Active bolster with hermetic seal

An active bolster for an automotive vehicle, comprising:

• a deformable base wall for mounting against a rigid structure of the vehicle;
• and
• a front wall overlying the base wall and forming an interior trim piece of the vehicle;
• wherein the base wall has a first surface facing the front wall, and the front wall has a second surface facing the base wall;
• wherein the base wall and front wall are comprised of molded plastic components, and the base wall and front wall are joined around a closed perimeter by a hermetic seal to form an inflatable bladder with an initial open space between the first and second surfaces, wherein the open space is configured to receive an inflation gas to expand the walls and remain sealed during a deployment of the active bolster;
• wherein a first one of the base wall and the front wall includes a wide rib projecting from the first surface continuously along the closed perimeter, the wide rib having a predetermined radial width along the closed perimeter;
• wherein a second one of the base wall and the front wall includes a plurality of narrow ribs projecting concentrically from the second surface continuously along the closed perimeter, wherein each narrow rib is welded to the wide rib to form the hermetic seal, and wherein each narrow rib has a respective radial width at each respective location along the closed perimeter less than half the radial width of the wide rib at the respective location.