Details: Rolls-Royce v. United Tech. Corp. was a review of an interference decision for patent applications involving turbine fan blades. After claim construction, the question of obviousness amounted to whether a foward sweep angle of the fan blade was obvious in view of a rearward sweep angle. UTC argued that a POISTA "would have found it obvious to try to reverse the sweep angle from rearward to forward sweep."
Instead of viewing obviousness as a matter of two choices (forward or rearward), the court instead saw a "broad selection of choices for further investigation", which "included any degree of sweep." The court noted that such a large number of choices goes against obvious-to-try, referring to the post-KSR obvious-to-try decision Abbott Labs. v. Sandoz, Inc., 544 F.3d 1341 (Fed. Cir. 2008):
To determine that an invention would have been obvious to try on the basis of the record before the time of invention, this court has clarified, with respect to inventions requiring selection of a species from a disclosed genus, that the possible approaches and selection to solve the problem must be "known and finite." See Abbott, 544 F.3d at 1351.
It's not clear that the large number of options alone would have led the court to find non-obviousness, because the record did not show any "design need or market pressure or other motivation" to try forward sweep. The court thus found that "the invention would not have presented itself as an option at all, let alone an option that would have been obvious to try."
My two cents: The issue of the number of options as it relates to obviousness usually comes up in the chemical arts. This is the only Federal Circuit decision I know of, outside of the chemical arts, that discusses this issue in depth. The next time I get an obviousness rejection that seems to rely on obvious-to-try, I'll see if I can re-frame the number of choices as large rather than small. If so, I'll use Rolls-Royce v. United Tech. Corp. to make this part of my argument.