| 摘要 |
1367001 Valve bags CANADIAN INDUSTRIES Ltd 1 March 1972 [24 March 1971 18 June 1971 2 Nov 1971] 9540/72 Heading B8K A valve bag of plastics film has a rear wall 21 of two plies and a front wall of two ply overlapping panels 22, 23, the panel 22 being interdigitated between plies 28, 29 of panel 23 and the inner ply 28 may be longer than the outer ply 29. By forming seals 30-34 extending partway across panels 22, 23 adjacent one end a valve is formed. In an alternative construction (Figs. 1 and 2, not shown) both plies of the panel 23 lie under the plies of panel 22. The seals may be continuous as shown or in the form of dots. The bag may be formed from a plastics tube or from separate sheets sealed together. The walls may comprise more than two plies, or only the panel 23 (forming the valve) need contain more than one ply. The bat may be of a heat sealable film or have a coating of a heat sealable material and may be made of films of olefine polymer or copolymer, of P.V.C. or low density polyethylene. |
