Perhaps the most challenging aspect of patent preparation and prosecution is describing an invention in terms that are clear enough to show novelty and non-obviousness, while yet preserving sufficiently broad claim scope to capture potential infringers. Here is a lesson from the world of garbage bags, in which the Federal Circuit held that a patentee had clearly disavowed meaning of a “short seal” that was part of the garbage bag. Poly-America, L.P. v. API Indus., Inc., 2016-1200 (Fed. Cir. Oct. 14, 2016) (Judge Reyna wrote the opinion, joined by Chief Judge Prost and Judge Hughes).
U.S. Patent No. 8,702,308 describes an “invention [that] is directed toward an improved construction of an elastic drawstring trash bag.” The claimed trash bag included “short seals” in upper corners of the bag. The patent, beginning with its title, and continuing with the “Summary of the Invention” and the written description, repeatedly “indicate[d] the significance of the extended short seal feature and the reduced upper opening width the extended short seals provide.” Further, during prosecution, the applicant distinguished prior art “from all of the ’308 patent’s independent claims on the basis that [the reference’s] short seals were not extended to reduce the bag’s ‘relaxed upper opening width’ in relation to the ‘bag proper width.’”
Two independent claims of the ’308 patent explicitly recited a narrowed bag width in conjunction with the short seals. However, independent claim 10 did not “expressly state any limitation as to the size of the short seals or the relationship between the size of the upper opening and the bag proper.” Claim 10 recites:
An elastic drawstring trash bag comprising:
a polymeric bag comprised of a first panel and a second panel, the first panel and the second panel joined at a first side, a second side, and a bottom,
a first hem formed in the first panel, the first hem having a first elastic drawstring disposed therein,
a second hem formed in the second panel, the second hem having a second elastic drawstring disposed therein,
the first panel, the first elastic drawstring, the second panel, and the second elastic drawstring inseparably joined together at a first short seal and at a second short seal, and
a first access cutout along the upper edge of the first panel and a second access cutout along the upper edge of the second panel, the first and second elastic drawstrings being accessible through the respective first and second access cutouts.
Claim 10’s lack of limitation regarding the extent of short seals notwithstanding, the district court properly construed “short seal” in claim 10 as “[a] seal for securing the elastic drawstring, which seal is located adjacent to a side seal, and that is not substantially aligned with the side seal, but extends inwardly from the interior edge of the side seal.”
This case fell squarely under the rubric of Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc). Under Phillips, the patentee can disavow claim scope either in the written description or in the prosecution history. The “disavowal must be clear and unequivocal,” but not necessarily “explicit.” Here, the applicant had responded to the examiner’s rejections with “a clear and unmistakable disavowal of short seals that do not extend inwardly.”
Further, there was no improper importation of specific embodiments from the specification, because every disclosed embodiment limited the extent of the “short seals.” Moreover, other independent and dependent claims could not be relied on for claim differentiation, because “claim differentiation does not serve to broaden claims beyond their meaning in light of the patent as a whole, and it cannot override clear statements of claim scope found in the specification and prosecution history.”
This case offers a lot of basic lessons, starting with the dangers of using the word “invention” anywhere in a patent specification. But beyond that, this case flags the dangers of painting with a broad brush, i.e., crafting a single argument for claims with different language, in responding to USPTO Office Actions. The patentee faced a severe uphill climb in arguing that the term “short seal” in claim 10 should be construed differently from that term in other claims after lumping the claims together for purposes of argument. One good practice is to argue claims by quoting from – not paraphrasing – claim language. One benefit of following this practice is that you might avoid explicit limitations from one independent claim being read as implied in another.