Sift-proof carton and method of manufacture

A method of sealing the ends of a four-sided sift-proof carton, each end of the carton having a pair of spaced minor flaps, an inner major flap and an outer major flap spaced from said inner major flap, each of said minor flaps and said inner and outer major flaps being formed with opposed ends, a fold line joining a side of the carton and a leading edge opposite said fold line, the spacing between said inner major flaps and said outer major flaps at the fold lines of the carton defining the depth of the carton, comprising:

• folding said spaced minor flaps from a spread position inwardly toward the center of the carton forming an exposed surface on each of said minor flaps between said fold line and said leading edge thereof;
• dispensing a strip of foamed adhesive material onto each of said opposed ends of said inner major flap between said fold line and said leading edge thereof with said inner major flap in a spread position relative to the sides of the carton;
• dispensing a first strip of foamed adhesive material onto each of said opposed ends of said outer major flap between said fold line and said leading edge thereof, and a second strip of adhesive material onto said outer major flap between said first strips with said outer major flap in a spread position relative to the sides of the carton;
• folding said inner major flap from said spread position toward the center of the carton so that said strips of foamed adhesive material on said inner major flap contact said exposed surfaces of said pair of minor flaps, said inner major flap having a width dimension between said leading edge and said fold line thereof which is substantially less than said depth of the carton so that a large gap is formed on said exposed surface of each of said minor flaps between said leading edge of said inner major flap and said fold line of said outer major flap with said inner major flap folded toward the center of the carton;
• folding said outer major flap toward the center of the carton so that said first strip of foamed adhesive material on each end of said outer major flap contacts said exposed surface of one of said pair of minor flaps and said second strip of adhesive material contacts said inner major flap, said first strips of foamed adhesive material on said outer major flap filling said gaps on said exposed surfaces of said minor flaps between said leading edge of said inner major flap and said fold line of said outer major flap to form a sift-proof seal thereat.