The scope and limitations of the doctrine of equivalent infringement in the United States

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"The principle of equivalence eliminates the unfairness that can result from overemphasizing the literal language of claims, thereby striking a better balance between the fair scope of patents and their publicity effects, and also providing the public with a balance between the incentives for innovation and the costs of uncertainty. ”

Source: IPRdaily Chinese Network (iprdaily.cn)

Author: Tang Aisi, Guangdong Junlong Law Firm

The scope of protection of a patent is not limited to the literal meaning of the claim, but covers all equivalent scopes of the technical features of the claim. If the court strictly sticks to literal infringement in patent infringement trials, it will make the right holder a victim of the literal meaning. As a result, U.S. courts have created a series of rules that extend liability for patent infringement beyond the literal sense, the most well-known and controversial of which is the Doctrine of Equivalent. The principle of equivalence is a principle formulated by the judge, which means that although one or more technical elements in the alleged infringing product or process are different from the technical elements in the claims, there is only a non-substantial difference between the two. This principle eliminates the unfairness that can result from overemphasizing the literal language of claims, thus striking a better balance between the fair scope of patents and their publicity effects, and also providing the public with a balance between the incentives to innovate and the costs of uncertainty.

The history of the principle of equivalence

The principle of equivalence can be traced back to 1853 with Winans v. Denmead case [1]. The scope of protection of the patent at issue in this case relates to a vehicle transporting coal, the body of which has the cross-sectional shape of a truncated cone, while the cross-section of the alleged infringing device is not circular but octagonal. The U.S. Supreme Court (U.S. Supreme Court) dismissed the defendant's argument that "it must be circular in order to constitute infringement," stating that "a patentee, after describing his invention, demonstrating its principles, and bestifying his invention and making a claim, is legally deemed to protect all forms in which his invention can be reproduced, unless he has indicated his intention to waive one of those forms." [2] Thus was born the theory of equivalence.

This was followed by the landmark case of Graver Tank v. Linde Air products [3] in 1950, which established the well-known Function-Way-Result test, which is still in use today. If the technical element to be identified performs the essentially same function in an essentially the same way in order to obtain essentially the same effect, the technical element constitutes an equivalent [4].

In addition to the well-known ternary test, the judge in Graver Tank established the well-known "known interchangeability" as an important equivalence test. The judge noted that an important factor in determining equivalence is whether a person skilled in the art would think of replacing an element contained within the scope of protection with an element that is not covered by the protection, and if the answer is yes, there is no substantial difference between the two[5]. This determination of interchangeability is a necessary test, and it is up to the patentee to prove that the elements involved are interchangeable with the features of the claims, so as to prove infringement according to the principle of equivalent. At the same time, known fungibility is a sufficient condition, and if it is proved that the fungibility is known, the existence of equivalence can be demonstrated, but it is worth noting that known fungibility is not the only way for the patentee to prove equivalence.

While the Graver Tank case established various factors that determine the equivalence principle, the principle of equivalence, as a rule based on the facts of each case, and the complexity of its application, still debates whether and how the doctrine of equivalence applies. Against this backdrop, the Federal Supreme Court passed the famous case of Warner Jenkinson vs. Hilton Davis in 1997,[6] which established the following well-known principles and views:

1) the existence of the equivalence theory is necessary to prevent plagiarists from evading legal liability;

2) in order to balance the interests of the parties and take into account the patent system, the doctrine of equivalence should be applied to each technical element and its equivalents, i.e., the "all-elements principle" or the "element-by-element principle", rather than making an equivalence judgment on the whole of the invention;

3) Appropriate rules for determining infringement should be adopted according to the circumstances of each case;

4) Equivalent infringement is a law derived from equity, and the principle of estoppel can be used to prevent its application, i.e., modifications or restrictive statements made for the purpose of granting in the course of patent application can no longer be asserted as falling within the scope of equivalent;

5) the date of occurrence of the infringement is used as the time point for determining the equivalent[7];

6) If each element of the controlled device or method is only "non-essential distinction" from each element of the claim, the controlled device or method constitutes an equivalent[8].

It can be seen that the Warner case established a second test that is different from the ternary test method in the Graver case, the "non-essential difference" test. However, most people believe that the "non-essential distinction" test is based on the ternary test, but it imposes specific restrictions on it through the all-elements principle. In other words, the "non-essential difference" is to determine whether there is a non-substantial difference between the two to be equivalent through the comparison of function, mode and effect, so as to determine whether the two are equivalent.

With regard to the principle of equivalence, Article 13 of the Several Provisions of the Supreme People's Court on Issues Concerning the Application of Law in the Trial of Patent Dispute Cases adopted by the mainland in 2001 provides as follows:

"Equivalent features" refers to features that achieve basically the same functions and achieve essentially the same effects by basically the same means as the recorded technical features, and which can be associated with those of ordinary skill in the art without creative labor when the alleged infringement occurs. ”

How to judge equivalence

The determination of equivalent infringement usually involves two steps, the first is to use the two methods mentioned above to test whether the equivalent is equivalent, and the second is to determine whether the corresponding legal bar has been triggered on a case-by-case basis. Step 2 is very important, even if it is judged in the first step that the equivalent has fulfilled the substantially the same function in the same way and obtains the substantially the same effect, if a certain equivalence restriction is triggered, such as the principle of estoppel, it still cannot be considered equivalent. In the following, I will explain in detail the common legal limitations to which the equivalence principle applies.

As mentioned earlier, the test equivalence method in the first step is mainly the use of the ternary test or the "non-essential difference" test. If the corresponding components, components, steps or their combination relationship with the technical features of the scope of the patent application are substantially the same as the technical features of the patent application scope, and the result (result) is substantially the same, it shall be judged that the corresponding components, components, steps or their combination relationship of the object to be identified are not substantially different from the technical features of the scope of the patent application, and shall be regarded as equivalent. "Substantially identical" means that the difference between the two is readily ascertainable by a person with ordinary knowledge in the technical field to which the invention belongs.

Limitations on the application of the principle of equivalence

As mentioned above, in order to prevent "unscrupulous counterfeiters" from evading the literal scope of protection of others' patents in a way that does not change substantially, the Federal Supreme Court created the principle of equivalent, which has existed for nearly two centuries, and has been the legal theory that has plagued the courts the most and caused the courts to have the most divergent opinions in patent infringement judgments. Therefore, in order to avoid the excessive expansion of the scope of equivalence beyond the literal scope of patent rights, the Federal Supreme Court has also established various legal bars in a series of proceedings to limit the application of the principle of equivalence.

01、全要件原则（All-element Rule or Element-by-element Rule）

The U.S. Supreme Court established the all-element doctrine in the aforementioned Warner case, stating that "each element must be judged separately from element, and not as a whole with respect to the whole invention, because each element is important in defining the scope of the right"[9]. The all-elements principle is not a limitation in itself, but is closer to the specific requirements for the application of the equivalence principle.

This principle stipulates that equivalence judgments must be applied on a case-by-case basis to technical features. For each technical feature in the claims, the product must have a part that can literally or equivalently interpret the feature. If the product does not contain the literal or equivalent features of each claimed technical feature, there is no infringement. In other words, when judging equivalence, it is necessary to apply a function/method/result or non-material difference test to each technical feature, and to make an equivalence judgment based on each result.

The all-elements principle aims to enhance the publicity effect of claims by requiring the accused product to include features that are identical or equivalent to each feature of the claim, providing the public with publicity on what content may constitute infringement and what may not.

With regard to the principle of all elements, Article 7 of the Interpretation of the Supreme People's Court on Several Issues Concerning the Application of Law in the Trial of Patent Infringement Dispute Cases (hereinafter referred to as the "2009 Judicial Interpretation") adopted by the mainland in 2009 contains the same provisions:

"When determining whether the accused technical solution falls within the scope of protection of the patent, the people's court shall examine all the technical features recorded in the claims asserted by the right holder.

If the accused technical solution contains technical features that are identical or equivalent to all the technical features recorded in the claims, the people's court shall determine that it falls within the scope of protection of the patent right; ”

02、禁止反悔原则（Prosecution History Estoppel or File Wrapper Estoppel）

The principle of estoppel was also established in the Warner case, the basic implication of which is that in the history of patent examination, what the patent applicant has waived in order to satisfy the requirements for obtaining a patent cannot be re-included in the scope of protection in an infringement action by applying the principle of equivalent.

In Warner, plaintiff Hilton Davis and defendant Warner, both pigment producers, filed a patent for an invention using membrane filtration. In the application filed, the plaintiff did not mention the pH value used in the method of purifying the pigments. During the patent examination process, the examiner cited a prior art that disclosed a filtration method with a pH of 9 or higher. Therefore, the plaintiff amended the claim to include the technical feature that "the pH value is about 6.0~9.0", but why the lower limit of the pH value was added became a key factor in the judgment of this case. The defendant argued that the pH value used by the method used was around 5.0, which was something that the plaintiff had expressly waived and did not fall into the category of equivalence. In its appellate opinion, the defendant pointed out that anything abandoned by the applicant in the course of the patent examination history, regardless of the reason, could not be re-included in the scope of protection.

In this regard, the Federal Supreme Court pointed out that when the defendant argues that the principle of estoppel is limited to the application of the principle of equivalence, the court must investigate not only the content of the waiver, but also the purpose and reasons for the waiver. In order to distinguish it from the prior art, the applicant did add the technical feature of "pH value is about 6.0~9.0", but this only gave up the range of pH value above 9, and did not prevent the plaintiff from occupying the range below pH value 6.0 on the principle of equivalence. In most cases, the amendment of the claims is related to the requirements for obtaining a patent, but in other cases, the patent office only requires a change in the language and does not limit the scope of equivalence. In this way, the court should investigate the reasons for the patentee's amendment of the claims in the relevant case.

In summary, the Federal Supreme Court in the Warner case affirmed that any amendment that narrows the scope of a claim in order to satisfy the provisions of patent law, such as a narrowing of the scope of a claim in order to grant or maintain the validity of the patent right, can lead to the application of the doctrine of estoppel, and the burden of proving that the amendment is not for the above purposes is on the patentee.

In the following period, the courts at all levels in the United States began to deviate from the main thrust of the Supreme Court in the above-mentioned Warner case, holding that the principle of estoppel should be applied regardless of whether it is due to the modification of the requirements for obtaining a patent or for other reasons, so that the equivalence theory cannot be applied.

In order to correct the error, the Federal Supreme Court affirmed the principle of estoppel established in the Warner case in the famous case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki[10] in 2002, and discussed in detail the relationship between the principle of estoppel and the doctrine of equivalence.

The Federal Supreme Court clarified two significant issues in the case:

The first question concerns what modifications of the claim features may trigger the estoppel principle. The Supreme Court reiterated its view in Warner that, while estoppel does not arise in all cases where the application is amended, the doctrine of estoppel applies where the amendment is "a substantial reason related to patentability". The Federal Supreme Court further affirmed that "substantive reasons relating to patentability" included narrowed amendments to meet the requirements of patent law, and that the plaintiff's amendment in Festo to satisfy § 112 of the Patent Act was the same as the use of estoppel in order to distinguish it from prior art[11].

The second question concerns whether the doctrine of estoppel prohibits the right holder from retrieving them through equivalence in the case of technical features that have been restricted, or can it still claim some of the equivalents? bar), which argued that the narrowed scope of protection merely indicates what is not covered by the claims, but does not necessarily accurately describe the scope of the claims, and that equivalent technical features can still be devised to circumvent the scope of protection[12], so there is no reason to reject equivalents altogether, especially those that could not have been foreseen at the time of amending the claims. In short, the amended claims only narrow the scope of protection, but their wording does not necessarily reasonably cover the scope of their actual invention, so there is still room for the application of the principle of equivalence to reasonably expand the scope of protection.

However, in response to the second question, the Federal Supreme Court further stated that the burden of proof lies with the patentee. In other words, the principle of estoppel applies when the presumption of the patentee chooses to narrow the scope of the claims, unless the patentee can prove that the specific equivalent could not have been foreseen at the time of the patent application (unforeseeability), or that the specific equivalent is so trivial that the patentee cannot reasonably be expected to include the scope of protection when drafting the claim[13].

Regarding the principle of estoppel in the United States, the 2009 judicial interpretation of the mainland has a similar provision in Article 6:

"Where a technical solution abandoned by a patent applicant or patentee through amendments to claims or specifications or a statement of opinion during the patent grant or invalidation procedure, and the right holder includes it within the scope of patent protection in a patent infringement dispute case, the people's court shall not support it. ”

03、捐献原则（Disclosure-dedication Rule）

The principle of donation means that if the patentee discloses a technical feature in the patent specification but does not record it in the claims, then it can be presumed that the technical feature was intentionally waived by the patentee and contributed to the public, and the right holder may no longer claim rights to the technical feature, and therefore may not use the technical feature to claim infringement equally.

The donation principle is a well-established rule of law that has been explained in a number of U.S. cases, including: Miller v. Brass Company[14], Unique Concepts, Inc. v. Brown [15], Maxwell v. J. Baker [16] and the famous Johnson Johnston Assoc v. R.E. Serv case [17]. Although the facts of the cases are different, they all expound the same legal spirit: to prevent the patentee from "profiting from both ends", that is, the patentee is not allowed to use a narrower range of claims in order to obtain authorization at the time of application, and in the subsequent infringement lawsuit, it tries to expand the scope of protection of the patent right by applying the principle of equivalence on the grounds of other equivalent schemes disclosed in the specification.

Subsequently, some members of the legal profession held that the judge should consider the subjective intention of the patentee to "omit" the relevant embodiments, and held that the lack of protection caused by negligence should be treated differently. The judge's landmark case in 2002, Johnson Johnston Assoc v. R.E. Serv,[18] answered this industry argument that the subjective intent of the patentee, whether negligent or willful, was irrelevant to whether the particular content was disclosed, and that the latter was an objective matter, in other words, the determination of the contribution principle did not need to take into account the subjective intent.

Article 5 of the 2009 Judicial Interpretation of the United States has a similar provision on the principle of donation in the United States:

"Where a technical solution that is only described in the description or drawings but not recorded in the claims is included in the scope of patent protection by the right holder in a patent infringement dispute case, the people's court shall not support it. ”

04、现有技术阻却（prior art ensnarement bar）

Prior art obstruction means that if the patentee has clearly known the relevant prior art solution when drafting the patent application documents, and clearly demarcates the scope of patent protection based on the prior art, which is equivalent to abandoning the prior art scheme, it is no longer possible to claim the application of the equivalence theory to include the prior art solution in the scope of protection in the infringement lawsuit. In short, the scope of equivalence should not include prior art.

The 1990 case of Wilson Sporting Goods Co. v. David Geoffrey & Associates[19] (hereinafter referred to as the Wilson case) is the most complete case in which prior art limitations are elaborated. Plaintiff Wilson sued competitor DGA and its distributor Dunlop for infringement of its US4560168 patent under the name Golf Ball. Wilson is one of the six competitors in the golf business, and Dunlop is also a significant player in the golf industry, selling the Slazenger golf balls to DGA, which in turn distributes them. In the first instance, the district court first found that Wilson's patent was valid and that Dunlop's golf ball constituted an infringement. Dunlop and DGA appealed to the Federal Circuit.

In the second instance, Dunlop argued that there was no difference in principle between his golf ball and the Uniroyal ball with prior art, so if his golf ball infringed Wilson's patent under the principle of equivalent infringement, then Wilson's patent protection also included prior art.

The Federal Circuit Court pointed out in the second instance that the patentee should not use the doctrine of equivalent infringement to obtain the scope that he could not legally obtain from the USPTO through a literal claim in the first place, and that the doctrine of equivalent infringement exists to prevent counterfeiting of the patent, not to expand the scope of protection available to the patentee. Since prior art can limit what the inventor can claim, it also limits the scope of allowable expansion of claims under the principle of equivalence[20].

If the alleged infringing product belongs to the prior art, or is obvious on the basis of the prior art, then the product does not constitute infringement. Allowing such products to be covered under the principle of equivalence would allow the patent holder to acquire rights that he could not have legally obtained in the first place during the patent application period. In applying prior art restraint, the court must treat the product as a whole to determine whether the product is patentable.

Unlike other legal limitations, prior art barriers are not based on the publicity of claims, but on the grantability of patents. The core of this obstacle is that if the technology formed by the "equivalent" substituting the corresponding technical features cannot be authorized, the "equivalent" is not a qualified equivalent, and therefore the alleged product cannot constitute equivalent infringement.

Article 14 of the 2009 Judicial Interpretation stipulates the prior art defense: "If all the technical features of the accused falling within the scope of protection of the patent right are the same or not substantially different from the corresponding technical features in a prior art solution, the people's court shall determine that the technology implemented by the accused infringer belongs to the prior art as provided for in Article 62 of the Patent Law." ”

There are similarities in the legal rationale of the prior art defence, which is also the prohibition on patentability of technology that covers technology in the public domain. The difference is that the use of prior art defense does not need to enter the step of determining infringement, but only needs to prove that the alleged infringing technology belongs to the prior art within the scope of the patent in question. However, it is clear that there are many limitations to the application and effect of the prior art defense as a negative defence rather than a right.

In addition, the Supreme People's Court of the Mainland has also elaborated on the spirit of prior technology obstruction in a number of cases, such as the (2021) Zui Gao Fa Zhi Min Zhong No. 192 case. In the judgment of the case, the Supreme People's Court pointed out that the description and claims can be seen that when drafting the claims and description of the patent in question, the patentee was clearly aware of the existence of two modes in the prior art: motor drive and fuel engine drive, and "environmental protection and pollution-free" is a new technical effect of this patent compared with the prior art. In this context, the patentee only records the motor drive in the claims of the patent in question, which clearly indicates that the drive mode in the technical solution of the patent in question is limited to the motor drive, and does not include the fuel engine drive. In this case, if the alleged infringing product falls within the scope of protection of the patent in question, the alleged infringing fuel engine drive and the motor drive are determined to have the same technical characteristics, which is not conducive to the play of the publicity function of the patent claims and the protection of the public's trust interests.

05. The equivalent of functional features can only be "after-arising", not technology that has appeared before authorization

For example, the scope of protection of a patent includes a "fastener", and the screws, nails, and bolts that appear at the time of the patent application can be used as possible embodiments of fastening, but new types of fasteners that may appear after the filing of the application, such as hook-and-loop fasteners, Velcro, etc., are considered to be "after-generation" technologies because they do not exist at the filing date of the patent.

The question then arises, why is it that in the judgment of equivalent infringement of non-functional technical features, the time point can be the date of occurrence of the infringement, while in the judgment of equivalence of functional features, the technology to be identified must appear after the date of grant and up to the date of infringement, but not before the date of grant?

With respect to functional features, the U.S. Patent Law provides in 35 U.S.C. §112(f)[21] that a patent applicant may use the means plus function method in the claims, but such expression is restrictively construed to cover the corresponding structure, material, or action described in the description and its equivalent. It can be seen that although claims are allowed to adopt a broader functional expression, in practice, whether in the process of patent granting or infringement determination, they are required to be limited to the specific embodiment of the disclosure of the specification and its equivalent. For the avoidance of doubt, the equivalence here is referred to as the equivalence in § 112(f).

The equivalence in § 112(f) is not equivalent under the principle of equivalence as described above. First of all, the two are applicable at different stages. The equivalent of §112(f) belongs to the category of literal interpretation of claims, which restricts the broad literal interpretation of claims by the specific embodiment disclosed in the specification, and belongs to the stage of determining literal infringement. On the contrary, the equivalence of equivalent infringement is applied only after the literal infringement is not established. The two occur at different stages, and if the plaintiff claims equivalent infringement, the two can be applied successively.

Secondly, the criteria for judging the two are different. In Valmont Industries, Inc. v. Reinke Mfg. Co.[22], the court made it clear that in an infringement determination involving functional features, in order to be established, the alleged infringing device must use the same or equivalent means to achieve the same function as described in the claim using the same or equivalent structure, material or steps described in the specification, which may be different from the substantially identical function in the equivalence test.

Finally, the equivalence of § 112(f) emphasizes that the change in the alleged device does not produce a "material change", i.e. it does not add any meaning to the structure, material or behavior disclosed in the patent specification. §112(f) equivalence is determined without a ternary test, as the judge concluded in Valmont that the "only problem" with §112(f) is the comparison of the structure of the device in question that performs the relevant function with the structure in the specification, and nothing more.

Having explained the differences, let's analyze why, in §112(f), the equivalents of functional features can only be "after-arising" and not pre-granted.

As mentioned above, the equivalence determination in §112(f) belongs to the stage of restrictive interpretation of claims, which are of course based on the current patent application, the scope of which is determined at the time of grant and cannot be extended to "late-mover technology". Therefore, if the technology to be identified as equivalent has appeared before the grant, and the patentee has not included it in the specification, it is deemed that the patentee has expressly waived its protection (which is a major disadvantage of using functional limitations), and can no longer be regarded as an equivalent way of disclosing embodiments in the specification, and is already considered not to be within the scope of protection at the stage of claim interpretation. Of course, it is also no longer possible to include protection again through equivalence in the subsequent equivalent infringement judgment (if any), as the prohibition of "two-way gain" has already been explained.

On the contrary, for non-functional features, the law does not require structural features to be limited to the scope of disclosure of the specification, as long as they do not violate the principle of estoppel and prior art limitations, whether it is a pre-grant technology or a "late-mover technology", both the technology before the grant date and the "late-mover technology" are qualified as equivalents and can be identified in the equivalent infringement. We can try to understand this from the legal rationale behind the principle of equivalent tort. First, the purpose of equivalent infringement is to make up for the imperfect generalization of the patent attorney when drafting the application, and it is not difficult to force others, and the agent cannot be required to include all possible embodiments (applicable to the technology at the time of application);

In summary, the equivalent (the equivalent of the specific structure disclosed in the specification) specified in §112(f) must be the "late-mover technology" that appears after the grant, and the "late-mover technology" in the subsequent equivalent infringement judgment should also be the "late-mover technology", and the two should be consistent to avoid the patentee's benefit.

Corresponding to the expression of structure + function in the United States, the legal concept used in mainland China is a functional feature, and the 2009 judicial interpretation has a similar provision in Article 4:

"For a technical feature expressed in a claim as a function or effect, the people's court shall determine the content of the technical feature in conjunction with the specific embodiment of the function or effect described in the description and drawings and its equivalent embodiment. ”

Article 8 of the Interpretation (II) of the Supreme People's Court on Several Issues Concerning the Application of Law in the Trial of Patent Infringement Dispute Cases, adopted in 2016, provides as follows:

"Compared with the technical features that are indispensable for the realization of the functions or effects referred to in the preceding paragraph as recorded in the description and drawings, the corresponding technical features of the accused infringing technical solution are basically the same means to achieve the same functions and achieve the same effects, and those skilled in the art can be associated without creative labor when the alleged infringement occurs, the people's court shall determine that the corresponding technical features are the same or equivalent to the functional features. ”

It can be said that the principle of equivalence is a legal principle that exists in almost all countries' patent systems, and its importance and necessity can be seen. The application of the principle of equivalence has not only brought challenges to legal practitioners, but also brought great enthusiasm and hope to the profession due to its complexity and case-by-case nature. It is hoped that the research and application of the equivalence theory will become more and more perfect and mature in the complex patent infringement cases in the mainland, so as to achieve a more ideal balance between the right holder and the public.

Resources:

[1] Winans v. Denmead, 56 U.S. 330 (1853)

[2] "the patentee, having described his invention, and shown its principles, and claimed it in that form which most perfectly embodies it, is, in contemplation of law, deemed to claim every form in which his invention may be copied, unless he manifests an intention to disclaim some of those forms."

[3] Graver Tank v. Linde Air products Co., 339 U.S. 605 (1950)

[4] a patentee may invoke this doctrine to proceed against the producer of a device "if it performs substantially the same function in substantially the same way to obtain the same result."

[5] An important factor is whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was.

[6] Warner Jenkinson Co., Inc. vs. Hilton Davis Chemical Co., 117S. Ct. 1040 (1997)

[7] noting that equivalency is properly evaluated at the time of infringement, not at the time of patent issuance

[8] [A] finding of infringement under the doctrine of equivalents requires proof of insubstantial differences between the claimed and accused products or processes.

[9] The way to reconcile the two lines of authority is to apply the doctrine to each of the individual elements of a claim, rather than to the accused product or process as a whole. Doing so will preserve some meaning for each of a claim's elements, all of which are deemed material to defining the invention's scope.

[10] Festo Corp. V. Shoketsu Kinzoku Kogya Kabushiki Co., 535 U.S. 722 (2002)

[11] Prosecution history estoppel is not limited to amendments intended to narrow the patented invention's subject matter, e. g., to avoid prior art, but may apply to a narrowing amendment made to satisfy any Patent Act requirement, including § 112's requirements concerning the patent application's form

[12] The narrowing amendment may demonstrate what the claim is not; but it may still fail to capture precisely what the claim is. There is no reason why a narrowing amendment should be deemed to relinquish equivalents unforeseeable at the time of the amendment and beyond a fair interpretation of what was surrendered.

[13] There are some cases, however, where the amendment cannot reasonably be viewed as surrendering a particular equivalent. The equivalent may have been unforeseeable at the time of the application; the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or there may be some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question. In those cases the patentee can overcome the presumption that prosecution history estoppel bars a finding of equivalence.

[14] Miller v. Brass Company, 104 U.S. 350 (1881)：the claim of a specific device or combination, and an omission to claim other devices or combinations apparent on the face of the patent, are, in law, a dedication to the public of that which is not claimed

[15] Unique Concepts, Inc. v. Brown, 939 F.2d 1558, 19 USPQ2d 1500 (Fed. Cir. 1991)

[16] Maxwell v. J. Baker, Inc., 86 F.3d 1098 (Fed. Cir. 1996)

[17] Johnson Johnston Assoc v. R.E. Serv, 285 F.3d 1046

[18] patentee's subjective intent is irrelevant to determining whether unclaimed subject matter has been disclosed and therefore dedicated to the public

[19] Wilson Sporting Goods Co. v. David Geoffrey & Associates, 904 F.2d 677 (Fed. Cir. 1990)

[20] A patentee should not be able to obtain, under the doctrine of equivalents, coverage which he could not lawfully have obtained from the PTO by literal claims. The doctrine of equivalents exists to prevent a fraud on a patent ..., not to give the patentee something he could not lawfully have obtained from the PTO had he tried. Prior art limits what an inventor could

[21] (f) ELEMENT IN CLAIM FOR A COMBINATION — An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.

[22] for a means-plus-function limitation to read on an accused device, the accused device must employ means identical to or the equivalent of the structures, material, or acts described in the patent specification. The accused device must also perform the identical function as specified in the claims.

(Original title: Scope and Limitation of the Principle of Equivalent Infringement in the United States)

Source: IPRdaily Chinese Network (iprdaily.cn)

Author: Tang Aisi, Guangdong Junlong Law Firm

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