This is one of the patents that established the derailleur world as we know it. Joanny Panel’s Le Chemineau was arguably the most influential design of the derailleur’s first three decades. More than this, its chainstay mounting, sliding rod, twin pulley wheels and pulley cage pivot concentric with the guide pulley established a pattern that many designers would follow until the start of the 1960s.

The co-inventor is listed as Claudius Bouiller. I think this should be Claudius Bouillier.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Joanny Panel and Claudius Bouiller
• Country: France
• Date: French application January 1912
• Derailleur brands: Chemineau, As, de Vivie
• Derailleurs: Le Chemineau