The Court of Appeals for the Federal Circuit (CAFC) found in Exmark Mfg. Co. Inc. v. Briggs & Stratton Power Prods. GRP., LLC, No. 2016-2197 (Fed. Cir. January 12, 2018) that a district court did not err in denying summary judgment for indefiniteness. Exmark, page 16. Specifically, the CAFC determined that the claim language and specification of U.S. Patent No. 5,987,863 (“the ‘863 patent”) provided reasonable certainty on how to determine whether a lawn mower baffle portion was long enough and straight enough to be considered “elongated and substantially straight” (claim 1 of the ‘863 patent) for the purposes of determining infringement. Exmark, page 16.
An annotated version of FIG. 4 of the ‘863 patent (see below) was provided on appeal illustrating the baffle portion 58 in question. Exmark, page 4. The baffle portion 58 is disposed between a first arcuate baffle portion 56 and a second arcuate baffle portion 60 (col. 4, lines 8-12 of the ‘863 patent) and extends in a “chord-like” fashion with respect to the second arcuate baffle portion 60. Exmark, page 4. The CAFC reasoned that no strict numerical precision was required for definiteness as long as some standard for measuring a term of degree was provided. Exmark, pages 18-19 (citing Nautilus, Inc. v. Biosig Instruments, Inc. 783 F. 3d at 1378) Here, the court found the claims and specification of the ‘863 patent provided that the baffle portion 58 “must be long enough and straight enough to at least connect these two arcuate portions [56 and 60] of the baffle.” Exmark, page 17.
Although any conceivable geometry, e.g., curved, wavy or jagged, could be theoretically employed to “connect” the two baffle portions 56 and 60, the CAFC found that “one skilled in the art would understand that the ‘substantially straight’ portions of the baffle must be sufficiently straight to connect two arcuate portions of the baffle.” Exmark, page 19. The CAFC did not suggest, however, that there was no limit to how askew a baffle portion could be and still be considered “substantially straight.” Rather, the CAFC looked to the specification of the ‘863 patent for guidance. The specification does not define any limits for substantial straightness, but it does refer to the baffle portion 58 as “relatively straight baffle portion 58” (col. 4, lines 11-12 of the ‘863 patent). Thus, the CAFC concluded that the “substantially straight” baffle portion is straight “relative to the curved baffle portions.” Exmark, page 18. The court suggests that as long as a competitor’s baffle portion was straighter than the arcuate portions, that it could be considered “substantially straight,” and the competitor should not be ensured that they had successfully designed around the ‘863 patent simply by designing in some curvature or irregularity into a baffle portion connecting two arcuate baffle portions.
The court also turned to functional language in the claim to provide further guidance in determining whether or not claim 1 might be indefinite. Exmark, page 19. The CAFC quoted Cox Commc’ns, Inc. v. Sprint Commc’n Co. LP, 838 F.3d 1224, 1232 stating “Functional language can ‘promote  definiteness because it helps bound the scope of the claims by specifying the operations that the [claimed invention] must undertake.’” Claim 1 of the ‘863 patent recites “said first elongated and substantially straight baffle portion being . . . disposed . . . in a chord-like fashion so that the cuttings from said first cutting blade will be deflected inwardly within the said circle defined by the blade tip path of said second cutting blade.” Although this language is recited in reference to the “chord-like” positioning of the baffle, the court extends the function of “deflecting clippings into the direction of the next blade” to also define the required length and straightness of the baffle portion. Exmark, page 19. Again, it is not clear a curved, wavy or jagged baffle portion could not direct clippings into the next blade if it were arranged to end the second arcuate baffle portion in a “chord-like” fashion.
Ultimately, the CAFC seemed to struggle in finding that the objective boundaries of the straightness of the recited “elongated and substantially straight” baffle portion could be understood by one skilled in the art with reasonable certainty. However, by suggesting that that “substantially” straight was at least “relatively” straight compared to the arcuate baffle portions, at least “some standard” (Exmark, page 18) for the required straightness was offered. Since the CAFC left open possibility that a somewhat curved baffle portion that is not quite as curved as the arcuate baffle portions and that directs clippings into the next blade might be interpreted as satisfying the “substantially straight” limitation of claim 1, this analysis may not be particularly satisfying to a competitor attempting to design around this particular claim feature.