A rotary positive-displacement machine, of the helical rotor type, and rotors therefor

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Listed from its EPO record in Patent Yard's archive of European patents past their term. Its claims, description and drawings are in the EPO PDF and on Google Patents, and the Claude kit works from them.

Why it's free to use

• Filed October 22, 1984 and granted January 24, 1990. A European patent lasts at most 20 years from filing, so its term ended October 22, 2004.
• A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by April 22, 2010.
• We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.