Patent Publication Number: US-7588038-B2

Title: Sump assembly for dishwasher

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Application Nos. P2004-0041109 and P2004-0041110, both filed on Jun. 5, 2004, and 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 dish washers, and more particularly, to a sump assembly for holding washing water and supplying the washing water to spray nozzles. 
     2. Discussion of the Related Art 
     The dish washer is a home appliance for washing dishes by spraying high pressure washing water to the dishes with spray nozzles. In general, the dish washer is provided with a tub having a washing space therein, a plurality of dish racks in the tub, spray nozzles for spraying the washing water to the dish racks, and a sump assembly for holding the washing water and supplying the washing water to the spray nozzles. 
     In operation of the dish washer, the washing water supplied from an outside of the dishwasher is stored in the sump assembly, and the sump assembly supplies the washing water to the spray nozzles. Then, the spray nozzles spray the washing water toward the dishes placed on the dish racks in the tub, for washing the dishes. The washing water contaminated as the dishes are washed drops down to a lower side of the tub, and stored in the sump assembly, again. 
     As the washing progresses, the washing water is contaminated, gradually. According to this, if the washing water is contaminated heavily, the contaminated washing water is drained from the sump assembly, and fresh washing water is supplied to the sump assembly. However, if contamination of the washing water is not heavy, the washing water is supplied from the sump assembly to the spray nozzles, again. In order to determine a level of contamination of the washing water, a sensor is provided to the sump assembly. 
     In general, the sensor is mounted on a bottom side of the sump assembly having the washing water held therein. However, in general, because the bottom side has sediment deposited thereon, the sensor fails to measure an accurate level of contamination due to the sediment. 
     In the meantime, because the sump assembly has a plurality of components assembled together, the washing water is liable to leak through joining portions of the components, or the like, to an outside of the sump assembly. If a water level of the sump assembly becomes low due to the leakage of the washing water to the outside of the sump assembly, a pump that pumps the washing water is liable to surfer from damage, or a heater that heats the washing water can be overheated. However, no dish washer has a structure for sensing the leakage of the washing water, presently. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a sump assembly for a dishwasher that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a sump assembly for a dishwasher, of which structure is improved so that a sensor can accurately measure a level of the contamination of washing water. 
     Another object of the present invention is to provide a sump assembly for a dishwasher in which the structure is improved for sensing leakage of washing water. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a sump assembly for a dishwasher comprises a sump housing for holding washing water, a pump provided to the sump housing for pumping the washing water, and a soil chamber housing for receiving a specified amount of the pumped washing water, wherein a sensor assembly is provided to the soil chamber housing for measuring a level of contamination of the received washing water. 
     The sump housing may include a recess for holding the washing water, and a sensor hole located on an upper surface outside the recess for engaging with the sensor assembly. The sump assembly further includes a soil chamber housing engaged with an upper surface of the sump housing. 
     The sensor assembly may include a channel for the pumped washing water to flow through, a light emitting unit for emitting a light, and a light receiving unit located on an opposite side of the channel from the light emitting unit for measuring an intensity of the light which passes through the washing water as the washing water flows through the channel. The sensor assembly may further include a ball in the channel for preventing transmission of the light between the light emitting unit and the light receiving unit when no washing water flows through the channel. The sensor assembly may further include barriers at a first channel opening and a second channel opening for preventing the ball from escaping from the channel. 
     Preferably, the channel may include a center portion of the channel having a lower height than heights of a first channel opening and a second channel opening, and the light receiving unit and the light emitting unit are located on an opposite side of each other in the center portion of the channel. 
     The sump assembly may further includes a control unit for stopping an operation of the dishwasher or generating a warning signal when the light receiving unit fails to receive the light from the light emitting unit during operation of the dishwasher. 
     In another aspect of the present invention, a sump assembly for a dishwasher comprises a sump housing for holding a washing water, a pump provided to the sump housing for pumping the washing water, a soil chamber housing for controlling the pumped washing water wherein a specified amount of the pumped washing water is provided to spray nozzles and rest of the washing water not provided to the spray nozzles bypasses the spray nozzles, and a sensor assembly in the soil chamber housing for measuring a level of contamination in the rest of the washing water that bypassed the spray nozzles. 
     The soil chamber housing may include a first guide flow passage for receiving a specified amount of the washing water and supplying the received washing water to a lower nozzle, and a second guide flow passage for receiving a specified amount of the washing water and supplying the received washing water to an upper nozzle. The soil chamber housing further includes a diverting valve at a branching portion of the first guide flow passage and the second guide flow passage for selectively guiding the specified amount of the washing water to the first guide flow passage or the second guide flow passage. The soil chamber housing includes a soil chamber for introducing the washing water that flows through the sensor assembly. 
     The sump assembly may further include a sump cover for engaging a bottom portion of the sump cover to an upper portion of the sump housing, enclosing the soil chamber housing between the sump cover and the sump housing. The sump cover may include a filter for filtering the washing water containing the contaminants that overflows from the soil chamber housing after passing through the sensor assembly. The sump cover may further include a plurality of apertures for allowing the washing water to pass through the filter to the sump housing. 
     The sump assembly may further include a drain pump for pumping out from the sump assembly the washing water held in the sump housing and from the soil chamber housing the washing water that bypassed the spray nozzle. The sump assembly may further include a disposer rotatably mounted in the sump housing for shredding contaminants in the washing. 
     In another aspect of the present invention, a sump housing for holding a washing water, guide flow passages for guiding a specified amount of washing water to spray nozzles, a bypass for supplying rest of the washing water not guided to the spray nozzles, a sensor assembly for measuring a level of contamination of the washing water introduced into the bypass, and a filter for filtering the washing water that passed through the sensor assembly. 
     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 and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; 
         FIG. 1  illustrates a perspective exploded view of a sump assembly in accordance with a preferred embodiment of the present invention; 
         FIG. 2  illustrates a plan view of the sump housing in  FIG. 1 ; 
         FIG. 3  illustrates a plan view of the impeller in  FIG. 1 ; 
         FIG. 4  illustrates a perspective view of the impeller in  FIG. 1 ; 
         FIG. 5  illustrates a plan view of the pump housing in  FIG. 1 ; 
         FIG. 6  illustrates a plan view of the soil chamber housing in  FIG. 1 ; 
         FIG. 7  illustrates a perspective view of the sump assembly in  FIG. 1  having a sump cover removed therefrom; 
         FIG. 8  illustrates an enlarged perspective view showing detail of the sensor assembly mounted on the sump assembly in  FIG. 7 ; 
         FIG. 9  illustrates a front view of the sensor assembly in  FIG. 8 ; 
         FIGS. 10A and 10B  illustrate side views showing operation of the sensor assembly in  FIG. 8 ; 
         FIG. 11  illustrates a plan view of the sump cover in  FIG. 1 ; and 
         FIG. 12  illustrates a perspective exploded view of a connector for connecting a pipe connected to a spray nozzle to the sump assembly in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Referring to  FIG. 1 , the sump assembly for a dishwasher includes a sump housing  290  for receiving and holding washing water provided from outside the dishwasher through a water supply pipe. The sump housing  290  has a recess  292  in a center area in bottom of the sump housing  290  for holding the washing water, and a water supply hole  291  on one side of the recess  292  for connecting a water supply pipe. A heater  320  is provided for heating the washing water in the recess  292 , and the recess  292  has an insertion hole  298  to insert the heater  320  in the recess  292  of the sump housing  290 . 
     The sump housing  290  has a coupling portion  296  on one side for coupling a drain pump  310 . As shown in  FIG. 1 , the coupling portion  296  is projected toward the recess  292 , and the drain pump  310  is mounted on an outer surface of the sump housing  290  such that an impeller  311  is placed in the coupling portion  296 . A first drain hole  302  is provided on one side of the coupling portion  296  in communication with the recess  292 , and a second drain hole  297  is provided to an upper surface of the coupling portion  296  in communication with a soil chamber  241  which will be described later. 
     The first drain hole  302  has a strainer or at least one strip for preventing sediment deposited in the recess  292  from entering into the drain pump  310 . The coupling portion  296  also has a nipple  299  for connecting a drain hose. Here, when the drain pump  310  is in operation, the washing water is discharged from the sump housing  290  and a soil chamber  241  to the outside through the first and second drain holes  302  and  297  and the drain hose. 
     A pump for pumping water from the sump housing  290  comprises a motor  330 , an impeller housing  256 , and an impeller  250 . As shown in  FIG. 1 , the motor  330  is mounted on the bottom of the sump housing  290 , having a shaft  331  of the motor  330  passed through the hole  293  on the bottom of the recess  292 . Furthermore, as shown in  FIG. 1 , the shaft  331  has a disposer  280  which has a plurality of blades for smashing contaminants in the washing water when the motor  330  is operated. 
     In addition, the shaft  331  has the impeller  250  coupled thereto. The impeller  250  draws washing water in an axial direction and discharges the washing water in a radial direction. The impeller  250  has an upper plate and a lower plate spaced from each other, and a plurality of blades  251  between the upper plate and the lower plate. The upper plate is covered, and the lower plate has an inlet  254  in the center area of the impeller  250  for insertion of the washing water. The upper plate has a hub  253  located in the center of the impeller  250 . The hub  253  has an insertion hole  252  for inserting the shaft  331 . As shown in  FIGS. 3 and 4 , there are a plurality of curved blades  251  between the upper plate and the lower plate to form an outlet for the curved blades  251  positioned adjacent to another to discharge the washing water introduced to the impeller  250  through the inlet  254 . 
     As shown in  FIG. 1 , the impeller housing  256  securely engages to a bottom side of the soil chamber housing  230  and encloses the impeller  250 . As shown in  FIG. 5 , the impeller housing  256  has a recessed portion  257  located at the center and on the bottom of the impeller housing  256  for receiving the impeller  250  therein. The recessed portion  257  has an inlet  256   a  which has a size substantially the same as the size of the inlet  254  of the impeller  250  for receiving the washing water from the sump housing  290 . 
     During the operation of the pump, the washing water is introduced to the impeller  250  from the sump housing  290  through the inlets  256   a  and  254 . Here, as shown in  FIG. 1 , a strainer  270  is provided to prevent contaminants in the washing water from entering into the impeller  250  and the impeller housing  256 . 
     A pumping flow passage  258  is provided along a circumference of the recessed portion  257 . An outlet  256   b  is provided in a circumferential surface of the impeller housing  256  for making the pumping flow passage  258  in communication with the outside of the impeller housing  256 . The outlet  256   b  at the end of the pumping flow passage  258  is tangential to an outside circumferential surface of the impeller housing  256 . The outlet  256   b  also has a sloped surface  259  for smooth guiding of the washing water passed through the pumping flow passage  258 . 
     In  FIGS. 1 ,  6 , and  7 , the sump housing  290  has the soil chamber housing  230  mounted thereon. The soil chamber housing  230  receives the washing water pumped by the pump and discharged through the outlet  256   b . The soil chamber housing  230  guides a portion of the washing water received therein to the spray nozzles of the dishwasher. The soil chamber housing  230  will be described in more detail. 
     The soil chamber housing  230  has a valve receiving portion in communication with the outlet  256   b . The valve receiving portion  235  has a first guiding flow passage for supplying the washing water to a lower nozzle of the dishwasher, and a second guiding flow passage  237  for supplying the washing water to an upper nozzle which are connected. The first guiding flow passage  236  extends from the valve receiving portion  235  to a center of the soil chamber housing  230 , and the second guiding flow passage  237  extends from the valve receiving portion  235  to an edge of the soil chamber housing  230 . The first guiding flow passage  236  and the second guiding flow passage  237  are connected to pipes which are connected to the lower nozzle and the upper nozzle, respectively. 
     The valve receiving portion  235  receives a diverting valve  260  for selectively guiding a portion of the washing water from the outlet  256   b  either to the first guiding flow passage  236  or to the second guiding flow passage  237 . The diverting valve  260  is rotated by a motor (not shown) mounted under the sump housing  290 . Furthermore, as shown in  FIGS. 1 and 2 , the sump housing  290  has a hole for connecting a shaft of the motor with the diverting valve  260  and a recessed portion  295  around the hole for receiving a lower end of the diverting valve  260 . 
     On a lower side of the soil chamber housing  230 , a housing receiving portion  240  is provided to engage with an upper edge of the impeller housing  256 . Furthermore, an impeller receiving portion  238  for receiving an upper portion of the impeller  250  to enclose the impeller  250  together with the impeller housing  256  is provided. The housing receiving portion  240  is, for example, a rib projected to a height from a bottom side of the soil chamber housing  230 . Accordingly, a space between an outside circumferential surface of the housing receiving portion  240  and an outside circumferential surface of the impeller receiving portion  238  becomes the pumping flow passage  231 . At the end of the pumping flow passage  231 , there are the outlet  256   b  and the sloped surface  259  as described above. 
     As shown in  FIGS. 1 and 6 , a hole  234  is located on a side of the sloped surface  259  with a bypass  233  connected thereto. Furthermore, a sensor receiving portion  232  is located at the end of the bypass  233  and at one of the ends of the soil chamber  241 . As shown in  FIGS. 6 and 7 , the soil chamber  241  extends along a circumference of the soil chamber housing  230 . A drain  242  is also provided at the other end of the soil chamber  241 , connected to the second drain hole  297  in the sump housing  290  shown in  FIGS. 1 and 2 . 
     Accordingly, a specified amount of the washing water pumped by the pump is introduced into the valve receiving portion  235  through the outlet  256   b  and supplied to the upper nozzle or the lower nozzle by the diverting valve  260 . The rest of the pumped washing water is introduced into the soil chamber  241  through the bypass  233  connected to the sloped surface  259 . During the pump operation and with the washing water in the sump housing  290  at a regular level, the washing water flows at a fixed rate to the soil chamber  241  through the bypass  233 . 
     A sensor assembly  400  for measuring the level of contamination in the washing water is provided to the sensor receiving portion  232  located between the bypass  233  and the soil chamber  241 . Since the level of contamination of the washing water is measured from the washing water flowing at a fixed rate, the sensor assembly  400  can more accurately measure the level of contamination than those of related arts whose contamination measurements are inaccurately taken with sediments and the like in the washing water. The sensor assembly  400  will be described with reference to  FIGS. 1 and 8  to  10 B. 
     Referring to  FIG. 1 , the sump housing  290  has a sensor hole  294  for the sensor assembly  400  to pass through. The sensor assembly  400  is mounted such that an upper end of the sensor receiving portion  232  is positioned at the sensor receiving portion  232  after the sensor assembly  400  passes through the sump housing  290  and the soil chamber housing  230 . 
     Referring to  FIGS. 8 and 9 , the sensor assembly  400  has a channel  490  in a middle of an upper portion of the case  410  in communication with the bypass  233  and the soil chamber  241 . Therefore, the washing water is introduced from the bypass  233  to the soil chamber  241  after passing through the channel  490 . 
     Referring to  FIG. 9 , in the case  410  of the sensor assembly  400 , a circuit board  450 , having a light emitting unit  430  and a light receiving unit  440 , is provided. The light emitting unit  430  and the light receiving unit  440  are arranged opposite to each other with reference to the channel  490 . Therefore, a light emitted from the light emitting unit  430  passes through the washing water in the channel  490  and reaches to the light receiving unit  440  on the opposite side of the channel  490 . Here, the sensor assembly  400  can determine the level of contamination of the washing water by an intensity of the light received in the light receiving unit  440 . Furthermore, a seal  470  under the case  410  for preventing leakage through the sensor hole  294  is provided, and a terminal  480  on a bottom side of the case  410  connected to the circuit board  450  is provided. 
     Referring to  FIG. 8 , the channel  490  has a ball  420  and barriers  460  located at an inlet and an outlet of the channel  490  for preventing the ball  420  from escaping from the channel  490 . 
     As shown in  FIGS. 10A and 10B , the channel  490  has a bottom surface of the channel having a low middle portion and high inlet and outlet portions. In the channel  490 , the passage on which the ball  420  travels has inclining slopes from the middle portion of the passage to the inlet and the outlet, respectively. 
     Furthermore, as shown in  FIG. 10A , when the washing water is not introduced to pass through the channel  490 , the ball  420  rests in the middle portion of the channel  490 . The position of the ball  420  in the middle portion of the channel  490  prevents the light from being received by the light receiving unit  440  since the ball in positioned between the light emitted unit  430  and the light receiving unit  440 . 
     As shown in  FIG. 10A , if the light receiving unit  440  cannot receive the light emitted from the light emitting unit  430  during the dishwashing operation, the washing water does not circulate due to various reasons such as inoperative pump or shortage of the washing water in the sump housing  290 . In such a case, a control unit of the dishwasher provides a warning signal, such as an alarm or a flashing signal, for the user to check for possible problems (e.g., malfunctioning pump or a leakage in the sump housing). Additionally, overheating of the heater  320 , which may lead to possible electrical shortage or even fire, can be prevented by turning off power and stopping operation of the dishwasher. 
     On the other hand, if there is an adequate amount of washing water in the sump housing  290 , the washing water passes through the channel  490  when the pump is in operation. As shown in  FIG. 10B , the ball  420  in the channel  490  is pushed by the washing water to the outlet side, clearing the passage in the middle portion of the channel  490 , thus enabling the light receiving unit  440  to receive the light from the light emitting unit  430 . 
     Here, the control unit determines the level of contamination of the washing water based on the intensity of the light received at the light receiving unit  440 . The control unit further determines, a washing time period, a washing number of times, a rinsing time period, a rinsing number of times, and so on. For an example, if the light reached at the light receiving unit  440  is very weak, which suggests that the washing water is heavily contaminated, the control unit increases the washing number of times by at least one time or the rinsing number of times by at least one time. 
     As shown in  FIG. 1 , a sump cover  220  covering an opened top of the sump housing  290  is provided. The sump cover  220  is, for example, shaped like a disc with a plurality of openings in a center portion and a plurality of apertures  221  on an outer circumference of the sump cover  220 . The plurality of openings in the center portion is covered with a mesh-shaped filter  227  as shown in  FIG. 11 . The openings occupied with the filter  227  are positioned on top of the soil chamber  241  to cover the soil chamber  241 . Furthermore, the plurality of apertures  221  receives the washing water passed through the filter from the tub of the dishwasher. In other words, the washing water passes through the filter from the bottom. The washing water then allows the filtered washing water to pass through the apertures  221  to the sump housing  290 . 
     Referring to  FIG. 11 , on a bottom surface of the sump cover  220 , a pocket  224  is provided for holding an upper end of the diverting valve  260 . A first communication hole  223  is provided at the center of the sump cover  220  for connecting the lower nozzle and the first guide flow passage  236 . Furthermore, a second communication hole  226  is provided on an end of the sump cover  220  for connecting the upper nozzle and the second guide flow passage  237 . 
     Referring to  FIG. 1 , a connector  210  is provided to the first communication hole  223  for connecting the pipe connected to the lower nozzle and the first guide flow passage  236 . 
     In  FIG. 12 , the connector  210  includes an upper piece  211  and a lower piece  219 . The lower piece  219  is cylindrical in shape and is designed to engage with the first communication hole  223  of the sump cover  220  and insert in the first guide flow passage  236  of the soil chamber housing  230 . On a side of the lower piece  219 , there is an opening  214  for connecting the first guide flow passage  236  and a passage of an inside of the lower piece  219 . Furthermore, there is an outlet  215  on a top of the lower piece  219  for discharging the washing water introduced into the lower piece  219  through the openings  214  to an upper side of the lower piece  219 . Also in  FIG. 12 , there is a flange  216  on the top portion of the lower piece  219 . When the lower piece  219  is engaged with the first communication hole  223 , the flange  216  is positioned against the sump cover  220  and inserted in a lower portion of the upper piece  211 . 
     The upper piece  211  is, for example, cylindrical in shape for inserting the top of the lower piece  219 , more particularly, having the flange  216  of the lower piece  219  inserted therein. The upper piece  211  has a flange  212  with holes  213  for fastening members, such as screws. Moreover, holes  225  corresponding to the holes  213  are provided in the vicinity of the first communication hole  223  of the sump cover  220 . Accordingly, the connector  210  can securely be fastened to the sump cover  220  with the fastening members. 
     The upper piece  211  of  FIG. 12  has an open top for connection to the pipe connected to the lower nozzle. Therefore, the washing water introduced into the first guide flow passage  236  is supplied to the lower nozzle through the connector  210  and the pipe. The second communication hole  226  at the edge of the sump cover  220  is connected to the pipe connected to the upper nozzle. Therefore, the washing water introduced into the second guide flow passage  237  is supplied to the upper nozzle through the pipe. 
     As shown in  FIGS. 1 and 2 , the sump housing  290  has a plurality of bosses  300  and  301 . In addition, as shown in  FIGS. 1 and 6 , the soil chamber housing  230  has a plurality of bosses  245  and  244  corresponding to the bosses  300  and  301 . Furthermore, as shown in  FIGS. 1 and 11 , the sump cover  220  is provided with holes  222  and  229  corresponding to the bosses  245  and  244 . Accordingly, the sump housing  290 , the soil chamber housing  230 , and the sump cover  220  are securely engaged with fastening members (e.g., bolts). 
     The operation of the sump assembly of the present invention will be described. When the dishwasher starts washing or rinsing, fresh water is introduced into the recess  292  in the sump housing  290  through the water supply hole  291  connected to the water supply pipe. The washing water introduced into the recess  292  is heated at the heater  320 . After fresh water is supplied, the motor  330  of the pump begins its operation, pumping up the washing water from the recess  292 . 
     Then, a specified amount of the washing water is introduced into the valve receiving portion  235  through the outlet  256   b , and guided either to the first guide passage  236  or the second guide flow passage  237  by the diverting valve  260 . The washing water from the first guide flow passage  236  is supplied to the lower nozzle through the connector  210 , and the washing water from the second guide flow passage  237  is provided to the upper nozzle through the second communication hole  226 . The washing water supplied to the lower nozzle washes the dishes on the lower rack in the tub of the dishwasher, and the washing water supplied to the upper nozzle washes the dishes on the upper rack in the tub of the dishwasher. 
     After the dishwashing operation is completed, the washing water used for dishwashing, along with contaminants such as food residue, fall to the bottom of the tub. Then, the contaminants and the washing water are introduced into the sump housing  290  through the apertures  221  of the sump cover  220  and are held in the recess  292 . As previously described, the washing water returned to the recess  292  after the dishwashing operation can contain much contaminants. The contaminants are then shredded and made into small pieces by the disposer  280  driven by the motor  330 . Thereafter, the washing water containing the shredded contaminants is pumped by the pump. 
     The washing water containing the shredded contaminants pumped up by the pump is introduced to the bypass  233  through the hole  234  by impeller  250  of the pump. Then, the washing water is introduced from the bypass  233  to the soil chamber  241  via the channel  490  of the sensor assembly  400 . In this instance, as described above, the level of contamination of the washing water passing through the channel  490  is accurately measured by the sensor assembly  400 . Furthermore, the control unit automatically controls the washing time period, the washing number of times, the rinsing time period, and the rinsing number of times, to name a few, based on the level of contamination of the washing water measured by the sensor assembly  400 . 
     The washing water that passed through the channel  490  of the sensor assembly  400  and introduced into the soil chamber  241  is supplied to the drain pump  310  through the drain  242 . However, because the drain pump  310  is not in operation, the washing water does not exit to the outside through the drain hose. Furthermore, the washing water containing the contaminants introduced to the soil chamber  241  remain in the soil chamber  241 . 
     With passage of time, a water level of the soil chamber  241  increases, such that the washing water introduced into the soil chamber  241  can overflow. When the washing water overflows, the overflowing washing water passes through the filter  227  and the apertures  221  in the sump housing  290 , and then returned to the sump housing  290 . However, of the contaminants introduced into the soil chamber  241 , large pieces are filtered at the filter  227  and accumulated in the soil chamber  227 . 
     As described before, the washing water introduced into the soil chamber  227  via the bypass  233  is filtered by the filter  227  and supplied to the sump housing  290 . The filtered washing water supplied to the sump housing  290  passes through above steps again, and supplied to the spray nozzles. Thus, the sump assembly of the present invention supplies the washing water to the nozzles while filtering the washing water during washing or rinsing. 
     In a case when the washing or rinsing time period is completed or the washing water is heavily contaminated, the drain pump  310  begins operation. The washing water and contaminants in the soil chamber  241  and the recess  292  of the sump housing  290  are discharged to the outside of the dishwasher via the drain hose by the drain pump  310 . 
     As previously described, in the sump assembly of the present invention, the sensor assembly  400  is mounted in the soil chamber housing  230  over the recess  292  of the sump housing  290  and inspects the washing water supplied thereto at a fixed rate pumped by the pump. Therefore, the sensor assembly  400  of the present invention can measure the level of contamination of the washing water accurately more than that of the related art, which had a sensor mounted on the bottom of the recess  292 . 
     As described before, if the washing water leaks from the sump assembly, the ball  420  of the sensor assembly  400  cuts off transmission of the light to the light receiving unit  440 . Then, the control unit generates a warning signal and cuts off power to the heater  320 . Subsequently, since the user can check for problems such as malfunctioning pump or a leakage from the sump assembly, the user can become aware of the status of the dishwasher easily and quickly. Furthermore, generating a warning signal or cutting off power can prevent in advance the dishwasher from being out of order or even causing fire by the overheating heater. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.