This patent really covers a front derailleur system developed by Terrot. But it contains a couple of points of interest even for those, like myself, who shun the oafish front derailleur in favour of its suaver rear cousin.
The first point of interest is the pulley cage for tensioning the chain. Unlike the arrangement on the 1905 Terrot modèle H, this design has the chain threading through the pulleys in the modern way.
The second point of interest is that the chainwheel has missing teeth and shifting ramps. All that is missing is some spurious branding combining any of the the words ‘ultra’, ‘hyper’, ‘super’, ‘glide’, ‘shift’ or ‘drive’.