Patent Publication Number: US-8973591-B2

Title: Dishwasher with a motor driven filter backflush system and associated backflush method

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to dishwashers, and more particularly to a system for backflushing filters in the dishwasher. 
     BACKGROUND OF THE INVENTION 
     Conventional dishwashers include a main pump and fluid distribution system for circulating wash fluid within the wash chamber via spray arm assemblies or jets. A drain pump and associated drain system are used to drain the wash fluid from the chamber at the appropriate time in the wash cycle. The wash fluid sprayed onto the dishwasher items is collected in a sump located in a lower portion of the wash chamber, and water entering the sump is filtered through one or more pre-pump filters to remove soil and sediment from the washing fluid. In certain dishwashers, one of these filters may be a fine filter system in flow communication with the main pump assembly to remove soil and sediment of a smaller size than those filtered by an upstream coarse filter. The main pump assembly draws wash fluid from the sump to recirculate in the wash chamber, and the coarse and fine filters are used to continuously filter the water in the sump during the re-circulation process. 
     It is an inherent tendency of the filters to accumulate relatively large amounts of foreign matter over time, particularly at the point at which the water path through the fluid distribution system is of least resistance. This location generally corresponds to the section of the filter directly in line with main pump. Removal of this matter is necessary to ensure proper flow of the wash fluid through the system. Certain prior art systems rely on flushing of the filters with wash fluid that is redirected from the spray arm assemblies or dedicated jets. These systems are relatively complicated and have other inherent drawbacks. 
     Accordingly, other system designs for flushing filters in a dishwasher in a cost-effective and relatively simple manner would be welcome. 
     BRIEF DESCRIPTION OF THE INVENTION 
     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. 
     According to certain aspects of the present disclosure, a dishwasher includes a wash chamber and a sump disposed below the wash chamber, wherein wash fluid supplied to the wash chamber collects in the sump. A main pump is configured to drawn wash fluid from the sump and recirculate the wash fluid back into the wash chamber, for example through one or more spray arm assemblies. One or more filters are operably disposed in the fluid distribution system to filter the wash fluid recirculated by the main pump. A backflush line is provided and has an outlet disposed at the downstream side of the filter. A backflush pump is configured to supply backflush fluid through the backflush line against the filter. A reservoir that is separate from the sump and sized to hold a measured amount of fluid is in communication with the backflush pump, wherein at a defined time, the pump draws backflush fluid from the reservoir and directs the fluid against the backside of the filter to flush particulates from the filter. 
     In a particular embodiment, the reservoir is filled with fresh water from a main fill line that is used to initially supply wash fluid to the wash chamber in a fill mode of the wash cycle. This may be accomplished in various ways. For example, in one embodiment, a main water valve in the main fill line is actuated to supply the initial wash fluid in the fill mode. The reservoir may be supplied with fresh water by a supply line that is in communication with the main fill line downstream of the main water valve such that the reservoir is supplied with water during each fill mode. In an alternate embodiment, the supply line may be in communication with the main fill line upstream of the main water valve, wherein an independently actuated isolation valve may be disposed in the supply line. With this embodiment, the reservoir can be filled independently of filling the wash chamber by actuation of the isolation valve for a defined time. 
     Particular embodiments may include a level sensor configured with the reservoir, wherein the reservoir is refilled upon the sensor reading a low water level condition. The sensor may be in communication with the isolation valve discussed above, wherein the isolation valve is automatically actuated to supply fresh water to the reservoir in response to a water level signal from the sensor. 
     In still a further embodiment, a main fill line supplies the initial wash fluid for the wash chamber by first filling the reservoir, which has an overflow outlet in fluid communication with the wash chamber. Thus, the wash chamber is filled with overflow after the reservoir has been filled, with the overflow outlet provided at a height in the reservoir to ensure a desired amount of fresh water in the reservoir for one or more flush sequences. 
     It is not necessary that the reservoir be filled with fresh water in all embodiments. For example, in a particular embodiment, the reservoir may include a receiving end that is in fluid communication with the wash chamber, wherein the reservoir is filled with wash fluid recirculated within the wash chamber by the main pump. With this embodiment, the receiving end of the reservoir may include a receiver structure configured in a wall (e.g. back wall, side wall, or front door panel) of the wash chamber at a location and orientation to “catch” wash fluid supplied into the wash chamber, for example by one or more of the spray arm assemblies. 
     In certain embodiments, the filter may be disposed upstream of the main pump (e.g., a pre-pump filter) such that particulates backflushed from the filter are directed to the sump during a backflush sequence of the wash cycle. In another embodiment, the filter may be disposed downstream of the main pump such that particulates backflushed from the filter are directed back through the main pump to a drain line or header during the backflush sequence. The dishwasher may include multiple filters, with each respective filter having a backflush line configured therewith. 
     In particular embodiments, the backflush pump may be a dedicated pump used strictly for filter flushing operations. In other embodiments, one of the other existing pumps, such as a drain pump or main circulation pump, may be configured with the appropriate lines and valves to also function as the backflush pump during the filter flushing sequence. 
     The present invention also encompasses various method embodiments for backflushing a filter in a dishwasher in accordance with various aspects discussed above. 
     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 
       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: 
         FIG. 1  provides a side partial cut-away view of an exemplary dishwasher that may be configured in accordance with aspects of the invention; 
         FIG. 2  is a schematic view of an embodiment of a dishwasher incorporating a filter backflush system in accordance with aspects of the invention; 
         FIG. 3  is a schematic view of a different embodiment of a dishwasher incorporating a filter backflush system; 
         FIG. 4  is a schematic view of still another embodiment of a dishwasher incorporating a filter backflush system; and 
         FIG. 5  is a schematic view of yet another embodiment of a dishwasher incorporating a filter backflush system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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. 
       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 . 
     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  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 . 
     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 a 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. 
     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 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 . 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. 
     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. 
       FIG. 2  illustrates an embodiment of a dishwasher  100  incorporating a filter backflush capability. The dishwasher  100  includes a fluid circulation assembly  170  configured below the wash chamber  106 . Although one embodiment of a fluid circulation assembly  170  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  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. 
     As wash liquid is pumped through the lower spray arm assembly  144 , and further delivered to the mid-level spray arm assembly  148  ( FIG. 1 ) and the upper spray arm assembly  145  ( FIG. 5 ), washing sprays are generated in the wash chamber  106 , and wash liquid collects in the sump  150 . The sump  150  may include a perforated plate  153  through which wash fluid drains, as well as cover  151  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 . 
     In one embodiment, 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 line  188 . The drain pump assembly  174  may include an electric motor for pumping fluid from the inlet line  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 line  188  and the drain valve  186  is opened, allowing fluid in the sump  150  to flow into the inlet line  188  and be discharged from the fluid circulation assembly  170  via the external drain  173 . 
     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, the water supply  200  includes a hot water inlet  204  and cold water inlet  206  to a main fill valve  208 . Upon actuation of the valve  208 , initial fill water is discharged through the valve  208  and a main fill line  202  into the wash chamber  106  via inlet  175 . 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. 
     Embodiments of a dishwasher  100  in accordance with aspects of the invention include one or more filters in the fluid circulation assembly  170 . The invention is not limited to any particular number of filters, type of filter, and so forth. In the embodiment depicted in  FIG. 2 , a coarse filter  210  is disposed in the sump  150  and serves to filter relatively large particulate matter from the wash fluid that drains into the sump  150 . An additional “finer” filter  212  is disposed in the sump  150  below the coarse filter  210  and serves to filter out smaller particulate matter that passes through the coarse filter  210 . The filters  210 ,  212  depicted in  FIG. 2  are pre-pump filters in that they are disposed on the suction side of the main circulation pump  172  and serve to filter the re-circulated wash fluid before it is discharged by the pump  172 . The invention is not, however, limited to pre-pump filters. For example, in the embodiment depicted in  FIG. 3 , a coarse filter  210  is located upstream (pre-pump) of the pump  172  and a finer filter  212  is disposed on the downstream side of the pump  172  and functions to filter out finer particular matter that is discharged by the pump  172  prior to the wash fluid being distributed to the spray arm assemblies  144 ,  145 ,  148  or other wash fluid distribution devices within the wash chamber  106 . 
     It should be appreciated that the invention is not limited to any particular type of filter  210 ,  212  within the fluid circulation system  170 . Conventional filters are well known in this regard, and any one or combination of such filters may be utilized with the present invention. For example, the filters  210 ,  212  may be removable filters that are seated within the lines or piping of the circulation assembly  170 . The filters may have a conical shape, or a flat plate-like shape, and so forth. 
     Referring again to  FIG. 2 , a backflush line  216  is provided in the fluid circulation assembly  170  and includes an outlet  218  that is disposed “downstream” of the respective filter  210 ,  212 . The outlet  218  is on the downstream side of the filter with reference to fluid flow through the filter during the wash cycle wherein the pump  172  draws the wash fluid from the sump  150  through the filters  210 ,  212 . The backflush line  216  may be any configuration of suitable conduit, including flexible hoses, pipes, and so forth. The outlet  218  may be variously configured. For example, the outlet  218  may be a nozzle that is configured to direct a relatively high-pressure spray against the downstream side of the respective filter  210 ,  212 , as depicted in FIG.  2 . The outlet  218  may, in this regard, include any manner of discharge port, orifice, and the like. 
     A backflush pump  234  is configured with the backflush line  216  and supplies backflush fluid through the line  216  against the filters. In the depicted embodiment, the backflush pump  234  is a separate dedicated pump for this purpose. It should be appreciated, however, that the invention is not limited to a dedicated pump  234 . For example, either of the other pumps  172 ,  174  may be operably configured to also function as a backflush pump with appropriate connections, isolation valves, and so forth. 
     A reservoir  220  that is separate from the sump  150  is configured with the backflush pump to provide a supply of backflush fluid to the pump. The reservoir  220  may have any suitable configuration and be located at any convenient location within the dishwasher  100 . For example, the reservoir  220  in the embodiment of  FIG. 2  may have a standpipe configuration with a sufficient volume to provide a measured amount of backflush fluid to the pump  234  in one or more filter flushing sequences. The reservoir  220  may be located alongside the conduit  154  that supplies the upper and mid-level spray arm assemblies  145 ,  148 . In an alternative embodiment, the reservoir  220  may have a tank-like configuration and be located, for example, within a corner of the cabinet structure  102  ( FIG. 1 ). In still further embodiments, the reservoir  220  may have a panel-configuration and be disposed along one of the sides of the cabinet  102 . It should be appreciated that the reservoir  220  may be variously configured within the scope and spirit of the invention. 
     In certain embodiments, the reservoir  220  is filled with fresh water that has not been previously recycled in the wash chamber  106 . This fresh water may be supplied with the initial filling of the wash chamber  106 . For instance, as depicted in  FIG. 2 , the reservoir  220  may be supplied via a supply line  226  that is in fluid communication with the main water supply  200 , for example by connection with the main fill line  202 . The supply line  226  may be downstream of the main fill valve  208  such that the reservoir  220  is filled upon actuation of the valve  208  to supply the initial wash fluid into the chamber  106  via the outlet  175 . Although not depicted in  FIG. 2 , a separate isolation valve may be provided in the supply line  226  in order to limit the amount of water delivered into the reservoir  220  during the fill mode of the wash cycle. 
     In the embodiment of  FIG. 2 , the supply line  226  that fills the reservoir  220  with fresh water is in communication with the water supply  200  upstream of the valve  208 . An isolation valve  228  is separately provided in the supply line  226  such that actuation of the valve  228  results in water being directed into the reservoir  220 . The isolation valve  228  is in communication with the controller  137  and can be actuated independently of the main fill valve  208 . Thus, in this embodiment, the reservoir  220  can be re-filled at any time, and is not dependent on actuation of the main fill valve  208  for a wash cycle. 
     In the embodiment of  FIG. 3 , any manner of suitable liquid level sensor  230  may be provided with the reservoir  220  to sense a low level condition within the reservoir. The sensor  230  may also be in communication with the controller  137 , which issues a command to the isolation valve  228  to open and thus allow filling of the reservoir  220  upon indication of a low level within the reservoir  220 . 
     In the embodiment depicted in  FIG. 4 , the main fill valve  208  directs water into the reservoir  220  via the main fill line  202 . This is different than the embodiments of  FIGS. 2 and 3  wherein the main fill line  202  empties directly into the wash chamber  106  via the outlet  175 . The reservoir  220  includes an overflow outlet  232  that opens directly into the wash chamber  106 . Once the water level within the reservoir  220  reaches the outlet  232 , continued filling of the reservoir results in overflow of the water into the wash chamber  106 . This operation continues until the desired amount of initial wash fluid is supplied to the wash chamber  106 . Thus, the reservoir  220  is initially filled with a predetermined amount of water, at which point the overflow continues in order to supply the wash chamber  106 . 
       FIG. 5  depicts yet another embodiment wherein the reservoir  220  is filled with re-circulated wash fluid from the chamber  106 . The reservoir  220  has a receiving end  222  that is open to the wash chamber  106  such that water re-circulated within the chamber  106 , for example via one of the spray arm assemblies, is also directed into the reservoir  220 . In this regard, any manner of suitable receiving structure  224  may be configured at the receiving end  222  in order to “catch” the water sprayed from the spray arm assembly  145 . Thus, it should be appreciated that in this particular embodiment, the reservoir  220  is not filled with “fresh water”, but with re-circulated wash fluid. The receiving end  222  may be configured in any wall of the wash chamber  106  depending on the location of the reservoir  220 , including the back wall, side walls, or in the front door panel. 
     As mentioned, the invention is not limited by the location of the filters  210 ,  212 . In the embodiment of  FIGS. 2 and 4 , the filters are upstream with respect to the main circulation pump  172 . Thus, backflushing of the filters via the backflush line  216  results in the particulates on the filter being directed back into the sump  150 . In the embodiment of  FIG. 3 , the filter  212  is downstream of the main circulation pump  172  and, thus, backflushing of the filter will result in particulate matter being directed back through pump to the drain pump header  188 . 
     The present invention also encompasses various method embodiments for backflushing a filter or filters in a dishwasher in accordance with aspects discussed above. For example, one embodiment of such a method includes collecting backflush fluid in a reservoir  220  that is separate from a sump  150  in a dishwasher  100 . During a backflush sequence, fluid is drawn from the reservoir  220  with a pump and directed against a downstream side of the filter  210 ,  212 . The pump may be a dedicated backflush pump  234 . 
     The method may include filling the reservoir  220  with fresh water that has not been re-circulated as wash fluid within the wash chamber  106 . In another embodiment, the method includes filling the reservoir with wash fluid that has been re-circulated in the wash chamber  106 . 
     The method may also include sensing the level of backflush fluid within the reservoir  220  and re-filling reservoir upon the level reaching a low set point. 
     In still another embodiment, the method may include initially filling the reservoir  220  in a fill mode with fresh water until the reservoir is filled to an overflow outlet that is in communication with a wash chamber, wherein continued filling of the reservoir results in overflow of fresh water into the wash chamber from the reservoir. 
     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.