An apparatus for forming a multi-ply sheet of paper in which a first web of cellulosic fibers is dry formed and consolidated, a second web of cellulosic fibers is separately dry formed and consolidated, and the two thus consolidated webs are combined into a single multi-ply sheet of paper or paperbo...http://www.google.es/patents/US4074959?utm_source=gb-gplus-sharePatente US4074959 - Apparatus for forming multi-ply fibrous sheets
