Delkor Systems, Inc. v. Pratt Industries, Inc. et al — Court Grants Summary Judgment of Noninfringement Based on Claim Construction of ‘Single Tear Line’

Background

Delkor Systems, Inc. owns U.S. Patent Nos. 9,555,919 and 10,421,580, both titled 'Convertible Package Assembly and Display System.' The patents describe a flat piece of packaging material that folds into a shipping box, which can then be converted into a retail-ready display case by removing the top portion along a tear line. Delkor alleged that Pratt Industries, Inc., Pratt Retail Specialties, LLC, and Pratt (Beloit Corrugating), LLC (collectively 'Pratt') infringed these patents by manufacturing and selling a corrugated cardboard package for shipping and displaying frozen pizzas.

Both parties moved for summary judgment on the issue of infringement. The parties agreed on the structure and function of the accused product, so the dispute centered on claim construction. The independent claims of both patents require that the package be formed from a 'single piece of packaging material with a single tear line' and that conversion from shipping to display configuration occur by 'separating the top portion from the bottom portion along the single tear line.' The accused product contains a cut-out handhold in the middle of the tear line, which Pratt argued means the product has two tear lines rather than a single tear line.

The Court’s Holding

The court construed the term 'single tear line' to require a continuous physical line through the case blank. The court reasoned that the plain meaning of 'tear' is to pull or rip apart, and a cut-out handhold cannot be torn because the material has already been removed. The specification repeatedly describes the tear line as 'continuous,' which supports a physical line that can be continuously torn, not two lines separated by a non-tearing feature. The court rejected Delkor's argument that the tear line could be composed of multiple sections including a handhold, noting that while the specification describes tear line sections, it describes them as continuous.

The court also rejected Delkor's reliance on U.S. Patent No. 5,657,872 (Leftwich), which the patents incorporate by reference. Although Leftwich discloses a 'line of weakness' with an aperture at its midpoint, the court found that Leftwich never describes the line as 'continuous,' whereas the asserted patents do so repeatedly. This suggests an intention to exclude designs like Leftwich's with non-continuous perforations separated by a cut-out. The court concluded that no reasonable jury could find that a handhold and a perforation are the same thing.

Applying this construction, the court held that the accused product does not meet the 'single tear line' limitation because it has a handhold separating two perforated tear lines. The court also rejected Delkor's doctrine of equivalents argument, finding that Delkor's own expert admitted the handhold affects how the product tears by making separation easier, which is a difference in function related to a key feature of the patented product. The court granted Pratt's motion for summary judgment of noninfringement, denied Delkor's motion for partial summary judgment on infringement, and directed the clerk to enter judgment for defendants and close the case.

Key Takeaways

• Claim construction that focuses on the plain meaning of terms and the specification's repeated use of descriptive language like 'continuous' can be dispositive of infringement at summary judgment when the parties agree on the accused product's structure.
• Incorporation by reference of a prior patent does not convert the incorporated patent's invention into the host patent's invention, and differences in how the patents describe a disputed term can support a construction that excludes the incorporated design.
• A patentee's doctrine of equivalents argument can fail when its own expert admits that an accused product feature creates a functional difference related to a key innovation of the patented invention.
• When a claim limitation is dispositive of noninfringement, a court need not address other disputed claim limitations or infringement arguments.

Why It Matters

This decision illustrates how claim construction can resolve patent infringement disputes at summary judgment when the material facts about the accused product are undisputed. The court's analysis demonstrates the importance of the specification's language in construing claim terms, particularly when the specification repeatedly characterizes a feature in a particular way. The ruling also shows that incorporation by reference of related patents does not necessarily broaden the scope of claim terms beyond what the host patent's own specification supports.