"Prior art defense" has been recognized as a restriction to the applicability of the Doctrine of Equivalents (hereunder DOEs) in Taiwan practice. Taiwan Intellectual Property Office issued the Patent Infringement Assessment Guidelines, stating that if all the technical features of the alleged object falling within the claimed scope of the disputed patent are the same as a single piece of prior art, or as a simple combination of the prior art with the ordinary skill in the art, the prior art defense could be applied and the alleged object does not infringe the disputed patent under the DOEs. Most of the previous decisions of Taiwan Intellectual Property and Commercial Court (hereunder IPC Court) on the issue of prior art defense have adopted the Patent Infringement Assessment Guidelines as the determination basis. Recently, the IPC Court had a patent case (No. 2022 Civil Patent Suit 58, February 2023) involving how to determine whether the accused product is identical to the prior art that has additional technical features.
In this case, the literal scope of the asserted patent (TW M581023) defines a clamping mechanism for a machine, which has a piston seat and a clamping rod, and the bottom surface of the piston seat extends upward with a projection, and the projection is used to push the clamping rod. The plaintiff claimed that the accused product could be literally read onto most of the elements of the asserted claims, except for the piston seat of the accused product that was covered by the scope of equivalents under DOEs. The plaintiff reasoned that the bottom surface of the piston seat of the accused product is of the same thickness without any projection, but said bottom surface is used to push the clamping rod. While the defendant did not deny this DOEs coverage, the defendant raised the prior art defense. In contest, the plaintiff argued that the piston seat of the defendant’s prior art has an additional O-ring, and said piston seat would squeeze this O-ring before pushing the clamping rod, so that said prior art is not fully identical to the accused product.
For this, the IPC Court first identified "the technical features of the accused product that fall within the claimed scope of the asserted patent", based on the limitations of the asserted patent claims. Since both parties did not argue that most of the technical features in the asserted claims can literally read on the accused product, the IPC Court's descriptions of the technical features of the accused product that fall within the asserted claims were almost identical to the wordings in the claims or claim languages of the asserted patent. For the piston seat of the accused product, the Court described it as "having a base of the same thickness to push up the clamping rod." Next, the IPC Court compared the foregoing description of the accused product with the overall content disclosed by the defendant’s prior art, and concluded that the components of the clamping mechanism of said prior art are identical to the technical features of the accused product, which can be read on the asserted claims. Moreover, the IPC Court found that the piston seat of clamping mechanism of said prior art has the same thickness at the bottom, and the clamping mechanism uses the bottom of the same thickness to push the clamping rod. Therefore, the technical features of the accused product that fall within the scope of the asserted patent are identical to those of said single prior art. The IPC Court confirmed that the prior art defense could be applied to said case and the accused product did not infringe the asserted patent under the DOEs.
As for the plaintiff's contest that the piston seat of the defendant’s prior art has an additional O-ring element which is different from the accused product, the IPC Court held that the O-ring does not affect the piston seat of said prior art to push the clamping rod, and that the technical features of the accused product that fall within the scope of the asserted patent do not involve the O-ring. Nor did the asserted patent define any O-ring. Therefore, the IPC Court held that it is unnecessary to consider the O-ring and the connection between the O-ring and other components, as disclosed by said prior art, when determining prior art defense.
Because the disputes of previous court cases involving in prior art defense were mostly related to the differences between the prior art and the accused product, the IPC Court focused on determining whether said differences could be a simple combination of the prior art and the ordinary skill in the art (such as No. 2012 Civil Patent Suit 45). On the other hand, the issue of this recent O-ring case is about whether the prior art with additional technical features would be the same as the accused product. The IPC Court focused on whether said additional technical features of the prior art would affect the structure or function of the prior art in relation to the accused product, and whether said additional technical features are in the claim scope of the asserted patent or are identical to the technical features of the accused product that fall within the scope of the asserted patent. Said judgment could be used as a reference for those who argue prior art defense as restrictions to the applicability of the DOEs in Taiwan.