Patent Prior Art and the Necessity Requirement for Inherency

A patent claim limitation can only be inherently disclosed by patent prior art when such limitation is necessarily a component of a disclosed subject matter. In Southwire Co. v. Cerro Wire LLC, No. 2016-2287 (Fed. Cir. Sept. 8, 2017), the Federal Circuit rejected the Patent Trial and Appeals Board’s reasoning that certain claim elements were inherent in patent prior art cited in an inter partes reexamination. Luckily for the Petitioner, the Federal Circuit then held that the standard obviousness analysis invalidated the claims based on the cited patent prior art, and upheld the Board’s invalidity determination.

At issue was Claim 1 of U.S. Patent 7,557,301. Claim 1 recited:

1. In a method of manufacturing a finished electrical cable having a conductor core and a jacket formed primarily of a first material, the jacket surrounding at least said conductor core and defining the outermost exterior surface of the finished cable, the improvement comprising

combining a preselected lubricant with said first material prior to the formation of said jacket in order to provide a reduced coefficient of friction of said cable outermost exterior surface and also reduce the amount of force required to pull the cable, during its installation through building passageways,

in which said lubricant is of the type which migrates through said jacket to be available at said outermost exterior surface of said finished cable during the cable’s installation through building passageways,

the finished electrical cable having the characteristic that an amount of force required to install said cable through corresponding holes in an arrangement of four 2" x 4" wood blocks having holes drilled at 15° through the broad face and the centerlines of the holes are offset 10" and pulled through at 45° to the horizontal from the last block is 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 through corresponding holes in said arrangement.

With the exception of the “30% reduction” of force required to pull the cable through the specialized wood block, the remainder of the claim limitations, e.g., the method of manufacturing a cable with a lubricant impregnated sheath, were taught by the cited prior art.

The Board found that the “30% reduction” was inherent in the prior art because the reference taught the same method steps as those in Claim 1. The Board reasoned that achieving the 30% reduction was inherent because it would have been obvious to one skilled in the art practicing the method disclosed by the patent prior art to select an appropriate lubricant to achieve the “30% reduction.”

 The Federal Circuit disagreed. For a limitation to be inherently disclosed by a piece of patent prior art, “the limitation at issue necessarily must be present.” (citing PAR Pharm., Inc. v. TWI Pharm., Inc., 773 F.3d 1186, 1194–95 (Fed. Cir. 2014)). The Federal Circuit pointed out that if one skilled in the art would have to select a certain type of lubricant for use with the patent prior art process to achieve the claimed result, then the claimed result could not necessarily be a result of the patent prior art process.

The court went on however, to explain that, because the prior art disclosed an “identical or substantially identical” process, it rendered Claim 1 prima facia obvious. The Patent Owner failed to produce any evidence that achieving the “30% reduction” would have been unexpected with the prior art process, or even that the prior art process produces something less than the “30% reduction.” The Federal Circuit thus found that Claim 1 was invalid as obvious in light of the cited patent prior art.

Lesson For Practice

When relying on inherency to provide a limitation in a piece of patent prior art, show how the patent prior art cannot be practiced without the limitation in question. When arguing against a limitation as being inherent in a piece patent prior art, show how the patent prior art can be practiced without the limitation in question. Lastly, whether arguing that a limitation is inherent or not, bolster your argument with a strong obviousness analysis.

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