Patent Publication Number: US-2009223951-A1

Title: Constructs and Methods for Heating a Liquid in a Microwave Oven

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/068,185, filed Mar. 4, 2008, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to various blanks, constructs, and methods for heating a food item, and particularly relates to various blanks, constructs, and methods for heating a food item in a microwave oven. 
     BACKGROUND 
     Microwave ovens often are used as a convenient means to thaw, heat, or reheat beverages, soups, and other liquid and semi-liquid food items (collectively referred to herein as “liquids”). However, such items are prone to uneven heating by microwave energy. In particular, the food item often tends to be overheated at its periphery and upper surface and underheated at its center and bottom surface. Thus, there is a need for a construct that promotes even heating of a liquid food item in a microwave oven. 
     SUMMARY 
     This disclosure is generally related to various methods and constructs (e.g., sleeves, sheaths, containers, etc.) for promoting uniform heating of a liquid in a microwave oven. The various methods and constructs generally employ one or more microwave energy shielding elements that alter the rate of heating of at least a portion of the liquid in a microwave oven. As a result, the food item may be heated more uniformly, top to bottom and/or center to periphery. In some instances, the food item even may be suitable for consumption upon removal from the microwave oven without stirring. The methods and constructs may be suitable for use with numerous food items, including those that are formed partially, substantially, or entirely from a liquid. 
     One exemplary method of promoting uniform heating of a liquid in a microwave oven comprises providing a container including a base and an upstanding wall that define an interior space for receiving a liquid. The liquid within the interior space has an uppermost portion and a lowermost portion, with the uppermost portion of liquid being prone to overheating relative to the lowermost portion. A microwave energy shielding element is substantially laterally aligned with the uppermost portion of liquid and the liquid in the container is exposed to microwave energy. In accordance with the exemplary method, the microwave energy shielding element reduces the transmission of microwave energy to the uppermost portion of liquid in the container, thereby substantially mitigating the overheating of the uppermost portion of liquid relative to the lowermost portion of liquid. 
     In one variation, providing the microwave energy shielding element comprises determining an anticipated top liquid level for the container, and joining the microwave energy shielding element to the wall of the container such that the microwave energy shielding element substantially overlaps the anticipated top liquid level. 
     In another variation, providing the microwave energy shielding element comprises determining an anticipated top liquid level for the container, mounting the microwave energy shielding element to a sheath for enwrapping the container such that the microwave energy shielding element substantially overlaps the anticipated top liquid level of the container, and enwrapping the container with the sheath. 
     In one exemplary embodiment, a container for providing even heating of a liquid food item in a microwave oven comprises a base and an upstanding wall that define an interior space for receiving a liquid. The liquid within the interior space has an uppermost portion adjacent to an upper portion of the wall and a lowermost portion adjacent to a lower portion of the wall. A microwave energy shielding element overlies the upper portion of the wall. The microwave energy shielding element is operative for reducing the transmission of microwave energy to the uppermost portion of liquid in the container. The microwave energy shielding element may include one or more apertures that allow the passage of microwave energy therethrough. The lower portion of the wall is at least partially transparent to microwave energy. 
     In another exemplary embodiment, a construct (e.g., a sheath) for promoting even heating of a liquid food item in a microwave oven comprises a main panel for at least temporarily enwrapping a wall of a conventional container. The main panel includes a microwave energy shielding element positioned to overlap with the anticipated top level of the liquid in the container. The construct also may include a pair of locking projections connected to the main panel. The locking projections are adapted to engage one another to maintain the main panel in a proximate relationship with the wall of the container. 
     The construct further may include a pair of end panels connected to the main panel. The end panels may be adapted to be brought into a substantially facing relationship with one another when the locking projections are engaged with one another, and in some embodiments, may serve as handles for the construct and container. When the construct is secured to the container, an upper edge of the microwave energy shielding element may be substantially parallel to an upper edge of the wall of the container, and a lower edge of the microwave energy shielding element may be substantially parallel to a lower edge of the wall of the container. 
     Other features, aspects, and embodiments will be apparent from the following description and accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description refers to the accompanying drawings, some of which are schematic, in which like reference characters refer to like parts throughout the several views, and in which: 
         FIG. 1A  is a schematic perspective view of an exemplary container for heating a food item in a microwave oven; 
         FIG. 1B  schematically depicts an exemplary blank that may be used to form the wall of the container of  FIG. 1A ; 
         FIG. 2A  schematically depicts a microwave heating construct for heating a food item in a microwave oven, in an unerected form; 
         FIG. 2B  schematically depicts the construct of  FIG. 2A  with a conventional container; and 
         FIG. 2C  schematically depicts the microwave heating construct in an erected form enwrapping the container. 
     
    
    
     DESCRIPTION 
     The present invention may be illustrated further by referring to the figures. For purposes of simplicity, like numerals may be used to describe like features. It will be understood that where a plurality of similar features are depicted, not all of such features necessarily are labeled on each figure. It also will be understood that various components used to form the blanks and constructs of the present invention may be interchanged. Thus, while only certain combinations are illustrated herein, numerous other combinations and configurations are contemplated hereby. 
       FIG. 1A  schematically depicts an exemplary construct  100 , for example, a container, for heating a food item in a microwave oven. The container  100  includes a base  102  and a substantially upstanding wall  104  that collectively define an interior space  106  for receiving a liquid or semi-liquid food item (collectively referred to herein as “liquid” food items), for example, a beverage, soup, stew, or sauce. The uppermost portion of the wall  104  generally comprises an edge or rim  108  that defines an opening for the container  100 . 
     A microwave energy interactive element  110 , in this example, a microwave energy shielding element (“shielding element”), is mounted to an interior side  112  of the wall  104 . In the illustrated example, the shielding element  110  comprises a circumferential “band” of microwave energy interactive material that includes an upper edge  114 , a lower edge  116 , and a pair of lateral ends  118  ( FIG. 1B ) spaced from one another, such that the shielding element  110  extends only partially around the circumference (or perimeter) of the wall  104 . However, in other embodiments, the shielding element  110  may extend continuously around the circumference (or perimeter) of the container wall  104  (or walls). 
     If desired, the ends  118  of the shielding element  110  may be somewhat rounded in shape and/or may have somewhat rounded corners. While not wishing to be bound by theory, is believed that providing a rounded shape in this manner serves to reduce the formation of undesirable fringe fields that might otherwise cause overheating or charring of the construct. 
     In this example, the upper edge  114  of the shielding element  110  is spaced from the rim  108  a distance d 1 . Although the exact position of the shielding element  110  may vary for each heating application, the shielding element is generally positioned on the wall  104  of the container to be adjacent to (or “overlapping”) the anticipated top (i.e., uppermost or maximum) liquid level for the container. In this example, the shielding element  110  is generally centered between the rim  108  and the base  102  of the container  100 . However, in other embodiments, the shielding element  110  may overlie only an upper portion or lower portion of the container. 
     When the container  100  is used to heat a food item in a microwave oven, the microwave energy shielding element  110  generally reduces or prevents transmission of microwave energy through the walls  104  to the interior space adjacent to the shielding element  110 , for example, to the medial and/or upper portion of liquid in the container in lateral alignment with the shielding element  110 . At the same time, microwave energy can pass freely through the various unshielded areas, including the areas of the walls  104  not covered by the shielding element  110 , the open “top” of the container  100 , and the base  102 . Depending on the particular food item being heated, the microwave energy shielded areas and unshielded areas can be arranged to control the rate of heating of particular areas of the food item prone to overheating or underheating. In this manner, a food item heated in the various constructs of the invention generally have a better, and more even, temperature profile between the top and bottom surfaces of the food item, and between the edge and center of the food item. 
     If additional heating is needed, the container  100  may include one or more apertures (not shown) within and/or circumscribed by the microwave energy shielding element. Such apertures may have any shape or size needed, as will be discussed further below. 
     Further, it is contemplated that one or more microwave energy interactive elements additionally or alternatively may overlie and/or may be joined to an exterior side of the wall  104 , the interior side of the base  102 , the exterior side of the base  102 , or any combination thereof. 
       FIG. 1B  schematically depicts an exemplary construct or blank  120  that may be used to form the wall  104  of the container  100  of  FIG. 1A  or numerous other containers or other constructs contemplated by the disclosure. The blank  120  may be characterized as having various dimensions, for example, lengths and widths. For purposes of reference only, some of such dimensions may be described with reference to a first dimension, extending in a first direction, for example, a longitudinal direction, D 1 , and a second dimension, extending in a second direction, for example, a transverse direction, D 2 . It will be understood that such designations are made only for convenience and do not necessarily refer to or limit the manner in which the construct is manufactured or erected. Each of the various dimensions may vary in relative and absolute value, depending on where the dimension is measured on the blank  120 . The blank  120  may be substantially symmetrical along a longitudinal centerline CL. 
     As shown schematically in  FIG. 1B , the blank  120  includes a main panel  104  (or wall panel  104 ) having a generally curved trapezoidal shape defined by a plurality of peripheral edges  108 ,  122 ,  124 ,  126  respectively joined to one another to define rounded corners. Edges  108 ,  122  are generally curved or arcuate and extend generally in the second direction, substantially equidistant from one another. Edges  124 ,  126  are substantially linear and extend generally in the first direction oblique to the longitudinal centerline CL, with the edges  124 ,  126  extending convergently from arcuate edge  108  towards arcuate edge  122 . Each edge may vary in dimension, and in one example, the respective lengths, L, of edges  124 ,  126  may be approximately equal. In contrast, arcuate edges  108 ,  122  may be characterized as having respective arc lengths S 1 , S 2 , with S 1  being greater than S 2 , such that the blank  120  has an overall corner to corner dimension that varies between widths W 1 , W 2 . 
     It is noted that the blank  120  illustrated schematically in  FIG. 1B  has somewhat rounded corners and, as a result, the precise boundaries between two abutting edges may be difficult to discern. Thus, while the various edges are described as having measurable lengths, it will be understood that the precise dimensions may vary depending on the manner in which the particular edge is measured. 
     Still viewing  FIG. 1B , a microwave energy shielding element  110  overlies and may be joined to a first side  112  of the main panel  104 . The shielding element  110  may be somewhat obround in shape (i.e., it may substantially resemble two semicircles connected by parallel lines tangent to their endpoints), except that it has a slight curvature generally tracking or corresponding to that of arcuate edges  108 ,  122  and therefore, may be referred to as “arcuate obround”, “curved obround”, or simply “arcuate” in shape. 
     If desired, the shape of the microwave energy shielding element  110  generally may correspond to or “track” the overall shape of the main panel  104 , such that the edges  114 ,  116  of the shielding element  110  have substantially the same radius of curvature as the respective edges  108 ,  122  of the main panel  104 , and/or such that edge  114  of the shielding element  110  is substantially equidistant from edge  108  of the main panel  102 , and/or such that edge  116  of the shielding element  110  is substantially equidistant from the edge  122  of the main panel  102 . 
     A second side  128  of the main panel  104  (hidden from view in  FIG. 1B , best seen in  FIG. 1A ) opposite the first side  112  also may have one or more microwave energy interactive elements if desired. The remaining area of the blank  120  is generally transparent to microwave energy. 
     In this example, the shielding element  110  is positioned a distance d 1  from edge  108 , a distance d 2  from edge  122 , a distance d 3  from edge  124 , and a distance d 4  from edge  126 . The various distances d 1 , d 2 , d 3 , d 4  are selected to provide the desired degree of shielding in a particular area, to reduce charring associated with the formation of fringe fields during exposure to microwave energy, and in the case of distances d 3 , d 4 , to prevent arcing between the lateral ends  118  of the shielding element  110  when the blank  120  is formed into a construct. In this example, d 3  is greater than d 4 , and d 1  and d 2  are approximately equal. However, other configurations are contemplated by the disclosure. 
     By way of illustration and not limitation, in each of various examples, d 1  independently may be from about 0.1 to about 10 cm, from about 0.3 to about 5 cm, from about 0.5 to about 3 cm, or from about 1 to about 2.5 cm, for example, about 1.9 cm; d 2  independently may be from about 0.1 to about 10 cm, from about 0.3 to about 5 cm, from about 0.5 to about 3 cm, or from about 1 to about 2.5 cm, for example, about 2.0 cm; d 3  independently may be from about 0.1 to about 10 cm, from about 0.3 to about 5 cm, from about 0.5 to about 3 cm, or from about 1 to about 2.5 cm, for example, about 1.8 cm; and d 4  independently may be from about 0.1 to about 10 cm, from about 0.3 to about 5 cm, from about 0.5 to about 3 cm, or from about 1 to about 2.5 cm, for example, about 0.80 cm. 
     Further, in each of various examples, S 1  independently may be from about 20 to about 100 cm, from about 30 to about 70 cm, or from about 35 to about 50, for example, about 42 cm; S 2  independently may be from about 15 to about 100 cm, from about 20 to about 70 cm, or from about 25 to about 50, for example, about 38 cm; W 1  independently may be from about 20 to about 100 cm, from about 30 to about 70 cm, or from about 35 to about 50, for example, about 41 cm; W 2  independently may be from about 15 to about 100 cm, from about 20 to about 70 cm, or from about 30 to about 50, for example, about 37 cm; and L independently may be from about 1 to about 30 cm, from about 2 to about 15 cm, or from about 5 to about 10 cm, for example, about 6.2 cm. However, other distances, dimensions, and configurations are contemplated hereby. 
     To prepare the blank  120  for use in the container  100 , edges  124 ,  126  may be brought towards each other to form a ring-like structure (not shown in isolation). The ends of the blank  120  then may be overlapped as needed to provide a sufficient joining area, while typically, but optionally, maintaining a desired distance or gap between the corresponding ends of the shielding element  110 . The precise gap may vary for each application. In each of various examples, the gap may be at least about 10 mm, at least about 12 mm, at least about 14 mm, at least about 16 mm, from about 10 mm to about 20 mm, or from about 11 mm to about 15 mm, for example, about 13 mm. However, other gap dimensions are contemplated hereby. 
     The overlapped ends of the blank  120  then may be joined using any suitable chemical, thermal, or mechanical means to form a tubular structure or construct that may be joined to a base panel (e.g. joined in a conventional manner to the periphery of a conventional circular base panel, or the like) to form a container, for example, as shown in  FIG. 1A . The tubular structure may be substantially uniform in diameter or may taper in diameter (e.g., may be frustoconical in shape), depending on the type of container to be formed. 
     According to another aspect of the disclosure, the tubular structure may be used as a sheath or sleeve that encircles all or a portion of the wall(s) of a conventional container, for example, a paper cup or bowl (not shown). The sleeve may be used as described above to reduce the rate of heating in the shielded areas, thereby providing a more even temperature profile throughout the food item, for example, a beverage, soup, sauce, or other suitable food item. Thus, in some instances, a cup of coffee that would otherwise need to be stirred or allowed to cool to achieve a desired consumption temperature may be consumed immediately after heating without the need for stirring and/or cooling. 
     Numerous variations are contemplated. In one embodiment, the microwave sheath may be provided to the user in a pre-constructed form that may be slipped over the wall of the container. The sheath and/or container may be provided with markings or other indicia that ensure proper positioning along the container wall. The sheath may be packaged in a flattened configuration and unfolded prior to use or may be provided in an open, erected configuration. Alternatively, the sheath may be provided in a flattened, open configuration, provided with a tab and slot (or other fastening means) for securing the sheath to the container. If desired, the sheath may be formed at least partially from a thermal insulating material, for example, a corrugated material, to enable the user to handle the container more comfortably. 
     It will be understood that any of such sheaths, in addition to any of the other constructs contemplated by the disclosure, may be adjustable, such that the user can position the sleeve or sheath as needed to align the shielding element with the upper portion of the liquid to be heated, or may be “self-locating”, that is, designed to engage the container at a specific location to ensure proper alignment of the shielding element and sufficiently intimate contact with the wall of the container. In some embodiments, such self-locating constructs may have a specific shape and/or dimensions that facilitate proper positioning on the container. For example, the sleeve may be dimensioned so that the user can slide the sleeve onto the container (e.g., from the base upward) only up to a specific point where the outer diameter of the container is equal to the inner diameter of the sleeve. Further, where the container has a tapered profile, the sleeve may have a similar profile, so that when the proper position is reached, the sleeve is in intimate contact with the wall of the container. 
       FIGS. 2A-2C  schematically illustrate another exemplary construct  200  for heating a food item in a microwave oven. The construct  200  may be similar to the blank  120  of  FIG. 1B , except for variations noted and variations that will be apparent to those of skill in the art. In  FIG. 2A , the construct  200  is shown in an open, substantially flat or planar configuration (also referred to as a “blank”). In  FIG. 2C , the construct  200  is shown with a conventional container C, in this example, a cup, prior to use. In  FIG. 2C , the construct  200  is shown in an erected configuration wrapped around the container (shown schematically with dashed lines). 
     Viewing  FIG. 2A , the construct  200  generally includes a plurality of panels joined along fold lines or other lines of disruption, for example, score lines. Each panel  200  may be characterized in its flattened form as having various dimensions, for example, lengths and widths. For purposes of reference only, some of such dimensions may be described with reference to a first dimension, extending in a first direction, for example, a longitudinal direction, D 1 , and a second dimension, extending in a second direction, for example, a transverse direction, D 2 . It will be understood that such designations are made only for convenience and do not necessarily refer to or limit the manner in which the construct is manufactured or erected. Each of the various dimensions may vary in relative and absolute value, depending on where the dimension is measured on the construct  200 . Portions of the construct  200  may be substantially symmetrical along a longitudinal centerline CL. 
     As shown schematically in  FIG. 2A , the flattened construct or blank  200  includes a main panel  202  including a plurality of peripheral edges  204 ,  206 ,  208 ,  210  defining a generally curved trapezoidal shape, such that the main panel  202  is suitable for enwrapping the wall W of a tapered container C (e.g., a frustoconical cup) ( FIG. 2B ). Edges  204 ,  206  are generally curved or arcuate and extend generally in the second direction, substantially equidistant from one another. Edges  208 ,  210  are substantially linear and extend generally in the first direction oblique to the longitudinal centerline CL. Each edge may vary in dimension, and in one example, the respective lengths, L, of edges  208 ,  210  may be approximately equal. In contrast, arcuate edges  204 ,  206  may be characterized as having respective arc lengths S 1 , S 2 , with S 1  being greater than S 2 , such that the blank  200  has an overall corner to corner dimension that decreases from width W 1  to W 2 . 
     Still viewing  FIG. 2A , a microwave energy shielding element  212  overlies and may be joined to a first side  214  of the main panel  202 . The shielding element  212  may be generally curved and/or obround in shape with rounded corners and/or lateral ends  216 , and generally may correspond to or track the overall shape of the main panel  202 , such that the upper and lower edges  218 ,  220  of the shielding element  212  have substantially the same radius of curvature as the respective proximate edges  204 ,  206  of the main panel  202 , and/or such that edge  218  of the shielding element  212  is substantially equidistant from edge  204  of the main panel  102 , and/or such that edge  220  of the shielding element  212  is substantially equidistant from the edge  206  of the main panel  202 . 
     A second side  222  of the main panel  202  (hidden from view in  FIG. 2A , best seen in  FIG. 2C ) opposite the first side  214  also may have one or more microwave energy interactive elements if desired. The remaining portions of the main panel  202  are generally transparent to microwave energy. 
     The precise location of the shielding element  212  may vary for each heating application. In general, the shielding element  212  may be positioned on the main panel  202  such that when the main panel  202  enwraps the wall W of the container C ( FIG. 2C ), the shielding element  212  is adjacent to (or “overlapping”) the anticipated top (i.e., uppermost or maximum) liquid level M (shown schematically with a dashed line in  FIG. 2B ) for the container C. In this example, although there are no exact boundaries, the construct or sheath  200  can be thought of as generally having an upper portion  224  and a lower portion  226 , with the microwave energy shielding element  212  mounted to the upper portion  224 . In use, the upper portion  224  of the sheath  200  generally lies adjacent to (i.e., in lateral alignment with) an uppermost portion of a liquid within the container (i.e., the top of the liquid and some quantity of liquid below the top liquid level), and the lower, unshielded portion  226  of the sheath  200  generally lies adjacent to (i.e., in lateral alignment with) a lower portion of the liquid in the container, as shown schematically in  FIG. 2C . 
     More particularly, in this example, the shielding element  212  is positioned a distance d 1  from edge  204 , a distance d 2  from edge  206 , a distance d 3  from edge  208 , and a distance d 4  from edge  210 . In this example, d 3  and d 4  are approximately equal and d 1  is greater than d 2 . However, other configurations and relationships are contemplated by the invention. For example, in each of various examples, d 1  independently may be from about 0.1 to about 10 cm, from about 0.3 to about 5 cm, from about 0.5 to about 3 cm, or from about 1 to about 2.5 cm, for example, about 2.1 cm; d 2  independently may be from about 1 to about 15 cm, from about 2 to about 10 cm, or from about 4 to about 8 cm, for example, about 6.3 cm; d 3  independently may be from about 0.05 to about 3 cm, from about 0.1 to about 1.5 cm, or from about 0.2 to about 1 cm, for example, about 0.46 cm; and d 4  independently may be from about 0.05 to about 3 cm, from about 0.1 to about 1.5 cm, or from about 0.2 to about 1 cm, for example, about 0.46 cm. 
     Further, in each of various examples, S 1  independently may be from about 10 to about 100 cm, from about 15 to about 40 cm, or from about 20 to about 30, for example, about 27 cm; S 2  independently may be from about 10 to about 100 cm, from about 20 to about 60 cm, or from about 30 to about 50, for example, about 37 cm; W 1  independently may be from about 10 to about 100 cm, from about 15 to about 60 cm, or from about 20 to about 35, for example, about 26 cm; W 2  independently may be from about 5 to about 60 cm, from about 10 to about 40 cm, or from about 15 to about 30, for example, about 19 cm; and L independently may be from about 40 to about 100 mm, from about 50 to about 80 mm, or from about 60 to about 70 mm, for example, about 62 mm. However, other distances, dimensions, and configurations are contemplated hereby. 
     Still viewing  FIG. 2A , the unerected sheath  200  includes a pair of somewhat C-shaped end panels  228 ,  230  joined to respective edges  208 ,  210  of the main panel  202  along respective oblique score lines  232 ,  234  or other lines of disruption (e.g., fold lines) extending generally in the first direction convergently towards the longitudinal centerline CL. 
     Each end panel  228 ,  230  can be characterized as having a plurality of sections. A first section  236  extends outwardly from the main panel  202  substantially perpendicular to respective edges  208 ,  210 , such that the first section extends obliquely with respect to the second direction D 2 . A second section  238  is substantially perpendicular to the respective first section  236  and extends generally in a direction oblique to the longitudinal centerline CL substantially parallel to the respective edge  208 ,  210  of the main panel  202 . A third section  240  extends obliquely from the respective second section  238  to the main panel  202 . 
     The blank  200  also includes a pair of locking features (e.g. tabs or projections)  242 ,  244  adapted to engage one another and secure the erected construct  200  to a container C, as shown in  FIG. 2C . Locking projection  242  extends from the main panel  202  along edge  208  proximate the third section  240  of end panel  228  along a line of disruption  246 , e.g. a score line or other type of fold line. The locking projection  242  extends substantially between and is separated from the first section  236  and the third section  240  of the end panel  228  by respective cuts or slits  248 ,  250 . A portion of the locking projection  242  proximate to the first section  236  of the end panel  228  also is partially separated from the main panel  202  along slit  252 , such that the portion of the locking projection proximate the first section  236  is free to flex and rotate in and out of the plane of the main panel  202  toward and away from the third section  240  of end panel  228 , and also is able to fold and rotate toward and away from the main panel  202  along score line  246 . 
     Locking projection  244  extends from the main panel  202  along edge  210  proximate to the first section  236  of the end panel  230  along a line of disruption  254 , e.g. a score line or other type of fold line. The locking projection  244  extends substantially between and is separated from the first section  236  and the third section  240  of end panel  230  by respective cuts or slits  256 ,  258 . A portion of the locking projection  244  proximate to the third section  240  of the end panel  230  also is partially separated from the main panel  202  along slit  260 , such that the portion of the locking projection proximate to the third panel  240  is free to flex and rotate in and out of the plane of the main panel  202  toward and away from the third section  240  of end panel  230 , and also is able to fold and rotate toward and away from the main panel  202  along score line  254 . 
     To use the construct  200  according to one acceptable method, the main panel  202  may be wrapped around the wall(s) of a container C (shown with dashed lines in FIG.  2 C), for example, a paper cup, and the end panels  228 ,  230  may be brought towards one another in a substantially contacting, facing relationship to form a handle  262 . In this configuration, the upper edge of the microwave energy shielding element  212  may be substantially parallel to the uppermost edge of the wall W (or the rim R) of the container C, and the lower edge of the microwave energy shielding element  212  may be substantially parallel to the lower edge of the wall W of the container C. The uppermost portion of locking projection  242  (i.e., proximate the first section  236  of end panel  228 ) and the lowermost portion of locking projection  244  (i.e., proximate to the third section  240  of end panel  230 ) may engage the respective slits  260 ,  252  of the other locking projection  244 ,  242 , such that the locking projections  242 ,  244  are secured to one another, as shown in  FIG. 2C . In this configuration, the main panel  202  forms a frustoconical construct with opposite ends that are fully open. 
     When exposed to microwave energy, the upper portion of the liquid in the container C, which would otherwise be prone to overheating, is shielded from the microwave energy. As a result, the upper portion of the liquid heats at a rate slower than the lower portion of the liquid, which is exposed to microwave energy through the base of the container and through the unshielded portion of the wall and sheath. As a result, the food item has a more uniform heating profile, and in some cases, may not even need to be stirred before consumption. If desired, the handle  262  may be used to lift the container C, with the rim R of the container C preventing the container C from sliding downward as the container C is elevated. Alternatively, the construct  200  may be removed and the container may be handled in a conventional manner. 
     It will be understood that although particular examples of handles and locking features are illustrated schematically in  FIGS. 2A-2C , numerous other handles and locking features are contemplated by the invention, and the handles and/or locking features may be omitted, for example, when the transversely opposite edges  208 ,  210  of the main panel  202  are attached to one another by another suitable means (e.g., using an adhesive material). Likewise, it will be understood that any of the various constructs of the invention may include other panels and features, as needed or desired for a particular heating application. 
     Numerous materials may be suitable for use in forming the various blanks and constructs of the invention, provided that the materials are resistant to softening, scorching, combusting, or degrading at typical microwave oven heating temperatures, for example, from about 250° F. to about 425° F. Such materials may include microwave energy interactive materials, such as those used to provide microwave energy shielding, and microwave energy transparent or inactive materials, such as those used as base materials for various constructs. 
     In the examples illustrated schematically in  FIGS. 1A-2C , the microwave energy shielding element  110 ,  212  may comprise a foil or high optical density evaporated material having a thickness sufficient to reflect a substantial portion of impinging microwave energy. Typically, shielding elements are formed from a conductive, reflective metal or metal alloy, for example, aluminum, copper, or stainless steel, in the form of a solid “patch” generally having a thickness of from about 0.000285 inches to about 0.05 inches, for example, from about 0.0003 inches to about 0.03 inches. Other such elements may have a thickness of from about 0.00035 inches to about 0.020 inches, for example, 0.016 inches. 
     Microwave energy shielding elements may be configured in various ways, depending on the particular application for which the element is used. Larger microwave energy reflecting elements may be used where the food item is prone to scorching or drying out during heating. Smaller microwave energy reflecting elements may be used to diffuse or lessen the intensity of microwave energy. A plurality of smaller microwave energy reflecting elements also may be arranged to form a microwave energy directing element to direct microwave energy to specific areas of the food item. If desired, the loops may be of a length that causes microwave energy to resonate, thereby enhancing the distribution effect. Microwave energy distributing elements are described in U.S. Pat. Nos. 6,204,492, 6,433,322, 6,552,315, and 6,677,563, each of which is incorporated by reference in its entirety. For instance, a container may include a microwave directing element on the base of the container, where, for example, the quantity of liquid to be heated is sufficiently large that the bottom and/or center of the liquid might otherwise be underheated relative to other portions of the food item. 
     Although microwave energy shielding elements are illustrated in  FIGS. 1A-2C , it will be understood that other microwave energy interactive elements (not shown) may be used. For example, the construct may include a thin layer of microwave energy interactive material (generally less than about 100 angstroms in thickness, for example, from about 60 to about 100 angstroms in thickness) that tends to absorb at least a portion of impinging microwave energy and convert it to thermal energy (i.e., heat) at the interface with a food item. Such “susceptor” elements often are used to promote browning and/or crisping of the surface of a food item. When supported on a film or other substrate, such an element may be referred to as a “susceptor film” or, simply, “susceptor”. 
     The microwave energy interactive material of a susceptor may be an electroconductive or semiconductive material, for example, a metal or a metal alloy provided as a metal foil; a vacuum deposited metal or metal alloy; or a metallic ink, an organic ink, an inorganic ink, a metallic paste, an organic paste, an inorganic paste, or any combination thereof. Examples of metals and metal alloys that may be suitable include, but are not limited to, aluminum, chromium, copper, inconel alloys (nickel-chromium-molybdenum alloy with niobium), iron, magnesium, nickel, stainless steel, tin, titanium, tungsten, and any combination or alloy thereof. 
     Alternatively, the microwave energy interactive material may comprise a metal oxide, for example, oxides of aluminum, iron, and tin, optionally used in conjunction with an electrically conductive material. Another metal oxide that may be suitable is indium tin oxide (ITO). ITO has a more uniform crystal structure and, therefore, is clear at most coating thicknesses. 
     Alternatively still, the microwave energy interactive material may comprise a suitable electroconductive, semiconductive, or non-conductive artificial dielectric or ferroelectric. Artificial dielectrics comprise conductive, subdivided material in a polymeric or other suitable matrix or binder, and may include flakes of an electroconductive metal, for example, aluminum. 
     Any of the numerous microwave energy interactive elements described herein or contemplated hereby may be substantially continuous, that is, without substantial breaks or interruptions, or may be discontinuous, for example, by including one or more breaks or apertures that transmit microwave energy therethrough. The breaks or apertures may be sized and positioned to heat particular areas of the food item selectively. The number, shape, size, and positioning of such breaks or apertures may vary for a particular application depending on type of construct being formed, the food item to be heated therein or thereon, the desired degree of shielding, browning, and/or crisping, whether direct exposure to microwave energy is needed or desired to attain uniform heating of the food item, the need for regulating the change in temperature of the food item through direct heating, and whether and to what extent there is a need for venting. 
     If desired, the microwave energy interactive element may be supported on a microwave inactive or transparent substrate, for example, a polymer film or other suitable polymeric material, for ease of handling and/or to prevent contact between the microwave energy interactive material and the food item. Examples of polymer films that may be suitable include, but are not limited to, polyolefins, polyesters, polyamides, polyimides, polysulfones, polyether ketones, cellophanes, or any combination thereof. In one particular example, the polymer film comprises polyethylene terephthalate. The thickness of the film generally may be from about 35 gauge to about 10 mil. In each of various examples, the thickness of the film may be from about 40 to about 80 gauge, from about 45 to about 50 gauge, about 48 gauge, or any other suitable thickness. Other non-conducting substrate materials such as paper and paper laminates, metal oxides, silicates, cellulosics, or any combination thereof, also may be used. 
     The microwave energy interactive material may be applied to the substrate in any suitable manner, and in some instances, the microwave energy interactive material is printed on, extruded onto, sputtered onto, evaporated on, or laminated to the substrate. The microwave energy interactive material may be applied to the substrate in any pattern, and using any technique, to achieve the desired heating effect of the food item. For example, the microwave energy interactive material may be provided as a continuous or discontinuous layer or coating including circles, loops, hexagons, islands, squares, rectangles, octagons, and so forth. 
     Various materials may serve as the base material for the construct. For example, the construct may be formed at least partially from a polymer or polymeric material. As another example, all or a portion the apparatus may be formed from a paper or paperboard material. In one example, the paper has a basis weight of from about 15 to about 60 lbs/ream (lb/3000 sq. ft.), for example, from about 20 to about 40 lbs/ream. In another example, the paper has a basis weight of about 25 lbs/ream. In another example, the paperboard having a basis weight of from about 60 to about 330 lbs/ream, for example, from about 80 to about 140 lbs/ream. The paperboard generally may have a thickness of from about 6 to about 30 mils, for example, from about 12 to about 28 mils. In one particular example, the paperboard has a thickness of about 12 mils. Any suitable paperboard may be used, for example, a solid bleached or solid unbleached sulfate board, such as SUS® board, commercially available from Graphic Packaging International. 
     The construct may be formed according to numerous processes known to those in the art, including using adhesive bonding, thermal bonding, ultrasonic bonding, mechanical stitching, or any other suitable process. Any of the various components used to form the apparatus may be provided as a sheet of material, a roll of material, or a die cut material in the shape of the apparatus to be formed (e.g., a blank). 
     It will be understood that with some combinations of elements and materials, the microwave interactive element may have a color that is visually distinguishable from the substrate or the support. However, in some instances, it may be desirable to provide a web or construct having a uniform color and/or appearance. Such a web or construct may be more aesthetically pleasing to a consumer, particularly when the consumer is accustomed to packages or containers having certain visual attributes, for example, a solid color, a particular pattern, and so on. Thus, for example, where the microwave energy interactive element is silver or grey in color, a silver or grey toned adhesive may be used to join the microwave interactive elements to the substrate, using a silver or grey toned substrate to mask the presence of the silver or grey toned microwave interactive element, using a dark toned substrate, for example, a black toned substrate, to conceal the presence of the silver or grey toned microwave interactive element, overprinting the metallized side of the web with a silver or grey toned ink to obscure the color variation, printing the non-metallized side of the web with a silver or grey ink or other concealing color in a suitable pattern or as a solid color layer to mask or conceal the presence of the microwave interactive element, or any other suitable technique or combination thereof. 
     The present invention may be understood further by way of the following examples, which are not to be construed as limiting in any manner. 
     EXAMPLES 
     Various cups of coffee were heated in different microwave ovens for different lengths of time and with different degrees of shielding according to the invention. A 12 oz. paperboard cup containing about 284 g of Starbuck&#39;s “Muldoon&#39;s Own Light Roast” coffee was used to conduct the evaluations. The height of the cup was 11 cm and the diameter of the opening at the top of the cup was about 8.8 cm. Temperatures were measured immediately before heating, immediately after heating, and one minute after heating. Temperatures were measured at the top of the beverage, at the middle of the beverage, and at the bottom of the beverage, generally along a central vertical axis and along the edge of the cup. The starting temperature of each coffee sample was about 66° F., except as otherwise indicated. 
     Example 1 
     Baseline heating characteristics at the center of the coffee were determined according to the procedure described above. The results are presented in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Temperature at center of coffee, no shielding 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Time (s) 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                  900 W Oven A 
                 120 
                 124 
                 130 
                 146 
               
               
                 1000 W Oven B 
                 90 
                 138 
                 144 
                 163 
               
               
                 1100 W Oven C 
                 75 
                 139 
                 146 
                 160 
               
               
                   
               
            
           
         
       
     
     Example 2  
     The heating characteristics at the center of the coffee were determined according to the procedure described above using a cup with a 3 cm shielding ring 2.1 cm from the top edge of the cup. The results are presented in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Temperature at center of coffee, 3 cm shield 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Time (s) 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                  900 W Oven A 
                 120 
                 123 
                 125 
                 131 
               
               
                 1000 W Oven B 
                 90 
                 135 
                 135 
                 136 
               
               
                 1100 W Oven C 
                 75 
                 146 
                 148 
                 149 
               
               
                   
               
            
           
         
       
     
     Example 3  
     Baseline heating characteristics at the edge of the coffee were determined according to the procedure described above. The results are presented in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Temperature at edge of coffee, no shielding 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Time (s) 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                  900 W Oven A 
                 120 
                 126 
                 131 
                 147 
               
               
                 1000 W Oven B 
                 90 
                 139 
                 145 
                 164 
               
               
                 1100 W Oven C 
                 75 
                 140 
                 145 
                 160 
               
               
                   
               
            
           
         
       
     
     Example 4  
     The heating characteristics at the edge of the coffee were determined according to the procedure described above using a cup with a 3 cm shielding ring 2.1 cm from the top edge of the cup. The results are presented in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Temperature at edge of coffee, 3 cm shield 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Time (s) 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                  900 W Oven A 
                 120 
                 123 
                 125 
                 132 
               
               
                 1000 W Oven B 
                 90 
                 134 
                 135 
                 135 
               
               
                 1100 W Oven C 
                 75 
                 146 
                 149 
                 150 
               
               
                   
               
            
           
         
       
     
     Example 5  
     The heating characteristics at the center and at the edge of the coffee were determined according to the procedure described above using a cup with a 2.5 cm shielding ring 2.1 cm from the top edge of the cup and a 3.5 cm shielding ring 2.1 cm from the top edge of the cup. The coffee samples were heated for about 90 seconds in an 1100 W Sharp microwave oven. The results are presented in Tables 5 and 6 with the results from the previous evaluations. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Temperature at center of coffee, various shields 
               
            
           
           
               
               
               
               
               
            
               
                 Shield 
                 Time (s) 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
               
               
                   0 cm 
                 90 
                 138 
                 144 
                 163 
               
               
                 2.5 cm 
                 90 
                 144 
                 145 
                 145 
               
               
                 3.0 cm 
                 90 
                 135 
                 135 
                 136 
               
               
                 3.5 cm 
                 90 
                 139 
                 140 
                 140 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Temperature at edge of coffee, various shields 
               
            
           
           
               
               
               
               
               
            
               
                 Shield 
                 Time (s) 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
               
               
                   0 cm 
                 90 
                 139 
                 145 
                 164 
               
               
                 2.5 cm 
                 90 
                 144 
                 144 
                 145 
               
               
                 3.0 cm 
                 90 
                 134 
                 135 
                 135 
               
               
                 3.5 cm 
                 90 
                 138 
                 140 
                 140 
               
               
                   
               
            
           
         
       
     
     The various temperatures were measured again after about 1 minute. The results are presented in Tables 7 and 8. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Temperature at center of coffee after 1 minute, various shields 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Shield 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
                   
               
               
                   
                   0 cm 
                 139 
                 143 
                 159 
               
               
                   
                 2.5 cm 
                 143 
                 143 
                 143 
               
               
                   
                 3.0 cm 
                 134 
                 134 
                 134 
               
               
                   
                 3.5 cm 
                 138 
                 139 
                 139 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Temperature at edge of coffee after 1 minute, various shields 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Shield 
                 Bottom (° F.) 
                 Middle (° F.) 
                 Top (° F.) 
               
               
                   
                   
               
               
                   
                   0 cm 
                 139 
                 144 
                 158 
               
               
                   
                 2.5 cm 
                 142 
                 143 
                 144 
               
               
                   
                 3.0 cm 
                 133 
                 133 
                 134 
               
               
                   
                 3.5 cm 
                 137 
                 137 
                 138 
               
               
                   
                   
               
            
           
         
       
     
     Table 9 summarizes the results of Examples 1-5 and other testing conducted. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Data from Examples 1-5 plus additional evaluations* 
               
            
           
           
               
               
               
            
               
                   
                 IMMEDIATE TEMPERATURES 
                 1 MINUTE STANDING TIME TEMPERATURES 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Initial 
                   
                 Time 
                 CENTER 
                 EDGE 
                 CENTER 
                 EDGE 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Test 
                 Temp (F.) 
                 Shield 
                 Oven 
                 (s) 
                 Bottom 
                 Middle 
                 Top 
                 Bottom 
                 Middle 
                 Top 
                 Bottom 
                 Middle 
                 Top 
                 Bottom 
                 Middle 
                 Top 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 66 
                 none 
                 B 
                 90 
                 138 
                 144 
                 163 
                 139 
                 145 
                 164 
                 139 
                 143 
                 159 
                 139 
                 144 
                 158 
               
               
                 2 
                 66 
                 none 
                 B 
                 120 
                 161 
                 166 
                 188 
                 161 
                 166 
                 189 
                 160 
                 165 
                 184 
                 160 
                 165 
                 184 
               
               
                 3 
                 66 
                 2.5 cm   
                 B 
                 90 
                 144 
                 145 
                 145 
                 144 
                 144 
                 145 
                 143 
                 143 
                 143 
                 142 
                 143 
                 144 
               
               
                 4 
                 66 
                 3 cm 
                 B 
                 90 
                 135 
                 135 
                 136 
                 134 
                 135 
                 135 
                 134 
                 134 
                 134 
                 133 
                 133 
                 134 
               
               
                 5 
                 66 
                 3.5 cm   
                 B 
                 90 
                 139 
                 140 
                 140 
                 138 
                 140 
                 140 
                 138 
                 139 
                 139 
                 137 
                 137 
                 138 
               
               
                 6 
                 76 
                 none 
                 C 
                 105 
                 152 
                 157 
                 172 
                 153 
                 157 
                 173 
                 150 
                 155 
                 168 
                 150 
                 156 
                 167 
               
               
                 7 
                 66 
                 none 
                 C 
                 75 
                 139 
                 146 
                 160 
                 140 
                 145 
                 160 
                 138 
                 144 
                 157 
                 139 
                 143 
                 157 
               
               
                 8 
                 66 
                 3 cm 
                 C 
                 75 
                 146 
                 148 
                 149 
                 146 
                 149 
                 150 
                 145 
                 147 
                 148 
                 146 
                 148 
                 149 
               
               
                 9 
                 66 
                 none 
                 A 
                 90 
                 123 
                 127 
                 143 
                 124 
                 128 
                 143 
                 121 
                 127 
                 139 
                 122 
                 128 
                 141 
               
               
                 10 
                 66 
                 none 
                 A 
                 105 
                 124 
                 130 
                 147 
                 127 
                 130 
                 146 
                 125 
                 130 
                 145 
                 126 
                 130 
                 144 
               
               
                 11 
                 66 
                 none 
                 A 
                 120 
                 124 
                 130 
                 146 
                 126 
                 131 
                 147 
                 125 
                 130 
                 145 
                 125 
                 129 
                 143 
               
               
                 12 
                 66 
                 3 cm 
                 A 
                 120 
                 123 
                 125 
                 131 
                 123 
                 125 
                 132 
                 122 
                 124 
                 129 
                 123 
                 125 
                 130 
               
               
                   
               
               
                 *All evaluations conducted using Muldoon&#39;s Own Light Roast, Initial weight = 284 g, 12 oz. paperboard cup 
               
            
           
         
       
     
     While the present invention is described herein in detail in relation to specific aspects and embodiments, it is to be understood that this detailed description is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the present invention and to set forth the best mode of practicing the invention known to the inventors at the time the invention was made. The detailed description set forth herein is illustrative only and is not intended, nor is to be construed, to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications, and equivalent arrangements of the present invention. All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are used only for identification purposes to aid the reader&#39;s understanding of the various embodiments of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention unless specifically set forth in the claims. Joinder references (e.g., joined, attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily imply that two elements are connected directly and in fixed relation to each other. Further, various elements discussed with reference to the various embodiments may be interchanged to create entirely new embodiments coming within the scope of the present invention.