Air bag cover with seamless interface tear seam and method and apparatus for producing same

摘要

A cover for an air bag unit is disclosed having a patterned tear seam therein defined by a partially bonded material same as the cover material. Apparatus for forming the cover includes a thin shell mold having an inner surface that is heated to melt thermoplastic material cast thereon. A powder box adapted to contain thermoplastic material therein for distribution onto the thin shell mold carries a gasket having a shape corresponding to the tear seam shape. The powder box and gasket are adapted to be connected to the thin shell mold for forming a sealed footprint on the inner surface during distribution of the cast material against heated surface portions of the thin shell mold to form a thermoplastic cover with a narrow gap therein conforming to the desired tear seam pattern. The cover while in the shell mold is coated along the margins of the gap with a plastic parting agent and then more of the same or similar thermoplastic material is deposited in the gap and over the parting agent to form a partially bonded thermoplastic tear seam.