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Prosecution History Did Not Clearly Limit Scope of Claims

September 24, 2002

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Last Month at the Federal Circuit - October 2002

Judges: Bryson (author), Clevenger, and Plager

In Schwing GmbH v. Putzmeister Aktiengesellschaft, No. 01-1615 (Fed. Cir. Sept. 24, 2002), the Federal Circuit affirmed-in-part, vacatedin- part, and remanded the district court’s judgment of noninfringement regarding two types of concrete pumps.

Schwing GmbH (“Schwing”) is the owner of U.S. Reissue Patent No. RE 32,657 (“the ‘657 patent”), which is a reissue of U.S. Patent No. 4,465,441 (“the ‘441 patent”). These patents disclose a concrete pump having a flexible elastic ring that is held in place by annular extensions from a cutting ring and a shutter mechanism to form a tight metal-to-metal seal. Schwing sued Putzmeister Aktiengesellschaft and Putzmeister, Inc. (collectively “Putzmeister”), alleging that two types of concrete pumps, a Bastardring II and a modified Bastardring II, manufactured by Putzmeister infringed various claims of the ‘657 patent.

The Bastardring II and the modified Bastardring II also use a flexible elastic ring (“ring”) to form a metal-to-metal seal. To hold the ring in place, the Bastardring II uses an annular extension on a cutting ring and an embedded metal ring in the ring near a shutter mechanism that lacks an annular extension. The modified Bastardring II uses a shutter mechanism with a grooved surface that abuts an end of the ring to hold the ring in place.

The district court granted SJ that the Bastardring II does not literally infringe the ‘657 patent because it lacks an annular extension on the shutter mechanism. The district court also granted SJ that the modified Bastardring II does not literally infringe, and that Schwing’s claims for infringement under the DOE against both the Bastardring II and the modified Bastardring II were barred by prosecution-history estoppel. Schwing appealed the second SJ.

On appeal, Schwing argued that the district court had erred in its construction of the phrase “annular extension,” which was defined in purely structural terms, giving rise to a genuine dispute of material fact to preclude SJ of noninfringement by the modified Bastardring II. The district court, relying on statements distinguishing over prior art in the prosecution history of the original ‘441 patent, interpreted “annular extension” to require “inhibiting radial expansion of a sealing ring.”

The Federal Circuit ruled that the district court had erred in its claim construction by reading functional limitations into the claim. The Court found that the statements in the prosecution history described the annular extensions in purely structural terms and did not suggest inhibiting radial expansion of the sealing ring. Despite this error, the Court concluded that Schwing had not demonstrated a genuine issue of material fact as to literal infringement by the modified Bastardring II because it lacks a shutter mechanism with an annular extension.

Regarding infringement under the DOE, Schwing alleged that the embedded metal ring of the Bastardring II and the grooved surface of the shutter mechanism of the modified Bastardring II are an equivalent to the claimed annular extension on the shutter mechanism. The district court also relied on prosecution-history statements distinguishing the prior art to give rise to an estoppel, barring application of the DOE. The Federal Circuit, however, found that the applicant did not rely on the annular-extension limitations to distinguish over the prior art. Accordingly, the Court ruled that the district court had improperly relied on those statements to bar application of the DOE.

Putzmeister also asked the Federal Circuit to affirm the district court based on narrowing claim amendments directed to the “annular extension” limitations. With regard to the Bastardring II, the Court found that the ‘657 patent criticized the use of an embedded metal ring to hold a flexible ring in place and barred infringement under the DOE. With regard to the modified Bastardring II, based on the recent Supreme Court’s Festo decision, the Court remanded the case to the district court to allow Schwing to rebut the presumption that a narrowing amendment bars the application of the DOE.