Patent GB-991984-A (GB)
Title: Process of manufacturing sacks
IPC: B65D30/24
Filed: 1963-01-24
Abstract: 991,984. Making plastics bags. H. LISSNER. Jan. 24, 1963 [Jan. 29, 1962; Feb. 12, 1962; March 2, 1962; April 13, 1962], No. 3023/63. Heading B5D. [Also in Division B8] A separating means 30 (Fig. 2) is inserted in the cross-bottom of a plastics bag, prior to folding in the sides 14 and welding, to prevent the bottom being welded to the bag walls. The means 30 may consist of two layers of which the one adjacent to the cross-bottom is of the same material as the bag whereas the one facing the interior of the bag has a higher melting point. Alternatively the means 30 may be of a material such as a layer of paper or metal foil, or a stripof wood or metal which does not unite with the bag bottom and may subsequently be removedthrough one or two slits disposed centrally in the bag wall or in the bag bottom. These slits may be closed by plugs (Fig. 9) which have layers 641, 642 which unite with the bag wall and a layer 643 acting as a separating means and preventing welding with the other bag wall. The separating means 30 may consist of arms which separate into the bag bottom and which are inserted into position through the above-mentioned slit and subsequently withdrawn after welding. The triangular end-flaps 17, 18 (Fig. 2) may be folded about the lines 25, 26 (Fig. 6) instead of 23, 24 and consequently a narrower weld suffices for complete sealing. A swordlike instrument 75 (Fig. 11) may be inserted through a valve sleeve or sheet into the bag bottom to prevent undesired welding. To form a separate valve hose within the bag a valve sheet 79 (Fig. 12) is folded together with a side flap 77 along the line 81 and the other side is folded together with the opposite side flap 76 along the line 82 after folding the side flap 77 outwardly at 80. The flap 77 is finally folded back into its central position and welded. Weld preventing means may be applied to the valve sheet to leave a T-shaped welding area, the bar of the T running along the longitudinal edge of the valve sheet. The valve sheet may be formed by an extension 89 (Fig. 16) of the bag wall. Weld preventing means 91 are provided on the valve sheet together with a lateral incision 92 to allow formation of a separate hose within the bag. A cover-strip may seal the bottom after the side flaps 14 (Fig. 2) have been folded over, and the side flaps may abut, overlap, or be spaced apart under the cover-strip. To reduce the welding area the marginal areas of the reversely folded half portions may be infolded once more. Instead of individual seams on the bag bottom the entire area may be welded by heating into a coherent, softened mass. To facilitate opening a valve hose for filling, a tape may attach it to the bag bottom. The outwardly projecting edge of the valve hose may be infolded or covered internally by an adhesive tape to strengthen the opening during filling of the bag and subsequently uncovered to give a clean edge for welding. The valve may be stiffened in its axial direction and folded into a bottom pocket after filling. An additional sheet 140 (Fig. 26) may be welded at 143, 144, 145 to the triangular portions of the cross-bottom and a valve tube 159, with triangular weld preventing means 127, 128 inserted in the triangles. The means 127, 128 are subsequently removed and further welds are made parallel to the edges 141 prior to turning in the bottom flaps and again welding these together. The valve may be inserted through a slot in the bottom sheet or tacked thereto. The bag tubing may be provided with two short parallel slits at its opening, which provide rectangular extensions 173, 174 (Fig. 30) and wall portions 169 when the end is opened out. A separating means 180 is placed between the bag bottom and the walls prior to welding the cover-strip at 183-186. The edges are then folded along lines 191, 192 and welded together along two parallel transverse lines. Alternatively the cover-strip may be placed beneath the rectangles 173, 174 and be covered on its undersurface with a weld preventing means, thus obviating the need for the separating means 180. The welds 185, 186 may be made after folding in the side sections. Rectangular strips may be removed from the tube ends prior to inserting a cover-strip and welding as before. If these rectangular strips are sufficiently deep (Fig. 35), the rectangles formed from the ends 314 will overlap when the bottom is flattened out and may be welded together both longitudinally and transversely prior to folding in the sides and welding again. A cover-strip 360 (Fig. 58) narrower than the distance between the edges 315 of the side flaps in spread condition may be welded to these at 365 so that the flaps are infolded when the bottom is flattened. The bottom sheets are advantageously made of a soft yieldable material compared with the bag material so that they can withstand extreme stresses applied to the bag. The bag may be carried or suspended by an arm inserted in the pockets formed in the cross-bottom.