The Risk of Functional Claiming is That the Functional Limitation may be an Inherent Characteristic of the Prior art

Leggett & Platt, Inc. v. Vutek, Inc., [2007-1515] (August 21, 2008) [PROST, Bryson, Archer] The Federal Circuit affirmed summary judgment of invalidity of L&P’s U.S. Patent No. 6,755,518 (the “’518 patent”).
DISCUSSION: Three questions of claim construction were presented on appeal: (1) cold UV, (2) freeze dots of the jetted ink, and (3) substantially cure. Based on these claim constructions the district court found the asserted claims either anticipated by, or obvious from, defendant’s patents. the district court construed the term “substantially cure” to mean “cured to a great extent or almost completely cured.” The Federal Circuit noted that the district court construed the term “substantially cure” to mean “cured to a great extent or almost completely cured.” Thus, the relevant portion of claim 1 simply requires a cold UV source (e.g., LEDs) that is “effective to impinge sufficient UV light on the ink” to cure the ink to a great extent or almost completely cure it. The Federal Circuit noted that because the claim is written with functional rather than structural language—it requires the cold UV assembly to be “effective to” substantially cure rather than requiring ink to be substantially cured—the claim limitation will be anticipated if the LEDs disclosed in the prior art are able to cure the ink to a great extent. As the Federal Circuit explained in In re Schreiber, the risk of functional claiming is that the functional limitation may be an inherent characteristic of the prior art.
The Federal Circuit noted that the prior art showed that 75-80% curing, which the Federal Circuit said a reasonable mind might well find to be “substantially cured”, however under the strict standard of summary judgment the Federal Circuit could not say, as a matter of law, that 75-80% cured is “cured to a great extent or almost completely cured.” The Federal Circuit said that it could, however, conclude as a matter of law that the prior art inherently discloses LEDs that are “effective to impinge sufficient UV light on the ink to” cure the ink to a great extent. The Federal Circuit said that under the principles of inherency, if the prior art necessarily functions in accordance with, or includes, the claims limitations, it anticipates. In other words, the prior art will anticipate by inherency if its LEDs necessarily are “effective to impinge sufficient UV light on the ink to substantially cure the ink.” Thus, while the prior art may not expressly disclose that the LEDs cure the ink to a great extent, it inherently discloses LEDs that are “effective to” do so.
The Federal Circuit rejected plaintiff’s argument that the prior art could not cure the ink as ignoring the difference between substantial cure and full cure is not insubstantial. The Federal Circuit also rejected plaintiff’s argument that some examples did not anticipate, as relying on the erroneous assumption that the disclosure of multiple examples renders one example less anticipatory.