Block bottom bag

• Main Authors: SYMONS LLOYD GEORGE, GREENHALGH MARGARET CLARE, GLASS JAMES STUART
• Format: Patent
• Language: English
• Published: 20.07.1965
• Subjects: ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS,e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES,DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; CONVEYING; HANDLING THIN OR FILAMENTARY MATERIAL; PACKAGES; PACKAGING ELEMENTS; PACKING; PERFORMING OPERATIONS; STORING; TRANSPORTING

965,338. Block-bottom bags. ST. REGISCONSOLIDATED PACKAGING Ltd. June 4, 1962 [June 8, 1961], No. 21462/62. Heading B8K. A bag is formed from heat-sealable fold-flat tube by folding in corners 17a (Fig. 3), and then heat sealing in position a cover 20. The cover 20 may consist of a flap 51, 52 (Fig. 11) and slits 53 may be formed in the tube before folding. A weld may reinforce the fold 60-60. The flaps 51, 52 of Fig. 11 are in opposite walls of the tube so that blanks can be cut from a tubular web without waste. A valve sheet 90 may be welded at 91 to the bag before the cover 20 is added, the corresponding end of the cover 20 being left unwelded. Further welds 93, 94 (Fig. 20) or 95 (Fig. 21) between the valve sheet and the cover sheet 20 may modify the shape of the valve. The valve sheet and the cover sheet 20 may extend beyond the margin of the bag, and may be welded at the edges to form a tube which can be folded over for closure. The tube may be gussetted. The valve flap may be sealed by heat-sealing, taping or gluing, and folded upwardly as shown at 98 in Fig. 26 to provide a pocket into which the projecting end of the valve tube formed with the cover sheet may be tucked. Alternatively a separate valve tube, which may be narrower than the bag, may be used (Fig. 30, not shown). A shield is used, when forming the welds for the bag, to prevent undesired welds from being formed. The welds may be formed by applying heat, by highfrequency heating, or by ultrasonic sealing. The bag may be formed of gusseted tube. Suitable materials are thermoplastic film, which may be laminated, and paper or fabric lined with thermoplastic sheet.