| 摘要 |
PROBLEM TO BE SOLVED: To provide a paper bag with a valve port wherein leakage is difficult to occur even if a fine powder is filled. SOLUTION: One of surfaces of an opening end of a cylinder is folded in an acute angle along a first crease (a) while forming triangular developing surfaces 4 at both corners to form a rectangular opening. A flat cylindrical valve inlet 5 narrower in width than a distance between second creases b, c is stuck to one of the developing surfaces 4. Both surfaces of the opening end are further folded in an obtuse angle sequentially along the pair of second creases b, c so that a gap 5a is left between right and left end rims of the valve port. Ends of a pair of trapezoidal folded portions 15, 16 are overlaid on the valve port 5 and the developing surface 4 to be pasted, and in addition, the trapezoidal portions 15, 16 are pasted together. An outer patch 7 is stuck to the bottom end thus obtained, forming the paper bag 1. A hot gluing adhesive is applied on an internal surface of the valve port 5 and an internal surface of a sealed portion 8 of the outer patch 7. Ends of the valve port 5 protrude from slant end rims 15a, 16a of the trapezoidal portions 15, 16.
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