This is the third of three derailleur patents held by Henry & Arthur Fitzpatrick of Burnley. It describes an unusually coherent device with a helical action and a clock spring to maintain chain tension. It, strikingly, anticipates French Patent # 934,933, taken out a year later, describing the mechanism used in the famous Spirax derailleur.

• Publisher: UK Intellectual Property Office
• Inventor: Henry Fitzpatrick & Arthur Alan Fitzpatrick
• Country: UK
• Date: Priority date September 1945
• Derailleur brands: Fitzpatrick
• Derailleurs: Unknown