WO2022056565A1

WO2022056565A1 - Device and method for producing a moulded pulp product

Info

Publication number: WO2022056565A1
Application number: PCT/AT2021/060325
Authority: WO
Inventors: Peter Paul Payr; Johannes PAYR; Hans Peter Arledter
Original assignee: Payr Engineering Gmbh
Priority date: 2020-09-16
Filing date: 2021-09-14
Publication date: 2022-03-24
Also published as: AT524245A1; EP4214362A1; AT524245B1

Abstract

The invention relates to a device for producing a moulded pulp product (1), comprising: a core mould (2), which can be dipped into a pulp and is mounted on a support plate (3), which core mould (2) has openings at which a negative pressure can be applied to suction the pulp; a transfer mould (11), which corresponds to the negative shape of the core mould (2) increased by the wall thickness of the moulded pulp product (1) prior to compaction and to which a negative pressure can be applied via openings in the transfer mould in order to transfer the moulded pulp product (1) from the core mould (2); and drive means for moving the core mould (2) and/or transfer mould in order to allow the moulded pulp product (1) to be transferred between the moulds. The openings in the core mould (2) have side walls (6) projecting into the interior of the core mould (2), these side walls (6) each being oriented for the most part at an acute angle to the pull-off direction (7) of the moulded pulp product (1) during removal from the core mould (2), and at least a proportion being formed as slots. In addition, the invention relates to a method for producing a moulded pulp product with the aid of a device of this kind.

Description

APPARATUS AND METHOD FOR MANUFACTURING A FIBER CAST PRODUCT

Technisches Gebiettechnical field

The invention relates to a device for producing a cast fiber product comprising a three-dimensional core mold that can be immersed in a pulp or washed around by a pulp, which is mounted on a carrier plate, the core mold having openings to which a vacuum can be applied to suck in the pulp, a transfer mold , which corresponds to the negative mold of the core mold that has been expanded by the wall thickness of the cast fiber product before compacting, and to which a vacuum can be applied via openings in the transfer mold to take over the cast fiber product from the core mold, as well as drive means for moving the core mold and/or transfer mold in order to transfer it of the molded pulp product between the molds. The invention also relates to a method for producing a molded fiber product using such a device, wherein the openings in the core mold have side walls protruding into the interior of the core mold, these side walls each being largely aligned at an acute angle to the direction of withdrawal of the molded fiber product when it is removed from the core mold are.

Stand der TechnikState of the art

Various products have been manufactured using fiber casting for a long time. For example, cartons are widely used for storing and transporting eggs, for transporting small appliances or spare parts for machines and vehicles. The current state of the art in pulp casting is to make an aluminum mold, for example by milling, in which a metal screen is then formed so that the water can be sucked out of the pulp through the screen and through some suction holes drilled in the mould. The screen is attached to the mold by various techniques, e.g. B. by soldering, welding and gluing.

During the casting process, the mold is immersed in pulp and the pulp is applied to the mold by sucking off the solvent. This leads to contamination of the screen by fiber fines and sticking of the fibers within the screen structure, which is why it has to be cleaned or replaced more often. In addition, this sticking to the screen means that only very simple shapes can be produced, and the wall thicknesses must also have a certain thickness during the production process in order to avoid tearing of the fiber cast product when it is removed from the mold.

Subsequent to the casting process, the removed fiber cast products are further dried by the action of heat according to the methods of the prior art, as a result of which the manufacturing process is slow and associated with increased energy costs.

the

JP

s5927440

B

2 shows a fiber casting mold with a core mold with conventional through openings arranged in the form of a sieve. The inner side walls of these through-openings are in each case aligned normal to the respective surface and not in the pull-off direction of the fiber cast product. An outer shape is also shown, which in some embodiments also has slit-shaped openings. However, this outer mold does not serve to support the pulp during the suction process, but rather smoothes the outside of the cast fiber product by moving the outer mold relative to the core mold during the suction process.

the

WHERE

WO 2016/101976

A

shows specific configurations of the inner sidewalls of the openings in a core mold. A specific orientation in the drawing direction of the molded fiber product in a majority of the inner side walls of the openings in all sections of a core mold is not disclosed.

the

GB

2456502

A

, the

, the

as well as the

show other core shapes with conventionally arranged screen-shaped openings, each provided with inner sidewalls oriented normal to the surface.

Darstellung der ErfindungPresentation of the invention

An object of the present invention is to significantly improve the fiber casting apparatus, particularly the casting mold. The casting mold should be inexpensive to produce and also allow complex shapes of cast fiber products to be produced, even with very small wall thicknesses. Furthermore, it is the object of the invention to optimize the entire casting process in such a way that the manufacturing process is accelerated and the use of energy is reduced. In particular, the initial dewatering during the manufacturing process is to be significantly improved, which will significantly reduce energy consumption during the drying process.

According to the invention, this object is achieved on the one hand by a device mentioned at the outset, in which at least some of the openings in the core mold are designed as gaps between lamellae aligned approximately parallel to one another, the gaps and thus also the lamellae being preferably arranged on those surfaces of the core mold which are oriented steepest to the pull-off direction of the molded fiber product with respect to the entire core mold. Such a shape can also be produced with more complex geometries, for example by 3D printing processes. Any number of openings in the form of suction channels can be provided along the surface of the core mold. Due to the orientation of the inner side walls of the suction channels, the fibers accumulate around the openings in an orientation which facilitates removal of the finished molded fiber product. Even very soft, thin-walled cast fiber products can be easily removed without sticking or tearing.

Surprisingly, the arrangement of the gaps on the steeper sections of the surface of the core mold has turned out to be a particularly effective shape for the suction openings. In particular in the case of production using 3D printing, a large number of lamellae arranged closely next to one another with gaps in between can be provided. Surprisingly, this shape of the openings has turned out to be particularly advantageous, especially in the area of very steeply inclined surface sections of the surface of the core mold, which are almost oriented in the direction of withdrawal. The gaps allow negative pressure to be applied over a large part of the surface of the molded fiber product, resulting in effective suction. At the same time, it is precisely in these steep areas that the majority of the fibers are aligned in the pull-off direction, which effectively prevents them from sticking to the core mold.

According to one possible embodiment, it is provided that at least some of the openings in the core mold are designed as bores distributed in a grid pattern over the surface of the core mold. The suction openings can be provided as bores distributed in a grid pattern, particularly in those portions of the surface of the core mold which are oriented more normally to the direction in which the fiber cast product is drawn off. If openings are provided in the finished cast fiber product, then no suction openings can be provided on the corresponding sections on the surface of the core mold, which means that the fibers from the pulp do not rest in these areas.

It is a particularly advantageous feature that connecting webs are provided between the lamellae in the gaps to stabilize the core mold, with the connecting webs being offset inwards in the gaps in steps relative to the surface of the core mold, so that a vacuum can also be applied in the area of the webs . The slats are designed to be correspondingly longer, especially in the case of relatively steep surface sections. So that the gap width between the slats can be kept constant, it is necessary to provide connecting webs between the slats at regular intervals. In order to ensure that the fibers are also adequately suctioned off and aligned in the area of the connecting bars, the connecting bars are offset into the gaps relative to the surface of the core mold, so that the vacuum applied can continue to act on the fiber cast product over the entire length of the gaps.

It is also a preferred feature that overpressure can be applied to the core mold to blow out the fiber cast product. This further facilitates the removal of the finished molded fiber product when transferring the product to a transfer mold.

On the other hand, the object of the invention is also achieved by a method according to the invention for producing a cast fiber product with the aid of the device described above. Such a procedure includes the following steps:
-) Dipping the core mold into a pulp or flushing the core mold with a pulp and applying a vacuum to the openings in the core mold, whereby a layer of fibers is applied to the core mold while the solvent is sucked off through the openings,
-) removing the core mold from the pulp while further sucking off the remaining solvent and merging the core mold and the transfer mold,
-) Pressing the core mold and the transfer mold together, whereby further solvent is sucked out of the fiber product, optionally with vacuum and compressed air support.
-) Transferring the cast fiber product to the transfer mold by adhesion forces becoming effective and, if necessary, by applying a negative pressure to the openings in the transfer mold and, if necessary, an overpressure to the openings in the core mold.

According to a preferred embodiment, it is provided that after the fiber cast product has been transferred to the transfer mold, the product is pressed between the transfer mold and another dry press mold for further mechanical dewatering, with a vacuum being applied either to the transfer mold or to the dry press mold to ensure a defined flow is applied to remove the pressed-out solvent, and after the pressing process the fiber cast product is transferred back to the transfer mold. Depending on the requirements, an overpressure can also be applied alternately to support the desired direction of flow at the other mold.

In this variant of the method according to the invention, a small proportion of the mechanical dewatering takes place by pressing the molds together during the transfer between core mold and transfer mold. The main part of the mechanical dewatering is then carried out between the transfer mold and another dry press mold. The dry press mold largely has the shape of the core mold. In particular, by pressing the dry press mold and the transfer mold together, the cast product produced is mechanically dewatered, as a result of which the dry content of the product is increased by at least 10-30%. As a result, significantly less energy has to be used in the subsequent drying steps using heat treatment and the production times are significantly reduced.

The extensive outsourcing of the mechanical dewatering step with the help of an additional dry press mold has the advantage of significantly reducing the cycle times for the creation of the pulp product, since the core mold is free again immediately after the first transfer to the transfer mold to be dipped into the pulp during the mechanical pressing step is carried out using the dry press mold.

It is an additional advantageous feature that immediately before the step of pressing the molded fiber product between the transfer mold and the dry press mold, the molded fiber product is oriented so that the narrowest side or one of the narrowest sides of the molded fiber product faces downward. Surprisingly, it has been shown that the orientation of the cast fiber product during the pressing process has a decisive effect on increasing the dry content.

After moving the core form out of the pulp, the less rewet there is, the more effective the dewatering by suction. Here, the position of the core mold ensures that the sucked-off water is guided away from the fiber fleece and that there is no rewetting due to capillary action.

The transfer to the transfer form takes place mainly through adhesion forces. This pressing process has little effect on the dry content. This was mainly achieved by the previous suction process on the way to the transfer form.

During the pressing process between the transfer mold and the dry press mold, a vacuum is applied either to the transfer mold or to the dry press mold to ensure a defined flow for removing the pressed-out solvent. Here, too, the position of the molds ensures that there is no rewetting.

If the narrowest side of the molded pulp product is oriented downwards, the solvent present in the still moist pulp will move to this area by gravity, causing the upward facing parts of the molded pulp product to have an increased dry content even before pressing. Similar to a funnel, the water converges in the narrowest part of the product. During the subsequent pressing process, during which suction continues to take place via the openings in the core mould, the solvent in the lower area can no longer escape and is effectively pressed out of the cast fiber product.

Finally, another advantageous feature is that after the final transfer of the molded fiber product to the transfer mold, the molded fiber product is transferred to a heated mold for further drying and shape stabilization. As a result, the stabilization of the shape of the fiber cast product can be further improved, particularly in the case of products with small wall thicknesses. This step can either take place directly between the original transfer mold and the heated mold, or a transfer to the heated mold can take place and the heating and shaping step then takes place between the heated mold and another transfer mold, which can also be heated.

Kurze Beschreibung der ZeichnungenBrief description of the drawings

The invention will now be described in greater detail using an exemplary embodiment and with the aid of the accompanying figures. show it
1 shows a schematic perspective view of a possible embodiment of a core mold for a device according to the invention,
2 shows a schematic detailed sectional view through an embodiment of a core mold,
FIG. 3 is a schematic perspective view of the underside of the core mold of FIG. 1;
4 is a perspective view of an embodiment of a transfer mold and
5 is a perspective view of one embodiment of a dry press mold.

Weg(e) zur Ausführung der ErfindungWay(s) for carrying out the invention

The core mold 2 shown schematically in FIG. 1 is designed as an example for the production of a cup. However, much more complex shapes can be produced depending on the application. The only condition is that there must be no undercuts in the pull-off direction 7 of the cast fiber product 1 (see FIG. 2), which would prevent the cast fiber product 1 from being pulled off. The core mold 2 has a carrier plate 3 . Openings in the form of bores 4 are provided in the flatter sections, which are oriented more normally to the drawing-off direction, and openings in the form of gaps 5 are arranged between lamellae 9 in the steep sections. In the particularly steep sections of the surface 8 of the core mold 2, the lamellae 9 and gaps 5 are preferably aligned with the draw-off direction 7, so that the gaps run as perpendicularly as possible along the steep surfaces. Between the slats 9 there are connecting webs 10 (see FIGS. 2 and 3), which are offset towards the surface 8 inwards.

FIG. 2 shows a detailed section of the core mold 2 from FIG. The core mold 2 can, for example, be glued or tightly screwed to the carrier plate 3 or be manufactured in one piece together with the carrier plate 3 . Vacuum can be applied to the openings 4.5 of the core mold 2. As can be seen in the section, the inner side walls 6 of both the bores 4 and the gaps 5 are largely aligned in the direction of the withdrawal direction 7, which is represented by an arrow. The fibers of the cast fiber product 1 shown in dashed lines are therefore also aligned in the direction of the withdrawal direction 7 when they are placed in the area of the

openings

4, 5, which makes it particularly easy to remove the cast fiber product 1, especially in the steep sections of the surface 8. The novel core shape also allows pulps with a high solvent content and particularly short fibers to be used, which allows the production of more complex shapes and products with thin wall thicknesses.

FIG. 3 shows the core mold 2 from FIG. 1 in a view obliquely from below. The connecting webs 10 are also clearly visible here, which connect the individual slats 9 to one another at a distance from the surface 8 .

4 and 5 show an embodiment of a transfer mold 11 and a dry press mold 13. The

molds

11, 13 are used here to produce a shell-shaped cast fiber product 1. The transfer mold 11 has openings 12 for applying a negative pressure or positive pressure. The dry press mold 13 also has openings 14 distributed over the mold for applying a negative pressure or positive pressure. The dry press mold 13 has essentially the same shape as the core mold 2 intended for this product, with the difference that the core mold has differently shaped openings. In the steep wall sections in particular, the openings in the core mold would be in the form of columns 5 .

The sequence of the method for producing a molded fiber product is described in more detail below. The pulp is prepared by combining the fiber material with one or more solvents and optionally additives in a disperser. For example, fibers with a diameter of 1 to 10 µm are used in the pulp. For example, cellulose fibers, waste paper or other natural vegetable fibers can be used as fibers. Water is usually used as the solvent. Various adhesives, for example, or also substances for changing the pH value can be added as additives.

In the first step of the fiber casting process, the core mold 2 mounted on a support plate 3 is dipped into the pulp. The core mold 2 is fixed on the carrier plate 3 in such a way that both negative and positive pressure can be applied within the core mold. For some tasks it is also better to fix the core mold in the installation position and to wash or flood the casting area with the pulp. The negative pressure applied is usually around 100 mbar or 10 kPa. In the case of coarser fibers, a somewhat higher pressure difference may be necessary in order to deposit the fibers quickly.

As soon as the pulping is completed after a few seconds, the core mold 2 is removed from the pulp and brought together with a transfer mold 11. The transfer mold 11 corresponds to the negative mold of the core mold 2, but expanded by the wall thickness of the cast fiber product 1 before compression. When brought together, the very soft cast fiber product 1 is pressed out between the core mold 2 and the transfer mold 11 using mechanical pressure. The core mold 2 continues to be suctioned off in order to quickly remove the excess solvent during the pressing process. In some applications, an overpressure may also be applied briefly via the suction openings 12 in the transfer mold 11 in order to further accelerate the mechanical removal of the solvent during the pressing process.

After pressing out, air with an overpressure of approx. 100 to 300 mbar (10 to 30 kPa) is applied to the core mold 2 to transfer the fiber cast product 1, whereby the fiber cast product 1 detaches from the core mold 2 and by applying negative pressure in the transfer mold 11 is handed over to them. The core mold 2, which is now free, moves back to the pulp and the sucked-off, pure solvent is backwashed through the bores 4 and gaps 5 to clean the core mold 2.

The core mold 2 is thus ready for the next casting. So that the cycle times can be kept short, the step of mechanical dewatering by pressing the cast fiber product 1 can also take place between the transfer mold 11 and another dry press mold 13 . As a result, the core mold 2 is free again immediately after the shaping step and the transfer to the transfer mold. It is advantageous if the molds are aligned during the mechanical dewatering step in such a way that the solvent still contained in the cast fiber mass collects at a narrow point of the cast fiber product due to gravity. As a result, it can be removed more effectively from the pulp mass during the pressing process, which makes the mechanical dewatering step even more efficient.

Subsequent to the mechanical dewatering step, the cast fiber product 1 is transferred with the transfer mold 11 to another mold, similar to the core mold 1, and heated there in order to achieve further drying and shape stabilization. In about 10 to 30 seconds, enough water has evaporated so that the cast fiber product 1 becomes stable and no longer warps during subsequent drying in the air or during subsequent drying if there is still residual moisture. The inner surface of the cast fiber product 1 is also smoothed by the heated mold, which in many cast fiber products 1 brings with it an increase in usability and quality. Depending on the wall thickness of the desired cast fiber product 1, production cycle times can be as little as one second.

Claims

Device for the production of a cast fiber product (1) comprising a three-dimensional core mold (2) which can be immersed in a pulp or around which a pulp can be washed, which is mounted on a carrier plate (3), the core mold (2) having openings to which a negative pressure can be applied suction of the pulp, a transfer mold (11), which corresponds to the negative mold of the core mold (2) expanded by the wall thickness of the cast fiber product (1) before compaction, and to which a negative pressure is applied via openings (12) in the transfer mold (11). to take over the cast fiber product (1) from the core mold (2), as well as drive means for moving the core mold (2) and/or transfer mold (11) in order to transfer the cast fiber product (1) between the molds (2, 11). enable, the openings in the core mold (2) having side walls (6) protruding into the interior of the core mold (2), and these side walls (6) each for the most part at an acute angle to the pull-off direction (7) of the pulp product (1) are aligned when removed from the core mold (2), characterized in that at least some of the openings in the core mold (2) are designed as gaps (5) between lamellae (9) aligned approximately parallel to one another, the gaps (5) and thus also the lamellae (9) are preferably arranged on those surface sections of the core mold (2) which, viewed in relation to the entire core mold (2), are oriented the steepest to the take-off direction (7) of the cast fiber product (1).
Device for producing a cast fiber product (1) according to claim 1, characterized in that at least some of the openings in the core mold (2) are designed as bores (4) distributed in a grid pattern over the surface (8) of the core mold (2).
Apparatus for producing a cast fiber product (1) according to Claim 1 or 2, characterized in that connecting webs (10) are provided between the lamellae (9) in the gaps (5) to stabilize the core mold (2), the connecting webs (10) relative to the surface (8) of the core mold (2) are offset inwards in the columns (5) so that a negative pressure can also be applied in the area of the webs (10).
Device for producing a cast fiber product (1) according to one of Claims 1 to 3, characterized in that an overpressure can be applied to the core mold (2) in order to blow out the cast fiber product (1).
Process for the production of a cast fiber product (1) with the aid of a device comprising a three-dimensional core mold (2) which can be immersed in a pulp or washed around by a pulp and which is mounted on a carrier plate (3), the core mold (2) having openings for the application of a negative pressure, which have side walls (6) protruding into the interior of the core mold (2), and wherein the side walls (6) are each mostly aligned at an acute angle to the pull-off direction (7) of the fiber cast product (1), and wherein at least a portion of the openings in the core mold (2) is formed as gaps (5) between lamellae (9) aligned approximately parallel to one another, and wherein the gaps (5) and the lamellae (9) are preferably arranged on those surface portions of the core mold (2). , Which with respect to the entire core mold (2) seen the steepest to the withdrawal direction (7) of the fiber cast product (1) are aligned, a transfer mold (11), which of the Wall thickness of the cast fiber product (1) before compacting corresponds to the expanded negative mold of the core mold (2), and which has openings (12) for applying a vacuum, as well as drive means for moving the core mold (2) and/or the transfer mold (11), characterized that the procedure includes the following steps:

-) Dipping the core mold (2) in a pulp or flushing the core mold (2) with a pulp and applying a vacuum to the openings in the core mold (2), whereby a fiber layer is applied to the core mold (2) while the solvent is sucked off through the openings,

-) removing the core mold (2) from the pulp while further sucking off the remaining solvent and bringing the core mold (2) and the transfer mold (11) together,

-) Pressing the core mold (2) and the transfer mold (11) together, as a result of which further solvent is pressed out of the cast fiber product (1), optionally with vacuum and compressed air support.

-) Transferring the cast fiber product (1) to the transfer mold (11) by adhesion forces becoming effective and, if necessary, by applying a negative pressure to the openings in the transfer mold (11) and, if necessary, an overpressure to the openings in the core mold (2).
Method according to Claim 5, characterized in that after the fiber cast product (1) has been transferred to the transfer mold (11), the product is pressed between the transfer mold (11) and a further dry press mold (13) for further mechanical dewatering, with either at the Transfer mold (11) or a vacuum is applied to the dry press mold (13) to ensure a defined flow to remove the pressed-out solvent, and the fiber cast product (1) is then transferred back to the transfer mold (11) after the pressing process.
A method for producing a molded fiber product (1) according to claim 6, characterized in that immediately before the step of pressing the molded fiber product (1) between the transfer mold (11) and the dry pressing mold (13), the molded fiber product (1) is aligned so that the narrowest side or one of the narrowest sides of the fiber cast product (1) points down.
Method for producing a cast fiber product (1) according to one of Claims 5 to 7, characterized in that after the last transfer of the cast fiber product (1) to the transfer mold (11), the cast fiber product (1) is transferred to a heated mold for further drying and shape stabilization will.