Plastic zipper having preventing function against unfairly unsealing, and the manufacturing method and manufacturing appartus thereof

The present invention relates to prevention against unfairly unsealing of a plastic zipper, of a plastic zipper with a slider, and of a bag equipped with the plastic zipper, which are easily opened and re-closable while they keep hermetic sealing, and which are used as packaging materials of foods, medicines, electronic products, etc.

Bags equipped with plastic zippers are widely used as packing materials for foods, medicines, electronic products and other goods. Especially, bags equipped with plastic zippers with sliders are widely used as packing materials which are easily opened and re-sealable.

However, with diversification of contents of packages, further more advanced air tightness has been required for a package, and an additional function of a package wherein broken seal can be detected after it has been hermatically sealed is desired because the sealed package which has been opened by wrong purpose or by an inaccurate error may cause various troubles such as mixing of foreign substances or spoiling of quality of contents in the package.

The inventor of the present application disclosed conventionally known examples of plastic zippers with the sliders having preventing function against unfairly unsealing in FIGS. 14 to 19 of WO 2005/048763 A1 (Patent document 1).

In the example illustrated in FIG. 14 (a partially sectioned perspective view) and in FIG. 15 which is a sectional view taken along arrows A-A′ in FIG. 14 of the above-mentioned Patent document 1, in a bag body having a zipper with a slider, the zipper and the slider fitted at the upper portion of the bag body are covered by a perforated covering film. Since a system is applied in this example wherein when a new bag is opened first, the zipper is opened or closed by the slider after the covering film is torn along the perforations, the system is simple and has a good operability. However, there is a disadvantage that the bag has bad appearance and inferior industrial productivity.

In the example illustrated in FIG. 16 (a partially sectioned perspective view) and in FIG. 17 which is a sectional view taken along arrows B-B′ in FIG. 16 of the above-mentioned Patent document 1, in a bag body having a zipper with a slider, a partitioning film having perforations is disposed inside the bag. A system is applied in this example wherein when a new bag is opened first, the perforations of the partitioning film are opened after the zipper is opened by the slider, and therefore, the bag has good appearance and productivity. However, when contents of the bag are fine particles such as powder, there causes a problem that the fine particles are clogged on a portion of the partitioning film and cannot be discharged smoothly.

FIG. 18 of the above-mentioned Patent document 1 discloses a system applied to a bag body having a zipper with a slider, wherein an upper portion of the zipper is spot welded under a condition wherein the slider is in a closed position, and the spot welded portion of a new bag body is cut off by the slider at the first cut. However, in this example, since the films at the upper portion of the zipper are closely in contact with each other, it is hard to judge from appearance whether or not the spot welded portion is cut off when the zipper is in a closed state.

In the example illustrated in FIG. 19 of the above-mentioned Patent document 1, perforations are formed at the upper portion of the zipper, i.e., at the portion above the engaging portion, and while the zipper is in a closed state, a part of the upper portion of the zipper is partially cut off, and then, a slider is disposed at the cut off portion. This example applies a system wherein the upper portion of the zipper is cut off from the perforations by means of the slider when it is opened, however, sometimes cutting off may not be done well. Further, this system can be adopted only such a type of zipper as having an (upper) flange portion projecting upward from the engaging portion.

The systems illustrated in FIG. 14 and FIG. 16 of the above-mentioned Patent document 1 have advantage that the hermetic seal of the bag can be secured even if the bag uses perforations, but the systems illustrated in FIG. 18 and FIG. 19 cannot be applied to usage requiring a long preservation such as retorted foods because sealing ability of the bag depends on the sealing ability of the zipper.

Further, the inventor of the present application proposed in Japanese Patent Application Laid-open No. 2004-026193 (Patent document 3) that in order to prevent unfairly unsealing of a zipper, at a mouth side end of one of a plastic zipper having a pair of male and female hooks, a covering piece covering up a mouth side end of the other hook is disposed and that the covering piece and the mouth side are welded together. However, the Patent document 3 discloses in concrete neither an apparatus nor a method for industrially carrying out such welding.

Further, in WO 03/022697 A1 (Patent document 2), the inventor of the present application disclosed a slider which is applicable to a hermetic plastic zipper wherein engaging portions are welded with each other via an easily peelable plastic layer. Although such a hermetic zipper has a high opening intensity, the slider disclosed in Patent document 2 can open the plastic zipper having high opening intensity such as disclosed in Patent document 2 while the slider is small and strong.

Furthermore, in the Patent document 1, the inventor of the present application disclosed a method for continuously producing a hermetic zipper, the plastic zipper having easily peelable plastic layer extending in a longitudinal direction of the plastic zipper, wherein the easily peelable plastic layer is welded by ultrasonic waves and which has a peeling intensity in a certain constant level.

Patent document 1: WO 2005/048763 A1

Patent document 2: WO 03/022697 A1

Patent document 3: JP 2004-026193

Patent document 4: JP 2004-209841

Patent document 5: JP 2004-196321

An object of the present invention is to provide a plastic zipper which solves the above-described problems inherent to the conventional plastic zippers, unsealing of which can be known at once from its appearance when the plastic zipper is unfairly or erroneously unsealed so that unfairly unsealing can be prevented, and which can be produced effectively.

Other objects of the present invention are to provide a manufacturing apparatus and a manufacturing method for manufacturing such a plastic zipper having preventing function against unfairly unsealing.