How to determine closest prior art in patent disputes

By Zheng Feng, Wanhuida Peksung IP Group
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In a patent invalidation procedure in China, inventiveness is the main point of a dispute determining whether an invention patent will be upheld. In determining inventiveness, the first consideration is whether the invention is not obvious to a person skilled in the art, and with respect to the method of determining whether an invention is not obvious, China’s Patent Examination Guidelines set out three steps.

郑风 Zheng Feng 万慧达北翔知识产权集团 资深律师 Senior Associate Wanhuida Peksung IP Group
Zheng Feng
Senior Associate
Wanhuida Peksung IP Group

The first step is to determine what prior art is the closest to the invention; the second step is determining the features that distinguish the invention from the closest prior art and, on the basis of such distinguishing features, determining the technical problem that the invention resolves; and the third step is determining whether any prior art contains technical teaching that would motivate a person skilled in the art to apply the distinguishing features to the closest prior art to resolve the technical problem that the invention is to resolve.

Although these rules have also been called the three-step method, the first of the three steps, namely determining the prior art that is the closest to the invention, is usually not scrutinised by the adjudicating authorities. This has resulted in a great deal of arbitrariness in the selection of the closest prior art, giving rise to unreasonable outcomes in some cases.

Although China’s three-step method draws on the rules of the European Patent Office (EPO), it does not draw on the EPO’s practice when it comes to the first step of selecting the closest prior art. The guidelines for examination in the EPO require that, “In selecting the closest prior art, the first consideration is that it must be directed to a similar purpose or effect as the invention, or at least belong to the same or a closely related technical field as the claimed invention.” When reviewing a case, the EPO is required, based on the above-mentioned rule, to render a determination as to whether the selection of the closest prior art is appropriate, which will be a focus of the dispute between the parties.

Section 3.2.1.1 of chapter 4 of part 2 of China’s Patent Examination Guidelines specifies how to determine the closest prior art by way of giving examples. This provision lacks definitiveness, and also allows for a fair amount of room for interpretation and, in administrative procedures, there is hardly any serious discussion on how to apply it. Once a case progresses to the administrative litigation procedure, the court will conduct a review of the lawfulness of the decision rendered by the Patent Re-examination Board and, due to the lack of a clear legal basis, this issue will, in practice, also be overlooked during the judicial review.

Since analysis of non-obviousness starts with the selection of the closest prior art, the ultimate outcome hinges on the selection of that closest prior art, which is worth the heeding of the adjudication authorities. One of the firm’s recent cases exemplifies this matter.

The patent at issue was a blower for a medical ventilator for treating sleep apnea syndrome. Such ventilators are household medical devices used by patients during sleep. To ensure the sleeping quality of the patient, since the launch of such devices, the elimination of noise has been a technical problem that requires a solution. The patent at issue better resolves the noise problem by improving the structure of the blower. The internal structure of all blowers in medical ventilators in the prior art is asymmetrical, whereas the patent at issue features a symmetrical blower structure and an unimpeded airflow passage, which effectively avoids an uneven airflow and further eliminates noise.

The patent invalidation petitioner found a prior art in the mechanical engineering field, which involves a blower with a symmetrical structure. However, this blower is used in centrifugal pumps in the engineering field and is characterised in that it can be easily assembled, but its structure fails to create an unimpeded airflow passage and there is no disclosure as to whether that structure could reduce noise. On the contrary, in practice, there is no urgent need for the elimination of noise in blowers in this field.

If a blower in the medical ventilator field is taken as the closest prior art, the distinguishing features of the patent at issue lies in the symmetry of the blower structure and the unimpeded airflow channel, and the technical problem solved is the elimination of noise. Despite the prior art of a blower with a similar symmetrical structure in the mechanical engineering field, a person skilled in the art is unlikely to derive a teaching to combine it with the closest prior art so as to obtain the patent at issue, because the one in the mechanical engineering field cannot resolve the noise problem. Accordingly, the patent at issue represents an inventive step.

However, the petitioner in the case selected the above-mentioned blower in the mechanical engineering field as the closest prior art, arguing that the distinguishing feature in comparison with the patent at issue lies in the technical fields of application, and as the blower can be applied in the medical ventilator field, a person skilled in art could draw a teaching to apply the above-mentioned blower from the mechanical engineering field in a medical ventilator, and thereby derive the solution of the patent at issue. Therefore, the patent at issue lacked inventiveness.

This inference is flawed. A blower in a medical ventilator has stringent requirements with elimination of noise to the extent that it will not interfere with sleep, whereas a blower used in the mechanical engineering field has no pressing need for the elimination of noise, and a person skilled in the art would lack the motivation to take a blower in the mechanical engineering field and use it in a medical ventilator to resolve the noise problem. In fact, this inference process also misled the adjudication authorities to overlook the differences between the prior art and the patent at issue, in terms of structure and technical effects.

So it can be seen that the selection of the closest prior art needs to be treated seriously. Particularly when based on the same prior art combination, selecting different prior art as the closest prior art may result in a different outcome on the determination of inventiveness, and serious consideration should be given as to whether there is any deviation in the “three-step method’s” determination process. Under such a circumstance, taking prior art of the same field as that of the invention at issue as the closest prior art should be the more reasonable way of proceeding.

Zheng Feng is a senior associate at Wanhuida Peksung IP Group

Wanhuida Peksung IP Group

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