What does it mean when the nuclear Soviet valve has been patented as a flash valve and can be used freely when it expires?

1, invalid patent refers to a patent whose patent application has not been approved, but has been authorized and declared invalid, or has lost its patent right and is no longer protected by the patent law for various reasons stipulated by law. Invalidated patents become a kind of free social public resources, and naturally become "well-known public resources" because of their expiration. 2. The patent is invalid for the following reasons: 1. Patents have exceeded the time limit stipulated in the patent law: the protection period of invention patents in China is 20 years, and the protection period of utility models and designs is 10 years. After the expiration of its effective protection, the patent no longer enjoys the exclusive right granted by the patent law, and falls into the well-known technical field, and the public can use it for free. 1985 patent law has been implemented for more than 20 years, and the patents applied for in the early stage have basically passed the time limit and become invalid patents. 2. The patentee terminates the patent right in advance. The main reasons for the patentee's early termination are as follows: the original invention was found to be not advanced enough, it was not implemented after applying for a patent, it was replaced by better technology, and it lost its meaning of existence, so it was forced to give up the patent and became an invalid patent; The applied patent itself lacks market development value, so there is no need to keep the patent; Difficulties in patent implementation: it cannot be implemented by itself or transferred. At the same time, I have to pay the patent fee every year, which is too heavy, so I gave up the patent right. The way to voluntarily give up includes not paying the annual fee according to the regulations; The patentee waives his patent right in writing. Patent annual fee, also known as patent maintenance fee, refers to the fee paid by the patentee to the patent management authority from the year when the patent right is granted in order to maintain the validity of the patent right. This is the obligation of the patentee according to law. The right of abandonment is a right enjoyed by the patentee according to law. Since then, the patented technology has become an invalid patent and entered the public domain, and anyone can use it free of charge. Generally speaking, the technology that the patentee gives up his patent right in writing is about to be replaced or eliminated, and it has little development and utilization value. 3. The patent applicant gives up after submitting the application and before obtaining the authorization. The main reasons for the patent applicant to give up the patent right are: (1) utility model and design. When the Patent Office makes the decision to grant the patent right, the patent applicant cannot obtain the patent right without paying the patent certificate fee and annual fee; (2) The invention patent cannot be obtained without substantive examination. Strictly speaking, this situation belongs to patent application, because it has never been patented. Accurately speaking, it can't be called an invalid patent, but an "invalid patent application". However, its invention has been recorded in the patent application documents issued after the filing date and is known to the public. 4. Patents declared invalid by others. Article 45 of the Patent Law stipulates that any unit or individual who thinks that the grant of the patent right is not in conformity with the relevant provisions of this Law may request the Patent Reexamination Board to declare the patent right invalid from the date when the patent administrative department of the State Council announces the grant of the patent right. Because the patent declaration is completely invalid and partially invalid, the resulting invalid patent is also completely invalid and partially invalid.