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Foreseeable Equivalents Can Be Found in the Prior Art

June 02, 2003

Decision icon Decision

Last Month at the Federal Circuit - June/July 2003

Judges: Mayer (author), Newman, and Lourie (per curiam)

In Pioneer Magnetics, Inc. v. Micro Linear Corp., No. 00-1012 (Fed. Cir. June 2, 2003), the Federal Circuit, on remand from the Supreme Court, affirmed a judgment of noninfringement under the DOE based on prosecution history estoppel.

The patent-in-suit (U.S. Patent No. 4,677,366) is directed to a “unity power factor power supply” circuitry that levels a varying input voltage into a constant output voltage and steady electrical current source. All but two of the nine originally filed claims were rejected during the prosecution of the application based on prior art. The remaining two claims were rejected as indefinite.

Pioneer Magnetics, Inc. (“Pioneer”) did not dispute the rejection, but instead amended the original claims to include limitations from claims 6 and 7 that were not disclosed in the prior art applied by the PTO. Pioneer explained that it had amended claim 1 to include the substantive limitations of claim 6 with some amendments to overcome the rejection raised for indefiniteness. Pioneer failed to explain, however, why it also amended claim 1 to define the multiplier circuit as a “switching analog” multiplier circuit. After other minor amendments, the patent issued.

While seeking interpretation of the claims, the parties requested the district court to identify what equivalents of the “switching multiplier” limitation, if any, were barred by prosecution history estoppel. In support of its motion, Pioneer offered a declaration by the prosecuting attorney that the reason he added the “switching” limitation to claim 1 was inadvertence. The district court had concluded that Micro Linear Corporation’s (“Micro Linear”) nonswitching multiplier was outside the permissible range of equivalents, given Pioneer’s narrowing amendment to add the switching limitation to claim 1. The parties stipulated to a preferred form of judgment for the appeal.

The Federal Circuit had previously affirmed the district court’s decision based on its en banc decision in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558 (Fed. Cir. 2000). However, the Supreme Court returned the decision to the Federal Circuit for reconsideration in light of its Festo decision. The parties did not dispute that claim 1 had been narrowed when amended to define the “multiplier” to a “switching analog multiplier.” Thus, the Federal Circuit examined the reasons why the claim was amended, noting that the burden was on Pioneer to establish that the reason for the amendment was not one related to patentability.

Pioneer argued that it had added the “switching” limitation by sheer inadvertence, not for reasons of patentability. The Federal Circuit rejected this argument and Pioneer’s corresponding declaration from its prosecuting attorney. The Court noted that only the public record of the patent prosecution could be a basis for determining the reasons for amendments. Otherwise, the Court explained, the publicnotice function of the patent record would be undermined. Moreover, the mere fact that the amendment was voluntary does not mean it did not relate to patentability. Thus, the Court concluded that claim 1 had been amended to overcome the prior art cited by the PTO and to obtain patentability.

Having determined that there was a narrowing amendment for reasons related to patentability, the Federal Circuit next turned to whether Pioneer could overcome the presumption that it had surrendered the equivalent in question. Based on the Supreme Court’s guidance in Festo that the presumption could be overcome if the equivalent was unforeseeable at the time of the application, the Court observed that the reference cited during prosecution by the PTO disclosed a nonswitching multiplier circuit. Therefore, the Court concluded, such a circuit was clearly known in the art and would have been foreseeable at the time of the amendment. Because a nonswitching multiplier circuit was foreseeable at the time of the amendment, the Federal Circuit ruled that Pioneer was estopped from arguing that a nonswitching multiplier circuit is equivalent to a switching multiplier circuit as claimed. Accordingly, the Court again affirmed the judgment of noninfringement.