There is a long and fevered debate amongst those who can be bothered about such things, about who really invented the parallelogram derailleur. This is a hot topic only because it is often written that Tullio Campagnolo’s 1951 Gran Sport was the first parallelogram design - when it clearly wasn’t. The fact that the Campagnolo Gran Sport completely redefined the derailleur world (something that earlier designs clearly failed to do) is often conveniently forgotten.
To my mind the list of contenders for the rather unimportant title of inventor of the parallelogram derailleur includes:
- Lucien Juy of Simplex with his September 1934 French patent # 778,474 - but this was for a fork type design (and one that mounted on the chainstay) and so may not be able to claim to be a true ancestor of modern designs.
- Charles Jeanmot of JIC with this December 1936 patent, which includes a highly modern looking parallelogram design with a sprung pulley cage with two pulley wheels. It differs from modern geometry only in that it mounts on the chainstay.
- Pierre Gardini, Georges Trottier and René Déchanet of Nivex with their November 1937 French Patent # 838,657. Their design had few distinctive new features over the 1936 JIC but it was properly sorted, manufactured in some volume and highly effective.
- Francesco Ghiggini who, according to Frank Berto, applied for Italian patents in 1937, 1938 and November 1941. Due to the neanderthal web presence of the Italian patents office, I have only been able to find a French patent that relates to the 1941 Italian patent (French patent # 978,189). This shows a parallelogram derailleur that mounts onto the end of the wheel spindle and has a single pulley wheel. Frank Berto claims that it was Ghiggini’s patents that were bought by Tullio Campagnolo in 1951.
- Leslie Bane of Constrictor with his October 1945 UK patent # 601,743. This was for an all aluminium design that mounts at the rear dropout but has only one pulley wheel.
So who has the strongest claim to be the inventor of the modern parallelogram derailleur? My answer would be Charles Jeanmot of JIC - and that this patent is the evidence.