Patent Abstract:
A dishwasher ( 100 ) for pot washing, comprising a detector ( 160 ) for automatically detecting what type of washing basket ( 140 ) has been placed in the dishwasher ( 100 ). This enables automatic selection of water pressure and granule control, such that more sensitive crockery and plates are not damaged. The detector can be an inductive sensor ( 160 ) that detects an indicating member ( 141 ) of the washing basket. The washing basket can comprise one or several indicating members, for enabling a more reliable detection. A method of operating such a dishwasher ( 100 ) comprises the steps of automatically detecting what type of washing basket ( 140 ) is placed in the dishwasher, and then controlling the water pressure and granule addition according to what washing basket was detected. A system comprises an above dishwasher and an above washing basket.

Full Description:
This application is a National Stage Application of PCT/EP2008/050766, filed 23 Jan. 2008, which claims benefit of Serial No. 0700194-4, filed 26 Jan. 2007 in Sweden and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
     FIELD OF THE INVENTION 
     The present invention relates to a dishwasher using granules for washing pots and pans and a washing basket for holding dirty dishes. It further relates to a method of operating the dishwasher and a system of a dishwasher and a washing basket. 
     BACKGROUND OF THE INVENTION 
     Dishwashers for pot washing traditionally operate with high water pressure and sometimes with granules added to the water. This efficiently cleans pots and pans, but will lead to breakage and scratching of traditional wares, such as crockery, cutlery and glasses. For this reason, separate dishwashers are provided in large-scale kitchens for handling traditional, more sensitive items. This is costly and space consuming. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages singly or in any combination. This is in one aspect solved by providing a dishwasher for pot washing which comprises a detector for automatically detecting what type of washing basket has been placed in the dishwasher. The water pressure and granule valve is controlled, so that the more sensitive crockery and glasses are not damaged. 
     In another aspect of the invention, a washing basket is provided which comprises indicating members. These members are used in conjunction with the detector in the dishwasher of the first aspect. 
     In yet another aspect, a method is provided for operating a dishwasher, said method comprising the steps of automatically detecting what type of washing basket has been placed in the dishwasher. 
     In another aspect, a system is provided which comprises a dishwasher of the first aspect and a washing basket of the second aspect. 
     Further embodiments are given by the dependent claims of the above given aspects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accumulator of the present invention will be more readily understood by reading the following detailed description in combination with the appended non-limiting drawings, where 
         FIG. 1  is a perspective view of a dishwasher according to the invention, 
         FIG. 2  is a perspective view of the dishwasher in  FIG. 1 , where a basket carrier has been placed on a central hub, 
         FIG. 3   a  is a side view of the dishwasher in  FIG. 2 , where a pot-washing basket with a canteen has been placed on the basket carrier, and  FIG. 3   b  is an enlarged view of a detector and an indicating member of  FIG. 3   a,    
         FIG. 4   a  is a top view of the dishwasher in  FIG. 1  and  FIG. 4   b  is an enlarged view of the bottom spraying tube and the central hub, 
         FIG. 5  is a schematical side view of the dishwasher according to the invention, having a pot-washing basket, 
         FIG. 6  is a schematical side view of the dishwasher according to the invention, having a standard washing basket for crockery and glasses, and 
         FIG. 7  is a schematical view of an algorithm for an operation method of the dishwasher according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Below, several embodiments of the invention will be described with references to the drawings. These embodiments are described for illustrative purposes only, in order to enable a skilled person to carry out the invention and to disclose the best mode. However, such embodiments do not limit the invention. Moreover, other combinations of the different features are possible within the scope of the invention. 
     A dishwasher  100  is shown in a perspective view in  FIG. 1 . The dishwasher comprises a stand  101 , a bottom wall  102  and a back wall  103 . The top and sides of the dishwasher is enclosed by, e.g., a vertically adjustable hood (not shown). The dishwasher in  FIG. 1  also comprises a hub  104 , which is arranged in a central part of the bottom wall  102 . The hub  104  comprises a rotatable portion, which is coupled to a driving unit, such as an electric motor (not shown). A different form of driving unit is possible, which may be placed in an offset position of the dishwasher. 
     The dishwasher  100  can further comprise a top washing tube  110 , side washing tube(s)  111  and a bottom washing tube  112 . Spraying nozzles  113  are arranged on the washing tubes. 
     The dishwasher may also comprise a top rinsing tube  120 , a side rinsing tube  121  and a bottom rinsing tube  122 , on which rinsing nozzles  123  are arranged. The exact location or number of washing tubes or rinsing tubes in the shown embodiments is merely exemplary. 
     With reference to  FIG. 2 , the dishwasher can moreover comprise a bottom screen  130 , which is mounted at a distance above the bottom wall  102 . A pot-washing basket  140  is seen arranged in the dishwasher, and a standardized pot  150  can be seen placed in the basket  140 , see  FIG. 3 . The lower part of the dishwasher may also comprise a granule compartment  170 , see  FIGS. 5 and 6 , where the granules are collected. This compartment  170  can be fitted with a granule valve  171 , for controlling the addition of granules to the washing water. 
     The bottom screen  130  is arranged at a distance above the bottom wall  102 , and can in one embodiment be placed above the highest water level in the dishwasher. The screen  130  will then obscure the view of the dirty dishwater, which improves the appearance of the interior of the dishwasher. The screen  130  can moreover be fitted with an upwardly extending peripheral edge  131 , indicated in  FIG. 1 , which captures e.g. cutlery and prevent them from falling into the dishwater or the granule compartment  170 . This edge  131  substantially extends along the entire outer periphery of the bottom screen  130 . 
     With reference to  FIG. 3   a , the dishwasher  100  is seen with the pot-washing basket  140  and a therein-placed canteen.  FIG. 3   b  shows an enlarged view of  FIG. 3   a , at the back wall  103 , where an inductive detector  160  is mounted to said back wall  103 . An indicating member in the form of an arm  141  is shown extending outwards from the pot-washing basket  140 . The basket  140  can have one or several indicating arms  141 . In one embodiment, at least two indicating arms  141  are provided on the basket. 
     In  FIGS. 4   a  and  4   b , the dishwasher is seen from above. The position of the bottom washing tube  112  is clearly visible. The lower spraying tube  112  makes it possible to e.g. wash glasses, bowls and canteens that are placed upside down in a standard washing basket  143  or in a pot-washing basket  140 . 
     The position of the spraying nozzles  113  can be seen clearly in  FIG. 4   b . The shown nozzles are provided with an elongated opening, for spraying a substantially planar jet. The nozzles are specially designed for spraying water and/or granules. The elongated openings of the spraying nozzles  113  are in the shown embodiment oriented towards the centrally located hub  104 , and this is indicated with phantom lines. This means that a planar fluid jet leaving the elongated opening will be perpendicular to the rotation of the washing basket  140 ,  143 , at each corresponding nozzle position. The nozzles are in one embodiment placed closer together at the outer periphery of the dishwasher, in order to compensate for the fact that the peripheral speed increases with the radius from the hub  104 . This improves the coverage of the water jets from the spraying nozzles  113 . Other nozzle shapes, such as circular, curved or similar, are possible for spraying water jets of different shapes. 
     The dishwasher comprises a water pump  180 , which can operate at different speeds, leading to different water pressures and flows. A low speed is used for washing up crockery, cutlery and glasses and a higher speed is used for pot washing. In one embodiment, the pump  180  comprises a squirrel-cage electric motor comprising two windings, where one winding gives a low speed and the other winding gives a higher speed. The speed of the water pump and the resulting water pressure should be adjusted to the specific machine and what type of glassware or pots that are going to be cleaned. In one embodiment, the high water pressure is about 0.8-1.0 atm gauge (1.8-2.0 atm absolute) and the low water pressure is about 0.2-0.4 atm gauge (1.2-1.4 atm absolute). The water flow is about 800-1100 liters per minute at high pressure, and it is about 300-450 liters per minute at low pressure. This depends on the specific application, and both higher and lower flows are possible. 
     The water pump  180  can also be driven by a standard electric motor, which is controlled by a speed regulator of a known type, such as a frequency changer or a variable-frequency drive. This is a more costly solution, but gives more flexibility and several different speeds and water flows can be chosen. 
     Alternative Embodiments 
     The dishwasher  100  comprises a means for detecting if a pot-washing basket  140  is placed in the dishwasher, in order to automatically separate between washing up of pots and more sensitive crockery and glasses. In one embodiment, this is detected by a wheel  146 , which rides on a peripheral edge on the pot-washing basket  140 . Such a wheel is often fitted in dishwashers of a known kind, for guiding the pot-washing basket  140  during its rotation in the dishwasher. If the wheel  146  rotates in a predetermined fashion, it can be determined if a pot-washing basket  140  has been inserted into the machine. 
     It is also possible to arrange an optical detector on a side, top or bottom wall of the dishwasher, for detecting a reflective surface (as an alternative indicating member) of the pot-washing basket  140 . Such a reflective surface can have been placed on the pot-washing basket  140 , in order to clearly distinguish between reflections from cutlery or glasses, on one hand, and the indicating reflective surfaces of the pot-washing basket, on the other hand. In one embodiment, two or more reflective surfaces are arranged so that a detection frequency can be obtained, which differs from the rotational speed of the pot-washing basket. This increases the accuracy of the detection, and the more sensitive crockery and glasses can more reliably be protected from damage. In one embodiment, the optical detector comprises, or works in conjunction with, a radiation source that emits electromagnetic radiation, such as visible light or infrared light. The vertical metallic bars on the pot-washing basket can in another embodiment be used as the indicating members  141 . 
     The indicating members  141  of the pot-washing basket  140  do not have to be evenly spaced, but can have any predetermined spacing. The spacing will affect the signal that is detected by the detector, but this will be compared to reference data that has been gathered in advance. The rotational speed of the basket will also affect the frequency of the detected signal. 
     It is also possible to arrange an ultrasonic unit or a capacitive sensor in the dishwasher, for detecting an indicating member on the pot-washing basket. 
     Optionally, it is possible to move the detector  160 , either linearly or in a circular path around the interior of the dishwasher, and keep the basket carrier stationary, for detecting the presence of a pot-washing basket  140 . 
     In one embodiment, all washing tubes  110 ,  111 ,  112  are supplied water from the same water pump  180 . The water pump  180  can operate at least two separate speeds, which leads to at least two different water pressures and flows. In another embodiment, two different water pumps are arranged in the dishwasher  100 . One water pump operates when high water pressure is desired (pot washing) and the other water pump operates when a low water pressure is desired (washing of crockery and glasses). The two water pumps can supply water to different washing tubes. In one embodiment, the water pump that delivers high water pressure is connected to the side washing tube(s)  111 , and the water pump that delivers low water pressure is connected to the top and bottom washing tubes  110 ,  112 . If wanted, the two water pumps can be operated simultaneously during pot washing. 
     In the above description, only the pot-washing basket  140  is shown with indicating members. However, the standard washing basket can similarly be equipped with indicating members  141 , which are arranged in a different fashion than on the pot-washing basket  140 . This makes it possible to distinguish the standard washing basket  143  from the pot-washing basket  140 . It is also possible to equip only the standard washing basket  143  with indicating members  141 , while the pot-washing basket  140  lacks indicating members  141 , such that the absence of detected signals will indicate that a pot-washing basket  140  has been placed in the dishwasher  100 . 
     Operation 
     The operation of the dishwasher is shown schematically in  FIG. 7  in the form of an algorithm. Additional steps are possible and not all the shown steps are necessary for carrying out the process of the invention. 
     The first step A involves initial steps, such as closing discharge valves and the hood (if either of them are open). In step B, the driving unit is started for rotating a basket  140 ,  143  that is placed on the basket carrier  145 . The water pump  180  is started at a low speed, which leads to a low water pressure and flow. In step C, a sensor is activated for checking that the basket is actually rotating. If not, the dishwasher is stopped in step D. Otherwise the dishwasher enters a detection phase in step E. A detector  160  is activated for detecting what type of washing basket  140 ,  143  that has been placed in the basket carrier, by counting pulses and determining the frequency of the pulses. In the embodiment shown in  FIG. 3 , the pulses are generated when the indicating arms  141  pass by the detector  160 , caused by the driving unit  104  rotating the basket carrier  145  and hence the basket  140 ,  143 . If two or more pulses are detected at a certain predetermined frequency, the dishwasher establishes the type of washing basket  140 ,  143  that has been placed in the dishwasher. Step G is chosen for a standard washing basket and step H for a pot-washing basket. In step H, high water pressure can be used together with granules, if wanted. If the standard washing basket is detected, low water pressure should be used and the granule valve  171  should be closed. Otherwise, the high-pressure water flow might damage sensitive crockery and glasses in the standard washing basket. 
     The pot-washing mode in step H can include additional steps, such as addition of granules, control of temperatures, duration of washing cycle etc. The standard washing mode in step G can include similar additional steps, with the exception of the granule step. 
     In the claims, the term “comprises/comprising” does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented. Additionally, although individual features may be included in different claims, the individual features may be combined separately in other combinations, and the inclusion of the features in different claims does not imply that another combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. The terms “a”, “an”, “first”, “second” etc do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way. 
     Although the present invention has been described above with reference to specific embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than those described above are equally possible within the scope of the appended claims.

Technology Classification (CPC): 0