IMPROVEMENTS IN AND RELATING TO PACKAGES

Abstract: To facilitate butt-welding, or L- or T-weld joints the edges of a plastics-coated paper-layered web (1) of packaging material is thickened e.g. by folding over and sealing down edge zones. The folding line (14) of each edge zone may be creased before folding, and the upstanding crease enclosed between the folded edge zone and the body of the web. The sealing of the edge zone may be effected by pressure rollers (21) holding the edge zones against a rotating cylindrical surface (22), whereby a curl or curvature is imposed upon the web.

Description: IMPROVEMENTS IN AND RELATING TO PACKAGING MATERIAL, AND PACKAGES FORMED THEREFROM This invention relates to packaging material, and packages formed therefrom. Packaging material in accordance with the invention is applicable to the production of a known form of packaging container, and will be described with reference to that application, but it should be understood that the packaging material described is not limited solely to that use. The known form of packaging referred to above is produced by bonding together two webs of material one of which is shaped by an endless chain of moulds into a series of deep channels extending transversely of the web and partitioned from one another by upstanding folded walls of the web, while the other web has edge zones divided into flaps. The undivided middle portion of the second-mentioned web is applied, and bonded, to the upper edges of the partitioning walls of the first-mentioned web, and the said side flaps folded down and sealed to the edges of the channels of the first-mentioned web, forming a chain of interconnected closed containers which can be separated from one another. Heretofore the aforesaid known containers have been made from webs of foamed plastics materials provided with surface coatings of homogeneous plastics suitable for heat-sealing. However, the use of such materials renders these containers too expensive for some intended uses, and the main purpose of this invention is to provide a packaging laminate of cheaper materials suitable for forming into a cheaper variety of the aforesaid known containers, and for other packaging purposes. With this end in view the invention consists in a packaging material in laminate sheet or web form incorporating a layer of paper and an outer coating layer of plastics on each face, adapted for edge-bonding, e.g. by butt welding or L-joint or T-joint welding, wherein an edge strip of the material -is thickened, and formed with a heat-sealable outer plastics surface. The edge zone or zones may be thickened by folding. The line of folding may be defined by an impressed crease-line. After such folding the ridge of the crease-line upstanding from one face of the material should project inwards between the areas folded together. The invention further consists in a method of, and an apparatus for, the production of packaging material as specified in the next preceding paragraph. A preferred form of the invention will now be described, merely by way of example, with reference to the accompany drawings wherein: Figure 1 illustrates the mode of production of the known form of container mentioned above; Figure 2 represents part of a known machine used to produce said known containers; Figure 3 represents, somewhat diagrammatically, in end view rollers and other pieces of apparatus in use to prepare packaging material in accordance with the invention; Figure 4 represents a plan view of the rollers shown in Figure 3; Figure 5 represents a perspective view, partly cut away, of a pair of rollers shown in Figures 3 and 4; Figure 6 represents in section the operation of forming a crease-line in packaging material by the rollers shown in Figure 5; Figure 7 represents in enlarged section part of the packaging material after creasing; ; Figure 8 represents in perspective a heating device for heating the edge zones of the material before folding; Figures 9 and 10 represent sectional views of the heater shown in Figure 8; Figure 11 represents a perspective view of a folding device adapted to fold the edge zones of the material, with end views of the device in successive stages of a folding operation; Figure 12 represents in enlarged section the creased zone shown in Figure 7 after it has been folded over; Figure 13 represents an end view of sealing rollers by which a folded edge zone is sealed to the inner area of the material; and Figure 14 represents an enlarged sectional view of an edge of the finished material provided by the folding and sealing with a thickened plasticssurfaced edge area. As previously stated the packaging material in accordance with the invention may be used in the production of a known form of container, and this form will be recognised by reference to Figures 1 and 2 of the accompanying drawings. A lower web 1 of packaging material is formed by moulds into double-fold, spaced, upstanding walls 2 defining between them valleys or channels extending transversely of the web. A second, upper web has a middle longitudinal zone 3 of substantially the same width as the top edges of the walls 2 of the lower web, and flaps 4 extending from the edges of the zone 3, dimensioned to correspond substantially to the end sections of the channels between the walls 2 of the lower web. These two webs are advanced together with zone 3 over the edges of the walls 2 , as illustrated, and the zone 3 is bonded to the top edges of the wall 2, while the flaps 4 are folded against, and bonded to, the end edges of the channels. The enclosures so formed may be loaded with contents and separated from one another. Details of this mode of package may be found in British Patent Specification No. 1332628 from which Figure 1 is taken. An example of means for moulding web 1, shown in Figure 1, is illustrated in Figure 2. A series of mould units 5 articulated to form an endless chain provide successive mould channels between adjacent units, and a rotatable roller array 6 presses down the flat web 1 into these channels where it conforms with the mould chain and is provided with upstanding transverse double fold walls with channels between them, substantially as illustrated in Figure 1, noting, however, that in Figure 2 the lower part of each channel is substantially serni-cylindrical rather than rectangular. A machine incorporating such a mould chain is disclosed in British Patent Specification No. 1487693 from which Figure 2 is taken. As previously stated webs 1 and 3,4 shown in Figures 1 and 2 have heretofore been formed of foamed plastics material (e.g. polyethylene or polystyrene) with a homogeneous plastics coating layer on each face (e.g. of similar plastics materials), but such materials render the product undesirably expensive for some purposes. To overcome this difficulty the present invention contemplates the replacement of at least the web 1 by a web of plastics-coated paper, which is substantially cheaper. A problem arising from such a replacement lies in the difficulty of firmly sealing the folded-down flaps 4 of the upper web to the edges of the channel-formed lower web 1 of plastics-coated paper. To meet this problem in accordance with the present invention the edges of the plastics-coated paper web 1 are thickened and provided with a heat-sealable plastics-surface, and a preferred procedure for achieving that result is illustrated in Figures 3-14 of the drawings herewith. Referring to Figures 3,4 and 5, the web 1, here formed of paper provided with plastics coating on each face is fed to the apparatus over a guide roller 7. The paper may be of the kind known as "Duplex" paper with the fibres of one face (intended for the outer surface of a carton formed from the web) being bleached, and the fibres of the opposite face unbleached. Each face of the paper web is coated with an affixed plastics film (e.g. of polyethylene). The roller 7 is provided with flanges 8 to prevent lateral displacement of the advancing web, as it proceeds over the upper roller 9 of a pair of rollers 9,10 urged together by adjustable pressurespring means 11. Passing round part of the roller 9 the web passes through the nip between the rollers 9,10, which, also are flanged to locate the web. Adjacent to, but slightly spaced from, each flange the roller 9 is provided with a peripheral groove 12 (exposed by the partially broken away flange in Figure 5), and in like position the roller 10 is provided with cooperating upstanding ribs or ridges 13. As the web runs between the rollers 9,10 these ribs and grooves co-operate to impress in the web, slightly spaced from each edge, a groove 14. A section of the co-operating rollers 9,10 performing this operation is shown in Figure 6, and a cross section of the grooved web is illustrated in Figure 7, showing the upstanding crease on the other face of the web. At each edge of the web the narrow edge zone outside the groove 14 is folded towards, and sealed to, the middle zone of the web, and for this purpose the web proceeds past heating means 15 which soften the plastics coating of the web in readiness for bonding, and folding means 15a by which the edge zones are folded inwards. A convenient form of heating means is illustrated in Figures 8, 9 and 10. A U-shaped tube 15 is provided at its mid-point with a hot-air inlet duct 16. The side limbs of the tube are substantially parallel, and the width of the heater corresponds substantially to the width of the web. The heater is positioned so that the side limbs are located over the edges of the web which advances beneath the heater in a direction parallel to the axes of the side limbs. The undersides of the side limbs are apertured or slotted as at 17, and hot air is directed through these openings onto the edge zones of the passing web, to soften the plastics coating thereon for sealing. The heater, shown in perspective in Figure 8, is illustrated in section in Figure 9, and a side-section of a side limb shown in Figure 10. After being heated the web passes to an edgefolding device which may conveniently be of the form shown in Figure 11. A rigid plate 18, e.g. of metal, is substantially flat at the end first approached by the web, but one half 19 of the plate on one side of the longitudinal centre-line of the plate is twisted in relation to the other half 20 of the plate, so that proceeding along the plate from the flat end to the other end, the twisted half 19 of the plate becomes increasingly inclined to the other half 20, until it is perpendicular thereto, and thereafter continues to an increasingly acute angle in relation to the other half 20, until it is folded into a position parallel to, and only slightly spaced from the other half 20. As the web reaches and slides along this folderplate the outer edge of the web is adjacent to the outer edge of the portion 19 of the plate, and as it advances the edge zone of the web is gradually folded up and over by the twisted length 19 of the plate until, at the remote end of the plate it is folded flat against the inner web surface. Successive stages of this folding operation are illustrated in Figure 11 by cross-sections of the plate at different points along its length. to reduce the friction of the web against the folder-plate, the plate may be fitted with rollers or replaced by a frame or race of rollers. A folder- device is provided at each edge of the web. The surface of the web which is heated is the surface intended to be the outer surface of a container made from the web, and it follows that as a result of the folding the plastics coating of the web surface intended to be the inner surface of a container extends round the folded web edge and appears as a narrow edge zone on the other web face. It should be noted that each edge groove 14 in the web provided by the rollers 9,10 runs on to a folder-plate substantially in line with the centre line of the plate and with the crease (Figure 7) upstanding therefrom. In consequence when the edge zone is folded over, the crease is directed inwardly between the web and its folded-over edge zone, as illustrated in Figure 12. To complete the preparation of the web the folded heated edge zones are pressed into sealing contact with the web by roller means. Since the web may be curved when being moulded in the course of forming containers (Figure 2), the web may be formed with a curl or curvature in the face of the web which is to be the interior surface of a container. This effect. may be achieved by pressing the web against a rotating cylindrical surface when sealing the folded edge zones. Referring to Figures 3 and 13 a pressure roller 21 running beneath each folded web edge presses the edge against a cylinder 22 provided with flanges 23 to prevent lateral displacement of the web. The diameter of the cylinder 22 is selected according to the degree of curl or curvature desired in the finished web. The roller 21 with appropriate pressure seals the folded edge zone to the body of the web. The edge of the roller 21 immediately adjacent to the portion of the folded edge which is thickened by the folding and by the inwardly directed crease (Figure 12) is rounded or chamfered as at 24 in order to avoid flattening of this thickened, plastics-faced edge. The finished web is drawn off and formed into a roll for subsequent presentation to a package-forming machine. A web of packaging material in accordance with the invention as described above may conveniently be used for the lower web 1 in the procedure referred to with reference to Figures 1 and 2 of the drawings herewith, when it is moulded into transverse channel shape in moulds such as illustrated in Figure 2. It will be noted that the curl or curvature imposed upon the web by the counter-pressure rotating cylinder 22, is in the sense which assists in the shaping of the web in the moulds shown in Figure 2. The upper web 3, 4 (Figure 1) when used with a web of material in accordance with this invention may be of the kind heretofore used (e.g. of foamed plastics material with plastics-coated surfaces) or it may also be formed of material in accordance with this invention. In either case the thickened edge of the lower web 1 is attached to the flaps of the upper web by butt-welding, or Lor T-joint welds. The heat-sealable plastics surface at the thickened edge of the lower web should be of the same plastics-coating material as that of the upper web to which it is to be bonded.

Claims: CLAIMS 1. Packaging material in laminate sheet or web form incorporating a layer of paper and an outer coating layer of plastics on each face, adapted for edge-bonding, e.g. by butt welding or L-joint or T-joint welding, wherein an edge strip of the material is thickened, and formed with a heat-sealable outer plastics surface-. 2. Packaging material as claimed in Claim 1 wherein the edge strip is thickened by folding in an edge zone of the material. 3. Packaging material as claimed in Claim 2 wherein the fold-line of the edge zone is defined by an upstanding crease in the material and the edge zone is folded in such a sense that said crease extends inwards between the folded edge zone and the adjacent zone of the material to which the edge zone is folded. 4. Packaging material as claimed in Claim 1, 2 or 3 formed with a natural curl or curvature along its length. 5. A web of packaging material as claimed in any of Claims 1 to 4 wherein each of the opposite edges of the web is thickened and provided with a heat-sealable plastics surface. 6. A method of producing a web of packaging material incorporating a layer of paper, and an outer coating layer of plastics on each face wherein the edges of the web are treated to thicken them and provided with a heat-sealable plastics surface on each thickened edge. 7. A method as claimed in Claim 6 wherein each edge of the web is thickened by folding in an edge zone of the web and sealing it to the inner web area. 8. A method as claimed in Claim 7 wherein the foldline of each edge zone is defined by a groove impressed in the web with a corresponding crease upstanding from the opposite face of the web. 9. A method as claimed in Claim 8 wherein the edge zone is folded in such a sense that the upstanding crease is embraced between the folded edge zone and the adjacent area of the web. 10. A method as claimed in Claim 9 wherein sealing pressure applied to bond the folded-in edge zone to the body of the web is restricted so that substantially no such pressure is applied to the folded areas embracing said crease between them. 11. A method as claimed in any of Claims 6 to 10 wherein sealing of the folded edge zones is effected by roller means which press the web against a curved surface to impart a longitudinal curl or curvature to it. 12. Apparatus adapted to carry into effect a method as claimed in any of Claims 6 to 11 comprising roller means adapted to impress a fold line in the form of a groove in one face of the web, and a corresponding upstanding crease on the opposite face, of the web, substantially parallel to, but slightly spaced from, each web edge. 13. Apparatus as claimed in Claim 12 comprising two cooperating rollers between which the web passes, one such roller being provided with peripheral grooves adjacent to its ends, and the other said roller being provided with peripheral impression ribs adjacent to its ends, positioned to cooperate with the said peripheral grooves in order to impress the web. 14. Apparatus as claimed in Claim 13 wherein said rollers are urged together by adjustable spring means. 15. Apparatus as claimed in Claims 12, 13 or 14 comprising means to heat the edge zones of the web. 16. Apparatus as claimed in claim 15 wherein edgezone heating is effected by hot air. 17. Apparatus as claimed in Claim 15 or 16 wherein the said heating means comprises a U-shaped tube adapted to convey heated air to its parallel side limbs which are slotted or apertured to direct the hot air on to the edges of the web when the heating means are mounted adjacent to the web surface with its side limbs over, and substantially parallel to, the web edges. 18. Apparatus as claimed in Claims 15, 16 or 17 comprising means for folding in the heated edge zones of the web over the adjacent inner zone of the web. 19. Apparatus as claimed in Claim 18 wherein the folding means comprise guide means, over which the edge zones of the web ride, the guide means being shaped to ensure that in the course of advance the edge zone of the web, in passing along the guide means, is gradually turned up, over and down, by a folding motion, to be against the adjacent inner zone of the web. 20. Apparatus as claimed in Claim 19 wherein the guide means comprises a plate or frame of which one half along a longitudinal median line remains substantially flat along its full length, while the other half is twisted in relation to the firstmentioned half, so that progressively along the length of the plate the second-mentioned half assume an angular relationship to the first-mentioned half, commencing with a progressively decreasing obtuse angle and proceeding, past perpendicular, to a progressively reducing acute angle, so that at the end of the plate the two half-surfaces are substantially parallel to one another. 21. Apparatus as claimed in Claims 18, 19 or 20 wherein the folding means are provided with rollers to reduce friction of the web therewith. 22. Apparatus as claimed in any of Claims 18 to 21 when appendant to Claim 12, 13 or 14 wherein the folding means are so positioned that they fold in each edge zone of the web in such a direction that the impressed web crease is embraced between the folded edge zone and the adjacent web area. 23. Apparatus as claimed in any of Claims 18 to 22 comprising means for applying sealing pressure to said folded edge zones in order to bond them to the web. 24. Apparatus as claimed in Claim 23 comprising roller means adapted to press said folded edge zones against a backing surface for sealing them. 25. Apparatus as claimed in any of Claims 12 to 24 comprising means for forming the web with a longitudinal curl or curvature. 26. Apparatus as claimed in Claim 25 when appendant to Claim 24 wherein during sealing of the edge zones the web is pressed against a curved counter-pressure surface. 27. Apparatus as claimed in Claim 26 wherein the counter-pressure surface is a rotatable cylindrical surface. 28. Apparatus as claimed in Claim 24 or in any of Claims 25, 26 and 27 when appendant to Claim 24 wherein the end edge of the pressure-applying roller means is rounded or chamfered. 29. Apparatus as claimed in any of Claims 12 to 28 wherein rollers over which the web passes are flanged at their ends to prevent lateral displacement of the web. 30. A packaging container formed of parts moulded from flexible packaging material bonded together, wherein one of the said parts is formed of material as claimed in any of Claims 1 to 5, and is bonded by its thickened edges to another part of the container. 31. A container as claimed in Claim 30 formed of two parts, wherein the second part is formed of foamed plastics sheet material with a homogeneous plastics coating on each face or of the same material as the first-mentioned part.

Inventors: ANDERSSON, PAR MAGNUS, STARK, SVEN OLOF SOREN, Andersson, Pär Magnus, Stark, Sven Olof Sören
Applicants: TETRA PAK INTERNATIONAL AB
Application year: 1982
Main classification: B31F1
IPC codes: B65D5, B65H45, B31F1, B65D65, B31F5, B65B9, B32B1