Packaging tube and its method of manufacture

Abstract

 A method for manufacturing a container having a longitudinal joint where the cut edges are not exposed to the interior of the container.
The invention is especially well suited for laminate tubes, i.e. metal foil containing tubes or corresponding high barrier material tubes, preferrably such material where high frequency welding is possible.
As a first step, two longitudinal end edges (15, 16) of a tube blank are placed with overlap such that one and the same side of the blank forms abutment surfaces (19, 20) in the region of the overlap and that the blank hereby forms a hollow body. One (16) of the longitudinal edges is placed such that one end portion thereof extends a distance outside the second edge along the entire length of the blank. A seal is obtained in the region of said overlap, between said abutment surfaces (19, 20).
Thereafter the overlap and the protruding end portions are folded down against the exterior of the tube body and a further welding operation is carried out, whereafter the region of the longitudinal joint is flattened and finally shaped into correspondence with the said outer contour ot the tube body.

Description

[0001] The present invention relates to packaging tubes and more precisely tubes or bottles having container bodies obtained by a longitudinal seal of overlapping edge portions of a blank, in the shape of a sheet or an integral web.

[0002] More precisely the invention relates to a new type of longitudinal seal having cut edges of a sheet or a web not exposed to the interior of the container body and thus of a type being not affectable or alternatively not affecting the tube interiour.

[0003] In such an application where it is desirable to manufacture a container body of a laminate compressing some sort of metal foil, for instance aluminum foil, it is of a decisive importance that the metal is insulated from the filling goods. One example of such an application is the case where the filling goods is tooth cream which normally contains very agressive components also visavi aluminum.

[0004] The other way around, if for instance the material of the container body comprises a paper or a cardboard layer, there is a problem of preventing absorption of liquid into said layer.

[0005] Of course, there are a number of solutions to the problem of blocking or insulating the cut edges of a packaging container from the filling goods. One example is the technique where a thin covering strip of a thermoplastics material having suitable sealing and barrier properties is used inside the package.

[0006] Another example of known technique is represented by the longitudinal seal where a longitudinal fin first is formed for facing the inside of the packaging container, and thereafter is rolled to a "cylinder" for hiding the cut edges inside said cylinder, and thereafter the total appearence is improved outwardly by applying a strip along the joint.

[0007] Also in the first mentioned case, where an integral strip is used for providing a sufficient cut edge protection, frequently there is a need for applying also an external strip, sometimes merely of aesthetic reasons, in other cases also for preventing absorption from the outside into a fibrous intermediate layer.

[0008] There are continous as well as intermittent manufacturing methods according to said technique. However, a mass production of this type of course is very sensitive to material costs, and this is perhaps the primary draw back of the known technical solutions for solving the longitudinal joint problems.

[0009] Frequently, there is needed a relatively wide strip for obtaining a good enough barrier protection.

[0010] Futheron, the strip application implies a further step of the manufacturing procedure and thus it contributes to increased manufacturing costs.

[0011] The object of the invention is to eliminate the draw backs of the known techniques for providing longitudinal seals in container bodies or container casings.

[0012] The present invention provides a method for forming a longitudinal joint in a tube-shaped body.

[0013] The method is characterized in that two longitudinal edges of a tube blank are arranged with overlapping edges so that one and the same side of the blank forms two abutment surfaces in the region of the overlap and the blank forms a hollow body, that one of said longitudinal edges is placed such that an edge portion thereof extends a distance outwardly from the second edge along the entire length of the blank, that a seal is formed in the region of the overlap, that the overlap and said edge portion are folded down against the ouside of the hollow body formed by the blank, and that the edge portion is sealed against the outside of the body formed by the blank.

[0014] In one embodiment the sealing of the edge portion is accomplished at the same time as the external shape of the hollow body is calibrated to the desired tube cross section.

[0015] In one embodiment the blank is of a heat-sealable material at least in the region of the seals in the overlap and the said edge portion, and the method is characterized in that the sealing region in the overlap is heat-activated in a first station, that the blank is pushed up on a mandral having a cross section and a circumference corresponding to the desired cross section and circumference of the tube-shaped body, that the overlap and the longitudinal edge portion are folded against the outside of the tube body, that the longitudinal edge portion is heat-activated, and that thereafter said edge portion and overlap are flattened against the tube body.

[0016] In a further embodiment the flattening is made against a further mandral provided with a longitudinal recess for accomodating the overlap and the longidudinal edge portion, such that there is obtained a gerenally smooth envelope surface of the tube body after the flattening.

[0017] In one embodiment the heat activation is obtained by high frequency activation of a high frequency weldable material in the sealing regions.

[0018] In one embodiment the longitudinal overlap is obtained by folding a strip-shaped blank into a chute.

[0019] In one embodiment the longitudinal overlap is obtained by folding a sheet type blank into a tube-shaped body.

[0020] The invention also provides a container, comprising a tube-­shaped body obtained by overlapping sealing of the edges of the blank. The container is characterized in that one of said longitudinal edges is placed such that an longitudinal edge portion thereof extends beyond the first edge, and such that the overlapping seal comprises a first longitudinal seal provided by letting the internal side of the body form two abutment surfaces, and a second seal provided between said longitudinal edge portion and the outside of the body.

[0021] The invention will now be exemplified by reference to the accompanying drawings, where

Fig. 1 schematically shows a continous method of manufacturing container bodies according to the present invention,

Fig. 2 is a cross section of a mandral in Fig. 1;

Fig. 3 shows a device for heat-activation of an edge portion before this end and an overlap portion are flattened and sealed,

Fig. 4 shows a device for flattening the longitudinal protruding edge portion and the overlap region, and

Fig. 5 schematically shows a device for continous longitudinal sealing of a tube or a tube-shaped tube body according to the basics of the present invention.

[0022] The reference numeral 10 in Fig. 1 denotes a blank for a container body. The blank in the figure is a laminate comprising metal or other barrier layer, and the laminate is such that, in regions where a seal is to be obtained during the over all process, the material has characteristics allowing use of high frequency welding technique for sealing. Of course, the basic idea is not limited to such a technique; instead there might for instance be used conventional heated jaws or hotair sealing technique, but in the preferred embodiment according to Fig. 1, there is used a high frequency welding unit 11 for softening of the layers of the laminate which are to be joined. The shaping of the blank 10 to a pipe-shaped body, basically of a cross section corresponding to a bellows, is obtained around a mandrel 12 which also may act as a guide for the blank 10 during the process, which may be a continous one or intermittent, for obtaining the intended, longitudinal seal according to the invention.

[0023] A pair of feeding wheels take care of the transport of the blank 10 through the welding station 11.

[0024] The mandrel 12 and the guide-rails 14 thereof position the blank 10 such that the longitudinal edges 15, 16 thereof are oriented as in Fig. 2.

[0025] The guide-rails 14 thus guarantee that a fin 17 is formed, where one and the same side 15 of a blank forms two abutment surfaces 19, 20 in the region of the overlap of the fin 17. This overlap is such that a longitudinal edge portion 21 is formed and has a thickness corresponding to the blank thickness, i.e. "singel layer thickness".

[0026] The mandrel in Fig. 2 is a direct continuation of the mandrel 12 in Fig. 1. Seen in the feeding direction 22 of the blanks in Fig. 1, a flattening rail 23 follows after the feeding rolls 13 and the high frequency welding unit 11, and takes care of the folding down of the fin 17 from the position shown in Fig. 2 to the position in Fig. 3.

[0027] In Fig. 3 there is shown a high frequency welding unit 24, which is thought to be located to the left relative the rail 23 in Fig. 1, i.e. in the feeding direction 1 downstreams the rail. The object of the high frequency welding unit 24 is to soften primarily the layer of the edge portion 21 facing the ouside of the body, but the unit may of course provide a further softening effect in excess to the one already obtained between the layers which form the surfaces 19 and 20.

[0028] In order to stabilize the "weld" just obtained by the unit 24 and just before that by the unit 11, there is a flattening roller 26 arranged downstream the unit 24 and at such a section 12′ of the mandrel or a separate mandrel portion where a recess 25 forms an accomodation space for the overlap portion of the joint and the protruding edge portion 21 of a singel layer material. The character curvature of the roller in the area of the flattening and the depths of the cavity and the shape thereof are such that the external contour of the tube will be generally smooth and integral.

[0029] As mentioned in connection with the preferred embodiments in Figs. 1-4, other welding arrangements and methods may be used, and it is of course also possible to work out from an integral web forming the blank for the container body.

[0030] This is schematically shown in Fig. 5. A roller of web-shaped material 27 is carried on a shaft 28 and guide plates or rails 29 form the web into a "bellows-shaped" cross section as appears from Fig. 1.

[0031] Downstreams The rail 29 there is a first high frequency welding device 30, and thereafter a pair of driving rolls 31 follow, a folding down member 32 for flattening the fin of the hose or pipe against the outside of the pipe, a second welding device 33 for softening of the protruding edge portion of the "single layer thickness". Thereafter there follows a flattening member 34 operating generally in the same manner as the member 26, and finally there is a saw 35 for sawing the pip or hose into suitable lengths.

[0032] Although the described embodiments relate to high frequency weldable material in the welding regions, there are other sealing possibilities and other choices of material. It is also possible to use an adhesive binder, for instance of the hotmelt type.

Claims

1. A method of forming longitudinal seal in a tube-shaped body, characterized in that two longitudinal edges (15, 16) of a tube blank (10) are brought to overlap such that one and the same side (18) of the blank forms two abutment surfaces (19, 20) in the region of the overlap and the blank hereby forms a hollow body, that one of said longitudinal edges is placed such that an edge portion (21) thereof extends a distance out from the other edge along the entire length of the blank, that a seal is formed in the region of the overlap, that the overlap and said edge portion (16) are folded against the external side of the hollow body formed by said blank, and that the edge portion (21) is sealed against the outside of the body formed by said blank.

2. A method as in claim 1, characterized in that the edge portions are sealed at the same time as calibrating the external shape of the hollow body to a desired tube cross section.

3. A method as in claim 2, where the blank is of a heat-­sealable material at least in the regions of the seals in the overlap and said edge portion, characterized in that the seal region in the overlap is heat-activated in a first station (11), that the blank is pushed up onto a mandral (12) having a cross section corresponding to the inner circumference of the tube-shaped body, that the overlap and the longitudinal edge portion are folded down against the external side of the tube body, that the longitudinal edge portion is heat-activated, and that said edge portion and overlap are flattened against the tube body.

4. A method as in claim 3, characterized in that the flattening is carried out against a further mandrel (12′) provided with a longitudinal recess (25) for accomodating the overlap and the longitudinal edge portion, such that there is obtained a generally smooth envelope surface of the tube body when flattening.

5. A method as in claim 4, characterized in that the heat-activation is carried out by high frequency welding of a high frequency weldable material in the sealing regions.

6. A method as in claim 5, characterized in that the longitudinal joint is obtained by folding a web shaped blank into a chute.

7. A method as in claim 5, characterized in that the longitudinal overlap is obtained by folding a sheet type of blank into a tube-shaped body.

8. A container comprising a tube-shaped body obtained by overlapping seaing of the longitudinal edge portions (15, 16) of a blank, characterized in that one (16) of said longitudinal edges is placed such that it extends beyond the first edge (15) with a longitudinal edge portion, and that the overlapping seal comprises a first longitudinal seal obtained in that the inside of the body comprises two abutment surfaces (19, 20) and a second seal obtained between said longitudinal edge portion (21) and the external side of the body.

Drawing