WO2001094234A1

WO2001094234A1 - Thin-walled container and method for production thereof

Info

Publication number: WO2001094234A1
Application number: PCT/EP2001/003696
Authority: WO
Inventors: Hartmut Möglich
Original assignee: Herrmann Ultraschalltechnik Gmbh & Co. Kg
Priority date: 2000-06-05
Filing date: 2001-03-31
Publication date: 2001-12-13
Also published as: DE10027735C1

Abstract

A thin-walled container is produced from a flexible base material (16), covered with a flexible layer (18) which may be welded by ultrasound. Said container comprises a first wall section (20) and a second wall section (22) which is arranged parallel and close to the first wall section (20) with a longitudinal edge (32). Furthermore a third wall section (24) is provided, which is arranged parallel to and at least partly lies close to the first wall section (20), has a longitudinal edge (30) and at least partly overlaps the longitudinal edge (32) of the second wall section (22) in the region of the longitudinal edge (30) thereof. The second wall section (22) and the third wall section (24) are welded to the first wall section (20) along a weld line (36) running overall transverse to the longitudinal edges (30, 32). The weld line (36) is offset into a plane (38) lying in the container wall in the region of the overlap (34) in the container.

Description

Title: Thin-walled container and method and device for its production

description

The present invention relates to a thin-walled container made of a flexible base material, which is coated with an ultrasonically weldable flexible layer, the container having a first wall section, a second wall section which is arranged parallel and close to the first wall section and has a longitudinal edge, and comprises a third wall section which is arranged parallel and at least in sections closely fitting to the first wall section, has a longitudinal edge and overlaps the longitudinal edge of the second wall section in the region of its longitudinal edge, the second and third wall sections being along a welding line which runs essentially transversely to the longitudinal edges are welded to the first wall section.

Such a container is known for example as a folding container for milk from the market. A flexible cardboard or a film is used as the base material, the cardboard being covered on both sides with a thin plastic layer. The known container is made from a one-piece sheet, which is first brought into a square and tube-like shape. The folding is carried out so that the two longitudinal edges of the sheet overlap and can be glued or welded together. In order to be able to close at least one end of the container in a liquid-tight manner, it is flattened at this end. In the area of the overlap of the longitudinal edges, three layers of the container wall are parallel and at the flattened end close together, whereas outside the overlap in the flattened area two layers of the container wall are arranged parallel to each other and close together. The layers of the container wall are then ultrasonically welded to one another in the flattened section transversely to their longitudinal edges along a welding line, so that this end of the container is closed in a liquid-tight manner.

In the case of the known container, however, it has been found that it often breaks open in the course of its "life" in the area of the originally liquid-tight weld, that is to say it leaks. This is particularly the case when a bend or bend is carried out along a bending line in the area of welding during further processing and later use.

The object of the present invention is therefore to develop a thin-walled container of the type mentioned at the outset in such a way that its tightness is ensured for production and over the average life to be expected.

This object is achieved in that the weld line in the area of the overlap is offset in a plane lying in the container wall.

According to the invention it was recognized that the leak points are often in the area of the overlap. One of the reasons for this is that the ultrasonically weldable flexible layer, with which the base material is coated, becomes hard during welding and a relatively brittle accumulation of material arises. This creates a zone with less flexibility in the area of the overlap. If there are mechanical loads in this area, such as deformations, bends or bends, form in cracks in the material that has become brittle and thrown up, which lead to the known leaks.

According to the invention, it has now been recognized that if the welding line is offset at least in the region of the overlap, the material melted during welding and subsequently hardened can be remotely milled from said bending line. As a result, the bending load - if present - is reduced or even eliminated in this area, which increases the service life of the welds lying in the weld line.

Advantageous developments of the invention are specified in the subclaims:

In a further development, a section along a bending line is bent in particular by 90 °, preferably by 180 °. A 90 ° turn is e.g. desired with a fold, which should result in a flat bottom. A turn of 180 ° is e.g. advantageous for closing the container in the upper area.

In another development, the bending line lies in the plane formed by the container wall and possibly at a distance from the welding line by a distance in the opposite direction to the offset. In this case, the area of the weld seam characterized by an accumulation of material is arranged particularly clearly away from the area loaded by the bend.

In a development of the invention, the wall sections are integrally connected to one another by one or more folds, in particular by 180 ° in each case. Such a thin-walled container is made of a one-piece material particularly inexpensive and yet liquid-tight due to the offset of the welding line according to the invention.

The invention also relates to a method for producing a thin-walled container according to one of the preceding claims, which comprises the following steps:

a) arranging a second wall section having a longitudinal edge parallel and closely fitting to a first wall section; b) arranging a third wall section having a longitudinal edge parallel and at least partially closely fitting to the first wall section, such that its longitudinal edge overlaps the longitudinal edge of the second wall section at least partially; c) welding the edge sections along a welding line which runs essentially transversely to the longitudinal edges.

In order to be able to produce a container that is liquid-tight during production and over its entire service life, the invention proposes that

d) the welding line is offset in the area of the overlap in a plane lying in the container wall.

A subordinate claim specifies a corresponding advantageous development of the method according to the invention, by means of which a favorable course of the welding line is achieved.

Finally, the invention also relates to a device for producing a thin-walled container, which has an ultrasonic welding sonotrode and a counter-holder (also called "anvil") with one during welding of the container facing working edge and also includes a front side facing the container during welding.

Ultrasonic sonotrodes and counterholders of this type are used primarily for the production of containers for foods such as milk, juices etc. The temperature maximum in the workpiece during welding is reached with an ultrasonic sonotrode where the amplitude of the ultrasonic waves introduced into the workpiece reaches its maximum. This position depends on from the position of the working edge facing the container during welding.

In order to be able to generate the offset of the welding line provided for the thin-walled container mentioned at the outset, it is proposed for the device mentioned in the above that the working edge has an area with an offset essentially parallel to the workpiece plane. This can be implemented easily and inexpensively in the manufacture of the sonotrode, so that the desired shape of the welding line can be produced easily.

In a development of the device according to the invention, the area with the offset in the front view has a trapezoidal basic shape. Such an offset is, on the one hand, easy to manufacture and avoids interruptions in the welding line due to the slowly rising and falling flanks during operation.

It is advantageous if the area with the offset has approximately the length of the overlap. As a result, the offset of the weld line is limited to the area of the overlap, which has manufacturing advantages in the further processing of the container to be manufactured.

The amount of the offset depends essentially on the amount of plastic thrown up in the area of the overlap. However, the offset should not be as high as desired for manufacturing-related reasons. In this regard, it has proven to be advantageous for conventional containers (for example milk and juice containers) if the height of the offset is approximately 0.5 to 4 mm.

Furthermore, it is stated that the front of the sonotrode and / or the front of the counter-holder has a recess, the depth of the recess or the sum of the depths of the recesses roughly corresponding to the thickness of a wall section of the container to be welded. This enables the working edge to also lie close to the workpiece to be welded in the area of the overlap, so that the necessary pressure can be applied to the workpiece in this three-layer area and the energy can be optimally transferred from the sonotrode to the workpiece without crushing which can lead to burns of the material to be welded during welding.

The invention also relates to a thin-walled container made of a flexible base material, which is coated with an ultrasonically weldable flexible layer, the container having a wall with at least a first wall section, a second wall section which is arranged parallel and close to the first wall section and has a longitudinal edge , and comprises a third wall section, which is arranged parallel and at least in sections closely adjacent to the first wall section, has a longitudinal edge and overlaps the longitudinal edge of the second wall section in the region of its longitudinal edge, the second and third wall sections running along a generally transverse to the longitudinal edges Weld line are welded to the first wall section.

For such a container, it is proposed that the weld line face at least in the area of the overlap is offset from a plane which is formed between the first and second or third wall section. In this way, the welding line and the area that is less flexible due to it can also be removed from the immediate vicinity of an existing bending line.

An exemplary embodiment of the invention is explained in detail below with reference to the accompanying drawing. The drawing shows:

FIG. 1 shows a view in the manner of an exploded perspective view of a section of a thin-walled container, a sonotrode and an anvil;

Figure 2 is a view similar to Figure 1 from a different perspective;

FIG. 3 shows an enlarged detail view from the front of a region of the sonotrode from FIG. 1;

Figure 4 is a perspective view of the front of the counter holder of Figure 1;

Figure 5 is a sectional view through the container section of Figure 1; and

Figure 6 is a rear view of the container section of Figure 1.

In FIG. 1, an upper section of a thin-walled container has the reference number 10, a sonotrode for ultrasonic welding has the reference number 12 and a corresponding counter-holder (“anvil”) has the reference number 14. As can be seen particularly well from FIG. 5, the container is made from a flexible base material 16, in the present case a thin cardboard. The material is coated on both sides with an ultrasonically weldable flexible plastic which bears the reference symbol 18 in FIG. Alternatively, the container could also be made of a plastic material, for example a plastic film. In this case - provided that the plastic can be welded - a special coating could be dispensed with.

The upper portion 10 of the container comprises a first wall portion 20, a second wall portion 22 and a third wall portion 24. All three wall sections 20, 22 and ^'24 are connected by folds 26 and 28 by 180 ° together in one piece. The second wall section 22 lies closely against the first wall section 20 and is arranged parallel to the latter. The same also applies to the third wall section 24, with the exception that this overlaps a longitudinal edge 32 (FIG. 2) of the second wall section 22 in the region of its longitudinal edge 30, that is to say no longer lies closely against the first wall section 20 in this region. The overlap formed in the area of the longitudinal edges 30 and 32 of the second wall section 22 and the third wall section 24 bears the reference number 34.

As can be seen particularly well from FIGS. 1 and 6, a cross-hatched weld line 36 runs in the area of the upper section 10 of the container transversely to the longitudinal edges 30 and 32 of the wall sections 22 and 24, along which the plastic coating 18 of the carton 16 at least partially melted, thrown up and hardened again. As a result, the wall sections 20, 22 and 24 are connected to one another along this welding line 36. The welding line 36, that is to say the area in which the maximum temperature is reached during the welding process, is offset in the area of the overlap 34 upwards in a trapezoidal manner. The offset area, like the rest of the welding line, is located in a plane 38 formed by the container wall 20, 22, and 24. That area of the welding line 36 that is offset bears the reference symbol 40. The height of the offset 40 depends on the the amount of material thrown up during welding and is usually 0.5 to 4 mm.

After welding, the upper section 10 of the container shown in the drawing is bent over a bending line 42 shown in broken lines by 180 °. The bending line 42 also lies in the plane 38 and - apart from the flanks of the area 40 - parallel to the welding line 36. However, it is spaced apart from the welding line 36 by a distance a from the welding line 36, contrary to the “bulge” formed by the offset 40 , The distance a is usually about 0.5 to 5 mm.

As can be seen from FIGS. 1 and 6, the bending line 42 runs in the area of the overlap 34 due to the offset 40 outside the welding line 36, that is also outside the welded areas. In this way, the weld seam between the wall sections 20, 22 and 24, which is less flexible due to the material attachment by the melt, is less or not at all stressed by the bending, so that the hardened melt of the plastic coating 18 does not tear due to the bending can. This creates a considerably increased security against leakage of the container at this point.

However, it should be expressly pointed out here that the advantages according to the invention are already at a lower level Offset 40 can be obtained. It is essential that the offset 40 of the welding line 36 removes the center of the melt formation from the bending line 42.

The offset 40 of the welding line 36 shown in FIGS. 1 and 6 is made possible by a special design of the sonotrode 12, which is now explained:

The sonotrode 12 has a front side 43 facing the upper section 10 of the container during welding, which is rounded in part-circle in cross-section in its upper and lower area, but forms a working edge 44 at the joints of the two areas. In its lateral center, the working edge 44 has an area with an offset 46 drawn up perpendicularly to the sonotrode plane, which has a trapezoidal basic shape in the view shown in FIGS. 1 and 3.

In the overall flat front 48 of the counter-holder 14 there is a recess 50 with a basic shape that is also trapezoidal in plan view (see FIG. 4). The depth of the recess 50 in the front 48 of the counter-holder 14 corresponds approximately to the thickness of the wall section 24. At this point it should be expressly pointed out that such a recess could also be present in the sonotrode and also in combination with the said offset. However, such a combination is more complex in terms of production technology and therefore more expensive. The front of the sonotrode as a whole could also be flat and that of the counter holder with a working edge with a corresponding offset.

For welding, the upper section 10 of the container is clamped between the working edge 44 of the sonotrode 12 and the front side 48 of the counter holder 14. The sonotrode 12 and the counter-holder 14 are arranged so that

Claims

claims

1. Thin-walled container (10) made of a flexible base material (16), which is coated with an ultrasonically weldable flexible layer (18), the container having a wall with at least a first wall section (20), a second wall section (22), which is parallel and close to the first wall section

(20) is arranged and has a longitudinal edge (32), and comprises a third wall section (24) which is arranged parallel and at least in sections closely fitting to the first wall section (20), has a longitudinal edge (30) and in the region of its longitudinal edge ( 30) overlaps the longitudinal edge (32) of the second wall section (22), the second (22) and the third wall section (26) along a welding line (36), which is generally transverse to the longitudinal edges (30, 32), with the first wall section ( 20) are welded, characterized in that the weld line (36) in the region of the overlap (34) has a section (40) which is offset in a plane (38) lying in the container wall (20, 22, 24).

2. Thin-walled container (10) according to claim 1, characterized in that a section along a bending line (42) is bent in particular by 90, preferably by 180 degrees.

3. Thin-walled container (10) according to claim 2, characterized in that the bending line (42) in the plane (38) formed by the container wall (20, 22, 24) and possibly from the welding line in the opposite direction to the offset (40 ) is spaced. Thin-walled container (10) according to one of the preceding claims, characterized in that the wall sections (20, 22, 24) are integrally connected to one another by one or more folds (26, 28), in particular by 180 degrees in each case.

A method of manufacturing a thin-walled container according to any one of the preceding claims, comprising the steps of: a) arranging a second wall section (22) having a longitudinal edge (32) in parallel and closely fitting against a first wall section (20); b) arranging a third wall section (24) having a longitudinal edge (30) parallel and at least partially closely fitting to the first wall section (20) such that its longitudinal edge

(30) overlaps the longitudinal edge (32) of the second wall section (22) at least in regions; c) welding the wall sections (20, 22, 24) along a total transverse to the longitudinal edges

(20, 32) extending welding line (36), characterized in that d) the welding line (36) is offset in the region of the overlap (34) in a plane (38) lying in the container wall (20, 22, 24).

Method according to Claim 5, characterized in that a section is mechanically deformed, in particular bent, along a deformation line (42) which is preferably in the plane (38).

Device for producing a thin-walled container (10) according to one of claims 1 to 4, which a

Ultrasonic welding sonotrode (12) and a counter-holder (14) with a working edge (44) facing the container (10) during welding and also with Welding includes the front (48) facing the container (10), characterized in that the working edge (44) has a region (46) with an offset substantially parallel to the workpiece plane (38).

8. The device according to claim 7, characterized in that the area (46) with the offset in the front view has a trapezoidal basic shape.

9. Apparatus according to claim 8, characterized in that the length of the area (46) with the offset corresponds approximately to the width of the overlap (34).

10. Device according to one of claims 7 to 9, characterized in that the height of the offset (46) is approximately 0.5 to 4 mm.

11. The device according to one of claims 7 to 10, characterized in that the front of the sonotrode and / or the front (48) of the counter-holder (14) has a recess (50), the depth of the recess (50) or The sum of the depths of the recesses corresponds approximately to the thickness of a wall section (20, 22, 24) of the container (10) to be welded.

12. Thin-walled container made of a flexible base material, which is coated with an ultrasonically weldable flexible layer, the container having a wall with at least a first wall section, a second wall section which is arranged parallel and close to the first wall section and has a longitudinal edge, and a third wall section, which is arranged parallel and at least in sections closely fitting to the first wall section, a longitudinal edge and in the area of its longitudinal edge overlaps the longitudinal edge of the second wall section, the second and third wall sections being welded to the first wall section along a welding line running generally transversely to the longitudinal edges, characterized in that the welding line is at least in the area of the overlap with respect to a plane is offset, which is formed between the first and second or third wall section.