## Facts

- Inventors obtained German patents (1879–1880) for an improved lamp-burner and later obtained a U.S. patent (U.S. Patent No. 289,571) covering, as relevant, a ring-shaped cap used with guide tubes in a lamp-burner.
- An inventor assigned an interest in the U.S. patent to Albert Gräff by an instrument absolute in form for consideration; a separate agreement executed the next day set payment terms and provided that title would revert to the inventor upon nonperformance.
- Gräff and J.F. Donnell (as assignees) sued Emile Boesch and Martin Bauer in equity for infringement of the U.S. patent based on defendants’ importation and sale in the United States of lamp-burners embodying Claim 1.
- Defendants had purchased the lamp-burners in Germany from a party who was authorized under German law or practice to sell them there, but who did not convey any U.S. patent license or consent from the U.S. patentee.
- The trial court found infringement, ordered an accounting, and ultimately awarded damages based primarily on plaintiffs’ claim that they were forced to lower prices to meet defendants’ competition; the court also denied defendants’ request for rehearing.

## Issues

1. Whether plaintiffs had title sufficient to maintain an infringement suit where an absolute-form assignment was followed by a separate agreement providing for reversion upon nonperformance.
2. Whether defendants avoided U.S. patent infringement liability by buying the accused articles abroad from a person authorized to sell them there.
3. What proof is required to recover damages based on price reductions allegedly compelled by infringing competition, and whether the awarded damages were supported by the evidence.
4. Whether the denial of a rehearing by the trial court was reviewable on appeal.

## Decision

- The Supreme Court held plaintiffs had sufficient title: the assignment was an absolute transfer subject to divestment by a condition subsequent (reversion upon nonperformance).
- The Court held defendants infringed: articles embodying an invention patented in the United States cannot be imported and sold in the United States without the U.S. patentee’s license or consent, even if purchased abroad from a person authorized to sell them there.
- The Court held the damages award could not stand as entered because plaintiffs did not adequately prove that the price reduction was caused solely by defendants’ infringement (or the extent attributable to it) with data permitting calculation of actual damages; the Court reduced damages to the amount supported by the record.
- The Court held the refusal to grant a rehearing was not reviewable on appeal.

## Legal Principles

- A patent assignment that is absolute in form may confer standing to sue even if a separate agreement provides for reversion upon nonperformance; this is treated as an absolute transfer subject to a condition subsequent.
- Authorization to sell a patented article abroad does not exhaust U.S. patent rights; importation and sale in the United States require the license or consent of the U.S. patentee.
- A patentee seeking damages for compelled price reductions must prove the reduction was due solely to the infringer’s acts or show the extent attributable to those acts and provide data from which actual damages can be calculated; speculative price effects are insufficient.
- Denial of a rehearing in the trial court is not subject to appellate review.

## Conclusion

The Court reaffirmed the territorial nature of U.S. patent rights by rejecting foreign-purchase exhaustion as a defense to U.S. importation and sales, treated an absolute-form assignment with a reversion clause as a present transfer for standing purposes, and required concrete proof to support price-depression patent damages, reducing the award accordingly.


Boesch v. Gräff, 133 U.S. 697 (1890)