Patent families

Legally, a patent family is made up of (a) an original patent, and (b) other patents which are additions or foreign filings of it, which have the same priority date. These rules and definitions apply since the Paris Convention of 1883. In the period of early aero, the definition is less clear or ambiguous because (a) many patents did not identify their parent in a foreign country, or not clearly; (b) before 1883, the patents did not have a common priority.

We have therefore extended the concept a patent family a bit. We'll say two patents are in the same family if they have the same diagrams. In practice this means they have the same inventors and filing dates that are within two years of one another and plausibly similar titles. Very few cases are close calls under this definition, and it would be good to list them below. This extended definition helps us identify which patents are not distinct; to find them, relate them, and discount them a little because they aren't technologically novel, though they are administrative events.

These authors made a similar, slightly stricter definition, in their paper/presentation at the Baltic Connections conference of April 2021: Matti La Mela, David Andersson, and Fredrik Tell, all of Uppsala University, 2021, Patent families and the value of historical patents, 1884-1914, On program.

There may be an earlier literature where this definition has been used before but I'm not aware of it.