Q: Patent inventor has passed away/ are royalties due his heirs from companies using the patents?

A: Theoretically yes, but in practice this is rare.

A patent is considered as personal property, just like a car, a stock portfolio, or an old masters painting. So, yes, you can inherit a patent just like any other personal property.

In order to collect license fees, or "royalties", based on the decedent's patent, several things need to occur.

Firstly, the decedent had to own the patent. What is important is not that he is the inventor, but that he is the assignee. If the inventor was employed as a scientist or an engineer, it is almost certain that the employer owned the patent, and not the decedent.

Secondly, there must be some sort of a license agreement between the companies using the patent, and the decedent. It is not like a company who wants to make the same product as claimed in the patent is going to just send a check every month to the owner of the patent. There must be an agreement.

Thirdly, the patent must be enforceable and valid. This means, for example, that it has not been found invalid in court. The most common reason for not being enforceable is because the patent expired. Patents pass into public domain 20 years after the filing of the application, so if the patent is from the 1980's or 1990's, for example, then the patent expired. Another common reason for a patent not being enforceable is because the maintenance fees have not been paid, and the patent lapsed.