## Facts

- Dovan Chemical Corporation, as assignee of Morris L. Weiss’s patent, sued Corona Cord Tire Company in equity seeking to enjoin infringement.
- The patent claimed a process for vulcanizing rubber by adding diphenylguanidine (a disubstituted guanidine) as an accelerator, and claimed the resulting vulcanized rubber product.
- The invention aimed to reduce vulcanization time and improve product quality by substituting diphenylguanidine for other known accelerators in rubber-sulfur vulcanization.
- The patent included narrower claims directed to diphenylguanidine and broader claims directed to a class of “disubstituted guanidines.”
- Priority was disputed: Corona contended others had discovered and reduced to practice diphenylguanidine’s usefulness as a vulcanization accelerator before Weiss.
- Patent Office proceedings involved a publication reference; Weiss submitted affidavits asserting earlier reduction to practice, later criticized as overstating timing and extent.
- The district court held the patent invalid; the Third Circuit reversed and found validity and infringement; another circuit had held the same patent invalid on priority grounds, prompting Supreme Court review.

## Issues

1. Whether Weiss was the first discoverer of diphenylguanidine’s utility as a vulcanization accelerator and had adequately reduced the process to practice.
2. Whether laboratory testing (e.g., producing properly vulcanized test slabs) can constitute reduction to practice for a process invention without commercial production.
3. Whether post-discovery printed publications within the statutory period barred patentability under Rev. Stat. § 4886.
4. Whether exaggerated statements in Patent Office affidavits negate the presumption of validity.
5. Whether a prior patent on producing a chemical substance determines priority as to discovering its utility in a different process.
6. Whether failure by an earlier discoverer to commercialize or promptly patent constitutes abandonment against a later patentee.
7. Whether claims broadly covering a class of related chemical compounds are invalid absent proof that substantially all claimed members share the asserted utility.

## Decision

- The Supreme Court reversed the Third Circuit.
- The Court held the patent invalid because Weiss was not the first discoverer of the use of diphenylguanidine as an accelerator in vulcanizing rubber.
- The Court held the broad claims to the class of disubstituted guanidines were too broad because the record did not establish a common utility across the entire claimed group.
- The Court rejected the view that commercial manufacture and sale were indispensable to reduction to practice; successful laboratory tests could suffice as a matter of law.
- The Court held that overstatements in affidavits did not, by themselves, eliminate the patent’s presumption of validity where the questioned statements were not necessary to satisfy the legal standard.
- The Court concluded the patent could not support injunctive relief against Corona.

## Legal Principles

- Substituting an ingredient in a known process, if patentable and first discovered, entitles the inventor to all advantages flowing from the substitution, not merely the specifically identified improvement.
- Priority in patent law distinguishes between inventing a process for producing a substance and discovering the substance’s utility as an ingredient in a different process; the former does not establish priority for the latter.
- Reduction to practice of a process may be shown through actual tests producing properly functioning specimens; commercial production or sales are not required.
- Under Rev. Stat. § 4886, a printed publication appearing after the inventor’s discovery and within the statutory period before filing is not necessarily a bar; priority of discovery and reduction to practice remain central.
- Failure by the first discoverer to commercialize or to seek a patent does not constitute abandonment as against a later discoverer or patentee.
- Chemical genus claims are invalid when they claim exclusive use of a broad group of related compounds without proof that the claimed members share a common property making each useful for the claimed process.

## Conclusion

The Supreme Court invalidated Weiss’s rubber vulcanization accelerator patent because Weiss lacked priority as to diphenylguanidine’s use and because the patent improperly claimed an unsupported broad class of disubstituted guanidines, defeating Dovan’s request for an injunction.


Corona Cord Tire Co. v. Dovan Chem. Corp., 276 U.S. 358 (1928)