UK Patent # 599,992 - Fitzpatrick

UK Patent 599,992 - Fitzpatrick main image

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.