| 摘要 |
PURPOSE:To prevent a warp of a tray by a method wherein embossed portions are formed near the bottom surfaces of quarter circular portions at four corners of the bottom surfaces,a flange is formed at an entire circumference of the bottom end surface and a central part of the bottom surface is formed as a circular planer drawn bottom surface. CONSTITUTION:Material forming a bottom surface 10 is extended to generate a surplus margin by embossed portions 14 made near quarter circular parts 11 at four corners of a tray 3 and some curved strains of projected shape are formed. When a food 1 is placed on the tray 3 and cooked with heating operation, a flange portion 12 becomes hot and in turn the bottom surface 10 becomes cold, resulting in making a difference in their thermal expansion to generate a relative pulling action between the flange part 12 and the bottom surface 10. The projected and deformed portions may accommodate their relative pulling actions. Also in the case that a cold food is placed on the tray after only the tray 3 is preheated, their relative pulling action generated between the flange 12 and the bottom surface 10 is accommodated by the projected and deformed portions to prevent a warp of the tray. With this arrangement, it is possible to prevent a warp of the tray and perform a better cooking without generating any dispersed heating. |
