Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Direct application of fluid pressure
Reexamination Certificate
2001-08-13
2004-06-15
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Direct application of fluid pressure
C264S046400, C264S101000, C264S293000, C264S321000, C264S327000, C264S510000, C264S520000, C264S553000, C264S554000
Reexamination Certificate
active
06749794
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method of manufacturing molded parts, such as automobile interior trim components, that have a molded-in surface texture, as well as an apparatus for carrying out such a method.
BACKGROUND INFORMATION
In various technical fields, and particularly in the automobile manufacturing industry, there is a constantly growing demand for various molded parts that have a surface texture molded into or onto the surfaces of such parts. For example, it is increasingly desired to provide interior trim components of a motor vehicle, such as headliners, door trim insert panels, column trim covers, consoles, parcel shelves, dashboards, and the like, with a surface texture such as an artificial leather grain, an artificial wood-like grain, a pattern of dots or lines or the like, simulated stitching lines, raised bumps and indented depressions or even molded-in text or logos. Such surface textures enhance the appearance of the visible surface of the molded part, or enhance the surface feel or grip characteristic provided by the surface, or provide intended information in the way of text or logos or the like.
In any event, however, the molded-in texture must be accurately and consistently represented or reproduced on the surface of the molded part, in order to achieve the intended effects. On the other hand, if the intended surface texture is inaccurately or distortedly reproduced on the surface of the molded part, this results in a visually unacceptable part which must be scrapped. Thus, it has been a significant problem in the industry, that defective or unacceptable surface texturing leads to a rather high reject and discard rate of such parts, although the parts may otherwise be fully in conformance with other requirements.
If has also been extremely difficult or impossible up to the present time, to achieve complex, or finely detailed surface textures, without distortion or misrepresentation, using conventionally known methods. One conventional method involves providing a flat starting sheet of cover stock that is pre-textured with the desired surface texture. Then, this pre-textured cover stock or cover sheet is deep-drawn and molded while being laminated with a backing substrate or the like. During this molding operation, which forms three-dimensional contours of the finished molded part, the pattern or surface texture of the cover sheet is necessarily distorted at different areas, depending on the degree of stretching and three-dimensional molding that has taken place at these respective areas. Namely, an area that is more deeply or extensively drawn and stretched will suffer an area expansion of the intended surface texture. Thus, a regular geometric pattern of dots or lines or the like on the starting cover sheet material will clearly show the areas of distortion resulting from the three-dimensional molding, and will generally not be acceptable. Text or the like can also not be provided at molded areas. Such a technique is generally only suitable for random textures of which a distortion is not readily apparent, or for providing a texture on areas that are not strongly contoured. Another problem of such a conventional process arises when the textured surface of the cover sheet is pressed in contact with a flat surface of a mold. In such a case, the surface texture will be at least partially crushed or flattened or “ironed out”, so that any resulting surface texture cannot have a very strong or roughly profiled texture.
To avoid the above-mentioned distortion that arises when deep-drawing or molding a pre-textured cover sheet, techniques have been developed to apply a surface texture onto a cover sheet or a surface of a molded part after the molding rather than before the molding operation. Such techniques are complicated, time consuming and not economical in production.
Two further conventional processes for forming a contoured skin sheet with a surface texture are the powder and spray slush methods. In the powder slush method, a thin galvanically fabricated zinc sheet is used as a contoured and textured mold which is heated and dipped into or coated with a polymer powder such as a polyvinyl chloride (PVC) powder, which then melts and forms a corresponding contoured and textured PVC skin on the zinc mold. The skin is peeled off, and can thereafter be applied onto a molded substrate. Alternatively, in the spray slush method, a liquid polymer such as polyurethane is sprayed onto the textured mold to form a textured skin, which can thereafter be peeled off and applied on a molded substrate. These slush skin methods are rather complicated, time consuming, and costly due to several additional required steps. Moreover, these processes generally use polyvinyl chloride and polyurethane materials, which are becoming ever more undesirable because they are not easily recycled, and they represent toxic risks and disposal problems. Also, the thin mold sheets have a relatively short useful life cycle, which leads to high tooling costs, and the surface textures that can be achieved are limited. Also, the conventional patterning or texturing processes all involve additional steps end additional work effort, beyond the molding operation itself.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide a method and an apparatus for producing a molded part having a surface texture that accurately represents the intended surface texture without distortion, and that is not limited as to the type of surface texture, but instead can be used to form synthetic leather grains, synthetic wood grains, patterns of dots and stripes or the like, raised bumps, indented depressions, synthetic stitching lines, text, logos, and the like with great detail, accuracy, and reproducibility. It is a further object of the invention to be able to mold the intended surface texture into the surface of the molded part during its molding fabrication, without requiring additional work steps or effort to achieve this surface texture. Another object of the invention is to use materials that are easily recyclable for the textured cover sheet, in combination with essentially any possible backing or substrate material. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a three-dimensionally contoured molded part including a substrate and a cover sheet laminated thereon, wherein the cover sheet includes a skin film and a foam backing that is adhered or bonded onto the substrate. The skin film is provided with a surface texture that is uniformly and consistently applied without distortion over three-dimensionally contoured areas of the molded part. Such a molded part may be produced, and the above objects have further been achieved according to the invention, in a method of molding a three-dimensionally contoured molded part having a surface texture.
The inventive method involves the following steps. A cover sheet is provided, which includes a surface skin film and a foam backing. The cover sheet is heated in such a manner so that the skin film is heated to at least its melting temperature while the foam backing is heated only to a temperature below its melting temperature. Thereby, particularly, the skin film material is entirely melted to a viscous liquid state, while the foam backing remains an elastic foam solid, whereby the foam backing acts as a solid carrier for holding and carrying the viscous liquid film. To some extent, the viscous liquid skin film material also penetrates into or partially saturates the open pores at the interface surface of the foam backing, somewhat like a liquid being absorbed into a sponge. However, since the foam backing is a closed-cell foam that is not permeable through its thickness, the extent of absorption of the viscous liquid skin film material into the foam backing is limited to the interface surface. Preferably the cover sheet is a foam-ba
Fasse W. F.
Fasse W. G.
Kuhns Allan R.
R + S Technik GmbH
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