The doctrine of double patenting seeks to prevent the unjustified extension of patent exclusivity beyond the term of a patent. The public policy behind this doctrine is that:
The public should . . . be able to act on the assumption that upon the expiration of the patent it will be free to use not only the invention claimed in the patent but also modifications or variants which would have been obvious to those of ordinary skill in the art at the time the invention was made, taking into account the skill in the art and prior art other than the invention claimed in the issued patent.
In re Zickendraht
, 319 F.2d 225, 232, 138 USPQ 22, 27 (CCPA 1963) (Rich, J., concurring). Double patenting results when the right to exclude granted by a first patent is unjustly extended by the grant of a later issued patent or patents. In re Van Ornum
, 686 F.2d 937, 214 USPQ 761 (CCPA 1982).
As a preliminary matter, there must be some common relationship of inventorship and/or ownership of two or more patents or applications. Since the doctrine of double patenting seeks to avoid unjustly extending patent rights at the expense of the public, the focus of any double patenting analysis necessarily is on the claims in the multiple patents or patent applications involved in the analysis.
There are generally two types of double patenting rejections. One is the "same invention" type double patenting rejection based on 35 U.S.C. §101, which states in the singular that an inventor "may obtain a patent". The second is the "nonstatutory-type" double patenting rejection based on a judicially created doctrine grounded in public policy and primarily intended to prevent prolongation of the patent term by prohibiting claims in a second patent not patentably distinguishing from claims in a first patent. Nonstatutory double patenting includes rejections based on one-way determination of obviousness and on two-way determination of obviousness. Nonstatutory double patenting could include a rejection which is not the usual "obviousness-type" double patenting rejection. This type of double patenting rejection is rare and is limited to the particular facts of the case. In re Schneller
, 397 F.2d 350, 158 USPQ 210 (CCPA 1968).For more information: