4 ms·

Wouldn’t those patents have expired? The 90s is now more than 20 years ago.

• AnimalMuppet 7y ago
  There's this ugly thing called a continuation. You file a patent in the 90s, the patent office says "I don't think so", you modify the patent, the PTO still says no, you modify it again, and so on. If I understand correctly, you can wind up with a patent with a priority date of when you first filed, but an expiration date of 20 years from when it was finally granted. (The "priority date" means that you need prior art from before that date to invalidate the patent.)