1. Case background
On June 27, 2013, the Jiangsu High People’s Court issued its final judgment in a patent infringement dispute concerning nickel foam. During the first-instance, appellate and retrial proceedings, a central issue was whether vacuum pressures differing by a factor of ten could be treated as equivalent and therefore establish infringement under the doctrine of equivalents.
The final judgment was numbered (2011) Su Zhi Min Zai Zhong Zi No. 1. The case was included among the Supreme People’s Court’s ten leading intellectual property cases.
The court found that the base vacuum pressure and operating vacuum pressure in the allegedly infringing process each differed from the corresponding patented values by one order of magnitude, or a factor of ten. These were clearly different values. The two pressures also interacted in their functions and effects during magnetron sputtering. It could not readily be concluded that such different base and operating pressures would produce substantially the same effects. Neither feature was identical or equivalent to the corresponding essential feature of the patent. The allegedly infringing process therefore fell outside the patent’s scope of protection and did not infringe it.
As technology develops and legal awareness increases, fewer disputes involve literal infringement in which every feature is identical. Disputes concerning similar features are more common. How, then, should equivalence between similar features be assessed?
2. Principles for assessing equivalent infringement
Under Article 7 of the Supreme People’s Court’s Interpretation on Several Issues Concerning the Application of Law in the Trial of Patent Infringement Disputes, infringement occurs where the allegedly infringing technical solution includes features identical or equivalent to all the essential features recited in a claim. If one or more corresponding features are neither identical nor equivalent, the solution does not infringe.
Article 17 of the Supreme People’s Court’s Several Provisions on Issues Concerning the Application of Law in the Trial of Patent Disputes defines equivalent features as those that use substantially the same means, perform substantially the same function and achieve substantially the same effect, and that a person of ordinary skill in the art could readily conceive without inventive work.
These provisions establish the following characteristics of equivalent infringement.
2.1 Equivalence is assessed between individual features
The comparison concerns individual technical features, not the two technical solutions as a whole. Infringement requires features identical or equivalent to every essential feature in the claim. One or more features that are neither identical nor equivalent preclude infringement. The two solutions should therefore be divided into corresponding features in the same way, and those features compared individually.
This approach matters because two solutions may be equivalent overall even though individual features are neither identical nor equivalent: their interaction may still solve the same problem and achieve the same result. Treating overall equivalence as sufficient would expand the patentee’s claim coverage and harm the public interest. A feature-by-feature assessment is therefore comparatively fair.
2.2 Conditions for equivalent features
Equivalent features require three elements that are “substantially the same”—means, function and effect—and the ability to conceive the feature readily without inventive work. This resembles an inventive-step analysis, but places greater emphasis on comparing individual features.
If feature A in the allegedly infringing solution would be obvious in view of corresponding feature A′ in the patent, involving merely a change in wording or an equivalent substitution of conventional means, the features should be treated as equivalent. If the allegedly infringing feature is non-obvious in relation to the patented feature, they should not be treated as equivalent.
In the nickel-foam case, the patent specified a base vacuum pressure of (1.1–4.7) × 10⁻³ Pa and an operating vacuum pressure of (2.7–4.7) × 10⁻² Pa. The allegedly infringing process used 2 × 10⁻² Pa and (2.0–2.5) × 10⁻¹ Pa respectively. Each difference was approximately one order of magnitude. In vacuum sputtering, a roughly tenfold pressure change is a clear difference.
According to the prior art discussed in the case, a higher base vacuum produces a purer sputtered film, but also demands greater pressure resistance and sealing performance. Creating a higher vacuum takes more time and may reduce production efficiency. A lower operating vacuum allows more argon to be introduced and increases sputtering efficiency. There was no evidence that the two markedly different sets of pressures would yield substantially the same film purity and sputtering efficiency. The different pressures also required different power supplies and pressure-resistant equipment.
The court therefore considered the vacuum-pressure feature in the allegedly infringing process non-obvious in relation to the corresponding patented feature. It concluded that the features were not equivalent and that the patent was not infringed.
The case also illustrates an important point about numerical ranges. Where two ranges have clear endpoints and differ substantially, equivalence should not readily be inferred.
Relating an equivalence assessment to inventive-step principles can simplify the analysis. In practice, however, other principles—including estoppel and the prior-art defence—must also be considered to determine infringement accurately.
