Method and apparatus of making air bag cover having a visually perceptible tear seam

摘要

A method and apparatus for making a thermoplastic air bag cover having a visually perceptible tear seam formed by a controlled amount of plastic sinkage during an injection molding process. A molten thermoplastic is injected into a mold cavity of a mold having a shape defining the air bag cover. The mold includes first and second mold halves which form the interior and exterior surfaces of the air bag cover. The first mold half has an outwardly extending projection which cooperates with a smooth inner surface of the second mold half to form the tear seam design in the air bag cover which appears on the outer surface of the air bag cover. The tear seam design formed on the outer surface of the air bag cover is primarily formed because of the near right angles formed at the top edges of the outwardly extending projection which cause the outer surface of the air bag cover to sink to a limited controlled extent during cooling of the plastic beneath its softening point. The completed air bag cover is then removed from the mold. The thickness of the air bag cover at the tear seam is within a range of 0.2 to 0.4 millimeters.