GB683467A - Improvements in and relating to multiply valve sacks - Google Patents

Abstract

683,467. Making paper bags. PAPER SACKS Ltd., and ROBINSON, P. G. May 18, 1950 [May 20, 1949], No. 13563/49. Addition to 623,313. Class 94(ii) The invention described in the parent Specification is modified by assembling the multi-ply bag lengths with their ends flush and the tongue on the innermost or other ply projecting beyond the flush edges, and either infolding the valve in each multi-ply length so that the tongue extends inwardly beyond the other plies at the valve to form a flexible closing member, and closing both ends of the bag tube by stitching a reinforcing strip across them, or folding both ends of the tube to form a block bottom closure with a valve at one corner and securing by stapling or by adhesive. Fig. 1 shows part of the web providing the ply from which the valve extension tongue 4 is obtained from transverse lines of perforations 3a, 3b and short longitudinal slits 4a, a corresponding recess being obtained at the tail end of the preceding bag length. When this ply is used as the innermost ply of a bag the recess 4 at the bottom is exposed to the interior of the bag and, to avoid the sifting of the contents between the plies at the recess, the margins thereof are pasted in known manner. Similar interply pasting may be employed at the valve corner. Fig. 4 shows a bag tube length with the overlapping longitudinal margins 5 of the webs secured together adhesively in known manner, and the valve corner infolded so that the valve tongue 4 extends beyond the margin 6 of the other infolded plies. The bag is subsequently machine stitched across the flush ends through reinforcing strips 7. Gusseted bags are produced by passing the webs through tubing machines provided with gusset-forming means. Fig. 9 illustrates a stage in the forming of a block bottom bag, the subsequent folding of the margins 9a, 9b being along the.chain lines 10. The width of the tongue 4 should be not less than the distance between the lines 10. In a modification, Fig. 7, (not shown) the tongues 4, instead of being of rectangular form, are bevelled at the corners and provided with short slits along the lines of fold to facilitate folding.