit of time can be increased with the very same fan, since a part-quantity of the circulated air is not directed through the drying material.

[0035] It has here proved to be particularly efficient if during the desorption phase, with the fan of the drying device, a total of at least 100 to 1,500 liters, and preferably at least 200 to 500 liters of air, is blown through the sorption unit. Advantageously, at least 50% of the air stream generated by the fan, and preferably at least 70% of the air stream generated by the fan, is directed as a first air sub-stream through the drying material.

[0036] The drying material in question is in particular a sorption means which has zeolite. Zeolite is a crystalline material, which in the framework structure contains silicon oxide and aluminum oxide. The regular framework structure contains cavities in which water molecules and heat release can be absorbed. Within the framework structure, the water molecules are exposed to strong field forces, the strength of which depends on the water quantity already contained in the lattice structure, and the temperature of the zeolite material.

[0037] As the drying material, in particular type Y zeolite is primarily suitable, since this material is particularly stable even under extreme hydrothermal conditions.

[0038] During the desorption phase, in the solution according to the invention, the drying material of the sorption unit is preferably raised or heated to the necessary desorption temperature with the aid of a heating device, in particular electrical heating device, installed within the sorption unit. If a zeolite material is used as the dehydratable drying material, the desorption temperature, according to the aspired degree of dehumidification, lies between 150.degree. C. and 280.degree. C.

[0039] In order to achieve a shortest possible desorption time, as is desirable, in particular, in commercial dishwashers, during the desorption phase a relatively high heat output must be introduced into the drying material. In this context, it is of advantage if a heating device having a multiplicity of heating elements, which are arranged preferably at uniform intervals within the reversibly dehydratable drying material, is used.

[0040] It has here been shown that a distance of 5 mm to maximally 25 mm, preferably to maximally 15 mm, between the individual heating elements is particularly preferred, since, with this distance, a specific heat output of over 6,000 W/kg of drying material (zeolite) can be penetrated. If the distance between adjacent heating elements is increased to over 25 mm, the specific heat output is reduced to 2,000 W/kg drying material.

[0041] The load per unit of area of the respective heating elements can be up to 6 W/cm.sup.2. The first air sub-stream, which during the desorption phase is continuously guided through the sorption unit, here prevents the permitted maximum contact temperatures from being exceeded in the desorption process. For zeolite, the permitted maximum contact temperature is in the desorption process around 550.degree. C. At higher temperatures, zeolites show an incipient degeneration.

BRIEF DESCRIPTION OF DRAWINGS

[0042] Below, an exemplary embodiment of the dishwasher according to the invention is described in greater detail with reference to the appended drawings, in which:

[0043] FIG. 1 shows schematically a dishwasher, in particular a commercial dishwasher, in the form of a box-type dishwasher according to an exemplary embodiment of the invention;

[0044] FIG. 2 shows schematically an exemplary embodiment of the drying device used in the dishwasher according to FIG. 1, and

[0045] FIG. 3 shows schematically the temperature distribution in that exemplary embodiment of the drying device used in the dishwasher according to the invention which is shown schematically in FIG. 2, during operation of the dishwasher.

DETAILED DESCRIPTION

[0046] The invention relates to commercial dishwashers, in particular crockery dishwashers or utensil dishwashers, in the form of a box-type dishwasher.

[0047] The dishwasher 1 according to the invention has a program control device 101 for controlling at least one cleaning program, and a treatment chamber 2, closable by a door (not shown in the drawings) or a hood (not shown in the drawings), in a machine housing, for the reception of washware which is to be cleaned (not shown), such as, for instance, crockery, cutlery, pots, pans and trays.

[0048] Under the treatment chamber 2 is found a wash tank 12 for receiving sprayed liquid from the treatment chamber 2. A wash pump 13 is provided to deliver wash liquid from the wash tank 12 through a wash liquid line system 16 to wash nozzles 11a, 11b, which in the treatment chamber 2 are directed at the region of the washware to be cleaned and spray the wash liquid onto the washware to be cleaned.

[0049] The sprayed wash liquid falls back into the wash tank 12 by gravitational force. As a result, the wash tank 12, the wash pump 13, the wash liquid line system 16, the wash nozzles 11a, 11b form together with the treatment chamber 2 a wash liquid circuit. The wash liquid line system 16 here connects the pressure side of the wash pump 13 to the wash nozzles 11a, 11b.

[0050] Furthermore, in the dishwasher 1 represented schematically in FIG. 1 is provided a rinse system for delivering rinse liquid by means of a rinse pump 14 through a rinse line system 17 to rinse nozzles 15a, 15b, which in the treatment chamber 2 are directed at the region of the washware to be cleaned.

[0051] During a rinse phase, the sprayed rinse liquid falls by gravitational force from the treatment chamber 2 into the wash tank 12. The rinse liquid system 17 here connects the pressure side of the rinse pump 14 to the rinse nozzles 15a, 15b.

[0052] In this context, it should be noted that the rinse system does not necessarily have to be equipped with a rinse pump 14. For instance, it is also conceivable that the hydrostatic pressure which is necessary for the spraying of the rinse liquid during a rinse phase is provided via a line network.

[0053] The wash nozzles 11a, 11b and the rinse nozzles 15a, 15b can be arranged in the regions above and/or below and--if so desired--also to the side of the washware region within the treatment chamber 2, and can respectively be directed toward the region in which the washware is positioned.

[0054] Preferably, a multiplicity of wash nozzles 11a is provided on at least one upper wash arm, a multiplicity of wash nozzles 11b on at least one lower wash arm, a multiplicity of rinse nozzles 15a on at least one upper rinse arm, and a multiplicity of rinse nozzles 15b on at least one lower rinse arm.

[0055] Before rinse liquid is sprayed during a rinse phase, during operation of the dishwasher 1 a quantity of wash liquid which corresponds to the rinse liquid is respectively pumped off from the wash tank 12 by means of a drain pump 5, the suction side of which is connected by a discharge line 4 to a sump of the wash tank 12.

[0056] If, prior to a first (initial) start-up of the dishwasher 1 designed in the form of a box-type dishwasher, the wash tank 12 is empty, this must firstly be filled with fresh water via a fresh water line (not shown in FIG. 1), or by means of the rinse system and its rinse pump 14 with rinse water or another rinse liquid or wash liquid.

[0057] The rinse liquid can be fresh water or fresh water mixed with rinse aid.

[0058] The wash liquid contains detergent, which is automatically added to the liquid contained in the wash tank 12 by a detergent metering device (not shown in FIG. 1).

[0059] The program control device 101 controls the wash pump 13, the rinse pump 14, the discharge pump 5, and the detergent solution pump (not shown in the drawings) in dependence on the cleaning program respectively chosen at the program control device 101 by an operator. At least one cleaning program is provided, preferably a plurality of optionally selectable cleaning programs are provided.

[0060] In that embodiment of the dishwasher 1 according to the invention which is represented schematically in FIG. 1, the rinse pump 14 is connected with its suction side to an outlet of a boiler 22. The boiler 22 additionally has an inlet, which is connected to a fresh water supply line 30 and via which either fresh water or fresh water with added rinse aid is supplied to the boiler 22. In the boiler 22, the liquid supplied via the inlet (pure fresh water or fresh water with added rinse aid) is heated up in accordance with the process flow.

[0061] Via the rinse pump 14 connected with its suction side to the boiler outflow 23, the rinse liquid heated up in the boiler 22 can be supplied for instance, during a fresh water rinse phase, via the rinse line system 17 to the rinse nozzles 15a and 15b.

[0062] Of course, it is also conceivable that the boiler 22 is supplied via the inlet and the fresh water supply line 30 with pure fresh water, to which, following warming in the boiler 22, a rinse aid is added.

[0063] That embodiment of the dishwasher 1 according to the invention which is represented schematically in FIG. 1 is also provided with a steam rinse system.

[0064] More specifically, the boiler 22 in the embodiment according to FIG. 1 serves not only to warm the rinse aid, but also to generate steam, as and when required.

[0065] The steam outlet 46 of the boiler 22, which steam outlet is provided for this purpose and at the same time also serves as a steam generator, is flow-connected via a steam line 40, at a place situated above the wash tank 12, to the treatment chamber 2, in order to lead into the treatment chamber 2, if necessary, the steam generated in the steam generator (boiler 22). The outlet opening of the steam line 40 is preferably located between the upper nozzles 11a, 15a of the wash or rinse system and the lower nozzles 11b, 15b. Of course, other positions are also possible, however.

[0066] In that embodiment of the dishwasher 1 according to the invention which is represented schematically in FIG. 1, the inlet 25 of the boiler 22 is connected via fresh water supply lines 24, 26 to a backflow preventer 16. The backflow preventer 16 serves to prevent fresh water from being able to be sucked back from the suction side of the rinse pump 14 into a fresh water supply line 30.

[0067] The backflow preventer 16 has an outlet 31, which is connected via fresh water supply lines 24, 41 to a water softener device 33. The water softener device 33 has, on the one hand, a salt container 42 connected to the fresh water supply line 41 and, on the other hand, arranged parallel to each other, first and second water softeners 35a, 35b. The two parallelly arranged water softeners 35a, 35b are connected via a corresponding fresh water line system and the fresh water supply line 24 to the outlet 31 of the backflow preventer 16.

[0068] The water softeners 35a, 35b of the water softener device 33 can be operated alternately by suitable piloting of valves 36 in order to soften the fresh water supplied to the boiler 22 via the fresh water supply lines 26 and 24.

[0069] The salt container 42 belonging to the water softener device 33 contains a suitable salt or a suitable chemical, with which, if necessary, a water softening agent added via the water softeners 35a, 35b, or a decay product formed upon the addition of a water softening agent, can be suitably regenerated.

[0070] The salt container 42 is refillable from the treatment chamber 2 of the dishwasher 1, via an opening closable with a cap 38, with the salt or the chemical.

[0071] That embodiment of the dishwasher 1 according to the invention which is represented schematically in FIG. 1 is also provided with a drying device 50. The drying device 50 serves to withdraw moisture continuously, or as and when required, from drying air which circulates in the treatment chamber 2 of the dishwasher 1, in particular during a drying phase. The circulating drying air is indicated in FIG. 1 by the arrow in the treatment chamber 2.

[0072] More specifically, and as is described in greater detail, in particular, with reference to the schematic representation in FIG. 2, the drying device 50 has a sorption unit 51, having a reversibly dehydratable drying material 52, and a fan 53, which is controllable via the program control device 101 and serves to form the air circuit indicated in FIG. 2 with the arrow in the treatment chamber 2, as and when required, such that an air stream is directed through the sorption unit 51 and then supplied to the treatment chamber 2 of the dishwasher 1 again.

[0073] As can be seen in particular from the representation in FIG. 1, the drying device 50 is preferably arranged above the treatment chamber 2 of the dishwasher 1, though other arrangements of the drying device can also be considered.

[0074] From the detailed view of the drying device 50 in FIG. 2 it can further be seen that the sorption unit 51 has a housing 54, which encloses at least some of the drying material 52. This housing 54 is formed, in particular, by a corresponding outer wall 55, by which the sorption unit 51 is separated outward.

[0075] According to the invention, in the drying device 50, a device, denoted in general terms by the reference numeral "56", for dividing up the air stream which is to be directed through the sorption unit 51 is used.

[0076] More specifically, and as can be seen, in particular, from the detailed view in FIG. 2, this device 56 is in particular designed so that the air stream which is to be directed through the sorption unit 51 is divided up into a first air sub-stream 57a and a second air sub-stream 57b, wherein at least some of the first air sub-stream 57a is directed through the drying material 52 of the sorption unit 51, and wherein, for cooling purposes, at least some of the second air sub-stream 57b is directed, at least in certain regions, along the outer wall 55 of the housing 54.

[0077] As can be seen from the detailed view represented in FIG. 2, the device 56 for dividing up the air stream both spatially and in relation to the flow path is arranged in a region between the fan 53 and the drying material 52 of the sorption unit 51. In particular, the device 56 is arranged on that narrow side of the drying material 52 which is facing toward the fan 53.

[0078] More specifically, the device 56 is arranged, starting from the drying material 52 of the sorption unit 51, in a region which is situated upward along the air stream. The effect of this is that the air stream 57 is already divided up into the first air sub-stream 57a and into the second air sub-stream 57b before it is guided into a region of the sorption unit 51.

[0079] More specifically, precisely the previous separation of the air stream makes it possible to define the volume streams of the air sub-streams 57a and 57b very accurately, and thus to adjust the mixed temperature of the resulting air stream at the exhaust opening 59 within a desired temperature range.

[0080] In particular, in the region of the sorption unit 51, a spatial separation of the air sub-streams 57a and 57b exists. That is to say that the air sub-streams 57a and 57b are directed downstream from the device 56 to different longitudinal sides of the sorption unit 51. More specifically, the first air sub-stream 57a is here directed to a side facing toward the treatment chamber 2, while the second air sub-stream 57b is directed to a longitudinal side of the sorption unit 51 which is facing toward the outer wall 55 of the housing 54. Hence on the outer wall 55 of the housing 54 is achieved a particularly good cooling effect, which is necessary, in particular, in those commercial dishwashers which are frequently used under continuous operation.

[0081] In the housing 53 of the sorption unit 51 is also provided a mixing region 58, in which the air of the first air sub-stream 57a is mixed with the air of the second air sub-stream 57b, to be precise once the first air sub-stream 57a has passed through the drying material 52 of the sorption unit 51.

[0082] Preferably, the mixing region 58 is provided still within the housing 54 of the sorption unit 51. In this way, an optimal mixing of the air of the first and second air sub-streams 57a, 57b can be effected, so that the air which has then been mixed can be supplied via an (in particular single) exhaust opening 59 again to the treatment chamber 2 of the dishwasher 1.

[0083] More specifically, and as indicated schematically in FIG. 2, in the exemplary embodiment of the dishwasher 1 according to the invention it is provided that the treatment chamber 2 has a single intake opening 60, which is flow-connected to the suction side of the fan 53. Via this single intake opening 60, the circulating air is sucked up with the aid of the fan 53. At a distance from the intake opening 60 is formed the (single) exhaust opening 59, which serves to supply the first and second air sub-streams 57a, 57b jointly again to the treatment chamber 2.

[0084] As already indicated, the air stream is divided into the first and the second air sub-stream in particular with the purpose that, with the second air sub-stream 57b, the sorption unit 51, and, in particular, the housing 54 of the sorption unit 51, can be cooled in certain regions.

[0085] For this purpose, in the solution according to the invention it is provided that the device 56 for dividing up the air stream which is to be directed through the sorption unit 51 is designed so that at least some of the second air sub-stream 57b is directed along the outer wall 55 of the housing 45 at least in certain regions in the interior of the housing 45.

[0086] On the other hand, the first air sub-stream 57a is directed through the drying material 52 of the sorption unit 51 such that the first air sub-stream 57a, once it has passed through the drying material 52, runs, at least in certain regions, parallel to the second air sub-stream 57b. In this region where the two air sub-streams 57a, 57b run parallel, in particular a heat transfer takes place from the (heated) first air sub-stream 57a to the still relatively cool second air sub-stream 57b, as is subsequently described in greater detail with reference to the representation in FIG. 3.

[0087] In that exemplary embodiment of the dishwasher according to the invention which is represented in the drawings, in particular an air separator 61 is used to divide up the two air sub-streams 57a, 57b. This air separator 61 has--as represented schematically in FIG. 2--an inlet and a first and a second outlet. The inlet of the air separator 61 is flow-connected to the pressure side of the fan 53, while the first air sub-stream 57a is supplied to the the sorption unit 51 via the first outlet of the air separator 61 and the second air sub-stream 57b is supplied thereto via the second outlet of the air separator 61.

[0088] More specifically, and as indicated in FIG. 2, the air separator 61 has 2 air baffles, which are arranged at an angle to each other. Preferably, the angle defined by the two air baffles is an acute angle pointing in the direction of the fan 53. Particularly preferably, at least one of those edges of the air baffles which lie opposite the angle is arranged on the drying material 52 of the sorption unit 51.

[0089] More specifically, in that exemplary embodiment of the dishwasher 1 according to the invention which is represented in the drawing, it is provided that the second outlet of the air separator 61 is flow-connected to a flow channel 62 designed in the form of an air bypass, wherein this flow channel 62 designed in the form of an air bypass is bounded, at least in certain regions, by the outer wall 55 of the housing 45 of the sorption unit 51.

[0090] Preferably, the flow channel 62, which is designed in the form of an air bypass, extends over the entire width of the housing 54 and has a constant height of 3 to 10 mm and preferably 4 to 6 mm.

[0091] In that exemplary embodiment of the dishwasher 1 according to the invention in the drawings, in addition to the air separator 61, an air-directing element 63, which is arranged in the housing 54 of the sorption unit 51, is used in order to direct the first and/or second air sub-stream 57a, 57b through the sorption unit 51. In particular, it is in this context conceivable to configure this air-directing element 63 in the form of an air baffle. Of course, other embodiments for the air-directing element can also be considered, however.

[0092] As can be seen from the representation in FIG. 2, the air-directing element 63, which is configured in particular in the form of an air-directing plate, is designed such that and arranged in the housing 54 of the sorption unit 51 such that, via this air-directing element 63, at least in certain regions, the first air sub-stream 57a is separated from the second air sub-stream 57b. In this respect, the air-directing element 63 extends as far as the mixing region 58, where the separation between the first and the second air sub-streams 57a, 57b is then abolished.

[0093] It is here in particular provided that the first air sub-stream 57a, coming from below, flows through the drying material 52, while the second air sub-stream 57b is guided above the drying material 52 on the outer wall 55 of the housing 54. Since the air-directing element 63, which is configured in particular in the form of an air baffle, is arranged in the housing 54 of the sorption unit 51 such that a flow channel 64 is formed between the air-directing element 63 and the drying material 52, the air of the first air sub-stream 57a, once it has passed through the drying material 52, can be supplied via this flow channel 64 ultimately to the mixing region 58.

[0094] With regard to the first outlet of the air separator 61, via which the first air sub-stream 57a is supplied to the sorption unit 51, it should be noted that this first outlet is flow-connected to a flow channel 65 bounded, at least in certain regions, by the drying material 52. As can be seen in this context from the representation in FIG. 2, it is advantageous if the effective flow cross section of this flow channel 65, which is bounded, at least in certain regions, by the drying material 52, decreases in the flow direction of the first air sub-stream 57a in order to ensure that the drying material 52 is flowed through as evenly as possible, viewed over the surface area, by the first air sub-stream 57a. To this end, in the embodiment represented by way of example in the drawings, there is provided a corresponding air-directing element 66, which runs at an angle and bounds the flow channel 65 in the downward direction.

[0095] As indicated schematically in FIG. 3, in the solution according to the invention, in particular a division of the air stream which is to be directed through the sorption unit 51 is provided, in which division the air of the first air sub-stream 57a, as it passes through the drying material 52, is warmed to a temperature between 150.degree. C. and 300.degree. C., preferably between 200.degree. C. and 250.degree. C., and even more preferably between 220.degree. C. and 230.degree. C. The air of the second air sub-stream 57b, which primarily serves to cool the sorption unit 51, has in the region of the air separator 61 a temperature of 60.degree. C. to 80.degree. C., which corresponds to the air temperature at the suction side of the fan 53. As it passes through the air channel 62 designed in the form of an air bypass, the air of the second air sub-stream 57b, due to the (warmed) first air sub-stream 57a, which runs, at least in certain regions, to the second air sub-stream 57b, is warmed to a temperature between 70.degree. C. and 120.degree. C., and preferably between 80.degree. C. and 100.degree. C., at the end region of the flow channel 62 designed in the form of an air bypass.

[0096] In the then following mixing region 48, the air of the first and second air sub-streams 57a, 57b is mixed and returned into the treatment chamber 2 of the dishwasher 1 with a mixed temperature between 130.degree. C. and 170.degree. C., and preferably between 140.degree. C. and 160.degree. C.

[0097] In practical usage, it has proved to be of advantage if at least 50%, and preferably at least 70%, of the air stream generated by the fan 53 is directed as the first air sub-stream 57a through the drying material in order to be able to realize the previously described temperature ranges. The quantity of air which is circulated per unit of time by the fan 53 should here be around 20 to 120 m.sup.3/h, preferably around 40 to 100 m.sup.3/h, and even more preferably around 80 to 100 m.sup.3/h.

[0098] The invention is not limited to the features implemented in the described exemplary embodiment, but emerges from a synopsis of all the features disclosed herein.

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