Despite an error by the Patent Trial and Appeal Board (PTAB or Board) in relying on inherency to render an obviousness determination, the US Court of Appeals for the Federal Circuit affirmed the PTAB decision, finding substantial evidence that the challenged patent claims were obvious. Southwire Company v. Cerro Wire LLC, Case No. 16-2287 (Fed. Cir., Sept. 8, 2017) (Lourie, J).

Southwire owns a patent directed to a method of manufacturing an electric cable that incorporates a lubricant into the outer sheath in order to reduce the pulling force needed to install the cable. Southwire’s patent claims recite that the use of the lubricant results in “at least about a 30% reduction in comparison to an amount of force required to install a non-lubricated cable of the same cable type and size.” Cerro filed a request for inter partes re-examination arguing that the claims were obvious over a combination of prior art. Ultimately, the PTAB concluded that because the prior art generally teaches reducing the coefficient of friction using a lubricant, it inherently teaches the claimed 30 percent reduction because it would have been obvious to have selected lubricant amounts to achieve the claimed reduction. The PTAB therefore found the claims obvious. Southwire appealed.

On appeal, Southwire challenged the PTAB’s reliance on inherency in making the obviousness determination, arguing that the alleged inherency is not present in the prior art. The Federal Circuit agreed that the PTAB erred in relying on inherency because there was no evidence the prior art necessarily achieves a 30 percent reduction in pulling force. Nevertheless, the Court found the PTAB’s error harmless because the PTAB also made factual findings supporting its obviousness determination—namely, that the claimed method applies the same process for the same purpose as disclosed in the prior art.

With regard to the 30 percent limitation, the Federal Circuit shifted the burden of proof to Southwire, noting that Southwire provided no evidence that the claimed 30 percent reduction would have been unexpected or unattainable from the process disclosed in the prior art, or that the process disclosed in the prior art did not produce the claimed reduction. Moreover, the Court noted that although the patent specification included a single mention that the lubricated specimens yielded a 50 percent reduction in pulling force, this passage did not provide any indication that a 30 percent reduction was something other than an observed result of an old process. The Court therefore affirmed the PTAB’s decision.

Practice Note: Patent drafters should include sufficient disclosure in the written description or provide evidence to support any (inherent) functional limitation relied in the claim.