Chapter §2.05 Specialized Claiming Formats

• Jurisdiction: United States

§2.05 Specialized Claiming Formats

In addition to the basic claiming techniques described above, U.S. patent claiming practice recognizes a number of specialized formats. The use of each specialized format is at the option of the claims drafter. Choice of claiming format can significantly impact the interpretation and scope of the claim in both ex parte examination and patent infringement litigation. Some of the most common specialized claiming formats are "means-plus-function" claims, "product-by-process" claims, Jepson claims, Markush claims, and Beauregard claims. Each format is discussed below.

[A] Means-Plus-Function Claims

[1] Functional Claiming Generally

Functional claiming refers generally to the notion of claiming an invention by what it does rather than what it is in terms of physical structure. For example, one might functionally claim a "means for fastening part A to part B" rather than reciting a specific structure such as "a nail" or "a screw." In the pharmaceutical arts, one might functionally claim "administering a therapeutically effective amount of drug X to a patient" rather than reciting a specific numerical dosage of X.⁴²⁰

[2] Statutory Basis: 35 U.S.C. §112(f)

Section 112(f) of the Patent Act governs a particular type of functional claiming.⁴²¹ The statute provides that an element in a patent claim for a combination (of two or more elements) can be claimed in terms of what the element does, rather than what its structure is. The claim expresses the element as a generic "means" that performs a recited function, without reciting any structure to perform the function. In other words, "[m]eans-plus-function claiming applies only to purely functional limitations that do not provide the structure that performs the recited function."⁴²²

Since the 1980s the use of means-plus-function claiming has declined precipitously,⁴²³ most probably because the Federal Circuit has made clear that means-plus-function elements operate to narrow (rather than expand) claim scope.⁴²⁴ Nevertheless, means-plus-function claiming remains a standard technique that is quite commonly encountered. Although means-plus-function claiming is used more frequently in claiming mechanical or electrical inventions than for chemical or biotechnological inventions, all patent practitioners need to understand the origins and operation of means-plus-function claiming.⁴²⁵

The historical backdrop of means-plus-function claiming is grounded in judicial disfavor of functional claiming as an instrument of overreaching by inventors. The U.S. Supreme Court in 1946 prohibited functional claiming at the exact point of novelty in Halliburton Oil Well Cementing Co. v. Walker.⁴²⁶ However, Congress statutorily overruled the Halliburton prohibition by enacting then ¶3 of 35 U.S.C. §112 in the 1952 Patent Act. Today, the means-plus-function claiming provision appears as the sixth and final paragraph of 35 U.S.C. §112 (renamed 35 U.S.C. §112(f) by the America Invents Act of 2011):

(f). Element in Claim for a Combination.—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. ⁴²⁷

Speaking as an en banc court in 2015, the Federal Circuit observed in Williamson v. Citrix Online, LLC,⁴²⁸ that

[i]n enacting this provision, Congress struck a balance in allowing patentees to express a claim limitation by reciting a function to be performed rather than by reciting structure for performing that function, while placing specific constraints on how such a limitation is to be construed, namely, by restricting the scope of coverage to only the structure, materials, or acts described in the specification as corresponding to the claimed function and equivalents thereof. See Northrop Grumman Corp. v. Intel Corp., 325 F.3d 1346, 1350 (Fed. Cir. 2003). ⁴²⁹

Several rules can be distilled from the statutory language. First, because the statute speaks of "[a]n element in a claim for a combination," the use of "single means claims"—that is, claims reciting only a single element expressed in means-plus-function terms—is prohibited. However, claims reciting two or more elements are permitted even though each element may be expressed in means-plus-function format. Thus, a claim (in its entirety) to a "widget comprising a means for fastening A to B" is not permitted, but a claim to a "widget comprising A, B, and means for fastening A to B" is. Similarly, a claim reciting a "widget comprising a means for [function X] and a means for [function Y]" is permissible because the claim includes more than one means-plus-function element.

More commonly, a claims drafter will use the means-plus-function format as a convenient shorthand technique to express those elements that can be performed by many different types of structures or devices. All such structures or devices need not be explicitly disclosed in the patent application, so long as at least one "corresponding structure" is clearly identified in the written description.⁴³⁰ In this manner, a claim can cover a relatively large number of possible structures without the patent application becoming excessively detailed.

For example, a claim to an athletic shoe might recite:

1. An athletic shoe comprising:

(i) a left upper portion,

(ii) a right upper portion,

(iii) a sole portion integrally connected to said left upper portion and to said right upper portion, and

(iv) means for detachably fastening said left upper portion to said right upper portion.

This claim includes four elements. Elements (i) through (iii) are structural elements—they recite physical items. Element (iv) is expressed in means-plus-function form, because it recites a generic "means" for performing a function, in this case the function of "detachably fastening said left upper portion to said right upper portion," without reciting any structure (such as shoe laces) that could be used to perform the fastening function.

[3] The Interpretation and Scope of Means-Plus-Function Elements

[a] Scope-Narrowing

If the athletic shoe claim in the example above was construed on its face without reference to the statutory language of 35 U.S.C. §112(f), one might conclude that the means element (iv) would read on (i.e., literally encompass) any and every possible structure in the universe that would perform the recited fastening function. Given the breadth of such a claim, it might be attacked as indefinite under 35 U.S.C. §112(b) (and possibly as non-enabled under 35 U.S.C. §112(a)).

However, because element (iv) is expressed in means-plus-function form (that is, reciting a generic "means" for performing a stated function without reciting any actual structure to perform the function), it must be interpreted in accordance with 35 U.S.C. §112(f). Because this statutory provision operates to narrow the scope of the claim, as explained below, paragraph 6 likely saves the claim from indefiniteness. On the other hand, the scope-narrowing effect of §112(f) can also result in a finding of noninfringement.

[b] Corresponding Structure

The critical last clause of §112(f) mandates that a means element in a patent claim "shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof."⁴³¹ This mandatory language requires reference to the written description portion of the patent to interpret the scope of a means-plus-function element in a claim. The written description portion of the patent (and/or the patent's drawings) must disclose the "corresponding structure" (or corresponding "material" or "acts") for the "means" (or "step") recited in the claim.

If the written description and/or drawings fail to adequately disclose the corresponding structure for the claim-recited "means," this failure renders the claim indefinite under §112(b).⁴³² As explained in In re Donaldson Co.:⁴³³

[a]lthough paragraph six [of 35 U.S.C. §112] statutorily provides that one may use means-plus-function language in a claim, one is still subject to the requirement [of 35 U.S.C. §112, ¶2] that a claim "particularly point out and distinctly claim" the invention. Therefore, if one employs means-plus-function language in a claim, one must set forth in the specification an adequate disclosure showing what is meant by that language. If an applicant fails to set forth an adequate disclosure, the applicant has in effect failed to particularly point out and distinctly claim the invention as required by the second paragraph of section 112. ⁴³⁴

As an example of adequately disclosed corresponding structure, assume that the written description portion of the athletic shoe patent in the above example⁴³⁵ stated that "a pair of shoe laces can be used to detachably fasten the left upper portion of the shoe to the right upper portion," and that the drawings of the patent depicted the use of shoe laces. The recited means for fastening in element (iv) of the claim would be interpreted in accordance with the last clause of §112, ¶6 as reading on (literally encompassing) the disclosed structure, that is, a pair of shoe laces, as well as any "equivalents thereof."

[c] Algorithms for Computer Structures

The Federal Circuit has adopted a special rule for the "corresponding structure" of a means-plus-function claim in which the disclosed structure is a programmed computer or microprocessor. For such inventions, the "disclosed structure is not the general purpose computer, but rather the special purpose computer programmed to perform the disclosed algorithm."⁴³⁶ The Circuit's 1999 decision in WMS Gaming, Inc. v. Int'l Game Tech.⁴³⁷ "established that the corresponding structure for a § 112 ¶ 6 claim for a computer-implemented function is the algorithm disclosed in the specification."⁴³⁸

The...