Czech Patent # 116,505 - unknown

Czech Patent 116,505 - unknown derailleur main image

This fascinating patent dates from 1961 - very early for a design of this sophistication. It clearly draws heavily on the look of the 1961 version of the Huret Allvit, although the operation of the parallelogram mechanism is rather different. The patentee mentions Huret in the text (along with Union and Favorit - which would have been pull-chain derailleurs at the time).

I have never seen a physical manifestation of this design - a pity.