Thermoforming device, packaging machine with a thermoforming device and method for operating the thermoforming device

Description

[0001] The invention relates to a deep-drawing device having the features according to the preamble of claim 1 and a packaging machine for producing filled bags with such a deep-drawing device as well as a method for operating the deep-drawing device.

[0002] In a common design, packaging units are often produced by first thermoforming film. A product is poured into the resulting cavities, which are then sealed with a cover film. This creates a double-layer film strip in which individual portions of the product are separated from each other. These portions are then separated in a cutting station.

[0003] Of course, during the production of such packaging units, it must be ensured that the film of the packaging unit can withstand external stresses so that the packaged product is adequately protected. If it was discovered during the production process of packaging units that the film was torn or partially thinned to such an extent that the film was leaking, the countermeasures used to be to increase the film thickness. The forming process parameters, such as the preheating temperature or preheating time of the film, can also be adjusted. This can prevent defects in the film packaging. However, the use of a thicker film can lead to increased environmental pollution. Furthermore, the necessary adjustments also result in higher production costs.

[0004] A further disadvantage of the packaging machines known from the prior art arises particularly when using water-soluble films. Water-soluble films, such as PVOH films, are well known from the prior art and are particularly useful in the packaging of detergents and cleaning agents, for example, for use in dishwashers or washing machines. The packaging units are placed in the corresponding machine and rinsed with water. As soon as the film dissolves, the detergent is released. The use of an increased film thickness, in turn, causes an increase in the dissolution time of the packaging unit. Furthermore, extremely irregular, non-reproducible dissolution times of the packaging units have been observed.

[0005] Consequently, it is the object of the invention to provide a thermoforming device which enables a process-reliable, environmentally friendly and at the same time cost-effective production of filled film bags.

[0006] This object is achieved by a deep-drawing device having the features of claim 1.

[0007] A further object of the invention is to provide a packaging machine that enables the reliable, environmentally friendly and, at the same time, cost-effective production of filled film bags.

[0008] This further object is achieved by a packaging machine having the features of claim 7.

[0009] A further object of the invention is to provide a method for deep-drawing film for the production of film packaging, which enables a process-reliable, environmentally friendly and at the same time cost-effective production of filled film bags.

[0010] This object of the invention is achieved by a method having the features of claim 8.

[0011] The invention is based on the finding that the irregular dissolution times of water-soluble films are at least largely due to uneven film thickness. Furthermore, it has been determined that the uneven film thickness arises during the deep-drawing process. During deep-drawing, the film is laid over the die. Such dies have complex geometries with different depths and shape radii. This circumstance leads to the film being thinned differently locally within the die after deep-drawing, and thus also having different film thicknesses locally.

[0012] It is known that in order to achieve improved flow behavior of the film, it must be heated before and / or during deep-drawing. Heating plates are used for this purpose, which heat the entire film. In order to not only improve the flow behavior of the film as a whole, but also to counteract partial thinning of the film, the deep-drawing device according to the invention for deep-drawing film comprises an arrangement of several die plates, which can be driven in a circulating path by a conveyor, each die plate having at least one die mold, and at least one mold vacuum device. The mold vacuum device comprises at least one first vacuum source for providing a vacuum, and the at least one first vacuum source is connectable via a first vacuum channel to the at least one die mold of each die plate for providing a vacuum for deep-drawing the film.and with at least one heating plate for heating the film, wherein the heating plate has an upper side facing away from the die plates and a lower side facing the die plate, and with a vertical direction extending from the underside of the heating plate to the upper side of the heating plate, and wherein the heating plate has at least one shape contour corresponding to the die shape on the underside, wherein the shape contour is designed such that a film section of the film lying between the shape contour of the heating plate and the die shape can be heated locally differently.

[0013] The shape of the heating plate makes it possible to apply different heat inputs locally to the film, thereby partially modifying its flow behavior. This allows the heat input to be reduced in the sections of the film subject to increased thinning, and the heat input to be increased in the sections of the film subject to reduced thinning. During deep drawing, the film material flows more from the heated sections of the film, which have a material surplus. In contrast, the material flow from the less heated sections of the film is reduced due to the lower heat input. This allows the material flow of the film to be precisely controlled, and the thinning process to be homogenized. Consequently, the film experiences uniform thinning. Using a film with increased film thickness to prevent material failure is no longer necessary.This allows the packaging units to be produced in an environmentally friendly and cost-effective manner. The targeted and uniform thinning of the films during thermoforming also allows the dissolution time of the films, especially PVOH films, in water to be adjusted reliably and reproducibly.

[0014] It is advantageous for the underside of the heating plate to have a flat base surface, with the mold contour forming a depression extending vertically from the base surface to the top of the heating plate. Preferably, the base surface is located completely below the mold contour in the vertical direction. Thus, the mold contour of the heating plate is at a greater distance from the film than the base surface of the heating plate. This also reduces the heat input from the mold contour to the film compared to the base surface.

[0015] It is advantageous for parts of the mold contour to be designed as free-form surfaces. The mold contour can be configured as a complex geometry, so that the distances within the mold contour to the film vary locally. Thus, the heat input across the entire mold contour to the film section also varies locally. The mold contour has a multitude of different depths relative to the base surface. If parts of the mold contour are designed as free surfaces, these also have a multitude of different depths relative to the base surface. The resulting distances lead to locally different heat inputs to the film and thus to locally different flow behavior of the film.

[0016] Furthermore, the heating plate is designed to be movable up and down vertically via a pressure plate. This allows the heat input to the film to be modified at least globally.

[0017] Particularly preferably, at least one capillary opening is formed on the mold contour of the heating plate, wherein the at least one capillary opening is connected to a first vacuum source and / or a second vacuum source via a second vacuum channel. The capillary opening is preferably designed as a capillary bore. If a vacuum is applied to the mold contour, the film is sucked onto the mold contour of the heating plate and thereby pre-stretched. Particularly preferably, several capillary openings are provided in the mold contour. When the film is sucked onto it, the film comes into contact at least partially with the mold contour. The heat input to the film is increased in the areas in which the film comes into contact with the mold contour of the heating plate.Therefore, in a particularly preferred embodiment of the deep-drawing devices, several capillary holes are provided in the mold contour and arranged relative to one another in such a way that, when a vacuum is applied, the film contacts the mold contour in specific areas where increased flow behavior is required. This can promote locally different heating of the film in the film section between the die shape of the die plate and the mold contour of the heating plate.

[0018] The method according to the invention for deep-drawing film for producing film packaging with a packaging machine according to the invention comprises the following steps: A film is fed to at least one die plate, the film is heated locally differently by the heating plate in the film section between the shape contour of the heating plate and the die shape.

[0019] To heat the film, the heating plate is preferably lowered toward the die plate until a certain distance is reached between the die plate and the heating plate, whereby the distance is adjustable to regulate the heat transfer to the film. By adjusting the distance between the heating plate and the film, the overall heat transfer can be adjusted. The distance between the heating plate and the film can be changed over time, especially during the deep-drawing process.

[0020] It is advantageous that the heating of the film is combined with a targeted pre-stretching of the film. For this purpose, in particular for pre-stretching the film on the mold contour of the heating plate, a vacuum is applied, whereby the film is sucked into the heating plate and adheres to the mold contour. This leads, on the one hand, to the film being stretched upwards towards the heating plate and pre-stretched. On the other hand, the film contacts the mold contour, in particular in the areas of the capillary openings, as a result of which the film is exposed to increased heat transfer in the contact areas. In a particularly preferred embodiment of the deep-drawing device, the capillary bores are arranged on the mold contour in such a way that heat is transferred through direct contact between the film and the mold contour in those areas of the film in which an increased material flow is to take place.

[0021] It is advantageously provided that the film, particularly after pre-stretching, is deep-drawn into the die of the die plate by a vacuum applied to the die. If a vacuum is applied to the die, the vacuum in the mold contour is preferably deactivated at the same time. This has the result that the deep-drawing force acting on the film, which is generated by the vacuum applied to the die, is not counteracted by a force generated by the vacuum on the mold contour. Rather, it can advantageously be provided to apply overpressure to the mold contour so that the film is additionally pressed into the die by a compressive force acting on the film due to the overpressure. The overpressure is preferably variably adjustable. The overpressure corresponds to blown air.

[0022] Several embodiments of the invention are described in more detail below with reference to the drawings. They show: Fig. 1 shows a side view of a packaging machine designed according to the invention with a continuously rotating conveyor and with cyclically moving forming, filling and sealing stations, Fig. 2 shows a perspective view of an embodiment of the heating plate with a forming contour, Fig. 3 shows a partial sectional view of the deep-drawing device with raised heating plate, Fig. 4 shows a partial sectional view of the deep-drawing device with closed heating plate, Fig. 5 shows a partial sectional view of the deep-drawing device with raised heating plate with capillary openings, and Fig. 6 shows a partial sectional view of the deep-drawing device with closed heating plate with capillary openings,

[0023] Fig. 1shows a side view of a section of a packaging machine 1 according to the invention for producing filled bags. For this purpose, the packaging machine 1 comprises a machine frame 8, a forming station 4, a filling station 5, and a sealing station 6. A film 2 is fed to the packaging machine 1 and deep-drawn in the forming station 4, so that cavities are formed in the film 2. In the present embodiment, the film 2 is designed as a film web. It may also be expedient to feed individual film sheets to the packaging machine.

[0024] The cavities are filled with a product in the filling station 5. A cover film 3 is then fed in and sealed onto the films 2 in the sealing station 6, closing the filled cavities. In a cutting station (not shown), the film unit formed in this way is separated into film bags. In the exemplary embodiment, the film 2 and the cover film 3 are water-soluble films, namely PVOH films, between which, for example, a detergent or cleaning agent is packaged. Filled film bags produced in this way are placed in a dishwasher, for example. There, the film material dissolves upon contact with water and releases the detergent it contains. The same applies analogously to the use of such a film bag in a washing machine.

[0025] The packaging machine 1 comprises the stationary machine frame 8 and a preferably continuously driven conveyor 7. The conveyor 7 can be a conveyor belt or the like and, in the preferred embodiment, is formed by articulated and chain-like elements on which a plurality of die plates 9, 9' are mounted. The latter are driven together with the conveyor 7, preferably continuously and in rotation around the machine frame 8. For the actual bag production process, they move on an upper horizontal track according to an arrow 30 and, after appropriate deflection, are then returned in the lower region of the machine frame 8 according to an arrow 31. The film 2, a preferably endless film web, is also preferably fed continuously and placed from above onto the conveyor 7 with the die plates 9, 9'.Between the filling station 5 and the sealing station 6, the cover film 3 is subsequently fed, preferably continuously, and placed from above onto the upper side of the film 2. In the applied state, the film 2 and the cover film 3 are moved synchronously and preferably continuously with the conveyor 7 according to the arrow 30.

[0026] The station for feeding the film 2 and the station for feeding the cover film 3 are stationary relative to the machine frame 8, as are stations (not shown) for applying water to support the sealing process and for perforating or laterally trimming the films. It can also be provided that the stations are at least partially attached to the machine frame 8. In the preferred embodiment of the packaging machine 1, the movement of the conveyor 7 is continuous. In such a embodiment of the packaging machine 1, the processes carried out here also operate continuously. In order to be able to carry out a continuous movement, the forming station 4, the filling station 5 and the sealing station 6 are not stationary relative to the machine frame 8, but are moved in sections synchronously with the conveyor 7 over a certain distance.Meanwhile, the film 2 is deep-drawn in the forming station 4, the product to be packaged is filled into the deep-drawn cavities in the filling station 5, and the cover film 3 is sealed onto the lower film 2 in the area of ​​the sealing ridges of the cavity in the sealing station 6. After each process is completed, the forming station 4, the filling station 5, and the sealing station 6 are cyclically moved back to their starting positions, where a new cycle of the respective process begins.

[0027] As in Fig. 1 As shown, the forming station 4 is formed by a deep-drawing device 12. The deep-drawing device 12 can be designed to accommodate only a single die plate 9, 9' and deep-draw the film 2 therein in one cycle. In the illustrated embodiment, the deep-drawing device 12 is designed to simultaneously accommodate several, here two consecutive, die plates 9, 9'.

[0028] As in the Figures 3 to 6As shown, a single die plate 9, 9' has at least one die mold 10 on its upper side. In a preferred embodiment of the deep-drawing device 12, it may also be expedient to provide a plurality of die molds 10. In the present, preferred exemplary embodiment, a die mold 10 is provided on each die plate 9, wherein the die mold is further divided into four individual cavities 36. In a particularly preferred embodiment, 44 or 48 products are produced on a single die plate 9, 9' in one process run, accordingly 44 or 48 die molds 10 are formed on a die plate 9, 9'. Each die mold 10 can have one or more individual cavities 36. Each die mold 10, preferably each individual cavity 36, is provided with at least one capillary bore 11, preferably a plurality of capillary bores 11.The capillary bores 11 are part of a first vacuum channel 26, via which the die molds 10 are connected to a first vacuum source 21. The capillary bores 11 of a die mold 10 open into a common pressure chamber 29, whereby the capillary bores 11 are fluidly connected to one another. Thus, pressure equalization takes place between the individual capillary bores 11 via the pressure chamber 29. The pressure chamber 29 is also part of the first vacuum channel 26. The first vacuum source 21 generates a vacuum, i.e., a negative pressure, whereby the vacuum of the die mold 10 can be switched on via a valve (not shown in detail), which is functionally arranged in the first vacuum channel 26 between the vacuum source 21 and the die mold 10. By means of the vacuum on the die mold 10, the film 2 is deep-drawn into the die mold 10.The vacuum channel 26 and the first vacuum source 21 are parts of a mold vacuum device 20, which serves to provide a vacuum in the individual cavities 36.

[0029] As in the Figures 2 to 6As shown, the deep-drawing device 12 comprises a heating plate 13. The heating plate 13 serves to heat the film 2 before it is deep-drawn. This promotes the material flow of the film. To heat the film 2, the die plate 9, 9' with the film 2 arranged on it is positioned below the heating plate 13. The heating plate 13 is then lowered until a distance a is set between the heating plate 13 and the film 2. The closer the heating plate 13 is positioned to the film 2, the greater the heat transfer to the film 2. The distance a can be selected to be larger or smaller depending on the required flow behavior of the film 2, whereby the overall heat transfer from the heating plate 13 to the film 2 can be adjusted. It can also be expedient to select a distance a of zero in order to achieve maximum heat transfer to the film 2. The heating plate 13 is moved up and down in the vertical direction 32 via a pressure plate 34.

[0030] In order to adjust the heat transfer from the heating plate 13 to the film 2 locally, the heating plate 13 has a shaped contour 16 ( Fig. 2). The heating plate 13 comprises an upper side 14 facing away from the die plate 9, 9' and a lower side 15 facing the die plate 9, 9'. The mold contour 16 is formed on the lower side 15 of the heating plate 13. During heating of the film 2, the mold contour 16 of the heating plate 13 and the die shape 10 of the die plate 9, 9' are aligned with one another in a vertical direction 32 of the deep-drawing device 12. The vertical direction 32 runs from the lower side 15 of the heating plate 13 to the upper side 14 of the heating plate 13. The vertical direction 32 is preferably directed opposite to the direction of gravity. The mold contour 16 is formed as a recess 19 in the heating plate 13. The shape contour 16 is designed in terms of its geometry such that when the film 2 is heated, the distances measured in the vertical direction 32 within the surface of the shape contour 16 to the film 2 are different.As a result, the heat transfer from the heating plate 13 to the film 2 is also different, which can modify the flow behavior of the film. Consequently, the geometry of the mold contour 16 of the die mold 10 is adapted such that the flow behavior of the film 2 in a film section 17 located between the mold contour 16 and the die mold 10 is favored during deep drawing. The mold contour 16 has an increased distance from the regions of the film section 17 that tend to increased thinning during deep drawing. This reduces the heat transfer in the corresponding regions of the film 2, reduces material flow, and prevents increased thinning. Furthermore, the geometry of the mold contour 16 is designed such that the mold contour 16 has a reduced distance from the regions of the film section 17 that tend to insufficient thinning during deep drawing.This increases the heat transfer to the corresponding areas of film 2, increases the material flow and prevents insufficient thinning.

[0031] As in the Figures 2 to 6As shown, a flat base surface 18 is formed on the underside 15 of the heating plate 13. The recess 19 of the mold contour 16 extends, starting from the base surface 18 in the direction of the top side 14 of the heating plate 13. Thus, the base surface 18 is preferably arranged completely below the mold contour 16 with respect to the vertical direction 32. Parts of the mold contour 16 are designed as free-form surfaces 16, whereby the distances to the film 2 can be adjusted very variably. The mold contour 16, in particular the free-form surfaces of the mold contour 16, have a plurality of different depths t 1 , t 2 with respect to the base surface 18. The mold contour 16 is preferably milled into the heating plate 13. For each matrix mold 10, a separate mold contour 16 adapted to the matrix mold 10 must therefore be created. If the die plates 9, 9' of a packaging machine 1 are changed, the heating plate 13 of the deep-drawing device 12 must also be replaced.In an alternative embodiment of the deep-drawing device 12, it may be expedient to provide a separate mold contour plate that can be attached to the heating plate 13. In such an embodiment, only the mold contour plate would need to be replaced, not the entire heating plate 13.

[0032] Once the film section 17 of the film 2 is locally heated by the mold contour 16 of the heating plate 13, the film 2 can be deep-drawn by applying a vacuum in the die 10 of the die plate 9, 9'. Due to the targeted, local heating of the film section 17 of the film 2, the film section 17 exhibits an optimized, uniform film thickness distribution in the deep-drawn state.

[0033] The Figures 5 and 6show a particularly preferred embodiment of the deep-drawing device 12 according to the invention, which enables pre-stretching of the film 2. For this purpose, at least one capillary opening 35 is provided on the mold contour 16 of the heating plate 13. The at least one capillary opening 35 is connected to a second vacuum source 27 via a second vacuum channel 28. Alternatively, the second vacuum channel 28 can also be connected to the first vacuum source 21 or to both the first vacuum source 21 and the second vacuum source 27. The vacuum sources 21, 27 and the corresponding vacuum channels 26, 28 are shown only schematically in all figures. The second vacuum source 27 and the second vacuum channel 28 are also part of a mold vacuum device 20.

[0034] In the preferred embodiment of the deep-drawing device 12 according to the Figures 5 and 6A plurality of capillary openings 35 are provided on the mold contour 16. Preferably, at least one, in particular a plurality of, capillary openings 35 are provided in each individual cavity 36 of the mold contour 16. The capillary openings 35 are preferably formed as bores. The capillary openings 35 open into a second pressure chamber 37, via which the capillary openings 35 are fluidly connected to one another. Accordingly, pressure equalization between the capillary openings 35 of the mold contour 16 takes place via the second pressure chamber 37. The second pressure chamber 37, like the capillary openings 35 of the mold contour 16, is part of the second vacuum channel 28.

[0035] To pre-stretch the film 2, a vacuum is applied to the mold contour 16 via the second and / or first vacuum source 21, 27, whereby the film section 17 of the film 2 is sucked onto the mold contour 16. The film 2 comes into contact with the mold contour 16, in particular in the area of ​​the capillary openings 35. In these areas, the film 2 directly contacts the heating plate 13, thereby increasing the heat transfer to the film 2. The capillary openings 35 are preferably distributed along the mold contour 16 in such a way that the film comes into contact with the heating plate 13 in those areas where the flow behavior of the film 2 is to be favored. The same also applies to the pre-stretching of the film 2. In particular, the areas that are to exhibit increased flow behavior are to be pre-stretched using the negative pressure of the capillary bores 35. The capillary openings 35 are to be distributed across the mold contour 16 accordingly.

[0036] Once the film section 17 is sufficiently heated and pre-stretched, the vacuum at the mold contour 16 is deactivated, and at the same time, the vacuum in the die 10 is activated. The film 2 is deep-drawn. Particularly preferably, an overpressure can also be applied to the mold contour 16 to promote the deep-drawing of the film 2. The overpressure is preferably variably adjustable. The overpressure corresponds to blown air. A new die plate 9, 9' is then assigned to the deep-drawing device 12, and the deep-drawing process is repeated.

Claims

1. Deep-drawing device for deep drawing a film, comprising an arrangement of multiple die plates (9, 9') which is drivable by a conveyor (7) on a circulating path, wherein each die plate (9, 9') has at least one mould (10), and having at least one moulding-vacuum device (20), wherein the moulding-vacuum device (20) comprises at least one first vacuum source (21) for providing a vacuum, and wherein the at least one first vacuum source (21) can be connected via a first vacuum channel (26) to the at least one mould (10) of each die plate (9, 9') to provide a vacuum for deep drawing the film (2), and having at least one hotplate (13) for heating the film (2), wherein the hotplate (13) has a top side (14) facing away from the die plates (9, 9') and a bottom side (15) facing towards the die plate (9, 9'), and having a vertical direction (32) extending from the bottom side (15) of the hotplate (13) to the top side (14) of the hotplate (13), characterized in that the bottom side (15) of the hotplate (13) has at least one shaping contour (16) corresponding to the mould (10), wherein the shaping contour (16) is designed such that a film portion (17) of the film (2) that lies between the shaping contour (16) of the hotplate (13) and the mould (10) can be locally differently heated.

2. Deep-drawing device according to Claim 1, characterized in that the bottom side (15) of the hotplate (13) has a flat base area (18), wherein the shaping contour (16) forms a depression (19) from the base area (18) in the vertical direction (32) to the top side (14) of the hotplate (13).

3. Deep-drawing device according to Claim 2, characterized in that the base area (18) lies completely underneath the shaping contour (16) with respect to the vertical direction (32).

4. Deep-drawing device according to one of Claims 1 to 3, characterized in that parts of the shaping contour (16) are designed as free-form surfaces (33).

5. Deep-drawing device according to Claim 4, characterized in that the shaping contour (16), in particular the free-form surfaces of the shaping contour (16), has a multiplicity of different depths (t) with respect to the base area (18).

6. Deep-drawing device according to one of Claims 1 to 5, characterized in that the hotplate (13) can be moved up and down in the vertical direction (32) above a pressure plate (34).

7. Deep-drawing device according to one of Claims 1 to 6, characterized in that at least one capillary opening (35) is formed on the shaping contour (16) of the hotplate (13), wherein the at least one capillary opening (35) is connected to a first vacuum source (21) and / or a second vacuum source (27) via a second vacuum channel (28).

8. Packaging machine for producing film packaging, comprising a deep-drawing device (12) according to one of Claims 1 to 7.

9. Method for deep drawing film for producing film packaging with a packaging machine according to Claim 8, wherein a film (2) is fed to at least one die plate (9, 9'), wherein the film (2) is locally differently heated in the film portion (17) between the shaping contour (16) of the hotplate (13) and the mould (10) by the hotplate (13).

10. Method according to Claim 9, characterized in that, to heat the film (2), the hotplate (13) is lowered in the direction towards the die plate (9, 9') until a distance (a) between the die plate (9) and the hotplate (13) is reached, wherein the distance (a) can be adjusted to regulate the transfer of heat to the film (2).

11. Method according to Claim 10, characterized in that, to pre-stretch the film (2), a vacuum is applied to the shaping contour (16) of the hotplate (13), as a result of which the film (2) is drawn in by the hotplate (13) and lies against the shaping contour (16).

12. Method according to one of Claims 9 to 11, characterized in that the film (2), in particular after pre-stretching, is deep drawn into the mould (10) of the die plate (9, 9') by a vacuum that is applied to the mould (10).