Prosecution history estoppel does not apply if arguments were “made in a different context”

In MTD Products, Inc. v. Andrei Iancu (MTD), MTD appealed to the Federal Circuit from an IPR decision holding all claims unpatentable of US 8,011,458.  The claims at issue concerned a zero-turn radius vehicle, typically a mower.  The claim term “mechanical control assembly” was at issue and in particular, whether or not the claim term was appropriately construed under Section 112, paragraph 6.

Although the term had not been so construed by the Examiner during the prosecution of the ‘458 patent, Appellant MTD had argued the claim language in order to overcome a rejection under 35 USC §102 (over Middlesworth).  In particular, MTD had argued that “The “configured” language is structural”, “The claimed confirguration is indeed structural”  “Middlesworth is not configured as claimed” and “For this reason, the Middlesworth assembly is not configured as claimed, and the rejection is overcome and should be withdrawn.” (emphasis original).  Though the Examiner had applied Middlesworth in three actions, it was not until MTD made the aforementioned arguments that the Examiner withdrew the rejection in favor of other prior art references.  MTD thus avoided application of prior art by arguing that the claim term “mechanical control assembly [configured to]…” denoted something different than what was disclosed in the prior art.  MTD Response

Toro requested, and was granted, an Inter Partes Review after being sued for infringement under the ‘458 patent in the Northern District of Ohio.  During the IPR proceedings, MTD argued that, although the claim was not construed as a means-plus-function limitation during prosecution, it should now be so construed in light of the Federal Circuit’s Williamson decision, which was issued after the prosecution of the ‘458 patent.  Williamson v. Citrix Online, 792 F.3d 1339 (Fed. Cir. 2015) (en banc).  The Board characterized this argument as follows:

In Williamson, the Federal Circuit abandoned characterizing as “strong” the presumption that a claim lacking the word “means” was not a means-plus-function claim.  Williamson, 792 F.3d at 1349.  Instead:

The standard is whether the words of the claim are understood by persons of ordinary skill in the art to have a sufficiently definite meaning as the name for structure.  When a claim term lacks the word “means” the presumption can be overcome and §112, para.6 will apply if the challenger demonstrates that the claim term fails to recite sufficiently definite structure or else recites function without reciting sufficient structure for performing that function.

In other words, during prosecution of the ‘458 patent MTD rather emphatically argued that the claim recitation associated with “mechanical control assembly” was structural to avoid a prior art reference.  This same argument is one way of responding to the invocation of  of Section 112, ¶6 with respect to a claim term, which patentees typically seek to avoid as it is generally considered to narrow claim scope.  And yet, in the IPR proceeding MTD took the opposite position and argued that Section 112, ¶6 applied to the claims, i.e., MTD argued that the claim term “mechanical control assembly” did not denote any particular structure, and so should be construed under Section 112, ¶6.   Unusually, doing so allowed the challenged patent to avoid application of the asserted prior art.

Even though Toro argued MTD had admitted that the term “mechanical control assembly” conveys particular structure in order to garner patentability of the ‘458 patent, the Federal Circuit vacated the Board’s obviousness conclusion (stating “which was predicated on its incorrect claim construction”) and remanded for further proceedings.   Specifically, the Court held:

While it would have avoided uncertainty and argument had MTD shared its current view that the claim limitation is written in means-plus-function format during the original prosecution, MTD’s statements did not clearly disclaim such an interpretation.  Rather, MTD’s statements indicated that the phrase “mechanical control assembly configured to” perform certain functions must be given weight because it connotes structure and thus is not merely an intended use.  These statements were not made within the context of of §112, ¶6.