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Specification Support for Numerical Range Endpoints

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In RAI Strategic Holdings, Inc. v. Philip Morris Prods. S.A.,
[1] (RAI), the United States Court of Appeals for the Federal Circuit (CAFC) vacated and remanded the Patent Trial and Appeal Board’s (PTAB) determination that the phrase “[a heating member] present on the heating projection along a segment having a length of about 75% to about 85% of a length of the disposable aerosol forming substance” of claims 10 and 27 of U.S. Patent No. 10,492,542 lacks support in the written description. This decision serves to reinforce the existing legal standard that a claimed numerical range may be implicitly supported considering the knowledge of a person having ordinary skill in the art, rather than being expressly supported by the written description

The focal point of the RAI decision concerns evaluating whether an upper endpoint of a claimed range can be supported by the specification if the specification describes the same endpoint as solely a lower endpoint of a range. More specifically, the specification of the ’542 Patent discussed that the aforementioned “heating member,” which is part of an electrically-powered tobacco smoking device, can be of multiple different lengths in relationship to the claimed “aerosol forming substance.” Some of the disclosed relationships include the heating member being “about 75% to about 125% the length of the inhalable substance medium,” or “about 80% to about 120%, about 85% to about 115%, or about 90% to about 110% the length of the inhalable substance medium.” Thus, the question that arose as a result of the claimsis whether two separate lower limits can be pieced together to form a cohesive range with both an upper and lower limit.   

In answering this question, the CAFC looked to a previous decision involving the written description requirement[2] that held the specification must “reasonably convey[] to those skilled in the art that the inventor had possession” of the claimed invention. While the CAFC noted the ’542 Patent’s specification did not expressly state the claimed range of “about 75% to about 85%,” the court noted that the invention was an electro-mechanical device belonging to the predictable arts, and that no portion of the specification indicated that changing the length of the heating member would change the operability or effectiveness of the invention. Indeed, from observing the figures of the patentit can readily be seen that changing the length of the tobacco substance would likely only require lengthening the device housing, which would amount to no more than a trivial design choice.  

On this basis, the CAFC determined that, despite the lack of an explicit disclosure of the claimed range in the specification of the ’542 Patent, the claims were nonetheless supported by the specification as filed. In support of this holding, the court noted that although the midpoint of the claimed range was 80%, and not 100% as recited by the specification, the claims are supported at least because the structure and functionality of the smoking device as a whole is not materially impacted by the heating member having a particular length. 

However, the basis of the determination that some claims of the ‘542 Patent were supported by the specification may have resulted in affirmance of the PTAB’s judgment of invalidity of other claims. As noted above, claims 10 and 27 of the ‘542 Patent were found to be supported by the specification under AIA 35 U.S.C. § 112 because the tobacco smoking device is simple in nature. In addition, the CAFC affirmed the PTAB’s rejection of certain other claims of the ’542 Patent under § 103 as being obvious in view of two prior art references. In support of this affirmation, the CAFC observed that it would be obvious to modify the smoking article of one prior art reference to have a heater with dimensions similar to the claimed structures in the ’542 Patent.  The CAFC further observed that the prior art describes that “the size and shape of [its] heating element 72 can be altered” and that the “[s]election of the power source and resistance heating elements can be a matter of design choice, and will be readily apparent to one skilled in the art.” Thus, the same rationale that the patent claims of the ‘542 Patent were supported under § 112 was applied to the invalidation of claims of the ‘542 Patent under § 103, because both aspects of the court’s decision result from the predictable nature of the field of tobacco smoking devices. 

The CAFC’s decision is similar in outcome to European Patent Office (EPO) Board of Appeals rulings as well. For example, longstanding EPO decisions[3],[4] provide that if a broad range [A - - - - - B] and a second range [C - - - D] contained within the broad range are explicitly disclosed in the application as filed, amendments directed to a range [C - - - - B] or the range [A - - - - D], which both contain the second range [C - - - D], will be considered allowable. As to amendments directed to the range [A - - C] or the range [D - - B],  which both do not contain the second range [C - - - D], they are allowable only if the skilled person would seriously contemplate working in those ranges.[5] The foregoing relates to the ability to combine disclosed end points of existing ranges. However, it may also be possible to generate new ranges from specific exemplified value points, in line with a separate decision.[6] Accordingly, amendments re-defining an end point of a disclosed range, such as [E - - - - F] being redefined based on a single point value “G” from an example that falls within the range to provide a new range [E - - G] or [G - - F], may be allowed provided that the single point value “G” is not inextricably linked to other features in the example. Otherwise, this likely would be considered an intermediate generalization that contravenes (the requirements of) Art. 123(2) of the European Patent Convention (EPC).

Looking at this issue from yet another perspective, the China National Intellectual Property Administration (CNIPA) has a standard that is similar to the EPO standard, although the CNIPA is generally less stringent regarding range disclosures. The cardinal rule governing any amendment to a Chinese patent application is that the amendment should not extend beyond the scope of disclosure contained in the initial description and claims. The scope of disclosure contained in the initial description and claims, according to the Patent Examination Guidelines, includes the content recited in the initial description and claims and content determined directly and unambiguously according thereto. Applying this rule to numerical ranges in claims, a broad range can be amended to any narrower range with endpoints chosen from 1) either of the endpoints of the broad range and/or 2) any specific values, such as intermediate points, within the broad range that are expressly disclosed in the initial description and claims. The Patent Examination Guidelines do not specifically consider whether disclosed limits of two different narrower ranges within the same broad range can be pieced together to form a cohesive range. However, such an amendment is theoretically permissible because the two disclosed limits would be the endpoints of the broad range, intermediate points within the broad range, or a combination thereof. Thus, the key to securing fallback positions in terms of claiming numerical ranges in Chinese patent applications is explicitly disclosing a sufficient and reasonable number of intermediate points in a broad range.

Overall, the CAFC’s decision in RAI serves as a reminder that invalidity under AIA 35 U.S.C. § 112(b) and AIA 35 U.S.C. § 103 are tied to the predictability and complexity of the invention. The court has repeatedly explained that the determination of whether a particular claim is supported by the specification or described by a prior art reference is linked to whether the deviation from the disclosure would be predictable to a person having ordinary skill in the art. The CAFC’s decision also highlights that the specification is typically interpreted in light of the knowledge of a person having ordinary skill in the art. In this way, the CAFC reinforced the importance of writing a specification that clearly identifies areas of the invention that may be modified by such a skilled person. 


[1] 92 F.4th 1085 (Fed. Cir. 2024).

[2] Ariad Pharmaceuticals, Inc. v. Eli Lilly & Co., 598 F.3d 1336 (Fed. Cir. 2010)

[3] Boards of Appeal of the European Patent Office - T 0002/81

[4] Boards of Appeal of the European Patent Office - T 925/98

[5] Boards of Appeal of the European Patent Office - T 1170/02

[6] Boards of Appeal of the European Patent Office - T 0201/83