Determination of Equivalents in a Patent Application

BlogIntellectual Property RightsPatent    July 28, 2021
Determination of Equivalents in a Patent Application Posted On

The doctrine stipulates that the scope of a patent is not confined to the literal terms laid in the claims; instead, it embraces all the equivalents to the claims described in the said application. In the absence of such a doctrine, the true essence of the patent and the monopolistic rights would never be realized to their full potential as it would enable the competitors to make unimportant changes to the invention to claim another set of rights altogether. The doctrine embraces fairness while affording appropriate protection to the proprietor of the rights ensuing from the patent.

Brief Introduction

The ‘Doctrine of Equivalence’ states that there are chances of non-literal infringement if an element of an accused product or service and a claimed element of a patented invention are found to be legally equivalent. It broadens the ambit of the patentee’s right as it enables him to claim those rights that are inconsequential alterations to the invention, which may not be expressly covered in the original claims. Therefore, it prevents fraudulent acts of substituting obvious equivalents for those elements in the claims that are not covered due to the limitation of language. However, it does not include within itself those equivalents that belong to the state of the art to arbitrarily extend the scope of the patent.

The doctrine may be invoked if the allegedly infringing device “performs substantially the same function in substantially the same way to obtain the same result.” The said doctrine is limited in scope through the application of different tests that are later discussed in this article.

What is an Equivalent?

As per Graver Tank & Mfg. Co vs. Linde Air Prods Co, 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,” as has also been mentioned above. Here, the alleged infringer’s invention will be looked at as a whole without bifurcating the claims. However, the courts took a turn in their approach after this case and introduced a certain degree of uncertainty in an attempt to evolve the doctrine.

In the Warner-Jenkinson case, the court proposed that “equivalency must be determined against the context of the patent, the prior art, and the particular circumstances of the case.” The court shall look into greater depths while assessing the purpose of each ingredient used, the qualities it possesses when it interacts with other components, etc.

How to Determine Whether an Element is an Equivalent?

For discovering whether an element is an equivalent of another, the following two factors shall be taken into consideration:

  • The test of equivalence
  • The legitimate limitation to equivalents

As mentioned above, to assess the test of equivalence, the following legal tests have been evolved:

  • All Elements Rule: As per this rule, infringement may be established if the allegedly infringing invention performs substantially the same overall function in substantially the same way to obtain substantially the same overall result as the claimed patent. Each element of both the inventions is put into brief comparison to discover infringement. If the product does not contain a literal or equivalent element for each claim limitation, then there can be no infringement.
  • Tri-Partite Test: This test has emerged from the ‘All-Elements Test,’ which states that infringement may occur when the infringing invention “performs substantially the same function in substantially the same way to obtain the same result” as the claimed invention.
  • Insubstantial Differences Test: This test rests on the fact that if an adequate difference between the alleged infringing device and the claimed invention can be made out, the question of infringement can be legitimately eliminated. However, where the difference is merely insubstantial, the infringement is said to have occurred following the principle laid under the doctrine of equivalence.
  • Obviousness Test: The said test has not been put to great use until yet. The test stipulates that where the difference between the two inventions (allegedly infringing and claimed invention) is such that it is non-obvious, the same is said to have a substantial difference, and thereby, the infringement is said to not have occurred. However, if the difference is obvious, the difference between the two inventions is insubstantial, and therefore, the allegedly infringing invention is caught under the doctrine of equivalents.
  • Known Interchangeability Test: Under this test, the onus of proving that the element in question is known to be interchangeable with elements within the claimed invention lies on the patent holder to successfully bring an infringement action.

The legal bars to the doctrine of equivalence may also prevent the application of the said doctrine. Therefore, to successfully assert infringement through the application of this doctrine, in addition to the tests of equivalence, the rights holder has to prove that the uncovered equivalence falls beyond any legal defense. There are four major legal bars, which are as follows:

  • Prosecution History Estoppel: This means that the claims of a patent shall be read in the light of the prosecution history or the process through which the relevant patent office issued the patent, which includes rejections, cancellations, and amendments. A patent holder is estopped from claiming equivalence of those claims that he surrendered by way of alternation or amendment of his application. Therefore, if one narrows his claims, it is said that the claims had once been mentioned, but due to amendment, were either narrowed or removed, and thus, are now relinquished. Thus, such antecedent claims cannot be claimed.
  • Public Dedication: There are instances where the proprietor discloses a few elements in his claims but does not necessarily claim them, for instance, mentioning an alternative of what is claimed. Here, what is not claimed becomes a part of the public dedication.
  • After Arising Equivalents for Means-Plus-Function Claims: As per this bar, a patent holder is barred from claiming equivalence over those elements that have been developed after the patent was granted. Therefore, if an invention is to be an equivalent of a claimed invention, it should be so before the patent was granted.
  • Prior Art Patentability: This bar creates a limitation upon the patent holder by stating that where a person skilled in the art would be able to conceive that the equivalent claimed was that which was already known of, the claims of the claimed patented invention cannot be broadened to cover more than what it should be eligible for. It prevents the rights holder from gaining rights over elements that he has not rightfully adduced.

Inherent Defects and Issues Emanating from the Doctrine

Inherent Defects and Issues Emanating from the Doctrine

The doctrine of equivalence suffers from some defects. It is criticized for the lack of certainty since there is no precise legislative framework. The doctrine has been evolving since the time of its inception, yet it has bred ambiguities. Many courts have addressed that the tests laid above may not suffice the requirement to adjudge equivalence.

The doctrine can have far-reaching effects since it may lead to broadening of claims despite the checks and balances held through the determination of equivalent claims and bars on equivalents. It may so happen that in furtherance of uncovering non-literal infringement, the doctrine may help envelop even those elements that may only be impliedly found in the Patent Application. It is directly in conflict with the public notice function since once a patent is granted, the public is put on notice as to what is protected and what is not; thereby, permitting exploration of what is not covered within the granted application. If, after reviewing the application, an invention is created that falls beyond the scope of the invention; but, which is later found to be infringing due to incidental non-literal overlapping, the public-notice function fails. The same is a concern that is also often brought up by those inventors who try to design around the invention in good faith.

Concluding Remarks

The doctrine of equivalence may suffer from the previously mentioned drawbacks; however, its importance cannot be denied. It is of significant importance to successfully plead a case of non-literal infringements since it helps restore the balance of monopolistic rights and public disclosure. It helps overcome the impact of overemphasizing literal terms and words used in a patent application to uncover the essence of the same to understand its scope and nature. In the absence of such an invention, the inventor would be deterred to make a complete disclosure since it would be easier to ride on the patented invention by making unsubstantial changes and twisting the bare wordings of the claimed invention. ✅ For more visit:

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