Don’t Forget the Specification When Applying BRI

A recent Federal Circuit decision illustrates the dangers of construing claims too broadly when applying the “broadest reasonable interpretation” (BRI) standard. Petitioners especially must remember that the BRI of a term must be “reasonable” in light of the specification. Relying on broad constructions that fail to account for narrowing language in the specification can lead to defeat.

In TF3 Ltd. v. Tre Milano, LLC, the Federal Circuit reversed an IPR decision finding claims relating to an automated hair curling device unpatentable for anticipation. The claimed device had an “elongate member” (the curler) inside a chamber with two openings, one for the hair to enter and a “secondary opening” for the hair to leave.  Although the claims did not state how the hair had to leave the chamber, the specification stated that the device “allows the styled length of hair to pass out of the secondary opening, i.e., to slide along the elongate member.” Further, the specification identified the feature of hair sliding off the curler as an improvement over the prior art.

In the IPR, the references that the petitioner advanced described a device in which the curler was ejected from the device with the hair still wound around it, rather than one in which the hair slid off the end of the curler. The PTAB held the BRI of the claims didn’t require that the hair be allowed to slide off the curler. This construction led to the anticipation finding.

The Federal Circuit found the PTAB’s constructions overly broad because they ignored the limiting language in the specification. The court noted that the use of “i.e.” in the specification passage quoted above signaled an intent to define how the hair passed through the opening: by sliding off the free end of the curler. The court also noted the specification’s emphasis on this feature in distinguishing the prior art. The court construed the terms at issue so as to require the device to operate as described in the specification, and on that basis reversed the PTAB.


It is often tempting for petitioners to construe challenged claims broadly in order to better read on a prior art reference. But petitioners must ensure that their proffered constructions do not ignore definitional language or stated distinctions over prior art. This requires very careful review of the intrinsic record. As this case shows, even two letters—“i.e.”—can, in the right circumstances, result in the claims being narrowed in ways that could be fatal to a challenge.