2182 Search and Identification of the Prior Art [R-08.2017]
The application of a prior art reference to a means- (or step-) plus-function limitation requires that the prior art element perform the identical function specified in the claim. However, if a prior art reference only teaches identity of function to that specified in a claim, then an examiner carries the initial burden of proof for showing that the prior art structure or step is the same as or equivalent to the structure, material, or acts described in the specification which has been identified as corresponding to the claimed means- (or step-) plus-function. Similarly, if the prior art reference teaches the identical structure or acts but is silent about performing the claimed function, a reasonable presumption is that the prior art structure inherently performs the same function. The examiner must provide a "sound basis for believing" that the prior art structure or acts would be capable of performing the claimed function. In re Spada, 911 F.2d 705, 708, 15 USPQ2d 1655, 1658 (Fed. Cir. 1990). See MPEP § 2114, subsection I, for more information on establishing inherency for functional limitations.
The means- (or step-) plus- function limitation should be interpreted in a manner consistent with the specification disclosure. The Federal Circuit explained the two step analysis involved in construing means- (or step-) plus- function limitations in Golight Inc. v. Wal-Mart Stores Inc., 355 F.3d 1327, 1333-34, 69 USPQ2d 1481, 1486 (Fed. Cir. 2004):
The first step in construing a means-plus-function claim limitation is to define the particular function of the claim limitation. Budde v. Harley-Davidson, Inc., 250 F.3d 1369, 1376, 58 USPQ2d 1801, 1806 (Fed. Cir. 2001). "The court must construe the function of a means-plus-function limitation to include the limitations contained in the claim language, and only those limitations." Cardiac Pacemakers, Inc. v. St. Jude Med., Inc., 296 F.3d 1106, 1113, 63 USPQ2d 1725, 1730 (Fed. Cir. 2002). The next step in construing a means-plus-function claim limitation is to look to the specification and identify the corresponding structure for that function. "Under this second step, ‘structure disclosed in the specification is "corresponding" structure only if the specification or prosecution history clearly links or associates that structure to the function recited in the claim.’" Med. Instrumentation & Diagnostics Corp. v. Elekta AB, 344 F.3d 1205, 1210, 68 USPQ2d 1263, 1267 (Fed. Cir. 2003) (quoting B. Braun Med. Inc. v. Abbott Labs., 124 F.3d 1419, 1424, 43 USPQ2d 1896, 1900 (Fed. Cir. 1997)).
If the specification defines what is meant by the limitation for the purposes of the claimed invention, the examiner should interpret the limitation as having that meaning. If no definition is provided, some judgment must be exercised in determining the scope of the limitation. See, e.g., B. Braun Medical, Inc. v. Abbott Labs., 124 F.3d 1419, 1424, 43 USPQ2d 1896, 1900 (Fed. Cir. 1997) ("We hold that, pursuant to [35 U.S.C. 112, sixth paragraph], structure disclosed in the specification is ‘corresponding’ structure only if the specification or prosecution history clearly links or associates that structure to the function recited in the claim. This duty to link or associate structure to function is the quid pro quo for the convenience of employing 112, paragraph 6." The court refused to interpret a means-plus-function limitation as corresponding to a disclosed valve seat structure, as argued by patentee, since there was no indication in the specification or prosecution history that this structure corresponds to the recited function, and there was an explicitly clear association between that function and a traverse cross section bar structure disclosed in the specification.).