Patent Publication Number: US-2020278136-A1

Title: Hydrophobic Coating on Evaporator to Enhance Food Preservation

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention pertains to the art of refrigerators and, more particularly, to enhancing the preservation of food stored in the refrigerator through air flow control. 
     Description of the Related Art 
     In general, a refrigerator will include one or more compartments used to store food items and a refrigeration system for cooling each compartment. A domestic refrigerator typically includes both a fresh food compartment for storing food items at a temperature above freezing and a freezer compartment for storing food items below freezing. Although separate refrigeration systems could be employed for each compartment, it is more common and economical to employ a single refrigeration system, along with an assembly to regulate and control the flow of cooling air to each of the compartments based on desired operating temperatures. A refrigeration system of this type mainly includes a compressor, a condenser and a condenser fan located in a machine compartment of the refrigerator, as well as an evaporator and evaporator fan located in or directly exposed to the freezer compartment. When a control system indicates that cooling is required in one or more of the compartments, the refrigeration system is activated, resulting in the evaporator becoming quite cold and the evaporator fan causing a flow of air to flow across the evaporator to create a flow of cold air which is then directed to the compartment(s) requiring cooling. The refrigeration system remains in operation until the cooling requirement of the compartment(s) is met. 
     In some types of refrigerators, the flow of cooling air is always directed into the freezer compartment and then at least some of the flow is diverted to the fresh food compartment, such as through an air flow duct having a flow regulating baffle. In other types of refrigerators, separate or comingled air flow ducting is employed for direct air flow to each compartment. In each case, the overall cooling system can be employed in a wide variety of refrigerator models, including top mount, bottom mount, side-by-side and French style refrigerators. In the situations where the cold air generated for the freezer is directed into the fresh food compartment for cooling food items in the fresh food compartment, the cold air entering the fresh food compartment typically has a low humidity level (very dry). This is particularly true in full no-frost refrigerator systems with a single evaporator located in the freezer compartment (perhaps behind a false rear wall such that any developed condensed water droplets (ice) are not visible) where ducts are employed to circulate cooling air to each compartment, with the cooling air for the fresh food compartment coming either directly from the freezer evaporator or from freezer compartment. In either case, when this dry air enters the fresh food compartment, the air extracts humidity from the fresh food in the compartment, thereby contributing to food dehydration which can have a significant negative impact on the overall appearance and shelf life of the food, as well as reducing the preservation performance of the refrigerator overall. 
     With the above in mind, there is seen to be a need in the art for a refrigeration system that can be utilized with various refrigerator configurations having freezer evaporators, wherein the system compensates for a dehydration effect created when a supply of air is directed across the freezer evaporator and directed into a fresh food compartment of the refrigerator. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a refrigerator including a fresh food compartment and a freezer compartment, as well as a refrigeration system including a freezer evaporator and an evaporator fan. The evaporator fan includes at least one blade, with the at least one fan blade having an outer surface including a hydrophobic coating. 
     When the refrigeration system is used in a cooling cycle, the evaporator becomes cold and operation of the evaporator fan causes a flow of cooling air to be directed over the evaporator and then into the fresh food compartment for cooling food items stored in the fresh food compartment, with the cold air coming either directly from the across the evaporator or through ducting from the freezer compartment. In either case, the inclusion of the hydrophobic coating operates to reduce dehydration of the food items in the fresh food compartment by limiting the loss of humidity in the cold air supply. 
     Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a refrigerator including an air flow system according to the present invention; 
         FIG. 2  is a cross-sectional view of the refrigerator of  FIG. 1 ; and 
         FIG. 3  is a cross-sectional view of a fan blade of the air flow system. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With initial reference to  FIG. 1 , a refrigerator  2  includes an outer shell or cabinet  4  within which is positioned a liner (not separately labeled) that defines a fresh food compartment  8 . In a manner known in the art, fresh food compartment  8  can be accessed by the selective opening of a fresh food door  10 . In a similar manner, a freezer door  12  can be opened to access a freezer compartment  13 . For the sake of completeness, fresh food door  10  and freezer door  12  of refrigerator  2  are shown with storage zones (not separately labeled) for supporting various food items in a manner widely known in the art. As is also known in the art, fresh food compartment  8  is shown provided with a plurality of shelves  20  and  21 , which are preferably vertically height adjustable. At a lowermost portion of fresh food compartment  8  is illustrated various laterally spaced shelves  28  and  29  below which are positioned spaced bins  31  and  32 , respectively. Certainly, the above described refrigerator style and structure are known in the art (generally referred to as a top-mount refrigerator) and presented only for the sake of completeness. At this initial point, it should be noted that the present invention is not limited for use with a top-mount style refrigerator, but may be utilized with other known refrigerator styles including bottom-mount, side-by-side, and French door style refrigerators. Therefore, refrigerator  2  is only presented as exemplary for purposes of explaining the invention. 
     As is also widely known in the art, fresh food compartment  8  is generally maintained at a temperature above freezing, typically in the range of 35°-40° F. On the other hand, freezer compartment  13  is to be maintained below freezing, i.e., below 32° F. For use in connection with maintaining desired operating temperatures in fresh food compartment  8  and freezer compartment  13 , a controller unit  50  is shown mounted in fresh food compartment  8 , with controller unit  50  receiving temperature signals from a freezer compartment temperature sensor  52  and a fresh food compartment temperature sensor  54 . By way of example, temperature sensors  52  and  54  can be constituted by thermistors. In addition, controller unit  50  establishes an interface for receiving freezer and fresh food compartment set point signals from user controlled selectors  56  and  58 , which can take various forms including dials, rotary knobs, buttons and the like. Controller unit  50  is part of an overall refrigeration system including a freezer evaporator  60  located in freezer compartment  13 , such as behind a rear or false wall  64  of freezer compartment  13 , as will be discussed in more detail below. 
       FIG. 2  schematically illustrates the location and components of the refrigeration system of refrigerator  2 . In the top-mount embodiment depicted, refrigerator  2  includes a lower machine compartment  70  having mounted therein a compressor  76 , a compressor motor  77 , a condenser  78  and a condenser fan  80 . Evaporator  60  is in fluid communication with both compressor  76  and condenser  78  through refrigeration conduits  92  and  94  respectively. Operation of compressor motor  77 , which can be operable at variable speeds, causes refrigerant to move through the refrigeration system conduits  92  and  94  in establishing evaporator  60  as a cold source for cooling freezer and fresh food compartments  13  and  8 . 
     In connection with cooling fresh food and freezer compartments  8  and  13 , evaporator  60  has associated therewith an evaporator fan  100 , including an evaporator fan motor  102  having a drive shaft  103  for driving at least one fan blade  104 . In one form, a plurality of fan blades  104  project from a central hub  106 . Certainly, various types of fans could be employed, including squirrel cage-type fans with multiple blades. In any case, during operation of evaporator fan motor  102 , the fan blade(s)  104  develop a flow of cooling air, including a first stream of cooling air  144  directed within ducting (not labeled) into and then through freezer compartment  13  and a second stream of air  146  within ducting  147  into and then through fresh food compartment  8 . The second stream of air  146  is regulated by means of an air baffle  148  which can be variably shifted between fully closed and fully opened positions by controller unit  50 . As the details and operation of such a cooling system is known in the art, such as set forth in U.S. Pat. No. 6,725,680 which is incorporated herein by reference, further details thereof will not be discussed further herein. 
     More important in connection with the invention is the inclusion of a hydrophobic coating  108  on at least the fan blade(s)  104  of evaporator fan  100 . In the particular embodiment referenced in  FIG. 3 , each fan blade  104  includes an outer surface  110  provided with a hydrophobic coating. More specifically, each fan blade  104  has opposing face surfaces  115  and  116 , with face surface  116  being located closer to evaporator motor  102  than face surface  115 . In accordance with the invention, it is preferable that both opposing face surfaces  115  and  116 , as well as central hub  106 , are provided with the hydrophobic coating  108 . At this point, it should be noted that, in accordance with the invention, different hydrophobic coatings can be employed and the use of this term includes super hydrophobic coatings. In particular forms of the invention, the coating  108  constitutes or consists of a fluorine-containing chemical, a silane-based chemical or a nano-coating. According to the invention, hydrophobic coating  108  can vary in thickness, preferably in the range of 0.05 mm-0.2 mm and, more preferably, approximately 0.1 mm, with “approximately” meaning plus or minus 20% in accordance with the invention. 
     In practice, it has been found that providing hydrophobic coating  108  significantly reduces dehydration of food items in the fresh food compartment  8  based on the flow of cooling directed into fresh food compartment  8  from freezer evaporator  60  during operation of the refrigeration system. That is, particular to the cases where air used to cool a fresh food compartment comes from a freezer evaporator, i.e., an evaporator used to cool a freezer compartment to below freezing temperatures, the inclusion of the hydrophobic coating operates to reduce dehydration of the food items in the fresh food compartment by limiting the loss of humidity in the cold air supply, thereby avoiding the potential for the extraction of a significant amount of humidity from the stored food items, resulting in food items, particularly fruits, vegetables, meats, various stored leftovers, etc., being preserved longer while retaining favorable appearances, mouth feel, texture and the like. 
     Although described with reference to preferred embodiments of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. For instance, although the at least one evaporator fan blade is specifically coated in accordance with the invention, additional flow structure associated with the cooling air flow for the fresh food compartment could also be coated, such as the overall evaporator and air ducting. In general, the invention is only intended to be limited by the scope of the following claims.