1. Field of the Invention
The present invention relates to the packaging art, and, more specifically, relates to plastic bags or packages formed from extruded polymeric resin sheet material. In particular, the present invention relates to plastic bags or packages of this general type which have zipper closures extruded from polymeric resin material and attached thereto to form a reclosable plastic bag or package.
2. Description of the Prior Art
Plastic bags and packages having zipper enclosure extruded from a polymeric resin material, such as polyethylene, are old in the art. Commonly, bags and packages of this type are formed from plastic sheet material on a form-fill-and-seal (FFS) machine and concurrently filled with a consumer item or items. During the formation of the bags or packages, zipper closure strips are introduced between two facing internal portions of the plastic sheet material and sealed thereto.
Recently, the need to attach zipper closure strips to previously formed or manufactured plastic bags has arisen. The bags in question are formed from a tube of polyethylene. During manufacture, the tube is flattened, and sealed transversely at regularly spaced intervals. The seals ultimately become the bottoms of the bags. Adjacent to each seal, the flattened tube is perforated, so that the bags may be separated from one another. The perforations form the mouths or tops of the bags. The tube, perforated and sealed as described, is wound up in the form of a roll including as many as several thousand individual bags. Individual bags are fed, bottom first, from the roll by automatic bag filling equipment, which sequentially deposits a consumer item or items into each bag and seals each bag transversely below the perforations at the mouth or top thereof.
Where bags have previously been formed or manufactured, however, the zipper closure strip or strips must be attached to the outsides of the bags. Such attachment is carried out by some form of heat sealing. Unfortunately, because there is no way to keep the two layers of a previously formed bag separated from one another, there is a tendency for them to be sealed to one another during the attachment process.
The present invention provides a solution to this problem.