Abstract:
A dishwashing appliance is provided that adjusts the pH during the cleaning process so as to allow for cleaning with both alkaline and acidic wash fluids. Alkali and acidic additives are used to improve the removal of substances that are pH sensitive. Such additives can be provided in predetermined amounts and/or a pH sensor can be used to regulate the amount of such additives that are utilized during the cleaning process.

Description:
FIELD OF THE INVENTION 
       [0001]    The subject matter of the present invention relates to the operation of a dishwashing appliance including pH modification of a wash fluid. 
       BACKGROUND OF THE INVENTION 
       [0002]    The cleaning process for a typical dishwashing appliance includes one or more washing, rinsing, and drying cycles. Conventionally, a wash fluid containing e.g., water and alkaline detergent is applied during a wash cycle. A rinse fluid containing e.g., water and possibly certain rinse or drying agents may be added during rinse and/or drying cycles. 
         [0003]    During these cycles in the cleaning process, particularly during the wash cycle, a variety of different substances may be present that can have an effect on the efficacy of the cleaning process. By way of example, food present on articles such as plates, cooking utensils, cups, etc. can comprise a variety of different materials such as sugars, starches, salts, proteins, and fats. Additionally, depending upon the water supply provided to the dishwashing appliance, various calcium compounds and/or other minerals may be present as well. 
         [0004]    Unfortunately, the solubility of these various substances in water can be affected by pH which, in turn, can have a substantial impact on the cleaning process. While sugars, some starches, and most salts may be soluble in water, proteins and fat emulsions can require a more alkaline wash fluid while certain minerals require a more acidic wash fluid before solubility or at least capture by the wash fluid can occur. As such, the efficacy of a wash fluid based solely on an alkaline detergent can be limited or even counterproductive. 
         [0005]    In addition, with continued pressure on natural resources, appliance manufacturers typically have a continued focus on efficiency in the design and operation of their products. For dish washing appliances, the amount of electricity, detergent, and/or water used during operation is carefully scrutinized for potential opportunities for improved conservation. Challenges are presented in attempting to reduce the amount of e.g., electricity, detergent, and/or water used during the cleaning process. By way of example, a reduction in any one of these parameters of may have a deleterious impact on the overall cleanliness of the articles present in the dishwasher. 
         [0006]    In view of problems that can include those identified above, a dishwashing appliance that can adjust pH during the cleaning process would be useful. More particularly, a dishwasher that can e.g., provide for adjustments to the pH of wash fluid(s) used during one or more cycles of the cleaning process would be beneficial. Such a dishwasher that can provide for such adjustments in a manner that can conserve one or more resources would also be useful. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    The present invention provides a dishwashing appliance that adjusts the pH during the cleaning process so as to provide for cleaning with both alkaline and acidic wash fluids. Alkali and acidic additives are used to improve the removal of substances that are pH sensitive. Such additives can be provided in predetermined amounts and/or a pH sensor can be used to regulate the amount of such additives that are utilized during the cleaning process. Additional 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. 
         [0008]    In one exemplary aspect, the present invention provides a method for operating a dishwasher appliance. The method includes the steps of providing fresh water W B  into a wash chamber of the dishwasher appliance; dispensing an alkaline material to increase the pH of water W B ; spraying water W B  onto one or more articles in the wash chamber; removing water W B  from the wash chamber; providing fresh water W A  into the wash chamber; dispensing an acidic material to decrease the pH of water W A ; spraying water W A  onto one or more articles in the wash chamber; and removing water W A  from the wash chamber. 
         [0009]    In another exemplary aspect, the present invention provides another method for operating a dishwasher appliance. This method includes the steps of providing a fresh water W P  into a wash chamber of the dishwasher appliance; spraying water W P  onto one or more articles in the wash chamber; and then measuring the turbidity of water W. If the turbidity of water W P  is below a certain predetermined value T L , then the method also includes the steps of providing fresh water W B  into a wash chamber of the dishwasher appliance; dispensing an alkaline material to increase the pH of water W B ; spraying water W B  onto one or more articles in the wash chamber; removing water W B  from the wash chamber; providing fresh water W A  into the wash chamber; dispensing an acidic material to decrease the pH of water W A ; spraying water W A  onto one or more articles in the wash chamber; and removing water W A  from the wash chamber. 
         [0010]    In another exemplary embodiment, the present invention provides a dishwasher appliance that includes a wash chamber and at least one spray assembly located in the wash chamber and configured for spraying fluids onto one or more articles located in the wash chamber. At least one processing device is configured for executing a basic wash cycle using a wash fluid having an alkaline pH value; executing an acid wash cycle using a wash fluid having an acidic pH value; and executing a rinse cycle using fresh water. 
         [0011]    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 
         [0012]    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: 
           [0013]      FIG. 1  provides a front view of an exemplary embodiment of a dishwashing appliance of the present invention. 
           [0014]      FIG. 2  illustrates a cross-sectional view of the exemplary embodiment of  FIG. 1 . 
           [0015]      FIGS. 3 ,  4 , and  5  illustrate exemplary methods of the present invention. 
       
    
    
       [0016]    The use of the same or similar reference numerals in the figures indicates same or similar features. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    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. 
         [0018]      FIGS. 1 and 2  depict an exemplary domestic dishwasher appliance  100  that may be configured in accordance with aspects of the present disclosure. For the particular embodiment of  FIG. 1 , the dishwasher  100  includes a cabinet  102  that extends between a front  114  and a back  116 . The cabinet  102  also extends between a top  110  and a bottom  112 . The cabinet  102  has a tub  104  therein that defines a wash chamber  106 . The tub  104  includes a front opening (not shown) and a door  120  hinged at its bottom  122  for movement between a normally closed, vertical position (shown in  FIGS. 1 and 2 ), 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. Latch  123  is used to lock and unlock door  120  for access to chamber  106 . Tub  104  also includes (e.g., defines) a sump  200  positioned adjacent bottom  112  of cabinet  102  and configured for receipt of dispensed fluids and additives (e.g., water, detergent (liquid or solid), washing fluid, rinse additives, drying additive, and/or any other suitable materials) during operation of appliance  100 . 
         [0019]    An inlet  160  is positioned adjacent sump  200  of appliance  100 . Inlet  160  is configured for directing liquid into sump  200 . Inlet  160  may receive liquid from, e.g., a fresh water supply (not shown) or any other suitable source. In alternative embodiments, inlet  160  may be positioned at any suitable location within appliance  100  such that inlet  160  directs liquid into tub  104 . Inlet  160  may include a valve (not shown) such that liquid may be selectively directed into tub  104 . Thus, for example, during the cycles described below, inlet  160  may selectively direct water and/or washing fluid into sump  200  as required by cycle of the appliance  100  and/or directed by one or more controllers or processing devices. 
         [0020]    Rack assemblies  130  and  132  are slidably mounted within the wash chamber  106 . Each of the rack assemblies  130 ,  132  is fabricated into lattice structures including a plurality of elongated members  134 . 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  FIGS. 1 and 2 ) in which the rack is located inside the wash chamber  106 . A silverware basket (not shown) may be removably attached to rack assembly  132  for placement of silverware, utensils, and the like, that are otherwise too small to be accommodated by the 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 rack assembly  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 head assembly  150  may be located above the upper rack  130 . 
         [0022]    The lower and mid-level spray-arm assemblies  144 ,  148  and the upper spray head assembly  150  are fed by a fluid circulation assembly  152  for circulating water and dishwasher fluid in the tub  104 . The fluid circulation assembly  152  may include a drain pump  154  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  144 ,  148  includes an arrangement of discharge ports or orifices for directing fluids (e.g., water, wash fluids, rinse fluids, etc.) onto articles such as e.g., dishes, cooking utensils, silverware, and/or other articles located in rack assemblies  130  and  132 . The arrangement of the discharge ports in spray-arm assemblies  144 ,  148  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 processing device or 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. By way of example, it should be understood that the processing device could include one or microprocessors and one or more memory devices. 
         [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  121  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]    As shown, a sensing device  161  is positioned in sump  200  of the appliance  100 . Sensing device  161  could be e.g., a pH sensor, turbidity sensor, or a combination thereof. In alternative embodiments, a pH sensor and/or turbidity sensor could be separately located and positioned at other locations within appliance  100 . Regardless, one or more sensors or sensing devices  161  are used, for this exemplary embodiment, to provide measurements of pH, turbidity, or both to processing device  137  during operation of appliance  100 . These measurements can be used by controller  137  as further described herein. 
         [0026]    It should be appreciated that the subject matter disclosed herein is not limited to any particular style, model, or other configuration of dishwasher, and that the embodiment depicted in  FIGS. 1 and 2  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. Other configurations may be used as well. 
         [0027]    Exemplary methods of the present invention will now be further described. For each exemplary method of the present invention, processing device  137  can be configured, for example, to operate appliance  100  according to the steps described. This may include receiving signals from other components of appliance  100  and providing instructions to one or more of the same as will be further described. 
         [0028]      FIG. 3  illustrates an exemplary method  300  of operation of dishwashing appliance such as e.g., appliance  100 . Step  305  includes providing fresh water W B  into a wash chamber of the dishwasher appliance. For example, processing device  137  may actuate a valve (not shown) connected to a fresh water supply in the user&#39;s home so as to fill sump  200  with a predetermined volume of water W B . As used herein, “fresh water” refers to water supplied from a source external to appliance  100  such as well or municipal water supply. After filling sump  200 , water W B  may be heated. For example, water W B  may be heated to a temperature of 130° F. or higher. Heating the water can e.g., provide thermal energy for cleaning and increase the solubility of alkaline materials added to water W B . 
         [0029]    Next, in step  310 , an alkaline material is dispensed into water W B  to increase the pH of water W B . The alkaline material can be provided, for example, from dispensing containers (not shown) that are located in or near appliance  100 . As used herein, “alkaline materials” refers to one or more substances in solid and/or liquid form that can be used to raise the pH of water W B . Examples include glycine and sodium hydroxide, borax and sodium hydroxide, carbonate-bicarbonate, and others may be used as well. The pH is raised so as to help provide a wash fluid comprised of water W B  and the alkaline material that will dissolve soils on articles placed in wash chamber  106  that are more soluble or only soluble in an alkaline wash fluid such as e.g., certain proteins and fats. By way of example, the pH may be raised to a level in the range of about 8 to about 12. Other ranges may be used as well. 
         [0030]    The addition of alkaline material may be accomplished by dispensing a predetermined amount of the alkaline material into water W B  located in sump  200 . For example, knowing the volume of water dispensed, the manufacturer could program processing device  137  to dispense a predetermined amount of the alkaline material. Alternatively, a pH sensor such as sensor  161  could be used in conjunction with sequential additions of alkaline material until the desired pH value is attained. For example, a predetermined amount of alkaline material could be added followed by operating appliance  100  in a wash cycle to spray water W B  onto articles in chamber  106  using spray assemblies  150 ,  148 , and  144 . Following this wash cycle, the pH could be checked using the pH sensor to determine if the desired pH level has been reached. If not, then alkaline material could be added to water W B  again and the process repeated until the desired pH level is obtained. Using the teachings disclosed herein, one of skill in the art will understand that other techniques may also be employed to attain the pH level desired. 
         [0031]    Once the alkaline material has been added, in step  315  water W B  is sprayed onto one or more articles (such as e.g., dishes, cooking utensils, and/or silverware) placed in the wash chamber  106  or racks  130  and/or  132 . For example, fluid circulation assembly  152  is operated and spray assemblies  144 ,  148 , and  150  are operated for a time sufficient to help dissolve and/or remove materials, particularly materials soluble in water W B  that is now alkaline due to the dispensing of the alkaline material therein. Following step  315 , water W B  now also contains soils from the articles including foods and other materials entrained in water W B  or dissolved therein. Water W B  is now removed or drained from the wash chamber  106  in step  320 . Together, steps  305 ,  310 ,  315 , and  320  (or variants thereof) can be referred to as a “basic” wash cycle in that a basic or alkaline fluid is used to wash articles in wash chamber  106 . 
         [0032]    In step  325 , fresh water W A  is provided into the wash chamber  106 . Again, such may be accomplished, for example, by using controller  137  to actuate one or more valves controlling a fresh water supply to appliance  100  so as to provide a predetermined volume of water into sump  200 . After filling sump  200 , water W A  may be heated. For example, water W A  may be heated to a temperature of 130° F. or higher. Heating the water can e.g., provide thermal energy for cleaning and increase the solubility of acidic materials added to water W A . 
         [0033]    Next, in step  330 , an acidic is dispensed into water W A  to decrease the pH of water W A . The acidic material can be provided, for example, from dispensing containers (not shown) that are located in or near appliance  100 . As used herein, “acidic materials” refers to one or more substances in solid and/or liquid form that can be used to lower the pH of water W A . Examples include citric acid, vinegar, and others may be used as well. The pH of water W A  is lowered so as to help provide a wash fluid comprised of water W A  and the acidic material that will dissolve material in water W A  and/or soils on articles placed in wash chamber  106  that are more soluble or only soluble in an acidic wash fluid such as e.g., certain limestones and mineral deposits. By way of example, the pH may be lowered to a level in the range of about 2 to about 5. Other ranges may be used as well. 
         [0034]    The addition of acidic material may be accomplished by dispensing a predetermined amount of the acidic material into water W B  located in sump  200 . For example, know the volume of water dispensed, the manufacturer could program processing device  137  to dispense a predetermined amount of the acidic material. Alternatively, a pH sensor such as sensor  161  could be used to pH measurements in conjunction with additional of acidic material until the desired pH value is attained. For example, a predetermined amount of acidic material could be added followed by operating appliance  100  in a wash cycle to spray water W A  onto articles in chamber  106  using spray assemblies  150 ,  148 , and  144 . Following this wash cycle, the pH could be checked using the pH sensor to determine if the desired pH level has been reached. If not, then acidic material could be added to water W A  again and the process repeated until the desired pH level is obtained. Using the teachings disclosed herein, one of skill in the art will understand the other techniques may also be employed to attain the pH level desired. 
         [0035]    Once the acidic material has been added, in step  335  water W A  is sprayed onto one or more articles (such as e.g., dishes, cooking utensils, and/or silverware) placed in the wash chamber  106  or racks  130  and/or  132 . For example, fluid circulation assembly  152  is operated and spray assemblies  144 ,  148 , and  150  are operated for a time sufficient to help dissolve and/or remove materials, particularly materials soluble in water W A  that is now acidic due to the dispensing of the acidic material therein. Following step  335 , water W A  now also contains soils from the articles including foods and other materials entrained in water W B  or dissolved therein. Water W A  is now removed or drained from the wash chamber  106  in step  320 . Together, steps  325 ,  330 ,  335 , and  340  (or variants thereof) can be referred to as an “acidic” wash cycle in that an acidic fluid is used to wash articles in wash chamber  106 . 
         [0036]    If desired, additional steps could be added to those shown in  FIG. 3  to provide still other exemplary methods of the present invention. For example, additional rinsing steps could be provided in which another volume of fresh water W R  is added to wash chamber  106 . Water W R  could then be sprayed onto articles in racks  130  and/or  132  for a time period sufficient to rinse such articles and remove soils or other residues remaining after the previously described wash steps. 
         [0037]    Another exemplary method  301  of the present invention is illustrated in  FIG. 4 . Method  301  includes part of the exemplary method  300  shown in  FIG. 3  except that an initial prewash cycle with turbidity measurement has been added. More particularly, in step  275  fresh water W P  is added into the wash chamber  106 . Next, in step  280  and for a predetermined period of time, water W P  is sprayed onto one or more articles in wash chamber  106  using e.g., spray assemblies  144 ,  148 , and  150 . Accordingly, step  280  provides a prewash that can be used to capture foods and other soils that may be water soluble or can be otherwise removed by water W. In step  285  the turbidity of water W P  is measured after or while spraying the articles for a predetermined period of time. This measurement may taken e.g., using a turbidity sensor for sensor  161  in sump  200  or in addition to sensor  161  at another location in sump  200 . 
         [0038]    In step  290 , the resulting turbidity measurement T M  is compared with a predetermined turbidity value T L . If turbidity measurement T M  is less than predetermined turbidity value T L , then steps  310  through  340  are executed as previously described with regard to  FIG. 3 . If, however, turbidity measurement T M  is greater than predetermined turbidity value T L , then an alternative cycle is executed as indicated in step  295 . By way of example, alternative cycle in step  295  might include draining water W P  from sump  106  and repeating steps  275  through  290  until turbidity measurement T M  is less than predetermined turbidity value T L . Such could be used as a prewash to e.g., remove heavy soils from the articles. In still another example, alternative cycle  295  might include a conventional wash cycle using an alkaline detergent. Other examples may be used as well. 
         [0039]      FIG. 5  illustrates still another exemplary method  302  of the present invention in which steps  305 ,  310 ,  315 ,  320 ,  325 ,  330 ,  335 , and  340  are executed in a same or similar manner to that described with regard to  FIG. 3  above. However, method  302  includes the use of a pH sensor (such as sensor  161  in sump  200  or another sensor in addition thereto) to provide for a determination of how much alkaline or acid material must be added to achieve the desired pH value for water in chamber  106 . 
         [0040]    More specifically, after providing fresh water W B  into wash chamber  106  in step  305  as previously described, the pH of water W B  is measured in step  306 . Knowing the quantity of water W B  added into chamber  106 , the amount of alkaline material needed to raise the pH to a desired level or range is determined in step  307 . In step  310 , this amount of alkaline material is added to water W B , which is followed by spraying the same onto articles in chamber  106  in step  315  as previously described. After spraying for a predetermined period of time, water W B  is drained from wash chamber  106  in step  320 . 
         [0041]    Next, in steps  325  and  326 , fresh water W A  is added to chamber  106  and its pH measured in a manner as previously described. Knowing the quantity of water W A  added into chamber  106 , the amount of acidic material needed to lower the pH to a desired level or range is determined in step  327 . In step  330 , this amount of acidic material is added to water W A , which is followed by spraying the same onto articles in chamber  106  in step  335  as previously described. After spraying for a predetermined period of time, water W A  is drained from wash chamber  106  in step  340 . 
         [0042]    Using the teachings disclosed herein, modifications of the steps described with exemplary method  302  can be used to provide still other exemplary methods of the present invention. After step  315 , for example, steps  307 ,  310 , and  315  could be repeated with successive additions of alkaline material until the desired pH level is achieved. Similarly, after step  335 , steps  327 ,  330 , and  335  could be repeated with successive additions of acidic material until the desired pH level is achieved. 
         [0043]    For the exemplary methods previously described, a wash cycle using an alkaline fluid is followed by a wash cycle using an acidic fluid. Using the teachings disclosed herein, however, it will be understood that the order could be reversed to provide still other exemplary methods of the present invention as well. 
         [0044]    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.