Homework 27: Argument for Hamilton Sundstrand

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In the case of Honeywell v. Hamilton Sundstrand, it was observed that the courts, while providing thorough discussion in many related aspects to the case at hand, neglected to address the issue of comparison of the two devices against the actual doctrine of equivalence itself. Hence, it is the desire of this brief to provide support for Hamilton Sundstrand expressly on this particular issue.

The doctrine of equivalence itself holds that elements are equivalent when they perform substantially the same function in substantially the same way to produce substantially the same result.

According to the court, it was correctly established by Honeywell that the subject(s) to which the doctrine of equivalence applies for these two patents is their respective uses for 1) a static pressure differential under low flow conditions in order to detect surge, in combination with 2) the inlet guide vane positions for the purpose of determining the flow conditions in order to detect surge. The following will be an analysis on an element-by-element basis, as recommended the courts in Warner-Jenkins v. Hilton Davis (1997).

Sundstrand’s device uses the inlet guide vane positions to solve the “double solution” problem, one related to incorrect readings because of high flow levels, by blocking the control signal during high-flow conditions. This is related to their choice of the DELPQP flow-related parameter, which becomes inversely related to the amount of flow under high-flow conditions. To solve this problem, the inlet guide vane position is used to determine the flow conditions and whether it is necessary to block the control signal. The Sundstrand device compares the DELPQP parameter to a set point based on air inlet temperatures in order to prevent surge.

Honeywell’s device uses the inlet guide vane positions to adjust the set point against which the flow-related parameter is measured. In order to avoid surges, the Honeywell invention establishes a minimum flow “set point.” This set point is a function of the position of the inlet guide vanes. The airflow out of the compressor is measured and compared to a “flow-related parameter” (measuring actual flow conditions), and thereby regulating the set point (desired flow conditions).

Thus, in the Sundstrand device, the IGV position is used to determine the flow condition, in order that the right solution for the DELPQP parameter (representing a pressure differential) might be obtained. This DELPQP parameter is then compared to a set point base on inlet temperatures. In the Honeywell device, the IGV positions are used to determine the set point, which is in turn compared to a flow-related parameter based on measurements of the flow (the pressure differential).

It may be conceded that the two devices perform substantially the same function, which is determining a set point for minimum flow, and produce substantially the same result, namely the prevention of surge. However, it is clear from the above description of the methods used, that the two devices do not perform these functions or achieve these results in substantially the same way. According to Valmont Industries v. Reinke Manufacturing (1993), all three conditions must be met.

This can be said especially since the Sundstrand device uses, not the IGV position, but temperature, a parameter not taken into account in the Honeywell device, to determine its flow set point. In addition, this point may be further supported by the fact that the two devices, while no doubt sharing some physical elements in common, nonetheless would require some other vastly different physical components in order to obtain their respective measurements and results.

Following this reasoning, the court is thus urged to rule in favor of Hamilton Sundstrand.