Double patenting is a judicially created doctrine intended to prevent improper timewise extension of a patent right by prohibiting the issuance of claims in a second patent that are not “patentably distinct” from the claims of a first patent.
The doctrine prohibits claims in a second patent that are merely an obvious variation of the claims of a first patent. If the patent applicant cannot convince the patent examiner that the claims of the second patent are not merely an obvious variation of the earlier claims, the remedy is to file a Terminal Disclaimer.