Sufficiently Similar For KSR Obviousness

KSR obviousness can be a tough one for applicants, perhaps rightly so. One area that often arises is when the examiner asserts that a claimed invention would be obvious because it can be obtained by applying a known technique (used to improve a first device) to a second device in order to improve the second device in a way similar to how the first device was improved. Sometimes this is explained by examiners as “using a known technique to improve a similar device in the same way.”

The question often comes down to: how similar is similar?

A recent case (Appeal 2019-001918, Application 14/422,368) illustrates the issue and one way to push back against these types of rejections. This case relates to airfoils used in turbomachines. Claim 1 is reproduced below:

1. A cantilevered airfoil, comprising:
an airfoil having a body section and a tip, the body section extending in a first direction that is angled relative to a radial direction, the tip of the airfoil angled radially in a second direction relative to the body section, wherein a centroid at the radially outermost section of the airfoil is circumferentially offset from a centroid at the radially innermost section of the airfoil such that the airfoil has a lean relative to the radial direction, the airfoil a cantilevered airfoil.

The examiner rejected the claim as obvious based on Baumann (allegedly disclosing cantilevered airfoil as claimed except for being radially angled (or having circumferential lean)). To remedy the defficiency of Baumann, the Examiner relies on Bushnell, in that it would have been obvious to impart a circumferential lean, as taught by Bushnell, to the airfoil of Baumann in order to improve vane flow separation control at the end wall region. Specifically, such a modification would be “a matter of using a known technique to improve a similar device in the same way. Id. (citing KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398 (2007)).”

The applicant’s position was that these references were distinct with one showing a cantilevered airfoil (Baumann) and one showing a non-cantilevered airfoil (Bushnell). In other words, the applicant was advancing the position that because Bushnell’s airfoil is not cantilevered, a skilled person would not modify Baumann’s cantilevered airfoil based on the teachings of Bushnell.

However, by framing the issue in terms of the KSR inquiry as to similar devices, the applicant was able to give more substance to their position and point out that there was “a lack of evidentiary support for the Examiner’s finding that Baumann’s cantilevered airfoil and Bushnell’s outlet guide vane are “similar devices.” The issue then turned to all of the ways in which the cited references were similar (examiner’s position) and dissimilar (applicant’s position). You can read the PTAB’s analysis in the decision as it turns on issues specific to the technology at hand, but the point is that the “sufficiently similar” framework often provides a good avenue for an applicant to attack an obviousness rejection relying on using a known technique to improve a similar device in the same way.

The PTAB’s conclusion is explained as follows:

In the final rejection, the Examiner nominally states a correct legal principle. It is generally correct that, if a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way, using the technique is obvious unless its actual application is beyond his or her skill.

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Nevertheless, we find Appellant’s arguments rebutting the Examiner’s reasons to combine Baumann and Bushnell to be persuasive. The Examiner has failed to show that the airflow characteristics about Bushnell’s fixed, fan section, outlet guide vane are sufficiently similar to the airflow about a cantilevered compressor vane and rotating seal land that a person of ordinary skill in the art would recognize that Baumann’s cantilevered airfoil would benefit from circumferential lean.

So, look for opportunities to attack obviousness rejections relying on using a known technique to improve a similar device in the same way when the examiner has not sufficiently established the similarity of the devices and their operation relative to the alleged known technique.