In our July 1997 Newsletter (N.S. 188) we reported on the Supreme Court's decision on the doctrine of equivalents in Warner-Jenkinson v. Hilton Davis. Since then a number of cases in addition to the Gentry Gallery case have addressed the question of the proper scope of claims both for literal infringement and infringement under the doctrine of equivalents. Additionally guidance has been given on the interrelation of the doctrine of equivalents and the provisions of the sixth paragraph of 35 USC 112 which defines the scope of claims reciting combinations of various means plus functions.

In Warner-Jenkinson, the Supreme Court emphasized the roles of the "all elements" rule and the doctrine of prosecution history estoppel in considering whether there was infringement under the doctrine of equivalents.

In Ethicon Endo-Surgery Inc. v. United States Surgical Corp. the Court of Appeals for the Federal Circuit took pains to point out that the "all elements" rule was really an "all limitations rule" and that two different physical components may be viewed in combination to serve as an equivalent to a single limitation of the claim as long as no claim limitation was wholly vitiated by looking at the alleged infringement in this way.

In a subsequent decision, Sage Products Inc v. Devon Industries Inc., the Federal Circuit placed emphasis on the role of the claims as providing notice to the public as to the forbidden territory. The court noted "as 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 its failure to seek protection for foreseeable alteration of its claimed structure". In applying as the test of infringement an evaluation of whether or not the difference from the literal scope of the claims was "insubstantial", the court therefore declined to extend the scope of the claims to cover an alleged "equivalent". The claim was for a disposal container for hazardous waste, such as hypodermic needles, that required an elongated slot at the top of the container body and a constriction extending over the slot. In the alleged infringing device there was a constriction which was alleged to be equivalent to the slot of the patent claim but this was inside the container rather than at its top. The court saw no reason to read the claim without its "structural encumbrances"; had it done so then the PTO would have had to examine a claim directed to the invention as it was now argued to be and not to the specific device actually claimed. The court noted

In determining what is an "insubstantial" change from the literal wording of the claims, the courts may consider whether the change was itself patentable over the patent in suit. However, even if it is, this does not automatically exclude operation of the doctrine of equivalents. For example in Zygo Corp. v. Wyco Corp. the Federal Circuit held that "[t]he nonobviousness of the accused device as evidenced by the grant of a United States patent is relevant to the issue of whether the change therein is substantial". On the other hand in Hoechst Celanese Corp. v. BP Chemicals Ltd the court held that "the fact of separate patentability presents no legal or evidentiary presumption of non-infringement".

An old doctrine, which dates back to Miller v. Bridgeport Brass Co. in 1881, has recently been subject to review in Federal Circuit decisions namely that "subject matter disclosed but not claimed in a patent application is dedicated to the public". In Maxwell v. J. Baker Inc., the court stated that the doctrine is equally applicable to application of the doctrine of equivalents as it is to construing a claim in the context of an allegation of literal infringement. Subsequently, however, in YBM Magnex v. ITC, the court explained that no general rule of law was established in the Maxwell case, indeed any such rule would be contrary to the Supreme Court's holding in Graver Tank. However, where two distinct alternatives were described in the patent, but only one had been examined, it was proper to deny Maxwell the opportunity to enforce the unclaimed embodiment as an equivalent of the one that was claimed.

The sixth paragraph of 35 USC 112 specifically states that in a combination claim the elements of the combination may be defined in means plus function language, i.e. as "means for injecting steam into a reaction" rather than by definition of the nature of the means employed. The statute specifically states "such claim shall be construed to cover the corresponding structure, material or acts described in the specification, and equivalents thereof".

Exactly what is meant by "equivalent" in this section is, however, still not entirely clear since the Court of Appeals for the Federal Circuit has held that the tests employed in applying the broadening effects of the doctrine of equivalents may not apply to the application of paragraph 6 of 35 USC 112. The Federal Circuit addressed this issue in Chiuminatta Concrete Concepts Inc. v. Cardinal Industries Inc. as follows:

Although an equivalence analysis under §112, ¶6 and the doctrine of equivalents are not coextensive (for example §112, ¶6 requires identical not equivalent function) and have different origins and purposes, their tests for equivalence are closely related. Both protect the substance of the patentee's right to exclude by preventing mere colorable differences or slight improvements from escaping infringement. They do so by applying similar analyses of insubstantiality of the differences. There is an important difference, however, between the doctrine of equivalents and §112, ¶6. The doctrine of equivalents is necessary because one cannot predict the future. . . .[A] variant based on after-developed technology could not have been disclosed in the patent. Even if such an element is not found to be a §112, ¶6 equivalent because it is not equivalent to a structure disclosed in the patent, this analysis should not foreclose it from being an equivalent under the doctrine of equivalents.

The court held, however, that in the case of technology that was available at the time of the patent, if there is non-equivalence under 35 USC 112, ¶6, this will normally preclude a finding of equivalence under the doctrine of equivalents also. In subsequent cases such as Mas-Hamilton Group v. La Gard Inc. the court has emphasized that the important question to be decided is whether the structure of the alleged infringement is equivalent to what has been described in the patent, not whether the function is equivalent. The same case also pointed out that "means for" language was not always a necessary requirement of a claim before paragraph 6 of 35 USC 112 would be applied.

Simply using the word "means" without functional language, as was done for example in Cole v. Kimberly-Clark Corp. by use of the words "perforation means" in respect of perforations that were provided down the side of a diaper does not necessarily bring the claim within the terms of this section. However, where the word "means" was coupled with a word that implies a function such as "spray means", it was held to be governed by this provision in Unidynamics Corp. v. Automatic Products Int'l Ltd.