A safety helmet includes an outer shell juxtapositionally secured with an inner shell defining an air chamber between the two shells, a plurality of cushioning bellows retained between the two shells, an air-penetrable layer adhered on an inside surface of the inner shell disposed around a wearer's head,...http://www.google.com/patents/US5204998?utm_source=gb-gplus-sharePatent US5204998 - Safety helmet with bellows cushioning device
