A patent is a monopoly right granted by a national or regional patent office to an inventor who has created something new, useful and non-obvious. Any invention demands huge investment of time, and resources in the form of research and development.

Doctrine of Equivalents and prior history estoppel

Introduction:
A patent is a monopoly right granted by a national or regional patent office to an inventor who has created something new, useful and non-obvious. Any invention demands huge investment of time, and resources in the form of research and development. Patent rights allow the owners to prevent others from exploiting their invention and allows them a fair return on their investment. the patent laws require inventors to describe their work in "full, clear, concise, and exact terms," thus maintaining the balance between the inventor’s interest and public interest.

At times, an imitation of the patent might not be an literal imitation but may provide the same effect. If such an imitation is allowed, it would defeat the purpose of granting the patent rights to the inventor. It would become more lucrative to make insignificant changes to the patent, assert that it does not fall within the literal language of the claims and enjoy larger returnd than the original inventor without expending much effort or resources. It was to counter such behavior that the Doctrine of Equivalence was evolved by the US Supreme Court in Winans v. Denmead[1]. The court ruled that infringement may occur even though the literal language of the claims was avoided.

Doctrine of Equivalents - Meaning:

Patent infringement can take two forms : literal infringement and infringement under the doctrine of equivalents. Literal infringement means each and every element of the claim has been imitated by the infringer. Infringement under Doctrine of Equivalents occurs when some other element of the accused device or process performs substantially the same function, in substantially the same way, to achieve substantially the same result. The Doctrine was evolved by the US Supreme Court in Winans v. Denmead[2]. The doctrine further received clarity in Graver Tank & Mfg. Co. v. Linde Air Products Co.[3] It was held that “Under this doctrine, an accused article or method that does not literally meet the limitations of a claim may nevertheless infringe. Thus, even if there is no literal infringement, infringement could be found under the doctrine of equivalents, if the accused article or method was equivalent to the claimed invention.[4]The doctrine of equivalents has created a tension between two important public policies. One policy focuses on the importance of providing public notice as to what infringes, by requiring clear and distinct claims. The other policy focuses on the need to prevent an infringer from avoiding liability by merely playingsemantic games or by making only minor changes in the accused article or method to avoid the literal language of the claims.[5] The Doctrine of equivalents is limited by (i) the doctrine of "prosecution history estoppel" and (ii) the prior art.

Doctrine of prosecution history estoppel – Meaning

Prosecution history estoppel precludes a patentee from obtaining under the doctrine of equivalents coverage of subject matter that has been relinquished during the prosecution of its patent application[6]. The U.S Supreme Court, in the case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.[7], cemented the application of the doctrine. The decision in Festo, the doctrine of prosecution history estoppel can be summarized as follows:
1. any narrowing amendment made to satisfy the requirements of the Patent Act may give rise to an estoppel;
2. an unexplained narrowing amendment is presumed to have been made to satisfy the requirements of the Patent Act;
3. an estoppel does not create an absolute bar to the application of the doctrine of equivalents;
4. The applicant is presumed to have surrendered the scope of protection between the claim before amendment and after amendment;
5. it is the applicant's burden to show that the particular equivalent in question was not surrendered.[8]

Operation of the Doctrine of equivalents in the U.S.A.
The evolution of this doctrine is credited to the case of Winans v. Denmead.[9]The Supreme Court stated that a patent would be valueless if the defendant can simply change the form of the invention claimed. In Warner-Jenkinson Co. v. Hilton Davis Chemical Co.[10] the Court then clarified and restricted the application of the doctrine of equivalents holding that: Each element contained in a patent claim is deemed material to defining the scope of the patented invention, and thus the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole.This restriction of the doctrine of equivalents is referred to as the all elements rule. The case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.[11], cemented the application of the doctrine and how it is limited by the doctrine of prosecution history estoppel. In its early development, the doctrine was usually applied in cases involving devices where there was equivalence in mechanical components. Subsequently, however, the same principles were also applied to compositions, where there was equivalence between chemical ingredients. Today the doctrine is applied to mechanical or chemical equivalents in compositions or devices.

Operation of the Doctrine of equivalents in the U.K.
The UK allegedly does not follow this doctrine but treats “non literal” infringement cases by simply resorting to what they creatively call “purposive construction”.

Operation of the Doctrine of equivalents in the India
The case which brought forward the doctrine in India was Ravi Kamal Bali vs Kala Tech And Ors[12]. The plaintiff, instituted an infringement suit seeking an interim injunction restraining Kala Tech, the defendant, from making, using, selling or distributing tamper proof locks/seals as it would be the infringement of his patent. He contended that Kala Tech’s product do the same work, in substantially the same way and accomplishes substantially the same result thereby contributing to the infringement. He also submitted that while considering the question of infringement of patents, the Court ought to apply the doctrine of equivalence by which a device is set to infringe a claim if it "performs substantially the same function in substantially the same way to obtain the same result". Although the interim injunction was not granted the importance of the case lies in in that , it was the first case where the doctrine was discussed in India.

Problems associated with the doctrine:
Despite the doctrine having been around for 150 years a precise, settled, linguistic framework id yet to evolve[13] This lack of a proper framework creates ambiguity and difficulty in application. When applied too broadly it interferes with the public notice function of the statutory claiming requirements.[14] If a member of the public, after reviewing the patent creates a product that falls outside the literal scope of the claims of the patent and is later found to have infringed the same patent under the doctrine of equivalents, then the notice function served by the claims has failed.[15]

It has been a common concern that those who were genuinely trying to design around an invention and thought in good faith that they had successfully done so can be held for infringement under the doctrine. [16] Another view that exists is that the modern doctrine of equivalents that protects inventions beyond the interpreted scope of claim language is not needed for fairness or efficiency and should be abolished. The fairness arguments lack theoretical justification, the doctrine imposes high social costs and likely impedes innovation, and doctrine of equivalents needlessly conflicts with other patent law doctrines and unduly complicates patent litigation procedures.[17]

Conclusion:
Despite the associated drawbacks the importance of the doctrine in ensuring the inventors their fair share cannot be overlooked. The courts in the U.S.A .have ensured proper application of the doctrine by developing various limitations. If the doctrine subject to limitations is derived into the Indian scenario it would be enormously beneficial.

End-Notes
[1]56 U.S. 330 (1854)
[2]56 U.S. 330 (1854)
[3]339 U. S. 605. 85 U.S.P.Q.2d 328 (1950).
[4]339 U. S. 605. 85 U.S.P.Q.2d 328 (1950).
[5]Glen Belvis , OVERVIEW OF THE DOCTRINE
OF EQUIVALENTS , available at http://www.brinksgilson.com/files/102.pdf
[6]Pharmocia & Upjohn v. Mylan Pharm., 170 F.3d 1373, 1376, 50 U.S.P.Q.2d 1033, 1037 (Fed. Cir. 1999).
[7](a/k/a SMC Corp.), 122 S. Ct. 1831, 62 U.S.P.Q.2d 1705
(2002).
[8]Glen Belvis , OVERVIEW OF THE DOCTRINE
OF EQUIVALENTS , available at http://www.brinksgilson.com/files/102.pdf
[9]56 U.S. 330 (1854)
[10]520 U.S. 17 (1997)
[11] (a/k/a SMC Corp.), 122 S. Ct. 1831, 62 U.S.P.Q.2d 1705
(2002).
[12]2008(110)Bom LR 2167
[13]Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997)
[14]Freedman Seating Co. v. Am. Seating Co
[15]Sterne Robert Greene MacPhail Donald R, The Doctrine of Equivalents, American Law Institute ABA CLE 18 (2000) 105, 109
[16]Scott Boone M, Defining and Redefining the Doctrine of Equivalents , The Journal of Law and Technology , 43 (2003) 645, 661
[17]Josh Sarnoff , Abolishing the Doctrine of Equivalents and Claiming the Future After Festo, 19 Berkeley Tech. L.J. 1157 (2004).