Abstract:
A paper composite for realizing packages in three-dimensional form having a layer of yieldable paper with a degree of yieldingness in any direction not less than 10% and impermeablilizing film having a yieldingness compatible with yieldable paper. A method for realizing packages where a leaf of composite is faced to a cavity of at least a mould, the leaf being bounded in correspondence of a continuous edge of the cavity, and subsequently tangentially stretching the leaf of composite to adhere to an inner surface of the cavity to obtain a concave valve. The valve has the shape of the cavity. The package obtained is a concave container having a closure film applied to the filling, and may have two concave valves joined together along the facing edges.

Description:
FIELD OF THE INVENTION 
     This invention relates to a paper composite for realizing three-dimensional packages for possibly solidifiable products in the liquid state, or for granular or powder products, a method for realizing such packages and a package obtained through the method. 
     BACKGROUND OF THE INVENTION 
     Methods for packaging in metered quantities possibly solidifiable liquid products or granular or powder products for consumption are known. In one of these methods, half-casings of substantially rigid plastics material for example polypropylene are thermoformed and joined together along their edges to form a cavity, which can then be filled by a traditional filling machine. If the product is to be used in the liquid state, granular state or powder state the package obtained in this manner is ready for marketing after sealing. If however the product is to be used in the solid state (for example ice-creams), after the filling operation the filled with the liquid product and sealed package is refrigerated and preserved under refrigerated conditions until its consumption. 
     Independently of the nature of the packaged material, these known packages have the advantage of being formable in practically any shape, but also have certain drawbacks, and in particular: 
     a considerable cost, related to the cost of the plastics material used, 
     practically no ecological merits, given the non-biodegradable nature of the plastics used, 
     a certain weight, with consequent transport costs, 
     a space requirement after use, in that the used package cannot be substantially reduced in volume compared with the full package. 
     It is also known to package generally liquid products using a continuous tubular element of polyethylene-coated cardboard which is filled in portions separated by transverse welds, transverse cuts then being made through said welds. The package is generally of tetrahedral, parallelpiped or cylindrical shape, depending on the manner in which the transverse welds are made and on the folding operations to which the package may be subjected after its separation from the continuous tubular element. 
     This known method considerably accelerates the packaging operations but has certain limitations both in terms of obtainable shapes, and of overall dimensions, of the package after its use, and of costs. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to eliminate such drawbacks and to realize a composite for forming metered packages, practically of any shape, for products in the liquid, granular or powder state, which has a low cost. 
     A further object of the invention is to realize very light packages, such as to minimize packing and transport costs. 
     A further object of the invention is to provide a method which enables the package to be reduced to minimum volume after use. 
     A further object of the invention is to provide a method which enables traditional commercially available packaging equipment to be used. 
     All these objects are attained according to the invention through a paper composite for realizing packages in three-dimensional form having a layer of yieldable paper with a degree of yieldingness in any direction not less than 10% and impermeablilizing film having a yieldingness compatible with yieldable paper. 
     The invention also foresees a method for realizing packages where a leaf of composite is faced to a cavity of at least a mould, the leaf being bounded in correspondence of a continuous edge of the cavity, and subsequently tangentially stretching the leaf of composite to adhere to an inner surface of the cavity to obtain a concave valve. The valve has the shape of the cavity. 
     The package so obtained a concave container having a closure film applied to the filling, and may have two concave valves joined together along the facing edges. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The present invention is described in detail hereinafter with reference to the accompanying drawings, in which: 
     FIG. 1 shows in enlarged section view a portion of paper composite according to the invention; 
     FIG. 2 schematically illustrates a line for implementing the method of the invention; 
     FIG. 3 is an enlarged perspective view of the open mould of FIG. 2; 
     FIG. 4 is a vertical section through a closed mould during the stage preceding the introduction of the pressurized fluid; 
     FIG. 5 shows the same view as FIG. 4, but during the stage following the introduction of the pressurized fluid; 
     FIG. 6 is a perspective view of a package extracted from the mould and awaiting filling; 
     FIG. 7 schematically shows in cross section view an open mould to implement the method in a different embodiment, 
     FIG. 8 is the same mould as FIG. 7 in a further embodiment, and 
     FIG. 9 shows a package extracted from the mould and awaiting filling. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As can be seen from the figures, the paper composite  2  according to the invention consists of a layer of yieldable paper  4  and of an impermeable plastic film  6 . The yieldable paper  4  presents a degree of yieldingness such as it enables it to be permanently extended transversely and longitudinally by at least 10%, and preferably by 20% and specifically by an extent such as to enable the desired final configuration without laceration of the package to be obtained. 
     The plastic film  6  is preferably of polyethylene or another possibly peelable thermoplastic material with degree of yieldingness not lesser than that of the layer of yieldable paper to which it couples and with suitable weldability characteristics. The film  6  may also include an aluminum alloy. 
     The joint between the two layers  4  and  6  is preferably formed continuously by traditional methods, which do not form part of the invention and are not further described. In the embodiment shown in FIG. 2 the composite  2  is wound around a reel  8  and is folded longitudinally so that the two polyethylene layers  6  face each other. 
     In the embodiment shown in FIGS. 2-4 the method of the invention also uses a mould formed from two half-moulds  10  movable relative to each other and each comprising a cavity  12  bounded by a slightly projecting rim  14  comprising an interruption  16 . The cavities  12  of the half-moulds  10 , the projecting rims  14  which bound them and the interruptions  16  in the projecting rims  14  perfectly mate when the two half-moulds  10  are brought together. 
     In the drawings the two half-moulds  10  are shown for simplicity with a single impression, whereas in practice it is preferable to use moulds with several impressions to accelerate the packaging operations. 
     It is also foreseen that the cavity  12  of each half-mould  10  extends externally into a duct  18  which opens into the interruption  16  provided in the rim  14  bounding the cavity  12 , and mates with the adjacent duct of the other half-mould  10 . 
     The method of the invention is as follows: after the composite  2  has been folded longitudinally into two parts and has been positioned in this folded state between the two half-moulds  10 , these are brought together so as to retain it between them (see FIG.  4 ). The two contacting rims  14  are then heated so that they thermoweld together the two polyethylene layers  6  lying between them, but with the exception of the interruption  16 . 
     After the thermoweld has been made, compressed air is introduced through the duct  18 , which air may be also hot, with the double purpose of heating the polyethylene  6  in order to soften and sterilize it, and to stretch the two sheets of yieldable paper  4  retained between the rims  14  to cause them to adhere to the surface of the respective cavity  12  (see FIG.  5 ). The stretching of the paper is facilitated by the softening of the polyethylene. 
     After this insufflation stage the two half-moulds  10  are separated to allow removal of the internally impermeabilized paper package  20  having a configuration corresponding to the cavities of the half-moulds  10 , this configuration being stable because of the permanent deformation to which the yieldable paper  4  and the polyethylene  6  forming the composite have been subjected (see FIG.  6 ). The half-moulds  10  may be kept or maintained in a heated condition during the insufflation stage while the compressed air or fluid is injected. 
     This package can then be transferred to the filling stage, preferably effected with automatic machines, and then to the stage for sealing the polyethylene  6  at the interruption  16 , through which the product to be packaged was introduced, which product may be liquid, pasty, granular or powder. 
     Depending on the nature of this product, the package  20  once sealed can be subjected to further treatment or be transferred to storage. For example if the product is to be consumed in the liquid state (shampoo, detergent, milk, water, etc.) or granular or powder, it can be stored directly. If the product has been temporarily heated to bring it to the liquid state, although being solid at ambient temperature (chocolate or cheese or soap), it is sufficient to wait for it to cool in order for it to assume and maintain the shape of the package  20 , which it does even after it has been removed for consumption. If however the product is a liquid for preparing an ice-cream or ice-lolly, it has to be frozen after filling, however this can be done shortly before consumption. 
     Briefly, independently of the product to be packaged, this first embodiment of the method according to the invention is based on the principle of using polyethylene, the traditional purpose of which is to impermeabilize the yieldable paper against the liquid product during its filling and storage, but also to impermeabilize the paper against the air, hence enabling paper to be subjected to an operation which was never previously possible. 
     If it is foreseen that the package could receive an extensive deposit of moisture (condensate), it is preferable for the layer of yieldable paper  4  to comprise a polyethylene film  6  on both its surfaces. 
     A second embodiment of the method according to the invention foresees that, after thermowelding the polyethylene, the fluid fed under pressure through the duct  18  is not air, but instead the actual liquid product to be packaged, this causing the paper to stretch until it adheres to the walls of the half-moulds  10 . Again in this case the product to be packaged can be variously treated depending on its nature, but in all cases the invention comprises the formation of the package within the mould by the actual product to be packaged. If this product is solidifiable, ie whether it is solid at ambient temperature but has been previously heated to facilitate filling, or whether it is liquid at ambient temperature but is to be refrigerated after filling, the invention involves mutual action between the liquid and the package. In this respect, during the filling the liquid product forces the paper and the polyethylene to assume the shape imposed by the mould within which it is housed, whereas during solidification it is the package, previously formed by the liquid, which now constitutes the mould for the liquid during the solidification. 
     In addition, in both the embodiment of the method according to the invention, in particular for packaging edible solidifiable liquid products, the filling stage can be preceded by inserting a traditional stick  21  for example of wood or plastic into the mould, to remain retained by the product as it solidifies and form the support necessary for hand-held products. 
     A third embodiment of the method according to the invention foresees that the leaf of composite  2  is faced with the layer of paper  4  to the cavity  22  of a mould  24  and then is bounded in correspondence of the continuous edge of this cavity. Subsequently the mould  22  is subjected to depression through suitable suction channel  26  provided threin so as to cause the tangential stretching of said composite until to obtain its adhesion to the inner surface of this cavity. In order to obtain a better stretching it is foreseen that a complementary punch  28  faces the cavity  22  of the mould, which during the suction step contributes, through mechanical way, to carry out the stretching of the paper. 
     It is preferable that such a mechanical effect is supported by a pneumatic effect, and for this purpose the punch  28  is provided with a plurality of channels  30 , through which it is possible to direct a jet of air, if desired hot, against the composite leaf. 
     The valve-shaped package  32  so obtained may be filled with the product to be packaged and subsequently may be closed through thermowelding of a transparent film  34  or of a complementary valve. 
     It any event, independently of the embodiment used, the composite according to the invention and the method to realize the desired prackages have considerable advantages, and in particular: 
     they enable packages to be formed practically without any limitation on their shape, 
     they enable traditional commercially available forming and filling equipment to be used, 
     they enable very light packages of low cost to be formed, which can be reduced to a minimum volume after use.