If ordinary meaning of claim term does not resolve disputed construction, court must construe term

April 10, 2008
Post by Blog Staff

In a decision last week, the Federal Circuit vacated and remanded a jury's finding of willful infringement case back to a district court, based on errors in claim construction and application of the doctrine of equivalents. The district court's original Markman hearing determined that no construction was necessary for a particular claim term, "only if," whose scope was disputed by the parties. The court held the term did not require construction, as it was two simple, plain English words that were well understood. The district court also permitted the jury to consider infringement under the doctrine of equivalents, finding that while the "only if" limitation was added for a substantial reason relating to patentability, the Festo presumption was rebutted because the rationale underlying the narrowing amendment was tangentially related to the equivalent at issue.The Federal Circuit held that it was error for the district court not to construe the "only if" limitation. While the court noted that "district courts are not (and should not be) required to construe every limitation present in a patent's asserted claims," in this case, because "the parties present[ed] a fundamental dispute regarding the scope of a claim term, it [was] the court's duty to resolve it." The court also determined that the addition of the "only if" limitation during prosecution was not tangential to the alleged equivalent, and therefore application of the doctrine of equivalents was precluded.More detail on O2 Micro Int'l Ltd. v. Beyond Innovation Tech. Co. after the jump.O2 Micro asserted infringement of three patents (the '615, '722, and '129 patents) directed to DC-to-AC converter circuits. The circuits allow conversion of low voltage direct current (DC) into higher voltage alternating currents (AC) and are marketed as inverter controllers to convert a DC power source to an AC power source. An important limitation of the patents includes a converter circuit utilizing a feedback control loop to control the amount of power delivered from the DC power source. The relevant limitation of the claims requires (emphasis added):

a feedback control loop circuit receiving a feedback signal indicative of power being supplied to said load, and adapted to generate a second signal pulse signal for controlling the conduction state of said second plurality of switches only if said feedback signal is above a predetermined threshold;
The "only if" limitation was added during prosecution in response to an obviousness rejection. The defendants' products have feedback control loops that have capability of shutting off when power is below a pre-determined threshold.The district court held a Markman hearing, and heard argument regarding the proper scope of the "only if" limitation. The plaintiff argued it needed no construction, while the defendants offered competing, although arguably compatible constructions. Ultimately, the district court decided no construction was necessary, as "only if" was two plainly understood English words.The district court also permitted the plaintiff to allege infringement under the doctrine of equivalents, holding that the "only if" limitation was only tangentially related to the equivalent in question. After these rulings, the jury returned a verdict that the defendants had willfully induced infringement. The defendants appealed.On appeal, the Federal Circuit first determined the defendants did not waive its right to appeal the claim construction issue by failing to make an objection to the court's jury instructions. The court stated that no additional objections to the claim construction are required after a Markman proceeding.Turning to the merits of the appeal, the court vacated the jury's finding of infringement. Because there was a dispute between the parties regarding the scope of the claims, the district court should have resolved the parties' dispute, stating that Markman hearings are to construe both the meaning and the scope of claim language. In this case, the words' ordinary meaning does not resolve the parties' dispute and therefore requires construction of the term's scope. As stated by the court:
A determination that a claim term "needs no construction" or has the "plain and ordinary meaning" may be inadequate when a term has more than one "ordinary" meaning or when reliance on a term's "ordinary" meaning does not resolve the parties' dispute. In this case, for example, the parties agreed that "only if" has a common meaning, but then proceeded to dispute the scope of that claim term, each party providing an argument identifying the alleged circumstances when the requirement specified by the claim term must be satisfied (e.g., at all times or during steady state operation). In this case, the "ordinary" meaning of a term does not resolve the parties' dispute, and claim construction requires the court to determine what claim scope is appropriate in the context of the patents-in-suit.
The court further noted that the district court's error in failing to construe the claim resulted in the jury improperly making a legal determination of the term's scope. As a result, the court remanded the case for proper claim construction.The second issue on appeal was the application of the doctrine of equivalents. The court once again sided with the Defendants. It was undisputed that the "only if" limitation was added for substantial reasons relating to patentability, so the only question was whether the Festo presumption that prosecution history estoppel barred application of the doctrine of equivalents was rebutted. The only grounds for such rebuttal raised on appeal was the "tangentially related" rationale. The court, in examining the record, found the amendment not tangentially related to the alleged equivalent, and therefore that prosecution history estoppel applied. As stated by the court:
Essentially, O2 Micro argues that exceptions to the "only if" limitation (e.g., during non-steady state operations) are merely tangential to the limitation itself. We find this argument to be without merit. The "objectively apparent" reason for the patentee's amendment was to require the feedback circuit to be operational "only if said feedback signal is above a predetermined threshold," as the claim language clearly states. No other reason is provided or suggested by the prosecution history. The equivalent alleged by O2 Micro is a feedback circuit that, during non-steady state operations, may be operational even though the claim language is not satisfied (i.e., the feedback signal is not above the predetermined threshold). This equivalent is simply not tangential to the reason for the amendment.
As a result, the Federal Circuit vacated the jury verdict, final judgment of infringement, and the permanent injunction granted by the district court, and remanded to the district court for further proceedings.To read the full decision in O2 Micro Int'l Ltd. v. Beyond Innovation Tech. Co., click here.

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