| 摘要 |
704,261. Paper and like bags. BRITISH CELLOPHANE, Ltd. April 10, 1952 [April 12, 1951], No. 8579/51. Drawings to Specification. Class 94 (2) A double wall flat bag is formed by folding over longitudinally a continuous extruded tube of thermoplastic material and heat sealing the four plies together at distances separated by the width of a bag and severing the bags along the seals so that the mouth of each bag is constituted by folded continuous edges of the material. By offsetting the folding of the tube one edge of the bag mouth may be arranged to protrude beyond the other. The heat sealing may be by a bar or by an electrically heated wire which simultaneously by a transverse movement severs the bags, in which case the tube material is held under tension or folded acutely at the severing point. The bags may be formed in a continuous and partly connected series. Alternatively a continuous flat tube may be heat sealed transversely at regular intervals, then severed along the seals to form flat closed "pillows" of material and the bag formed by tucking one half of the pillow inside the other by hand. To facilitate this the pillows may be formed of trapezoidal form. ' |
