Bartell Industries, Inc. (“Bartell”) appeals the April 13, 1999 judgment, following a bench trial, of the United States District Court for the Eastern District of Arkansas, Civil Action No. J-C-95-143 (“Allen Engineering”), holding that Bartell’s riding trowel models TS-65, TS-78, and TS-88
*fn1 infringed certain claims of United States Patent No. 5,108,220 (“’220 patent”), assigned to Allen Engineering Corporation (“Allen”), and the same court’s Order of February 2, 2001, entering judgment for Allen and awarding doubled damages in the amount of $463,485.10. Because the district court did not construe the claims in suit and did not identify the specific claims it held to be infringed under the doctrine of equivalents, we vacate the judgment of infringement and the award of damages based thereon. Moreover, because the district court failed to apply the proper legal test in considering whether Allen’s sales of the Red Rider more than one year prior to the filing date of the ’220 patent constituted an on-sale bar to the patenting of the invention claimed therein, we vacate the district court’s determination that the patent is not invalid under 35 U.S.C. � 102(b). Because claims 1-4, 13, and 23 of the ’220 patent are indefinite, we reverse the district court’s holding that those claims are not invalid under 35 U.S.C. � 112. We affirm the district court’s finding that Bartell has not established the intent to deceive necessary to its claim of inequitable conduct before the Patent and Trademark Office based on Allen’s failure to disclose its Red Rider trowel during the prosecution of the ’220 patent. Finally, we affirm the district court’s finding that the typographical error contained in certain patent identification labels on the Allen trowels was not material and does not affect any eventual calculation of damages. The case is remanded for further proceedings consistent with this opinion.
I. BACKGROUND
This appeal relates to concrete riding trowels, which are machines used to smooth the surface of freshly poured concrete. Such trowels are powered by an internal combustion engine and are steered by the manipulation of a control stick or sticks. Since the steering of early trowels was relatively poor, research focused on improvements to the responsiveness of the steering. Allen’s first model of such a trowel was known as the “Red Rider.” It featured dual control sticks, and was a “front-facing” trowel, meaning that the operator sat on a forward facing seat, as distinct from “straddle-type” trowel seats, which were similar to motorcycle seats. Sales of the Red Rider began in 1988; over one hundred units were ultimately sold. Allen’s further research efforts ultimately resulted in the development of another riding trowel model, known as the “Flying Frame,” which was introduced to the market in 1990.
