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2184 Determining Whether an Applicant Has Met the Burden of Proving Nonequivalence After a Prima Facie Case Is Made [R-11.2013]

The specification need not necessarily describe the equivalents of the structures, material, or acts corresponding to the means-(or step-) plus-function claim element. See In re Noll, 545 F.2d 141, 149-50, 191 USPQ 721, 727 (CCPA 1976) (if the meaning of equivalents is well understood in patent law, then an applicant need not describe in his specification the full range of equivalents of his invention). Cf.Hybritech Inc. v. Monoclonal Antibodies, Inc., 802 F.2d 1367, 1384, 231 USPQ 81, 94 (Fed. Cir. 1986) (“a patent need not teach, and preferably omits, what is well known in the art”). Where, however, the specification is silent as to what constitutes equivalents and the examiner has made out a prima facie case of equivalence, the burden is placed upon the applicant to show that a prior art element which performs the claimed function is not an equivalent of the structure, material, or acts disclosed in the specification. See In re Mulder, 716 F.2d 1542, 1549, 219 USPQ 189, 196 (Fed. Cir. 1983).

If the applicant disagrees with the inference of equivalence drawn from a prior art reference, the applicant may provide reasons why the applicant believes the prior art element should not be considered an equivalent to the specific structure, material or acts disclosed in the specification. Such reasons may include, but are not limited to:

  • (A) Teachings in the specification that particular prior art is not equivalent;
  • (B) Teachings in the prior art reference itself that may tend to show nonequivalence; or
  • (C) 37 CFR 1.132 affidavit evidence of facts tending to show nonequivalence.

When the applicant relies on teachings in applicant’s own specification, the examiner must make sure that the applicant is interpreting the means- (or step-) plus- function limitation in the claim in a manner which is consistent with the disclosure in the specification. If the specification defines what is meant by “equivalents” to the disclosed embodiments for the purpose of the claimed means- (or step-) plus- function, the examiner should interpret the limitation as having that meaning. If no definition is provided, some judgment must be exercised in determining the scope of “equivalents.” Generally, an “equivalent” is interpreted as embracing more than the specific elements described in the specification for performing the specified function, but less than any element that performs the function specified in the claim. See, e.g., NOMOS Corp. v. BrainLAB USA Inc., 357 F.3d, 1364, 1368, 69 USPQ2d 1853, 1856 (Fed. Cir. 2004) (where only one embodiment is described, the corresponding structure is limited to that embodiment and equivalents thereof). To interpret means- (or step-) plus-function limitations as limited to a particular means (or step) set forth in the specification would nullify the provisions of 35 U.S.C. 112 requiring that the limitation shall be construed to cover the structure described in the specification and equivalents thereof. D.M.I., Inc.v.Deere & Co., 755 F.2d 1570, 1574, 225 USPQ 236, 238 (Fed. Cir. 1985).

The scope of equivalents embraced by a claim limitation is dependent on the interpretation of an “equivalent.” The interpretation will vary depending on how the element is described in the supporting specification. The claim may or may not be limited to particular structure, material or acts (e.g., steps) as opposed to any and all structure, material or acts performing the claimed function, depending on how the specification treats that question. See, e.g., Ishida Co. v. Taylor, 221 F.3d 1310, 55 USPQ2d 1449 (Fed. Cir. 2000) (The court construed the scope of a means-plus-function claim element where the specification disclosed two structurally very different embodiments for performing the claimed function by looking separately to each embodiment to determine corresponding structures. The court declined to adopt a single claim construction encompassing both embodiments since it would be so broad as to describe systems both with and without the fundamental structural features of each embodiment.).

If the disclosure is so broad as to encompass any and all structures, materials or acts for performing the claimed function, the claims must be read accordingly when determining patentability. When this happens the limitation otherwise provided by “equivalents” ceases to be a limitation on the scope of the claim in that an equivalent would be any structure, material or act other than the ones described in the specification that perform the claimed function. For example, this situation will often be found in cases where (A) the claimed invention is a combination of elements, one or more of which are selected from elements that are old, per se, or (B) apparatus claims are treated as indistinguishable from method claims. See, for example, In reMeyer, 688 F.2d 789, 215 USPQ 193 (CCPA 1982); In reAbele, 684 F.2d 902, 909, 214 USPQ 682, 688 (CCPA 1982); In re Walter, 618 F.2d 758, 767, 205 USPQ 397, 406-07 (CCPA 1980); In reMaucorps, 609 F.2d 481, 203 USPQ 812 (CCPA 1979); In reJohnson, 589 F.2d 1070, 200 USPQ 199 (CCPA 1978); and In reFreeman, 573 F.2d 1237, 1246, 197 USPQ 464, 471 (CCPA 1978).

On the other end of the spectrum, the “equivalents” limitation as applied to a claim may also operate to constrict the claim scope to the point of covering virtually only the disclosed embodiments. This can happen in circumstances where the specification describes the invention only in the context of a specific structure, material or act that is used to perform the function specified in the claim.


When deciding whether an applicant has met the burden of proof with respect to showing nonequivalence of a prior art element that performs the claimed function, the following factors may be considered. First, unless an element performs the identical function specified in the claim, it cannot be an equivalent for the purposes of 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph. Pennwalt Corp.v.Durand-Wayland, Inc., 833 F.2d 931, 4 USPQ2d 1737 (Fed. Cir. 1987), cert. denied, 484 U.S. 961 (1988).

Second, while there is no litmus test for an “equivalent” that can be applied with absolute certainty and predictability, there are several indicia that are sufficient to support a conclusion that one element is or is not an “equivalent” of a different element in the context of 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph. Indicia that will support a conclusion that one element is or is not an equivalent of another are set forth in MPEP § 2183.


In determining whether arguments or 37 CFR 1.132 evidence presented by an applicant are persuasive that the element shown in the prior art is not an equivalent, the examiner should consider and weigh as many of the above-indicated or other indicia as are presented by applicant, and should determine whether, on balance, the applicant has met the burden of proof to show nonequivalence. However, under no circumstance should an examiner accept as persuasive a bare statement or opinion that the element shown in the prior art is not an equivalent embraced by the claim limitation. Moreover, if an applicant argues that the means- (or step-) plus-function language in a claim is limited to certain specific structural or additional functional characteristics (as opposed to “equivalents” thereof) where the specification does not describe the invention as being only those specific characteristics, the claim should not be allowed until the claim is amended to recite those specific structural or additional functional characteristics. Otherwise, a claim could be allowed having broad functional language which, in reality, is limited to only the specific structure or steps disclosed in the specification. This would be contrary to public policy of granting patents which provide adequate notice to the public as to a claim’s true scope.


Finally, as in the past, applicant has the opportunity during proceedings before the Office to amend the claims so that the claimed invention meets all the statutory criteria for patentability. An applicant may choose to amend the claim by further limiting the function so that there is no longer identity of function with that taught by the prior art element, or the applicant may choose to replace the claimed means- (or step-) plus-function limitation with specific structure, material or acts that are not described in the prior art.



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Last Modified: 02/16/2023 12:58:21