| 摘要 |
PROBLEM TO BE SOLVED: To provide a square paper cup less easily deformed on the whole with a top curl portion forming a straight portion largely reinforced as a flange in a general flange-pressing step which is a method of forming the flange by squeezing the top curl portion by using the heat, the ultrasonic wave, etc., for reinforcement to form the flange without any problems in forming the square paper cup. SOLUTION: In this square paper cup having the top curl portion on an opening end of a square barrel portion, a notch is formed in a portion forming a corner portion of a blank constituting the barrel portion to form the top curl portion on the opening end, and the top curl portion is pressed to form the flange portion.
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