The pack is sealable material, e.g. weldable foil, is formed from a tube in this material by inter-folding and sealing together the super-imposed sides (1,2) of the foil at the top and bottom of the pack. These sides are folded together such that the main weld (10) joins the outer surfaces of the foil. This is pref. effected by first producing a U-section fold (1',1" and 2' and 2") in the superimposed end sides extending at right angles to these sides and then folding the extreme portions (1"' and 2"') inwards between the inner uprights (2', 2") of this U-section so that the subsequent welding operation produces a main join (10) between the said outer surfaces. Used for forming pack by inter-folding and seal-welding the super -imposed sides at the ends of a tube in e.g. heat-sealable foil material. The arrangement produces a reliable weld by sealing together (10) the outer surfaces (as opposed to, or in addition to welding the inner surfaces at 5) of the material so that the strength of the weld cannot be affected by the presence of the contents of the pack partic. if this is filled with a powder which could adhere to its inner surfaces.
展开▼
