One Case a Day | China: The Confusion of Naming Technical Features in the Mechanical Field – "Preheating Furnace" Case (2024) Supreme People's Court Zhi Xing Zhong No. 870

Case Introduction

In the mechanical field, it is common to name technical features based on their function, process stage, or effect. Compared to technical fields such as chemistry and materials, the scope of protection for mechanical technology relies more on textual descriptions of structure, connection relationships, and working mechanisms, rather than on the names of the technical features themselves.

In actual drafting, a common bad habit is to overly rely on names to describe technical features, lacking specific structural features, functional differences, or distinguishable technical effects corresponding to those names. This makes it difficult to support the technical contribution intended to be reflected by the name in subsequent judgments of inventiveness.

In fact, whether a technical feature constitutes a distinguishing feature does not depend on differences in its name. Instead, it should be comprehensively judged based on the common understanding of a person skilled in the art, considering whether there are substantive differences in structure, function, purpose, and technical effects. Merely distinguishing at the name level without changes in technical substance generally cannot constitute an effective distinguishing technical feature.

The "Preheating Furnace" case shared today addresses the issue of "whether differently named technical features in the mechanical field necessarily constitute distinguishing technical features" and provides a relatively clear judicial interpretation, offering certain reference significance for the drafting and inventiveness judgment of mechanical patents.

Case Information

• Application Number: 202221013454.9
• Invention Title: A Fixed Grate Pre-Combustion Furnace Suitable for Cement Kiln Processing of Alternative Fuels
• Invalidation Decision Information: No. 561421
• First-Instance Information: (2023) Jing 73 Xing Chu No. 13228
• Second-Instance Judgment Date: May 30, 2025
• Second-Instance Judgment: (2024) Supreme People's Court Zhi Xing Zhong No. 870

Basic Facts

The involved patent protects a fixed grate pre-combustion furnace suitable for cement kiln processing of alternative fuels. In response to the relevant invalidation request, the patentee amended the claims. The amended Claim 1 is as follows:

1. A fixed grate pre-combustion furnace suitable for cement kiln processing of alternative fuels, characterized in that it comprises a furnace body, the left side of the furnace body is provided with a feeding port [3], the lower part of the feeding port [3] is provided with a blowing air port [5], the interior of the furnace body opposite the blowing air port [5] is provided with a horizontal pyrolysis section, the pyrolysis section is provided with a pyrolysis section grate [1], the right side of the pyrolysis section is provided with a combustion section inclined from top to bottom, the combustion section is provided with multiple combustion section grates [2], the combustion section grates [2] are arranged in steps along the combustion section, the bottom of the combustion section is provided with a horizontal discharge section, the right side of the furnace body at the discharge section is provided with a discharge port, the furnace body above the pyrolysis section is provided with a tertiary air inlet [4]; the width A of the pyrolysis section ranges from: 500~1200mm; the inclination angle α of the combustion section ranges from: 12.5°~45°; the single-layer effective width B of the combustion section grates ranges from: 200~450mm; the height H between adjacent layers of combustion section grates ranges from: 100~400mm.

According to the records in the specification, ... from the feeding port [3], materials are fed into the pyrolysis section grate [1] in the pyrolysis section of the furnace body, tertiary air enters the furnace body through the tertiary air inlet [4], heating the materials on the pyrolysis section, where the materials undergo drying and partial pyrolysis gasification reactions, and blowing air is provided by the blowing air port [5] located on the side of the furnace body for blowing transport and material turning; the materials enter the combustion section grates [2] and begin to burn under the action of tertiary air. The combustion section is provided with multiple levels of combustion section grates [2], and the materials are continuously loosened and air-selected by high-pressure air blown from the blowing air port [5] located on the side, moving from the upper to the lower layer, providing a good combustion environment and optimizing the reaction conditions of the materials. The furnace body is provided with a raw material scattering port [7], an injection port [8], and temperature and pressure monitoring devices. When it is detected that the bed layer or upper hot flue gas temperature exceeds the set temperature value, the raw material system sprays through the raw material scattering port [7] for temperature regulation. This device can adjust the ratio of tertiary air to control the gasification combustion reaction process. During gasification combustion, the reaction temperature is generally 700~900°C.

The invalidation requester cited a prior patent of the patentee as Evidence 4 (CN215676501U), which discloses a structure as shown in the figure below. An air inlet pipe [2] is installed at the airflow inlet [1], and three air outlets are set at the outlet of the air inlet pipe, meaning that after airflow enters the air inlet pipe, it enters the furnace from the three air outlets. The airflow refers to high-temperature gas, with a temperature range of 900~1000°C. The lower end of the material inlet is connected to a combustion platform [16], so that materials first reach the combustion platform for primary pre-combustion. After materials enter the combustion platform [16], they stay for 5-15 minutes, utilizing the heat of the high-temperature gas to achieve primary pre-combustion. After primary pre-combustion on the combustion platform [16], the materials ... stay on the first combustion step [17] for 2-4 minutes to achieve first-stage combustion...

Controversial Focus

Whether the combustion platform in Evidence 4 is equivalent to the pyrolysis section grate in this patent.

Views of the Parties

The challenged decision held that Claim 1 protects a pre-combustion furnace product, which only limits that the pyrolysis section is a horizontal platform with a width range of 500-1200mm, and does not reflect that there are other substantive structural differences between its pyrolysis section and the combustion platform described in Evidence 4, apart from the aforementioned differences (horizontal/quasi-horizontal platform, platform width).

The patentee argued that Claim 1 limits the pyrolysis section and its width range, while Evidence 4 discloses a combustion platform and platform dimensions, which are clearly different.

The first-instance court held that Evidence 4 does not disclose the pyrolysis section and pyrolysis section grate in this patent, and the challenged decision's determination that the combustion platform in Evidence 4 is equivalent to the pyrolysis section grate in this patent is improper. However, the patentee's claim that there are other structural differences between the two also lacks basis.

Second-Instance Court View

The second-instance court held that Paragraph [0015] of the specification of this patent records: "The utility model provides a fixed grate pre-combustion furnace suitable for cement kiln processing of alternative fuels, which can meet two combustion methods, combustion and gasification, according to different fuel characteristics..." Paragraph [0036] records: "Materials are fed into the pyrolysis section grate [1] in the pyrolysis section of the furnace body, tertiary air enters the furnace body through the tertiary air inlet [4], heating the materials on the pyrolysis section, where the materials undergo drying and partial pyrolysis gasification reactions" and "This device can adjust the ratio of tertiary air to control the gasification combustion reaction process. During gasification combustion, the reaction temperature is generally 700~900°C." The above content indicates that in this patent, whether in the pyrolysis section or the combustion section, the materials targeted and the reaction temperature are the same. If the same materials can burn in the combustion section, they will inevitably burn or partially burn in the pyrolysis section as well. Although the structure corresponding to the "combustion platform [16]" in Evidence 4 is named "pyrolysis section grate [1]" in this patent, based on the working principle recorded in the specification of this patent and the fact that the patentees of this patent and Evidence 4 are the same, there is no substantive difference in product structure and working principle between the technical solution of this patent and that of Evidence 4.

Furthermore, Claim 1 of this patent protects a pre-combustion furnace product, which only limits that the pyrolysis section is a horizontal platform with a width range of 500-1200mm. Although the patentee claimed that pyrolysis involves less oxygen contact than combustion and that the blowing power is different, it does not reflect that there are other substantive structural differences between its pyrolysis section and the combustion platform described in Evidence 4, apart from whether the platform is horizontal and the platform width. Moreover, the specification of this patent does not record the effects claimed by the patentee. At the same time, it is well-known in the field that the first-level platform receiving materials is usually designed larger due to reasons such as untreated materials, high moisture content, and larger accumulation. Therefore, the patentee's claim that the pyrolysis section is wider than the combustion section is actually a conventional technical means in this field, more related to the scale of material processing. That is, a person skilled in the art can design platforms with different width ranges according to the material processing scale. Evidence 4 also clearly records that the residence time of materials on the combustion platform [16] is longer than that on subsequent combustion steps, and it can also be seen from Figure 2 of Evidence 4 that its combustion platform [16] is wider than the subsequent combustion steps.

Finally, whether on the pyrolysis section grate [1] of this patent or the combustion platform [16] of Evidence 4, whether materials undergo pyrolysis or combustion mainly depends on the material type, reaction temperature, and air or oxygen content. However, the structural settings and working principles related to materials, reaction temperature, air, or oxygen content on the pyrolysis section grate [1] of this patent and the combustion platform [16] of Evidence 4 are the same or basically the same. This patent does not record that, under unchanged other technical means, merely changing its pyrolysis section grate [1] can bring unexpected technical effects, nor has the patentee submitted corresponding evidence to prove possible unexpected technical effects. In summary, the first-instance judgment's determination of the distinguishing technical features of Claim 1 of this patent relative to Evidence 4 and the actual technical problem solved by this patent is erroneous, and this court corrects it.

Feng Shangjie (Gasoll Feng)