U.S. Means-Plus-Function Claims

March 7, 2000
HARAKENZO World Patent & Trademark
(Takamasa ARAI)

Although means-plus-function language is expressly authorized in the Patent Act, 35 U.S.C. §112, sixth paragraph, the scope and proper interpretation of means-plus-function language may be difficult to determine and even controversial at times.
Here, the means-plus-function Claims will be explained by citing an article ("Taking the Mystery Out of Means-Plus-Function Claims" Vol. 13, Issue 2, Fall 1999) written by Darin Bartholomew, a patent attorney of BIRCH, STEWART, KOLASCH & BIRCH, LLP, a patent attorney.

1. In re Al-Site
In Al-Site Corp. v. VSI International Inc ., 50 U.S.P.Q.2d 1161 (Fed. Cir. 1999), a claim recites "fastening means." The specification defined the fastening means as a rivet or the combination of a button and a hole. The specification did not make reference an "adhesive (adhering member)" as the fastening means.

The Federal Circuit sustained the jury's finding that "adhesive (e.g., glue) was a literal equivalent of the rivet or a button and a hole under 35 U.S.C. §112(6)." Thus, the Federal Circuit affirmed a finding of literal infringement of the alleged infringing device.

2. In re Chiuminatta
In Chiuminatta Concrete Concepts Inc. v. Cardinal Industries Inc ., 46 U.S.P.Q.2d 1752 (Fed. Cir. 1998), a claim recites "means ... for supporting the surface of the concrete." The specification defined the means for supporting as a flat "skid plate."
The alleged infringing device used rollers, instead of the skid plate, to perform a similar, but not identical , function.

The Federal Circuit concluded that the patentee was not entitled to an interpretation of the means-plus-function language that included both the rollers and skid plate, because the specification did not disclose or suggest that the claimed means included rollers.

There was no hint in the specification that the skid plate could be replaced by small wheels adjacent to the blade for supporting the concrete. Moreover, the specification discussed the use of rollers for another purpose of supporting and stabilizing the saw, as opposed to supporting the concrete. Thus, the Federal Circuit held that the lower court erred in finding literal infringement under section 112(6) as a matter of law.

3. "interchangeability"
In interpreting literal equivalents under section 112(6), Chiuminatta and Al-Site both consider the interchan eability of the accused structural element and the claimed structural element.

In re Al-Site , the interchangeability was found to be dispositive of equivalency, perhaps because of the deference given to a jury's finding of infringement. In contrast, in re Chiuminatta interchangeability was held to be an important factor that was not dispositive of equivalency.	

4. Different
Outcomes in Chiuminatta and Al-Site Can the different outcomes in Chiuminatta and Al-Site be explained other than on the above procedural differences between a summary judgement and a jury finding? The fact such a question exists is more important than its ultimate answer.

Cases that interpret literal equivalents under section 112(6) show us that if the patent holder cannot rely on the express content of the specification to show infringement of means-plus-function language, means-plus-function claims may be interpreted in an unpredictable manner with inconsistent results.

Even if the underlying structure for a claimed means-plus-function element is functionally interchangeable with an allegedly infringing element, substantial structural differences between the underlying structure and the alleged structure may lead to a finding of no equivalents under 35 U.S.C. section 112(6).

It is preferable to apply the following techniques so that means-plus-function claims are favorably interpreted.

(a) Adding
lists of structural or procedural examples to define means-plus-function elements in claims.

(b) Using
claim differentiation to encourage certain broader claim interpretation.

(c) Taking
claims outside the scope of means-plus-function interpretational rules.

However, even though these techniques are applied, claims are not necessarily interpreted favorably. The foregoing techniques (a) to (c) will be detailed as follows.

(a) Adding
lists of structural or procedural examples Ordinary claims containing the word "means" in combination with a function require the court or party interpreting the claims to find structural equivalents in the specification that perform the same function as the means-plus-function language in the specification. Thus, the author of a patent application should provide an explicit definition of a means in the specification where the means is claimed. Further, the means may be equated to an illustrative list of possible alternative structural elements or procedures. At least one of the alternative structural elements should be featured in a drawing to facilitate comprehension of the invention.

Means-plus-function claims do not include all means for performing a given function that were outside of the inventors contemplation at the time of the application.
If the specification contains one or more examples of structures or procedures that meet the means-plus-function language of a claim, the attorney may be able to point to such examples and use them as a sound basis for comparison to any alleged infringing device or procedure. The examples can be open-ended to leave room for characterizing the invention as the infringing device within reasonable limits under the literal equivalents of section 112(6) and the doctrine of equivalents. The inventor is fully entitled to patentable subject matter that he discloses and expressly sets forth in his patent application; any patent rights that are enforceable beyond the scope of the express disclosure are best regarded as a matter of chance or luck.

Sometimes means-plus-function language is used like wallpaper that superficially hides holes in the structural walls of a patent application. Means-plus-function language should not be used as a church for not delving into the true technical substance of the invention. If no identifiable examples of the means-plus-function structures are included in the specification, a patent examiner, a potential licensee, or a fact-finder in a trial may become skeptical of the enforceability or the merits of the invention.

(b) Claim
Differentiation It is preferable to differentiate claim so as to realize a broader interpretation of means-plus-function language. Claim differentiation signifies that different claims in the same application or patent should be presumed to cover different inventions or a different scope of the same invention.

In the context of maximizing the scope of literal equivalents under section 112(6), claim differentiation is most useful where multiple examples of structure reading on the means plus function are presented in the specification.

The claim differentiation pointed out by Mr. Darin Bartholomew means that an invention should be interpreted not from a single point but from various points. Basically, it is difficult to interpret an invention from a single point. It may be preferable that an invention is interpreted from various points positively and is claimed so as to protect the invention more strongly.

b-1) Example
Showing Utility of Claim Differentiation Laitram Corp. v. Rexnord Inc ., 19 U.S.P.Q.2d 1367 (Fed. Cir. 1991) illustrates the potential significance for proper strategic use of claim differentiation. In Laitram, an independent claim was defined broadly with a means-plus-function feature that was further defined in structural terms in a dependent claim depending upon the independent claim.

The Federal Circuit held that a dependent claim which explains or defines a means-plus-function element in an independent claim may be read into the independent claim if no other structural variations of the means-plus-function limitation were set forth in the specification. However, the Federal Circuit did not foreclose the possibility of establishing literal equivalents of the independent claim where the claim differentiation doctrine yields to meet the statutory objectives of section 112(6).	

If application of the claim differentiation doctrine is appropriate and consistent with the statutory objectives of section 112(6), the broader independent claim should be interpreted as including something other than the particular structure disclosed in the narrower dependent claim. The patent attorney can use claim differentiation to his advantage by using a variety of dependent claims that further define the "means-plus-function" language of an independent claim. Alternately, the patent attorney can use claim differentiation to his advantage where the specification describes multiple alternative structures or procedures for the means-plus-function element in an independent claim, which is further defined in at least one dependent claim.

b-2) Example
Showing Limit of Claim Differentiation However, the utility of claim differentiation still may be limited by the scope of the original written description, in view of Gentry Gallery, Inc. v. Berkline Corp ., 45 U.S.P.Q.2d 1498 (Fed. Cir. 1998). That is, if limitative recitations are given in the description, claims are also interpreted to be limited.

In re Gentry Gallery , the patent in suit was directed to a sectional sofa having two reclining seats. One particular feature of the invention provided controls for the reclining seats on a console between the reclining seats. In contrast, the prior art provided such controls at the ends of the sofa.

The broadest claim was not expressly limited to having the recliner controls on a console. However, several dependent claims recited a sectional sofa in which the recliner control means were restricted to a console.

At trial, Gentry argued that the doctrine of claim differentiation established that the broadest claims covered more than recliner controls restricted to a console.

The Federal Circuit invalidates the broadest claim as being directed to an apparatus beyond the scope of the original specification, in violation of 35 U.S.C. §112, first paragraph. The Federal Circuit found that the written disclosure only disclosed sectional sofas having recliner controls located on a console between the reclining seats, and therefore did not support claims broader than that (i.e., claims in which the recliner controls are not located on a console). Therefore, claims which contain means-plus-function language must be supported adequately by the originally filed specification under 35 U.S.C., first paragraph, to take advantage of claim differentiation.

(c) Avoiding
Means-Plus-Function Interpretation Rules
Means-plus-function language brings in various interpretational doctrines that view as excessive baggage. To be free of such baggage, in some cases alternative functional language to means-plus-function wording may be used to fall outside of the scope of means-plus-function interpretation (the word "means" and the phrase "means for" should be avoided).

However, merely removing "means" is not necessarily a guarantee that a functionally expressed claimed element will not be interpreted under the rubric of a means-plus-function limitation.

Certain means-plus-function claims may receive more favorable treatment than others. If means-plus-function language is defined in a claim itself by structural limitations, no need may exist to refer to the specification for guidance in interpreting the claims.

However, if the structural limitations merely address incidental or collateral structural limitations without adequately defining the means-plus-function limitation, reference to the specification is warranted.

Thus, by defining means-plus-function limitation sufficiently by structural limitation, claims are interpreted clearly, so that the court may capture the broadest intent of the claimant.

It may be considered that the foregoing explanation given by Darin Bartholomew shows the following point.
That is, even if claims are made without using means-plus-function language (for example, merely a phrase "controller that controls..." is used instead of using a phrase "control means for controlling..."), there may occur a case where inadequate definition disclosed in the description brings about interpretation as in means-plus-function language (interpretation limited to the content disclosed in the description).
Further, even in the case where means-plus-function language is defined in a claim itself by structural limitation, there is no guarantee that the description is not referred to for guidance in interpreting the claim, so that it is preferable to make the description substantial in content as much as possible.
Thus, however a claim may be worded, it is preferable to equate the means to an illustrative list of possible alternative structural elements or procedures as much as possible. At least one of the alternative structural elements should be featured in a drawing to facilitate comprehension of the invention.

5. Relationship with "Equivalents" under the Doctrine of Equivalents
In Odetics, Inc. v. Storage Technology Corporation ., 51 USPQ2d 1225 (Fed. Cir. 1999), the Federal Circuit indicated some responses as to whether or not "equivalents" under the doctrine of equivalents and "equivalents" under 35 U.S.C. section 112(6) should be examined in the exactly same manner.

In re Odetics , the Federal Circuit presented some comparatively flexible rules described below so as to establish literal infringement of means-plus-function limitation. However, analysis of means-plus-function claim limitation under the doctrine of equivalents has not been completed yet in re Odetics , so that an indefinite legal area in U.S. Patent Law remains to be clarified.

5-1) Judgement on Equivalency of Means-Plus-Function Limitation
A Prescription in 35 U.S.C. section 112(6)
According to 35 U.S.C. section 112(6), claim limitation made by means-plus-function language should be interpreted so that the claim limitation contains a structure and its equivalents, corresponding to a function in claim, that are recited in the description.

A Literal
Infringement of Means-Plus-Function Limitation
To establish literal infringement of means-plus-function limitation in accordance with 35 U.S.C. section 112(6), an accused structure has to meet the following conditions.
(a) The accused
structure has the same function as a function recited in the claim, and
(b) the accused
structure is the same as a corresponding structure recited in the description, or is equivalent to the corresponding structure recited in the description.

A Whether
Judgement on Equivalency Is Required or Not as to Each Component
According to 35 U.S.C. section 112(6), it is not required to judge equivalency of respective components in two corresponding structures as a criterion to clarify whether or not an alleged structure is equivalent to a corresponding structure recited in the description.

In a structure recited in the description so as to correspond to claimed functions, an individual component itself is not limitation of claim. Claim limitation comprehends whole structure corresponding to claimed functions. Thus, even in a case where an accused structure is different from a corresponding structure recited in the description in the number of components, literal infringement of means-plus-function limitation can be established.

In Odetics , the Federal Circuit found it an error that the District Court had analyzed an equivalent structure of 35 U.S.C. section 112(6) by focusing on a component of a structure, recited in the description, that corresponds to "rotation means" according to claims. According to the Federal Circuit, as a criterion to specify an equivalent structure, it is not required to judge equivalency of respective components of a corresponding structure recited in the description and an accused structure that is argued to be equivalent in terms of a structure.

Instead of this, as a criterion to specify an equivalent structure, it is required to merely apply a rule, which concerns insubstantiality of differences between both the inventions, to a concrete structure under dispute. Thus, the Federal Circuit held that a legal basis on which the District Court had admitted JMOL (post-trial motion for Judgement as a Matter of Law) was error. Further, the Federal Circuit approved that there exists a substantial evidence supporting a jury's verdict of infringement. Thus, the Federal Circuit reversed the District Court's admittance of JMOL, and ordered that the jury's verdict should be revived.

5-2) As to "Equivalents" Based on the Doctrine of Equivalents and "Equivalents"
Based on 35 U.S.C. Section 112(6)

A Similarity of the Both The Federal
Circuit explains a relationship between an evaluation criterion to clarify an equivalent structure stated in 35 U.S.C. section 112(6) and an evaluation criterion to clarify infringement based on the doctrine of equivalents. According to this, the evaluation criteria of the both are similar to each other in that insubstantial differences are studied with respect to differences between the claimed invention and the alleged infringing device, but are not identical to each other.

A three-part-function test
There is a "three-part-function test" (three-element test to evaluate whether or not a claimed invention is identical to an alleged infringing device in terms of "function", "way", and "result") as the evaluation criterion to clarify infringement based on the doctrine of equivalents. If any one of these three elements is substantially different from a corresponding element of the claimed invention, infringement based on the doctrine of equivalents is not established.

	 A two-part-function test
In contrast, there is a "two-part-function test" (two-element test to evaluate whether or not an alleged infringing device is identical to a claimed invention in terms of "way" and "result") as the evaluation criterion to specify an equivalent structure stated in 35 U.S.C. section 112(6).

This evaluation criterion does not contain judgement on whether "function" is similar or not. This is because literal infringement on means-plus-function limitation is not established unless a function obtained by an accused structure is identical, not similar, to a function defined in claim.

Thus, in the case where respective differences are insubstantial in terms of "method" and "result", the structure is judged to be equivalent. In other words, if the accused structure performs the completely same function in the substantially same manner as a structure recited in the specification, the accused structure is regarded as equivalent under 35 U.S.C section 112(6).

[Referential documents]
(1) BSKB NEWS
("Taking the Mystery Out of Means-Plus-Function Claims" written by Darin Bartholomew, Vol. 13, Issue 2, Fall 1999)

(2) U.S. Patent
Judgement News 5 ("Comparatively flexible rule with respect to literal infringement on means-plus-function claim limitation", AIPPI (1999) Vol. 44, No.12, pages 694 to 699)