This is the first of two patents covering the wacky design of the Marelmo derailleur. It is a single spring design - one spring both tensions the chain and moves the pulley cage sideways in opposition to the tension of the control cable.
This first iteration of the design was a sliding rod system with a fixed main body, much like an early 1950s design - except that it was top-normal. Later, the second iteration mounted the sliding rod on a fancy articulating rig with a sprung pivot.
The patent lists Giorgio Marchigiano as the inventor and Gianpietro Mogno and Luigi Ezzu as assignees or something!