Dishwasher with microfilter

Abstract

A dishwasher and a method of treating utensils in the dishwasher wherein the dishwasher has a tub at least partially defining a treating chamber, a liquid spray system, a liquid recirculation system fluidly coupling the treating chamber to the spray system to recirculate wash liquid from the treating chamber to the spray system, and filters capable of removing particles from the wash liquid.

What is claimed is: 
     
         1 . A method of treating utensils in a dishwasher having a treating chamber for receiving utensils, a spray system for spraying wash liquid in the treating chamber, and a recirculating system for recirculating sprayed liquid from the treating chamber to the spray system to treat the utensils according to a cycle of operation, the method comprising:
 spraying wash liquid from the spray system into the treating chamber;   recirculating the sprayed wash liquid from the treating chamber back to the spray system for subsequent spraying;   filtering the wash liquid to remove particles greater than 150 microns, as the wash liquid is recirculated, to form a filtered wash liquid;   after the spraying of wash liquid, spraying a rinse liquid into the treating chamber;   recirculating the sprayed rinse liquid from the treating chamber back to the spray system for subsequent spraying; and   filtering only a portion of the rinse liquid to remove particles larger than 40 microns, as the rinse liquid is recirculated.   
     
     
         2 . The method of  claim 1  wherein the filtering only a portion of the rinse liquid comprises microfiltering the rinse liquid to remove particles larger than 150 microns to form a microfiltered rinse liquid. 
     
     
         3 . The method of  claim 1  wherein the filtering only a portion of the rinse liquid comprises ultrafiltering the rinse liquid to remove particles larger than 40 microns to form an ultrafiltered rinse liquid. 
     
     
         4 . The method of  claim 1  wherein the portion of the rinse liquid that is filtered is 30% or less of the total volume of the rinse liquid. 
     
     
         5 . The method of  claim 2  wherein the portion of the rinse liquid that is microfiltered is 30% or less of the total volume of the rinse liquid. 
     
     
         6 . The method of  claim 1  wherein all of the sprayed wash liquid is recirculated. 
     
     
         7 . The method of  claim 6  wherein all of the recirculated wash liquid is filtered. 
     
     
         8 . The method of  claim 1  wherein the filtering the wash liquid comprises filtering the wash liquid to remove particles greater than 1 millimeter to form a filtered wash liquid. 
     
     
         9 . The method of  claim 1  wherein the only a portion of the rinse liquid is fluidly separated from the recirculated rinse liquid prior to filtering. 
     
     
         10 . The method of  claim 9  wherein the only a portion of the rinse liquid is fluidly combined with the recirculated rinse liquid after filtering. 
     
     
         11 . The method of  claim 2  wherein the only a portion of the rinse liquid is fluidly separated from the recirculated rinse liquid prior to microfiltering. 
     
     
         12 . The method of  claim 11  wherein the only a portion of the rinse liquid is fluidly combined with the recirculated rinse liquid after microfiltering. 
     
     
         13 . An automatic dishwasher for treating utensils according to a cycle of operation, comprising:
 a tub at least partially defining a treating chamber for receiving utensils for treatment;   a spray system comprising at least one sprayer for spraying wash and rinse liquid in the treating chamber;   a recirculation system fluidly coupling the treating chamber to the spray system to recirculate wash and rinse liquid from the treating chamber to the spray system;   a first filter fluidly coupled to at least one of the recirculation system and the spray system to filter the wash and rinse liquid recirculated from the treating chamber to the spray system; and   a second filter fluidly coupled to the first filter to remove particles larger than 40 microns from only a portion of the rinse liquid after it is filtered by the first filter;   wherein the second filter only filters rinse liquid during a rinse phase of the cycle of operation, and wherein only a portion of the rinse liquid that has been filtered by the first filter is filtered by the second filter.   
     
     
         14 . The automatic dishwasher of  claim 13  wherein the second filter is a microfilter fluidly coupled to the first filter to remove particles larger than 150 microns from only a portion of the rinse liquid after it is filtered by the first filter. 
     
     
         15 . The automatic dishwasher of  claim 13  wherein the only a portion of the rinse liquid that is filtered by the second filter is 30% or less of the total volume of the rinse liquid filtered by the first filter. 
     
     
         16 . The automatic dishwasher of  claim 14  wherein the only a portion of the rinse liquid that is microfiltered is 30% or less of the total volume of the rinse liquid filtered by the first filter. 
     
     
         17 . The automatic dishwasher of  claim 13  wherein the first filter is fluidly coupled to the recirculation system such that all of the recirculated rinse liquid passes through the first filter. 
     
     
         18 . The automatic dishwasher of  claim 17  wherein the second filter is fluidly coupled to the first filter such that only a portion of the rinse liquid filtered by the first filter passes through the second filter. 
     
     
         19 . The automatic dishwasher of  claim 13  wherein the only a portion of the rinse liquid that has been filtered by the first filter is fluidly separated from the recirculated rinse liquid prior to filtering by the second filter. 
     
     
         20 . The automatic dishwasher of  claim 19  wherein the only a portion of the rinse liquid that has been filtered by the first filter is fluidly combined with the recirculated rinse liquid after filtering by the second filter.