GB704160A - Improvements in and relating to multiply paper blockbottom valve bags or sacks - Google Patents

Abstract

704,160. Paper bags. PAPER SACKS, Ltd., GROSSET, W. E., and OWENS, W. V. Jan. 2, 1952 [Jan, 26, 1951], No. 2079/51. Class 94 (2) In a multiply paper blockbottom bag or sack having three or more plies 1, 2, 3 at each face of a flattened bag tube progressively overlapping and forming flaps adhesively secured together in forming the blockbottom closure, the corners of the latter are formed by overlapping tongues each exposing areas of at least two plies for adhesion with the naps, the tongues being laterally defined by slitting longitudinally the webs forming the plies and longitudinally defined by transversely perforating individually in a stepped manner each of the webs before passing them into a multiply bag tube forming machine. The bag lengths are then formed by rupturing the multiply bag tube along the perforations and no paper is thus wasted. As shown, with the end flaps of the upper face of the flattened bag tube bent inwards to form the corners, at least one ply at each corner tongue is preferably left unexposed and, at a valve corner, if'the tongue of one ply, e.g. 2, extends beyond all the others a flexible valve seal 2x is formed by it when the rectangular closure flaps 6, 7 have been sealed down along the lines 9, 9a, except at the valve corner. In a modification the webs are slit so that the tongues overlap laterally as well as longitudinally so exposing further areas of lower plies for adhesion to the plies of the flaps. In a further modiflcation the uppermost plies at a valve corner are of the same length.