Application of the foreseeability principle in patent infringement litigation

In June 2022, the Supreme People’s Court again applied the foreseeability principle in Hongrun Precision Instruments v Tangkula Instruments et al (2021) to deny the patentee’s claim of equivalent infringement. This is despite the foreseeability principle not being explicitly provided for in current Chinese law and judicial interpretations, and its judicial application still controversial. The increasing application of the foreseeability principle by the Supreme People’s Court and local courts in recent years, serving as a limitation on the application of the equivalence principle, is worthy of attention.

Specifically, the foreseeability principle means that if a technical feature was clearly known or sufficiently foreseeable by the patentee at the time of drafting the patent application, but was not included in the protection scope of the claims, then the equivalence principle cannot be applied to this technical feature during the infringement comparison. The legal basis of the foreseeability principle is that the application of the equivalence principle must ensure sufficient legal certainty and foreseeability of the patent protection scope, otherwise the public cannot reasonably determine the protection scope of the patent rights based on the content of the claim publicity and cannot reasonably avoid infringement, thus preventing the public from freely implementing the technology in the public domain, which is contrary to the original intention of the patent law to encourage innovation.

The key to applying the foreseeability principle is to prove that the patentee had explicit knowledge or sufficient foresight of the technical feature when drafting the patent application document. The author will illustrate how the foreseeability principle can be asserted and applied in patent infringement litigation in conjunction with judicial practice and cases.

Evidence of explicit knowledge. Explicit knowledge means that the patentee knows the technical feature with clarity and certainty, which must be proven by explicit evidence rather than inference. Possible evidence includes the background technology section of the patent application document, the patentee’s other patent applications, dissertation writings and statements or assertions made in other cases.

For example, in Xuzhou Zhongsen Intelligent Equipment v Changzhou Great Garden Machinery and Ningbo Anglin Intelligent Equipment (2021), the patentee introduced the existence of both motor-driven and fuel engine-driven methods in the background technology section of the patent specification but only limited the motor-driven method in the claims, and then asserted in the infringement litigation that the fuel engine-driven method constituted equivalent infringement. The Supreme People’s Court held that based on the “hedge trimmer” as defined in the claims, the introduction of motor-driven and fuel engine-driven methods in the background technology section of the specification, and the purpose of the invention section on “environmental protection and pollution-free”, a general technician in the field could fully understand that the patentee did not seek to protect the technical solution of powering the hedge trimmer with a fuel engine. Under such circumstances, if the fuel engine-driven and electric motor-driven were to be considered as equivalent technical features in determining whether the infringing product fell within the scope of the patent in question, it would be detrimental to the role of patent claim publicity and the protection of the public’s reliance interests. Therefore, the Supreme People’s Court held that the equivalence principle could not be applied in this case.

Evidence of sufficient foreseeability. Sufficient foresight means that a general technician in this field can fully foresee it in advance. Given that “sufficient foresight” is a presumption, the court will need to make a judgment based on the level of technical skill and common knowledge of a general technician in this field to which the patent relates. From the court’s precedents, there are two prevailing circumstances as follows.

(1) Technical features of different categories with clear classification criteria in the field. For example, the Supreme People’s Court held in Sun Junyi v Renqiu Bocheng Plumbing Equipment (2015) that when applying for the patent in question, the patentee defined the technical solution claimed for protection as a water inlet sleeve with a tapered upper surface, not a flat surface. Both the tapered and flat surfaces were technical solutions generally known to the general technicians in the field. In determining infringement, the technical feature “tapered surface” cannot be extended to “flat surface” for protection. Also, in Beijing Xingao Technology v Taiyuan Caiwei Manor Special Agricultural Development and Shanxi Xiaoniu Power Sports Technology (2019), the Supreme People’s Court held that the technical feature of elastic support sheets aligned in equal height as an alternative feature had been foreseen by the patentee when applying for the patent, but was not included in the patent claims in question, so this technical feature should not be regarded as an equivalent to the “elastic support sheets aligned in high and low positions” in the patent claims. In both cases, flat and non-flat (including tapered) and equal-height and non-equal-height alignments are obvious and common classifications in the field, and the two are in an either-or relationship. The court can therefore find that the other technical feature is sufficiently foreseeable even without evidence.

(2) To prove the explicit knowledge of the patentee by a large number of technical documents. In Hongrun Precision Instruments v Tangkula Instruments et al (2021), the defendant submitted to the court a large number of technical documents, including journal articles and patents, which had been published before the filing date, to prove that polycarbonate could be used to make instrument case frames before the filing date. The court held that this evidence sufficiently proved that the patentee had explicit knowledge of the above technical feature but did not include it in the claims’ protection scope; therefore, the equivalence principle could no longer be applied in this case.

In patent infringement litigation, applying the foreseeability principle helps reinforce the claims’ publicity principle. Meanwhile, it also means that higher requirements are placed on the patentee to prepare the application documents, to which enterprises should give due attention.

Chen Jian is a director at Wan Rui Law Firm. Wan Rui Law Firm is a member of Sanyou IP Group