| 摘要 |
A machine and method for forming a single thickness bottom in a bag of heat-sealable sheet material such as polyethylene film from a folded strip of such material of indefinite length, the folded edge having an inwardly folded gusset therein forming a pair of double thickness marginal panel portions. The machine includes an anvil having longitudinally extending faces lying in planes symmetrically inclined above and below a central horizontal plane, each anvil face having a groove formed therein in the shape of two legs of an isosceles right triangle whose altitude lies in a vertical plane perpendicular to the direction of strip movement. During strip movement the panel portions are folded apart and are drawn along the anvil faces. The strip is momentarily stopped, and clamping means immediately upstream and downstream of the anvil grooves tightly retain the panels stationary on the anvil, with portions bridging the grooves. A pair of electrically heated cutting and sealing knives, each having an edge registering with one of the anvil grooves but of narrower width than the groove, are brought into sealing and cutting relation with the strip panel portions which bridge the grooves, sealing the perpendicular strip panel edges and cutting triangular chips from the panels. Upper and lower vacuum hoods immediately inwardly of the grooves communicate with a vacuum source for removal and disposal of the chips. The anvil is cooled to minimize film build-up, desirably by circulating cooling water through its hollow interior. After chip removal the vacuum supply is interrupted, the knives and clamping means are retracted, and the strip is then indexed downstream, with means being provided to support the strip panels in a common plane with the remaining portion of the strip. Individual bags are formed from the strip downstream of the present machine by conventional sealing and cutting transversely of the strip intersecting the apex of the triangular cut-outs in the strip panels. |
