Method and apparatus for forming Z-shaped folds in a tubular film and for inserting the latter into a woven tubing

Z-shaped folds are formed in a tubular film and the latter is inserted into a woven tubing as the latter is woven and collapsed in a circular loom. The tubular film is squeezed between pairs of pinch rollers and is then inflated to form a bubble, which is supported by annular surfaces at the weaving ring and at a distance from the latter so that the bubble bulges between the annular surfaces so as to form an annular bead. A Z-shaped annular fold is formed in that tubular film in that edge portion of said annular bead which is remote from the weaving ring is pushed into the latter. For the fixation of the Z-shaped folds e.g., at the portions which will subsequently form the rims at the open ends of the bags to be made, it may be desirable to apply adhesive to the tubular film above the Z-shaped folds and to force said adhesive-coated portions against the inside surface of the surrounding woven tubing.