Patently Strategic Podcast: Means-Plus-Function and the Risk of Losing Your Way

A Means for Broad Coverage

Inventors and practitioners alike are continually trying to push the bounds of protection on innovations. Whether it’s describing a telegraph as a means for communication or a lightbulb as a means for lighting an environment, using broad language, like “means for” language, to cover all the possible workarounds might seem more advantageous than disadvantageous, at first glance. In patent law, this broad language or “means for” phraseology is called functional language because it describes the device or system in terms of what it accomplishes rather than the actual structure. However, using functional language has lost favor over time. For example, a blog published by Patently-O in 2011 shows that the use of “means for” language has dropped precipitously from about 1990 to present day. What has turned this seemingly advantageous practice into a disadvantageous one?

A System Configured to Work Around

In some instances, while use of “means for” language has reduced, alternative functional language like “a mechanism configured to” or “a module capable of” has increased over time. This surge in alternative “means for” language has caused courts to tighten their view of means-plus-function language to provide guideposts, at least in theory, for identifying when language is viewed as functional language versus the seemingly more preferred structural language. In particular, as the panel discusses, the Williamson v. Citrix Online, LLC 792 F.3d 1339 case decided by the Federal Circuit in 2015 shifted away from a strong presumption against a means-plus-function interpretation absent “means for” language and instead established the “nonce word” doctrine. Nonce words are basically those words that inherently lack any structural connotation but instead require a second word, a modifier, to impart some structure to the word. For example, “mechanism” alone is a nonce word and may trigger a means-plus-function interpretation. However, when “detent” is added to “mechanism”, a means-plus-function interpretation may now be avoided.

Function Plus Structure (Somewhere)

When does the statute (35 U.S.C. 112(f)) say that a means-plus-function interpretation should be imparted to a claim term versus avoiding means-plus-function? In general, a means-plus-function interpretation applies when the claim recites a function without reciting structure for performing the function. In such scenarios, where 35 U.S.C. 112(f) applies, the claim term(s) are limited to the structure(s), material(s), etc. disclosed in the specification. When the claim recites structure and function, 35 U.S.C. 112(f) does not apply. When 35 U.S.C. 112(f) does not apply, the claim terms may be construed more broadly, for example based on the knowledge of one of skill in the art, the plain meaning of the claim terms at the time of filing, the description of the claim terms in the specification as filed, etc.

All said, a mean plus function interpretation can be o.k., if, and it’s a big IF, the specification clearly and wholly describes at least one structure or algorithm that performs all the functions in the claims. In the event that it is deemed that the specification does not provide this support, the patent could be invalidated for failing to teach one of skill in the art how to make and use the invention.

A Fundamental Tension

These complexities harken back to the fundamental deal of the patent system. Long term progress of science and the useful arts is promoted by trading a government-granted window of exclusivity to inventors in exchange for an enabling public disclosure that teaches the public how to make and use the invention. This predictably leads to some tensions in the system. Inventors understandably want the broadest possible and most future-proof coverage for their ideas. The health of the broader public innovation ecosystem, however, depends on not wholesale blocking of iteration and competition by granting exclusive rights that can go well beyond what was specifically invented in the scope of any given granted patent.

There’s a tremendous amount of nuance in the surrounding rulings, in this tension, and in the general understanding surrounding means-plus-function claiming, to the point of seeming overly pedantic at first glance, but it’s important to remember that word choice matters a great deal in the world of patenting. You’re using the English language to draw a picture around highly technical concepts. The precision with which this is done, down to the semantic level, can make all of the difference when it comes to your patent application being rejected or granted – and the future likelihood of your ability to assert your rights or defend against invalidation. Word choice too narrow or overly specific – and you can easily be designed around by competitors. Word choice too broad and only describing what something is vs. what it does and you risk rejection or invalidation for what will be ruled as linguistic tricks to get more coverage than what you actually invented. The tension is real and the case law interpretation is fluid, but it all still comes down to determining if the chosen words will enable a person of ordinary skill in the art to carry out an invention – in the interest of other inventors being able to build on the idea, while also avoiding trespassing with infringement.

Episode Overview

In this episode of Patently Strategic, the panel walks through several court cases, some in the software space and some in the device space, that either: invalidated a patent for failing to define structures in the specification for the all the means-plus-function claim terms or maintained validity of the patent because the specification provided sufficient structure for all the means-plus-function claim terms. The panel wraps up with some practical tips for supporting means-plus-function language or avoiding means-plus-function interpretation all together.

Discussion Panel

Ashley is joined today by our always exceptional group of IP experts including:

  • Kristen Hansen, Patent Strategist at Aurora
  • David Jackrel, President of Jackrel Consulting
  • David Cohen, Principal at Cohen Sciences
  • Shelley Couturier, Patent Strategist and Search Specialist




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