PACKAGING SHEET FOR WRAPPING ROUND MATERIAL WOUND INTO A ROLL AND THE METHOD OF WRAPPING THE PACKAGING SHEET

Abstract: Packaging sheet for wrapping round material wound into a roll, such as a paper roll (5), comprises exterior layers (1, 2) of mainly paper, kraft paper, kraft liner, board or the like on the opposite faces of the sheet and between the said layers (1, 2) a layer of plastics (3). At at least one of the opposite longitudinal edges of the sheet, the plastics layer (3) solely constitutes the surface of the margin area (4) of the sheet on at least one of the opposite faces of the sheet, thus reducing the thickness of the sheet at said margin area (4). The plastics surface of the margin area (4) is preferably heat-sealable.

Description: Packaging sheet for wrapping round material wound into a roll and the method of wrapping the packaging sheet The present invention relates to a packaging sheet presented by the preamble of claim 1. The invention relates also to a method of using such packaging sheet in course of wrapping the sheet round material wound into a roll. It is known technique in packaging big paper rolls or the like material, which is wound into a roll, to use such packaging sheet wherein the outer and inner layer of paper, board or the like material is laminated together by means of an interposed plastics layer. The plastics layer serves in insulating the moisture and also strengthens the sheet. In packaging sheets of prior art the said layers are of equal breadth, ie. the elongate sheet is of equal thickness at every point along its breadth. As for example a paper roll is packaged within such sheet, the sheet is wrapped round the roll to form several overlapping windings, eg. three or four windings. The breadth of the packaging material exceeds the axial heighth of the cylindrical roll and the margins adjacent the longitudinal edges of the sheet extend outwardly beyond the planes of the ends of the roll. In course of wrapping, the outward portions of the said packaging sheet margins are folded over the ends of the roll and after the winding has been completed, an end label is fastened onto the end of the roll by gluing or hot sealing. Both ends of the roll are treated simultaneously using the above procedure, which is usually done in a specific machine. The drawback in the above procedure is the fact, that the folds in the end of the roll become thick and uneven. The aforementioned features cause among other thinks depressions to the rolls wrapped within the package and they couse also problems as far as the tightness of the fastened end label is concerned. As the rolls are stacked to form hig piles, the unevenness of the ends will be accumulated. As to the drawbacks discussed hereinabove, an object of the invention is to provide an improvement. For realising this, the packaging sheet in accordance with the invention is mainly characterised by the features set forth in the characterising portion of claim 1. Due to the reduced thickness at the margin area of the sheet, it is possible to provide a packaging sheet, whose folding can be effected more easily and more evenly. This results in tighter fastening of the end label to the said folds. According to a preferred embodiment of the packaging sheet, the surface of the margin area of reduced thickness is heat sealable. This makes it possible to make use of the surface of the margin area when the end labels are fastened by hot sealing to the folds. The invention relates also to a method of wrapping the packaging sheet round material wound into a roll, which method takes advantages of the packaging sheet of the invention. The method in accordance with the invention is mainly characterised by the features set forth in the characterising portion of claim 6. The features of the method are partly discussed already above, but it must also be noted, that the relation of the breadth of the margin area to the overall breadth of the packaging sheet is chosen so, that the thicker portion of the sheet adjacent the margin area will cover the corner between the cylindrical surface of the roll and the end surface of the roll, thus shielding effectively the contents of the package at this region prone to damages. The invention will be hereinafter described in more detail with reference to the appended drawings, wherein Fig. 1 is a perspective view of the packaging sheet of the invention, where a transverse cut is made, showing the proportions of the thickness of the material slightly exaggerated, Fig. 2 illustrates the use of the packaging sheet of the invention in course of wrapping the sheet round paper rolls, Fig. 3 is a cross section of an end of the package according to one embodiment of the invention and Fig. 4 is a view of the end of the package like in Fig. 3, showing an alternative embodiment of the invention. Fig. 1 shows a packaging sheet in accordance with the invention. The packaging sheet is in a form of a continuous elongate sheet and it comprises on one face an exterior layer 1 of paper, board or the like, and on the opposite face an other exterior layer 2 of paper, board or the like and an plastics layer 3 between the said layers 1 and 2. The exterior layers 1, 2 are laminated together by means of the plastics layer 3 using conventional technique of laminating together continuous sheets. The layer 3 between the exterior layer acts as an moisture insulating layer in conventional packaging sheets and in the sheet according to this invention as well. In accordance with the invention, one of the layers 1, 2, ie. in Fig. 1 the layer 1 has smaller breadth than the plastics layer 3, thus leaving the plastics layer exposed at both edges of the elongate sheet at margin areas, which are denoted by reference numerals 4. The plastics layer 3 covers on these areas the exterior layer 2 situated on the opposite face of the sheet. The breadth of the plastics layer 3 is constant along the length of the sheet and exceeds that of the exterior layer 1 by ca. 15-30 cm. According to a preferred embodiment of the invention, the margin areas 4 lie symmetrically in relation to the center line of the sheet, in which case the breadth of the margin areas -4 are equal and ca. 7,5-15 cm. Both edges of the plastics layer 3 can sideways reach the edge of the opposite exterior layer 2 or leave a small marginal portion of the layer 2 uncovered, as shown by Fig. 1. This depends on the method of manufacture. The exterior layers 1 and 2 can be of kraft paper, kraft liner, board or the like packaging material and the plastics layer 3 joining the layers 1, 2 together may be of any plastics materials suitable for laminating. The plastics material has preferably also good he.at-sealing properties, and polyethylene can be mentioned as preferred material in this respect. The plastics layer 3 can constitute the bare surface of the margin area of the sheet also towards both directions, ie. on the side of the layer 1 and on the side of the layer 2. This depends on the method of manufacture of the sheet. As the plastics layer 3 is laminated between the layers 1 and 2, it is, however, preferable, that one of the layers 1, 2 is of at least equal breadth with the plastics layer 3, thus serving as a backing layer, and the other of the layers 1, 2 is smaller in breadth than the plastics layer. Fig. 2 illustrates the method of wrapping packaging sheet round a paper roll 5. The cylindrical paper roll 5 is wrapped within the sheet so, that at an initial stage the sheet is wound around the roll, during which stage the edges of the sheet will project outwards from the plane of the end of the roll, this being due to the fact that the overall breadth of the packaging sheet is greater than the axial height of the cylindrical roll. This point is denoted by arrow A in Fig. 2. The wrapping is usually performed automatically in a special machine, which folds these outwardly projecting edges over the ends of the roll simultaneously as the sheet is wound over the cylindrical surface of the roll. The resulting radial folds are denoted by reference numerals 6 in Fig. 2. Fig. 2 shows the alternative, where the plastics surface of the margin area 4 is on the side away from the roll and the surface of ■ the exterior layer 2 backing the plastics layer comes in contact with the end of the roll. Prior to folding the margin area 4 over the end of the roll, a protective inner end label may be placed on the end of the roll. It must be noted, that although Fig. 2 illustrates the one end (arrow A) before the folding and the other end (arrow B) after the folding, the folding operation is effected simultaneously at both ends in wrapping machines. 5 After the desired number of windings have been wound around the roll, the folding has also been accomplished and end labels 8 can be placed against both ends of the package. The surface facing the package is covered with heat sealable plastics 10 material, which attaches the lable onto the end of the package. As seen in Fig. 2, the margin area 4 forms an annular heat-sealable area at the end of the package, which contributes to firm attachment of the end label 8 to the package. Moreover, the portions of 15 the margin area 4 folded against each other in the folds 6 are sealed together. The attachment of the end label 8 on to the folds 6 is illustrated in Fig. 3, showing one part of the end of the package in cross section. 20 Fig. 4 shows an alternative to the attachment of Fig. 3. In this method, an inner end label 8 has been placed against the end of the roll before the folding of the margins over the end. The end label is of a similar construction as in Fig. 3, but it has been 25 placed so, that the heat sealable plastics layer is on the side away from the roll. Moreover, the sheet is wrapped round the roll so, that the plastics surface of the margin area 4 is on the side towards the roll and the exterior layer 2 backing the 30 plastics layer 3 is on the side away from the roll. Now, when the margin area 4 is folded over the end of the roli and the end label 8, the plastics surface of the margin area 4 will be situated on the inner surface of the folds, the term "inner" meaning the position in relation to the package in this context, and it is in contact with the heat sealable surface of the inner end label 8. This may be a very advantagous alternative, when one will make it sure, that no foreign object can penetrate to the interior of the package between the surface of the folds folded together on the side facing the end of the roll, because, as shown by Fig. 4, the plastics surface of the margin area 4 will be heat-sealed to the inner end label 8 at its portions in contact with the lable 8 and those surface portions of the margin area 4, which are not in contact with the lable 8, are folded against each other and are sealed to each other by their facing plastics surfaces. The sheet and the inner end label are thus fastened to each other so, that no radial passages from the exterior into the interior of the package will be present in that layer of folds in the packaging material, which will become closest to the inner end label 8. If Desired, an additional outer end label can be placed and fastened over the folds 6. The fastening of the end labels by hot sealing is a conventional operation, which is realised with a heated plate-like tool, which presses the label and the surface to be sealed against each other. As shown by Fig. 2, the breadth of the margin areas 4 at both edges of the sheet is chosen so, that the thicker portion of the sheet adjacent the margin area 4, constituted of the layers 1, 2 and 3 together, covers the corner 7 between the cylindrical surface of the roll and the end surface of the roll. It is advantageous to extend the thicker portion beyond the corner over the end of the roll, because at this corner region the roll must be protected by a thicker layer of packaging material. The packaging sheet of the present invention can be manufactured using conventional laminating technique and using conventional machines. In practice the laminating can be effected so, that a continuous sheet constituting one of the exterior layers 1, 2 is laminated onto the plastics layer 3, this sheet being smaller in breadth than the plastics layer 3. The sheet can be disposed symmetrically in relation to the plastics layer 3 so, that the margin areas 4 on both edges of the packaging sheet will have equal breadth and exact same properties. It becomes apparent from the above description of the method of manufacture, that one additional advantage of the invention is saving in material of one of the exterior layers when manufacturing the packaging sheet. For the raw material of the plastics layer 3, a continuous pre-fabricated sheet can be used or the layer can be formed by extrusion between the exterior layers 1 and 2. The invention, can be varied within the scope of the appended claims. For example, if heat-sealing is not utilised in fastening the end labels, they can be fastened by gluing. It must be also noted, that in order to effect hot sealing, only one surface does need to have a heat sealable surface, provided that the opposite surface is of suitable material, such as paper, board or the like.

Claims: Claims : 1. Packaging sheet for wrapping round material wound into a roll, such as a paper roll (5), the sheet comprising exterior layers (1, 2) of mainly paper, kraft paper, kraft liner, board or the like on the opposite faces of the sheet and between the said layers (1, 2) a layer of plastics (3), c h a r a c¬ t e r i s e d in that at at least one of the opposite longitudinal edges of the sheet, the plastics layer (3) solely constitutes the surface of the margin area (4) of the sheet on at least one of the opposite faces of the sheet, thus reducing the thickness of the sheet at said margin area (4). 2. Packaging sheet as claimed in claim 1, c h a r¬ a c t e r i s e d in that the plastics layer (3) constitutes the surface of the margin area (4) at both opposite longitudinal edges of the sheet. 3. Packaging sheet as claimed in claim 2, c h a r¬ a c t e r i s e d in that the margin areas (4) are of equal breadth. 4. Packaging sheet as claimed in any of claims 1 to 3, c h a r a c t e r i s e d in that one of the exterior ' layers (1, 2) is of at least equal breadth with the plastics layer (3), covering the said layer (3) on one of the opposite faces of the sheet. 5. Packaging sheet as claimed in any of claims 1 to 4, c h a r a c t e r i s e d in that the plastics surface of the margin area (4) is heat-sealable. 6. Method of wrapping packaging sheet as claimed in claim 1 round material wound into a roll, such as a paper roll (5), c h a r a c t e r i s e d in that the margin area (4) constituted of the plastics layer surface is folded over the end of the roll at its whole breadth such that the thicker portion of the sheet adjacent the margin area (4) covers the corner (7) between the cylindrical surface of the roll and the end surface of the roll. 7. Method as claimed in claim 6, wherein the plastics surface of the margin area (4) is heat- sealable, c h a r a c t e r i s e d in that the sheet is wrapped round the roll (5) so, that the plastics surface of the margin area (4) will be situated on the outer surface of the folds (6) after folding over the end of the roll, whereafter an end label (8) is placed against the outer surface of the folds (6) and fastened onto the folds by hot sealing. 8. Method as claimed in claim 6, wherein the plastics surface of the margin area (4) is heat- sealable, c h a r a c t e r i s e d in that prior to folding the margin area (4), an inner end label (8) is placed against the end of the roll (5) and the sheet is wrapped round the roll (5) so, that the plastics surface of the margin area will be situated on the inner surface of the folds (6) after folding against the inner end label (8), whereafter the folds are fastened onto the inner end label (8) by hot sealing. 9. Method as claimed in claim 6 or 7, c h a r a c¬ t e r i s e d in that the surface of the end label (8) coming in contact with the plastics surface of the margin area (4) is constituted of a heat sealable plastics layer.

Inventors: LAINE JOUNI, MYLLAERI ESA, LAINE, JOUNI, MYLLAERI, ESA
Applicants: PLASTIROLL OY
Application year: 1988
Main classification: B65D85
IPC codes: B65D85