On July 31, the Federal Circuit withdrew its opinion in American Axle & Manufacturing, Inc. v. Neapco Holdings LLC (original opinion discussed here) and provided a substitute opinion. The court’s goal was to clarify why a claim directed to manufacturing a driveshaft with liners requiring “tuning a mass and a stiffness of at least one liner” was patent ineligible.

In its revised opinion, the court relied again on the Supreme Court’s two-step test established in Mayo and Alice and emphasized that claim 22 was ineligible because it required nothing more than the application of a natural law (Hooke’s law) to tune the liner to dampen certain vibrations. Hooke’s law is an equation that describes the relationship between an object’s mass, its stiffness, and the frequency at which the object vibrates.

The court further expounded upon O’Reilly v. Morse (1853), where the Supreme Court held a claim that used the natural law of electro-magnetisim for marking or printing intelligible characters was patent ineligible because it did not express what process or machinery was required to achieve the result. Similarly, the American Axle claim recites a natural law (Hooke’s law) and a result to be achieved (producing a liner to dampen specific vibrations). And just as the claim in O’Reilly did not recite any engineering to achieve a result, claim 22 does likewise.

The impact of the decision can be measured by the interaction between the dissenting judge and the majority. First, the dissenter argued that the claims do not actually recite any particular natural law.

The majority retorted that claim 22 expressly requires varying frequency attenuation (tuning) based on mass and stiffness, and that what Hooke’s law does is precisely to relate frequency to mass and stiffness. In all but name, therefore, claim 22 recites Hooke’s law. Where a patent claim on its face, and as construed clearly, invokes a natural law, and nothing else, to accomplish a desired result, the claim will be held ineligible.

The dissent further argued that the failure of the claims to designate how to achieve the desired result is exclusively an issue of enablement, not to be confused with patent eligibility. The majority responded that this criticism fails to distinguish between two distinct “how” requirements in patent law. The first requirement deals with patent eligibility and requires that the claim itself go beyond stating a functional result; it must identify “how” that functional result is achieved via concrete structure and/or steps.

The second distinct “how” requirement, namely of enablement, requires that once the concrete physical structures or actions are set out in the claim, the specification must provide enough information for a relevant skilled artisan to be able to make and use the claimed structures or perform the claimed actions. “Although the word ‘how’ is used in both contexts, neither requirement replaces the other.”

The dissent objected further that even if the claim fails step one of the Alice/Mayo test (whether the claims are directed to a law of nature, natural phenomenon, or abstract idea), it should nevertheless be found patent eligible under step 2. In step 2, claims will not be held ineligible if the claims contain an “inventive concept.” American Axle had argued that liners were never used previously to attenuate bending mode vibrations and that the use of liners to attenuate multiple vibration modes was also unconventional. However, the majority explained that, insofar as claim 22 merely claims the achievement of results, it is directed to ineligible matter. The abstract idea itself cannot supply the inventive concept at step two.

An important takeaway from this case is to include sufficient structure and/or steps when drafting claims, as opposed to just claiming the result. Functional language that simply claims the result, in combination with use of a natural law (which may not even be explicitly stated in the claim!), may prove insufficient.