In Inline Plastics Corp. v. EasyPak, LLC, [2014-1305] August 27, 2015, the Federal Circuit vacated the district court’s claim construction of “frangible section” as being improperly limited to the preferred embodiment, and therefore reversed the district court’s judgment of non-infringement.

The preferred embodiment of the “frangible section” is described as having a pair of parallel score lines, although an alternative embodiment is described as having a single score line.  EasyPak argued that the prosecution history supports construing frangible section as requiring at least two score lines, but the Federal Circuit disagreed,  noting that the examiner did not require such limitation, and it was not a condition of patentability.

in distinguishing a prior art reference, the applicant described the prior art as having a single score line, but the Federal Circuit observed that this was not the basis for distinction.  The Federal Circuit further found that claim differentiation also supported the broader construction of frangible section, because the alternative embodiment specifically mentioned a single score line.

Although all’s well that ends well, the patent applicant’s description of the prior art formed the basis for the iinfringer’s claim construction arguments.  When characterizing and distinguishing prior art, it is probably best not to mention any aspect of the prior art that is not necessary to the basis for distinguishing the prior art.