Abstract:
A dishwasher includes wash chamber, a wash system for supplying washing fluid to wash arms to clean articles arranged in the wash chamber, and a washing fluid manifold having an inlet portion, an outlet portion and a passage interconnecting the inlet and outlet portions. A filter chamber is fluidly connected to the washing fluid manifold for removing food soil from the washing fluid. A venturi is provided in the passage for establishing a low pressure region. A sampling port for feeding the filter chamber is located in the low pressure region. In addition, a bleed port is provide near an inlet of the filter chamber. In this manner, washing fluid enters the filter chamber at low pressure to increase the efficiency of a filtering process, while washing fluid enters the wash arms at a high velocity to efficiently perform a washing operation.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention pertains to the art of dishwashers and, more particularly, to a system for limiting pressure in a filter chamber in a dishwasher.  
         [0003]     2. Discussion of the Prior Art  
         [0004]     A typical dishwasher includes a closed system where washing fluid is pumped from a sump into upper and lower wash arms such that kitchenware retained on vertically spaced racks within a tub of the dishwasher will be sprayed with the washing fluid for cleaning purposes. The washing fluid is heated, filtered and recirculated. Prior to recirculating the washing fluid, the fluid is directed through one or more filters to remove soil from the fluid, with the soil being collected in a chamber. Periodically, the system is purged in order to drain the collection chamber of the soil.  
         [0005]     In general, washing fluid is circulated in the system at a relatively high pressure in order to ensure an adequate fluid supply to the upper and lower wash arms. At some point in the system, washing fluid is passed or diverted into a filter chamber, often at the same, relatively high pressure that is supplied to the wash arms. Unfortunately, supplying the filter at high pressure will often reduce the overall efficiency of the filtering process. When operating at high pressure, the filter becomes clogged quickly, causing food soils to be released back into the wash system to circulate with the washing fluid. Without proper filtration, the level of food soils circulating in the washing fluid will rise, resulting in a decrease in the overall efficiency of the washing operation.  
         [0006]     Based on the above, there exists a need for a system to limit pressure in a filter chamber of a dishwasher. More specifically, there exists a need for a system that minimizes the pressure of washing fluid entering the filter chamber while, at the same time, ensuring proper operation of the wash arms.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention is directed to a dishwasher including a tub having top, bottom, rear and opposing side walls that collectively define a wash chamber. In a manner known in the art, the dishwasher is provided with a wash pump for establishing a flow of washing fluid in the wash chamber and a drain pump for selectively withdrawing washing fluid from the wash chamber during portions of a washing operation. In addition, the dishwasher includes a washing fluid manifold having an inlet portion for receiving the flow of washing fluid, an outlet portion that directs the flow of washing fluid upward into the wash chamber and a passage interconnecting the inlet and the outlet portions. A filter chamber is fluidly connected to the washing fluid manifold for removing fool soil and other debris from the washing fluid. The filter chamber includes an inlet for receiving washing fluid flowing through the manifold and an outlet that leads back into the wash chamber.  
         [0008]     In accordance with the invention, a venturi is arranged in the passage interconnecting the inlet and outlet portions of the washing fluid manifold. With this arrangement, the flow of washing fluid passing through the venturi increases in velocity, while at the same time decreasing in pressure. In this manner, the venturi establishes a low pressure zone in the passage. In accordance with a preferred embodiment of the invention, a sampling port is provided in the low pressure zone portion of the passage. The sampling port enables a portion of the washing fluid, flowing through the passage, to be diverted into the filter chamber.  
         [0009]     In accordance with the most preferred embodiment of the invention, in addition to the venturi, a bleed port is located proximate to the inlet of the filter chamber. The location and size of the bleed port serves to further reduce the pressure of the washing fluid entering the filter chamber. With this arrangement, the pressure of the washing fluid entering the filter chamber can remain low for efficient filter operation while, at the same time, the velocity of the washing fluid that is supplied to the wash arms is held high for efficient cleaning purposes.  
         [0010]     Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an upper right perspective view of a drawer-type dishwasher incorporating a pump and filter system employing the pressure limiting system of the present invention;  
         [0012]      FIG. 2  is an upper perspective view of a washing tub of the dishwasher of  FIG. 1 ;  
         [0013]      FIG. 3  is a lower perspective view of the washing tub of  FIG. 2 , illustrating portions of the pump and filter system of  FIG. 1 ;  
         [0014]      FIG. 4  is a partial, cross-sectional view taken along a bottom wall portion of the washing tub of the present invention;  
         [0015]      FIG. 5  is an enlarged view of a portion of  FIG. 4 ;  
         [0016]      FIG. 6  is a partial, cross-sectional view of a bottom wall portion of the washing tub illustrating a valve sealing a fine particle collection chamber portion employed in connection with the overall invention;  
         [0017]      FIG. 7  is a partial, cross-sectional view of a bottom wall portion of the washing tub of  FIG. 6  illustrating the valve open position wherein fine soil particles are guided to a drain pump;  
         [0018]      FIG. 8  is a partial perspective view of a flow plate portion of the pump and filter system constructed in accordance with a first embodiment of the present invention; and  
         [0019]      FIG. 9  is a partial, perspective view of a flow plate portion of the pump and filter system constructed in accordance with a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     With initial reference to  FIGS. 1 and 2 , a dishwasher constructed in accordance with the present invention is generally indicated at  2 . As shown, dishwasher  2  includes a support frame  4  arranged below a kitchen countertop  6 . Also below kitchen countertop  6  is shown cabinetry  8  including a plurality of drawers  9 - 12 , as well as cabinet doors  13  and  14 . Although the actual dishwasher into which the present invention may be incorporated can vary, the invention is shown in connection with dishwasher  2  depicted as a dual cavity dishwasher having an upper drawer  16  and a lower drawer  18 . As best illustrated in  FIG. 1 , upper drawer  16  takes the form of a slide-out drawer unit having a small or medium capacity so as to be used for cleaning glassware and the like, while lower drawer  18  is illustrated as a larger capacity drawer for washing items such as dinnerware, cookware and other large sized objects. Of course, upper and lower drawers  16  and  18  could also be similar in size.  
         [0021]     Upper drawer  16  is shown to include a front wall  20 , a rear wall  21 , a bottom wall  22  as well as opposing side walls  23  and  24  that collectively define an upper washing tub  28 . Upper washing tub  28  is provided with a dish rack  30  for supporting various objects, such as glassware, utensils and the like, to be exposed to a washing operation. Upper washing tub  16  is slidingly supported within support frame  4  through a pair of extendible drawer support guides, one of which is indicated at  31 . In the embodiment shown, bottom wall  22  actually forms part of a sump  33  that, as will be discussed more fully below, manages a flow of washing fluid within drawer  16 .  
         [0022]     As best shown in  FIGS. 2-4 , bottom wall  22  is provided with a recessed portion  34  having a generally U-shaped cross section defining an intake ring  35 . A coarse particle strainer  36  extends about recessed portion  34  to trap/prevent large articles, such as utensils, bones and the like, from entering sump  33 . Toward that end, coarse particle strainer  36  is includes a plurality of openings, one of which is indicated at  37 , provided with a coarse filter screen (not shown) formed from, for example, a polyester mesh, plastic or stainless steel. Coarse particle strainer  36  traps larger objects that are collected in a coarse particle collection chamber  38 , while allowing other particles to enter into sump  33 .  
         [0023]     Referring to  FIG. 3 , sump  33  includes a plurality of fluid conduits  67 - 69  formed along bottom wall  22  of washing tub  28 . Alternatively, conduits  67 - 69  could be detachably secured to bottom wall  22 . In any event, fluid conduit  67  constitutes a wash fluid supply conduit, fluid conduit  68  constitutes a wash fluid recirculation conduit and fluid conduit  69  constitutes a wash fluid drain conduit. Each of fluid conduits  67 - 69  provides wash fluid flow management during a washing operation. Preferably, fluid conduits  67 - 69  are spaced from, and arranged substantially parallel to, one another on bottom wall  22 , with conduits  67  and  69  extending from a central portion  71  of intake ring  35  to an outer edge portion  74  of washing tub  28 . More specifically, supply conduit  67  includes a first end  78  which is in fluid communication with an interior portion of washing tub  28  and leads to a second end  79 . Second end  79  is provided with an attachment flange  80 . Likewise, recirculation conduit  68  extends from a first end  81 , which extends beyond intake ring  35  toward a front portion of drawer  16  to a second end  82 . In a manner corresponding to supply conduit  67 , recirculation conduit  68  is provided with a corresponding attachment flange  83 . Finally, drain conduit  69  extends from a first end  85  to a second end  86  which is also provided with an attachment flange  88 .  
         [0024]     In addition to managing the flow of washing fluid in dishwasher  2 , sump  33  serves as a mounting platform for a plurality of wash system components. As best shown in  FIG. 3 , a wash pump  110  and a drain pump  111  are mounted to washing tub  28  along outer edge portion  74 . Preferably, wash pump  110  includes a wash motor housing  115  and a wash pump housing  116 . More preferably, wash pump housing  116  includes a supply outlet  119  and a recirculation inlet  120  that conducts wash fluid back from washing tub  28  to pump housing  116 . Toward that end, wash pump housing  116  is generally F-shaped, with supply outlet  119  and recirculation outlet  120  projecting into attachment flanges  80  and  83  of supply and recirculation conduits  67  and  68  respectively. In the embodiment shown, a heater element  122  is positioned within recirculation conduit  68  to heat the washing fluid that is circulating into and out of washing tub  28 . With this arrangement, a substantially closed loop recirculation system is formed within washing tub  28 . Likewise, drain pump  111  includes a drain motor housing  123  and a drain pump housing  124 . Drain pump housing  124  includes an inlet port (not shown) and an outlet port  126  adapted to be interconnected to a drain hose (not shown). The inlet port is preferably provided with a chopping mechanism  130 , as best represented in  FIGS. 6 and 7 , for macerating food particles before being expelled with the washing fluid from washing tub  28  during periodic drain or purging operations.  
         [0025]     Referring to  FIGS. 2 and 4 - 7 , dishwasher  2  includes a filter assembly  140  arranged centrally within coarse particle strainer  36 . In accordance with the preferred form of the invention, filter assembly  140  is actually divided into a filter chamber  143  and a washing fluid manifold  145 . Washing fluid manifold  145  is configured to receive a flow of washing fluid from wash pump  110  through an inlet portion  148  and thereafter direct or guide the washing fluid through a passage  149  to an upward into washing tub  28 . As will be discussed more fully below, washing fluid manifold  145  is provided with a sampling port  153  that diverts a portion of the washing fluid flowing through passage  149  into filter chamber  143 .  
         [0026]     Filter assembly  140  includes a cover member  155  having a plurality of large openings, one of which is indicated at  158 . Preferably, cover member  155  is secured in place through a plurality of fasteners (not shown) that extend through a plurality of mounting bosses  159 . In the embodiment shown, openings  158  are provided with a fine mesh filtering screen, which is partially shown at  160 , for entrapping soil from the washing fluid in filter chamber  143 , while permitting cleansed washing fluid to be directed back upward into washing tub  28 . Therefore, openings  158  are provided solely over filter chamber  143  of filter assembly  140 . In addition, cover member  155  is provided with a central opening  162  including an annular lip  163  ( FIG. 5 ) that defines a recessed flange  164 . As will be detailed more fully below, central opening  162  provides a passage for a stationary hub member  170  ( FIGS. 6 and 7 ) that extends upward beyond cover member  155  into washing tub  28 .  
         [0027]     As best shown in  FIG. 5 , stationary hub member  170  is adapted to rotatably support a wash arm  172  that directs jets of water onto kitchenware and the like arranged upon dish rack  30 . In the embodiment shown, wash arm  172  includes a plurality of upwardly projecting openings  173 , each of which includes a corresponding upstanding annular flange  174 . Flange  174  is adapted to snap-fittingly receive an adjustable jet cap (not shown) that can be oriented, either at the factory or by a consumer, to obtain an optimal water spray in washing tub  28 . In addition to upwardly projecting openings  173 , wash arm  172  is provided with a plurality of downwardly projecting openings  175  that are directed onto mesh screen  160 . In any event, stationary hub member  170  includes an outer surface  178  that defines a central passage or conduit  180  that guides washing fluid from washing fluid manifold  145  up into wash arm  172 . In addition, extending about outer surface  178  is a sealing surface  184  that abuts cover member  155  to provide a seal about stationary hub  170 . Actually, sealing surface  184  is forced against recessed flange  164  of central opening  159  in the presence of a flow of washing fluid to establish the seal. This particular configuration limits pressure losses to increase washing efficiency. Stationary hub member  170  includes a central shaft  187  that, when in position, abuts against a bottom portion (not separately labeled) of washing fluid manifold  145 . Shaft  187  causes an upper portion  188  of stationary hub  170  to project above cover member  155 . In this manner, stationary hub  170  is properly positioned to facilitate the assembly of wash arm  172 . In the embodiment shown, upper portion  188  is provided with an outlet  189  that opens into wash arm  172 . Arranged centrally on upper portion  188  is an attachment lug  191  provided to rotatably support wash arm  172  above stationary hub  170 .  
         [0028]     As outlined above, a portion of the washing fluid that is directed into wash arm  172  is diverted into filter chamber  143  through sampling port  153 . Soil particles too large to pass through filtering screen  160  are trapped within filter chamber  143  and, ultimately, collect into a fine particle collection chamber  215  ( FIGS. 6 and 7 ). Fine particle collection chamber  215  is provided with an opening  218  that leads into drain passage  69 . Opening  218  is provided with a valve  225  that, during select portions of a washing operation, opens to allow the soil particles collected within fine particle collection chamber  215  to pass into drain passage  69 . Preferably, valve  225  is constituted by an electrically activated solenoid-type valve that, upon activation, causes a plunger  227  to be drawn into a valve body  228 , thus allowing passage through opening  218 . Actually, in accordance with the most preferred form of the present invention, drain passage  69  constitutes a bifurcated drain passage having a coarse particle portion  236  and a fine particle portion  237 . Thus, as best shown in  FIGS. 6 and 7 , large soil particles flowing into intake ring  35  travel with the washing fluid and ultimately collect within coarse particle collection chamber  38 . The coarse particles are withdrawn from dishwasher  2  during various drain/purge operations performed by drain pump  111 . In addition, fine soil particles collecting within fine soil particle collection chamber  215  are withdrawn from filter chamber  143  during the various drain/purge operations concurrently with coarse soil particles from coarse soil particle collection chamber  38 . Alternatively, in the event that filter screen  160  becomes clogged, valve  225  can open, as shown in  FIG. 7 , allowing the passage of soil into fine particle conduit  237  in order to prevent an excessive pressure build-up within fine soil filter chamber  143 . With this particular arrangement, a multi-size particle collection system can be incorporated into dishwasher  2  without allowing fine soil particles and coarse soil particles to intermix prior to draining.  
         [0029]     With particular reference to  FIG. 4 , filter assembly  140  includes a flow plate  246  over which passes fluid leading from washing tub  28  and filter chamber  143  back into intake ring  35  to be recirculated with the washing fluid. Flow plate  246  includes an annular plateau  247  that leads to a downwardly projecting lip  248  which extends into intake ring  35 . In addition, interposed between coarse particle strainer  36  and flow plate  246  is an annular filter ring  249  that prevents large objects from entering into, and possibly clogging, intake ring  35 . Annular filter ring  249  rests within a notch  250  defined by an inner perimeter of coarse particle strainer  36 . Annular filter ring  249  extends through an angled portion  251  that includes a plurality of openings  252  and abuts annular plateau  247 . In still further accordance with the present invention, filter assembly  140  includes a bleed valve  260  ( FIGS. 6 and 7 ) that enables air trapped within lower portions of sump  33  during an initial fill portion of the washing operation to pass up into washing tub  28 . More specifically, as washing fluid enters washing tub  28 , sump  33  and fluid conduits  67 - 69 , air may become trapped within various regions of filter assembly  140  and sump  33 . Thus, during an initial operation of wash pump  110  to recirculate washing fluid in washing tub  28 , air may be ingested into wash pump  110  causing cavitation or hesitation of wash pump  110 . In order to prevent this particular problem, as washing fluid is being introduced into washing tub  28 , air being displaced by the washing fluid is allowed to pass upward through bleed valve  260  and escape into washing tub  28  so as to purge any trapped air from within filter assembly  140  and sump  33 . In this manner, the overall performance of dishwasher  2  can be enhanced with particular focus being upon noise reduction and increasing pump life.  
         [0030]     In any event, the particular construction and arrangement of filter assembly  140  contributes to forming a washing tub  28  with minimal vertical height, without sacrificing washing operation performance. In other words, sump  33  and filter assembly  140  of the present invention enables the construction of drawer-type dishwasher  2  that includes many of the advantageous features of larger dishwashers, such as multi-stage filtering, wash fluid flow management, food choppers and the like without increasing an overall vertical height of dishwasher  2 . In addition, the construction of sump  33  simplifies the overall assembling process for dishwasher  2 . Furthermore, washing tub  28  can be provided with a turbidity sensor  300  ( FIG. 3 ) to control advantageous washing operations, particularly unscheduled drain or purging operations. In general, the structure described above is provided for the sake of completeness and the present invention is particularly directed to a system for reducing pressure in filter chamber  143 .  
         [0031]     In accordance with a preferred embodiment of the invention as shown in  FIG. 8 , washing fluid manifold  145  includes a flow restrictor  300  arranged within passage  149 . Flow restrictor  300  functions to create a low pressure zone or region in washing fluid manifold  145 . More specifically, the flow of washing fluid entering inlet portion  148  initially enters passage  149  at a first pressure and at a first velocity. Flow restricter  300  is preferably constituted by a venturi, as generally indicated at  303 . As shown, venturi  303  includes a first tapered portion  305  exposed to inlet portion  148  of washing fluid manifold  145 . First tapered portion  305  leads to a second tapered portion  310  through a narrow, throat section  315 . With this construction, the pressure of the washing fluid entering throat section  315  is reduced while, at the same time, the washing fluid flow experiences an increase in velocity. The increase in velocity of the washing fluid enables proper operation of, for example, wash arm  172 , while the low pressure ensures efficient operation of filter assembly  140 . In the most preferred form of the invention, sampling port  153  is located in the low pressure region of washing fluid manifold  145  and, most preferably, within flow restrictor  300 . That is, in order to ensure that filter chamber  143  is supplied with washing fluid at a low pressure, sampling port  153  is preferably located within throat section  315 .  
         [0032]     In still further accordance with the invention, in order to supplement the pressure reduction accomplished by passing the washing fluid through venturi  303 , filter chamber  143  is provided with a bleed port  340 . As shown, bleed port  340  is located in a bottom wall (not separately labeled) of filter chamber  143 . In order to prevent soil from being released into washing tub  28 , bleed port  340  is preferably positioned directly adjacent to an inlet  345  to filter chamber  143  from sampling port  153 . In accordance with the invention, bleed port  340  is defined by a first cross-sectional area, inlet  345  is defined by a second cross-sectional area, and sampling port  153  is defined by a third cross-sectional area. In the most preferred form of the present embodiment, the cross-sectional area of sampling port  153  is sized so as to be less than the combined cross-sectional areas of bleed port  340  and inlet  345 . In this manner, washing fluid entering filter chamber  143  can be maintained at a low pressure to further ensure efficient filtration and removal of soil particles from the washing fluid prior to re-entering washing tub  28 .  
         [0033]      FIG. 9  is presented to reference certain modifications which can be made in accordance with the invention. More particularly, the embodiment of  FIG. 8  sets forth the combination of sampling port  153  located in throat section  315 , venturi  303  and bleed port  340 . However, it should be initially noted that sampling port  153  can be repositioned in accordance with the invention.  FIG. 9  illustrates an embodiment wherein sampling port  153  is located closely adjacent to inlet portion  148 , rather than in throat section  315 .  FIG. 9  also illustrates a potential modification wherein venturi  303  is not employed. That is, the flow for filtering and spraying purposes could be established through only the use of sampling port  153  and bleed port  340 . In addition, it should be noted that the combination of sampling port  153  and venturi  303  could be utilized without the inclusion of bleed port  340 . Regardless, the most preferred embodiment of the invention incorporates each of sampling port  153 , venturi  303  and bleed port  340 . However, although described with reference to preferred embodiments of the invention, it should be readily apparent to one of ordinary skill in the art that various changes and/or modifications can be made to the invention without departing from the spirit thereof. In general, the invention is only intended to be limited to by the scope of the following claims.