Patent Publication Number: US-9429351-B2

Title: Demand air door heater for refrigerator

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to refrigeration systems, and in particular to a heater for a door that controls air flow between two compartments of the refrigeration system. 
     Refrigeration systems may include an insulated freezer compartment and an insulated refrigeration compartment. A refrigeration unit including a compressor, condenser, and evaporator may be utilized to cool the freezer compartment. A powered door (“air door”) selectively opens and closes to control air flow from the freezer compartment to the refrigerator compartment. The air door thereby controls the flow of cold air from the freezer compartment into the refrigerator compartment to control the temperature in the refrigerator compartment. A thermostat in the refrigeration compartment may be set to a target temperature, and a temperature sensor in the refrigeration compartment may monitor the actual temperature in the refrigeration compartment. In the event the temperature in the refrigeration compartment is above the target temperature, the door to the freezer compartment is opened, thereby allowing cold air from the freezer compartment to flow into the refrigeration compartment until the temperature drops below the target temperature value. 
     Ice or frost buildup at the door may, however, interfere with opening and closing of the air door. Heaters have been developed to melt the ice and frost from air doors. However, heaters generally require energy for operation, and known door heater arrangements may provide less than optimum efficiency. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is a refrigeration system including a freezer compartment and a refrigerator compartment. The system further includes a powered cooling unit that reduces a temperature of air in the freezer compartment. A passageway fluidly interconnects the freezer compartment and the refrigerator compartment. A first sealing surface extends around at least a portion of the passageway. The system further includes a barrier that closes off the passageway when in a closed position to thereby to prevent air flow from the freezer compartment to the refrigerator compartment. The barrier permits air flow from the freezer compartment to the refrigeration compartment when the barrier is in an open position. The barrier defines a barrier surface that faces the passageway when the barrier in its closed position, and a second sealing surface extending around the barrier surface. The first and second sealing surfaces engage one another to prevent air flow past the barrier when the barrier is in the closed position. The system further includes an electrically powered actuator that shifts the barrier between the opened and closed positions. The system also includes an electric heating element extending along one of the first and second sealing surfaces. The system also includes a controller that utilizes at least one operating parameter of the refrigeration system as an input to control the electrically powered actuator and the electric heating element. The powered actuator and the electric heating element are actuated simultaneously. The barrier may comprise a door that pivots or slides. 
     Another aspect of the present invention is a method of controlling air flow between a freezer compartment and a refrigeration compartment of a refrigeration system. The method includes providing a barrier that moves between opened and closed positions to control air flow between a freezer compartment and a refrigeration compartment. An electrically powered actuator is provided to move the barrier between the opened and closed positions. An electric heating element is provided adjacent the barrier to melt ice to permit the barrier to open and/or close. A sensor indicating if the barrier is opened or closed is also provided. An operating parameter of the refrigeration system is used as a control input to determine when the barrier is to be opened and closed. When the barrier is to be opened, electric power is simultaneously provided to the electrically powered actuator and to the electric heating element until the barrier is open. When the barrier is to be closed, electric power is simultaneously provided to the electrically powered actuator and to the electric heating element until the barrier is closed. The electrically powered actuator and the electric heating element may be connected in parallel whereby electrical power is supplied to the electrically powered actuator and electric heater from a single electrical power source. The operating parameter may comprise an air temperature in the refrigeration compartment. 
     Another aspect of the present invention is a refrigeration system including a freezer compartment, a refrigeration compartment, and a passageway between the freezer compartment and the refrigeration compartment. The system includes an electrically powered barrier or door that opens and closes to control air flow through the passageway. The door forms a seal closing off the passageway when the door is in the closed position. The system includes an electric heating element adjacent the seal. The electric heating element is connected in parallel to the electrically powered door. The system also includes a controller selectively supplying electrical power to the electrically powered door and to the electrical heating element based on at least one operating parameter of the refrigeration system. The operating parameter may comprise a temperature of the refrigeration compartment. The electrical heating element may comprise an electrical resistance wire forming a loop about an opening of the passageway. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a refrigeration system according to one aspect of the present invention; 
         FIG. 2  is a partially schematic isometric view of a heated air door according to one aspect of the present invention; 
         FIG. 3  is a partially schematic isometric view of a heated air door according to another aspect of the present invention; and 
         FIG. 4  is an electrical circuit diagram of the refrigeration system. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     With reference to  FIG. 1 , a refrigeration system  1  according to one aspect of the present invention may include an insulated refrigeration compartment  5  and an insulated freezer compartment  10  that are formed by an insulating structure  12 . The insulating structure  12  may include access doors  14  and  16 , respectively, which permit user access to food, beverages, or other items stored in the compartments  5  and  10  in a known manner. A divider wall  18  separates the refrigeration compartment  5  and freezer compartment  10 . A passageway  20  through divider wall  18  fluidly interconnects the refrigerator compartment  5  with the freezer compartment  10 . A powered barrier such as air door  22  selectively opens and closes to permit flow of air  24  between the refrigeration compartment  5  and the freezer compartment  10 . A refrigeration unit  26  cools the freezer compartment  10 . The refrigeration unit  26  may comprise a conventional refrigeration unit having a compressor, condenser, capillary tube, and evaporator. 
     A controller  28  is operably connected to a temperature sensor  30 . The temperature sensor is configured to provide the controller  28  with the temperature of the air inside the refrigeration compartment  5 . A switch  32  and powered door  22  are also operably connected to the controller  28 . Switch  32  provides a signal to the controller  28  indicating if the door  22  is in an open position or in a closed position. As discussed in more detail below, an electric heating element  34  is disposed adjacent powered door  22  about passageway  20  to thereby heat and melt ice and/or frost that may otherwise form on or adjacent powered door  22 . 
     With reference to  FIG. 2  powered door  22  may comprise barrier member such as door member  36  that is pivotably coupled to a support structure  38  for rotation about an axis “A.” An electric motor  40  provides for powered rotation of door member  36 . The door member  36  may be pivotably mounted to support structure  38  utilizing a shaft or pin  42 . 
     Support structure  38  forms an opening  44  to passageway  20 . Opening  44  can be selectively closed off by door member  36  upon actuation of electric motor  40 . Support structure  38  includes a first sealing surface  46  that sealingly engages a second sealing surface  48  extending around perimeter  50  of door member  36 . The first sealing and second sealing surfaces  46  and  48 , respectively, are ring-like in shape and provide a seal such that air cannot pass through opening  44  and passageway  20  when door member  36  is in a closed position. It will be understood that various pivoting doors, electric motors, and corresponding components are known in the art, and the basic operation of these components is therefore known. 
     An electric heating element  52  extends around the opening  44  adjacent the first and second sealing surfaces  46  and  48  to melt ice and/or frost that could otherwise build up on one or both of the first and second sealing surfaces  46  and  48 . In a preferred embodiment, the support structure  38  is a polymer material, and electric heating element  52  comprises a heating wire that is molded into the support structure  38 . The electric heating element may comprise a heating wire  52 A that is molded into door member  36 , and extends around perimeter  50  of door  46 . Thus, the electric heating element may comprise a stationary component that extends around opening  44  in divider wall  18 , or it may be molded into door member  36  whereby the electric heating element moves with the door  36 . 
     The electrical heating element  52  may be positioned directly adjacent the areas where ice and/or frost tend to form. Ice and/or frost that builds up on or adjacent the first and second sealing surfaces  46  and  48  tends to prevent full closure of the door  36 , thereby interfering with the proper operation of the power door  22 . Thus, the electric heating element  52  may comprise a ring extending around opening  44  directly adjacent the first sealing surface  46  to provide efficient heating in the areas most prone to ice and/or frost buildup, and to prevent build up of ice and/or frost in the regions where the ice and/or frost is likely to interfere with the powered door  22 . As discussed in more detail below, the electric heating element  52  and electric motor  40  may be wired in parallel with input wire  52  electrically connecting electric motor  40  to electric line  54 , and with input wire  53  electrically connecting electric heating element  52  to electric line  54 . The electric motor  40  and the electric heating element  52  are thereby turned on and off simultaneously based on whether or not electrical power is supplied to a single electric line  54 . 
     With further reference to  FIG. 3 , a powered barrier, such as air door  22 A includes a support structure  38 A, and a barrier or door member  36 A that translates linearly to selectively close off an opening  44 A to passageway  20 . The door member  36 A may be slideably connected to support structure  38 A by linear guides  56 , and an electrically powered linear actuator  40 A provides for powered reciprocating movement of the door member  36 A in the direction of the arrow “B” to selectively open and close opening  44 A. An electric heating element  52  may be molded into support structure  38 A to form a ring around opening  44 A to prevent buildup of ice and/or frost in the vicinity of opening  44 A. The support structure  38 A may form a first sealing surface  46 A extending around  44 A, and a lower surface of door member  36 A may form a second sealing surface  48 A that engages first sealing surface  46  when door  36 A is in a closed position to thereby seal off opening  44 A to passageway  20 . The door member  36 A and support structure  38 A may be made of a molded polymer material or other suitable material. Electrically powered linear actuator  40 A selectively shifts the door  36 A between the opened and closed position. It will be understood that door member  36 A and support structure  38 A may be configured as required for a particular application. For example, door member  36 A and support structure  38 A may be structurally similar to the movable and fixed plates disclosed in U.S. Pat. No. 4,903,501 to Harl, the entire contents of which are hereby incorporated by reference. Various types of linearly translating, electrically actuated barriers/air doors are known in the art, and the details of the door  36 A, guides  56 , and support structure  38 A will not, therefore, be described in detail herein. 
     Electrical heating element  52  and powered actuator  40 A are preferably electrically connected in parallel, such that the electrically powered actuator  40 A and electrical heating element  52  are both supplied with electrical power from a single line  54 . With further reference to  FIG. 4 , electrical circuit diagram  58  of the refrigeration system  1  includes a controller  28  that is operably connected to a control input line  60  and control output line  62 . An electrical line  54  is connected to a power supply  54  to thereby supply power to the electrical actuator  40  or  40 A, and to electrical heating element  52  and/or  52 A. Switch  32  is operably connected to the door member  36  or  36 A to thereby provide a control input to the controller  28  indicating if the door  36  or  36 A is opened or closed. The power source  64  may comprise line voltage (e.g. 120 V, 60 Hz) or it may a DC power supply (e.g. 12 V). Temperature sensor  30  is also operably connected to controller  28 , and provides controller  28  with a signal corresponding to the temperature of air in the refrigerator compartment  5 . A thermostat  66  may be utilized to set a target temperature of the air the refrigeration compartment  5 . Thermostat  66  is also operably connected to controller  28 . 
     In use, controller  28  compares the measured temperature in the refrigeration compartment  5  to a target temperature from thermostat  66 . If the temperature in the refrigeration compartment  5  is greater than a target temperature, controller  28  generates a signal causing electrical power to be supplied to both the powered actuator  40  and the electrical heating element  52 . Electrical power is supplied to the powered actuator  40  and electric heating element  52  until switch  32  provides a signal indicating that the door  36  has opened. In the event ice and/or frost buildup has occurred, thereby preventing door member  36  from immediately opening, electrical power is supplied to electrical heating element  52  until the ice melts, door member  36  opens, thereby actuating the switch  32 . 
     In use, if controller  28  determines that a temperature in refrigerator compartment  5  is lower than a target temperature set by thermostat  66 , controller  28  will generate a signal causing electrical power to be supplied to the power actuator  40  and electric heating element  52  until switch  32  generates a signal indicating that the door member  36  has shifted to the closed position. The powered door system  22 A of  FIG. 3  may operate in a substantially identical manner. 
     Thus, electrical power is simultaneously supplied to the electric motor  40  (or  40 A) and electric heating element  52  (or  52 A) until the door member  36  (or  36 A) shifts to the desired opened or closed position. This arrangement ensures that the air door reaches the correct position, and also turns off the electric heating element  52  once the door member  36  reaches the correct position. This arrangement reduces energy consumption compared to independently-controlled heating elements. 
     It will be understood that the rotating air door of  FIG. 2  and the sliding air door of  FIG. 3  are examples of two types of powered barriers. The present invention may be utilized in connection with a wide range of powered barriers, and the present invention is therefore not limited to a specific door configuration.