Patent Application
20120128909
The invention relates to a molded insert for a molded part mold, more specifically a foam mold or galvano-mold, with an upper part and a corresponding lower part, with a cavity, more specifically a hollow, wherein the molded part mold creates a shape of a material, more specifically a foam, that is introduced in the cavity. The invention furthermore relates to a method for manufacturing a molded part and to a molded part.
In order to manufacture molded foam parts from foam systems, such as soft, semi-hard, hard and integral foam, foaming molds are typically used, which are manufactured from different base materials, depending on the intended use and required output or service life. Plastic material, plastic casting resins or plastic plates are used for instance for prototype or pre-series molds, whereas molds made of aluminum and/or steel are used for production runs, respectively for production of great quantities and complex parts.
These forms mostly consist of a lower shell and an upper shell which are connected by lateral hinges. When closed, both “halves” form a desired hollow space which is also called a cavity and which forms the required molded part.
Slides and inserts or the like, which are inserted and actuated manually, semi automatically and automatically, are used for demolding “undercuts”, ribs and the like. When the form is open and/or closed, a prepared foam system is introduced into the cavity by means of a gating system via a mixing head.
A negative or undesirable property of the aforementioned systems is that the foam adheres to the aluminum or steel of the foaming molds and can often only be removed mechanically.
In order not to damage the parts during demolding or to be able to remove them intact, diverse release agents are used. These release agents prevent an “adhesion” of the foam parts to the surface of the molds. Wax-based release agents, which are liquefied by means of solvents in order to be applied by means of a spray pistol or a brush, are mostly used.
These release agents must be applied before each cycle. In doing so the solvent evaporates and the wax leaves a relatively thin layer on the surface of the mold.
This is an independent process which must be stable in order to ensure an unchanging quality of the parts. The release agents are usually applied manually at the foaming plant by a worker by means of a spray pistol and the produced spray and release agent vapors must be aspirated.
Due to the repeated addition of the release layer, a thickening wax layer forms more specifically on the smaller radiuses or on the ribs, which must be regularly removed.
The application of the release layer as well as the regular removal of the wax residue represents a great time and cost expenditure, associated with a repeated interruption of the production process.
A thin release layer also remains on the molded parts themselves. This layer is only unproblematic when the part does not have to be processed any further, i.e. when it is a finished part.
However, should the foam parts be subsequently laminated, this layer of release agent residue makes it more difficult to glue the laminating material onto the foam. The lamination is carried out for instance by means of a leather or a foil. Thus, the foam part must be cleaned before lamination.
The described release agents are also used in the manufacture of spray skin or deep-drawn foil. So-called galvano-molds are frequently used for manufacturing spray skins and deep-drawn foils. Surfaces for door coverings, instrument panels or center consoles for instance are manufactured by means of these galvano-molds.
Two-part polyurethane systems for instance are sprayed onto these galvano-molds. A skin is thereby formed, the thickness of which varies depending on the incorporated quantity and which is removed from the mold after a corresponding reaction time. As explained above, release agents, which are added either manually or automatically, must be used in order to be able to demold or remove the produced skin.
The spray skins thus manufactured are frequently underfoamed with a support resulting in more complex components. To this end, it is also necessary to ensure that the spray skin is freed of any release agents.
Another disadvantage is that galvano-molds are very expensive to manufacture. Amongst other reasons, this is due to the fact that these forms are frequently impressed with a surface grain, which is supposed to impress the skin to be manufactured with a leather-type surface grain for instance.
Molded foam parts are furthermore frequently coated in so-called coatings. Such a coating is a protection layer. Without this protection layer, the surfaces of molded foam parts tend to pale and to become brittle when exposed to UV-light. The protection layer prevents the exposure to UV-light for instance by absorbing the UV-light.
For instance, coatings can be varnishes which are added to foam molds before the foaming processes and subsequently homogeneously bond with the foam. After demolding, the foam is then practically covered with the “coat”. The reject rate with molded foam parts covered in coating is relatively high and can amount to up to 30%. Release agents must also be used for clean demolding.
In the manufacture of carpets, such as are used for instance in vehicle construction, the back side of the carpet—mostly a thermally preformed carpet—is provided with a relatively thin-walled foam layer. The aim of this measure is to increase foot comfort, to absorb tolerances, and to achieve sound insulation. In order to be able to remove this extensive foam skin from the tool after the reaction time, a thin-walled foil, which has been thermoformed beforehand, is usually placed on the corresponding tool side as a release medium and disposed of after stripping. This process is costly in terms of labor and costs.
The object of the invention is to improve the prior art.
The object is solved by a molded insert for a molded part mold, more specifically a foam mold or galvano-mold, with an upper part and a corresponding lower part, with a cavity, more specifically a hollow, wherein the molded part mold creates a shape of a material, more specifically a foam, that is introduced in the cavity, wherein the molded insert is adapted to be disposed on the molded part mold so that in the disposed state, a cavity with a reduced volume is formed and the molded insert contributes to impressing the material.
Thus, a speedy exchange of the actual forming cavity can be ensured.
Furthermore, by removing the molded insert from the molded part mold, it is possible to wait for the reaction time to run out while already manufacturing the next foam part by means of molded inserts newly introduced into the molded part mold.
The following terms must be explained:
The “molded part mold” is a conventionally manufactured molded part mold, for instance made of aluminum or steel, which is usually used for manufacturing a molded part. The molded part mold more specifically includes a “foam part” with an upper part and a corresponding lower part. Thereby, the upper and lower part can be separated in order to remove a molded part. Foams which reproduce the shape formed by the upper part and the lower part can furthermore be injected into the closed foam mold, thus forming the foam molded part.
The molded part mold can furthermore be configured as a galvano-form. The galvano-form can also have an upper part and a corresponding lower part, only a lower part or an upper part being usually used. Thin formations such as skins can be manufactured with galvano-forms. Particularly high quality skins are produced by slightly etching the galvano-form, so that it has a so-called grain. In this manner, skins having a leather-type surface structure for instance can be manufactured.
The “molded insert” can completely fill the molded part mold or only cover parts of the molded part mold. Finally, the molded insert can be a plate or any other substantial object which is demolded together with the molded part.
The “cavity” is a hollow space formed by the molded part mold. In this context, in a one-piece molded part mold, it is more specifically referred to as “hollow”. The cavity and the hollow have in common that when introducing a material, such as a foam for instance, the form of the cavity or of the hollow is reproduced by the material.
The “introduced material” is more specifically a liquid or foamed material, which forms a solid body through a hardening process. For instance, the material can be a plastic foam, more specifically a soft, semi-hard, hard and/or integral foam. Epoxy resins can also be used as introduced material. Impregnated fibers such as fiber mats impregnated with epoxy resin (prepregs) which harden in the cavity, can also be introduced. Powdery materials such as those used in a slush molding method are also included.
In this context, “adapted to be disposed” means more specifically that the molded insert is adapted to the molded part mold in such a manner that the molded part mold receives the molded insert and that the molded part to be manufactured can be manufactured by means of the molded insert. A form-fit disposition is preferred, so that the molded part mold can act uniformly on the molded insert.
In order to manufacture molded parts without release agents, a surface of the molded insert related to the volume reducing cavities can have a slight or no interfacial tension. The interfacial tension must thereby be determined by the introduced material as well as the material of the related surface. The slight interfacial tension applies more specifically to steel and aluminum which form the surface of a convention molded part mold.
Since the quantitative values of the interfacial tension depend on the system used, which interacts with the surface, it is sufficient if for this specific system, the above condition is met. More specifically with the “foam” system, it is important that when the foam is hardened, the interfacial tension between the hardened foam and the surface of the molded insert be lower than with aluminum or steel.
The literature often refers to a surface tension instead of an interfacial tension. In the following, these terms must considered as synonyms.
Since merely the material property of the surface of the molded insert is significant with regard to being free of a release agent, the surface of the molded insert related to the volume reducing cavity can be coated.
In another embodiment, the surface of the molded insert related to the volume reducing cavity is formed by a plastic material. Thus, alternatives in terms of materials to aluminum and steel can be made available.
Slight interfacial surface tensions or interfacial tensions can be achieved by forming the surface of the molded insert related to the volume reducing cavity with a polyolefin, more specifically with polyethylene.
In another embodiment, the molded insert has a temperature conducting element which is more specifically made of metal. The temperature gradient of the material in the molded insert relative to the actual molded part mold made of aluminum or steel for instance, can be increased or reduced by means of this temperature conducting element. Thus it is possible to heat the material in the molded insert as well as to efficiently cool the material in the molded insert. Metals with good heat conducting properties are preferably used, though other heat conductors or insulators can also be used.
In order to also ensure a good temperature conductivity of the molded insert, the thickness of the material of the molded insert can amount to between 0.8 mm and 8 mm and most preferably approximately 2.5 mm. It is thereby particularly advantageous for heat conductivity to use very low material thicknesses.
In another embodiment the molded insert is manufactured as an injection molded part. In this manner, molded insert can be manufacture in great numbers, thus considerably reducing costs.
In order to ensure a determined fixation and a determined detach of the molded insert into or from the molded part mold, the molded insert can have a fastening element which allows a detachable solid assembly in the molded part mold. More specifically clamping or screwing devices are possible embodiments of the fastening element.
In order to give stability to the molded insert, the molded insert can form a support structure.
In order to reduce weight or to obtain a determined heat insulation, the support structure can have hollow spaces.
In another embodiment, joined partial molded inserts form the molded insert. More specifically extensive molded inserts such as carpet coverings in automobiles can thus be manufactured.
In order to form a molded insert with the partial molded inserts that is as homogeneous as possible, the partial molded inserts can have connection elements which can form a stable molded insert. Thereby, the connection elements can for instance be base on a type of groove and spring principle. Screw connections with dedicated threads can also be implemented.
In another aspect of the invention, the object can be solved by a method for manufacturing a molded part with a molded part mold with a cavity which impresses a form onto an introduced material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 023 684.8 | Jun 2009 | DE | national |
| 10 2010 010 330.6 | Mar 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE10/00613 | 6/2/2010 | WO | 00 | 1/17/2012 |
