2. Terminated and invalid patents. All countries in the world stipulate that patents have a certain time limit (called prescription), and the patented products of patented technology that exceed the time limit become public wealth, and anyone can use them for free. In addition, it is necessary to pay an annual fee to safeguard its patent right. According to statistics, 60% of the patents in the world were abandoned within half the time limit, and the patents were terminated. The third category is the patent that has obtained the patent right, which was later revoked or declared invalid by the administrative organ, and its patent right is "regarded as nonexistent from the beginning"
3. Unauthorized "patents". Only the patent application number has no patent number, and there is no patent application, which is not a patent at all, but we should pay attention to whether it is possible to obtain a patent right in the future.