Federal Circuit Finds Claimed Invention Obvious, Reversing Trial Judge & Jury

Scott Daniels | August 27, 2015

ABT Systems v. Emerson Electric

August 19, 2015

Before: Prost, Clevenger & Schall, opinion by Schall


A jury found the ‘017 patent (U.S. Patent No. 5,547,017) to be valid and infringed, and awarded reasonable royalty to the patentee as damages. The trial judge subsequently denied the accused infringer’s motion for JMOL that the patent was invalid as obvious. On appeal, the Federal Circuit concluded that the claimed invention was obvious and that the trial judge should have granted the JMOL motion. The Federal Circuit therefore remanded the case to the trial judge with instructions to enter judgment in favor of the accused infringer.


According to the ‘017 specification, certain prior art discloses heating, ventilation and air conditioning (HVAC) systems that recycle air in “auto mode” in which the fan runs only when the thermostat calls for heating or cooling. Other prior art HVAC systems operate in “constant fan mode” in which the fan runs continuously regardless of whether there is a call for heating or cooling.

The ‘017 patent claims a control for running an HVAC system intermittently when the thermostat is not calling for heating or cooling.

Representative claim 1 recites:

A fan recycling control apparatus for a central air conditioning (CAC) system comprising:

a circulating fan;

a central air conditioning system with ducts to distribute cooled and heated conditioned air throughout a building;

a thermostat for activating and deactivating both the central air conditioning system and the circulating fan; and

a recycle control for periodically activating and deactivating only the circulating fan after a preselected time period, since the central air conditioning system or the circulating fan have been deactivated from the selectable constant fan mode.

By periodically cycling between working and not working, the fan achieves a Goldilocks combination of good air circulation and reduced energy cost.

The District Court Trial

At trial, the accused infringer asserted that the ‘017 claims were invalid as obvious over four prior art references, either alone or in combination.

  • Cornelius disclosed a circulation fan that cycles on and off when there is no call for heat and a timer to operate the fan at predetermined intervals, but did not disclose the timer being tied to the deactivation of the heating elements.
  • Vogelzang disclosed periodic fan operation when there is no call for heating or cooling, but did not disclose running the fan periodically based on when the heating or cooling elements are deactivated.
  • Petrone disclosed single-shot fan operation, after use, to drain the coils, but did not disclose periodic air circulation following deactivation of the cooling elements.
  • Nakatsuno disclosed driving the fan intermittently to improve user comfort and reduce energy consumption, but only a single-shot fan cycle following a predetermined delay after system deactivation.

The jury issued a verdict in favor of the patentee, and the trial judge denied the accused infringer’s motion to set aside the verdict. The judge explained that the jury could reasonably find that the references did not disclose “‘periodic’ fan operation that was dependent upon the deactivation of the heating or cooling function of the system, and further that was adaptable to modern air conditioning systems.” The judge also cited a statement of long-felt need, in the patent specification.

Federal Circuit Appeal

The Federal Circuit began its analysis by stating that (1) it presumes that the jury resolved all factual disputes between the parties in favor of the prevailing party, here the accused infringer, and (2) it accepts as true the jury’s factual findings, provided that those findings are support by substantial evidence. The Court then explained that there was very little difference between the parties regarding the disclosure of the prior art references, the differences between the claims and the references, and the level of skill in the art.

The Federal Circuit then acknowledged that a reasonable juror could have found that, while technology for activating a fan after a predetermined time period following the end of a heating or cooling cycle existed in the prior art, but that it might have been implemented as a single event at the end of a cooling cycle for purposes of draining cooling coils.

The shortcomings of the prior art were acknowledged: Cornelius does not satisfy the “activating and deactivating only the circulating fan after a preselected time period, since the central air conditioning system has been deactivated” requirement of claim 1 and Vogelzang likewise does not teach a periodic fan that “operates as a function of when a heating or cooling cycle ends.” Both Cornelius and Vogelzang disclose a timer that may be unassociated with the deactivation of the heating and cooling cycles.

The Federal Circuit then framed the appellate issue as whether one would have combined elements from the several prior art references, in particular, whether one would have combined references that disclose “single-shot” fan operation as a function of the time when heating or cooling cycles end with references that teach periodic fan cycles during periods of time when there is no call for heating or cooling.

A combination of the primary references with the secondary references would result in the claimed invention: the timer of Vogelzang or Cornelius, modified by the predetermined and compressor-dependent interval of Nakatsuno or Petrone, would have yielded a predictable result: a fan system that would activate periodically following the end of a heating or cooling cycle, as claimed in the ‘017 patent.

The Federal Circuit concluded that it would be obvious from that disclosure itself to set the periodic fan to run as a function of when the heating or cooling cycle ended. The references are analogous because the nature of the problem to be solved in both the ’017 patent and Vogelzang (as well as Cornelius and Nakatsuno) is to alleviate air stagnation during periods of no heating or cooling.


(1) A common problem in the references might constitute a reason to combine, without requiring “motivation.”

(2) Simple mechanical inventions have second class status, as compared with the technologies regarded as more complex.

(3) Secondary considerations usually fail to overcome obvious attacks.

(4) Opinions of counsel that a patent is obvious are possible after KSR.

Full Opinion

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