Abstract:
An improved package comprising a self-venting mechanism that provides an indication of high temperature venting. The package includes a fin seal with an aperture positioned in the fin seal to act as a vent when the package and its contents are heated in a microwave oven. The pressure in the package is vented by allowing steam to escape through the aperture upon partial separation of the fin seal up to the aperture.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Currently there are many types of packages in which food is purchased. It is often desirable to be able to heat and/or cook food in the same packaging in which it is purchased. This can prove challenging when the method of heating employs a microwave oven. When food is heated in a substantially closed container in a microwave oven, pressure builds within the package due to the production of steam. It is therefore advantageous to have a package that provides a mechanism that will allow the release of steam from the package to avoid rupturing the package. 
         [0002]    Packages exist that allow heating and/or cooking of the food within the package in a microwave oven through the use of a vent. The most common of these packages are microwaveable popcorn packages. Typically, the microwaveable popcorn package has a preformed steam vent which has an opening at the same position where the package is to be opened once the popcorn is popped. This results in the consumer experiencing hot steam coming out from inside the package as the consumer opens the package. 
         [0003]    Another type of package exists that employs a standard side seal on a microwaveable flexible pouch. Such a package is described in US Published Patent Application 2005/0276885. Once the side seal is formed in the pouch, an aperture is formed through the panels that make up the side seal. The aperture is to perform as a steam vent with the seal separating up to the aperture as steam pressure builds up in the package. The aperture also doubles as a way of hanging the pouch on a hanger or store display. However, it has been found that this seal with the aperture ruptures past the seal during microwave heating in a fin seal type package. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention includes a package for containing food and heating food in a microwave oven. The package includes a fin seal, wherein the fin seal has an aperture positioned to act as a vent when the package and its contents are heated in a microwave oven. The aperture provides a reliable venting location so the user is alerted as to which portion of the packaging may expose the user to escaping high temperature steam. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of a package of the present invention. 
           [0006]      FIG. 2  is a perspective view of a step of producing the package of the present invention. 
           [0007]      FIG. 3  is perspective view of the subsequent steps of producing the package of the present invention. 
           [0008]      FIG. 4  is a perspective view of still a further step of the process of making the package of the present invention. 
           [0009]      FIG. 5  is a perspective view of still another step of the process of making the package of the present invention. 
           [0010]      FIG. 6  is a perspective view illustrating the package in a microwave oven. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0011]    A venting mechanism for a microwaveable flexible package is generally illustrated at  10  in  FIG. 1 . The package of this invention includes a safety vent mechanism  12  positioned in a fin seal  14 . The safety vent mechanism  12  is identified by indicia  16  which inform the user where hot steam is being vented from the package  10 . Positioning the vent in the fin seal  14  eliminates rupturing of the package  12  during microwaving of the food as further explained herein. 
         [0012]    The package  12  in most aspects is a typical food package suitable for cooking food in a microwave. The package is made from a continuous sheet  13  of flexible polymeric film as illustrated in  FIG. 2  that is moving in the general direction of arrow  15 . Typically, such packaging is made of multi-layered polymeric films with some layers acting as oxygen barriers, while others, especially the interior layer acting as an adhesive layer to form the package. 
         [0013]    For purposes of this application, the fin seal  14  is a seal that is formed by placing edge sections  22  and  24  of the sheet  13  on each other as the sheet  13  moves in the direction of arrow  15 . The edge sections  22  and  24  are adhesively secured to each other using a conventional process that is well known. In doing so, the package  10  is sealed along the edge sections  22  and  24  to form a “fin” seal. The methods used to seal edge portions  22  and  24  include heat, ultrasonic or adhesive sealing techniques or any combination thereof. 
         [0014]    Once the fin seal is formed, the film moving in the general direction of arrow  15  is folded to form folded edges  17  and  19  which then define opposing walls  18  and  20  of the package. The fin seal  12  generally lies flat adjacent the wall  18 . 
         [0015]    As further illustrated in  FIG. 4 , a vent hole  11  is formed in the fin seal  12  (which is illustrated in a vertical position). Once the vent hole  11  is formed, the film  13  is then sealed and cut to form a sealed bottom edge  21 . Preferably, the vent hole is formed by a cutting action that does not seal the edges of the vent hole. Hot needle punching will for example seal the edges of the vent hole (melt the edges of the polymer layer or layers in addition to the sealing layer) which may stop the steam from escaping through the vent hole. A mechanical punching mechanism or other mechanism which cuts through the two layers of film  13  without the use of heat and/or does not seal the edges of the vent hole will permit steam to escape through the vent hole. 
         [0016]    The top edge of the package  23  remains in an open position and will be sealed once the package is filled with food, such as vegetables. 
         [0017]    The seal  12  is formed such that once steam is created during the microwaving process, and sufficient pressure is built up within the package, the fin seal will start to separate. The fin seal will start to separate until the separation reaches the vent hole  28 . Once the separation of the fin seal reaches the vent hole  28 , steam is released from the package. 
         [0018]    Since the integrity of the fin seal is not compromised during microwave heating, the contents of the package stay within. In this way, the food being microwaved within the package does not escape the package. Due to the indicia warning of the location of the vent, the user of the microwave package knows where on the package that the steam is being vented, and can then avoid the hot steam coming out of the package. 
         [0019]    In use, the package  10  containing food to be heated is placed in a microwave oven  30  as illustrated in  FIG. 6 . The package is placed with the fin seal facing upwardly. The wall  18  faces towards the top of the oven  13 . When the package is heated, the water that is within the food or within the package is heated and vaporizes to form steam. The steam then builds pressure within the package. As the pressure inside the package increases, the fin seal weakens and separates until it reaches the vent hole  11 . Once the separation reaches the vent hole  11 , steam is released through the vent hole. 
         [0020]    In a preferred embodiment of this invention, the fin seal  14  is about 12 mm wide and extends the entire length of one side of the package  10 . The vent hole  11  should be of a size sufficient to allow steam to be released to eliminate further pressure building within the package. In a preferred embodiment, the vent hole  11  is circular in shape but other shapes are within the scope of this invention. Vent hole sizes ranging from 1.6 mm to 6.0 mm in diameter produced the best results. 
         [0021]    To a certain extent, the rate of steam production within the package will be a function of the moisture content of the food product within. In view of this, the vent hole diameter may have to be adjusted to accommodate the amount of steam being produced and being vented during microwaving. 
         [0022]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.