## Facts

- Consolidated Electric Light Company, as assignee of Sawyer and Man’s U.S. Patent No. 317,076 (issued 1885) for an electric incandescent lamp, sued McKeesport Light Company in equity for infringement.
- The accused lamps were made under Thomas A. Edison’s patents and system, and the defense relied principally on Edison’s U.S. Patent No. 223,898 (issued 1880).
- Sawyer and Man’s patent described an incandescent conductor sealed in a transparent, exhausted chamber to exclude oxygen, emphasizing carbon conductors made from “vegetable fibrous material.”
- The patent’s claims, as construed, included broad claims to incandescent conductors of carbon made from fibrous or textile materials and a narrower claim specifically directed to “carbonized paper.”
- The circuit court (W.D. Pa.) held the broad claims invalid and dismissed the infringement suit; the patentee appealed to the Supreme Court.

## Issues

1. Whether claims covering incandescent conductors made from carbonized “fibrous or textile” materials were invalid for indefiniteness and lack of an enabling disclosure commensurate with their breadth.
2. Whether the patent’s narrow claim to an incandescing conductor “formed of carbonized paper” was valid and, if valid, whether Edison’s bamboo-based filament infringed it.

## Decision

- The Supreme Court affirmed the decree dismissing the bill for infringement.
- With the exception of the third claim directed to an incandescing conductor formed of carbonized paper, the patent’s claims were too indefinite to support a valid monopoly.
- The patentee could not claim a broad class of fibrous/textile carbon materials without a disclosure teaching skilled artisans how to make and use the invention across that class.
- Edison’s commercially successful bamboo filament did not fall within any legitimately enforceable claim asserted against the accused lamps.

## Legal Principles

- A patent must describe the invention and the manner of making and using it in full, clear, concise, and exact terms sufficient to enable skilled artisans to practice the invention (Rev. Stat. § 4888).
- Broad material claims are invalid when the specification and proof show only limited successful embodiments and do not identify a general quality or method that makes the entire claimed class workable.
- A patentee cannot preempt an entire field of experimentation by claiming a large genus of materials while disclosing only a narrow species and leaving later inventors to discover the operative species through substantial experimentation.
- Indefinite, overbroad claims—especially those functionally reaching unknown future embodiments—cannot sustain a patent monopoly where the disclosure does not define the invention’s boundaries or enable its full scope.

## Conclusion

The Court held that Sawyer and Man’s attempt to monopolize all carbonized fibrous or textile filaments for incandescent lamps failed because the claims exceeded what the patent definitively described and enabled; only a narrow carbonized-paper claim arguably survived, and it did not reach Edison’s bamboo filament, so the infringement suit was properly dismissed.


Consol. Elec. Light Co. v. McKeesport Light Co., 159 U.S. 465 (1895)