Damaging the toggle chain was a major issue with both hub-gears and pull-chain derailleurs. Just leaning your bike against a wall could end your ride there and then.

This patent covers a metal tube to protect the fragile darlings - not a bad idea.

A protective tube like this would also give the humble Simplex Tour de France derailleur some of the attributes and cachet of the, then new, Simplex 543.

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• Publisher: L’Institut national de la propriété industrielle
• Inventor: Lucien-Charles-Hippolyte Juy
• Country: France
• Date: Priority date December 1954
• Derailleur brands: Simplex
• Derailleurs: none