Patent ID: 8454054

Claim:
An active bolster for mounting at an interior trim surface of an automotive vehicle, comprising: a plastic-molded, expandable inner wall; a plastic-molded outer wall overlying the inner wall, wherein the inner wall has a first surface facing the outer wall and the outer wall has a second surface facing the inner wall, and wherein the inner wall and outer wall are joined around a closed perimeter region to form an inflatable bladder with an open central volume between the first and second surfaces; and an inflator for coupling an inflation gas into the central volume to inflate the active bolster in response to a crash event of the vehicle; wherein one of the first or second surfaces includes a plurality of concentric ribs upstanding from the one surface within the closed perimeter region for providing attachment between the inner and outer walls which is preserved during inflation of the inflatable bladder, wherein the concentric ribs include an innermost rib and an outermost rib; wherein each concentric rib has a respective window, wherein the windows are respectively offset to provide a serpentine path through the concentric ribs from the central volume to atmosphere outside the outermost rib, and wherein at least one of the windows is closed by a breakaway seal configured to prevent flow of the inflation gas through the serpentine path until it ruptures at a predetermined pressure during inflation of the inflatable bladder.