In Shoes by Firebug LLC, v. Stride Rite Children's Group, LLC, Appeals 2019-1622, and 2019-1623 (Fed. Cir. June 25, 2020), the Federal Circuit affirmed the PTAB's IPR decisions that the claims of two challenged Firebug patents, directed to illumination systems for footwear, were unpatentable for obviousness. Although the PTAB erred in determining that the word "textile" in the preamble of both patents was not limiting (the term was limiting in one of the patents), the court concluded that this error did not affect the PTAB's conclusions that all challenged claims were obvious.
Both of Firebug's patents (the '038 patent and the '574 patent) include the term "textile footwear" in the challenged claim preambles, and include the word "footwear," but not "textile" in the body of the claims. Specifically claim 1 of the '574 patent recites "a footwear" in the claim body, but claim 1 of the '038 patent recites "the footwear."
In evaluating whether the "textile" feature in the claim preambles should be considered limiting, the Federal Circuit noted that "a preamble is not limiting where a patentee defines a structurally complete invention in the claim body and uses the preamble only to state a purpose or intended use for the invention," and that dependence on a particular disputed preamble phrase for antecedent basis may limit claim scope because it indicates a reliance on both the preamble and claim body to define the claimed invention."
In this regard, the Federal Circuit determined that the body of claim 1 of the '038 patent recites a structurally complete invention, but the body of claim 1 of the '574 patent does not. Particularly, the court noted: "the first limitation of the body of claim 1 of the '038 patent reintroduces 'a footwear' which 'comprises a sole and an upper.'" (Shoes by Firebug LLC, pages 8-9).
Furthermore, the court discussed that the description of the '038 patent explained that the textile material was only one type of material that could be used. For example, the '038 patent discussed that leather, synthetics, and plastics could also be used. Thus, the court concluded that because the body of claim 1 of the '038 patent recited a structurally complete article, and because the use of a textile material was not necessary, the textile feature in the claim preamble did not limit the claim.
In contrast to claim 1 of the '038 patent, the court determined that the preamble of claim 1 of the '574 patent did limit the claim. Specifically, the court reasoned that "footwear" in the body of claim 1 of the '574 patent relied on the claim preamble for antecedent basis. In this regard, the Federal Circuit explained:
While antecedent basis alone is not determinative of whether a preamble is limiting, use of preamble terms to define positive limitations in the body of claims can evince an inventor's intent that the preamble limit the scope of the claim. That is the case here. Because the claim requires that the illumination system be housed in the textile footwear recited in the preamble, the preamble is essential to understanding the structural limitations of the illumination system. (Shoes by Firebug LLC, page 10).
Thus, the court concluded that the preamble limited claim 1 of the '574 patent. Nonetheless, the court concluded that the textile feature was obvious and that the PTAB's error in treating the preamble of the '574 patent was harmless. Although the PTAB's error in treating a preamble as non-limiting did not affect the outcome of this case, the Federal Circuit's decision is a helpful reminder that use of the definite article "the" in the body of a claim to refer to a term in the claim's preamble may be enough to render the preamble as a limitation of the claim.