Abstract:
A heat sealing device includes an insulated platen that protects heat sensitive lidding materials from sustaining heat damage. Generally, the platen is encased in an insulative material and houses an insulation plate within its perimeter. The insulative material and plate protect that portion of the lidding material that is external and internal to the seal area respectively. Thus, only that portion of the lidding material to be sealed to a tray is exposed to high temperatures.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/380,814, filed May 15, 2002. 
     
    
     
       BACKGROUND  
         [0002]    This invention relates generally to packaging for food products and specifically to heat-sealed packaging for food products.  
           [0003]    In retail food markets is common to see food products such as meat and poultry placed in a tray with a clear flexible material wrapped around the tray. This type of packaging however is prone to leakage. For example, liquid contents such as blood, juice or water may leak out of the package to soil the surrounding area.  
           [0004]    Generally, the clear flexible lidding material used in this type of packaging is a type of polyethylene, which is relatively low cost. However, polyethylene is heat sensitive and is not typically heat sealed to a performed tray.  
           [0005]    Other types of lidding material are available that withstand the heat-sealing process. However these types of lidding materials can be quite expensive.  
           [0006]    Thus, there is a need for a way to heat seal a low cost lidding material to preformed trays.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a sectional partial of a package according to some embodiments of the present invention;  
         [0008]    [0008]FIG. 2 is a sectional partial view of a heat sealing device according to some embodiments of the present invention; and  
         [0009]    [0009]FIG. 3 is a sectional view of a heat sealing system that utilizes the heat sealing device of FIG. 2. 
     
    
     DETAILED DESCRIPTION  
       [0010]    Referring to FIG. 1, a completed food package includes a food item  6  that is situated in a preformed tray  2  with lidding material  1  heat-sealed  5  thereto. The tray  2  may include a base  3  and a layer  4 . The base  3  may be a conventional base made from materials such as plastic or paperboard. Likewise, the layer  4  may be made from a material such as polyethylene that coats or is laminated to the base  3 . The food item  6  may be any food item including perishable foods such as meat or poultry.  
         [0011]    According to some embodiments of the present invention, the lidding material  1  may be a sheet of thin flexible polyethylene. The polyethylene may be an unsupported polyethylene such as Clysar®, which is produced by DuPont Packaging and Industrial Polymers (Wilmington, Del.). Alternately, the polyethylene may be an irradiated polyethylene material available from SYFAN U.S.A. (9900 Stirling Road, Suite 302, Cooper City, Fla. 33024) or from Cryovac, a division of Sealed Air Corp. (Duncan, S.C.). The polyethylene material that forms the lidding  1  and the polyethylene material that forms the layer  4  are heat seal compatible.  
         [0012]    Generally, the lidding material  1  is positioned over the tray  2  so that a portion of the material  1  comes in contact with a flange on the tray  2 . Thereafter, a heat seal  5  is created between the lidding material  1  and the flange. The heat sealing of the lidding material  1  to the tray  2  is described in more detail below.  
         [0013]    Referring to FIG. 2, in some embodiments of the present invention a heat sealing device may include a sealing platen  7 , an insulator  10  and an insulation plate  8 . The insulator  10  is attached to and encases the platen  7  whereas the insulation plate  8  is housed within the interior of the platen  7 . One or more heating elements  19  such as an electric heating element are situated within the body of the platen  7 . The heating element  19  heats the platen  7  in a conventional manner. Generally, the heating element  19  heats the platen  7  to a temperature that is high enough to seal the lidding material  1  to the tray  2 . In some embodiments, the platen  7  may be coated with a non-stick material such as Teflon® (DuPont Teflon®, Barley Mill Plaza 10-2357, Wilmington, Del. 19880-0010).  
         [0014]    The insulator  10  may be fabricated from a material such as high temperature silicon rubber, ceramic, syntactic foam or other insulating materials. Similarly, the plate  8  may also be fabricated from an insulating material such as high temperature silicon rubber, ceramic, syntactic foam or other insulating materials. Generally, the insulating properties of the insulator  10  and insulation plate  8  may prevent heat from damaging the susceptible heat sensitive lidding material  1 .  
         [0015]    The insulation plate  8  may have a contoured side and a non-contoured side that are opposed. The contoured side may complement the general shape of the food item that is being packaged. For example, in the case of packaging a cut of meat, the plate  8  may be concave to complement that portion of the meat that extends above the tray  2 .  
         [0016]    In some embodiments of the present invention, a carrier plate  9  may be utilized to couple the insulation plate  8  to the platen  7 . For example, the insulation plate  8  may be vulcanized, glued or laminated to the carrier plate  9 . Thereafter, a plurality of bolts  13  may attach the plates  8  and  9  to the platen  7 . Generally, the bolts  13  extend downwardly through the platen  7  and the carrier plate  9  to attach the plates  8  and  9  to the platen  7 .  
         [0017]    In some embodiments, there may be a void area  11  between the platen  7  and the carrier plate  9 . The void area  11  may be created by insulating spacers  12  that are disposed between the platen  7  and the carrier plate  9 . Further, the bolts  13  may secure the spacers  12  between the platen  7  and the carrier plate  9 .  
         [0018]    The insulation plate  8  and carrier plate  9  may include air ventilation holes  14 . The holes  14  may prevent air from becoming entrapped during heat-sealing. For examples, air that may otherwise be trapped between the plate  8  and the lidding  1  may pass through holes  14  to the void area  11 .  
         [0019]    In some embodiments, a drive shaft  18  may be connected to an air cylinder  24  (FIG. 3) to drive the movement of the insulated platen  7 . However, other embodiments may employ any suitable means for powering the movement of the shaft  18 . In particular, the end of the drive shaft  18  that is proximate to the platen  7  is connected to a swivel or ball foot  17 . The foot  17  is connected to a mounting block  16 , which is connected to the top of the platen  7 . In this way, the platen  7  may be lowered to contact the lidding material  1  during the heat-sealing process. Further, one or more guide shafts  15  may be utilized to position the platen  7  over the lidding  1  and tray  2 .  
         [0020]    Referring to FIG. 3, a sealing station  25  may include an upper  23  and a lower housing  22 . The insulated platen  7  is situated within the upper housing  23 . Generally, the sealing station  25  is part of a tray sealing machine (not shown). Examples of suitable tray sealing machines include World Class Packaging Machines&#39;, INPACK Packaging Systems (Ross Industries, Inc., 5321 Midland Road, Midland, Va. 22728) or Reiser&#39;s INPACK Tray Sealing System (Robert Reiser &amp; Co. Inc., 725 Dedham St., Canton, Mass. 02021). However, some embodiments of the sealing device/sealing station  25  may be adapted for use in in-line Form/Fill/Seal machines.  
         [0021]    Before creating a seal, a tray  2  filled with food product  6  is placed into a tray support carrier  21 . The carrier  21  transports the tray  2  to a specific location within the sealing station  25 . However, in some embodiments, the tray  2  may be delivered to the sealing station  25  by other means. While within the sealing station  25 , the lidding material  1  is placed over the carrier  21 . Typically, the lidding material  1  is of a width sufficient to cover the entire carrier  21 . Transport of the lidding material  1  to the sealing station  25  may be by known means.  
         [0022]    After the tray  2  and the lidding material  1  are properly positioned, the lower housing  22  is raised. Raising the housing  22  lifts the tray carrier  21  into contact with the upper housing  23  thereby clamping the lidding material  1  between the carrier  21  and the upper housing  23 . The heated platen  7  may then be powered downward to have pressured contact with the lidding material  1  thereby creating a heat seal  5  between the lidding material  1  and the flange on the tray  2 .  
         [0023]    The insulator  10  that surrounds the platen  7  protects that portion of the heat sensitive lidding material  1  external to the seal  5  from the elevated temperature of the platen  7 . For example, the insulator  10  may protect the lidding material  1  between the housing  23  and the platen  7 . Likewise, the insulation plate  8  protects that portion of the lidding material  1  that is internal to the seal  5 . For example, the plate  8  protects the lidding material  1  over the food product  6  from heat produced by the platen  7 .  
         [0024]    Air trapped between the insulation plate  8  and the lidding material  1  may have a negative effect on the quality of the seal  5 . Thus, the air ventilation holes  14  through the plates  8  and  9  have been provided to allow for the escape of air into the void area  11 .  
         [0025]    After the lidding material  1  is sealed to the tray  2 , the heated platen  7  is raised to its original position and the lower housing  22  is retracted. In some embodiments, when the lower housing  22  is retracted, the tray carrier  21  may be lowered as well. Thereafter, the tray  2  containing the sealed in food product  6  may be transported to the next station in the packaging machine. In some embodiments the next station that the carrier  21  visits includes a lidding severing device (not shown) that cuts the lidding around the periphery of the tray  2 . In other embodiments, the lidding severing device may be within the sealing station, which is known as “cut in place”.  
         [0026]    While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.