Flexible container having interlocking rib and groover closure elements

1,160,371. Strip fastenings. SEISAN NIPPON SHA K.K. 21 Oct., 1966 [24 Oct., 1965], No. 47321/66. Heading E2S. Material for forming plastics bags comprises sheet plastics material having co-operating fastening elements 16, 17 projecting from a surface of the sheet material, the said fastening elements being adapted to interengage with one -another, one of the fastening elements being a male rib formed with an undercut indined surface 22 on one side and a non- undercut contour on the other side; the other fastening element being in .the form of a female rib with a groove, having a projection 40 directed towards the interior of the groove on the side co-operating with the undercut inclined surface of the male rib, the inclination of a surface of the projection which engages the undercut surface and of the undercut surface of the male rib corresponding to one another, the other side of the groove engaging the non-undercut side of the rib, and being connected, exteriorly of the rib, to the adjacent sheet material by means of a web 43 to facilitate opening of a bag formed from the material. The sheet material is provided with two flaps 14 and 15 beyond the fastening elements to enable the fastening elements to be separated and the construction, of the fastening elements is such that separation by pulling the flaps 14 and 15 apart is easy but separation under the pressure of. contents in the bag is resisted by the engagement of the undercut surface 22 and the. corresponding surface of the projection 40..In a modification the non-undercut contour consists of a convex portion and a concave portion and the female rib has a second projection which engages the convex portion. In a further modification the female rib instead of being provided with the second projection has a substantially flat end portion which overlies the convex portion.