| 摘要 |
Apparatus for heat-sealing polymer films which shrink when heated include provision for moving the zone of application of heat and pressure during the heat sealing process. This allows for shrinking of the polymer film in a region adjacent to the heat seal so that the film thickens and is more resistant to failure in use through peeling. The apparatus includes a pair of sealing bars (4, 5) one of which (4) is wedge-shaped and the other of which (5) is flat. Both bars are heated and one of them can be moved in direction (12) to apply pressure to film located between the bars. At the beginning of the heat sealing step pressure is applied over an initial zone along the apex of the wedge. Subsequently the bare (4) is rolled around an axis located near to the apex of the wedge, in the direction shown by the right hand end of arrow (13), to apply heat and pressure over a wider zone located adjacent to the initial zone. |
