METHOD FOR FIXING THE INNER SACK OF A UNIT-LOAD SACK TO THE OUTER SACK

Abstract: The invention concerns a method for fixing the inner sack (22) of a unit-load sack (20) to the outer sack (21), in which method the inner sack is fixed to the outer sack by using an adhesive material. Adhesive material (23) is applied exclusively either to the outer face of the inner sack (22) or to the inner face of the outer sack (21), and, as the adhesive, an adhesive material is used whose adhesion is sufficient to support the inner sack's own weight but which permits movement of the adhesive joint between the inner sack and the outer sack when the unit-load sack (20) is being filled with bulk goods.

Description: Method for fixing the inner sack of a unit-load sack to the outer sack The invention concerns a method for fixing the inner sack of a unit-load sack to the outer sack, in which method the inner sack is fixed to the outer sack by using an adhesive material. From the prior art, a number of different modes are known for fastening the inner sack of a unit-load sack to the outer sack. It is a commonly used mode that the inner sack is fixed to the outer sack, for example by sewing, from behind side joints that have been formed to the inner sack. Similarly, a folded inner sack is fixed to the outer sack from behind the joints placed at the ends of the folds, for example, by sewing. In some commonly used solutions, the inner sack is fixed to the outer sack by means of separate fastening pieces. In the FI Patent No. 87,914, a method is described for fastening the inner sack of a unit-load sack to the outer sack, in which method the inner sack is fixed to the outer sack by means of an adhesive material. The inner sack is glued into the outer sack from above the area of closing of the inner sack after the unit-load sack has been filled with bulk goods. The gluing, preferably hot-melt gluing, is carried out either onto the outer face of the outer sack or onto the inner face of the outer sack. In the FI Laid-Open Publication No. 88,145, a method is described in which at least one cut or weakening has been formed in the top portion of the inner sack and the inner sack has been fixed from the area at least partly defined by the cut or weaken¬ ing, from at least one fastening point, to the outer sack. In the publication EP-0, 158,361, a method is described for fastening a loose inner sack to the outer sack. In this prior-art method, a sticky adhesive material has been fitted in the folds in the outer sack and in the folds in the inner sack. The folds in the inner sack that contain adhesive material are preferably placed halfway in relation to the corresponding folds in the outer sack. When the inner sack is filled with bulk goods, expanding of the inner sack, i.e. adhering of the adhesive-containing areas on the inner sack to the outer sack and adhering of the adhesive-containing areas on the outer sack to the inner sack, takes place so that the inner sack maintains its alignability in relation to the outer sack. Since the inner sack is, as a rule, made of a very thin flexible material, it can often be wrinkled or twined when it is placed into the outer sack. If an inner sack that is in such a way wrinkled or twined is fixed to the outer sack, it cannot expand to its full volume, and there is a risk that holes are formed into the inner sack. The wall of an inner sack damaged in this way does, of course, not endure loads when the inner sack is filled with bulk goods. This is why, in the paper EP-0, 158,361, the mode of gluing described above is employed. The purpose of the fixing of the inner sack is to prevent flowing down of the inner sack along with the bulk goods in the sack when the unit- load sack is emptied. If the inner sack could flow down into the discharge opening, this would have the conse- quence that the discharge opening is blocked and part of the bulk goods cannot be discharged out of the inner sack. It is a further important purpose of the fixing of the inner sack that it is desirable to prevent access of water into the inner sack filled with bulk goods. The prior-art fastening methods involve a number of significant drawbacks. Some of the fastening solutions known from the prior art are very difficult to carry into effect in practice, because some modes of fastening require very precise alignment of the outer sack and the inner sack. On the other hand, the use of separate fastening pieces requires the use of extra material, which results in a separate step of work. In the method of the paper EP-0, 158, 361, the adhesive is spread into very narrow bends or folds in order that, in connection with opening of the folds, the adhesive material should not adhere to the opposite member too early and in order that the inner sack should be aligned correctly in relation to the outer sack so that no detrimental strains are formed between the inner sack and the outer sack, which strains might produce a hole in the inner sack. Technically, such application of adhesive material is very difficult to carry out. In respect of a unit-load sack, the adhesive material can be applied to the lateral areas of the fabric if the unit-load sack is made of separate pieces by means of joints. Such a solution is, however, a laborious, expensive investment and produces an abundant loss of time, as a result of which the manufacture of the unit-load sack becomes relatively expensive. The object of the present invention is to provide an improvement over the prior-art solutions for fixing the inner sack of a unit-load sack to the outer sack. It is a specific object of the invention to provide a method for fixing the inner sack of a unit-load sack, which method is very easy to carry out and, moreover, reliable and does not cause damage to the inner sack. The method in accordance with the present invention is characterized in that adhesive material is applied exclusively either to the outer face of the inner sack or to the inner face of the outer sack, and that, as the adhesive, an adhesive material is used whose adhesion is sufficient to support the inner sack's own weight but which permits movement of the adhesive joint between the inner sack and the outer sack when the unit-load sack is being filled with bulk goods. By means of the method in accordance with the invention, a number of remarkable advantages are obtained over the prior-art methods. By means of the method in accordance with the present invention, the drawbacks arising from the alignment of adhesive zones in pairs used in the method described in the paper EP-0, 158,361 are avoided. In the method of the present invention, when the adhesive zones are placed on the outer sack, these adhesive zones do not interfere with the fitting of the inner sack into the outer sack. The method of the present invention even permits that the inner sack and the outer sack are glued together weakly before the filling of the inner sack starts, i.e. before the expansion of the inner sack starts. It is the main feature of the method of the present invention that the inner sack is not detached from the outer sack by the effect of its own weight. Owing to the method in accordance with the present invention, the adhesive joint or joints between the inner sack and the outer sack may glide even to a relatively great extent when the unit- load sack is filled without producing any problems whatsoever. A unit-load sack produced by means of the method of the present invention, i.e. an inner-sack/outer-sack combination, can be delivered to the users so that the adhesive material is ready in its place in connection with the deliveries of unit-load sacks. In such a case, the user of the unit- load sack does not have to carry out any extra operations in connection with filling of the unit-load sack, such as, for example, fixing the inner sack to the outer sack by means of a tape. On the other hand, during emptying of the unit-load sack, the user does not have to carry out any extra operations in order to keep the inner sack in its position during emptying of the unit- load sack. The invention will be described in detail with reference to some preferred embodi¬ ments of the invention illustrated in the figures in the accompanying drawings, the invention being, however, not supposed to be confined to said embodiments alone. Figure 1 is a schematic sectional view of a prior-art method for gluing together of a unit-load sack and an inner sack. Figure 2 is a schematic sectional view of a preferred embodiment of the outer sack used in the method in accordance with the invention. Figure 3 is a schematic sectional view of a second preferred embodiment of the outer sack used in the method in accordance with the invention. Figure 4 is a schematic sectional view of a preferred embodiment of the inner sack used in the method in accordance with the invention. Figure 5 is a schematic sectional view of a second preferred embodiment of the inner sack used in the method in accordance with the invention. Figure 6 is a schematic sectional view of a third preferred embodiment of the inner sack used in the method in accordance with the invention. Figure 7 is a schematic sectional view of a fourth preferred embodiment of the inner sack used in the method in accordance with the invention. Figure 8 is a schematic sectional view of a fifth preferred embodiment of the inner sack used in the method in accordance with the invention. Figure 9 is a schematic sectional view of a sixth preferred embodiment of the inner sack used in the method in accordance with the invention. Figure 10 is a schematic sectional view of a seventh preferred embodiment of the inner sack used in the method in accordance with the invention. Fig. 1 illustrates a unit-load sack known from the paper EP-0, 158, 361, which is denoted generally with the reference numeral 10. The unit-load sack 10 consists of an outer sack 11 and of a separate inner sack 12. The outer sack 11 has folds 13, and the inner sack 12 has folds 14. Into the folds 13 and 14, sticky adhesive material 15 has been placed. The folds 14 with adhesive material 15 in the inner sack 12 are placed substantially halfway between the folds 13 with adhesive material 15 in the outer sack 11. When the inner sack 12 is filled with bulk goods, the inner sack 12 expands and is glued onto the outer sack 11. The mode of positioning of the adhesive material as illustrated in Fig. 1 involves the numerous drawbacks that were described above. In the embodiment as shown in Fig. 2, the unit-load sack is denoted generally with the reference numeral 20. In this embodiment, adhesive material 23 is applied to the folded areas 24 of the outer sack 21 only, in the way indicated in the figure. When an inner sack 22 is fitted into such an outer sack 21, it is noticed that the adhesive areas 23 do not interfere with the fitting of the inner sack 22 into the outer sack 21. In the method in accordance with the present invention, adhesive is applied to the inner face of the outer sack 21, but not into the narrow space formed by a bend or fold 24 but, on the contrary, to the outer face of the folded area 24. When a unit- load sack 20 as shown in Fig. 2 is filled, the inner sack 22 can expand fully freely and does not meet the adhesive areas 23 on the outer sack 21 until when the inner sack 22 and the outer sack 21 have already almost attained their ultimate shape. In the embodiment as shown in Fig. 3, adhesive areas 33 have been fitted to the inner face of the outer sack 31 in the unit-load sack 30, said adhesive areas being placed substantially opposite to one another and relatively far from the folded areas 34 of the outer sack 31. Into such an outer sack 31, the inner sack can be fitted, for example, either in the way denoted with the reference numeral 32a or in the way denoted with the reference numeral 32b. This embodiment is inferior to that illus¬ trated in Fig. 2, because the inner sack 32a or 32b meets the adhesive areas 33 very soon after the inner sack starts being filled. In fact, the inner sack 32a or 32b may even adhere to the outer sack 31 weakly before the inner sack is filled, but this is not harmful, because the adhesive material is an adhesive material whose adhesive capacity permits movements of the adhesive joint or joints between the inner sack 32a or 32b and the outer sack 31 as the inner sack is being filled with bulk goods. In the embodiment as shown in Fig. 4, the inner sack 42 of the unit-load sack has been folded into a sort of a "wave form", and adhesive material has been applied to the areas 43. The adhesive areas 43 are placed on the outer face of the inner sack 42. The adhesive areas 43 are placed at a substantial distance from the wave ridge or wave ridges 44 of the inner sack 42 and from the wave bottom 45, in the area between the wave ridge 44 and the wave bottom 45. When such an inner sack 42 is fitted into the interior of the outer sack, which is not shown, the solution of Fig. 4 operates in a way substantially similar to the mode of operation of the solution as shown in Fig. 2. The embodiment shown in Fig. 5 is in the other respects the same as the embodi¬ ment shown in Fig. 4, but in the embodiment of Fig. 5 the adhesive areas 53 are placed at the edges of the folded inner sack 52 as far from the wave ridge 54 and from the wave bottom 55 as possible. When such an inner sack 52 is placed inside the outer sack, which is not shown, the adhesive areas 53 adhere to the outer sack almost immediately in a way substantially similar to the embodiment as shown in Fig. 3. This solution is not detrimental either, because the adhesive material can be chosen in a way similar to the embodiment shown in Fig. 3. In the embodiment shown in Fig. 6, the inner sack 62 has been folded into the form of an almost closed ring, and the adhesive areas 63 are placed on the inner face of the inner sack 62 at the edges, which form the open point 64 provided in the shape of a folded ring of the inner sack 62. When such an inner sack 62 is fitted into the outer sack, which is not shown, the solution operates substantially equally well as the embodiments as shown in Figs. 2 and 4 do. The inner sack 72 shown in Fig. 7 is a folded inner sack, and the adhesive areas 73 are placed on the outer face of the folded inner sack 72 at points from which the fold 74 starts being directed inwards. When such an inner sack 72 is fitted into the unit- load sack, which is not shown, the solution shown in Fig. 7 operates substantially equally well as the solutions shown in Figs. 2, 4 and 6 do. The inner sack 82 shown in Fig. 8 has been bent into the shape of a substantially open TJ. The adhesive area 83 is placed in direct vicinity of the tip 84 of one branch of the U-section. The solution shown in this embodiment also operates substantially equally well as the solutions shown in Figs. 2, 4, 6 and 7 do. In the embodiment as shown in Fig. 9, the inner sack 92 has been bent into the shape of a substantially oval ring, and the adhesive area 93 is placed in direct vicinity of one of the overlapping ends 94 of the bent inner sack 92. In the embodiment shown in Fig. 10, the inner sack 102 has been bent substantially in the same way as in the embodiment of Fig. 9, but the adhesive area 103 is placed substantially opposite to the area in which the ends 104 of the bent inner sack 102 overlap each other. The solutions illustrated in Figs. 9 and 10 also operate substantially equally well as the solutions illustrated in Figs. 2, 4 and 6...8 do. In the method in accordance with the invention, as the adhesive material, preferably such an adhesive material is used whose adhesive capacity is sufficient to support the inner sack's own weight but which permits movements in the adhesive joint between the inner sack and the outer sack when the unit-load sack is being filled with bulk goods. Thus, as the adhesive material, it is possible to use a glue of low cohesion, such as, for example, preferably a self-adhesive glue. As the adhesive material, it is possible to use, for example, a glue that is activated by the effect of outside condi¬ tions. One such adhesive material is a glue activated by the effect of UV radiation. To such an adhesive material it is possible to add a catalyst which produces adhesion of the adhesive material by the effect of UV radiation. As the adhesive material, it is also possible to use a glue that is activated by the effect of humidity contained in air, of rainwater, or equivalent. To such an adhesive material, it is possible to add an inorganic or organic hygroscopic agent. For example, an ethylvinylalcohol-based hygroscopic agent is highly suitable and usable for the purpose of the invention. Above, just some preferred embodiments of the invention have been described, and it is obvious to a person skilled in the art that numerous modifications can be made to said embodiments within the scope of the inventive idea disclosed in the accom¬ panying patent claims.

Claims: Claims 1. A method for fixing the inner sack (22,32a;32b,42,52,62,72,82,92, 102) of a unit-load sack (20,30) to the outer sack (21,31), in which method the inner sack is fixed to the outer sack by using an adhesive material, characterized in that adhesive material (23,33,43,53,63,73,83,93,103) is applied exclusively either to the outer face of the inner sack (22,32a;32b,42,52,62,72,82,92,102) or to the inner face of the outer sack (21,31), and that, as the adhesive, an adhesive material is used whose adhesion is sufficient to support the inner sack's own weight but which permits movement of the adhesive joint between the inner sack and the outer sack when the unit-load sack (20,30) is being filled with bulk goods. 2. A method as claimed in claim 1, characterized in that adhesive material (23) is applied to the inner face of the folded outer sack (21), to the outer face of the folded area (24). 3. A method as claimed in claim 1, characterized in that adhesive material (33) is applied to the inner face of the folded outer sack (31) to constitute adhesive areas which are placed substantially opposite to one another and substantially far from the folded areas (34) of the outer sack (31). 4. A method as claimed in claim 1, characterized in that adhesive material (43) is applied onto the outer faces of the inner sack (42) that has been folded substantially into wave form so as to constitute adhesive areas which are placed at a substantial distance from the wave ridge (44) and from the wave bottom (45) of the inner sack (42). 5. A method as claimed in claim 1 , characterized in that adhesive material (53) is applied onto the outer faces of the inner sack (52) that has been folded substantially into wave form so as to constitute adhesive areas (53) which are placed substantially at the edges of the inner sack (52) that has been folded into wave form. 6. A method as claimed in claim 1, characterized in that adhesive material (63) is applied onto the outer faces of the inner sack (62) that has been folded into the form of an almost closed ring so as to constitute adhesive areas which are placed substan¬ tially at the edges of the inner sack (62) opposite to the open point (64) of the inner sack (62) which is in the form of an almost closed ring. 7. A method as claimed in claim 1, characterized in that adhesive material (73) is applied onto the outer face of the folded inner sack (72) to constitute adhesive areas at points at which the fold (74) starts being directed inwards. 8. A method as claimed in claim 1, characterized in that adhesive material (83) is applied onto the outer face of the inner sack (82) that has been bent into a substan¬ tially open U-shape in direct vicinity of at least one of the tips (84). 9. A method as claimed in claim 1 , characterized in that the inner sack (92) is bent substantially into an oval ring shape so that the ends of the inner sack (92) overlap each other, and that adhesive material (93) is applied onto the outer face of the inner sack (92) in direct vicinity of at least one of the overlapping ends (94). 10. A method as claimed in claim 1 , characterized in that the inner sack (102) is bent substantially into the shape of an oval ring so that the ends (104) of the inner sack (102) overlap each other, and that adhesive material (103) is applied onto the outer face of the inner sack (102) in an area that is placed substantially opposite to the area in which the ends (104) of the bent inner sack (102) overlap each other. 11. A method as claimed in any of the claims 1 to 10, characterized in that the adhesive material that is used is a glue of low cohesion, preferably a self-adhesive glue. 12. A method as claimed in any of the claims 1 to 10, characterized in that the adhesive material that is used is a glue that is activated by the effect of external conditions. 13. A method as claimed in claim 12, characterized in that the adhesive material that is used is a glue that is activated by the effect of UV radiation. 14. A method as claimed in claim 13, characterized in that to the adhesive material a catalyst is added which produces adhesion of the adhesive material by the effect of UV radiation. 15. A method as claimed in claim 12, characterized in that the adhesive material that is used is a glue that is activated by the effect of humidity contained in air, of rainwater, or equivalent. 16. A method as claimed in claim 15, characterized in that an inorganic or organic hygroscopic agent is added to the adhesive material.

Inventors: NYMAN PER, NYMAN, PER
Applicants: NYMAN PER, ROSENLEW AB OY W, NYMAN, PER, OY W. ROSENLEW AB
Application year: 1995
Main classification: B65D88
IPC codes: B65D88