Automated folding and welding of shrink wrap film around box - with control of weld location and trimming

摘要

Box-shaped packages are wrapped in thermoplastic film by passing the box through the plane of a curtain of film which is wider than the box by more than the depth of the box, to form an overlong sleeve. The film is deflected, welded and trimmed so that one panel (2a) of film covers the base and another (2b) covers both sides and the top of the box, the panels being welded together (3,4) alongside the base edges (1a,b) of the box. Automated flaps fold the ends of the sleeve over the ends of the box to form lap welded panels (5,6) and excess material (9) left parallel to the sides of the box is then automatically trimmed off. Used esp. for packs of containers of e.g. lubricants enclosed in shrink-wrap film to contain any leakage from individual containers. Opt. the film may include microperforations to allow passage of air or water vapour without loss of liquids. The fold pattern used minimises the area of film used while ensuring complete enclosure and locating the welds at positions which are not sensitive to mutual damage by other packs positioned alongside.