Corning Glass Works v. Sumitomo Electric U.S.A., Inc.
868 F.2d 1251 (1989)
Premium Feature
Subscribe to Lexplug to listen to the Case Podcast.
Rule of Law:
Infringement under the doctrine of equivalents occurs when an accused device contains an equivalent for each limitation of a patent claim. A substituted element is equivalent if it performs substantially the same function, in substantially the same way, to achieve substantially the same result as the claimed limitation.
Facts:
- Corning Glass Works (Corning) developed and patented an optical waveguide fiber, a technology crucial for long-distance telecommunications.
- Corning's U.S. Patent No. 3,659,915 ('915) described a fiber with a fused silica core and cladding.
- The '915 patent specified adding a 'positive' dopant to the core, which increases the core's refractive index (RI) relative to the cladding, causing light to be guided within the core.
- The patent specification only mentioned dopants that increased the RI of the core.
- Sumitomo Electric U.S.A., Inc. (Sumitomo) manufactured and sold an optical waveguide fiber known as the S-3 fiber.
- Sumitomo's S-3 fiber created the necessary RI differential not by adding a positive dopant to the core, but by adding a 'negative' dopant (fluorine) to the cladding.
- This negative dopant in the cladding decreased its RI relative to the pure fused silica core, achieving the same light-guiding effect as Corning's method.
Procedural Posture:
- Corning Glass Works sued Sumitomo Electric U.S.A., Inc. and its affiliates in the U.S. District Court for the Southern District of New York, alleging patent infringement.
- A separate action by a Sumitomo subsidiary seeking a declaratory judgment of patent invalidity and non-infringement was consolidated with Corning's lawsuit.
- Following a bench trial, the district court found that Sumitomo's S-3 fibers did not literally infringe Corning's '915 patent but did infringe under the doctrine of equivalents.
- The district court also ruled on the validity of other patents and infringement of another.
- Sumitomo, as the appellant, appealed the judgment of infringement to the U.S. Court of Appeals for the Federal Circuit.
Premium Content
Subscribe to Lexplug to view the complete brief
You're viewing a preview with Rule of Law, Facts, and Procedural Posture
Issue:
Does a product that achieves a required refractive index differential by adding a negative dopant to the cladding infringe a patent claim requiring the addition of a positive dopant to the core, under the doctrine of equivalents?
Opinions:
Majority - Nies
Yes, Sumitomo's fiber infringes under the doctrine of equivalents because substituting a negative dopant in the cladding is equivalent to the claimed limitation of adding a positive dopant to the core. To determine infringement, a court must assess whether the accused device contains every limitation of the claim, either literally or by a substantial equivalent. Here, Sumitomo argued that an 'element' (a doped core) was entirely missing from its S-3 fiber, precluding infringement under the 'All Elements' rule. The court rejected this, clarifying that 'element' means a claim 'limitation,' not necessarily a physical component. The proper analysis is whether an equivalent for the specific limitation has been substituted in the accused device. Applying the function/way/result test to the limitation, the court found that adding a negative dopant to the cladding performs substantially the same function (creating an RI differential) in substantially the same way (by altering the RI of one component relative to the other) to obtain the same result (a functioning optical waveguide). Therefore, the substitution was an equivalent, and the S-3 fiber infringed Corning's patent.
Analysis:
This case significantly clarifies the application of the doctrine of equivalents, particularly the 'All Elements' rule from Pennwalt. The court establishes that equivalency is assessed on a limitation-by-limitation basis, not a component-by-component basis, preventing infringers from avoiding liability by simply shifting the location of an inventive feature. This decision provides patentees with broader protection against modifications that achieve the same outcome through technically inverted or alternative means. It solidifies the principle that the function, way, and result of a substituted feature, rather than its literal or physical correspondence to the claim language, is the cornerstone of the equivalency analysis.
