DK160018B - CONTAINER, NECESSARY FOR MILK PRODUCTS AND MACHINE AND PROCEDURE FOR MANUFACTURING THE CONTAINER - Google Patents

Abstract

1. A container at least partially made of plastic, and in particular a container for milk products, the container including a tubular side wall and a bottom fixed to the side wall, the container being characterized in that the side wall (1) is constituted by a rectangular thermoplastic sheet (2) having its short sides welded together to constitute a closed contour, and by two end closure members substantially perpendicular to the side wall and respectively constituting the bottom (4) and the lid (3), each closure member (3, 4) including a groove (10) for receiving an edge of the side wall (1), and the edge being ultrasonically welded in the corresponding groove (10).

Description

in

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BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a container, particularly for dairy products and at least partially made of plastic, comprising a tubular side wall and a bottom wall attached to the side wall. It also relates to machine 5 and to a method of making containers of this kind.

Plastic cups have to a very large extent displaced wax-coated cardboard cups or glass as yogurt containers. Compared to glass beakers, 10 plastic beakers have the advantage of being lighter, less brittle and better suited for direct printing of labeling on the beaker. Unfortunately, plastic containers, which are usually made of polystyrene or polypropylene, lack some of the utility advantages that glass containers have, and in particular, they do not provide a correspondingly good barrier from the surrounding medium. Plastics and especially polystyrene are relatively permeable to gases normally found in the atmosphere, such as oxygen, carbon dioxide and water vapor. These gases can diffuse through the container wall and flush the quality of the product, even during its normal shelf life. As a result, the taste quickly deteriorates.

The object of the invention is to provide a container which allows the quality of the product to be maintained unchanged during its shelf life.

The preservation of the product which constitutes the container load is also partly dependent on the measures taken at the container filling. Preferred embodiments of the invention disclose a container which can be sterilized by purely physical means, which is in accordance with current trends in the legal provisions.

The presently used containers are further comprised of a hollow body which is closed with a lid or a cap which is sealed or clamped to the container body. Cups can thus be made by blow molding.

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2 or injection molding utilizing the properties of the plastic material. Since container manufacturing usually takes place in a company far from the place where the product is manufactured and filled on containers, unfortunately there is a need for transport of empty containers, e.g. by road, which, in spite of various techniques for stacking containers, entails the transport of considerable amounts of empty space.

Another object of the invention is to provide a container which is formed immediately before it is filled, which results in more efficient transport and makes it easier to obtain perfectly sterile filling conditions.

IN USA. U.S. Patent No. 4,187,768 is disclosed to produce a paper container having a surface coated with a thermoplastic film. The container is made up of a bottom component and a side wall component which are ultrasonically welded together. The periphery of the bottom component is folded such that the 20 fold is surrounded by another fold at the bottom of the side wall. The top of the container is folded. The method disclosed in the patent is slow because of the need for folding and because it always takes longer to weld see plastic to paper than to weld see 25 plastic to plastic. The welding is performed by a relative displacement between the container and an ultrasonic probe, which further extends the manufacturing time. A further factor is that the larger the container, the longer it will take to produce it by the method described in U.S.A. patent.

It is a further object of the invention to provide a method for producing containers of any cross-section and at a production rate which is largely independent of the size of the containers.

For practical reasons, milk products are usually packaged in single portions or portion packages.

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3 Both for practical reasons and for commercial reasons, it is desirable to group such portion packages into groups of two, four, eight or twelve. There may also be a desire for the milk products to be different within such a group, ie. adjoining containers contain different products. Both the division of the product into batch units and the assembly of different products into a common group increases packaging costs. For the sake of mechanical strength, such groups also usually require an additional collector, usually a box or box.

Another object of the invention is to provide a container which can be easily joined with other similar containers to a group without having to pack a group thus formed, which further reduces the total cost considerably.

The container according to the invention is characterized in that the side wall is formed of a rectangular sheet of thermoplastic, whose short side edges are welded to each other to form a closed contour, and of two end closure elements which are substantially perpendicular to the side wall and constitute a lid and said bottom, respectively, that each end closure element has a groove for receiving an edge of the side wall and that the edge is ultrasonically welded into the associated groove.

The components are thus automatically centered relative to each other by the edges of the side walls being accommodated in the grooves. Once the components are properly positioned, they are relatively easily welded to form a tight joint. It can be noted that the components assembled for welding have the advantage of concentrating the ultrasound and the quality of the resulting welding is good.

The closure elements mentioned above, which will hereinafter be designated respectively the bottom of it 4

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the lower element welded prior to filling the container, and the cap or lid of the upper element welded after filling the container. These elements are preferably injection molded independently of the extrusion of the sidewall.

Thus, the sidewall, lid and bottom are planar before being transported to the place where they are assembled, which allows optimization of the means of transport used.

The invention also relates to a machine for making the present containers, which machine is characterized in that it has means for stacking the rectangular sheets, the bottom forming closure elements and the top forming closure elements, means for sterilizing the components, means for folding the sheet and ultrasonic welding of its short sides to form sidewalls, 20 means for inserting one edge of the sidewall gene into the groove in a bottom extending substantially perpendicular to the sidewall, a welding head for ultrasonic welding of the edge of the sidewall in the groove at the bottom, which head is one of the welding electrodes, means for filling the container with a portion of filler material, means for snap-mounting the lid to the top edge of the side wall, so that the top edge penetrates the groove in the lid, substantially perpendicular thereto, and a welding head for ultrasonic welding of the lid to the top edge of the side wall.

The invention also relates to a process for producing a container as further described in claim 8.

All components are thus fed to the machine in flat or sheet form. This facilitates in high

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5 degree sterilization of the components, e.g. with ultraviolet radiation or the like, and the following operations can easily be performed in an inert atmosphere.

5 There are many advantages to fabricating the side walls of extruded sheet material. First, several layers can be extruded simultaneously. The resulting composite sheet can be made impermeable to gas by incorporating an impermeable layer, which improves the storage of the product in the container. Second, there is no difficulty in labeling the outside of the container with print. Third, there is no material waste, which is of great importance when dealing with composite sheets, as it is difficult to recycle clippings of laminates.

When fresh milk products are transported, the vibrations emanating from the transport exert a pumping effect on the products, whereby serum is excreted from the mass of yogurt or other product. An earlier technique for reducing this disadvantage consists in the use of generally tapered containers with the largest diameter at the bottom. This shape prevents the yogurt from moving upwards towards the decreasing diameter of the container. Unfortunately, such containers are not suitable for stacking within each other when empty, or on top of each other when full. Containers according to the present invention are preferably prismatic with the side walls perpendicular to the end closure elements. This ensures that the resulting structure is mechanically strong enough that multiple layers of full containers can be stacked on top of one another. In order to reduce the aforementioned "pumping effects", the insides of the container sidewalls have been advantageously embossed during extrusion of the sidewall sheet, whereby the yogurt is "locked" to the wall and prevented from moving relative to the container during transport.

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6 An embodiment of the invention will now be described in more detail with reference to the drawing, in which: FIG. 1 is a perspective exploded view of a group of containers according to the invention; FIG. 2 is a front view of a single container; FIG. 3 is a vertical section through this container; FIG. 4 is a perspective view of a single extruded sheet which can be transformed into the side walls of a container; FIG. 5 is a section through a laminated wall material; FIG. 6 is a schematic perspective view of an extruder for extrusion of sidewall sheets; FIG. 7 is a block diagram of a container forming machine; FIG. 8 is a schematic perspective view of a machine according to FIG. 7, 20 FIG. 9 is a partially cut-away perspective view of a machine for forming the sidewall; and FIG. 10 is a partially sectioned perspective view of means for conveying containers through a filling apparatus.

FIG. 1 is a perspective exploded view of a group of four containers of the type seen from the front in FIG. 2 and in section in FIG. 3. According to the invention, each container comprises three parts, namely a side wall 1, a cover or lid 3 and a bottom 4. The bottom 4 and 30 the lid 3 have grooves 10 which occupy the bottom and top edges respectively of the side wall 1 and which are ultrasonic paths. st to the side wall. This welding method is preferred over other known methods because of its speed and because it retains the organoleptic characteristics of the container. The side wall 1 is formed by overlapping the ends of a plastic sheet 2, see FIG. 4 wherein fold extrusion lines 6A are preformed during extrusion.

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As best seen in FIG. 3, the lid 3 has a recess 12 which is lower than the top edge of the side wall 1. The container bottom 4 has a recess 13 which projects below the bottom edge of the side wall 1. Thus, in the embodiment shown, the lid is concave and the bottom convex. The reverse arrangement with a convex lid and a concave bottom could also be used. The profiles of the lid 3 and the bottom 4 are complementary, so that the convex bottom of one container can be accommodated in the concave lid of another container, whereby the containers can be stacked precisely with their side walls 1.

This ensures that such a stack has maximum mechanical strength sufficient to withstand the loads normally encountered during stacking and handling. The lid 3 and the bottom 4 have edge flanges defining the grooves 10 in such a way that the top and bottom edges of the sidewall 11 are securely received in the grooves, possibly by snap mounting, prior to the welding mentioned above. This ensures accurate joining of the three parts.

In the drawing, the containers are shown as beakers with square cross sections. This is an advantageous configuration since it allows for the formation of compact container groups without the waste of space. However, other cross-sections are also possible, and in particular a circular cross-section could be used.

Pig. 4 is a perspective view of a sheet 2 before being converted to the sidewall 1 by folding. The sheet has an inside 5 and an outside 7 (seen in 30 relative to the finished container). The exterior 7 is smooth and intended to provide decoration and / or information about the product which constitutes the container filler. the inside 5 is embossed with a pattern of intersecting, raised ribs 6. It is known to use ribs on the walls of containers, but so far the purpose has been to reinforce the container.

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6 the walls and not providing the container with means for holding the stuffing, ie. lock the stuffing to the wall. This holding or locking function is enhanced by using a diagonal pattern as shown, but alternatively, other patterns could be used. The benefits of leaving a "thick" stuff, such as yoghurt, sticking to the walls is that the stuffing remains homogeneous in the container regardless of the shocks that occur during the transport of the filled containers. The embossing also contributes to the overall strength of the container, but its resistance to vertical crushing lies primarily in that its side wall is vertical and welded to the end pieces, ie. the lid 3 and the base 4, thereby giving the structure an appropriate stiffness.

The sheet 2 is made by extrusion, and if the sidewall 1 is to have polygonal cross-section, fold marks 6A in the sheet are preformed during its extrusion to facilitate subsequent folding. The folding marks 6A may advantageously have a weak waveform.

As mentioned above there is a need for assembly of portion packs for group units of a size suitable for marketing. FIG. 1 shows an example of such group formation. Generally, a group is formed by joining the top and / or bottom closure elements into groups of at least two each. In the example shown, four lids 3 are joined. The joint is made at the same time as the lids are formed, e.g. by hot pressing or injection molding. Between 30 adjacent and joined lids there are tear strips 8. Tear strips 8 extend only over a portion of the opposite edges of the lids, and in the FIG. 1 with four lids, there is a central hole 9.

Such a hole enables a handling tool not shown, e.g. a bar with barbs can be inserted through several layers of stacked container groups, which 9

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ensures that the layers are held in relation to each other.

The central hole can also be used for the manual transport of a single group of containers.

Obviously, the containers must be easy to open when they reach their final destination. Thus, in each lid 3 there is a weakening line 14 which defines a field 11 which can be removed from the lid. To facilitate removal, field 11 has a pull tab not shown.

In view of the shape of the end members 3 and 41 and the strength of the side walls 1 against vertical crushing, several groups of containers can be placed on top of each other to form a uniform assembly. This arrangement results in a great improvement in the efficiency with which vehicles and storage space can be filled, and e.g. in a given volume, up to 2.2 times as much milk product can be stored as with previously known containers. Furthermore, the containers no longer need to be packed in a box or box, which significantly reduces costs. Once a predetermined number of containers are assembled both horizontally and vertically, they can be prevented from falling apart by simple strapping. In the example described, the vertical alignment and centering 25 are related to the convex bottoms being accommodated in the concave lids. Exactly the same effect could be achieved with convex lids incorporated in concave bottoms. The crucial point is to ensure that vertical forces are transmitted directly from a sidewall to the sidewall adjacent in vertical direction 30.

FIG. 5 is a cross-section through a sheet 2 or through a lid or bottom. As mentioned above, preferred embodiments of the invention entail preservation of the stuffing in the container. This has been achieved by improving the wall impermeability to gases. If this were done simply by increasing

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10 the wall thickness, one would quickly encounter practical manufacturing limits. Gas impermeability is better achieved by producing the container walls of a laminate material including at least one layer which is impervious to the gases which should not be able to diffuse into the container, e.g. oxygen. The structure of such a layer constitutes a barrier to diffusion of one or more gases through the wall. Suitable barrier or barrier materials include copolymers of 10 ethylene-vinyl alcohol (EVAL) and polyvinylidene (PVDC). FIG. 5 is a cross-section through such a laminate material with an outer layer 7, an inner layer 5 and a middle layer 15. In some cases other materials are added to these main layers to ensure proper adhesion between the layers. The inner and outer layers 5 and 7 may consist of polystyrene or polypropylene when the middle layer 15 is made of EVAL or PVDC.

The barrier thus created retains the "good old fashioned" taste of the product throughout its shelf life 20 without requiring chemical antioxidants and using modern materials that can be extruded rather than blown.

FIG. 6 shows the process for extrusion of the sidewalls 1. Three extruders 16, 17 and 18 supply three streams of high viscosity material to a nozzle assembly 19 which delivers three material layers 5, 7 and 15. A set of rollers 20 produces the embossing 6 of the inside, i.e. the side facing inwards into the finished container. The three-sheet sheet is then cooled at 21 and 30 its outer surface 7 is imprinted by means of a printing roller 22 and a dye 23. The printed surface is then dried in an oven 24 and by means of a scissors 25 the sheet 2 is cut to a length equal to the desired container height. The width of the web leaving 35 from the nozzle assembly 19 is equal to the perimeter of the finished sidewall plus the overlap in the weld. Year-

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jaw 2 is counted, stacked and packed at 26. It will be seen that there is no waste of material in the manufacture of sheets 2, which is particularly important in a laminated material.

5 The lids 3 and the bottoms 4 can be formed of the same material as the side walls 1 or of another material. They can be hot pressed or injection molded. Depending on the given conditions, they may have different colors so that each product in a mixture of products traded in the same container group can be identified by color-coding one or both container ends. As mentioned above, the lids 3 are manufactured in groups of two, four, eight or twelve and the containers are welded onto the lids without breaking the coherence of the groups. The bottoms 4 can also be made in groups, but they can also be applied individually. Alternatively, the bottoms may be joined together in groups to form container groups while the lids are individually applied.

As a typical example, machines that fill the containers with single portions operate at a speed of approx. 40,000 servings per hour. Thus, it is desirable that the machines for producing the packaging operate at a similar speed. FIG. 7 and 8 25 are respectively a block diagram and a perspective exploded view of a machine for making containers according to the invention and intended to be placed in the same establishment which manufactures the filling goods.

As mentioned above, the components for the containers are manufactured elsewhere and delivered flat-sheeted, which makes the loading of trucks for transport extremely efficient compared to the transport of poorly formed empty containers. The FIG. 7 and 8 include three stacking stations 27, 28, 35 and 29 for sheets 2, bottoms 4, and lids 3, respectively.

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12, 34, e.g. works with ultraviolet radiation and where the components are sterilized in the flat state. The sheets 2 stacked at the station 27 are led to a forming station 30, where they are folded in square and welded along a generator. In parallel with this operation, a set of bottoms 4 is supplied to a station 30 and mounted on top of the tubular side walls 1 in a group of cups. Pressure is applied to ensure that the edges of the sidewalls 1 penetrate into the grooves 10. The assembly of sidewalls and bottoms then passes an ultrasonic welding head 31 where the cups as such are finalized. The cups are then turned and delivered to a filling station 32 which is followed by means for attaching lids or groups of lids to the cups and by means 35 for welding the lids 3 on the cups. In a station 36, groups of filled beakers are automatically placed on a pallet.

FIG. 9 is a partially sectioned perspective view of a station where the sidewalls 1 are made of sheets 2. The stacking station 27 is of conventional type. After passing the ultraviolet light at 34, the sheets are folded by a combination of guides 39 and 41 and welded along the edge 25 by an ultrasonic probe 40. Where the two side panels are welded there is a small overlap.

FIG. 10 is a partially sectioned perspective view of the filling station 32. After the beaters 30 have been turned, they enter a housing 45. They are moved through the housing 45 by an endless belt 51 which is advanced stepwise by a roller 42 which is again pulled from a drive shaft 44 through a malt cross 43. The purpose of the stepwise feeding is to ensure that the cups are stationary during filling and subsequent welding of the lid. The cups are shot simultaneously

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13 by means of a piston 46 driven from a pinion 49 which cooperates with an eccentric mechanism 48 including a cam 50 coupled to the piston 46 through an arm which can pivot about a fixed shaft 47. The assembly is constructed so that the stroke of the piston 46 is substantially equal to one advance step of the conveyor belt 51.

Considering the construction of the containers, the machine for their manufacture is advantageously module-built and comprises the following main modules: forming the side wall, placing the bottom, filling and placing the lid.

Secondary modules can e.g. include modules for automatic delivery of stacks, modules for automatic quality control (as shown schematically at 52 in Fig. 8) for statistical purposes, and a module for automatic palletizing. The movements of the various operations for packaging the product do not require any continuous walking assembly line. The movement 20s have little amplitude and do not require any high torque. The accuracy of the components obtainable makes it possible to avoid the complicated positioning means of conventional machinery.

In the machine described above, each beaker constitutes its own positioning means. This significantly simplifies the sterilization and maintenance of sterile conditions throughout the production line, resulting in lower construction costs. Costs are also kept down by the fact that the machinery in the production line, such as the ultrasonic welding probes and beaker fillers are standard machines available for purchase.

The invention can be used for packaging products in powder, paste or liquid form and not only food products. The invention involves the following new combination of characteristics: Good protection of the product, no extra box or box for

Claims (8)

A container, in particular for milk products and at least partially made of plastic, comprising a tubular side wall (1) and a bottom (4) attached to the side wall 10, characterized in that the side wall (1) is formed of a rectangular sheet. (2) of thermoplastic, whose short side edges are welded to each other to form a closed contour, and of two end closure elements which are substantially perpendicular to the side wall and constitute a lid (3) and said bottom respectively (4) that each end closure element (3, 4) has a groove (10) for receiving an edge of the side wall (1) and that the edge is ultrasonically welded into the associated groove (10). Container according to claim 1, characterized in that the side wall (1) is embossed (6) on its inside (5) and smooth on the outside (7). Container according to claim 1 or 2, characterized in that the outer surface (12) of the lid (3) is complementary to the outer surface of the bottom (4), the outer surface (12, 13) of one of the closing elements (3, 4) being concave and the outside of the second closure element (4, 3) project with respect to the edges of the side surface (1), the projection of which is substantially equal to the depth of the concavity such that the edge of a side wall (1) after the containers have been filled, closed and stacked, aligned with the sidewall of the adjacent container in the stack. Container according to any one of the preceding claims, characterized in that the lid (3) includes a tear-off field (11). DK 16CG18B Container according to any one of the preceding claims, characterized in that at least one of its components (1, 3, 4) is constituted by a laminate (5, 15, 17) which forms a barrier to gas diffusion. Group of containers according to any one of the preceding claims, characterized in that at least one of the end closure elements (3, 4) of each container in the group is joined to the corresponding end closure element (3, 4) on an adjacent container in the group by means of 10 of a tear strip (8). Machine for making containers according to any one of the preceding claims, comprising at least one ultrasonic welding electrode, characterized in that it has 15 means (27, 28, 29) for stacking the elongate sheets (2), the bottom - forming closure members (4) and the top forming closure members (3), means (34) for sterilizing the components (1/3, 4), 20 means (30) for folding the sheet (2) and ultrasonic welding of its short sides means for forming sidewalls (1), means for inserting one edge of the sidewall (1) into the groove (10) in a bottom (4) extending substantially perpendicular to the sidewall, a welding head (31) for ultrasonic welding the edge of the side wall (1) in the groove (10) at the bottom (4), which head is one of the welding electrodes, means (32) for filling the container with a 30 portion filling material, means (33) for snap-mounting the lid (3) to the top edge of the side wall (1) so that the top edge penetrates into the groove (10) il the yoke, substantially perpendicular thereto, and a welding head (35) for ultrasonic welding of the lid to the top edge of the side wall (1). DK 160018 B Process for making a container, especially for dairy products, characterized in that a rectangular plastic sheet (2) is formed by extrusion and one of the sides of the sheet (6) is embossed that injection elements are injection molded to form a lid (3). , respectively, bottom (4), and wherein each element has a groove (10) that the short sides of the rectangular sheet are welded together ultrasonically to form a sidewall (1) with a closed contour, the bottom edge of the sidewall ( 1) is inserted into the groove (10) into a bottom forming closure element (4) extending substantially perpendicular to the sidewall (1) and the edge of which is ultrasonically welded within the groove (10) and the lid forming closure element (3) ), after filling the container, is mounted on the top edge of the side wall (1) in such a way that the edge is inserted into the groove in the lid, substantially perpendicular to the lid, after which the ultrasonic welding is performed.