A Decision rendered by the IPC Court in 2022 on a patent infringement lawsuit attracted much attention from practitioners since it brought about the question of whether a second post-grant amendment conducted during the prosecution of an invalidation action constitutes a violation of the doctrine of “file wrapper estoppel” if it deleted part of the contents added to the specification by the first amendment.
As a general rule, the IPC Court, in this Decision, elaborated that the doctrine of “file wrapper estoppel” only applies to the situation where, during the patent filing or maintenance process, any amendment, correction, or argument that narrows the scope of the claims shall prevent the applicant/patentee, from claiming those abandoned rights on the basis of the doctrine of “equivalents.” At this rate, the doctrine of “file wrapper estoppel” is merely one of the limitations imposed on the doctrine of “equivalents” while it does not have any bearing on the statutory reasons allowed for post-grant amendments. In essence, if a patentee conducts two post-grant amendments during the prosecution of an invalidation action, the first amendment shall be deemed withdrawn when the second amendment is filed, according to Article 77.3 of the Patent Act. If the second amendment falls within the statutory reasons and requirements set out in Article 67 of the Patent Act, including (1) to delete claims; (2) to narrow the scope of claims; (3) to correct misstatements or mistranslations; and (4) to clarify uncertainties, it shall not be disallowed. Moreover, except for correcting translation errors, no amendments should go beyond the scope disclosed in the specification, claims, or drawings at the time of filing and besides, it is not allowed to substantially expand or alter the scope of the claims as published.
During the prosecution of the invalidation action filed by the defendant against the patentee’s patent for "Crossbow Arrow Loading Device." (hereinafter referred to as "the disputed patent"), the patentee filed two post-grant amendments. The defendant thus argued that, by the first amendment, the patentee incorporated some technical features into the specification that defined the engaging part 30 and the joining part 14 as a wing and a slot, respectively. However, such description was deleted when conducting the second amendment so as to allow the engaging part 30 and the joining part 14 to be interpreted not limited to a wing and a slot. As such, the two amendments conducted in a row constituted a violation of the doctrine of “file wrapper estoppel,” as a result of which, the second amendment shall be deemed invalid.
The IPC Court held that the technical features added to the specification of the disputed patent by the second amendment were already illustrated in the drawings at the time of filing the disputed patent. The addition of the "engaging part" and "joining part" further narrowed the working relationship between the arrow box and the bow body recited in the amended claims. Such amendment did not exceed the scope disclosed in the specification, claims, or drawings at the time of filing, nor did it substantially expand or alter the scope of the claims of the patent as published. Therefore, there was no reason whatsoever to disallow the second post-grant amendment.
It appears, from the court decision, that the doctrine of “file wrapper estoppel” cannot be based on to prevent the patentee from asserting his patent right interpreted in accordance with the second allowed post-grant amendment conducted during the prosecution of an invalidation action.