| 摘要 |
<p>A former shoulder 15 has a hollow 41 and a lower edge 42. A film drive assembly includes rollers 21, 22 mounted on vertically spaced parallel axes and a belt 24 mounted on the rollers. One roller projects above the former shoulders lower edge or above the former shoulder base plate. Ideally a roller projects into the hollow. There can be two belts each supported by three rollers, the largest 23 of which drives the belt with the others idling. The belt preferably moves in a triangular path, the path length between the driving roller and an idling roller being horizontal. There may be a heating bar to heat film material for sealing. A further idler roller 29 may be outside the belt to urge it towards the driver roller. There can be sealing jaws whose outer surface move slower than the belt when they are brought together to seal; and possibly reverse.</p> |
