Written by Jirui Zheng

 

Infringement Case Study: Equivalence Infringement Principle for Technical Features Defined by a Numerical Range

 

I. Question Raised

 

In the judicial practice of patent infringement litigation in China, there is a strict attitude towards the application of the equivalence principle to numerical features. Does this mean that numerical features are not subject to the equivalence principle? Can infringement be avoided simply by amending the numerical features of a product differ from those specified in the claims?

 

II. Case Summary

 

The patent in question is an invention patent with the patent number 201310348393.0, titled "A Locking Device of Telescopic Tube." The focal point of the dispute is whether the transverse width (L) of the limiting surface of the alleged infringing product, which is 0.45 times the inner diameter of the hoop clamp, is equivalent to the technical feature described in the claim, which specifies a ratio of "0.5-0.8 times."

 

Furthermore, the Supreme People's Court found that claim 1 of the involved patent application had been amended several times during the substantive examination, including the addition of the feature from original claim 2: "The locking device of the telescopic tube according to claim 1, wherein the transverse width (L) of the limiting surface of the limiting block (9) is 0.5-0.8 times the inner diameter of the hoop clamp (4)." The examiner pointed out in the fourth office action that the amended claim 1 lacked inventiveness. Consequently, the applicant further amended claim 1 to add the technical features "the back of the limiting block (9) is an arc surface" and "the arc surface of the back of the limiting block (9) fits against the inner circular wall of the tube (7)". The patent was eventually granted.

 

III. Judgment

 

When assessing whether technical features defined by numerical ranges constitute an equivalent feature, unless a person skilled in the art, after reading the claims, specification, and drawings, believes that the technical solution particularly emphasizes the role of the specific numerical value or range in defining the technical feature, it should also be considered based on whether the difference in the numerical values has a substantial impact on the overall technical solution.

 

At the same time, strict limitations should be imposed when applying the equivalence principle. It is required that the difference in numerical value or range reflect the same technical means, and achieve the same technical function and effect. In addition, factors such as the technical field, type of invention, and content of claim amendments should be considered. Taking into consideration of the above, the equivalence principle applies only when an equivalent technical feature does not violate the reasonable expectations of the public regarding the scope of protection of the claims and fairly protect the interests of the patentee.

 

In this case, the disputed technical feature "the transverse width of the limiting surface of the limiting block (L) is 0.5-0.8 times the inner diameter of the hoop clamp" is not the inventive point of the patent in question. By reading the description, a person skilled in the art can understand that the role of this numerical range in the technical solution is to ensure the stability of the inserted tube.

 

Therefore, for numerical values particularly close to the defined range that can solve the same technical problem, there is still possibility to include them into the scope of equivalent technical features. Given that the difference of numerical ratio between the alleged infringing product and the claimed range is only 0.05, which is within a range of 10%, the technical means adopted by both are fundamentally the same to a person skilled in art, and the achieved functions and effects are substantially the same. In this case, it should be recognized that the numerical features as equivalent.

 

Comment

 

Numerical features in claims should be considered in a strict manner when applying the equivalence principle, mostly due to the fact that claims are publicly available. When determining whether a numerical feature constitutes an equivalent feature, it is necessary to consider the technical field, the type of invention, the modified contents of the claims, and whether the technical solution emphasizes technical features defined by the numerical value or range. Taken into consideration of the above factors, equivalence principle is applied when it does not violate the public’s reasonable expectations for the protection scope of the claims and can fairly protect the interests of the patent rights.

 

                                                                                                                                     Source: Supreme People's Court Guiding Case (No. 985)