EP2566762B1

EP2566762B1 - Method for folding the end of a packaging container, a plunge used in such method, and a packaging container formed with said method

Info

Publication number: EP2566762B1
Application number: EP11716933.4A
Authority: EP
Inventors: Håkan ZETTERSTRÖM; Henrik Holm
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2010-05-05
Filing date: 2011-05-02
Publication date: 2016-03-02
Anticipated expiration: 2031-05-02
Also published as: BR112012027320B1; BR112012027320B8; ES2571140T3; WO2011138252A1; EP2566762A1; AR081291A1; RU2012152082A; BR112012027320A2; MX2012012593A

Description

TECHNICAL FIELD

The present invention relates to a method for folding the bottom of a packaging container, in particular a packaging container comprising a transversal seal. The present invention also relates to a plunge used in said method, and a packaging container formed with said method.

BACKGROUND

Typical packaging containers for containing pourable product, such as liquid or semi-liquid foodstuff, are made from a packaging laminate comprising a paper core, which core is sandwiched between layers of plastic and optionally a metal foil, such as aluminium foil.
The packaging laminate has a web form before it is formed directly into packaging containers in a continuous fashion, or formed into blanks, which blanks in turn are formed into packaging containers. In the former case the longitudinal edges of the web of packaging material is are sealed to form a tube, and said tube is continuously filled and sealed transversally and severed to form pillow-shaped packages, in well-known manner. The pillow-shaped packages are folded into packaging containers, such as the aseptic Tetra Brik® containers provided by the present applicant. In the latter case the blanks are formed into packaging containers having one end open, which open end is sealed and folded after the product has been filled through it. One example of such a container is the Tetra Top® container, which is a carton bottle. This type of packaging container is formed by a sleeve formed from the blank onto the end of which a plastic top and opening device are attached. The packaging container is then filled through its open bottom end, which is subsequently transversally sealed and folded.
A folding device used for the latter type of packaging container is disclosed in US 2009/0163339A1 . In order to avoid unnecessary details confusing the understanding of the present invention, it is to be understood that the skilled person is aware of the existence and details of the described type of folding systems, since they do exist today.
The present invention may be used to improve the folding of the end of any of the above types of packaging containers, and in principle any container having a transversal seal according to what is to be described later on in this description.

SUMMARY OF THE INVENTION

For the accomplishment of the above objectives the a folding method according to the present invention comprises the steps of;
on a packaging container having a sleeve shape with a first end and a second end, said second end comprising a transversal seal such as to form a fin shape with a fin extending in an upright position, away from said first end:

positioning a central portion of the fin in an upright position,
pressing said central portion in the direction of said first end, this forming a pair of flaps in the lateral ends of the transversal seal,
releasing the positioning of said central portion,
folding the laterals ends of the fin inwards towards said first end and finalizing the folding procedure.

In one or more embodiment the method comprises the steps of arranging second portions of the fin adjacent to the central portion to follow a curved path, which step may be performed simultaneously with the step of positioning the central portion.
In still further embodiments the very same step may involve arranging portions of the fin outside the second portions in a folded position, towards a bottom of the packaging container, prior to the step of folding the lateral ends.
A device configured for folding a transversally sealed end of a packaging container having a sleeve shape with a first end and a second end, said second end comprising the transversal seal such as to form a fin shape with a fin extending in an upright position, away from said first end, the device comprising:

a plunge having a central, rectilinear slot portion configured for positioning a central portion of the fin in the upright position during transfer in the direction of said first end.

In one or several embodiments the rectilinear slot portion, in both ends thereof, extends as a curved slot portion.
In still further embodiments the plunge may comprise sloping guide surfaces extending past a longitudinal centerline of the slot and adapted to guide selected portions of the fin from an upright to a folded position.
Beneficial effects of the present invention, and particular embodiments thereof, will be obvious from the following detailed description of embodiments.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figs. 1-4 are schematical side views illustrating a method according to a first embodiment of the present invention.
Fig. 5 is a cross section of a part of a packaging container shown in Fig. 4.
Fig. 6 is a plan view of an embodiment of a plunge which may be used in the method of the present invention.
Fig. 7 is a perspective view of the plunge of Fig. 6.
Fig. 8 is a schematic partial side view illustrating the plunge of Fig. 6 aligned with a packaging container.

DETAILED DESCRIPTION OF AN EMBODIMENT

As an introduction to the present invention reference is made to Figs. 1-4, illustrating a folding method according to a first embodiment of the present invention. Fig. 5 further illustrates a schematic cross section of a critical area of a folded packaging container.
Before the method of the first embodiment is applied to a packaging container 2, the packaging container 2 a first end 4 of the packaging container 2 has been closed. For the purposes of the present invention the method used for closing of the first end 4 is irrelevant, and examples include sealing and folding, attaching an opening device and a top, etc. After sealing of the first end, the partly formed packaging container 2 has been filled with its content, and this is the state shown in the schematic side view of Fig. 1. It should be noted that even if the method of the present embodiment is performed on a partly sealed, and fully filled packaging container the present invention may also be applied in regard of sealing of a first end of an empty packaging container, before filling the packaging container with its contents and sealing a second end thereof.
Between Fig. 1 and Fig. 2 the packaging container 2 has been subjected to sealing jaws clamping and sealing a second end 6 of the packaging container. Again, there are several alternatives for clamping and sealing a packaging container, such as induction heating, direct heating, use of adhesive, etc, and the present invention should not be limited in this aspect. In the present embodiment induction heating is used. As a result a fin-shape is achieved, as shown in Fig. 2, with the transversal seal 8 being defined by a sealing area.
Fig. 3 then illustrates the key steps of the present invention, where a central portion 10 of the transversal seal 8 has been kept in an upright position, and simultaneously been pressed down. Since the packaging container 2 is fully sealed at this stage it does not have to be positioned in an upright position, so "pressed towards the first end 2" may be a more general expression, and "pressed towards an opposing end" even more so. In Fig. 8 the direction of movement of the plunge is indicated by the double-headed arrow at P. As a result of pressing down the central portion 10, two lateral flaps 12, 14 will emerge on either side of it. As a final step in the forming process the lateral flaps 12, 14 are folded inwards (towards a centreline of the packaging container 2) and downwards (towards the opposing end 4 of the packaging container 2), to give the second end 6 of the packaging container 2 its final form. Before, or rather "when", performing this step the central portion 10 is gradually released, and is laid flat onto the bottom of the packaging container as is shown in Fig. 4 as the flaps 12, 14 are pressed thereon.
In Fig. 4 a portion of interest has been marked at 16. An enlarged sectional view of this portion is illustrated in Fig. 5. This portion of interest usually is a critical region of all packaging containers formed by sealing and folding an end thereof, in particular if using a paper-based packaging material being inelastic. In this region a single fold comprises the two layers 8A and 8B of the transversal seal 8, folded over themselves, and the folded region of material adjacent to the transversal seal, forming a third layer 8C folded over the folded transversal seal. As a starting point these layers have equal length (see Fig. 2), yet it is apparent from Fig. 5 that the innermost layers 8A and 8B have a shorter distance to travel than the outermost layer 8C, so either the innermost layers will wrinkle in a more or less uncontrolled manner or the outermost layer 8C will rupture or crack, damaging or destroying the integrity of the packaging container 2. This problem is well known in the packaging industry, and several approaches have been used to solve it, including using a more resilient laminate sandwiching the paper core, such that even if the inelastic paper core ruptures the layers sandwiching it will maintain the integrity of the packaging container. Other examples include forming creasing lines in the packaging material such that the wrinkling of the innermost layers 8A and B will be predictable.
In evaluation tests packaging containers folded according to the inventive methods has proven significantly better results concerning amount of cracks and ruptures, and an attempt to explain the reason why follows. For the present embodiment the portions 10' and 10" of the transversal seal 8, on both sides of the central portion 10 will include the section where the critical fold of Fig. 5 is formed. In prior art, where the fin is laid flat towards the bottom prior to forming the fold, the fin will eventually start to fold as the flaps 12, 14 are folded. Once a folding location is initiated, stresses will be concentrated to this single location, thus increasing the risk of cracks or ruptures. For the present invention and in the present embodiment, however, each portion 10' and 10" adjacent to the central portion 10 provides a length over which wrinkles will be distributed, such that stress is not concentrated to a single wrinkle. There may very well be more factors responsible for the result of using a method according to the present invention, or an embodiment thereof
Another beneficial effect of the present embodiment, and of the invention as such, is that it enables for the bottom of the container to be folded at its full width, which e.g. results in a smooth(er) bottom of the packaging container, and a well-defined shape of the same. Both these properties are beneficial for the visual appearance of the packaging container, and the stability thereof. "Folded at its full width" may be better understood from studying Fig. 4, where a correct folding of the flaps 12, 14 enables for the edge 17 to fold at a correct location. Furthermore, the present invention facilitates for the edges adjacent to the edge 17 to maintain a rectilinear shape too. The straightforward explanation may be that since the central portion of the transversal seal is kept upright, the forces applied to either side of the transversal seal are kept in equilibrium, and no pushing or pulling force is exerted onto the edges adjacent to the edge 17. These beneficial effects may be further enhanced by increasing the pressure inside the packaging container, which is described below.
In a further embodiment the portions 10' and 10" are given a curved shape as the fin 8 is pressed towards the first end 4 of the packaging container, which further aids in locating the region for a fold. In yet a further or related embodiment the portions of the transversal seal 8 in the region of the flaps 12, 14 are pressed towards a bottom of the packaging container 2 in the step of pressing the central portion 10, in an upright position, towards the first end 4. "Pressed towards a bottom" is meant to define that while the portion 10 is maintained upright, the portions in the region of the flaps 12, 14 are essentially laid flat, or at least forced in that direction.
It should also be recognized that the present embodiment discloses an example of one of the simpler package configurations, where the bottom surface is defined by a rectangle and where two flaps 12, 14 are sufficient. As the shape of the bottom surface is more complex, i.e. by going from rectangular to octagonal, the number of folds and flaps are likely to increase; still, the teachings of the present invention may still be applied.
According to a further embodiment the present invention may comprise the step of applying a pressure onto two opposing lateral sides of the packaging container 2. It has proven to be beneficial for the folding quality to increase the internal pressure of the packaging container.
The present invention also relates to a plunge used for performing the inventive method. A plunge 20 according to a first embodiment of the present invention is illustrated in the plan view of Fig. 6. In shows the plunge 20 from below, i.e. it illustrates the side facing the packaging container. The rectilinear portion of the slot 22 is where the central portion of the fin is located during plunging. For reasons described referring to the inventive method, the slot 22 may have curved end portions 24, 26. Other details may be tailor made to the specific packaging container.
Further details which are present on the plunge 20 of the present embodiment but may be left out on other embodiments are; two guide surfaces 28 sloping away from the side facing the packaging container. The guide surfaces 28 are located at both ends of the slot 22 and extend past a longitudinal centreline of the slot 22. In this way end portions of the transversal seal 8 (the fin) will by folded to one side in a controlled fashion as the plunge 20 moves in the direction of the packaging container. The guide surfaces 28, at their ends remote from the centreline of the slot 22, may have a form such as to locate the upper edge of the transversal seal 8, as is illustrated in Fig. 6. Fig. 7 is a perspective view of the plunge of Fig. 6, giving an improved comprehension of the configuration of the plunge 20. The general design of the plunge 20, not described in further detail here, relates to design being specific for a particular packaging container. Surfaces and edges between surfaces are adapted to fit a crease pattern of a specific packaging container, with the purpose of improving the quality of resulting folds and edges on the packaging container.
The length of the rectilinear portion of the slot 22 corresponds to a width of a side panel of the packaging container 2. This is consequently also true for the length of the central portion 10. For a brick-shaped packaging container the side panel would correspond to the sides of the packaging container which are parallel to the transversal seal and extends from the first end 4 to the second end 6. The plunge of Figs. 6 and 7 are intended for a packaging container having a more elaborate shape, yet the side panel will still follow the definition given above.
Fig. 8 is a side view illustrating a plunge aligned with a packaging container. By comparing with Figs. 6 and 7 the design and alignment of the plunge 20 should be readily understood. The packaging container 2 is shown from one side, in the direction of the transversal seal 8. The packaging container 2 of Fig. 8 is provided with a plastic top portion 5 having an opening device 7 (e.g. a screw cap) arranged thereon. The double-headed arrow P indicates the direction of motion of the plunge 20.

Claims

A method comprising the steps of; on a packaging container (2) having a sleeve shape with a first end (4) and a second end (6), said second end comprising a transversal seal (8) such as to form a fin shape with a fin extending in an upright position, away from said first end (4):
positioning a central portion (10) of the fin in an upright position,

pressing said central portion (10) in the direction of said first end, while said central portion of the transversal seal is simultaneously kept in an upright position, this forming a pair of flaps (12, 14) in the lateral ends of the transversal seal (8),

releasing the positioning of said central portion (10),

folding the laterals ends (12, 14) of the fin inwards and towards said first end (4) and finalizing the folding procedure.
The method of claim 1, further comprising the step of arranging second portions (10', 10") of the fin adjacent to the central portion (10) to follow a curved path, which step may be performed simultaneously with the step of positioning the central portion.
The method of any preceding claim, wherein the step of positioning the central portion (10) in an upright position, involves arranging the outermost portions of the fin towards a bottom of the packaging container, prior to the step of folding the lateral ends (12, 14).
The method of any preceding claim, further comprising the step of applying pressure on the exterior of the packaging container for increasing the pressure inside the packaging container during the whole or part of the folding procedure.
A device for performing the method according to claims 1-4, wherein a plunge (20) is adapted to pressing the central portion (10) towards the first end (4), wherein the plunge(20) has a central, rectilinear slot portion (22) configured for positioning a central portion (10) of the fin in the upright position during transfer in the direction of said first end (10).
The device of claim 5, wherein the rectilinear slot portion (22), in both ends thereof, extends as a curved slot portion (24, 26).
The device of claims 5 or 6, wherein the plunge (20) further comprises sloping guide surfaces (28) extending past a longitudinal centerline of the slot (22), which guide surfaces (28) are configured to guide selected portions of the fin from an upright to a folded position.
The device of any one of claims 5-7, wherein the length of the central, rectilinear portion (22) of the slot corresponds to a width of a lateral side panel of a packaging container for which it is used.
The device of any one of claims 5-8, wherein the device further comprises a clamping device, adapted to exert pressure on the exterior of the packaging container during folding of the same.