Method of distributing heat in food containers adapted for microwave cooking and novel container structure

• US 5,338,921 A
• Filed: 02/16/1993
• Issued: 08/16/1994
• Est. Priority Date: 02/16/1993
• Status: Expired due to Term

• Current Assignee: Graphic Packaging International LLC (Graphic Packaging International Incorporated)
• Original Assignee: Universal Packaging LLC
• Inventors: Tomich, Robert, Maheux, David
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US08/017,808
• Time in Patent Office: 546 Days
• Field of Search: 219/10.55 E, 219/10.55 F, 219/728, 219/730, 219/759, 426/107, 426/109, 426/111, 426/113, 426/234, 426/241, 426/243, 99/DIG. 14, 156/272.2, 156/158, 156/163, 156/164
• US Class Current: 219/730
• CPC Class Codes: B65D 2581/3455 Packages having means for improving the internal circulation of air
• CPC Class Codes: B65D 2581/3466 Microwave reactive material applied by vacuum, sputter or vapor deposition
• CPC Class Codes: B65D 2581/3472 Aluminium or compounds thereof
• CPC Class Codes: B65D 2581/3494 Microwave susceptor B65D2581/3487 takes precedence
• CPC Class Codes: B65D 81/3453 Rigid containers, e.g. trays, bottles, boxes, cups
• CPC Class Codes: Y10S 99/14 Induction heating

Abstract

An improved technique for uniformly distributing crisping or browning heat supplementation in disposable paper food carton or containers and the like used for microwave cooking, in which a metallized susceptor film is employed mounted to but intermediately spaced from the adjacent inner wall of the container to define and seal an air pocket which, in heating, improves the uniformity of the browning result through convection into air pocket and responsive flexing of the film.

Claims

1. A method of uniformly distributing the heat generated by microwave interaction with a thin, flexible and non-self-supporting metallized film carried adjacent and co-extending over a substantial area of an inner wall of a disposable container for food to be exposed to microwave energy, as in an oven, that comprises, adhering the periphery of said metallized film to said wall peripherally to mount the film with substantially its major intermediate area loosely and flexibly spaced from said wall to define an air pocket between the film and said wall, and exposing the container with food therein to microwave-interacting heat generated along the metallized film, as it flexes in response to such convection, more uniformly to heat, crisp and/or brown the food in the container.

2. A method as claimed in claim 1 and in which the adhering is effected by heat-sealing a border of the film to the container wall.

3. A method as claimed in claim 1 and in which the adhering is effected by adhesively securing a border of the film to the container wall.

4. A method as claimed in claim 3 and in which the metallized film is laminated to a backing sheet and the border of the backing sheet is adhesively secured to the container wall.

5. A method as claimed in claim 1 and in which the metallized film comprises a plastic sheet having a metallized layer.

6. A method as claimed in claim 1 and in which the metallized film comprises a composite of a metal layer laminated to a backing sheet.

7. A method as claimed in claim 1 and in which the air pocket is totally sealed between the film and said wall.

8. A method as claimed in claim 1 and in which the metallized film comprises an insulating carrier that, together with the container wall, insulates the sealed air pocket.

9. A method of uniformly distributing the heat generated by microwave interaction with a thin, flexible and non-self-supporting metallized film carried adjacent and co-extending over a substantial area of an inner wall of a disposable container for food to be exposed to microwave energy, as in an oven, that comprises, adhering a limited region of said metallized film to said wall to mount the film with substantially its major intermediate area loosely and flexibly spaced from said wall to define an air pocket between the film and said wall, and exposing the container with food therein to microwave-interacting heat generated along the metallized film, as it flexes in responses to such convection, more uniformly to heat, crisp and/or brown the food in the container.

10. A method as claimed in claim 9 and in which said adhering is effected over a plurality of limited regions to provide a plurality of said air pockets over the film.

11. A method of uniformly distributing the heat generated by microwave interaction with a thin, flexible metallized plastic film carried along a co-extensive wall of a container for food to be exposed to microwave energy, as in a oven, that comprises, adhering said metallized plastic film to only limited regions of said wall to mount the film thereon loosely and flexibly with intermediate air pocket (s) between the adhering regions of the film and said wall, and exposing the container with food therein to microwave energy simultaneously to heat the air in said pocket(s) and cause convection-spreading of the microwave-interacting heat generated along the metallized film, as it flexes in response to such convection, more uniformly to heat, crisp and/or brown the food.

12. In a container for food to be exposed to microwave energy, as in an oven, the combination of a thin, flexible metallized plastic film;

a container wall co-extensive with the film throughout its extent and means for adhering the periphery of the film to and closely adjacent the container wall while maintaining substantially the major intermediate area of the film loosely and flexibly spaced from though adjacent said wall throughout the film to define an included air pocket between the film and said wall.

13. A container as claimed in claim 12 and in which the adhering means comprises a border heat-sealed to said wall.

14. A container as claimed in claim 13 and in which said border is offset from the edges of the sheet.

15. A container as claimed in claim 12 and in which the adhering means comprises an adhesive border.

16. A container as claimed in claim 15 and in which the film is laminated to a backing sheet and the adhesive border is provided peripherally of the backing sheet.

17. A container as claimed in claim 12 and in which the container walls are formed of coated paper stock, the plastic film is a polyester sheet, and the metallizing of the film is by one or more thin metal layer(s).

18. A container as claimed in claim 12 and in which the said container wall is the inner wall of the container cover.

19. A container as claimed in claim 18 and in which the area of the metallized film is a substantial portion of the area of the said inner wall of the container cover and corresponds to the top surface of the food-to-be-cooked.

20. In a disposable foldable-wall container for food to be exposed to microwave energy, as in an oven, the combination of a thin, flexible metallized layer, a container wall co-extensive with and adjacent the layer throughout its extent, and means adhering limited regions only of the layer to the inner surface of the container wall, while maintaining the substantially major intermediate area of the layer loosely and flexible spaced from though adjacent said wall throughout the layer to define an included air pocket(s) between the layer and said wall.

21. A method of forming a disposable foldable-wall container for food to be exposed to microwave energy, as in an oven, that comprises, forming paper stock container blanks and feeding the same successively along a belt with the portion of each blank forming an inner surface of a container wall and successively passing a predetermined region;

feeding a thin, flexible, non-self-supporting metallized film to a vacuum-holding station disposed above said predetermined region;

providing heatable means shaped to define the periphery of the successive container walls of successive container blanks passing said region;

overlaying said successive sections of the film upon the corresponding inner surfaces of the container walls, while activating said heatable means to heat-seal the film sections along their peripheries to the corresponding inner walls of the successive container blanks to define and seal air pockets between the respective film sections and the corresponding container blank walls.

22. A method as claimed in claim 21 and in which a peripheral adhesive boarder is applied to the container blank inner wall before heat-sealing the film to such border.