| 摘要 |
1,026,108. Plastics valve bags. ST. REGIS PAPER CO. July 3, 1964 [July 5, 1963], No. 27488/64. Heading B8K. [Also in Division B5] A plastics valve bag has walls 2, 3, 4, 5, 6 (Fig. 3, not shown) made from flexible thermoplastic sheet material with a side seam uniting the overlapping side walls 2, 6 and incorporating a valve opening within the overlap of the side walls 2, 6; there being a valve sleeve 9 consisting of a rectangular sheet of flexible thermoplastic material folded over once upon itself and the outer surfaces being jointed to the overlapping walls by extruded stripes 7, 12 of thermoplastic material from which the bag is formed, one stripe also joining the overlapping side walls 2, 6 along the length of the bag; there being also an end closure uniting the top edges of the valve sleeve and the conterminous edges of the bag walls. The bags may be made from a continuous web which is cut into lengths along the top edges of the valve sleeves 9 and closure is effected by sewing, adhesive tape, heat sealing or preferably, by a preliminary heat sealing of the edges and then extruding a continuous U-shaped cross-section stripe of molten thermoplastic material over the edges. In a modification the flaps of the valve sleeve 9 are cuffed on both sides before being joined to the bag. Suitable materials are polyethylene, polypropylene, polyvinyl chloride, and polyvinylidine chloride resins; the thickness of the valve sheet is one half or less that of the bag walls. |
