Pennwalt Corporation v. Durand-Wayland, Inc.
833 F.2d 931 (1987)
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Rule of Law:
To find patent infringement under the doctrine of equivalents, the accused device must contain every element of a claim or its substantial equivalent. The absence of even a single element or its equivalent precludes a finding of infringement, as the analysis must be conducted on an element-by-element basis, not on the invention as a whole.
Facts:
- Pennwalt Corporation (Pennwalt) holds U.S. Patent No. 4,106,628 for an automatic sorter for items like fruit, which can sort by color, weight, or both.
- The patent specification describes a sorter using a 'hard-wired' network of discrete electrical components.
- The patent claims require a 'position indicating means' that continuously tracks the physical location of an item as it moves along a conveyor.
- This 'position indicating means' limitation was added during patent prosecution to distinguish the invention from the prior art.
- Durand-Wayland, Inc. (Durand-Wayland) manufactures and sells sorting machines that use a microprocessor and software to perform the sorting functions.
- Durand-Wayland's machines store an item's weight and color data in a memory queue, but do not continuously track the item's physical position on the conveyor.
- Instead of tracking physical location, Durand-Wayland's machine uses pointers to access the stored data when the item reaches a discharge point, which is a different operational method than that claimed by Pennwalt.
Procedural Posture:
- Pennwalt sued Durand-Wayland for patent infringement in the U.S. District Court for the Northern District of Georgia, a court of first instance.
- Following a nonjury trial, the district court entered a judgment finding Pennwalt's patent valid but not infringed, either literally or under the doctrine of equivalents.
- The district court awarded costs to Durand-Wayland but denied its motion for attorney fees.
- Pennwalt, as appellant, appealed the finding of noninfringement to the U.S. Court of Appeals for the Federal Circuit.
- Durand-Wayland, as cross-appellant/appellee, appealed the holdings on patent validity and the denial of its request for attorney fees.
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Issue:
Under the doctrine of equivalents, does a device that omits a specific function recited in a patent claim, or performs that function in a substantially different way, infringe the patent?
Opinions:
Majority - Bissell
No. A device that omits even one function recited in a patent claim, or fails to perform its substantial equivalent, does not infringe under the doctrine of equivalents. The doctrine is not a tool to erase meaningful structural and functional limitations of a claim upon which the public is entitled to rely. Infringement requires an element-by-element analysis, where the plaintiff must show the presence of every claim element or its substantial equivalent in the accused device. Here, the district court correctly found that Durand-Wayland's sorter did not perform the same function as Pennwalt's claimed 'position indicating means,' nor did it perform an equivalent function. Pennwalt's patent specifically requires a means for 'continuously indicating the position of an item,' a limitation added to secure patentability. Durand-Wayland’s machine, which stores data in memory queues without tracking the item's physical location, performs a substantially different function. Because this claimed function is missing from the accused device and no equivalent is substituted, there can be no infringement under the doctrine of equivalents.
Dissenting - Bennett
Yes. The majority's rigid element-by-element comparison is little more than a redundant literal infringement inquiry that renders the doctrine of equivalents unduly restrictive and inflexible. Supreme Court and Federal Circuit precedent, particularly in cases like Graver Tank and Hughes Aircraft Co. v. United States, require applying the doctrine of equivalents to the 'claimed invention as a whole.' The majority's approach effectively overrules this precedent sub silentio and elevates form over substance, allowing an infringer to escape liability by making insubstantial changes. The substitution of a microprocessor and software for hard-wired circuitry to perform the same overall sorting function is precisely the kind of technological update that the doctrine should cover. The district court should have determined whether the accused device, viewed as a whole, performed substantially the same function in substantially the same way to achieve the same result, rather than ceasing its inquiry upon finding a difference in a single claim element.
Analysis:
This landmark in banc decision firmly established the 'all elements' or 'element-by-element' rule as the controlling framework for the doctrine of equivalents in patent law. By rejecting a more holistic 'invention as a whole' analysis, the court significantly narrowed the doctrine's scope, making it more difficult for patentees to prove infringement against products that omit or alter even a single claimed feature. The decision strengthens the public notice function of patent claims, providing competitors with greater certainty when 'designing around' existing patents. However, it also sparked significant internal debate within the Federal Circuit, as reflected in the forceful dissent, setting the stage for future Supreme Court review of the doctrine's proper application.
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