Abstract: Packaging bags are produced by cutting a larger material sheet into individual portions and folding each of these individual pieces to form a main body having a front wall, a back wall, side walls which stand up from a flat bottom. A lid for closing the upper opening is uniformly sloped upward from the front wall to the back wall. A ridge is formed, extending upward from the back wall, for sealing the bag closed. A trapezoidally folded flap extends upward from the back wall and is folded forward over the seal ridge. A pair of fastening tapes is used to keep the flap detachably attached to the seal ridge such that the bag, after it is once opened, can be closed again. Instead of the fastening tapes, an elongated member serving like a belt loop may be used to keep the flap retractably inserted under it to keep the flap closed.

Abstract: It is an object of the present invention to manufacture efficiently packing bags which are packed in cases of corrugated fiberboard or the like at a good filling rate without dead space. A film sheet 14 from a bobbin 13 is formed to a quadrangular barrel body 24' along the outside of a cylinder 21 through a former 20, a top plane 10 is squeezed and sealed in a onesidedly slant manner, and then the quadrangular packing bag thus manufactured is transferred, through a guide chute 55, on a belt conveyor 54 in the regular posture (a) or inverse posture (b) to a case of corrugated fiberboard or the like. Conventional packing bag manufacturing mechanisms can be used, packing bags can be mass-produced fully automatically in a uniform manner at a high accuracy, and packing bags thus manufactured can be packed in cases of corrugated fiberboard or the like without dead space, thus reducing costs of transport securely.