This SunTour patent from 1981 describes a set of parallelogram-free derailleur designs that use a continuous loop of wire, toothed band or even roller chain to keep the pulley cage aligned to the chainline. SunTour never used these systems on a production model. But, 30 years later, both Tiso and FSA created prototypes that used a tooth belt in almost exactly the way described here.

• Publisher: Japan Patent Office
• Inventor: Nobuo Ozaki
• Country: Japan
• Date: Priority date October 1981
• Derailleur brands: SunTour with inspiration for Tiso and FSA
• Derailleurs: none - but is curiously simliar to the Tiso electronic derailleur