Press forming method of cup-shaped fiber product, fiber pressing mold and cup-shaped fiber product

Abstract

The invention relates to a method for press-forming a fibrous article at high pressure and high temperature by means of a press pad device (2) and a press device (3, 4), in which the fibrous article (1) comprises a bottom (11), a side wall (12) and an edge portion (10), in which the press device (3, 4) comprises two press members (3, 4), wherein a first stamping member (3) is used to form at least the bottom portion (11) and a second stamping member (4) is used to form the edge portion (10). The invention also relates to a fiber pressing tool (2, 3, 4) and a fiber product (1).

Description

Technical Field

[0001] The present invention relates to a method for pressing and molding a cup-shaped fiber product under high pressure and high temperature by means of a pressure pad device and a punching device, wherein the cup-shaped fiber product comprises a bottom, a side wall and an edge portion, and a fiber pressing mold for implementing the method. Background Art

[0002] Cup-shaped fiber products can be made by pressing a fiber web or fiber sheet. Typically, a combination of natural fibers (e.g., wood pulp fibers), synthetic fibers (e.g., polyolefin-based fibers) and other additives (such as adhesives or dyes). In many applications, it is preferred that such fiber webs consist essentially only of natural fibers, with or without additives. Typical process conditions are 150-250 degrees Celsius and a pressure of 100-10000 bar (200-2000 bar). The moisture content is usually less than 20%.

[0003] The fibrous product may be in the form of a hollow product, such as a packaging bag or a closure (lid, screw cap or the like), but may also be a flat product. The product may be formed from a web of material and punched / cut during forming, e.g. the product has been completely or partially separated from the web of material to allow for deeper forming. Such a product is typically finished by cutting the material into a shape suitable for the final shape. Typically, for example, it is cut into a circle to form a round packaging bag.

[0004] Compression forming is usually performed using two tools, where the outer tool pad and the inner tool (punch) can be composed of multiple parts to enable ejection of the finished product. Typically, the pad opens when the punch is folded. The piston, parts of the piston or parts of the pad can also be made of a compressible material that can generate greater vertical compression forces by reshaping the tool material during compression (typically against the sides of the cavity).

[0005] When the product is formed, the upper edge is typically uneven because the material is folded when it is pressed into the tool. The uneven material can be cut horizontally or vertically after or during the product is formed. In both cases, cutting residues are formed, which must be handled during the production process and are preferably recycled. If the cutting is performed in the same operation as the stamping, the design of the upper part of the tool is limited because the edges of the two parts must be suitable for the cutting process. This can make it difficult to feed the material into the pad. Cutting in the same operation as the stamping also leads to the problem of pressing the material with sufficient force while cutting. Therefore, the cut edge of the material may be poorly shaped. The above-mentioned known methods are shown in EP 3 736099 and WO 2020 / 165780.

[0006] A manufacturing mold for producing a board-shaped pulp product with a smooth outer edge is known from CN-20132641774. The mold comprises a convex pressure pad device, a central concave punch device and an annular outer punch device, wherein the outer punch device is used to form a smooth outer edge. Summary of the invention

[0007] The object of the present invention is to eliminate or at least minimize the above disadvantages, which is achieved by a method as defined in claim 1 and / or a fiber pressing mold as defined in claim 13 and / or a fiber product as defined in claim 14.

[0008] Thanks to the invention, cutting of the cup-shaped product after press forming can be completely avoided. In addition to eliminating the need for further cutting and eliminating the need to handle scraps, the invention also allows a better product, because the quality of the product edge can be more or less customized, for example providing higher quality at the edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the following, the invention will be described with reference to preferred embodiments of exemplary stampers and methods according to the invention by schematically describing the manufacture of specific preferred examples, wherein:

[0010] Figure 1 shows a schematic cross-sectional view of a pressing die in a first stage of producing a cup-shaped cylindrical fiber product;

[0011] Figure 2 A schematic cross-sectional view showing a pressing die in the second stage of producing a cup-shaped cylindrical fiber product;

[0012] Figure 3 Shown with Figure 2 Same schematic cross-sectional view, but the die is provided with a groove for forming a cup-shaped cylindrical fiber product with a thread. DETAILED DESCRIPTION

[0013] exist Figure 1 and Figure 2 , a fiber pressing mold for forming a fiber product 1 is shown, comprising a pressure pad device 2 and a punching device. The punching device comprises two punching members 3, 4, wherein the first punching member 3 is used to form at least the bottom 11 of the fiber product 1, and the second punching member 4 is used to form the edge portion 11 of the fiber product. In the illustrated embodiment, the second punching member 4 can move along the periphery of the first punching member 3.

[0014] The pressure pad device 2 comprises a main body 20 having an overall height H2. The pressure pad device 2 is formed with a cavity 22. In this embodiment, the cavity is relatively large to achieve a cup-shaped fiber product 1, i.e. including a vertical side wall 12 between the edge portion 10 and the bottom 11. Therefore, the cavity 22 comprises a bottom surface 23 and a vertical side wall 24, which in this embodiment is formed by an annular cylindrical surface. The overall height H22 of the cavity 22 (i.e. extending horizontally from the bottom surface 23 of the cavity to the upper surface 21 of the main body 20) is arranged so that it is greater than the height H12 of the fiber product 1. Preferably H2 is at least 10% greater than H12, more preferably at least 15% greater.

[0015] The first punching member 3 comprises a body 30 adapted to fit into the cavity 22 so that a gap can be formed between its vertical side wall 34 and the vertical side wall 24 of the cavity 22, thereby achieving the desired thickness t12 of the side wall 12 of the fiber product 1. This is achieved by making the transverse dimension D2 of the cavity 22 twice t12 larger than the transverse dimension D3 of the first punching member 3. For a person skilled in the art, it is obvious that the definition of "vertical" must be understood as substantially vertical, i.e. including a shape in which the side wall 12 (one or both surfaces thereof) deviates from a few degrees from exactly 90° relative to the horizontal plane of the bottom 11.

[0016] In the embodiment shown, a product 1 having a circular shape is produced, which is achieved by using circular side walls 24, 34, the cross-sectional diameters of which are respectively D2 and D3. As will be appreciated by those skilled in the art, other shapes other than a perfect circle can of course be used, for example only along the side wall 24 of the pressure pad device 2. The second punching member 4 has an annular body 40, which is arranged to slide along the outer side wall 34 of the first punching member 3, and whose height H4 is less than the height H3 of the first punching member 3. The end face 41 of the annular body 40 is used to form the edge portion 10 of the fiber product 1.

[0017] When the fiber product 1 is press-formed using the mold, the pre-cut blank (not shown per se) is introduced into the cavity 22 of the press pad device 2. The height H22 of the cavity 22 is such that the entire pre-cut blank can be positioned within the cavity 22, i.e., no part of the pre-cut blank protrudes above the upper surface 21 of the press pad device 2. In a first step, the first punching member 3 is applied with a force F1 to move downward into the cavity 22, and then the pre-cut blank is pushed into the cavity 22 and forms an intermediate product 1A having an uneven upper edge 10A, see Figure 1 The height H22 of the cavity 22 is such that all of the portion of the uneven upper edge 10A can be located below the upper surface 21 of the pressure pad device 2 .

[0018] Subsequently, a force F2 is applied to the second punching member 4 to move it along the outer side wall 34 of the first punching member 3, so that it is pressed downward into the cavity 22 in the gap between the outer side wall 34 of the first punching member 3 and the cavity side wall 24. High temperature is used during production, and high pressure is applied by means of the pressure pad device 2 and the punching members 3 and 4 to form the fiber product 1. The pressing temperature can be in the range of 150-250°C, and the pressure applied by the punches 3 and 4 is at least 200bar. In some applications, preferably, the pressure P3 generated by the force F2 applied to the edge portion 10 of the product is higher than the pressure P2 generated by the force F1 applied to the first punching member 3.

[0019] As shown, the first punching member 3 forms at least the bottom 11 of the fiber product 1 and the second punching member 4 forms the edge portion 10. This basic principle can also be used for fiber products with flat shapes. Preferably, the first punching member 3 at least partially forms at least the bottom 11 before the second punching member 4 starts to form the edge portion 10.

[0020] Preferably, the device is controlled (e.g., sensor-controlled) such that the first punching member 3 stops pressing at a given distance H3B relative to the position H0 of the pressure pad device 2, and the second punching member 4 stops pressing at a given distance H4B relative to the position H0 of the pressure pad device 2. Of course, the latter position can also be set relative to the first punching member 3. Most preferably, pressing stops when the upper end of the first punching member 3 is located at a given distance H4B relative to the position H0 of the pressure pad device 2, thereby achieving a given thickness t11 of the bottom 11.

[0021] As shown, the fibrous product 1 may include a substantially vertical side wall 12, and the second punching member 4 stops at a given distance H4B, a given distance H12 from the bottom 11, so that the edge portion 10 is positioned to achieve the desired height H12 of the product 1. As described above, the second punching member 4 may be applied with a force F2, which produces a pressure P3 on the upper edge portion 10 that is different from the pressure P2 produced by the first punching member 3, which may provide advantages. In many applications, it may be advantageous to apply the second punching member 4 to produce a higher pressure P3 than the pressure P2 applied by the first punching member 3. If the edge portion 10 is given a pattern or ribs, and / or if a portion of the side wall 12 below the edge portion 10 is given a pattern or ribs, such as ribs protruding inwardly 14 and / or outwardly 15, for example, forming Figure 3 This may be particularly advantageous with the threads and / or ridges shown.

[0022] In addition, if Figure 3As shown, due to the elastic properties of the fiber, the force F2 applied by the second punching member 4 obtains a pressure P4 near the edge portion 10 that is higher than the pressure P3 obtained lower in the side wall 12 below the edge portion 10 .

[0023] Due to the invention, great flexibility is provided in the production of the fiber product, for example a higher density is obtained in the edge portion 10 than in the bottom portion 11. The higher local density of the edge portion reduces the permeability of moisture and liquids. In addition, it facilitates the easy production of edge portions with a desired appearance, such as a straight surface. In addition, it facilitates the easy production of side walls arranged with protruding elements (such as threads and / or ribs, etc., the material partially consisting of natural fibers, A).

[0024] Preferably, the fibrous material in the fibrous product 1 is in the form of natural fibers from wood. Furthermore, the amount of water in the pre-cut blank (eg a round blank) before pressing must not exceed 20% of the fiber weight.

[0025] Furthermore, by designing the mould so that the entire pre-cut blank can be pressed downwards into the pad 2 and below the upper end surface of the pad 2 and forming the upper edge portion 11, a product having a given height and volume of material can be manufactured. Although the fibers have been repositioned during the pressing with the first punching member 3, the second pressing can achieve the desired result. Therefore, despite the slight change in the density of the upper edge portion 11, the final product can still be successfully obtained without any problems with wrinkles and / or local differences in the upper edge of the preformed product. In particular, post-forming can advantageously compress the side walls of the cup-shaped product by means of the first punching member 3 applying a pressure P2 less than the pressure P1 on a limited horizontal surface. The second punching member can be regarded as producing a kind of re-forming, which also helps to form inward or outward structures with different gap thicknesses or shapes, for example Figure 3 projections, reinforcements or threads as shown.

[0026] Another benefit is that the shaping of surfaces with precise patterns or ribs can be achieved with the aid of the present invention, ie shapes that would not be possible if cutting were required to shape the final product.

[0027] According to a variant of the invention (not shown), the second punching member 4 can be arranged to cut off an undesirable portion (not shown) of the final fiber product 1, for example at a given distance from the bottom. Preferably, this is performed so that first the pressing end face 41 of the second punching member 4 first at least partially compresses the edge portion 10, and the cutting edge (not shown) of the second punching member finally compresses the edge portion 10 and cuts off the undesirable excess portion in a final step.

Claims

1. A method for pressing and forming a fiber product under high pressure and high temperature by means of a pressure pad device (2) and a punch device (3, 4), characterized in that: The fiber product (1) comprises a bottom (11) and an edge portion (10), and the punching device (3, 4) comprises two punching members (3, 4), wherein the first punching member (3) forms at least the bottom (11) and the second punching member (4) forms the edge portion (10), wherein the second punching member (4) stops at a given distance (H12) from the bottom (11), the edge portion (10) is located at the farthest position from the bottom (11), and wherein the second punching member (4) can move along the periphery of the first punching member (3), and the fiber product also comprises a side wall (12), and after forming at least the bottom (11), the upper edge (10A) of the fiber product (1) is located in the cavity (22) of the pressure pad device (2).

2. The press forming method according to claim 1, characterized in that: The side wall (12) extends vertically relative to the horizontal plane where the bottom (11) is located.

3. The press forming method according to claim 1, characterized in that: The first punching member (3) at least partially forms at least the bottom portion (11) before the second punching member (4) starts to form the edge portion (10).

4. The press forming method according to claim 1 or 2, characterized in that: The entirety of the upper edge (10A) is located below the upper surface (21) of the main body (20) of the pressure pad device (2).

5. The press forming method according to any one of claims 1 to 3, characterized in that: The second punching member (4) at least partially cuts off the undesired portion of the final fiber product (1) at a given distance (H12) from the bottom (11).

6. The press forming method according to claim 1, 2, 3 or 4, characterized in that: The second punching member (4) stops pressing at a given distance (H4B) relative to the position (H0) of the pressure pad device (2) and / or the first punching member (3), so that the edge portion (10) is located at the given distance.

7. The press forming method according to any one of claims 1 to 5, characterized in that: The end of the first punching member (3) stops pressing at a given distance (H3B) relative to the position (H0) of the pressure pad device (2), so that the bottom (11) reaches a given thickness (t11).

8. The press forming method according to any one of claims 1 to 6, characterized in that: Forces (F1, F2) are applied to the first punching member and the second punching member (3, 4), respectively, so that different pressures (P2, P3) are achieved on the edge portion (10) when pressing with only the first punching member (3) compared to when pressing with the second punching member (4), and a higher pressure (P3) is achieved when pressing with the second punching member 4.

9. The press forming method according to claim 1, characterized in that: The material consists partly of natural fibers, which come from wood.

10. The press forming method according to claim 1, characterized in that: The pressing temperature is 150-250°C and the pressure on the bottom (11) is at least 200 bar.

11. The press forming method according to claim 1, characterized in that: The amount of water in the material does not exceed the amount of the fibers, and the weight of water in the material does not exceed 20% of the weight of the fibers.

12. The press forming method according to claim 1, characterized in that: The edge portion (10) and / or the side wall (12) are provided with patterns and / or ribs (14, 15).

13. A fiber pressing die, comprising a pressing pad device (2) and a punching device (3, 4), for forming a fiber product (1) comprising a bottom portion (11) and an edge portion (10), characterized in that: The punching device (3, 4) comprises two punching members (3, 4), wherein the first punching member (3) is used to form at least the bottom (11) of the fiber product (1) and the second punching member (4) is used to form the edge portion (11) of the fiber product, and wherein the second punching member (4) is arranged to stop at a given distance (H12) from the bottom (11), and the edge portion (10) is positioned farthest from the bottom (11), and wherein the second punching member (4) is arranged to move along the periphery of the first punching member (3), and the second punching member (4) is arranged to stop at a given distance (H12) from the bottom (11) to also form the side wall (12) of the fiber product (1) and the upper edge (10A) of the fiber product (1) in the cavity (22) of the pressure pad device (2).

14. A fiber product comprising a bottom (11), a vertical side wall (12) and an edge portion (10), characterized in that: The density of the edge portion (10) is higher than that of a portion of the side wall (12) which is closer to the bottom (11) than the edge portion (10).

15. The fiber product according to claim 14, characterized in that The side wall (12) has a pattern or ribs at a portion between the edge portion (10) and the bottom portion (11), and has ribs protruding inwards (14) and / or outwards (15), and the ribs form threads and / or convex edges.

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