WO2011075054A1

WO2011075054A1 - Package forming device

Info

Publication number: WO2011075054A1
Application number: PCT/SE2010/051382
Authority: WO
Inventors: Fredric Ericsson; Anders Magnusson
Original assignee: Tetra Laval Holdings & Finance S.A.
Priority date: 2009-12-18
Filing date: 2010-12-15
Publication date: 2011-06-23
Also published as: CN102656092B; CN102656092A; CN102101549A

Abstract

Wrinkles in one end of a packaging container are avoided by using a package forming device for forming packaging containers from a tube (128) of packaging material travelling in a machine direction (MD) by sequentially clamping the tube (128) between pairs of opposing sealing jaws (106, 106') for forming transversal seals, such that a tube segment on a downstream side of a general pair of sealing jaws will belong to a first packaging container and a tube segment on the upstream side of said general pair of sealing jaws will belong to a second packaging container, said device comprising: a leading pair of sealing jaws (106), a leading volume box (108) arranged upstream each leading sealing jaw (106), adapted to shape a leading tube segment (P) during sealing, wherein support means (106') are arranged to support an upstream end of the leading tube segment (P), upstream the upstream end of the leading volume box (P), such as to avoid wrinkles in the upstream end of the leading tube segment (P), and thereby in one end of a leading packaging container (P). To that end the support means are arranged to engage the tube segment before the leading volume box has reached its end position.

Description

PACKAGE FORMING DEVICE Technical Field

The present invention relates to a package forming device, and in particular to a package forming device forming packages from a tube of packaging material.

Background

When forming packaging containers made of packaging material such as laminate, there are at least two general techniques to follow. According to one technique each package is formed from an individual blank severed from a web of packaging material, which is formed into an individual packaging container, which in turn is filled with product. According to a second technique the web of material is longitudinally sealed to form a tube, and during sealing the tube is filled with product and then transversally sealed and severed to form individual containers. The present invention relates to the second technique. The skilled person realizes that the above description merely represents a rough classification and not an exhaustive list. To elucidate the relevant area further there are numerous different types of prior art apparatuses and arrangements for sealing packages once they have been filled with food and/or beverage products in filling machines. The packages are often manufactured from a tube of packaging material which is conveyed through a filling machine. The packaging material may consist of one or more layers of material depending upon the type of product which is to be filled in the packages. Certain packages are manufactured, for example, from a layer of plastic which is sealable by means of melting heat, occasionally a plurality of plastic layers, while other packages consist, for example, of a plurality of different material layers, such as a fibrous material, e.g. paper, which is coated on both sides with layers of meltable or fusible plastic, for example

polyethylene, and may also include an additional material layer, for example of aluminium, which functions, as a barrier in aseptic packages.

The tube is conveyed in a per se known manner through the filling machine at the same time as it is filled with the product, sealed and given its final configuration. The individual packages are sealed in that two sealing jaws which are displaced towards one another grip and compress the tube in transverse zones uniformly distributed along the length of the tube. The jaws generally consist of a counter jaw and a jaw for generating heat, for example a so-called ultrasound horn which generates the heat by means of ultrasound. The heat may also be generated in other ways, for example by means of constant heat or induction heating, for sealing of each respective compressed tube segment by melting associated plastic material and thereafter severing each respective tube segment so that individual packaging containers are obtained. Thereafter each packaging container is folded into the desired shape, which often is assisted by prearranged creasing lines in the packaging material.

A sealing assembly in the context of the present invention comprises pairs of counteracting sealing jaws, as mentioned above. The jaws may be arranged on a continuous belt drive or on a linear actuator mechanism, which is disclosed in e.g. EP 0 887 273 and EP 1 325 868, respectively.

In some instances the sealed and folded packaging container exhibits unacceptable production errors resulting from an imperfect sealing and/or forming. These errors, such as dents, may be an aesthetic problem only, yet it may also result in defective seals.

Summary

The present invention aims at providing a novel sealing assembly for a package forming machine eliminating or alleviating the above mentioned problem, by means of a well-defined sealing jaw interaction. This aim is achieved by a filling assembly according to claim 1 given the characterizing features thereof. Specific embodiments are defined in the dependent claims. To this end the present invention provides a package forming device for forming packaging containers from a tube of packaging material travelling in a machine direction (MD) by sequentially clamping the tube between pairs of opposing sealing jaws for forming transversal seals, such that a tube segment on a downstream side of a general pair of sealing jaws will belong to a first packaging container and a tube segment on the upstream side of said general pair of sealing jaws will belong to a second packaging container, said device comprising:

a leading pair of sealing jaws,

a leading volume box arranged upstream the leading sealing jaws, adapted to shape a leading tube segment during sealing,

wherein support means are arranged to support an upstream end of the leading tube segment, upstream the upstream end of the leading volume box, such as to avoid wrinkles in the upstream end of the leading tube segment, and thereby in one end of a leading packaging container. The idea of using a support upstream the leading volume box shows surprising results. One explanation of these results may be that the tube is prevented from

"collapsing" after leaving the support of the leading volume box, and that a "collapse" would lead to wrinkle initiations in the material. It may also be that the support reduces tensile loads in the tube of packaging material, and that this is a factor that reduces the wrinkling tendencies.

In one or more embodiments the support is effected by a trailing sealing jaw. This has the benefit of reducing the number of components in the sealing assembly. By choosing a suitable path for the trailing sealing jaw it may effectively be used for the inventive purpose. It should be noted that this will require careful considerations, since every action on the tube of packaging material from the sealing jaw and the volume box will inevitably affect the tube and in particular the product contained therein, at the risk of causing pressure gradients, foaming and splashing. This may adversely affect the filling, sealing and forming process.

Brief Description of the Drawings

Fig. 1 is a schematic partial view of a filling machine in which the inventive sealing assembly may be arranged.

Fig. 2 is a schematic view of a sealing assembly according to one embodiment of the present invention.

Fig. 3 is a schematic view of the sealing assembly of Fig. 2, a few moments before the point in time for Fig. 2.

Fig. 4 is a perspective view illustrating a packaging container manufactured with a filling machine using the inventive sealing assembly.

Detailed Description of Embodiments

Fig. 1 illustrates a part 10 of a machine for manufacturing packages from a web 12 of packaging material. The packaging material is of the initially described type, i.e. a paper core layer coated with a thermoplastic material. When passing through this particular part of the machine, a sealed tube is formed from the initially essentially plain web 12. The forming of the tube is effected by means of a number of tube-forming means 14, 16 and a device 18 comprised in the machine 10. The main task of the tube forming means 14, 16 is to initiate shaping (step A) of the web 12 into a tube 20 with an overlapping joint 22 between two mutually opposing edge sections 24 and 26 of the web, and these means are not described in detail herein. The device 18 is arranged to control a twist of the tube in relation to a sealing apparatus 28 for transverse sealing of the tube. The device 18 is further arranged to finish the shaping of the web by giving the tube 28 a desired diameter before longitudinally sealing the overlapping joint 22.

Further downstream the tube 28, now filled with product, is sealed with horizontal sealing jaws, clamping and sealing the tube 28. First a lower jaw clamps and seals a lower end of the packaging container (to be) and then an upper jaw clamps and seals an upper end of the container. The production process, and inevitably also the sealing process, is performed at a high rate; in the order of 10 000 packaging containers or more may be produced per hour. A problem that may occur is that as the lower jaw clamps the lower end of the packaging container it causes the product to splash upwards in the tube 28, which in turn may cause a faulty amount of product in the package if the upper jaws clamps the tube 28 with an inappropriate timing. This problem and a suggested solution is disclosed in EP 0 882 651. Further, the jaws may be arranged on a continuous belt drive or on a linear actuator mechanism. Such arrangements of jaws are commonly used, and are e.g. disclosed in e.g. EP 0 887 273 and EP 1 325 868.

Fig. 2 is a schematic view of a sealing assembly 100 according to a first embodiment of the invention, as applied to a continuous belt drive. The tube 102 of packaging material has been filled with its content and is sealed using the sealing assembly 100. The sealing assembly comprises a number of essentially identical sealing aggregates 104 arranged on the continuous belt (not shown). Each aggregate comprises a sealing jaw 106 and a "volume box" 108 pivotally connected to the sealing jaw 106. Two opposing sealing jaws 106 are used to clamp the tube 102 of packaging material, and one of the opposing sealing jaws may comprise an inductor, with which it is possible to weld the material of the tube 102 of packaging material such that a seal is effected in a known manner. A skilled person knows that there are several alternatives to induction heating for the purpose of sealing one end of the packaging container in the making, yet use of induction heating has proven particularly well suited for the present application in terms of speed and reliability.

The purpose of the volume box 108 is to confine the expansion of the filled tube 102, and thereby shape the tube such that a preset volume of fluid is contained in the finalized packaging container. The packaging material is generally non-resilient, being a paper laminate, yet the configuration of the filled tube 102 will always strive towards a minimization of potential energy, and depending on the rigidity of the tube 102, any unsupported portions may loose their shape in an unwanted way. It should be noted that the volume box does not have to be pivotably connected to the sealing jaw, yet in the present embodiment the arrangement provides a convenient solution.

From the above and from Fig. 2 and 3 in particular it is evident that the volume box 108 has an end position in which it confines the tube to its ultimate shape. This is illustrated by the lower sealing jaw/volume box aggregate of Fig. 2. The volume box 108' also has a disengaged position (or rather several positions) in which it does not engage the tube 128 at all, as illustrated by the upper sealing jaw/volume box aggregate of Fig. 2, or the upper aggregate of Fig. 3. Obviously the volume box has several intermediate positions on its way from a disengaged position to the end position.

The sealing jaw 106 is drawn by the belt along two pairs of cam tracks having an overall oblong shape. A first pair of cam tracks (not shown) guides leading cam followers 110, such as wheels, of the sealing jaw 106 and a second pair of cam tracks (not shown) guides trailing cam followers 112 of the sealing jaw 106. In this way the position and inclination of the sealing jaw 106 may be well defined at all times.

The volume box 108 is at its leading end guided by its pivotal connection to the sealing jaw 106 and at its trailing end it is supported by a pair of cam followers 114, which are guided by a third pair of cam tracks (not shown). In this way the position and the inclination of the volume box 108 may be well defined at all times. Also, the inclination of the volume box 108 may be controlled independently from the inclination of the sealing jaw 106. The skilled person realizes that there are constructional limitations for positioning and inclination of the individual components. These limitations are a result of the actuation mechanism, may it be a belt driven cam construction, a mechanical solution or a hydraulic/pneumatic construction, or a combination thereof. These limitations, however, are of no consequence for the present inventions ability to achieve its objectives.

The skilled person is aware of that there may be restrictions in regard of the relative movement with the inductor of the sealing jaw 106 and the tube 102 of packaging material. These restrictions may involve that there should be no relative movement after contact has been made between the sealing jaw 106 and the tube 102, which would increase the risk of dented, wrinkled or in other ways malformed packages. The prevention of relative movement is consequently an operational parameter to consider carefully in the design of the system.

In the sealing assembly of this first embodiment of the present invention the trailing sealing jaw is positioned in such a way relative to the leading volume box, that the tube of packaging material is prevented from "collapsing" in an unsupported manner. It must be emphasized that this "collapse" may not be particularly pronounced, yet it has, for some materials, proven to be significant enough to affect the packaging material in such a way that dents may be formed as the tube is sealed and folded. By defining an angle a as the offset angle relative to the central axis of the tube of packaging material, this may be expressed as the trailing sealing jaw is positioned in such a way relative to the leading volume box such that a for the tube as it extends between the leading volume box and the trailing sealing jaw may be controlled.

This is visualized in the schematic drawing of Fig. 3, which illustrates an earlier moment in the approach of the leading and trailing sealing aggregates. Here it is shown how the path of the leading volume box is configured to tilt the volume box away from the tube before the same is supported by the trailing sealing jaw, such as to restrict the angle a. In other words the trailing sealing jaw 106' engages the tube 128 before the leading volume box has reached its end position.

It may also be mentioned that the words "leading" and "trailing" are used as relative terms, the container described as the "trailing" container will be the "leading" container in the next indexing step, and the "trailing" pair of sealing jaws will become the "leading" pair of sealing jaws.

In this context it should also be noted that the support of the tube is performed on the downstream end of a trailing packaging container P' for avoiding dents on a leading container P. Note that the designation P is used for the packaging container as well as for the tube segment used to form the packaging container, and the same is valid for P'. It may also be mentioned that the packaging container in question may be a wedge shaped container, see Fig. 4, having a rectangular base when it has been folded, wherein the dents in question are formed near the rectilinear seal of the wedge shaped end (the upper end in the drawings). For this reason the volume boxes may in one or several embodiments be arranged to render the packaging container a wedged shape, such that one end of the container (e.g. the trailing end) is forced closer to a centreline of the tube than the opposing end (e.g. the leading end), see the shadowed area, corresponding to the schematically illustrated cross sections of previous drawings. In one or more embodiments the volume box may force the container to slope

continuously from the first end to the opposing end. It should be noted that this refers to a view as the one showed in Fig. 2. It is evident from Fig. 4 that the relationship will be somewhat the opposite if viewing a cross section at a right angle relative to the one of Fig. 2 (at right angles to the shadowed area) in the YZ-plane. According to another aspect of the inventive idea may be said to reside in correlating the movement of the leading volume box 108 and the support upstream thereof, and in one embodiment the leading volume box 108 and the trailing sealing jaw 106'. This correlation enables prevention of a "collapse" of the tube, and thus supposedly the appearance of wrinkles found in prior art systems.

Also, for each specific case with its individual properties regarding tube dimensions, quality of packaging material, shape of packaging container, etc, it would be relevant to discuss a quantitative value for a, yet the invention should not be construed as limited to these specific values. If the skilled person would be given the input of the idea supporting the tube of a trailing container in order to prevent defects on a leading container, as defined and described in the present invention the invention as defined in the claims would be clear and readily enabled.

Claims

1. A package forming device for forming packaging containers from a tube (128) of packaging material travelling in a machine direction (MD) by sequentially clamping the tube (128) between pairs of opposing sealing jaws (106, 106') for forming transversal seals, such that a tube segment on a downstream side of a general pair of sealing jaws will belong to a first packaging container and a tube segment on the upstream side of said general pair of sealing jaws will belong to a second packaging container, said device comprising:

a leading pair of sealing jaws (106),

a leading volume box (108) arranged upstream each leading sealing jaw (106), adapted to shape a leading tube segment (P) during sealing,

wherein support means (106') are arranged to support an upstream end of the leading tube segment (P), upstream the upstream end of the leading volume box (108), such as to avoid wrinkles in the upstream end of the leading tube segment (P), and thereby in one end of a leading packaging container (P), characterized in that the support means (106') are arranged to contact the tube (P) with the leading volume box (108) in a tilted position, i.e. before the leading volume box (108) has reached an end position.

2. The package forming device of claim 1, wherein said support of the leading tube segment (P), is effected on sides facing towards the sealing jaws (106, 106'), such as to prevent the sides of the tube (128) from tilting outwards.

3. The package forming device of claim 1 or 2, further comprising a pair of trailing sealing jaws (106'), wherein the pair of trailing sealing jaws (106') are used for said support of the leading tube segment (P).

4. The package forming device of claim 3, wherein said support is effected to reduce the angle of the tube (128) extending between the upstream end of the leading volume box (108) and the trailing sealing jaw (106') as compared to an unsupported position.

5. The package forming device of any preceding claim, said device being adapted to form packaging containers having a rectangular base end and a linear top end, wherein the wrinkles avoided relates to wrinkles in the vicinity of the linear top end.