Patent Publication Number: US-7909940-B2

Title: Dish washing machine with steam generator and method of controlling same

Description:
This application claims the benefit of Korean Patent Application No.10-2007-0052695 and Korean Patent Application No. 2007-0052694, both of were filed on May 30, 2007. Both applications are hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dish washing machine and a method for controlling a dish washing machine that includes a steam generator, wherein, the washing machine is adapted to discharge residual water in the steam generator. 
     2. Discussion of the Related Art 
     Generally, dish washing machines are well known as devices that automatically wash dishes in the washing compartment of the dish washing machine by spraying wash water, under high pressure, on the dishes, thus, removing foreign matter such as food particles and food residues attached to the surface of the dishes. It is understood that dish washing machine&#39;s wash items other than dishes, such as glassware, pots, pans, utensils and the like. However, for ease of discussion, the following disclosure will refer only to dishes. 
     One important factor associated with dish washing machines is how effectively the machine removes food particles and food residues on or attached to the surface of dishes. In order to improve washing capability, dish washing machines increase the force (i.e., the spray pressure) of the wash water to more effectively remove foreign matter form the surface of the dishes. However, if the spray pressure of the wash water is too high, the dishes may break or otherwise become damaged. Further, when washing dishes with increased spray pressure, the dish washing operation is less efficient because the amount of wash water required increases. 
     SUMMARY OF THE INVENTION 
     Accordingly, the following disclosure describes a dish washing machine and a method of controlling a dish washing machine that substantially obviates one or more of the problems associated with the related art. More specifically, described herein is a dish washing machine that includes a steamed generator, and a method for controlling the same, where the dish washing machine safely, effectively and efficiently washes dishes without having to employ excessive spray pressure or an excessive amount of wash water. Still further, the following disclosure describes a dish washing machine and a method for controlling a dish washing machine that comprises a steam generator, where the washing machine is capable of discharging water, such as, residual water, from the steam generator thereby protecting the pump used for discharging the residual water and protecting the heater that beats the water in the steam generator. 
     Various advantages, objects, and features of the invention will be set forth in part in the written description and drawings that follow. Other advantages, objectives and features will become apparent to those having ordinary skill in the art based on the following description and drawings and/or from practicing the invention. 
     In accordance with one aspect of the present invention, the aforementioned advantages and objects are achieved by a method for controlling a dish washing machine that includes a steam generator. The method comprises a washing procedure that includes generating steam to aid in washing items that are in the dish washing machine. The method also comprises a water discharging procedure for discharging water in the steam generator. 
     In accordance with another aspect of the present invention, the aforementioned advantages and objects are achieved by a dish washing machine that comprises a tub which defines a dish washing space, in which items are washed, and a steam generator that supplies steam to the dish washing space to aid in washing the items. The steam generator, in turn, comprises a residual water outlet, through which, residual water in the steam generator is discharged. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention illustrate various aspects and embodiments of the present invention together with the description. In the drawings: 
         FIG. 1  is illustrates a dish washing machine according to an exemplary embodiment of the present invention; 
         FIG. 2  is a graph depicting the relationship between the number of steam-washing cycles and the amount of impurities in the residual water; 
         FIG. 3  illustrates a steam generator in accordance with exemplary embodiments of the present invention; 
         FIG. 4  illustrates an exemplary embodiment of a residual water discharging unit according to exemplary embodiments of the present invention; 
         FIG. 5  illustrates an alternative exemplary embodiment of the residual water discharging unit according to the present invention; 
         FIG. 6  is a view schematically illustrating yet another exemplary embodiment of the residual water discharging unit, according to the present invention; and 
         FIG. 7  is a flow chart illustrating a method for controlling a dish washing machine in accordance with exemplary embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a dish washing machine according to an exemplary embodiment of the present invention. The dish washing machine includes, for example, a case  100  that defines the outer appearance of the dish washing machine. The dish washing machine also includes a door  120  and a control panel  130  mounted to the case  100  or to the door  120 . The control panel  130  enables the user to operate the dish washing machine. 
     Turning now to the inside of the dish washing machine, a tub  110  is arranged within the case  100 , the tub  110  defining a washing compartment  150  or space where the dishes are positioned during washing. Beneath the tub  110  is a sump  200 , which collects wash water during the wash cycle. Located in the sump  200  is a pump  210  for pumping the wash water in the sump  200 . A filter (not shown) for filtering contaminated wash water is also located in the sump  200 . Still further, there is a first heater  290  arranged in the sump  200  to heat the wash water in the sump  200 . 
     The dish washing machine further includes a first water supply conduit (e.g., a pipe or tube)  250  connected to the sump  200 . The first water supply  250  supplies fresh water from an external water supply source to the sump  200 . A water drainage conduit  270  is also connected to the sump  200 , which drains the wash water from the sump  200  to a location external to the dish washing machine. A first water supply valve  255  for controlling the supply of fresh water to the sump  200  is positioned in the first water supply conduit  250 , as shown. 
     At least one rack is arranged within the tub  110 , that is, within the washing compartment  150 . At least one spray arm is also arranged in the washing compartment  150 , to spray towards at least one rack and the dishes positioned therein, the wash water that is pumped out of the sump  200  by the pump  210 . 
     For illustration,  FIG. 1  shows two racks, an upper rack  160  and a lower rack  170 . These racks are arranged in an upper and lower portion of the washing compartment  150 , respectively.  FIG. 1  also shows an exemplary upper spray arm  230  and an exemplary lower spray arm  220 , arranged such that the spray arms spray water provided by the pump  210  toward the upper rack  160  and the lower rack  170 , respectively. In addition, a nozzle  240  may be arranged in a top portion of the washing compartment  150 . The nozzle  240  sprays wash water provided by the pump  210  in a downward direction from the top portion of the washing compartment  150 . 
     The dish washing machine according to the exemplary embodiment of the present invention illustrated in  FIG. 1  is configured not only to spray wash water into the washing compartment  150 , but to also spray or otherwise supply steam to the washing compartment  150 . Accordingly, the dish washing machine illustrated in  FIG. 1  includes a steam generator  300  for generating the steam that is supplied to the washing compartment  150 . Preferably, the operation of the steam generator  300  is independent of the aforementioned first heater  290  in the sump  200 . 
     In the exemplary embodiment shown in  FIG. 1 , the steam generator  300  communicates with the first water supply  250 , via a second water supply conduit (e.g., pipe or tube)  260 . The steam generator  300  also communicates with the washing compartment  150 , via a steam supply conduit  280 . A second water supply valve  265  for controlling the supply of water to the steam generator  300  is positioned in the second water supply conduit  260 . 
     The steam generator  300  includes a case  310 , which defines a space therein for containing the water supplied thereto. The steam generator  300  also includes a second heater  320  for heating the water contained in the case  310 , and a water level sensor  330  for sensing the water level in the case  310 . 
     The water level sensor  330  may be configured, for example, to sense a minimum water level and a maximum water level. The minimum water level is set so as to prevent the second heater  320  in the steam generator  300  from overheating. Thus, the ability to detect a minimum water level and, therefore, prevent the second heater  320  from over-heating is a safety feature. To achieve this, the minimum water level should be set at a water level that is higher than the position of the second heater  320  within the steam generator  300 . On the other hand, the maximum water level should be set to prevent water supplied to the steam generator  300  from overflowing. 
     In order to supply steam at a desired time, a steam supply valve (not shown) may be installed in the steam generator  300 . The steam supply valve is configured to open and close the steam supply conduit  280 . 
     A controller (not shown) is also provided to control the operation of the dish washing machine. The controller is electrically connected to the various electrical and electromechanical components, for example, the control panel  130 , the pump  210 , the heaters  290  and  310 , the steam generator  300 , and the valves to control the operation of the dish washing machine. 
     Hereinafter, the basic operation of the dish washing machine, according to exemplary embodiments of the present invention, will be described. When it is desired to wash dishes, the user places the dishes on the racks  160  and/or  170  and closes the door  120 . Thereafter, the user selects the desired dish washing machine mode and initiates the operation of the dish washing machine using the control panel  130 . During the operation of the dish washing machine, wash water is sprayed from the spray arms  220  and  230  and nozzle  240 . The water eventually falls downward and into the sump  200 . The wash water is then pumped out of the sump  200  by the pump  210 , and is re-circulated to the spray arms  220  and  230  and nozzle  240 . During the circulation of wash water from the sump  200  to the spray arms  220  and  230  and nozzle  240 , the wash water is filtered to remove food residue. This prevents the wash water from becoming excessively dirty, and also to prevent the spray arms  220  and  230 , as well as nozzle  240 , from becoming clogged. 
     The dish washing machine according to the present invention, includes a steam generator  300 , as previously stated. Thus, during certain wash cycles, the steam generator  300  generates steam, which is supplied to the washing compartment  150  via the steam supply conduit  280 . The use of steam, as described herein, enhances the washing capability and efficiency of the dish washing machine, at least in part, because of the high-temperature and high-humidity properties of steam. For example, when dishes are washed using steam and wash water, foreign matter strongly adhering to the dishes more easily soaks up the moisture associated with the steam and wash water. Thus, the more thoroughly soaked foreign matter can be more effectively removed from the dishes. In addition, the dish washing machine, according to the present invention, more efficiently washes dishes because it is unnecessary to increase the pressure of the wash water of the wash water in order to remove foreign matter from the dishes, thus, less wash water is required. 
     Hereinafter, the basic operation of the steam generator  300  will be described. First, water is supplied to the steam generator  300 , and stored within the case  310 , via the second water supply conduit  260  when the second water supply valve  265  opens. The second water supply valve  265  closes, thereby shutting off the water being supplied to the steam generator  300 , when a maximum water level is sensed by the water level sensor  330 . The second heater  320  then heats the water contained in the steam generator  300 . This generates steam, which is supplied to the washing compartment  250  via the steam supply conduit  280 . 
     As the water in the steam generator  300  is converted to steam and, thereafter, is supplied to the washing compartment  150 , the water level in the steam generator  300  begins to decrease. If the water level sensor  330  senses a minimum water level, the operation of the second heater  320  is stopped. The reason why the operation of the second heater  320  is stopped when the water level in the steam generator  300  reaches the minimum water level is to prevent any safety hazard caused by the second heater  320  overheating. Water is again supplied to the steam generator  300 , if necessary, via the second water supply conduit  260 , and the process repeats in this manner until the steam operation is completed. 
     Of particular importance here, is the fact that impurities are typically found in the water supplied to the steam generator  300 . For example, calcium hydrocarbonate (Ca(HCO 3 ) 2 ) may exist in the water supplied to the steam generator  300  in dissolved form. Generally, this precipitates out in the form of calcium carbonate (CaCO 3 ), otherwise known as lime, when the water is heated. Thus, with each use of the steam generator  300 , more and more calcium carbonate may precipitate out and continue to build up inside the steam generator  300 . This problem may be particularly severe in Europe and American, where water tends to be relatively hard (i.e., contains a high concentration of impurities). 
     The water remaining in the steam generator  300 , before or after a steam-washing cycle which, as stated, typically contains impurities, is referred to herein as residual water. The concentration of impurities is even greater in the water below the minimum water level. The reason being, as the impurities precipitate out, they settle in the water towards the bottom of the steam generator  300 . The ever increasing concentration of impurities can damage the second heater  320 , and ultimately result in a failure. This is because the impurities, such as lime, can erode the second heater  320 . 
       FIG. 2  is a graph depicting the relationship between the number of steam-washing cycles and the amount of impurities that may exist in the residual water. In the graph, the X-axis represents the number of steam-washing cycles and the Y-axis represents the amount of impurities, such as lime, in the steam generator  300 . In addition, plot “A” represents the case in which the residual water is not discharged (e.g., flushed) from the steam generator  300 , and plot “B” represents the case in which the residual water is discharged from the steam generator  300 . From a comparison of plot “A” and plot “B”, it is evident that discharging the residual water in the steam generator  300  is desirable as plot “B” reflects a lower concentration of impurities than “A”. Accordingly, it is of particular interest herein to describe a dish washing machine, including a steam generator and a method of removing impurities, such as calcium, magnesium and other impurities, by discharging the residual water in the steam generator  300 . 
       FIG. 3  is a more detailed view of the steam generator  300 , according to an exemplary embodiment of the present invention. As shown, the steam generator  300  includes a residual water outlet  340 , through which, residual water is discharged. Preferably, the residual water outlet  340  may be positioned at a height “h” above the bottom of the case  310 , as shown. Alternatively, the residual water outlet  340  may be positioned at the bottom of the case  310 . In the latter case, it is possible to completely discharge the residual water from the case  310  and, therefore, further reduce the amount of impurities. However, if the residual outlet  340  is positioned at the bottom of the case  310 , doing so may increase the likelihood of damaging the pump  351 , shown in  FIG. 4 , which will be discussed in more detail below. More specifically, larger impurity particles tend to accumulate at the bottom of the case  310 , as compared to smaller impurity particles. If the residual water outlet  340  is at the very bottom of case  310 , the larger particles are more likely to be discharged through, for example, pump  351 . The exposure of pump  351  to these particles increases the likelihood of damaging the pump. 
     When the residual water outlet  340  is positioned at a certain height, for example, the height “h”, as described above, it is possible to minimize the risk of damage to pump  351 , while at the same time reducing the amount of impurities, particularly, smaller particles in the water in case  310 . 
     In addition to preferably positioning the residual water discharge outlet  340  a height “h” above the bottom of the steam generator case  310 , the residual water outlet  340  may be further positioned below the second heater  320 . By doing this, the risk of damaging the second heater  320  is minimized, that is because, the exposure of the second heater  320  to impurities is reduced, due to the fact that the level of the residual water in the case  310  is below the position of the second heater  320 , thereby, isolating the second heater  320  from the impurities. 
       FIG. 4  illustrates an exemplary embodiment of the present invention, wherein the aforementioned pump  351  is included in the residual water discharging unit  350 . Pump  351  is provided, for example, as shown. This embodiment of the residual water discharging unit  350  also includes a first connecting conduit  352 , which connects pump  351  to the residual water outlet  340 . The residual water discharging unit  350  further includes a second connecting conduit  353  connected to pump  351 , and at the other end thereof, it opens into tub  110 . 
     In accordance with the exemplary embodiment illustrated in  FIG. 4 , the residual water in case  310  can be discharged into the interior of tub  110 , i.e., into the washing compartment  150 , through the use of pump  351 , and eventually, the water is drained from the dish washing machine via the water drainage conduit  270 . 
       FIG. 5  illustrates another exemplary embodiment of the present invention, wherein the residual water discharging unit  360  includes a pump  351  and a second connecting conduit  363 , as shown. Specifically, the conduit  363  is connected, at one end thereof, to pump  351 , and at the other end thereof, to water drainage conduit  270 . 
     In accordance with this exemplary embodiment, the residual water discharging unit  360  discharges the residual water in case  310  to water drainage conduit  270 , which in turn, drains the residual water from the dish washing machine. 
       FIG. 6  illustrates yet another exemplary embodiment of the present invention, wherein the residual water discharging unit  370  includes a pump  351  and a second connecting conduit  373 . The second connecting conduit  373  is connected, at one end thereof, to pump  351 . The second connecting conduit  373  is configured to discharge the residual water directly outside the dish washing machine. 
     We now turn our attention to the methods of discharging residual water in accordance with exemplary embodiments of the present invention. It should be noted, when the residual water in the steam generator  300  is discharged just after the generation of steam, the residual water discharging pump  351  may be damaged because the residual water in the case  310  is hot and because the pump  351  and the conduits are generally made, at least in part, using materials, such as rubber, which are subject to deformation if exposed to high-temperature residual water. 
     Of course, the discharging pump  351  and the corresponding conduits might be made from materials that are not subject to deformation when exposed to high-temperatures. However, this is undesirable due to increased manufacturing costs. Therefore, it is necessary that the method, in accordance with exemplary embodiments of the present invention, discharge the residual water from the steam generator  300  and, at the same time, prevent the residual water discharging pump  351  and/or the corresponding conduits from being damaged. 
       FIG. 7  is a flow chart illustrating a method for controlling the above-described dish washing machine, in accordance with exemplary embodiments of the present invention. As shown, the control method may include a residual water discharging procedure S 100  for discharging water from the steam generator  300 . In accordance with one exemplary embodiment of the present invention, the residual water discharging procedure S 100  is executed prior to the generation of steam which occurs during the washing procedure. At this point, prior to the generation of steam, the residual water contained in the steam generator  300  has a relatively low temperature. Discharging the residual water at this point would be advantageous because there is little risk of damaging the discharge pump and, possibly, the corresponding conduits due to the temperature of the residual water in the steam generator. 
     The method illustrated in  FIG. 7 , of course, includes a washing procedure S 110 , which may involve two sub-procedures: a preliminary washing procedure S 120 , which uses wash water without steam, and a main washing procedure S 130 , which uses wash water and steam. During the preliminary washing procedure S 120 , the dishes may be washed using wash water with or without detergent. The primary purpose of the preliminary washing procedure S 120  is to rinse the dishes so as to loosen or remove as much foreign matter attached to the dishes as possible. 
     As stated, the main washing procedure S 130  is a procedure that employs not only wash water, but also steam. Wash water and steam maybe simultaneously sprayed during the main washing process S 130 . Alternatively, the main washing procedure S 130  may involve a procedure for spraying steam on the dishes, and a separate, independent sub-procedure for spraying wash water on the dishes. The main washing procedure S 130  may further involve repeating the above-described water and/or steam procedures. 
     In accordance with another exemplary embodiment of the present invention, where the washing procedure S 110  involves a preliminary washing procedure S 120  and a main washing procedure S 130 , it is possible to perform the residual water discharging procedure S 121  after or during the preliminary washing procedure S 120 , as illustrated in  FIG. 7 . In the latter case, the total washing time can be minimized because no separate, dedicated time is needed to perform for the residual water discharging procedure S 121 . Again, there is no risk of damaging the residual water discharging pump  351  if the temperature of the residual water in the steam generator  300 , at this point, is relatively low as the preliminary washing procedure S 120  does not involve steam. 
     Referring again to  FIG. 7 , the control method according to still another exemplary embodiment of the present invention may include a residual water discharging procedure S 140 , to discharge water from the steam generator  300 , after the execution of the washing procedure  110 . In accordance with this exemplary embodiment, cold or cool water may be mixed with the water already contained in the steam generator  300  prior to discharging. This will lower the temperature of the residual water contained in the steam generator  300 , thereby lessening the likelihood that the residual water discharging pump  351  will be damaged. 
     Alternatively, or in addition to mixing cold or cool water with the water in the steam generator  300 , the residual water discharging procedure S 140  may be performed after a given period of time elapses following the completion of the washing procedure S 110 . This time period would allow the temperature of the water in the steam generator  300  to drop to a relatively low temperature, thereby minimizing the likelihood of damage to the residual water discharging pump  351 . 
     If the residual water discharging procedure S 140  involves mixing cool or cold water with the water in the steam generator  300 , or waiting a given time period to allow the residual water to cool down, it may be desirable to include a temperature sensor (not shown) in the steam generator  300 . If so, the residual water discharging procedure S 140  may be executed in response to the temperature sensor indicating that the water in the steam generator is sufficiently cool (i.e., that the temperature of the residual water is less than or equal to a predetermined temperature that will not damage the pump  351  and/or the corresponding conduits). 
     The control method, illustrated in  FIG. 7 , in accordance with yet another exemplary embodiment may include a drying procedure S 150 . During the drying procedure  150 , cold or hot air may be introduced into the washing compartment  150  to dry the dishes. If the method employs a drying procedure S 150 , the residual water discharging procedure S 160  may be performed after or during the drying procedure S 150 , as shown. As in the previous embodiment, it may be desirable to permit the water in the steam generator to sufficiently cool by waiting a given period of time or by mixing cool or cold water with the water contained in the steam generator  300 . Again, employing a temperature sensor may facilitate this process by providing an indication when the water in the steam generator  300  has sufficiently cooled. 
     In accordance with another exemplary embodiment of the present invention, the washing procedure S 110  may include a rinsing procedure S 170 . The rinsing procedure S 170  involves spraying fresh wash water, that is, water containing no detergent, onto the dishes. The rinsing procedure S 170  would be performed after the main washing procedure S 130 . In this embodiment, the residual water discharging procedure S 171  may be performed after or during the rinsing procedure S 170 , as illustrated in  FIG. 7 . Again, it may be advantageous to mix cool or cold water with the water in the steam generator  300  or wait a given time period before performing the residual water discharging procedure S 171 , for the reasons stated above. Further, a temperature sensor may be employed, again, for the reasons previously stated. 
     It should be noted that each of the residual water discharging procedures S 100 , S 121 , S 140 , S 160  and S 171  appear in  FIG. 7  with “dashed” lines. This is to illustrate that while performing only one residual water discharging procedure during the course of a single dish washing operation is the most likely scenario, it is within the scope of the present invention to perform more than one residual water discharging procedure during a dish washing operation, in accordance with any one or more of the aforementioned exemplary embodiments. 
     It will be apparent to those skilled in the art that modifications and variations of the present invention are possible without departing from the spirit of and/or scope of the present invention. Thus, it is intended that present invention covers these modifications and variations provided they come within the scope of the appended claims and their equivalence.