Amending claims to distinguish a prior art reference may serve as a disclaimer that limits claim scope, not only for infringement purposes but for invalidity purposes as well. Applicants considering claim amendment as a means of overcoming a prior art rejection are advised to consider downstream implications for both validity and infringement of any resulting patent.
In Sentry Protection Products, Inc. v. Eagle Mfg. Co., No. 04-1392 (Fed. Cir. March 11, 2005), the federal circuit affirmed the grant of summary judgment to Eagle that Sentry's '781 patent was invalid and not infringed, but vacated the summary judgment grant of noninfringement of Sentry's '611 patent.
Sentry's '781 and '611 patents are directed to barriers for protecting structural columns from damage from moving vehicles while minimizing damage to the vehicles or their drivers. At issue were a claimed plurality of "impact protection components,” each of which was a "single unitary part." During prosecution, patentees added the "single unitary part" language to overcome a reference showing a column protection device having multiple parts, e.g., made of an inner tube surrounded by a protective outer shell. Thus, the district court construed the claim term to mean a single part, complete by itself without additional pieces. Based on this construction, the district court held the '781 patent invalid based on a prior art patent to Chase. In addition, the district court held that Sentry could not obtain any damages for infringement of its '611 patent, so the issue of infringement was moot.
On appeal, the federal circuit affirmed the construction of "single unitary part" based on the prosecution history. By disclaiming the use of multiple components to overcome a prior art rejection, Sentry gave up coverage of multipart impact protection components. Based on this claim construction, the district court properly held as invalid the '781 patent based on the Chase reference which disclosed all of the elements of Claims 10 and 23 of the '781 patent.
Reversing the summary judgment grant that no damages could be awarded for infringement of the '611 patent (because Eagle produced a non-infringing embodiment upon receipt of actual notice), the court held that a genuine issue of fact remained as to whether Sentry's product marking prior to its providing actual notice (§287) to Eagle constituted constructive notice of its '611 patent.
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