| 摘要 |
According to the present disclosure a method is provided wherein tubular thermoplastic material is intermittently fed between opposed transversely extending seal bars operating in timed relation with the intermittent feeding of the web to sequentially perform cutting and sealing of the web during its period of repose. To insure a clean straight transverse cut, which occurs momentarily before transverse sealing, the web is held under tension between longitudinally spaced draw and feed rolls. Immediately after the web is transversely severed, the seal bars are brought into pressure engagement transversely sealing the web along a margin which will define the bottom of the bag. While the sealed portion of the web is at the sealing station, cooling air is discharged along the sealed portion of the web to effect cooling. Before the web is fed an additional increment, it is momentarily fed rearwardly to avoid the possibility of adherence to the seal bars. |
