Before Michel and Lourie, Circuit Judges, and Restani, Judge.*fn*
This case is an appeal and cross-appeal from a judgment entered November 8, 1991, in the United States District Court for the District of Oregon, Civil No. 88-1253-FR. Con-Vey/Keystone, Inc. (Con-Vey) filed suit against A M Industries, Inc. (AMI) claiming infringement of claims 9 and 10 of Con-Vey's U.S. Patent 4,640,655. AMI counterclaimed for a declaration of invalidity and non-infringement. The district court held that Con-Vey's patent was not infringed and was not invalid. We affirm.
The invention described and claimed in the '655 patent is a continuous breakdown hoist used to unload stacked tiers of lumber onto a conveyor belt for further processing. This hoist is more efficient than a standard breakdown hoist because the latter cannot feed lumber continuously, thereby experiencing a delay of twenty-five to forty seconds between the discharge of the final portion of a first load of lumber and the discharge of the first portion of the next load. The claimed invention eliminates this delay by having forks hold the load in place while movement of a skid continues to discharge the final portion of the first load. During this continuous discharge, the second load of lumber is so positioned that it can be immediately discharged after the first load.
Independent Claim 9 and dependent Claim 10 are the only claims in dispute. The relevant portion of Claim 9 is its last clause, which reads "means for moving the skid means and fork means relative to one another to move the tiers of a load supported by the fork means successively over the load-supporting elements, whereby the topmost tiers [slide] successively off the load and onto the skid elements."
The district court found that the specification and claims of the '655 patent describe tier-discharging means with skids that move relative to the accumulator forks and the frame of the machine. It further concluded that the claims describe accumulator forks that only move in and out of the load path rather than up and down along the load path. The court finally concluded that AMI's hoist lacked movable skid means and therefore did not infringe. Convey appeals this decision.
The parties dispute the scope of the phrase "moving the skid means and fork means relative to one another." Con-Vey argues that AMI infringes its claims because this phrase covers a hoist having a tier-discharge means that discharges tiers of lumber either by moving the skid means toward the fork means or by moving the fork means up toward the skid means. Con-Vey also argues that the district court improperly compared AMI's hoist to the preferred embodiments rather than to the claims of Con-Vey's patent and ignored the ordinary meaning of the word "relative."
Claim interpretation is a question of law which we review de novo. Specialty Composites v. Cabot Corp., 845 F.2d 981, 986, 6 USPQ2d 1601, 1604 (Fed. Cir. 1988). To determine the meaning of the claims, we review claim language, the specification, and any relevant prosecution history. ZMI Corp. v. Cardiac Resuscitator Corp., 844 F.2d 1576, 1579, 6 USPQ2d 1557, 1560 (Fed. Cir. 1988).
Claim 9 recites a means for moving skid and fork means relative to one another in such a way as to move tiers of the load over the load-supporting elements. It specifies a fork means as "means mounted on the frame for movement into and out of the load path." Upon review of the figures of the '655 patent, as well as the description, it is apparent that fork movement into and out of the load path does not cause the tiers of the load to move up and over the load supporting elements. The relative movement between the skid and fork means required by the claims must be produced by movement of the skid means along the load path while the fork means remains stationary. Therefore, we conclude that the district court was correct when it found that the proper interpretation of the claims is that the skid means must be movable along the load path to effect discharge.
Con-Vey also argues that the district court erred by considering only the preferred embodiments when determining the meaning of the claim language "moving the skid means and fork means relative to one another." Courts should not ignore any meaningful disclosure in a patent specification and focus only on preferred embodiments. However, when the preferred embodiments constitute the best indication of the meaning of claim language, which is not contradicted elsewhere in the specification, it is not error to use them in interpreting the claims. Thus, upon review of the record, we conclude that the district court did not err when it reviewed the patent specification, referred to both embodiments of the invention, and concluded that it is the tier-discharging means or skid means that moves along the path relative to the main frame to discharge the lumber.
Con-Vey also challenges the trial court's Conclusion of non-infringement. Literal infringement, infringement under the doctrine of equivalents, and determination whether an accused device is an equivalent under 35 U.S.C. § 112, P 6, are questions of fact which we review under the clearly erroneous standard. Durango Assocs., Inc. v Reflange, Inc., 843 F.2d 1349, 1357, 6 USPQ2d 1290, 1295 (Fed. Cir. 1988); see SRI Int'l v. Matsushita Elec. Corp. of Am., 775 F.2d 1107, 1125, 227 USPQ 577, 589 (Fed. Cir. 1985);
For literal infringement to exist, every element of a means-plus-function claim or its substantial equivalent must be found in an accused device. Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 934, 4 USPQ2d 1737, 1739-40 (Fed. Cir. 1987), cert. denied, 485 U.S. 961 (1988). The district court found that the AMI hoist does not have a moving skid means or the claimed "means for moving the skid means." Nor does it have any such means, according to § 112, P 6, equivalent in structure to that disclosed in the specification.
Con-Vey argues that under § 112, P 6, it is entitled by virtue of its means claim to a broader scope of protection than merely the disclosed embodiments. However, in determining the scope of equivalents to be given a means-plus-function claim, this court stated in Pennwalt Corp.:
Thus, it was not legal error (as Pennwalt asserts) for the district court to have made a comparison between Durand-Wayland's structure and the structure disclosed in the specification for performing a particular function. The statute means exactly what it says: To determine whether a claim limitation is met literally, where expressed as a means for performing a stated function, the court must compare the accused structure with the ...