Before Lourie, Clevenger, and Rader, Circuit Judges.
The opinion of the court was delivered by: Clevenger, Circuit Judge.
Middleton, Inc. (Middleton) appeals the decision of the United States District Court for the Northern District of Illinois, granting summary judgment of noninfringement in favor of Minnesota Mining & Manufacturing Co. (3M). See Middleton, Inc. v. Minnesota Mining & Mfg. Co., No. 96-C6781, slip op. at 13 (N.D. Ill. Nov. 24, 1998). The district court determined, based on its claim construction, that no reasonable jury could find that 3M's product--"FloorMinders"--infringes Middleton's U.S. Patent No. 4,944,514, either literally or under the doctrine of equivalents. Because the district court's claim construction was erroneous with respect to the limitation "material for finishing," we vacate on the basis of that limitation and remand the case for further proceedings.
Middleton is the owner of U.S. Patent No. 4,944,514 (the `514 patent), entitled "Floor Finishing Material and Method." The `514 patent discloses the use of an adhesive-backed flexible sheet for finishing smooth floor surfaces, such as athletic courts, bowling lanes, and commercial and residential floors of wood, linoleum, terrazzo and concrete. The specification teaches that appropriate boundary lines, team logos, and other such markings may be applied to the undersurface of the adhesive finishing sheet prior to applying the finishing sheet to the floor. See `514 patent, col. 5, lines 61-68.
The application that matured into the `514 patent is a continuation-in-part of two parent applications, which, in turn, derive from a common grandparent. The grandparent application is primarily directed to a method and product for finishing bowling lanes. That application was abandoned by the applicant in favor of S/N 940,428 (the `428 application) for a bowling lane refinishing material, and S/N 203,617 for a bowling lane refinishing method. The `514 patent essentially incorporates the product and method of the two parent applications, but expands the disclosure beyond the practice of refinishing bowling lanes.
3M manufactures and sells a product called "FloorMinders," which allows advertising, decoration, safety information, and other types of images to be applied directly to a smooth floor surface. FloorMinders is comprised of (1) a base film called Controltac, (2) a graphic image, and (3) a top film called Scotchcal. See Middleton, No. 96-C6781, slip op. at 2, n. 3. Both the top film and the base film consist of a flexible plastic material backed with an adhesive. The top film is clear, and the base film may be either clear or white. FloorMinders is manufactured by sandwiching a customer's logo, message, or other graphic between the adhesive layer of the top film and the nonadhesive layer of the base film. The customer then applies FloorMinders in the desired location by adhering the adhesive surface of the base film to the floor. In its advertising brochures, 3M states that FloorMinders is durable for at least six months.
The only independent claim of the `514 patent at issue in this case is claim 4, which reads as follows:
1. On a floor having a flat top surface and an improved material for finishing the top surface of the floor, the improvement comprising:
at least one elongated sheet including a uniform flexible film of clear plastic material having a thickness between about one mil and about twenty-five mils and
a continuous layer of adhesive material disposed between the top surface of the floor and the flexible film, the adhesive layer releasably adhering the flexible film onto the top surface of the floor. `514 patent, col. 6, line 66 - col. 7, line 10 (emphasis added).
The district court held a Markman hearing to determine the proper scope of claim 4. After hearing arguments from counsel on both sides, the court construed the disputed elements as follows:
Material for finishing: "a material that makes more durable the underlying surface of the floor, and is applied for that purpose."
Uniform flexible film: "the material must be of a uniform thickness, and excludes material in which there are any variations in thickness." See Middleton, Inc. v. Minnesota Mining & Manufacturing Co., No. 96-C6781, slip op. ...