HK1116137B - Method and device for making a sealing and use of such method - Google Patents

Description

Method and device for producing a seal and use of the method

Technical Field

The present invention relates to a method and an apparatus for sealing a web of material and to the use of the method.

More specifically, the invention relates to a method for producing a seal in a portion of a material web, wherein the material web comprises a first extension with a first number of material layers and a second extension with a second number of material layers, at least one of the material layers being included in both the first and the second portion, the portion of the material web having a width which intersects a transition from the first to the second portion of the material web, the method comprising mutually joining opposite faces of the material layers of the material web in the portion; and to the use and apparatus of said method.

Background

WO99/41155 discloses an apparatus for manufacturing container blanks (containers) by interconnecting opposite wall portions of a web of material along a joint.

The material web comprises two side wall webs transferred in parallel opposing relationship along a production line and a bottom wall web provided with a double fold between the two side wall webs. The webs are thus joined to form a common material web and the webs are sealed to each other along the connecting portions by means of sealing tools which are joined to the material webs.

The material web may comprise a web folded in the M-shape in the longitudinal direction. A container blank manufactured in such a material web will obtain two side walls from the outer portions of the web and a bottom wall from the double-folded middle portion of the web.

Sealing along the joint may present problems affecting its reliability. In practice it has been found that it is difficult to provide a reliable seal in the transition between an area of the material web comprising two material layers and an area comprising four material layers. If the pressure is insufficient, a duct extending parallel to the transition tends to form, which obviously results in the container blank not being liquid-proof.

On the other hand, if the pressure is dimensioned to prevent the formation of the duct, the pressure must be so high that the bottom wall forming portion of the material web is subjected to tensile and/or bending stresses that may lead to cracking.

Therefore, a sealing method capable of removing the above-described problems is required.

Disclosure of Invention

As mentioned above, it is an object of the present invention to provide a method, a use of the method, and an apparatus, which are able to solve the above problems, wholly or partly.

In order to achieve this object, the invention provides a method according to claim 1, a use of said method according to claim 9 and an apparatus according to claim 10. Various embodiments of the inventive method are evident from the dependent claims 2-8 and various embodiments of the inventive device are evident from the dependent claims 11-14.

Thus, according to the invention, a method is provided for producing a seal in a portion of a material web of plastic material, which material web comprises a first extension with a first number of material layers and a second extension with a second number of material layers. Wherein one of said layers of material is included in both said first and second portions and said portion of the web of material has a width which intersects a transition from the first to the second portion of the web of material. The method comprises mutually joining opposite faces of the material layer of the material web in said portion.

The method is characterized by forming the projections and recesses by movement of material in the portion and orienting the projections and recesses to have a width across the transition.

A method is thus provided which allows a reliable seal to be provided in a portion of the material web in which the material web has a transition from a first number of material layers to a second number of material layers.

In particular, a reliable seal is provided by forming the protrusion and recess which penetrate the transition and thereby prevent the formation of a through duct extending parallel to the transition from the first side to the second side of the seal.

These protrusions and recesses can be provided even with relatively moderate pressure, which means that a reliable seal can be formed while subjecting the material web to appropriate treatment. The protrusions are formed by material that is removed from the recesses and filled into the protrusions.

The protrusions and recesses also provide the advantage that the precision in the subsequent optional punching or cutting operation along the portion of the material web does not have to be as high as required by the prior art.

The method of the invention can be applied in the packaging industry and comprises the step of making said seal constitute a part of a coupling portion of a container blank. The method further comprises the step of feeding the material layer of the material web by: i.e. in the form of two opposite and parallel side wall webs from which the container blank obtains two opposite side walls and a bottom wall web provided between the two side wall webs folded into a double-wall shape, from which the bottom wall web obtains a double-folded bottom wall.

It will be appreciated that it is of utmost importance in the packaging industry to be able to produce liquid-proof container blanks, in particular container blanks without through-going ducts extending parallel to a transition of the above-mentioned type from the compartment to the outside of the container blank, which through-going ducts are however not subjected to undue handling during the manufacturing process, which would lead to marking or cracking of the walls of the container blank.

The method of the invention may comprise the step of forming said projections and recesses in connection with providing said seal. The present method thus means that said protrusions and recesses can be formed in said portion of the material web with time and cost efficiency. The method also has the advantage that the accuracy of the pressure does not have to be as high as required by the prior art, which results in less defective products and easier machine set-up.

In the method according to the invention, the material web may be in the form of a plastic material.

In the method of the present invention, each of the projections may have a triangular cross section or a cup-shaped cross section.

According to the method of the invention, the opposite faces of the material layer of the material web may be joined to each other in said portion by means of a heat sealing process. In the heat sealing process, particularly in the form of a web of plastic material, a reliable seal can be obtained with time, cost and throughput efficiency.

According to the invention there is also provided the use of the above method in the production of a container blank having two opposing side walls and a double folded bottom wall. The walls are interconnected along an upper link along which the side walls are interconnected and a first and a second lower link along which the bottom wall is linked to the respective side walls, the first and second lower links becoming upper links in first and second transitions, respectively.

Since the method of the invention is used for producing container blanks, the above-mentioned advantages are achieved, so that container blanks with a reliable seal in the above-mentioned transition can be provided.

Finally, according to the invention, an apparatus for sealing a portion of a web of plastic material is provided. The portion has a width that extends through the transition of the material web, and on a first side of the transition the material web has a first number of layers of material and on a second side of the transition the material web has a second number of layers of material. The apparatus comprises a sealing tool having an area engageable with the portion of the material web to join opposite faces of the layer of material of the material web.

The device is characterized in that the region of the sealing tool has at least one groove arranged to provide by the movement of material a width across the convex part of the transition portion when the region is engaged with the portion.

The device of the invention allows providing a reliable seal in said portion of the material web, more specifically by means of an area of the sealing tool, wherein said area acts to redistribute material in the material web by material allowed to fill said groove when said area is engaged with the material web. A bulge will thus be formed in the material web, which bulge prevents the occurrence of through-channels extending parallel to the transition. Moreover, a reliable seal can be provided even when a relatively moderate pressure is applied, which ensures that the material web is properly treated.

In the device of the invention, the recess may have a triangular or cup-shaped cross-section.

The region of the device according to the invention also has at least one further groove, adjacent grooves being separated by an intermediate portion having a flat abutment surface. This may provide a plurality of adjacent projections to further improve the reliability of the seal.

The apparatus of the invention may also be arranged to produce container blanks from a plastic material comprising a binder of a polyolefin material and a filler of a mineral material.

For exemplary purposes, various embodiments of the present invention will now be described with reference to the drawings.

Drawings

Fig. 1 is a perspective view of a material web comprising two side wall webs and a double-folded bottom wall web arranged between the two side wall webs.

Fig. 2 is a perspective view of a seal in a portion of a material web according to fig. 1, wherein the seal is performed according to the prior art.

Fig. 3 and 4 are a perspective view and a cross-sectional view, respectively, illustrating a method of making a seal in a portion of the web of material shown in fig. 1, in accordance with the present invention.

Fig. 5 is a perspective view of a web of material in a portion of which a seal is made according to the method illustrated in fig. 3 and 4.

Fig. 6 is a cross-sectional view of an alternative embodiment of the sealing tool of the present invention.

Fig. 7 is a top view of another embodiment of a sealing tool according to the present invention.

Fig. 8 is a top view of a container blank.

Detailed Description

With reference to figure 1, figure 1 shows a material web 1 comprising a first extension 2 and a second extension 3, wherein the first extension 2 has four layers of material and the second extension 3 has two layers of material, two of the layers of material being included in both the first portion 2 and the second portion 3. In the embodiment shown in fig. 1, the material layer comprises two opposite and parallel side wall webs 20 and a bottom wall web 21 arranged between the two side wall webs and folded into a double-walled shape, the material web 1 having a transition 5 in the transverse direction, wherein the transition 5 extends from a first extension 2 comprising the two side wall webs 20 and the bottom wall web 21 to a second extension comprising only the side wall webs 20.

In the embodiment shown, the number of layers of material changes from two to four in the transition 5.

In conventional production, for example in the production of container blanks from a material web 1 of the type shown in fig. 1, difficulties arise in reliably sealing 9 in the portion 7 of the width across the transition 5.

Referring now to fig. 2, the difficulties are illustrated in fig. 2. The difficulty is manifested in the formation of a through duct 8 extending parallel to the transition 5, transversely to the seal 9. Obviously, this duct 8 will render the blank unusable in its production.

The reason why the through duct 8 is formed is that: in the portion 7 extending through said transition 5, the sealing tool (not shown) encounters the material web 1 with a non-uniform thickness when acting on the material web 1. As mentioned above, the formation of the duct 8 can be avoided by applying a sufficiently high pressure, which however leads to other problems in case the material web 1 is subjected to tensile and/or bending stresses which may lead to cracking.

Referring now to fig. 3 and 4, fig. 3 and 4 show a sealing tool 10 of an apparatus (not shown) for making a seal 9 in a portion 7 of a material web 1.

The apparatus may be comprised in a sealing station of a machine for producing container blanks, for example.

The sealing tool comprises a body 11 having a lower joint face 12. A plurality of parallel grooves 13 are formed in the engagement surface 12, the grooves 13 being triangular in cross-section. The cross-section of the recess 13 may also be cup-shaped, for example, as shown in fig. 6. The recesses 13 are arranged such that the engagement surface 12 has a substantially flat intermediate surface 14 between the recesses 13.

In the illustrated embodiment, the sealing tool 10 further comprises a sealing device, indicated by a, in the form of a heating device. It will be appreciated, however, that the sealing means may also be in the form of a device for induction sealing, an ultrasonic device, or the like.

It should be noted, however, that the heating means, the means for induction sealing or the ultrasonic means may be provided elsewhere in the apparatus of the invention, for example in a seat 26 below the sealing tool 10, as shown in fig. 4 and 6.

The sealing tool 10 is movably arranged in the apparatus to be moved towards the abutment 26 so that the engagement surface 12 is moved into engagement with the material web 1 arranged between the sealing tool 10 and the abutment 26 and out of engagement with the material web 1.

With reference to fig. 3 and 4, a method for producing a seal 9 in a portion 7 of a material web 1 is schematically illustrated in fig. 3 and 4.

A material web 1 of the type described above with reference to fig. 1 is arranged between the sealing tool 10 and the abutment 26 in the following manner: i.e. the sealing tool 10 is placed directly above the portion 7 of the material web 1, which portion 7 has a width which intersects the transition 5 of the material web 1 from the first portion 2 to the second portion 3. The sealing tool 10 is oriented such that its groove 13 has a certain width through said transition 5.

Subsequently, the sealing tool 10 is moved towards the material web 1 and the underlying abutment 26 so that the engagement surface 12 of the tool 10 is moved into engagement with the material web 1, as is particularly evident from fig. 4.

Under the influence of pressure, the engagement surface 12 of the sealing tool 10 acts on the portion 7 of the material web 1, and the material located in said portion 7 will melt to the necessary extent by means of the heat generated by said heating means, whereby the opposite surfaces of the material layers of the material web 1 can be joined to each other. Each material layer may include a laminate having a melt layer provided on a face forming the inside, the melt layer having a melting point lower than that of other layers included in the laminate. In this way, it is ensured that only the surfaces that need to be joined can be joined to one another in a true manner.

In the sealing process the intermediate surface 14 of the joint surface 12 will serve to move the melted material into the space defined by said groove 13, whereby a protrusion 15 is formed in said portion 7 and an intermediate recess 16 is formed by the intermediate surface 14 of the joint surface 12.

These protrusions 15 and recesses 16 have the same width as the grooves 13 and the intermediate surface 14 of the tool 10 and thus have a width across said transition 5 of the material web 1 from the first 2 to the second 3 portion. As is more clearly shown in fig. 5, the seal 9 shown therein is included in a joining section along which the side wall webs 20 and the bottom wall web 21 of the material web 1 are joined to one another.

Said projections 15 and recesses 16, which extend transversely to the transition 5 and are formed uniformly under moderate pressure, prevent the through duct 8 from appearing in the seal 9, as shown in fig. 2. This is due to the fact that the protrusions 15 and recesses 16 either cut off and thereby block the possible ducts 8, or prevent such ducts altogether.

Thus, an arrangement is provided which makes it possible to manufacture a seal 9 without a through duct 8 extending parallel to the transition 5, and at the same time the material layers of the material web 1 are subjected to a suitable treatment. The device also has the advantage that the precision in the subsequent punching or cutting operation and the pressure precision in the sealing do not have to be as high as in the prior art.

It should be understood that the invention is not limited to the illustrated embodiments.

For example, the joining face 12 of the sealing tool 10 can be included as the region 25 in the profile 17 of the tool 18 shown in fig. 7 and also in the apparatus for producing a container blank as shown in fig. 8.

In the shown embodiment, the tool 18 of the apparatus is arranged to produce the container blank 6 shown in fig. 8 from an elongated material web 1 shown in fig. 1, which material web 1 comprises a material layer formed by two opposite and parallel side wall webs 20 and a bottom wall web 21 arranged between the two side wall webs and folded into a double-walled shape, which material web 1 has a transition 5 in the transverse direction from a first layer structure comprising the two side wall webs 20 and the bottom wall web 21 to a second layer structure comprising only the side wall webs 20.

The container blank 6 made from the material web 1 may have two opposite side walls 22 and a double-folded bottom wall 23, the container blank 6 having its side walls 22 from the respective side wall webs 20 and its bottom wall 23 from the bottom wall web 21. The side walls and bottom wall are joined to each other along joint 24.

To produce the container blank 6, the profile 17 of the tool 18 is applied to the material web 1 to join the opposite faces of the side wall webs 20 and the bottom wall web 21 of the material web 1 along said joining portion 24.

In the portion 7 of the joining section 24, the areas 25 of said profile 17 for producing the seal 9 form the joining surfaces 12 described above with reference to the sealing tool 10 shown in fig. 3, the portion 7 of the joining section 24 having a width which penetrates a transition 7 of said type in the material web 1.

It is thus possible to produce container blanks 6 with positive links 24 in portions 7, said portions 7 having a width extending through a transition 5 of the type described. In particular, a projection 15 and a recess 16 are also formed in said portion 7, wherein said projection 15 and recess 16 prevent the presence of the through duct 8 which would otherwise form a compartment of the container blank communicating with the outside.

It should also be understood that the invention is not limited to the embodiments shown.

It will thus be appreciated that the apparatus of the invention may also be designed so that the profile of its sealing tool does not have a region of recesses, whereas a region with recesses is formed in the support, on which the sealing tool can be applied, with the web of material arranged between the sealing tool and the support.

It is also possible to design the abutment corresponding to the sealing tool as shown in fig. 3, 4 and 6, so that the two profiles with the type of zone as described above come together with the material web arranged between them.

The sealing tool of the apparatus of the invention may be arranged to engage the material web while moving simultaneously therewith to allow continuous production of container blanks. It is also contemplated that the sealing tool may be arranged in stationary engagement with the material web for producing container blanks in a batch operation.

Accordingly, many modifications and variations are possible and the scope of the invention is therefore intended to be limited only by the appended claims.

Claims (15)

1. A method of producing a seal (9) in a portion (7) of a material web (1) of plastic material,

the material web (1) comprising a first extension (2) with a first number of material layers (20, 21) and a second extension (3) with a second number of material layers (20), at least one material layer (20) of the first number of material layers (20, 21) and the second number of material layers (20) being comprised in both the first extension (2) and the second extension (3),

the portion (7) has a width that runs through a transition (5) from the first extension (2) to the second extension (3) of the material web (1),

the method comprising mutually joining opposite faces of the first number of material layers (20, 21) and the second number of material layers (20) of the material web (1) in the portion (7),

the method is characterized in that:

-arranging the portion of the material web (1) between a seat (26) and a sealing tool (10), whereby at least one of the seat or the sealing tool comprises a recess (13),

bringing together the seat (26) and the sealing tool (10) so as to form a protrusion (15) and a recess (16) by moving the material in the portion (7) into the groove (13), and

the protrusions (15) and recesses (16) are oriented to have a width across the transition (5).

2. A method according to claim 1, wherein the protrusions (15) and the recesses (16) are integrally formed, while opposite faces of the first number of material layers (20, 21) and the second number of material layers (20) of a material web (1) are joined to each other in the portion (7).

3. The method according to claim 1 or 2, wherein the web of material (1) is supplied in the form of a plastic material.

4. The method according to claim 1, wherein the cross-section of each of the projections (15) is set to be triangular.

5. A method as claimed in claim 1, wherein the cross-section of each projection (15) is given a cup shape.

6. A method as claimed in claim 1, further comprising the step of making said seal (9) form part of a join (24) of the container blank (6).

7. The method according to claim 6, further comprising the step of providing the first number of layers (20, 21) and the second number of layers (20) of material of the material web (1) in the form of two opposite and parallel side wall webs (20) and a bottom wall web (21) arranged between the two side wall webs folded in a double-walled shape,

the container blank (6) obtains two opposite side walls (22) from the side wall web (20) and a double-folded bottom wall (23) from the bottom wall web.

8. The method according to claim 1, wherein the opposite faces of the first number of material layers (20, 21) and the second number of material layers (20) of a material web (1) are joined to each other in the portion (7) by a heat sealing process.

9. A method as claimed in claim 1, for producing a container blank (6), the container blank (6) having: two opposite side walls (22) and a double folded bottom wall (23), the side walls (22) and the bottom wall (23) of which are interconnected along an upper join (24) and a first and a second lower join (24), wherein the side walls (22) are interconnected along the upper join (24), the bottom wall (23) is joined to the respective side wall (22) along the first and second lower join (24), the first and second lower joins (24) becoming the upper join (24) in the first and second transition (7) respectively.

10. An apparatus for sealing a portion (7) of a web (1) of plastic material,

the portion (7) has a width of a transition (5) through the material web (1),

the material web (1) has a first number of material layers (20, 21) on a first side of the transition (5) and a second number of material layers (20) on a second side of the transition (5),

the apparatus comprising a sealing tool (10) having an area (25) and a seat (26) engaging with the portion (7) of the material web to join opposite faces of the first number of material layers (20, 21) and the second number of material layers (20) of the material web (1),

the method is characterized in that:

at least one of the region (25) or the seat (26) of the sealing tool (10) has at least one recess (13), the at least one recess (13) being arranged to provide a protrusion (25) having a width extending through the transition (5) by moving material into the recess (13) when engaging the region (25) and the seat (26) with the portion (7).

11. A device as claimed in claim 10, wherein the cross-section of the groove (13) is triangular.

12. A device as claimed in claim 10, wherein the cross-section of the recess (13) is cup-shaped.

13. A device according to any one of claims 10 to 12, wherein said area (25) or said seat (26) has at least one further recess (13), adjacent recesses (13) being spaced apart by an intermediate face (14) having a flat abutment face.

14. The apparatus according to claim 10, wherein the apparatus is arranged to produce the container blank (6) from a plastic material comprising a binder of a polyolefin material and a filler of a mineral material.

15. The apparatus according to claim 10, wherein the sealing tool (10) is adapted to the support (26), the web (1) being arranged between the sealing tool (10) and the support (26).