Abstract:
A method of operating a dishwasher containing a volume of liquid for prewashing includes the steps of spraying items in the dishwasher by operating a circulation pump assembly to achieve prewashing with only the volume of liquid; filtering the volume of liquid with a filter assembly to remove particles from the items by operating the circulation pump assembly; and flushing the particles out of the filter assembly using at least some of the volume liquid by operating a drain pump assembly. Related filter assemblies and dishwasher designs are also disclosed.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates generally to filter systems which can be used in a dishwasher. 
       BACKGROUND OF THE INVENTION 
       [0002]    Dishwashers of various types have been proposed wherein items are placed in a wash chamber which is filled and emptied according to desired wash sequences. Recently, dishwasher manufacturers have focused even more on efficiency in implementing new designs. Thus, an amount of electricity, an amount of detergent, and an amount of water used are all monitored in an attempt to provide efficient and environmentally sensitive machines. 
         [0003]    Typically, a dishwasher goes through one or more pre-wash cycles to clean food particles, grease, etc. from the items in the dishwasher before detergent is added for cleaning. During a pre-wash cycle, various sprayers in the wash chamber of the dishwasher spray water on the items in the wash chamber to loosen and remove and such debris. After each pre-wash cycle, the water used is typically pumped out of the drain to remove whatever came off the items during the pre-wash cycle. A second pre-wash cycle and sometimes a third pre-wash cycle are then utilized with new water to further remove items before washing starts with detergent. 
         [0004]    Each prewash cycle can use up to a gallon of water or more. Therefore, reducing the amount of cycles and/or re-using the water would be desirable. However, reusing the water in current machines would re-introduce the debris removed in a previous pre-wash cycle, thereby defeating the purposes of the pre-wash cycle. 
         [0005]    Accordingly, other designs for filtering devices and related dishwashers and methods of operation, including those addressing one or more drawbacks of conventional devices and dishwashers would be welcome. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
         [0007]    According to certain aspects of the present disclosure a dishwasher is disclosed with an efficient prewash function including a cabinet for holding items to be washed, a wash compartment in the cabinet having a sump for collecting liquid, and at least one spray assembly for spraying a liquid into the cabinet. A circulation pump assembly circulates the liquid from the sump to and through the spray assembly into the wash compartment for prewashing, and a drain pump assembly pumps the liquid from the sump out of a drain after prewashing is completed. A controller communicates with the circulation and drain pump assemblies for directing liquid flow path and direction. A filter assembly includes a housing having a first end, a second end, a passageway between the first and second ends, and a filter membrane within the passageway. The filter assembly receives a working flow for prewashing via the first end from the sump, filtering particles from the working flow via the filter membrane, and transmitting the working flow via the second end during a prewash cycle. The filter assembly receives a flushing flow after prewashing via the second end from the sump, transmitting the flushing flow through the filter membrane to flush out particles filtered from the working flow, and transmitting the flushing flow via the first end to the drain. Various options and modifications are possible. 
         [0008]    According to certain other aspects of the disclosure, a method of operating a dishwasher containing a volume of liquid for prewashing includes the steps of spraying items in the dishwasher by operating a circulation pump assembly to achieve prewashing with only the volume of liquid; filtering the volume of liquid with a filter assembly to remove particles from the items by operating the circulation pump assembly; and flushing the particles out of the filter assembly using at least some of the volume liquid by operating a drain pump assembly. Again, various options and modifications are possible. 
         [0009]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
           [0011]      FIG. 1  provides a side partial cut-away view of an exemplary dishwasher that may be configured in accordance with aspects of the invention; 
           [0012]      FIG. 2  is a schematic view of one possible fluid system the dishwasher of  FIG. 1 ; 
           [0013]      FIG. 3  provides a diagrammatical view showing the methods and flow paths used by the dishwasher according to certain aspects of the invention; 
           [0014]      FIG. 4  provides a diagrammatical view showing the methods and flow paths used by the dishwasher according to other aspects of the invention; 
           [0015]      FIG. 5  provides a cross-sectional view of one example of a filter assembly according to certain aspects of the invention during filtration; 
           [0016]      FIG. 6  provides a cross-sectional view of the filter assembly of  FIG. 5  during flush; 
           [0017]      FIG. 7  shows a portion of an alternate filter assembly; and 
           [0018]      FIG. 8  shows a portion of another alternate filter assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0020]    As discussed in greater detail below, embodiments of the present disclosure relate to a filtering system that can be used with a dishwasher.  FIG. 1  depicts an exemplary domestic dishwasher  100  that may be configured in accordance with aspects of the disclosure. For the particular embodiment of  FIG. 1 , the dishwasher  100  includes a cabinet  102  having a tub  104  therein that defines a wash chamber  106 . The tub  104  includes a front opening (not shown in  FIG. 1 ) and a door  120  hinged at its bottom  122  for movement between a normally closed vertical position (shown in  FIG. 1 ) wherein the wash chamber  106  is sealed shut for washing operation, and a horizontal open position for loading and unloading of articles from the dishwasher. Upper and lower guide rails  124 ,  126  are mounted on tub side walls  128  and accommodate upper and lower roller-equipped racks  130 ,  132 , respectively. Each of the upper and lower racks  130 ,  132  is fabricated into lattice structures including a plurality of elongate members  134 , and each rack  130 ,  132  is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outside the wash chamber  106 , and a retracted position (shown in  FIG. 1 ) in which the rack is located inside the wash chamber  106 . A silverware basket (not shown) may be removably attached to the lower rack  132  for placement of silverware, utensils, and the like, that are too small to be accommodated by the upper and lower racks  130 ,  132 . 
         [0021]    The dishwasher  100  further includes a lower spray-arm-assembly  144  that is rotatably mounted within a lower region  146  of the wash chamber  106  and above a tub sump portion  142  so as to rotate in relatively close proximity to the lower rack  132 . A mid-level spray-arm assembly  148  is located in an upper region of the wash chamber  106  and may be located in close proximity to upper rack  130 . Additionally, an upper spray arm assembly (not shown) may be located above the upper rack  130 . 
         [0022]    The lower and mid-level spray-arm assemblies  144 ,  148  and the upper spray arm assembly are fed by a fluid circulation assembly for circulating water and dishwasher fluid in the tub  104 . The fluid circulation assembly may be located in a machinery compartment  140  located below the bottom sump portion  142  of the tub  104 , as generally recognized in the art. Each spray-arm assembly includes an arrangement of discharge ports or orifices for directing washing liquid onto dishes or other articles located in the upper and lower racks  130 ,  132 , respectively. The arrangement of the discharge ports in at least the lower spray-arm assembly  144  provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of the lower spray-arm assembly  144  provides coverage of dishes and other dishwasher contents with a washing spray. 
         [0023]    The dishwasher  100  is further equipped with a controller  137  to regulate operation of the dishwasher  100 . The controller may include a memory and microprocessor, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. 
         [0024]    The controller  137  may be positioned in a variety of locations throughout dishwasher  100 . In the illustrated embodiment, the controller  137  may be located within a control panel area of door  120  as shown. In such an embodiment, input/output (“I/O”) signals may be routed between the control system and various operational components of dishwasher  100  along wiring harnesses that may be routed through the bottom  122  of door  120 . Typically, the controller  137  includes a user interface panel  136  through which a user may select various operational features and modes and monitor progress of the dishwasher  100 . In one embodiment, the user interface  136  may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface  136  may include input components, such as one or more of a variety of electrical, mechanical or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface  136  may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. The user interface  136  may be in communication with the controller  137  via one or more signal lines or shared communication busses. 
         [0025]    It should be appreciated that the invention is not limited to any particular style, model, or other configuration of dishwasher, and that the embodiment depicted in  FIG. 1  is for illustrative purposes only. For example, instead of the racks  130 ,  132  depicted in  FIG. 1 , the dishwasher  100  may be of a known configuration that utilizes drawers that pull out from the cabinet and are accessible from the top for loading and unloading of articles. 
         [0026]      FIG. 2  schematically illustrates an embodiment of a fluid circulation assembly  170  configured below the wash chamber  106 . Although one embodiment of a fluid circulation assembly that is operable to perform in accordance with aspects of the disclosure is shown, it is contemplated that other fluid circulation assembly configurations may similarly be utilized without departing from the spirit and scope of the invention. The fluid circulation assembly  170  includes a circulation pump assembly  172  and a drain pump assembly  174 , both in fluid communication with the sump  150 . Additionally, the drain pump assembly  174  is in fluid communication with an external drain  173  to discharge used wash liquid. Further, the circulation pump assembly  172  is in fluid communication with lower spray arm assembly  144  and conduit  154  which extends to a back wall  156  or other side wall of wash chamber  106 , and upward along the back wall  156  for feeding wash liquid to the mid-level spray arm assembly  148  ( FIG. 1 ) and the upper spray arm assembly. This configuration also applies to a drawer-type of dishwasher, as mentioned above. 
         [0027]    As wash liquid is pumped through the lower spray arm assembly  144 , and further delivered to the mid-level spray arm assembly  148  and the upper spray arm assembly (not shown), washing sprays are generated in the wash chamber  106 , and wash liquid collects in the sump  150 . The sump  150  may include a cover to prevent larger objects from entering the sump  150 , such as a piece of silverware or another dishwasher item that is dropped beneath lower rack  132 . A coarse filter and a fine filter (not shown) may be located adjacent the sump  150  to filter wash liquid for sediment and particles of predetermined sizes before flowing into the sump  150 . Furthermore, a turbidity sensor may be coupled to the sump  150  and used to sense a level of sediment in the sump  150  and to initiate a sump purge cycle where the contents or a fractional volume of the contents of the sump  150  are discharged when a turbidity level in the sump  150  approaches a predetermined threshold. The sump  150  is filled with water through an inlet port  175  which outlets into wash chamber  106 . 
         [0028]    As shown, a drain valve  186  is established in flow communication with the sump  150  and opens or closes flow communication between the sump  150  and a drain pump inlet  188 . The drain pump assembly  174  is in flow communication with the drain pump inlet  188  and may include an electric motor for pumping fluid at the inlet  188  to an external drain system via drain  173 . In one embodiment, when the drain pump is energized, a negative pressure is created in the drain pump inlet  188  and the drain valve  186  is opened, allowing fluid in the sump  150  to flow into the fluid pump inlet  188  and be discharged from fluid circulation assembly  170  via the external drain  173 . Alternatively, pump assemblies  172  and  174  may be connected directly to the side or the bottom of sump  150 , and the pump assemblies may each include their own valving replacing drain valve  186 . Other fluid circulation systems are possible as well, drawings fluid from sump  150  and providing as desired within wash chamber  106  or draining out of washing machine  100 . 
         [0029]    Referring to  FIG. 2 , a water supply  200  may be configured with the inlet port  175  for supplying wash liquid to the wash chamber  106 . The water supply  200  may provide hot water only, cold water only, or either selectively as desired. As depicted, water supply  200  has a hot water inlet  204  that receives hot water from an external source, such as a hot water heater and a cold water input  206  that receives cold water from an external source. It should be understood that the term “water supply” is used herein to encompass any manner or combination of valves, lines or tubing, housing, and the like, and may simply comprise a conventional hot or cold water connection. 
         [0030]      FIG. 3  shows one diagrammatical example of an operating method and structures used in certain aspect of the present disclosure. As shown, the liquid flow paths are different than found in  FIG. 2 . For example, wash chamber  106  has a sump  150  and a water supply  200 . Sump  150  has a first outlet  208  in communication with circulation pump assembly  172 , a second outlet  210  in communication with filter assembly  212  and a third outlet  214  in communication with drain pump assembly  174 . It should be understood that sump  150  may instead have only one or two outlets with corresponding valving (not shown) to distribute the three flows. Liquid from sump outlet  210  follows path  216  through filter assembly  212  and exits  218  to circulation pump assembly  172 . 
         [0031]    During normal prewashing, circulation pump assembly  172  receives liquid directly from sump  150  via sump outlet  208  and pumps the liquid along one or more paths  220  to one or more spray assemblies  144  within wash chamber  106 . Spray assemblies  144  spray liquid onto the contents of wash chamber  106 , the liquid following various paths  222  back to sump. Particles from the items placed in the wash chamber  106  for washing collect in the liquid. 
         [0032]    However, during a filtering portion of the prewashing, circulation pump assembly  172  sends liquid received from filter assembly  212  along a recirculation path  224  back to sump  150 . Liquid leaves sump via second outlet  210  and passes through a filter membrane  226  in filter assembly  212  back to circulation pump assembly  172 . 
         [0033]    Dishwasher  100  can accordingly operate a first prewash cycle for a conventional duration, followed by a filtration cycle using the same prewash liquid. After filtration cycle, most particles will be removed from the liquid, and the same liquid can be used for a second prewash. Again, the second prewash cycle can be run for a conventional amount of time. Typically, some additional particles are generated during a second prewash, although the amount is generally reduced. Another, filtration cycle can then be run to again reduce the amount of particles in the liquid. If desired, a third prewash cycle can then be run, again using the same liquid. 
         [0034]    Once sufficient prewashing cycles have been completed, the liquid in sump  150  can be drained via third outlet  214  using drain pump assembly  174  which passes liquid  228  to filter assembly  212 . The liquid follows path  230  through filter assembly  212  and filter membrane  226 , passing out of the filter along path  232  out the external drain  173 . When this flushing cycle is performed, the particles previously trapped by filter membrane  226  are flushed out of external drain. However, only one flush cycle need be performed even though multiple prewash cycles have been performed, thereby conserving water as compared to conventional devices. 
         [0035]    Accordingly, two or more prewash cycles can be run using the same original supply of liquid. Since a prewash cycle may use up to a gallon or more of liquid per cycle, substantial savings on water usage can be achieved by reusing liquid during successive prewash cycles in this fashion. 
         [0036]      FIG. 4  shows a modified version of the cycles and structures shown in  FIG. 3 , in which alternating filtration and prewash spraying are not used. Instead, filter assembly is kept in-line at all items during prewash spraying by spray assemblies  144 . Bypass conduits  208  and  224  are thus not needed in  FIG. 4 . 
         [0037]    Instead, flow out of sump  150  during prewashing always goes through filter assembly  212  to circulation pump assembly  172  and then to spray assembly  144 . Due to the filtration prewashing may be performed longer than one conventional cycle, for example the duration of two or more cycles. Afterwards, drain pump assembly  174  can be used to flush filter assembly  212 , as above. The cycle of  FIG. 4  may be shorter in duration as filtration and prewash spraying are conducted at the same time. 
         [0038]    Either of the cycles described above can therefore provide prewashing in an amount equivalent to at least two conventional prewash cycles with a single filling of the wash compartment with liquid. The amount of prewashing can be measured not just by time of spraying but also by the amount of a particle content remaining in the liquid. If desired, in either cycle, a sensor of various types (not shown) can determine a characteristic of the prewash liquid (such as turbidity, etc.) to estimate the particle content of the liquid. Such sensor could be located for example between the sump  150  and the filter assembly  212 . Accordingly, active feedback can be provided during the prewash cycle to stop prewashing and filtration if low particle content is detected, thereby saving time and electricity. Also, it should be understood that controller  137  can manage all elements described above, including pumps, valves, sensors and any optional items or modified structures mentioned. 
         [0039]      FIGS. 5 and 6  show one example of a filter assembly  212  suitable for use with the present disclosure. As shown, assembly  212  includes two halves  234 , 236  joined at a central flange interface  238 . Filter membrane  216  may comprise a fine nylon and/or polyester weave, mesh, or non-woven material, or any other type of fine material. The membrane  216  may have openings in the range of about 50 to about 300 microns, and may for example in one embodiment have openings of about 150 microns. Opening sizes can be different across membrane  216  as well, whereby a maximum opening size is within the ranges above. 
         [0040]    Filter membrane  216  may be formed in a bag shape with a mounting ring  240  around the open top held in place by the flange interface area. Providing an elongated housing allows a correspondingly lengthy filter membrane  216  and larger filtration surface.  FIG. 5  shows filtration, where particles  242  and liquid enter inlet  244 , and the particles are substantially trapped by membrane  216 . Liquid flows out of outlet  246 .  FIG. 6  shows flushing, where liquid flows in inlet  248 , though membrane  216  and out outlet  250  taking along particles  242  collected previously. 
         [0041]    As shown, membrane  216  can be turned inside-out by the reverse flow during the flush to remove the particles. Using a movable bag-shaped membrane, as opposed to a relatively planar membrane, a rigid membrane or screen, for example, allows for better cleaning out of the particles during flush. 
         [0042]    Also, it should be noted that the volume of the bag-shaped membrane should be larger than the expected volume of the particles removed during the prewash. If not, the membrane could become clogged before the desired end of the prewash cycle. 
         [0043]      FIG. 7  shows a modified filter assembly  312  where membrane  316  includes multiple portions having different opening sizes. As shown, three portions  317 ,  319  and  321  are provided, each having a different maximum opening (pore) size. Accordingly, portion  317  at the distal end of membrane  316  may have a smaller opening size (such as about 100 microns), whereas portions  319  and  321  have successively larger opening sizes (about 200 and about 300 microns, respectively, in this example). Arranging the membrane with a smaller opening size toward the distal end where particles initially collect and a larger opening size toward the other end may allow for better flow through the membrane as particles accumulate. 
         [0044]      FIG. 8  shows another modified filter assembly  412  where membrane  416  includes multiple separate bag-shaped members. A shown, three such members are provided  417 ,  419 , and  421 . Member  417  is the largest and has the smallest opening size (for example 100 microns). Member  419  is smaller and has a larger opening size (for example 200 microns). Member  421  is the smallest and has the largest opening size (for example 300 microns). Using multiple sizes in separate bag-shaped members is another way to potentially avoid clogging. 
         [0045]    It should be understood that the two approaches above (different opening sizes on one bag and multiple bags with different opening sizes) can be combined as well. Also, it should be understood that three different opening sizes and/or bags are not required. Two, or more than three, could be employed if desired. Finally, it should be understood that the particle sizes given herein are not limiting and other sizes could be used depending on the application and other characteristics of the washing machine. 
         [0046]    It should be understood that various modifications are possible. For example, numerous variations as to the construction of the filter assembly, the arrangement of the liquid connections are possible. Also, the timing, operating, and sequencing of the prewash, filter and flush cycles could all be modified within the scope of the present invention. 
         [0047]    In view of the above, simple and reliable methods of operating a dishwasher, as well as filtering devices for dishwashers are provided. Suing the present disclosure, substantial water and electricity savings are possible. Such filtration device can be used not only within a dishwasher but also within other devices. 
         [0048]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.