Patent ID: 7188861

Claim:
A cover structure for an air bag device comprising: a cover including a first member having a plane-like portion and a second member having a vertical portion connected through a curved part with said plane-like portion; and a rupturable groove formed on a surface of said cover opposite to an air bag in said air bag device, said rupturable groove configured to rupture in response to inflation of the air bag and to thereby form an opening to expose the air bag, wherein said rupturable groove comprises at least, a first groove part formed to extend rightward and leftward on the second member, second groove parts formed to extend forwardly and backwardly on the first member and third groove parts formed to connect the first and second groove parts, wherein each of said first, second and third groove parts includes a circular arc having a radius different from each other to be formed smoothly throughout said first and second members, wherein said third groove part includes a plurality of circular arcs each having a radius different from each other to connect the first and second groove parts, such that said rupturable groove extends to coincide substantially with a direction of shearing force applied on the cover when the rupturable groove is ruptured, and wherein the radius of the circular arc in the second groove is larger than the radius of the circular arcs in the third groove.