IP News

In Honeywell Int'l, Inc. v. Hamilton Sundstrand Corp., 2006-1602 (Fed. Cir. April 18, 2008), the Federal Circuit held that Honeywell did not rebut the presumption of prosecution history estoppel arising from its rewriting of dependent claims into independent form coupled with the cancellation of the original independent claims during prosecution.

The asserted claims related to a system (and method for utilizing the same) for controlling unwanted airflow surges through aircraft gas turbine engines. Prior art systems provided wide safety margins by drawing more air than required into the engine's compressor, but were inefficient. Honeywell's patent relates to the use of inlet guide valves ('IGVs'), which operate like Venetian blinds to regulate the air drawn into the compressor. The invention compares actual airflow to a 'set point,' which represents the desired flow conditions and makes adjustments accordingly. The set point in Honeywell's invention is a function of the position of the IGVs. During prosecution, Honeywell cancelled three independent claims in response to an obviousness rejection and rewrote claims depending from the same into independent form. The rewritten dependent claims each contained additional limitations related to IGVs and their position that were not present in the original cancelled independent claims.