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:
On the purpose of best mode:
“Manifestly, the sole purpose of this latter requirement is to restrain inventors from applying for patents while at the same time concealing from the public preferred embodiments of their inventions which they have in fact conceived.” (quoting In re Gay).
On subjective and objective inquiries:
“The best mode inquiry focuses on the inventor's state of mind as of the time he filed his application—a subjective, factual question… [but] whether the inventor concealed a better mode of practicing his invention than he disclosed is a function of not only what the inventor knew but also how one skilled in the art would have understood his disclosure.”
On the distinction from enablement:
“A patent applicant must disclose the best mode of carrying out his claimed invention, not merely a mode of making and using what is claimed. A specification can be enabling yet fail to disclose an applicant’s contemplated best mode.”
On what was concealed:
“Because Chemcast used only R‑4467, because certain characteristics of the grommet material were claimed elements of the '879 invention, and because Rubright himself did not know the formula, composition, or method of manufacture of R‑4467, section 112 obligated Rubright to disclose the specific supplier and trade name of his preferred material.”
On the inadequacy of the disclosure:
“Given the specification and the level of skill or understanding in the art, skilled practitioners could neither have known what Rubright's contemplated best mode was nor have carried it out. Indeed, on these facts, they would not even have known where to look.”
On the result:
“In this situation and on these facts, where the inventor has failed to disclose the only mode he ever contemplated of carrying out his invention, the best mode requirement is violated.”
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:
On the distinction from enablement:
“If … the applicant develops specific instrumentalities or techniques which are recognized at the time of filing as the best way of carrying out the invention, then the best mode requirement imposes an obligation to disclose that information to the public as well.”
On the inadequacy of disclosure:
“Even though there may be a general reference to the best mode, the quality of the disclosure may be so poor as to effectively result in concealment.” (citing In re Sherwood).
On what was missing:
“The facts found by the district court, when placed in the proper framework, plainly demonstrate that the TiCuSil brazing technique used by Coherent was not adequately disclosed.”
Key holding on the six-stage braze cycle:
“The six stage braze cycle employed by Coherent, and developed by it, [is] necessary to the enjoyment of the invention taught by the patents in suit by a person skilled in the art of laser construction, and [is] not sufficiently disclosed by the patents in suit.”
On concealment:
“Far from being a ‘production specification,’ Coherent did not disclose any details about its brazing process. It is this complete lack of detail which effectively resulted in its concealment.”
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:
On the need for concealment, not mere nondisclosure
“There is no objective standard by which to judge the adequacy of a best mode disclosure. Instead, only evidence of concealment (accidental or intentional) is to be considered. That evidence, in order to result in affirmance of a best mode rejection, must tend to show that the quality of an applicant’s best mode disclosure is so poor as to effectively result in concealment.” (In re Sherwood, quoted at 607 F. Supp. at 1555)
On the role of ordinary skill in the art
“In evaluating the quality of the applicant’s best mode disclosure, the Court should read into the specification any information which is ‘known to those having ordinary skill in the art.’ Thus, a failure to disclose all of the information in the possession of the inventor is not fatal where the application of routine skill in the art would allow practice of the invention.” (In re Howarth, cited at 607 F. Supp. at 1555)
On why the omission of P.F. resin did not invalidate the patent
“In this case, the ’199 patent can be practiced without any knowledge of the use of resin. While the use of P.F. resin adds useful qualities to the Kalmin 70 riser sleeve, the ’199 patent can be practiced commercially, as is done in England, without the addition of P.F. resin.” (607 F. Supp. at 1555)
On well-known industry practices filling disclosure gaps
“Even if the use of P.F. resin is necessary to meet the best mode disclosure requirement, P.F. resin has been used within the industry for waterproofing purposes for many years. As such, the failure to disclose the use of P.F. resin is the type of omission which can be rectified by the application of routine skill and does not constitute concealment.” (607 F. Supp. at 1555–56)
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:
On the purpose of the requirement:
“Manifestly, the sole purpose of this latter requirement [best mode] is to restrain inventors from applying for patents while at the same time concealing from the public preferred embodiments of their inventions which they have in fact conceived.”
On why the improved valve had to be disclosed:
“The fact that there were ‘problems’ with a component part… would be unlikely to alter Angell’s contemplation of the valve installed in the pilot plant. This is underscored by the seriousness of the slug problem… which the 636 patent valve occasioned and which the pilot plant valve eliminated.”
On the extruder omission:
“Although Angell testified that not just any extruder would satisfactorily work in his process, use of a blank box, without more, would not necessarily defeat his patent. … However, the question here involves the best mode requirement, and Angell’s own testimony shows that some extruders do a better job than others.”
Rejecting the “good faith” defense:
“We are not persuaded that the failure to set forth the best mode contemplated by an inventor of carrying out his invention must rise to the level of active concealment or grossly inequitable conduct in order to warrant invalidation of a patent.”
On broad, generic disclosure vs. best mode:
“We do not accept the proposition that where an inventor, as here, clearly knows a specific material that will make possible the successful reproduction of the effects claimed by his patent, but does not disclose it, speaking instead in terms of broad categories, he may nevertheless be considered as having described the best mode contemplated by him.” (quoting Dale Electronics).