Abstract:
A refrigerated unit is well suited for storing fruits and vegetables. A household-sized refrigerated unit includes a storage space for retaining fruits and vegetables. The temperature within the storage space is controllable within a range of approximately 40-65 degrees Fahrenheit. The humidity level within the storage space is regulated to prevent unnecessary desiccation of the fruit and vegetables, and to prevent excessive condensation. The unit is provided with a mechanism for regulating the level of ethylene gas within the storage space to either retard or accelerate ripening, as desired.

Description:
[0001]     This application is a non-provisional of U.S. Provisional Application No. 60/558,171, which is hereby incorporated in its entirety. 
     
    
     FIELD OF INVENTION  
       [0002]     This invention relates to refrigerated systems for storing and preserving produce such as fruits and vegetables. More particularly, this invention relates to a consumer-sized refrigerated unit for storing fruits and vegetables at optimal storage conditions.  
       BACKGROUND  
       [0003]     The optimal conditions for storage of many fruits and vegetables are difficult to create in a standard household refrigerator. The ideal temperature for the storage of moderate temperature fruits and vegetables is generally between forty (40) and sixty-five (65) degrees Fahrenheit (approximately 4-18 degrees Celsius). The fresh food compartment of most household refrigerators is kept at a temperature below what is ideal for storage of these fruits and vegetables, in order to provide appropriate conditions for storing other fresh foods such as milk, eggs, meat, and beverages.  
         [0004]     Additionally, the humidity level in the fresh food compartment may be too low as a result of the moisture that is naturally removed from the chilled air that cools the fresh food compartment. The difficulties of low humidity may be compounded by any blowing or other movement of air in the fresh food compartment that may accelerate the evaporation process. As a result, if the humidity level of the fresh food compartment is too low, it will cause excessive desiccation of the fruits or vegetables, which is not desirable. On the other hand, if the humidity level is too high, that results in excessive condensation of water, which creates its own problems. Ideally the humidity level will be approximately ninety percent (90%) relative humidity.  
         [0005]     As produce ripens, it produces ethylene gas. Ethylene gas acts as a catalyst to stimulate additional ripening and eventually senescence. Typically storage times for fruits and vegetables can be enhanced by eliminating excess ethylene from the air. On occasion, it is desired to ripen produce more rapidly. On these occasions it is desirable to retain the ethylene gas in close proximity to the fruit in order to accelerate the natural ripening process. Apples and tomatoes produce relatively high levels of ethylene gas.  
         [0006]     Different fruits and vegetables may benefit from different storage conditions. As a result, it is beneficial to have separate compartments in order to permit different storage conditions for various fruits and vegetables at the same time.  
         [0007]     While it is known in the art to provide separate compartments within household refrigerators for storage of fruits and vegetables, these compartments commonly lack some or all of the features necessary for optimal storage of moderate temperature fruits and vegetables.  
         [0008]     What is needed in the art is a household refrigeration unit that is dedicated to the storage of moderate temperature fruits and vegetables. Preferably the unit will allow control of temperature in a range of 40-65 degrees Fahrenheit (4-18 degrees Celsius), control of humidity levels to prevent excessive drying of the fruits and vegetables and to prevent excessive condensation, and control of ethylene gas levels to accelerate or retard ripening.  
       SUMMARY OF THE INVENTION  
       [0009]     The invention is directed to a household refrigeration unit for the storage of moderate temperature fruits and vegetables. The unit is provided with a chiller for removing heat from a storage space. Preferably the unit is provided with a control that permits the temperature within the storage space to be maintained at a desired temperature. Most preferably the temperature control will permit the storage space to be maintained at a desired temperature in the range of 40-65 degrees Fahrenheit. Preferably the unit is also provided with a mechanism for controlling the humidity level within the storage space. Most preferably the humidity control mechanism will permit the humidity level within the storage space to be maintained at a humidity high enough to prevent excessive drying of fruits and vegetables, but low enough to avoid condensation of water on the fruits and vegetables. Preferably the unit is provided with a mechanism to control ethylene levels in the storage space. Most preferably, ethylene can be removed from the storage space to retard ripening, or ethylene can be selectively retained in the storage space to accelerate ripening. Preferably the storage space may be divided into separate compartments with different conditions as to temperature, humidity level, and/or ethylene level, to permit optimal storage of various types of fruits and vegetables simultaneously within the same unit.  
         [0010]     According to one embodiment of the present invention, a refrigerated unit for preserving produce includes an insulated cabinet that includes a storage space. A chiller is operably associated with the storage space for removing heat from the storage space. A temperature control mechanism is operably associated with the chiller for controlling the chiller to regulate an air temperature within the storage space. A humidity control mechanism is operably associated with the storage space for regulating a relative humidity level within the storage space. An ethylene control mechanism is operably associated with the storage space for regulating a level of ethylene within the storage space.  
         [0011]     According to another embodiment of the present invention, a consumer-sized refrigerator includes a first compartment and a second compartment. A temperature control mechanism will maintain an air temperature in the first compartment at a substantially different level than an air temperature in the second compartment. A humidity control mechanism maintains a humidity level in the first compartment that is substantially different than a humidity level in the second compartment. An ethylene control mechanism may be provided to remove ethylene from said first compartment.  
         [0012]     According to another embodiment of the present invention, a method of preserving fresh produce includes providing an insulated cabinet having an enclosed storage space and placing fresh produce within the storage space. An air temperature within the storage space is maintained between forty and sixty-five degrees Fahrenheit by using an associated chiller. A humidity level within the storage space is regulated, and an ethylene level within the storage space is regulated.  
         [0013]     Accordingly, it is a primary object of the present invention to provide an improved household unit for storage of moderate temperature fruits and vegetables that optimizes storage conditions through the control of temperature, humidity level, and/or ethylene level.  
         [0014]     Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description in conjunction with the drawings, and from the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is partial side view of a refrigeration unit according to the present invention that includes a temperature control mechanism, a humidity level control mechanism, and an ethylene level control mechanism.  
         [0016]      FIG. 2  is a partial side view of a refrigeration unit according to the present invention that utilizes traditional cold control to regulate the temperature in the storage space, a passive open air container to provide humidity, and natural convection to provide ethylene removal.  
         [0017]      FIG. 3  is a partial side view of a refrigeration unit according to the present invention that utilizes an electronic temperature control system, a passive condensate system with a wick to aid in evaporation of water into the storage system to control humidity, and a filter to help remove ethylene from the storage space.  
         [0018]      FIG. 4  is partial side view of a refrigeration unit according to the present invention that utilizes an electronic temperature control system, a closed container with semi-permeable membrane to control humidity levels, and a forced air exchange to help remove ethylene from the storage space.  
         [0019]      FIG. 5  is a partial side view of a refrigeration unit according to the present invention that utilizes an electronic temperature control system, an ultrasonic oscillator to disperse water droplets into the air, and an ultraviolet light in combination with a photo catalyst to remove ethylene from the storage space.  
         [0020]      FIG. 6  is a partial side view of a refrigeration unit according to the present invention that utilizes an electronic temperature control system, a condensate water and wick system for maintaining humidity, and a controlled air exchange system for controlling ethylene levels in the storage space. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]     The present inventive produce preservation system is embodied in a refrigerated storage unit  10 .  FIG. 1  shows an embodiment of a storage unit  10  according to the present invention. The storage  10  includes an insulated cabinet  12  having a storage space  14 . A door  11  may be attached to the cabinet  12 , for example by hinges (not shown) to provide access to the storage space  14 . A contact seal or gasket (not shown) is provided along the periphery of the door  11  to provide an airtight, or nearly airtight, seal between the door  11  and the cabinet  12 . Support structures  16 , such as shelves or racks, may be provided within the storage space  14  to support fresh produce  18 , such as fruits and vegetables. A chiller  20  is used to refrigerate the storage space  14 . A temperature control mechanism  22  is used to control the chiller  20  and adjust the temperature within the storage space  14  to a desired temperature. Preferably the chiller  20  and temperature control mechanism  22  are suitable to maintain the temperature within the storage space at any temperature within the range of 40-65 degrees Fahrenheit. Those of ordinary skill in the art will understand that various devices and arrangements are available for controlling the temperature within storage space. Some of the preferred mechanisms are discussed in more detail below; however, the invention should not be limited to the preferred mechanisms discussed, and any arrangement that will effectively maintain the temperature within the storage space  14  in the desired range may be used.  
         [0022]     Still with reference to  FIG. 1 , a humidity level control mechanism  24  is provided to maintain the humidity level within the storage space  12  at a desired level. A relatively high humidity of 90% or more is ideal for extending the storage life of fruits and vegetables  18  without suffering deleterious effects from drying. However, it is preferred to keep the humidity level from approaching 100%, as that leads to excessive condensation which causes problems. Standing water can deteriorate the structure of the fruits and vegetables, and can provide a medium for bacteria to grow. Preferred humidity control mechanisms  24  are discussed in more detail below; however, the invention should not be limited to the preferred mechanisms discussed, and any arrangement that will effectively maintain the relative humidity in the desired range may be used.  
         [0023]     With further reference to  FIG. 1 , an ethylene removal mechanism  26  is provided with the storage unit  10  to regulate the amount of ethylene that remains in the storage space  14 . Ethylene gas is a natural byproduct from fruits and vegetables as they ripen. The ethylene also acts as a catalyst to further speed the ripening process of many fruits and vegetables when they are exposed to ethylene. Generally to extend the shelf life of fruits and vegetables, it is desired to remove ethylene from the storage space  14  in order to slow the ripening process. In certain instances it may be desirable to retain the maximum amount of ethylene within the storage space  14  in order to accelerate the ripening process for fruits and vegetables that need additional ripening to be ready to eat. Preferred ethylene removal mechanisms  26  are discussed in more detail below; however, the invention should not be limited to the preferred mechanisms discussed, and any arrangement that will effectively remove ethylene from the storage space  14  may be used.  
         [0024]     The storage space  14  may be subdivided into compartments  28  in order to vary the conditions within the storage  14  to be optimized for more than one type of fresh produce  18 . For example, if the storage space  14  is divided into a top compartment  28   t  and a bottom compartment  28   b , it would be possible to remove ethylene from the bottom compartment  28   b , in order to slow the ripening process for any produce  18  within that compartment, while simultaneously retaining the ethylene in the top compartment  28   t  in order to accelerate the ripening process within that compartment. Those of ordinary skill in the art will be aware of numerous options for compartmentalizing a refrigerated storage space  14 .  
         [0000]     Temperature Control Mechanisms  
         [0025]     As noted above, those of ordinary skill in the art should be aware of several temperature control mechanisms  22  that would be effective in regulating the temperature within the storage space  14  in the desired range.  FIG. 2  illustrates an embodiment of the present invention that utilizes a traditional “cold control” mechanism  30  to regulate the temperature within the storage space  14 . According to this cold control mechanism  30 , an adjustment mechanism  32 , such as a knob or slidable lever, is provided to set a desired level of cooling. The chiller  20  is attached to the adjustment mechanism  32 , and cycles on and off according to the setting. For a colder setting, the chiller  20  cycles on more often and/or for longer periods of time and/or at increased capacity. For a warmer setting, the chiller  20  cycles on less frequently and/or for shorter time periods and/or at decreased capacity. The adjustment mechanism can be adjusted up or down depending the desired temperature for the storage space. Alternatively, a thermostat may be provided to sense the temperature within the storage space  14 . The thermostat will turn the chiller on when the temperature in the storage space  14  is above a desired level, and will shut the chiller off when the temperature in the storage space is at an appropriate temperature.  
         [0026]      FIG. 3  illustrates an embodiment of the storage unit  10  that includes an electronic temperature control  31 . An electronic temperature control can be comprised of logic, power supply, power switching, temperature sensing, and user interface. Logic may duplicate a traditional cold control, or implement multiple inputs and outputs to control, temperature, relative humidity and/or ethylene level.  
         [0027]     Preferably the temperature control mechanism will be effective in maintaining a temperature within the storage space  14  within the range of 40-65 degrees Fahrenheit. Most preferably the temperature will be selectable within that range.  
         [0000]     Humidity Control Mechanisms  
         [0028]     Those of ordinary skill in the art should be aware of various mechanisms for controlling the humidity level within the storage space  14 . A humidity sensor may be incorporated into the humidity control mechanism. The mechanisms for controlling humidity can be categorized as passive, or active. One such passive mechanism is illustrated in  FIG. 2 . According to this mechanism, condensate water  33 , which is a natural byproduct from the chiller, is collected in a pan  34 , or other open container, at the bottom of the storage space  14 . The water  33  in the pan  34  will evaporate into the storage space  14  until it reaches an equilibrium when the air within the storage space is saturated. The pan  34  may incorporate an overflow drain with a trap to an evaporation means near the high side (compressor, condenser) of the refrigeration system. In this manner, the humidity within the storage space  14  is kept at a high level.  
         [0029]     Another passive mechanism for controlling humidity is shown in  FIG. 3 . According to this mechanism, condensate water  33  from the chiller  20  is collected with a wick  36 . The wick extends into the storage space  14 , and the water evaporates from the wick  36  into the storage space  14  to raise the humidity level in the storage space  14 . Preferably the wick  36  is made from an antimicrobial material to prevent the growth of potentially harmful mildew or other contaminants. The wick  36  has the advantage over the open pan  34  mechanism of increasing evaporation surface area within the storage space  14 .  
         [0030]     A third passive mechanism for regulating humidity levels is the use of a semi-permeable membrane  38 .  FIG. 4  illustrates such a mechanism. The membrane is placed in a location to have dry air passing over the exterior side of it to draw moisture through the membrane  38  when the humidity level gets too high. Aside from the membrane  38  the storage compartment  28   t  would be sealed. The cold air from the chiller  20  is on the exterior side of the membrane and is therefore generally dry air. The membrane  38  will allow a limited amount of moisture out of the compartment  28   t  to prevent excessive condensation, but will also prevent the compartment  28   t  from becoming too dry. A shape memory polymer laminated to fabric can form the semi-permeable membrane  38 . Such a product is commercially available under the name DIAPLEX, which is manufactured by Mitsubishi. A fan  46  may be provided in order to encourage the flow of dry air across the semi-permeable membrane and to enhance heat transfer.  
         [0031]     An active mechanism for controlling humidity is illustrated in  FIG. 5 . According this mechanism, an ultrasonic oscillator  40  is used to create a fog of tiny water droplets within the storage space  14 , or a compartment  28  within the storage space  14 , in order to maintain a high humidity level. The oscillator  40  may use condensate water  33 , or may be connected to an external water supply such as a water line  45 .  
         [0000]     Ethylene Removal Mechanisms  
         [0032]     As noted above, those of ordinary skill in the art will be aware of numerous mechanisms for removing ethylene from the storage space  14  in order to extend the shelf life of fruits and vegetables. An ethylene sensor may be incorporated into the ethylene regulating mechanism. Some of the preferred mechanisms are discussed hereafter.  
         [0033]     The first mechanism is shown in  FIG. 2 , and comprises openings  42  provided in the insulated cabinet  12  which permit a natural air flow through the storage space  14 . The flow of air through the storage space  14  will naturally remove the ethylene gas, and replace it with fresh air. Vent covers  43 , such as screens, mesh wire, or filters, may be used to cover the openings  42  in order to prevent dust, insects or other contaminants from entering the storage space  14  through the openings  42 .  
         [0034]     A second passive mechanism is shown in  FIG. 3 . According to this mechanism a filter  44 , is placed in the storage space  14  to filter the ethylene out of the air in the storage space  14 . The filter  44  may use activated carbon, peat, or similar material to clean the air. The filter media would require periodic replacement as it becomes saturated. Alternatively, potassium permanganate, which reacts with ethylene, may be used in the filter  44 . If potassium permanganate or similar consumer reagent is used, it will be necessary to resupply the reagent periodically as it is consumed. A stirring fan  45  may be provided to increase the flow of air into the filter  44 , and to prevent stratification of the air within the refrigerated compartment  28 .  
         [0035]      FIG. 4  shows an additional mechanism for removing ethylene from the storage space  14 . This mechanism is similar to that shown in  FIG. 2 , except that a fan  45  is used to force air flow into and/or out of the storage space  14 , instead of relying on natural convection to drive the air flow. This could be combined with the filter  44  discussed above. The fan  45  also circulates the air within the storage space  14  to prevent stratification. Baffling  51  may be provided to guide the air flow within the storage space  14 .  
         [0036]      FIG. 5  shows an ultraviolet (UV) light  48  used in conjunction with a photocatalyst  50  to degrade ethylene within the storage space  14 . Preferably the photocatalyst  50  is comprised of titanium dioxide coated glass tubes. When the ethylene is exposed to the UV radiation and the photocatalyst  50 , it oxidizes to form carbon dioxide and water. Advantageously, the photocatalyst  50  is not consumed in the reaction and does not need to replenished under normal conditions. A fan  45  mixes the air within the storage space  14  to prevent stratification and to make sure any ethylene in the storage space is brought in contact with the UV light  48  and catalyst  50 .  
         [0037]      FIG. 6  shows a controlled air exchange system that can be used to remove ethylene from the storage space  14 . This system utilizes a fan  46  to move air through the storage space  14  through openings  42 . Dampers  52  are provided to selectively control the air exchange. Dampers  52  can be opened to allow air flow into or out of unit to remove ethylene or closed to contain the ethylene in the unit. The fan  45  may be used to draw in external air as well as to mix the air in the storage space  14  to prevent stratification. The adjustment of the dampers  52  between open and closed positions may be manual or automatic. By providing a supply of fresh external air, and exhausting the internal air that contains ethylene, the ethylene level in the storage space  14  can be regulated.  
         [0038]     The various mechanisms for controlling temperature, humidity and ethylene levels may be combined in numerous combinations, and the invention should not be limited to the particular combinations described and illustrated herein.  
         [0039]     Presently preferred embodiments of the present invention and many of its improvements have been described with a degree of particularity. The previous description is of preferred examples for implementing the invention, and the scope of the invention should not necessarily be limited by this description.