Method of packaging an article using thermally shrinkable film

Abstract: A package in which an article (1) is sealingly enclosed with a thermally shrinkable film (2) having a row perforations (3) used as air discharge port during shrink packaging. A strip (4) of a film is disposed inside of the package to close the perforations (3) and to prevent moisture and germs from entering into the package during storage and transportion of the package.

Description: This invention relates to a method of packaging an article using thermally shrinkable film. A packaging method in which an article to be packaged is enclosed with a thermally shrinkable film, and the resulting enclosure is sealed and heated to package the article by thermal shrinkage of the film, is now widely put into practice. Since it is necessary to discharge air from the inside of the sealed enclosure in order to effect the thermal shrinkage of the film, one or more small perforations are generally formed in the film. Such perforations, however, cause problems because air, moisture or germs can enter the package therethrough, and also because the package tends to be prematurely torn at the perforated portion. To cope with this problem, a method is proposed in which such perforations are covered with a label after the shrink packaging. While this method is effective in preventing intrusion of moisture and germs into the package through the perforations, it is difficult and economically disadvantageous to automatically apply the label precisely onto a predetermined portion of the package. JP-U-63-144,442 discloses a package including an enclosed soft bag and a thermally shrinkable, plastic film enclosing the soft bag and having an air discharge opening, characterized in that the package is obtained by a method including the steps of applying a moisture-proof sheet to the soft bag, enclosing the soft bag with the plastic film so that the air discharge hole is covered with moisture-proof sheet, and thermally shrinking the plastic film. The application of the moisture-proof sheet onto the soft bag is effected by means of bonding, adhesion or fusion. One problem of the technique described immediately above is that it is necessary to dispose a sheet applying device upstream of an enclosing device in order to perform the entire process in a fully automated mode. This technique has another problem in that it is difficult to enclose the soft bag with the film while precisely positioning the air discharging hole in register with the moisture-proof sheet on the bag. US-A-2545243 discloses a method of packaging an article in which the article is first wrapped in a film of a thermally shrinkable synthetic resin, and then overlapping portions of the film are sealed together by applying sufficient heat to the film at spaced points to cause rows of apertures to be formed and the overlapping film portions to become fused together around the apertures. The article being packaged is protected from damage during the sealing operation by means of a strip of parchment positioned between the article and the overlapping portions of the film which are to be joined together. The apertures which are formed during sealing permit air within the package to escape while the ends of the wrapping are being closed. The present invention has been made with the foregoing problems of the conventional shrinkable packaging in view. The present invention provides a method of packaging an article, comprising the steps of: providing a first, thermally shrinkable, synthetic resin film having a row of perforations; superimposing a strip of a second synthetic resin film on said first film to entirely cover said perforations therewith; then sealingly enclosing said article with said first film such that said strip is disposed between said first film and said article, thereby to obtain a sealed enclosure in which said perforations are exposed to an outer surface thereof; and then heating said enclosure to cause said first film to be shrunk with said perforations serving as outlets of air contained in said enclosure. The present invention will be described in detail below with reference to the accompanying drawings, in which: Fig. 1 is a perspective view diagrammatically showing a package according to an embodiment of the present invention; Fig. 2 is a cross-sectional view taken on line II-II in Fig. 1; and Fig. 3 is a flow chart schematically showing an apparatus for carrying out packaging method according to the present invention. In the embodiment of the invention illustrated in Figs. 1 and 2, an article 1 is enclosed by a first, thermally shrinkable, synthetic resin film 2 having a row of perforations 3. Interposed between the article 1 and the first film 2 is a strip 4 of a second, thermally shrinkable, synthetic resin film. The strip 4 which has a width of generally 2-10 cm is located to cover the row of perforations 3. The first and second films 2 and 4 may be formed of the same or different resin. However, it is preferred that the strip 4 of the second film have a shrinkability similar to that of the film 2, since the finish of the package is made more attractive. Any known thermally shrinkable film may be used for the purpose of the present invention. Illustrative of suitable thermally shrinkable films are single layer films of polypropylene, polyethylene or poly(vinyl chloride) and composite films having a layer of the above resin. Gas-barrier films such as single layer films of nylon, polyethylene terephthalate, an ethylene-vinyl alcohol copolymer or poly(vinylidene chloride) and composite films having a layer of the above resin may also be suitably used. The package of this embodiment may be prepared as follows. At first, a first, thermally shrinkable, synthetic resin film 2 having a row of perforations 3 is overlaid with a strip 4 of a second synthetic resin film so that the perforations 3 are covered with the strip 4. This can be performed by, as shown in Fig. 3, feeding the strip 4 unwound from a roll 8 to a transfer path of the film 2 unwound from a roll 9 and severing the both films to a predetermined length in a cutting station 10. An article is enclosed by the first film 2 in an enclosing station 11 such that the strip 4 is disposed between the first film 2 and the article 1. Fuse-bonding is performed to seal the film 2 thereby to obtain a sealed enclosure which has sealing portions 5 (Fig. 2) and 5a and 5b (Fig. 1) and in which the perforations 3 are exposed to an outer surface thereof. The thus obtained enclosure is introduced into an oven 12 to heat the film 2 so that the film 2 is shrunk with the perforations 3 serving as outlets of air contained in the enclosure. In the foregoing embodiment, various modifications may be made. For example, it is desirable to apply a hot melt adhesive over the surface of the strip 4 which is in contact with the film 2 having the perforations 3. The adhesive is melted in the thermal shrinking stage of the film 2 to permit the separation of the strip 4 from the film 2 but, after the completion of the shrinkage, functions as an adhesive so that the perforations 3 are completely sealed. The use of a film, as the strip 4, which has a tendency of causing blocking when contacted with the film 2 is also preferable to obtain improved sealing therebetween. The number of rows of perforations 3, the number of the perforations 3 in each row and the size of each perforation 3 may be suitably determined in view of required air discharging rate. By forming a row of the perforations 3 with an only small space therebetween, the row of perforations 3 can be used for tearing the package therealong.

Claims: A method of packaging an article (1), comprising the steps of: providing a first, thermally shrinkable, synthetic resin film (2) having a row of perforations (3); superposing a strip (4) of a second synthetic resin film on said first film (2) to entirely cover said perforations (3) therewith; then sealingly enclosing said article (1) with said first film (2) such that said strip (4) is disposed between said first film (2) and said article (1) thereby to obtain a sealed enclosure in which said perforations (3) are exposed to an outer surface thereof; and then heating said enclosure to cause said first film (2) to be shrunk with said perforations (3) serving as outlets of air contained in said enclosure. A method as claimed in Claim 1, wherein said second film is thermally shrinkable. A method as claimed in Claim 1 or Claim 2, wherein a hot melt adhesive is applied over the surface of said strip (4) of second synthetic resin film which is in contact with said first film (2), whereby after completion of said heating step said perforations (3) are completely sealed. A method as claimed in any preceding claim, wherein said strip (4) is formed of a synthetic resin film which has a tendency of causing blocking when contacted with said first film (2).

Inventors: WANO TOYOKI, YAMASHITA HIDEYUKI, WANO, TOYOKI, YAMASHITA, HIDEYUKI
Applicants: NISSIN FOOD PRODUCTS LTD, OKURA INDUSTRIAL CO LTD, NISSIN FOOD PRODUCTS CO., LTD., OKURA INDUSTRIAL CO. LTD
Application year: 1992
Main classification: B65B11
IPC codes: B65D75, B65D33