This patent is for an all-encompassing rubber cover for the parallelogram of a derailleur, and also mentions coating the main elements of the derailleur with PTFE to allow it to be as easy to clean as a non-stick saucepan.
I often think of Henry Juy as a bit of a copycat, picking up the ideas of others and, sometimes, patenting them. When I first saw this patent I thought that it was for a pale imitation of the Vivo Grunge Guard, but note the dates. This patent dates from 1988. Vivo's patent for the Grunge Guard dates from 1994, a full six years later. It appears that Henry is more innovative than he seems.