United States: "Essential" Steps From Specification May Limit Scope Of Patent Claims

In construing the scope of a product claim, the U.S. Court of Appeals for the Federal Circuit held that the process for making a product can be within the scope of a product claim when the "patentee makes clear that the process steps are an essential part of the claimed invention." Andersen Corp. v. Fiber Composites, LLC, Case Nos. 05-1434, 06-1009 (Fed. Cir., Jan. 26, 2007) (Bryson, J.).

Andersen asserted two groups of patents related to polymer-wood composites against Fiber Composites. The first group of patents (Group I) claim "composite compositions," which are described in the patents as an intermediate composite materials capable of being extruded into structural parts. The second group of patents (Group II) claim "composite structural members," which are described in the patents as the extruded parts themselves. Fiber Composites contended that these claim terms should be construed to include an intermediate pelletization process that is used to manufacture the composite invention. Since this limitation is not expressly contained in the claims themselves, Fiber Composites cited the specification to support its claim construction. Under this construction, Fiber Composites would escape infringement as it uses a direct extrusion process in which the polymer and wood fibers are first mixed and melted in an extruder and then, without an intermediate step, directly forced through a die to form the finished structural part.

The district court agreed with Fiber Composites’ construction in regard to the Group I patents, holding that "composite compositions" should be construed to include the pelletization process from which it is made. However in construing the Group II patents, the district court ruled that the scope of the "composite structural members" is limited to the extruded product and does not include the pelletization process. Fiber Composites appealed.

In reversing the district court’s grant of summary judgment for infringement of the Group II patents, the Federal Circuit found ample support for Fiber Composites’ proposed limitation by viewing the specification and the prosecution history together. The Federal Circuit construed the claims of both groups of patents to be limited to an intermediate pelletization process. The Court reasoned that, as in the case of the Group I common specification, the Group II common specification states that the claimed superior properties of the structural members are only achieved through the essential step of the intermediate pelletizing process. Thus, the Court reasoned that the pelletizing step is not merely a preferred embodiment, because the specification uses "language of requirement, not preference."

Also, after reviewing the prosecution history of the Group II patents, the Court found that the applicants clearly disavowed the direct extrusion process for making the "composite structural members." Just as during the prosecution of the Group I patents, the applicant distinguished prior art based on the intermediate pelletization process used in the present invention.

Practice Note: Patent prosecutors should use caution when using language of requirement (as opposed to preference) in the specification to describe the invention, as such language may be claim-limiting.