| 摘要 |
<p>A plastics sack incorporates a valve which allows air to be sucked from the interior while it is being filled, so that there are no air pockets left, and which is easily sealed by welding afterwards. The wall (1) of the bag has a set of perforations through it which match a corresponding set of holes in a plastics sheet (14') forming part of the valve. This valve consists of two plastics layer (14, 14') which have been previously welded together along two lines (7, 8) one end. The first sheet (14') is welded over the perforations by a ring shaped weld (16), then the remaind of the two sheets are welded together at that end by a c V shaped (20), so that the only communication, which the interior of the bag through the perforations, is between the parallel welds and the open end (21) remote from the perforation.</p> |
