Microwavable container having active microwave energy heating elements for combined bulk and surface heating

• US 6,150,646 A
• Filed: 06/24/1999
• Issued: 11/21/2000
• Est. Priority Date: 08/26/1996
• Status: Expired due to Term

• Current Assignee: Graphic Packaging International LLC (Graphic Packaging International Incorporated)
• Original Assignee: Graphic Packaging Corporation (Graphic Packaging International Incorporated)
• Inventors: Lai, Laurence, Zeng, Neilson
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US09/242,893
• Time in Patent Office: 516 Days
• Field of Search: 219/728, 219/729, 219/735, 219/730, 219/734, 219/759, 426/107, 426/234, 426/243, 99/DIG. 14
• US Class Current: 219/728
• CPC Class Codes: B65D 2581/344 Geometry or shape factors influencing the microwave heating properties
• CPC Class Codes: B65D 2581/3452 Packages having a plurality of microwave reactive layers, i.e. multiple or overlapping microwave reactive layers
• CPC Class Codes: B65D 2581/3489 Microwave reflector, i.e. microwave shield B65D2581/3487 takes precedence
• CPC Class Codes: B65D 2581/3494 Microwave susceptor B65D2581/3487 takes precedence
• CPC Class Codes: B65D 77/042 the inner container being of polygonal cross-section formed by folding or erecting one or more blanks, e.g. carton
• CPC Class Codes: B65D 81/3453 Rigid containers, e.g. trays, bottles, boxes, cups
• CPC Class Codes: Y10S 99/14 Induction heating

Abstract

A microwavable container includes an outer sleeve (12) and an inner tray (14) within the sleeve designed to carry a food product. A first active microwave energy heating element (28) is on the sleeve and disposed opposite the tray. A second active microwave energy heating element (74-102) is within the tray. The second microwave energy heating element has patterns of microwave energy interactive material on the bottom (60) and side walls (62) of the tray configured to permit a controlled degree of penetration of incident microwave energy through the bottom wall to channel microwave energy towards a central region of the tray and to promote browning of a food product carried by the tray about its periphery.

Claims

1. A microwavable container comprising:

an outer sleeve;

an inner tray within said sleeve, said inner tray having a bottom wall and at least one upstanding side wall about the periphery of said bottom wall;

a first active microwave energy heating element within said sleeve, said first active microwave energy beating element disposed opposite a food product carried by said tray; and

a second active microwave energy heating element on said tray, said second active microwave energy heating element having patterns of microwave energy interactive material on said bottom and side walls, wherein said first and second active microwave energy heating elements cooperatively control transmission of incident microwave energy towards a central region of said food product, while promoting browning of an outer surface of said food product.

2. A microwavable container as defined in claim 1 wherein the microwave energy interactive material on said side walls has a plurality of slots formed therein.

3. A microwavable container as defined in claim 2 wherein the slots adjacent the corners of said tray are curved to enhance browning of the food product in the corner regions of said tray.

4. A microwavable container as defined in claim 3 wherein opposed ends of at least some of said slots are bulbous.

5. A microwavable container as defined in claim 4 further comprising at least one layer of suscepting material on said at least one upstanding side wall and overlying said microwave energy interactive material.

6. A microwavable container as defined in claim 5 further comprising at least one layer of suscepting material on said bottom wall and overlying said microwave energy interactive material.

7. A microwavable container as defined in claim 2 wherein said elongate slots are arranged in rows.

8. A microwavable container as defined in claim 7 wherein said rows of slots are staggered.

9. A microwavable container as defined in claim 8 further comprising at least one layer of suscepting material on said at least one upstanding side wall and overlying said microwave energy interactive material.

10. A microwavable container as defined in claim 9 further comprising at least one layer of suscepting material on said bottom wall and overlying said microwave energy interactive material.

11. A microwavable container as defined in claim 1 wherein said pattern of microwave energy interactive material on said bottom wall includes at least one meandering loop.

12. A microwavable container as defined in claim 11 wherein the length of said at least one meandering loop is approximately equal to an integer multiple of the effective wavelength of the incident microwave energy.

13. A microwavable container as defined in claim 12 wherein said pattern of microwave energy interactive material on said bottom wall further includes a ring about the peripheral edge of said bottom wall and wherein said at least one meandering loop is open, said loop being coupled to said ring by bridges.

14. A microwavable container as defined in claim 13 wherein said pattern of microwave energy interactive material on said bottom wall further includes a plurality of spaced loops and islands.

15. A microwavable container as defined in claim 1 wherein said first active microwave energy heating element includes a pattern of microwave energy interactive material, said pattern including a ring about the periphery of said microwave energy heating element and defining a centrally located aperture.

16. A microwavable container as defined in claim 15 wherein said pattern of microwave energy interactive material further includes an array of microwave energy interactive elements within said aperture.

17. A microwavable container as defined in claim 16 wherein said microwave energy interactive elements are in the form of circular or hexagonal islands.

18. A microwavable container as defined in claim 16 wherein said microwave energy interactive elements are in the form of loops, each of said loops surrounding an island.

19. A microwavable container as defined in claim 1 wherein said pattern of microwave energy interactive material on said bottom wall includes a peripheral ring and centrally positioned, concentric octagonal rings coupled to said peripheral ring by bridges.

20. A microwavable container as defined in claim 19 wherein said concentric octagonal rings are coupled by pairs of diverging bridges.

21. A tray for a microwavable container comprising:

a bottom wall;

at least one upstanding side wall about a periphery of said bottom wall; and

an active microwave energy heating element within said tray, said active microwave energy heating element having patterns of microwave energy interactive material on the bottom wall and the at least one upstanding side wall of said tray, said patterns configured to control transmission of incident microwave energy towards a central region of a food product carried by said tray, and further configured to brown an outer surface of said food product, wherein said pattern of microwave energy interactive material on said bottom wall includes at least one meandering loop, the length of which is approximately equal to an integer multiple of the effective wavelength of the incident microwave energy.

22. A microwavable container as defined in claim 21 wherein said pattern of microwave energy interactive material on said bottom wall further includes a ring about the peripheral edge of said bottom wall and wherein said at least one meandering loop is open, said loop being coupled to said ring by bridges.

23. A microwavable container as defined in claim 21 wherein said pattern of microwave energy interactive material on said bottom wall further includes a plurality of spaced loops and islands.

24. A microwavable container as defined in claim 21 wherein the microwave energy interactive material on said side walls has a plurality of slots formed therein.

25. A microwavable container as defined in claim 24 wherein the slots adjacent the corners of said tray are curved to enhance browning of said food product in the corner regions of said tray.

26. A microwavable container as defined in claim 25 wherein opposed ends of at least some of said slots are bulbous.

27. A microwavable container as defined in claim 26 further comprising at least one layer of suscepting material on said at least one upstanding side wall and overlying said microwave energy interactive material.

28. A microwavable container as defined in claim 27 further comprising at least one layer of suscepting material on said bottom wall and overlying said microwave energy interactive material.

29. An active microwave energy heating insert to be placed under a microwavable container comprising:

a substrate; and

an active microwave energy heating element on an upper surface of said substrate, said active microwave energy heating element including a pattern of microwave energy interactive material, said pattern configured to control transmission of incident microwave energy towards a central region of a microwavable container supported on said insert, wherein said pattern of microwave energy interactive material includes at least one meandering loop, the length of which is approximately equal to an integer multiple of the effective wavelength of the incident microwave energy.

30. An active microwave energy heating insert as defined in claim 29 wherein said pattern of microwave energy interactive material further includes a ring about the peripheral edge of said substrate and wherein said at least one meandering loop is open, said loop being coupled to said ring by bridges.

31. An active microwave energy heating insert as defined in claim 29 further comprising at least one layer of suscepting material on said substrate and overlying said microwave energy interactive material.