Patent Publication Number: US-10788250-B2

Title: Ice making assemblies and methods for making clear ice

Description:
FIELD OF THE INVENTION 
     The present subject matter relates generally to ice making appliances and methods, and more particularly to appliances and methods for making substantially clear ice. 
     BACKGROUND OF THE INVENTION 
     In domestic and commercial applications, ice is often formed as solid cubes, such as crescent cubes or generally rectangular blocks. The shape of such cubes is often dictated by the environment during a freezing process. For instance, an ice maker can receive liquid water, and such liquid water can freeze within the ice maker to form ice cubes. In particular, certain ice makers include a freezing mold that defines a plurality of cavities. The plurality of cavities can be filled with liquid water, and such liquid water can freeze within the plurality of cavities to form solid ice cubes. 
     In typical ice making appliances, water in the cavities begins to freeze and solidify first from its sides and outer surfaces (including a top water surface that may be directly exposed to freezing air), and then in and through the remaining volume of water occupying the cavity. In other words, the exterior surfaces of an ice cube freeze first. However, impurities and gases contained within the water to be frozen may be trapped in a solidified ice cube during the freezing process. For example, impurities and gases may be trapped near the center or the bottom surface of the ice cube, due to their inability to escape and as a result of the freezing liquid to solid phase change of the ice cube surfaces. Separate from or in addition to the trapped impurities and gases, a dull or cloudy finish may form on the exterior surfaces of an ice cube (e.g., during rapid freezing of the ice cube). Generally, a cloudy or opaque ice cube is the resulting product of typical ice making appliances. 
     Although typical ice cubes may be suitable for a number uses, such as temporary cold storage and rapid cooling of liquids in a wide range of sizes, they may present several disadvantages. As an example, impurities and gases trapped within an ice cube may impart undesirable flavors into a beverage being cooled (i.e., a beverage in which the ice cube is placed) as the ice cube melts. Such impurities and gases may also cause an ice cube to melt unevenly or faster (e.g., by increasing the exposed surface area of the ice cube). Evenly-distributed or slow melting of ice may be especially desirable in certain liquors or cocktails. Additionally or alternatively, it has been found that substantially clear ice cubes (e.g., free of any visible impurities or dull finish) may provide a unique or upscale impression for the user. 
     Accordingly, further improvements in the field of ice making would be desirable. In particular, it may be desirable to provide an appliance or methods for rapidly and reliably producing substantially clear ice. 
     BRIEF DESCRIPTION OF THE INVENTION 
     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. 
     In one exemplary aspect of the present disclosure, a method of making ice is provided. The method may include providing a volume of water within a mold cavity defined within an ice mold. The ice mold may be positioned within a freezer chamber. The mold cavity may include a cavity opening at a top portion thereof. The cavity opening may extend in a vertical direction in fluid communication between the freezer chamber and the mold cavity. The method may also include maintaining the freezer chamber below a first sub-freezing temperature during an ice formation cycle as a portion of the volume of water freezes to a frozen volume. The method may further include heating the ice mold during the ice formation cycle at a heating element mounted within the ice mold. 
     In another exemplary aspect of the present disclosure, an ice making appliance is provided. The ice making appliance may include a cabinet, an ice mold, a heating element, and a controller. The cabinet may define a freezer chamber. The ice mold may be positioned within the freezer chamber. The ice mold may define a mold cavity extending vertically in fluid communication with the freezer chamber through a vertical opening. The heating element may be mounted within the ice mold in conductive thermal communication with the mold cavity. The controller may be in operable communication with the heating element. The controller may be configured to initiate an ice making operation. The ice making operation may include maintaining the freezer chamber below a first sub-freezing during an ice formation cycle subsequent to a volume of water being received within the mold cavity, and heating the ice mold during the ice formation cycle at the heating element as a portion of the volume of water freezes to a frozen volume. 
     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 
       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. 
         FIG. 1  provides a side plan view of an ice making appliance according to exemplary embodiments of the present disclosure. 
         FIG. 2  provides a schematic view of an ice making assembly according to exemplary embodiments of the present disclosure. 
         FIG. 3  provides a cross-sectional schematic view of a portion of an ice making assembly according to exemplary embodiments of the present disclosure. 
         FIG. 4  provides a cross-sectional schematic view of a portion of an ice making assembly according to exemplary embodiments of the present disclosure. 
         FIG. 5  provides a flow chart illustrating a method of operating an ice making appliance in accordance with an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). 
     Turning now to the figures,  FIG. 1  provides a side plan view of an ice making appliance  100 , including an ice making assembly  102 .  FIG. 2  provides a schematic view of ice making assembly  102 .  FIG. 3  provides a cross-sectional schematic view of a portion of ice making assembly  102 .  FIG. 4  provides a cross-sectional schematic view of a portion of ice making assembly  102  according to other exemplary embodiments of the present disclosure. 
     Generally, ice making appliance  100  includes a cabinet  104  (e.g., insulated housing) and defines a mutually orthogonal vertical direction V, lateral direction, and transverse direction. The lateral direction and transverse direction may be generally understood to be horizontal directions H. As shown, cabinet  104  defines one or more chilled chambers, such as a freezer chamber  106 . In certain embodiments, such as those illustrated by  FIG. 1 , ice making appliance  100  is understood to be formed as, or as part of, a stand-alone freezer appliance. It is recognized, however, that additional or alternative embodiments may be provided within the context of other refrigeration appliances. For instance, the benefits of the present disclosure may apply to any type or style of a refrigerator appliance (e.g., a top mount refrigerator appliance, a bottom mount refrigerator appliance, a side-by-side style refrigerator appliance, etc.) that includes a freezer chamber. Consequently, the description set forth herein is for illustrative purposes only and is not intended to be limiting in any aspect to any particular chamber configuration. 
     Ice making appliance  100  generally includes an ice making assembly  102  on or within freezer chamber  106 . In some embodiments, ice making appliance  100  includes a door  105  that is rotatably attached to cabinet  104  (e.g., at a top portion of the cabinet  104 ). As would be understood, door  105  may selectively cover an opening defined by cabinet  104 . For instance, door  105  may rotate on cabinet  104  between an open position (not pictured) permitting access to freezer chamber  106  and a closed position ( FIG. 1 ) restricting access to freezer chamber  106 . 
     A user interface panel  108  is provided for controlling the mode of operation. For example, user interface panel  108  may include a plurality of user inputs (not labeled), such as a touchscreen or button interface, for selecting a desired mode of operation. Operation of ice making appliance  100  can be regulated by a controller  110  that is operatively coupled to or in wireless communication with user interface panel  108  or various other components, as will be described below. User interface panel  108  provides selections for user manipulation of the operation of ice making appliance  100  such as (e.g., selections regarding chamber temperature, ice making speed, or other various options). In response to user manipulation of user interface panel  108 , or one or more sensor signals, controller  110  may operate various components of the ice making appliance  100  or ice making assembly  102 . 
     Controller  110  may include a memory (e.g., non-transitive media) and one or more microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of ice making appliance  100 . 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. Alternatively, controller  110  may be constructed without using a microprocessor (e.g., using a combination of discrete analog or digital logic circuitry; such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software. 
     Controller  110  may be positioned in a variety of locations throughout ice making appliance  100 . In optional embodiments, controller  110  is located within the user interface panel  108 . In other embodiments, the controller  110  may be positioned at any suitable location within ice making appliance  100 , such as for example within cabinet  104 . Input/output (“I/O”) signals may be routed between controller  110  and various operational components of ice making appliance  100 . For example, user interface panel  108  may be in operable communication with controller  110  via one or more signal lines or shared communication busses. 
     As illustrated, controller  110  may be in communication with the various components of ice making assembly  102  and may control operation of the various components. For example, various valves, switches, etc. may be actuatable based on commands from the controller  110 . As discussed, user interface panel  108  may additionally be in communication with the controller  110 . Thus, the various operations may occur based on user input or automatically through controller  110  instruction. 
     In some embodiments, ice making appliance  100  includes a sealed cooling system  112  for executing a vapor compression cycle for cooling ice making assembly  102  or air within ice making appliance  100  (e.g., within freezer chamber  106 ). Sealed cooling system  112  includes a compressor  114 , a condenser  116 , an expansion device  118 , and an evaporator  120  connected in fluid series and charged with a refrigerant. As will be understood by those skilled in the art, sealed cooling system  112  may include additional components (e.g., at least one additional evaporator, compressor, expansion device, or condenser). Moreover, at least one component (e.g., evaporator  120 ) is provided in thermal communication with freezer chamber  106  to cool the air or environment within freezer chamber  106 . Optionally, evaporator  120  is mounted within freezer chamber  106 , as generally illustrated in  FIG. 1 . 
     Within sealed cooling system  112 , gaseous refrigerant flows into compressor  114 , which operates to increase the pressure of the refrigerant. This compression of the refrigerant raises the refrigerant temperature, which is lowered by passing the gaseous refrigerant through condenser  116 . Within condenser  116 , heat exchange (e.g., with ambient air takes place) to cool the refrigerant and cause the refrigerant to condense to a liquid state. 
     Expansion device  118  (e.g., a mechanical valve, capillary tube, electronic expansion valve, or other restriction device) receives liquid refrigerant from condenser  116 . From expansion device  118 , the liquid refrigerant enters evaporator  120 . Upon exiting expansion device  118  and entering evaporator  120 , the liquid refrigerant drops in pressure and vaporizes. Due to the pressure drop and phase change of the refrigerant, evaporator  120  is cool relative to freezer chamber  106 . As such, cooled air is produced and refrigerates freezer chamber  106 . Thus, evaporator  120  is a heat exchanger which transfers heat (e.g., from air passing over evaporator  120  to refrigerant flowing through evaporator  120 ). 
     Optionally, ice making appliance  100  further includes a valve  122  for regulating a flow of liquid water to ice making assembly  102  from a suitable water source (e.g., on-board water tank or municipal water source). Valve  122  is selectively adjustable between an open configuration and a closed configuration. In the open configuration, valve  122  permits a flow of liquid water to ice making assembly  102 . Conversely, in the closed configuration, valve  122  hinders the flow of liquid water to an ice mold  130 . 
     In certain embodiments, ice making appliance  100  also includes an air handler  124  mounted within (or otherwise in fluid communication with) freezer chamber  106 . Air handler  124  may be operable to urge a flow of chilled air (i.e., active airflow—as indicated at arrows  126 ) within freezer chamber  106 . Moreover, air handler  124  can be any suitable device for moving air. For example, air handler  124  can be an axial fan or a centrifugal fan. In some embodiments, air handler  124  is in operable (e.g., electrical or wireless) communication with controller  110 . 
     As shown, an ice mold  130  may be provided within freezer chamber  106 . For example, ice mold  130  (e.g., the entirety of ice mold  130  or, alternatively, a sub portion thereof) may be removably positioned within freezer chamber  106  such that a user may selectively place ice mold  130  within freezer chamber  106  (e.g., during ice making operations) and remove ice mold  130  from freezer chamber  106  (e.g., to remove frozen ice cubes or billets from ice mold  130 ) as desired. As shown, ice mold  130  includes an insulated mold body  131  and generally defines one or more mold cavities  134  in which water may be received and ice cubes or billets (e.g., solid masses or blocks of ice that may be further melted to a final shape) may be formed. Generally, each mold cavity  134  may extend the vertical direction V between a top portion  136  and a bottom portion  138 . 
     In some embodiments, mold body  131  includes one or more insulated sidewalls  132  positioned about the mold cavities  134  and defining a vertical opening  140 . A base wall  142  (e.g., insulated base wall) may extend below the insulated sidewalls  132  and mold cavities  134 . It is understood that ice mold  130  may be formed from any suitable material. In some embodiments, one or more thermally insulating materials are utilized to form ice mold  130 . The sidewalls  132  may be insulated sidewalls  132  and the ice mold  130  may be an insulated ice mold  130 . As an example, one or more of the sidewalls  132  may define a sealed insulation volume to surround at least a portion of mold cavity  134 . The sealed insulation volume may generally prevent the passage of air or oxygen to or from a volume within each sidewall  132  (e.g., as a substantially evacuated a vacuum or a volume filled with a set mass of gas, such as nitrogen, oxygen, argon, or a suitable inert gas). As another example, one or more of the sidewalls  132  may be formed or filled with a solid insulating material (e.g., a rigid polyurethane insulating foam) to hinder to heat transfer between each mold cavity  134  and its surrounding environment (e.g., freezer chamber  106 ). 
     Optionally, the mold cavities  134  may be defined as open voids in fluid communication with freezer chamber  106 . For instance, air or water may freely pass through the top portion  136  of mold cavity  134 . After entering mold cavity  134 , however, air or water will be prevented from passing through the bottom portion  138 . In some such embodiments, vertical opening  140  of the mold body  131  has a horizontal diameter that is equal to or greater than the horizontal diameter of the mold cavity  134 . 
     In certain embodiments, a removable sleeve  152  is provided for selective insertion/removal within the mold body  131 . In turn, one or more of the mold cavities  134  may be defined by a corresponding removable sleeve  152  (e.g., from top portion  136  to a bottom portion  138 ). As shown, removable sleeve  152  may be shaped to generally complement the surfaces of sidewalls  132  and base wall  142 . Removable sleeve  152  may thus fit through and within vertical opening  140 . A cavity opening  135  (e.g., parallel to or concentric with vertical opening  140 ) is defined through removable sleeve  152  at the top portion  136  of the corresponding mold cavity  134 . During use, a volume of water may be provided to removable sleeve  152  (e.g., through cavity opening  135 ) and ice may be formed therein (i.e., as at least a portion of the volume of water within mold cavity  134  transitions to a frozen volume). Once a volume of water is frozen (e.g., as an ice cube or billet), removable sleeve  152  and the frozen volume may be removed together from mold body  131 . As is understood, removable sleeve  152  may be formed from any suitable material, such as a synthetic polymer capable of maintaining a predetermined elastic shape as removable sleeve  152  is subjected to disparate temperatures (e.g., as removable sleeve  152  is placed into and removed from freezer chamber  106 ). 
     Turning specifically now to  FIG. 3 , in some embodiments, the insulated sidewalls  132  may extend along substantially all of mold cavity  134 . For instance, the sidewalls  132  may extend along the vertical direction V from the top portion  136  to the bottom portion  138 . The sidewalls  132  may enclose a corresponding removable sleeve  152  (e.g., when the removable sleeve  152  is received within the mold body  131 ). 
     Turning specifically now to  FIG. 4 , in other embodiments, the insulated sidewalls  132  may extend along a limited portion of mold cavity  134 . For instance, the sidewalls  132  may extend along the vertical direction V from the bottom portion  138  to the predetermined ballast height  148  within mold cavity  134 . In other words, the vertical extension or height of the sidewalls  132  may terminate at the ballast height  148 . When the removable sleeve  152  is received within the mold body  131 , at least a portion of the removable sleeve  152  extends above the vertical opening  140  and insulated sidewalls  132 . Thus, the sidewalls  132  may be shorter than the removable sleeve  152 . 
     Advantageously, the relative position of sidewalls  132  may contain heat at and below the ballast height  148 . In turn, formation of a liquid ballast within mold cavity and below a frozen volume may be promoted. 
     Returning generally to  FIGS. 1 through 4 , a heater  182  is generally positioned in conductive thermal communication with a mold cavity  134 . For instance, within mold body  131 , a heater  182  may be positioned below each mold cavity  134 . In some such embodiments, each mold cavity  134  may be provided with a corresponding heater  182  therebelow. Generally, heater  182  includes, or is provided as, a suitable electrical heating element (e.g., resistive heating element, radiant heating element, etc.). In some embodiments, each heater  182  is in operable (e.g., electrical or wireless) communication with controller  110 . 
     During use (e.g., an ice formation cycle), heater  182  may be selectively activated to conduct heat to the mold cavity  134 , thereby hindering at least a portion of the volume of water within mold cavity  134  from freezing. In some instances, a liquid ballast may be formed from a portion of the volume of water within the mold cavity  134  (e.g., at the bottom portion  138 ) while a frozen volume is formed from another portion of the volume of water above the liquid ballast. Advantageously, impurities may settle within the liquid ballast and be prevented from becoming frozen or encased within the frozen volume. 
     In optional embodiments, a suitable phase change material (PCM) is positioned in thermal communication with mold cavity  134 . For instance, a PCM segment  184  may be positioned within the mold body  131  below the vertical opening  140 . Within the PCM segment  184 , one or more solid or nonpermeable surfaces may enclose the PCM material (e.g., vegetable oil based PCM). In exemplary embodiments, the PCM segment  184  is formed below the mold cavity  134 . In particular, PCM segment  184  may extend along the bottom portion  138  of the corresponding mold cavity  134 . When the removable sleeve  152  is placed within mold body  131 , a bottom end of the removable sleeve  152  may be supported on the PCM segment  184 . Optionally, PCM segment  184  may be positioned between the heater  182  and the mold cavity  134  (e.g., along the vertical direction V). Advantageously, PCM segment  184  may promote even or consistent heat distribution and encourage formation of the liquid ballast below a frozen volume of water within mold cavity  134 . 
     When assembled, an air handler  124  may be positioned above (or otherwise located at a position to) direct an active airflow  126  across the top portion  136  of mold cavity  134  or removable sleeve  152  (e.g., perpendicular to cavity opening  135 ). Thus, an active airflow  126  may be selectively motivated across ice mold  130 , thereby accelerating heat transfer from mold cavity  134 . For instance, air handler  124  may be configured to motivate the active airflow  126  at one or more predetermined flow rates (e.g., volumetric flow rates) within freezer chamber  106 . 
     In some embodiments, one or more sensors are mounted on or within ice mold  130 . As an example, a temperature sensor  144  may be mounted to ice mold  130 . Temperature sensor  144  may be in operable (e.g., electrical or wireless) communication with controller  110  and configured to detect the temperature within ice mold  130  or mold cavity  134 . Temperature sensor  144  may be formed as any suitable temperature detecting device, such as a thermocouple, thermistor, etc. Optionally, temperature sensor  144  may be mounted at a predetermined height along one of the sidewalls  132 . In some such embodiments, the predetermined height is the ballast height  148  below the top portion  136  of mold cavity  134 , as illustrated in  FIG. 3 . Alternatively, the temperature sensor  144  may be mounted at another suitable location within mold body  131 , such as below the bottom portion  138  of mold cavity  134 , as illustrated in  FIG. 4 . 
     As noted above, during use (e.g., during ice making operations), a liquid ballast  150  may form below a frozen volume (e.g., ice cube or billet) within mold cavity  134 . Advantageously, impurities within the volume of water from which the frozen volume is formed may accumulate within the liquid ballast  150  as a portion of the volume of water freezes. Detection of a predetermined temperature at the temperature sensor  144  (e.g., at the ballast height  148 ) may indicate the frozen volume has reached the ballast height  148 . Optionally, controller  110  may be configured to adjust one or more operations of the ice making assembly  102  in response to determining that the ice mold  130  has frozen to the ballast height  148 . 
     Referring now to  FIG. 5 , various methods (e.g., method  500 ) may be provided for use with the ice making appliance  100  or ice making assembly  102  ( FIG. 1 ) in accordance with the present disclosure. In some embodiments, such as the exemplary embodiments illustrated by method  500 , all or some of the various steps of the methods may be performed by controller  110  ( FIG. 1 ). For example, controller  110  may, as discussed, be operably coupled to or in operable communication with one or more of sealed cooling system  112 , valve  122 , interface panel  108 , air handler,  124 , or temperature sensor  144  ( FIG. 2 ). During use, controller  110  may send signals to receive signals from some or all of these components. Controller  110  may further be operably coupled to or in operable communication with other suitable components of the appliance  100  or assembly  102  to facilitate operation of the appliance  100  or assembly  102  generally. Present methods may advantageously facilitate the formation or creation of substantially clear ice cubes or billets. Moreover, such methods may advantageously permit substantially clear ice to be produced in less than 14 hours (e.g., following initiation thereof). 
       FIG. 5  depicts steps performed in a particular order for purpose of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that (except as otherwise indicated) the steps of method  500  disclosed herein can be modified, adapted, rearranged, omitted, or expanded in various ways deviating from the scope of the present disclosure. 
     As shown in  FIG. 5 , at  510 , the method  500  includes providing a volume of water within the mold cavity defined within the ice mold. In some embodiments, the ice mold is an insulated ice mold. Thus, the ice mold may include one or more insulated sidewalls, as described above. The cavity opening may extend vertically and generally be exposed or uncovered (e.g., relative to surrounding environment). When positioned within the freezer chamber, the cavity opening may thus be in fluid communication between freezer chamber and the mold cavity. 
     It is understood that the volume of water provided to the mold cavity may be provided manually or, alternatively, automatically. For instance, when provided manually, the volume of water in mold cavity may be poured directly by a user supplying the water to mold cavity. By contrast, when provided automatically, the controller may control or actuate the valve of the ice making assembly to open, thereby permitting volume of water to flow to the mold cavity. Additionally or alternatively, a pump of a water distribution assembly may be actuated to provide water from a suitable water source (e.g., on-board water tank or municipal water source). Although described as automatic, is understood that controller may operate (e.g., transmit one or more signals to the valve) in response to one or more user input signals received from the user interface. Moreover, it is understood that the volume of water may be provided to the mold cavity while the ice mold is positioned within or, alternatively, outside of freezer chamber. However, the purposes of the method  500 , once the volume of water is provided within the mold cavity, the ice mold is understood to be positioned within the freezer chamber (e.g., for the duration of steps  520  through  540 ). 
     At  520 , the method  500  includes maintaining the freezer chamber below a first sub-freezing temperature during an ice formation cycle. The ice formation cycle may be performed while the ice mold (and thereby the volume of water within the mold cavity) is positioned within the freezer chamber. Thus, the ice mold is maintained or held below the first sub-freezing temperature for the duration of the ice formation cycle as a portion of the volume of water freezes to a frozen volume (e.g., ice cube or billet). During the ice formation cycle, the freezer chamber may be maintained at a relatively stable temperature (e.g., between −10° Fahrenheit and 10° Fahrenheit). In some embodiments, the first sub-freezing temperature may be 10° Fahrenheit. In other embodiments, the first sub-freezing temperature may be 5° Fahrenheit. In further embodiments, the first sub-freezing temperature may be 0° Fahrenheit. 
     As described above, the sealed cooling system may be activated or otherwise directed to cool the freezer chamber. For instance, during the ice formation cycle, heat may be drawn from the freezer chamber or ice mold at the evaporator. As would be understood, the sealed cooling system may be selectively activated by the controller (e.g., based on one or more temperature signals received from a temperature sensor mounted to the ice making appliance or within the freezer chamber). 
     At  530 , the method  500  includes heating the ice mold during the ice formation cycle (e.g., during at least a portion of the ice formation cycle). In particular, the heater (i.e. one or more heating element thereof) within the ice mold may be activated to generate heat directed at the mold cavity. For instance, the heater may conduct heat generated by electric resistance at a heating element to the mold cavity from a position below the mold cavity, as described above. The heater may be activated continuously during  530  or, alternatively, intermittently. If activated intermittently, activation may be according to a predetermined cycle or according to signals received from one or more portion of the ice making assembly (e.g., based on one or more temperature signals received from a temperature sensor mounted to the ice making appliance or within the freezer chamber). 
     At  540 , the method  500  may include directing the freezer chamber to a second sub-freezing temperature during an ice maintenance cycle. Generally,  540  is performed subsequent to  520  (e.g., immediately following completion of the ice formation cycle). Moreover, during  540 , the frozen volume is understood to remain within the freezer chamber (e.g., within the mold cavity or separate therefrom in a discrete ice container). Thus, the frozen volume is maintained or held at the second sub-freezing temperature for the duration of the maintenance cycle. Optionally, the heater may be deactivated or otherwise held in an inactive state during  540  or for the duration of the maintenance cycle. 
     The second sub-freezing temperature may be greater than the first sub-freezing temperature. In turn, transitioning from the ice formation cycle to the maintenance cycle may require increasing the temperature within the freezer chamber. Such an increase may occur gradually and as a result of natural heat absorption by the ice making appliance. Optionally,  540  may include deactivating or limiting operation of the sealed cooling system. The sealed cooling system may continue to draw heat from the freezer chamber (e.g., through the evaporator), but at a rate less than would be provided during the ice formation cycle. The second sub-freezing temperature may be a relatively stable temperature (e.g., between 20° Fahrenheit and 32° Fahrenheit). In some embodiments, the first sub-freezing temperature may be 20° Fahrenheit. In other embodiments, the first sub-freezing temperature may be 25° Fahrenheit. In further embodiments, the first sub-freezing temperature may be 30° Fahrenheit. 
     In some embodiments,  540  is contingent upon completion of the ice formation cycle. In other words, the method  500  may include ensuring that the ice formation cycle is complete before initiating  540  and the ice maintenance cycle. Completion of the ice formation cycle may include determination of one or more predetermined conditions. As an example, the ice formation cycle may have predetermined time (e.g., span of time measured from initiation of the ice formation cycle) after which the ice formation cycle expires. Thus, the ice formation cycle may end upon the predetermined time elapsing. Optionally, the predetermined time may begin when the volume of water is provided within the freezer chamber (e.g., at  510 ). As another example, the ice formation cycle may end upon a predetermined condition being detected at the ice mold. Optionally, the predetermined condition may include detecting a set temperature been reached at the temperature sensor (e.g., at the ballast height). Detection of the set temperature may indicate that the frozen volume has reached (i.e., frozen to) the ballast height and is therefore at a desired size. Furthermore, it is understood that any other suitable predetermined condition for ascertaining the size of the frozen volume or extent to which the provided volume of water has frozen may be utilized. 
     In optional embodiments, method  500  includes directing an active airflow across the ice mold. For instance, as described above the air handler within the freezer chamber may be activated or rotated to motivate air within the freezer chamber to flow (i.e., as an active airflow) over or across the ice mold. The active airflow may be provided at one or more periods of the method  500 . In particular, the active airflow may be provided at  520 ,  530 , or for the duration of the ice formation cycle. In some such embodiments, the active airflow is motivated a predetermined flow rate (e.g., volumetric flow rate). In other words, the flow rate of the active airflow may remain constant during the ice formation cycle. In other embodiments, active airflow is motivated at a variable flow rate. The flow rate may increase or decrease based one or more received signals or user inputs. For instance, the variable flow rate may be set according to a specific user input. Additionally or alternatively, the variable flow rate may be set automatically according to a sensed condition (e.g., one or more signals received from, for example, the temperature sensor or the pressure sensor mounted to the ice mold). 
     Optionally, the active airflow may further be provided at  540  or for the duration of the maintenance cycle (e.g., at a flow rate that is less than a flow rate during the ice formation cycle). Alternatively, the active airflow may be halted during  540  or for the duration of the maintenance cycle. 
     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.