A narrower range inside a disclosed range is usually described

How to read the ledger below. Each numbered point carries the kind of evidence behind it. ESTABLISHED is stated in the authority's own text, with a locator. IMPLEMENTED is the rule as the authority actually applied it. OBSERVED is carried by a source outside this one. ASSUMED is the drafter's inference, flagged as such and not the authority speaking. Quotations are checked against a cached copy of the primary source by script.

In one paragraph

The Federal Circuit reversed the Patent Trial and Appeal Board on written description in RAI Strategic v. Philip Morris on 9 February 2024 and held that a claimed heating member subrange narrower than any range spelled out in the specification was still adequately described, because the electro-mechanical technology was predictable, the limitation was simple, and no evidence showed the narrower range was a different invention from the disclosed one. The same decision affirmed the Board on obviousness, so the claims survived the support challenge and fell anyway.

Reader summary

The specification disclosed heating-member lengths as a series of nested ranges: 75% to 125%, 80% to 120%, 85% to 115%, 90% to 110%. The claims recited a subrange whose upper limit was 85%. No range with that upper limit appears anywhere in the specification, and the Board held the claims unsupported for exactly that reason.

The Federal Circuit reversed. The governing question is not whether the claimed numbers appear verbatim but whether the narrower range describes a different invention from the one disclosed. Where nothing suggests it does, a broader disclosed range describes a subrange within it.

Two features of this case did the work, and both are the kind of thing a practitioner can assess at the drafting desk. The technology was electro-mechanical and therefore predictable, and the limitation was simple, being the length of a heating member. The court has long held that the level of detail written description demands varies with the predictability of the art and the complexity of the limitation, and here both pointed the same way, so less detail sufficed.

The counterweight is stated in the same opinion and should travel with the holding: where it is clear that the broad described range pertains to a different invention than the narrower claimed range, the broader range does not describe the narrower one. That sentence is the limit, and it is what distinguishes this case from the blaze-marks line in the rest of this tier.

Why this matters when you are drafting

Continuation claims are frequently narrower than the parent's disclosed ranges, and this is the case that says that is ordinarily fine. The common move, claiming a tighter range to distinguish art that emerged after filing, does not require the tighter numbers to appear verbatim. Claim 2 is the authority for that.

Ask the right question, which is not "are these numbers in the spec." Claim 3 reframes it: does the narrower range describe a different invention? That is a question about what the specification conveys possession of, not about literal antecedent basis, and it is answerable at the drafting desk.

Know where the holding is weak. Claim 4 is the limit and claim 10 is the honest inference. The more unpredictable the art and the more complex the limitation, the less this case helps, and the closer you are to the blaze-marks cases in the rest of this tier. In a chemical or biological family, a narrower claimed range is a much harder argument.

Nested ranges with a preferred value are a good disclosure pattern. Claim 9 shows the shape the court finds workable. Drafting the parent with a graded series rather than one flat range preserves room for later continuations to claim inside it.

Winning on support is not winning. Claim 1: these claims survived section 112(a) and still fell on obviousness. Support is necessary and not sufficient, and a corpus that only tracked support would have reported this case as a clean win.

What the authority establishes

1. [ESTABLISHED, the split disposition] "we hold that substantial evidence supports the Board's obviousness finding but does not support the Board's finding that certain claims lack written description support under 35 U.S.C." (P. 2.) The patent lost on obviousness and won on support.

1. [ESTABLISHED, the written-description holding] "we conclude that no reasonable fact finder could find that the claimed subrange is not within the appellant's invention". (P. 10.)

1. [ESTABLISHED, the test restated as the absence of a difference] "under the facts of this particular case, there is no evidence that the claimed subrange results in a different invention than the invention disclosed in the specification". (P. 10.)

1. [ESTABLISHED, and this is the limit that must travel with the holding] "here it is clear, for instance, that the broad described range pertains to a different invention than the narrower (and subsumed) claimed range, then the broader range does not describe the narrower range" and the written description requirement would not be satisfied. (P. 6.)

1. [ESTABLISHED, the sliding standard] "level of detail required to satisfy the written description requirement varies depending on the nature and scope of the claims and on the complexity and predictability of the relevant technology". (P. 5.)

1. [ESTABLISHED, how that standard applied here] "Given the predictability of electro-mechanical inventions such as the one at issue here, and the lack of complexity of the particular claim limitation at issue" (P. 9.), namely "reciting the length of a heating member", "a lower level of detail is required to satisfy the written description requirement than for unpredictable arts". (P. 9.)

1. [ESTABLISHED, the factual setup] "The '542 patent specification discloses a broader range than that which is claimed." (P. 8.) The claimed subrange's upper limit appears in no disclosed range.

1. [IMPLEMENTED, the burden is on the challenger to show a difference] The court frames the inquiry as an absence: there is no evidence the subrange is a different invention (claim 3), and no reasonable fact finder could conclude otherwise (claim 2). That places the work on the party asserting a lack of support, rather than requiring the patentee to point at literal antecedents.

1. [ESTABLISHED, an analogous authority the court relies on] The opinion draws on a case where "The specification stated a broader range of wrappings formed 'at the rate of 4-12 turns per inch, with 8 turns per inch being preferred.'" (P. 7.) Nested ranges with a preferred value are the recurring shape.

1. [ASSUMED, drafter's inference, flagged as such] Claims 5 and 6 make this holding weakest exactly where the rest of Tier B is strongest, in unpredictable arts such as the chemical and biological subject matter of the blaze-marks cases. The opinion does not draw that contrast; it follows from applying its own sliding standard across this corpus.

Quotations, verified against the source

All from the Federal Circuit's opinion. Page locators computed from the docket stamp.

Two spans below begin mid-word because the opinion presents them with a quoter's bracketed capital, as "[T]he level of detail" and "[w]here it is clear". Per §7.4 a bracketed alteration is the quoter's and is not part of the source text, so each span is quoted from the word the source itself wrote.

• "we hold that substantial evidence supports the Board's obviousness finding but does not support the Board's finding that certain claims lack written description support under 35 U.S.C." (P. 2.)
• "level of detail required to satisfy the written description requirement varies depending on the nature and scope of the claims and on the complexity and predictability of the relevant technology" (P. 5.)
• "here it is clear, for instance, that the broad described range pertains to a different invention than the narrower (and subsumed) claimed range, then the broader range does not describe the narrower range" (P. 6.)
• "The specification stated a broader range of wrappings formed 'at the rate of 4-12 turns per inch, with 8 turns per inch being preferred.'" (P. 7.)
• "The '542 patent specification discloses a broader range than that which is claimed." (P. 8.)
• "Given the predictability of electro-mechanical inventions such as the one at issue here, and the lack of complexity of the particular claim limitation at issue" (P. 9.)
• "a lower level of detail is required to satisfy the written description requirement than for unpredictable arts" (P. 9.)
• "there is no evidence that the claimed subrange results in a different invention than the invention disclosed in the specification" (P. 10.)
• "we conclude that no reasonable fact finder could find that the claimed subrange is not within the appellant's invention" (P. 10.)

Tensions and open questions

"Different invention" is the operative test and is not defined. Claims 3 and 4 turn on it, and the opinion supplies examples rather than a standard. What evidence would establish that a subrange is a different invention is left to later cases.

The holding is expressly fact-bound. Claim 3 says "under the facts of this particular case." That qualifier limits how far the result travels, even though claim 5's sliding standard is general.

How this sits with the blaze-marks line is not addressed here. The rest of Tier B concerns specifications disclosing many possibilities from which claims later select. A range is a continuum rather than a list of species, and whether that distinction or the predictability of the art is doing the work is not resolved by this opinion.

Unresolved by this record: whether the same reasoning reaches a subrange claimed in a continuation filed long after the parent. Nothing read here turns on when the narrower claim was drafted.

What this record does and does not cover

The written-description analysis was read end to end, including the range discussion and the predictability reasoning, because that is the reason this record exists.

What was NOT read closely, and is therefore outside what this record can support: the obviousness analysis beyond its holding and outcome and the technical detail of the references. This record says nothing about why the claims were obvious, only that they were held so on substantial evidence. The Board decision and the patent are known here only through the court's characterization.

Currency

This record was verified against its primary source on 2026-08-15. That is a fidelity check: the quotations, locators and attribution are accurate to that source. Whether the authority has since been narrowed, distinguished, abrogated or reversed has not been checked here. Confirm it still stands before relying on it.