Piggy Pushers case; does a gripper element transform a sock into a shoe?
Piggy Pushers, LLC, sued Skidders Footwear, Inc., in
the Western District of Michigan for patent infringement.
After construing the asserted claims and granting summary
judgment of noninfringement, the district court
entered final judgment in favor of Skidders. Piggy Pushers
appeals. For the reasons set forth below, we affirm.
Of shoes and socks:
Because some preambles are limiting and others not, we focus on the sole concrete issue at stake in deciding whether the particular preambles here are limiting— namely, whether, when the elements recited in the body of the claims are combined as claimed, the result must itself be a sock. We think the answer plain from the specification, which uniformly describes what results from combining the sock member with the gripper member as itself remaining a “sock.” ’779 patent, cols. 1 and 2 (back- ground of the invention; summary of the invention). In particular, the specification distinguishes a sock from a “shoe,” which can be undesirable or difficult to put on an infant; so the addition of the gripper cannot transform the sock into a shoe. ’779 patent, col. 1, lines 22-25. More generally, introducing the invention, the specification explains that “socks can be disadvantageous on smooth floor surfaces . . . because there is a very low coefficient of friction between fabric material of the socks and the floor surface,” id., col. 1, lines 17-20 (emphasis added), and that the inventors have conceived and described a particular kind of “sock” that overcomes that problem, without the use of a “shoe,” and does so for crawling infants, not just those who can walk,
The requirement that the combined elements form a “sock” is a “fundamental characteristic of the claimed invention.” Poly-Am., L.P. v. GSE Lining Tech., Inc., 383 F.3d 1303, 1310 (Fed. Cir. 2004) (internal quotation marks omitted). We therefore affirm the construction of the preambles as limiting to the extent necessary to express the idea that the claims each cover a sock, not a shoe or another article that may be derivative or partly made up of a sock but is not itself a sock. See Am. Med. Sys., Inc. v. Biolitec, Inc., 618 F.3d 1354, 1358 (Fed. Cir. 2010) (“Whether to treat a preamble term as a claim limitation is determined on the facts of each case in light of the claim as a whole and the invention described in the patent.”) (internal quotation marks omitted).