Patent Board Allows an Open-Ended Numerical Range

The Patent Trial and Appeal Board (PTAB) has reversed a rejection of a patent application for using an open-ended numerical range in a claim.

The matter of Ex Parte Qiu (Appeal 2020-001512) involves a patent application for a chemical compound (shown above). One claim includes the following:

wherein the compound comprises substantially no other anionic pendant functional groups, except those selected from the group consisting of: sulfate, carboxylate, phosphate, phosphonate, and sulfonate, wherein the compound has a number average molecular weight of no more than 10,000 grams/mole and an average number of anionic groups of greater than 2.

(Emphasis added by the PTAB.)

The specification disclosed examples where the average number of anionic groups range from 2.09 to 15.

As the PTAB noted,

For an applicant to comply with the 35 U.S.C. § 112, first paragraph, written description requirement, the applicant’s specification must “convey with reasonable clarity to those skilled in the art that, as of the filing date sought, he or she was in possession of the invention.”

35 U.S.C. § 112 states that for a patent application

The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.

The patent examiner rejected the application based on the lack of an upper limit for the range “greater than 2,” on the basis that it failed to meet the written description requirement.

The patent applicant pointed out that the Federal Circuit (which handles appeals in patent cases) had held that open-ended ranges in patent applications aren’t inherently improper.

The Federal Circuit held in the 2007 case of Anderson Corp. v. Fiber Composites,

As we have said, “[o]pen-ended claims are not inherently improper, as for all claims their appropriateness depends on the particular facts of the invention, the disclosure, and the prior art. They may be supported if there is an inherent, albeit not precisely known, upper limit and the specification enables one of skill in the art to approach that limit.”

The PTAB noted that this principle applies both to the written description and enablement requirements in patent law.

Enablement, or sufficiency of description, is the requirement in patent law that the disclosure must be in enough detail to allow someone skilled in the art covered by the patent to carry out the claimed invention.

The patent applicant pointed out that since the claim required an upper limit for the molecular weight of the compound (“no more than 10,000 grams/mole”), the specification as a whole allowed someone of ordinary skill in the art to determine the inherent upper limit on the number of anionic groups for any particular compound circumscribed by the claimed requirements.

Takeaway: Although open-ended ranges may be allowed, it can be a better practice (and potentially avoid trips to the PTAB) to include specific endpoints in a patent application claiming a range.

Categories: Patents