This article originally was written for the American Intellectual Property Law Association 2015 Partnering in Patents conference.


In June of 2013, the President announced several legislative recommendations and executive actions stemming from a White House Task Force on High-Tech Patent Issues.[2] One area of attention for the task force focuses upon perceived dangers of claim terms that refer to the function of an invention as opposed to its tangible structure. Such terms are seen as inherently less specific than structural terms, thus hindering the public’s ability to understand and appreciate the scope of issued patents. This lack of transparency of the patent system undermines the effectiveness of our innovation incentive program and hinders the ability of other innovators to build up or design around prior patented technology.

In response to this concern over patent clarity, the President’s second executive action addresses functional claim language:

Executive Action 2: Tightening Functional Claiming (renamed as “Clarity in Patent Claims”). The AIA made important improvements to the examination process and overall patent quality, but stakeholders remain concerned about patents with overly broad claims — particularly in the context of software. The PTO will provide new targeted training to its examiners on scrutiny of functional claims and will, over the next six months develop strategies to improve claim clarity, such as by use of glossaries in patent specifications to assist examiners in the software field.[3]

In response, the United States Patent and Trademark Office (USPTO) began “a multi-phased training program for all examiners that focuses on evaluating functional claiming and improving the clarity of the examination record.”[4] As of August 2015, the USPTO has published seven of eight anticipated training modules seeking to implement Executive Action 2 in order to address “overly broad claims.” These modules are presented in the form of PowerPoint presentations, with commentary.[5] This paper discusses certain aspects of these training modules as they relate to mechanical inventions.

In addition, the recent Williamson v. Citrix Onlinex[6] Federal Court decision from June 2015 is discussed. In this case, the Federal Circuit withdrew an earlier opinion and substituted a new en banc section addressing means-plus-function claims. The en banc court reversed the precedent that called for a “strong” presumption if the term “means” was used or not used, and instead holds that the question is “whether the words of the claim are understood by person of ordinary skill in the art to have a sufficiently definite meaning as the name for structure.” The USPTO training modules, which were completed prior to the recent en banc decision of Williamson v Citrix Online, are considered in light of current Federal Circuit law. Finally, certain practical suggestions directed to patent practitioners are offered.

Examination Procedure under Executive Action 2

USPTO’s first training module seeking to carry out Executive Action 2 is entitled “35 USC 112(f): Identifying Limitations that Invoke 112(f).”[7] The well known means-plus-function statutory language provides:

112(f).  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.[8]

A stated goal of the first training module is that “clearly identifying 112(f) limitations and their scope prevents potential over assertion of claims in an issued patent against a third party.”[9]  To accomplish this objective, examiners are taught the longstanding 3-prong analysis to determine if 112(f) is invoked.  Specifically, a claim limitation should be interpreted according to 112(f) if it meets the following 3-prong analysis:

(A) The claim limitation uses the term “means” or “step” or a term used as a substitute for “means” that is a generic placeholder (also called a nonce term or a non-structural term having no specific structural meaning) for performing the claimed function;

(B) The term “means” or “step” or the generic placeholder is modified by functional language, typically, but not always linked by the transition word “for” (e.g., “means for”) or another linking word or phrase, such as "configured to" or "so that"; and

(C) The term “means” or “step” or the generic placeholder is not modified by sufficient structure, material, or acts for performing the claimed function.[10]

This test is often described as resulting in a first presumption that 112(f) applies when the term “means” is used according to Prong A above. Importantly, the first presumption will still apply, however, if the term “means” was merely substituted with a “generic placeholder.” The first training module suggests that the terms “information, data, instructions, and software per se” may be merely generic placeholders. This first presumption would be rebutted by the inclusion of sufficient structure to perform the function in accord with Prong C.[11]

A second presumption states the converse: the “absence of the term ‘means’ with functional language raises a rebuttable presumption that the claim element is not to be treated under § 112(f).”[12]

Notably, the first training module promotes having an examiner shift the burden of § 112(f) determination onto the applicant by suggesting, “[i]n cases where it is unclear whether 112(f) is invoked, it would be appropriate to reject the claim under 112(b) as being indefinite.”[13]   

Examiners are further cautioned that,

Special care needs to be taken to determine whether the term “unit” is being used as a substitute for “means” in this instance. The examiner must carefully consider the term in light of the accepted meaning in the technology as well as any definition/guidance for the meaning of the term given in the specification for the application under examination. If it is determined that the term “unit” itself does not limit the scope of the claim to any particular manner for achieving the claimed function and is a “non-structural nonce term” just serving as a generic placeholder then it would meet Prong A. Every application must be evaluated on its own merits as there is no per se list of approved substitute terms.[14]

With respect to Prong B of the three-prong analysis, practitioners should be aware that they do not avoid § 112(f) by omitting the term “for.”[15] Other linking words and phrases such as “so that,” or “configured” are also indications that a function is being recited within the claim.[16] In other cases, no linking words may be necessary at all.[17]

With respect to Prong C of the three-prong analysis for § 112(f), any structure recited in the claim modifying the “means” that is sufficient to perform the function pulls the limitation from § 112(f) consideration.[18] As evidenced by the examples given by the USPTO, sufficiency seems to a very low standard. The USTPO also suggests that examiners consider the specification when determining whether a claim term imparts sufficient structure.[19] Lastly, the hypotheticals given to examiners distinguished the phrase “displaying means,” which invokes § 112(f) from the phrase “a display means,” which allegedly does not.[20] For the practitioner, once may conclude from these examples that the use of the noun form of a term when reciting claim elements helps avoid invoking § 112(f) claim construction.

A second training module, “35 USC 112(f): Making the Record Clear”, focuses upon emphasizing to examiners that their office actions should include clear written analysis of the three-prong test discussed above. The record should contain clear explanations of when presumptions are overcome, and clear conclusions of when § 112(f) is being applied to a claim limitation.[21]

A third training module, “35 USC 112(f): Broadest Reasonable Interpretation and Definiteness of § 112(f) Limitations,”[22] provides guidance on the scope of claims with and without the application of § 112(f). When outside of § 112(f) interpretation, examiners are instructed to construe the claim language “in accordance with its plain meaning in light of the specification as it would be understood by one of ordinary skill in the art” where the specification does not add limitations to the claims.[23] When inside of realm of § 112(f), examiners are instructed to construe the claim terms as the “corresponding structure, material, or acts disclosed in the specification, and equivalents, for performing the recited function.”[24] In other words, corresponding disclosure of structure within the specification (and equivalents) are read as a limitation into the claim.[25]

When § 112(f) is invoked, failure to have sufficiently linked corresponding disclosure of structure for performing the function can result in an unbounded indefinite claim under § 112(b).[26] While indefiniteness may be a growing concern in software cases, mechanical patents often include at least one figure that may illustrate enough structure to avoid some concerns related to these indefiniteness rejections. Further, applicants have an opportunity to respond with amendments or arguments to address any of these indefiniteness concerns of an examiner. Even so, practitioners should be encouraged to fully describe the structure and operation of a mechanical invention even if there is never any intent to invoke § 112(f).

When § 112(f) is invoked, the examiners are instructed to consider the corresponding structure and equivalents.[27] An equivalent is said to “perform the identical function specified in the claim.”[28] Examiners are instructed to apply a prior art reference as teaching an equivalent for anticipation purposes if the corresponding element passes either: 1) the function, way, result test, 2) the interchangeability test, or 3) the insubstantial differences test.[29]

Continuing the USPTO’s theme of providing a clear record, a fifth training module[30] once again instructs that “the meaning or scope of claim terms should be clarified if necessary with explanatory remarks in the Office action.”[31]

In May 2015, the USPTO released a sixth module entitled “Examining Functional Claim Limitations: Focus on Computer/Software-related Claims.”[32] This module focuses on the interpretation of functional claim terms when 35 USC 112(f) is not invoked. Examiners are guided through the interpretation of functional claim terms for properly applying prior art and establishing clear boundaries of claim scope protection. Non-112(f) functional claims are described as follows: “The other way functional language is typically used is when it is recited with some structure, material or action to define a particular capability or purpose served by that recited structure, material or action.”[33] The module provides an example concerning a cup and a spout:

The other way functional language is typically used is when it is recited with some structure, material or action to define a particular capability or purpose served by that recited structure, material or action.

A simple example is a cup with a spout. This can be defined using structural terms as “a cup having a rim with an outwardly extending V-shaped section.” It could also be defined using functional terms as “a cup having a rim shaped to facilitate pouring a stream of liquid.” In the latter case, the shape of the rim structure is further described by the function it is designed to perform.

In rare circumstances, functional language can also be used without invoking 112(f) or without any recitation of structure, material or actions. In these situations, it is necessary to ensure that the boundaries of the claim limitation can be understood.[34]

While considering a claim as-a-whole requires consideration of all the terms and phrases of the claim, whether features are given sufficient weight to constitute a possible patentable distinction may come down to differentiating an intended use or intended result from a function ,i.e., a required action that imposes limited on the claimed structure.[35] An intention expressed in a claim will generally not impart a patentable distinction.[36]  An intention is neither what the device is, nor how the device works, but is simply a suggestion of theoretical utility.

In the seventh training module, released July 2015, the USPTO addresses the written description requirement: “Examining Claims for Compliance with 35 U.S.C. 112(a).”[37] In this first of two modules on enablement, examiners are given a refresher course on the requirements of 35 U.S.C. § 112(a). Among other guidance, examiners are reminded that an applicant must provide sufficient written description support under § 112(a) for an original genus claim. The specification must describe more than a narrow species in order to provide evidence that the inventors have contemplated the entire genus.[38]

An eighth and final module further addressing enablement under 35 U.S.C. §112(a) is due out in the Fall of 2015.

Williamson and § 112(f) as Applied by Courts

The practical impact of having a claim limitation construed as a means-plus-function claim can be significant. The Manual of Patent Examining Procedure warns that “section 112(f) or pre-AIA section 112, sixth paragraph, limitations will, in some cases, be afforded a more narrow interpretation than a limitation that is not crafted in ‘means plus function’ format.”[39]  Consequently, a patentee who receives unintentional means-plus-function treatment typically ends up with a more narrow patent than intended.

To avoid an unnecessarily narrow interpretation before the USPTO during prosecution or before a court during litigation, patent drafters ideally will present claims that make as clear as possible when §112(f) is and is not intended by the applicant.  Best practice often dictates presenting several claims of varied scope, including claims that invoke § 112(f) and claims that do not.

If one strictly followed statutory language, Courts agreed that the starting point should be whether the patent drafter used the word “means” in the claim. As set forth above in the 3-prong analysis, presumptions are then created one way or the other. However, the strength of these presumptions has undergone some changes. The summary by Professor Jason Rantanen below discusses the evolving treatment by the Federal Circuit:

Under Federal Circuit precedent from the 1990’s, “the presumption can be overcome and § 112, para. 6 will apply if the challenger demonstrates that the claim term fails to “recite[] sufficiently definite structure” or else recites “function without reciting sufficient structure for performing that function.”  Id. (citing Watts v. XL Sys., Inc., 232 F.3d 877, 880 (Fed. Cir. 2000)).

Subsequent cases raised that presumption first to a “strong” one (Lighting World), then to a “strong one that is not readily overcome” (Inventio), and then to an even higher bar: “[w]hen the claim drafter has not signaled his intent to invoke § 112, ¶ 6 by using the term ‘means,’ we are unwilling to apply that provision without a showing that the limitation essentially is devoid of anything that can be construed as structure” (Flo Healthcare Solutions) (emphasis added by court).[40]

Prior to June 2015, the wording patentees selected was given strong deference and protected with a heightened presumption.

In the case of Williamson v Citrix Online[41] the Federal Circuit holds that “a heightened burden” of invoking a § 112(f) interpretation in the absence of the term “means” is “unjustified.”[42] In Williamson, the parties contested possible infringement and invalidity of U.S. Patent 6,155,840 directed to collaborative learning through providing distributed training through a virtual classroom.[43] The invention combines one or more presenters, one or more audience members, and a distributed learning server through a network.[44] Independent claim 8 is provided below, with the key phrase emphasized.

8. A system for conducting distributed learning among a plurality of computer systems coupled to a network, the system comprising:

A presenter computer system of the plurality of computer systems coupled to the network and comprising:

A content selection control for defining at least one remote streaming data source and for selecting one of the remote streaming data sources for viewing; and

A presenter streaming data viewer for displaying data produced by the selected remote streaming data source;

An audience member computer system of the plurality of computer systems and coupled to the presenter computer system via the network, the audience member computer system comprising:

An audience member streaming data viewer for displaying the data produced by the selected remote streaming data source; and

A distributed learning server remote from the presenter and audience member computer systems of the plurality of computer systems and coupled to the presenter computer system and the audience member computer system via the network and comprising:

A streaming data module for providing the streaming data from the remote streaming data source selected with the content selection control to the presenter and audience member computer systems; and

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.[45]

At the district court, the phrase “a distributed learning control module” was construed as invoking 35 U.S.C. § 112, para. 6.[46] However, failing to find sufficient linking disclosure within the description, claim 8 was held invalid for being indefinite.[47] Of note, the same district court claim construction opinion interpreted the phrase “a streaming data module” to also invoke § 112, para. 6 because of the term “module.”[48] The term "module," as used in the disputed terms, does not connote sufficient structure to avoid a means-plus-function construction under § 112, para. 6.[49] The test used was whether the term "fails to recite sufficiently definite structure or else recites [a] function without reciting sufficient structure for performing that function."[50] "What is important is whether the term is one that is understood to describe structure, as opposed to a term that is simply a nonce word or a verbal construct that is not recognized as the name of structure and is simply a substitute for the term 'means for.'"[51]

On the other hand, the phrase “a content selection control for…” was construed without any discussion of §112, para 6.[52] Instead, the district court found that “the noun ‘control’ is ‘a device or mechanism used to regulate or guide the operation of a machine, apparatus, or system.’”[53]          

On appeal the patentee argued that the district court failed to properly weigh the evidence when construing the “module” limitations because the presumption again applying § 112, para. 6 is a strong one when the term “means” was not used.[54]

The Federal Circuit then conceded that precedent suggested that the presumption against invoking § 112(f) “is a strong one that is not readily overcome.”[55] Further, "[w]hen the claim drafter has not signaled his intent to invoke § 112, ¶ 6 by using the term 'means,' we are unwilling to apply that provision without a showing that the limitation essentially is devoid of anything that can be construed as structure."[56] The court had even referred to instances where § 112(f) was applied without “means” as a seldom occurrence.[57] All told, the court admitted that prior cases resulted in “a heightened  bar to overcoming the presumption that a limitation expressed in functional language without using the word "means" is not subject to § 112, para. 6.”[58]

In spite of this historical precedent, the majority of the en banc court then proceeded to return to “a balanced analytical scale,” finding the heighted bar to be “unjustified…unwarranted [and] uncertain in meaning and application.”[59] The court also “overrule[d] the strict requirement of "a showing that the limitation essentially is devoid of anything that can be construed as structure."[60]

Therefore, to the extent necessary, the court reinstated the test applied by the district court where “the standard is whether the words of the claim are understood by persons of ordinary skill in the art to have a sufficiently definite meaning as the name for structure.”[61] When a claim term lacks the word "means," the presumption can be overcome and § 112, para. 6 will apply if the challenger demonstrates that the claim term fails to "recite sufficiently definite structure" or else recites "function without reciting sufficient structure for performing that function."[62]

The result for Williamson is that the term “module” was considered to be “a well-known nonce word that can operate as a substitute for "means" in the context of § 112, para. 6.”[63] Generic terms such as "mechanism," "element," "device," and other nonce words that reflect nothing more than verbal constructs may be used in a claim in a manner that is tantamount to using the word "means" because they "typically do not connote sufficiently definite structure" and therefore may invoke § 112, para. 6.”[64] Further, “the prefix ‘distributed learning control’ does not impart structure into the term "module." These words do not describe a sufficiently definite structure.”[65]

In a dissenting opinion, Judge Reyna took the opportunity to comment on the judicially created presumptions surrounding 35 U.S.C. § 112(f) that even the term “means” may not need to result in a positive presumption, instead the statutory language of “means or steps” is simply a generic way of describing and allowing the use of functional claiming .[66]

Judge Newman’s strong dissent fell far the other way. Newman asserted that § 112(f) is clear that a combination expressed as “a means”…shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.[67] The majority’s opinion means that “everyone must guess whether the claimed “module” is claimed as a function or an apparatus or something else.”[68] “The result is fresh uncertainty, for the judge to invoke [§ 112(f)] although the patentee chose otherwise and wrote the specification and claims on a different legal standard.”[69]

Final Examples and Comments

As discussed above, avoiding the term “means” is not a guarantee that a claim term will avoid being found purely functional and subject to § 112(f).  In 2006, the Federal Circuit enumerated the following set of generic terms that typically do not represent sufficiently defined structure: “mechanism,” “means,” “element,” and “device.”[70]  These terms have been described as merely setting up a black box for performing a function.[71] Other examples are set forth in the MPEP (MPEP § 2181(I)(A)) and include “module for,” “unit for,” “component for,” “member for,” “apparatus for,” “machine for,” or “system for.”[72]

Some examples, however, of fairly generic terms have been held to be sufficiently structural to avoid § 112(f). These terms include: “filters,” “brakes,” “clamp,” “screwdriver,” and “locks.”[73] Other examples of generic terms that have been found to be sufficiently structural to avoid §112(f) include: “detent mechanism,”[74] “digital detector,”[75] “reciprocating member,”[76] “connector assembly,”[77] “perforation,”[78] “sealingly connected joints,”[79] and “eyeglass hanger member.”[80] Each of these terms brings to mind something one can see and hold in their hand. Each of these structural terms is not so broad as to literally convey merely “something you can hold in your hand.” In other words, something more, albeit slightly, descriptive than “a device.”

Further, Lighting World blessed “connector assembly,” not for the term “assembly” but primarily for the term “connector.”[81] In addition, Greenberg found that “detent mechanism” was outside of § 112(f) not because of the term “mechanism,” but the sufficiently structural term “detent.”[82]

Therefore to avoid unintentionally falling into § 112(f), nonce words can often be avoided altogether. For example, “eyeglass hanger member” could have been simplified to only “eyeglass hanger.” Further, the elements of the claims could have been recited as nouns that denote structure, “even if the noun is derived from the function performed.”[83] For example, instead of “streaming data module”, try “data streamer”, and instead of “colorant selection mechanism,” consider “colorant selector.”

By eliminating the strong presumption against the application of § 112(f), the Williamson court may be increasing the range of claim limitations captured by § 112(f), and therefore resulting in more claims limited to the structure disclosed and its equivalents.  Best practice likely remains the same, though.  Where possible, patent drafters should disclose, describe, and illustrate as many alternative embodiments as possible to give the generic claims their maximum breadth.  By providing several embodiments for each element, the inventors can maximize scope of protection up to the prior art and receive maximum credit for their contributions to the technology.    

In conclusion, the MPEP repudiates the notion that all functional language is improper:  “There is nothing inherently wrong with defining some part of an invention in functional terms. Functional language does not, in and of itself, render a claim improper.”[84] A functional limitation must be evaluated and considered, just like any other limitation of the claim, for what it fairly conveys to a person of ordinary skill in the pertinent art in the context in which it is used.