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Claim Term “Substantially” Used as a Term of Magnitude, Not Approximation

October 17, 2003
Arner, Erika Harmon

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Last Month at the Federal Circuit - November 2003

Judges: Gajarsa (author), Bryson, and Prost

In Deering Precision Instruments, L.L.C. v. Vector Distribution Systems, Inc., No. 02- 1013 (Fed. Cir. Oct. 17, 2003), the Federal Circuit affirmed the district court’s finding of no literal infringement but vacated the lower court’s grant of SJ of no infringement under the DOE.

At issue was U.S. Patent No. 4,744,428 (“the ‘428 patent”), assigned to Deering Precision Instruments, L.L.C. (“Deering”), for a portable scale having sliding weights. All five claims of the ‘428 patent require a sliding weight “when in its zero position having a portion thereof disposed substantially in an imaginary plane containing the fulcrum,” referred to as the zero-position element. The accused device included a sliding weight that, at its zero position, was no closer than 0.10 inches from an imaginary plane containing the fulcrum.

Reviewing the district court’s claim construction, the Federal Circuit examined the meaning of the zero-position element, particularly the phrase “substantially in an imaginary plane,” noting that the term “substantially” has dual ordinary meanings. In a claim, “substantially” can be either a term of magnitude, meaning “significantly” or “considerably,” or a term of approximation, meaning “largely” or “essentially.” Looking to the written description, the Court determined that “substantially” in these claims was a term of magnitude requiring a not insubstantial portion of the sliding weight to intersect the imaginary plane. Because the sliding weight of the accused device did not penetrate the imaginary plane at any point, the Court affirmed the lower court’s finding of no literal infringement.

Turning to the DOE, the Court considered the prosecution history of the ‘428 patent. In particular, the Court noted that the original application included two independent claims, one broadly reciting “a sliding weight movably carried by the beam” and the other containing the zeroposition limitation. In response to the first Office Action, the patentee cancelled the broader independent claim and added a new independent claim containing the zero-position limitation. The narrower original independent claim issued unamended.

Citing the Supreme Court’s opinion in Festo, the Federal Circuit held that the patentee’s cancellation of the original independent claim and the addition of the narrower independent claim amounted to a clear surrender of the broader subject matter of a sliding weight without the zeroposition limitation. The Court reasoned that because the patentee made the amendments in response to an examiner’s rejection, they were made for reasons of patentability and, therefore, gave rise to a presumption of prosecution history estoppel barring the patentee from arguing infringement under the DOE. The Court further noted that the estoppel applied equally to all claims containing the zero position limitation, even those that were not amended during prosecution. Finally, the Court remanded the case to the district court for further proceedings to determine whether the patentee could rebut the presumption of prosecution history estoppel.