Abstract:
A display assembly for containing and displaying perishable products includes a case having at least one wall and defining an internal volume, a quantity of gas contained in the case, the gas including ethylene emitted from the perishable products, and an electro hydrodynamic thrust device positioned in the case. The electro hydrodynamic thrust device ionizes a portion of the quantity of gas. The ionized gas includes at least one reactive oxygen species, and the at least one reactive oxygen species reacts with the ethylene to break down the ethylene.

Description:
BACKGROUND 
     The present invention relates to preserving perishable products in a display case. 
     SUMMARY 
     In one embodiment, the invention provides a display assembly for containing and displaying perishable products. The display assembly includes a case having at least one wall and defining an internal volume, a quantity of gas contained in the case, the gas including ethylene emitted from the perishable products, and an electro hydrodynamic thrust device positioned in the case. The electro hydrodynamic thrust device ionizes a portion of the quantity of gas. The ionized gas includes at least one reactive oxygen species, and the at least one reactive oxygen species reacts with the ethylene to break down the ethylene. 
     In another embodiment the invention provides a method of retrofitting a display case for displaying perishable food. The method includes inserting an electro hydrodynamic thrust device into the display case, connecting the electro hydrodynamic thrust device to a power source, and creating an ion wind with the electro hydrodynamic thrust device. The method further includes moving air through the electro hydrodynamic thrust device with the ion wind, ionizing the air in response to reacting the air with the ion wind, and creating reactive oxygen species in response to ionizing the air. The method further includes directing the reactive oxygen species into the display case with the thrust of the ion wind, sanitizing at least one surface in the display case with reactive oxygen species, and reacting ethylene with the reactive oxygen species to break down the ethylene in the display case, thereby reducing the quantity of ethylene in the display case. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a display case for supporting perishable products according to some aspects of the present invention. 
         FIG. 2  is an end view of an electro hydrodynamic thruster according to some embodiments of the present invention. 
         FIG. 3  is a cross-sectional view of the electro hydrodynamic thruster taken alone line  3 - 3  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates a display assembly  10  including a display case  12  that includes a back wall  14 , a bottom wall  16 , and a cover  18  that are supported on legs  20 . The display case  12  has an internal volume that extends between the back wall  14 , the bottom wall  16  and the cover  18 . The illustrated display case  12  includes two shelves  22   a ,  22   b  each of which include at least one basket  24   a ,  24   b  for containing and displaying perishable goods, such as flowers. In another embodiment, the baskets  24   a ,  24   b  are omitted and produce (such as fruits and vegetables) are displayed on the shelves  22   a ,  22   b . The cover  18  (typically made of clear glass) is moveable with respect to at least one of the back wall  14  and the bottom wall  16  to permit a user to access the perishable goods. In other constructions, no glass cover is used and the case has an open front and top to provide uninhibited access to the products within the case. Some cases have an open front and are closed on the top and at least some of the sides, whereas other cases have an open top and are closed some or all of the sides. In further constructions, the front and sides of the case are open and the top and back are closed. In still other constructions, the front, sides and top are open and only the back is closed. 
     Perishable goods often emit gasses as they are flowering (in the case of flowers) or ripening (in the case of produce). One such gas that is often produced is Ethylene. These gasses often speed up the flowering or the ripening and thus, shorten the shelf-life of the perishable goods. Further, produce often has some bacteria growing on at least one of its surfaces. The bacteria will multiply on the produce as well as on the shelves  22   a ,  22   b , even in a refrigerated atmosphere, and especially in the non-refrigerated embodiment shown in  FIG. 1 . The bacteria often shorten the shelf-life of the perishable goods. 
     The display assembly  10  further includes at least one electro hydrodynamic (EHD) thruster  30 . One such EHD device is described in U.S. Pat. No. 2,765,975 (hereinafter “U.S. Pat. No. 2,765,975”). This EHD device utilizes small wires spaced along a chamber. The small wires are connected to a positive voltage source which ionizes the molecules in close proximity to the charged wires. The voltage in the small wires and the ionized molecules create an ion wind which moves air through the chamber. In contrast to fans and other air-moving devices, the generated ion wind moves the air through the chamber without creating much if any noise. 
     One major difference between the present invention and the EDH of U.S. Pat. No. 2,765,975 is that the EHD of U.S. Pat. No. 2,765,975 includes a duct element  30  with ion neutralizing grids  34  that neutralize air prior to exiting the outlet orifice  32  (see col. 2, lines 57-69, FIG. 1). However, the present invention would omit such neutralizing elements because the ions are utilized to generate reactive oxygen species (ROS) such as atomic oxygen (O), ozone (O 3 ), hydroxyl (OH), and reactive nitrogen species (RNS) such as nitric oxide (NO), nitrogen dioxide (NO 2 ), etc. The ROS and RNS are created in quantities suitable to kill microorganisms on the perishable goods and within the display case  10  and to neutralize the ethylene produced by the perishable goods. If the ROS and RNS are created in greater quantities, the ROS and RNS may start to react with the perishable goods and thus, shorten the life of the perishable goods. Alternatively, if the ROS or RNS are created in lesser quantities, the microorganisms would multiply substantially unchecked and the ethylene would be allowed to accumulate, thus shortening the life of the perishable goods. 
     Another major difference between the present invention and the EDH of U.S. Pat. No. 2,765,975 is that the EHD of U.S. Pat. No. 2,765,975 moves neutralized air at a substantial velocity and is used in place of a fan. In contrast, the present invention moves air with ROS and RNS at a relatively slow velocity to permit the ROS and RNS to have elongated contact with the perishable goods. If the air moves too quickly, the ROS and RNS do not have time to react with the ethylene and kill the microorganisms on the perishable goods and in the display case  10 . 
     As shown in  FIG. 1 , the EHD  30  moves air as described above and directs the air along an air flow path designated by arrows  36 . The air flow path defines an air curtain over the products within the display area. The air is discharged into the display space from the top through a discharge outlet and the air exits the display space at the bottom from of the case through a return inlet. From the return inlet, the air is recirculated through the EHD  30 . Alternatively, the air can flow in the opposite direction around the display case  10 . A plurality of EHD  30  units can be positioned along the bottom of the display case  10  or an elongate EHD  30  unit can extend along substantially an entire width of the display case  10 . 
     An alternative construction for an EHD thruster  130  is shown in  FIGS. 2 and 3 . The EHD thruster  130  includes a first insulating tube  132 , an ion collector  134 , a second insulating tube  136 , a corona wire  138 , and an inner tube  140 . An air space  142  is defined between the second insulating tube  136  and the corona wire  138 . Air flows in an air inlet  144  and out an air outlet  146 . A plurality of spacers  148  are placed in the EHD thruster  130  between the second insulating tube  136  and the corona wire  138  to maintain the desired air space  142 . At least one of the corona wire  138  and inner tube  140  can have a spiral design, and thus are easily adapted to different length EHD thrusters  130  because of the spiral design. The corona wire  138  and inner tube  140  can easily be removed from the outer insulating tube  132  for cleaning or replacement. 
     A power source  150 , such as an electrical outlet or a battery, is connected to the EHD thruster  130  near the air inlet  144  and is connected to at least one of the ion collector  134  and the corona wire  138  to power the EHD thruster  130 . 
     In operation, the EHD thruster  130  can be inserted into a display case, such as the display case  10  of  FIG. 1  and can be powered by an electrical outlet or a battery to create a charge near the air inlet  144  and thereby move air through the EHD thruster  130  without requiring the use of any moving parts (e.g., a fan or blower). 
     The EHD thruster  30 ,  130  produces ROS and RNS and moves the ROS and RNS along a flow path in the display case by means of an ion wind. The ROS and RNS react with at least some of the ethylene and kill at least some of the microorganisms on the perishable goods and in the display case. The EHD thruster lengthens the shelf life of the perishable goods without or without the use of refrigeration. 
     In embodiments that utilize an evaporator coil of a refrigeration unit, one or more fans of the refrigeration unit can passively or actively move air through the EHD thruster. For example, the one or more fans can directly move air though the EHD thruster, or can create a small vacuum to draw air into or out of the EHD thruster. In other embodiments, the refrigeration unit can omit any fan or blower and can rely on the ion wind created by the EHD thruster to move air through the evaporator coil. 
     Various features and advantages of the invention are set forth in the following claims.