Method and station for coating a packaging tray

Abstract

A method for coating a packaging tray (5) with a coating film (7) using a tray coating station (4), wherein the tray coating station (4) comprises a packaging tray holder (13) for receiving the packaging tray (5), a tool upper part (11) and a tool lower part (12), wherein a movable dome (26) is attached to the tool upper part (11) and a press insert (39) is attached to the tool lower part (12), comprising the following steps: clamping an outer clamping area (22) of the coating film (7) between the tool upper part (11) and the tool lower part (12), clamping an inner clamping area (29) of the coating film (7) to the packaging tray (5) by means of the dome (26), wherein the inner clamping area (29) is located between the outer clamping area (22), forming an overhanging area (28) of the coating film (7) onto the packaging tray (5),that the protruding area (28) curves under an edge (15) of the packaging tray (5), wherein the protruding area (28) is located between the outer clamping area (22) and the inner clamping area (29), pressing the curved protruding area (28) against the edge (15) of the packaging tray (5) by means of the pressing insert (39) such that a double fold (37) is formed, and separating the coating film (7) in a separation area (31), wherein the separation area (31) is located between the double fold (37) and the outer clamping area (22).

Description

[0001] The present invention relates to a method for coating a packaging tray with a coating film using a tray coating station, a tray coating station or a packaging machine comprising a tray coating station. State of the art

[0002] Methods and devices for coating packaging trays with a film are known from the prior art. Typically, the film is sealed to the packaging tray in a material-bonded manner.

[0003] The disadvantage of these applications is that the film is irreversibly bonded to the packaging tray after coating. This is particularly problematic if the film needs to be separated from the packaging tray again, for example, to recycle the tray. This is not possible with a packaging tray coated using a conventional method. Task

[0004] Based on the known state of the art, the technical problem to be solved is to specify a method and / or a device that enables the simple and reliable coating of a packaging tray with a film. Ideally, the film should be easily removable from the packaging tray after coating, in order to at least recycle the packaging tray. Solution

[0005] This problem is solved according to the invention by a method for coating a packaging tray with a coating film using a tray coating station according to claim 1, a tray coating station for coating a packaging tray with a coating film according to claim 11 or a packaging machine, preferably a tray sealing machine, comprising a tray coating station for coating a packaging tray with a coating film according to claim 15.

[0006] Advantageous embodiments of the invention are covered in the dependent claims.

[0007] One aspect of the invention relates to a method for coating a packaging tray with a coating film using a tray coating station. The tray coating station comprises a packaging tray holder for receiving the packaging tray, a tool upper part, and a tool lower part. A movable dome is attached to the tool upper part. A press insert is attached to the tool lower part. The method comprises the following steps: Clamping an outer clamping area of ​​the coating film between the upper and lower tool parts, clamping an inner clamping area of ​​the coating film to the packaging tray by means of the dome, wherein the inner clamping area is located within the outer clamping area, forming an overhanging area of ​​the coating film onto the packaging tray such that the overhanging area curves under an edge of the packaging tray, wherein the overhanging area is located between the outer clamping area and the inner clamping area, pressing the curved overhanging area against the edge of the packaging tray by means of the press insert such that a double fold is formed, and separating the coating film in a separation area, wherein the separation area is located between the double fold and the outer clamping area.

[0008] The process offers the possibility of reversibly bonding the coating film and the packaging tray. This is particularly advantageous if the coating film needs to be separated from the packaging tray again, for example, to recycle the packaging tray and / or the coating film.

[0009] The packaging tray can be flat and have a circumferential rim. Optionally, the packaging tray can have a contour, in particular a recess, with the circumferential rim, at least in sections. The rim can have a first side and a second side, in particular wherein the second side is opposite the first side. The second side can have an inner and an outer section, in particular wherein the inner section is located between the outer section. The packaging tray receptacle can contact the inner section of the rim of the packaging tray and optionally an intermediate section of the packaging tray to receive the packaging tray. The packaging tray receptacle can be configured to not contact the outer section of the rim of the packaging tray.

[0010] The outer clamping area and / or the inner clamping area can be completely enclosed. Optionally, multiple clamping areas, in particular opposing clamping areas, can be provided.

[0011] Clamping the coating film between the upper and lower tool parts can be understood spatially, meaning it can be either direct or indirect. The outer clamping area can be clamped directly via the upper tool part, in particular a clamping surface, and the lower tool part, in particular a clamping surface. Optionally, the outer clamping area can be clamped indirectly to the upper tool part via a clamping frame, in particular a clamping frame surface. The clamping frame can be movably mounted on the upper tool part. For this purpose, the clamping frame can have at least one drive, in particular a pneumatic one. The drive can be mounted between the upper tool part and the clamping frame, in particular outside the area where the coating film is arranged.The clamping frame can be moved towards the upper part of the tool, so that the outer clamping area of ​​the coating film is clamped between them. Depending on the coating film, particularly its thickness, and / or the clamping force required to clamp the coating film, the clamping frame can be moved to varying distances towards the upper part of the tool. The clamping force can be generated between the upper part of the tool and the clamping frame. A gap can exist between the clamping frame and the upper part of the tool, while the outer clamping area of ​​the coating film is clamped between the upper part of the tool and the clamping frame. The clamping frame can, for example, be plate-shaped. The clamping frame can be spatially arranged between the upper part of the tool and the lower part of the tool. The upper part of the tool and the clamping frame can be moved together towards the lower part of the tool, in particular by being pressed against it.Optionally, the lower tool part can be moved towards the upper tool part, particularly the clamping frame, and especially pressed against it. This closes the gap between the clamping frame and the upper tool part. The clamping force of the coating film arranged between the upper tool part and the clamping frame can be increased. The clamping force can be generated between the upper and lower tool parts. Therefore, to close the tray coating station, the upper tool part can be moved towards the lower tool part, and especially pressed against it, or vice versa. Optionally, the lower tool part can be moved towards the clamping frame, and especially pressed against it.Optionally, the upper part of the tool, together with the clamping frame and the clamped outer clamping area, can be moved relative to the lower part of the tool, especially in the direction of the lower part of the tool, and in particular pressed against it.

[0012] The dome can be moved towards the lower part of the tool or the packaging tray receptacle to clamp the inner clamping area. To move the dome, it can be driven by a drive device, in particular an electric, pneumatic, or hydraulic one. The dome, in particular a dome clamping surface, can be pressed against the packaging tray, in particular the first side of the edge of the packaging tray, at the packaging tray receptacle to clamp the inner clamping area.

[0013] The protruding area can be located between the outer and inner clamping areas. To bend the protruding area, it can be drawn under the edge of the packaging tray, particularly the second side of the edge, especially its outer section, using a suction and / or blowing device, or pressed with compressed air. The protruding area can be bent under the edge, particularly the outer section of the edge. Before bending the protruding area, a first distance of the dome clamping surface with respect to the base of the lower mold part can be greater than a second distance of the upper mold clamping surface with respect to the base of the lower mold part, particularly in a side view. This allows the protruding area to be easily bent under the edge of the packaging tray.The upper and / or lower tool part can each have at least one opening for introducing air into and expelling it from the closed shell coating station. Before curving, the protruding area can be heated by the heated dome to such an extent that it becomes ductile.

[0014] The double fold can be formed on the outer section of the rim. To form the double fold, the curved overhang can be pressed against the packaging tray using the press insert, in particular a press insert surface. For this purpose, the press insert can be mounted, for example, on the lower part of the tool or the packaging tray holder and moved towards the rim of the packaging tray. The press insert surface can be as large as or smaller than the outer section, in particular its area, of the second side of the rim. The press insert, in particular the press insert surface, can be heated by a heating device, in particular an electric one. The temperature of the press insert can depend on the coating film, in particular its material and / or its thickness. The temperature of the press insert can be lower than the melting point of the coating film.The temperature of the press insert can be high enough to allow the coating film to stretch. The temperature of the press insert can be greater than 80 °C, preferably greater than 100 °C, preferably greater than 120 °C. The temperature of the press insert can be less than 250 °C, in particular less than 200 °C, preferably less than 180 °C. While the double fold is being formed, air can be blown into the tray coating station through the opening in the upper part of the tool and / or through an opening in the dome. Optionally, air can be drawn out of the tray coating station through the opening in the lower part of the tool. This presses the coating film against the packaging tray to prevent it from detaching from the tray.

[0015] Preferably, the double fold is positively connected to the packaging tray, and in particular, not materially bonded. This allows the packaging tray and the coating film to be completely separated again. This can be particularly advantageous for recycling the packaging tray and / or the coating film. By avoiding a material bond, e.g., by melting the packaging tray and / or the coating film or by bonding the packaging tray and the coating film with an adhesive, the process and / or the design of the tray coating station is ideally simplified. A heating device and the energy required to seal the coating film to the packaging tray can be dispensed with. A unit for applying the adhesive can also be omitted.Ideally, the installation space can be reduced, maintenance costs lowered and / or operating and manufacturing costs reduced.

[0016] Preferably, the packaging tray comprises fibrous material, in particular paper or cardboard. This allows the packaging tray to be manufactured in an environmentally friendly manner and / or be recyclable. In principle, the packaging tray and / or the coating film can comprise recyclable material.

[0017] Preferably, the coating film is a mono-film, in particular consisting of amorphous polyethylene terephthalate (APET). This improves the recyclability of the coating film. Optionally, the durability of the coating film can be improved and / or its weight reduced. Ideally, manufacturing costs for coating the packaging tray can be reduced. Optionally, the coating film can comprise amorphous polyethylene terephthalate (APET). The coating film can comprise plastic. The thickness of the coating film can be less than 150 µm, preferably less than 100 µm, and particularly less than 90 µm, especially in its unformed state. The thickness of the coating film can be greater than 60 µm, preferably greater than 70 µm, and particularly greater than 80 µm, especially in its unformed state. The thickness of the coating film can be constant, especially in its unformed state.Optionally, the coating film can consist of several layers. The layers can be the same or different.

[0018] Preferably, the inner clamping area is clamped to the first side of the rim, and the double fold is formed on the second side of the rim, which faces the first. This allows the coating film to be attached to the packaging tray easily and reliably. The first side of the rim can face the upper part of the tool, in particular the dome, especially the dome clamping surface. The second side of the rim can face the lower part of the tool, in particular the packaging tray receptacle.

[0019] Preferably, the double fold comprises a first layer and a second layer, wherein the first layer rests against the second side of the edge of the packaging tray and the second layer rests against the first layer. In particular, the first layer can be bonded to the second layer. This allows for a secure attachment of the coating film to the packaging tray, especially in contrast to a simple fold, thus enabling a reliable coating. A bonded connection between the first and second layers of the double fold is not necessary to attach the coating film to the packaging tray. However, a bonded connection between the first and second layers allows the double fold and the coating to be made particularly stable and secure.To create the metallurgical bond, the second layer can be heated, particularly by the heat from the heated dome and / or upon contact with the heated press insert, to such an extent that it melts, at least partially. The molten second layer can then be metallurgically bonded to the first layer by pressing it against the first. For this purpose, the heated press insert can be heated to a temperature above the melting point of the coating film. The temperature of the press insert can be at least as high as the melting point.

[0020] The size of the first layer and / or the second layer can depend on the edge of the packaging tray, in particular the outer section of the second side of the edge, and / or the press insert, in particular the press insert surface, and / or the method of separating the coating film. The first layer and the second layer, in particular their areas, can be substantially the same size. Optionally, the second layer, in particular after separation, can be smaller than the first layer. The second layer can, in particular when separated with a knife, completely cover the first layer. In particular when separated without a knife, the second layer can partially cover the first layer.

[0021] Preferably, the coating film is separated while the inner clamping area and the packaging tray are clamped, and while the double fold and the packaging tray are clamped. This allows for safe and precise separation. It prevents the double fold from being damaged by forces acting during separation or even the coating film from being detached from the packaging tray.

[0022] Preferably, the coating film is cut, particularly with a knife, or torn, particularly by means of compressed air and / or tensile force. This allows the coating film to be separated easily and reliably. The coating film can be cut, particularly in the separation zone, upon contact with the knife. For this purpose, the coating film, particularly the separation zone, can be moved relative to the knife, or vice versa. For example, the knife can be fixed to the lower part of the tool. The packaging tray holder can be movably mounted on the lower part of the tool, particularly via at least one (compression) spring connected to both the lower part of the tool and the packaging tray holder. The packaging tray holder, together with the clamped coating film, can be moved towards the lower part of the tool and the knife. As soon as the knife contacts the coating film, it can be separated.Optionally, the blade can be movably mounted on the lower part of the tool, in particular the packaging tray holder. To move the blade, it can be driven by a drive unit, in particular an electric, pneumatic, or hydraulic one. The blade can be moved towards the upper part of the tool to separate the coating film. The blade can be positioned spatially outside the packaging tray holder, in particular the press insert, in particular such that the blade can move outside the packaging tray holder, in particular the press insert. In particular, when the blade is moved towards the upper part of the tool, it can move past the edge of the packaging tray. This ensures that the coating film is separated in the cutting area.

[0023] Preferably, the tensile stress in the separation zone is increased to at least the tensile strength of the coating film in order to separate the coating film in the separation zone. This allows the coating film to be separated easily and reliably, in particular torn. The tensile stress can be generated by means of the suction and / or blowing device, in particular by drawing air out of or blowing it into the closed tray coating station. When the tensile stress of the coating film is at least equal to its tensile strength, it can tear. In the context of the invention, the tensile strength of the coating film can be its tear strength. It can indicate the maximum mechanical tensile stress with which the coating film can be subjected before it tears.The tensile stress required to separate the coating film can depend on the temperature of the press insert and / or the heated dome described below. By heating the coating film as described below, its tensile strength can be locally reduced. Preferably, the heating can be carried out using the heated press insert and / or a heated dome and / or outer dome such that the separation area of ​​the coating film has a temperature gradient that increases towards the inner clamping area and / or curved overhang area and / or double fold. The temperature gradient can reduce the tensile strength of the heated separation area, particularly compared to a cold state (i.e., at room temperature), at least section by section, especially at the warmest section, by 4–15 N / mm². For example, the tensile strength of the coating film in a cold state can be approximately 20 N / mm².For example, the warmest section of the coating film can be heated to a temperature at which the tensile strength is only approximately 10 N / mm² to 16 N / mm². The temperature at the warmest section of the separation zone can be equal to or less than the temperature of the press insert, the dome, and / or the outer dome. The temperature gradient at the separation zone can be less than 90 °C, particularly less than 70 °C. The temperature gradient at the separation zone can be greater than 40 °C, particularly greater than 50 °C. Preferably, the coating film can be separated at the warmest section. The warmest section can be adjacent, particularly directly, to the double fold, particularly its second layer.

[0024] Preferably, the dome, the packaging tray holder, and the press insert, particularly together with the clamped coating film, are moved relative to the lower part of the tool, or vice versa, to increase the tensile stress in the separation area. This has the advantage that no additional component is required to tension the coating film. The dome, the packaging tray holder, and the press insert can therefore each perform a dual function: on the one hand, clamping the inner clamping area of ​​the coating film to the packaging tray, holding the packaging tray, or pressing the double fold; and on the other hand, generating or increasing the tensile stress in the separation area of ​​the coating film. The drive device of the dome can be designed to actively move the dome and passively move the packaging tray holder and the press insert.This means that when the dome moves, the packaging tray holder and the press insert can move along with it without an additional drive. This allows for a smaller installation space, reduced maintenance, and lower costs for the tray coating station and the process. Alternatively or additionally, the packaging tray holder can be moved relative to the lower tool part via a drive, particularly an electric, pneumatic, or hydraulic one. Relative movement is particularly useful when the inner clamping area and the packaging tray are clamped, and when the double fold and the packaging tray are clamped. If the coating film is to be stretched but not torn, the relative movement must be limited to a maximum extent that the tensile stress of the coating film does not increase to its tensile strength.Especially when the coating film is to be cut with a knife, it can be advantageous to tension the coating film before and during cutting. This can enable a particularly precise cut. If the coating film is to be torn, the relative movement should be limited to at least the point where the tensile stress of the coating film is increased to its tensile strength. The degree of relative movement required for tensioning and / or tearing can depend on the deformability and / or tear strength of the coating film. The relative movement can be limited by a stop. In the simplest case, the lower or upper part of the tool can limit the movement.

[0025] Preferably, particularly after clamping the outer clamping area, a section of the coating film between the outer clamping area and an inner surface of the dome, which is preferably heated, is drawn in or pressed with compressed air to stretch the coating film. This allows the coating film to be adapted to the size of the packaging tray. The coating film can be drawn / pressed against the inner surface by means of the suction and / or blowing device. For this purpose, the dome can have an opening for the introduction or exhaust of air. The section of the coating film between the outer clamping area can comprise the overhang, the inner clamping area, an inner area between the inner clamping area, and optionally the separation area. The dome can have the dome clamping surface and an inner surface arranged between them. The dome clamping surface can be completely closed or have recesses. The dome can be flat.For example, the dome can have a flat clamping surface and a flat inner surface. Or the dome can have at least a concave shape. For example, the dome can have a flat clamping surface and a concave inner surface. The dome, in particular the clamping surface and the inner surface, can be heated by means of a heating device, especially an electric one. This can heat the coating film. This can improve, in particular increase, the extensibility of the coating film. The temperature of the dome can depend on the coating film, in particular its material and / or its thickness. The temperature of the dome can be lower than the melting point of the coating film. The temperature of the dome can be high enough that the coating film is extensible. The temperature of the dome can be, for example, greater than 50 °C, preferably greater than 70 °C, preferably greater than 100 °C.The temperature of the dome can be less than 160 °C, preferably less than 140 °C, and preferably less than 120 °C. The tray coating station can be evacuated during the stretching of the coating film. Preferably, the tray coating station comprises an outer dome, which is particularly heated. Specifically, after the outer clamping area is clamped, the area of ​​the coating film between the outer clamping area and the outer dome is drawn against it or pressed against it using compressed air to stretch the coating film. The coating film can thus be drawn / pressed against a larger contact area formed by the dome and the outer dome. This allows the coating film to be adapted particularly well to the size of the packaging tray. The dome can be located between the outer dome and the outer dome.During the stretching of the coating film, the dome clamping surface and an outer dome surface that can contact the coating film can lie, preferably almost, on the same plane. This allows the coating film to be stretched easily and evenly, particularly without damaging it. The outer dome, especially the outer dome surface, can be heated by means of the dome heating device. Optionally, the dome and the outer dome can be heated by separate heating devices. The outer dome can be heated to essentially the same temperature as the dome.

[0026] Preferably, after or during the clamping of the inner clamping area, the inner area of ​​the coating film is formed against the packaging tray, particularly the first side of the packaging tray. This allows the heated, stretched coating film to be easily shaped to the form of the packaging tray. The inner area can be drawn against the packaging tray, particularly by means of a suction and / or blowing device, or pressed against it using compressed air. Upon contact with the packaging tray, the inner area of ​​the coating film can cool and harden according to the contour of the packaging tray. To accelerate cooling, the packaging tray holder can be cooled, particularly to less than 25 °C, preferably to less than 20 °C, and preferably to less than 10 °C.

[0027] Another aspect of the invention relates to a tray coating station for coating a packaging tray with a coating film, wherein the tray coating station comprises: a tool upper part and a tool lower part for clamping an outer clamping area of ​​the coating film, a packaging tray holder for receiving the packaging tray, a dome for clamping an inner clamping area of ​​the coating film to the packaging tray, wherein the dome is movably arranged on the tool upper part, wherein the inner clamping area is located within the outer clamping area, a suction and / or blowing device for forming an overhang of the coating film onto the packaging tray in such a way that the overhang curves under an edge of the packaging tray, wherein the overhang is located between the outer clamping area and the inner clamping area.and a heated press insert for pressing the curved overhang area against the edge of the packaging tray in such a way that a double fold is formed, wherein the press insert is movable relative to the packaging tray receptacle, and a release agent for separating the coating film in a separation area, wherein the separation area is located between the double fold and the outer clamping area.

[0028] Preferably, the release agent is a knife, and / or the release agent is formed by the suction and / or blowing device, wherein the suction and / or blowing device is designed to increase a tensile stress of the separation area, in particular to at least a tensile strength of the coating film, and / or the release agent is formed by the dome, the packaging tray holder and the press insert, wherein the dome, the packaging tray holder and the press insert are movable relative to the lower part of the tool in order to increase the tensile stress of the separation area, in particular to at least the tensile strength.

[0029] Preferably, the upper part of the tool comprises a clamping frame, which is movable relative to it, wherein the outer clamping area can be clamped indirectly between the upper part of the tool and the lower part of the tool via the clamping frame.

[0030] Preferably, the press insert is movably mounted on the lower part of the tool, in particular the packaging tray holder, and / or the packaging tray holder is movably mounted on the lower part of the tool.

[0031] Another aspect of the invention relates to a packaging machine, preferably a tray sealing machine, comprising a tray coating station configured to carry out the method in at least one of the variants disclosed in this patent. The tray coating station can be in at least one of the variants disclosed in this patent.

[0032] The features or explanations described for one of the aspects (process, tray coating station or packaging machine) can be transferred to and combined with the other aspects, either individually or in combination.

[0033] The invention is explained below using exemplary embodiments. The following are shown: Figure 1 a schematic side view of a packaging machine according to a first embodiment; Figure 2 a schematic side view of a shell coating station according to a first embodiment in a first operating state; Figure 3 a schematic, partial side view of a packaging tray; Figure 4 a schematic side view of a shell coating station according to the first embodiment in a second operating state; Figure 5 a schematic side view of a shell coating station according to the first embodiment for a third operating state; Figure 6 a schematic side view of a shell coating station according to the first embodiment for a fourth operating state; Figure 7a schematic side view of a shell coating station according to the first embodiment for a fifth operating state; Figure 8 a schematic side view of a shell coating station according to the first embodiment for a sixth operating state; Figure 9 a schematic side view of a shell coating station according to the first embodiment for a seventh operating state; Figure 10 a schematic side view of a shell coating station according to a second embodiment for a seventh operating state; Figure 11 a schematic side view of a shell coating station according to a third embodiment to a sixth operating state; Figure 12 a schematic side view of a shell coating station according to the third embodiment to a seventh operating state; Figure 13a schematic, partial side view of a coated packaging tray after the coating film has been torn; Figure 14 a schematic, partial side view of the coated packaging tray after the coating film has been cut; and Figure 15 A schematic side view of a shell coating station according to the third embodiment in a second operating state.

[0034] Figure 1Figure 1 shows a schematic side view of a packaging machine 1 according to one embodiment. It can include a frame 2. The packaging machine 1 can also have a feed conveyor 3. It can also have a tray coating station 4, which will be described in more detail later. Empty packaging trays 5 can be conveyed to the tray coating station 4 by the feed conveyor 3. The packaging trays 5 can be transferred to the tray coating station 4 by a gripper device 6 and reversibly coated there with a coating film 7. After coating, areas corresponding to the packages or packaging units can be cut out of the web of the coating film 7. A film remnant grid 8 of the coating film 7 remains, which is wound up by a device 9 for winding the film remnant grid 8.The coated packages can be transferred from the tray coating station 4 to a conveyor belt 10 via the gripper device 6. From there, they can be conveyed, for example, to a filling station (not shown) to be filled with a product.

[0035] In the Figures 2 Figures 4 to 9 show the tray coating station 4 in a schematic sectional view at different phases of the coating process. According to Figure 2, the tray coating station 4 includes a packaging tray holder 13. A single packaging tray 5 is arranged on the packaging tray holder 13.

[0036] Packaging tray 5 is described in detail in Figure 3The packaging tray 5, as shown in the present embodiment, comprises cardboard. This allows the packaging tray 5 to be manufactured in an environmentally friendly manner. Furthermore, the packaging tray 5 coated according to the described method can be easily separated from the coating film 7 and is therefore easily recyclable. Figure 3The figure shows only a section of the packaging tray 5 in the state in which it is held by the packaging tray holder 13. The section shows the right side of the packaging tray 5; that is, the section can be mirrored on the left edge of the image to show the complete sectional view. In the present embodiment, the packaging tray 5 has a recess 14 with a surrounding rim 15. The rim 15 has a first side 16 and a second side 17 opposite the first side 16. The packaging tray 5 is arranged in the tray coating station 4 such that the first side 16 faces the upper tool part 11 and the second side 17 faces the lower tool part 12 (see figure). Figure 2The second side 17 has an inner section 18 and an outer section 19, with the inner section 18 located between the outer section 19. The packaging tray receptacle 13 contacts the inner section 18 of the packaging tray 5 as well as the side walls 20 of the packaging tray 5 located between the rim 15. The packaging tray receptacle 13 does not contact the outer section 19 of the rim 15 of the packaging tray 5. This is particularly necessary so that the coating process, as detailed below, can be carried out.

[0037] As from Figure 2 As can be seen, the tray coating station 4 further comprises a tool upper part 11, a tool lower part 12 and a clamping frame 21. These serve to clamp a circumferentially closed outer clamping area 22 of the coating film 7 (see Figure 4For this purpose, the coating film 7 is placed between the clamping frame 21 and the tool upper part 11, and the clamping frame 21 is moved upwards to a tool upper clamping surface 23 of the tool upper part 11 and pressed against it (see Figure 4 To move the clamping frame 21, it is movably mounted on the upper part of the tool 11 and is driven by a pneumatic drive (not shown). In the present embodiment, the coating film 7 is a monofilm consisting of amorphous polyethylene terephthalate (APET) with a constant thickness of approximately 80 µm (in its unformed state). This improves the durability of the coating film 7 and reduces its weight.

[0038] After the outer clamping area 22 of the coating film 7 is clamped (see Figure 4 ), the coating film 7, as in Figure 5shown, heated, and stretched. For this purpose, a dome 26 with a heated concave inner surface 27 is provided at the shell coating station 4. A section 25 of the coating film 7, located between the outer clamping area 22, is drawn onto the heated inner surface 27 by means of a suction device (not shown). For this purpose, an opening 24 for air extraction is provided in the dome 26. When the coating film 7 is drawn onto the dome, it stretches. The stretched coating film 7 can then be used in a subsequent step (see Figure 7 ) simply adapted to the size of the packaging tray 5 and molded onto it. The stretched area 25 of the coating film 7 comprises an overhang area 28, described in more detail below, a completely enclosed inner clamping area 29, an inner area 30 between the inner clamping area 29 and a separation area 31 (see Figure 6 , 7 , 9, 10 , 12The dome 26 comprises, in addition to the heated concave inner surface 27, a similarly heated flat dome clamping surface 32 that surrounds the inner surface 27. The dome 26 is heated by an electric heating device (not shown) to a temperature below the melting point of the coating film 7, in this case to approximately 60 °C. Upon contact with the dome 26, the coating film 7 is heated sufficiently to become more easily and widely stretched. Furthermore, contact with the heated dome 26 also heats the protruding area 28 of the coating film 7, located between the outer clamping area 22 and the inner clamping area 29, to the point where it becomes stretchable.

[0039] While the coating film 7 is suctioned onto the dome 26, as in Figure 6As shown, the tray coating station 4 is closed. For this purpose, the lower tool part 12 is moved upwards towards the upper tool part 11 and the clamping frame 21 and pressed against it. In the present embodiment, the coating film 7 is thus indirectly clamped between the upper tool part 11 and the lower tool part 12 via the clamping frame 21. Closing the tray coating station 4 also further reinforces the clamping of the outer clamping area 22 of the coating film 7, so that the subsequent steps of the coating process can be carried out.

[0040] As from Figure 6As further shown, when the lower tool part 12 is moved towards the upper tool part 11 and the clamping frame 21, the packaging tray holder 13, along with the packaging tray 5 mounted on it, moves along with it. At the same time, the dome 26 moves towards the lower tool part 12. The dome 26, the lower tool part 12, and the packaging tray holder 13 are moved until the coating film 7 contacts a dome clamping surface 32 of the dome 26 at the inner clamping area 29, thus clamping the inner clamping area 29 to the first side 16 of the edge 15 of the packaging tray 5. Figure 6 As illustrated, the inner clamping area 29 is located within the outer clamping area 22.

[0041] While the inner clamping area 29 is clamped to the first side 16 of the rim 15 of the packaging tray 5, air is drawn out of the tray coating station 4 through an opening 38 in the upper part of the tool 11, in addition to the air being extracted through the opening 24 in the dome 26. A suction and blower device (not shown) is arranged on the upper part of the tool 11 for this purpose. The suction prevents the coating film 7 from slipping or being damaged when the inner clamping area 29 is clamped. Furthermore, air is drawn towards the lower part of the tool 12 by means of a suction and blower device (not shown) arranged on the lower part of the tool 12. An opening 48 is provided on the lower part of the tool 12 for this purpose. Due to these suction actions, the air inside the tray coating station 4 is almost completely extracted, i.e., the tray coating station 4 is evacuated.

[0042] As from Figure 7As can be seen, after the inner clamping area 29 has been clamped to the first side 16 of the rim 15 of the packaging tray 5 and the outer clamping area 22 has been clamped between the upper tool part 11 and the lower tool part 12, the coating film 7 is no longer drawn against a heated inner surface 27. Instead of air being drawn upwards through the opening 24 in the dome 26 and the opening 38 in the upper tool part 11, air is blown through these two openings into the tray coating station 4. Air is also drawn through the opening 48 towards the lower tool part 12. Due to the suction effect, the inner area 30 of the coating film 7 is formed against the packaging tray 5, in particular pressed against the surfaces of the side walls 20 and a base 33 of the packaging tray 5 facing the recess 14.Since the tray coating station 4 was evacuated in the previous process step, it is possible to apply the coating film 7 to the packaging tray 5 particularly quickly and without wrinkling. Furthermore, the heating and stretching of the coating film 7 carried out in the previous step contributes to the fact that the coating film 7 can be easily shaped to the form of the packaging tray 5 without being damaged. Upon contact with the packaging tray 5, the coating film 7 cools and hardens according to the contour of the packaging tray 5. Additionally, the suction action shapes the heated overhang 28 against the packaging tray 5 in such a way that the overhang 28 curves under the edge 15 of the packaging tray 5. As shown in... Figure 7As can be seen, the overhang area 28 is curved so that it is curved into the area of ​​the outer section 19 of the second side 17 of the edge 15. The curvature is favored by the fact that a first distance 34 of the dome clamping surface 32 with respect to a base 35 of the lower tool part 12 is greater than a second distance 36 of the upper tool clamping surface 23 with respect to the base 35.

[0043] Next, as in Figure 8As shown, the curved overhang 28 is formed into a double fold 37. During this process step, air is preferably blown through the openings 24 and 38 into the tray coating station 4 to press the coating film 7 against the packaging tray 5. A heated press insert 39 is movably mounted on the packaging tray holder 13 to form the double fold 37. A press insert surface 40 of the press insert 39 is heated by an electric heating device (not shown) to a temperature below the melting point of the coating film 7, in this embodiment to approximately 60 °C. To form the double fold 37, the press insert 39 is moved upwards towards the packaging tray 5 and presses the curved overhang 28 against the outer section 19 of the edge 15 of the packaging tray 5 with its warm press insert surface 40 (see also Figure 13The resulting double fold 37 has two layers. A first layer 41 lies directly against the second side 17 of the rim 15 of the packaging tray 5. A second layer 42 lies directly against the first layer 41. The double fold 37, in contrast to a simple fold, enables a particularly secure attachment of the coating film 7 to the packaging tray 5 and thus a particularly secure coating.

[0044] At the end of the in Figure 8In the illustrated process step, the inner clamping area 29 of the coating film 7 is clamped to the first side 16 of the rim 15, and the double fold 37 is formed on the second side 17 of the rim 15, which is opposite the first side 16. There is no material bond between the coating film 7 and the packaging tray 5, but rather a purely form-fit connection. This makes it possible to attach the coating film 7 to the packaging tray 5 simply and reliably. Furthermore, the packaging tray 5 and the coating film 7 can be completely separated from each other. This is particularly advantageous for recycling the packaging tray 5 and / or the coating film 7. The coating process and the design of the tray coating station 4 are also simplified, for example, by eliminating the need for an adhesive and a device for applying it to the coating film 7 or the packaging tray 5.Ideally, the installation space of the shell coating station 4 will be reduced, maintenance effort reduced and / or operating and manufacturing costs lowered.

[0045] While the inner clamping area 29 and the packaging tray 5 are clamped, and the double fold 37 and the packaging tray 5 are clamped, the dome 26, the packaging tray holder 13, and the press insert 39, together with the clamped coating film 7, are lowered relative to the tool base 12 to increase the tensile stress of the separation area 31. The separation area 31 is located between the double fold 37 and the outer clamping area 22. To allow movement of the packaging tray holder 13, it is movably mounted to the tool base 12 via a (compression) spring (not shown) connected to both the tool base 12 and the packaging tray holder 13. The described relative movement has the advantage that no additional component is required to tension the coating film 7.The dome 26, the packaging tray holder 13, and the press insert 39 each perform a dual function: firstly, clamping the inner clamping area 29 of the coating film 7 to the packaging tray 5, holding the packaging tray 5, or pressing the double fold 37; and secondly, generating or increasing the tensile stress in the separation area 31 of the coating film 7. For this downward movement, the dome 26 is actively driven by an electric drive device (not shown). The packaging tray holder 13 and the press insert 39 are passively moved along with the dome 26. This means that only one drive device is required, saving installation space and reducing the effort and costs for the operation and maintenance of the tray coating station 4. In the present embodiment, the described movement extends to the point where the coating film 7 is stretched but not torn.This means that in this process step, the tensile stress is increased to such an extent that the tensile strength of the coating film 7 is not reached. In the context of the invention, the tensile strength of the coating film indicates its tear resistance. It specifies the maximum mechanical tensile stress with which the coating film 7 can be subjected before it tears. Tensioning the separation area 31 is particularly advantageous for the separation of the coating film 7 described below.

[0046] The coating film 7 is separated while the inner clamping area 29 and the packaging tray 5 are clamped, and the double fold 37 and the packaging tray 5 are clamped. This enables safe and controlled separation. Furthermore, it prevents the double fold 37 from being damaged by forces acting during separation or even the coating film 7 from being detached from the packaging tray 5. To separate the coating film 7, according to the first embodiment, similar to the process described in Figure 7 In the illustrated process step, air is drawn in and forced towards the lower part of the tool 12 by means of the suction and blowing device arranged on the upper part of the tool 11 and the suction and blowing device arranged on the lower part of the tool 12 (see Figure 9This further increases the tensile stress in the separation area 31 until it reaches its tensile strength, causing the coating film 7 to tear in the separation area 31. According to the first embodiment, the suction and blowing devices thus form a separating agent 47 for separating the coating film 7. If the coating film 7 is already pre-stressed, a weaker suction effect is sufficient to separate it. The tensile stress required to separate the coating film 7 is further reduced by the heat exerted on the separation area 31 by the press insert 39 and the heated dome 26, thereby lowering the tear strength of the coating film 7. The press insert 39 and the dome 26 heat the coating film 7 at the inner clamping area 29 and at the double fold 37 (see figure). Figures 5 to 8), so that the separation area 31 experiences a temperature gradient increasing towards the inner clamping area 29 and double fold 37. The temperature gradient reduces the tensile strength of the heated separation area 31, particularly compared to a cold state (i.e., at room temperature), at least sectionally, especially at a warmest section 43, by approximately 10 N / mm². The temperature at the warmest section 43 of the separation area 31 is approximately 80% of the temperature of the press insert 39 or the dome 26. Due to the action of temperature, tensile stress, and atmospheric pressure, the coating film 7 tears at the warmest section 43 of the separation area 31, which is directly adjacent to the second layer 42 of the double fold 37 (see Figure 13 ).

[0047] Figure 10 Figure 1 shows an alternative method of separating the coating film 7 using the previously described tray coating station 4. The [details of the process] Figures 2 and 4 to 8The process steps shown are applied identically in this second embodiment. Instead of the one shown in Figure 9 In the illustrated separation process using the suction and blowing devices, the dome 26, the packaging tray holder 13, and the press insert 39 form the separating agent 47. Starting from the lowered position of the dome 26, the packaging tray holder 13, and the press insert 39 in Figure 8The dome 26, the packaging tray holder 13, and the press insert 39, together with the clamped coating film 7, are lowered further relative to the tool base 12 to increase the tensile stress of the separation area 31 to at least its tensile strength. Upon reaching this tensile strength, the coating film 7 tears. This enables particularly easy and reliable separation of the coating film 7. The degree of relative movement required depends on the deformability and / or tear resistance of the coating film 7. In this context, the tool base 12 forms a stop for the packaging tray holder 13 and limits the relative movement.

[0048] The Figures 11, 12 and 14 show a shell coating station 4 according to a further embodiment in a schematic sectional view in different phases of the coating process, in particular during the pressing of the double fold 37 ( Figure 11 ) and when separating the coating film 7 ( Figure 12 ). The ones in the Figures 2 and 4 to 8 The process steps shown are applied almost identically in this third embodiment. According to the third embodiment, the shell coating station 4 comprises, in addition to the dome 26, an outer dome 44 enclosing the dome 26. The outer dome 44, in particular an outer dome surface 45, is heatable and movably mounted on the upper part of the tool 11. After the outer clamping area 22 of the coating film 7 is clamped, the coating film 7 is, as shown in Figure 15As shown, the coating film 7 is stretched. For this purpose, the area 25 of the coating film 7, located between the outer clamping area 22, is drawn against both the heated dome 26 and the heated outer dome 44. This provides a larger contact area for stretching the coating film 7, and the coating film 7 can be adapted particularly well to the size of the packaging tray 7. The dome 26 and the outer dome 44 are heated to approximately the same temperature by means of the same heating device. During the stretching of the coating film 7, the dome clamping surface 32 and the outer dome surface 45, which each contact the coating film 7, are located almost on the same plane, i.e., equidistant from the base 35 of the tool lower part 12. This allows the coating film 7 to be stretched easily and evenly, and in particular without being damaged.

[0049] Instead of the in Figure 9 illustrated separation by suction action or of the in Figure 10In the illustrated separation by relative movement, the coating film 7 is cut according to the third embodiment with a knife 46 as a separating agent 47. The knife 46 is fixedly mounted on the lower part of the tool 12. Spatially, the knife 46 is arranged outside the packaging tray receptacle 13, in particular the press insert 39, such that the packaging tray receptacle 13 and the packaging tray 5 can move past the knife 46 within the knife 46 (see Figure 12When the cutting area 31 comes into contact with the blade 46, it is cut. For this to occur, the packaging tray holder 13, together with the clamped coating film 7, is moved towards the lower tool part 12 and the blade 46. The relative movement required for cutting is at most large enough to increase the tensile stress of the coating film 7 at least to its tensile strength. The degree of relative movement required depends on the deformability and / or tear resistance of the coating film 7. In this context, the lower tool part 12 forms a stop for the packaging tray holder 13 and limits the relative movement.

[0050] Particularly when the coating film 7 is cut with the knife 46, it is advantageous that the coating film 7 is prepared before and during cutting, as shown in Figure 8The described (downward movement of the dome 26, the packaging tray holder 13 and the press insert 39 together with the clamped coating film 7 relative to the tool base 12) is tensioned. This enables a particularly precise cut.

[0051] Figure 13The coating film 7 is illustrated after separation by tearing using air pressure or by the relative movement of the dome 26, the packaging tray holder 13, and the press insert 39. In principle, the double fold 37 varies in size, especially after separation, depending on the size of the outer section 19 of the second side 17 of the edge 15 of the packaging tray 5, the size of the press insert 39, and the release agent 47 used. The release agent 47, in particular, influences the surface area of ​​the second layer 42 of the double fold 37 compared to the first layer 41. When separating with the suction and blowing device or with the dome 26, the packaging tray holder 13, and the press insert 39 as the release agent 47, the second layer 42 is smaller than the first layer 41. The second layer 42 only partially overlaps the first layer 41.This is the case because the press insert area 40 is smaller than the outer section 19 of the second side 17 of the edge 15. The coating film 7 is torn at the warmest section 43 of the separation area 31, which is directly adjacent to the second layer 42 of the double fold 37. The warmest section 43 is located spatially outside the press insert 39 and even below the outer section 19 of the second side 17 of the edge 15. Thus, after the coating film 7 is torn at the warmest section 43, the second side 42 of the double fold 37 is smaller than its first layer 41.

[0052] In contrast, when separating with the knife 46, the first layer 41 and the second layer 42 of the double fold 37 are essentially the same size, and the second layer 42 completely covers the first layer 41 (see Figure 14 ). This is the case because the knife 46 cuts the coating film 7 outside the edge 15.

Claims

1. A method for coating a packaging tray (5) with a coating film (7) using a tray coating station (4), wherein the tray coating station (4) comprises a packaging tray holder (13) for receiving the packaging tray (5), a tool upper part (11) and a tool lower part (12), wherein a movable dome (26) is attached to the tool upper part (11), and wherein a press insert (39) is attached to the tool lower part (12), the method comprising the following steps: clamping an outer clamping area (22) of the coating film (7) between the tool upper part (11) and the tool lower part (12), clamping an inner clamping area (29) of the coating film (7) to the packaging tray (5) by means of the dome (26), wherein the inner clamping area (29) is located within the outer clamping area (22), and forming an overhanging area (28) of the coating film (7) onto the packaging tray. (5)that the protruding area (28) curves under an edge (15) of the packaging tray (5), wherein the protruding area (28) is located between the outer clamping area (22) and the inner clamping area (29), pressing the curved protruding area (28) against the edge (15) of the packaging tray (5) by means of the pressing insert (39) such that a double fold (37) is formed, and separating the coating film (7) in a separation area (31), wherein the separation area (31) is located between the double fold (37) and the outer clamping area (22).

2. Method according to claim 1, wherein the inner clamping area (29) is clamped to a first side (16) of the edge (15) and wherein the double fold (37) is formed on a second side (17) of the edge (15) opposite the first side (16).

3. Method according to claim 1 or 2, wherein the double fold (37) comprises a first layer (41) and a second layer (42), wherein the first layer (41) abuts the second side (17) of the edge (15) of the packaging tray (5) and wherein the second layer (42) abuts the first layer (41).

4. Method according to one of the preceding claims, wherein the separation of the coating film (7) takes place while the inner clamping area (29) and the packaging tray (5) are clamped and while the double fold (37) and the packaging tray (5) are clamped.

5. Method according to one of the preceding claims, wherein the coating film (7) is cut, in particular with a knife (46), or torn, in particular by means of compressed air and / or tensile force.

6. Method according to one of the preceding claims, wherein a tensile stress of the separation area (31) is increased to at least a tensile strength of the coating film (7) in order to separate the coating film (7) in the separation area (31).

7. Method according to one of the preceding claims, wherein the movable dome (37), the packaging tray holder (13) and the press insert (39) are moved relative to the tool lower part (12) or vice versa to increase a tensile stress of the separation area (31).

8. Method according to one of the preceding claims, wherein, in particular after clamping the outer clamping area (22), an area (25) of the coating film (7) between the outer clamping area (22) is drawn or pressed by means of compressed air against an inner surface (27) of the dome (26), in particular a heated one, in order to stretch the area (25).

9. Method according to claim 8, wherein the shell coating station (4) comprises an outer dome (44), in particular a heated one, wherein in particular after clamping the outer clamping area (22), the area (25) is drawn against the outer dome (44) or pressed by means of compressed air in order to stretch the area (25).

10. Method according to one of the preceding claims, wherein after or during the clamping of the inner clamping area (29) an inner area (30) of the coating film (7) is formed onto the packaging tray (5), in particular its first side (16), wherein the inner area (30) is located between the inner clamping area (29).

11. Tray coating station (4) for coating a packaging tray (5) with a coating film (7), the tray coating station (4) comprising: a tool upper part (11) and a tool lower part (12) for clamping an outer clamping area (22) of the coating film (7), a packaging tray holder (13) for receiving the packaging tray (5), a dome (26) for clamping an inner clamping area (29) of the coating film (7) to the packaging tray (5), wherein the dome (26) is movably arranged on the tool upper part (11), wherein the inner clamping area (29) is located within the outer clamping area (22), a suction and / or blowing device for forming an overhang area (28) of the coating film (7) onto the packaging tray (5) such that the overhang area (28) curves under an edge (15) of the packaging tray (5),wherein the overhang area (28) is located between the outer clamping area (22) and the inner clamping area (29), and a press insert (5) for pressing the curved overhang area (28) against the edge (15) of the packaging tray (5) such that a double fold (37) is formed, wherein the press insert (39) is movable relative to the packaging tray receptacle (13), and a release agent (47) for separating the coating film (7) in a separation area (31), wherein the separation area (31) is located between the double fold (37) and the outer clamping area (22).

12. Tray coating station according to claim 11, wherein the release agent (47) is a knife (46), and / or wherein the release agent (47) is formed by the suction and / or blowing device, wherein the suction and / or blowing device is configured to increase a tensile stress of the separation area (31), in particular to at least a tensile strength of the coating film (7), and / or wherein the release agent (47) is formed by the dome (26), the packaging tray holder (13) and the press insert (39), wherein the dome (26), the packaging tray holder (13) and the press insert (39) are movable relative to the lower part of the tool (12) in order to increase the tensile stress of the separation area (31), in particular to at least the tensile strength.

13. Tray coating station (4) according to claim 11 or 12, wherein the upper tool part (11) has a clamping frame (21), in particular movable relative to it, wherein the outer clamping area (22) can be clamped indirectly between the upper tool part (11) and the lower tool part (12) via the clamping frame (21).

14. Tray coating station (4) according to one of claims 11 to 13, wherein the press insert (39) is movably mounted on the tool base (12), in particular the packaging tray holder (13), and / or wherein the packaging tray holder (13) is movably mounted on the tool base (12).

15. Packaging machine (1), preferably tray sealing machine, comprising a tray coating station (4), in particular according to one of claims 11 to 14, which is configured to carry out the method according to one of claims 1 to 10.

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