This patent is for the design of Simplex’s initial fork derailleur - the Super Simplex. One crucial feature of this design is that it uses a parallelogram to move the fork in a controlled way - leading some to (justifiably in my opinion) claim that this is the first parallelogram derailleur.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Lucien Juy
• Country: France
• Date: French application September 1934
• Derailleur brands: Simplex
• Derailleurs: Super Simplex