In an air intake device in a helmet, a recess is defined in a front wall of a shell of a cap body so as to be recessed inwardly of the shell, and has an opening defined in an upper surface of the recess to communicate with the inside of the cap body. A shutter plate is inserted into the opening for opening...http://www.google.es/patents/US5388277?utm_source=gb-gplus-sharePatente US5388277 - Air intake device in helmet
