This Super-Rapid design moves the guide pulley along a slanting path - cleverly maintaining a reasonably constant chain gap.

I was struck by the inevitable similarity of these drawings to those used by SunTour to explain its slant parallelogram design.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Onofre Forton
• Country: France
• Date: French application July 1938
• Derailleur brands: Super-Rapid
• Derailleurs: Super-Rapid Record, Super-Rapid Record Léger