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Claim Invalid Given Lack of Written Description in Original Application

August 29, 2001

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Last Month at the Federal Circuit - September 2001

Judges: Bryson (author), Gajarsa, and Linn

In TurboCare Division of Demag Delaval Turbomachinery Corp. v. General Electric Co., No. 00-1349 (Fed. Cir. Aug. 29, 2001), the Federal Circuit affirmed-in-part, vacated-inpart, and remanded a district court’s decision granting SJ of invalidity as to one claim of the patent at issue and SJ of noninfringement as to four other claims.

Steam turbines convert steam energy into mechanical work by directing steam through narrow openings called nozzles. A standard steam turbine includes an outer casing, stationary internal walls known as diaphragms, both fixed and moving nozzles, and a central rotating shaft. Each diaphragm includes a group of fixed nozzles and a central opening for the shaft. These diaphragms divide the turbine into stages. Each stage includes a group of moving nozzles rigidly mounted on the shaft. The fixed nozzles direct steam flow so as to impinge on blades of the moving nozzles, causing the shaft to rotate.

For maximum turbine efficiency, all of the steam should pass through both the fixed and moving nozzles. However, steam leakage through the central opening of any diaphragm, along the shaft, will bypass the fixed nozzles of the associated stage and will not be properly directed to the blades of the moving nozzles. As a result, turbine manufacturers normally employ shaft-seal systems to reduce such leakage.

The TurboCare Division of Demag Delaval Turbomachinery Corporation (“TurboCare”) owns U.S. Patent No. 4,436,311 (“the ’311 patent”) directed to a shaft-seal system with two positions, the “small” and “large” clearance positions. The claims of the ’311 patent also recite a “radial positioning means” biasing the shaft-seal rings to the large clearance position. The radial positioning means of the preferred embodiment employs S-shaped springs applying outwardly directed forces to the shaft-seal rings. At high turbine loads, steam admitted to an annular space between the casing and the outer surfaces of the rings overcomes this bias, forcing the rings inward to the small clearance position.

TurboCare sued General Electric Company (“GE”) in the United States District Court for the District of Massachusetts, alleging infringement of five claims of the ’311 patent by four versions of shaft-seal rings for GE turbines. On GE’s motion, the district court granted SJ of invalidity as to one claim for lack of an adequate written description and SJ of noninfringement with respect to the other four claims. The district court’s decision rested, in part, on prosecution history concerning specific pathway configurations for admitting steam to the annular space and the court’s interpretation of the “radial positioning means” limitation to exclude GE’s use of flat springs applying inwardly directed forces to GE’s shaft-seal rings.

On appeal, the Federal Circuit agreed with the district court that TurboCare had claimed, after the filing date, a specific location of the radial positioning means that found no support in the original disclosure. As a result, the Federal Circuit affirmed the invalidity of that claim for lack of an adequate written description.

Additionally, after interpreting the “radial positioning means,” “large clearance position,” and “small clearance position” limitations, the Federal Circuit determined that two versions of GE’s shaft-seal rings did not infringe the ’311 patent. The Court also determined that the other two versions did not literally infringe the ’311 patent, but remanded the issue of infringement under the DOE based upon its claim constructions.

In its analysis, the Federal Circuit found sufficient structure in the asserted claims to overcome the means-plus-function presumption attached to the term “radial positioning means.” Further, the Court found Festo not applicable to a specific claim amendment because that amendment had not actually narrowed the literal scope of the asserted claims.