Equivalence infringement, or the doctrine of equivalence, was officially introduced into Chinese patent law legislation in 2009, through the implementation of the Chinese Supreme Court's judicial interpretation, which stated the following:

Equivalent features shall mean features which use identical means to achieve identical functions and realise identical effects, and which can be contemplated by people skilled in the art without creative effort.

The Chinese court has since developed a three-step method to determine equivalence infringement, which is conveniently referred to by the Chinese legal community as the "three (basically identical) plus one (obviousness)" approach.

"Three plus one" approach

Step 1: Ascertain distinguishing technical features

Basically, a claim chart will be drafted so that all technical features can be compared one by one. If distinguishing technical features in the claim are identified, which differ from that of the accused product or process, then those features will be further analysed for equivalence infringement.

Step 2: Conduct three "basically identical" assessments

The distinguishing technical features will be compared with the accused infringing features to assess whether they use identical means to achieve functions which are identical and which result in identical effects. Please note that the weight placed on the means versus the functions and effects will be different. Usually the analysis of the technical means is deemed the most important, whilst that of the technical functions and effects is secondary. In other words, if the technical means are assessed as being identical, the court will then proceed to the analysis of the functions and effects. If the technical means are found to be different, the court will not consider the functions and effects, as a determination of non-equivalence will have been made.

Step 3: Determine obviousness for the replacement

The obviousness of the replacement is assessed from the point of view of the person skilled in the art, in order to determine whether they can conceive of the replacement of the three identical means/functions/efforts without creative effort. If so, equivalent infringement can be established.

The Chinese court has stressed that equivalent infringement means that the technical features are equivalent, but not the technical solutions as a whole. In other words, even if the technical solutions as a whole are equivalent, this does not necessarily lead to equivalence infringement. One must break down and analyse the detailed technical features in order to conclude equivalence infringement.

Although the "three plus one approach" articulates the test, in practice there can be a great deal of discretion given to the courts which can lead to inconsistency in determining the existence of equivalent technical features. Usually, different levels of generalisation can lead to different conclusions, especially in the assessment of identical technical means. To give a quick example, a welded connection and a bolted connection can be deemed as equivalent when considered as connection methods, but can be viewed as being different from the perspective of detachable connection methods. Consequently, it is important to be able to articulate the inventive points and check which type of generalisation/category those inventive points relate to. If the invention is about facilitating repair and transport, then the detachable connection aspect is more important so that the welded connection is not deemed equivalent to the bolted connection.

Basically identical means

As mentioned above, the analysis of the technical means is primary amongst the three "basically identical" assessments. If the means are not equivalent, it is usually not an equivalent technical feature, and there is no need to analyse the functions or effects.

Basically identical means typically include a simple change of position of the components, process steps, and/or a simple interchange of the product features. Broadly speaking, identical means relate to common interchangeable features in the art, or features with substantially identical working principles.

In YMTT vs. Deyuan, which involved fireproof curtains, the stainless steel wire rope was located at the side of the refractory fibre blanket in the accused product, while the wire rope was placed in the middle of the refractory fibre blanket in the subject patent. However, inserting stainless steel wire rope into the blanket serves the purpose of increasing the strength of the product, and the change of position does not affect such purpose. Thus, the Beijing High Court deemed that this constituted basically identical means and subsequently found equivalence infringement.

In Gree vs. Midea, which involved air conditioners, the accused product included a non-detachable mounting plate while the subject patent incorporated a detachable one. The Guangdong High Court considered the title of the patent, which included the word "detachable", to mean that the feature was an essential part of the invention. Accordingly, the technical means were deemed different and thus equivalence infringement could not be found.

Basically identical functions

The analysis of the technical functions should refer to/be based upon the technical principles described in the patent specification, and review what effects are realised by the technical means in the accused technical solution and in the patented solution. For product structures, identical functions refer to the mechanical or electrical functions that a technical feature realises. For chemical products, they relate to the chemical reactions that an element achieves.

In Wantefu vs. Kelinzhong, which involved a type of needle used to puncture hematomas, the Beijing High Court considered that a normal medical needle achieves a different function from that of a hematoma-puncturing needle. A normal medical needle injects cleansing liquids to impregnate and dissolve the hematoma. Compared with the patented hematoma puncture needle, it takes quite a long time and does not breakdown the hematoma. Thus, the technical functions are different, and there is no equivalence infringement.

Basically identical effects

A basically identical effect generally means that the effects achieved by the technical means in the accused technical solution are not substantially different than those in the patented claims. If the technical effect realised does not create an obvious improvement or deterioration, then it will be deemed to be substantially the same.

In Jerrat vs. JZTH which involved an elastic damping buffer, the subject patent's one-way flow limiting device opened during a compression stroke and closed during a return stroke, enabling the bumping head to have a "quick in and slow out" effect. The accused product operated in the opposite way, with its one-way flow-limiting device being closed during a compression stroke and opened during a return stroke, thus achieving a "slow in and quick out" effect for the bumping head. Accordingly, the technical effects were different so equivalence infringement could not be found.

Functional features

Particular difficulty can arise regarding the determination of equivalent infringement for functional features. Functional features are those technical features defined through their functions rather than the usual structures, components, steps, etc. They are employed if there are no suitable conventional means (through structure, component, etc.) to define a technical feature. Since the literal meaning of a functional feature encompasses all technical means to realise the function, they are sometimes employed by patent drafters to gain a broader scope of protection for the claims, despite the fact that such an approach would fail to meet the requirements for clarity under patent law.

Currently, Chinese courts have generally adopted a more restrictive or cautious approach when determining equivalence infringement for functional features. According to the Supreme Court's 2009 Interpretation, the scope of a functional feature shall be determined by the embodiments recorded in the patent specification for realising such functions, as well as equivalent embodiments thereof. Referring to the Supreme Court's 2016 Interpretation, the functions and effects must be "identical" rather than "basically identical", in order for equivalence infringement to be found for functional features, as summarised in the table below. There is obviously a stricter set of criteria for assessing functional features than for normal features.

Criteria for equivalence infringement Normal features Functional features
Technical means Basically identical Basically identical
Technical functions Basically identical Identical
Technical effects Basically identical Identical
Obviousness Obvious replacement Obvious replacement

Consequently, in practice when determining equivalence for functional features, the court will usually disregard the broad scope prescribed by the literal meaning of a functional feature, and go straight to the analysis of the corresponding technical embodiments, which are described in the patent specification, and will then assess whether they are equivalent to the accused product or process. Consequently, the patentee often cannot expect that the protection scope of a claim is broader in China, simply because the functional features are employed in the claim.

In SEB vs. ASD, which involved a pressure cooker, the technical feature relating to a "locking device of the safety pin" was deemed a functional feature. Zhejiang High Court then looked into the patent specification and found the locking mechanism was realised by the combination of interlocking flanges with a latch against a flange. Such a technical embodiment is not equivalent to the notch insertion type locking device in the accused product, and thus equivalence infringement could not be found.

In Lexuer vs. Chen, which involved hot water bags/bottles, the subject patent contained an inner layer, an outer layer and an insulation layer. The insulation layer was a functional feature. According to the patent specification, the insulation function was realised by synthetic thermal insulation cotton, which was arranged between the inner and the outer layer and completely encapsulated and separated the inner and outer layers from each other. In the accused product, the insulation layer was replaced by a hollow cotton cushion, whose width was the same as the inner and outer layer but the length was just half of the length of the inner and outer layer. The cotton cushion was attached to both sides of the inner and outer layers. The Supreme Court reasoned that the purpose of providing an insulation layer in the subject patent was to control the thermal air convection between the inner and outer layers, thereby stopping or reducing the heat transfer to achieve the function of thermal insulation. The hollow cotton cushion in the accused product was of the same material (i.e. cotton) as the insulation layer of the subject patent, and is provided in the same structure between the inner and outer layer. Although the size of the cotton cushion does not fully cover the inner and outer layers as the subject patent did, the function of thermal insulation was the same, and there was no substantial difference in the effect. Consequently, it was deemed an equivalent feature.

Limitations to equivalence infringement

Equivalence infringement is subject to a few exceptions or limitations, most notably three principles, the all element principle, the donation principle and the estoppel principle.

Donation principle

The SPC has established that, technical solutions, which are described in the patent specification but not written into the claims, will be deemed to be donated to the public domain. The patentee cannot claim literal or equivalence infringement for those technical solutions, which are not recorded in the claims.

In Huyan vs. HTD, which involved moulds for plastic containers, the linkage plate was positioned on the mould plate in the subject patent claims, whilst the linkage plate was arranged on the right side of the mould plate in the accused product. Although the patent specification also described a technical solution which was similar to positioning the linkage plate on the right mould plate, the Supreme Court deemed that such a technical solution, which was present in the patent specification but not recited in the claims, had been donated to the public and did not belong to the protection scope of the subject patent. Therefore, there was no equivalent infringement.

Estoppel principle

The patentee's amendments or responses during patent prosecution can have certain estoppel effects for subsequent patent infringement proceedings. Specifically, if the patentee has amended the patent application, or responded to an office action by way of limiting or abandoning some protection scope of the claims, then it will not be permitted to re-claim an infringement relating to the limited or abandoned scopes during a subsequent infringement proceeding. For literal infringement, it is usually not necessary to consider the estoppel principle. For equivalence infringement, however, the estoppel principle is often used by the defendant as a counter argument against the application of doctrine of equivalence.

In Aonuo vs. Wushi, which involved drugs for preventing calcium deficiency, the patentee amended the independent claim by replacing "soluble calcium" with "active calcium". The Supreme Court found that soluble calcium refers to "calcium gluconate, calcium chloride, calcium lactate, calcium carbonate and active calcium" in the patent specification. Therefore, calcium gluconate and active calcium are two independent types of soluble calcium. Thus, the patent amendment suggests that the patentee has given up protection of the technical solution involving calcium gluconate. The patentee is now estopped from claiming that calcium gluconate, as used in the accused product, is an equivalent feature to active calcium in the amended claim.

All element principle

The basis of patent infringement is the all element rule, i.e. all technical features in the claim are deemed as identical or equivalent to those of the accused product or process. Therefore, if one or more claimed technical features are absent in the accused product or process, and then equivalence infringement does not stand.

In Liang vs. Li, which involved machines for producing composite paperboards, the accused product lacked two technical features recited in the patent claim, i.e. side gluing device and splicing device. The corresponding functions were realised by manual labour instead. The patentee insisted on equivalent technical features. The Supreme Court disagreed and ruled that the accused product lacked the corresponding technical features, which were in the claims, which did not relate to equivalent features. According to the all element principle, patent infringement could not be found.


The doctrine of equivalence principle has been utilized in Chinese patent trials for over ten years, and is relatively harmonized with international practice. This means the criteria and principles developed in the US and EU practice, such as the "three plus one" approach in assessing the equivalence, and the donation and estoppel principle to limit the equivalence, are all applicable in China.

In practice, the doctrine of equivalence usually applies to the following five scenarios in China: (1) exchange of common technical elements; (2) simple moving of the position of a product feature; (3) simple breakdown and combination of technical features; (4) simple change of steps in a method claim; and (5) simple and minor increase or decrease of quantity.

To maximize the potential of the doctrine of equivalence, the applicant is advised of three tips below.

  1. Prevention is better than cure. The impact of doctrine of equivalence must be considered as early as the patent drafting stage. The applicant should be very careful with using limitation language in the independent claims, such as numerical ranges, or phrases like "at least", "no more than", "equal to", or sequenced steps such as "first step, second step, ..." in method claims.
  2. Similarly, the applicant should include as many embodiments as possible in the patent specification, and describe the working principle and/or technical effects of each embodiment or each inventive point as detailed as possible, to increase the chance and scope of future interpretation under the doctrine of equivalence.
  3. During patent prosecution, care must be taken to avoid or minimize the impact of prosecution history estoppel on the future interpretation of the doctrine of equivalence. When responding to office actions and/or making amendments to patents, a balance should be achieved between expediting patent grant and preserving maximum patent scope under the doctrine of equivalence.

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