What if my patent has already expired? — You may still be able to collect some past damages if your patent expired less than six years ago.
U.S. patent law allows a patent owner to collect damages accrued up to six years preceding the filing of a lawsuit. For example, if your patent expired a year ago and you filed a lawsuit immediately, you may be able to claim damages for the five years preceding its expiration.
Does a patent expire automatically after 7 years? can another person request a similar patent with minor physical
and marketing changes? How can I find out if a patent has