This is Claudius Bouillier’s crucial patent for the very original Le Cyclo 2 speed derailleur. It has the classic, twin cable mechanism rotating a sleeve to drive the pulley cage laterally using a peg in a helical groove in the main axle. The pivot of the pulley cage is concentric with the guide pulley.

For over 20 years this basic design dominated the world market for touring derailleurs.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Claudius Bouillier
• Country: France
• Date: French application April 1924
• Derailleur brands: Cyclo
• Derailleurs: Le Cyclo