April 7, 2022by Matthew Barnet

U.S. patent claims typically use the terms “comprising” and “consisting of” when reciting components of a composition. “Comprising” indicates that the composition must include the recited components, but also can include unrecited components, while “consisting of” indicates that the composition excludes unrecited components.

The term “comprising” advantageously provides the applicant with broader scope of protection than “consisting of.” However, such breadth sometimes opens claims to additional prior art. In such cases, “consisting of” can be helpful to distinguish the claims from the prior art.

When claims use both “comprising” and “consisting of,” the scope of the claims must be analyzed carefully. This issue is illustrated in the recent case of Ex parte Rankin (Appeal No. 2021-001726).

Independent claim 40 recited (in part) a composition comprising:

(i) a gel base consisting of:

a wax or oil and;

a salt; and

(ii) titanium dioxide, zinc oxide, barium sulfate, or a combination thereof dispersed in the gel base.

The examiner rejected claim 40 as anticipated by two different references disclosing gels containing titanium dioxide. The gels also included polymeric gelling agents. In each case, the examiner took the position that the gelling agent was within the scope of the claim based on the open “comprising” term in the preamble. For example, in one anticipation rejection, the examiner stated that claim 40 “is interpreted to mean that the gel base consists of a wax or oil, and a salt, but it does not exclude addition of other components, such as the block polymers taught by [the cited reference] to make the final…product.”

In contrast, the applicant argued that the closed “consisting of” term excluded the polymeric gelling agents of the prior art. For example, the applicant alleged that the gels of the cited reference “differ structurally from the gel of claims 40-55 due to the latter being composed exclusively of a wax or oil and salt and therefore excluding the polymers…as constituent structural components.”

The PTAB agreed with the applicant. The PTAB acknowledged that “the ‘comprising’ language in the claim allows the mixture of the gel base and titanium dioxide, zinc oxide, barium sulfate or combination to include additional components dispersed in the gel base.” However, due to the “consisting of” language, “the gel base may contain only the recited wax or oil and salt…[W]e do not agree [with the examiner] that the claim language allows for the addition of ingredients to the gel base.” Accordingly, the PTAB reversed the anticipation rejections.

Takeaway: Whenever a claim uses both “comprising” and “consisting of,” the scope of the claim must be analyzed carefully. The closed, “consisting of” term might be intended to exclude a component disclosed in the prior art, but the examiner might take the position that the component is within the claim scope due to the “comprising” term. In such cases, it is important to clearly identify how the components of the prior art correspond to the claim. In Rankin, the applicant successfully argued that the polymeric gelling agent of the prior art was a component of the gel base (thus excluded by the “consisting of” term) rather than a component dispersed in the gel base (which would have been included by the “comprising” term).

Judges: Adams, Grimes, Jenks

by Matthew Barnet

Matthew E. Barnet, Ph.D., is a patent attorney and partner at Element IP. His practice focuses on patent procurement and client counseling, including expertise in validity and infringement opinions.