Failure to Disclose How Algorithm Factors Are Weighted, Calculated, Leads to Invalidity

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By Tamlin H. Bason  

Oct. 22 --An algorithm relating to a means-plus-function claim that merely lists a number of relevant factors but fails to disclose how to weigh or calculate those factors to achieve a claimed result is indefinite, the U.S. Court of Appeals for the Federal Circuit ruled Oct. 22 (Ibormeith IP, LLC v. Mercedes-Benz USA, LLC, Fed. Cir., No. 2013-1007, 10/22/13).

The court affirmed the invalidation of all claims of a patent aimed at detecting and alerting drivers that become sleepy at the wheel. The Federal Circuit found the claims invalid under 15 U.S.C. § 112(f) because the disclosed structure--the algorithm--“identifies factors that may be related to driver drowsiness, but there is no disclosure of even a single concrete relationship between the various factors that are used to compute an outcome to warn of driver drowsiness.”

Patent Alerts Drowsy Drivers

Ibormeith IP LLC is the assignee of a patent (U.S. Patent No. 6,313,749) aimed at providing audio-visual warnings to motorists that pose a risk of falling asleep at the wheel. Independent claims 1 and 9 of the '749 patent include a means-plus-function limitation on “computational means” to detect when a driver is sleepy.

Ibormeith argued that the structure for both claims is found in a table in the specification. The table discloses a “sleep propensity algorithm” that identifies a number of factors, such as circadian rhythm patterns and time of day, that Ibromeith claimed were relevant to determining when a driver may be sleepy.

Ibormeith filed an infringement suit against Mercedes-Benz USA LLC based on the latter's Attention Assist system that monitors a driver's drowsiness levels. Mercedes moved for summary judgment on the grounds that the claims were indefinite. Judge Faith S. Hochberg of the U.S. District Court for the District of New Jersey ruled against Ibormeith after determining that the algorithm did not adequately disclose structure and thus failed to comply with Section 112(f). Ibormeith appealed.

Factors Identified; Method Not

Claim 9 says that the invention is directed at “A sleepiness monitor for a vehicle driver and vehicle.” The means-plus-function portion of Claim 9 discloses:

computational means for computing steering transitions and weighing that computation according to time of day, to provide a warning indication of driver sleepiness.  


Table 10 identifies a number of factors that relate to driver sleepiness. The table also contains the following algorithm with S mod identifying driver sleepiness:

S mod = S cir + S zerox + S rms + S light + S temp + S sleep + S road + S trip.  


Ibormeith argued that, despite its use of plus signs in the algorithm, it was not disclosing that a warning signal could issue based on a mere addition of the factors listed in Table 10. Rather, Ibormeith's expert testified that the specific computation disclosed was a mere “template.”

“He further stated,” the court said, “that the '749 patent requires one who implements the drowsiness detection system to determine which factors to use in the algorithm, how to obtain them, how to weight them (for example, by multiplication or addition) how to combine them, and when to issue the warning.”

The court construed this argument as an attempt to seek broad protection in order to reach the accused Mercedes products.

“That position, however, fails in the necessary attempt to steer a course that permits proof of infringement yet avoid invalidity,” the court said. Moreover, even if Table 10 did disclose “a single, definite algorithm that simply adds all of the disclosed variables,” then that algorithm would nonetheless be indefinite due to a lack of accompanying structure, the court said.

Ibormeith, the court noted, did not disclose how these factors listed in the algorithm should be weighted, or how specifically they are calculated in order to result in a warning being issued to the driver. Indeed, “Neither Table 10 nor the associated tables disclose how to perform the weighting of the S circ or any other factor,” Judge Richard G. Taranto said. “Table 10 merely lists inputs without specifying any single formula or function or algorithm defining the contribution of any of the inputs to a computation.”

The court said, “A description of an algorithm that places no limitations on how values are calculated, combined, or weighted is insufficient to make the bounds of the claim understandable.”

Distinguishing Typhoon Touch, WMS Gaming

Ibormeith argued that its algorithm provides as much specificity as did the algorithms at issue in Typhoon Touch Techs., Inc. v. Dell, Inc., 659 F.3d 1376, 2011 BL 284463, 100 U.S.P.Q.2d 1690, (Fed. Cir. 2011) , and WMS Gaming Inc. v. Intl. Game Tech., 184 F.3d 1339, 51 U.S.P.Q.2d 1385 (Fed. Cir. 1999). The court found those cases easily distinguishable.

In Typhoon Touch, the Federal Circuit ruled that it is not necessary for a means-plus-function claim pertaining to a computer-implemented innovation to include the mathematical algorithm so long as the algorithm is recited in prose in the specification. The court here noted that in that case, “The described process of straight-forward matching of user-entered data with data in memory was a routine, concrete algorithm.”

In WMS Gaming, the Federal Circuit found an algorithm in a means-plus-function claim in a patent on an electronic slot machine appropriately disclosed. Notably,WMS Gaming found that a figure in the specification limited and gave structure to the algorithm.

WMS Gaming, like Typhoon Touch, did not rely on a specification passage like the one in the '749 patent, which, Ibormeith itself insists, does not indicate which factors should be used and in what combination and with what relative weights,” the court said. It affirmed the district court's ruling in favor of Mercedes-Benz.

Judges Alan D. Lourie and Sharon Prost joined the opinion.

Patrick F. Solon of Niro, Haller & Niro, Chicago, represented Ibormeith. Scott W. Doyle of Shearman & Sterling LLP, Washington, D.C., represented Mercedes-Benz.


To contact the reporter on this story: Tamlin Bason in Washington at

To contact the editor responsible for this story: Naresh Sritharan at

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