A patent is issued for a fixed term–14 years for design patents; 20 years for other types–during which the patent holder has a right to exclude others from making, using or selling the subject of the patent. There are, however, certain circumstances under which a patent claim may become ineffective for the purposes of enforcing exclusive patent rights against possible infringers. United States patent law allows a patentee to request a reissue of a patent, a procedure used when a patent as issued needs to be corrected. There may be an error in the specification that undermines the validity of the patent, or a patentee may determine that the scope of the patent as issued is narrower or broader than intended. As long as the error occurred without deceptive intention, the patentee may seek a reissue of the patent.
The patent laws protect those who in good faith relied on the scope of the patent as originally issued in making, using, or selling some invention or process, who are said to have acquired intervening rights. If such use of the invention or process was not covered by the patent as originally issued, the statute protects that use. In such a case, a court has no discretion and must find that there is no infringement on the basis of the absolute intervening rights. Even if a person or business has not used the invention but has made substantial preparation towards making, using or selling it prior to the patent’s reissue, equitable intervening rights may still be found. In contrast to absolute intervening rights, a court will determine whether there has been a sufficient investment of time and money to find that equitable intervening rights have been obtained that justify protecting the investment by finding that no infringement of the reissued patent has occurred.
A similar situation occurs when a patentee seeks a reexamination of a patent. In such a case the patentee or a third party may discover evidence that a patent is not valid and wish to amend the claim in order to obtain patent protection or obtain a ruling from the United States Patent and Trademark Office (USPTO) that the claim as set out in the patent is valid. If the patent as reexamined contains a patentable new claim, intervening rights will protect the use or substantial preparation for the use of a process or invention not covered by the original patent in the same way as with a reissued patent.
The final way in which intervening rights may be established is when utility patent maintenance fees are not paid on time or within the six-month grace period following the due dates for those fees, which are payable at three different times over the life of a 20-year utility patent. Although the USPTO allows a patentee of an expired patent to petition the USPTO to reinstate a patent when failure to pay maintenance fees on time was unintentional or unavoidable, the law protects persons who relied on the presumption that the patent had been abandoned to use, make or sell the subject of the expired patent, or to make substantial preparations to use it. In such cases, intervening rights will be found to have been established in the same manner as in reissued and reexamined patents.