US Patent 8161597 Shop vacuum cleaner with cyclonic separator

A shop vacuum cleaner has a series of dust separation stages, with the large majority of the dust being preseparated in a cyclonic separator and deposited into a first drum or barrel. The remaining dust is carried in the air stream is filtered out in a pre-filter in a second vacuum cleaner drum. A final filter cartridge is fitted onto the intake of the vacuum head. The vacuum cleaner machine exhausts clean, filtered air into the ambient.