## Facts

- Chemcast and Arco manufactured sealing members, including grommets used to seal openings in sheet-metal panels.
- The asserted patent claimed a “dual-durometer” grommet made from two portions of differing hardness: a softer elastomeric base and a harder locking portion, bonded together to lock into a panel opening and form a continuous seal.
- Only claim 6 was in suit; it specified hardness ranges: the base was less than 60 Shore A and the locking portion more than 70 Shore A.
- The inventor (a Chemcast employee) successfully made the claimed grommet using a proprietary PVC composite developed by a supplier after substantial effort; the formulation was treated as a trade secret.
- At filing, the proprietary PVC composite was the only material that had produced a grommet meeting the inventor’s requirements.
- The specification did not identify the supplier, the commercial designation of the compound, or the proprietary formulation; instead it described generic materials and potential ingredients.
- Chemcast sued Arco for infringement; Arco asserted invalidity for failure to disclose the best mode under 35 U.S.C. § 112.

## Issues

1. Whether the inventor contemplated a best mode for practicing the invention at the time of filing.
2. Whether the specification adequately disclosed that best mode under 35 U.S.C. § 112 when it omitted the specific proprietary PVC compound and its supplier and provided only generic material descriptions.
3. Whether enablement, if satisfied, avoids invalidity for failure to disclose the best mode.

## Decision

- The Federal Circuit affirmed the judgment that claim 6 was invalid for failure to satisfy the best-mode requirement of 35 U.S.C. § 112.
- The court agreed that the inventor subjectively had a best mode in mind: the specific proprietary PVC compound from the supplier was his preferred way to practice the invention.
- The court held the disclosure was objectively inadequate because the specification withheld identification of the specific compound and supplier and did not provide information sufficient for skilled artisans to practice the preferred embodiment without undue effort.
- The court rejected the argument that an enabling disclosure cures a best-mode defect; the requirements are distinct and independently enforced.

## Legal Principles

- Section 112 (first paragraph) imposes separate enablement and best-mode obligations; compliance with one does not establish compliance with the other.
- Best mode uses a two-part analysis:
  - Subjective: whether the inventor actually contemplated a best mode at the time of filing.
  - Objective: whether the specification discloses that mode sufficiently for persons skilled in the art to practice it.
- When an inventor’s best mode depends on a particular commercial material or source, broad disclosure of a class of materials may be insufficient; the preferred product and identifying information may need to be disclosed.
- An inventor may not secure patent exclusivity while withholding material information about the preferred implementation to preserve trade-secret protection.

## Conclusion

Because the inventor knew the proprietary PVC compound from a particular supplier was his preferred mode and the specification failed to disclose that compound or its identifying source information, claim 6 was invalid under § 112’s best-mode requirement even if the disclosure could enable other workable versions of the grommet.


Chemcast Corp. v. Arco Indus. Corp., 913 F.2d 923 (Fed. Cir. 1990)