A Primer on Indefiniteness and Means-Plus-Function
|Written by Gene Quinn
Patent Attorney & Founder of IPWatchdog, Inc.
Principal Lecturer, PLI Patent Bar Review Course Posted: April 18, 2012 @ 6:10 pm
Over the last several weeks I have been rather irritated by two algorithm cases decided by the United States Court of Appeals for the Federal Circuit. See Show me the Algorithms and CAFC Kills Means-Plus-Function. In these cases the Federal Circuit was determining the validity of software patent claims written in “means-plus-function” style, which is authorized pursuant to 35 U.S.C. 112, ¶ 6. Essentially, means-plus-function claiming allows the drafter to claim the invention based on the functionality rather than the more traditional (and preferred) claim technique that employs structure within the body of the claim itself.
A claim term is functional when it recites a feature by what it does rather than by what it is. There is nothing intrinsically wrong with the use of such claim language, although it is becoming more and more apparently (if it wasn’t already apparent enough) that the Federal Circuit frowns upon means-plus-function claiming.
Nevertheless, § 112, ¶6 expressly authorizes a form of functional claiming (means-plus-function claiming). The statute says:
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.
The basic law relative to § 112, ¶6 explains that a decision on whether a claim is indefinite under § 112, ¶ 6 requires a determination of whether those skilled in the art would understand what is claimed when the claim is read in light of the specification. Traditionally, claim terms are typically given their ordinary and customary meaning as understood by one of ordinary skill in the pertinent art. The question with means-plus-function claiming, however, is whether evidence from that mythical individual skilled in the art is even admissible. No structure in the specification means the person of skill in the art cannot save the disclosure by understanding. Thus, means-plus-function claims are largely valid at the mercy of a federal judge who in all certainty is not one of skill in the art and who likely has an aversion to such claiming techniques because they prefer dealing with tangible structure.
So how do you know when you will get hit with the peculiar disclosure requirements invoked when you rely upon § 112, ¶6? If a claim limitation recites a term and associated functional language, the examiner should determine whether the claim limitation invokes § 112, ¶ 6. The claim limitation is presumed to invoke § 112, ¶ 6 when it explicitly uses the phrase “means for” or “step for” and includes functional language. That presumption is overcome when the limitation further includes the structure necessary to perform the recited function.
By contrast, a claim limitation that does not use the phrase “means for” or “step for” will trigger the rebuttable presumption that§ 112, ¶ 6 does not apply. This presumption is a strong one that is not readily overcome. However, § 112, ¶ 6 will not apply if persons of ordinary skill in the art reading the specification understand the term to be the name for the structure that performs the function, even when the term covers a broad class of structures or identifies the structures by their function. The term is not required to denote a specific structure or a precise physical structure to avoid the application of § 112, ¶ 6 .
What is important is whether the term is one that is understood to describe structure, although it might not bring to mind any particular structure. For example, the court in Personalized Media Communications held that the term “detector,” although broad, is still structural for purposes of § 112, ¶ 6 because it is not a generic structural term such as “means,” nor is it a coined term lacking a clear meaning. Similarly, in Lighting World, Inc. v. Birchwood Lighting, Inc., the Federal Circuit held the term “connector assembly” means a unit that joins, fastens, or links each pair of adjacent support members. The fact that more than one structure may be described by the term “connector assembly,” or even that the term may encompass a multitude of structures, does not make it any less a name for structure.
When the claim limitation does not use the phrase “means for” or “step for,” it is necessary to determine whether the claim limitation uses a nonstructural term (i.e., a term that is simply a substitute for the term “means for”). Examiners will apply § 112, ¶ 6 to a claim limitation that uses a nonstructural term associated with functional language, unless the nonstructural term is (1) preceded by a structural modifier, defined in the specification as a particular structure or known by one skilled in the art, that denotes the type of structural device, or (2) modified by sufficient structure or material for achieving the claimed function.
The following is a list of non-structural terms that may invoke § 112, ¶ 6 : “mechanism for,” “module for,” “device for,” “unit for,” “component for,” “element for,” “member for,” “apparatus for,” “machine for,” or “system for.” This list is not exhaustive, and other non-structural terms may invoke § 112, ¶ 6 .
The following are examples of structural terms that have been found not to invoke § 112, ¶ 6 : “circuit for,” “detent mechanism,” “digital detector for,” “reciprocating member,” “connector assembly,” “perforation,” “sealingly connected joints,” and “eyeglass hanger member.”
A limitation will not invoke § 112, ¶ 6 if there is a structural modifier that further describes the non-structural term. For example, although a nonstructural term like “mechanism” standing alone may invoke § 112, ¶ 6 when coupled with a function, it will not invoke § 112, ¶ 6 when it is preceded by a structural modifier (e.g., “detent mechanism”). By contrast, when a non-structural term is preceded by a non-structural modifier that does not have any generally understood structural meaning in the art, the phrase may invoke § 112, ¶ 6 when coupled with a function (e.g., “colorant selection mechanism,” “lever moving element,” or “movable link member”).
To determine whether a word, term, or phrase coupled with a function denotes structure, it is necessary to check whether: (1) The specification provides a description sufficient to inform one of ordinary skill in the art that the term denotes structure; (2) general and subject matter specific dictionaries provide evidence that the term has achieved recognition as a noun denoting structure; and (3) the prior art provides evidence that the term has an art-recognized structure to perform the claimed function.Examiners will apply § 112, ¶ 6 to a claim limitation that meets the following conditions: (1) The claim limitation uses the phrase “means for” or “step for” or a non-structural term that does not have a structural modifier; (2) the phrase “means for” or “step for” or the non-structural term recited in the claim is modified by functional language; and (3) the phrase “means for” or “step for” or the non-structural term recited in the claim is not modified by sufficient structure, material, or acts for achieving the specified function.
When it is unclear whether a claim limitation invokes § 112, ¶ 6 or not, a rejection under § 112, ¶ 2 may be appropriate. Similarly, when applicant uses the phrase “means for” or “step for” in the preamble, a rejection under § 112, ¶ 2 may be appropriate when it is unclear whether the preamble is reciting a means (or step) plus function limitation or whether the preamble is merely stating the intended use of the claimed invention. If applicant uses a structural or nonstructural term with the word “for” in the preamble, the examiner should not construe such phrase as reciting a means-plus-function limitation.
Once the examiner determines that a claim limitation is a means-plus-function limitation invoking § 112, ¶ 6, the examiner should determine the claimed function and then review the written description of the specification to determine whether the corresponding structure, material, or acts that perform the claimed function are disclosed. The disclosure must be reviewed from the point of view of one skilled in the relevant art to determine whether that person would understand the written description to disclose the corresponding structure, material, or acts. To satisfy the definiteness requirement under § 112, ¶ 6 , the written description must clearly link or associate the corresponding structure, material, or acts to the claimed function. A rejection under § 112, ¶ 2 is appropriate if the written description fails to link or associate the disclosed structure, material, or acts to the claimed function, or if there is no disclosure (or insufficient disclosure) of structure, material, or acts for performing the claimed function. A bare statement that known techniques or methods can be used would not be a sufficient disclosure to support a means-plus-function limitation.
A rejection under § 112, ¶ 2 may be appropriate in the following situations when examining means-plus-function claim limitations under § 112, ¶ 6 : (1) When it is unclear whether a claim limitation invokes § 112, ¶ 6 ; (2) when § 112, ¶ 6 is invoked and there is no disclosure or there is insufficient disclosure of structure, material, or acts for performing the claimed function; and/or (3) when § 112, ¶ 6 is invoked and the supporting disclosure fails to clearly link or associate the disclosed structure, material, or acts to the claimed function.
When the examiner cannot identify the corresponding structure, material, or acts, a rejection under § 112, ¶ 2 should be made, thus rendering the means-plus-function claim indefinite. If the written description sets forth the corresponding structure, material, or acts in compliance with § 112, ¶2, the claim limitation must be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.
So what should you do? Time and time again in patent practice you are always better off filing the most complete disclosure you possibly can at the earliest date possible. Describe things generally and build to ever more specific embodiments and alternative descriptions, explaining all the variations and possibilities with as much detail as you possibly can. This is the winning approach even if you do not use means-plus-function claims, but it is absolutely essential if you are going to use means-plus-function claims.
Should you avoid means-plus-function claims? The answer is no, not really. Means-plus-function claiming is an excellent way to make sure that you have captured within the claims all of the various means disclosed in the application. Claiming all the possible permutations can be costly, so using a couple of means-plus-function claims in an attempt to have the claim scope as broad as the disclosure may be a very good strategy. Means-plus-function claims cannot, however, be the primary claims and for goodness sakes don’t file patent applications with only means-plus-function claims. Means-plus-function should be used like a seasoning — such as a very powerful garlic! A little may be OK but too much is a poor choice.- - - - - - - - - -
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About the Author
Gene Quinn is a Patent Attorney and the founder of the popular blog IPWatchdog.com, which has for three of the last four years (i.e., 2010, 2012 and 2103) been recognized as the top intellectual property blog by the American Bar Association. He is also a principal lecturer in the PLI Patent Bar Review Course. As an electrical engineer with a computer engineering focus his specialty is electronic and computer devices, Internet applications, software and business methods.