Method for depositing fibres into a mould

Abstract

Disclosed is a method for depositing fibres into a mould. The method comprises the steps of - providing a mould (20), - introducing an injection lance (30) into the mould (20), - injecting pulp through the injection lance (30) into the mould (20) to deposit a layer of fibres onto an inner surface (22) of the mould (20). During the injection step, the injection lance (30) is moved from a lower position within the mould (20) to a higher position within the mould (20).

Description

[0001] The present invention relates to a method for depositing fibres into a mould in accordance with the preamble of the independent claim.

[0002] Different containers for holding liquid are known from the prior art. For example, glass bottles or plastic bottles have become popular for holding beverages.

[0003] Containers which are made of fibre-based material have likewise already been proposed.

[0004] Such containers are typically produced from a pulp. The production process is a two-stage process. In the first stage, a blank of a container is produced and in the second stage, the blank is dried and, if necessary, cured.

[0005] The pulp is a mixture of fibres and water, in particular natural fibres such as hemp fibres, cellulose fibres or flax fibres or a mixture thereof. The pulp may have additives, which, for example, improve curing of the compressed pulp or have an influence on the later appearance or generally change the properties of the pulp or of the later container.

[0006] Typically, to produce the blank, pulp is injected into a mould until a sufficiently thick layer of fibres has been deposited on the inner surface of the mould. The mould can be porous or made from a mesh which allows water to be drained off.

[0007] As soon as the desired thickness of the layer is received, the injection of the pulp is interrupted. A flexible balloon having the shape of an inner contour of the to be produced container is introduced into the mould and blown up such that the layer of fibres is pressed against the inner surface of the mould. This results in a drainage of water from the fibres.

[0008] The layer of fibres is not only drained, but also compacted. These steps are performed to form a blank inside of the mould. This blank has an inherent stability.

[0009] Typically, moulds are made form two halves such that the blank can be demoulded.

[0010] The blank, as present in the mould after pressing with the flexible tool is not yet ready to use. Indeed, the blank has to be dried and / or cured. These next steps are typically performed outside of the mould, either in a second mould, e.g. as disclosed in WO 2023 / 232995 A1, or without a mould at all. In each case, the blank has to be demoulded from the mould and transferred to a different place or into a second press-mould.

[0011] To receive a uniform product, unique process conditions have to be met, such as for example curing temperatures or curing time. These conditions are dependent on the properties or characteristics of the blank. For example, thicker blanks need longer to dry compared with thin blanks. If a blank has concurrently thin and thick areas, process conditions are always a compromise.

[0012] It is thus an aim of the invention to remedy at least one of the disadvantages of the prior art. In particular, a method for depositing pulp into a mould is to be provided which enables to produce a uniform blank which can be preferably processed with a narrower range of parameters. In particular, the aim is to provide a method for obtaining a blank with uniform properties over most of its extent.

[0013] This object is achieved by the method for depositing fibres into a mould as defined in the independent claim. Further embodiments emerge from the dependent claims.

[0014] The method comprises the steps of: providing a mould, introducing an injection lance into the mould, injecting pulp through the injection lance into the mould to deposit a layer of fibres onto an inner surface of the mould.

[0015] During the injection step, the injection lance is moved from a lower position within the mould to a higher position within the mould.

[0016] This movement allows to control the injection point of the pulp relative to the shape of the mould and thus to the shape of the product to be received.

[0017] In contrast to a static position of the injection lance, an aggregation of pulp, resulting in an increased thickness of a wall or certain areas of the blank, can be avoided. Furthermore, the risk that already deposited fibres are flushed away due to a continuous injection at the same point can be reduced.

[0018] Furthermore, a respective movement can lead to a deposition of pulp in areas, which have typically a thinner layer due to geometric boundaries, either of the shape of the product or of the mould.

[0019] The deposition of the fibres may be influenced by the direction or intensity of the flow of the pulp, respectively, of the water drained off the pulp. In areas of the mould where drainage of the water is only possible in small quantities, placing the lance close to these areas leads to a higher deposition. A uniform distribution of fibres can be achieved.

[0020] It can be advantageous to repeat the movement of the lance, in particular, to move the lance back to the lower position and to repeat the injection step. The fibres can thus be deposited in layers. If the fibres are deposited this way, the deposited fibres can set and gain some stability.

[0021] This repetition can also be made for one or more intermediate positions. Additionally, or alternatively, the injection can also take place during downward movement of the lance. It could also be advantageous to inject the pulp intermittently at several locations along the movement direction of the lance.

[0022] In particular, the movement of the lance can be non-linear. For example, in areas of the mould with a narrow diameter, the movement of the lance can be faster than in areas with a wider diameter. A slow movement leads to an increased deposition of fibres.

[0023] By definition, a low position means a position, in which the injection lance is inserted deep into the mould, whereas a high position or an upper position is a position, in which the injection lance is close to an opening of the mould. This definition is particularly relevant if the method is used with moulds which are upside down.

[0024] Preferably, the injection lance is initially placed next to an upper end of the mould. This provides a unique and reproducible starting point for the method.

[0025] Advantageously, after initially placing the injection lance next to the upper end, the mould is back flushed with a flushing solution, in particular water, and the flushing solution is discharged via the injection lance.

[0026] By way of back flushing the mould can be rinsed and clogged pores reopened, or clogging can be avoided.

[0027] The step of back flushing can be processed similarly to the step of injection, in particular, combined with a movement of the injection lance. This allows to generate a specific flow within the mould and / or on certain areas of the mould which, e.g. are susceptible to clogging.

[0028] As indicated, the flushing solution is preferably discharged via the injection nozzle. Hence, no additional of different element is necessary to enable back flushing of the mould. If water is used as flushing solution, there is no need of a separated circulation system.

[0029] After the back flushing step or alternatively, through the back flushing step, the injection lance is moved into the lower position. This results in a closed system without any interruption after the first placement of the injection nozzle until finishing of the injection of the pulp.

[0030] As soon as the layer of fibres has a desired thickness, the injection of the pulp is stopped.

[0031] At this stage, the mould is still filled with pulp or water.

[0032] For emptying the mould, after the injection step, a gaseous fluid, in particular air, can be injected into the mould via the injection lance to expel a fluid component, in particular water, from the mould and thus from the remaining pulp. The remaining fibres will agglomerate on the deposited layer and the water pressed through the layer and the emptying process is thus accelerated, in particular compared to a drainage of water by gravity.

[0033] Even if the arrangement is upside down, expelling the water via a gaseous fluid can be advantageous because the deposited fibres can be set down and / or compressed. The deposited layer thus gains stability.

[0034] For a specific deposition of the fibres or ejection of the fluid from the injection lance, the injection lance can be provided with a nozzle. The pulp is then injected into the mould through the nozzle. The nozzle enables to provide a specific geometry and thus specific fluid dynamics on its exit.

[0035] During the injection step, specific manufacturing parameters can be controlled via a controller. Examples of specific manufacturing parameters can be the pressure of the pulp, the position of the injection lance, the duration of injection, the volume of the injected pulp and the speed of the movement of the lance. This enables to provide a targeted deposition of the fibres within the mould.

[0036] Preferably, the specific manufacturing parameters are determined by the controller based on input parameters. The input parameters are preferably chosen from a list comprising: desired property of the blank or the product to be manufactured, such as thickness of the layer or parameters and / or properties of the pulp, such a density or temperature. Some of those parameters can also be automatically provided to the controller, in particular, by sensors.

[0037] Various aspects of the invention will be described by way of example with reference to schematic drawings. These show: Figure 1:A cut view through a mould before starting the injection step; Figure 2:a cut view through the mould of figure 1 at the starting of the injection step; Figure 3:a cut view through the mould of figure 1 at the end of the injection step.

[0038] Figure 1 shows a cut view through a mould 20 before starting the injection step. An injection lance 30 is placed on top of the mould 20, in particular, next to an upper end 21 of the mould 20. The mould 20 is already back flushed and ready for the injection. The injection lance 30 is fluidly connected to a pulp reservoir which is not shown.

[0039] The injection nozzle 30 is subsequently moved into a lower position within the mould 20, as indicated in figure 2.

[0040] Figure 2 thus shows a cut view through the mould 20 of figure 1 at the start of the injection step. The injection lance 30 is moved into a lower position of the mould 20, and pulp is ejected from the injection lance 30. The fibres contained in the pulp are deposited on the mould 20, in particular on an inner surface 22 of the mould 20 and a layer of fibres builds up on the inner surface 22 of the mould 20.

[0041] The injection lance 30 is, during the injection step, moved upwards into the position as illustrated in figure 3. This means that the injection lance 30 is moved from a position deep into the mould 20 to a position close to an opening of the mould 20.

[0042] Figure 3 thus shows a cut view through the mould 20 of figure 1 at the end of the injection step.

[0043] The injection lance 30 has been moved to an upper position and the ejection of pulp from the injection lance 30 has been stopped.

[0044] At this stage, compressed air can be provided to the injection lance 30 to expel the remaining fluid from the mould 20 to empty the mould 20.

Claims

1. Method for depositing fibres into a mould, comprising the steps of - providing a mould (20), - introducing an injection lance (30) into the mould (20), - injecting pulp through the injection lance (30) into the mould (20) to deposit a layer of fibres onto an inner surface (22) of the mould (20), characterized in that during the injection step, the injection lance (30) is moved from a lower position within the mould (20) to a higher position within the mould (20).

2. Method according to claim 1, wherein the injection lance (30) is moved back to the lower position and the injection step is repeated.

3. Method according to claim 1 or 2, wherein the injection lance (30) is initially placed next to an upper end (21) of the mould (20).

4. Method according to claim 3, wherein, after placing the injection lance (30) next to the upper end (21), the mould (20) is back flushed with a flushing solution, in particular water, and the flushing solution is discharged via the injection lance (30).

5. Method according to claim 4, wherein the injection lance (30) is subsequently moved into the lower position.

6. Method according to at least one of claims 1 to 5, wherein after the injection step, a gaseous fluid, in particular air, is injected into the mould (20) via the injection lance (30) to expel a fluid component, in particular water, from the mould (20).

7. Method according to at least one of claims 1 to 6, wherein the injection lance (30) is provided with a nozzle and the pulp is injected through the nozzle.

8. Method according to at least one of claims 1 to 7, wherein during the injection step specific manufacturing parameters are controlled via a controller.

9. Method according to claim 8, wherein the specific manufacturing parameters are chosen from a list comprising: speed of the movement, duration of the movement, pressure and / or volume of the injected pulp.

10. Method according to claim 8 or 9, wherein the specific manufacturing parameters are determined by the controller based on input parameters.

11. Method according to claim 10, wherein the input parameters are chosen from a list comprising: properties of the pulp and properties of a product to be manufactured.

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