Patent Eligibility Issues After Justices' American Axle Denial

July 6, 2022
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The U.S. Supreme Court's denial of American Axle & Manufacturing Inc.'s petition for certiorari last week leaves undisturbed the U.S. Court of Appeals for the Federal Circuit's expansion of the two-step Mayo/Alice test to "the types which have historically been eligible to receive the protection of our patent laws"[1] — namely, expansion into the electromechanical technological arts.[2]

The Federal Circuit's certiorari-denied precedential 2020 American Axle v. Neapco Holdings decision held that the automobile propshaft liner tuning claim limitation of American Axle's U.S. Patent No. 7,774,911 — the '911 patent — was the claim's focus.[3]

Moreover, the tuning limitation was held to be directed to a natural law (Mayo/Alice step 1)[4] and had nothing more (Mayo/Alice step 2), resulting in affirmance of the district court's finding of patent ineligibility.[5]

This article discusses expansion in coverage of the Mayo/Alice test for U.S. patent subject matter eligibility after the recent American Axle denial and how patent applicants can mitigate the impact of this denial.

How the Mayo/Alice Test Applies to Electromechanical Software Patents

The Supreme Court's 2012 Mayo Collaborative Services v. Prometheus Labs Inc. decision set forth a two-part framework for deciding patent eligibility for a diagnostic — bio/life science — patent.[6]

In the 2014 Alice Corp. v. CLS Bank decision, the Supreme Court applied the two-step test announced in Mayo to a computer-implemented — software — invention for hedging risk, holding that merely "[s]tating an abstract idea while adding the words 'apply it with a computer'" is not sufficient to confer eligibility.[7]

In American Axle, the Federal Circuit further applied Mayo/Alice to a new field of invention heretofore rather insulated from eligibility challenges — namely, the mechanical arts and industrial process machines.

In American Axle, the body of representative claim 22 in the '911 patent at issue includes three limitations:

  •  Limitation (A), "providing a hollow shaft member,";
  •  Limitation (B), "tuning a mass and stiffness of at least one liner"; and
  •  Limitation (C), "inserting the at least one liner into the shaft member."

Because the claim body limitations (A) and (C) were well-known, as admitted in the description of the '911 patent,[8] the Federal Circuit's analysis hinged on claim body limitation (B), the infamous tuning limitation.[9]

The tuning limitation was constructed as "controlling the mass and stiffness of at least one liner to configure the liner to match the relevant frequency or frequencies."[10] Controlling characteristics — e.g., mass and stiffness — are software, and as such, received the Alice treatment.

When a software innovation is the only inventive claim limitation of the patent application or asserted patent, and by default the focus, even when categorized as an electromechanical software Innovation — e.g., controlling characteristics — eligibility may be successfully challenged under the Mayo/Alice framework.

The reason is that the focus of the claim is no longer structural — a patent eligible machine innovation — but rather software focused, which has consistently been subjected to the Alice/Mayo framework.

Problematic Result-Oriented Claims

Under the Mayo/Alice framework, a determination is first made regarding "whether the claims are directed to a law of nature, natural phenomenon, or abstract idea," which are ineligible concepts.[11] If so, a determination is made as to whether the claims embody an inventive concept or significantly more than the ineligible concept itself.[12]

To avoid a negative determination regarding patent eligibility, the patent claim is required to include "the specificity required to transform [the] claim from one claiming only a result to one claiming a way of achieving it."[13]

American Axle's claim failed to explain the specificity or series of steps involved in applying Hooke's law to vehicle propshaft manufacturing. Rather, American Axle's claim "defines a goal ('tuning a liner' to achieve certain types of vibration attenuation)."[14]

The tuning limitation could be accomplished by applying Hooke's law on a computer, which would accomplish a result — i.e., reduce dual-directional vibrations.

Hooke's law naturally holds that mass and stiffness have the effect of damping — or reducing vibrations. And as such, controlling or tuning mass, and stiffness to have that effect — and nothing else — is the epitome of result-oriented claiming.

Hooke's law — the patent-ineligible natural law — is not explicitly recited in claim 22. But the parameters of Hooke's law — mass and stiffness — are unaccompanied by anything beyond the result — reduced bidirectional vibrations.

Insights From Diamond v. Diehr

The electromechanical patent claim at issue in the Supreme Court's 1981 Diamond v. Diehr decision is much richer — and much narrower — than the claim at issue in American Axle.[15]

Comparing claim 1 of Diehr's U.S. Patent No. 4,344,142 to claim 22 of American Axle's '911 patent, one can see immediately that the Arrhenius equation in Diehr — the patent-ineligible natural law — comprised a relatively small part of the patent-eligible method claim.

Unlike in American Axle, Diehr's claim has:

  • Data gathering steps — provided database including constant dependent on press mold, monitoring elapsed time, providing temperature;
  • Number crunching — constantly determining, calculating, comparing; and
  • An output-based corrective action — open press when comparison indicates.

Although a corrective action may not always be necessary,[16] the data gathering and number crunching steps give life to Diehr's claim 1 that American Axle's claim fatally lacks.

In the same respect, the Federal Circuit noted that the claimed method did not "specify how target frequencies are determined or how, using that information, liners are tuned to attenuate two different vibration modes simultaneously, or how such liners are tuned to dampen bending mode vibrations."[17]

In a similar respect, the dissent in American Axle suggests that the '911 patent includes data gathering of propshaft structure information — "different characteristics of the liners are controlled corresponding to the structure of the propshaft."[18]

This propshaft structure information could be like the "constant dependent on the press mold" in Diehr because it is what the natural law is applied to. But a step of obtaining/identifying information regarding the "structure of the propshaft" is missing from the claims of American Axle's '911 patent.

The result may have been more like in Diehr, if the '911 patent had, for example, additionally included steps of:

  • Obtaining the propshaft structure information;
  • Calculating, based on the obtained propshaft structure information, mass and stiffness information using a table associating different types of propshaft structure with different mass and stiffness characteristics; and
  • Controlling mass and stiffness of a liner design based on the calculated mass and stiffness information.

What could have American Axle added to the claimed method to transform into a patent-eligible application of Hooke's law? Would this type of claim language above have had a better result? Undoubtedly, additional claim limitations, such as data gathering and number crunching as in Diehr, arguably could have prevented the holding the claim is directed to only a natural law.

Moreover, the Federal Circuit suggested the FEA models disclosed by American Axle's experts would have changed the eligibility analysis.[19] However, those features were not disclosed in the patent, much less, claimed.


Considering the Supreme Court's denial of American Axle's petition for review, patent applicants may see an uptick in patent eligibility challenges in the art units that are not focused on pure information processing, such as industrial manufacturing processing. Thus, claim drafting will continue to be important, given lingering concerns about broad functional claiming.

These concerns are likely to persist, whether under Section 112 or 101 of the Patent Act. As such, it is important to draft claims carefully from the outset to preserve a patent's eligibility, validity and value.

To avoid an unfavorable result on the Mayo/Alice test, patent applicants may consider a Diehr-based strategy for electromechanical software innovations, including at least three phases:

  • Data gathering — e.g., receiving, collecting, obtaining and accessing data;
  • Number crunching — e.g., calculating, determining and identifying using the gathered data; and
  • Outputting — e.g., displaying or audibly outputting — or having a corrective action (an output-based trigger condition like Diehr's press open).

According to the Federal Circuit, claims must have specificity that does not correspond to a result but instead limits the claim to methods of achieving the result. To comply, having a structure like in Diehr — i.e., data gathering, number crunching and output or action — may be helpful.

The data gathering and number crunching steps are what American Axle was arguably missing for eligibility. To apply the natural law or abstract idea, it would make sense to claim the gathering of the data to which it is to be applied, and to perform a calculation, beyond merely applying the natural law, before the final step of doing something — e.g., controlling characteristics, opening a rubber mold press.

Additionally, if the focus of the claim is software, patent applicants should also explain, in the original specification, the patent landscape — existing technology — and how the ordered combination of claim elements provide a specific improvement to the existing technology or the computer itself.[20]

Originally published


[1] American Axle & Manufacturing, Inc. v. Neapco Holdings LLC , 967 F.3d 1285, 1306 (Fed. Cir. 2020), cert. denied, No. 20-891, 2022 WL 2347622 (U.S. June 30, 2022) (Moore, K. dissenting) (quoting Diamond v. Diehr , 450 U.S. 175, 184, 101 S.Ct. 1048, 67 L.Ed.2d 155 (1981)).

[2] U.S. Patent No. 7,774,911 at issue in American Axle has an International Patent Classification (IPC) of B23Q17/00 ("Arrangements for indicating or measuring on machine tools") and B23P1700 ("Metal-working operations").

[3] American Axle, at 1292 ("[t]o determine what a claim is 'directed to' at step one, we look to the 'focus of the claimed advance.'") quoting Trading Techs. Int'l, Inc. v. IBG LLC , 921 F.3d 1378, 1384 (Fed. Cir. 2019).

[4] Id., at 1297 ("claim 22, like claim 8 in O'Reilly, is directed to a natural law because it clearly invokes a natural law, and nothing more, to accomplish a desired result").

[5] Id., at 1298 ("As toMayo/Alicestep 2, nothing in claim 22 qualifies as an 'inventive concept' to transform it into patent eligible matter").

[6] Mayo Collaborative Services v. Prometheus Labs., Inc. , 566 U.S. 66 (2012)

[7] Alice Corp. v. Pty. Ltd. v. CLS Bank. Intern. , 573 U.S. 208, 223 (2014).

[8] American Axle at 1290 ("According to the '911 patent's specification, prior art weights, dampers, and hollow liners that were designed to individually attenuate each of the three propshaft vibration modes—bending, shell, and torsion—already existed. '911 patent, col. 1, l. 53–col. 2, l. 38. But these prior art damping methods were assertedly not suitable for attenuating two vibration modes simultaneously.See id.")

[9] Id. at 1292 ("independent claim 22 of the '911 patent is patent ineligible under section 101 because it simply requires the application of Hooke's law to tune a propshaft liner to dampen certain vibrations.").

[10] Id. at 1292 (quoting J.A. 15, 1047) ("[t]he district court construed the claim 22 limitation 'tuning a mass and a stiffness of at least one liner' to mean 'controlling the mass and stiffness of at least one liner to configure the liner to match the relevant frequency or frequencies.' No party contests the district court's construction on appeal.").

[11] Id. at 1292 (quoting Alice, 573 U.S. at 217, 134 S.Ct. 2347 (citing Mayo, 566 U.S. at 77, 132 S.Ct. 1289)).

[12] Id. at 1292 (quoting Alice, at 217–18, 134 S.Ct. 2347 (brackets omitted) (quoting Mayo, 566 U.S. at 72–73, 132 S.Ct. 1289) ("If the claims are so directed, we then ask whether the claims embody some "inventive concept"—i.e., whether the claims contain "an element or combination of elements that is 'sufficient to ensure that the patent in practice amounts to significantly more than a patent upon the ineligible concept itself.' "

[13] Id. at 1296 quoting SAP Am., Inc. v. InvestPic, LLC , 898 F.3d 1161, 1167 (Fed. Cir. 2018)

[14] Id. at 1293.

[15] Diamond v. Diehr, 450 U.S. 175, 185 (1981).

[16] Thales Visionix Inc.. v. United States , No. 15-5150 (Fed. Cir. 2017) (the final limitation of the software patent claim at issue resulted in "determin[ing] an orientation" and was found to be patent eligible).

[17] American Axle at 1298

[18] American Axle at 1315 (Moore, K. dissenting) ("[t]he specification explains that different characteristics of the liners are controlled corresponding to the structure of the propshaft. '911 patent at 7:56–8:43. It even provides a working example of tuned liners for use in a propshaft with specific dimensions and 8:2–23.").

[19] Id. at 1285 ("[t]his case would be significantly different, if, for example, specific FEA models were included in claim 22. But they are not. What is missing is any physical structure or steps for achieving the claimed result. The focus of the claimed advance here is simply the concept of achieving that result, by whatever structures or steps happen to work."); See also Id. ("While AAM may have discovered patentable refinements of the prior art process, such as particular uses of 'sophisticated FEA [finite element analysis] models during its design process,' 45, neither the specifics of any novel computer modelling, nor the specifics of any experimental modal analysis are included as limitations in claim 22.").

[20] Manual of Patent Examining Procedure (MPEP) at 2106.05(a) ("[i]n determining patent eligibility, examiners should consider whether the claim 'purport(s) to improve the functioning of the computer itself' or 'any other technology or technical field'" quoting Alice at 225). See also Enfish, LLC v. Microsoft Corp. , 822 F.3d 1327 (Fed. Cir. 2016) (in finding the software claims patent eligible, the Federal Circuit stated that a relevant inquiry at Alice Step 1 is "to ask whether the claims are directed to an improvement to computer functionality versus being directed to an abstract idea").

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