The legal concept of obviousness is tricky. A claimed invention is found obvious if the prior art teaches or suggests all claim limitations and one of ordinary skill in the art would have been motivated to combine the relevant teachings of the references. The inherent subjectivity of such an analysis can lead to reasonable people disagreeing on whether an invention is ultimately patentable. But it does not end there — like an onion, obviousness has layers. Normally, whether the references themselves provide enabling disclosure is not relevant. Except when it is.
Raytheon is the owner of U.S. Patent No. 9,695,751, which was challenged by General Electric (GE) in an inter partes review before the Patent Trial and Appeal Board (PTAB). Of note are claims 1-3 of the patent, shown in part below.
1. A gas turbine engine comprising:
a fan including a plurality of fan blades . . . ;
a compressor section;
a combustor in fluid communication with the compressor section;
a turbine section in fluid communication with the combustor, the turbine section including a fan drive turbine and a second turbine . . . ; and
a speed change system configured to be driven by the fan drive turbine to rotate the fan about the axis; and
a power density at Sea Level Takeoff greater than or equal to 1.5 lbf/in3 and less than or equal to 5.5 lbf/in3 and defined as thrust in lbf measured by a volume of the turbine section in in3 measured between an inlet of a first turbine vane in said second turbine to an exit of a last rotating airfoil stage in said fan drive turbine.
2. The gas turbine engine as recited in claim 1, wherein the fan drive turbine has from three to six stages.
3. The gas turbine engine as recited in claim 2, wherein said number of fan blades is less than 18 and the second turbine has two stages.
In the words of the court, “[t]he ‘751 patent generally claims a geared gas turbine engine with two turbines and a specific number of fan blades and turbine rotors and/or stages.” Further, the “key distinguishing feature of the claims is the recitation of a power density range that the patent describes as being ‘much higher than in the prior art.'” Here, power density is defined as sea-level-takeoff (SLTO) thrust divided by the engine turbine volume.
During the proceeding, Raytheon disclaimed claims 1 and 2 (among others), leaving claim 3 as representative. GE’s obviousness contentions for claim 3 relied only on a single reference, a non-patent literature document by Knip.
Knip is “a 1987 NASA technical memorandum that envisions superior performance characteristics for an imagined advanced turbofan engine incorporating all composite materials.” It is undisputed that such an engine could not be built in 1987 and still cannot be built today. But such speculation allowed Knip “to assume aggressive performance parameters for an advanced engine, including then-unachievable pressure ratios and turbine temperatures.” Nonetheless, Knip does not disclose SLTO thrust, turbine volume, or power density for this hypothetical engine. GE asserted that “because power density is a result-effective variable, even if Knip did not disclose a turbine section volume and/or SLTO thrust that resulted in a power density within the claimed range, it would have nevertheless been obvious to a skilled artisan to modify the thrust and/or turbine volume for Knip’s engine to optimize the power density.”
Before the PTAB, Raytheon argued that “GE’s expert employed a flawed methodology in deriving the power density of Knip’s advanced engine from the parameters that Knip disclosed,” and that Knip’s disclosure failed to enable a skilled artisan to make the claimed invention. GE countered by stating that “the issue of whether Knip enabled its advanced engine was irrelevant to the question whether a skilled artisan reviewing Knip could make the ‘751 Patent’s engine (using any already available materials) without undue experimentation.” Note the subtle difference in the points being made — Raytheon is alleging that Knip does not enable one to make the invention of the ‘751 patent, while GE is addressing whether Knip enables one to make Knip’s own engine.
In any event, the PTAB ultimately found Knip enabling because it allowed “a skilled artisan to “determine a power density as defined in claim 1, and within the range proscribed in claim 1.” As a result, the PTAB concluded that Knip rendered the claims obvious.
On review, the Federal Circuit set forth the delicate interactions between obviousness and enablement. Writing for the Court, Judge Chen noted that “[i]n general, a prior art reference asserted under § 103 does not necessarily have to enable its own disclosure, i.e., be ‘self-enabling,’ to be relevant to the obviousness inquiry.” To that point, “a reference that does not provide an enabling disclosure for a particular claim limitation may nonetheless furnish the motivation to combine, and be combined with, another reference in which that limitation is enabled.” Further, “such a reference may be used to supply claim elements enabled by other prior art or evidence of record.”
Thus, the point at issue in this case was whether a skilled artisan could have made the claimed invention regardless of whether the cited references are self-enabling. Of particular relevance to single-reference obviousness contentions such as one made by GE, is that “a standalone § 103 reference must enable the portions of its disclosure being relied upon.”
The Court found that the PTAB erred by focusing on whether Knip enabled determination of a power density. The PTAB should have considered “whether Knip enabled a skilled artisan to make and use the claimed invention.” The PTAB’s conclusion of obviousness could have been supported “if GE had presented other evidence to establish that a skilled artisan could have made the claimed turbofan engine with the recited power density.” But that did not happen. Therefore, according to the Court, “Knip’s self-enablement (or lack thereof) is not only relevant to the enablement analysis, in this case it is dispositive.”
The Court also found GE’s use of expert testimony to be lacking, because its expert constructed “a computer model simulation of Knip’s imagined engine” rather than the actual engine. In contrast, Raytheon’s expert presented unrebutted evidence of non-enablement — the “unavailability of the revolutionary composite material contemplated by Knip.” Raytheon also “submitted evidence that the exceptional temperature and pressure parameters cited in Knip had not been achieved through other means as of the priority date.”
Moreover, GE argued that a skilled artisan could achieve the claimed power density by optimizing Knip’s engine. But the Court rejected this notion, stating that “[i]f a skilled artisan cannot make Knip’s engine, a skilled artisan necessarily cannot optimize its power density.”
For these reasons, the Court reversed the PTAB’s finding of claim 3 to be obvious.
This case is interesting, though it presents an avenue for arguing for non-obviousness that is unlikely to be available in practice very often. Here, the Knip reference was admittedly speculative, and gaps between Knip’s speculation and reality matched up with the gaps in GE’s arguments. By adding in other references or reasoning, the outcome may have differed. Perhaps the holding here is best summarized by Judge Chen writing “if an obviousness case is based on a non-self-enabled reference, and no other prior art reference or evidence would have enabled a skilled artisan to make the claimed invention, then the invention cannot be said to have been obvious.”
 Also like an onion, obviousness as a legal principle has the ability to make one involuntarily cry.
Raytheon Technologies Corp. v. General Electric Co. (Fed. Cir. 2021)
Panel: Circuit Judges Lourie, Chen, and Hughes
Opinion by Circuit Judge Chen