| 摘要 |
In flat bag-making machines, a web which is thermoplastic or coated with a thermoplastic layer is withdrawn from a supply roll and continuously advanced, formed into a tubing in a tube-making device, whereafter the tubing is processed to form flat bags in that welded or hot glued seams are formed and the tubing is transversely cut. The apparatus comprises a carrier, which supports the web and on which the heated welding or hot gluing jaws are mounted to be reciprocable to and from the carrier, whereas the carrier itself is reciprocable relative to the web in the direction of travel thereof in such a manner that the movement of the carrier relative to the web is zero for a time which is sufficient for the welding or gluing operation. The carrier consists of a rocker, which is pivoted on an axis that is transverse to the direction of travel of the web and extends through the transverse center plane of the rocker, the latter is pivotally movable within a loop which is formed in the web by means of two stationary guide rollers, and the rocker is provided with drive means which impart to the rocker a rocking motion at a peripheral velocity which is temporarily equal to the velocity of travel of the web. |
