Table of Contents

Best Mode

CAFC upholds invalidity due to failure to disclose best mode (posted 07/31/25)

In Chemcast Corp. v. Arco Indus. Corp. 1), the Federal Circuit affirmed invalidation of a patent on best‑mode grounds under 35 U.S.C. § 112. The court held that the inventor, Rubright, failed to disclose the specific material, hardness, and supplier of the rigid portion of his dual durometer grommet—even though this was the only embodiment he contemplated at the time of filing. While the specification generically described suitable rigid materials, the court found this disclosure insufficient, emphasizing that best mode requires disclosure of the inventor’s actually contemplated preferred embodiment, not just an enabling disclosure. The decision reinforces that concealment of trade names or sources of materials integral to the best mode, whether intentional or not, violates § 112.

Court holdings:

CAFC invalidates patents for failure to disclose best mode

In Spectra-Physics v. Coherent, 2) the Federal Circuit invalidated two laser patents under the best mode requirement of 35 U.S.C. § 112, first paragraph. Although the specifications identified brazing and disclosed TiCuSil as the preferred brazing material for attaching copper cups to a ceramic discharge tube, the inventors failed to disclose the six-stage TiCuSil braze cycle they actually used and knew to be essential for reliable operation. The court held that merely mentioning TiCuSil without detailing the specific braze process effectively concealed the inventors’ contemplated best mode, even though the patents were otherwise enabling. The decision underscores that an inventor must disclose not only a general technique but also the specific implementation regarded as best at the time of filing, even if the omission is inadvertent.

Court holdings:

N.D. Ohio: Best mode adequately disclosed when the omitted subject matter was already well known in the industry (posted 07/31/25)

In Foseco Int’l Ltd. v. Fireline, Inc., 3), the Northern District of Ohio examined whether U.S. Patent No. 4,041,199, covering a refractory riser sleeve for casting steel, was invalid for failing to disclose the best mode. Fireline argued that Foseco should have disclosed the use of phenol formaldehyde (P.F.) resin as part of the best mode. The court held that, although the patent did not mention the resin, the omission did not amount to concealment because the invention could be practiced without it, and P.F. resin was already well-known in the industry.

Court holdings:

CAFC holds patent invalid for failing to disclose valve design (posted 07/31/25)

In Union Carbide Corp. v. Borg-Warner Corp., 4) the court affirmed invalidation of Angell’s patent for a process of molding foamed thermoplastic articles because the specification failed to disclose the best mode contemplated by the inventor at filing. Evidence showed that Angell had developed and used, in a pilot plant, an improved valve that eliminated the problem of unfoamed slugs, as well as a specially designed two‑stage extruder built to prevent gas leakage. Neither the improved valve nor the extruder design was disclosed in the ’636 patent application. Although Angell argued he believed the disclosed equipment was sufficient and that he acted in good faith, the court held that best‑mode compliance does not turn on intent to conceal; rather, the law requires disclosure of the inventor’s actually contemplated preferred embodiments. The ruling underscores that even inadvertent omission of a known better valve or extruder, integral to practicing the invention as contemplated, constitutes a best‑mode violation.

Court holdings:

1)
913 F.2d 923 (Fed. Cir. 1990)
2)
Spectra-Physics Inc. v. Coherent Inc. (Fed. Cir. 1987)
3)
607 F. Supp. 1537 (N.D. Ohio 1984)
4)
550 F.2d 355, 193 U.S.P.Q. 1 (6th Cir. 1977)