Is It Really There? Inherency in Obviousness and Functional Claiming

By: A. Rusty Rogers


In a recent decision, the Federal Circuit upholds an invalidation of a patent directed to manufacturing electric cables during inter partes review, despite acknowledging the Patent and Trial and Appeal Board’s (PTAB) misapplication of inherency principles in the obviousness context.

When formulating a rejection, examiners must consider what prior art references teach and whether every limitation of a claim under examination is anticipated or obvious.  In some cases, examiners may premise anticipation rejections under 35 U.S.C. § 102 or obviousness rejections under 35 U.S.C. § 103 on inherent features that, while not explicitly defined or disclosed, would necessarily flow from the teachings of the prior art. In the anticipation context, examiners often rely on inherency arguments to establish a rejection where functional elements of a claim have not been shown, yet are nonetheless inseparable from other physical limitations that may be shown by a prior art document.

Inherency becomes more complex when establishing a prima facie case of obviousness because an inherent feature, by definition, is unrecognized by a skilled artisan viewing the prior art. As discussed in In re Rijckaert, 9 F.3d 1531, 1534 (Fed Cir. 1993), “[t]hat which may be inherent is not necessarily known.  Obviousness cannot be predicated on what is unknown.”  In other words, the inherent limitation itself cannot be used as a motivation to modify or combine references.  Instead, the rejection must be premised on the assertion that an inherent limitation flows naturally from other teachings in the art, and that a skilled artisan would have been motivated to modify the prior art without guidance as to the inherent feature.

In Southwire Co. v. Cerro Wire LLC, 2016-2287, (Fed. Cir. Sep. 8, 2017), the Federal Circuit upheld the invalidation of Southwire owned U.S. Pat. No. 7,557,301 (‘301 patent) during an inter partes proceeding initiated by Cerro.  The ‘301 patent is directed to a method of manufacturing an electric cable, wherein a lubricant is incorporated into an outer sheath, which reduces the pulling force required to install the cable.  The PTAB found that the invention was obvious in view of U.S. Pat. No. 6,160,940 (Summers) and a number of secondary references.  In particular, the PTAB found that Summers described a fiber optic cable that is suitable for installation in a cable passageway and that to reduce resistance to a cable pulling force, the plastic material used to form the cable can include a friction reducing additive that migrates to the surface of the cable jacket.  The PTAB noted that where the claimed and prior art products are produced by identical or substantially identical processes, a prima facie case of either anticipation or obviousness has been established.  In its decision invalidating the ‘301 patent, the PTAB asserted that the undisclosed limitation of “at least about a 30% reduction” in pulling force recited in the claims was inherent in the combination of references.

On appeal to the Federal Circuit, Southwire argued that the finding of obviousness was improper as being based on the determination that Summers inherently disclosed a 30% reduction in pulling force recited in the claims, because nothing had established that the limitation would necessarily be present.  Rather, Southwire contended, a skilled artisan would have no reason to select lubricant concentrations that achieved a 30% reduction in pulling force with the certainty required for inherency-based obviousness.

The Federal Circuit noted that inherency may be used to supply a missing claim limitation, but acknowledged that the limitation must necessarily be present in the teaching of a reference in order to be inherent.  To this end, the Federal Circuit found that the Board did not provide an adequate explanation for finding that a reduction of 30% in the pulling force would necessarily result from prior art process.  Nevertheless, the Federal Circuit held that, while the PTAB erred in finding it inherent that the Summers process necessarily would achieve a 30% reduction in pulling force, the PTAB had made the requisite factual findings to find the limitation obvious by the standard rationales.  Specifically, the reference disclosed the same process for manufacturing electric cables, the steps did not differ in any material way, and there were no unexpected results.

Referencing In re Best, 562 F.2d 1252, 1254 (CCPA 1977), the Federal Circuit noted that where all process steps are expressly disclosed by a prior art reference, except for a functional limitation, the Patentee may need to rebut a presumption that the function is inherent.  Here, the Federal Circuit also held that Southwire failed to substantiate the presence of unexpected results to rebut any finding of obviousness, and presented no evidence in the declarations that any of Southwire’s products embodied the claimed 30% reduction in pulling force, or any other, claim limitation.  The Federal Circuit then concluded that there was no indication that the limitation was anything other than mere quantification of the results of a known process and affirmed the invalidation of the ‘301 patent.

Southwire provides an excellent reminder that practitioners should carefully examine how rejections are formulated and identify when an examiner is relying on an inherent showing of certain claim limitations.  Inherency arguments occur frequently in both anticipation and obviousness contexts, usually in the form of implicit or explicit assumptions, and identifying these leaps in logic can be useful in deconstructing claim rejections in a response.  An examiner must show that inherent features are necessarily present to establish a claim rejection.  Thus, practitioners should first point out what claim limitations are being asserted as inherent in view of the prior art, and highlight any differences in the claimed subject matter that create uncertainty that inherent limitations will necessarily flow from elements that are shown by the prior art.

However, the corollary to Southwire is also that, even where an inherency rejection is successfully dismantled, limitations that merely seek to quantify features of a known process will not overcome other theories of obviousness.  In such as case, novel qualitative limitations like those in Southwire should be tied to other claim limitations (or combinations of limitations) not described in the prior art – structural elements, concentrations or ratios of compositional components, unique method steps, and the like – to first address the other obviousness rationales.  Then inherency may be addressed by creating uncertainty that, even where individual elements of a claim are known, a skilled artisan would have no reasonable expectation that the inherent limitation would necessarily flow from the unique limitation or combination – and thus no motive to modify or combine the references as presented by the examiner exists.