PACKAGING MACHINE WITH A COOLED FORMING TOOL

Description

[0001] The present invention relates to a forming tool for forming a packaging material, in particular a mono-plastic film, in a packaging machine. Furthermore, the present invention relates to the packaging machine itself and to a method for forming a material web or for producing a packaging tray.

[0002] Cooled forming tools are known from the prior art, for example in US 3,958,394 A, WO 2017 / 089572 B1, EP 3,390,234 B1, DE 10 2019 204821, and US 2008 / 152772 A1, and are often part of a packaging machine. In these packaging machines, a cavity is thermoformed into a flat web of material, such as a film, which is then filled with the packaged goods, such as food, medical products, or other non-food items. For this process, the material web must be heated with a heating element before thermoforming. Especially with mono-films consisting of a single material, the heating must be rapid, with high energy input, uniform, and within a very narrow temperature range. The formed material web is cooled during or after the forming process.Especially with mono-films, the cooling of the formed material web must be rapid, otherwise dimensionally stable and / or precisely fitting packaging trays cannot be achieved, for example, due to shrinkage. Conventional forming tools do not meet these requirements, or only do so inadequately.

[0003] The object of the present invention was therefore to provide a forming tool and a packaging machine as well as a method for forming a web of material which do not have the disadvantages of the prior art.

[0004] The problem is solved by a forming tool according to claim 1 and a packaging machine according to claim 7.

[0005] The statements made regarding this subject matter of the present invention apply equally to the other subject matter and vice versa. Features of this subject matter of the present invention can be incorporated into other subject matter and vice versa.

[0006] The present invention relates to a forming tool used for forming, in particular deep drawing, a web of material in a packaging machine. During forming, the web of material is preferably stationary, and a format of several packaging cavities is formed into the web simultaneously. For this purpose, the forming tool according to the invention has a format of X x Y forming cavities, but at least one forming cavity, each of which has a die into which the web of material is pressed and / or drawn. In particular, as soon as contact is established between the web of material and the forming cavity, the web of material is cooled.

[0007] The mold trays of a given format can be manufactured from a single piece, for example, by machining a block. Alternatively, a mold tray can consist of several parts, such as a rim and a separate base. The base can be movable, for example, to allow the production of packaging recesses with varying depths. The mold tray, or sections thereof, can be machined or 3D printed. The mold tray preferably features channels, at least in sections, through which a vacuum can be created between the material web and the surface of the mold tray. This vacuum draws the material web towards the mold tray and / or improves the contact between the material web and the mold tray.

[0008] According to the invention, the mold trays are cooled by forced convection; that is, by means of a moving, in particular pumped, coolant, for example a cold liquid, especially cold water or a cold aqueous solution or a liquid gas, or cold air, wherein water or an aqueous solution or a liquid gas is preferred. The coolant should preferably be approved for use in food processing. Preferably, the coolant is circulated in a circuit that includes a pump and a heat sink. The mold trays can be part of a cooling circuit, here the evaporator, which is known, for example, from refrigerators or air conditioners.

[0009] This coolant preferably cools the surface of the mold tray that comes into contact with the material web during forming, such that the temperature of the mold tray does not increase, or only increases negligibly, upon contact with the heated material web. The formed material web, especially the packaging recesses, thus retains the desired deep-drawn shape or pronounced contour. So-called "shrinkage" is at least minimized, which would otherwise lead, for example, to the undesirable rounding of contour edges. Cooling only the frame in which the mold trays are located is insufficient, particularly when processing mono-films. Cooling the mold trays solely by heat conduction, radiation, and / or natural convection and / or convection caused by movement of the entire tool is inadequate.

[0010] The cooling of the contact surface of a mold shell does not have to be uniform, but can vary locally. For example, areas of the molded material web that are particularly prone to shrinkage can be cooled more intensively. This can be achieved, for example, by selectively directing the coolant flow.

[0011] To achieve cooling by convection, for example, a cooling channel is provided in each mold tray through which the coolant is directed. Preferably, each mold tray or die in which a packaging cavity is formed has its own channel, so that the cooling of each mold tray is preferably at least substantially the same and / or independent of the cooling of the other mold trays of the format. Alternatively or additionally, groups of mold trays share a common channel.

[0012] Preferably, each mold cavity or die of the molding tool has a coolant inlet and a coolant outlet. The inlet of each mold cavity is preferably connected to a manifold from which the coolant for the mold cavities is drawn, so that the coolant for all mold cavities has the same supply temperature and the cooling of the mold cavities does not affect each other, or only to a minimal extent.

[0013] Preferably, the channel in each mold shell is provided as close as possible to its contact surface with the material web, so that the cooling of the material web takes place as directly as possible.

[0014] Alternatively or additionally, the side of the mold shell facing away from the material web can be surrounded by a coolant that provides the necessary convection for cooling. For this purpose, a cavity is preferably provided below the mold shells, for example, between the mold shells and the frame and / or between the mold shells and a support plate on which the mold shells are mounted. This cavity is filled with coolant and can have channels that guide the coolant along a specific path. The cavity can also include flow obstructions or mixers to mix the coolant and / or create turbulent flow.

[0015] The mold trays of a format can be cooled identically or differently, with preference being given to all mold trays being cooled and / or maintained at the same temperature or temperature profile within the same unit of time. For example, it may be preferable for mold trays in the outer region of the format to be cooled less than those in the central region.

[0016] According to the invention, the molding tool has a support plate. The mold shells are preferably connected directly or indirectly to this support plate. The support plate can consist of one or more plates, in particular parallel plates, preferably arranged horizontally, with a gap between the plates, the volume of which can be used as a coolant inlet or outlet and / or as a coolant distribution point to the individual mold shells.

[0017] According to the invention, a coolant distribution system and / or coolant supply line to the mold shells is provided in the carrier plate and / or the frame. For this purpose, the carrier plate and / or the frame can have one or more coolant lines. The coolant then flows from the frame and / or the carrier plate to the mold shells and / or away from them. The frame and / or the carrier plate can be at least partially 3D printed to avoid machine-related restrictions regarding the routing of the cooling channels. However, the frame and / or the carrier plate can also be machined, at least in sections.

[0018] Preferably, the mold shells are made of a material, in particular a metal, with a high thermal conductivity coefficient, especially by 3D printing. Aluminum is a preferred material.

[0019] According to a preferred embodiment of the present invention, the molding trays or a portion thereof are provided with a drive mechanism that allows for height adjustment relative to the tool frame and / or on a support plate. The height adjustment, for example of the base of the molding tray, can be used to change the volume of the die, in particular its depth, and thus the depth of the resulting packaging cavity. In this preferred embodiment, the molding tray or a portion thereof, for example its base, is moved to a desired height before production begins and then remains there throughout the entire forming process of the material web. Alternatively or additionally, the height adjustment, for example of the base of the molding tray or of the entire molding tray relative to the tool frame, can be used to change the contact time between the material web and at least one molding tray or a portion thereof.In this embodiment, the mold or a part thereof is moved in the direction of the material web before and / or during molding, in particular raised, and then moves together with the material web, especially downwards, particularly after contact has been established between the material web and the mold or a part thereof, and preferably in such a way that contact between the material web and the mold is maintained. This preferred embodiment of the present invention achieves particularly rapid or intensive cooling of the material web because the material web does not come into contact with the mold only upon reaching its final shape, but rather because the contact time between the material web and the mold is maximized. The material web is preferably formed against the mold by means of a vacuum and reversibly held in contact with it.For further deformation, the mold is then moved downwards, and the material web is preferably further shaped, in particular deep-drawn. The material web is cooled throughout the entire contact time between the material web and the mold.

[0020] Alternatively or additionally, the height adjustment can be designed such that, after the material web has been formed, the mold shell or a part of the mold shell remains in contact with the material web at least temporarily and at least partially, while the molding tool is already opening to release the material web for further transport, for example by moving the mold shell or a part of the mold shell with a drive relative to the frame of the tool and / or on a carrier plate, in particular upwards, and preferably in such a way that the contact between the material web and the mold shell is initially maintained, preferably until the maximum desired stroke of the height adjustment of the mold shell is reached in order to change, in particular to extend, the contact time.This preferred embodiment of the present invention achieves particularly rapid or intensive cooling of the material web because, after reaching its final shape with the mold shell, the material web remains in contact for an additional period of time, thereby maximizing the contact time between the material web and the mold shell. After reaching the maximum desired stroke of the height adjustment of the mold shell, the mold preferably opens further, thereby ending the contact between the material web and the mold shell, as the mold shell is now moved away from the material web, at least until the material web is released for further transport.Alternatively or additionally, after further transport of the material web and preferably after re-closing the forming tool in preparation for forming the next format, the height adjustment can remain in the previously achieved desired or another preferred stroke position in order to virtually pick up the material web to be formed.

[0021] Preferably, a seal is provided between the frame and the outer circumference of the format on mold shells and / or between the frame and the support plate, for example to prevent the escape of coolant or cooling gas.

[0022] Preferably, a coolant supply line and a coolant outlet are routed through the frame.

[0023] In the event that the volume, in particular the drawing depth of the mold shell, is varied by means of insert plates, these preferably have a coolant channel and / or are surrounded by a coolant flow.

[0024] Preferably, at least one temperature sensor is provided on the mold shells to measure their temperature. This measurement can be used, for example, to control the coolant flow or its supply temperature. Alternatively or additionally, the temperature of the coolant in the area of ​​the mold shell or downstream of it can also be measured and, if necessary, used for the aforementioned control.

[0025] Preferably, the material web is a monoplastic film, i.e., a plastic film consisting of at least one layer and / or a single material, or predominantly of a single material, for example, at least 95 wt.% of a single material and / or a mixture of substances from one material group, and preferably considered recyclable and / or moderately or highly recyclable; in contrast to multilayer films or films consisting of a mixture of substances from different material groups, which are considered not recyclable or at most only slightly recyclable. Preferably, the material of the monofilm is 100 wt.% or predominantly, in particular at least 95 wt.%, polypropylene (PP), polyethylene (PE), or polyethylene terephthalate (PET), or a mixture of substances from only one material group, for example, polyolefins, such as PP and PE.

[0026] For example, a monofilm can consist of at least 95 wt% of at least one PP layer bonded to a PE sealing or peel layer. Preferably, the thickness of the monofilm is 200–500 µm, more preferably 290–350 µm. Preferably, the temperature window is 135–137 °C, or the temperature window covers a range of preferably 3 Kelvin. Preferably, the formed monofilm is cooled to 50–120 °C.

[0027] Preferably, 0.2 - 5 seconds are needed to cool the material web to the desired temperature at which further transport is then possible.

[0028] The problem is also solved with a packaging machine according to claim 7.

[0029] The statements made regarding this subject matter of the present invention apply equally to the other subject matter and vice versa. Features of this subject matter of the present invention can be incorporated into other subject matter and vice versa.

[0030] The present invention relates to a packaging machine for producing packaging, in which a substrate web, for example a plastic film or a material web comprising, in particular, a layer of cardboard, paper, or another material other than plastic, is unwound from a supply roll and preferably transported intermittently / in cycles along the packaging machine in a transport plane. In a forming station, this substrate web is then first formed by means of a thermoforming tool to form, for example, a recess and / or a structure, in particular an anti-slip structure, into the substrate web. The forming station generally comprises a lower and an upper tool, which are moved relative to each other for forming and relative to each other for further transport of the substrate web.The lower tool is located below and the upper tool above the transport plane of the base material web. In the packaging machine according to the invention, several packages arranged in a so-called format are typically processed simultaneously and subsequently transported along the packaging machine at the same time. Before and / or during thermoforming, the base material web is heated with a heating element. The base material web is then covered with a packaged product, in particular a food item such as sausage, ham, or cheese, and in a subsequent step, sealed with a top film or top material web in a sealing station, with the top film typically being sealed to the base film web. For this purpose, another heating element is used, which provides the heat energy required for sealing.The completed packaging is then separated by cutting it from the bottom and top material webs, for example, using a cross and longitudinal cutter. The longitudinal and cross cutters can also be provided as contour die-cutters. The top material web is also unwound from a supply roll and can also be deep-drawn, for example, in a top film forming station. Downstream of at least one supply roll, relative to the transport direction of the respective film web, a dancer is preferably located to maintain the tension in the respective material web at least substantially constant. The dancer can be a linear or a rotary dancer.

[0031] Preferably, the heating element that heats the deep-drawn material web is located in and / or upstream of the forming tool(s) of the forming station. The heating element can be rigidly connected to the tool, for example the upper tool, and / or its frame and can, for example, be moved vertically together with it.

[0032] In the forming station, the material web is formed after heating, in particular deep-drawn, and cooled during and / or after forming.

[0033] The problem is also solved by a method for forming a material web according to claim 8.

[0034] The statements made regarding this subject matter of the present invention apply equally to the other subject matter and vice versa. Features of this subject matter of the present invention can be incorporated into other subject matter and vice versa.

[0035] The subject matter of the present invention relates to a method for forming a web of material, for example in a packaging machine, in particular in a so-called "form-fill-seal" packaging machine.

[0036] The material web is preferably a plastic film, in particular a so-called monofilm, i.e., a film that preferably consists of a single material, especially PP, PE, or PET. According to the invention, the material web is heated before it is formed, in particular by deep drawing. This heating is carried out with the heating element described above.

[0037] The method according to the invention ensures that the material web is cooled quickly and in such a way that shrinkage is at least minimized.

[0038] Preferably, the cooled mold shells move along with the material web during its deformation.

[0039] Preferably, cooling is carried out with a liquid coolant, the volume flow of which is particularly preferably controlled.

[0040] Preferably, a packaging tray, in particular made of a monofilm, is produced using the method according to the invention.

[0041] Another preferred object of the present invention is a method for forming a material web, in which the material web is brought into contact with a heating element for heating and is subsequently formed and cooled in a format of mold trays, wherein, after forming the material web, the movement of the frame and the mold tray away from the material web differs.

[0042] The statements made regarding this subject matter of the present invention apply equally to the other subject matter and vice versa. Features of this subject matter of the present invention can be incorporated into other subject matter and vice versa.

[0043] Preferably, the frame of the mold shell precedes the mold shell. This makes it possible, for example, for the contact between the frame of the lower tool and the material web to be broken or eliminated, while the mold shell remains in contact with the material web, thus continuing to be cooled.

[0044] The invention will now be described in more detail below. Figures 1 to 3 These explanations are merely exemplary and do not restrict the general concept of the invention. Figure 1 schematically shows the packaging machine according to the invention. Figures 2 - 3 Each shows an embodiment of the forming tool according to the invention.

[0045] Figure 1Figure 1 shows the packaging machine 1 according to the invention, which has a forming station 2, a filling station 7, and a sealing station 15. The packaging machine can be a so-called thermoformer. A substrate web 8, here a plastic film 8, in particular a monofilm made of PP or PET, is unwound from a supply roll and transported intermittently along the packaging machine according to the invention from right to left. With each cycle, the substrate web 8 is advanced by one format length / feed length. For this purpose, the packaging machine has two transport means 21 (see Figure 5), in this case two endless chains each, which are arranged to the right and left of the substrate web 8. At least one gear is provided for each chain at both the beginning and the end of the packaging machine, around which the respective chain is deflected. At least one of these gears is driven.The gears in the infeed and / or outfeed sections can be connected to each other, preferably by a rigid shaft. Each transport element has a plurality of clamping elements / grippers that grip the sub-material web 8 in the infeed section and transmit the movement of the transport element to the sub-material web 8. In the outfeed section of the packaging machine, the clamping connection between the transport element and the sub-material web 8 is released. A heating element is provided downstream of the infeed section and upstream of the forming station 2, which heats the sub-material web 8, particularly when it is stationary. The forming station 2 has a lower die 4 and an upper die 3. The lower die 4 can be moved up and down, as indicated by the double arrow, moving upwards towards the sub-material web 8 for forming and downwards for further transport of the sub-material web 8.In the raised position, the substrate web is preferably clamped between the two tools 3 and 4. The substrate tool 4 can be arranged on a lifting table 5, which, as symbolized by the double arrow, can be vertically adjustable to generate the movement of the substrate tool described above. Further along the packaging machine, the packaging recesses 6 formed in the substrate web, or the substrate web 8 itself, are then filled with the product 16 in the filling station 7. In the subsequent sealing station 15, which also consists of an upper tool 12 and an optionally vertically adjustable lower tool 11, a top film 14 is bonded to the substrate web 8 by sealing. This transfers the movement of the substrate web 8 to the top film web 14.In the sealing station, the upper tool and / or optionally the lower tool are lowered and raised before and after each film transport. The upper film 14 can also be guided in transport devices or transported by conveyor chains, whereby these transport devices then only extend in front of the sealing station and, if necessary, upstream. Otherwise, the descriptions given for the transport devices of the lower film apply. The upper film can also be heated with a heating element and / or deep-drawn. For sealing, a sealing frame, for example, is provided as the lower tool 11, which has an opening for each packaging cavity into which the packaging cavity, if present, is immersed during sealing, i.e., during the upward movement of the lower sealing tool. For sealing, the upper and lower material webs are pressed together between the upper and lower tools 12, 11 and bond under the influence of heat and pressure.After sealing, the tools 11, 12 are moved vertically apart again. A dancer, for example a rotary dancer, can be provided between the supply roll of the top material web 14 and the sealing tool, which keeps the material web 14 at a constant tension as much as possible. Those skilled in the art understand that a dancer is also preferably provided in the area of ​​the bottom material web 8, preferably downstream of the supply roll. Preferably, the dancer is a linear dancer. Before and / or during sealing the top material web to the bottom material web, gas exchange preferably takes place in each packaging cavity. For this purpose, the air present in the packaging cavity is first partially extracted and / or replaced by an exchange gas.For this purpose, holes can be made in the sub-material web 8 in the area of ​​the transport chains within each format. Air between the material webs 8, 14 is extracted through these holes and / or exchange gas is injected. Further along the packaging machine, the finished packages are separated, for example, by the cross cutter 18 and the longitudinal cutter 17. In this case, the cross cutter 18 can also be raised and lowered by a lifting device 9. According to another embodiment, the sealing tool 11, 12 has a punch that cuts the sub- and top material webs before, during, and / or after sealing. Preferably, several packages are produced simultaneously in each cycle, arranged as a matrix in a so-called format.Preferably, the heating element 19 comprises means by which the contact between the material web and the surface of the heating element can be established or improved. Such means are, for example, vacuum nozzles that draw the material web towards the surface of the heating element.

[0046] Figure 2Figure 1 shows a first embodiment of the forming tool 3, 4 of the forming station 2, in this case the lower tool 4 and the upper tool 3. At least the lower tool 4 is designed to be raised and lowered, as described above. The lower tool 4 has a frame 33 within which a set of forming trays 35 is located. Each forming tray forms a packaging recess 6 in the material web 8. Each forming tray can be made in one piece or in multiple pieces. For forming, the material web 8 is heated downstream of a heating element 19 and is preferably clamped between the two tools 3, 4. The material web 8 is preferably a mono-plastic film. Preferably, each forming tray has vacuum channels (not shown) by means of which the heated material web is formed into the forming tray.Alternatively or additionally, a punch (not shown) can be provided to form the material web 8. In this case, the tool optionally has a carrier plate 29 to which the mold shells are attached, for example, by screwing them on. The carrier plate's vertical position relative to the frame can be adjusted by means of the drive 34, for example, to produce different packaging cavity volumes with one tool. In this case, the carrier plate 29 is made up of two spaced-apart plates. The volume between the plates is connected to a coolant supply 31, in this case cooling water, which is designed, for example, as a hose or is telescopic. The volume between the plates serves as a supply and discharge point for the coolant to and from the individual mold shells. A bulkhead element 32 can be located between the plates of the carrier plate 29, or at its edge or surface.A seal 36 is provided to guide the coolant along a specific path and / or to prevent unwanted coolant leakage into the tool. The coolant flow is preferably designed such that all mold shells are supplied with coolant at the inlet of the same temperature. The mold shells are therefore preferably connected in parallel with respect to the coolant flow, particularly the inlet. Preferably, the mold shell 35 itself has a channel 31, 31a, 31b through which the coolant flows and cools it. In the present case, the channel 31, 31a, 31b is a bore. However, the mold shell with the channel 31, 31a, 31b can also be manufactured by 3D printing. The mold shell is preferably made of metal, in particular aluminum, or a highly thermally conductive plastic. The convection required for cooling is generated by the flow of the coolant in the channels 31, 31a, 31b.The coolant is preferably circulated in a loop via a heat sink. The loop includes at least one pump.

[0047] Figure 3 shows an alternative or a supplement to the embodiment according to Figure 2 In the present case, a cavity volume is provided between the mold shell or the format of mold shells and the frame or a support plate. This volume can be varied by a vertical movement of the mold shell. As shown, the volume 28 is flooded with a coolant that flows into the volume via the inlet 27 and out of the volume via the outlet. Cooling of the mold shell 35 occurs via convection. For further details, please refer to the descriptions in [reference to relevant section]. Figure 2 referred. Reference symbol list:

[0048] 1 Packaging machine 2 Forming station, thermoforming station 3 Upper tool of the thermoforming station 4 Lower tool of the thermoforming station 5 Lifting table, carrier of a tool of the sealing, thermoforming station and / or the cutting device 6 Packaging trough 7 Filling station, insertion station 8 Material web, sub-material web 9 Lifting device, lift 10 Central area of ​​the heating element 11 Lower tool of the sealing station 12 Upper tool of the sealing station 13 Lower part of the material web clamping device 14 Top material web, lid material web 15 Sealing station 16 Packaging item 17 Longitudinal cutter 18 Transverse cutter 19 Heating element 20 Direction of travel 26 Coolant drain 27 Coolant inlet 28 Cavity, in particular between the frame and the forming shell 29 Carrier plate 30 Forming tool; 31, 31a, 31b Channel, cooling supply line, cooling water supply 32 Bulkhead, sealing plug, seal 33 Frame 34 Drive, height adjustment 35 Moving part, molded shell 36 Seal

Claims

1. Forming tool (3, 4) of a packaging machine, comprising a frame (33) and a set of forming cavities (35), in each of which a material web is formed and which are cooled, wherein the forming cavities (35) are each cooled by convection, characterized in that it comprises a carrier plate (29), and in that a coolant distribution or coolant supply line to the forming cavities is provided in the carrier plate (29) and / or in the frame.

2. Forming tool according to claim 1, characterized in that a coolant line (31b) is provided in the forming cavity (35).

3. Forming tool according to claim 1 or 2, characterized in that the side of the forming cavity (35) facing away from the material web is flushed by a coolant.

4. Forming tool according to one of the preceding claims, characterized in that a cavity (28) is provided below the forming cavities, through which a coolant flows, and / or in that the forming cavities are printed, and / or in that the forming cavities or parts of the forming cavity are height-adjustable by means of a drive (34).

5. Forming tool according to one of the preceding claims, characterized in that a seal is provided between the frame and the outer periphery of the set of forming cavities and / or between the frame and the carrier plate.

6. Forming tool according to one of the preceding claims, characterized in that a cooling-liquid supply line (27) and a cooling-liquid discharge line (26) are routed through the frame.

7. Packaging machine (1) comprising a forming station (2), a filling station (7), a sealing station and a longitudinal and / or transverse cutter (17, 18), wherein a material web (8) is transportable along a direction of travel (20), in particular intermittently, characterized in that it comprises a forming tool according to one of the preceding claims.

8. Method for forming a material web, wherein the material web is brought into contact with a heating element for heating and is subsequently formed and cooled in a set of forming cavities (35), characterized in that the forming cavities of a forming tool according to one of claims 1 to 6 are cooled by convection.

9. Method according to claim 8, wherein a material web is a mono-film.

10. Method according to claim 8 or 9, characterized in that the cooled forming cavities move together with the material web during forming.

11. Method according to one of claims 8 to 10, characterized in that the cooling is effected with a liquid coolant whose volumetric flow rate is regulated.

12. Method according to one of claims 8 to 11, for producing a packaging tray, in particular from a mono-film.

13. Method according to one of claims 8 to 12, characterized in that, after forming of the material web, the movement of the frame and the movement of the forming cavity away from the material web differ from one another.

14. Method according to claim 13, characterized in that the frame leads ahead of the forming cavity.