METHOD FOR FORMING THREE-DIMENSIONAL SOFT SHAPES AND PACKAGES OF PAPER MATERIAL, AND PACKAGE OBTAINED BY THE METHOD

Abstract: A method for forming three-dimensional soft shapes and packages of paper material, characterised by positioning at least one yieldable paper sheet (6, 12, 24) to face at least one aperture (4) provided in a support (2), securing said sheet to the surrounding edge of said aperture, then stretching said sheet to deform it inwards/outwards of said aperture to obtain a concave half-shell.

Description: METHOD FOR FORMING THREE-DIMENSIONAL SOFT SHAPES AND PACKAGES OF PAPER MATERIAL, AND PACKAGE OBTAINED BY THE METHOD. This invention relates to a method for forming three-dimensional soft shapes and packages of paper material, and a package obtained by the method. An object of the invention is to provide a method for forming three- dimensional soft shapes and packages of paper material. A further object of the invention is to provide a method for forming very lightweight shapes and packages of low cost and able to be reduced to a minimal size after use. A further object of the invention is to provide a method for forming shapes and packages which are biodegradable. A further object of the invention is to provide a method for forming shapes and packages of the most varied configurations. All these and further objects are attained according to the invention by a method as described in claim 1. Some preferred embodiments of the invention are described in detail hereinafter with reference to the accompanying drawings, on which: Figure 1 is a schematic view showing a device for implementing the method for forming shapes and packages according to the invention; Figure 2 shows a first modification thereof; Figure 3 shows a second modification thereof; Figure 4 shows a third modification thereof; Figure 5 shows a fourth modification thereof; Figure 6 shows a package obtained by the method; Figure 7 shows a device used to form closed shapes; Figure 8 shows a modification thereof; and Figure 9 shows a package obtained with the device of Figure 8. As can be seen from the figures, in a first embodiment the method of the invention uses a substantially flat frame 2 comprising an aperture 4, the shape of which corresponds to the mouth of the package to be obtained. Against said aperture 4 there is then rested a sheet 6 of yieldable paper having a degree of yieldability such as to enable it to be permanently extended transversely and longitudinally by at least 8%, and preferably 20%, and of very high ultimate tensile stress to ensure that the final desired configuration is obtained without tearing. To achieve a high degree of air impermeability, the paper material can comprise a number of sheets, or comprise added lacquers, inks or glues, or be formed by joining a number of sheets together with water-based glue. The yieldable paper material is preferably produced by traditional methods which do not in themselves form part of the invention, and are not further described. The sheet of paper material is then applied to the support aperture and secured to the closed edge of this aperture, for example by means of a ring 8. A jet of compressed air is then fed onto said yieldable paper sheet to stretch the sheet and hence cause it to assume a substantially spherical cap shape (see dashed line in Figure 1 ). If more than one yieldable sheet not joined together are used, a plurality of shapes of the same configuration are obtained after the air blowing stage. In the embodiment shown in Figure 2, on the aperture 4 of the frame 2 there is fixed an elastic membrane 10 of impermeable material on which a sheet of yieldable paper 12 is rested, both being retained along the continuous edge of the aperture. A jet of compressed air is then fed onto said membrane 10 to deform the membrane and stretch the yieldable paper sheet 12 lying against it. In the embodiment shown in Figure 3, the membrane 10 and superposed yieldable paper sheet 12 are again used, but stretching is effected by a punch 14, the head of which is shaped in accordance with the half-shell to be obtained. Again in this case the effect of the mechanical action performed by the punch is to stretch the yieldable paper. This mechanical effect is preferably combined with a pneumatic effect, for which purpose the punch 14 comprises a plurality of channels 15 through which the paper material can be struck by an air jet (see Figure 4). In the embodiment shown in Figure 5, a counter-mould 16 reproducing the final shape of the object to be formed is applied to the frame on the same side as the yieldable paper sheet. In this case the compressed air jet acting on the membrane stretches the yieldable paper against the base of the cavity of the counter-mould 16, to obtain a shape complementary to said base. In a different embodiment (not shown on the drawings) the yieldable paper sheet is stretched by an air stream with polystyrene chips added. In a further embodiment particulate material is added to the air stream. In yet further embodiment (not shown on the drawings) the yieldable paper sheet is stretched by producing a vacuum and hence drawing the yieldable paper sheet into the mould. In the embodiment shown in Figure 7, the frame consists of two half- moulds 2,2' movable relative to each other and each comprising a cavity bounded by an edge 18 having an interruption 20. The half-mould cavities, their bounding edges and the edge interruptions perfectly mate when the two half-moulds are brought together. The cavity of each half-mould is prolonged outwards as a conduit 22 which opens in correspondence with the interruption 20 provided in the edge 18 bounding the cavity, and mates with the adjacent conduit of the other half-mould. In the method of the invention, a yieldable paper sheet 24 is rested on each half-mould, between the two facing yieldable paper sheets there being inserted an elastic membrane 26 of the balloon form with its mouth 28 positioned substantially in correspondence with the conduit 22. The two half-moulds are then brought together and those parts of the sheets in mutual contact are joined together by known methods. After this joining has been achieved, a compressed fluid is fed through the mouth 28 of the membrane 26 to stretch the two sheets of paper material retained by their edges, to cause them to adhere to the surface of the respective cavity. After this blowing operation, the two half-moulds are spaced apart to allow removal of a paper package with a configuration corresponding to the cavity of the two half-moulds. Simultaneously, the compressed fluid is expelled from the balloon membrane, which is then extracted from the paper package. It is also possible to use an impermeable membrane of bag type not of elastic material, but deformable to a certain extent without returning to its original shape, this method allowing yieldable paper packages to be obtained having a configuration which is an "enlargement" of the bag. This embodiment is particularly advantageous in obtaining packages having an outer envelope of yieldable paper and an inner container of impermeable material. This embodiment also has the further advantage that when the product contained in the container has been consumed, the yieldable paper envelope can be torn up and disposed of in appropriate containers for paper, while the impermeable bag can be disposed of in a different container for sorted collection. In the embodiment shown in Figure 8, the method consists of inserting into a tunnel-shaped mould 30 with a profiled wall, a yieldable paper sheet 32 having its longitudinally edges joined together to form a tube. After applying two end plugs 34 to the mould, air is blown in through suitable apertures (not shown on the drawings) to obtain the shape 36 shown in Figure 9. From the aforegoing it is apparent that the method for forming shapes and packages of the invention has numerous advantages, and in particular: - it enables shapes and packages to be obtained practically without any limit on their configuration, - it enables very lightweight, low-cost shapes and packages to be formed which after use can be reduced to minimal bulk and in addition are biodegradable.

Claims: C L A I M S 1. A method for forming three-dimensional soft shapes and packages of paper material, characterised by positioning at least one yieldable paper sheet (6, 12,24) to face at least one aperture (4) provided in a support (2), securing said sheet to the surrounding edge of said aperture, then stretching said sheet to deform it inwards/outwards of said aperture to obtain a concave half-shell. 2. A method as claimed in claim 1 , characterised by using a yieldable paper sheet having a degree of transverse and longitudinal yieldability equal to at least 8% and preferably 20%. 3. A method as claimed in claim 1 , characterised in that said sheet is stretched by pressurized fluid. 4. A method as claimed in claim 1 , characterised in that said sheet is stretched by a jet of compressed air. 5. A method as claimed in claim 3, characterised in that a solid in particulate form is added to the fluid. 6. A method as claimed in claim 1 , characterised in that the yieldable paper sheet is stretched by a stream of polystyrene chips. 7. A method as claimed in claim 1 , characterised in that said sheet is stretched by a punch (14). 8. A method as claimed in claim 7, characterised in that the mechanical effect is combined with a pneumatic effect by feeding a jet of compressed air onto the sheet of paper material through said punch. 9. A method as claimed in claim 2, characterised by removably interposing an air-impermeable membrane (10,26) between the fluid and the yieldable paper sheet. 10. A method as claimed in claim 1 , characterised by stretching the yieldable paper sheet against at least one half-mould (16) having a shape complementary to the shape of the half-shell to be obtained. 11. A method as claimed in claim 10, characterised by stretching the sheet by vacuum created between the sheet and the inner wall of the half-mould. 12. A method as claimed in claim 1 , characterised by: - forming from the yieldable paper sheet a tube (32) and joining its longitudinal edges together, - then inserting said sheet into a substantially cylindrical mould (30) having its wall diameter greater than the diameter of the mouths of the mould, - stretching the sheet so that it adheres to the mould wall. 13. A package obtained by the method claimed in one or more of claims 1 to 11 , characterised by consisting of a shape presenting a concavity. 14. A package obtained by the method claimed in claims 1 to 11 , characterised by consisting of two concave shapes joined together along their adjacent edges. 15. A package obtained by the method claimed in claim 12, characterised by being obtained from a shape substantially closed in correspondence with a longitudinal edge.

Inventors: TRANI GIORGIO, TRANI, GIORGIO
Applicants: TRANI GIORGIO, TRANI, GIORGIO
Application year: 1997
Main classification: B31F1
IPC codes: B31F1