Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-02-26
2002-09-03
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Attachment
Reexamination Certificate
active
06443484
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a decorative covering for air bag covers, especially for use in motor vehicles. The invention also relates to an air bag cover comprising a molding including designed burst lines and a decorative covering applied to the molding, for example, for use in a motor vehicle.
A molding as defined in the following is a component protecting or covering an air bag operating means as well as the air bag impact padding, it comprising designed burst lines or locations which on deployment of the air bag burst by the impact padding in assuring emergence of the impact padding.
Such air bag systems are well-known in motor vehicles, it being particularly air bags incorporated in the steering wheel or dashboard for reducing the risk of injury to the driver and front-seat occupant in a head-on collision that find wide application, although air bag systems incorporated in the doors, door pillars or seats for protecting the driver and front-seat occupant from injury by side impact have also since become popular. Air bag systems are likewise incorporated on the rear side of the front seats so that occupants in the rear of the vehicle can be protected by air bag systems.
2. Prior Art
Moldings for air bag covers are often injection molded in plastics materials, other known methods of production being, for example, foaming parts of plastics materials or foaming metal parts in place. To ensure satisfactory functioning of the air bag systems these moldings are provided with designed burst lines or locations which burst open at a predefined bursting force and ensure satisfactory deployment of the air bag located underneath. To enhance the visual finish and feel or to adapt air bag covers to the interior finish of the vehicle the moldings are often lacquered or provided with a decorative covering. Depending on the interior finish of the vehicle such decorative coverings are made of genuine leather, substitute leather such as Alcantara or artificial leather, or of films of plastics.
The designed burst lines usually divide the molding of the air bag cover into one or more portions which on inflation of the air bag in the air bag module form one or more flaps on bursting of the designed burst line which open up to the side to allow the air bag to deploy charged with the gas made available by the inflator.
In accordance with prior art decorative coverings of leather are fabricated multiply sectioned and stitched together in the region of the designed burst lines of the molding. Depending on the designed bursting force the stitch length, strength and material of the thread are selected so that for a defined bursting force the thread snaps to permit satisfactory emergence of the impact padding. When such decorative coverings are stitched together the seam needs to be precisely positioned on the designed burst lines so that when the air bag is deployed the impact padding is able to satisfactorily emerge by the thread snapping. Precisely positioning the stitched leather decorative covering on the molding is extremely difficult since during lamination or rear foaming the decorative covering may be distorted which spoils the visual appeal and may even result in rejection of the leather decorative covering already fabricated at high expense. In addition, where for instance an air bag cover for an impact pot is incorporated in a steering wheel, a highly complicated form of burst seam is needed which can only be produced by intensive labor at high expense.
Disclosed by European patent application 0 428 935 is an air bag cover in which a molding covering the air bag operating means and the air bag impact padding is provided which comprises burst lines designed to burst open on deployment of the air bag in assuring emergence of the air bag impact padding. The molding is covered by a decorative covering of a vinyl plastics which is weakened all along the designed burst lines of the molding by it being nicked. Nicking the decorative covering is implemented on a pliant base. The problem in this prior art is that nicking the decorative covering down to a predefined remaining thickness is difficult to implement.
Described in the German laid-open patent 195 16 230 is a method for reducing the material thickness of the decorative covering along the designed burst lines of the molding to facilitate initial bursting of the decorative covering when the air bag is deployed. For this purpose the decorative covering is placed on greatly restrict the freedom in designing such air bag covers, resulting in compromises either as to the visibility of burst lines on the surface of the cover lid or on the design geometry of the flaps and the surface of the cover lid. Hitherto in this arrangement the weakened portions in the decorative covering extended along the full length of the designed burst lines of the molding of the air bag cover.
Known from EP 0 770 522 A1 is an air bag arrangement comprising a decorative covering, a foamed layer and a backing. The air bag cover has notches at the edge in the decorative covering as well as in the backing for initiating bursting.
SUMMARY OF THE INVENTION
The invention is based on the object of providing an air bag cover as well as a corresponding decorative covering for air bag covers which are simple and cost-effective in production whilst permitting high freedom in designing the surface of the air bag cover and decorative covering as well as the flap geometry in ensuring instant bursting of the decorative covering and molding of the air bag cover located therebelow when the air bag is deployed.
This object is achieved by a decorative covering having the features as set forth in claim
1
and by an air bag cover having the features as set forth in claim
6
.
The gist of the invention is, for the first time, to weaken the decorative covering not along the entirety of the designed burst lines of the molding, but merely in a locally confined initiating site. Tests have indicated that weeakening the decorative covering in an initiating site results in stress peaking at the base of the notch in the initiating site when the air bag is deployed. It is this stress peak that initiates bursting at ed, bursting progresses to totally part the decorative covering without the decorative covering having been previously weakened outside of the initiating site.
It is thus now possible, for the first time, to burst the decorative covering by weakening only a locally confined site, the initiating site, so that bursting is initiated there. When such a decorative covering is employed on an air bag cover, the decorative covering is applied to the molding comprising the designed burst lines so that the decorative covering covers at least one locally confined initiating site at which bursting the decorative covering is initiated along the designed burst lines of the molding when the air bag is deployed. Since in accordance with the invention the decorative covering is machined only in a locally confined initiating site so that due to the notch effect bursting is initiated in this precisely defined locally confined initiating site, there is now no need for complicated machining of the decorative covering along the designed burst lines of the molding. In addition, there is now no need for design grooves which correspondingly restrict the freedom in design since there is now no longer any need to compensate tolerances stemming from fabrication of the decorative covering by the design grooves. It is the stress peak at the base of the notch of the initiating site that initiates bursting of the decorative covering, bursting then progressing along the designed burst lines of the molding.
When the air bag is deployed it is thus assured that both the molding and the decorative covering applied thereto burst totally and instantly in a defined site so that one or more flaps are formed which open up to the side to allow the air bag to deploy charged with the gas made available by the inflator.
In accordance with one preferred embodiment the initiating site
Dickson Paul N.
Eldra Kunststofftechnik GmbH
Fleming Faye M.
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