Patent Application
20070144665
This invention generally relates to a laser welded article including at least two parts assembled to each other. More particularly, this invention relates to a laser welded article including a first part with a first surface finish and a second part with a second surface finish different than the first part.
Plastic parts such as tubes and manifolds are often fabricated from several separately molded parts that are assembled to each other to form a desired completed assembly. Many methods of assembling plastic parts are known in the art including ultrasonic welding, and laser welding. Ultrasonic welding requires specially designed joints that are costly and relatively difficult to implement. Laser welding requires a much simpler joint design and is applicable to many differing applications.
Laser welding utilizes a laser that is directed through a laser transparent part to a laser absorbing part. The laser absorbent part heats due to the heat energy provided by the laser and transmits this heat to the adjacent laser transparent part. As plastic material melts in this location, plastic from each part intermingles and once cooled forms the desired joint.
Many automotive components are formed of black plastic. The black color provides several aesthetic advantages over brighter colors. A black color typically attracts less attention than brighter colors. This is especially so for engine components. The black color provides a more pleasing appearance. The black color is often provided by a carbon black additive. Carbon black dye provides stability, and does not deteriorate visually with age.
Disadvantageously, carbon black is laser absorbent meaning that any part utilizing carbon black will not allow a sufficient amount of laser heat energy to pass through, and therefore a laser translucent component cannot utilize a carbon black dye.
Accordingly, it is desirable to develop a method and process for laser welding plastic parts that achieves the desired appearance and that does not discolor in a laser transparent part.
A method according to this invention produces a plastic article including a first laser absorbent part having a first surface finish and a second laser transparent part with a second surface finish that is different than the first surface finish.
The example plastic article includes the first part that is visible with a first surface finish that is textured and grained. The second part is not substantially visible and includes a substantially smooth non-textured surface finish. The first and second parts are attached to each other by a laser welding process. The textured surface finish provides a desired appearance for visible surfaces while still providing the desired laser properties in combination with the second part to facilitate the laser welding process.
One of the first and second parts includes a carbon black dye that provides a desired black color. The other of the first and second parts does not include the black dye but instead utilizes another dark colored dye. The carbon black dye is utilized on the laser absorbent part and another material is utilized to provide a substantially similar appearance in a laser transparent part.
Accordingly, the method according to this invention provides a process for laser welding plastic parts that achieves the desired appearance and that provides a desired visible appearance.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
Referring to
The laser welded joint 20 is produced by directing laser energy through the first part 12 for absorption by the second part 14. The first part 12 is a laser translucent material providing for the transmission of energy from the laser beam 24 to the second part 14. The second part 14 comprises a laser absorbent material such that energy striking the second part 14 heats the second part 14 and causes a melting of plastic. The melted plastic of the second part 14 causes a melting in the plastic of adjacent portions of the first part 12. Melted plastic material from the first and second parts intermingle and when cooled form a weld 26.
The plastic tube assembly 10 of this invention includes a first surface finish on the first part 12. The first surface finish is a grained structure provided by a texture in a mold utilized to form the molded part. A smooth molded surface provides a high reflectivity, even in black molded parts. The smooth surface can in some instances show scratches, dirt and grease that accumulate through handling and assembly in automotive components. However, a grained surface is not necessary in non-visible portions of a plastic article.
The plastic tube assembly 10 of this invention includes the first surface finish 16 having a grained structure and a second surface finish 18 having a different and smooth non-textured surface finish as compared to the first surface finish 16. The smooth surface finish is on a non-visible portion of the plastic tube assembly 10. The different surface finishes provide the desired appearance while also providing a substantially non-uniform surface finish.
A carbon black dye that provides a substantially laser absorbent plastic part is utilized in the visible or first part 12, while a non black dye that is dark in color such as red, purple or blue is utilized on the laser transparent part.
Referring to
Referring to
The smooth surface finish 58 of the second part 54 includes a substantially high reflectivity, where the textured surface finish 56 of the second part has relatively low reflectivity. The low reflectivity is provided by the grained surface texture 56 that disperses potentially reflective rays in random directions, rather than uniformly as is provided by the smooth surface finish 58.
The second part 54 includes a laser absorbent material such that substantially all of the laser energy of the laser beam 24 passes through the first part 52 and is absorbed by the second part to form the weld 62. The second part 54 is colored utilizing the laser absorbent carbon black or other known laser absorbent materials and additives.
Referring to
The second part 76 is provided with a textured surface portion 78 such that the visible parts of the manifold assembly 70 are substantially of a uniform textured appearance. However, the entire intake manifold is not of a uniform appearance or reflectivity.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
