Chief Judge Gregory M. Sleet recently clarified the effect of the term “comprising” in claim construction. See Hollingsworth & Vose Filtration Ltd. v. Delstar Tech., Inc., et al., C.A. No. 10-788-GMS (D. Del. Sept. 25, 2012). This came as part of the Court’s order clarifying its previous claim construction order, in which it construed the following language found in Claim 1 of U.S. Patent No. 6,623,548: “filter material comprising: a blend of polypropylene fibres and dry spun halogen free acrylic fibres” to mean “a mixture of fibres that includes at least polypropylene fibres and dry spun halogen free acrylic fibres. Dry spun halogen free fibres means halogen free acrylic fibres made by a process of dry spinning in which the polymer is formed into fibres by extrusion into a gas such as air and not by extrusion into a liquid coagulation bath.” Id. at 1 n.1; D.I. 50 at 1 (previously discussed here).
The Court clarified its previous construction to address the defendants’ question whether, in Claim 1, “the ‘blend’ is open to the inclusion of other types of unrecited fibres, or whether it is only the ‘filter material’ that can include other types of unrecited fibres.” Id. at 1-2 n.1 (quoting D.I. 53 at 5). The Court clarified that the word “blend,” as used in Claim 1, “is not limited to only polypropylene fibres, dry spun halogen free acrylic fibres, and polyvinyl chloride fibres but, rather, is open to the inclusion of other types of unrecited fibres, including wet spun halogen free acrylic fibres.” Id. at 1. That clarification, however, was not the result of the interplay of the words “comprising” and “blend,” as urged by the plaintiff. The Court explained that “[t]he transition ‘comprising’ generally renders the preceding term (e.g., the ‘filter material’) open-ended, but it has no such effect on subsequently recited claim elements (e.g., the ‘blend’).” Id. at 1-2 n.1 (citing Dippin’ Dots, Inc. v. Mosey, 476 F.3d 1337, 1343 (Fed. Cir. 2007) (previously discussed on Patently-O)). However, the Court agreed with the plaintiff that “like ‘comprising’—the term ‘blend’ itself ordinarily conveys the concept of ‘including, but not limited to.’” Id. at 1-2 n.1. Citing the Federal Circuit’s decision in Mars, Inc. v. H. J. Heinz Co., 377 F.3d 1369 (Fed. Cir. 2004) (recognizing that the term “mixture” is open-ended), the Court found that the defendant’s acknowledgement that “[t]he blend is a mixture of fibres” required that the claim term “blend” not be limited to a blend of only the subsequently recited fibres. Id. at 1-2 n.1.