Legal analysis: After the patent protection expires, the patent has no statute of limitations. The limitation of action during the period of patent protection is three years, counting from the day when the obligee knows or should know that the right has been damaged. Where it is otherwise provided by law, no application may be filed after the expiration of the patent protection period. Invention patents are valid for 20 years from the date of filing, and utility models and designs are valid for 10 years from the date of filing. At the same time, an annual fee must be paid to maintain the patent. When it expires, it will become an open technology, which has no legal effect and can be realized by anyone for free.
Legal basis: Article 188 of the Civil Law of People's Republic of China (PRC) requests the people's court to protect civil rights, and the limitation of action is three years. Where there are other provisions in the law, those provisions shall prevail.
The limitation period of action shall be counted from the date when the creditor knows or should know that the right is damaged and the debtor knows it. Where there are other provisions in the law, those provisions shall prevail. However, the people's court shall not protect the rights that have been damaged for more than 20 years. Under special circumstances, the people's court may decide to extend the time according to the application of the obligee.