I am not entirely sure what this patent is describing. But I think that it is a first try at a design for a sprung chain that shortens itself when not under tension. In its second iteration, this was a key part of the J.Wi.S derailleur system.

This is one of three Austrian Patents that relate to the J.Wi.S derailleur system. This one was granted in 1937 and displays the double headed eagle of Austria. The other two were granted in late 1938, after the Anschluss, and these show an eagle holding a Swastika.

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• Publisher: Österreichisches Patentamt
• Inventor: Robert Pollak
• Country: Austria
• Date: Priority date August 1936
• Derailleur brands: J.Wi.S, Wanderer
• Derailleurs: none