Date: 30 January 2026

【Volume 165】

I. Introduction: The Tension Between Numerical Features and the Doctrine of Equivalents

Numerical or parametric features (such as ratios, dimensions, concentrations, and temperatures) in patent claims provide clear notice to the public, while leaving the patent inherently susceptible to design-around. In early Chinese judicial practice, courts tended to deny the applicability of the doctrine of equivalents to numerical features. In recent years, however, the Supreme People’s Court (hereinafter as “SPC”) has made it clear that numerical features are not per se excluded from equivalence-based infringement. At the same time, courts have imposed a series of limiting doctrines—including the “express exclusion principle”, “rule of dedication”, and “the doctrine of prosecution history estoppel”—to firmly restrain patentees from retrospectively expanding the scope of protection beyond clearly defined claim boundaries. Based on the current legal framework and the adjudicative views of the Supreme People’s Court, this article systematically examines the judicial standards, representative court decisions, and emerging trends in Chinese courts’ assessment of equivalence infringement involving parametric features, and further offers practical insights for patent drafting and litigation strategy.

II. General Framework for Determining Infringement by Equivalence and Representative Decisions

i. Application of “the Triple Identity Test Plus the Lack of an Inventive Step” Test

According to Several Provisions of the Supreme People's Court on Issues concerning the Application of Law in the Trial of Cases Involving Patent Disputes¹ published by the SPC, an equivalent feature must satisfy the requirements that “the means, function, and effect” are substantially the same, and must be one that a person ordinarily skilled in the art could conceive of without the exercise of inventive effort.

Representative Decision I: SPC IP Civil Final Judgment No. 985 (2021)

In this case, the claim limited a certain structural ratio to 0.5–0.8, while the accused infringing embodiment employed a ratio of 0.45. The SPC held that where such a numerical limitation does not constitute the key inventive point underlying the grant of the patent, and where the difference falls within a range of minor adjustments foreseeable to a person ordinarily skilled in the art, equivalence may still be established provided that no substantial difference arises in function or effect. This decision demonstrates that numerical proximity and the significance of the numerical limitation to the patent’s technical contribution are decisive factors in SPC’s determinations of infringement by equivalence.

Representative Decision II: SPC IP Civil Final Judgment No. 373 (2021)

This case involved a difference between 1.05 m and 1.06 m in large-scale shield tunneling equipment. The SPC emphasized that, in the context of macroscopic equipment, a minor numerical deviation does not necessarily result in a substantive difference in technical effect. In the absence of countervailing evidence, a finding of infringement under the doctrine of equivalents may still be established.
This decision highlights that SPC will take into account the scale and characteristics of the relevant technical field, rather than relying solely on a formalistic comparison of numerical values.

III. Major Limiting Principles on Equivalence of Numerical Features and Representative Decisions

i. Express Exclusion Principle

The Interpretation (II) of the SPC on Several Issues Concerning the Application of Law in the Trial of Patent Infringement Disputes², which came into effect on April 1, 2016, provides that where a claim clearly defines numerical boundaries using terms such as “less than” or “not exceeding,” and the specification demonstrates that such boundaries have substantive technical significance, technical solutions falling outside those boundaries shall principally not be covered under the doctrine of equivalents.

Representative Decision III: SPC IP Civil Final Judgment No. 516 (2019)

In this case, the claims defined the spacing between structures as “less than 15 mm,” whereas the accused embodiment adopted a spacing of 15–17 mm. The SPC held that, since the patentee had expressly chosen “less than 15 mm” as the boundary of protection, it must bear the corresponding legal consequences and may not recapture numerical ranges that were deliberately excluded through the doctrine of equivalents.
This case is regarded as a classic application of the express exclusion principle in disputes involving numerical features.

ii. Rule of Dedication

Where the specification discloses a broader numerical range but the claims assert only a portion thereof, the unclaimed portion may be deemed to have been dedicated to the public.

Representative Decision IV: SPC IP Civil Final Judgment No. 1198 (2020)

In this case, the specification expressly disclosed that a current range of 1.6–2.0 A could achieve the intended technical effects, whereas the claims were limited to a maximum of 1.8 A. The court held that, by choosing to claim only up to 1.8 A, the patentee had made a deliberate reservation with respect to the 1.8–2.0 A range, which therefore fell outside the scope of protection under the doctrine of equivalents.

This case highlights the significant risks arising from inconsistencies between the disclosure in the specification and the scope defined by the claims.

iii. The Doctrine of Prosecution History Estoppel

According to Article 6 of the Interpretation of the SPC on Several Issues Concerning the Application of Law in the Trial of Patent Infringement Disputes³ , promulgated in 2009, a numerical range that has been abandoned as a result of restrictive amendments or statements made during the prosecution procedure shall principally not be reclaimed through the doctrine of equivalents in an infringement action.

Representative Decision V: SPC IP Civil Final Judgment No. 48 (2023)

In this case, in order to overcome an objection regarding the inventive step, the patent applicant deliberately narrowed the component ratio to a single point value (0.5%) and emphasized its technical effects in the prosecution history. The SPC held that such conduct constituted an abandonment of other ratio ranges, and that the doctrine of prosecution history estoppel should therefore apply, precluding a finding of infringement under the doctrine of equivalents.
The court further clarified the allocation of the burden of proof, holding that the patentee bears the burden of proving that the amendment did not constitute a surrender of scope; failing such proof, estoppel is presumed to apply.

III. Major Limiting Principles on Equivalence of Numerical Features and Representative Decisions

Overall, Chinese courts have reached a clear consensus: numerical or parametric features do not per se exclude the potential of infringement under the doctrine of equivalents, but the threshold for its application is significantly higher than that for structural features. The courts focus on not only a simple comparison of numerical proximity, but also a retrospective examination of whether the patentee made a clear and deliberate choice regarding the numerical boundary during drafting and prosecution, and whether such a choice was sufficient to give rise to public’s reasonable reliance as to the scope of protection.

For patentees, parametric features are a double-edged sword. While they can serve as powerful tools for precise protection, they may also become constraints that narrow the scope of rights. Going forward, the competitive advantage of patents containing parametric features will depend not merely on the precision of the claimed values, but more critically on “the strategic consistency” between the specification and the claims—namely, whether reasonable flexibility for equivalents has been preserved, or whether excessive narrowing to secure grant has unduly sacrificed future rights protection. For potential infringers, careful comparison of claim language, the disclosure of the specification, and the prosecution history may reveal room to argue express exclusion or dedication to the public, thereby forming a key line of defense. Accordingly, how the patent is strategically structured at the drafting stage will have a decisive impact on the outcome of future infringement and invalidation disputes.

[1] http://gongbao.court.gov.cn/Details/1f735e48a7599073f7787ac6339990.html

[2] http://gongbao.court.gov.cn/Details/409a66a5e85613e92594a31b410220.html

[3] http://gongbao.court.gov.cn/Details/409a66a5e85613e92594a31b410220.html