Designing around patent is considered legitimate

It is common to find competitive inventors to work on the uncovered aspect of a patent claim and design around it to escape the sword of infringement. Intentional “designing around” the claim of a patent is legitimate so long as it is not by itself wrong. In Slimfold Mfg. Co. v. Kinkead Indus., Inc., 932 F.2d 1453, 1457 (Fed. Cir. 1991) U.S. federal court observed that “designing around” the claim of a patent is not by itself a wrong which must be compensated by invocation of the doctrine of equivalents.”

In the case, the Court appears to have been overly concerned with the fact that the Type II door was deliberately designed to avoid infringement of the Ford patent. In Texas Instruments, Inc. v. U.S.I.T.C., 805 F.2d 1558, 1572, 231 USPQ 833, 841-42 (Fed. Cir. 1986) Federal court observed that it is only when the changes are so insubstantial as to result in “a fraud on the patent” that application of the equitable doctrine of equivalents becomes desirable.

Insubstantial changes and Graver Tanak ‘Tripartite test’

In the Ford patent case, the Court applied the ‘Tripartite test’ established in GraverTank Mfg. Co. v. Linde Air Products Co., 339 U.S. 605, 608, 70 S.Ct. 854, 856, 94 L.Ed. 1097 85 USPQ 328, 330 (1950), which states that “the differences between an accused device and a claimed device are considered to be insubstantial only when the accused device performs substantially the same function in substantially the same way to achieve substantially the same result as the claimed device. The determination of whether an accused device meets this strict test is one of fact. When the Court applied Graver Tanak ‘Tripartite test’ in the Ford Patent case, the Court observed that:

“In the present case, as often happens in the doctrine of equivalents cases, there is no material dispute about the “function” and the “result” prongs of the test. Both the claimed pivot rod assembly and the corresponding but different assembly of the Type II door have a means which engages the pivot rod so as to hold it in a retracted position during shipment and assembly. The question is whether they do so in substantially the same way. We are convinced that the district court’s finding that they do is clearly erroneous.”

To substantiate this finding, the Court observed that:

“First of all, we note that the claimed invention is a mechanical combination in a crowded field (a total of 34 patents are listed on the reissue application as having been considered by the examiner). Such an invention is entitled only to a narrow scope of equivalents.

“Furthermore, the Kinkead styrofoam wedge operates in a substantially different way from the claimed latching means, which Kinkead has eliminated. The wedge is a separate piece placed at the lower part of the assembly. It acts as a friction device, not only between the pivot rod and the sleeve but also the facing sheet of the door. The claimed latching means, on the other hand, is indeed a latch which acts between the upper part of the sleeve and the head portion of the pivot rod. As its name implies, the latching means latches, i.e., grabs onto the head portion of the pivot rod. A latch and a wedge, applied in different locations, have very different modes of operation, and we are left with a firm conviction that Kinkead’s modification with respect to the Type II door results in a device which does not operate in substantially the same way, and thus was sufficient to avoid infringement under the doctrine of equivalents. It does not meet the Graver test. Accordingly, the district court’s finding to the contrary is reversed. The Type II door is not an infringement.”

In this case, the Court applied the ‘Graver Tank tripartite test’ to find the design deference in the infringing product and ruled that Kinkead’s modification with respect to the Type II door results in a device which does not operate in substantially the same way. In simple words, this design found favour with the Court.

Position in India

However, the ‘Silomat Dolly patent’ infringer was not so successful in convincing the Delhi High Court that their modified Dolly with two missing elements does not infringe the patented carriage for the horizontal transfer of motor vehicles in an automatic mechanical car parking. In the Sotefin SA v. Indraprastha Cancer Society and Research Centre & Ors [(COMM) 327/2021, 17 February 2022] case, the Delhi High Court was faced with a question of alleged infringement of a patent for a carriage for the horizontal transfer of motor vehicles in an automatic mechanical car parking (Silomat Dolly case). The Court found that all the elements of the plaintiff’s patent claim did not entirely correspond with the defendant’s product as the infringing product lacked two elements. To resolve the issue of whether the defendant’s product with the 2 elements less still infringed the plaintiff’s patent or not, the Court resorted to the doctrines of non-literal infringement. Courts looked into the functional aspect of these two non-essential elements.

The first element absent from the defendant’s product was hinges, which the configuration installed at the defendant’s premises did not use. A closer look at the defendant’s product revealed that although the defendant’s product did not include the hinge, which emulated the movement of an elbow joint, this product did have a structure that behaved as a shoulder joint and provided for multi-directional movement.

Court found that the elbow-jointed hinge in the claimed invention and the shoulder joint in the defendant’s product, prima facie, did not substantially differ in functionality and achieved substantially the same result in substantially the same way. The Court concluded that the hinge was a non-essential part of the claimed invention, and even in the absence of such a hinge, the defendant’s product did not substantially differ from the claimed invention in its operation.

The second non-essential element is the immobilization of the rear wheels. This second element missing from the defendant’s product was responsible for immobilising the rear wheels. The Court found that the claimed invention involved immobilising the wheels at the front and back, whereas the defendant’s product had the means to immobilize the wheels only at one end. The Court applied the doctrine of pith and marrow to hold that this difference between the claimed invention and the defendant’s product had no material effect on the working of the invention.

The Court ruled that “this indicated that the variation between the two was insignificant and the Defendant’s product did not have enhanced functionality in view of the differences with respect to the claimed invention.” Based on these findings, the Court held that “the Defendant’s product was insignificantly different from the patented invention and that the Plaintiff had successfully established a strong prima facie case of infringement against the Defendant.

In this case, the clever design around the attempt by the infringer was not successful, as the Court found that eliminating two non-essential elements from the Silomat Dolly patent was not enough to prove the improved design around the patented invention.

The doctrine of Equivalents’-Triple Identity Test’

Whenever courts in India have found that the alleged infringer is attempting to design around the patented invention, they do not hesitate to apply the Doctrine of Equivalents. In applying the Doctrine of Equivalents, the Court essentially seeks to prove that every element of the patented invention or its substantial equivalent is present in the alleged infringing product or process, in conjunction with the triple identity test, i.e., performing the same function, in the same way, and achieve the same result. For instance, in C.T.R. Manufacturing Industries Ltd vs Sergi Transformer Explosion (Bombay High Court 23 October 2015) case Bombay High Court concluded that

“58. The Differential Relay’s use in conjunction with the Buchholz Relay seems to me to be the ‘pith and marrow’ of C.T.R.’s Patent ……..and, to use the words of Wadia J in Lallubhai Chakubhai v Chimanlal & Co [A.I.R. 1936 Bom 99] what Sergi seems to have done is to take from C.T.R. the substance of its invention. Wadia J said that sometimes a patent is infringed by taking only a part, but that depends on whether the part so lifted and for which protection is sought is a new and material part, especially in the case of a combination. I read the word ‘part’ in this phrasing not to mean an individual integer per se but a portion of the patent. This has been the law for a very long time: if the defendant really has taken the substance and essence of the plaintiff’s combination, its ‘pith and marrow’, the mere fact that certain parts are added or omitted does not mean there is no infringement.”

The Court went on further to rule that the P.R.V. fails the Catnic Test :

“79. I return finally to what seems to me to lie at the heart of the present case, and that is a contradiction inherent in Sergi’s defence. Sergi claims the P.R.V. to be essential to both its product and its patent. But if it is essential, it cannot possibly be sidelined with an “or”, as is shown in Sergi India’s brochure and even in the comparative chart. It cannot be an alternative. It must necessarily be deployed, without fail, every single time. That is not even what Sergi puts forth in its own documentation, and I do not think it is enough to say, “Look, we use the P.R.V. and C.T.R. does not. Therefore, there is no infringement”, unless it is shown that the P.R.V. is not optional. The DTL tender makes it optional, and even Sergi’s use of it, marked with the word “OR”, makes it so. Clearly, this puts the matter beyond the pale. The P.R.V. fails the Catnic test and fails it utterly.” [Bombay High Court 23 October, 2015]

The valiant attempt by Sergi to design around the C.R.T. patent was not so successful as the Court junked the Sergi argument that they use the P.R.V. and C.T.R. does not; therefore, there is no infringement. The Court applied the Catnic test to prove, stating that the information in the DTL tender makes it optional, and even Sergi’s use of it, marked with the word “OR”, makes it so. Therefore, clever designing around by adding an optional element may not save the infringer from liability of infringement.


Intentional “designing around” the claims of a patent or otherwise is not by itself wrong. Designing around patents is one of the ways to promote improvement in patented inventions for the benefit of the public and promote progress in technology. Inherent in our language-based claim patent system is the understanding that the protected invention is what the claims say. Every infringer believes that it is possible to avoid infringement by staying clearly away from the technical coverage of the claims. The Court in all jurisdictions, however, may dive deep and invoke the doctrine of equivalents or pith and marrow to ascertain the infringement of the existing patent where they suspect possible use of designing around the patented invention. Thus, the first question that the Court may ask is, “Has a substantial change been made?”

If the answer to that question is “no”, an accused infringer may be held liable for improperly trying to appropriate the claimed invention. In the C.R.T. infringement case, clever designing around by adding an optional element was not successful. And so was the attempt to omit two non-essential features in the Dolly case. However, if designing around the invention does not meet the Graver tripartite test, it is likely to be declared as not an infringement, as happened in the Ford patent in the U.S. The best option for the inventors who are inclined to design around the existing patent is to seek expert advice to stay clear from the ambit of the existing patent claims.

Author – DPS Parmar

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