An apparatus for the manufacture of selectively apertured thermoplastic sheet or film, comprising a rotatable molding element means for receiving the film and which means has a predetermined pattern therein wherein as the film is contacted with the rotatable molding element means and a fluid pressure...http://www.google.es/patents/US4636161?utm_source=gb-gplus-sharePatente US4636161 - Screen for selectively perforating thermoplastic film
Screen for selectively perforating thermoplastic film
