Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Composite article making
Reexamination Certificate
2003-01-17
2004-12-21
Foelak, Morton (Department: 1711)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Composite article making
C521S048000, C521S048500, C521S138000, C521S182000
Reexamination Certificate
active
06833094
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention is plastic components and, more particularly, the invention relates to automotive parts made of thermoplastic materials that are stable at elevated temperatures and materials for making, methods of manufacture of the same.
A modern automobile is manufactured from a large number of parts. Each of the parts that make up an automobile typically has a number of desired properties that are distinct to a particular part. In a particular automobile part, it may be more or less desirable for the part to be lighter or heavier, more rigid or flexible, or paintable or not.
For those parts that comprise the “body in white” of an automobile, that is the parts that pass through an automobile assembly plant's painting operation, the ability to withstand high temperatures is desirable so that important manufacturing efficiencies can be obtained. In normal vehicle assembly operations, vehicle subassemblies are subject to electro-coating at temperatures in excess of 390° F. and, after painting, vehicle subassmblies are cycled through paint drying ovens where they are exposed to temperatures in excess of 270° F. It is important that parts passing through these conditions do so in good condition. One problem that can arise at these temperatures is the release of “molded-in” stress contained in the part that changes the shape of the part or compromises the strength of the part
This is because many components are assembled to a vehicle, including the front end of the vehicle, require precise alignment and durable mounting mechanisms. Headlights, fenders, fascia and a radiator are examples of parts that may be attached directly or indirectly to a grill opening reinforcement. Grill opening reinforcements have been found to be helpful in tying together such components with the forward section of front fenders and the frame of a vehicle as it is being assembled. Other integrated front end modules that support other parts include bumper reinforcements, radiator supports, and inner fender reinforcements. These parts are relatively large and must maintain close tolerances for critical dimensions to meet strict fit and finish standards.
Traditionally, automobile parts for the “body in white” parts have been made from metal because of the tolerance of those materials for the temperatures of the painting operations of the modern automotive industry. For example, grill opening reinforcements and other integrated front end modules have been manufactured from a plurality of sheet metal stampings that are either welded or fastened together.
Metal parts have the disadvantage of being heavy and not as easily formed as plastic parts. Metal integrated front end modules are heavy and add to the overall vehicle weight thereby decreasing the fuel efficiency of the automobile. While metal parts have the benefits of being strong and easily surviving high temperature environments, they can be also unacceptably expensive. Being formed in multiple pieces, metal integrated front end modules require labor intensive assembly operations. Quality control is required to assure proper location of the mounting mechanisms for multiple parts assembled to the integrated front end module.
Recently, sheet molding compound (SMC) has been used to manufacture grill opening reinforcements. SMC grill opening reinforcements are generally slightly less weight than metal grill opening reinforcements. However, for the manufacture of certain parts, such as grill opening reinforcements (GORs), thermoset plastic part, such as those made from sheet molding compound (SMC), cannot readily have necessary features molded into them. Rather, SMC grill opening reinforcements require a substantial investment in tooling for both molding the SMC and finishing the SMC parts after molding. It is generally necessary to machine a SMC grill opening reinforcement by drilling, purring or shaping with a router fastener holes and locating surfaces. Also, the SMC process is relatively slow requiring a large number of mold cavities to manufacture parts on a production basis. SMC is also not a recyclable material which means that at the end of the car's life cycle or if there is any scrap in manufacturing process, it is necessary to dispose of the SMC grill opening reinforcement in landfill instead of recycling. This is because the thermoset plastic, once set, can only be recycled by rendering the part into ash that can only be resold for a minimal economic recovery.
Some exterior auto and truck parts such as fenders, quarter panels, doors, trim parts bumpers, fender extensions and other molded exterior parts of are currently made of moldable thermoplastic polymers to obtain resistance to permanent deformation on impact and corrosion resistance. Typical moldable thermoplastic polymers that are being use for these parts are polypropylene, styrenics, and various heteroatom polymers. While such polymers can be molded into auto and truck parts that are substantially lighter than currently used sheet metal parts, they have limitations. In particular, such parts ordinarily do not pass through industry-standard standard painting operations with acceptable strength and durability. Further, such molded plastic parts have molded-in stress that releases when the part is exposed to heat, such as in a painting operation, thereby altering the dimensions or shape of the part. The release of the molded-in stress leads to unacceptable fit and finish of parts to other parts, and can lead to unacceptable deviations in the alignment of connected parts.
Prior technology has been developed to utilize injection molded thermoplastic parts that are attached to automobile vehicle bodies prior to electro-coating and paint drying oven exposure but are expensive. Exposure of large weight bearing parts to high temperatures results in a loss of dimensional stability since the weight of parts attached to injection molded parts causes the injection molded parts to sag. This results in poor fit and finish and difficulties in assembling components after being exposed to high temperatures. Further, parts must not only demonstrate adequate fit and finish in the short term, but must have adequate torsional stability to prevent cracking. For example, grin opening reinforcements are subject to torque while the automobile is being driven, especially if the road has bumps or holes. A strong, but brittle, part can eventually crack or even fail, which is an unacceptable outcome.
Therefore, there is a need for dimensionally stable parts that exhibit torsional stability and can survive high temperature painting operations. It would be advantageous if such parts could be made from materials that are less expensive and more recyclable than existing parts exhibiting sufficient dimensional stability, torsional stability, and high temperature tolerance.
A number of patents relate to various aspects of motor vehicle component technology. For example, U.S. Pat. Nos. 6,293,615 and 6,287,442 to Tarahomi, disclose an injection molded thermoplastic integrated front end reinforcement made from a fiber reinforced thermoplastic polymer that includes at least 65% post-consumer recycled polyethylene terephthalate. The patents disclose that the polyethylene terephthalate is reinforced with at least 45% glass fibers and mineral filled. The '615 and '442 patents which are commonly owned, are incorporated by reference into this application as if fully set forth herein.
U.S. Pat. No. 6,136,249 to Takeuchi et al. discloses a process for producing a bumper made of synthetic resin that includes a core and an outer layer covering the core. The '249 patent is incorporated by reference into this application as if fully set forth herein.
U.S. Pat. Nos. 5,814,673 and 6,180,685 to Khait disclose methods of making polymeric particulates wherein polymeric scrap material, virgin polymeric material and compounds thereof are supplied to intermeshing extruder screws which are rotated to transport the polymeric material along their length and subject the polymeric material
Foelak Morton
Patent Holding Company
Welsh & Katz Ltd.
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