US Patent 7441802 Air-bag device

In an airbag (2), a length extending from a sewn portion (10) to a right periphery of a presser plate (13) is set such that a length (L1) is shorter than a length (L2) wherein the length (L2) is at an attachment side base cloth (3) side and the length (L1) is at a cloth-like piece (9) side. When the airbag (2) is expanded in emergency situations, the attachment side base cloth (3) is expanded while it moves away outwardly from the cloth-like piece (9), thereby opening a vent hole (8), so that the airbag (2) is eased in abrupt expansion directing toward an occupant. When the airbag (2) becomes a sufficient size to protect the occupant, it bends instantaneously a retaining plate (17) to release the parallel portion (9B) of the cloth-like piece (9) from the presser plate (13), so that the cloth-like piece (9) is brought into intimate contact with the attachment side base cloth (3) to close the vent hole (8), thereby protecting the occupant with reliability.