Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1996-09-05
1999-06-29
Seidleck, James J.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
428 341, 524494, 524492, 524493, B29D 2200, B29D 2300, B32B 108
Patent
active
059166495
DESCRIPTION:
BRIEF SUMMARY
The invention relates to highly heat-resistant moldings of vehicle lamps or headlamps produced by injection molding and/or transfer molding and the process for the preparation of such moldings.
Vehicle lamps and headlamps are composed of a multitude of moldings which are subjected to increased heat load with increasing reduction in size of the components. In particular, hollow reflector bodies for lamps are subjected to extremely high heat loads due to the smaller-sized construction of vehicle lamps and/or headlamps, corresponding to the designers' requirements. Legal regulations, however, require extreme accuracy and stability of the radiation power and radiation direction adjusted. Accordingly, it is required that highly heat-loaded moldings of vehicle lamps and/or headlamps meet a number of minimum criteria in order that they can be employed according to their intended purpose. Thus, for example, an extreme mechanical dimensional stability of the moldings is required which results in a high accuracy of reflection. This may be exemplified by reflectors of headlamps which are allowed virtually no deformation even under the action of heat since otherwise the direction of radiation, for example, the inclination angle of the dipped headlights, is changed. Also, the impact resistance of the materials has to meet high requirements because such impacts cannot be excluded during the operation and repair of a vehicle lamp or headlamp.
In addition, in order to ensure the special high level of the accuracy of reflection, in particular when adjusting the reflector to the vehicle loading, a high dimensional stability of the inserted moldings is required.
Due to the high emission of heat, especially by lamps, in particular vehicle lamps and headlamps with high luminous powers, a high heat load occurs in various components of a vehicle lamp or headlamp. Accordingly, a great heat-resistance is a precondition for highly heat-loaded moldings. As a rule, thermoplastic materials are less suitable due to the softening which occurs at higher temperatures since their heat resistance is usually not sufficient. In addition, it is also required that the coeffcient of thermal expansion of the materials be as low as possible for ensuring the accuracy of reflection. Another criterion which must be met in the preparation of highly heat-resistant moldings for vehicle lamps and headlamps is a low mold shrinkage of the materials to be employed in order that a highly reproducible series production with high production accuracy can be performed.
In order to meet all those requirements, metallic moldings, e.g. reflectors, have frequently been used until today which in turn involve drawbacks in terms of metal processing technology. Accordingly, for headlamp reflectors made of plastics, in particular those according to ECE regulations, only molding materials are suited having a high dimensional stability, that is extremely low mold shrinkage, extremely low coefficient of linear expansion (.alpha. value), while having sufficiently high mechanical strength. As a rule, these requirements cannot be met by thermoplastic materials so that especially thermosetting materials have prevailed in the prior art. In addition, especially with reflectors, there is always a desire for a high surface quality of a direct metal-coating meeting the optical requirements and an extremely low degassing rate for avoiding critical scaling on the functional surfaces, i.e. especially of the reflecting surface of the headlamp.
The best prerequisites for high dimensional stabilities, low .alpha. values and low degassing rates are presented, in principle, by organic, especially thermosetting molding materials having high contents of mineral fillers. However, with increasing filler content, limits are set to direct vapor deposition meeting the functional requirements so that a coating prior to metal-coating becomes necessary. Moreover, per se known molding materials having high contents of mineral fillers are extremely difficult to process since the flowability of such mat
REFERENCES:
patent: 5043369 (1991-08-01), Bahn et al.
patent: 5256604 (1993-10-01), Aitken
Hegemann Klaus
Schmitz Konrad
Hella KG & Hueck Co.
Rajgurn U. K.
Seidleck James J.
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