Law360, New York (March 30, 2016, 10:37 AM ET) — Patent claim strategy is an important component of claim drafting. Inventors want good coverage of their inventions, and claiming various aspects of the invention in a variety of ways can provide such coverage. One very popular way of structuring patent claims is to recite function. If a patent claim issues that recites a functional element, the claim, on its face, covers anything capable of performing that function. Such claims, if properly supported by a broad and sufficiently detailed disclosure, may provide the broadest coverage of the invention in some cases. For example, in cases where the function is itself novel and inventive and the structure is not, such as in programmed machine claims, a functional claim may be helpful. In cases where novelty and inventiveness lie in the function performed by the structure, claims that recite a structure performing a function may be helpful. In other cases, a functional formula may be used to establish context for later claims.

There are three types of patent claims that include function: means-plus-function claims, express function claims and implied function claims. Means-plus-function claims recite “means for” performing a function. This format is expressly authorized by the text of 35 U.S.C. § 112(f), which states, in relevant part:

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

Express function claims are claims that recite a nominal structure that performs, or can perform, a function, without including the word “means.” Such claims generally fall into two sub-categories — claims that are construed as means-plus-function claims under Section 112(f) despite omitting the word “means,” and claims that are not. Claims of the form “an X configured to Y” are express function claims, where X is the structure and Y is the function. Other verbs may take the place of the word “configured,” such as positioned, disposed, arranged and the like. “For” may also be used in place of “to” in reciting the function, and when “for” is used, “configured” and similar words can be omitted.

For many years, “means-plus-function” was the preferred format for functional claiming, but that format has declined in usage from about 23 percent of U.S. applications filed in 2001 to about 5 percent of U.S. applications filed in 2013. At the same time, patents issuing in the U.S. with at least one claim using the word “configured” have gone from about 12 percent to about 40 percent.

A subcategory of express function claims are operating machine claims of the form, “an X that Y.” Such claims carry the risk that only a machine in operation can infringe the claim. For this reason, the “configure to” format is commonly used to avoid the requirement of a currently operating machine, since a machine that is not currently operating, but is merely “configured to” perform the function, will infringe.

Implied function claims nominally recite structure, but using a name for structure that implies a function. Examples include “support member,” “divider,” “heater,” “particle sweeper” and the like. The function is implied in the name of the structure without resorting to “for” or “to.”

Reciting “means” in a claim creates a rebuttable presumption that the claim is a means-plus-function claim under Section 112(f). TecSec Inc. v. Int’l Bus. Mach. Corp., 731 F.3d 1336, 1347 (Fed. Cir. 2013). If the claim is a means-plus-function claim, and corresponding structure recognizable by a person of ordinary skill in the art as capable of performing the recited function is not found in the specification, the claim is invalid under 35 U.S.C. § 112(a). Biomedino LLC v. Waters Techs. Corp., 490 F.3d 946 (Fed. Cir. 2007). For a software invention, the corresponding structure must include an algorithm for performing the recited function. Ibormeith IP LLC v .Mercedes-Benz USA LLC, 732 F.3d 1376 (Fed. Cir. 2013).

Means-plus-function claims are construed under Section 112(f) according to their corresponding structure. Such claims cannot cover any structure other than the corresponding structure disclosed in the specification, and equivalents thereof known at the time the patent issued, Personalized Media Comm’n LLC v. U.S. International Trade Commission, 161 F.3d 696 (Fed. Cir. 1998), although some cases have purported to apply the doctrine of equivalents to language of the claim that was not part of the recited means, for example to find an equivalent function. See, e.g., WMS Gaming Inc. v. Int’l Game Tech., 184 F.3d 1339 (Fed. Cir. 1999). The Federal Circuit has repeatedly held that the construction clause of Section 112(f) is a limiting clause. See Pennwalt Corp. v. Durand-Wayland Inc., 833 F.2d 931, 934 (Fed. Cir. 1987); Laitram Corp. v. Rexnord Inc., 939 F.2d 1533,1536 (Fed. Cir. 1991); Valmont Indus. V. Reinke Mfg. Co., 983 F.2d 1039, 1042 (Fed. Cir. 1993).

The Federal Circuit has approved the use of express function claim format to limit claims. Welker Bearing Co. v. PHD Inc., 550 F.3d 1090 (Fed. Cir. 2008). The same general approach applies in determining whether an express function claim is construed as a means-plus-function claim under Section 112(f). The standard is whether the word used to specify the structural element is a sufficiently definite name for structure that would be understood as such by a person of ordinary skill in the art. If not, then the claim is treated as a means-plus-function claim.

In Williamson v. Citrix Online LLC, 792 F.3d 1339 (Fed. Cir. 2015), the en banc Federal Circuit applied Section 112(f) to an express function claim. Finding that the phrase “distributed learning control module” did not include or connote, to a person of ordinary skill in the art, structure for performing the recited functions, the Federal Circuit determined that Section 112(f) applies to such claims, and that the presumption that Section 112(f) does not apply to a claim that does not recite the word “means” is no longer “strong.” A panel of the Federal Circuit proceeded to invalidate the claim for lack of support.

The claim in controversy recites:

a distributed learning control module for receiving communications transmitted between the presenter and the audience member computer systems and for relaying the communications to an intended receiving computer system and for coordinating the operation of the streaming data module.

This is an example of an express function claim. The word “means” does not appear in the claim, but three functions of the “distributed control learning module” are expressly recited in the claim, receiving, relaying, and coordinating. The en banc reviewing court determined that a person of ordinary skill in the art would discern no structure from the phrase “distributed learning control module”, so the claim must be read under Section 112(f). The panel, upon turning to the specification to find corresponding structure, determined that structure was disclosed corresponding to the “receiving” and “relaying” functions, but not to the “corresponding” function. Because corresponding structure was not disclosed for every recited function, the claim was held invalid as indefinite.

A popular format used for express function claims is a structure “configured to” perform a function. As noted above, about 40 percent of all patents issuing today in the U.S. have at least one claim with the word “configured,” suggesting many U.S. patent may use “configured to” language in at least one claim. To claim inventions that involve a machine that performs a special function, the express function format can be useful if the drafter of the specification understands the requirements for means-plus-function claims and plans to use Section 112(f) advantageously.

Because express function claims may or may not be interpreted as Williamson claims, careful claim strategy, drafting and support of express function claims may provide options for broader coverage when asserting claims in litigation. An express function claim supported by disclosure of multiple different structures corresponding to the function may cover more embodiments than reciting one of the corresponding structures in the claim. For example, if an “image reader” is claimed with the express function, “configured to read a color image,” and a scanner and a photoreceptor array are disclosed as corresponding structures, more embodiments can be covered if the claim is interpreted under Section 112(f) compared with a claim that merely
recites the scanner.

In some cases, details of the supporting structure not appearing in the claim, and not even essential for performing the function, have been held to limit the claim. In Welker, structure corresponding to a “mechanism for moving said finger” was found to be a “rotating central post,” over the patentee’s objection that the rotating central post was not essential to performing the function. Because the accused device did not include a rotating mechanism, summary judgment of noninfringement was rendered.

If the invention does not involve a special function, but the structural components work together according to their functions, it may be advantageous to use the implied function claim format. Such claims are unlikely to be interpreted under Section 112(f) (see Welker), so normal rules of claim construction under Phillips apply. However, use of the implied function format, if properly supported by disclosure, may cover more embodiments than purely structural claim elements. For example, “display” may be a broader term in a claim than “glass panel.”

It is generally helpful to include claims having different formats in a single application, provided the subject matter of the application supports use of the different formats. For example, in an application directed to an invention with a special structure and a special function, the drafter should consider use of express function claims and implied function claims, possibly along with means-plus-function claims. With structural inventions, the drafter should consider use of pure structure claims along with implied function claims. Proper use of functional claiming, including claim strategy, dependency and support in the specification, will provide many options for future litigation in the event the different formats
issue in a patent.

—By Ronald G. Embry, Patterson & Sheridan LLP

Ronald Embry  is a partner in the Houston office of IP boutique law firm Patterson & Sheridan.

The opinions expressed are those of the author(s) and do not necessarily reflect the views of the firm, its clients, or Portfolio Media Inc., or any of its or their respective
affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.