Generally, wpi and wpa search from two ways: topic and classification; It can also be searched through the patent index of ca; You can also search foreign patent databases including American patent full text, ep patent full text and wo patent full text through the Internet. And the obtained information will be verified by China patent database to confirm whether these foreign patents have applied for China patents and whether they have expired, so as to obtain a number of relevant foreign invalid patents.
Methods of inquiring foreign invalid patents;
1. In general, it can be inferred whether the patent naturally terminates as invalid due to the expiration of the protection period. The protection period of invention patents in most foreign countries is 20 years, and the protection period of utility model patents ranges from 5 years to 10 years.
Second, by inquiring about the legal status of the patent register of the State Patent Office. Patents that are terminated in advance or declared invalid by the Patent Office because the applicant gives up the patent right can only be determined by inquiring about the legal status on the patent register of the patent office in that country.
3. You can directly go to the official websites of patent offices in various countries or the website of the European Patent Office for free inquiry and download the original text, or you can enter the inquiry through the related link "Major Foreign Intellectual Property Websites" on the website of China National Intellectual Property Administration.