Patent applications that describe a “preferred embodiment” often include claims directed to that embodiment.  After all, if an embodiment is “preferred,” it is likely worthy of claim coverage.  Nevertheless, applicants are not required to focus their claims on a preferred embodiment; they are free to claim any alternative embodiments described in the specification.  A special issue of claim construction arises, however, when an application describes a “preferred embodiment,” but a question is raised as to whether that embodiment is covered by the claims.

The Court of Appeals for the Federal Circuit recently considered this issue in Accent Packaging, Inc. v. Leggett & Platt, Inc., No. 2012-1011 (Fed. Cir. Feb. 4, 2013).  In the district court, Accent alleged that Leggett infringed U.S. Patent Nos. 7,373,877 (“the ’877 patent”) and 7,412,992 (“the ’992 patent”).  The patents, which are related and have nearly identical specifications, describe and claime a wire tier device used to bundle trash or recyclables.  According to the written descriptions, the wire tier includes four “elongated operator bodies” capable of gripping a wire, twisting two ends of the wire together using a “knotter,” cutting the wire, and ejecting the wire from the knotter so that the trash or recyclables being bound can be moved away and a new bundle can be tied.  Importantly, the written descriptions set forth a preferred embodiment where two elongated operator bodies are operably coupled to both the knotter and the cover.

Leggett’s accused product included only two elongated operator bodies.  Thus, Leggett argued that it did not infringe the ’877 patent because its product did not meet the claim limitation of “each of the operator bodies being operably coupled with a respective one of said gripper, knotter, cutting element and cover.”  Leggett argued that the terms “each of” and “a respective one” required four elongated operator bodies, each operably coupled to one and only one of said gripper, knotter, cutting element, or cover.  Leggett made separate arguments regarding noninfringement of the ’992 patent.  The district court agreed with Leggett regarding the ’877 patent and granted summary judgment of noninfringement.

On appeal, Accent argued that the district court erred by construing the claims to require that each elongated operator body be coupled to one and only one operator element.  The Federal Circuit agreed with Accent and reversed the district court’s ruling on summary judgment regarding the ’877 patent.  The court explained that, “in the preferred embodiment of the invention, two elongated operator bodies are operably coupled to both the knotter and the cover,” and, thus, Leggett’s position that each elongated operator body must be coupled to one and only one operator element must be incorrect.  Accent Packaging, slip op. at 12.  “Put differently, the preferred embodiment features an elongated operator body that is operably coupled to one or more operator elements.”  Id.  The basic principle invoked by the court was that “a claim interpretation that excludes a preferred embodiment from the scope of the claim is rarely, if ever, correct.”  Id. (citation omitted).  The court also noted that the “indefinite article ‘a,’” as used in Accent’s claims, generally carries the meaning of “one or more” in open-ended claims containing the transitional phrase “comprising,” unless the patentee has shown a clear intent to limit “a” to “one.” Id.

Accent Packaging illustrates that care must be taken in deciding whether or not to describe an embodiment as “preferred” in a patent application.  The case demonstrates that courts are generally inclined to read claims to cover a preferred embodiment unless a convincing reason to exclude the embodiment is provided.  For practitioners, this can have positive and negative implications.  Describing an embodiment as “preferred” in an application may help, as it did for Accent, if an accused infringer seeks to limit the claims in a manner arguably inconsistent with the preferred embodiment.  However, including a preferred embodiment in a specification can also pose risks, as it may anchor the claims to a single embodiment and potentially limit the patentee’s ability to argue that alternative embodiments are covered.  While practitioners should carefully consider the tradeoffs in describing an embodiment as “preferred,” Accent Packaging also suggests that use of the open-ended transitional phrase “comprising” and the indefinite article “a” remains a good practice if claim breadth is desired.