The Doctrine of Equivalence is ONLY Applicable for the Comparison of Technical Features

Issue 14 [Key Point] By Yao Bingbing,[Patent]

[Key Point]

When an IPR infringement case is adjudicated, different technical features are often further analyzed under the doctrine of equivalence; if judged as having equivalent features, they will be subject to patent protection. In judicial practice, however, many people have misunderstood or misused the doctrine by failing to start their analysis with a comparison of the different technical features. Instead they only consider the function and effect of the technical design in reaching the conclusion that the involved technical design is equivalent. Obviously, such a concept is inconsistent with the Patent Law because it enlarges the scope of patent protection.

Case Overview

Plaintiff: Shanghai European-Asian Synthetic Material Co. Ltd ("EA Company")

Defendant: Changshu South-East Plastic Co., Ltd ("SE Company")

EA Company claimed that, on July 30, 1999, it was granted an invention patent for patent number 95111734.3 under the name of "the technical process for grinding-roller crushing for phenolics" upon its application with the State Intellectual Property Office (SIPO) files on August 24, 1995. Taking advantage of the patented invention, EA Company obviously improved its product quality by creating a uniform distribution of grain sizes for its phenolic moulding plastics product, reducing the occurrence of over crushing and realizing its goal of granulation. With this advantageous technology, EA Company led the industry in China for injection moulding plastics, exported more than 50% of its products to other countries, and enjoyed a higher price than other companies on the domestic market. From many of its clients, EA Company learned that the Defendant, SE Company, began to produce products with the same technical indicators, such as granularity, from October, 2001 on, and also purchased and put into operation two sets of MY.8 hydraulic mills manufactured by Wuxi Commissariat Engine Factory in August, 2001 and March, 2002 respectively.

The Plaintiff requested that the Defendant: 1. stop its infringement immediately; 2. destroy the infringing products; 3. destroy the machinery and equipment used for the infringement; 4. apologize publicly in a newspaper; 5. pay RMB 2,000,000 as damages for the infringement, and RMB 130,000 for other costs incurred, and pay the Plaintiff's legal costs.

SE Company argued that its technical process for phenolic moulding plastics was obviously different from the patented technical process of the Plaintiff and that the two were neither identical nor equivalent. Further, the Defendant argued that the technical parameters of its MY8A hydraulic grinding roller mill were obviously different from Plaintiff's patent and as a result Plaintiff's claim was unsupported and caused no infringement. The Defendant requested that the Plaintiff's claim be dismissed.

The court found upon hearing that:

1. EA Company submitted an application to SIPO for a patent claim for "the technical process for grinding-roller crushing for phenolics" on August 24, 1995 and was granted a patent for the invention under patent number 95111734.3 on July 30, 1999, and the grant was announced on September 1, 1999. The patent has been valid up to the present.

The independent claim is:  for a kind of technical process for grinding-roller crushing for phenolics, with phenolics processed as a raw material in the following way:
(1) phenolics is heated and rolled into flakes; and the
(2) flakes are crushed.

Its technical features are as follows: after step (1) and (2) the material enters a rotating grinding roller with a vis-à-vis velocity difference to be crushed; the fast roller wheel (1) and the slow roller wheel (2) of the grinding roller have the same diameter; the center distance of the two wheels is D+0.3~0.65mm, spiraled teeth are the same at 7~8 degrees; each of the two fast roller wheels has 10 teeth per inch, i.e., Z=10; the fast roller wheel (1) and the slow roller wheel (2) are mounted sharp edge to sharp edge; the velocity ratio between the fast/slow (note: it is written in the original text, but it should be "fast" only) roller wheel and the slow roller wheel is V=2.5:1.

2. EA Company (Party A)and Xiamen Siqi Synthetic Material Co., Ltd (SIQI Company, Party B) entered into a patent license agreement on July 20, 2000, by which EA Company allowed SIQI Company to exploit the patent for a period of 10 years (starting July 5, 2000, ending July 5, 2010) and SIQI Company paid EA Company RMB 500,000 as a fee for exploitation of the patent.

3. The Technology Development Company of Wuxi Commissariat Engine Factory ("Commissariat Engine Factory", Party A) and SE Company (Party B) entered into a sales contract for commissariat engine products on August 16, 2001, by which Party B agreed to order one MY.8 hydraulic mill, priced RMB 49,000 from Commissariat Engine Factory. The quality requirements, technical standards and the conditions and terms of the supplier's liability for quality were in accordance with the "ex-factory requirements of Commissariat Engine Factory". Other matters were also arranged between the parties. Later, the above parties entered into another sales contract on April 5, 2002, which was almost the same as the first one except for the price and the type of grinding roller. Commissariat Engine Factory provided the technical parameters according to the buyer's processing requirements, as well as the mill's technical parameters for the grain processing, and authorized Wuxi Xishan Huadong Commissariat Engine Co., Ltd. to manufacture the mills. Presently, the two hydraulic mills are being used on SE Company's production line for phenolic moulding plastics. Through a field inspection of one of the mills, the following technical parameters were obtained: the diameter of the fast/slow roller wheel is 250X800mm; the center distance (CD) between the two wheels is D+1mm; the roll flute gradient (twist) is 4.6°; the two roller wheels has eight teeth per inch, i.e., Z=8; the fast/slow roller wheels are mounted dull to sharp, and the velocity ratio (38:25 teeth) is V=1.52:1.

4. Through a comparison between the independent claim of the Plaintiff's patent and the allegedly infringing technical process of the Defendant (because the Defendant has requested to keep its technology confidential, only the part which is allegedly identical to the Plaintiff's is listed here), it was found that the Defendant used a twin screw extruder and produced cold-pressed flakes, and after the two steps, placed the phenolic moulding plastics into the hydraulic mill; the mill used a rotating grinding roller with proportional velocity difference; the fast and slow roller wheels having the same diameter; and except for the above, all of the remaining techniques were different.

The Plaintiff's patent imposes limits on the patent claim by deeming the equipment structure for the processing art as a distinguishing feature from the prior art. According to the general principle of full coverage for determining patent infringement, patent infringement will not be found when an allegedly infringing product does not fully cover the independent claim for the patent, or there is a technical difference between them. Therefore, because the Defendant, Changshu Southeast Company has used techniques in the production of phenolic moulding plastics, which are different from the patent claim of the Plaintiff in terms of the distance between the fast and slow roller wheels, the spiral teeth, the number of teeth, the installation method of the fast and slow roller wheels and the velocity ratio, Defendant's product does not constitute an infringement to the patent. Therefore, the claim of the Plaintiff was dismissed. Dissatisfied with the judgment, the Plaintiff appealed and the second-instance court dismissed the appeal and affirmed the first instance judgment.

Analysis of the Judgment

I. Conditions for application of the doctrine of equivalence

The doctrine of equivalence means that, despite the difference in wording, the allegedly infringing product or method has one or more technical features which can be determined through analysis as equivalent to those as in the independent claims to be protected. Here, the allegedly infringing product should be regarded as subject to the protection of the patent right. When the doctrine of equivalence is applied, generally each technical element of the allegedly infringing product or process is compared with the patented technical features, so as to determine if the allegedly infringing product or process has fundamentally employed the same means, realized the same functions and caused the same effects. However, properly judging the appropriateness of the technical equivalence depends on a sound mastery of the nature of the invention, the degree of creativity and the degree of difficulty. The patent concerned in this case is for a combination invention developed on the basis of prior arts.

One category of patents may be called an "application invention"; that is, to apply the publicly known equipment or methods for new purposes, or to apply the publicly known technology in other fields producing unexpected technical effects. According to the claim documents and specifications of the Plaintiff, the patented features are the improvements made to the original mill, i.e, the common hydraulic mill for grain processing is used as a crusher on the existing production line for phenolic moulding plastics. However, the common mill for grain processing has already been used widely in other fields (such as the plastics industry) for many years. As evidence, the Defendant submitted a Japanese Patent & Utility Model Gazette (Patent Pucblic Notification 57-151305), which published, on Sep. 18, 1982, an invention patent for "a kind of crushing method for thermoset synthetic resin moulding plastics". The patent specification clearly states that a roller mill is used in the invention. The so-called "hydraulic mill" manufactured by the Commissariat Engine Factory should be formally named as a "roller mill".

Therefore, it does not constitute a new invention to apply a mill in plastics processing, but is simply one of the processing methods selected given the texture of processed plastics and the quality requirements for the products. In this case, the mill application is a method designed by referring to the current technical parameters for grain processing in order to reduce the occurrence of over crushing stressed by the Plaintiff. The grain processing industry has various parameters for raw materials to be processed and requirements for processing. In particular, two roller wheels can be mounted in four ways: sharp to sharp, dull to dull, dull to sharp and sharp to dull. In the Plaintiff's case, two roller wheels are mounted sharp to sharp, while in the case of the Defendant, sharp to dull. In addition, other parameters were selected from the existing sets of parameters and provided by the manufacturer (Commissariat Engine Factory) to the Defendant depending on the processing requirement of the buyer (Defendant). If the doctrine of equivalence were applied as claimed by the Plaintiff, it would mean that all the mills with various data used for grain processing could be protected by the patent, with the mill of the Defendant being one kind. Under this reasoning, the patented technology of the Plaintiff does not involve creativity but involves a prior art as it also uses one of the parameters. Corresponding to the technical scheme of the Plaintiff, the parameters of the Defendant's mill also indicate a complete technical scheme for the production process, and both are among the various combinations already widely used for grain processing. Under the doctrine of equivalence, there must be interchangeable technical features and not merely interchangeable complete technical schemes. Therefore, the doctrine of equivalence should not be applicable herein.

II. Limitation of the application of the doctrine

The doctrine of equivalence provides for a certain amount of equity power to enable the judge to compare the technical features more objectively, and to avoid being mired in the comparison of wording. This equity helps to prevent equivalent results from non-creative work to escape punishment for infringement. However, each limitation in the patent claim is substantial and important, and to accuse another party of infringement, a patentee must find from the other party's design the part corresponding to all limitations in its own invention instead of permitting the doctrine of equivalence to be used as a tool for re-writing patent claims on a large scale. In other words, it is not acceptable for the doctrine of equivalence to be used in an overly broad manner while leaving some meaningful limitations in a patent claim neglected when an infringement is determined. Objectively speaking,  other public entities should also be considered with respect to their possible options when the patentee is considered. 

III. How to apply the doctrine correctly

From its inception to its wide use by many countries, the doctrine of equivalence has always been controversial. In practice, sometimes the doctrine is applied strictly, and at other times loosely. Despite questions arising in academic circles and among practitioners, undoubtedly the doctrine of equivalence will continue to play an indispensable role in providing sufficient protection for patent rights. In China's judicial practice, there have been precedents established concerning the correct application of the doctrine. However, it wasn’t until 2001 that the Supreme People's Court clarified the conditions for application of the doctrine in its Several Provisions on the Application of Law in Hearing Patent Disputes. How could the court apply the doctrine correctly when determining if there is any equivalency existing between an allegedly infringing product and a patent claim? The determination of whether equivalence exists should not be done just theoretically, but should be performed on a case-by-case basis. It is beneficial to clarify this point with the following straightforward case.

Plaintiff Cheng Zaizhong was granted a patent, number 96232194.X, for a utility model for "a type of connection fitting with a theft-proof screw bolt". There is only one patent claim existing for a type of connection with a theft-proof screw bolt, including a screw bolt and a screw cap. The features are as follows: the said screw bolt has protruding teeth on the head and neck, and the said screw cap has a protecting edge extending in the axial direction on the outer ring of the upper end face, and a cylinder-shaped binding nut which sinks into the protecting edge of the screw cap with grooves evenly distributed on the periphery.

The Defendant, Nanjing Jiangbiao Group, produces the allegedly infringing product, "screw bolt", a similar product to the Plaintiff's patented one. Compared with the independent claim in terms of technical features, the defendant's product also consists of a screw bolt and a screw cap with the screw bolt having protruding teeth on the head and neck, and the screw cap having circular steps on the upper side wall which concaves to the outer-wall direction and a regular-hexagon-shaped locking nut which sinks into the concave area.

It can be seen in comparison that the locking nut of the allegedly infringing product, has a regular-hexagon shape, which is different from the binding nut with evenly distributed grooves contained in the plaintiff's patented product. To put it more simply, the technical feature of the allegedly infringing product has a nut that is added with another fastener ("binding nut" for the Plaintiff and "locking nut" for the Defendant) which can sink into the groove. All the other technical features are the same.

Then, is the "regular-hexagonal-shaped locking nut" in the alleged infringing product equivalent to the "cylinder-shaped binding nut with evenly distributed grooves on the periphery"? The premise for determining equivalence is again that the technical features in the patent claim should be analyzed and interpreted so as to decide whether there is identity or equivalence in the scope of protection and technical features. Whether the two technical features are equivalent should depend on such factors as the instruction manual for the patent, the prior art context and the technology concerned. Compared with the prior art, the patented technique of the Plaintiff is actually designed to prevent any unauthorized removal of the screw, thus it has a screw bolt with protruding teeth on the head and neck, and a screw cap with a special binding nut which can sink into the cap. This is proven by the instruction manual which states explicitly that the patent intends to provide a solution for the traditional connecting fittings which, consisting of a screw bolt and nut, are not theft-proof. When steel towers supporting high-tension wires are connected with the traditional connecting fittings, there surely exists the risk that the tower components may be stolen. To prevent this, the structural feature in the patent claim above provides a solution. According to the design, with the protruding teeth at the head and neck part of the screw bolt, the protruding teeth are wedged into the hole of the connecting fittings once the screw cap is screwed down, so that the screw bolt will not rotate, and the binding nut sinking into the protecting edge can act to stop the screw cap from being unscrewed. Therefore, it does not only provide a reliable solution against theft, but it also can prevent the connecting fittings from loosening due to wind-induced vibration. From this analysis, it is seen that the major objective of the patented invention is to provide an anti-removal connecting fitting. When the doctrine of equivalence is applied, as a rule, all the technical features should be determined. Although this does not mean that the technical features between the patented product and the allegedly infringing product should correspond with each other on a one-to-one basis, the technical features in the patented product must be expressed in the allegedly infringing product. Because all of the technical features between the two are the same except for the structure of the binding nut, an analysis should be done concerning this technical feature. In order to provide a solution for the theft-proof function of the connecting fitting, the screw cap, using a structural feature different from that of the conventionally-shaped screw cap in the public domain, can only be mounted and removed with special tools. Further, this has been written in the patent claim as a distinguishing feature. Therefore, the inclusion of such a distinguishing feature in the protection scope should not be interpreted as being part of the prior art in the public domain.

Theoretically or technically, if there are six grooves with each groove side equal to a half of the external diameter of the cylinder and a zero groove depth, the screw cap is a regular hexagon. However, a regular-hexagon-shaped screw cap is a standard unit in the mechanical field. None of the typical technicians in the field would consider such a screw cap as having a cylinder with grooves, nor would anyone technically believe that there exists a zero groove depth (which only means a plane). Therefore, the limiting technical features in the patented product should exclude a regular-hexagon-shaped screw cap as a structural feature. In some sense, to determine whether equivalency exists is to interpret the patent claim. Then, is the "regular-hexagonal-shaped locking nut" of the allegedly infringing product equivalent to the "cylinder-shaped binding nut with evenly distributed grooves on the periphery" of the plaintiff's patented product?

According to the method of "means – functions – effects- consistency" for determining equivalence as established by the judicial interpretation of the Supreme People's Court, it is found that the locking unit in the alleged infringing product is a standard unit which is used to replace the special binding nut in the patented product, a common feature that can be thought of by a typical technician in the field without creative labor. Such a technical feature is essentially identical to that of the patented product, and can also realize a certain theft-proof effect. The only difference is that the locking nut here can be removed or mounted with a standard box wrench and its theft-proof function is not as good as the special binding nut. According to the above analysis, the Defendant's product can be determined to be an equivalent infringing product.

To gain a further understanding of equivalence, some assumptions can be made by taking advantage of the conditions of the above case. If the technical feature of the "sinkable locking nut" in the alleged infringing product is a prior art and the Defendant uses this as a defense for non infringement, can the doctrine of equivalence still be applicable? Or, in other words: if the Plaintiff's patent has improved the prior art and invented a connecting fitting where the screw bolt has protruding teeth and the screw cap has a sinkable binding nut with a special structure, the designated technical feature in the structure would become indispensable to the patent claim. Here, the prior art (sinkable locking nut) should not be included as being equivalent in scope for the purposes of patent protection, because the special binding nut is a distinguishing feature from the prior art. In other words, the doctrine of equivalence should not be applied to such a circumstance, and the scope of protection should be determined by strictly abiding by the specification of technical features in the patent claim. The technical features in the allegedly infringing product, upon comparison, are different from those in the patented product and thus do not constitute an infringement. The reason lies in the failure of the allegedly infringing product to realize the function of the patented product, as well as to have the same effect as the patented product. Therefore, the determination of equivalence cannot be made by sticking to a fixed mode of analysis, nor  can it be determined without analyzing the specific circumstances of each case.

In conclusion, the general trend for applying the doctrine of equivalence in patent infringement should be to avoid arbitrary expansions that may lead to misunderstandings and improper applications in favor of an analysis that "applies all technical features" under strict limitations.

About the author:
    Yao Bingbing is a judge from the IP Tribunal of Nanjing Intermediate People's Court.

                                                                                      (Translated by Ren Qingtao)

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