Patent Application
20250171964
The invention relates to a method for producing a receptacle with a hollow body made of fiber material and having an opening and a connection element arranged on the hollow body and surrounding the opening according to the preamble of claim 1, in particular a method based on the fiber molding process. The invention also relates to a device for producing a receptacle according to said method.
Molded fiber products, called “molded pulp” in English, are used for various applications, in particular as transport packaging and as molded inserts in packaging to protect sensitive goods. With the aim of further reducing the amount of plastic waste caused by packaging material, the use of molded pulp to hold cosmetic and food products has also attracted increased attention. In particular, the aim is to use hollow bodies made of fiber material with a sealable opening as jars for cosmetic products, such as creams, or as receptacles for food products, such as liquids. Achieving suitable mechanical properties and producing such hollow bodies made of fiber material pose challenges.
Achieving suitable mechanical properties is particularly important in the region of the opening of the hollow body. Since it must be possible to tightly seal the opening for the use of the hollow body for cosmetic and food products, sealing films and/or sealing caps made of polymers are regularly arranged as closures at the openings. The closures must be firmly attached to the hollow body so that they do not come loose in an uncontrolled manner. A firm connection of a sealing film may be achieved by gluing or welding the sealing film. A smooth surface to which the sealing film is attached is advantageous for this. A tight connection of sealing caps may be achieved by firmly pushing or screwing on the cap. This requires high strength of the sealing caps and the region where a sealing cap is placed, which is why the fiber material is regularly reinforced.
In order to meet the above requirements, it is known in practice to provide receptacles as a combination of a molded fiber product having an opening and a connection element reinforcing the region of the opening. In practice, the connection element of such a receptacle may be formed from a polymer by injection molding and have a higher strength, a higher hardness and/or a smoother surface-suitable for the adhesion of sealing films-than the fiber material of the hollow body. This makes it easy to attach a closure to the connection element, which securely closes the opening of the hollow body (or receptacle). The connection element may also have special structural details such as an external thread with which an internal thread of a closure designed as a screw cap cooperates. The applicant has developed a thermoplastic material that consists exclusively of biodegradable or bioinert components. If the connection element and the closure of a receptacle are formed from biodegradable biopolymers, the entire receptacle may be biodegradable.
The production of these receptacles has been complex to date. In production processes known from the prior art, the molded fiber product is first produced using a pulp molding process. The connection element is produced separately and connected to the dried fiber product by form-fitting or substance bonding. Alternatively, the connection element may be injection molded onto the dried fiber product.
For example, EP 1 221 413 A1 discloses a receptacle with a molded fiber product having on its inner surface and/or its outer surface a resin layer formed by applying a coating, wherein a certain thickness ratio of the resin layer to the molded article is formed and the inner and outer surfaces have an average centerline roughness (Ra) of 0.5 to 20 μm. The fiber product is formed in a multi-step process. First, pulp is poured into a cavity of a split mold. The water in the pulp is sucked out through holes in the wall of the split mold, which are covered with a net, forming the fiber product on the wall. Then, an elastic and expandable pressing tool is inserted into the cavity of the molded fiber product and expanded to dewater and compact the molded fiber product. Once the molded fiber product has been compacted, the pressing tool contracts again and is removed. The split mold is opened to remove the wet fiber product. The molded fiber product is then pre-dried, coated and finally dried. Optionally, the receptacle has a connection element with 40 to 90% by weight of natural fibers and a binder. The process of attaching the connection element to the fiber product is not described in detail.
Similar methods for producing a hollow body from fiber material in the form of a bottle using a split mold and an expandable pressing tool are also described in EP 1 081 285 B1 and in WO 2003/010386 A1. These publications also do not disclose the process of attaching a connection element to the fiber product.
A method according to the preamble of claim 1 is known from the publication JP 2001-303 500 A.
The object of the invention is to provide a method and a device which enable the efficient production of a receptacle as described above. In particular, the method shall enable a short process duration and a low energy input, as well as allow for a reliable connection between the connection element and the hollow body and enable reliable handling of the hollow body.
According to the invention, this task is solved by a method with the features of claim 1 and by a device with the features of claim 12. Advantageous embodiments are shown in the dependent claims.
The method described herein for producing a receptacle comprises the following method steps:
The split suction mold is composed of several suction mold parts, in particular two halves. The hollow fiber molded product is formed in the closed state of the suction mold when the suction mold parts are joined together and the wall of the suction mold encloses a largely closed cavity. The wall of the suction mold has a porous, water-permeable inner surface through which a pulp can be sucked in. This inner surface may be realized in the conventional way by a suction mold which has a largely solid base body made of plastic or metal, into which a strainer body is inserted to form the porous inner wall. However, it is also possible to produce the parts of the suction mold using, for example, additive producing techniques in 3D printing, wherein fluid channels are formed in the material of the molded parts during printing. The pores of the molded parts are connected to a suction device, which sucks water through the wall of the suction mold. The wall of the split suction mold further contains at least one suction mold opening, which connects the cavity with an environment outside the suction mold. The suction mold opening may be formed in a contact region of at least two suction mold parts and thus have a circumference that may be divided. Features of the method relating to the formation of the suction mold opening are described further below.
For the method according to the invention, a holding device is provided on which a connection element is arranged. The holding device is an elongate body which has at least one section with a cross-section conforming to the shape of the opening of the receptacle to be produced. For example, the cross-section may be round if the opening of the receptacle is to be round. If the opening is rectangular, said cross-section of the holding device has a rectangular shape. Similarly, in the case of an oval or other non-circular opening, the cross-section of the holding device corresponds to the cross-section of the opening. The cross-section of the holding device only has to correspond to the shape of the opening of the receptacle to be produced in a region that is assigned to the opening of the receptacle to be produced. The regions of the holding device remote from the opening of the receptacle to be produced may have any differing cross-section. The connection element may be arranged on the holding device by means of a feeding device, wherein the feeding device places the connection element in a predetermined position on the holding device. The feeding device may, for example, arrange the connection element on the holding device in such a way that it partially or completely surrounds the section of the holding device in the region of the opening of the receptacle to be produced.
The holding device and the connection element arranged on it are jointly placed in the suction mold. In doing so, the connection element is arranged in the suction mold opening and the holding device protrudes through the suction mold opening such that it is arranged partly in the cavity and partly outside the suction mold. If the suction mold opening is formed in a contact region of at least two suction mold parts and has a divisible circumference, the holding device with the connection element may be placed in the opened suction mold and the mold parts may then be closed. If the suction mold opening is not formed in a contact region of at least two suction mold parts, the holding device with the connection element may be inserted into the suction mold through the suction mold opening in the longitudinal direction of the holding device until the connection element is located in the suction mold opening. The suction mold opening may be slightly larger than the connection element, at least in one section. In this case, the connection element may be held by the holding device in the suction mold opening in such a way that a gap is formed between the connection element and the suction mold opening.
After the holding device and the connection element have been arranged in the suction mold opening, the split suction mold is closed and a pulp is sucked into the cavity by immersing the suction mold and/or the holding device in a basin filled with pulp. The holding device may be hollow so that the pulp is sucked into the suction mold through the hollow holding device. The pulp contains water and fiber material. The fiber material usually consists of cellulose such as waste paper or other recycled fibers, but also fresh fibers, depending on the requirements on the optical properties of the molded fiber product. The pulp may contain further additives that positively influence the properties of the molded fiber product.
The pores in the porous wall of the suction mold are designed in such a way that the water penetrates the pores, and the fiber material is deposited on the wall when the pulp is sucked in. The wall thickness of the hollow body formed increases with increasing suction time. In particular, a fiber layer, in which the connection element is embedded, forms between the wall of the suction mold and the holding device. The fiber layer of the hollow body and the connection element are connected by form-fitting. The connection element may have a connecting wall with holes that extends approximately parallel to the porous wall. The connecting wall, for example made of injection-molded thermoplastic, can have a wall thickness in the order of 1 mm and holes with a clear area of e.g. 20 mm2. If the connection element surrounds an opening of the receptacle, the connecting wall can extend along the opening in a ring shape and have a width (wall thickness) of approx. 5 to 15 mm. The fibers deposited on the wall form a layer that extends through the holes in the connecting wall and embeds the connecting wall in this way. The connection element is thus firmly anchored in the fiber layer.
As soon as a sufficient amount of fiber material has been deposited in the cavity of the suction mold and/or a predetermined time has elapsed for the suction of fiber material, the formed hollow body with the connection element arranged on it is compacted. Compacting means that water contained in the molded fiber product is mechanically removed from the molded fiber product. For this purpose, a relative overpressure can be generated in the inner volume of the hollow body, which forces water out of the wall of the hollow body. The relative overpressure in the suction mold can be generated by applying a negative pressure outside the suction mold parts, which is directed through the porous wall of the mold parts to the inner wall of the mold parts and causes the fiber material to be deposited on the porous wall. Compacting the molded fiber product increases its mechanical stability and facilitates handling of the molded fiber product. However, an expandable pressing tool, described further below, can also be used to, in addition, mechanically press the moisture out of the formed fiber layer in the suction mold already.
The hollow body with the connection element can be dried by applying heat.
The receptacle produced in this way can, for example, be filled with a flowable product, in particular a cream or a drink. The opening of the receptacle can then be fitted with a closure that is tightly connected to the connection element.
The method described above has a plurality of advantages. The connection element can be positioned very precisely and quickly in the suction mold opening by means of the holding device. Furthermore, by forming the fiber material layer of the hollow body around the connection element, a particularly firm connection between the connection element and the hollow body can be achieved. This is because the pulp has a low viscosity and can therefore penetrate even into delicate geometric shapes (e.g. undercuts or holes in a connecting wall) of the connection element, where it dries and cures.
In practice, the holding device can be hollow, and the pulp can flow through the holding device into the cavity of the suction mold. This way, the entire inner cross-section of the hollow holding device is available for the pulp to flow into the suction mold and enables the suction mold to be filled quickly and completely.
The hollow body is removed from the split suction mold on the holding device. The holding device simplifies handling of the hollow body and transportation to further processing steps. The hollow body can then be transported on the holding device into a transfer mold complementary to the hollow body or into a split press mold. In other words, the hollow body can be transported on the holding device from the suction mold directly into the press mold complementary to the hollow body. Alternatively, the hollow body can be transported from the suction mold into the transfer mold complementary to the hollow body and from there into the likewise complementary press mold. Details of the transfer mold and the press mold are described further below. The removal of the hollow body from the suction mold and the transportation of the hollow body located on the holding device enable precise and quick positioning of the hollow body in the transfer mold or the press mold. The holding device also enables safe, i.e. damage-free, removal and transportation of the hollow body because the holding device can mechanically support the hollow body. This is because when the holding device with the hollow body is moved out of the split suction mold, one region of the hollow body rests on the holding device. Particularly safe removal and transportation are possible if the holding device supports the hollow body substantially over its entire length, for example if the holding device extends into the hollow body as far as its base.
For the purpose of removing and transporting the hollow body, it is advantageous if the suction mold opening is formed in a contact region of at least two suction mold parts, as described above. The split suction mold can be opened before or after the hollow body has been compacted, and the hollow body is removed from the opened suction mold with the holding device.
Removing and transporting the hollow body on the holding device is particularly quick and easy in practice if the holding device is pivoted about an axis located outside the cavity for transportation into the transfer mold or the split press mold. The holding device can protrude from the cavity for this purpose, with one end of the section protruding from the cavity being pivotably mounted about a pivot axis formed transversely to the longitudinal direction of the holding device. After opening the split suction mold, the holding device with the hollow body can be pivoted by 180°, for example, from a suction mold part of the split suction mold into a transfer mold or the opened split press mold. After the holding device has been pivoted and the hollow body is positioned in the transfer mold or the press mold, the transfer mold or the press mold is moved in the longitudinal direction of the holding device and thus the hollow body is pulled off the holding device.
In practice, the hollow body can be compacted in the suction mold and/or in the press mold. Compaction in the suction mold makes it easier to remove the hollow body, which is very wet without compaction, from the suction mold. However, it is possible that the pores and structures in the wall of the suction mold are replicated in the surface of the hollow body. In addition to compaction in the suction mold or as an alternative thereto, the hollow body can therefore be compacted in a press mold specially provided for this purpose. For this purpose, the hollow body is transported from the suction mold into the press mold.
The split press mold is formed from a plurality of press mold parts. In the closed state, the press mold has a wall that is designed substantially complementary to the hollow body and the connection element. Furthermore, the press mold has a press mold opening that is aligned with the opening of the hollow body arranged in the press mold. The wall of the press mold can have either no pores or very small pores compared to the pores in the wall of the suction mold. It can also have decorative structures (grooves or protrusions) that are embossed into the wall of the container during the pressing process. The wall of the press mold can also include a suction channel that is fluidly connected to the interior of the press mold and through which water can be removed. The hollow body can be inserted into the open press mold and removed from it after pressing. When the hollow body is arranged in the closed press mold, the wall of the press mold encloses the hollow body and the internal pressure in the inner volume of the hollow body is increased by a pressing tool so that the hollow body is compacted. Excess water flows out of the hollow body, preferably through the suction channel.
In practice, the hollow body can be compacted by expanding an expandable pressing tool inserted into the hollow body when the hollow body is inside the press mold. In this way, the hollow body is dewatered quickly and efficiently, and it is conferred the desired surface structure both on the inside by the pressing tool and on the outside by the inner surface of the wall of the press mold.
In practice, the expandable pressing tool can consist of a bladder or a balloon made of an elastomer or another rubber-elastic material and can be arranged on a second holding device, which can be inserted in particular through the press mold opening into the inner volume of the hollow body arranged in the press mold. The second holding device has a closable fluid line which is tightly connected to the pressing tool, through which a fluid can be pressed into the interior of the pressing tool at overpressure. The fluid used can be, for example, water, oil, air, industrial gases or a mixture of the above fluids.
To compact the hollow body with the pressing tool in the press mold, the second holding device is inserted into the inner volume of the hollow body and the pressing tool is expanded by pressing in the fluid, wherein the pressing tool expands like a balloon, comes to rest against the inner surface of the hollow body and presses it against the wall of the press mold. The isostatic fluid pressure leads to a uniform compaction of the wall of the hollow body. After a predetermined pressing time or a predetermined dewatering of the hollow body, the fluid is drained from the pressing tool through the fluid line, causing it to contract again, and the pressing tool is pulled out of the receptacle with the second holding device.
It is also possible to compact the hollow body with the pressing tool in the suction mold. For this purpose, the first holding device can be pulled out through the suction mold opening when the suction mold is in the closed state and the second holding device can be pushed into the hollow body through the suction mold opening. Compaction then takes place in the same way as compaction in a press mold. Alternatively, the pressing tool can also be arranged on the holding device that carries the connection element.
In practice, the hollow body can be dried from the inside using radiant heat and/or a stream of hot air. For this purpose, a rod-shaped heating device can be inserted through the opening of the hollow body. The heating device can be activated in the hollow body, where it can emit infrared radiation, UV radiation and/or microwave radiation. Additionally or alternatively, a stream of hot air can exit through the rod-shaped heating device, which stream of hot air flows along the inner surface of the hollow body and exits from the opening of the hollow body into the environment. Drying the hollow body removes residual moisture from the fiber material. This allows optional coatings to solidify on the inner surface of the hollow body. Details on the application of optional coatings are explained further below.
In practice, the connection element can be injection-molded from a thermoplastic and pushed onto the holding device in a cured state. Injection-molded connection elements made of thermoplastic can be designed geometrically freely, i.e. with only few structural limitations. Such a connection element can, for example, have a grid-shaped jacket section with holes, which forms a connecting wall and is arranged in the region of the opening of the receptacle. The connecting wall has holes that are penetrated by the fiber material of the hollow body.
In a further practical embodiment of the method, the hollow body can be pre-dried in an oven before compaction. In this case, the hollow body can be located in a part of the press mold or of the transfer mold that is transported through the oven. Or the hollow body may be placed on a conveyor belt that transports the hollow body through the oven. Pre-drying can reduce the water content of the hollow body before it is compacted. In particular, the oven can be a continuous oven. Due to the reduced residual moisture in the hollow body, greater dimensional stability of the hollow body is achieved in the subsequent compaction step.
In another practical embodiment, the inner surface of the hollow body can also be coated with a biodegradable coating solution. To coat the inner surface, a tube fluidly connected to a supply of a coating solution can be inserted through the opening of the receptacle into the inner volume of the hollow body. The coating solution can then be introduced into the inner volume through the tube. This can form a coating that is suitable for contact with food or liquids. If the coating is applied after compaction and before final drying, the coating can be particularly resistant.
In practice, coating the inner surface is particularly easy if the hollow body is rotated after it is filled with the coating solution, thereby wetting its inner surface. For this purpose, a reservoir of the coating solution can be formed in the hollow body, wherein excess coating solution is poured out after wetting the inner surface. Rotation can be carried out by means of a rotation device, by means of which the hollow body is rotated about the axis of the opening of the receptacle.
The invention also relates to a device for producing a receptacle according to one of the embodiments of the method described above. The device comprises
This device is used in particular to implement the method described above.
In practice, the device may further comprise at least one of the following features:
Further practical embodiments and advantages of the invention are described below in connection with the drawings.
To produce a receptacle with a hollow body 1 made of fiber material and an opening 2 and with a connection element 3 arranged on the hollow body 1 and surrounding the opening 2, a split suction mold 4 with a porous wall 5 is first provided. The suction mold 4 is rotationally symmetrical and divided along its central longitudinal plane into two suction mold parts 4a, 4b. The suction mold parts 4a, 4b are connected to one another at a first end such that they can pivot about a pivot axis and can be opened along the pivot axis. In the closed state, the suction mold parts 4a, 4b enclose a cavity 6 with their inner wall 5, which cavity is connected to the environment by means of a suction mold opening 7 in the suction mold 4. The wall 5 has pores (not shown) which fluidly connect the inner wall 5 of the cavity 6 with a suction device (not shown). In an inner region of the suction mold parts 4a, 4b, which is not shown, the pores are guided to first suction channels 9, through which the pores and the cavity 6 are fluidly connected to a suction device. In the embodiment shown, the suction channels 9 are formed by steel tubes, which are attached to the suction mold part 4a and support the suction mold 4.
The suction mold opening 7 is located at an end of the suction mold 4 opposite the first end in a contact region of the two suction mold parts 4a, 4b. Thus, when the suction mold 4 is opened, the suction mold opening 7 is also opened.
A first holding device 8 is arranged in a region in front of the suction mold opening 7. The first holding device 8 has two sections 8a, 8b. The first section 8a is designed hollow cylindrical and the second section 8b, which protrudes from the first section 8a, is designed as a bent perforated plate and extends over part of the circumference of the first section 8a. The second section 8b is integrally or at least seamlessly connected to the first section 8a, and both sections 8a, 8b have the same curvature. The first holding device 8 is thus an elongated body, which is arranged pivotably, by means of a shaft 10 oriented transversely to the longitudinal direction of the first holding device 8, in a shaft support attached to the suction mold 4. The first holding device 8 can be pivoted from the position shown in
In the vertical orientation of
After the connection element 3 has been arranged on the first section 8a of the first holding device 8, the tube of the feeding device 11 is removed from the first holding device 8 and the holding device 8 is pivoted about the pivot axis of the shaft 10 into the cavity 6 and the suction mold opening 7, as shown in
The closed suction mold 4 with the first holding device 8 inside is immersed in a basin 14 filled with pulp 13. The suction mold 4 is attached to a hollow rotating shaft 15 via the suction channels 9. The interior of the hollow rotating shaft 15 is connected to the suction device, which generates a negative pressure and sucks in water. This negative pressure is directed through the tubular stainless steel suction channels 9 to the wall 5 of the suction mold 4. All suction molds 4 connected to the rotating shaft 15 via the suction channels 9 are moved through the pulp basin 14 when the rotating shaft 15 rotates.
The pulp 13 is sucked through the hollow cylindrical first section 8a of the holding device 8 into the suction mold 4. While the water of the pulp 13 passes through the pores, the fiber material of the pulp 13 is deposited at the pores and forms a layer along the entire wall 5 of the cavity 6 of the suction mold 4. In this way, a hollow body 1 is formed from deposited fibers on the wall 5 of the suction mold 4.
When a sufficient amount of pulp has been deposited on the wall 5 of the suction mold 4, the suction mold 4 is removed from the pulp basin 14, brought into a removal position and opened, as shown in
In the removal position, the formed hollow body 1 on the first holding device 8 is removed from the opened suction mold 4 and transferred to a transfer mold 17 complementary to the hollow body 1. The transfer mold 17 has a shape that is substantially identical to the suction mold part 4b. In particular, the transfer mold 17 also has a recess that is complementary to the first holding device 8. For the purpose of transferring the hollow body 1 from the suction mold 4 to the transfer mold 17, the transfer mold 17 is positioned in front of the suction mold opening 7 in mirror symmetry to the suction mold part 4b. The first holding device 8 is then pivoted about the pivot axis of the shaft 10 so that the hollow body 1 and the connection element 3 come to rest in the transfer mold 17. In the example shown in
In a next step, the transfer mold 17 is moved along the longitudinal axis of the first holding device 8 by a conveying device 18, as shown in
The conveyor belt 18 is part of a continuous oven 19 known from the prior art, through which the hollow body 1 and the connection element 3 are moved in the transfer mold 17. The heat generated by the continuous oven 19 causes the water content of the hollow body 1 to be reduced by evaporation. While the hollow body 1 is being dried in the continuous oven 19, the rotating shaft 15 with the suction mold 4 and the first holding device 8 attached to it is rotated further and returned to the start of the process in order to produce another molded fiber product.
After the hollow body 1 and the connection element have passed through the continuous oven 19, they are transferred to a split and open press mold 20, in which the hollow body 1 with the connection element 3 arranged on it is further compacted.
The press mold 20 may have two or more press mold parts 20a, 20b. In the closed state, one wall of the press mold parts 20a, 20b encloses a second cavity, which is designed substantially complementary to the hollow body 1. Smaller pores are introduced into the wall of the press mold 20 than into the suction mold 4, so that the compaction of the hollow body 1 in the press mold 20 results in a smooth surface of the hollow body 1. The pores in the wall of the press mold are fluidly connected to each other and through second suction channels 22 to a second suction device (not shown). The press mold 20 also has a press mold opening in a contact region of the press mold parts 20a, 20b, which is designed complementary to the connection element 3 on the hollow body 1. As intended, the connection element 3 arranged on the hollow body 1 comes to rest in the press mold opening, so that the opening 2 of the hollow body 1 is aligned with the press mold opening.
When the hollow body 1 is arranged as intended in a press mold part 20a, the press mold 20 is closed. A second holding device 23 with a pressing tool 24 arranged thereon is then inserted through the opening 2 in the connection element 3 into the inner volume of the hollow body 1, as shown in
Due to the isostatic pressure of the fluid in the pressing tool 24 and the elasticity of the pressing tool 24, the hollow body 1 is pressed uniformly against the wall of the press mold 20, and is thereby compacted, dewatered and solidified. This also solidifies the connection between the wall of the hollow body 1 and the connection element 3. At the same time, the surface of the wall is embossed on the hollow body 1.
The water escaping from the hollow body 1 during compaction is extracted via the pores in the wall of the press mold 20 and the second suction channels 22. After a predetermined time or when a predefined amount of water has been removed from the hollow body 1, the fluid is drained from the pressing tool 24 so that the elastic pressing tool 24 contracts and assumes its original shape shown in
The hollow body 1 and the connection element 3 are then removed from the press mold 20 using the aforementioned transfer device 21 and transferred to a coating station shown in
When the hollow body 1 is filled with the predetermined amount of coating solution, the hollow body is rotated by a rotation device 26 about an axis coaxial with the opening 2. In
As an alternative to rotating the hollow body 1 by rolling it along an inclined plane, the hollow body 1 can also be gripped by a gripping device in the horizontal alignment of its longitudinal axis and the gripping device can be rotated.
Thus aligned, the coated hollow body 1 is transferred from the transfer device 21 to a drying station shown in
The process is complete when the hollow body 1 has finished drying and is transferred from the drying station to a storage area.
The features of the invention disclosed in the present description, in the drawings and in the claims may be essential, both individually and in any combination, for the realization of the invention in its various embodiments. The invention is not limited to the described embodiments. It may be varied within the scope of the claims and taking into account the knowledge of the relevant person skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022105316.4 | Mar 2022 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/055183 | 3/1/2023 | WO |
