I used to manage intellectual property for a large operating company. It is much more of a slippery slope than most people realize. A patent is issued when the examiner can find no "prior art" has been granted. Included in the patent are many things; the invention as stated, it's useful applications, it's unique properties etc. Once issued, the company must protect it. The patent is not bulletproof. It's legality is based on the assumption that the prior art does not exist, based on the examiner's research. An infringement must be challenged in court by the owner. Once a defense starts, any number of things can invalidate part or all of a patent. The application may be different or simply not included in the patent, such as different materials used, different operating conditions etc. It could be used in a country where the patentee has not filed for coverage. The one that scares the bejesus out of a patent owner is that they file a complaint and suit and then company X (and maybe Y and Z) come forth with documentation that they have practiced "the art" in the past and/or knew of the technology and simply held it internally as a Trade Secret or did not pursue it in order to prevent dissemination of the knowledge. All these result in a big KABOOM of the patent and everyone can wade in. My guess is that in most of the situations you mention, the original patent owners were likely concerned by the fact that they also stood on the shoulders of others, and if they raised a stink, someone may come against them.

Last edited by AGS; 10/15/24 12:51 PM.