The Doctrine of Equivalents: Becoming a Derelict on the Waters of Patent Law

• Publication year: 2021

84 Nebraska L. Rev. 1113. The Doctrine of Equivalents: Becoming a Derelict on the Waters of Patent Law

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Charles W. Adams(fn*)

The Doctrine of Equivalents: Becoming a Derelict on the Waters of Patent Law

TABLE OF CONTENTS

I. Introduction ...................................................... 1113
II. The Central Definition and Peripheral Definition
Systems .......................................................... 1116
III. A Vestige of the Central Definition System in 35 U.S.C.
§ 112 ¶ 6 ....................................................... 1121
IV. Development of the Doctrine of Equivalents ....................... 1122
A. Winans v. Demead .............................................. 1122
B. Graver Tank ................................................... 1123
C. Warner-Jenkinson .............................................. 1128
D. Festo ......................................................... 1136
V. The Current Law of the Doctrine of Equivalents and Its
Future Prospects .................................................. 1149
VI. Conclusion ....................................................... 1156

I. INTRODUCTION

In the field of patent law, the doctrine of equivalents extends the scope of a patent beyond its literal language to cover inconsequential variations of a patentable invention. Although the doctrine of equivalents introduces undesirable uncertainty into the scope of patent protection, both the United States Supreme Court and the Court of Appeals for the Federal Circuit have repeatedly reaffirmed the doctrine. Nevertheless, the doctrine of equivalents is in decline. The Supreme Court significantly limited the doctrine twice in the last ten years,(fn1) and two recent en banc decisions of the Court of Appeals for

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the Federal Circuit(fn2) have further restricted the doctrine. In its most recent case, the Supreme Court grounded its rationale for the doctrine in the limitations of language.(fn3) Ironically, this rationale presages further restrictions on the doctrine because it suggests that the doctrine is not needed, except in rare cases when language is incapable of demarcating the scope of patent protection. Thus, the doctrine of equivalents appears destined to become a "derelict on the waters of the law."(fn4)

The patent statutes confer on a patentee the exclusive right to make, use or sell a patented invention in the United States for a twenty year term.(fn5) An exclusive right to make, use or sell a patented invention is not necessarily an economic monopoly, however. Even though a patentee may have an exclusive right to an invention, the patentee will not have an economic monopoly if there are alternatives to the invention that are practical substitutes for it.(fn6) For a patent to confer a monopoly that has economic value to its owner, its claims must cover not only the particular device or process the inventor developed but all of the substitutes for it as well so that "there is no alternative way for competitors to provide the same economic functionality to their customers without infringing the claims."(fn7) Otherwise, the patent will have no more value to its owner than a publication in a technical journal.(fn8)

The claims of a patent are analogous to the metes and bounds in a legal description of real property, and they stake out the intellectual property that the patent covers. The scope of the claims a patentee is entitled to is limited both by previous discoveries (i.e., the prior art) and by the inventor's contributions. In order to be patentable, an invention must be novel,(fn9) and therefore, a claim that intrudes on prior

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art is invalid. A claim is also invalid if it goes beyond what the inventor actually created and disclosed in the patent application.(fn10)

However, patent claims are permitted to cover variations of the invention, even though the inventor did not produce physical embodiments of them, if they would be apparent from the written description of the invention in the patent application to a hypothetical person of reasonable skill in the inventor's field.(fn11) For example, if the inventor made a working model out of balsa wood, the claim might state that the device was constructed of wood; or more generally, of a carbonbased material; or more generally still, of a rigid material. The claim might even omit any limitation on materials used to construct the device so that the claim would extend to any material so long as the claim satisfies the novelty requirement and it would be apparent to a person of reasonable skill in the inventor's field how to make the device from any material based upon what was disclosed in the patent application.

It is the responsibility of the patent attorney to draft claims that not only are valid but also cover variations of the invention so that they provide meaningful protection. There are a variety of reasons, however, why patent claims may fail to cover every variation of the invention that would be apparent to a person of reasonable skill in the inventor's field. The most obvious is that the claims drafter may not foresee all the variations that would be apparent to a person of reasonable skill in the inventor's field. Another reason is that the claims drafter may inadvertently omit an obvious variation or include an unnecessary limitation in the claims as a result of a mistake. Alternatively, a patent attorney may narrow a broad claim by amendment during the patent prosecution process in response to a patent examiner's rejection of the claim. Finally, it is conceivable that variations that are apparent with the benefit of hindsight may not have been foreseeable to a person of reasonable skill in the inventor's field at the time the patent application was filed.

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The doctrine of equivalents expands the scope of patent protection in some circumstances to cover variations of the invention that are not within the literal terms of the claims. While there is no statutory basis for the doctrine of equivalents, and it has been characterized as an anomaly,(fn12) the Supreme Court has repeatedly reaffirmed the doctrine over the past 150 years.(fn13) Although the Supreme Court and the lower federal courts continue to recognize the doctrine of equivalents, they have not clearly defined the circumstances in which it is available, nor demarcated the extent to which it expands the scope of patent protection. The consequent lack of certainty has adverse consequences for both patentees and their competitors because determining whether potentially competing products are infringing may require an expensive jury trial with the risk of damages and injunctive relief. A major source of this uncertainty is the fact that neither the Supreme Court nor the lower federal courts have articulated a convincing rationale for the doctrine of equivalents.

This Article provides a critical analysis of the doctrine of equivalents. In Part II, the Article describes the evolution of American patent law from central claiming to peripheral claiming. Next, Part III discusses a statutory vestige of central claiming that is found in paragraph 6 of section 112 of title 35 of the United States Code for particular types of claims having a combination of elements. Part IV surveys the four leading Supreme Court cases addressing the doctrine of equivalents and discusses the limitations these cases have placed on the doctrine. Part V summarizes the current law and discusses future prospects for the doctrine of equivalents.

II. THE CENTRAL DEFINITION AND PERIPHERAL DEFINITION SYSTEMS

Patents have not always included claims. The earliest patent statute in the United States, the Patent Act of 1790, required only a

specification in writing, containing a description, accompanied with drafts or models . . . which specification shall be so particular, and said models so exact, as not only to distinguish the invention or discovery from other things before known and used, but also to enable a workman or other person skilled in the art or manufacture, whereof it is a branch, or wherewith it may be nearest connected, to make, construct, or use the same, to the end that the public may have the full benefit thereof, after the expiration of the patent term.(fn14)

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In the absence of claims, the invention was defined using a central definition system.(fn15) The patent contained only a description of a particular embodiment of the invention, and the courts extended patent protection to all equivalent embodiments.(fn16) Under a central definition system, a doctrine of equivalents was needed to prevent competitors from copying the invention but avoiding infringement by making minor changes to the particular embodiment described.

Although it was not necessary under a central definition system to describe variations of an invention in order to define it more broadly, there was nothing to prevent an applicant from doing so. Describing variations of an invention in the patent application might facilitate a court's later finding infringement if a defendant produced one of the variations. Also, defining an invention broadly in the patent application served to give better notice of the scope of the invention to the public than setting out only the single embodiment that the inventor had made. For example, a patent from 1799 included the following expansive language: "The drawings accompanying this description are not laid down by any scale of measurement because the forms, sizes, and the proportions of the whole and its parts may be indefinitely varied."(fn17) The first claims appeared in Robert Fulton's patent for a steamboat.(fn18)

The earliest statutory reference to claims appeared in the Patent Act of 1836, which provided that an inventor "shall particularly specify and point out the part, improvement, or combination, which he claims as his own...