1. Field of the Invention
The present invention pertains to the application of zipper strips in the transverse direction. More particularly, the present invention pertains to the use of a narrow band of untreated surface on the leading edges of the flanges that permits the tack sealing of the flanges together by non-continuous sealing bars.
2. Description of the Prior Art
In the prior art, the application of a zipper to a film is taught in such references as U.S. Pat. No. 4,909,017 entitled xe2x80x9cReclosable Bag Material, Method and Apparatusxe2x80x9d, issued on Mar. 20, 1990 to McMahon et al. However, in a xe2x80x9cpinch and pullxe2x80x9d configuration, such as is disclosed in U.S. patent application Ser. No. 09/244,519 entitled xe2x80x9cPinch and Pull Open Reclosable Bag and Zipper Thereforxe2x80x9d, filed on Feb. 4, 1999 for Johnson, there has been a tendency for the leading edge of a zipper to jam as the web moves over the collar. Similar prior art can be found in U.S. patent application Ser. No. 09/393,206 entitled xe2x80x9cTransverse Direct Zipper Tapexe2x80x9d, filed on Sep. 9, 1999 for Malin et al.
It is therefore an object of the present invention to reduce the tendency for a leading edge of a zipper to jam as the web moves over the collar in a form fill and seal (FFS) device.
This and other objects are achieved by removing the heat resistant coating from the leading edge of the base web and likewise from portions of the four legs of a flange zipper strip in a pinch, grip and pull configuration of a form fill and seal (FFS) device. Further, a serrated seal bar is used in the web direction to seal down the leading edge to keep the fourth or top edge of the flange from curling or flipping up, without sealing into the bag. The serrated seal is both a carrier seal and a tack seal that breaks open when the package is opened for use.
USPTO Backgrounds
USPTO Backgrounds