Claim Construction Lessons from Your KitchenIn this claim construction analysis, the Federal Circuit panel disagreed about what the holes were in Advanced Fiber Technologies’ (AFT) patents—literally.

Advanced Fiber Technologies (AFT) Trust v. J&L Fiber Services, Inc., No. 2011-1243 (Fed. Cir. Apr. 3, 2012) (Judges Lourie, Prost, and Dyk)

This patent infringement case involves AFL’s patent for screening tools in the pulp and paper industry. As you probably know, paper is made from trees. To make paper, you have to screen out the “stock” (a mixture of paper pulp and water) to keep out sticks or other big pieces of unwanted stuff. It’s not unlike straining homemade chicken stock or draining pasta. Sometimes you might use a sieve, and sometimes you might use a colander.

AFL’s patent covers a device to screen paper pulp. Although there are a couple of other issues, the major question in the case boils down to this: Does the patent cover devices that are like sieves and colanders, or just devices like colanders?

This case is a little different from your typical claim construction case because the critical term, “perforated,” doesn’t actually appear in the claims—it shows up in the district court’s definition of “screening medium” and “screening plate,” which are in the asserted claims. But since “perforated” is an essential term in the correct construction of “screening medium,” the Federal Circuit agreed that it was appropriate for the district court to interpret “perforated.” Also, AFL’s patent is a reissued patent—that is, AFL resubmitted the patent to the Patent & Trademark Office after it issued to fix errors in the patent. In a reissue, all of the claims are reviewed, and a party may have to overcome rejections to claims that the examiner allowed the first time around.

The district court construed “screening medium” as “a perforated barrier through which stock is passed to remove oversized, troublesome, and unwanted particles from good fiber.” It then relied on general and technical dictionary definitions of “perforate” and “perforation” to construe “perforated,” which it interpreted as “pierced or punctured with holes.” This construction requires a screen to be made from a solid sheet that has holes poked into it, like a traditional colander. I’ll call this the “colander construction.”

The district court acknowledged that the colander construction contains a discrepancy with the written description of AFL’s patent. The written description includes 1 sentence that reads, “A wedgewire screening plate may be used.” Wedgewire is made by assembling closely spaced wires rather than by poking holes. It’s similar to a sieve and looks like this:

Claim Construction Lessons from Your Kitchen • wz54 1

The district court concluded that this discrepancy didn’t matter because none of the claims explicitly recite wedgewire; it only appears in the written description. Based on the “colander construction,” the district court said J&L’s screening devices (which use wedgewire) didn’t infringe AFL’s patent.

The majority of the Federal Circuit panel disagreed with the district court’s claim construction approach. According to the majority, the district court’s big mistake was its reliance on dictionary definitions—which are extrinsic evidence—that contradicted the written description and claims, which are intrinsic evidence. That’s a claim construction no-no.  (There has been some disagreement about the proper role of dictionary definitions in the claim construction process.)

The majority also had something to say about the fact that only 1 sentence in the written description mentioned wedgewire:

The fact that the embodiment is disclosed in a single sentence is not a license to ignore that disclosure. Indeed, as a general matter, brevity in patent disclosure should be applauded, not impugned. A disclosed embodiment is a disclosed embodiment, no matter the volume of ink required to adequately describe it.

(See pages 16-17 of the AFT opinion, citations omitted.) The Federal Circuit then construed “perforated” as “having holes or openings.” This construction encompasses both colander-like and sieve-like screening devices. Since it concluded that the district court’s construction of “perforated” was too narrow, the court sent the case back to the district court to reconsider infringement in light of the new construction.

Don’t Let This Slip Through the Cracks

In dissent, Judge Dyk concluded that the district court’s “colander construction” was correct. He saw enough evidence in the intrinsic record to support a claim limitation that excludes a wedgewire (or sieve-like) structure. He looked at the claim language, which require holes or openings to be made “through” a screening plate, and at the definitions AFT itself provided from the technology-specific Handbook of Pulp & Paper Terminology, which defines a “perforated plate” as a “screen plate with straight through holes, usually made by a punch.” To Judge Dyk, the intrinsic evidence didn’t actually contradict the extrinsic evidence on which the district court relied.

To justify the discrepancy that the “colander construction” creates with the 1-sentence wedgewire mention, Judge Dyk noted that not all embodiments disclosed in the specification fall within the scope of the claims. In his view, AFL made statements during the reissue prosecution that explicitly exclude a sieve-like screen. So he would have left the district court’s construction as is.

Since the Federal Circuit reviews claim construction de novo, this case really does come down to the different panelists perceptions of the evidence. Just reading the opinion and the dissent, it’s hard to tell if the district judge made a legal error by relying on outside evidence that contradicts the patent’s internal evidence, or if it’s just a matter of interpretation. Good thing chicken stock straining—through a sieve or a colander—is a lot simpler.