Motor vehicle instrument panel with flexible tethering hinged air bag deployment door

A method of forming a cover assembly for concealing an inflatable air bag system of a motor vehicle, said method comprising the steps of:

• forming an interior trim panel from a first plastics material having a frangible tear seam defining an air bag deployment door in said panel and an integral mounting/hinge flange extending transversely from an inner side surface of said door adjacent said tear seam and adapted to be secured to the structure of the vehicle, the first plastics material being flexible in a limited temperature range enabling the flange to act as a hinge about which the door may swing outwardly upon separation of the tear seam and outward deployment of an air bag of the supplemental passenger restraining system while further acting as a primary tether to retain the door attached to the vehicle structure within said limited temperature range but being subject to breakage along a juncture zone between the flange and door at temperatures below said limited temperature range;
• forming a supplemental tethering hinge separately from the panel from a second plastics material that is relatively more flexible than said first plastics material at temperatures below said limited temperature range having a flange portion and a door portion;
• positioning said flange portion of said supplemental tethering hinge against said mounting/hinge flange of said panel and positioning said door portion of the supplemental tethering hinge against the inner side surface of the door of the panel and positioning the flange portion of the supplemental tethering hinge against an adjacent surface of the flange of the panel such that an intermediate portion of the supplemental tethering hinge spans the juncture zone between the flange and door of the panel;
• heating the panel and supplemental tethering hinge at their interface sufficiently to locally remelt the first and second plastics materials and thereby weld the supplemental tethering hinge to the panel;
• and
• installing the panel and supplemental tether hinge assembly on the vehicle structure with the door of the panel arranged in overlying covering relation to the air bag restraining system.