Abstract:
A food tray is provided with an upper tray and a lower tray containing food products, in which the upper tray rests snugly in the lower tray and a lid seals the upper tray. Vent holes in the lower tray allow steam released from the food product in the lower tray to escape out of the lower tray. Each of the upper tray and lower tray may have flanges to allow the upper tray to be lifted out of the lower tray without difficulty.

Description:
TECHNICAL FIELD 
     Food trays. 
     BACKGROUND 
     Microwavable food trays are well known including designs by the inventor of the invention disclosed in this patent document. In one prior design by the inventor, disclosed in Publication No. WO 2007/056866, published May 24, 2007, an upper tray was loosely nested in a lower tray, with a gap between the trays to allow steam to vent from the lower tray during cooking. With such a design, however, steam escaping from the lower tray might burn a user&#39;s fingers when they picked up the upper tray. In another design, sold in Europe, and also mentioned in the Publication No. WO 2007/056866, snugly nested rectangular upper and lower trays provided separate compartments for different foods. This design, made of paperboard, was defective in that steam could build up between the snugly nested trays. 
     SUMMARY 
     Therefore, in an embodiment there is provided a food tray, in which food products may be heated by a microwave, comprising an upper tray containing a first food product, a lower tray containing a second food product, and a lid sealing the upper tray. The upper tray rests snugly in the lower tray to prevent flow of steam between the upper tray and the lower tray beyond a close fit line on the lower tray, and the lower tray has at least a vent hole below the close fit line for escape of steam when the second food product is subject to microwave energy. 
     In an embodiment, the food tray is made from cardboard or paperboard, and in another embodiment is rectangular. 
     In an embodiment, each of the upper tray and lower tray has a flange, and the flange of the upper tray extends farther outward than the flange of the lower tray, allowing the upper tray to be more easily removed from the upper tray. Other embodiments can be found in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       There will now be given a brief description of a food tray, by reference to the drawings, by way of illustration only, and in which: 
         FIG. 1  is a cross-section of an embodiment of a food tray; and 
         FIG. 2  is a perspective view of an embodiment of a food tray. 
     
    
    
     DETAILED DESCRIPTION 
     In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite article “a” before a claim feature does not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims. 
     Referring to  FIG. 1 , an embodiment of a food tray  10  is shown to include an upper tray  12  resting snugly in a lower tray  14 , to prevent flow of steam between the upper tray  12  and the lower tray  14  beyond a close fit line  16  on the lower tray  14 . In this embodiment, the close fit line  16  is where contact between the upper tray  12  and lower tray  14  ceases. In this embodiment, both the upper tray  12  and lower tray  14  may be rectangular in a horizontal cross-section through the trays and taper downward with the same taper, although  FIG. 1  also applies to a tray that is circular or elliptical (oval) in plan. The direction horizontal is defined by the normal position of the trays in use, that is, with the top upward. Same taper means that the tapers of the trays match each other, that is, have the side walls have the same slope in relation to the horizontal. 
     The close fit line  16 , as shown in  FIG. 1 , may correspond to the depth that the upper tray  12  reaches when seated in lower tray  14 . If the downward taper of the upper tray  12  and lower tray  14  is the same, then the close fit line  16  will be at the depth the bottom of the upper tray  12  reaches in the lower tray  14 . The close fit of the upper tray  12  and lower tray  14  in this case extends the full height of the upper tray  12 , but this is not necessary and the close fit line could be above the bottom of the upper tray  12 . Snugly nested in this embodiment means that there is contact between the upper tray  12  and lower tray  14  all around the perimeter of the upper tray  14 . Thus, steam pressure, absent any other outlet for steam as for example the vent holes  24  described below in relation to  FIG. 2 , would build up within the lower tray  14  when moist food in the lower tray  14  is subject to microwave heating energy. An example of a close fit line above the bottom of the upper tray  12  is where the upper tray  12  is stepped inward part way down the wall of the upper tray, with only the upper part of the upper tray  12 , above the step, being snugly fit with the lower tray  14 . 
     In the embodiment shown, each tray of food tray  10  is formed at least of side walls defining an encircling wall  15  and  17 , a top and a bottom. Each side wall and the bottom in this embodiment is rectangular. In other embodiments, the food tray  10  may be round or elliptical or have other shapes such as polygonal shapes. 
     The upper tray  12  has an encircling wall  15  with a top or rim and a flange  18  extending outward from the top of the encircling wall  15 . The lower tray  14  has an encircling wall  17  with a top, or rim and a flange  20  extending outward from the top of the encircling wall. The flange  18  of the upper tray  12  extends beyond the flange  20  of the lower tray  14  to facilitate the removal of the upper tray  12  from the lower tray  14 . The flange  18  of the upper tray  12  in an embodiment may extend approximately 2-10 mm outward from the rim  26  of the upper tray  12  in a food tray  10  of approximate lateral dimensions 6-8 cm by 8-10 cm. The flange  18  of the upper tray  12  may be sealed to the flange  20  of the lower tray  14 . A lid  22  is heat sealed to the flange  18  of the upper tray  12 , where the lid and the flange  18  of the upper tray  12  are coextensive. Alternatively, the lid  22  is glued to the flange  18  of the upper tray  12 , or in another embodiment, instead of a lid or in addition to a lid the entire food tray  10  is sealed with shrink wrap. 
     Referring to  FIG. 2 , an embodiment of a food tray  10  is shown to include upper tray  12  lifted out of lower tray  14 . When the upper tray  12  is lowered into the lower tray  14  to rest snugly in the lower tray  14 , the bottom surface of the lower tray reaches close fit line  16 , and steam is prevented from flowing between the upper tray  12  and lower tray  14 . Vent holes  24  in the lower tray  14  are below the close fit line  16  to allow for escape of steam when the second food product is subject to microwave energy. One or more vent holes  24  may be used. The vent holes  24  may have any suitable shape and should be sufficiently large to prevent steam build up in the lower tray  14  when moist food in the lower tray  14  is subject to microwave heating energy. Preferably, the vent holes  24  are located fairly close to the close fit line  16  but above a level of food in the lower tray  14 . To allow food to fill the lower tray to a maximum amount, close to the base of the lower tray, the side walls of the upper tray may be stepped inward near the base of the lower tray to allow the vent holes  24  to be above the base of the lower tray, but still below a close fit line. The vent hole or holes  24  may be distributed in any convenient fashion around the encircling wall  17  of the food tray. The food tray  10  may be made of any suitable material such as paperboard, which allows labels to be printed directly on the food tray  10 , or plastic, such as injected plastic, which can be covered by a sleeve, with the label printed on the sleeve or directly on the plastic.