TOOL FOR THE MANUFACTURE OF FOAM PARTS

Description

[0001] The invention relates to a tool for producing foam parts according to the preamble of claim 1.

[0002] Tools (cf. WO 2019 / 009704 A1) used to manufacture foam parts, for example parts made of expanded polypropylene (EPP), are usually made of aluminum. During the manufacturing process, the foam particles are filled into the cavity of the tool and foamed by applying heat. For this purpose, openings are provided in the walls of the tool or between adjacent walls to blow in steam for heating or to expel air displaced by the steam. Creating these openings in the walls is complex. Alternatively, tools made of sintered metallic material are used, which is permeable to air and steam, allowing hot steam and displaced air to pass directly through the walls. In both cases, however, the metal forming the walls is first heated, or the walls cool the incoming steam, resulting in poor energy efficiency.DE 100 07 911 A1 discloses a tool of the type mentioned above, whose filaments consist of threads. Similar tools are known from DE 102 31 567 A1, DE 10 2006 056 228 A1, DE 299 24 215 U1, and DE 199 07 279 A1.

[0003] It is therefore an object of the invention to further develop a tool of the type mentioned at the outset in such a way that it at least largely avoids the disadvantages mentioned above.

[0004] This object is achieved according to the invention by a tool having the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims.

[0005] The invention is based on the idea of designing the walls of the tool to be at least partially vapor- and air-permeable, so that steam can be introduced into the cavity and displaced air can be expelled from the cavity. This is achieved by at least one of the walls not being solid, but having at least one filament wall section that encompasses at least part of the inner surface of the respective wall and that has several layers of parallel, thread-like filaments. In particular, when the filaments are made of a plastic, for example a polyetherimide, a polyamide, a polyester, or a material mixture comprising at least two of these materials, the tool is not only lightweight, but the filament wall section absorbs less heat when hot steam is introduced than a metal wall section and cools the steam less, making the tool more energy-efficient.

[0006] It is preferred that the filaments of adjacent layers extend in different spatial directions. In particular, they can extend in spatial directions perpendicular to one another, so that the filaments are arranged crisscrossing. The layers of filaments are expediently arranged parallel to one another and span mutually parallel planes defined by the central longitudinal axes of the filaments of a layer. Furthermore, it is preferred that each filament wall section has 2 to 30 layers, and preferably 10 to 20 layers, of filaments and / or is 1 mm to 10 mm thick.

[0007] Typically, the filaments are not so tightly packed that they prevent the passage of steam or air. However, steam or air passage is further enhanced if the filaments in each layer are at least partially spaced apart and / or have interruptions. A large number of such deliberately created leaks allow for very efficient steam passage and heat transfer, as well as very efficient removal of air displaced from the cavity.

[0008] Advantageously, a support structure is arranged on the side of at least one of the filament wall sections, and preferably of each filament wall section, facing away from the cavity. This support structure is preferably made of the same material as the filament wall section. In order to facilitate the passage of steam or air through the filament wall section in question, it can be provided that parts of the support structure extend through the layers of filaments and preferably as far as the inner surface of the wall in question. The support structure preferably has a plurality of thread-like support filaments, wherein advantageously at least some of the support filaments extend through the layers of filaments. In this way, the passage openings already described above can be created by displacing adjacent filaments away from one another when a support filament passes through.The ends of some of the support filaments conveniently extend to the inner surface, so that the passage of steam through all filament layers is facilitated.

[0009] The support filaments advantageously have a larger cross-section than the filaments. Furthermore, they expediently have a curved shape, at least partially and preferably over their entire length. In this way, steam passage openings and channels are created in the support structure, which enable hot steam to pass through the support structure to the filament wall section and enable displaced air to be effectively removed. These openings or channels are then also larger than openings or channels extending through the filament wall section, whose filaments have a smaller cross-section and, thanks to their parallel arrangement, can be in contact with one another over long distances. The support structure can be described as a structure that is open-pored in all directions.

[0010] It may be provided that only one of the walls has a filament wall section. However, it is preferred that each of the walls has at least one filament wall section. Furthermore, it is preferred that the filament wall section of at least one of the walls encompasses its entire inner surface, thus enabling a large-area introduction of hot steam and a large-area discharge of displaced air.

[0011] To manufacture the tool, the preferred method is a 3D printing process, which is used according to the invention for the production of the filaments. With such a 3D printing process, even delicate structures such as the filament wall sections can be precisely manufactured.

[0012] The invention will be explained in more detail below with reference to an embodiment shown schematically in the drawing. Fig. 1 shows a tool in the form of a manufacturing mold for producing foam parts in a perspective view; Fig. 2 shows a section through the tool according to Fig. 1 ; Fig. 3 a plan view of an inner surface of the tool according to Fig. 1 and 2 ; Fig. 4a-c a filament wall section in schematic representation in perspective view, in top view and in side view and Fig. 5a, b a support structure in schematic representation in perspective view and in top view.

[0013] The tool 10 shown in the drawing is used to produce molded parts from foam. It has walls 12 that enclose a cavity 14 whose shape and size correspond to the shape and size of the molded part to be produced and thus represents its negative. The cavity 14 is delimited by the inner surfaces 16 of the walls 12.

[0014] Each of the walls 12 has a filament wall section 18, which encompasses all or a large part of the inner surface 16 of the respective wall 12. Each filament wall section is constructed from several layers 20, twenty in the illustrated embodiment, of thread-like filaments 22 made of a plastic, wherein the filaments 22 of each layer 20 extend parallel to one another and adjacent to one another. The filaments 22 of the adjacent layer 20 extend perpendicular to the filaments 22 of the first-mentioned layer 20, so that the filaments 22 of adjacent layers always extend in different, mutually perpendicular spatial directions. The layers 20 span planes extending parallel to one another. Fig. 3the uppermost layer 20 facing the cavity 14 can be seen. On the side of each filament wall section facing away from the inner surface 16, a support structure 24 is arranged, which is made up of support filaments 26, which are also thread-like, but each have a curved course over their entire length and a larger cross-section than the filaments 22. Some of the support filaments 26 extend through the associated filament wall section 18 and end at the respective inner surface 16. This creates gaps 28 between the filaments 22 in the filament wall section 18, at which gaps 28 adjacent filaments 22 are arranged at a distance from one another in places.

[0015] To produce a molded part, the cavity 14 is filled with foam particles. Hot steam is introduced into the cavity 14 through the walls 12, and any air present in the cavity 14 is displaced through the walls 12. Due to the curved and interwoven support filaments 26, the support structures 24 form passageways for steam and air, while the gaps 28 adjoining them form further passageways for the passage of steam and air through the filament wall sections 18.

[0016] The tool 10 is manufactured by 3D printing from a plastic or a plastic mixture. The filament wall structures 18 and the support structures 24 are made of the same material.

[0017] In summary, the invention relates to a tool 10 for producing foam parts, which tool has a plurality of walls 12 enclosing a cavity 14 corresponding to the shape of the foam parts to be produced, each wall 12 having an inner surface 16 adjacent to the cavity 14. According to the invention, at least one of the walls 12 has at least one filament wall section 18, which comprises at least part of the inner surface 16 of the respective wall 12 and which has a plurality of layers 20 of thread-like filaments 22 running parallel to one another.

Claims

1. Tool for the manufacture of foam parts, which tool has several walls (12), which enclose a cavity (14) corresponding to the shape of the foam parts to be manufactured, wherein each wall (12) has an inner face (16) adjoining the cavity (14), wherein at least one of the walls (12) has at least one filament wall part (18), which comprises at least one part of the inner face (16) of the associated wall (12), and wherein the at least one filament wall part (18) has several layers (20) of thread-like filaments (22) extending parallel to one another, characterized in that the filaments (22) are manufactured by means of a 3D printing process.

2. Tool according to claim 1, characterized in that the filaments (22) of mutually adjacent layers (20) extend in different spatial directions and in particular in mutually perpendicular spatial directions.

3. Tool according to one of the preceding claims, characterized in that the layers (20) are disposed parallel to one another and span mutually parallel planes.

4. Tool according to one of the preceding claims, characterized in that each filament wall part (18) has two to thirty layers (20) and preferably ten to twenty layers (20) of filaments (22).

5. Tool according to one of the preceding claims, characterized in that each filament wall part (18) is 1 mm to 10 mm thick.

6. Tool according to one of the preceding claims, characterized in that the filaments (22) consist of a polyether imide, a polyamide, polyester, a metal-containing material or a material mixture containing at least two of those materials.

7. Tool according to one of the preceding claims, characterized in that the filaments (22) of each layer (20) are at least partly disposed with space between one another and / or contain interruptions.

8. Tool according to one of the preceding claims, characterized in that a bracing structure (24) that preferably consists of the same material as the filament wall part (18) is disposed on the side, facing away from the cavity (14), of at least one of the filament wall parts (18) and preferably of every filament wall part (18).

9. Tool according to claim 8, characterized in that parts of the bracing structure (24) extend through the layers (20) of the filaments (22) and preferably up to the inner face (16) of the associated wall (12).

10. Tool according to claim 8 or 9, characterized in that the bracing structure (24) has a plurality of thread-like bracing filaments (26).

11. Tool according to claim 10, characterized in that at least some of the bracing filaments (26) extend through the layers (20) of the filaments (22) and in that in particular at least the ends of some of the bracing filaments (26) extend up to the inner face (16) of the associated wall (12).

12. Tool according to one of claims 10 or 11, characterized in that the bracing filaments (26) have a larger cross section than the filaments (22).

13. Tool according to one of claims 10 to 12, characterized in that the bracing filaments (26) have a curved trajectory that extends at least partly and preferably over their entire length.

14. Tool according to one of the preceding claims, characterized in that each of the walls (12) has at least one filament wall part (18) and / or in that the filament wall part (18) of at least one of the walls (12) comprises its entire inner face (16) and / or in that the bracing filaments (26) are manufactured by means of a 3D printing process.

15. Method for the manufacture of a tool according to one of the preceding claims, characterized in that the filaments (22) and if necessary the bracing filaments (26) are manufactured by means of a 3D printing process.