By Timothy B. McCormack, Attorney
Rule Summary: A finding of patent infringement requires that the accused device or method embody or practice every limitation of at least one claim of the asserted patent. Further, the asserted patent must be valid and enforceable.
Rule Detailed: patent infringement requires an interpretation of the claim (usually does at a Markman hearing) and a comparison of the claim with the accused device or product. Below is a detailed summary of how this works.
There are two ways of finding infringement of a patent. The first way is literal infringement and the second is infringement through the Doctrine of Equivalents.
The determination of infringement is a two-step process. First, the language of the claim must be interpreted (as noted above). Second, the accused device must be compared to the claim language as interpreted. SSIH Equipment S.A. v. United States Int’l Trade Comm’n, 718 F.2d 365, 376, 218 USPQ 678, 688 (Fed. Cir. 1983). If the accused device contains all of the limitations specified in the claim, infringement is made out (literal infringement). If some limitations of the claim are not literally satisfied, infringement may be found in appropriate circumstances under the doctrine of equivalents. Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 935-36, 4 USPQ.2d 1737, 1738-40 (Fed. Cir. 1987) (in banc) cert. denied, 485 U.S. 961, 1009, 108 S.Ct. 1226, 1474, 99 L.Ed.2d 426, 703 (1988); see also, Read v. Portec Inc., 970 F.2d 816, 523 USPQ.2d 1426 (Fed. C.V. 1992).
1. Literal Infringement
It is now well settled that literal infringement is found when the accused devise falls within the scope of the asserted claims that are properly interpreted. For literal infringement, each limitation of the claim must be met by the accused device exactly. Any deviation from the claim precludes a finding of literal infringement. Johnson v. Ivac Corp., 885 F.2d 1574, 1577, 12 USPQ.2d 1382, 1384 (Fed. Cir. 1989). In other words, if a patent claims elements A and B and C and D and E and F, all six elements must be in the accused devise to find literal infringement.
2. Doctrine of Equivalents
Infringement under the Doctrine of Equivalents is found when all the claim elements are still met exactly or by a substantial equivalent. Under the doctrine of equivalents, a patentee must show that the accused device performs substantially the same function, in substantially the same way, to achieve substantially the same result. Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 607, 70 S.Ct. 854, 855, 94 L.Ed. 1097 (1950). “The ‘substantially the same way’ prong of the test may be met if an equivalent of a recited limitation has been substituted in the accused device.” Malta v. Schulmerich Carillons, Inc., 952 F.2d 1320, 1325-26, 21 USPQ.2d 1161, 1164-65 (Fed. Cir. 1991), cert. denied, 504 U.S. 974, 112 S. Ct. 2942, 119 L.Ed.2d 566 (1992). Thus, infringement requires that each limitation of a claim be met exactly or by a substantial equivalent.
As a matter of terminology under the doctrine of equivalents, I speak only of infringement of a claim and of an equivalent to a limitation of the claim. See Malta, 952 F.2d at 1325-26, 21 USPQ.2d at 1164-65. Specifically, we avoid speaking of “equivalency” between the accused device and the patented invention. To speak of “equivalency” to the invention creates confusion and is technically inaccurate. The statutory requirement for liability is “infringement” of a patent, not “equivalency” between devices or methods. 35 U.S.C. § 281. Equivalency to limitations of the claim must be the focus of the inquiry, particularly in jury trials. Malta, 952 F.2d at 1327, 21 USPQ.2d at 1166. Otherwise, laymen may be led to comparison of devices, rather than between the accused device and the claim, and to rely on generalities in the overall purpose of the devices. For example, a pen and a pencil may for many purposes or uses be generally equivalent, but claim limitations drawn to a pen would not under the doctrine of equivalents cover a pencil and vice versa.