METHOD, CASTING MOLD, AND PRODUCTION DEVICE

Description

The present invention relates to a method for producing a fiber-based blank from pulp, in particular a container or a fiber-based closure element for a container, to a casting mold for producing a fiber-based blank from pulp, and to a production device comprising a casting mold according to the preamble of the independent claims.

A fiber-based container was proposed in WO 2012/139590 A1. To produce this container, so-called pulp is injected into an upside-down mold and pressed against a corresponding wall in this mold using a flexible balloon and compressed accordingly. The pulp is compressed and heated to a temperature of around 180° C. in order to dry the container.

The pulp is a mixture of fibers and water, in particular natural fibers, such as hemp fibers, cellulose fibers or flax fibers or a mixture thereof. Optionally, the pulp has additives that, for example, improve the curing of the compressed pulp or have an influence on the later appearance or generally change the properties of the pulp or the later container.

Because the pulp consists of different components whose properties can vary, the injection process is also very difficult to control. In particular, the type and amount of pulp deposited within the mold is largely left to chance. This is reflected in different properties in the finished container, for example in different wall thicknesses and thus in different strengths or in different surfaces.

The object of the invention is to eliminate at least one or more disadvantages of the prior art. In particular, a method and a casting mold are to be provided which make it possible to control and preferably regulate the deposition of the pulp.

This object is achieved by the methods and devices defined in the independent claims. Further embodiments result from the dependent claims.

A method according to the invention for producing a fiber-based blank from pulp comprises the steps of:

• • providing a casting mold,
  • filling the casting mold with a process liquid, in particular water, such that a liquid reservoir is formed in the casting mold,
  • applying pulp to the liquid reservoir in the casting mold.

Filling the casting mold with a process fluid makes it possible to create certain process conditions within the casting mold. The liquid reservoir provides a standing column that is substantially free of turbulence and/or eddies.

By applying pulp to this liquid reservoir, two media with comparable properties are brought into contact. For example, if water is used as a process fluid, the liquid reservoir also consists of water. The pulp is also a substantially water-based mixture. So if the pulp is applied to the liquid reservoir, these two media do not mix. The liquid reservoir is practically replenished by the pulp. The liquid reservoir therefore provides a standing water column that is only extended by applying pulp to this water column.

A casting mold for producing a fiber-based blank is typically permeable to liquid and has two mold halves that can be separated from each other. These two mold halves provide a cavity into which the pulp is introduced. In a simple form, the casting mold can be made, for example, from a metal grid having an outer boundary that is impermeable to liquid such that a liquid reservoir can be provided within this casting mold. In a simple form, the outer boundary can be provided, for example, by a container, wherein said container can be flooded.

The cavity substantially corresponds to a negative impression of the blank to be produced and, like the blank, has a mouth opening. The pulp is introduced accordingly via the mouth opening. In a container shaped like a bottle, the mouth opening is the pouring opening at the neck of the bottle. However, the blank can, for example, also take the form of a container that is open at the top and has no specific opening, such as a bowl, a cup or a tray.

These are provided with an opening that, when used as intended, usually points upward. Accordingly, the pulp is introduced via the opening cross section of the corresponding opening. However, it can also be provided that the casting mold in such wide-neck containers, such as cups, is closed with a lid in the region of the opening and a separate mouth is provided here in order to introduce the pulp into the casting mold.

After the pulp has been applied to the liquid reservoir, the liquid reservoir can be replaced by draining the liquid reservoir through the casting mold in a targeted manner. By draining the liquid reservoir, the pulp flows into the casting mold.

The draining process can be controlled by an overpressure that is applied to the pulp. Additionally or alternatively, it can be provided to remove the liquid reservoir in the casting mold using a vacuum such that the pulp is sucked into the mold.

Draining of the liquid reservoir can also be controlled by an orifice, for example, such that the draining speed is limited, or it can be regulated, by restricting the draining volume.

By draining the liquid reservoir, a flow of pulp can occur, in particular within the casting mold, and the inflowing pulp can settle on an inner wall of the casting mold, and thus the cavity.

By depositing the pulp on an inner wall of the mold, a wall of the later blank is built up. Controlling or regulating pressure or volume as mentioned above can affect the settling process and, accordingly, the structure of the wall.

Additionally or alternatively, different pulps can be introduced into the casting mold one after the other. By such a serial introduction of different pulps, a layered structure of the blank can be created within the casting mold. For example, pulps can be used that differ in color or in their properties, in particular their fiber properties or their functional properties, such as barrier properties.

It can be provided that the liquid reservoir is drained from the casting mold at a plurality of points. These points can correspond to different segments or regions of the later blank and thus also to the casting mold.

By draining the liquid reservoir at a plurality of points, the flow of the pulp within the casting mold can be directed such that the settling of the pulp can also be controlled and regulated. This allows the wall of the blank to be constructed in a targeted manner and the amount and the respective location of the deposited or settled pulp to be controlled in a targeted manner.

In this case, pulp settling refers to the settling of the fibers contained in the pulp, in the present case on the inner wall of the casting mold in the cavity.

It can be provided that the liquid reservoir is drained from the casting mold through the plurality of points in a specific time sequence.

This allows for precise control of the pulp flow and thus targeted distribution of the fibers. Accordingly, the structure of the blank wall can be controlled in a targeted manner and a fiber distribution within the blank wall can be created that meets specific requirements.

For example, in regions subject to increased force, a thicker structure can be achieved than in the rest of the blank. For example, blanks can be created for containers that are optimized in terms of weight, stackability (top load), fiber orientation, and much more. By depositing fibers in a targeted manner, increased deposition of fibers can be avoided in places that are hardly subject to stress. This is not possible with conventional methods. The wall thickness of the blank, and thus of the container, typically always corresponds to the wall thickness required to absorb the highest force, since the conventional methods used do not allow for targeted control of the fiber settling process.

It can be provided that a corresponding casting mold has a plurality of drain openings that are opened in a specific time sequence. In the present case, the term “draining” refers to the removal of liquid from the casting mold.

Preferably, the pulp is introduced into the casting mold at an overpressure; in particular an overpressure is generated after the pulp has been applied to the liquid reservoir, i.e. during the draining of the liquid reservoir. The pressure can be built up in particular before the liquid reservoir is drained.

By building up excess pressure, the flow of pulp can be controlled more precisely.

Before the pulp is introduced, the casting mold can be backwashed by filling it with process liquid. The process liquid can be discharged through a mouth opening in the casting mold that corresponds to the opening of the blank. This allows easy backflushing of the casting mold, wherein the backflushing liquid and the process liquid are preferably identical. As soon as the backwashing process is stopped, the casting mold is already filled with a liquid reservoir as described here and the pulp can be applied to the liquid reservoir immediately.

This simplifies the entire process. Fibers that are still in the backwash liquid have no negative impact and are at most directly reused in the subsequent steps and deposited accordingly in the casting mold. Because no further process steps are necessary between backwashing and the application of pulp, this method is also comparatively faster.

A further aspect relates to a casting mold for producing a fiber-based blank from pulp, in particular for carrying out the method for producing a fiber-based blank from pulp, as described in the present method. The casting mold is permeable to liquid and has at least one closable drain opening for draining liquid from the interior of the casting mold, in particular from a cavity. In particular, the casting mold has a cavity that is permeable to liquid.

A closable drain opening allows a supply of liquid to be provided within the casting mold and at the same time pressure can be built up because the mold can be closed through the drain opening. In addition, the drain opening makes it possible to create a specific flow within the casting mold when a liquid reservoir in the mold is replaced with pulp by draining it. By creating a specific flow, the settling of fibers from the pulp can be controlled in a targeted manner.

Alternatively, it can also be provided that the casting mold has a plurality of closable drain openings such that a liquid can be drained from the interior of the casting mold at a plurality of points.

As already described, a specific distribution of the pulp, i.e. a specific settling of the fibers from the pulp inside the casting mold, can be enforced by means of a plurality of drain openings. This allows for the specific and targeted construction of a wall of the container. In particular, by opening or closing the individual drain openings in a targeted manner, the flow within the casting mold can be changed and the flow can be directed to different locations or segments of the casting mold in a time sequence.

The individual drain openings can be arranged at different heights in the direction from an opening in the blank to the bottom of the blank, and thus at corresponding positions on the casting mold. In addition, they can be distributed over the circumference of the blank. This makes it possible, for example, to create a plurality of drainage levels.

It can be provided that the closable drain openings are designed as valves, in particular as pinch valves. This makes it possible, on the one hand, to open and close them in a targeted manner and, on the other hand, to control the volume that is discharged through the respective drain openings by changing the flow rate. This allows the direction and strength of the flow to be directly influenced.

As already described, the casting mold has an outer boundary that is impermeable to liquids. The drain openings can thus be arranged in this outer boundary, which makes it possible to provide certain points on the casting mold where an increased flow occurs. These are the points where the drain openings are located.

A further aspect relates to a production device comprising a casting mold for producing a fiber-based blank from pulp as described herein, in particular for producing a fiber-based blank according to the method as described herein.

The production device preferably has a control apparatus for controlling the drain openings.

By providing a production device, a coordinated system can be provided, wherein all components are pre-set to work together.

The method according to the invention is explained below with reference to schematic figures. In the figures:

FIG. 1: shows a casting mold;

FIG. 2A to 2E: show individual method steps;

FIG. 3: shows, by way of example, further typical fiber-based containers that can be produced by means of the method according to the invention;

FIG. 4: shows, by way of example, a typical fiber-based closure that can be produced by means of the method according to the invention.

FIG. 1 shows a casting mold 20 for a blank for a container in the shape of a bottle. In the present case, the casting mold 20 has two casting mold halves, wherein only one half is shown in FIG. 1. A cavity 22 is arranged within the casting mold 20, which cavity is surrounded by an outer boundary 23 that is impermeable to liquid. The cavity 22 is permeable to water and in the present case is formed from a metal grid or sieve. The liquid-impermeable outer boundary 23 has a hollow space 24 in which the cavity 22 is arranged. The casting mold 20 has a plurality of drain openings 21. The drain openings 21 connect an exterior of the casting mold 20 to the cavity 24. The casting mold 20 also has an inlet opening 25 that opens directly into the interior of the cavity 22. The drain openings 21 are arranged at different heights and can thus define different drain levels.

In the present case, the position designation “height” is defined on the basis of the illustration shown in FIG. 1 and thus on the container in its position of use, i.e. in an upright form with a drain opening at the top and a container base at the bottom on which the container stands.

Valves are arranged at both the inlet opening 25 and the drain openings 21 to close the respective openings.

The inlet opening 25 can, as shown here, be provided with a branch 26, which can also be closed.

FIG. 2A to 2E show individual method steps or process steps. These figures each show a simplified cross section through the casting mold 20 according to FIG. 1. As can be seen from FIG. 2A, the casting mold 20 is filled with a process liquid 30 such that a liquid reservoir 31 is formed within the casting mold 20. In the present case, the casting mold 20 is closed, i.e. the drain openings 21 are closed. The liquid reservoir 31 completely fills the hollow space 24 and also flows through and fills the cavity 22.

The casting mold 20 is connected with its inlet opening 25 to a corresponding reservoir in which pulp 40 is located. In the illustration according to FIG. 2A, the pulp 40 has already been applied to the liquid reservoir 31 in the casting mold 20. The branch 26 at the inlet opening is closed.

From FIG. 2B it can now be seen that the liquid reservoir 31 is specifically drained from the casting mold 20, in particular in the direction of the arrows P1 through the drain openings 21 arranged at the top in the present illustration. For this purpose, they are opened. Pulp 40 now flows through the inlet opening 25 into the interior of the cavity 22. The fibers in the pulp 40 are retained inside the casting mold 22, namely on the wall of the cavity 22. Here, a wall 101 of the later blank is constructed. The fibers are practically filtered out of the pulp so that only the liquid portion of the pulp penetrates into the cavity 24. This is shown by the hatching different from that of pulp 40. By opening or closing the drain openings 21 accordingly, a corresponding flow can be set within the casting mold 20 such that the fibers are deposited at desired locations or points within the cavity 22.

As soon as, for example, enough pulp has been deposited in the upper region in the present illustration, the now open drain openings 21 can be closed and other drain openings 21 can be opened. This can be seen, for example, from the illustration in FIG. 2C. Here, the drain openings 21 located further down in relation to the open drain openings 21 according to FIG. 2B are opened. The process liquid 30 now flows out of the mold in the direction of the arrows P2 and the pulp 40 settles at other locations within the cavity 22. The wall 101 is further constructed. In the next step, the lowest drain opening 21 can be opened. This is shown in FIG. 2D. The process liquid 30 still remaining in the casting mold 20 is now completely displaced by the pulp 40 and flows in the direction of the arrow P3. The construction of the wall 101 of the blank 100 is now finished.

A valve at the inlet opening 25 is then closed so that no further pulp can flow in. The liquid still remaining in the casting mold 20 is completely drained off and the resulting blank 100 is demolded. The casting mold 20 is now empty, although fiber residues from the pulp 40 may still adhere to the cavity 22. These fiber residues can be backwashed. In this case, process liquid 30 is introduced into the casting mold 20 through the drain openings 21. This is shown in FIG. 2E by the arrows P4. As the process fluid flows in, fiber residues are released from the cavity 22 and discharged through the branch 26, which is shown by the arrow P5. For this purpose, the inlet opening 25 is closed and the branch 26 is opened. This prevents the process liquid from being flushed into the pulp reservoir. After a certain time, the drain openings 21 are closed and the flushing process is finished. At this point, the interior of the mold, i.e. the hollow space 24 and the cavity 22, is again filled with process liquid 30, as shown in FIG. 2A. The branch 26 can be closed and new pulp can be applied to the liquid reservoir by opening the inlet valve 25.

FIG. 3 shows, by way of example, further typical fiber-based containers that can be produced by means of the method described here. Thus, a container 100 is visible that corresponds to the container 100 from the description of FIGS. 1 and 2. This container 100 is also in the shape of a bottle and also has a thread on the bottle neck. The container 100′ is in the shape of a bowl; the container 100″ is in the shape of a cup.

FIG. 4 shows an example of a typical fiber-based closure 300 that can be produced using the method described here.