Patent Publication Number: US-7581552-B2

Title: Drive unit for dish washing machines

Description:
The present disclosure relates to subject matter contained in priority Korean Application No. 2005-0002810, filed on Jan. 12, 2005, the disclosure of which is herein expressly incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dish washing machine, and more particularly, to a drive unit for dish washing machines that is capable of improving wash water filtering performance and wash water filtering capacity, effectively preventing a filter of the dish washing machine from being blocked by solid waste, and facilitating discharge of the solid waste. 
     2. Discussion of the Related Art 
     Generally, a dish washing machine is a machine that injects wash water to dishes to wash the dishes. A conventional dish washing machine is illustrated in  FIG. 1 . The construction of the conventional dish washing machine will be described hereinafter with reference to  FIG. 1 . 
     As illustrated in  FIG. 1 , the conventional dish washing machine comprises: upper and lower injection arms  4  and  5 ; upper and lower racks  6  and  7 ; and a drive unit  10 , all of which are mounted in a tub  1 . To the drive unit  10  are connected upper and lower connection pipes  2  and  3  for pumping wash water and a drain hose  9  for draining the wash water. The upper and lower connection pipes  2  and  3  are connected to the upper and lower injection arms  4  and  5 , respectively. The upper rack  6  is disposed above the upper injection arm  4 , and the lower rack  7  is disposed above the lower injection arm  5 . 
     The upper and lower injection arms  4  and  5  are rotatably disposed above the drive unit  10 . Each of the upper and lower injection arms  4  and  5  has injection holes for allowing wash water to be injected to the corresponding rack therethrough. In addition, the lower injection arm  5  has injection holes for allowing wash water to be injected therethrough to remove food particles from a filter of the drive unit. 
     The drive unit  10  will now be described in detail with reference to  FIG. 2 . The drive unit  10  comprises: a sump  20  for receiving wash water; a heater  30  mounted to the sump  20  for heating wash water; a washing pump mounted to the sump  20  for pumping out wash water; a drain pump mounted to the sump  20  for draining wash water; and filtering device for guiding some of the pumped-out wash water to the upper and lower injection arms  4  and  5  and filtering the remainder of the pumped-out wash water. 
     The sump  20  has a wash water receiving space  21  for substantially receiving wash water defined therein. Also, the sump  20  has a drain chamber  22 , which is partitioned from the wash water receiving space  21 . To the outside of the wash water receiving space  21  is mounted a flow channel control device  25 . To the flow channel control device  25  is connected a flow channel control valve  26  via a shaft. 
     The washing pump comprises: a washing motor  41  disposed below the sump  20  for generating a driving force; and an impeller  42  mounted in the filtering device for pumping out wash water. The impeller  42  is connected to a shaft of the washing motor  41 . The drain pump is mounted to the drain chamber  22  of the sump  20 . The drain pump comprises a drain motor  51  and an impeller  52 . 
     The filtering device comprises: a pump housing  60  having a space for allowing the impeller  42  to be mounted therein; a filter housing  70  mounted for covering the top of the pump housing  60 ; and a cover  80  mounted for covering the top of the filter housing  70  and the top of the sump  20 . The pump housing  60  is disposed at the lower surface of the filter housing  70 . The cover  80  is disposed at the upper surface of the filter housing  70 . 
     The filter housing  70  has a solid waste chamber  75  defined therein. The solid waste chamber  75  has an outlet port  75   a , which communicates with the drain chamber  22 . The outlet port  75   a  extends a predetermined distance downward from the solid waste chamber  75  such that the outlet port  75   a  can be inserted into the drain chamber  22 . The filter housing will be described below in more detail. 
     The cover  80  has a filter  81 , which corresponds to the solid waste chamber  75  of the filter housing  70 . At the cover, around the filter  81 , are formed a plurality of collection holes  82 . The collection holes  82  communicate with the sump  20 . 
     The filter housing  70  will now be described in detail with reference to  FIG. 3 . As shown in  FIG. 3 , the filter housing  70  comprises: a wash water inlet port  72  for allowing wash water pumped out from the impeller  42  to be introduced therethrough; main flow channels  73   a  and  73   b  and a sampling flow channel  74  connected to the wash water inlet port  72 ; and a solid waste chamber  75  connected to the sampling flow channel  74 . At the outlet port  75   a  of the solid waste chamber  75  is mounted an opening/closing valve for allowing wash water and food particles to be discharged from the solid waste chamber  75  to the drain chamber  22  when a draining operation is performed. 
     At the wash water inlet port  72  of the filter housing  70  is rotatably mounted a flow channel control valve  26  for opening or closing the main flow channels  73   a  and  73   b . The flow channel control valve  26  is connected to the flow channel control device  25 , which is mounted to the sump  20 , via a shaft. At the edge of the channel control valve  26  is formed an opening/closing rib  26   a  for opening or closing the main flow channels  73   a  and  73   b.    
     The operation of the dish washing machine with the above-stated construction will now be described. The dish washing machine successively or selectively performs a preliminary washing operation, a main washing operation, a rinsing operation, a heating and rinsing operation, and a drying operation to wash dishes. Draining operations are performed between the respective operations. Hereinafter, the main washing operation will be described in detail. 
     When the main washing operation is initiated, the washing motor  41  is rotated, and therefore, the impeller  42  is rotated. The impeller  42  pumps out wash water (containing a detergent) from the sump  20  to the wash water inlet port  72  of the pump housing  60 . At this time, the flow channel control device  25  is rotated, and therefore, the flow channel control valve  26  either selectively opens the main flow channels  73   a  and  73   b , as shown in  FIG. 5A  and  FIG. 5B , or simultaneously opens the main flow channels  73   a  and  73   b , as shown in  FIG. 3 . As a result, some of the wash water in the wash water inlet port  72  is introduced into the upper injection arm  4  and/or the lower injection arm  5  through the main flow channel  73   a  and/or the main flow channel  73   b , and the remainder of the wash water is introduced into the solid waste chamber  75  through the sampling flow channel  74 . 
     Preferably, the flow channel control valve  26  simultaneously or alternately opens the main flow channels  73   a  and  73   b  such that the wash water can be supplied to not only the upper injection arm  4  but also the lower injection arm  5 . At this time, some of the wash water is always introduced into the sampling flow channel  74  irrespective of which main flow channel(s) is opened by the flow channel control valve  26 . 
     The wash water introduced into the sampling flow channel  74  is directly guided into the solid waste chamber  75 . The wash water guided into the solid waste chamber  75  overflows through the filter  81 , which is disposed above the solid waste chamber  75 . At this time, the filter  81  filters the wash water such that foreign matter is separated from the wash water. 
     The filtered wash water and the wash water dropping from the upper and lower injection arms  4  and  5  is introduced again into the sump  20  through the collection holes  82  of the cover  80 . In this way, the wash water is filtered. It should be noted that some of the wash water is not filtered for a short period of time, but almost all of the wash water is filtered during the main washing operation. 
     After the washing operation is completed as described above, a draining operation is initiated. When the draining operation is initiated, the drain pump  51  and impeller  52  are operated. At this time, the wash water and the food particles are introduced into the drain pump  51  and impeller  52  from the sump  20  by a suction force of the drain pump  51  and impeller  52 . At the same time, the wash water and the food particles are introduced into the drain pump  51  and impeller  52  from the solid waste chamber  75  through the outlet port  75   a , as shown in  FIG. 5B . The wash water and the food particles introduced into the drain pump  51  and impeller  52  are drained out of the dish washing machine through the drain hose  9 . 
     However, the conventional dish washing machine has the following problems. First, the wash water pumped out from the sump is directly introduced into the solid waste chamber through the sampling flow channel. As a result, relatively large-sized solid waste is introduced into the solid waste chamber, and therefore, the filter of the cover is frequently blocked. 
     Secondly, the solid waste chamber is eccentrically disposed at a predetermined position of the filter housing such that the solid waste chamber deviates from the flow channel control valve and from the main flow channels. As a result, the size of the solid waste chamber is relatively decreased, and therefore, the filtering capacity is reduced. When the filtering capacity is reduced, the filter is frequently blocked. 
     Thirdly, the water pressure applied to the solid waste chamber is increased when the filter is blocked. As a result, the wash water is drained from the solid waste chamber through the drain hose. Consequently, wash water is excessively wasted. Fourthly, it is necessary to supplement wash water as the amount of wash water wasted is increased. When the heating and washing operation is performed, the supplemented wash water must be heated by the heater. As a result, the power consumption is increased, and time necessary to perform the heating and washing operation is increased. 
     Fifthly, the filter of the cover is easily deformed due to accumulated fatigue acting on the filter as the filter is frequently blocked. Sixthly, the bottom surface of the solid waste chamber is horizontally disposed, and therefore, solid waste, such as food particles, remains in the solid waste chamber. Consequently, the rinsing operation is not sanitarily performed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a drive unit for dish washing machines 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 drive unit for dish washing machines that is capable of improving wash water filtering performance and wash water filtering capacity, effectively preventing a filter of the dish washing machine from being blocked by solid waste, and facilitating discharge of the solid waste. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a drive unit for dish washing machines comprises: a sump for receiving wash water; and a housing assembly having: a first solid waste chamber for filtering some of the wash water pumped out from a washing impeller; a second solid waste chamber disposed to communicate with the first solid waste chamber, the second solid waste chamber having a bottom surface, which is not level with a bottom surface of the first solid waste chamber such that the bottom surfaces of the first and second solid waste chambers are stepped; and a filter disposed in correspondence to the first and second solid waste chambers. 
     Preferably, the second solid waste chamber is disposed such that the second solid waste chamber deviates from the first solid waste chamber. More preferably, the bottom surface of the first solid waste chamber is lower than that of the second solid waste chamber. Also preferably, the first solid waste chamber is provided at the bottom surface thereof with an inlet/outlet port for allowing wash water to be introduced into the first solid waste chamber therethrough when a washing operation is performed and allowing solid waste, which is separated from the wash water by filtering, to be discharged out of the first solid waste chamber therethrough when a draining operation is performed. 
     Preferably, the bottom surface of the first solid waste chamber and/or the bottom surface of the second solid waste chamber is inclined downward toward the inlet/outlet port. More preferably, the first and second solid waste chambers are partitioned from each other at the side opposite to the inlet/outlet port. Also preferably, communication holes are formed at the regions of the housing assembly surrounded by the first and second solid waste chambers, respectively, the communication holes communicating with the sump for discharging leaked wash water to the sump. 
     Preferably, the housing assembly comprises: a pump housing disposed in the sump, the pump housing having a washing impeller located therein; a flow channel housing disposed to cover the top of the pump housing, the flow channel housing having the first solid waste chamber; a filter housing disposed above the flow channel housing, the filter housing having the second solid waste chamber; and an arm holder disposed above the flow channel housing, the arm holder having the filter, which covers the tops of the first and second solid waste chambers. More preferably, the flow channel housing has flow channels for guiding some of the pumped-out wash water to washing arms. Also preferably, the filter housing has a filter opening, which corresponds to the first solid waste chamber. 
     In another aspect of the present invention, a drive unit for dish washing machines, comprises: a sump for receiving wash water; a pump housing disposed in the sump, the pump housing including a washing impeller located therein; a flow channel housing disposed to cover the top of the pump housing, the flow channel housing including a first solid waste chamber for filtering some of the wash water pumped out from the washing impeller; a filter housing including a second solid waste chamber disposed to communicate with the first solid waste chamber, the second solid waste chamber having a bottom surface, which is not level with a bottom surface of the first solid waste chamber such that the bottom surfaces of the first and second solid waste chambers are stepped; and an arm holder disposed above the filter housing, the arm holder having a filter positioned in correspondence to the first and second solid waste chambers. 
     Preferably, the first solid waste chamber is provided at the bottom surface thereof with an inlet/outlet port for allowing wash water to be introduced into the first solid waste chamber therethrough when a washing operation is performed and allowing solid waste, which is separated from the wash water by filtering, to be discharged out of the first solid waste chamber therethrough when a draining operation is performed. Also preferably, the first and/or second solid waste chambers is inclined downward toward the inlet/outlet port. 
     In a further aspect of the present invention, a drive unit for dish washing machines, comprises: a sump for receiving wash water; and a housing assembly having: a solid waste chamber for filtering some of the wash water pumped out from a washing impeller, the solid waste chamber having at least three steps; and a filter disposed corresponding to the solid waste chamber. 
     Preferably, the solid waste chamber is provided at the lowest step thereof with an inlet/outlet port for allowing wash water to be introduced into the solid waste chamber therethrough when a washing operation is performed and allowing solid waste, which is separated from the wash water by filtering, to be discharged out of the solid waste chamber therethrough when a draining operation is performed. Also preferably, all the steps of the solid waste chamber are inclined downward toward the inlet/outlet port. 
     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 above and other objects, features and advantages of the present invention will be made apparent from the following description of the preferred embodiments, given as non-limiting examples, with reference to the accompanying 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  is a side view illustrating the construction of a conventional dish washing machine; 
         FIG. 2  is an exploded perspective view illustrating the drive unit for dish washing machines of  FIG. 1 ; 
         FIG. 3  is a plan view illustrating the structure of the flow channel of the filter housing of  FIG. 2 ; 
         FIG. 4  is a sectional view illustrating flow of wash water in the drive unit of  FIG. 2  when a washing operation is performed; 
         FIG. 5A  is a plan view illustrating flow of wash water in the filter housing of  FIG. 2  when a washing operation is performed; 
         FIG. 5B  is a plan view illustrating flow of wash water in the filter housing of  FIG. 2  when a draining operation is performed; 
         FIG. 6  is a perspective view illustrating a drive unit for dish washing machines according to the present invention; 
         FIG. 7  is an exploded perspective view illustrating the drive unit for dish washing machines of  FIG. 6 ; 
         FIG. 8  is a perspective view illustrating a flow of wash water in the flow channel housing of  FIG. 6  when a washing operation is performed; 
         FIGS. 9 and 10  are perspective views illustrating flow of wash water in the housing assembly, excluding the arm holder, of  FIG. 6  when a washing operation is performed; and 
         FIG. 11  is a perspective view illustrating flow of wash water in the housing assembly, excluding the arm holder, of  FIG. 6  when a draining operation is performed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is further described in the detailed description which follows, by reference to the noted plurality of drawings by way of non-limiting examples of preferred embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings. 
       FIG. 6  is a perspective view illustrating a drive unit for dish washing machines according to the present invention. As shown in  FIG. 6 , the drive unit comprises: a sump  100  for receiving wash water; and a housing assembly  200  for pumping and filtering the wash water. The housing assembly  200  comprises: a first solid waste chamber  221  for filtering some of the wash water pumped out from a washing impeller  120 ; a second solid waste chamber  231  disposed to communicate with the first solid waste chamber  221 , the second solid waste chamber  231  having a bottom surface, which is not level with a bottom surface of the first solid waste chamber  221  such that the bottom surfaces of the first and second solid waste chambers  221  and  231  are arranged in the shape of a step; and a filter  241  (See  FIG. 7 ) disposed corresponding to the first and second solid waste chambers  221  and  231 . 
     The second solid waste chamber  231  is disposed such that the second solid waste chamber  231  deviates from the first solid waste chamber  221 . For example, the first solid waste chamber  221  and the second solid waste chamber  231  are connected to each other and have the shape of a ring. In this case, the first and second solid waste chambers  221  and  231  take the shape of a circular arc. Preferably, the second solid waste chamber  231  is constructed to cover the top of a predetermined region of the housing assembly  200  where a flow channel control valve  130  and main flow channels  222  are disposed. As a result, the region of the housing assembly  200  where the solid waste chamber cannot be formed due to the flow channel control valve and the main flow channels in the conventional art is available to be used as the solid waste chamber, and therefore, the size of the solid waste chambers  221  and  231  is considerably increased. However, the shape of the first and second solid waste chambers  221  and  231  is not limited to the above-mentioned ring. For example, the first and second solid waste chambers  221  and  231  may be formed in the shape of, for example, a square or rectangular frame, a triangular frame, or an elliptical doughnut. 
     Preferably, the bottom surface of the first solid waste chamber  221  is lower than that of the second solid waste chamber  231 . In this case, the region of the housing assembly  200  where the flow channel control valve  130  and the main flow channels  222  are not disposed is effectively utilized to increase the size of the first solid waste chamber  221 . Preferably, at the bottom surface of the first solid waste chamber  221  an inlet/outlet port  225  is formed (See  FIG. 7 ) for allowing wash water to be introduced into the first solid waste chamber  221  therethrough when a washing operation is performed and allowing solid waste, which is separated from the wash water by filtering, to be discharged out of the first solid waste chamber  221  therethrough when a draining operation is performed. 
     Alternatively, the bottom surface of the second solid waste chamber  231  may be lower than that of the first solid waste chamber  221 . In this case, it is natural that the inlet/outlet port  225  is formed at the second solid waste chamber  231 . Also preferably, the bottom surface of the first solid waste chamber  221  and/or the bottom surface of the second solid waste chamber  231  is inclined downward toward the inlet/outlet port  225 . In this case, the wash water is smoothly discharged from the first and second solid waste chambers  221  and  231  to a drain pump when the draining operation is performed. 
     Preferably, the first and second solid waste chambers  221  and  231  communicate with each other in the vicinity of the inlet/outlet port  225 . In this case, the first and second solid waste chambers  221  and  231  are inclined downward to the inlet/outlet port  225 . Consequently, the difference in height between the bottom surface of the first solid waste chamber  221  and the bottom surface of the second solid waste chamber  231  is maximized in the vicinity of the inlet/outlet port  225 . 
     More preferably, the first and second solid waste chambers  221  and  231  are partitioned from each other at the side opposite to the inlet/outlet port  225 . For example, both ends of the first solid waste chamber  221  are connected to both ends of the second solid waste chamber  231  when the first and second solid waste chambers  221  and  231  are connected to each other such that the first and second solid waste chambers  221  and  231  are arranged in the shape of a ring. At one of the two connections where the first and second solid waste chambers  221  and  231  are connected to each other, which is opposite to the wash water inlet side, a partition rib  234  is formed. Consequently, the wash water introduced into the first solid waste chamber  221  is prevented from flowing along the first and second solid waste chambers  221  and  231  in the circumferential direction. 
     Also preferably, communication holes  228  and  238  are formed at the regions of the housing assembly  200  surrounded by the first and second solid waste chambers  221  and  231 , respectively. The communication holes  228  and  238  communicate with the sump  100  for discharging leaked wash water to the sump  100 . Preferably, the communication holes  228  and  238  are disposed such that the communication holes  228  and  238  deviate from an impeller location part  211  where the washing impeller  120  is located. 
     The drive unit for dish washing machines will now be described in more detail with reference to  FIG. 7 . As shown in  FIG. 7 , the housing assembly  200  comprises a pump housing  210  disposed in the sump  100 . The washing impeller  120  is located in the pump housing  210 . The housing assembly  200  further comprises: a flow channel housing  220  disposed to cover the top of the pump housing  210 , the flow channel housing  220  having the first solid waste chamber  221 ; a filter housing  230  disposed above the flow channel housing  220 , the filter housing  230  having the second solid waste chamber  231 ; and an arm holder  240  disposed above the flow channel housing  220 , the arm holder  240  having the filter  241 , which covers the tops of the first and second solid waste chambers  221  and  231 . 
     Between the pump housing  210  and the flow channel housing  220  is disposed a sealing member  140  for preventing leakage of wash water. Also, another sealing member, which is not shown, is disposed between the flow channel housing  220  and the filter housing  230 . Still another sealing member, which is also not shown, is disposed between the filter housing  230  and the arm holder  240 . Each of these sealing members can be of any appropriate type and of any appropriate material, and will have a shape corresponding to a shape of the junction between the respective elements being sealed thereby. 
     The impeller location part  211  is formed at the pump housing  210  such that the washing impeller  120  is located in the impeller location part  211 . At the pump housing  210  an insertion part  212  is also formed, through which the flow channel control valve  130  is inserted. The pump housing  210  with the above-stated construction is located in the sump  100 . In this case, it is possible to connect the impeller  120  to the shaft of a washing motor (not shown) after the pump housing  210  is located in the sump  100 . Consequently, easier installation of the impeller  120  is accomplished. 
     The main flow channels  222 , which guide some of the pumped-out wash water to washing arms, are formed at the flow channel housing  220 . At the flow channel housing  220  a sampling flow channel  223  is provided for guiding some of the pumped-out wash water to the first and second solid waste chambers  221  and  231  through a drain chamber  110 . More specifically, the inlet/outlet port  225  is formed at the flow channel housing  220 . The inlet/outlet port  225  is connected to the drain chamber  110 . The sampling flow channel  223  is formed by vertically partitioning the inlet/outlet port  225 . Consequently, relatively large-sized solid waste is deposited when the wash water in the sampling flow channel  223  passes through the drain chamber  110 . In this way, a primary filtering operation is performed. The filtered wash water is introduced into the first and second solid waste chambers  221  and  231  where the wash water is secondarily filtered. At the drain chamber  110  a drain pump (not shown) is mounted. 
     At the filter housing  230  a filter opening  232  is formed, which corresponds to the first solid waste chamber  221 . The filter opening  232  of the filter housing  230  and the top of the second solid waste chamber  231  are covered by the filter  241  of the arm holder  240 . The filter  241  of the arm holder  240  is arranged in the shape of a ring. 
     The communication holes  228  and  238  are formed at the flow channel housing  220  and the filter housing  230 , respectively, such that the communication holes  228  and  238  communicate with the sump  100 . The communication holes  228  and  238  deviate (i.e., are spaced) from the impeller location part  211  of the pump housing  210 . Consequently, wash water that leaks in the regions of the flow channel housing  220  and the filter housing  230  surrounded by the solid waste chambers  221  and  231  is collected into the sump  100  through the communication holes  228  and  238 , respectively. 
     At the edge of the filter hosing  230  collection holes  233  are formed. Each of the collection holes  233  has an opened outside, and communicates with the sump  100 . Each of the collection holes  233  may be formed in various shapes. At the upper end of the edge of the sump  100  are preferably formed fixing ribs  111 , which are inserted into the collection holes  233  of the filter housing  230 , respectively, for securely fixing the filter housing  230 . 
     After the pump housing  210  is mounted in the sump  100 , the washing impeller  120  is mounted in the pump housing  210 . At this time, the impeller  120  is securely fitted on the shaft of the washing motor (not shown). Subsequently, the flow channel housing  220 , the filter housing  230  and the arm holder  240  are mounted one by one. After that, the sump  100 , the pump housing  210 , the flow channel housing  220 , the filter housing  230  and the arm holder  240  are securely fixed to one another by means of fixing members  270 . 
     Although not shown, a solid waste chamber having at least three successive steps may be provided and is within the scope of the present invention. In this case, the inlet/outlet port  225  is preferably disposed at the lowest step of the solid waste chamber. Also preferably, all the steps of the solid waste chamber are inclined downward toward the inlet/outlet port  225 . In this structure, the wash water is filled in the respective steps one by one, and solid waste is easily drained when the draining operation is performed. 
     As described above, the housing assembly  200  is configured by mechanically assembling the flow channel housing  220 , the filter housing  230  and the arm holder  240 . Alternatively, the flow channel housing  220 , the filter housing  230  and the arm holder  240  may be integrally fixed to one another by thermal fusion to configure the housing assembly  200 . Also, it is easily understood that the above-mentioned various flow channels may take various forms. 
     The operation of the drive unit for dish washing machines with the above-stated construction according to the present invention will now be described in detail. Specifically, a main washing operation will be described with reference to  FIGS. 8  to  10 . When the main washing operation is initiated, the impeller  120  introduces wash water from the sump  100  to the impeller location part  211 . The wash water is pumped out, and is then introduced to the wash water inlet port of the flow channel housing  220 . 
     As the flow channel control valve  130  is rotated, as shown in  FIG. 8 , the main flow channels  222  are selectively, simultaneously, or alternately opened or closed. At this time, some of the pumped-out wash water is introduced into the upper injection arm and/or the lower injection arm through the main flow channels  222 . Also, some of the pumped-out wash water is introduced into the sampling flow channel  223 . At this time, the wash water is introduced into the sampling flow channel  223  irrespective of which main flow channel(s)  222  is opened by the flow channel control valve  130 . 
     The wash water introduced into the sampling flow channel  223  flows into the drain chamber  110  through the inlet/outlet port  225 . A pollution level detecting device  224  is mounted in the sampling flow channel  223 . The pollution level detecting device  224  serves to detect the pollution level of the wash water and transmit the detected pollution level of the wash water to a control unit. Introduction of the wash water into the drain chamber is not illustrated in  FIG. 8 . 
     Relatively large-sized food particles, which are contained in the wash water in the drain chamber  110 , are deposited on the bottom surface of the drain chamber  110 . Consequently, the food particles are primarily separated from the wash water in the drain chamber  110 . The drain chamber  110  serves as a submerged tank when the washing operation is performed. 
     Referring to  FIG. 9 , the wash water introduced into the drain chamber  110  flows into the first solid waste chamber  221  through the inlet/outlet port  225 . At this time, food particles are accumulated in the first solid waste chamber  221  from the partition rib side to the wash water inlet side. Also, relatively large-sized food particles are deposited in the drain chamber  110 . As a result, relatively small-sized food particles are introduced into the first solid waste chamber  221 , and therefore, the amount of food particles introduced into the first solid waste chamber  221  is decreased. 
     As the amount of wash water introduced into the first solid waste chamber  221  is gradually increased, the wash water is introduced into the second solid waste chamber  231 , as shown in  FIG. 10 . At this time, the partition rib  234  prevents the wash water from flowing from the first solid waste chamber  221  to the second solid waste chamber  231 . Also, food particles are accumulated in the second solid waste chamber  231  from the partition rib side to the wash water inlet side. As a result, the filter  241  is effectively prevented from being blocked. 
     As described above, the wash water is introduced into the first and second solid waste chambers  221  and  231  via the drain chamber  110 . Consequently, the water pressure applied to the first and second solid waste chambers  221  and  231  is relatively decreased as compared to the prior art, and therefore, the amount of food particles introduced into the first and second solid waste chambers  221  and  231  is decreased. Also, the filtering capacity is increased, and therefore, the filter  241  of the arm holder  240  is effectively prevented from being blocked. Moreover, the food particles are accumulated in the first and second solid waste chambers  221  and  231  from the partition rib side to the wash water inlet side, and therefore, the filter  241  is effectively prevented from being blocked. 
     The wash water introduced into the first and second solid waste chambers  221  and  231  as described above overflows through the filter  241 . At this time, relatively small-sized food particles contained in the wash water are secondarily separated from the wash water by the filter  241 . The filtered wash water is introduced again into the sump  100  through the collection holes  233  of the filter housing  230 . Here, the pumping force of the impeller  120  creates water pressure, by which the wash water is introduced into the first and second solid waste chambers  221  and  231  via the drain chamber  110 . 
     A small amount of wash water leaks through gaps between the flow channel housing  220 , the filter housing  230  and the arm holder  240 , and is then introduced into the regions of the housing assembly  200  surrounded by the first and second solid waste chambers  221  and  231 . The leaked wash water is collected into the sump  100  through the communication holes  228  and  238 . Consequently, the drive unit is sanitarily used. 
     After the washing operation is completed, a draining operation is initiated. When the draining operation is initiated, the drain pump is operated. At this time, the wash water and the food particles are introduced into the drain chamber  110  from the sump  100 . At the same time, the wash water and the food particles are introduced into the drain chamber  110  from the first and second solid waste chambers  221  and  231  through the inlet/outlet port  225 , as shown in  FIG. 11 . The bottom surfaces of the first and second solid waste chambers  221  and  231  are inclined downward toward the inlet/outlet port  225 . Consequently, discharge of the food particles from the first and second solid waste chambers  221  and  231  is facilitated. Also, circulation of the food particles in the first and second solid waste chambers  221  and  231  is prevented by the partition rib  234 . Consequently, the food particles are completely discharged when the wash water is drained. The wash water and the food particles introduced into the drain chamber  110  are drained out of the dish washing machine through the drain port. 
     As apparent from the above description, the drive unit for dish washing machines according to the present invention has the following effects. First, some of the pumped-out wash water is deposited in the drain chamber, and is then introduced into the first and second solid waste chambers. As a result, a small amount of solid waste, such as relatively small-sized food particles, is introduced into the first and second solid waste chambers. Consequently, the filter is effectively prevented from being blocked, and an increase of the water pressure in the first and second solid waste chambers is prevented. 
     Secondly, the second solid waste chamber is disposed above the flow channel control valve and the various flow channels. Consequently, the solid waste chambers can be constructed irrespective of the positions where the flow channel control valve and the main flow channels are disposed. Furthermore, the size of the solid waste chambers is relatively increased, and the filtering capacity is also increased. 
     Thirdly, relatively small water pressure is applied to the first and second solid waste chambers. As a result, the wash water is not excessively drained, and therefore, supplementing of the wash water is not necessary. Consequently, the amount of consumed wash water and the power consumption are prevented from being excessively increased. Furthermore, deformation of the filter is effectively prevented. 
     Fourthly, the bottom surfaces of the first and second solid waste chambers are inclined downward toward the wash water draining side. As a result, solid waste, such as food particles, are effectively prevented from remaining in the first and second solid waste chambers when the draining operation is performed. Consequently, the rinsing operation is sanitarily performed. 
     Fifthly, the communication holes are formed at the regions of the housing assembly surrounded by the first and second solid waste chambers, respectively. As a result, the wash water leaking from between the flow channel housing and the filter housing is drained through the communication holes. Consequently, the drive unit for dish washing machines according to the present invention is more sanitarily used. 
     Although the invention has been described with reference to an exemplary embodiment, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein. Instead, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. 
     The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description is taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice.