Finding that continuity of disclosure was not maintained throughout a chain of related patents, the U.S. Court of Appeals for the Federal Circuit reversed a district court’s previous holding that the patent at issue was entitled to the benefit of the filing date of an earlier patent under 35 U.S.C. § 120. Zenon Environmental, Inc. v. United States Filter Corp., Case Nos. 06-1266, -1267 (Fed. Cir., Nov. 7, 2007) (Lourie J.; Newman, J., dissenting).

The plaintiff, Zenon Environmental, owner of a patent directed to “large systems for the microfiltration of liquids,” asserted its patent against its primary competitor, U.S. Filter. The patent was the sixth patent to issue in a series of related applications, and it disclosed and claimed a gas distribution system that was originally disclosed in the grandparent application—the grandparent application having been incorporated by reference into the patent in suit. However, in several intervening patent applications, rather than incorporating by reference the entire grandparent application, i.e., in toto, the inventor only cited the grandparent application with respect to the “details relating to the construction and deployment of a vertical skein” and omitted any reference to the gas distribution system disclosed in the grandparent application.

Citing Lockwood v. Am. Airlines, Inc., the Federal Circuit stated that under § 120, in order for a subsequent application to claim priority back to an earlier application, the subsequent applications must comply with the written description requirement of § 112. Specifically, a proper incorporation by reference requires that a person of ordinary skill in the art is able to determine whether the host document describes the incorporated material with sufficient particularity. In this instance, the Court concluded that since the intervening patents disclose an entirely different gas distribution system and that applicant did not clearly and specifically incorporate the grandparent application by reference, there was no continuity of disclosure in the family chain. Hence, the later application was found not to be entitled to claim the benefit of the filing date of the grandparent application.

Far worse (from the patent owner’s perspective) was the Court’s conclusion that since it was not disputed by the parties that the grandparent application “disclose[d] each and every element” of the asserted claims and was filed more than one year prior to the filing of the application for the patent in suit, the grandparent anticipated, and thus invalidated, the patent in suit.

Practice Note: The incorporation by reference of earlier applications is routinely used in patent practice. However, care should be exercised to avoid any limiting effect where the object is to incorporate previous patent applications or patents. This case reminds patent practitioners to be cautious when invoking incorporation of prior applications by reference. One unintentional misstep may result in dire consequences.