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Narrow Claiming and the Scope of Equivalents

  • Mar 2001
  • Article
  • Intellectual Property Today, Vol. 8, No. 3, March 2001, page 22


"I meant what I said

And I said what I meant....".[2]

Federal Circuit decisions over the past five years have shown that what is meant in a patent as the scope of the invention can in some circumstances actually be found in the claims. A court can find, even in the absence of limiting prosecution history or prior art, a limited scope of equivalents for narrowly drawn claims. A stark demonstration of the limiting effect of narrow claim language is found in the recent decision in Moore U.S.A., Inc. v. Standard Register Co.[3], where the Federal Circuit held that 47.8% is not an equivalent of a claimed "majority" (i.e., 50.001%+).

Under the doctrine of equivalents, a product or process that does not literally infringe upon the express terms of a patent claim may nonetheless be found to infringe if there is "equivalence" between the elements of the accused product or process and the claimed elements of the patented invention.[4]Equivalence is a question of fact[5] based on insubstantial differences between the accused product or process and the claimed elements.[6] The essential inquiry is whether the accused product or process contains elements identical or equivalent to each claimed element of the patented invention.[7] The doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole.[8] The doctrine of equivalents cannot effectively eliminate an element in its entirety.[9] The prosecution history[10] of a patent and the prior art[11] both serve as legal limits to the scope of equivalents.

The doctrine of equivalents, when applied broadly, conflicts with the definitional and public-notice functions of the statutory claiming requirement.[12] There is an inherent conflict between the role of the doctrine of equivalents in preventing a 'fraud on the patent' and the primacy of the claims in defining the scope of a patentee's exclusive rights.[13]

Over the past five years the Federal Circuit has issued a series of decisions developing a framework for restricting the scope of equivalents based on narrow claim language. In one approach, the Federal Circuit has focused on whether embodiments disclosed, but not claimed, were "distinct" enough from claimed embodiments to exclude the unclaimed embodiments as equivalents. In a second approach, the Federal Circuit has relied on the "foreseeability" of the limiting potential of "clear structural limitations" to limit equivalents. In a third approach, the Federal Circuit in an unpublished opinion relied on "clear definite numerical limitations". The Federal Circuit used all three approaches, either explicitly or implicitly, in reaching the Moore decision.

Embodiments that are "distinct", but not claimed

The 1996 Federal Circuit decision in Maxwell v. J. Baker, Inc.[14] (Lourie, Skelton and Schall) signaled that "subject matter disclosed by not claimed in a patent application is dedicated to the public".[15] The Maxwell patent concerns fastening tabs in shoes. A plastic filament passing through the fastening tabs keeps a pair of shoes together for display in stores. The patent disclosed and claimed a first embodiment in which a portion of a fastening tab was positioned between the inner and outer soles on the bottom of the shoe. In addition, the patent disclosed, but did not claim, an alternative embodiment in which the fastening tab was stitched into a lining seam of the shoes at the sides or back of the shoes. Because the patent did not claim the alternative embodiment, the Federal Circuit found that Maxwell dedicated the alternative embodiment to the public.

In 1998 the Federal Circuit in YBM Magnex Inc. v. International Trade Commission[16] (Rich, Smith and Newman) clarified the Maxwell decision and indicated that a patent disclosing two distinct embodiments, while claiming only one, could not enforce the unclaimed embodiment as an equivalent of the embodiment that was claimed.[17] Thus, the YBM Magnex court reasoned that in Maxwell a fastening tab attached to the bottom of a shoe and a fastening tab attached to the side of a shoe were distinct embodiments. Because only one of these distinct embodiments was claimed, the other was dedicated to the public.

In YBM Magnex, in contrast to Maxwell, the Federal Circuit declined to find distinct embodiments. YBM was the owner of a patent with claims directed to "[a] permanent magnet alloy consisting essentially of, in weight percent, ... 6,000 to 35,000 ppm oxygen ... ." The patent disclosed, but did not claim, oxygen contents in the range between 5,450 and 6,000 ppm. The Federal Circuit found that Maxwell did not foreclose, as a matter of law, application of the doctrine of equivalents to encompass oxygen contents of 5,450 to 6,000 ppm.

The utility of the "distinct, but not claimed, embodiment" approach to limiting the scope of equivalents of narrow claims is questionable at present. What makes one embodiment "distinct" and another not? Until the Federal Circuit defines a "distinct embodiment", instead of simply concluding the existence of more than one, the approach provides little guidance to the public. Interestingly, while Judge Newman authored the YBM Magnex opinion advancing the "distinct, but not claimed, embodiment" approach, in the Moore decision (discussed below) Judge Newman dissented against the panel majority's finding of a distinct, unclaimed embodiment dedicated to the public.[18] It would appear that what now passes as a "distinct embodiment" is in the eye of the beholder.

"Foreseeable" limiting potential of "clear structural limitations"

The second approach to limiting the scope of equivalents of narrow claims is found in the 1997 Federal Circuit decision in Sage Products Inc. v. Devon Industries Inc.[19] (Mayer, Rader and Schall). This approach focuses on the "foreseeable" limiting potential of "clear structural limitations". In Sage Products, the Federal Circuit affirmed a summary judgment that an accused medical waste disposal container with two interior constrictions and a slot between the two interior constrictions is not an equivalent of a disposal container with "an elongated slot at the top of the container body" and "a barrier means comprising a first constriction extending over said slot". After finding that the limitation "top" meant "highest point" and the limitation "over" meant "above", the Federal Circuit concluded that each of the patentee's theories of infringement by equivalents would improperly eliminate at least one limitation from the claims.

The Federal Circuit emphasized that:

"Because this issued patent contains clear structural limitations, the public has a right to rely on those limits in conducting its business activities. This court will not remove such a limitation under a doctrine designed to prevent 'fraud on a patent'".[20] (emphasis added)

"...[A]s between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the cost of his failure to seek protection for this foreseeable alteration of its claimed structure."[21] (emphasis added)

"For a patentee who has claimed an invention narrowly, there may not be infringement under the doctrine of equivalents in many cases, even though the patentee might have been able to claim more broadly. If it were otherwise, then claims would be reduced to functional abstracts, devoid of meaningful structural limitations on which the publish could rely."[22] (emphasis added).

Thus, in Sage Products, the Federal Circuit found that "clear structural limitations" with foreseeably narrow meanings could restrict the scope of equivalents. However, the Federal Circuit provided little guidance to the public regarding what is, and is not, clearly structural and "foreseeable".

In Tanabe Seiyaku Co. v. International Trade Commission[23] (Plager, Schall and Bryson), the Federal Circuit affirmed a decision by the ITC that an accused process did not infringe a claim directed to a method of preparing a benzothiazeprine derivative. The Federal Circuit concluded that in Tanabe Seiyakuthe accused process using butanone (CH3-CH2-CO-CH3) was not an equivalent of the claimed process using acetone (CH3-CO-CH3). The relevant limitation recited "acetone", which is a species of the genus "lower alkyl ketone". Because "lower alkyl acetate" was disclosed in the specification, the Federal Circuit reasoned that the skilled artisan would know that the patentee could have used the term "lower alkyl ketone" to describe a class of ketone solvents including butanone and acetone, if the patentee had so intended. Because the patentee did not due so, but instead sharply restricted the claims, the scope of equivalents was correspondingly narrow.[24] Thus, in Tanabe Seiyaku the Federal Circuit indicated that reciting a narrow chemical species in a claim, when use of a broader chemical genus including the species is foreseeable, will exclude compounds falling within the genus other than the species from the scope of equivalents of the species.

In Overhead Door Corp. v. Chamberlain Group Inc.[25] (Michel, Rader and Schall) the Federal Circuit did not find "clear structural limitations" that would limit equivalents. In Overhead Door, the Federal Circuit overruled a summary judgment that a software-driven memory selection system was outside the scope of equivalents of a hardware memory selection switch as a matter of law. The Federal Circuit found that the district court's reliance on Sage Productswas inappropriate because the patent at issue did not contain any clear structural limitations that would preclude a reasonable jury from finding a software system to be equivalent to the claimed hardware. In contrast to the situation in Sage, application of the doctrine of equivalents to cover the accused software did not vitiate the "memory selection switch" element.[26]

In Zodiac Pool Care Inc. v. Hoffinger Industries Inc.[27] (Bryson, Skelton and Gajarsa), the Federal Circuit affirmed a judgment as a matter of law that an accused pool cleaning system did not include an equivalent of a stop, for preventing upward flexing of a peripheral edge of a flexible disc surrounding a water inlet, that was "substantially inward of the peripheral edge". The Federal Circuit refused to consider function/way/result issues in view of "clear structural limitations" present in the claims and absent in the accused system. Relying heavily on Sage Products, the Federal Circuit found that no reasonable jury could find that an accused stop which extends to the peripheral edge of a disk is equivalent to one that is "substantially inward" of the very same disk.[28] To the Federal Circuit, the two stops were "not even close".[29] Thus, in Zodiac Pool Care the Federal Circuit reiterated its decision in Sage Products that clear structural limitations alone can limit the scope of equivalents.

In Vehicular Technologies Corp. v. Titan Wheel International Inc.,[30] (Plager, Clevenger and Rader, per curiam) the Federal Circuit affirmed a summary judgment that, as a matter of law, an accused spring assembly including a single spring and a plug fitted into the spring and bearing against a pin is not the equivalent of a "spring assembly consisting of two concentric springs bearing against one end of [a] pin". The Federal Circuit found that the claimed two spring assembly performed a key backup function that was not performed by the accused device. However, rather than considering differences in this function on the scope of equivalents, the court focused on the requirement in the claim that two springs be present. While acknowledging that the recitation "consisting of" did not foreclose infringement by equivalents, the court felt that this recitation emphasized that, to infringe by equivalents, an infringing structure had to include two springs. In a concurring opinion, Judge Rader likened Vehicular Technologies Corp. to Sage Products, Inc., finding that a skilled patent drafter would have readily seen the limiting potential of the "consisting of two concentric springs" limitation as excluding from equivalents structures with fewer than two springs. Judge Rader had little sympathy for the patentee, who had learned of the accused infringement during the two year period allowed for reissuing, but failed to amend the claims to cover the accused single spring device.

Clear, definite numerical limitations

A third approach limiting the scope of equivalents of narrow claims is found in the March 31, 1998, Federal Circuit decision in Brunswick Corp. v. U.S.[31](Mayer, Newman and Clevenger)(unpublished), prior to the YBM Magnex decision on May 27, 1998, discussed above. The Brunswick court assertedly followed the holding in Maxwell that "subject matter that is disclosed in the specification, but not claimed, is dedicated to the public". The Brunswick majority affirmed a finding by the U.S. Court of Federal Claims that certain unmodified polyester/steel cloth screens did not infringe a patent directed to radar camouflage screens under the doctrine of equivalents.

In Brunswick, the claimed camouflage included an electrically resistive layer having, at radio frequencies exceeding 2000 MHz, "a surface resistivity falling between a lower limit of 100 ohms and an upper limit of 1,000 but considerably different from 377 ohms".

However, in following Maxwell, the Brunswick majority focused on the limiting nature of the claims. Without being explicit, the panel majority appeared to be focusing on differences in how numerical ranges are claimed to decide whether or not the numerical limitations limit the scope of equivalents.

"Nor do we understand the rule of Maxwell, supported by the broad concept of dedication to the public of disclosed but unclaimed matter, to be any less applicable to a case in which a clear, definite numerical limitation is placed on a claimed range than to a case in which an alternative configuration of an article is disclosed but not claimed. In any event, this case certainly does not mean that all subject matter outside the literal claims, of whatever nature, is dedicated to the public in all situations."[32] (emphasis added).

Thus, while ostensibly following Maxwell, the panel majority appeared to find that a "clear, definite numerical limitation" can, by itself, limit the scope of equivalents of a numerical limitation, much the same as Sage Products found that a "clear structural limitation" can, by itself, limit the scope of equivalents of a structural limitation. Although the scope of equivalents sought by Brunswick included surface resistivities disclosed in the specification, because the accused product was outside the definite limits recited in the claim, the panel majority found no infringement by equivalents. Thus, in Brunswick the recitation of "lower limit" and "upper limit" limited numerical equivalents to the recited range. The majority contrasted "lower limit" and "upper limit" with less definite limitations such as "relatively small", "about" and "approximately", which presumably do not limit numerical equivalents.[33]

The Moore decision

The three approaches discussed above came together in the September 22, 2000, decision Moore U.S.A., Inc., v. Standard Register Company[34] (Newman,Michel and Clevenger). In Moore, the Federal Circuit affirmed a summary judgment that an accused mailer type business form, with adhesive running 47.8% of the length of margin, did not, as a matter of law, infringe by equivalents a claim in which the adhesive extended a "majority" of the length of the margin.

In emphasizing the second approach ("foreseeable" limiting potential of "clear structural limitations" from Sage) to limiting the scope of equivalents of narrow claims, the court focused on the foreseeable narrowness of the claimed "majority".

"If our case law on the doctrine of equivalents makes anything clear, it is that all claim limitations are not entitled to an equal scope of equivalents. Whether the result of the All Limitations Rule [citation omitted], prosecution history estoppel [citation omitted], or the inherent narrowness of the claim language [citation omitted], many limitations warrant little, if any, range of equivalents.

In this case, we hold that the applicant's use of the term "majority" is not entitled to a scope of equivalents covering a minority for at least two reasons. First, to allow what is undisputedly a minority (i.e. 47.8%) to be equivalent to a majority would vitiate the requirement that the "first and second longitudinal strips of adhesive ... extend the majority of the length of said longitudinal marginal portions." [citation to '464 patent omitted]. If a minority could be equivalent to a majority, this limitation would hardly be necessary, since the immediately preceding requirement of a "first and second longitudinal strips of adhesive disposed in said first and second longitudinal marginal portions, respectively, of said first face" would suffice. Second, it would defy logic to conclude that a minority --- the very antithesis of a majority --- could be insubstantially different from a claim limitation requiring a majority, and no reasonable juror could find otherwise."[35] (emphasis added)

The court also applied the first approach ("distinct, but unclaimed, embodiments" from Maxwell (as clarified in YBM Magnex)) to limiting the scope of equivalents of narrow claims:

"[W]hile Moore argues that the written description's teaching that the length of the first and second strips may be about "half of the length" of the longitudinal marginal portions gives rise to a scope of equivalents that would cover a "minority," our case law reveals that Moore is mistaken. In Maxwell v. J. Baker, Inc. [citation omitted], we explained the contrary principle the "subject matter disclosed in the specification, but not claimed, is dedicated to the public" in determining infringement under the doctrine of equivalents. Id. at [citation omitted]. Having fully disclosed two distinct embodiments, one in which the first and second longitudinal strips extend a majority of the length of the longitudinal marginal portions, and one in which they do not, Moore is not entitled to "enforce the unclaimed embodiment as an equivalents of the one that was claimed." YBM Magnex, Inc. v. International Trade Comm'n [citation omitted].[36] (emphasis added)

The third approach ("clear, definite numerical limitations" from Brunswick) to limiting equivalents is also implicit in Moore, because the structure at issue in the accused product was no different than the structure featured in the claim. Both structures were strips of adhesive. Only the numbers associated with the lengths of the strips were different.

Thus, the Moore decision marked the coming together of the three approaches used in recent years by the Federal Circuit to limit equivalents of narrow claims. Particularly remarkable in Moore is the majority's willingness, despite the disclosure of adhesive strips running less than a majority of the margin, to draw a clear distinction between 47.8% and 50+%, and to exclude 47.8% from the Moore invention, based on Moore's choice of "majority" as an explicit claim limitation.

What will be hatched in the future ?

The recent decisions culminating in Moore show that the Federal Circuit is willing to find legal limits on the scope of equivalents based solely on the narrowness of claim limitations. The narrow limitations can be structural or numerical.

What the Federal Circuit will, and will not, consider to be a "clear structural limitation" with "foreseeable" limiting potential remains to be seen.

On the other hand, the cases provide some guidance regarding what the Federal Circuit will consider to be a "clear, definite numerical limitation" that limits the scope of equivalents.

It appears that the Federal Circuit will restrict equivalents of claim limitations asserting, for whatever reason, an abrupt boundary to a range of numbers defining an invention. The assertion of an abrupt boundary can be found in the explicit or implicit use of imperative claim language.

For example, in Moore the limitation "majority", which cannot encompass a minority, implicitly means "no less than greater than 50%". The imperative "no less than" means that anything "less than" is outside the invention.

Similarly, in Brunswick the recitation of lower and upper "limits" expresses a imperative that anything outside the bounds set by the limits is outside the invention.

In light of Brunswick and Moore, it appears that the Federal Circuit will probably find that imperative claim language (explicit or implicit) such as "no less (greater) than", "not less (greater) than" and "at least (most)" (which is similar in tone and meaning to "not less (greater) than") will sharply limit equivalents, much like Moore's "majority". To find an equivalent outside the range defined by one of these imperative limitations would impermissibly eliminate from a claim the imperative feature of the limitation.

What numerical language will not limit equivalents? Brunswick's comparison of a lower "limit" and an upper "limit" with inexact terms such as "relatively small", "about" and "approximately" indicates that inexact limitations such as "from about A to about B" do not limit numerical equivalents. YBM Magnex, e.g., confirms that an explicit recitation of a numerical range such as "from A to B" also does not limit equivalents. Because claim language such as "less (greater) than A" replaces "less(greater) than" for the B end of a range "from A to B", without asserting anything about the A end of the range, claim language such as "less (greater) than A" should not limit equivalents of the A endpoint. Thus, the recitation of a numerical range without expressing an imperative should not limit the scope of numerical equivalents.

Thus, it appears that substitution of "greater than 50%" for the "majority" limitation in Moore would have avoided the sharply restricted scope of equivalents accorded the Moore claims.

Following Moore, it becomes even more important that the claim drafter say in the claim what the drafter means, and mean what the drafter says, so that the drafter remains "faithful one hundred per cent" to whatever has been invented.

Published in Intellectual Property Today, Vol. 8, No. 3, March 2001, page 22.