We have covered the issue of design choice in several previous posts (here). The PTAB issued two new informative decisions on this issue, one affirmed and one reversed, that shed light on to how examiners and PTAB judges should approach the issue.
In the first case (United Technologies), the issue related to certain dimensions of a feather seal in a turbine. While the specification provided criticality for some claimed features of the seal, it did not provide any such evidence related to the claimed dimensions. As such, it was relatively easy for the PTAB to affirm the rejection.
In the second case, (frozen dessert manufacturing), the issue related to the location of a claimed passage being within a cold storage element. Here, the applicant argued that changing the location of the passage in the prior art would modify the operation of the prior art and thus would not achieve the same function as the claimed invention. The PTAB explained the decision in the overall KSR framework by noting that the examiner did not provide rational underpinnings to explain why a person skilled in the art would have modified the cited references. As explained by the Board (emphasis in bold added):
We discourage examiners from relying on “design choice” because it is generally a mere conclusion, which is no substitute for obviousness reasoning based on factual evidence. Nonetheless, “design choice” may be appropriate where the applicant fails to set forth any reasons why the differences between the claimed invention and the prior art would result in a different function or give unexpected results. See In re Chu, 66 F.3d 292, 298-99 (Fed. Cir. 1995). However, in this case, Appellants have explained how moving the combined passage member to cold storage as claimed would result in a different function than that shown by Meserole. Namely, combining the air and dessert mix inside the cold storage would prevent the entrained air from increasing the temperature of the mixture. See Br. 15; see also Spec. 26 (discussed supra). By contrast, because Meserole injects air directly from the compressor 25a into the cooled dessert mix at “air injection point 35,” we agree with Appellants that Meserole’s air injection increases the temperature of the mixture of dessert mix and air. See Br. 15. See also, Meserole, fig. 4. The Examiner has not set forth an explanation or technical reasoning why moving the combined passage member 35 of Meserole to cold storage would not result in a different function than that shown by Meserole, as Appellants suggest. We therefore find the Examiner’s proposed modification of Meserole is not an obvious design choice and reverse the Examiner’s rejection of claims 6, 8, and 10 under 35 U.S.C. § 103(a).
So, when facing a design choice rejection, it may be helpful to cite to these decisions. But if the only difference you have is a dimension, and you have no record evidence (beyond mere attorney argument) that the dimension is critical, then you may want to consider alternative approaches rather than simply arguing against the design choice rejection.