It is possible that a few drafting errors still exist in a granted claim due to drafting or examination carelessness, which may cause interested parties to understand the claim controversially in a post-grant proceeding. A recent Supreme Court decision shows that correction of the drafting errors can be allowed with conditions:

If a claim phrase in an invention or utility model patent is obviously wrong in expression, but people skilled in the art can find its unique correct explanation clearly, directly and without any doubt in accordance with the disclosure of its specification, the explanation can be used to define the claim's scope.

Patent Invalidation Dispute on "A Precise Rotation Compensator"

The Supreme Court proved this attitude in the (2011) Xing Ti Zi No. 13 Decision, regarding the validity of a patent for utility model No. ZL200720128801.1 entitled a precise rotation compensator (the '801 patent). The compensator is used in heat pipelines to absorb axial thrusts and displacement in the pipelines by rotating its inner and outer tubes. Claim 1 recites as below:

A precise rotation compensator comprising an outer tube, an inner tube, a pressing flange, an extension tube and a sealant layer, wherein a flexible graphite layer is filled between the inner tube (1) and the outer tube, the pressing flange is positioned on an end of the flexible graphite layer and connected to a second flange on an end of the outer tube via bolts, several steel balls are provided between an inner convex ring of the outer tube and an outer convex ring of the inner tube, the other end of the outer tube is connected to the extension tube, and a gap is formed between the two tubes, characterized in that the extension tube and inner tube are coaxial straight tubes of an identical inner radius; and the outside of the pressing flange and the inside of the outer tube are tight-fitting. (Highlighted by the author)

However, the embodiment of the Description discloses that "the straight extension tube 5 is positioned out of the outer tube 4 and has the same inner radius as that of the inner tube 1, and a gap (1-10mm) is formed between the extension tube 5 and the inner tube 1." Figure 1 illustrates the relationship among the outer tube 4, extension tube 5 and inner tube 1.


 In Figure 1, 1—inner tube, 2—pressing flange, 3—bolt, 4—outer tube, 5—extension tube, 6—out convex ring of the inner tube 6, 7—steel balls, 8—inner convex ring of the outer tube 5, and 9—flexible graphite filling layer.

 Petitioner filed an invalidation petition before the Patent Re-examination Board ("PRB"), challenging the inventiveness of the '801 patent, and claiming that the highlighted feature of claim 1 was not supported by the Description under Article 26. 4[1] of the Patent Law. The PRB cited the disclosure in the embodiment of the Description and concluded that the outer tube 4 and the extension tube 5 were fixedly connected without any gap being formed therebetween, however, between the extension tube 5 and the inner tube 1 a gap was formed. Patentee's argument of "obvious typos" of the highlighted feature was rejected by the PRB for the reason that "obvious typos were limited to obvious spelling and punctuation errors only" under the Guidelines for Examination. The PRB invalidated the '801 patent in its No. 13091 Decision, which was affirmed by the trial and appellate courts. Finally, Patentee appealed the Decision before the Supreme Court.

The Supreme Court held that a claim feature may have drafting errors like inexact wordings or expressions due to objective limitations on lingual accuracy and prosecution experience. It divided the drafting errors into obvious and nonobvious under their nature and extent. According to the Supreme Court, an error is obvious if people skilled in the art can find it immediately after reading other claims and determine its single right meaning by combining their knowledge with the disclosure in the Description and Drawings of the patent.

As disclosed in the '801 patent, the rotation compensator used in pressure pipelines shall meet testing requirements on wielding seams, pressure resistance and air-proof, and no leakage shall occur at wielding seams or filling places of sealant material. Therefore, the Supreme Court held that people skilled in the art should understand that the outer tube 4 and the extension tube 5 must be connected seamlessly otherwise transmitting media would leak out of the tubes. The compensator of claim 1 comprises the outer tube 4, the inner tube 1, the pressing flange 2, the extension tube 5 and the sealant material 9, wherein an end of the outer tube 4 is connected to the inner tube 1 via the pressing flange 2 and the other end is connected to the extension tube 5. The compensator absorbs axial thrusts and displacement of the heat pipelines by way of rotating the inner and outer tubes. Thus, neither between the inner and outer tubes nor between the outer and extension tubes is a connection formed with a gap. For people skilled in the art, they can directly and undoubtedly determine that "a gap being formed between the two tubes" means that a gap is formed between the extension tube 5 and the inner tube 1.

In addition, the Supreme Court held that if a patent was invalidated under Article 26 (4) only, but the patentee was not permitted to correct the obvious error in the claims, Article 26(4) might be used as a punitive tool against patentee's inappropriate claim drafting.

The Supreme Court overruled No. 13091 Decision as well as the lower courts' affirmations, maintaining the '801 patent's validity.

Comments of Lifang

The "obvious drafting errors" in §8.3, Chapter 2, Pat 1 of the Guidelines for Examination used to include obvious typos of spelling and punctuation, but the Supreme Court expanded them to obvious technical errors. Under the Court's ruling, an obvious technical error refers to one that people skilled in the art, based on their general knowledge, can identify and reach a single right explanation immediately after reading the claims, description, drawings or the file history. Such an obvious technical error usually has an "obvious" and "clearly defined" literal meaning, and results in a different claim scope if it is revised. On the other hand, such a technical error is sort of covert that people skilled in the art may have to compare the claim feature in question to the description or the file history, sometimes with necessary technical analysis, before its single right answer is determined.

The skilled in the art shall be the person to determine whether a claim feature is of an obvious technical error. If a claim feature comprises a phrase that makes the claim or the feature obviously contrary to the technology disclosed in description, or renders the technical solution apparently not doable or the technical problems unresolved, or causes the claim apparently inconsistent with what disclosed in the description, the phrase contains an obvious technical error. "A unique right answer that can be determined immediately" can be interpreted as an answer that can be deducted clearly, directly and without any doubt from the description and drawings. However, when considering whether a claim error is obviously wrong in technique, it is advised to put other claims, the description and file history, or patentee's specific response to the invalidation petition into account before a conclusion is reached.

Moreover, it seems that the Supreme Court would be more tolerable in interpreting drafting errors in a claim feature. The Court can cite the description to define a limitedly flexible explanation, in order to avoid mechanical understanding to the literal meaning of the feature.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.