This is the earliest patent for a derailleur that I have found that is held by Albert Raimond, the ‘patron’ of Cyclo and one of the titanic figures of derailleur history.

I am not entirely clear what genuinely original ideas are added to Claudius Bouillier’s 1924 patent - but it’s now a 3 speed and has some nice touches like the flanged polygonal tension pulley. The operating mechanism has also been turned around - with the peg now mounted on the main axle and the spiral cut into the sleeve instead of vice-versa.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Albert Raimond
• Country: France
• Date: French application April 1926
• Derailleur brands: Cyclo, Cyclo Gear Company
• Derailleurs: Le Cyclo, Cyclo Standard