Patent Publication Number: US-2011048472-A1

Title: Dishwasher

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a dishwasher having a washing container for accommodating dishes to be washed and having a hot-water intake fitting, which is provided for supplying the washing container with hot water from an external hot water supply. 
     In modern dishwashers, the dishes to be washed are cleaned automatically in a washing container using water according to a wash program that can usually be selected. A wash program here usually comprises a plurality of consecutive partial wash cycles, in which the water is dosed with cleaning materials and/or additives depending on the partial wash cycle in progress and is brought to a temperature that is suitable for the partial wash cycle in progress. 
     A typical wash cycle performed by a wash program includes, in particular, a prewash cycle, one or more cleaning cycles, a rinse cycle and a final drying cycle. 
     The prewash cycle is used for removing larger pieces of dirt from dishes. These larger pieces of dirt are basically removed mechanically, so in many cases there is no need for detergent during the prewash phase. In this cycle, the water temperature may vary in a wide range, for example from 15° C. to 50° C. 
     The subsequent cleaning cycles are used for complete removal of all dirt. Detergent is added to the water for this purpose, which usually has the best cleaning action if the water is heated, in particular if the water is at a temperature of about 40° C. to 55° C. 
     A subsequent rinse cycle is used particularly for preventing spotting on the dishes, which could arise from dissolved substances in the water such as salt and/or chalk. Rinse agent is added to the water during the rinse cycle for this purpose. Another function of the rinse cycle is to prepare for the subsequent drying cycle. The dishes are therefore heated during the rinse cycle by using particularly hot water having a temperature of 60° C. to 70° C. for example. In the final drying cycle, water drops attached to the hot dishes evaporate and condense on the inside face of the washing container because of the lower temperature prevailing here. 
     In order to bring the water provided for washing to the required temperatures, it is standard practice, particularly in North America, to supply the washing container with hot water from an external hot water supply. Hence dishwashers intended for this region have a hot-water intake fitting provided as standard that can be connected to the external hot water supply. Dishwashers of this type themselves then have either no heater or at most a lower-power heater. 
     In dishwashers operated with pre-heated water, the temperature intended for the dishes is often not reached during the rinse cycle because the temperature of the water supplied via the hot-water intake fitting is too low. The convection arising from the intrinsic heat of the items being washed is then too low in the subsequent drying cycle, so that often an inadequate drying result is obtained specifically with those types of dishwashers having a hot water supply. 
     To overcome the problem of inadequate drying of the washed dishes, a drying heater, for example, would be possible, which heats the air inside the washing container during the drying cycle. An unreasonable amount of energy input is required, however, to achieve a substantial improvement in the drying performance. It would also be possible to have ventilation flaps or ventilation fans, which can be used during the drying cycle to release moist air from the washing container to the environment. Such solutions would again be impractical and too costly. In addition, because of the air outlet hole required, they would mean changing the design of the dishwasher and would considerably increase the noise level of the dishwasher. Furthermore, the vented air would cause a significant deterioration in the atmosphere in the room surrounding the dishwasher. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a dishwasher designed to operate with pre-heated water that has improved drying of the dishes. 
     For a dishwasher of the type cited in the introduction, the object is achieved in that it comprises a storage container, which is in thermally conductive contact with the washing container, and a cold-water intake fitting, which is provided for supplying the storage container with cold water from an external cold water supply. 
     Considerable cooling of at least part of the wall of the washing container of the dishwasher can be achieved using the storage container that is in thermally conductive contact with the washing container, in particular if the tank is full of fresh cold water. By this means, it is possible to increase the condensation of steam onto the inside face of the washing container and thereby in turn the propensity of water drops attached to the dishes to evaporate, so that the drying result can be improved considerably. This is particularly advantageous for the dishwasher according to the invention if its hot-water intake fitting, in particular fitted as standard, is connected to an external hot water supply, i.e. an external hot water supply installation. The reason is that then, in particular during the respective drying cycle of the wash cycle of a running dishwashing program, by filling the storage container with cold water, a greater temperature difference can be produced between the inside of the washing container containing the items placed within it for washing and the wall that is in thermally conductive contact with the storage container. 
     At the same time, the additional design costs for a dishwasher according to the invention are extremely low. In addition, there is no increase in the power consumption nor in the external noise while the dishwasher is running. Furthermore, there is no need to make any changes to the dishwasher design. 
     According to an advantageous development of the invention, the control device of the dishwasher according to the invention can be designed such that, in particular during a drying cycle, i.e. for the period of a drying cycle of a running wash program, the storage container contains cold water, in particular is full of cold water. This can ensure improved condensation and hence drying performance in the washing container, in particular if the hot-water intake fitting of the dishwasher according to the invention is connected separately from the cold-water intake fitting to an external hot water supply, for the purpose of filling with hot water for partial wash cycles, such as a cleaning cycle and/or rinse cycle for instance. 
     In particular, it can be advantageous for this purpose if the control device is designed for automatic control of a wash program, in which at, or after, the end of a rinse cycle and/or during a drying cycle, in particular at the start of a drying cycle, a control valve of the cold-water intake fitting is opened at least for a time in order to supply, in particular to fill, the storage container with cold water. 
     In particular, it may be advantageous if the control device controls the outflow of the storage container in such a way that cold water stored for one or more partial wash cycles such as the pre-rinse cycle, for instance, of a running wash program, can be emptied systematically from the storage container into the washing container. For this purpose, the outflow of the storage container is opened and cold water is channeled into the washing container through the supply tank in the manner of a lock-gate system. 
     According to an advantageous development of the dishwasher according to the invention, the storage container is assigned a controllable outlet that leads into the washing container. Water that is no longer needed in the storage container can thereby be pumped out easily via a pump that is already fitted for the purpose of pumping water out of the washing container. In this case, the water coming from the storage container can be used for washing dishes in a subsequent, later dishwashing program before it is finally pumped out of the dishwasher. This can reduce water consumption of the dishwasher. This is advantageous especially when the volume of cold water held in the storage container has already reached room temperature. 
     In particular, it can be advantageous if the control device is designed for automatic control of a wash program, in which, at the start of the newly selected wash program, a control valve of the controllable outlet of the storage container is opened at least for a time in order to supply the washing container with water, which was stored by the previous dishwashing program, from the storage container. This can advantageously save water, in particular, that was provided as cooling water in the storage container for the drying cycle of the earlier, previous dishwashing program. 
     A partial wash cycle of a wash program for which this water, which is temporarily held in the storage container, can be used, is normally a prewash cycle at the start of a newly started dishwashing program or a cleaning cycle. Such wash cycles are carried out at relatively low temperatures. The water in the storage container coming from a previous wash program is generally at approximately room temperature after being held for a sufficiently long time after the previous wash program has finished until a new dishwashing program is started. Such a temperature is usually sufficient for a first wash cycle of a wash program, so that there is often no need for heating. At most, relatively little energy is needed to achieve a desired or necessary target temperature. Instead of using the heater belonging to the dishwasher to achieve the intended temperature, it is also possible to mix the water from the storage container with water from the external hot water supply. This can be done in the washing container via the separate hot-water intake fitting. Alternatively, in an additional or independent arrangement from this, the hot-water intake fitting can also be connected to the storage container so that the hot water and cold water are mixed either here or, for this possible, advantageous connection variant, also in the washing container if the control valves of the hot-water intake fitting and of the cold-water intake fitting and also the valve of the storage-container outlet are open. The desired temperature can thereby be set exactly for all advantageous connection variants, so that energy can be saved compared with a dishwasher that washes solely using hot water from the external hot water supply. This is because it is possible to allocate only that amount of hot water that is actually needed for the respective partial wash cycle of a wash cycle. For instance, in dishwashers operated solely using hot water, the first wash cycle, for example, is often carried out at a temperature that is unnecessarily high from the dishwashing viewpoint. 
     According to an advantageous development of the invention, the storage container can lie in surface-contact with the washing container. This enables good heat transfer from the washing container to the storage container. Costly heat-conducting components are not required. A substantial improvement in the drying result of the dishwasher is thereby achieved with a low-cost design. 
     According to an advantageous development of the dishwasher according to the invention, the storage container can be arranged on a side wall of the washing container. The side wall of a washing container is sufficiently rigid to bear even a full storage container. This means it is possible to fix the storage container directly onto the washing container, which improves the heat transfer from the washing container to the storage container. In addition, the side wall of a washing container particularly has a substantially flat design, so that it is easily possible to make a surface-to-surface contact between storage container and washing container. Hence, for example, a simple-to-make cuboid-shaped storage container can be used. 
     According to an advantageous development of the invention, the storage container can be a plastic part. In particular, it is made of polypropylene and/or polyethylene. Such tanks can be made, for instance, using suitable extrusion or molding processes. In addition, storage containers made of plastic exhibit a certain degree of flexibility, so that with suitable fixing they can fit particularly well against the washing container, especially when they are full, which again improves the drying. Of course other materials, ideally heat conductors, for instance metallic materials, in particular stainless steel, can also be used. 
     According to an advantageous development of the invention, the storage container can be arranged on an upper section of the washing container. Since higher temperatures prevail in the upper section of the washing container than in a lower section during the drying cycle, this further improves the steam condensation in the washing container, which further improves the drying result. In addition, arranging the storage container on an upper area of the washing container, in particular having the outlet hole of the storage container at a height above the floor of the washing container, means that it is possible to empty the storage container without difficulty at the end of the drying cycle by means of gravity. 
     According to a particularly preferred development of the invention, a control device is designed for automatic control of a wash program, in which at, or after, the end of a rinse cycle and/or during a drying cycle, in particular at the start of a drying cycle, a control valve of the cold-water intake fitting is opened at least for a time in order to supply, in particular to fill, the storage container with cold water. A drying cycle of a wash program usually follows immediately after a rinse cycle. Whereas relatively hot rinse water is circulated in the washing container while the rinse cycle is running, no water is circulated during the drying cycle. Instead, at, or shortly after, the start of the drying cycle, the water collecting in the lower area of the washing container is pumped out of the dishwasher. If, as intended, the storage container is not supplied with cold water particularly until during the drying cycle rather than some time beforehand, this prevents the water in the storage container being heated by the hot rinse water. In principle, the storage container can be supplied by opening a control valve of the cold-water intake fitting from the start of the drying cycle onwards. Advantageously, the storage container is not filled in particular, however, until pumping out the hot rinse water has finished. A significant amount of heat is thereby carried out of the washing container, so that the water in the storage container remains cold longer and hence its cooling action is retained for longer. It is also advantageous in this case if a program pause or drip-off phase is provided between the end of pumping out the rinse water and starting to fill the storage container, in order to enable thereby rinse-water droplets on the inside face of the washing container and on the dishes to drip off, which ultimately results in the water that was introduced into the storage container after the drip-off phase remaining cold even longer, so that the drying performance is again improved. By modifying the control device that exists anyway for controlling a control valve of the cold-water intake fitting, full automation of the supply process of the washing container is possible in particular at reasonable cost. There is no need for an operator to intervene manually, so user convenience is not impaired. 
     According to an advantageous development of the dishwasher according to the invention, the storage container is designed to hold a volume of cold water that is substantially sufficient for a wash cycle, for example for a prewash cycle or for a cleaning cycle, of a wash program. In particular, the storage container is designed to hold a volume of cold water that is largely equal to the washing-bath volume required for a first partial wash cycle, in particular for a prewash cycle or for a cleaning cycle, of a selected wash program. The maximum possible energy saving can be achieved in this manner. 
     In an advantageous exemplary embodiment of a dishwasher according to the invention, the hot-water intake fitting leads, in particular additionally, into the storage container. A particularly simple design of the dishwasher can be implemented in this way if there is no cold water supply available. For instance, the hot water and cold water can be carried from the storage container via the same fittings, such as pipes, valves etc. 
     According to an advantageous development of the invention, the hot-water intake fitting and/or the cold-water intake fitting is allocated an open flow length. The open flow length(s) can be arranged in the storage container, for instance. The open flow lengths prevent water being siphoned back towards the hot water supply or the cold water supply respectively, which could occur if dynamic processes create a temporary negative pressure. It is thereby possible to prevent, in particular, too low a water level in the storage container and/or in the washing container. 
     According to an exemplary embodiment of the dishwasher according to the invention, an external adapter or adapter built into the appliance can be provided for the purpose of optionally connecting the hot-water intake fitting and the cold-water intake fitting to a common water supply. The adapter can be used when there is only one water supply, i.e. a single type of water supply connection, at the location in which the dishwasher is to be operated. Where, however, there is a hot water supply and also a cold water supply at the respective installation location of the dishwasher then the adapter is not used. The adapter can be used if there is only a cold water supply or a one hot water supply. Hence the adapter allows operation of a dishwasher according to the invention at locations in which this would otherwise not be possible. In addition, no fundamental changes to the wash program are necessary. If the common water supply is a cold water supply, however, the power consumption increases. Furthermore, if the common water supply is a hot water supply, a deterioration in the drying result can be avoided in particular by the storage-container outlet being opened during the respective drying cycle in order for hot water to flow through into the washing container, i.e. no water is then stored temporarily during the respective drying cycle. In particular, where there is no cold water supply, it can obviously be advantageous for the control valve in the hot-water intake fitting to be closed by means of the control device to stop or prevent the intake of hot water via the storage container during the respective drying cycle. 
     According to a preferred embodiment of the dishwasher according to the invention, the control device is designed to adapt a wash program where there is no connection between the hot-water intake fitting and a common water supply or where there is no connection between the cold-water intake fitting and a common water supply. In this case, sensors may be present, by means of which the control device detects whether or not the hot-water intake fitting or the cold-water intake fitting is connected to a water supply. Said sensors may be, in particular, flow sensors or pressure sensors. In addition, temperature sensors may be advantageous, so that it is also possible to detect whether the respective water intake fitting is connected to a cold water supply or to a hot water supply. The wash program can be adapted, in particular, such that where there is no connection to a hot water supply, hot water is replaced by cold water, which is then heated. On the other hand, where there is no cold water supply, in particular the step “fill the storage container with cold water or drain cold water from the storage container” can be dispensed with. In this case, the storage container is taken, in particular, into a flow-through state by opening its outlet, in particular its outlet valve, by means of the control device. The sequence of a wash program can be optimized and especially shortened by this means. 
     In general terms, the control device can hence advantageously control the control valve of the cold-water intake fitting and/or the control valve of the hot-water intake fitting and the outlet of the storage container in such a way that for one or more partial wash cycles of the wash cycle of a selected dishwashing program, cold water and/or hot water flows through the storage container and into the washing container. 
     The subclaims describe other embodiments and developments of the invention. The advantageous embodiments and developments of the invention explained above and/or disclosed in the subclaims can here be applied separately or else also in any combination with each other in the dishwasher according to the invention and in the method according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, its embodiments and developments and its advantages are explained below with reference to drawings, in which: 
         FIG. 1  shows a schematic 3-dimensional diagram of an advantageous exemplary embodiment of a dishwasher designed and connected according to the invention; 
         FIG. 2  shows a first functional block diagram of the dishwasher of  FIG. 1 ; 
         FIG. 3  shows an advantageous timing diagram for the purpose of explaining how the dishwasher of  FIG. 2  works; 
         FIG. 4  shows a modified functional block diagram of a second advantageous exemplary embodiment of a dishwasher designed according to the invention, and 
         FIG. 5  shows a further advantageous exemplary embodiment of a dishwasher designed according to the invention, which is connected in an alternative manner. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
     In the following figures, corresponding parts are given the same reference symbols. A reference symbol and explanation is given here only to those components of a dishwasher that are necessary for understanding the invention. Obviously the dishwasher according to the invention may contain other parts and components. 
       FIG. 1  shows a schematic 3-dimensional diagram of an advantageous exemplary embodiment of a dishwasher  1  according to the invention. This comprises a washing container  2 , which can be closed by a door  3 , to create a wash cabinet for washing dishes. 
     A hot-water intake fitting  4  (shown schematically) is arranged on the rear side of the dishwasher  1 , as is common practice with dishwashers provided for the North American market. Said fitting comprises a hot water connector  5 , to which a connecting hose  6  is connected. The connecting hose  6  is connected to an external hot water supply WH in the intended manner. The standard practice is to connect it, as shown, to a hot water tap WH. The hot-water intake fitting  4  comprises components (not shown in  FIG. 1 ) that enable hot water to be piped from the hot water tap WH into the washing container  2 . 
     In addition, the dishwasher  1  comprises a storage container  7 . The storage container  7  is arranged on a side wall  8  of the washing container  2  in such a way that heat can transfer from the washing container onto the storage container. The storage container  7  is shaped as a very flat cuboid. For instance, its width equals approximately 2 cm say, so that it can be arranged easily on a side wall of the washing container, in particular between a side wall  8  of the washing container  2  and a wall of an outer case that may be present on the dishwasher  1 . The outer case may not be required, in particular for built-in dishwashers. The height and depth of the washing container may each equal between 40 and 50 cm, for example. This can achieve a tank capacity of 3 to 4 l, for example. This volume is sufficient for performing a first wash cycle of a wash program solely using water from the storage container  7 . The flat construction results in a large contact area between the washing container  2  and the storage container  7 . Good heat transfer is thereby possible. 
     Whilst the washing container  2  may be made of stainless steel, the storage container  7  is preferably made of plastic. The storage container can be made, in particular, of polypropylene and/or polyethylene, which is a low cost plastic that can be processed easily. For instance the storage container  7  can be made easily by extrusion processes or molding processes. Alternatively, it is also possible to make it from a metallic material, in particular stainless steel, or another thermally conducting material. Since the side wall  8  of the washing container  2  is substantially planar in form, the inwards-facing thermal-contact surface of the storage container  7  also has a planar form and hence can be made easily. The flexibility of the storage container inherent to its material means that it can fit against the washing container  2  particularly well, especially when the storage container  7  is full. This again has a positive impact on the heat transfer. 
     In order to be able to fill the storage container  7  with cold water, a cold-water intake fitting  9  is provided, which comprises a cold water connector  10 . Connected to this cold water connector  9  is a connecting hose  11 , which is connected to an external cold water supply KH. In this case it is once again standard practice to connect it, as shown, via a cold water tap KH of the external cold water supply KH. The cold-water intake fitting  9  comprises means (not shown in  FIG. 1 ) that enable cold water to be supplied from the cold water tap KH into the storage container  7 . 
     If the storage container  7  is full of cold water during a drying cycle of a wash program of the dishwasher  1 , then the inside face of the side wall  8  of the washing container  2  is cooled because of the thermally conducting contact between storage container  7  and washing container  2 . This boosts condensation of steam contained in the washing container  2  on the side wall  8 . This results in a better drying result during execution of the wash program. The storage container  7  is here arranged advantageously on an upper section of the washing container  2 , because usually there are higher temperatures here than in a lower section, so that cooling of the side wall specifically here results in a particularly good drying performance. 
     A pump well  12  is provided in a lower area of the washing container  2 . A pump for circulating water in the washing container  2  during a wash cycle is provided in the pump well  12 . In addition, a heater for heating the water contained in the washing container  2  is provided in the pump well  12  or in another position in the liquid circulation system of the dishwasher  1 . A pump for pumping out water, for example at the end of a wash cycle, is also provided in the pump well  12 . The different pump functions, however, can also be performed by a single pump in conjunction with switchable connectors and/or output fittings, in particular valves. The pump well  12  is here connected via means (not shown) to a drain connector  13  such that water can be pumped by a drain pump out of the washing container  2  via a drain hose  14  connected to the drain connector  13  into a drain fitting A, for example a drainage pipe A. 
     The dishwasher  1  also comprises a control device  15  for controlling the sequence of a wash program. Various wash programs, which can be selected by an operator, can be saved in the control device  15 . The control device is arranged here in the exemplary embodiment inside the door  3  of the washing container  2 , although it could also be arranged in another position of the dishwasher  1 . 
       FIG. 2  shows a functional block diagram of the dishwasher of  FIG. 1 . The hot-water intake fitting  4  comprises a control valve  16 , which can be controlled by the control device  15 . The control valve  16  of the hot-water intake fitting  4  is arranged down stream of the hot water connector  5 . The inflow of hot water to the washing container  2  can thereby be controlled by the control device  15  as a function of the selected wash program. An open flow length  17  is provided downstream of the control valve  16 . The open flow length  17  is known as an air gap, which is used to prevent water being siphoned back out of the washing container  2  should dynamic processes create a negative pressure in the external hot water supply. This prevents dirty water used for the wash getting into the hot water supply. 
     The cold-water intake fitting  9  likewise comprises a control valve  18 , which can be controlled by the control device  15 . This control valve  18  is arranged between the cold water connector  10  and another open flow length  19 . It is possible to supply the storage container  7  with cold water by means of the control valve  18 . Arranged at the lower end of the storage container  7  is a controllable outlet  20 , which leads into the washing container  2 . The controllable outlet  20  comprises a control valve  21  that can likewise be controlled by the control device  15 . It is thereby possible to let water contained in the storage container  7  flow into the washing container  2  as a function of the selected wash program. In order to prevent water running out of the dishwasher  1  in the event of a fault, for example a fault with the control valve  21 , the storage container  7  is provided with an overflow that leads into the washing container  2 . 
     The electrical components that are arranged in the pump well  12  are likewise controlled by the control device  15 . Water contained in the washing container  2  can hence be systematically heated, circulated via a spray device  23  and pumped out to the outside via the drain connector  13 . 
       FIG. 3  illustrates how the dishwasher according to the invention works. In  FIG. 3 , the curves K 1 , K 2  and K 3  are plotted along a common time axis t. Curve K 1  here represents the temperature of the inside face of the side wall  8  of the washing container  2  in the area of the storage container  7 . In addition, the curve K 2  shows the volume of water contained in the washing container  2 . Finally, curve K 3  shows the volume of water contained in the storage container  7 .  FIG. 3  shows a final phase of a first wash program SP 1  and, offset in time from this, an initial phase of a second wash program SP 2 . At time t 0 , a rinse cycle KG of the wash program SP 1  begins. The temperature of the side wall  8  here lies at an initial value T s , which essentially equals the wash temperature of a previous cleaning cycle. The washing container  2 , like the storage container  7  too, is empty at time t 0 . At time t 0 , however, the control valve  16  is opened, so that hot water flows into the washing container  2  with a certain intake temperature. This process lasts until time t 1 , at which point the control valve  16  is closed. 
     At time t 1 , the circulating pump of the pump well  12  is switched on. If the intake temperature of the hot water does not equal a desired target rinse temperature, a heater in the liquid circulation system, in particular in the pump well  12 , is also switched on to provide additional heating. This is the case here in the exemplary embodiment. As a result, the temperature of the side wall  8  of the washing container  2  increases gradually up to a maximum value T m , which is reached at a time t 2 . At this time t 2 , both the circulating pump and the heater are switched off. The drying cycle TG starts from time t 2 . When most of the water distributed by the spray device  23  in the washing container  2  has run out, the water collecting in the pump well  12  is pumped outside at the end of the rinse cycle KG, so that the washing container  2  is substantially empty at time t 4 . A substantial amount of thermal energy is removed from the washing container  2  by pumping out the relatively hot water of the rinse cycle KG. From time t 4  to time t 5 , a program pause or drip-off phase is provided for the purpose of allowing hot water that is still present in the top section of the washing container  2 , in particular on the items to be cleaned and/or dish baskets, to collect in the pump well  12 , so that additional heat energy is removed from the top section of the washing container  2 . The temperature of the side wall  8  of the washing container  2  falls approximately logarithmically from time t 2  to t 5 . The reason for this is that the washing container  2  is no longer heated in this time period while the side wall  8  of the washing container  2  is simultaneously dissipating heat to the outside. As a result, there is a temperature difference between the dishes located in the washing container  2  and the inside face of the side wall  8 . This encourages evaporation of water on the dishes, which then condenses on the relatively cold side wall  8  and can run off. The more water that condenses the better this evaporation. 
     To boost this condensation process, the storage container  7  is filled with cold water starting at time t 5 , i.e. after the drip-off phase, by opening the control valve  18 . Once the storage container  7  has been completely filled at time t 6 , the control valve  18  is closed again. At a time t 7 , which is defined by the wash program, the drying cycle TG and the wash program SP 1  are finished together. An excellent drying result can be achieved because of cooling the washing container  2  with cold water in the storage container  7  from time t 5  to time t 7 . 
     If the operator switches the dishwasher on again at time t 8 , a second wash program SP 2  is started. This wash program SP 2  can have the same sequence as the wash program SP 1  or have another sequence. At time t 8 , the temperature of the washing container  2  essentially equals an ambient temperature T a . The washing container  2  is empty and the storage container  7  is full. After an initialization phase up to time t 9 , during which a self-test is performed, for instance, the control device  15  opens the control valve  21 . This causes the storage container  7  to empty and the washing container  2  to fill. At time t 10 , the circulating pump of the pump well  12  is then started up so that the actual prewash of the dishes begins. Water can be saved overall by using stored water from the storage container  7 . At the same time, energy is saved because the water from the storage container  7  has a temperature that essentially equals the ambient temperature and hence is normally warmer than the water from a building cold water supply. 
     This means that it is normally possible to dispense with heating the water in the washing container  2  during the prewash cycle VG. At the same time, there is also no need to take hot water from the external hot water supply. This also results in an energy saving, however, compared with those dishwashers in which hot water from an external hot water supply is used for prewashing. This is because hot water from a building hot water supply normally has a temperature that is unnecessarily high for prewashing during a prewash cycle VG. 
       FIG. 4  shows a modified functional block diagram of a dishwasher  1  according to the invention. The essential difference from the exemplary embodiment discussed with reference to  FIG. 2  is that the hot water is not fed directly into the washing container  2  but is fed first into the storage container  7 . Hence the hot-water intake fitting  4  is also connected to the storage container  7  in addition to the cold-water intake fitting  9 . This simplifies the mechanical design of the dishwasher  1 . The dishwasher  1  of  FIG. 4  is here operated on the principle described with reference to  FIG. 3 . The storage container  7  is used here as a tank only for storing cold water. As regards the hot water, however, it is used solely as a flow path. Hence, if the washing container  2  is to be filled with hot water, the control valve  16  of the hot-water intake fitting  4  and the control valve  21  of the outlet  20  of the storage container  7  are opened simultaneously. 
       FIG. 5  shows a dishwasher  1  according to the invention, in which the hot-water intake fitting  4  and the cold-water intake fitting  9  are connected via an external or appliance-fitted adapter  24 , in particular an adapter built into the appliance, to a common water supply GH. The common water supply GH may be a cold water supply or a hot water supply. It is advantageous to use the adapter  24  when there is only one water supply available in the area of the dishwasher  1 , such as only a hot water supply for instance. The adapter  24  allows the dishwasher  1  to be operated at locations in which this would otherwise not be possible. This does not make full use of the advantages of the dishwasher according to the invention, however. 
     Particularly when there is only a hot water supply available, and the hot-water intake fitting  4  that leads to the washing container  7  and the cold water supply fitting  9  that leads to the storage container  7  are connected to this, it can be advantageous if the control device  15  opens the control valve  18  of the cold-water intake fitting  9  and the control valve  16  of the hot-water intake fitting  4  and the outlet  21  of the storage container  7  during the respective rinse cycle and especially the subsequent drying cycle, in order to avoid incoming warm water or hot water being held temporarily in the storage container during the period of the respective drying cycle. Then the storage container acts only as a flow path and not as a storage device. If, however, its outlet were blocked or closed and if it were hence to store incoming hot water, this would be associated with an impairment or degradation in the condensation process in the washing container. 
     Of course it can also be advantageous if the control device  15  controls the control valve  18  of the cold-water intake fitting  9  and/or the control valve  16  of the hot-water intake fitting  4  and the outlet valve  21  in the outlet  20  of the storage container  7  in such a way that for one or more partial wash cycles such as the prewash cycle, cleaning cycle and/or rinse cycle, for instance, of the wash cycle of a selected dishwashing program, the hot water from the external hot water supply, which is the only supply available, flows through the storage container  7  and into the washing container  2  and is not stored in the storage container. 
     Conversely, where there is only a cold water supply available, to which then both the cold-water intake fitting  9  and the hot-water intake fitting  4  are connected, it can be advantageous to use the storage container as a storage device for cold water during the respective drying cycle by the outlet valve  21  being kept closed by the control device  15  during the drying cycle. It is then possible to keep this stored water until a later, newly started dishwashing program for reuse for a partial wash cycle such as a prewash cycle or cleaning cycle, for instance, by the control device  15  opening the outlet valve  21 .