## Facts

- Rodime PLC owned U.S. Patent No. B1 4,638,383 covering a 3.5-inch micro hard-disk drive system.
- A key claim limitation concerned track density measured in tracks per inch (tpi), affecting storage capacity.
- In the prosecution leading to the original patent, certain claims recited a lower-bound track-density limitation stated as “at least 600 tpi.”
- During USPTO reexamination, Rodime amended various claims by changing the limitation from “at least 600 tpi” to “at least approximately 600 tpi.”
- Quantum Corporation, a disk-drive manufacturer, sued in the District of Minnesota for a declaratory judgment that the reexamined claims were invalid because the amendments impermissibly broadened claim scope in violation of 35 U.S.C. § 305.
- Rodime counterclaimed for infringement.
- The district court granted summary judgment for Quantum, holding claims 4, 6, 7, 9, 14, and 19–27 invalid for improper broadening during reexamination.
- Rodime appealed.

## Issues

1. Whether amending a numerical lower bound from “at least 600 tpi” to “at least approximately 600 tpi” broadened the scope of the claims during reexamination in violation of 35 U.S.C. § 305.
2. If the amendment broadened scope, whether the affected reexamined claims are invalid.

## Decision

- The Federal Circuit affirmed the summary judgment.
- The court held that changing “at least 600 tpi” to “at least approximately 600 tpi” broadened the claims because it covered some track densities below 600 tpi that were outside the original claims.
- The court rejected Rodime’s argument that industry usage would understand “600 tpi” to mean an approximation and therefore the amendment was only clarifying.
- Because § 305 prohibits any enlargement of claim scope in reexamination, the broadened claims (4, 6, 7, 9, 14, and 19–27) were invalid.

## Legal Principles

- Under 35 U.S.C. § 305, reexamination may not include amended or new claims that enlarge the scope of any original claim.
- A claim is impermissibly broadened if it is broader in any respect, even if it is narrower in others.
- Broadening exists if the amended claim encompasses any subject matter that would not have infringed the original claim.
- Adding “approximately” to a strict numerical limitation can broaden claim scope when it expands the covered range (including values slightly outside the original bound).

## Conclusion

The Federal Circuit held that Rodime’s reexamination amendment adding “approximately” to a fixed numerical lower bound enlarged claim scope, violating § 305, and therefore the amended claims were invalid.


Quantum Corp. v. Rodime PLC, 65 F.3d 1577 (Fed. Cir. 1995)