US Patent 9420842 Protective helmet

A protective helmet includes an outer shell and a controlled air dissipation (CAD) assembly installed within the outer shell. The CAD assembly includes an inner shell liner releasably mounted to the outer shell, a primary bellows unit disposed between an outer surface of the inner shell liner and the inside surface of the outer shell, and a secondary bellows unit disposed between an inner surface of the inner shell liner and the head of a person wearing the protective helmet.