The present invention relates to a method for the pro¬ duction of a food package as set forth in the preamble of claim 1.

A food package produced by the application of a method of the invention is intended to be used especially as a package for so-called processed foods. An increasing tendency in modern foodstuffs industry is to supply the consumers with foodstuffs processed as far as pos¬ sible. Thus, the requirements set for a food package are essential. Critical factors include food package manufacturing technique, package properties and simpli¬ city in use.

Generally speaking, the following qualities are required of a food package, especially a food package containing processed food: cold resistance (deep-freezing quality) , heat resistance (conventional oven, microwave oven) , storage and handling properties, mechanical strength and qualities having to do with actual serving and eat¬ ing. The requirements set for materials used especial¬ ly as- plastic films or sheets in food packages include e.g. film joining properties (e.g. hot-sealing proper¬ ties), possibility of film shaping (e.g. deep drawing) etc. The materials used in food packages in addition to plastic films should be capable of providing a ne¬ cessary mechanical strength. Furthermore, the package space confined by plastic films should be capable of withstanding treatments improving the shelf life of a foodstuff, such as e.g. protective gas filling, pas¬ teurization or sterilization.

Publication WO 86/04880 discloses a package, comprising

a combination of a first film and a supporting struc¬ ture joined together by a deep-drawing technique as well as a second film attached to the combination and serving as a cover. The supporting structure is not an independently shape-retaining, sufficiently rigid package space forming structure, but said first film joins the supporting structure wall portions and floor together for an assembly in the shape of a package space during the building of such combination. The second film is attached to the combination after it has been assembled.

An object of this invention is to introduce a method for the production of a food package meeting the above requirements, mainly characterized by the following steps:

A) shaping a first film,

B) placing a food product inside a compart¬ ment formed by the first film,

C) sealing the compartment with a second film or the like serving as a cover film,

D) fabricating a supporting structure com¬ prising a shaped portion,

E) placing a combination formed by the first and second films in contact with the sup¬ porting structure in a manner that the first film fits into the shaped portion of said supporting structure, and

F) joining the combination and the support¬ ing structure together.

The above steps make it possible to apply a preferred manufacturing technique by using prior known deep-draw¬ ing packers as well as provide a highly practical pack-

age .

According to one preferred application of the method, the package space of a combination formed by the first and second films can be subjected to at least one treatment, such as a protective gas treatment, pasteu¬ rization or sterilization prior to joining the combi¬ nation to a supporting structure, whereby the support¬ ing structure is not damaged during such treatment.

It is preferred that a supporting structure as ell as a combination formed by the first and second films be joined together at an edge joint between said films. In addition, it possible to join the supporting struc¬ ture and the first film together by using dot-shaped and/or line-shaped junctions. Certain functional ^" ad¬ vantages are gained by these solutions.

Other characterizing features of the invention are set forth in the annexed subclaims.

The invention is described in more detail in the fol¬ lowing specification, wherein reference is made to the embodiments shown in the accompanying drawings. In the drawings

fig. 1 is a so-called exploded view of one embodiment of a package of the invention,

fig. 2 is a cross-sectional view of the package shown in fig. 1 including further two partial enlarge¬ ments of the package walls,

fig. 3 is a perspective view of an embodiment of a package of the invention, whose package space

comprises two compartments for different food products, and

fig. 4 is a diagrammatic sketch of -a packing sequence.

Referring to fig. 1, reference numeral 1 designates a first film, made of a plastics material. This film is shaped, preferably deep drawn, so as to include at least one compartment 1 * for a food product contained in the package. The shaped portion, its flanges are provided with a lap 1" as part of the first film. The first film 1 is manufactured and shaped during the first step of food package production. The second step comprises placing a food product E inside compart¬ ment 1 * . In the third step, compartment 1 ' is sealed with a second film 2, serving as a cover film and made of a plastics material, or the sealing is effected with some other cover material. The sealing is effect¬ ed between the edge portion 2" of second film 2 and the lap 1" of first film 1 for- providing an edge joint, shown particularly in figs. 2 and 3. The central port¬ ion 2' of second film 2 can be flat, as in fig. 1, or it can be more or less shaped e.g. by deep drawing the same way as first film 1.

When joined together, said first 1 and second 2 films provide a combination in the form of a sealed elastic package whose interior comprises a package space 4 for a food product/food products E.

At this stage of production, if necessary in terms of the shelf life or preparation of a food product, this combination is preferably subjected to various types of treatments, such as protective-gas filling. One possibility here is e.g. vacuum filling technique.

This is possible for the reason that, at this stage, the combination can be deflated since the plastic films are resilient and possible deformations at this time bear no significance as to the final qualities of a package. Thus, the air can be exhausted from package space 4 and vacuum filling technique can be applied to fill said package space 4 with an inert protective gas. Combination 1 , 2 returns to its original shape after the vacuum filling. Similar treatments include pas¬ teurization and sterilization for improving the shelf life of a food product contained in package space 4. These treatments can be preferably effected just at this stage as combination 1 , 2 is still in a resilient condition and the treatment is not restricted by the properties of a supporting structure, nor is the sup¬ porting structure damaged as a result of such treatment.

Following the above treatments, the combination in the form of an elastic package consisting of first 1 and second 2 films is placed inside the shaped portion 5' of a supporting structure 5 in a manner that the shaped first film portion fits into the corresponding portion of supporting structure 5. The shaped supporting struc¬ ture portion 5' and said shaped compartment 1 * of first film 1 are substantially of equal size, so the lap 1" of film 1 lays itself upon a shoulder, preferably a flange 5" surrounding the shaped portion of supporting structure 5. At this time, there is effected the join¬ ing between the combination formed by first 1 and sec¬ ond 2 films and supporting structure (joint 6, especial¬ ly in fig. 2) . Dot-shaped and/or line-shaped junctions 7 can be provided on the shaped supporting structure portion 5' between supporting structure 5 and first film 1.

Depending on shelf-life requirements and ultimate use and sealing, said films 1 and 2 can be optionally made of various materials. Particularly, if hot sealing is used for a joint 3, the films will be selected in a manner that films 1 and 2 join together and film 1 joins also to the supporting structure. If one of the above joints is effected by gluing, there will be more possibilities of selecting the films.

A bottom corner of the food package is shown enlarged in detail B of fig. 2. This illustrates dot-shaped or line-shaped junctions 7 between supporting struc¬ ture 5 and first film 1 for effecting a possibly ne¬ cessary attachment of irst film 1 to the shaped port¬ ion 5' of supporting structure 5.

The supporting structure 5 can be fabricated by using cardboard, paperboard or plastics. The supporting structure can be a pre-made cardboard box or tray whose material comprises cardboard or paperboard, possibly coated with a hot-sealing layer of plastics (PET) . The supporting structure can also be obtained by using an erectable package which is assembled to its final form prior to fitting a combination formed by films 1 and 2 inside the supporting structure. The assembly is effected by applying a gluing, clamp-hook or a like technique from cardboard or paperboard. The support¬ ing structure can also be shaped by press moulding or deep drawing. The supporting structure material can be selected and its shaping effected according to the intended use of a food package. An essential feature of supporting structure 5 is to provide a necessary mechanical protection for a possibly processed food product placed inside the combination formed by films 1 and 2 and to allow the utilization of ^" such support-

ing structure at the time when a food package is used e.g. as a plate or other base. The supporting struc¬ ture need not possess liquid or gas tightness qualities.

As particularly shown in fig. 3, film 2 can be provided with a tear-off indication 8, whereat the removal of a cover-film serving second film 2 can be initiated for consuming the food products. Particularly in the em¬ bodiment shown in fig. 3, a combination formed by films 1 and 2 is divided into two compartments by means of a partition 9. Thus, one and the same food package can be furnished with different types of food products, e.g. a ready-made meal. In the case shown in fig. 3, the shaped portion of film 1 includes a folding lap, extending from the floor up to cover film 2 and joined thereto, said partition 9 being fitted therebetween. It is obvious that the package can include even more compartments whenever necessary.

In package manufacturing technique, it is possible to apply methods known from plastic films handling tech¬ nique, whereby the shaping of a first film especially by deep drawing can be effected on a wide web of plast¬ ic film in a manner that a plurality of shaping pro¬ cedures are simultaneously effected in the lateral di¬ rection of a web followed by placing the food products inside the above-mentioned shaped portions. This is followed by laying a cover film web matching the width of said film web upon the first film web, a possible protective-gas filling and forming the above-mentioned joints 3. Thereafter, the parallel, still unified com¬ binations are forwarded to possible pasteurization and sterilization stages. This is followed by fitting the combinations inside the supporting structures and finished food packages are separated from each other

to form either individual packages or groups of pack¬ ages.

Preferable applications may include various pies, such as meat and Karelian pies, pizzas, ready-made food portions, processed baking dishes, soups etc., either deep-frozen or fresh. Food products can be pre-cooked or uncooked as the case may be.

One example of a preferred embodiment of films 1 and 2 especially for food packages intended for microwave ovens and/or conventional ovens can be the following combined film structure. As a hot-sealing (especially for joint 3) layer, said films 1 and 2 can be provided with amorphous, crystallizable polyester (PET) . Since this type of plastic is well sealable with heat and deep drawable, it will soften and go shapeless by it¬ self at a temperature of 100°C to 130 C. When the above film is combined with another film whose soften¬ ing point is above 150 C (e.g. PP, orientated PET, PA etc.) , the result will be a composite film capable of resisting high temperatures (150 C to 250°C) since during the thermal treatment of a food package the polyester crystallizes on the surface of a carrier layer as a high temperature resistant film. The above layers can be joined together by laminating, co- extruding or coating. The surfaces of carrier films can be treated with a heat-resistant lacquer, if ne¬ cessary.

Fig. 4 illustrates schematically the method sequence, the reference numerals corresponding to those used in figs. 1 to 3.