This is an interesting patent. It shows the same basic derailleur as in Spanish patent # 153,083, but with the single pulley replaced by a double pulley cage. This was par for the course at the time. The interest lies in the fact that this pulley cage is not independently articulated - but is rigidly bolted to the main arm of the derailleur. It’s like a single pulley derailleur - but with two pulleys! The drawings show a conspicuously small chain gap - so small that I find it hard to imagine that the design was practical.
It is almost as if someone in a bar had sketched a double pulley derailleur on a beer mat, and an over eager Nicholás Arregui Gallastegui had rushed to patent it.