Abstract:
A dishwasher provides forced air flow in a counter-convectional direction so as to exhaust air out of a bottom portion of the washing volume in contrast to normal convective air flow.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
     BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to dishwashers and in particular to dishwashers providing forced air flow during the drying cycle.  
         [0002]     Dishwashers, such as those used in a home, may provide for a washing cycle followed by a drying cycle, the latter intended to dry the washed dishes sufficiently so that they may be immediately removed from the dishwasher and stored without additional manual drying. In many cases, the drying cycle includes activation of a heating element exposed at the bottom of the washing volume to heat the dishes and create an upward convective flow of hot air.  
         [0003]     Improved drying of the dishes during the drying cycle can be obtained by venting the washing volume using vents typically located at the bottom edge of the dishwasher door and through the door near the top of the door. The vents allow cooler dry air to enter the dishwasher volume at the bottom of the door, drawn by the convective air flow, and heated moist air to be discharged through the door near its top.  
         [0004]     One drawback to vents is that they can increase the noise emitted from the dishwasher during the washing cycle and accordingly, it is known to provide for vents having an electrically actuable door that may block the vents during the washing cycle thereby cutting emitted noise. One vent of this type is described in U.S. Pat. No. 6,293,289 entitled: “Surge Pressure Vent For Low Noise Dishwasher”. Venting can also be obtained by partially opening the door at the conclusion of the washing cycle as disclosed in U.S. Patent Application US 2004/0163684 entitled: “Automatic Door For Dishwasher”. Both of these patents are assigned to the assignee of the present invention and hereby incorporated by reference.  
         [0005]     Venting systems can be improved by the addition of a blower to increase the passage of air through the washing volume. Generally such blowers are arranged to reinforce the natural convective flow of air thereby obtaining the benefit from the blower and the convection action of the heater used during the drying cycle.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The present inventors have discovered that a blower directed to promote counter-convective air flow downward through an opening near the bottom of the dishwasher volume provides significantly improved dish drying with relatively low air flow. Although the inventors do not wish to be bound by a particular theory, this improvement results from a concentration of water vapor near the bottom of the dishwasher volume because of the relatively greater density of water vapor with respect to air. Downward air flow thus quickly expels the water vapor reserving the drier, heated air near the top of the washing volume which continues to absorb water as it eventually flows downward together with new dry air pulled in from the room at the top of the washing volume. The method appears to work with relatively low air flow volumes which may prevent undue mixing of possibly stratified air and water vapor.  
         [0007]     Specifically then, the present invention provides a dishwasher having a housing forming a washing volume for receiving dishes and including a door openable for access to the washing volume and closeable for containing wash water within the housing. The housing includes a first and second opening communicating between inside and outside of the washing volume where the second opening communicates with the washing volume at an area close to the bottom of the washing volume. A blower operating during the dish drying cycle moves air into the washing volume through the first opening to exhaust air out of the washing volume through the second opening.  
         [0008]     Thus it is an object of the invention to preferentially exhaust air near the bottom of the washing volume to rapidly eliminate water vapor, improving the drying of the dishes.  
         [0009]     The first opening may be a vent near the top of the washing volume, for example, in the roof of the housing.  
         [0010]     It is thus another object of the invention to provide a general downward flow of air within the washing volume to take advantage of drier air near the top of the washing volume for absorbing additional moisture.  
         [0011]     It is thus another object of the invention to provide an inlet area for air significantly removed from exhausted water vapor that may exit near the lower edge of the door.  
         [0012]     The first opening may be a vent in the door.  
         [0013]     It is thus another object of the invention to work with standard vent systems that provide ready access to the air inlet area.  
         [0014]     The first opening may be between the door and a housing caused by partial opening of the door.  
         [0015]     It is thus another object of the invention to further improve dish drying capabilities provided in high end dishwashers that use automatic door opening to augment dish drying.  
         [0016]     The second opening may be at a lower edge of the door.  
         [0017]     It is thus another object of the invention to work with exiting vent structures which often use venting near this door edge.  
         [0018]     The second opening may be a trap blocked by standing water in the washing volume during the wash cycle and unblocked by removal of the standing water during the drying cycle.  
         [0019]     It is thus another object of the invention to provide improved efficiency in drying of dishes while cutting noise transmission during dishwashing.  
         [0020]     A filter may be provided at the first opening to filter air received within the washing volume.  
         [0021]     It is thus an object of the invention to prevent material introduced in the downward air stream from settling on the dishes.  
         [0022]     The blower may be positioned at the first opening.  
         [0023]     Thus it is another object of the invention to remove the blower from standing water that may be contained in the washing volume.  
         [0024]     The blower may be on the outside of the housing.  
         [0025]     It is thus another object of the invention to remove the blower from water spray.  
         [0026]     The second opening may communicate with the outside of the housing at an area proximate to the floor.  
         [0027]     It is thus another object of the invention to divert moist and heated air away from the operator&#39;s face and hands.  
         [0028]     The blower may have a flow rate of less than ten cubic feet per minute.  
         [0029]     It is thus another object of the invention to provide an air flow that does not promote turbulence within the washing volume.  
         [0030]     The washing volume may not include an exposed air heater.  
         [0031]     It is thus another object of the invention to eliminate standard convective flow that may work against the flow induced by the present invention and to reduce the costs and disadvantages of an exposed hearing element.  
         [0032]     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]      FIG. 1  is a perspective view of a standard residential dishwasher as positioned beneath a counter, the latter shown in cutaway and with the door opened;  
         [0034]      FIG. 2  is a cross-sectional view through the dishwasher of  FIG. 1  along lines  2 - 2  of  FIG. 1  showing the door closed and a first embodiment of the invention providing counter-convection air flow using a top mounted intake fan;  
         [0035]      FIG. 3  is a cross-sectional view through the intake fan in the cross-sectional plane of  FIG. 2  showing mounting of the fan above an actuator-controlled vent door for reducing noise and shielding the fan from water spray;  
         [0036]      FIG. 4  is a cross-sectional detail view of  FIG. 2  showing a lower door corner in an embodiment in which a sound trap is provided at a lower vent by standing water within the washer volume;  
         [0037]      FIG. 5  is a simplified cross-sectional view of the cabinet of  FIG. 2  showing alternative air flow paths in another embodiment; and  
         [0038]      FIG. 6  is a view similar to that of  FIG. 5  showing yet additional embodiments with alternate air flow paths. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0039]     Referring now to  FIG. 1 , a dishwasher  10  for fitting beneath a countertop  12  may include a cabinet  14  enclosing a washing volume  16 . The washing volume  16  may hold one or more racks  18  into which dishes may be loaded for cleaning as accessed through a front opening closeable by a door  20 . Referring also to  FIG. 2 , the door  20  may be closed against door seals  22  so as to contain water within the washing volume  16  during a wash cycle.  
         [0040]     During a wash cycle, heated water is sprayed on the dishes within the washing volume  16  by stationary or movable nozzles (not shown). At the conclusion of the wash and rinse cycles as determined by a cycle timer (not shown), water is drained from the lower portion of the washing volume  16  in preparation for drying of the dishes, and in a first embodiment of the invention, a heater element  27  is activated heating the air within the washing volume  16 .  
         [0041]     At this time the cycle timer activates an air intake fan  29  positioned at a vent opening in a roof  52  of the cabinet  14  drawing intake air  28  from outside the washing volume  16  beneath a countertop  12  to produce a counter-convection or downward air flow  30  within the washing volume  16  with the air ultimately exhausting through the lower vent  24  at the lower edge of the door  20  to flow along the floor as exhaust air flow  26 . Notably, no moist air is injected in between the dishwasher  10  and the countertop  12  or under other cabinet areas. The downward air flow  30  serves to preferentially exhaust the air at the bottom of the washing volume  16 .  
         [0042]     Filtration of the intake air  28  may be provided by sound insulating batting  32 , for example, also serving to reduce the sound emitted by the dishwasher  10  and being, for example, a fiberglass mat or the like wrapped around the cabinet  14  and beneath the countertop  12 . Alternatively, a dedicated filter to be described can be used.  
         [0043]     Referring now to  FIG. 3 , the intake fan  29  may include a standard muffin-style propeller fan  40  having an air flow without back pressure of less than ten cubic feet per minute and providing a downward air flow toward the dishwasher  10 . The fan  40  may alternatively be other fan styles including squirrel-cage-type fans and, as used herein the terms fan and blower will be used interchangably to indicate any mechanism for moving air at relatively low pressures and velocities as opposed to compressed air jets.  
         [0044]     The fan  40  is held within a housing  42  beneath a grate  44  in and at the top of the housing  42 . The grate  44  may provide support for an inline filter  46  that may optionally be used instead of or with the filtration provided by the batting  32 .  
         [0045]     The fan  40  draws air through the grate  44  and directs it downward through the housing, a hole in the roof  52  of the cabinet  14 , and a second grate  48  beneath the fan  40 .  
         [0046]     The second grate  48  is formed by a removable bezel  50  positioned within the washing volume  16 . The bezel  50  may twist to lock onto the housing  42  thereby sandwiching the roof  52  of the cabinet  14  and a gasket  54  between the housing  42  and the bezel  50  with the fan  40 , and most of the housing  42  and the fan  40  remaining outside of the washing volume  16 .  
         [0047]     A flapper door  56  is positioned within the housing  42  in the path of air flow. In the preferred embodiment, the flapper door  56  employs an elastomeric disk  57  held on an arm  58  to pivot about an axis  60  so that the flapper door  56  may swing between an open position shown in  FIG. 3  and a closed position with the elastomeric disk  57  seating against a seat portion  62  of the housing  42 . When the elastomeric disk  57  is in the closed position, it seals the housing  42  so as to close the washing volume  16  from communication with the fan  40  and the air outside of the washing volume  16 .  
         [0048]     The arm  58  is linked to an actuator  64 , such as a wax motor or other electrical actuator, to close the flapper door  56  during the washing cycle under control of the cycle timer thereby reducing noise transmission and protecting the fan  40  and surrounding the cabinet and countertop  12  from water spray, heat, and high humidity. Conversely, the actuator  64  under control of the cycle timer may open the flapper door  56  after the washing and rinse cycles and during the drying cycle when the fan  40  is operating. Wiring to the fan  40  and actuator  64  is not shown in  FIG. 3  for clarity.  
         [0049]     Referring now to  FIG. 4 , effective closure of the lower vent  24  during the washing cycle may be obtained by means of a trap  66  created with standing water  68  at the bottom of the cabinet  14  during the washing cycle. As is known in the art for dishwashers using conventional convection drying, the standing water may rise to a level to cover a lower edge of a trap dike  70  to prevent sound flow around the dike indicated by arrow  72  from inside the washing volume  16  to outside air. Upon conclusion of the wash cycle, when the standing water  68  is drained, this path of arrow  72  is free and exhaust air  26  may exit per the present invention.  
         [0050]     Referring now to  FIG. 5  from the above description, it will be recognized to those of skill in the art, that modification may be made to these preferred embodiments. For example, instead or in addition to the fan  29 , an exhaust fan  76  may be placed near the bottom of the washing volume  16  to receive air from that lower portion of the washing volume  16  and to exhaust that air to the ambient environment. Fan  76  may include a baffle system and/or an electrically actuatable door for noise control and protection of the fan  76 .  
         [0051]     In one alternative embodiment, the air may be received into the washing volume  16  through a partial opening between the door  20  and the cabinet  14  in systems that provide for automatic door opening. In this case, the venting opening for the fan  40  may be displaced toward the rear of the cabinet and may provide air to a duct  78  possibly including condensing elements  80  for exit near the front of the dishwasher  10  at floor level as indicated by arrow  82 .  
         [0052]     Alternatively, air may be received through a vent  84  positioned near the top of the cabinet  14 , possibly at a rear upper edge, and may include a conventional baffle system for retaining water or an electrically actuatable door.  
         [0053]     Referring to  FIG. 6 , it will be understood that a preferential venting of the moisture laden air near the bottom of the washing volume  16  may also be accomplished with a variety of intake fans, for example, an intake fan  90  positioned on a door vent  92  of otherwise conventional design for drawing in air near the top of the cabinet as indicated by arrow  94 . Alternatively, a vent fan  96  may be placed on a side or rear wall of the cabinet  14  at its upper edge.  
         [0054]     While not preferred, exhausting of the moisture laden air starting at the bottom of the washing volume  16  can also be accomplished with a fan  100  mounted near the bottom of the washing volume  16  drawing in air to exhaust near the front lower edge of the door  20 .  
         [0055]     Referring again to  FIG. 2  in one embodiment, the heater element  27  may be eliminated and the drying cycle may rely on the heat retained in the dishes themselves and cabinet from the heated water used in the washing cycle together with the counter-convection air flow of the present invention Elimination of the heater element reduces offsetting convective flow, the space and cost required by the heater element  27 , the power consumption of the heater element  27  which exceeds that of the fan  40 , and the risk of damage to dishes and their components that may be close to or touch the heater element  27 .  
         [0056]     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.