Written Description Compliance Requires Lack of Different Inventions Achieved by Claimed and Disclosed Ranges

| April 19, 2024


Decided: February 9, 2024

Chen, Stoll, and Cunningham.  Opinion by Stoll.


The CAFC addressed a question of written description compliance where a numerical range set forth in a patent claim is narrower than and encompassed by a disclosed range in the specification. The CAFC found that the written description requirement is met under fact-specific circumstances where substantial evidence indicates that a skilled artisan would see no different inventions resulting from the claimed range and the disclosed range.


RAI appealed a final written decision by the Patent Trial and Appeal Board in a post-grant review (PGR) finding certain claims of RAI’s U.S. Patent No. 10,492,542 (“the ’542 patent”) unpatentable.  RAI challenged, among other issues,[1] the Board’s finding that claims 10 and 27 of the ’542 patent lack adequate written description under 35 U.S.C. § 112.

The ’542 patent relates to electrically powered “smoking articles” which, as in e-cigarettes, use an electrical heating element to heat tobacco or like substance to form an inhalable vapor or aerosol.  Claims 10 and 27—added by preliminary amendment in the underlying application which is a continuation from a former application having no such claims in the original filing—specify that the heating element has a certain range of length, which is not disclosed verbatim in the specification.

The written description requirement is a question of fact subject to substantial evidence review. The CAFC prefaced the written description analysis with the general threshold for compliance: the disclosure must “reasonably convey[ to a skilled artisan] that the inventor had possession of the claimed subject matter as of the filing date.”  The CAFC then discussed precedents finding written description support, or lack thereof, for claimed ranges that are narrower than ranges described in specifications.

Courts finding adequate written description: Wertheim, Blaser, Kolmes[2]

In Wertheim, the parameter at issue was “solids content of the concentrated coffee extract.”  The claimed range “between 35% and 60%” was found adequately supported by the specification disclosing a broader range of “25% to 60%” along with specific examples where the parameter was either “36% or 50%.”  The Wertheim court held that presence of a clear indication that “the broad described range pertains to a different invention than the narrower (and subsumed) claimed range” (emphasis added) would negate adequacy of written description, whereas absence of such indication would support written description compliance.

Two subsequent courts followed Wertheim.  InBlaser, the claimed range of temperature for heating a reaction blend for acylation, “80º to 200º C.” was found adequately supported by the disclosure of a broader range of “between 60º and 200º C.”  In Kolmes, the claimed range of wrapping rate for cut-resistant yarn, “8–12 turns per inch,” was found adequately supported by the disclosure of a broader range of “4–12 turns per inch, with 8 turns per inch being preferred.”

Courts finding no adequate written description: Baird, Indivior[3]

Baird involved a patent application which included claims copied from an issued patent for an interference proceeding, i.e., the applicant was not the original author of the copied claims. The parameter at issue was a quench bath temperature in production of stretch-orienting polypropylene. The claimed range was “from about 40[º F] to … about 60 [º F].”  While this range was explained in the issued patent as having certain criticality, the applicant’s specification disclosed a broader range of “between 32º F and 176º F,” while silent on the narrower range. Finding lack of adequate support, the Baird court reasoned that the copied claim pertained to a “different” invention from that disclosed in the specification.  

In Indivior, the parameter at issue was a concentration of certain polymers in thin film formulation.  Disputed claims recited two numerical ranges: (A) “about 40 wt % to about 60 wt %” and (B) “about 48.2 wt % to about 58.6 wt %.”  The specification disclosed broader  ranges—or lower bounds without express upper bounds—of “at least 25” and “at least 50,” as well as specific instances of “48.2” and “58.6” gleaned from data tables.  The specification also stated that the parameter may be at “any desired level.”  The claimed range (A) failed the written description requirement because the specification did not literally recite the range or the endpoints, while the “any desired level” statement obscured the scope of the invention. The claimed range (B) also failed the written description requirement because, although the endpoints were disclosed at least implicitly, it was unclear that the specification described the range bound by these endpoints.

Application to Claims 10 and 27 of the ’542 patent

After summarizing the precedents, the CAFC turned to the claims at issue.  Claims 10 and 27 both recite that a heating member used in the smoking device has “a length of about 75% to about 85% of a length of the disposable aerosol forming substance.”  The specification describes four progressively narrow, nested ranges for the parameter: “about 75% to about 125%,” “about 80% to about 120%,” “about 85% to about 115%,” and “about 90% to about 110%.”  The Board’s finding of no written description was driven by the fact that the upper endpoint “85%” of the claimed range does not have a corresponding upper endpoint in any of the disclosed ranges.

The CAFC found that the written description requirement is met.  To reach the conclusion, the CAFC centered its analysis on “different invention” test set forth in Wertheim, restating that “[t]he specification need not expressly recite the claimed range to provide written description support.”  The factual inquiry looked to specific factors, including:

  • Express disclosure in the specification: Although the claimed range itself is not literally disclosed, both of its endpoints are identified as part of the disclosed ranges. 
  • Predictability and complexity of the invention: Since the smoking device invention relates to a relatively predictable, electro-mechanical field, and the claim language is simple, the level of clarity or details required to satisfy the written description requirement is low.
  • Lack of indication that the claimed parameter affects the invention: The specification nowhere indicates that “operability, effectiveness, or any other parameter” of the invention is impacted by changing the claimed parameter.

Based thereon, the CAFC found no “different invention” arising from the claimed range than that disclosed in the specification.

            The CAFC distinguished Indivior and Baird relied upon by the Board.  Unlike Indivior, the ’542 patent discloses the endpoints and contains no inconsistent statements regarding the range (e.g., that “any desired level” may work); plus the predictability of the electro-mechanical invention is higher than the chemical invention set forth in the Indivior claims. Also, unlike Baird where the claimed range was shown to have criticality over the boarder disclosed range, no evidence was presented in the present case that the broader disclosed range operates differently than the claimed range. 

            Additionally, the CAFC dismissed an expert testimony offered by Phillip Morris pointing to different center points of the disclosed range (100%) and the claimed range (80%).  The expert evidence was not enough to overcome the intrinsic evidence and the case law supporting adequacy of the written description.  


            This case exemplifies one way in which a court may apply case-by-case analysis of written description compliance.  Where the claimed range is narrower than and subsumed in the disclosed range, the “different invention” test may not only examine the express disclosure and the nature of the technology, but also may consider whether varying the parameter inside and outside the claimed range would make any difference.

While the test could be useful in establishing written description support—given that a patent specification typically describes numerical ranges in connection with one general inventive concept—caution should be used in asserting lack of different inventions emanating from different numerical ranges; such admission might be used by an opponent to support obviousness of the claimed range.  The dilemma may be avoided, for example, by drafting an original disclosure to describe both commonalities and differences across broad and narrow ranges as well as specific values of a key parameter.

[1] RAI’s other argument challenged the Board’s obviousness finding of other claims of the ’542 patent, which was affirmed by the CAFC on appeal.

[2] In re Wertheim,541 F.2d 257 (C.C.P.A. 1976), In re Blaser, 556 F.2d 534 (C.C.P.A. 1977), and Kolmes v. World Fibers Corp., 107 F.3d 1534 (Fed. Cir. 1997).

[3] In re Baird,348 F.2d 974 (C.C.P.A. 1965), and Indivior UK Ltd. v. Dr. Reddy’s Laboratories S.A., 18 F.4th 1323 (Fed. Cir. 2021). 

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