Brief in favor of Honeywell for infringement - Due 4/4 (901422128)

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Brief in favor of Honeywell

Honeywell brought an infringement suit against Sundstrand for a device used to control airflow surge in auxiliary power units (APUs) which occurs when the flow through a compressor is not high enough. The surge control systems are designed to maintain a minimum level of airflow through the compressor at all times. In the Honeywell patent, a “set of adjustable inlet guide vanes (IGVs)…regulate the amount of ambient air drawn unto the load compressor.” The IGVs’ position is used to determine a set point for desired flow conditions which are compared to actual flow conditions in a feedback loop to regulate the surge bleed valve and prevent surging. Sundstrand invented a similar device, the APS 3200, which uses the inlet temperature to determine the set point, which is used in a similar fashion. In the APS 3200, the position of the IGVs is used to determine if the APU is experiencing high flow conditions, in which case the control signal is blocked because it produces an ambiguous signal which may cause the system to open the surge bleed valve unnecessarily. In the most recent CAFC case, Sundstrand maintains that Honeywell cannot make use of the doctrine of equivalents because a narrowing amendment made during the patent prosecution surrendered the technology used by Sundstrand. The CAFC sided with Sundstrand on this issue, relying on prosecution history estoppel to bar Honeywell from using the doctrine of equivalents. There are several flaws in the CAFCs analysis which should be taken into consideration by the Supreme Court.

First, as discussed by Judge Newman, the CACF majority concluded that Honeywell surrendered its claims to the technology used by Sundstrand during patent prosecution when the application was amended at the insistence of the patent examiner to rewrite dependent claims as independent claims. The Court maintains that the equivalent at issue here was foreseeable at the time of the application and therefore should have been claimed by Honeywell.

With regards to the surrender of specific claims, it is a matter of fact determined by the courts that the original independent claims, which were dropped and replaced by previously dependent claims, made no mention of IGVs so it is incorrect to conclude that Honeywell surrendered specific technology in the amended application which was never present in the original application. In this instance, the CAFC seems to have incorrectly determined that the mere cancellation of the original dependent claims, which included no narrowing amendment or limiting argument in the estoppel, served to surrender every potential equivalent. This effectively restricts a patentee’s access to the doctrine of equivalents; a doctrine intended to protect inventors from insubstantial changes to their patent claims as stated in Graver Tank. It is common practice for broader claims to be cancelled in the prosecution and dependent claims rewritten as independent claims, but this is irrelevant to whether a claimed element is amended or narrowed, a fact which the CAFC overlooks in this case by failing to analyze the original claims for content which was narrowed or surrendered.

The Court also errs when it states that the technology used by Sundstrand, although developed a decade after Honeywell’s patent, was foreseeable to those skilled in the art and thus should have been claimed as an equivalent by Honeywell. The Supreme Court in Warner-Jenkinson stated that the proper time for evaluating interchangeability is at the time of infringement, not at the time of patent application. Therefore the Court cannot conclude surrender of a technology which was not specifically included in the patent claims when it was not known, in its entirety, at the time of patent application. This standard essentially precludes the application of the doctrine of equivalents to future technology which was not included in the original application and therefore any analysis of foreseeability not applied to “readily known equivalents” at the time of application limits the doctrine in a way not intended by the Supreme Court. With these considerations in mind, it is clear that Honeywell should be allowed to assert the doctrine of equivalents in this case. A jury already determined the equivalence between the two technologies involved here and therefore since the doctrine is applicable it must be determined if an estoppel is reasonable based on the prosecution history which the facts of the case should it clearly is not. Therefore, the Supreme Court should find in Honeywell’s favor the infringement of their patents based on the doctrine of equivalents.

If this alone is not sufficiently convincing, the Supreme Court should also apply the triple identity test discussed by the Warner-Jenkinson Court for determining equivalence for mechanical systems. The test identifies and compares the “function served by an element, the way it serves that function, and the result thus obtained.” In this case, both Honeywell’s and Sundstrand’s technologies serve to control airflow through a compressor to prevent surges, do so by evaluating actual airflow into the APU and comparing that to a set point determined by other parameters in a feedback loop, and controlling the surge bleed valves to maintain a proper airflow through the APU. Under this precedent, it is clear that the Sundstrand APS 3200 is equivalent to Honeywell’s patent and was not surrendered during the patent prosecution.