Computer-implemented “control means” requires description of step-by-step algorithm even if not key feature of claimed invention

Nicolas Seckel | April 4, 2012

Ergo Licensing, LLC v. Carefusion 303, Inc.

March 26, 2012

Panel: Newman, Linn and Moore.  Opinion by Moore.  Dissent by Newman.


Another reminder that under US patent law, a “means-plus-function” element recited in a patent claim covers only the corresponding structures described in the specification and their equivalents.  If insufficient or no corresponding structures are described in the specification, the claim is invalid as indefinite.  The rule is strictly applied even if the functional element is only a peripheral aspect of the invention.  Here, the patent claims were directed to a multichannel drug infusion system.  A “control means” was recited (for controlling the motor that adjusts the drug dosage).  The Federal Circuit affirms the invalidity of the claims.  The specification disclosed a “control device,” but no “step-by-step process.” Since the recited function could not be performed by a general computer without special programming, disclosure of an algorithm was required to avoid “pure functional claiming.”


Ergo Licensing is the exclusive licensee of U.S. Patent No. 5,507,412 on a multichannel metering system.  Ergo sued Carefusion 303, Inc. for patent infringement.  The claims recite various flow sources, discharge lines, switches, and a “control means for controlling” the fluid flow adjusting means. 

The District Court granted summary judgment of invalidity for indefiniteness, on the ground that the disclosure of a “control device” in the specification was insufficient structure for the “control means.”

Ergo appealed, and the Federal Circuit affirms.  Under 35 U.S.C. 112, paragraph 6 of the US patent statute, a “means-plus-function” element recited in a patent claim covers only the structures and materials described in the specification as performing the function, and their equivalents.  If insufficient or no corresponding structures are described in the specification, the claim is invalid as indefinite.

In Aristocrat Techs. Austl. Pty Ltd. v. Int’l Game Tech., 521 F. 3d. 1328 (Fed. Cir. 2008), the Federal Circuit confirmed that in a case where a “control means” (of a gaming machine claim) is implemented by a computer, description of a “general purpose computer” is insufficient corresponding structure, unless accompanied by the description of an “algorithm” to transform the computer into a “special-purpose computer.”  In re Katz Interactive Call Processing Patent Litig., 639 F.3d 1303 (Fed. Cir. 2011) recognized an exception to this rule when the function to be performed is co-extensive with a general purpose computer, such as general “means for receiving, processing, storing.”

Here, the Court finds that the “control device” is not a known structure, and that the control function cannot be performed by a general-purpose computer without any special programming, so that the description of an algorithm was required. The Court relies in particular on the testimony of Ergo’s own expert to find that “there were at least three different types of control devices commonly available and used at the time to control adjusting means: microprocessors, discrete circuits connected to stepper motors, and analog circuits.”  The exception of Katz is limited to “rare circumstances” which are not applicable to this case.

Judge Newman dissents.  She would have found sufficient structure in the introductory description of control devices in state-of-the-art patent documents, and the description of the operation of the “control device” in the following passages (bold emphasis added):

Col. 3, lines 48-56: [T]he said flow-measuring means send a flow-proportional measured quantity to the control device, and the said measured quantity is compared with stored limit values there.  If necessary, the control device generates a warning signal, which is displayed on the operating surface.  If the metering of the fluid flow is to be switched over to manual operation, manual metering can be blocked by the control device when the limit value is exceeded or not met.

Col. 3, lines 25-28: When the manual operating switch is actuated, the control device generates a control command, by which the predetermined adjusting means is switched into the switched-off position.

It is worth noting that, at the District Court, Ergo’s claim construction brief had argued that the structural description was sufficient because the “control means” was not a “key feature” of the claimed invention, but surprisingly, Ergo had not discussed the algorithm issue.  Ergo’s expert had apparently not addressed this issue either.  In view of the Federal Circuit’s strict jurisprudence, today’s patentee litigants would be expected to demonstrate the presence of step-by-step algorithms in the patent description.

Also, in this case, the published priority German application used the same German term for “control device” in the description and “control means” in the claims (“Steuereinrichtung”).  Ergo’s misadventure suggests that a careful review of English translations of foreign applications before US filing can be useful to evaluate the consequences of selecting a particular terminology.

“Algorithms in prose”: comment on description of structure and operation

The Ergo Court distinguishes Typhoon Touch Technologies, Inc. v. Dell, Inc., 659 F.3d 1376 (2011) (authored by Judge Newman), which held that an algorithm implementing the “means for cross-referencing said responses with one of said libraries of said possible responses” in a portable, keyboardless computer claimed in U.S. Pat. No. 5,379,057 was sufficiently described.  The algorithm in Typhoon was “in prose” in the following passages (bold emphasis added):

Col. 3, lines 43-48: Cross-referencing entails the matching of entered responses with a library of possible responses, and, if a match is encountered, displaying the fact of the match, otherwise alerting the user, or displaying information stored in memory fields associated with that library entry.

Col. 14, lines 57-68: Cross-Referencing imports that, for each answer field, the entered response can be related to a library to determine if the response can be related to a library to determine if the response in the answer field is existent in the library.  In other words, the answer information is cross-referenced against that specific libraryIf it is available in that library, then, corresponding to that library entry, an action is executed.  For instance, the associated action can involve an overlay window that alerts the user of the fact of the match with the library entry, or displays the contents of an information field stored in association with that entry in the memory.

In Typhoon, the Court had relied on the patentee’s statement “that this description contains sufficient algorithmic structure for the routine programmatic procedures needed to provide cross referencing responses to inquires,” and on the absence of contrary evidence.  In contrast, in Ergo, the Court finds no “step-by-step process for controlling the adjusting means.”  Beyond the case-specific circumstances, these decisions show the interest of buttressing claims with a detailed description, not only of the structure, but also of the operation of the device or system.

“Controller”: comment on the choice of functional and/or structural terms

In Telcordia Techs., Inc. v. Cisco Sys., Inc., 612 F.3d 1365 (Fed. Cir. 2010), The Federal Circuit held that the description of a “controller” was sufficient corresponding structure for “monitoring means… for evaluating the integrity of the multiplexed subrate communications…” According to the Telcordia court, the term “controller” would have been recognized as “an electronic device with a known structure” in the context of the claimed communication network node.

The term “controller” of Telcordia was used in a different technological context than the “control device” of the patent at issue in Ergo, but these contrasting decisions should serve as a reminder to use a rich and diverse vocabulary in patent descriptions to diversify claims and to improve claim support, not only during prosecution, but also after issuance.

Full Decision

Patent At Issue

Subscribe | 登録



词典 / 辞書 / 사전
  • dictionary
  • dictionary
  • 英語から日本語

Double click on any word on the page or type a word:

Powered by