Patent Publication Number: US-7585373-B2

Title: Dishwashing machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a dishwasher with a washing container and devices for washing dishes by means of rinsing liquor and with a sorption drying device which is connected in an air-conducting manner to the washing container via an outlet of the washing container and an inlet of the washing container, and is provided with a sorption column encompassing reversible dehydratable material. 
     2. Description of Related Art 
     As is known, conventional dishwashers perform a washing process whose programme sequence generally consists of at least one “Pre-wash” partial programme step, a “Clean” partial programme step, at least one “Intermediate wash” partial programme step, a “Clear wash” partial programme step and a “Dry” partial programme step. To increase the cleaning effect the rinsing fluid or rinsing liquor is heated before or during a partial programme step. The rinsing fluid is normally heated by means of electrical heating elements. Different drying systems are known for drying the items to be washed in a dishwasher. 
     DE 20 16 831 discloses, for example, a dishwasher of the type already mentioned in which the air is conducted from the washing container through a sealable opening in the wall of the washing container on reversibly dehydratable material, and from there to the outside through an opening. Desorption of the reversibly dehydratable material takes place during the non-operating phase of the device, the water vapour formed thereby being conducted to the outside through the opening. The dishwasher described is disadvantageous from the energy viewpoint because the regeneration of the reversibly dehydratable material takes place during a non-operating phase of the appliance, i.e. at a time when none of the partial programme steps already described is being carried out. A further disadvantage consists in the fact that the possibility of damage to the surrounding kitchen furniture cannot be ruled out as a result of the discharge of the water vapour formed during regeneration of the reversibly dehydratable material to the outside. In this case the regeneration is associated with an additional energy requirement which is additional to the energy required during the partial programme steps. 
     In order to minimise the energy expended during operation of a dishwasher, DE 103 53 774.0 of the applicant discloses a dishwasher with a washing container and devices for washing dishes by means of rinsing liquor which is provided with a sorption column which is connected in an air-conducting manner to the washing container and encompasses reversibly dehydratable material, where on the one hand the sorption column is used for drying the dishes and on the other hand the thermal energy utilised for desorption of the sorption column is used to heat the rinsing liquor and/or the dishes in the washing container, at least in part. 
     To solve the same problem DE 103 53 775.9 of the applicant proposes conducting air from a processing space and/or from ambient air through a sorption column and into the processing space for operating an appliance in the at least one “Dry” partial programme step, where the sorption column encompasses reversibly dehydratable material and moisture is extracted from the air during its through-passage. 
     Heating the items to be washed in the partial programme step preceding the “Dry” partial programme step is no longer normally necessary due to the use of reversibly dehydratable material with a hydroscopic property, e.g. zeolith. This allows a substantial saving in energy. 
     EP 0 358 279 B1 discloses a dishwasher with a closed drying system in which the air from the washing container circulates through a drying device that can be regenerated by heating and from this device back into the washing container. The drying device is assigned to the heater arranged outside the washing container for the rinsing liquor, this heater preferably being a geyser. The outlet of the washing container is located in the ceiling of the washing container, whilst the inlet is integrated in the rinsing tank of the washing container. The outlet of the washing container is connected to the sorption drying device by means of an air duct. Since the sorption drying device is assigned to the heater for the rinsing liquor it is arranged in a region underneath the rinsing tank. 
     A common feature of all the arrangements described above is that the integration of the sorption drying device in a dishwasher is only conceptually described. The object of this invention is therefore to provide a dishwasher in which a sorption drying device can be integrated easily and at low cost and which allows energy-efficient operation. 
     BRIEF SUMMARY OF THE INVENTION 
     An exemplary embodiment of the present invention provides a dishwasher with a sorption dryer and an air duct having a condensation surface in communication with the sorption dryer and a washing container. 
     A dishwasher according to the invention, particularly a domestic dishwasher, has a washing container and devices for washing dishes by means of a rinsing liquor, as well as a sorption drying device which is connected in an air-conducting manner to the washing container via an outlet of the washing container and an inlet of the washing container, and which is provided with a sorption column encompassing reversibly dehydratable material, the outlet of the washing container being connected by an air duct to the sorption drying device. According to the invention the air duct is designed at least in part as a condensation surface. 
     In the method according to the invention for operating a dishwasher, particularly a domestic dishwasher, with at least one “Drying” partial programme step in which is conducted from a washing container and/or ambient air through a sorption column and back into the washing container, the sorption column encompassing reversibly dehydratable material and moisture being extracted from the air as it passes through the sorption column, the air supplied to the sorption column is fed at least in part past a condensation surface in order to extract from the air taken from the washing container some of its moisture before the air having a residual moisture content is fed to the sorption column. 
     It is therefore possible, during the “Drying” partial programme step, to allow some of the water bound in the moist air to condensate, so that it need no longer be de-moistened by the sorption drying device. This enables a structurally simple, extremely energy-efficient dishwasher to be produced since the drying process can be completed within a shorter time. 
     In a suitable design of the dishwasher according to the invention the condensation surface is created by a heat-conducting connection to the washing container and/or to the ambient air. Here ambient air can be actively conducted to the air duct in a further design by means of a fan in order to obtain the condensation surface. This creates a highly spatially economic dishwasher which can be arranged in a space-saving manner, for example, between a housing wall and the washing container. Suitably no heating of the rinsing liquor and/or the items to be washed can take place in one design of the method in a partial programme step preceding the “Drying” partial programme step, e.g. “Clear washing”, in order to provide as low a temperature of the washing container as possible for increasing the efficiency of the condensation surface. 
     In a suitable design the air duct extends along a lateral wall of the washing container. The outlet of the washing container is located in an upper section of the washing container wall to form as large a condensation surface as possible. On the other hand, the sorption drying device is preferably arranged underneath the rinsing tank for reasons of space and to create the desired condensation surface. The advantage of this is that an optimum heating element of the sorption drying device does not increase the air flow until it flows along the air duct, thus allowing condensation of the moist air in the washing container along the air duct. 
     A barrier against penetrating water is suitably formed in the air duct adjacent to the outlet. This barrier may represent a cover overlapping the outlet, but it may also be designed so that the section of the air duct connected to the outlet is initially guided a short distance upwards along a lateral wall and is only then guided along the lateral wall of the washing container or in wound sections downwards towards the sorption drying device. The barrier is therefore formed by a section of a wall of the air duct, which prevents moisture from penetrating the sorption drying device containing electrical functional elements during a partial programme step in which items to be washed are loaded with rinsing liquor. 
     In a further suitable design provision is made for the air duct to have an actuatable valve for discharging water condensed in the air duct in the bottom region. The condensed and discharged water must then no longer be absorbed by the reversibly dehydratable material, so that the sorption column of the sorption drying device can be designed smaller than a conventionally designed sorption drying device without a condensation surface. This again advantageously provides valuable space. 
     In a further suitable design the air duct has a pressure-regulating means which, in the case of excess pressure in the washing container, provides pressure equalisation. The pressure-regulating means may be designed as an actively operable valve. According to another design the pressure-regulating means may open or close passively according to the pressure inside the washing container, and may be designed as a valve, for example. A vacuum is formed in the air duct during the “Drying” partial programme step, in which the fan of the sorption drying device is “in operation”, so that the pressure-regulating means has a sealing action. However, in the case of excess pressure, e.g. due to an expansion thrust, the pressure-regulating means can open and therefore reduce the pressure generated inside the washing container. The integration of the pressure-regulating means in the air duct of the sorption drying device enables the device ventilation that would otherwise be present in any dishwasher to be dispensed with. 
     Because of the sorption drying device preferably arranged in the bottom region of the dishwasher underneath a rinsing tank, it is appropriate to integrate the inlet of the washing container in the rinsing tank itself, since this enables a further air duct to be dispensed with. This allows simpler production at lower cost. 
     According to a further suitable design the outlet and/or inlet is/are provided with a passive means for sealing against penetrating water in the simplest case this may be cover over the outlet and/or inlet which is preferably designed so that at the same time the direction of the air flow is established to achieve the best possible turbulence of the air in the washing container for effective moisture absorption. 
     In an alternative design the outlet and/or the inlet may be provided with active sealing means. The sealing means may be designed, for example, so that it can be actuated by applying a voltage. The sealing means may therefore be designed so that it is motor or hydraulically driven. It is particularly advantageous here if voltage is also applied to the sealing means when voltage is applied to the fan, enabling the sealing means to open to provide air circulation to the sorption drying device. Here the inlet and outlet need only be open during the regeneration phase of the sorption column and during the “Dry” partial programme step. During the other partial programme steps the sealing means provide such sealing to prevent spray water from penetrating the sorption drying device provided with electrical functional elements. 
     In a further suitable design the sealing means may also be actuated by a temperature-sensitive memory metal. Here the sealing means is not actuated electrically but on the basis of the temperatures prevailing during different partial programme steps. 
     According to a further design the sorption column is used for drying the dishes on the one hand and the thermal energy utilised for desorption of the sorption column is used for heating the rinsing liquor in the washing container and/or the items to be washed on the other. The dishwasher can be designed, in terms of its operating principle, as described in DE 103 53 774.0 of the applicant, the contents of which are incorporated in this application where appropriate. The machine described here differs in terms of a preferred arrangement of the sorption drying device 
     According to a preferred feature, air is conducted from the washing container and/or from the ambient air during a partial programme step with rinsing liquor to be heated, preferably during the “Clean” and/or “Pre-wash” and/or the “Clear wash” partial programme step through the sorption column and back into the washing container 
     An electric heating element is suitably arranged for desorption of the reversibly dehydratable material and for heating the rinsing liquor and/or the items to be washed. The electrical heating element is preferably arranged in the reversibly dehydratable material or in a pipe to the sorption column. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in further detail in the following with reference to the figures, in which: 
         FIG. 1  shows an exemplary embodiment of a dishwasher of the invention according to a first variant, and 
         FIG. 2  shows a further exemplary embodiment of a dishwasher of the invention in which the device ventilation is integrated in the sorption drying device. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
       FIG. 1  shows, in a diagrammatic representation, a dishwasher  1  of the invention according to a first variant, with a washing container  2 , in which are arranged crockery baskets, not shown, for the storing of items to be washed, not shown either. The structure of the dishwasher according to the invention may in principle be as described in DE 103 53 774 and/or DE 103 53 775 of the applicant, the contents of which are also incorporated in this application if appropriate. Dishwasher  1  is provided with a sorption column  10  which is connected in an air-conducting manner to washing container  2  and encompasses reversibly dehydratable material  11 , e.g. zeolith, sorption column  10  being used on the one hand for drying and on the other hand for heating air passed through. Washing container  2  has an outlet  5  which is arranged in the exemplary embodiment described in a central region and has a pipe designed as air duct  17  leading to sorption column  10 , and an inlet  8  of sorption column  10  arranged in the exemplary embodiment described in a rinsing tank  6 . In addition to sorption column  10 , a sorption drying device  21  has a fan  9  and an electric heating element  12 , a housing  14  of the fan and a housing  13  of sorption column  10  being formed integrally underneath rinsing tank  6  of the dishwasher. The passage of air through sorption drying device is denoted by arrows A, B and C. 
     To increase the efficiency of sorption drying device  21 , particularly during the “Drying” partial programme step, air duct  17  is designed as a condensation surface  18  and is connected in an air-conducting manner to washing container  2  and/or by means of a housing wall to ambient air. To ensure maximum efficiency it is advantageous to dispense or almost dispense with heating of the washing space and/or the items to be washed in the partial programme step preceding the “Drying” partial programme step, generally “Clear wash, which is easily possible due to the drying process described. Consequently moist air flowing through air duct  17  may condensate on the walls of the air duct during the “Drying” partial programme step. The drying process in itself preferably takes place as described in DE 103 53 774 and/or DE 103 53 775. The condensate can be discharged from air duct  17  by means of valve  19 , shown diagrammatically, so that this quantity of moisture need not be absorbed by sorption column  10 . The advantage of this is that sorption column  10  can be dimensioned smaller, reducing the space requirement of the same. The liquid discharged from air duct  17  can either be removed from dishwasher  1  via a drain outlet of the same, not shown, or can be stored intermediately for a subsequent washing programme section. 
     Alternatively or additionally condensation surface  18  may be formed by ambient air, where this air can be conveyed actively, for example, by an (additional) fan to air duct  17  (not shown). Other parts of the dishwasher can also be used for drying. 
     To prevent the penetration of spray water during a partial programme step which items to be washed undergoes in washing container  2 , in air duct  17  and hence in the electrical functional elements (fan  9 , heating element  12 ), air duct  17  is first guided upwards from outlet  5 , then along the washing container wall downwards to sorption drying device  21 . Consequently a barrier  16  is formed in the air duct, which barrier reliably prevents the penetration of water. 
     Correspondingly, inlet  8  has a sealing means  15  which, in the exemplary embodiment, is designed as a cover with a flow function. Both outlet  5  and inlet  8  could be provided with an actively actuated sealing means according to another variant, not shown, which sealing means would be open during the operation of sorption drying device  21  and closed in the remaining partial programme steps. Particularly advantageous here is a direct coupling to the operation of fan  9  and/or electric heating element  12 . Thus the active sealing means could be actuated by means of a motor or hydraulically, the actuation being dependent on the operation of the sorption drying device. Alternatively the use of a memory metal would also be conceivable, which metal could be brought into an opening or closing position according to the varying temperatures during different partial programme steps. 
       FIG. 2  shows a section of a further exemplary embodiment of a dishwasher  1  according to the invention, in which a valve  20  is integrated in air duct  17 , which performs the function of device ventilation in the case of an expansion thrust. In the simplest case valve  20  can be designed as a mechanical valve which is retained in the closing position for example, due to the fan (not shown) in sorption drying device  21  and due to the vacuum generated thereby in a closing position as long as sorption drying device  21  is in operation (continuous line). In the case of an expansion thrust the excess pressure generated inside the washing container is distributed along air duct  17  as far as valve  20 , the latter opening (dotted line). This ensures that no damage can be caused to the dishwasher due to an excess pressure that is suddenly generated. 
     Moreover, the design shown in  FIG. 2  corresponds to a dishwasher of the invention according to the first variant, where air duct  17  is connected in an air-conducting manner to washing container  2  and/or a housing wall to form a condensation surface  18 . Sorption drying device  21 , shown only diagrammatically, is arranged laterally underneath rinsing tank  6 , for example, inlet  8  being formed in the border region between rinsing tank  6  and washing container wall  22 . To prevent the penetration of water in sorption drying device  21 , a (passive) sealing means  15  in the form of a flow-influencing plate is provided, for example, above outlet  8 . 
     With this invention a dishwasher is provided which can be produced economically and with which the items to be washed in the washing container can be cleaned and dried efficiently, with the possibility of minimising the associated energy expenditure. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Dishwasher 
           2  Washing container 
           5  Outlet 
           6  Rinsing tank 
           8  Inlet 
           9  Fan 
           10  Sorption column 
           11  Reversibly dehydratable material 
           12  Electrical heating element 
           13  Fan 
           14  Fan 
           15  Sealing means 
           16  Barrier 
           17  Air duct 
           18  Condensation surface 
           19  Valve 
           20  Valve 
           21  Sorption drying device 
           22  Washing container wall 
           23  Housing wall 
         A,B,C Air passage