The Perils of Claiming Open-Ended Ranges – A Reminder Courtesy of the Federal Circuit


Patent prosecutors drafting claims that recite open-ended ranges (e.g., at least 10%, greater than 5 units) were again warned of the perils of claiming more than has been disclosed. In a recent decision by the Federal Circuit, MagSil Corp. v. Hitachi Global Storage Tech., Inc., the Court affirmed the trial court’s determination that the asserted claims were invalid as a matter of law for lack of enablement. The Court found that the open-ended range recited in the independent claim was not enabled because the disclosure provided support for only a small portion of the claimed open-ended range, citing to the dual function of enablement for both ensuring there is adequate disclosure to support a claimed invention and preventing claims broader than the disclosed invention. Patent practitioners reciting open-ended ranges should consider taking one or more steps to better ensure validity of their claims, including reciting the structure that enables the recited range in the claim, adding dependent claims that close the open-ended range, and providing examples in the specification that support a wide spectrum of values, and in particular values that fall within the high end of the open-ended range.

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