Abstract:
A method of washing dishes in a dishwasher that includes a Start Stop sequence in a wash segment of one or more of the dishwashing cycles. The Stop Start sequence includes the steps of pausing the operation of the wash pump, operating the wash pump to circulate wash water in the dishwasher for a short period of time, and repeating the steps of pausing and operating the wash pump for a short period of time a predetermined number of times. The Stop Start sequence is preceded by, and may be followed by, a period of continuous operation of the wash pump.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is directed to a wash cycle for a dishwasher. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]    [0003]FIG. 1 is a perspective view of a dishwasher for carrying out the invention.  
         [0004]    [0004]FIG. 2 is a schematic, cross-sectional view of the dishwasher of FIG. 1, showing the dishracks mounted within the tub and the spray arm feed system.  
         [0005]    [0005]FIG. 3 is a simplified block diagram of a dishwasher control system employed for carrying out the invention.  
         [0006]    [0006]FIG. 4 is a sectional view of the pump assembly used in conjunction with the invention, illustrating fluid flow through the wash pump to the spray arms and to the soil separator.  
         [0007]    [0007]FIG. 5 is a schematic illustration of the pump and soil separation and collection system of the pump assembly used in conjunction with the invention and illustrating fluid flow to drain.  
         [0008]    [0008]FIG. 6 is a flow chart of the operation of a dishwasher in a normal cycle according to one embodiment of the invention.  
         [0009]    [0009]FIG. 7 is a flow chart of the operation of a dishwasher during the main wash segment of the normal cycle illustrated in FIG. 6.  
         [0010]    [0010]FIG. 8 is a flow chart of the operation of a dishwasher in a normal cycle-light soil cycle according to another embodiment of the invention.  
         [0011]    [0011]FIG. 9 is a flow chart of the operation of a dishwasher during the main wash segment of the normal cycle-light soil illustrated in FIG. 8. 
     
    
     DETAILED DESCRIPTION  
       [0012]    In accordance with the invention as shown in the drawings, and particularly as shown in FIGS. 1 and 2, an automatic dishwasher generally designated  10  includes an interior tub  12  forming an interior wash chamber or dishwashing space  14 . The tub  12  includes a sloped bottom wall  16  that defines a lower tub region or sump  18  of the tub. A pump assembly  20  is located in the bottom wall  16  and operates to draw wash liquid from the sump and pump it to a lower spray arm assembly  22 , a mid-level spray arm assembly  24  and an upper spray arm assembly  34 . The lower spray arm  22  is positioned beneath lower dishware rack  26  and the mid-level spray arm assembly  24  is associated or positioned below a dishware rack or basket  28 .  
         [0013]    The lower spray arm assembly  22  may be mounted to the upper portion of the pump assembly  20  and receive wash liquid from the pump. Since the mid level spray arm assembly  24  and upper spray assembly  34  are remote from the pump, means must be provided to supply wash liquid remotely to these upper spray devices  24  and  34 . To that end, a supply tube  30  extends generally rearwardly from the pump assembly  20  to the rear wall of the tub and then runs upwardly to supply wash liquid to upper spray devices  24  and  34 . The spray arm feed system construction and operation is explained in U.S. Pat. No. 6,431,188 to Laszczewski et al, entitled “DISHWASHER SPRAY ARM FEED SYSTEM”, herein incorporated by reference. In that patent, the spray arm feed system is fully explained.  
         [0014]    As shown in FIG. 3, the operation of the wash pump motor  21  within the dishwasher, together with other components such as a heater  33 , inlet valve  31 , and a drain pump motor  32  to carry out a number of different preprogrammed automatic cycles are operated by a control device that, in this embodiment, comprises a microcomputer control  40 . The microcomputer control  40  can be located in the control console of the door, or elsewhere in the dishwasher. The microcomputer control  40  receives as inputs user selections entered manually by the user at selectors  41  that can be mounted on the console  42 . The information obtained by the microcomputer control  40  from the console  42  is typically in the form of digital signals developed as a function of the status of the switches involved. The microprocessor control  40  may receive signals from sensors or other components of the dishwasher as is well known to those skilled in the art. The particular cycle and option selected by the user as well as other data are displayed to the user by a display unit  43  that may comprise a light emitting diode (LED) display controlled by digital signals supplied to it by the microcomputer control  40 .  
         [0015]    The wash pump motor  21  and other electrically operated components of the dishwasher are all controlled by the microcomputer control  40  through a power controller  45  that may comprise a set of electromechanical relays or other power controlling devices such as silicon controlled rectifiers (SCRs) or Triacs. Power controller  45  may be located in the console  42 , but can be located elsewhere in the dishwasher as is well known to those skilled in the art.  
         [0016]    The microcomputer control  40  may be of any conventional type, and can be formed on an integrated circuit. The dishwasher cycles are programmed in a memory  44  addressable by the microcomputer control  40 .  
         [0017]    Referring to FIG. 4 and FIG. 5 it can be understood that the pump assembly  20  includes a wash pump chamber  232 , the pump inlet  236 , the main outlet  238  and the secondary outlet  240  that can be formed in part by a member  225  which forms part of the tub bottom  16 . While this structure is shown as a particular embodiment of the invention, it is clearly just one example of how the present invention may be practiced.  
         [0018]    Wash liquid drawn into the pump inlet  236  passes through a chopper assembly  250 . The chopper assembly includes a sizing plate  252  and a chopper blade  254 . The chopper blade  254  rotates adjacent the sizing plate  252  and chops food particles entrained within the wash liquid to size sufficient to allow the food particles to pass through the sizing plate. After being chopped and sized by the chopper assembly  250 , the soils are drawn, along with the wash liquid, into the pump chamber  232 .  
         [0019]    Within the pump chamber  232 , the soils are partially separated and concentrated by the operation of a filter plate  260  located within the pump chamber  232 . The filter plate  260  is a flat filter with an inner diameter (I.D.) greater than the outer diameter (O.D.) of the wash impeller  230  and which is located about the wash impeller  230  perpendicular to the axis of rotation of the wash impeller  230 . The filter plate  260  separates the pump chamber into first region or side  262  and a second region or side  264 . During the dishwasher operation, wash liquid is drawn through the pump inlet  236 , into the eye of the wash impeller  230   a , and is moved outwardly from the center of the impeller  230  by the impeller vanes  230   b.    
         [0020]    Wash liquid coming off of the impeller  230  is divided into two portions by the filter plate  260  such that a first portion passes from the impeller into the first region  262  of the pump chamber  232  and a second portion passes from the impeller into the second region  264  of the pump chamber  232 . The main outlet  238  provides an outlet for the first region  262  of the pump chamber  232 . The secondary outlet  240  provides an outlet for secondary region  264  of the pump chamber  232 . The secondary outlet  240  is sized relatively small such that when the wash impeller  230  is pumping wash liquid, the pressure in second region  264  of the pump chamber  232  is greater than the pressure in the first region  262  of the pump chamber  232 . The pressure difference across the filter plate  260  is caused by the fact that the ratio of the first portion of wash liquid pumped from the impeller  230  into the first region  262  to the second portion of wash liquid pumped from the impeller  230  into the second region  264  is greater than the ratio of the size of the main outlet  238  to the size of the secondary outlet  240 .  
         [0021]    It can be understood, therefore, that a portion of the wash liquid coming off the wash impeller  230  into the second region  264  of the pump chamber  232  passes through the secondary outlet  240  and the remainder passes through the filter plate  260  traveling from the second region  264  of the pump chamber  232  into the first region  262  of the pump chamber  232 . This flow through the filter plate  260  from the second region  264  to the first region  262  results in the filtering of soils and a concentrating of soil in the second region  264  such that the wash liquid sent through the secondary outlet  240  has a concentration of soils greater than the concentration of soils in the wash liquid being drawn into the eye of the pump impeller, at least for a first portion of the wash cycle.  
         [0022]    Wash liquid and entrained soils flow, therefore, through the secondary outlet  240  into the soil collector  270 . As shown in FIG. 4, the soil collector includes a main body  272  and a top panel  274 . The main body  272  is a generally circular, cup-like member which is secured to the bottom wall  16  of the wash tub  12 . The main body  272  includes an outer flange that forms a coarse grate through which wash liquid flows on its path toward the pump inlet  236 . The main body  272  has a center opening or conduit  275  that receives fluid flow from the main outlet  238  of the pump chamber  232 . A bearing hub  277  may be partially positioned in the center conduit  275  for directing wash liquid to the spray arm assembly  22 . The main body further includes an inlet  276  for receiving wash liquid from the secondary outlet  240 .  
         [0023]    The main body  272  further includes a downwardly projected portion  286  that defines a soil accumulation region or sump  288  for the soil collector  270 . As the soil laden wash liquid proceeds within the separation channel  280 , water passes upwardly through the filter screen panel  284  leaving the soils within the separation channel  280 . Within the soil separation channel  280 , soils are directed to generally accumulate in the soil accumulation region or sump  288 .  
         [0024]    As shown in FIG. 5, a drain pump  294 , separate from the wash pump  228 , is provided for draining wash liquid from the dishwasher tub  12 . The drain pump  294  includes a drain motor  32  drivingly connected to a drain impeller  297  located within a housing. Located at the bottom of the downwardly projected portion  286  is an outlet opening  290  that is fluidly connected with an inlet area  292  for the drain pump  294 . An opening  296  is also provided into the inlet area  292  from the sump  18 . A flapper type check valve  298  is provided at the opening  296  for selectively controlling the flow of liquid from the sump  18  into the inlet area  292  of the drain pump  294  based on the pressure difference across the valve  298 . Preferably, when the wash pump  228  is operating, pumping fluid into the soil collector  270  and pressurizing the inlet area  292 , the pressure in the inlet area  292  will be greater than the sump  18  such that the valve  298  will be closed. When the wash pump  228  is not pressurizing the inlet area  292 , the flapper may open to allow wash liquid to flow from the sump  18  into the inlet area  292 . The pump assembly  20  construction and operation is explained in U.S. Pat. No. 6,418,943, to Miller, entitled “WASH LIQUID CIRCULATION SYSTEM FOR A DISHWASHER”, herein incorporated by reference. In that patent, the operation of the wash liquid recirculation system, the constructional features and operation of the pump assembly and soil collector as well as the drain mode of the pump assembly are explained.  
         [0025]    The pump assembly  20  and microcomputer control  40  can be arranged to provide an automatic purge system. The automatic purge system is explained in U.S. Pat. No. 6,182,674, to Jozwiak et al, entitled “PUMP AND SOIL COLLECTION SYSTEM FOR A DISHWASHER”, herein incorporated by reference. The operation of the automatic purge filtration system (apf) can operate in conjunction with the drain pump  294  of the pump assembly  20  under the control of the microprocessor control  40 . As explained in the &#39;674 patent the apf includes a pressure switch, not shown, for sensing the pressure within the soil collector. When the pressure within the soil collector exceeds a predetermined limit level, the drain pump  294  is energized by the microcomputer control  40  through the power controller  45  such that soils are cleared or purged from the soil collector. This operation may be repeated as many times as needed during a step in a cycle when the apf mode is enabled by the microprocessor control  40 .  
         [0026]    Referring to the embodiment of FIG. 6 and FIG. 7, the dishwasher program according to the invention operates the dishwasher in the following manner. Referring to FIG. 6, a normal wash cycle can include Pre-Wash  50 , Main Wash  51 , Rinse  52 , Final Rinse  53  and Dry  54  segments. Each of the segments can include one or more steps such as Fill, Pause, Pump, Drain, Heat, and others. As is well known to those skilled in the art a normal wash cycle can include an additional segment or segments such as an additional rinse segment. For example, an additional rinse could be added after Rinse  52  at the user&#39;s option, or preprogrammed in the microcomputer control. The normal wash cycle, as well as other preprogrammed cycles, can be programmed in the microcomputer control  40 . As is well known to those skilled in the art the microcomputer control  40  causes the power control  45  to energize the pump motor  21 , heater  33 , valve  31  and/or drain pump motor  32  and other components such as dispensers to cause the dishwasher to perform the steps required to deliver the preprogrammed cycle. In a Fill step the microcomputer causes the fill valve  31  to be energized allowing water to flow into the dishwasher. In a Pause step all the operating components, pump motors, heater and the like are de-energized. In a Pump step the wash pump motor  21  is energized causing the wash pump  228  to circulate wash water through the dishwasher. In a step including Heat, the heater element  33  is energized to heat wash water in the sump  18 . In a Drain step the drain pump motor  32  is energized causing drain pump  294  to pump wash water to drain. In a Pump &amp; Heat &amp; Detergent step the wash pump motor  21  and heater element  33  are energized to heat and circulate wash water in the dishwasher and detergent is dispensed into the dishwasher. In a Pump &amp; Heat-Thermal Hold step the wash pump motor  21  and heater  33  are energized to circulate heated wash water in the dishwasher until a predetermined temperature is detected by a thermal sensor, not shown, sensing the temperature of the wash water. A Pump &amp; Heat-Thermal Hold step can be arranged to be of indefinite duration determined by detection of a predetermined temperature, or may have a limit to the duration determined by the microcomputer control  40  as is well known to those skilled in the art.  
         [0027]    A Stop Start Wash sequence according to the invention in this embodiment occurs in the Main Wash segment  51 . Referring to FIG. 7, Main Wash segment  51  includes Fill  60 , Pause  61 , Pump &amp; Heat &amp; Detergent  62 , Pump &amp; Heat-Thermal Hold  63 , Pause  64 , Pump  65 , Pump  66 , Drain and Pump  67  and Drain  68  steps as described above. In this embodiment Pump &amp; Heat-Thermal Hold segment  63  includes activation of the apf mode. The Pause  64  and Pump  65  steps are repeated a number of times to provide the Stop Start Wash sequence in Main Wash segment  51 .  
         [0028]    The duration of Pause step  64  is sufficient for the wash pump  228  to stop and allow wash water being circulated in supply tube  30  to drain back into the pump assembly  20 . As wash water in supply tube  30  drains back into the pump assembly  20  soil particles collected on the food chopper sizing plate  252  and filter plate  260  in the pump chamber  232  are flushed off the respective plates. When Pump step  65  begins following Pause step  64  the resumption of wash water flow through the pump assembly  20  provides a new opportunity for food particles to be washed into the soil collector  270 . The Pause step  64  can be 15 seconds long. The duration of Pause step  64  can be longer or shorter than 15 seconds, for example 10 to 20 seconds long. Thus, one of the advantages of the invention is improved movement of soil particles into the soil collector to reduce the amount of soil particles recirculated in the wash water.  
         [0029]    When Pump step  65  begins there is a surge of wash water through the distribution system including supply tube  30  and spray arms  22 ,  24  and  34 . The surge of wash water at the beginning of Pump step  65  provides extra scrubbing energy to dislodge soil particles still present on ware being washed in the dishwasher. Thus, another advantage of the Start Stop Wash sequence is an increase in the number of pump starts at the beginning of each Pump step. Pump step  65  can be 45 seconds long. The duration of Pump step  65  can be longer or shorter than 45 seconds, for example 30 to 90 seconds long.  
         [0030]    In the embodiment of FIG. 7 the Pause  64  and Pump  65  steps are repeated 10 times to provide the Stop Start Wash sequence. The number of repeats or loops in the Stop Start Wash sequence can be more or less than 10 times. Following is a table setting forth an example of the duration of each of the steps in the Main Wash segment  51  and when automatic purge filtration, apf, is enabled.  
                                                                     Time (minutes)                                            Fill 60   1:35               Pause 61   0:05           Pump &amp; Heat &amp; Detergent 62   0:45           Pump &amp; Heat 63   Thermal Hold   (apf)           Pause 64   0:15   loop           Pump 65   0:45   10X           Pump 66   12:30            Drain &amp; Pump 67   1:00           Drain 68   1:00                      
 
         [0031]    It will be appreciated by those skilled in the art that the times for the steps in the embodiment shown above can be adjusted to be longer or shorted as desired. In addition, as mentioned above, the Thermal Hold in Pump &amp; Heat step  63  can be limited by the microcomputer control  40  if desired, or be determined by the time required to heat the recirculating wash water to the predetermined temperature. The inventive method described in this embodiment can be employed in other dishwasher cycles.  
         [0032]    Turning to FIG. 8 and FIG. 9 another embodiment of the inventive dishwasher cycle is shown. In FIG. 8 a normal wash cycle for low soil is shown. In this embodiment the normal cycle-low soil cycle includes Pre-Wash  70 , Main Wash  71 , Rinse  72 , Final Rinse  73  and Dry  74  segments. Each of the segments can include one or more steps such as Fill, Pause, Pump, Drain, Heat, and others. The normal wash-low soil cycle can be programmed in the microcomputer control  40 . In this embodiment the Stop Start Wash sequence according to the invention occurs in the Main Wash segment  71 . Referring to FIG. 9, Main Wash segment  71  includes Fill  80 , Pause  81 , Pump &amp; Heat &amp; Detergent  82 , Pump &amp; Heat  83 , Pump &amp; Heat-Thermal Hold  84 , Pause  85 , Pump  86 , Drain &amp; Pump  87  and Drain  88  steps. The operation of the dishwasher in these steps is the same as described above in connection with the embodiment of FIG. 6 and FIG. 7. In this embodiment automatic purge filtration (apf) is provided in the Pump &amp; Heat  83 , and Pump &amp; Heat-Thermal Hold  84  steps. As in the previous embodiment, the Pause  85  and Pump  86  steps are repeated a number of times to provide the Stop Start Wash sequence in Main Wash segment  71 . In this embodiment the Start Stop Wash sequence is provided at the end of the Main Wash segment rather than at the beginning of Main Wash segment  51  of the previous embodiment.  
         [0033]    The function of the Start Stop Wash sequence in this embodiment is the same as in the previous embodiment. The duration of Pause step  85  is sufficient for the wash pump  228  to stop and allow wash water in supply tube  30  to drain back into the pump assembly  20 . The Pause step  85  can be 15 seconds long. The duration of Pause step  85  can be longer or shorter than 15 seconds, for example 10 to 20 seconds long. As in the previous embodiments, one of the advantages of the invention is improved movement of soil particles into the soil collector to reduce the amount of soil particles recirculated in the wash water.  
         [0034]    When Pump step  86  begins there is a surge of wash water through the distribution system including the supply tube  30  and spray arms  22 ,  24  and  34 . The surge of wash water at the beginning of Pump step  86  provides extra scrubbing energy to dislodge soil particles still present on ware being washed in the dishwasher. As in the previous embodiment, another advantage of the Start Stop Wash sequence is an increase in the number of pump starts at the beginning of each Pump step, such as Pump step  86 . Pump step  86  can be 45 seconds long. The duration of Pump step  86  can be longer or shorter than 45 seconds, for example 30 to 90 seconds long.  
         [0035]    In the embodiment of FIG. 9 the Pause  85  and Pump  86  steps are repeated 5 times to provide the Stop Start Wash sequence. The number of repeats may be more or less than 5 times. In this embodiment the duration of the steps of the Main Wash segment  71  and enablement of the apf mode by the microcomputer control can be as follows.  
                                                                     Time (minutes)                                            Fill 80   1:35               Pause 81   0:05           Pump &amp; Heat &amp; Detergent 82   0:45           Pump &amp; Heat 83   7:00   (apf)           Pump &amp; Heat 84   Thermal Hold   (apf)           Pause 85   0:15   loop           Pump 86   0:45   5X           Drain &amp; Pump 87   1:00           Drain 88   1:00                      
 
         [0036]    It will be appreciated by those skilled in the art that the times for the steps in the embodiment shown above can be adjusted to be longer or shorted as desired.  
         [0037]    Although the description of the two embodiments above are of a “normal” wash cycle, other wash cycles (i.e. heavy soil, pots and pans, etc.) could be used without departing from the scope of the present invention. Typically, these other cycles differ from a “normal” cycle in that more, or longer or shorter wash and/or rinse cycles are employed.  
         [0038]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.