Abstract:
A dishwasher includes a first washing chamber and a second washing chamber capable of performing a washing operation separately and/or concurrently. Each washing chamber includes a wash pump, a drain pump and a heating unit that are operatively connected to a controller. When initiating a washing fluid in one washing chamber, the controller determines if the other washing chamber is active. If the other washing chamber is active, the heating unit for the one washing chamber is operated at a low power level. However, if the other washing chamber is inactive, the one washing chamber is operated at a high power level to rapidly heat the washing fluid and thus shorten the duration of the washing operation.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention pertains to the art of dishwashers and, more particularly, to a rapid heat system for a multi-tub type dishwasher that diverts power from an inactive washing tub to an active washing tub so as to rapidly heat washing fluid in the active washing tub. 
         [0003]    2. Discussion of the Prior Art 
         [0004]    In general, various types of dishwashers are known in the art. One type of dishwasher which is experiencing increased popularity is a drawer-type dishwasher. Typically, a drawer-type dishwasher includes a drawer or pull-out washing tub slidably mounted in a cabinet. A dish rack is provided within the washing tub to support dishware and other items during a washing operation. In some cases, the dishwasher will include first and second drawers or washing tubs arranged in an upper and lower configuration. A washing operation can be performed in either one, the other, or both of the washing tubs. That is, the first and second washing tubs are capable of performing washing operations individually or simultaneously. 
         [0005]    Most household dishwashers are powered by a dedicated, generally, 15-20 amp supply circuit. When both the first and second washing tubs are operating simultaneously, power must be shared so the supply circuit is not overloaded. Generally, sharing power between the first and second washing tubs does not pose any problems. Wash pumps, drain pumps and other control elements do not, in most cases, have high power requirements. However, heating units employed to heat a washing fluid do possess high power requirements. 
         [0006]    Given that the first and second washing tubs are capable of operating both individually and simultaneously, the first and second washing tubs include corresponding first and second heating units. Thus, in order to ensure that the supply circuit is not overloaded, the combined current draw of both the first and second heating units cannot exceed a current rating of the supply circuit. With this configuration, the ability to quickly heat washing fluid in either the first and/or second washing tubs is limited. That is, even if only one of the first and second washing tubs is operating or active, the heating element must still operate at a relatively low power level. 
         [0007]    Based on the above, there exists a need in the art for a system to rapidly heat washing fluid in a drawer-type dishwasher. More specifically, there exists a need for a system that can direct power to rapidly heat one washing tub of a two drawer dishwasher if the other washing tub is inactive. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is directed to a dishwasher including a first washing tub, preferably defined by a first drawer, and a second washing tub, preferably defined by a second drawer. The dishwasher is capable of performing a washing operation in each of the first and second washing tubs separately and/or simultaneously. Toward that end, the first and second washing tubs have associated wash pumps and drain pumps, but preferably a common controller. In addition, the dishwasher includes first and second heating units associated with the first and second washing tubs respectively. More specifically, each of the first and second heating units is operable at multiple heating levels so as to heat washing fluid during select portions of a washing operation. The controller is operatively connected to each of the first and second heating units, as well as each wash pump and drain pump. 
         [0009]    In accordance with a preferred embodiment of the present invention, prior to activating the first heating unit to heat washing fluid in the first washing tub, the controller determines whether the second washing tub is active. A washing tub can be defined as being active if, for example, a washing operation is underway or if its associated heating unit is being powered. In any event, if the second washing tub is active, the controller will establish a low power level requirement and operate the first heating unit, i.e., the heating unit associated with the first washing tub, at a low or normal power level. On the other hand, if the second washing tub is inactive, the controller will establish a high power level requirement and operate the first heating unit at a high power level so as to rapidly heat the washing fluid and, thus shorten the washing operation. 
         [0010]    In accordance with one aspect of the preferred embodiment, each of the first and second heating units is constituted by a dual element heating unit. In this manner, when the controller establishes the low power level requirement for the first heating unit, only one of the dual elements is activated while, for a high power level requirement, both of the dual elements are activated. In accordance with another aspect of the preferred embodiment, each of the first and second heating units is constituted by a high capacity heating element operated by a microprocessor. In this manner, when the controller establishes a low power level requirement, the microprocessor establishes a corresponding low heat setting while, for a high power level requirement, the microprocessor establishes a corresponding high heat setting. In this manner, in the event that only one of the first and second washing tubs is active, the controller will divert power from the inactive washing tub to the active washing tub in order to rapidly heat the washing fluid and shorted the washing operation. 
         [0011]    Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an upper right perspective view of a drawer-type dishwasher incorporating a rapid heat system constructed in accordance with the present invention; 
           [0013]      FIG. 2  is an upper perspective view of a wash tub of the dishwasher of  FIG. 1 ; 
           [0014]      FIG. 3  is a lower perspective view of the wash tub of  FIG. 2 , illustrating a heating unit assembly constructed in accordance with one aspect of the present invention; and 
           [0015]      FIG. 4  is a flow diagram illustrating operation of the rapid heat system of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    With initial reference to  FIGS. 1 and 2 , a dishwasher constructed in accordance with the present invention is generally indicated at  2 . As shown, dishwasher  2  includes a support frame  4  arranged below a kitchen countertop  6 . Also below kitchen countertop  6  is shown cabinetry  8  including a plurality of drawers  9 - 12 , as well as cabinet doors  13  and  14 . In accordance with the invention, dishwasher  2  constitutes a dual cavity dishwasher having an upper washing unit  16  and a lower washing unit  18 . As best illustrated in  FIG. 1 , upper washing unit  16  takes the form of a slide-out drawer unit, having a small or medium capacity, so as to be used for cleaning glassware and the like, while lower cavity  18  is illustrated as a larger capacity drawer for washing larger sized items, such as dinnerware, cookware and the like. 
         [0017]    As shown, upper washing unit or drawer  16  includes a front wall  20 , a rear wall  21 , a bottom wall  22  and opposing side walls  23  and  24  that collectively define a first washing tub or chamber  28 . In a manner known in the art, first washing tub  28  is provided with a dish rack  30  for supporting various objects, such as dishware, glassware, and the like, to be exposed to a washing operation. Upper washing unit  16  is slidingly supported within support frame  4  through a pair of extensible drawer support guides, one of which is indicated at  33 . In a similar manner, lower washing unit  18  includes front, rear, bottom and opposing side walls (not shown) that collectively define a second washing tub  34 . 
         [0018]    For the sake of completeness,  FIG. 2  illustrates a main filter housing  38  provided on bottom wall  22  within first washing tub  28 . Main filter housing  38  is actually positioned within a central, generally U-shaped, intake ring  40  (see  FIG. 3 ) arranged along bottom wall  22 . In any event, main filter housing  38  includes an outer or first radial strainer  42 , an inner or second radial strainer  43  and a cover  44 . Actually, second radial strainer  43  is associated with a fine particle filter chamber including a fine mesh filter screen (not shown) provided within each of a plurality of large openings  45  arranged about cover  44 . A hub member  47  is arranged on cover  44  and serves as a support for a wash arm  49 . In a manner known in the art, wash arm  49  sprays washing fluid onto kitchenware placed within first washing tub  28  to remove food debris and other soil particles. 
         [0019]    With particular reference to  FIG. 3 , dishwasher  2  also includes a sump  64  having a plurality of fluid conduits  67 - 69  extending along bottom wall  22  of first washing tub  28 . In the embodiment shown, fluid conduit  67  constitutes a wash fluid supply conduit, fluid conduit  68  constitutes a wash fluid recirculation conduit, and fluid conduit  69  constitutes a wash fluid drain conduit, wherein each of fluid conduits  67 - 69  provides washing fluid flow management during a washing operation. Preferably, fluid conduits  67 - 69  are spaced from and arranged substantially parallel to one another across bottom wall  22 , with conduits  67  and  69  extending from a central portion  71  of intake ring  40  to an outer edge portion  74  of first washing tub  28 . More specifically, supply conduit  67  includes a first end  78 , fluidly connected to wash arm  49 , that leads to a second end  79 . Second end  79  is provided with an attachment flange  80 . Likewise, recirculation conduit  68  extends from a first end  81 , fluidly exposed to washing tub  28 , that leads to a second end  82 . In a manner corresponding to supply conduit  67 , recirculation conduit  68  is provided with an attachment flange  83 . Finally, drain conduit  69  extends from a first end  85  that is in fluid communication with main filter housing  38  to a second end  86  which is also provided with an attachment flange  88 . 
         [0020]    In addition to managing the flow of washing fluid in dishwasher  2 , sump  64  serves as a mounting platform for a plurality of wash system components. As best shown in  FIG. 3 , a wash pump  110  and a drain pump  111  are mounted to first washing tub  28  along outer edge portion  74 . Preferably, wash pump  110  includes a wash motor housing  115  and a wash pump housing  116 . More preferably, wash pump housing  116  includes a fresh water inlet  118 , a supply outlet  119  for directing washing fluid toward wash arm  49  and a recirculation inlet  120  that conducts wash fluid back from first washing tub  28  into wash pump housing  116  where the wash fluid is once again directed to wash arm  49 . Toward that end, supply outlet  119  and recirculation outlet  120  project into attachment flanges  80  and  83  of supply and recirculation conduits  67  and  68  respectively. With this arrangement, a substantially closed loop recirculation system is formed for first washing tub  28 . Likewise, drain pump  111  includes a drain motor housing  123  and a drain pump housing  124 . Drain pump housing  124  includes an inlet portion  125  and an outlet port  126  adapted to be interconnected to a drain hose (not shown). Inlet portion  125  is preferably provided with a chopping mechanism (not shown) for macerating food particles to be expelled with washing fluid from first washing tub  28  during periodic drain or purging operations. 
         [0021]    In accordance with one form of the invention, dishwasher  2  includes a heating unit  240  for heating washing fluid during select portions of a washing operation. In the embodiment shown, heating unit  240  is arranged within recirculation conduit  68  so as to heat the washing fluid flowing from washing tub  28 . That is, in accordance with the embodiment shown, wash fluid flowing from first washing tub  28  through recirculation conduit  68  can be heated by selectively activating heating unit  240 . 
         [0022]    At this point, it should be understood that second washing tub  34  includes structure corresponding to that described above with respect to first washing tub  28 , including a corresponding heating unit shown in phantom at  242  in  FIG. 1 , and is independently controllable. In general, the structure described above has only been described for the sake of completeness. A more detailed description can be found in commonly owned patent application filed on even date herewith, entitled “Multi-Use Sump for a Drawer-Type Dishwasher”, and incorporated by reference. Instead, the present invention is particularly directed to the particular control and operation of heating unit  240 . 
         [0023]    In accordance with the present invention, dishwasher  2  includes a control unit or CPU  250  (see  FIG. 1 ). Control unit  250  is operatively connected between at least wash pump  110 , drain pump  111  and heating unit  240 . In accordance with one preferred embodiment, heating unit  240  is selectively operable at multiple power or heat levels that are established by control unit  250 . As will be detailed more fully below, control unit  250  can establish a low power level setting for heating unit  240  or, alternatively, establish a high power level or rapid heat setting for heating unit  240 . Toward that end, heating unit  240  can include one heating element  260  that can be selectively operated at low or high power levels, or first and second heating elements  260  and  261  which can be selectively operated individually or in combination. If heating unit  240  includes only one heating element  260 , heating element  260  is preferably constituted by a high capacity heating element controlled through a microprocessor  268  that, in the embodiment shown, is contained within control unit  250 . More specifically, high capacity heating element  260  in this embodiment is operable at two rates, i.e., a low power/normal heat setting or a high power/rapid heat setting as particularly established by microprocessor  268 . In the second embodiment, to establish a low/normal power level setting, control unit  250  activates first heating element  260 , and to establish a high power level, control unit  250  activates both first and second heating elements  260  and  261 . 
         [0024]    In still further accordance with the invention, dishwasher  2  includes at least one sensor  280  operatively coupled to first and second washing tubs  28  and  30 , as well as control unit  250 . As will be detailed more fully below, sensor  280 , when signaled by control unit  250 , determines whether a particular one of first and second washing tubs  28  and  30  is active. Sensor  280  can determine that a particular washing tub  28 ,  30  is active either by sensing that heating unit  240 , associated with the particular washing tub  28 ,  30  is operating or, alternatively, by sensing whether a washing operation is currently underway in the particular washing tub  28 ,  30 . 
         [0025]    Reference will now be made to  FIG. 4  in describing a preferred method of operation for dishwasher  2 . After loading dishes or the like into first and/or second washing tub  28 ,  30 , a consumer activates one or both of washing tubs  28  and/or  30  through a control element (not shown) as represented at  310 . At this point washing fluid begins to enter and fill, for example, first washing tub  28  to a predetermined level as shown at step  320 . Once the washing fluid reaches a predetermined level, it is desired to activate wash pump  110  to circulate the washing fluid in first washing tub  28 , while activating heating unit  240  to heat the washing fluid. However, in accordance with the invention, prior to activating heating unit  240 , control unit  250  polls sensor  280 , in step  330 , to inquire whether second washing tub  30  is active. If sensor  280  signals control unit  250  that second washing tub  30  is active, heating unit  240  is operated at the low power setting, as represented in step  340 , and the washing operation continues regularly. If, on the other hand, sensor  280  signals control unit  250  that second washing tub  30  is inactive, additional power is available so that heating unit  240  can be operated in a high or rapid heat level, as represented in step  350 . After establishing the particular heating step  340  or  350  to employ, the washing operation continues to completion as represented in step  360 . 
         [0026]    Based on the above, if only one of the first and second washing tubs  28  and  30  is activated, washing fluid recirculating in the active washing tub  28 ,  30  is heated more rapidly than if both washing tubs  28 ,  30  were operating. Since the washing fluid is brought to temperature in less time than during a regular washing operation when in the rapid heat mode, the time required to complete a washing operation is reduced. Although described with reference to preferred embodiments of the present invention, it should be readily apparent to one of ordinary skill in the art that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, the use of the terms first and second are for exemplary purposes only and should not be construed as limiting. In addition, the sensor could use various other types of indicators other than washing operation and heater activation to determine whether a washing chamber is active. For example, current switch, LED and the like sensors would also provide an indication of the operation of a particular washing tub. In addition, although the most preferred embodiments of the invention are associated with drawer-type dishwashers, the invention is also applicable to other types of dishwashers. Furthermore, the arrangement of the pumps, heating units and the like on the tubs can be readily changed without deterring from the invention. In general, the invention is only intended to be limited by the scope of the following claims.