Packing containers and blanks therefor

In a packing container of the type which is manufactured from a plane, substantially rectangular blank of a substantially rigid but foldable and tearable material, said blank including a crease line pattern, an edge zone along one side thereof, and four rectangular end panels adjacent said edge zone, said blank being formed into a tube having two ends, a first of said two ends having a bottom closure and a second of said two ends being closed by a bellow folding including a sealing fin, said sealing fin being formed from said edge zone, two of said four rectangular end panels being placed obliquely to each other and another two of said panels each being divided into three triangular panels and folded inwardly of said tube to form said bellow folding, four material layers of said blank being joined to one another in said sealing fin, the improvement comprising said sealing fin including a top line adjacent said one side thereof and a footline adjacent said bellow folding and a tearing indication is provided in said sealing fin along a line between and parallel to said top line and said footline to weaken the material layers along said tearing indication, a first seal being formed between the material layers between said tearing indication and said footline and a second seal being formed between the material layers between said tearing indication and said top line, said first seal immediately adjacent the tearing indication being substantially weaker than said second seal immediately adjacent the tearing indication so that said tearing indication defines a boundary line between strongly sealed material layers and weakly sealed material layers.