| 摘要 |
A sheet of side gusset material 3 is folded into halves, superposed into two layers and interposed between webs of panel material 1 and 2. One of the webs of panel material 1 is folded along a longitudinal folded line 8 to make the webs of panel material 1 and 2 open and make an open surface formed on the webs of panel material 1 and 2. One of the layers of side gusset material 3 is folded along the longitudinal folded line 8 to make the layers of side gusset material 3 open along with an auxiliary gusset portion 7 and make an open surface formed on the layers of auxiliary gusset portion 7. A web of bottom gusset material 4 is superposed on the open surfaces of panel material 1 and 2 and auxiliary gusset portion 7. The web of bottom gusset material 4 and the auxiliary gusset portion 7 are heat sealed with each other while the webs of panel material 1 and 2 and the sheet of side gusset material 3 are heat sealed with each other widthwise of the webs of panel material 1 and 2 with the open surfaces kept being formed. The web of bottom gusset material 4 and at least one of the webs of panel material 1 are heat sealed with each other longitudinally of the webs of panel material 1 and 2 with the open surfaces kept being formed. |
