How the disavowal exception trashed a patent infringement claim

April 17, 2017
Patterson Thuente IP

Courts in infringement cases construe terms in patent claims by their plain and ordinary meaning — usually. As the patentee in Poly-America, L.P. v. API Industries, Inc., learned the hard way, the Federal Circuit doesn’t take that approach when the disavowal of claim scope applies.

Trial court tosses case

Poly-America owns a patent for “an improved construction of an elastic drawstring trash bag.” A main feature of the invention is the use of inwardly extended “short seals” in the upper corners of the bag that reduce the width of the bag’s upper opening. When coupled with elastic drawstrings, the narrowed opening allows the drawstrings to wrap around the rim of a trash receptacle more securely than previous trash bags (or “prior art”) that lack a narrowed upper opening.

Poly-America sued API Industries for infringement of the patent. The trial court interpreted “short seal” to mean a seal for securing the elastic drawstring that extends inwardly from the interior edge of the bag’s side seal. Under this interpretation, API’s bag didn’t infringe the patent because its short seals didn’t extend inwardly.

After the trial court ruled in API’s favor, Poly-America appealed. It argued that the court erred by interpreting “short seal” to require the limitation of an inward extension that reduces the upper width of the trash bag.

Bottom falls out

As the Federal Circuit noted, patent claim terms generally are given their ordinary and customary meaning — that is, the meaning they would have to a “person of ordinary skill” in the relevant area at the time of the invention. But courts depart from a patent’s plain and ordinary meaning when the inventor “disavows” the claim’s full scope by narrowing terms in the patent’s claims through intrinsic evidence contained in the patent’s specification or during patent prosecution. The standard for disavowal, whether in the specification or during prosecution, requires “clear and unequivocal” evidence that the invention includes or doesn’t include a particular feature.

Although the disavowal must be clear and unequivocal, it doesn’t need to be explicit. For example, an inventor could disavow claims lacking a particular feature when the specification describes “the present invention” as having that feature.

In this case, Poly-America’s patent specification included just such language, stating that “one of the characteristics of the present invention is a reduction in upper width … resulting from the extended short seals.” The court found this to be a clear statement describing a characteristic feature of the invention.

The court observed that a patentee also can disavow claims lacking a particular feature when the specification distinguishes or disparages prior art based on the absence of that feature. The patentee’s specification stated that prior art bags are difficult to secure over trash receptacle lips and that the extended short seals reduce the bag’s upper opening, making it easy to fit around a trashcan.

Open and shut

The appellate court’s decision provides an illustration of the importance of careful patent drafting. Unfortunately, Poly-America’s own patent language ended up sealing its fate.

Poly-America, L.P. v. API Industries, Inc., No. 16-1200, Oct. 14, 2016 (Fed Cir.)