Disparaging a particular feature in the prior art generally constitutes a disclaimer of that feature in the claimed invention. Here, for example, a trash bag with so-called “short seals” in its upper corners was found to be limited to a design in which the short seals narrow the upper opening of the bag to provide a tighter fit around a trash can, even though not all claims made this explicit, because the specification extolled this benefit of using short seals over prior art trash bags. “[A]n inventor may disavow claims lacking a particular feature when the specification distinguishes or disparages prior art based on the absence of that feature.” It may therefore be best to avoid overly characterizing the prior art in the specification.
Background / Facts: The patent being asserted here is directed to an improved construction of an elastic drawstring trash bag. The specification describes so-called “short seals” at the bag’s upper corners. The specification explains that the short seals reduce the width of the bag’s upper opening, allowing the drawstrings to wrap around the rim of a trash receptacle more securely than prior art trash bags that do not have a narrowed upper opening. While all of the claims recite the use of short seals, some claims do not explicitly provide for a narrowed opening.
Issue(s): Whether the specification disavows trash bags with short seals that do not narrow the upper opening width.
Holding(s): Yes. “[A]n inventor may disavow claims lacking a particular feature when the specification distinguishes or disparages prior art based on the absence of that feature.  That is exactly what the specification to the  patent does by stating that prior art bags are difficult to secure over trash receptacle lips and explaining that the use of extended short seals reduces the claimed bag’s upper opening, making it easy to fit around a trashcan.” Moreover, “[e]very embodiment described in the specification has inwardly extended short seals and every section of the specification indicates the importance of inwardly extended short seals. These two facts provide together a proper reason to limit the claims in this way.”