§251 Reissue of Defective Patents

Summary

If a patent is partly or fully invalid because of mistakes in its description, drawings, or claims, the Director must reissue it when the owner returns the old patent and pays the required fee. The reissued patent covers the same invention shown in the original patent and runs for the remaining term of the original patent. No new subject matter may be added. The Director can issue more than one reissued patent for separate parts if the applicant asks and pays a fee for each. Most rules for patent applications also apply to reissue requests. A full assignee (one who owns the whole patent) may apply and swear the papers if they do not try to broaden the original claims or if the assignee filed the original application. A reissue that makes the claims broader is allowed only if applied for within two years after the original patent was granted.