A safety helmet comprises an impact-resistant structure which is fastened to the inner surface of a shell of the safety helmet and is formed of an impermeable fabric, a plurality of foam bodies enclosed by the impermeable fabric, and an air valve fastened to the impermeable fabric such that the air valve...http://www.google.sh/patents/US6681408?utm_source=gb-gplus-sharePatent US6681408 - Impact resistant structure of safety helmet
