In evaluation of patent infringement, the claims and specifications of the alleged infringing product are compared to the claims and specifications of the original patent. This comparison may be made by literal interpretation, or it may be holistic, holding a party liable for infringement even though the new device or process does not fall within the literal scope of the original patent claim. In the second case, the original patent is deemed to be equivalent to the claimed new invention.
In Raj Parkash v Mangat Ram Chowdhry and Ors, 1978, which was decided under the Indian Patents Act, 1970, the court stated, “It is the pith and marrow of the invention claimed that has to be looked into”, and that adjudicators should “not get bogged down or involved in the detailed specifications and claims made by the parties”.
The court also held that “if the infringing goods are made with the same object in view which is attained by the patented article, then a minor variation does not mean that there is no piracy. A person is guilty of infringement, if he makes what is in substance the equivalent of the patented article.”
This means that where the plaintiffs’ claim is wide enough to cover several methods for achieving a particular result, the question facing adjudicators is whether the method followed by the defendants is covered by that claim, not whether the defendants followed the same method as that actually followed by the plaintiffs.
In Ravi Kamal Bali v Kala Tech and Ors, 2008, the principle of pith and marrow was not applied in arriving at the decision, but was inherent in the plaintiffs’ plea that the tamper-proof locks produced by the defendants fell within the scope of the claims of the plaintiff’s patent, as they were equivalent to the technology applied by the plaintiff.
The principle of not limiting the interpretation of claims to literal language is well recognized in both the US, where it is known as the doctrine of equivalents, and in the UK, where it is known as the doctrine of purposive construction. However, the principle is applied differently in these two patent jurisdictions.
The first US decision to use the doctrine of equivalents to extend the cover of patent protection beyond literal infringement was Winans v Denmead, 1854. The non-literal principle has been applied since Graver Tank & Manufacturing Co v Linde Air Products Co, 1950, in which the function-way-result (or tripartite) test was developed: where the allegedly infringing device or process performs substantially the same function in substantially the same way to yield substantially the same result as a previous invention.
In addition, when an alleged infringer makes only insubstantial changes to a patented invention, he is said to have infringed the patent under the doctrine of equivalents, or to have committed equivalent infringement.
However, the application of the doctrine of equivalents in the US is beset with difficulties and is undergoing change. The doctrine was narrowed after Festo Corporation v Shoketsu Kinzoku Kogyo Kabushiki Co Ltd, 2002. It is applied on an element-by-element basis, and no longer defines an equivalent element solely with reference to the tripartite test.
In the UK the doctrine of purposive construction is applied via the Protocol on the Interpretation of Article 69 of the European Patent Convention, which requires the member states to draw a balance between literal interpretation of claims and regarding them as a guideline only. Further, a distinction is made between the essential and non-essential parts of a claim.
There is no statutory provision regarding equivalence under the prevailing Indian Patents Act, 1970: the law provides that the claim or claims shall be on the matter disclosed in the specification. However, the decision of Raj Parkash suggests that the Indian courts apply the doctrine of purposive construction as in the UK. This is natural, given that Indian law follows the English law in essence and substance.
There are two reasons not to limit a claim to its literal language. First, holistic interpretation protects a patentee from the manipulation of language, which could otherwise be exploited by an “unscrupulous copyist” who appropriates the essence of the invention, but avoids infringement by making insubstantial changes to the invention and circumvents the literal language of the claim.
Second, holistic interpretation protects a patentee from unforeseen advances in technology. An invention may rely on new principles that are not yet fully understood. In the rush to file applications, inventors and their attorneys often fail to anticipate the full potential scope and impact of the invention, which is only discovered through later development or commercialization of the invention. By allowing a patent claim to cover a wide range of equivalents, a pioneering inventor is provided a greater scope of protection commensurate with the inventor’s contribution to the art.
Abhai Pandey is a lawyer with Lex Orbis IP Practice, a law firm specializing in intellectual property issues.
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