Abstract:
An appliance is provided with a pump for drawing liquid from a wash chamber of the appliance. The pump is operated such that the pump cycles on and off during a cycle of the appliance. By cycling on and off, air locks affecting the pump can be eliminated or reduced.

Description:
FIELD OF THE INVENTION 
       [0001]    The present subject matter relates generally to appliances with pumps and methods for operating the same. 
       BACKGROUND OF THE INVENTION 
       [0002]    Dishwasher appliances generally include a drain pump. The drain pump removes liquid (e.g., water, detergent, etc.) from a wash chamber of the appliance. For example, liquid can collect in a sump disposed at a bottom of the wash chamber during operation of the dishwasher appliance. The drain pump can be in fluid communication with the sump such that the drain pump urges liquid from the sump to a drain where the liquid can flow out of the appliance. 
         [0003]    During operation, drain pumps can experience a condition called an air lock that negatively affects operation of the drain pump. An air lock is a pocket or bubble of air located within the drain pump or connected piping or hoses. The air lock can prevent or impede the drain pump from creating a flow of liquid out of the wash chamber. Thus, the air lock can severely reduce or completely obstruct the flow of liquid out of the wash chamber. 
         [0004]    A design goal for dishwasher appliances can include water and energy conservation. Drain pumps experiencing an air lock do not function at optimum efficiency. For example, a drain pump experiencing an air lock can take a greater amount of time to remove liquid compared to an identical drain pump operating without the air lock. Thus, air locks can contribute to greater energy consumption by the dishwasher appliance. 
         [0005]    In addition, air locks can generate greater number of service calls regarding the dishwasher appliance. Due to the negative effects of air locks, appliance owners can attribute the reduced performance on a clog and call a service technician for repair. However, such service calls can be unnecessary due to the transitory nature of the air locks. Thus, air locks can contribute to consumption of valuable service technician and user resources on unnecessary repair calls. 
         [0006]    To eliminate air locks, certain drain pumps include features for directing air out of the drain pump. For example, certain drain pumps can be positioned or oriented such that creation of an air lock is hindered. In particular, such drain pumps are constructed to allow air to escape the drain pump and surrounding piping or hoses. However, such designs offer limited reliability in reducing air locks. Thus, such designs can still suffer air locks. 
         [0007]    Accordingly, a dishwasher appliance with features for reducing or eliminating air locks within a pump of the appliance would be useful. Also, a dishwasher appliance with features for at least partially removing air locks from a pump of the appliance would be useful 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    Aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention. 
         [0009]    An appliance is provided with a pump for drawing liquid from a wash chamber of the appliance. The pump is operated such that the pump cycles on and off during a cycle of the appliance. By cycling on and off, air locks affecting the pump can be eliminated or reduced. 
         [0010]    In a first exemplary embodiment, an appliance is provided. The appliance includes a tub defining a wash chamber for receipt of articles for washing, a drain, and a drain pump in fluid communication with the wash chamber of the tub and the drain. The drain pump is configured for selectively directing liquid out of the wash chamber of the tub to the drain. A processing device is in communication with the drain pump. The processing device is configured for activating the drain pump for a first period of time, deactivating the drain pump for a second period of time, starting the drain pump for a third period of time, stopping the drain pump for a fourth period of time, and initiating the drain pump for a fifth period of time. The steps of activating, deactivating, starting, stopping, and initiating are performed during a drain cycle. The drain cycle has a drain interval. The drain interval includes the first, second, third, fourth, and fifth periods of time. 
         [0011]    In a second exemplary embodiment, a method for operating an appliance is provided. The appliance has a drain pump for directing liquid out of a wash chamber of the appliance. The method includes activating the drain pump for a first period of time, deactivating the drain pump for a second period of time, starting the drain pump for a third period of time, stopping the drain pump for a fourth period of time, and initiating the drain pump for a fifth period of time. The steps of activating, deactivating, starting, stopping, and initiating are performed during a drain cycle. The drain cycle has a drain interval. The drain interval includes the first, second, third, fourth, and fifth periods of time. 
         [0012]    In a third exemplary embodiment, an appliance is provided. The appliance includes a tub that defines a wash chamber for receipt of articles for washing. A pump is in fluid communication with the wash chamber of the tub. The pump is configured for selectively drawing liquid out of the wash chamber of the tub. A processing device is in communication with the pump. The processing device is configured for: activating the pump for a first period of time; deactivating the pump for a second period of time; starting the pump for a third period of time; stopping the pump for a fourth period of time; and initiating the pump for a fifth period of time. The steps of activating, deactivating, starting, and stopping are performed during an initial portion of a specific cycle of the appliance in order to clear an air lock condition from the pump. The step of initiating is performed during a remainder of the specific cycle of the appliance. 
         [0013]    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 
         [0014]    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: 
           [0015]      FIG. 1  provides a side partial cut-away view of a dishwasher appliance according to an exemplary embodiment of the present subject matter. 
           [0016]      FIG. 2  is a schematic view of a fluid system of the dishwasher appliance of  FIG. 1 . 
           [0017]      FIG. 3  illustrates an exemplary method of operating a dishwasher appliance according to an embodiment of the present subject matter. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    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. 
         [0019]      FIG. 1  depicts an exemplary embodiment of a dishwasher appliance  100 . Dishwasher appliance  100  includes a cabinet  102  having a tub  104  therein that defines a wash chamber  106 . Tub  104  has a door  120  hinged at its bottom  122  for movement between a normally closed vertical position (shown in  FIG. 1 ) wherein wash chamber  106  is sealed shut for washing operation, and a horizontal open position for loading and unloading of articles from wash chamber  106  of dishwasher  100 . 
         [0020]    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 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 rack is substantially positioned outside wash chamber  106 , and a retracted position (shown in  FIG. 1 ) in which rack is located inside wash chamber  106 . A silverware basket (not shown) may be removably attached to lower rack  132  for placement of silverware, utensils, and the like, that are too small to be accommodated by upper and lower racks  130 ,  132 . 
         [0021]    Dishwasher  100  further includes a lower spray assembly  144  that is, e.g., rotatably mounted within a lower region  146  of wash chamber  106  and above a tub sump portion  142  so as to rotate in relatively close proximity to lower rack  132 . A mid-level spray assembly  148  is located in an upper region of wash chamber  106  and may be located in close proximity to upper rack  130 . Additionally, an upper spray assembly (not shown) may be located above upper rack  130 . 
         [0022]    Lower and mid-level spray assemblies  144 ,  148  and upper spray assembly are fed by a fluid circulation assembly (not shown) for circulating water and dishwasher fluid in tub  104 . The fluid circulation assembly may be located in a machinery compartment  140  located below bottom sump portion  142  of tub  104 , as generally recognized in the art. Each spray assembly includes an arrangement of discharge ports or orifices for directing washing fluid onto dishes or other articles located in upper and lower racks  130 ,  132 , respectively. In an exemplary embodiment, the arrangement of the discharge ports in at least lower spray assembly  144  provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of lower spray assembly  144  provides coverage of dishes and other dishwasher contents with a washing spray. 
         [0023]    Dishwasher  100  is further equipped with a processing device or controller  137  to regulate operation of dishwasher  100 . Controller  137  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 exemplary 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. 
         [0024]    Controller  137  may be positioned in a variety of locations throughout dishwasher  100 . In the illustrated exemplary embodiment, 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 bottom  122  of door  120 . Typically, controller  137  includes a user interface panel  136  through which a user may select various operational features and modes and monitor progress of dishwasher  100 . In one exemplary embodiment, user interface  136  may represent a general purpose I/O (“GPIO”) device or functional block. In one exemplary embodiment, 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. User interface  136  may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. User interface  136  may be in communication with controller  137  via one or more signal lines or shared communication busses. 
         [0025]    It should be appreciated that the invention is not limited to any particular style, model, or other configuration of dishwasher, and that the exemplary embodiment depicted in  FIG. 1  is for illustrative purposes only. For example, instead of racks  130 ,  132  depicted in  FIG. 1 , 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. Also, the present subject matter may be utilized in other appliance as well, e.g., washing machine appliances. 
         [0026]      FIG. 2  schematically illustrates an exemplary embodiment of a fluid circulation assembly  170  disposed below the wash chamber  106 . Although one exemplary embodiment of fluid circulation assembly  170  that is operable to perform in accordance with aspects of the disclosure 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. 
         [0027]    Fluid circulation assembly  170  includes a circulation pump assembly  172  and a drain pump assembly  174 , both in fluid communication with sump  150 . Additionally, drain pump assembly  174  is in fluid communication with an external drain  173  to discharge used wash liquid, e.g., to a sewer or septic system (not shown). Further, 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 back wall  156  for feeding wash liquid to 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. 
         [0028]    As wash liquid is pumped through lower spray arm assembly  144 , and further delivered to mid-level spray arm assembly  148  and the upper spray arm assembly (not shown), washing sprays are generated in wash chamber  106 , and wash liquid collects in sump  150 . Sump  150  may include a cover to prevent larger objects from entering sump  150 , such as a piece of silverware or another dishwasher item that is dropped beneath lower rack  132 . A coarse filter and a fine filter (not shown) may be located adjacent sump  150  to filter wash liquid for sediment and particles of predetermined sizes before flowing into sump  150 . 
         [0029]    A turbidity sensor (not shown) may be coupled to sump  150  and used to sense a level of sediment in sump  150  and to initiate a sump purge cycle where the contents or a fractional volume of the contents of sump  150  are discharged when a turbidity level in sump  150  approaches a predetermined threshold. Sump  150  is filled with water through an inlet port  175  which outlets into wash chamber  106 , as described in greater detail below. 
         [0030]    Referring to  FIG. 2 , a water supply  200  may be configured with inlet port  175  for supplying wash liquid to wash chamber  106 . Water supply  200  may provide hot water only, cold water only, or either selectively as desired. As depicted, water supply  200  has a hot water inlet  204  that receives hot water from an external source, such as a hot water heater and a cold water input  206  that receives cold water from an external source. 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. 
         [0031]    As shown in  FIG. 2 , a drain valve  186  is established in flow communication with sump  150  and opens or closes flow communication between sump  150  and a drain pump inlet  188 . Drain pump assembly  174  is in flow communication with drain pump inlet  188  and may include an electric motor for pumping fluid at inlet  188  to an external drain system via drain  173 . In one embodiment, when drain pump assembly  174  is energized, a negative pressure is created in drain pump inlet  188  and drain valve  186  is opened, allowing fluid in sump  150  to flow into fluid pump inlet  188  and be discharged from fluid circulation assembly  170  via external drain  173 . 
         [0032]    Alternatively, drain and recirculation pump assemblies  172  and  174  may be connected directly to the side or the bottom of sump  150 , and drain and recirculation pump assemblies  172 ,  174  may each include their own valving replacing drain valve  186 . Other fluid circulation systems are possible as well, drawings fluid from sump  150  and providing fluid as desired within wash chamber  106  or draining fluid out of washing machine  100 . 
         [0033]    During operation of drain pump assembly  174 , an air lock condition can develop within drain pump assembly  174 . For example, the air lock condition can develop within drain pump assembly  174  during periods of inactivity by dishwasher appliance  100 . The air lock condition can also develop within drain pump assembly  174  when drain pump assembly  174  has completely drained sump  150  and sump  150  is subsequently refilled. As will be understood by those skilled in the art, the air lock condition corresponds to a pocket bubble of air disposed within drain pump assembly  174  or related piping or hoses. 
         [0034]    The air lock condition can negatively affect operation of drain pump assembly  174 . For example, drain pump assembly  174  has an optimum fluid drain rate. However, when drain pump assembly  174  is experiencing the air lock condition, drain pump assembly  174  operates in a less efficient manner such that fluid drains from sump  150  at a rate below the optimum fluid drain rate. As discussed in greater detail below, dishwasher appliance  100  includes features for clearing or at least partially removing the air lock condition from drain pump assembly  174  such that drain pump assembly  174  operates at a rate at or closer to the optimum fluid drain rate. 
         [0035]      FIG. 3  illustrates a method  300  for operating a dishwasher appliance (e.g., dishwasher appliance  100 ) in order to improve draining performance. For example, method  300  can clear or at least partially remove an air lock condition from drain pump assembly  174  of dishwasher appliance  100 . Controller  137  of dishwasher appliance  100  may be programmed to perform the steps of method  300 . Method  300  can be used to clear an air lock condition in other pumps, e.g., circulation pump assembly  172  or a drain pump in a washing machine appliance. 
         [0036]    At  310 , controller  137  activates drain pump assembly  174  for a first period of time, t 1 . Thus, at step  310 , drain pump assembly  174  is urging liquid from sump  150  to drain  173  for period t 1 . As an example, period t 1  may be about three seconds. However, as discussed in greater detail below, period t 1  may be any suitable period of time, e.g., about one, two, four, five, or more seconds. 
         [0037]    At  320 , controller  137  deactivates drain pump assembly  174  for a second period of time, t 2 . Thus, at step  320 , drain pump assembly  174  is not urging liquid from sump  150  to drain  173  for period t 2 . As an example, period t 2  may be about one and one-half seconds. However, as discussed in greater detail below, period t 2  may be any suitable period of time, e.g., about one, two, three, four, five, or more seconds. 
         [0038]    Steps  310  and  320  correspond to a first drain pulse initiated by controller  137 . Thus, in steps  310  and  320 , drain pump assembly  174  is turned on for period t 1  and turned off for period t 2 . The first drain pulse can assist in clearing or at least partially removing an air lock condition from drain pump assembly  174 . 
         [0039]    At  330 , controller  137  starts drain pump assembly  174  for a third period of time, t 3 . Thus, at step  330 , drain pump assembly  174  is urging liquid from sump  150  to drain  173  for period t 3 . As an example, period t 3  may be about three seconds. However, as discussed in greater detail below, period t 3  may be any suitable period of time, e.g., about one, two, four, five, or more seconds. 
         [0040]    At  340 , controller  137  stops drain pump assembly  174  for a fourth period of time, t 4 . Thus, at step  340 , drain pump assembly  174  is not urging liquid from sump  150  to drain  173  for period t 4 . As an example, period t 4  may be about one and one-half seconds. However, as discussed in greater detail below, period t 4  may be any suitable period of time, e.g., about one, two, three, four, five, or more seconds. 
         [0041]    Steps  330  and  340  correspond to a second drain pulse initiated by controller  137 . Thus, in steps  330  and  340 , drain pump assembly  174  is turned on for period t 3  and turned off for period t 4 . The second drain pulse can assist the first drain pulse in clearing or at least partially removing an air lock condition from drain pump assembly  174 . 
         [0042]    As discussed above, steps  310 - 340  correspond to cycling or pulsing drain pump assembly  174  on and off in order to clear or at least partially remove an air lock condition from drain pump assembly  174 . Thus, steps  310 - 340  may be performed as an initial portion of a drain cycle of dishwasher appliance  100  in order to remove an air lock condition that may be present in drain pump assembly  174 . Subsequent to steps  310 - 340 , drain pump assembly  174  may operate such that fluid is drained from sump  150  at about the optimum fluid drain rate during a remainder of the drain cycle, e.g., during step  350  described below. 
         [0043]    At  350 , controller  137  initiates drain pump assembly  174  for a fifth period of time, t 5 . Thus, at step  350 , drain pump assembly  174  is urging liquid from sump  150  to drain  173  for period t 5 . Period t 5  corresponds to a period of time sufficient to remove a particular volume of fluid from sump  150 . Thus, period t 5  can vary depending on the type of drain cycle selected. For example, during a full drain cycle when substantially all liquid is removed from wash chamber  106 , t 5  corresponds to a period of time sufficient for drain pump assembly  174  to remove substantially all liquid from sump  150 . Alternatively, during a partial drain cycle when only a portion of the liquid within sump  150  is removed from sump  150 , period t 5  corresponds to a period of time sufficient for drain pump assembly  174  to remove a portion of the volume of liquid within sump  150 . 
         [0044]    As discussed above, steps  310 - 340  may be performed during the initial portion of the drain cycle, and step  350  may be performed during the remainder portion of the drain cycle. The entire drain cycle (initial and remainder) may be performed during a drain time interval Δt drain . The interval Δt drain  may be calculated as 
         [0000]        Δt   drain   =t   1   t   2   t   3   t   4   t   5 . 
         [0045]    To reiterate, it should be understood that steps  310 - 350  may be performed during a single drain cycle of appliance  100 . Steps  310 - 340  may be performed to remove an air lock condition, and step  350  may be performed subsequent to steps  310 - 340  such that drain pump assembly  174  operates at about the optimum fluid drain rate. In particular, the steps of activating  310 , deactivating  320 , starting  330 , and stopping  340  may be performed during the initial portion of the drain cycle to clear any air lock condition, and the step of initiating  350  may be performed during the remainder portion of the drain cycle to drain a volume of liquid from the sump  150  at about the optimum fluid drain rate. Periods t 1 , t 2 , t 3 , t 4 , and t 5  of steps  310 - 350  may be substantially sequential during the drain cycle. However, brief pauses or transition periods may be present between the steps. 
         [0046]    It should be understood that steps  310 - 340  of method  300  may be performed during every drain cycle of appliance  100 . Thus, during steps  310 - 340 , an air lock condition may or may not be present in drain pump assembly  174 . Thus, drain pump assembly may be operating at the optimum drain rate during steps  310 - 340  such that steps  310 - 340  are unnecessary. However, by always performing steps  310 - 340  in the initial portion of the drain cycle, any air lock conditions that may be present in drain pump assembly  174  will be mitigated. 
         [0047]    As will be understood by those skilled in the art, the selection of specific periods t 1 , t 2 , t 3 , and t 4  can vary depending upon the specific geometry of drain pump assembly  174 . Thus, periods t 1 , t 2 , t 3 , and t 4  may be tuned for various drain pump assemblies. However, in various exemplary embodiments, periods t 1  and t 3  may be greater than periods t 2  and t 4  or vice versa. Further, periods t 1  and t 3  may be about equal. Also, periods t 2  and t 4  may be about equal. 
         [0048]    Method  300  may further include additional pulses or cycles to purge an air lock condition from drain pump assembly  164 . For example, in  FIG. 3 , method  300  includes two pulses. However, method  300  can include any suitable number of additional pulses when the geometry of drain pump assembly  174  requires, e.g., one, two, or more additional pulses. 
         [0049]    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.