Patent Application
20070224382
The present invention relates to the elimination of visible parting lines on plastic molded articles.
Injected molded products are in common use today, particularly in the automotive industry. Many of these plastic products are made by a plastic injection molding process. In these processes, cavities formed in molds are filled with molten plastic material which, when cooled and ejected from the mold, forms the completed product.
Due to the complex structure and configuration of many of the molded plastic products, the products are often injection molded with parting lines formed by the molding process visible on the exposed surfaces. These parting lines can be apparent, for example, on molded plastic components for door panels for the automotive industry.
Mold parting lines on the exposed surfaces of molded products and components are typically not aesthetically pleasing.
It is an object of the present invention to provide an improved plastic molded product without mold parting lines on its exposed viewing surfaces. It is also an object of the present invention to provide an improved plastic injection molding process which produces a molded product without parting lines on any of the viewing surfaces.
The above objects are met by the present invention which provides an improved plastic injection molding process and an improved molded plastic product or component which eliminates parting lines on the exposed or viewing surfaces. The molded part is produced in a two-shot process utilizing a rotational mold. A first portion of the molded product is produced in a first cavity on the rotational mold, and the second portion or layer of the product, namely the outer skin layer, is produced in a second cavity on the rotational mold. Preferably, the first portion of the product is formed of a hard plastic material, while the second portion is formed of a softer thermoplastic elastomer material.
The second portion of the product is formed in the mold with a part thereof that is not attached to the first portion. After the molded part is removed from the mold, the non-attached part is folded over onto the first portion in a post-molding operation. The portion which is folded over is then glued or otherwise securely affixed to the first portion.
These and other features, benefits and advantages of the present invention will become apparent from the following description when viewed in accordance with the accompanying drawings and appended claims.
Plastic molded products or components, particularly those used in the automotive industry, typically require having an outer layer or viewing surface which is aesthetically pleasing and does not have any blemishes or parting lines. Such surfaces are also called “Class A” surfaces. The opposite or non-visible side of the molded products or components is typically called the “Class B” surface. The molded products often have a base or substrate portion and an outer or skin portion made from a different material. The outer or visible layer often can be a softer material, such as a thermoplastic elastomer material, and can be molded with the desired texture or other ornamentation.
A two-shot final molded product is shown in
In accordance with the present invention, the molded product 10 is made in a two-shot molding process, preferably by use of a rotational mold. In a rotational mold, there is typically one core portion of a mold tool and a pair of cavity portions. In the first step of the rotational molding process, the core member is mated with the first cavity member and a portion of the molded product is produced. Thereafter, the core portion or the cavity portion of the rotational molding machine is rotated lining the second cavity portion with the core portion. The first molded portion remains in the core portion and then when the second cavity portion is mated with the core portion, the second layer of material is molded over or onto the first molded portion. This creates a two-shot molded product.
These steps are illustrated in
In accordance with the present invention, after the mold cavity 24 is filled with the plastic material forming the molded part 36 in the shape shown, the first cavity member 22 is separated from the core member 20. The rotation of the rotating platen on the rotational mold aligns the core member 20 with a second cavity member 40. This is shown in
The molded product as completed by the rotational molding process is shown in
In order to form the final product 10 from the molded product 10′ when it is removed from the mold, flap member 44 is bent over or formed into the position 44′ by any conventional post-molding operation. The flap portion 44 is securely affixed to the corresponding flange portion 46 of the first molded portion 36. Flap portion 44 can be secured to the flange portion 46 in any conventional manner, such as by crimping, gluing, plastic welding or the like. The portions 44 and 46 can also be mechanically interlocked together with a tab 50 or the like which is positioned through an opening 52 in the flap portion 46′ as shown in
With the present invention, the presence of a parting line on the final molded product is eliminated. The two-shot skin material is molded in a flat condition and is then wrapped over the underlying substrate in a post molding operation in order to create a seamless looking part. The skin member is molded out of its final position. A fixture can be provided adjacent the rotational molding machine in order to bend or form the flap member into its final position. If necessary, an oven or other heating mechanism can be used to make the flap more pliable and easier to fold into its final position.
While particular embodiments of the invention have been shown and described, numerous variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.
