A vacuum cleaner has a first cyclonic cleaning stage and a second cyclonic stage positioned in series with the first cyclonic cleaning stage. The second cyclonic stage comprises a plurality of second stage cyclones. A passage connects the first cyclonic cleaning stage outlet and the second stage cyclones...http://www.google.es/patents/US6782585?utm_source=gb-gplus-sharePatente US6782585 - Upright vacuum cleaner with cyclonic air flow
