Liquid Dynamics Corp. v. Vaughan Co., No. 06 C 5611, 2008 WL 3007996 (N.D. Ill. Aug. 4, 2008) (Kennelly, J.).
Judge Kennelly construed “approximately” as used in plaintiff Liquid Dynamic’s (“LD”) patent for wastewater treatment tanks, and denied defendant Vaughan Co.’s (“Vaughan”) motion for summary judgment. The claim at issue required that flow generators were located “between approximately 30 percent and 70 percent” of the radial distance from the center to the inside wall of the tank. LD argued that approximately was defined by industry standard tolerances of 10%. Vaughan argued that approximately was limited to 5% based upon the broadest range of 25%-75%.
The Court held that the intrinsic evidence – patent’s specification and prosecution history – made clear that 25%-75% were not the outer limits of flow generator placement. But the intrinsic evidence did not clarify what those outer limits were or what approximately meant. The Court, therefore, relied upon the extrinsic evidence – plaintiff’s expert’s affidavit – and held that 10% was an industry standard.
The Court denied Vaughan’s motion for summary judgment that argument-based estoppel precluded doctrine of equivalents. Vaughan argued that LD gave up any range beyond 25% – 75% during prosecution. For the same reasons the Court defined approximately as extending beyond the 25% – 75% range, the Court held that LD had not surrendered equivalents beyond the 25%- 75% range.