Homework 9: Honeywell Brief (Ackroyd)

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In this case, Honeywell sued Sunstrand for infringement for a device to control airflow surge in auxiliary power units (APUs). Honeywell’s technology was more efficient than anything previous invented in the prior art. Honeywell made a change to its patent during the amendment process. The crucial issue of this case stems from this change, which involved changing a dependent claim in the patent to an independent claim. This change was necessitated by the initial rejection due to a prior art. The court focuses too much on the question of whether the doctrine of equivalents can be applied due to prosecution history estoppel. Honeywell was not allowed to use the doctrine of equivalents to prove that Sunstrand infringed because they had removed the independent claims from the original application. The court applied prosecution history estoppel in the wrong manner. By making changes to the application, the applicant surrenders equivalents concerned directly with the claims prior to the changes. The court incorrectly decided that the applicant also surrendered dependent claims, even though they were not changed. The removal of the claims by the applicant does not make this a case of prosecution history estoppel, and so it should not be applied. In making this error, the court in effect places a limit upon the applicability of the doctrine of equivalents to a patentee’s application.

Another error made in the court’s analysis of this case lies in the fact that it considered Sunstrand’s technology, which was invented a full ten years after Honeywell’s patent, to be foreseeable. Certainly, the lapse in time between similar inventions suggests that the latter of the two ought not to be considered foreseeable. Therefore, it is unreasonable for the court to decide that the later invention should have been claimed by Honeywell as an equivalent. According to Warner-Jenkinson, equivalence ought to be evaluated when infringement occurs, not when the original patent is applied for. It logically follows that the court should not have said Honeywell should have surrendered a certain technology which was not even yet known. Sunstrand’s argument that the technology was foreseeable is invalidated by the time it took them to develop said technology.

Foreseeability and equivalence seem to contradict each other. On the one hand, the doctrine of equivalents protects the patent owner from another inventor infringing through the use of a similar, yet not exactly equivalent, device. Foreseeability contradicts the protection afforded by this doctrine, by providing on the other hand “that the claims continue to define patent scope in all foreseeable circumstances, while protecting patent owners against insubstantial variations from a claimed element in unforeseeable circumstances.” It is for this reason that foreseeability should not be applicable, because it reduces the protection given to the patentees.

In summary, the court ruled unjustly against Honeywell in this case for two reasons. First, it misused the prosecution history estoppel in application to this patent and its constituent claims. Second, the court incorrectly applied the concept of foreseeability to this case. When the patent was prosecuted, the equivalent proposed by Sunstrand was unforeseeable, because the equivalent was not created by Sunstrand until a decade later. The court ought to have decided in favor of Honeywell based on equivalence, it having been shown that Sunstrand infringed.