FIELD OF THE INVENTION
This invention is related to film wrapping bundles of articles or articles with heat shrink film by providing a film having better tear strength when lifting the bundle. A bundle is defined to include an article or a collection of articles.
BACKGROUND OF THE INVENTION
After heat shrinking a film wrapped bundle moving on a conveyor, the sides of the bundles are not covered with the film. This creates an opening on each side of the bundle for manually lifting the bundle by gripping the film through the opening. British Patent GB 1,341,644 discloses that to reduce the risk of tearing during the manually lifting of the bundle, the edges of the film can be folded, This reference does not describe an enabling disclosure of an apparatus or a teaching how the folded edges can be achieved.
The objective of this invention is to provide a commercial process and apparatus for folding the film edges of a thin film to create an overlap whereby the tear strength of the openings is substantially increased.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an unshrunk film moving on a conveyor having a twisted plate to lift the film and to fold the edges of the film.
FIG. 2 shows a static seal and film folding rollers.
FIG. 3 shows a heat shrunk film wrapped bundle having folded edges.
FIG. 4 shows a film roller pressing against the film as the film moves on the twisted plate.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1, 2 and 3 show a heat shrink film 1 leaving rollers 14 and 15 and moving on top of twisted plate 4. Twisted plate 4 lifts and turns the edge of the moving film upward to establish a fold point for overlapping the edge of the film. The twisted plate causes the edge of the film to fold from its upward position to overlap the film. The overlapping of the film causes the folded film to move underneath the twisted plate. Film folding rollers 3 and 5 press down on film 1 to establish the desired width of the film overlap. A wider fold is formed as the film formed roller 3 and 5 increases the distance the film 1 is lowered. The location of film roller on the film with respected to the twisted plate point can be anywhere adjacent the length of the twisted plate as long the width of the fold can be adjusted by lowering the film. Preferably the location of the roller on the film is adjacent the length of the twisted plate at its midpoint. Rollers 3 and 5 can be substituted by a single roller running across the film. Afterward film 1 with folded edges is moved over roller 6 to an electrostatically sealer 7 where the fold is sealed. The film with the sealed folds is used to film wrap a bundle of containers at film wrapping station 11. After film wrapping, the bundle is conveyed to a heat shrink tunnel 12 where the folded edges of the film form an opening 10 where the folded edges provide a tear resistant opening after heat shrinking. FIG. 4 shows a film folding roller support rod 8 supporting film folding rollers 3 and 5 while pressing against film 1.
Usually a one inch fold is sufficient to achieve a desired tear strength Other sealing devices can be used such as heat or glue to maintain the fold. The heat shrink film with the folded edges can be substituted for any film used for film wrapping bundles or articles with a heat shrink film. U.S. Pat. No. 9,216,832 issued on Dec. 22, 2015, U.S. Pat. No. 7,836,670 issued on Nov. 23, 2010 and U.S. Pat. No. 6,761,014 issued on Jul. 13, 2004 invented by Alain Cerf are incorporated by reference in their entirety. These patents show various conventional film wrapping bundle technologies such as film wrapping and heat shrinking. During heat shrinking the folded edges can bond together to further increase the tear resistance when manually lifting the product.
Patent Application
20200156841
