Patent GB-695196-A (GB)
Title: Improvements in and relating to multi-ply valve sacks
IPC: B65D30/24
Filed: 1949-07-20
Abstract: 695,196. Paper bags. PAPER SACKS, Ltd., GROSSET, W. E., and OWENS, W. V. July 12, 1950 [July 29, 1949], No. 19132/49. Class 94(ii) In making multiply diamond corner blockbottom valve bags of the type wherein the plies at each face of a flattened bag tube length are overlapped progressively and form stepped or staggered margins, the plies are so shaped that longitudinal tongues are provided which project beyond the outermost ply at diagonally opposite corners of the bag length and extend laterally substantially to or beyond the transverse folding lines of the face flaps, so that when closing the ends of the bag the face flaps are adhesively secured to margins of the projecting tongues. The diagonally opposite tongues projecting as stated may be formed on one ply only, or one tongue may be on one ply and the other tongue on another ply; alternatively, two pairs of diagonally opposite tongues may be provided, one pair being on one ply, or distributed between two plies, and the other pair being on another ply, or distributed between two plies. Fig. 3 shows a four-ply arrangement comprising plies 1-4 each of which is formed from a web that is perforated transversely and slit longitudinally at bag-length intervals, so that when detached by the application of longitudinal tension a tongue formed in one transverse edge is accompanied by a complementary recess in the edge from which it is detached. As shown a tongue 5 on the upper edge of the ply 3 and a tongue 6 on the lower edge projects beyond the outermost ply, and these tongues include the lines c-c and d-d about which the associated plies are folded inwardly to form a tube of bag length, the lapped longitudinal margins being secured together by adhesive in known manner. Fig. 4 shows the relative positions following the first fold towards the formation of a diamond block-bottom, with the tongue 5 at the corner 8 projecting inwardly to provide a flexible projection which will prevent sifting through a valve formed at that corner. At the lower corner 9 the tongue 6 extends inwardly beyond the normal edge 12 and provides an additional pasting area, while the recesses 6a and 5a at the other corners 7 and 10 provide greater flexibility. Fig. 6 shows the final form of the folded bag, wherein side portions 19 and 20 are folded inwardly about lines 21, 22 subsequent to the folding of the side portions 15, 16 about the lines 17. 18. An integral sealing label 23 may be provided by slitting the outer ply 1 longitudinally as far as the diamond edge 24 at one corner 7, and omitting the paste line at the corner 8. In a modification employing three plies the intermediate ply 25, Fig. 7 (not shown), is provided with extension tongues at diagonally opposite corners, and corresponding recesses at the other corners, while in a further modification Figs. 11-14 (not shown) employing five plies, the diagonally opposite tongue extensions are applied to corresponding parts of both the third and fourth plies, thereby providing adjacent tongues 40, 41 at one corner and similarly adjacent tongues 42, 43 at the diagonally opposite corner, one tongue of each pair extending slightly beyond the other and thus providing a 3 ply lock at the corners. Specification 623,313 is referred to.