Expanding the Use of Hypothetical Analysis When Evaluating Patent Infringement Under the Doctrine of Equivalents
Publication year | 1993 |
I. Introduction
A patent is a grant to exclude others from making, using, or selling a claimed invention without the patent holder's permission.(fn1) The patent holder has the right to bring a civil action when she believes her patent has been infringed.(fn2) Defining the limits of a patent holder's right to exclude others from making, using, or selling the patented invention, however, has proved to be a formidable task. Early in American patent history, an equitable doctrine was established to provide a patent holder with a remedy against items that were practically, but not quite exactly, identical to the claimed invention.(fn3) This has become known as the doctrine of equivalents. The doctrine of equivalents method evaluates whether an item infringes on a patent when it is not precisely covered by the express language of the patent but is substantially the same.
The equitable nature underlying the doctrine of equivalents can be illustrated by a simple example. Imagine a world without paper clips of any sort. One day our hero, John Clip, while idly sitting at his desk, wraps a short length of wire around an eraser. The wire eventually drops from the eraser next to a stack of paper catching several pages together and Eureka! the paper clip is invented. Mr. Clip's patent claim reads: "I claim-A non-invasive paper fastening device comprising a piece of metal wire having three 180 U-bends, said bends all lying in a single geometric plane."
Much to his distress, Mr. Clip's financial success from the paper clip is undermined by Ms. Shiphty who, appreciating the commercial potential of the paper clip, sets out to manufacture an imitation that just avoids the patent claim language. She flanges the ends of the paper clip outward slightly, thus avoiding the "one plane" limitation of the patent. Mr. Clip cannot argue that Ms. Shiphty's device is exactly what he claimed because, in patent parlance, her device does not "read on" his patent.(fn4) Mr. Clip's right to exclude is so narrow that he will lose the benefit of his invention because Ms. Shiphty marginally circumvents the patent claim's express language. The doctrine of equivalents attempts to avoid such abuse of patent rights.(fn5)
Despite the obvious inequities involved in this example, the edges of the doctrine of equivalents are defined by closer cases, and the doctrine is frequently clarified by the Federal Circuit.(fn6) Among the more recent decisions attempting to clarify application of the doctrine of equivalents is
Accordingly, the purpose of this Comment is twofold: first, to bring the reader up-to-date on the doctrine of equivalents, and second, to suggest an improvement on the doctrine's application that is consistent with recent developments. This Comment proposes that the hypothetical technique should be expanded to evaluate more than prior art alone. Before exploring how this new use of the hypothetical would work, however, it is necessary to explain the doctrine of equivalents' history, the factors that affect the range of equivalents, and the methods to determine and apply equivalents.
II. Origin of the Doctrine of Equivalents
The doctrine of equivalents appeared in the United States over one hundred years ago,(fn11) and the United States Supreme Court first applied the doctrine in
While
The policy set out in
In spite of such arguments, both
III. Limitations on the Permissible Range of Equivalents
Four sources of information limit the range of equivalents that a patentee may be allowed to obtain: the patent, the prosecution history of the patent,(fn26) the prior art related to the patent, and the degree to which the invention is of a pioneering nature.(fn27)
A court should begin an infringement analysis by looking at the face of the patent.(fn28) The patent claim defines the literal limits of what the patent holder may exclude others from making, using, or selling. Claim construction is a matter of law for the court to decide.(fn29) A patent also has a specification that describes the invention and methods for making it and using it. The patent specification is secondary to the claim, and while it may help a court understand what is claimed, it cannot be the basis for limiting the range of equivalents.(fn30) The patent claim and patent specification work together to define the maximum range of equivalents. Only after a court interprets the patent, concludes that no literal infringement exists, and determines that finding the patent not infringed may be unfair to the patentee, may the court evaluate the patent under the doctrine of equivalents.(fn31)
Under this doctrine, a court should first look to the patent's prosecution history.(fn32) Prosecution history is the history of a patent's evolution from the first version of the patent submitted to the Patent and Trademark Office (PTO) to the patent as issued.(fn33) Where the patentee has made concessions to the patent examiner in the way of restrictions in language of claims to obtain the patent, these concessions or restrictions may be used to limit the patentee.(fn34) In particular, in a subsequent infringement action, the patentee is prevented or estopped from asserting claim interpretations that encompass the...
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