As discussed in a previous post, in re Schulhauser (a precedential PTAB opinion) is turning out to be a significant case for control-system-related inventions. Schulhauser enables the USPTO to consider read out limitations of a claim that can be labeled “conditional.” For example, if a claimed method recites two options dependent on a sensed parameter, prior art showing only one option based on the sensed parameter can anticipate the claim. An example quote from a recent PTAB decision is illustrative:

Under the precedent of the Board, when construing a method claim according to its broadest reasonable interpretation, conditional steps in process claims need not be carried out to be within the scope of the claim.

Not surprisingly, Schulhauser continues to be used by examiners, and the PTAB, to reject claims with so-called conditional limitations. However, Schulhauser is increasingly cited for more general propositions relating to what might be called anticipation by happenstance. This is where the prior art disclosures might create operations that would anticipate the claimed method steps in operation. Such conjecture is usually based on some mental exercises in considering how a prior art disclosure would perform in use.

A recent example is 14/478,552, where the invention relates to a method of reducing engine induced aircraft cabin resonance. Claim 1 includes the following steps (with the underlined steps being some of the limitations in dispute):

sensing core engine speed of a first turbofan gas turbine engine;
sensing core engine speed of a second turbofan gas turbine engine; and
in a control system:
processing the core engine speed of the first turbofan gas turbine engine and the core engine speed of the second turbofan gas turbine engine to determine a core engine speed difference between the first and second turbofan gas turbine engines;
processing the core engine speed difference to supply a variable inlet guide vane (VIGV) offset value;
receiving a signal indicating that fan speed synchronization of the first and second turbofan gas turbine engines has been enabled;
upon receipt of the signal, processing the core engine speeds of the first and second turbofan gas turbine engines to determine which has a lower core engine speed; and
applying the VIGV offset value to a VIGV reference command associated with the turbofan gas turbine engine having the lower core engine speed, to thereby cause the VIGV s of the turbofan gas turbine engine having the lower core engine speed to move to a more closed position.

The cited art, Snow, calculated a speed differential (positive/negative) and so was found to determine which engine had a lower speed. However, the cited art did not control the slower engine, but rather had them tied together in a fixed primary-secondary relationship. Nevertheless, the examiner and PTAB both found that the cited art anticipated the claim elements since the cited art could create a situation where the claimed actions occur. Such a result was due in part to the way in which the claim language was crafted, in what might be called more result-oriented claiming.

Specifically, the PTAB explained the decision by noting that “… sometimes, Snow’s error signal will be used to adjust the slower engine, so long as the slave engine is the slower engine. Accordingly, we affirm the rejection of claim 1…” Of note, the PTAB confirmed that the result is different for device claims that recite the control system (e.g., a control system to. . . set the turbofan gas turbine engine having a lower core engine speed as a slave turbofan gas turbine engine”). This conforms with some of the discussion in our previous post linked above, which noted that one option to guard against a Schulhauser construction was to “… include system claims with instructions stored in memory, as these structural elements should not be considered optional in the same sense as the reasoning in Schulhauser.”

Applicants should be careful in crafting the claim elements and consider how Schulhauser may be relied on by the USPTO. Here, the applicant tried to argue that the claims required a link between the determination of which engine has a lower speed and the application of the actuator offset, but such an argument was unpersuasive because the claim was not so limited. Specifically, the PTAB explained that:

It is of no moment for purposes of claim 1 that Snow does not use the results of that determination as a basis to determine to which engine to apply the variable inlet guide vane (VIGV) offset or VSV actuator signal because claim 1 recites no such requirement. Rather, claim 1 only requires the application of the VIGV offset to the engine having the lower speed, and this will occur, as would be expected at least some of the time in Snow.

So, be careful with your claim scope and make sure to consider how the USPTO might apply prior art under Schulhauser.