Package making – Methods – Conforming by stretching or shrinking of cover over contents
Reexamination Certificate
2001-12-05
2004-04-13
Sipos, John (Department: 3721)
Package making
Methods
Conforming by stretching or shrinking of cover over contents
C053S441000, C053S373400, C053S373700, C053S051000
Reexamination Certificate
active
06718736
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a top-seal wrapping device and a top-seal wrapping method. The present invention particularly relates to a top-seal wrapping device for covering an opening of a tray with a stretch film, welding the stretch film to a peripheral portion of the tray opening, and thermally cutting the stretch film. The present invention also relates to a top-seal wrapping method for performing such wrapping.
BACKGROUND ART
An over-wrapping method has been widely used for wrapping fresh foods, such as meat and fish, as well as processed foods such as precooked meals. In a conventional over-wrapping method, a tray is entirely wrapped with a film after arranging the intended contents or a wrapping target therein.
In the over-wrapping method, however, the tray and contents must be wrapped entirely, and the film portions must be overlapped with each other for sealing. Therefore, the film must have a size that is several times as large as the planar size of the tray. In many cases, the film portions overlap each other on the bottom of the tray, and the bottom surface of the tray is pressed against a heater plate for sealing. Therefore, the sealing ability or reliability is low.
However, a method, which will be referred to as a top-seal method, has been used instead of the over-wrap method in some cases. In the top-seal method, a film is arranged only over the opening at the top of the trap, and is welded to the peripheral portion of the tray around the opening. In this top-seal method, the required amount of film can be reduced when compared with the over-wrap method.
This top-seal method has been widely employed for wrapping mushrooms such shimeji mushrooms and others. More specifically, the top-seal method is implemented primarily in such a manner that adhesive is applied to a side surface of a tray around an opening, and ends of a film covering the opening are adhered thereto. Alternatively, the top-seal method is implemented in such a manner that a tray and a film having a larger area than the planar area of the tray are held between dies, and are welded together by pressure and heat applied thereto.
Between the above methods, the method of performing the welding with dies can hermetically seal the tray containing contents, i.e., a target to be wrapped, and therefore is superior to the over-wrap method. In the prior art, however, dedicated dies corresponding to tray forms and sizes are employed, and a hard film is used for the wrapping.
It may be envisaged to weld a stretch film (stretchable film) to the tray instead of a hard film. However, stretch film is liable to wrinkle, and when stretch film is placed over the tray the stretch file and contents may exhibit a less desirable appearance than when using the hard film. It is necessary to transport the stretch film, which is thin and does not have sufficient rigidity, to and from a position for welding. Therefore, a large and/or complicated mechanism may be required for the transportation.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a wrapping device and a wrapping method for performing wrapping by welding a stretch film to a tray. Particularly, an object of the present invention is to provide a wrapping device and a wrapping method, which has a good appearance after the wrapping, and can employ a transporting mechanism with a compact structure.
According to a first aspect of the present invention, the present invention provides a top-seal wrapping device for covering a top opening of a tray containing a wrapping target with a stretch film, welding the stretch film to a peripheral portion of the tray around the opening, and thermally cutting the stretch film. The top-seal wrapping device includes a stretch mechanism, a control portion, and a film winding portion. The stretch mechanism stretches the stretch film. The control portion controls the stretching of the stretch film by operating the stretch mechanism at least before welding the stretch film to the tray. The film winding portion winds up the stretch film after the thermal cutting.
In the wrapping device of this aspect, the stretch film covers the opening of the tray, is welded to the peripheral portion of the tray around the opening, and is thermally cut.
The stretch film thus cut is wound up. Owing to the structure operating as described above, a transporting mechanism having a compact structure can be used for transporting a thin stretch film having low rigidity. In the prior art, the stretch film is transported by belts holding the opposite sides of the film, or by chains moving in the transporting direction and having clamps for holding the film. This requires a large and/or complicated structure, and increases costs. In contrast to this, the wrapping device of this aspect is provided with a film winding portion for ensuring the continuity of the stretch film. Therefore, a stretch film, which is thin and does not have sufficient rigidity, can be transported without holding or pinching it. Accordingly, the transporting mechanism can have a compact structure.
Further, the stretch mechanism is arranged for stretching the stretch film at least before welding the stretch film to the tray. Therefore, wrinkles of the stretch film covering the opening of the tray are expanded before welding so that the appearance is improved in the wrapped state.
According to a second aspect of the present invention, the top-seal wrapping device of the first aspect further has a feature such that the stretch film is thermally cut at a position outside a portion welded to the peripheral portion around the tray opening.
According to a third aspect of the present invention, the top-seal wrapping device of the first or second aspect further has a feature such that the control portion operates the stretch mechanism to apply a tension to a portion of the stretch film near the cut portion at least after welding the stretch film.
In this structure, the tension is applied to the portion near the cut portion after thermally cutting the stretch film. Therefore, the cutting can be completed even when an uncut portion is left. Further, the tension may also be applied to the stretch film during the thermal cutting. This allows easier cutting of the stretch film.
Since the stretch film is stretched after the cutting, problems can be suppressed such as the remaining portion of the cut stretch film clinging to the tray or the like.
According to a fourth aspect of the present invention, the top-seal wrapping device of the first, second, or third aspect further includes a film transporting mechanism and a lift mechanism. The film transporting mechanism transports the stretch film. The lift mechanism lifts the tray to push the stretch film transported by the film transporting mechanism against the tray. The control portion operates the stretch mechanism to stretch the stretch film before contact of the tray with the stretch film, and also controls the stretch mechanism to reduce tension of the stretch film after the contact of the tray with the stretch film.
In this structure, the lift mechanism pushes the tray against the stretch film to achieve a state in which the stretch film covers the opening of the tray.
Further, the stretch film is stretched before the tray comes into contact with the stretch film. Therefore, no wrinkles are present in the stretch film when it comes into contact with the tray, and the opening of the tray is covered with the stretch film without a wrinkle.
Further, tension of the stretch film is reduced after the tray comes into contact with the stretch film. Therefore, a disadvantage in which the stretch film is excessively stretched due to relative movement between the stretch film and the tray caused by the lift mechanism after contact between the stretch film and the tray can be suppressed.
According to a fifth aspect of the present invention, the top-seal wrapping device of any one of the preceding aspects further has a feature such that the stretch mechanism is arranged between a supply position of the stretch film and
Kawanishi Norio
Oguri Toshio
Huynh Louis
Ishida Co. Ltd.
Shinjyu Global IP Counselors, LLP
Sipos John
LandOfFree
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