According to the relevant judicial interpretations, in interpreting the content of a patent claim, the People’s Court should rely on the description in a patent claim and take into account of the comprehension by an informed ordinary technician of the same patent claim after perusal of the specifications and attached drawings.  However, in practice some incorrect terms may somehow appear in a patent claim. Will the court uphold the plea filed by the patentee in an infringement suit for correcting such erroneous description in the patent claim by employing the terms used in the specifications and drawings? 

In the patent infringement case brought by Wuxi Longsheng Cable Factory before the Supreme Court for review (ref. (2012) Min Ti Zi No. 3), the above-mentioned issue was highlighted. The Supreme Court published its decision with detailed jurisprudential analysis, which should be well noted.

In the hearing, both the patentee and the experts for testimony insisted that certain technical terms in patent claim 1 were incorrect and should be replaced by the equivalents in the patent specifications and attached drawings so as to prove that the alleged infringing method was consistent with the technical features described in patent claim 1.

The Supreme Court held that normally the meaning of a specific term in claim 1 is irreplaceable by that of a common term used in the patent specifications and the attached drawings. The reasons were given by the court as follows. Firstly, when determining the meaning of a term created by a patent drafter, we should interpret the term as an informed ordinary technician in the specific discipline or industry rather than simply replace such coined term with a common phrase used in the discipline or industry by arguing that the coined term is not commonly used. 

Secondly, when interpreting the terms in a claim, each of these terms shall be deemed to have distinct meaning, instead of being unnecessary. Thirdly, if an ordinary technician is able to readily understand a term in a claim which is not afterward defined in the specifications, such technician’s comprehension of the term should prevail and the specifications should not be employed to overturn the content of the claim. Otherwise, the interpretation will end up in substantial alteration of the patent claim and, in effect, open a window of opportunity for patentee to amend the patent claim unlawfully, which will thus prejudice the declaration and definition of right that the patent claim purports. 

On the other hand, the Supreme Court also pointed out that in certain circumstances the inaccurate expression in the patent claim may be rectified by using the terms in the specifications. If an informed ordinary technician in the discipline or industry becomes aware of an obviously erroneous term in the claim immediately after reading the specifications and the attached drawings, and at the same time is able to revise such term definitively, straightforwardly and without any doubt, such revision is allowed.

The merit in this case is that it clarifies whether and to what extent the specifications and the attached drawings may be used to construe a patent claim. Notwithstanding the limited admissibility, it is highly advisable for the patent drafter to use his best endeavor to employ clear, accurate and complete expressions in preparing the patent claim so as to avoid future annoyances for patent enforcement.