EP1957371B1 - Shrinking process for producing solid, transportable and printable containers and device for carrying out said shrinking process - Google Patents

Abstract

The invention relates to a shrinking process for producing solid, transportable and printable containers by wrapping the articles to be packaged with a film in such a manner as to produce an overlapping section of the film ends on the base area, heating by heat exchange or convection in order to seal the free ends in the area of overlap, and finally heating in a shrinking oven, the container so produced being stabilized by the shrinking process. The method comprises first locally limiting the incoming hot air to the base area of the container to form a peripheral shell in the area of the bottle bottoms, the shape of the container being stabilized thereby, while the container is continuously transported during stabilization and the hot air directed onto the base area of the container in a bundle of discretely distributed gas jets is thereby discharged and guided back after a locally limited heat transfer with the film, and more hot gas is directed laterally against the continuously transported container at an increased lateral blow speed in order to complete the shrinking process. The invention further relates to a device for carrying out the shrinking process.

Description

The invention relates to a shrinking process for the production of solid, transportable and printable containers, in particular bottle containers with a height / width ratio of> 1, consisting of a wrapping of the goods to be packaged with a film so that an overlapping region of the film ends is formed on the bottom surface, heating or convection heating to fuse the free ends in the overlap area and a final heating while simultaneously stabilizing the resulting package by the shrinking operation.

Shrinking processes for the production of solid, transportable and printable containers are nowadays carried out in many forms in film packaging, which is used as a sales unit of bottles. The film also serves as an advertising medium, for example in beverage bottles, which are wrapped with a shrink film. Usually, hot gases are used to heat the shrink films, in which the heat energy is transferred by convection to the surface of the material to be heated.

The WO 02/36436 A1 describes a multi-zone shrink tunnel with a pre-shrink zone with heated ambient air and a heat zone in which a lateral, final Heißluftbeaufschlagung the wrapped in foil goods. The goods are here first, preferably using a solid transport tray, combined into groups and wrapped in foil. The foil ends which overlap at the bottom of the container are sealed by blowing hot air over a wide area and are subjected to the final shrinkage process after a pre-shrinking process. So that the finished containers are printable, they must have constant dimensions and flat surfaces. In addition, the printable area should provide sufficient resistance to the pressure roller resting on the print roller, since otherwise a blurred printed image is produced. These requirements lead to containers with the same spatial dimension and reproducible relative positions of the transported goods.

It has been found that particularly during transport during the packaging of goods with high center of gravity, such. For bottles with a height / width ratio of significantly> 1, preferably> 2, the upright in the overlap region of the film ends goods tend to change their position relative to the other objects by tilting. The unavoidable vibrations and vibrations of the container during the manufacturing process and during transport cause instability and unevenness of the shrinkage during the shrinking process. It was therefore attempted to produce a container with the same spatial dimension and reproducible relative positions of the objects to each other using a solid tray. However, since these are mass products with relatively low unit prices, the separate supply of a shell for the production of particularly stable containers due to the increased economic use of material and energy is out of the question.

For certain products, heating of the entire product is limited, e.g. in foods such as chilled dairy products or carbonated, pressurized beverages. Therefore, the shrinking temperatures were lowered, thereby prolonging the process time. However, the lower temperatures caused problems in the welding, so that not always the required strength in the container shell was achieved.

The inventors also found that sealing the overlapping foil ends at lower temperature avoids significant heating of the products themselves, but especially with the continuous transport of the containers involves the problem that the enveloping film is inflated and slipping on side blowing with hot air. This reinforced the already described Tilting of individual objects of the goods to be packaged or to change their position.

The object of the present invention was therefore to offer a shrinking process and a device for carrying out this shrinking process, the production of a solid container of goods with a height / width ratio of> 1, preferably> 2, with constant packing density and geometric shape without separate tray allows the individual goods to be heated at best superficially. For units that are or may only be heated on their surface, this means that the core temperature must be kept low and the energy released to the environment must be reduced. Other aspects include space requirements, process control with flexible container sizes and reduction of environmental pollution through outgassing of film materials.

This object is achieved by a shrinking process according to claim 1 and a device for carrying out the shrinking process according to claim 7. Further advantages emerge from the dependent claims and the following description.

With the new shrinking process, efficient energy transfer could be achieved, optimizing the heat transfer coefficient between the media involved, the type and size of each heated surface and the flow rate of the hot gas throughout the heat exchange or convection area, as well as the gas exchange with the environment , Through certain measures, the core temperature could be kept low and the packaging film was welded locally by narrow limitation of high temperatures, the individual objects (packaging goods) were briefly heated only on their surface to the required shrinking temperature. Furthermore, the energy output to the environment could be reduced by the fact that the hot air serving to weld the foil ends overlapping in the bottom region was directed only to the bottom surface of the container and thus zonal limited. Thus, a rapid stabilization of the shape of the container by "in-situ" formation of a marginal shell could be achieved, so that the goods already at the beginning of Shrinking process were fixed in position to each other. As a result, the container already stabilized on the bottom surface with hot air at the side was also able to withstand higher pressure loads, so that the blowing process could be limited to a short duration of treatment.

At the same time resulted during continuous transport, especially in containers with a large footprint the advantage that heat accumulation in the middle of the parking space or an inadmissible heating of the goods to be packaged could be avoided by the hot air acted upon. So far, there was a danger that the side parts of the container heated by the hot air flowing on all sides and influenced the shrinking process of the enveloping film irregularly. This problem could be solved by a rapid continuous transport of the container on a net-like structure in combination with a zonal impact on the bottom surfaces by hot air. Here, hot air is introduced into bundles of discretely distributed gas jets in a convection zone, which is bounded by the container bottom on the one hand and exhaust vents on the other. The incoming hot air is deflected under intimate interaction with the film at the bottom of the container and recycled in the reverse flow direction in the gas circulation system. This form of hot gas guide will be referred to as reverse flow hereinafter. By a parallel movement of the convection zone and the bottom of the can at different speeds it is achieved that the convection zone migrates slowly during the transport of the container over the entire bottom surface, without causing heat accumulation or irregular shrinkage of the film on the container sides. Due to the special gas flow in the form of a reverse flow, the heat transfer takes place in a defined convection zone from the hot gas into the bottom surface of the container. In this case, the zonal energy input can be optimally adapted to the material thickness or density of the film by controlling the flow velocity of the hot gas and optimally via the exactly definable heat exchange or convection surface.

Fig. 1

prinzipieller Aufbau einer Schrumpfanlage zur Herstellung von festen, transportfähigen und bedruckbaren Gebinden (Vorderansicht und Seitenansicht).

Fig. 2

perspektivische Ansicht einer erfindungsgemäß ausgebildeten Schrumpfvorrichtung

Fig. 3

prinzipielle Darstellung zur Umkehrströmung und Ausbildung einer Randschale anhand eines Querschnitts durch eine Luftaustauschplatte

Fig. 4

Transport eines Gebindes über eine erfindungsgemäß ausgebildete Vorrichtung zur Heißgasbeaufschlagung im Bodenbereich des Gebindes

Fig. 5

perspektivische Ansicht der Vorrichtung zur Heißgasbeaufschlagung

Fig. 6

Gesamtansicht der Vorrichtung zur Ausbildung einer Randschale

Fig. 7

Aufbau einer erfindungsgemäß ausgebildeten Vorrichtung zur Ausbildung einer Randschale

Fig. 8

Ablaufschema des erfindungsgemäßen Verfahrens zur Herstellung von festen transportfähigen und bedruckbaren Gebinden.

The advantages mentioned above are achieved according to the invention in a surprisingly simple and economical manner. In the following the invention will be explained in more detail with reference to several embodiments. Show it:

Fig. 1

basic structure of a shrinking plant for the production of solid, transportable and printable containers (front view and side view).

Fig. 2

Perspective view of a shrinking device designed according to the invention

Fig. 3

schematic representation of the reverse flow and forming a peripheral shell based on a cross section through an air exchange plate

Fig. 4

Transport of a container via an inventively designed device for Heißgasbeaufschlagung in the bottom region of the container

Fig. 5

Perspective view of the device for hot gas

Fig. 6

Overall view of the device for forming a peripheral shell

Fig. 7

Structure of an inventively designed device for forming a peripheral shell

Fig. 8

Flow chart of the process of the invention for the production of solid transportable and printable containers.

In the upper part of the Fig. 1 the device according to the invention for carrying out a shrinking process is shown in front view. It can be seen the supply and exhaust air system 5, 7 with the container 1, which is arranged on a conveyor belt 2 via a hot air source 3. The hot air applied in reverse flow (see arrow directions in Fig. 3 ) serves to form a pre-stabilizing edge shell 32 in the bottom region of the container.

In the right part of Fig. 1 the container 1 is shown in a system which has a lateral hot air supply 5. The goods (bottles) of the container are conveyed through a conveyor belt 6 in the product running direction through the shrinking 4. As soon as the container 1 with the enveloping film 8 passes in front of the hot air supply 5, there is the risk that the film casing is inflated by the air pressure and thereby threatens to slip. This is prevented by the previously formed edge shell in the region of the bottom of the container, which stabilizes the shape of the container and thus the arrangement of the goods.

In the lower section of the Fig. 1 the shrinking system is shown in side view, wherein in the left part of the system laterally next to the hot air source 3, an exhaust system 7A 7B is indicated. The exhaust air is completely or partially recycled or recycled for the preparation of the hot air, so that in conjunction with the continuous transport heat accumulation can be avoided.

In the right part of the shrinking system, the horizontally acting hot air nozzles 5a 5b are shown. These initiate the all-round shrinkage process on the container enclosed by a wrapping film 8. In the perspective view Fig.2 the two sections (formation of the edge shell, finish shrinkage) are analogous to Fig. 1 shown. Under the conveyor belt 2, the hot air supply is designed as a reverse flow. In the convection region, the net-like structure of the conveyor belt 2 is partially covered by the slides 10, 11. This ensures that only the bottom surface 12 of the transported container or a sub-area is acted upon by the incoming hot air (mitwandernde convection zone).

In section 4 of the system, the hot gases flow at high pressure from the laterally disposed nozzles 5. The flow rate can be further increased and directed over the entire surface constantly against the film 8, since the container on the bottom surface has already been stabilized so that the order the bottle-shaped goods 13 turned over film 8 withstands a high lateral pressure load.

With a final cooling by blowing with cold air (not shown), on the one hand, the plastic is transferred from the plastic region into the elastic region, the maximum stresses in the material increasing and solidifying. On the other hand, the film also shrinks during this cooling, whereby the tensions in the film increase and the container stabilizing holding forces reach the required size. If the environment is too hot, it must be actively cooled because the ambient air temperature is insufficient to solidify.
In connection with in Fig. 3 illustrated partial cross section through an air exchange plate, the principle of the reverse flow is to be explained below:

The container 1 stands on a mesh or lattice-like structure 9, so that the hot air flowing out of the nozzle field 33 via the nozzle 14 has access to a Convection zone 15 of the conveyor belt 6 has. In the convection zone 15, the heat transfer from the hot gas by convection takes place in the bottom surface 12 of the container. After deflection on the surface of the container bottom, the hot gas flows in the direction of arrow via suction openings 16, 17 back into the exhaust air area.

Fig. 4 shows the transport of the container 1 via an inventively according to the principle of the reverse flow formed air exchange plate 29 with convection zone 15 for forming a stabilizing edge shell. The flow direction of the hot supply air 5 is deflected into the exhaust air system 7a, 7b. Not shown is the zonal control of the longitudinal and transverse slides 23, 26. This is necessary in order to achieve the follow-on movement of the convection zone and bottom surface 12 of the container while avoiding heat build-up.

On the left edge of the picture is in partial cross section of Fig. 5 a preferred variant of the invention designed according to the air exchange plate 29 for the discrete hot air in the area of the bottom of the container. The air exchange plate 29 includes sliding ribs 31, on which the net-like conveyor belt 18 is supported. The container 1 contains a plurality of products 19 enveloped by a shrink film 20.

When the transport of the container 1 takes place in the direction of the arrow via the air exchange mat 29, the supply air units 21 and the exhaust air units 22 are controlled by means of a transverse and longitudinal slide arranged in register. This control, also called "zone activation", is in Fig. 6 and Fig. 7 and is described in detail below:

Zone activation can be done manually or automatically. In the example below Fig. 6 the container 1 is conveyed in the direction of the arrow over the reticulated conveyor belt 18 in the sphere of influence of the hot air source 3 (vertical arrow). In the examples shown here, the longitudinal slide 23 is set manually. This can be adjusted via an eccentric adjustment 24 Fig. 7 respectively. In the transverse direction, the slider adjustment is controlled by a zone activation 25, with the help of the cross slide 26 depending on the position of the product or the container 1 on the conveyor belt 18 either activate the supply air or switch off. To control the zone activation a perforated plate as a cross slide 26 and pipes 27 for the hot air supply and a separation housing 28 for the supply and exhaust air are required according to the embodiment.

The above example shows how, in the device according to the invention, the hot gas is conducted to form a stabilizing edge shell on the principle of the reverse flow. The heating surface is represented by an air exchange plate, which includes a special gas guide in which the gas is transferred from an open to a closed loop system. On the heating surface is a field of pits, e.g. in channel or bell shape, wherein in each bell a centrally arranged Zulufteinheit is arranged in the form of a nozzle which has a very small distance from the heating surface. On the side of the bell are one or more exhaust units in the form of suction, whose diameter and number is selected so that the inflowing supply air is sucked off after deflection at the bottom of the container.

In connection with the partial cross section through a sliding plate to Fig. 3 and 5 the reverse flow can be explained on the basis of a basic representation. The container 1 stands on a net or grid-like structure 9 or 10, so that the hot air flowing up from a sink or bell has access to the convection zone 15. In the convection zone 15, the heat transfer from the hot gas by convection takes place in the bottom surface of the container. After deflection on the surface of the container bottom, the hot gas flows via suction openings 16, 17 back into the exhaust air area.

In this arrangement it is ensured that the recesses or in the present case, the bells are always completely or at least at the edge completely covered by the bottom of the container. The reverse flow minimizes the amount of false air. Even with the use of less energy and a low supply air, the formation of a stabilizing edge shell is achieved. This is true even with a parallel relative movement of object and heating surface, as the convection zone mitwandert.

Furthermore, the device according to the invention can be controlled in wide sections of the convection zone. For this purpose, a zone with the required energy requirement is supplied via temperature and flow profiles that the user can specify depending on the path. The energy requirement is calculated or determined empirically based on the material thickness, the material density or on the heat capacities of the film to be heated. Thereafter, the film can be tempered specifically.

1. 1. Umhüllen des Gebindes mit einer Folie
2. 2. Ausbilden des Bodenbereichs mit überlappenden Folienenden
3. 3. Anblasen der Überlappung mit in Umkehrströmung geführter Heißluft bei 200 bis 210°
4. 4. zonal begrenzte Haltezeit bis zum Schmelzen der Folie, Dauer 1 - 2 Sekunden bei Strömungsgeschwindigkeiten von 25 - 35 Meter pro Sekunde
5. 5. Formstabilisierung des Gebindes durch Ausbildung einer Randschale im Bodenbereich
6. 6. vollständiges Schrumpfen der Folie durch seitliches Anblasen mittels Heißluft bei erhöhtem Druck
7. 7. Anblasen mit Kaltluft zur Verfestigung der Folie

A schematic overview of the process sequence during shrinking is shown in the enclosed Fig. 8 , Herein mean:

1. 1. wrapping the container with a foil
2. 2. Forming the bottom area with overlapping foil ends
3. 3. Blowing the overlap with guided in reverse flow hot air at 200 to 210 °
4. 4. zonally limited hold time until the film melts, lasting 1 - 2 seconds at flow rates of 25 - 35 meters per second
5. 5. Shape stabilization of the container by forming a peripheral shell in the bottom area
6. 6. complete shrinkage of the film by blowing side by hot air at elevated pressure
7. 7. Blowing with cold air to solidify the film

By cooling in the last process step, on the one hand, the plastic is transferred from the plastic region into the elastic region, the maximum stresses in the material increasing and solidifying. On the other hand, the film also shrinks during this cooling whereby the tensions in the film increase and the container stabilizing holding forces are greater. If the environment is too hot, it must be actively cooled because the ambient air is insufficient to solidify.

List of Reference Description

1

container

2

conveyor belt

3

Hot air source

4

shrink wrapping machine

5

Hot air supply

1. a) hot air nozzles
2. b) hot air nozzles

6

conveyor belt

7

exhaust system

1. a) exhaust system
2. b) exhaust air system

8th

foil

9

net-like structure

10

pusher

11

pusher

12

floor area

13

bottle-shaped goods

14

jet

15

convection

16

Suction opening ( Figure 3 ) Sliding plate ( Figure 5 )

17

Suction opening ( Figure 3 ) Sliding bridge ( Figure 5 )

18

Mesh-like conveyor belt

19

Products ( Figure 5 ) Influence range of the supply air ( Figure 6 )

20

shrink film

21

supply nozzles

22

exhaust nozzle

23

longitudinal slide

24

Eccentric

25

zone activation

26

Cross slide perforated plate

27

Tube

28

separating housing

29

Air change plate

30

slide plate

31

sliding webs

32

peripheral shell

33

nozzle array

Claims (12)

1. Shrinking process for the production of solid, transportable and printable packages or containers, especially of bottle packages having a height/width ratio of >1 and containing heat-sensitive pourable or flowable products, consisting of enveloping the articles to be packaged with a film such that, on the base surface, an overlapping section of the ends of the film is formed, heating by heat exchange or convection in order to fuse the free ends together in the area of overlap, and a final heating in a shrink oven, the package or container so produced being stabilised by the shrinking process,
   characterized in that
   the inflowing hot air is first zonally confined to the base surface of the package or container, for forming a peripheral shell in the region of the bottoms of the bottles, and that during this process the shape of the package or container is stabilised, i.e. becomes rigid;
   that during the stabilisation, the package or container is continuously transported and, during this process, the hot air, which is directed, in a bundle of discretely distributed gas jets, onto the base area of the package or container, is deflected and returned following a zonally confined heat exchange with the film;
   and that, in the shrink oven, further hot gas is directed laterally against the continuously transported package or container at an increased lateral blow velocity in order to complete the shrinking process.
2. Shrinking process according to any one of the preceding claims, characterised in that the film is welded so as to form a base of the package or container and at the same time is shrunk, whereby a positive-locking shape of the base surface of the package or container is formed.
3. Shrinking process according to any one of the preceding claims, characterised in that the packages or containers are moved on a conveyor device while the welding process is taking place, with the inflowing hot air being sucked off following the heat exchange and being controlled in such a way that the welding is confined to the area of overlap or to a partial area of the base.
4. Shrinking process according to any one of the preceding claims, characterised in that the zonal application of hot air is accomplished by activation of discretely distributed supply air units and drawing-off air units which can be controlled mechanically, hydraulically or electrically.
5. Shrinking process according to any one of the preceding claims, characterised in that in the drawing-off air unit there is created a partial vacuum which is sufficient to accelerate the hot air, coming from the supply air unit, in the area of overlap and to guide it at increased velocity over the film ends that are to be welded together.
6. Shrinking process according to any one of the preceding claims, characterised in that the supply air units and drawing-off air units are controlled by transverse slides or longitudinal slides, with individual units of the discretely distributed supply air units and drawing-off air units being activated in accordance with the zonal application of hot air onto the film ends in the area of overlap.
7. Device for carrying out a shrinking process for producing solid, transportable and printable packages or containers, especially bottle packages having a height/width ratio of >1 and containing heat-sensitive pourable or flowable products, consisting of a packaging machine in which the articles to be packaged are wrapped with a film, heated and then packaged to form a solid package or container in a shrink oven, wherein the packages or containers are moved on a transport belt while being heated, characterized in that said transport belt (6) has a netlike structure (9), wherein in the heating area underneath the transport belt there are arranged discretely distributed supply air and drawing-off air units (21, 22), whereas in the shrinking area hot-air nozzles (5) are directed against the packages or containers, for lateral application of hot air at increased blowing velocity,
   and that underneath the netlike structure the supply air units and drawing-off air units (21, 22) are provided with transverse and longitudinal slides, which are arranged in a register-like manner, to effect a zonal confinement of the hot air stream to the base area of the package or container.
8. Device according to claim 7, characterised in that the supply air and drawing-off air is guided in a closed circuit underneath the transport belt (6).
9. Device according to claim 7 or 8, characterised in that each supply air unit and drawing-off air unit (21, 22) is arranged in a recess provided in a slide plate (16), and that the supply air units and drawing-off air units required for heating the base surface, which are present in the form of discretely distributed recesses in the slide plate (16), are activated by means of transverse and longitudinal slides (23, 26) which are arranged in a register-like manner.
10. Device according to claims 7, 8, 9, characterised in that said recesses are embodied as bells or channels.
11. Device according to any one of the preceding claims, characterised in that the gas flow is embodied as a reverse flow, with the flow velocity of the hot gas being reversed after the heat exchange with the base surface.
12. Device according to any one of the preceding claims, characterised in that the outflow direction or the inflow direction of the supply air units and drawing-off air units (21, 22) are arranged next to one another in a parallel manner.

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