Vertable tray and lid assembly for heating foods

Claim 1

A tray and lid assembly loaded with a pre-cooked meal which rests on the tray but is out of physical contact with the lid, the loaded assembly being first placed in storage in a cooling chamber and thereafter being transferred to a heating oven to reheat the food to a serving temperature whereby in the cooling mode the meal is subjected to a temperature well below ambient temperature, and in the heating mode to a temperature well above ambient temperature, said assembly comprising: A. an open-mouthed tray having a polygonal shape provided with side walls whose junctions form corners, said tray being fabricated of synthetic plastic material non-reactive with the meal, said tray being also provided with a continuous outwardly-extending flange which surrounds the open mouth and has a peripheral bead; B. a lid having the same shape as the tray and fabricated of the same material, whereby the tray and lid have the same positive thermal coefficient, said lid having a continuous downwardly-extending skirt, the inner wall of the skirt having a rib thereon to define at its junction with the lid a cavity to receive the bead of the flange, the rib being interrupted at the corners to create air vents; and a continuous underside strip which at ambient temperature is received within the mouth of the tray; said lid in the cooling mode contracting to a somewhat greater extent than the loaded tray in which the meal acts as a heat sink to retard cooling of the tray to cause said strip to shift inwardly with respect to said mouth to create an air leakage path and to cause said bead to press into said cavity to create an outer seal preventing infiltration of ambient air into the assembly, said lid in the heating mode expanding to a somewhat greater extent than the loaded tray in which the meal acting as a heat sink retards heating of the tray to initially cause heated and expanding air within the tray to escape through said air leakage path and said vents, after which said strip is pressed against the sides of the tray to form an inner seal preventing the escape of volatile constituents from the meal.