| 摘要 |
A method for continuous fabrication of bags from a longitudinally advanced two-layer thermoplastic film web fed tangentially onto a rotating drum for carrying out transverse web seam welding and severing, with high speed operations facilitated by tensioning the web as it is being fed onto the drum, and with web tension release just before or as the seam welding is effected to ensure good quality seaming. Apparatus including a continuously rotating welding drum; circumferentially spaced resiliently mounted projecting longitudinal welding anvils; a welding bar engageable with the web on the anvils; feed rolls spaced from and a web guide roll adjacent the drum tangentially directing web onto the drum to be carried past the welding bar under vacuum gripping to discharge guide tapes; a drum-adjacent bag pick-off vacuum roll passing finished bags to discharge conveyor tapes; a web loop forming tensioner between the feed and guide rolls including a reciprocating loop former roll engageable with one web side; and drive means for effecting a web sealing and severing contact of the welding bar at an anvil, for loop forming roller reciprocation to develop tension drawing the in-fed web taut onto the drum and to release the web tension for welding, and for continuously rotationally driving the drum; the drum having a numerously finely perforated web-accepting circumferential surface and, therebeneath, divided chamber structure between successive anvils, and means for subjecting chambers to web gripping suction and web lifting air pressure to aid discharge of finished bag from the drum. A variant welding bar structure is disclosed. |
