Abstract:
A dishwasher having a removable filtration system includes a main coarse filter screen having a central opening for removably fitting the filter screen around a water distribution manifold. The filter screen includes an outer circumferential rim portion have an elastomeric seal over-molded thereto which is press-fit into a channel in a lower sump unit such that the filter screen is suspended over a sump enclosure. A finer, secondary strainer extends through the filter screen and provides secondary filtering of washing fluid entering the sump enclosure through the filter screen. Preferably, the filtration system also includes a non-removable or backup strainer which provides coarse straining of washing fluid should a user fail to properly reinstall the removable filter screen and/or the secondary strainer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention pertains to the art of dishwashers and, more specifically, to a dishwasher including a removable filtration system. 
         [0003]    2. Description of the Related Art 
         [0004]    Dishwashers for use in the home typically have a filter arrangement to filter material from wash liquid circulating in the dishwasher to prevent such material from re-depositing on dishware being washed. Many dishwashers have at least one filter interposed between a tub sump and the circulation pump for the dishwasher. Some dishwashers are known to have a bypass filter arrangement, such as a flow-through filtration system, independent of the circulation pump, to filter wash liquid upstream of the circulation pump. Flow-through filtration wash systems require periodic removal of filter screens for cleaning by a consumer. Consumers are expected to remove, clean and properly reinstall filter components on a regular basis. However, problems may occur when a consumer fails to replace the filters properly before a new wash cycle. For example, dishwasher spray nozzles may become plugged with debris, causing significant performance degradation and potentially requiring professional repair of the machine. Additionally, debris may collect around the rim of a removable filter screen or may even bypass the filter screen if a proper seal is not maintained between the filter screen and its support base. Again, performance of the dishwasher may be degraded by such debris entering the pump and distribution systems of the dishwasher. 
         [0005]    With the above in mind, there exists the need for an inexpensive and easy-to-use dishwasher filtration system that provides further protection against damage from debris entering the dishwasher&#39;s pump and distribution system. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is directed to a dishwasher having a removable filtration system. In general, the removable filtration system includes a main coarse filter screen having a central opening for removably fitting the filter screen around a water distribution manifold. The filter screen includes an outer circumferential edge have an elastomeric, over-molded seal which can be press-fit into a channel in a lower sump unit such that the filter screen is suspended over a sump enclosure. When installed, a top wall of the over-molded seal is substantially flush with a top wall of the sump unit, thus preventing debris from bypassing the filter screen or accumulating around the peripheral edge of the filter screen. The filter screen further includes an aperture through which a secondary strainer extends into the sump enclosure. The secondary strainer provides finer filtering of washing fluid entering the sump enclosure through the filter screen, as well as providing a course screen for over-flow protection. Preferably, the filtration system also includes a non-removable or backup strainer which provides coarse straining of washing fluid should a user fail to properly reinstall the removable filter screen and/or secondary strainer, or should one of the filter screen or strainer become damaged. 
         [0007]    Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a partial perspective view of a dishwasher constructed in accordance with the present invention, with a door of the dishwasher being open; 
           [0009]      FIG. 2  is a partial perspective view of a water distribution and filtration system of the dishwasher of  FIG. 1 ; 
           [0010]      FIG. 3  is a partial exploded view of the removable filtration system of the present invention; 
           [0011]      FIG. 4  is a partial cross-sectional view of a removable filter screen of the present invention; 
           [0012]      FIG. 5  is a top perspective view of a sump system of the dishwasher of  FIG. 1 ; 
           [0013]      FIG. 6  is a top perspective view of the sump system of  FIG. 5  including a non-removable filter of the present invention; and 
           [0014]      FIG. 7  is a perspective view of the non-removable filter of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0015]    With initial reference to  FIGS. 1 and 2 , a dishwasher constructed in accordance with the present invention as generally indicated at  2 . As shown, dishwasher  2  includes a tub  5  which is preferably molded of plastic so as to include integral bottom, side, and rear walls  8 - 11  respectively, as well as a top wall (not shown). Tub  5  defines a washing chamber  14  within which soiled kitchenware is adapted to be placed upon shiftable upper and lower racks (not shown), with the kitchenware being cleaned during a washing operation in a manner widely known in the art. Tub  5  has attached thereto a pivotally supported door  20  used to seal chamber  14  during the washing operation. In connection with the washing operation, door  20  is preferably provided with a detergent tray assembly  23  within which a consumer can place liquid or particulate washing detergent for dispensing at predetermined portions of the washing operation. Of course, dispensing detergent in this fashion is known in the art such that this arrangement is only being described for the sake of completeness. 
         [0016]    Disposed within tub  5  is a filtration system generally indicated at  30 . In the preferred embodiment, filtration system  30  includes a central main strainer or filter screen  36  and a secondary, fine strainer  39 . Extending about a substantial portion of filtration system  30 , at a position raised above bottom wall  8 , is a heating element  44 . In a manner known in the art, heating element  44  preferably takes the form of a sheath, electric resistance-type heating element. 
         [0017]    Dishwasher  2  further includes a circulation pump (not shown) adapted to direct washing fluid from a sump unit  50  (best seen in  FIGS. 5 and 6 ) to a water distribution manifold indicated at  53 . In a manner known in the art, water distribution manifold  53  supplies washing fluid to at least a lower wash arm  55  and a conduit  57  leading to an upper spray arm (not shown). Additionally, water distribution manifold  53  may be in fluid communication with a spray manifold assembly  59  including a plurality of spray discs  62 . The manner in which wash arm  54  and spray manifold assembly  59  are utilized is known in the art, such that this structure will not be described further herein. 
         [0018]    Details of sump unit  50  utilized in dishwasher  2  are depicted in  FIGS. 3-6 . Sump unit  50  generally comprises a sump enclosure  68  with filter screen  36  preferably disposed over a top opening of enclosure  68 , and a recessed main intake  73  having an outlet  80  leading to a circulation pump (not shown) for circulating fluid through water distribution manifold  53  to wash arm  55 , conduit  57  and manifold assembly  59 . In accordance with the present invention, a filter support surface  83  extends around the upper perimeter of sump enclosure  68 . Filter  36  is supported along its outer circumferential edge  90  by filter support surface  83  and seals against filter support surface  83  in a manner more fully discussed below. 
         [0019]    Filter screen  36  is substantially circular and includes a main body portion  100  have an aperture  105  there through, and arm portions  108  and  109  which define a central opening  112  in the form of a slot there between. As depicted best in  FIG. 3 , central opening  112  of filter screen  36  fits around water distribution manifold  53 . Filter screen  36  preferably constitutes a first-pass coarse screen having a shape that aids in channeling wash liquid. More specifically, filter screen  36  includes a dam portion indicated at  123  which aids in channeling a flow of washing fluid across filter screen  36  to secondary strainer  39 . Additionally, filter screen  36  is oriented with respect to sump unit  50  such that outer circumferential edge  90  is at a greater height than an inner filter edge  126  of aperture  105 . The resulting downwardly sloping configuration of filter screen  36  facilitates the flow of washing fluid to sump unit  50  and the distribution of food particles or debris across filter screen  36 . 
         [0020]    As depicted in  FIG. 4 , outer circumferential edge  90  of filter screen  36  comprises an inwardly curved flange portion  130  that basically establishes an open loop. An annular elastomeric seal  133  extends about substantially the entire outer surface of flange portion  130 , with seal  133  including a bottom wall  136 , a side wall  137  and a top wall portion  138 . In the preferred embodiment of the present invention, seal  133  is constituted by an over-molded flexible rubber seal. Support surface  83  is generally defined by a bottom wall portion  140  extending laterally from a sidewall  143  of sump unit  50 , and an upstanding wall portion  146  extending vertically from bottom wall portion  140 . Together, bottom wall portion  140  and side wall  143  define a channel  150  into which outer circumferential edge  90  of filter screen  36  can be inserted. Preferably, channel  150  is further defined by an upstanding side wall portion  152  extending from side wall  143 , with seal  133  directly abutting side wall portion  152 . 
         [0021]    Filter screen  36  is preferably somewhat flexible in nature, allowing for some flexing of inwardly curved flange portion  130  and the integrated seal  133 . In use, arm portions  108  and  109  of filter screen  36  are fit around water distribution manifold  53  and outer circumferential edge  90  is press-fit into channel  150  such that seal  133  fits snuggly within channel  150 , i.e., directly abuts bottom wall  136  and is slightly compressed between side walls  137  and  152 , while top wall portion  138  of seal  133  is substantially flush with a top wall portion  158  of sump unit  50 . With this configuration, food and debris will not be able to collect between filter screen  36  and sump unit  50  at outer circumferential edge  90 , nor will food or debris be able to bypass filter screen  36  by flowing around outer circumferential edge  90 . Additionally, over-molded seal  133  cannot be lost or improperly positioned with respect to filter screen  36 , allowing for quick and easy installation of filter screen  36  within channel  150 . 
         [0022]    During normal operation, wash water flows through filter screen  36  into sump enclosure  68  and larger food particles from dishes or tableware disposed in dishwasher  2  collect on filter screen  36 . Wash fluid within enclosure  68  is further filtered by secondary strainer  39  before exiting into main intake  73 . In a preferred embodiment, secondary strainer  39  includes a twist lock feature wherein secondary strainer  39  includes flanges (not shown) which engage sump enclosure  68  about the periphery of intake  73  to selectively lock secondary strainer  39  in place. However, other locking arrangements that accommodate the easy removal of secondary strainer  29  could be employed. In any case, sump enclosure  68  is sloped such that fluid therein is directed to a fine screen portion  162  of secondary strainer  39  before entering main intake  73 . Secondary strainer  39  also works as a main filter bypass should wash fluid become backed-up within washing chamber  14 . More specifically, if wash fluid cannot flow sufficiently through filter screen  36 , the level of fluid within washing chamber  14  will rise slightly to the height of inlets  166  located about the periphery of secondary strainer  39 . Wash fluid will then flow through inlets  166  through a coarse screen portion  168  of secondary strainer  39  and into main intake  73 . In a manner known in the art, wash fluid exits main intake  73  through outlet  80  and is recirculated within dishwasher  2  via a circulation pump (not shown). If filter screen  36  becomes plugged or blocked, a user may simply lift secondary strainer  39  clear of filter screen  36  and remove filter screen  36  from dishwasher  2  for cleaning. Likewise, secondary strainer  39  may be removed and cleaned by a user when desired and replaced for the next wash cycle. 
         [0023]    In the case where a user forgets or fails to return filter screen  36  and/or secondary strainer  39  to their proper positions within dishwasher  2 , or in the case where either one or both of filter screen  36  and secondary strainer  39  becomes damaged, washing fluid flowing through intake  73  will still be filtered before entering outlet  80  by a non-removable or back-up strainer  170 , depicted in  FIGS. 6 and 7 . Non-removable strainer  170  is preferably permanently fixed, or at least designed such that a user cannot easily remove strainer  170  from dishwasher  2  and is arcuate in shape to conform to the arc around inlet  80 . Optionally, non-removable strainer  170  may be adapted to be retrofit within intake  73 . Preferably, non-removable strainer  170  includes a coarse screen  173  adapted to prevent debris from entering outlet  80  that would be potentially damaging to the fluid distribution system of dishwasher  2 . 
         [0024]    Although described with reference to a preferred embodiment of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, although depicted as generally circular in shape, it should be understood that a variety of screen shapes could be utilized with the present invention. In general, the invention is only intended to be limited by the scope of the following claims.