Claudius Bouillier, aged 62 at the time, maintains his position as one of the most innovative of the early derailleur designers with this patent. It is for a chainstay mounted, sliding rod type, twin pulley, derailleur with the pulley cage pivot concentric with the guide pulley - all very conventional for the time. However, in this case, the sliding rod is mounted at an angle in order to maintain a more equal chain gap.

I don’t think that this device ever made it onto the market.

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• Publisher: L’Institut national de la propriété industrielle
• Inventor: Claudius Bouillier
• Country: France
• Date: French application May 1949
• Derailleur brands: As
• Derailleurs: unknown