DE10027735C1 - Thin-walled container, e.g. folded milk container, has overlapping wall sections that can be ultrasound welded transverse to their longitudinal edges, with offset section in area of overlap - Google Patents

Abstract

The container (10) has a flexible base material with a flexible layer that can be ultrasound welded and has three overlapping wall sections, where second and third wall sections are welded along a weld line (36) transverse to their longitudinal edges. The weld line has a section in the area of the overlap (34), which is offset in a plane containing the container walls. The container (10) has a flexible base material with a flexible layer that can be ultrasound welded. The container has a wall with at least two parallel wall sections (20,22) that narrowly overlap and a longitudinal edge (30). A third wall section (24) is parallel to and narrowly overlaps the first wall section, at least partly and has a longitudinal edge that overlaps the longitudinal edge of the third wall section. The second and third wall sections are welded along a weld line (36) transverse to their longitudinal edges. The weld line has a section in the area of the overlap (34), which is offset in a plane containing the container walls. Independent claims are included for a method and a device for manufacturing the container.

Description

The present invention relates to a thin-walled container made of a flexible base material, which with a ultrasonically weldable flexible layer is coated, wherein the container has a wall with at least a first Wall section, a second wall section that is parallel and is arranged close to the first wall section and has a longitudinal edge, and a third wall section comprises parallel and at least partially narrow is arranged adjacent to the first wall section, one  Has longitudinal edge and in the area of its longitudinal edge Longitudinal edge of the second wall section overlaps, the second and third wall sections along a total welding line running transversely to the longitudinal edges with the first wall section are welded.

Such a container is e.g. B. as a folding container for milk known from the market. As a base material this one flexible cardboard or a film is used, the cardboard is coated on both sides with a thin plastic layer. The known container is made from a one-piece sheet manufactured, initially in a square and tube-like Is brought into shape. The folding is carried out so that the both longitudinal edges of the sheet overlap and with each other can be glued or welded. At least one end to be able to close the container in a liquid-tight manner is flattened at this end.

In the area of the overlap of the longitudinal edges are therefore on the flattened end three layers of the container wall parallel and close together, whereas outside the overlap in the flattened area two layers of the container wall are arranged parallel to each other and closely fitting. The Layers of the container wall are now flattened Section across its longitudinal edges along a Weld line welded to each other by ultrasound, see above  that this end of the container is sealed liquid-tight is.

As is known from DE 195 00 971 C2, the Closure seam with a recessed Ultrasonic tool are generated so that the Material accumulation in the overlap area taken into account becomes.

In the known container, however, it has been found that during his "life" he often worked in the field of originally liquid-tight welding breaks up, so is leaking. This is particularly the case if the Welding during further processing and later Use a bend or bend along a bend line is carried out.

The present invention therefore has the task of a thin-walled containers of the type mentioned so far form that its tightness for production and over the average expected lifespan is guaranteed.

This task is solved in that the welding line in the Region of the overlap has a section which in a level in the container wall is offset.  

According to the invention, it was recognized that the leak points often in the area of the overlap. One of the reasons this is because the ultrasonic weldable flexible Layer with which the base material is coated, at Welding becomes hard and a relatively brittle one Material accumulation arises. This will in the area of Overlap created a zone with less flexibility. If there are mechanical loads in this area, e.g. B. Deformations, bends or bends form in the material, which has become brittle and thrown up, cracks which lead to the known leaks.

According to the invention, it has now been recognized that when the Welding line is offset at least in the area of the overlap, that melted during welding and then hard material kept away from said bending line can be. As a result, the bending load - if available - reduced or even eliminated in this area, what is the lifespan of those in the weld line Welds increased.

The container can be made from an ultrasound weldable plastic coated cardboard or alternatively also made of a plastic material, e.g. B. a plastic film be made.  

Advantageous developments of the invention are in Subclaims specified:

In a further development, a section is along a Bending line, in particular by 90 ° or by 180 °, bent over. A 90 ° fold is e.g. B. in a fold desired, which should result in a flat floor. A fold around 180 ° B. for closing the container in the upper Area advantageous.

In another development, the bending line lies in the plane formed by the container wall and is of the Weld line by a distance in the opposite direction to the Offset spaced. Here is the one Material accumulation marked area of the weld particularly clearly from that burdened by the bend Area located away.

In a development of the invention, the wall sections through one or more folds, in particular around each 180 °, connected in one piece. Such a thin-walled container is made of a one-piece material particularly inexpensive and due to the invention Offset of the welding line is still liquid-tight.  

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 one having a longitudinal edge Wall section parallel and close to a first Wall section;
• b) arranging a third having a longitudinal edge Wall section parallel and at least narrow in some areas adjacent to the first wall section, such that its Longitudinal edge at least partially the longitudinal edge of the overlapping second wall section;
• c) welding the edge sections along a total welding line running 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

• a) the weld line in the area of the overlap in one in the Container wall lying level is offset.

Finally, the invention also relates to a device for Production of a thin-walled container, which one Ultrasonic welding sonotrode and a backstop (too Called "anvil") with one when welding the container  facing working edge and one also during welding front of the container includes.

Such ultrasonic sonotrodes and counterholders are used especially for the production of containers for food, such as Milk, juices etc. used. The temperature maximum in Workpiece during welding is ultrasonically Sonotrode reached where the amplitude of the in the workpiece introduced ultrasonic waves reached their maximum. This Position depends u. a. from the position of the when welding Working edge facing the container.

To now the thin-walled container mentioned at the beginning to be able to generate the intended offset of the welding line for the above device suggested that the Working area with an offset parallel to the Has container wall level. This is in the making of the Sonotrode easy and inexpensive to implement, so that desired shape of the welding line can be easily generated.

In a development of the device according to the invention the area with the offset in the front view trapezoidal Basic form. On the one hand, such an offset is simple manufacture and avoids by slowly turning on and off descending edges during operation interruptions of the Welding line.  

It is advantageous if the length of the area with the Offset roughly corresponds to the width of the overlap. Hereby the offset of the welding line to the area of the Limited overlaps, which adds manufacturing advantages 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 be arbitrarily high in connection with the further processing related manufacturing reasons Not be. Has proven favorable in this regard for Usual containers (e.g. milk and juice containers) proved if the height of the offset is approximately 0.5 to 4 mm.

It is also provided that the front of the sonotrode or the front of the counter bracket or both front one Have recess, the depth of the recess or the Sum of the depths of the recesses roughly the thickness of one Corresponds to the wall section of the container to be welded. This enables that also in the area of the overlap Working edge lies close to the workpiece to be welded, see above that even in this three-layer area the necessary pressure applied to the workpiece and the energy optimally from the Sonotrode can be transferred into the workpiece without Crushes occur which, when welded, result in burns of the material to be welded.

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

Fig. 1 is a view in the manner of an exploded perspective view of a portion of a thin-walled container, a sonotrode and an anvil;

Fig. 2 is a view similar to Figure 1 from a different perspective.

Fig. 3 is an enlarged detail view from the front of a portion of the horn of FIG. 1;

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

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

Fig. 6 is a rear view of the container portion of Fig. 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 of 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. 5.

The upper portion 10 of the container includes 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 integrally connected to each other by folds 26 and 28 by 180 °. The second wall section 22 lies closely against the first wall section 20 and is arranged parallel to the latter. The same 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 area of its longitudinal edge 30 , that is to say no longer lies closely against the first wall section 20 in this area. The overlap formed in the area of the longitudinal edges 30 and 32 of the second wall section 22 and of 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 is melted, thrown up and hardened again at least in some areas. 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 region in which the maximum temperature is reached during the welding process, is offset trapezoidally in the region of the overlap 34 . The offset region, like the rest of the weld line, is located in a plane 38 formed by the container wall 20 , 22 , and 24. That area of the welding line 36 which is offset is identified by the reference symbol 40 . The height of the offset 40 depends on 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 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 accumulation 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 can also be obtained with a smaller offset 40 . 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 during welding of the upper portion 10 of the container facing front side 43, which is part-circular rounded at its upper and lower region in the cross section, but is at the joints of the two regions a working edge 44th In the middle, the working edge 44 has an area with an offset 46 drawn up perpendicular to the sonotrode plane, which in the view shown in FIGS. 1 and 3 has a trapezoidal basic shape.

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 return 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 such that the recess 50 is arranged in the front 48 of the counter-holder 14 in the region of the overlap 34 of the two wall sections 22 and 24 . Due to the recess 50 in the front 48 of the counter-holder 14 , the working edge 44 of the sonotrode lies completely against the upper section 10 of the container despite the thickening in the area of the overlap 34 , so that the ultrasonic energy is effectively coupled into the area to be welded.

During operation, the welding line 36 , that is to say the region in which the temperature during welding is maximum and the plastic coating is melted, is where the ultrasonic vibrations form a "wave crest". The position of this wave crest lies at a constant distance from the working edge 44 of the sonotrode 12 . Due to the shape of the working edge 44 of the sonotrode 12 , the offset 40 of the welding line 36 is therefore achieved during operation.

Claims (11)

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 ) is arranged parallel and close to the first wall section ( 20 ) and has a longitudinal edge ( 32 ), and comprises a third wall section ( 24 ) which is arranged parallel and at least in sections closely adjacent to the first wall section ( 20 ), a longitudinal edge ( 30 ) and in the area of its longitudinal edge ( 30 ) overlaps the longitudinal edge ( 32 ) of the second wall section ( 22 ), the second ( 22 ) and the third wall section ( 24 ) along a welding line (transversely to the longitudinal edges ( 30 , 32 )) 36 ) are welded to the first wall section ( 20 ), characterized in that the weld line ( 36 ) in the area of the overlap ( 34 ) has an Absc cut ( 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 is bent along a bending line ( 42 ), in particular by 90 or 180 degrees. 3. Thin-walled container ( 10 ) according to claim 2, characterized in that the bending line ( 42 ) in the plane formed by the container wall ( 20 , 22 , 24 ) ( 38 ) and from the welding line in the opposite direction to the offset ( 40 ) lies. 4. 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. 5. A method for producing a thin-walled container according to one of the preceding claims, comprising the following steps:

• a) arranging a second wall section ( 22 ) having a longitudinal edge ( 32 ) parallel and closely fitting to 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 ) at least partially the longitudinal edge ( 32 ) of the second wall section ( 22 ) overlaps;
• c) welding the wall sections ( 20 , 22 , 24 ) along a welding line ( 36 ) which runs overall transversely to the longitudinal edges ( 20 , 32 ),

characterized in that

• a) the welding line ( 36 ) in the area of the overlap ( 34 ) is displaced in a plane ( 38 ) lying in the container wall ( 20 , 22 , 24 ).

6. The method according to claim 5, characterized in that a section along a deformation line ( 42 ) lying in the container wall plane ( 38 ) is mechanically deformed, in particular bent. 7. Device for producing a thin-walled container ( 10 ) according to any one of claims 1 to 4, which has an ultrasonic welding sonotrode ( 12 ) and a counter-holder ( 14 ) with a working edge ( 44 ) when welding the container ( 10 ) and also comprises during welding the front side ( 48 ) facing the container ( 10 ), characterized in that the working edge ( 44 ) has an area ( 46 ) with an offset parallel to the container wall 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. The device according to claim 8, characterized in that the length of the region ( 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 0.5 to 4 mm. 11. The device according to one of claims 7 to 10, characterized in that the front of the sonotrode or the front ( 48 ) of the counter-holder ( 14 ) or both front sides have 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.