1. The Halliburton case (US Supreme Court, 1946):

1. Claim:
   means associated with said pressure responsive device for tuning said receiving means to the frequency of echoes from the tuning collars of said tuning section to clearly distinguish the echoes of said couplings from each other.

2. Court's opinion:
   the patentee should be limited to claiming his specific means (a tuned acoustical pipe) rather than all possible means.

2. The amended patent law (1952):

35 USC section 112, paragraph 6 (paragraph 3 at 1952).

3. From 1953 to 1994:

When making a determination of patentability under 35 U.S.C. 102 or 103, past practice was to interpret a "means or step plus function" limitation by giving it the "broadest reasonable interpretation." Under the PTO's long-standing practice this meant interpreting such a limitation as reading on any prior art means or step which performed the function specified in the claim without regard for whether the prior art means or step was equivalent to the corresponding structure, material or acts described in the specification

4. The Donaldson case (CAFC, 1994):

The "broadest reasonable interpretation" that an examiner may give means-plus-function language is that statutorily mandated in paragraph six. Accordingly, the PTO may not disregard the structure disclosed in the specification corresponding to such language when rendering a patentability determination.

1. Basis: 35 USC section 112, paragraph 6:

"An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof."

2. Referring to the specification

1. Imputing limitations from the specification into the claims is not required, but rather requires construing a limitation already in the means-plus-function clause by properly referring to the specification for the meaning of a particular word.

3. No "magic word"

1. There is no special language necessary for a claim to fall within the scope of section 112. Using the guideline, no longer must the word "means" be used at all. Any object, called "means", "device", "apparatus" or even a specific noun, like "doorknob", followed by language of any sort suggesting it performs a function "so as to", "for", "such that" would meet the guideline.

1. a jet driving device so constructed and located on the rotor as to drive the rotor . . . ["means" unnecessary]. (Ex parte Stanley, 1958)
   The term "device" coupled with a function is a proper definition of structure in accordance with the last paragraph of 35 U.S.C. 112. The addition of the words "jet driving" to the term "device" merely renders the latter more definite and specific.

2. "printing means" and "means for printing" which would have the same connotations. (Ex parte Klumb, 1967)

3. force generating means adapted to provide . . . (De Graffenreid v. United States, 1990)

4. call cost register means, including a digital display for providing a substantially instantaneous display for . . . .(Intellicall Inc. v. Phonometrics, Inc.,1992)

5. reducing the coefficient of friction of the resulting film [step plus function; "step" unnecessary] (In re Roberts, 1973)

6. raising the pH of the resultant pulp to about 5.0 to precipitate . . . .(Ex parte Zimmerley, 1966)
   In the event that it is unclear whether the claim limitation falls within the scope of 35 U.S.C. 112, sixth paragraph, a rejection under 35 U.S.C. 112, second paragraph may be appropriate.

4. Factors to be considered in deciding equivalence

1. 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, sixth paragraph.

2. Among the indicia that will support a conclusion that one element is or is not an equivalent of another are:

1. Whether the prior art element performs the function specified in the claim in substantially the same way, and produces substantially the same results as the corresponding element disclosed in the specification. (The concepts of equivalents as set forth in Graver Tank are relevant to any "equivalents" determination.)

2. Whether a person of ordinary skill in the art would have recognized the interchangeability of the element shown in the prior art for the corresponding element disclosed in the specification.

3. Whether the prior art element is a structural equivalent of the corresponding element disclosed in the specification being examined. That is, the prior art element performs the function specified in the claim in substantially the same manner as the function is performed by the corresponding element described in the specification.

4. Whether there are insubstantial differences between the prior art element and the structure, material or acts disclosed in the specification.

3. Relationship to the Doctrine of Equivalents:

The Doctrine of Equivalents equitably expands exclusive patent rights. One is not restricted to a specific structure that may be claimed or to any or all of the structures in the specification, but can find equivalents anywhere.
In contrast, section 112, paragraph 6 limits the broad language of means-plus-function limitations in combination claims to what is disclosed, plus equivalents of the structures, materials, or acts in the specification.

5. Single Means Claim

1. A single means claim does not comply with the enablement requirement of 35 U.S.C. 112, first paragraph:
   " The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention."

2. A possible problem in this area is with an improvement or a Jepson-type claim, where, in the body of the claim, a single new element might be claimed that cooperates with several old elements in the preamble to make up a complete machine or apparatus.
   It is thought that such a claim is truly a claim to a combination, so that the body of the claim following the Jepson transition phrase could properly consist of a single means expression.
   However, there may be some difference of opinion on that score, so it might be good tactics to put at least one other element, means or otherwise, in the body of the claim.

1. Recite various alternatives in the specification

1. To broaden the scope of a "means" limitation in a claim at the time the specification is being prepared, the claim writer should expressly recite in the specification various alternatives which may be considered for features to be claimed in "means" limitations.

2. But including those alternatives also opens up the "means" limitation to the possibility that numerous equivalent alternatives exist.

2. In the specification , describe the function claimed

1. Another technique for broadening the scope of a "means" limitation is to describe in the specification the part or element of an object that performs the function claimed, possibly also indicating that part is a means for performing a function.

3. Put at least two elements in the body of the claim.

1. It might be good tactics to put at least one other element, means or otherwise, in the body of the claim.

4. Employing qualifying expressions

1. In writing means clauses, as many qualifying words or expressions should be employed in the means clause as are necessary to limit the claim to the scope desired.

2. Where no such qualifying expressions are important, none should be used.

5. Use exact statutory language

1. It is recommended that one use the exact statutory language "means for…(performing an act)" rather than the possibly equivalent expressions permitted or deemed as falling under section 112, paragraph 6, because the statute only recites "means" or "step" and a court interpreting a claim may follow the statutory words and not follow the Patent Office guidelines or might hold that the Patent Office guidelines do not apply to the particular claim limitation then under review.

6. Avoid "double inclusion"

1. Double inclusion: one element is included in the claim twice under two different names (discussed in section 21).

2. Although one should avoid the practice where possible, it is permissible to claim "means for [doing thing A], including means for [doing thing B]" if B is a part of A.

3. In referring back to a previously recited means element, later in the claim, one merely gives it a convenient distinctive name, such as "the container-reciprocation means".

4. The use of the definite article "the" (or "said") is also required, to avoid a double inclusion of the same element in the claim language.

5. Wherever possible, it is best to avoid identifying a means only as "first means", "second means", etc.

7. Avoid using means expression with generic terms

1. It is recommended that means expressions be avoided where there is a definite generic word of the same scope available and particularly where "means" is placed after the descriptive generic word.

8. About using "means" to claim a plurality of elements

1. Sometimes there may be one or more than one, or more than two of the same type of elements disclosed, and the claim writer does not wish to limit the claim to a particular number. Use of the noun "means" (or "step") following what then becomes the descriptive adjective may ease the reader's reference to the claimed means. But use of "means" in that clause is not needed. The word "comprising" or the equivalent in the claim preamble encompasses the full range of numbers of the recited elements.

2. There are occasions where use of the word "means" following the noun is not only sensible, it is the only apparent way to cover the full range of elements that accomplish the objective.

9. Use of the word "means" does not always constitute a "means-plus-function" clause

1. Merely adding "means" without reciting a function of that means does not convert the claim element into the element governed by 35 USC section 112, paragraph 6.

2. Use of the word "means" in a claim does not always constitute a "means-plus-function" clause. The term "means" as opposed to "means for", may be used in a non-means-plus-function claim, as when indicating a tool or device having a particular structure to carry out its intended function.

10. A "means" clause does not cover a human being.

11. No objection to having one element as a part of two different means

1. There is no objection to having one or more specific elements of structure included as a part of two different means clauses, as long as the entire train of parts to perform each function is not identical.

2. If the disclosure has truly one completely indivisible element for performing both functions, then classic textbook law is that he cannot make the claim to separate means bacause of double inclusion, or double reading of elements.