METHOD FOR FIXING A FIRST CONSTRUCTION MADE OF A PLASTIC MATERIAL TO A SECOND CONSTRUCTION MADE OF A PLASTIC MATERIAL

Abstract: The invention concerns a method for fixing a first construction (31) made of a plastic material to a second construction (32a, 32b) made of a plastic material. In the method, the first construction and the second construction are fixed to one another by means of seaming devices (34), which form seams (33) at the desired locations. The first construction (31) is placed, in its ring-shaped, between the film faces (32a, 32b) that form the second construction, in which case, during seaming, there are at least four material layers placed one above the other. The first construction (31) is fixed by seaming from the desired locations by means of seams (33) to the second construction (32a, 32b) so that the outer face of the first construction (31) is fixed by seaming to the inner face of the second construction (32a, 32b), but the inner faces of the first construction (31) are not fixed to one another by seaming.

Description: Method for fixing a first construction made of a plastic material to a second construction made of a plastic material The invention concerns a method for fixing a first construction made of a plastic material to a second construction made of a plastic material, in which method the first construction and the second construction are fixed to one another by means of seaming devices, which form seams at the desired locations. For example, in unit-load sacks, inner sacks made of a plastic material, as a rule of polyethylene, are used. With respect to the prior art, reference is made to the FI Patent No. 90,331, in which a unit-load package meant for bulk goods is described, which package consists of an inner package and an outer package. The inner package is an inner sack made of a flexible material and provided with a support structure, which sack is placed on a base for the time of filling with bulk goods, preferably by suspending or supporting the sack above the base. The outer package is an outer package which surrounds the inner package and the base tightly, which is made of a plastic material, and which provides adequate stability. In the manufacture of the inner sack described above, in principle, an inner ring has to be fixed to an outer ring. In the prior art, this has been made so that two rings of different lengths are fitted one inside the other and, after that, the rings are fixed to one another by means of seaming devices by seaming through two material thicknesses. It is a drawback of this solution that fitting of two rings of different lengths inside one another is relatively difficult and automation is complicated as the length of the inner sack is more than 3.5 metres. From the prior art, a solution is also known in which the frame of the inner sack is made of two plane films, to which possible cover and bottom constructions are fixed in a separate step. In such a case, the outer film is provided with pleats or folds fitted with a certain spacing. The manufacture of the frame of the inner sack takes place so that two plane films are seamed together in the cross direction of the machine, after which the ring-shaped construction is formed by means of a vertical seam. It is a drawback of this prior-art solution that the seamed blank is not yet a finished product, but, in order to provide a finished product, one more separate working step is required, i.e. the fixing of the bottom and of the top to the frame. The object of the invention is to provide an improvement over the prior-art methods. It is a more specific object of the invention to provide a method which permits fixing of a first construction made of a plastic material to a second construction made of a plastic material in one working step in the same machine into a finished product. The objectives of the invention are achieved by means of a method which is charac¬ terized in that the first construction is placed, in its ring-shaped form, between the film faces that form the second construction, in which case, during seaming, there are at least four material layers placed one above the other, and that the first construction is fixed by seaming from the desired locations by means of seams to the second construction so that the outer face of the first construction is fixed by seaming to the inner face of the second construction, but the inner faces of the first construction are not fixed to one another by seaming. By means of the method in accordance with the invention, a number of significant advantages are obtained. By using the method in accordance with the present invention, for example, the inner sack of a unit-load sack can be manufactured in one machine as one step into a finished sack. In the method in accordance with the invention, the inner ring can be easily placed between two plane films or between a hose film that has been opened at the side. In the method in accordance with the invention, the seaming process itself is also quicker than in the prior-art methods. In a preferred embodiment of the invention, the inner film is preferably chosen so that the outer face of the inner film is readily seamable and the inner face of the inner film poorly seamable, respectively. In this way it is ensured that, in the seaming process, all of the four film layers placed one above the other are not seamed together. If necessary, in the interior of the inner ring, it is possible to place separate material pieces in the locations meant for the seams, in which case the four individual film layers are not seamed together even if all the faces of the films were readily seamable. The invention will be described in detail with reference to a preferred embodiment of the invention illustrated in the figures in the drawings, the invention being, yet, not supposed to be confined to said embodiment alone. Figure 1 is a schematic illustration of a prior-art seaming method. Figure 2 is a schematic illustration of a second prior-art seaming method. Figure 3 is a schematic illustration of a preferred embodiment of the seaming method in accordance with the invention. Figure 4 is a schematic illustration of a second preferred embodiment of the seaming method in accordance with the invention. In the prior-art seaming method shown in Fig. 1 the inner sack 10 is manufactured as follows. The inner ring 11 and the outer ring 12 are placed one inside the other, and the seaming devices 14 form the seams 13 in the way shown in Fig. 1. The most important drawback of this prior-art method is the fitting of two ring-shaped constructions of different lengths one inside the other. In the prior-art seaming method shown in Fig. 2, the inner sack 20 is made of two plane films, i.e. not out of an inner ring and an outer ring. In Fig. 2, the inner film 21 has been placed on the top and the outer film 22 on the bottom, the seaming devices 24 form the seams 23 at the locations shown in Fig. 2. It should be noticed in particular that the outer film 22 is provided with pleats or folds 25 placed at a certain distance from one another. In Fig. 2, the manufacture of the inner sack 20 takes place in the cross direction of the machine in respect of the seaming. After this, a separate additional working step is required in order to produce a finished inner sack, i.e. formation of a ring by means of vertical seams (not shown). It is the most important drawback of this prior-art method that the product, i.e. , for example, the inner sack, cannot be manufactured completely by means of one working step and by means of one machine. In Fig. 3 the product in accordance with the invention composed of a first construc¬ tion made of a plastic material and of a second construction made of a plastic material is denoted generally with the reference numeral 30. In this embodiment, the product 30 is the inner sack of a unit-load sack. The inner sack 30 is formed by placing an inner ring 31 between two plane films 32a and 32b. Into the plane films 32a and 32b longitudinal folds 35 have been formed. The constructions 31 and 32a and 32b are seamed by means of seaming devices 34, whereby the seams 33 are formed. It should be noticed in particular that in the method in accordance with the invention the seams 33 are formed in the desired way so that all of the four film layers are not fixed together by seaming. Finally, seams 36 are still formed at the outer edges of the plane films 32a and 32b, whereby the outer ring of the inner sack 30 is formed. The inner film 31 should preferably be chosen so that the outer face of the inner film 31 is readily seamable and the inner face poorly seamable. In such a case the plane films 32a and 32b are fixed to the inner ring 31 by seaming in the correct way. If both the outer face and the inner face of the inner ring 31 are readily seamable, in such a case it is preferable to place separate material pieces in the interior of the inner ring 31 at the locations of the seams 33 in order to make sure that all of the four film layers are not fixed to one another by seaming. In the embodiment shown in Fig. 4 the product composed of a first construction made of a plastic material and of a second construction made of a plastic material is denoted generally with the reference numeral 40. Also in this embodiment, the product 40 is the inner sack of a unit-load sack. The inner sack 40 is formed by placing an inner ring 41 between a hose film 42 that has been opened at one edge 47. Also in this embodiment, the inner ring 41 is placed between two film faces 42a and 42b. Longitudinal folds 45 have been formed into the film faces 42a and 42b. The constructions 41 and 42a and 42b are seamed by means of seaming devices 44, whereby the seams 43 are formed. Finally, a seam 46 is formed at one outer edge of the film faces 42a and 42b, i.e. at the opened edge 47, whereby the outer ring of the inner sack 40 is formed. The seaming method in accordance with the invention is highly advantageous for the manufacture of products made of a plastic material, such as, for example, inner sacks of unit-load sacks. The seaming process is very rapid, and the finished product can be produced by means of one machine in one working step without need of any additional working steps. Of course, the method in accordance with the invention can be applied to fixing together of a variety of constructions made of different plastic materials. Above, just one preferred embodiment of the invention has been described, and it is obvious to a person skilled in the art that numerous modifications can be made to said embodiment within the scope of the inventive idea defined in the accompanying patent claims.

Claims: Claims 1. A method for fixing a first construction (31,41) made of a plastic material to a second construction (32a,32b;42,42a,42b) made of a plastic material, in which method the first construction and the second construction are fixed to one another by means of seaming devices (34,44), which form seams (33,43) at the desired loca¬ tions, characterized in that the first construction (31,41) is placed, in its ring-shaped form, between the film faces (32a,32b;42a,42b) that form the second construction, in which case, during seaming, there are at least four material layers placed one above the other, and that the first construction (31,41) is fixed by seaming from the desired locations by means of seams (33,43) to the second construction (32a,32b; 42a,42b) so that the outer face of the first construction (31,41) is fixed by seaming to the inner face of the second construction (32a,32b;42a,42b), but the inner faces of the first construction (31,41) are not fixed to one another by seaming. 2. A method as claimed in claim 1, characterized in that seams (36,46) are formed at least at one outer edge of the film faces (32a,32b;42a,42b) that form the second construction. 3. A method as claimed in claim 1 or 2, characterized in that longitudinal folds (35,45) are formed into the film faces (32a,32b;42a,42b) that form the second construction. 4. A method as claimed in any of the claims 1 to 3, characterized in that the plastic material of the first construction (31,41) is chosen so that its outer face is readily seamable and its inner face poorly seamable. 5. A method as claimed in any of the claims 1 to 3, characterized in that separate pieces of material are placed at the locations of the seams (33,43) in the interior of the first construction (31,41), which is in the ring-shaped form. 6. A method as claimed in any of the claims 1 to 5, characterized in that the product (30,40) composed of the first construction (31,41) and of the second construction (32a,32b;42a,42b) is the inner sack of a unit-load sack, in which inner sack the first construction (31,41) is fitted to operate as a support structure of the second construction (32a,32b;42,42a,42b) constituting the inner sack. 7. A method as claimed in any of the claims 1 to 6, characterized in that the second construction (32a,32b) is composed of plane films. 8. A method as claimed in any of the claims 1 to 6, characterized in that the second construction (42,42a,42b) is composed of a hose film (42) which has been opened at one edge (47) and whose faces (42a,42b) form the film faces.

Inventors: KOSKINEN ERKKI, NYMAN PER, KOSKINEN, ERKKI, NYMAN, PER
Applicants: KOSKINEN ERKKI, NYMAN PER, UPM KYMMENE OY, KOSKINEN, ERKKI, NYMAN, PER, UPM-KYMMENE OY
Application year: 1996
Main classification: B29C65
IPC codes: B29C65, B65D88