Key Mfg. Group, Inc. v. Microdot, Inc.

• Decision Date: 13 February 1991
• Docket Number: No. 90-1342,90-1342
• Citation: 925 F.2d 1444,17 USPQ2d 1806
• Parties: KEY MANUFACTURING GROUP, INC., Plaintiff-Appellee, v. MICRODOT, INC., Defendant-Appellant.
• Court: U.S. Court of Appeals — Federal Circuit

Page 1444

925 F.2d 1444

17 U.S.P.Q.2d 1806

KEY MANUFACTURING GROUP, INC., Plaintiff-Appellee, v. MICRODOT, INC., Defendant-Appellant.

No. 90-1342.

United States Court of Appeals, Federal Circuit.

Feb. 13, 1991.

Rehearing Denied March 15, 1991.

Jerold I. Schneider, Spencer & Frank, Washington, D.C., argued, for plaintiff-appellee. With him on the brief was Catherine M. Voorhees.

Kenneth J. Jurek, Mayer, Brown & Platt, Chicago, Ill., argued, for defendant-appellant. With him on the brief was Rosanne J. Faraci.

Before PLAGER and RADER, Circuit Judges, and FRIEDMAN, Senior Circuit Judge.

RADER, Circuit Judge.

The United States District Court for the Eastern District of Michigan adjudged Microdot, Inc. (Microdot) liable for infringement of reexamined United States Patent No. B1-4,123,961 ('961 patent) owned by Key Manufacturing Group, Inc. (Key). The district court held that Microdot's capped wheel nuts infringe the '961 patent claims literally and under the doctrine of equivalents. Key Mfg. Group, Inc. v. Microdot, Inc., 15 USPQ2d 1195 (E.D.Mich.1990). This court reverses.

BACKGROUND

Both Key and Microdot manufacture capped wheel nuts used to attach a wheel to a car axle. The wheel nuts have several sides or "wrench flats" to permit a tool to grasp the nut for tightening or loosening. The nut body has two faces. The nut face in direct contact with the wheel is the "wheel face." The opposite or exterior face is the "cap face."

The '961 patent discloses and claims a decorative nut and stainless steel cap for attachment to the nut body. The stainless steel cap has sides corresponding to the wrench flats. Welds secure the decorative cap to the cap face of the nut body. Claim 1 of the '961 patent reads as follows:

1. A decorative nut for holding a wheel on a motor vehicle and exposed to view on the wheel, said nut having a central threaded aperture, polygonal sides, a first end adapted to engage a wheel, a second end opposite said first end and having an end face extending at right angles to the axis of the nut, and a sheet metal cap for the nut and having a section extending over the polygonal sides of the nut and an end section adapted to cover the second end of the nut, said section extending over the polygonal nut sides including a plurality of cap wrench flats respectively associated with and oppositely facing said polygonal nut sides, said cap wrench flats and said polygonal nut sides being disposed between said first and second ends of said nut, said end section being connected to the section of the cap which covers the polygonal nut sides by a section formed fully around the perimeter of the cap and having an extension at right angles to the axis of the nut so as to be parallel to said end face, such connecting section being in juxtaposed contact throughout a substantial area with and welded to said end face, the position of welded contact between the connecting section and the end face resulting in shear forces being applied to the weld in response to the application of forces on the capped wrench flats which create moments about the central axis of the nut.

(Emphasis added.) The highlighted portion constitutes the disputed "at right angles" and "substantial area" claim language. The invention is illustrated in the '961 patent in part as follows:

NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLE

NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLE

NOTE: OPINION CONTAINS TABLE OR OTHER DATA THAT IS NOT VIEWABLE

Microdot's nut is similar in many respects to the '961 disclosed nut. It differs, however, in significant particulars. The '961 claims require "an extension" of the decorative cap "at right angles to the axis of the nut so as to be parallel to said end face." The cap face of Microdot's nut body and the cap itself have a fifteen degree outward taper. Key does not dispute this fact. Key asserts, however, that no technologically significant difference exists between Microdot's fifteen degree taper and Key's zero degree interface.

Another difference is the area of contact between the decorative cap and the nut. The '961 claims require "contact throughout a substantial area." Microdot argues that its cap is not in contact with the nut over a substantial area.

In 1987, Key sued Microdot for infringement of the '961 patent. After a bench trial, the district court upheld the validity of the '961 patent. The district court also concluded that the reexamined claims, as amended, and the original claims were identical within the meaning of 35 U.S.C. Secs. 252, 307(b) (1982). Finally, the district court concluded that Microdot's nuts literally infringed the '961 claims. Key Mfg. Group, Inc. v. Microdot, Inc., 679 F.Supp. 648, 4 USPQ2d 1687 (E.D.Mich.1987). The district court found literal infringement despite its conclusion that "[t]he Microdot capped wheel nuts differ[ ] from those of Key." Id. at 660, 4 USPQ2d at 1697.

On appeal from that judgment, this court affirmed the validity holding, but vacated the infringement judgment. The district court had ignored some claim limitations. This court stated that "[a]ll claim limitations are significant and must be considered" in an infringement analysis. Under the doctrine of equivalents as well, "claim limitations cannot be ignored, and 'the plaintiff must show the presence of every element or its substantial equivalent in the accused device.' " Key Mfg. Group, Inc. v. Microdot, Inc., 854 F.2d 1328 (Fed.Cir.1988) (table) (opinion available on Westlaw) (citing Lemelson v. United States, 752 F.2d 1538, 1551, 224 USPQ 526, 533 (Fed.Cir.1985)). This court remanded for the district court to "provide sufficient factual findings on infringement to enable a meaningful review of the merits of its judgment." Id.

On remand, the district court addressed the claim limitations of "substantial area" and "at right angles to the axis of the nut". Key Mfg. Group, Inc. v. Microdot, Inc., 15 USPQ2d 1195 (E.D.Mich.1990). The district court determined that the "substantial area" limitation is met by a weld "sufficient to hold the cap and nut together in response to shear forces applied during the loosening or tightening of the wheel nut." Id. at 1199. The "right angles" limitation is met if "at least a portion of the weld" is at right angles to the axis of the nut. Id. at 1200.

The trial court thus concluded that Microdot's wheel caps infringed the '961 claims literally and under the doctrine of equivalents. With respect to "substantial area," the trial court opined that Microdot's wheel caps use welds with enough strength to resist shearing. Id. at 1201. Further, the district court found that at least a portion of the weld was at right angles to the axis of the nut. Thus, according to the trial court, Microdot literally infringed the '961 claims. Id. at 1202.

The district court concluded that the Microdot nuts also infringe under the doctrine of equivalents. The court opined that the "substantial area" language describes the function of holding the nut and cap together. Thus, the trial court decided that any contact area is equivalent "as long as the weld is placed in shear during the application of wrenching forces and retains the cap and nut together, as the patent teaches." Id. at 1203. The district court determined that Key added the "at right angles" language during prosecution merely to "clarify the location of the weld on the nut body and in contrast to the wrench flats," rather than to distinguish prior art. Id. Thus, even though Microdot's nut included

a taper, the district court granted Key "a range of equivalents which includes a fifteen degree taper...." Id. at 1204.

DISCUSSION

Claim Interpretation

The district court erred in interpreting claim 1. Before analyzing a claim to determine whether infringement occurs, the court must properly interpret the claim. Improper claim construction can distort the entire infringement analysis. Bausch & Lomb, Inc. v. Barnes-Hind/Hydrocurve, Inc., 796 F.2d 443, 450, 230 USPQ 416, 421 (Fed.Cir.1986), cert. denied, 484 U.S. 823, 108 S.Ct. 85, 98 L.Ed.2d 47 (1987). Claim interpretation is a question of law. Moleculon Research Corp. v. CBS, Inc., 793 F.2d 1261, 1270, 229 USPQ 805, 811 (Fed.Cir.1986), cert. denied, 479 U.S. 1030, 107 S.Ct. 875, 93 L.Ed.2d 829 (1987). While a factual dispute over the meaning of terms in a claim may arise, in this case there is no assertion that the words on which the issue of infringement turns have anything other than their common, ordinary meaning. See Howes v. Medical Components, Inc., 814 F.2d 638, 643, 2 USPQ2d 1271, 1273 (Fed.Cir.1987). Thus, in the absence of a factual issue, proper interpretation of claim 1 is a question of law freely reviewable by this court on appeal. See Durango Assocs. Inc. v. Reflange Inc., 843 F.2d 1349, 1356, 6 USPQ2d 1290, 1295 (Fed.Cir.1988).

The district court's interpretation of claim 1 conflicts with the claim's straightforward language as supported by the specification and file history. Further, its construction of claim 1 erased all the limitations which distinguished the '961 structure from the prior art. Claim 1 expressly requires the decorative cap to come into contact with the cap face of the nut body at right angles to the nut's axis. The district court found that Microdot's nut has a 15-degree taper on both the cap face and the cap itself. The district court cannot disregard this difference between...